title:
The Prelude to and Aftermath of the Giant Flare of 2004 December 27:
  Persistent and Pulsed X-ray Properties of SGR 1806-20 from 1993 to 2005

abstract:
  On 2004 December 27, a highly-energetic giant flare was recorded from the
magnetar candidate SGR 1806-20. In the months preceding this flare, the
persistent X-ray emission from this object began to undergo significant
changes. Here, we report on the evolution of key spectral and temporal
parameters prior to and following this giant flare. Using the Rossi X-ray
Timing Explorer, we track the pulse frequency of SGR 1806-20 and find that the
spin-down rate of this SGR varied erratically in the months before and after
the flare. Contrary to the giant flare in SGR 1900+14, we find no evidence for
a discrete jump in spin frequency at the time of the December 27th flare
(|dnu/nu| < 5 X 10^-6). In the months surrounding the flare, we find a strong
correlation between pulsed flux and torque consistent with the model for
magnetar magnetosphere electrodynamics proposed by Thompson, Lyutikov &
Kulkarni (2002). As with the flare in SGR 1900+14, the pulse morphology of SGR
1806-20 changes drastically following the flare. Using the Chandra X-ray
Observatory and other publicly available imaging X-ray detector observations,
we construct a spectral history of SGR 1806-20 from 1993 to 2005. The usual
magnetar persistent emission spectral model of a power-law plus a blackbody
provides an excellent fit to the data. We confirm the earlier finding by
Mereghetti et al. (2005) of increasing spectral hardness of SGR 1806-20 between
1993 and 2004. Contrary to the direct correlation between torque and spectral
hardness proposed by Mereghetti et al., we find evidence for a sudden torque
change that triggered a gradual hardening of the energy spectrum on a timescale
of years. Interestingly, the spectral hardness, spin-down rate, pulsed, and
phase-averaged of SGR 1806-20 all peak months before the flare epoch.


title:
RAPTOR observations of delayed explosive activity in the high-redshift
  gamma-ray burst GRB 060206

abstract:
  The RAPid Telescopes for Optical Response (RAPTOR) system at Los Alamos
National Laboratory observed GRB 060206 starting 48.1 minutes after gamma-ray
emission triggered the Burst Alert Telescope (BAT) on-board the Swift
satellite. The afterglow light curve measured by RAPTOR shows a spectacular
re-brightening by ~1 mag about 1 h after the trigger and peaks at R ~ 16.4 mag.
Shortly after the onset of the explosive re-brightening the OT doubled its flux
on a time-scale of about 4 minutes. The total R-band fluence received from GRB
060206 during this episode is 2.3e-9 erg/cm2. In the rest frame of the burst (z
= 4.045) this yields an isotropic equivalent energy release of ~0.7e50 erg in
just a narrow UV band 130 +/- 22 nm. We discuss the implications of RAPTOR
observations for untriggered searches for fast optical transients and studies
of GRB environments at high redshift.


title: The Origins of Fluorescent H2 Emission From T Tauri~Stars

abstract:
  We survey fluorescent H2 emission in HST/STIS spectra of the classical T
Tauri stars (CTTSs) TW Hya, DF Tau, RU Lupi, T Tau, and DG Tau, and the
weak-lined T Tauri star (WTTS) V836 Tau. From each of those sources we detect
between 41-209 narrow H2 emission lines, most of which are pumped by strong
Ly-alpha emission. H2 emission is not detected from the WTTS V410 Tau. The
fluorescent H2 emission appears to be common to circumstellar environments
around all CTTSs, but high spectral and spatial resolution STIS observations
reveal diverse phenomenon. Blueshifted H2 emission detected from RU Lupi, T
Tau, and DG Tau is consistent with an origin in an outflow. The H2 emission
from TW Hya, DF Tau, and V836 Tau is centered at the radial velocity of the
star and is consistent with an origin in a warm disk surface. The H2 lines from
RU Lupi, DF Tau, and T Tau also have excess blueshifted H2 emission that
extends to as much as -100 km/s. The strength of this blueshifted component
from DF Tau and T Tau depends on the upper level of the transition. In all
cases, the small aperture and attenuation of H2 emission by stellar winds
restricts the H2 emission to be formed close to the star. The Ly-alpha and the
H2 emission blueshifted by 15 km/s relative to RU Lupi are extended to the SW
by 0.07 arcsec, although the faster H2 gas that extends to about 100 km/s is
not spatially extended. We also find a small reservoir of H2 emission from TW
Hya and DF Tau consistent with an excitation temperature of about 2.5x10^4 K.


title:
On the luminosity function of galaxies in groups in the Sloan Digital
  Sky Survey

abstract:
  Using galaxy groups identified in the Fourth Data Release of the Sloan
Digital Sky Survey (SDSS), we compute the luminosity function for several
subsamples of galaxies in groups. In all cases, the luminosity functions are
well described by Schechter functions, down to the faintest magnitudes we
probe, $M_{\rb}-5\log(h)\sim-16$. For the general luminosity function of
galaxies in groups in the five SDSS bands, we observe that the characteristic
magnitude is brighter in $\sim 0.5$ magnitudes compared to those obtained for
field galaxies by Blanton et al.. Even when the observed faint end slope is
steeper in galaxy groups, it is statistically comparable with the field value.
We analyze the dependence of the galaxy luminosity function with system masses
finding two clear trends: a continuous brightening of the characteristic
magnitude and a steepening of the faint end slope as mass increases. The
results in $\gb$, $\rb$, $\ib$ and $\zb$ bands show the same behavior. Using
the $u-r$ color to split the galaxy sample into red and blue galaxies, we show
that the changes observed as a function of the system mass are mainly seen in
the red, passively evolving, galaxy population, while the luminosities of blue
galaxies remain almost unchanged with mass. Finally, we observe that groups
having an important luminosity difference between the two brightest galaxies of
a system show a steeper faint end slope than the other groups. Our results can
be interpreted in terms of galaxy mergers as the main driving force behind
galaxy evolution in groups.


title:
Detecting Sunyaev-Zel'dovich clusters with PLANCK: III. Properties of
  the expected SZ-cluster sample

abstract:
  The PLANCK-mission is the most sensitive all-sky submillimetric mission
currently being planned and prepared. Special emphasis is given to the
observation of clusters of galaxies by their thermal Sunyaev-Zel'dovich (SZ)
effect. In this work, the results of a simulation are presented that combines
all-sky maps of the thermal and kinetic SZ-effect with cosmic microwave
background (CMB) fluctuations, Galactic foregrounds (synchrotron emission,
thermal emission from dust, free-free emission and rotational transitions of
carbon monoxide molecules) and sub-millimetric emission from planets and
asteroids of the Solar System. Observational issues, such as PLANCKs beam
shapes, frequency response and spatially non-uniform instrumental noise have
been incorporated. Matched and scale-adaptive multi-frequency filtering schemes
have been extended to spherical coordinates and are now applied to the data
sets in order to isolate and amplify the weak thermal SZ-signal. The properties
of the resulting SZ-cluster sample are characterised in detail: Apart from the
number of clusters as a function of cluster parameters such as redshift z and
total mass M, the distribution n(sigma)d sigma of the detection significance
sigma, the number of detectable clusters in relation to the model cluster
parameters entering the filter construction, the position accuracy of an
SZ-detection and the cluster number density as a function of ecliptic latitude
beta is examined.


title:
The X-ray-to-Optical Properties of Optically-Selected Active Galaxies
  Over Wide Luminosity and Redshift Ranges

abstract:
  We present partial-correlation analyses that examine the strengths of the
relationships between L_UV, L_X, Alpha_OX, and redshift for optically-selected
AGNs. We extend the work of Strateva et al. (2005), that analyzed
optically-selected AGNs from the Sloan Digital Sky Survey (SDSS), by including
52 moderate-luminosity, optically-selected AGNs from the COMBO-17 survey with
corresponding deep (~250 ks to 1 Ms) X-ray observations from the Extended
Chandra Deep Field-South. The COMBO-17 survey extends ~3 magnitudes deeper than
the SDSS and probes the moderate-luminosity AGNs that numerically dominate the
AGN population in the Universe. We also include recently published observations
of 19 high-redshift, optically-selected AGNs, and 46 luminous, low-redshift
AGNs from the Bright Quasar Survey. The full sample used in our analysis
consists of 333 AGNs, extending out to z~6, with 293 (88%) having X-ray
detections. The sample spans five decades in UV luminosity and four decades in
X-ray luminosity. We confirm that Alpha_OX is strongly anti-correlated with
L_UV (13.6 sigma), the highest significance found for this relation to date,
and find evidence suggesting that the slope of this relation may be dependent
on L_UV. We find that no significant correlation exists between Alpha_OX and
redshift (1.3 sigma), and constrain the maximum evolution of AGN UV-to-X-ray
flux ratios to be less than 30% (1 sigma) out to z=5. Using our sample's high
X-ray detection fraction, we also find a significant anti-correlation (3.0
sigma) between Alpha_OX and L_X . We make comparisons to earlier studies on
this topic and discuss implications for X-ray vs. optical luminosity functions.


title:
Star Clusters with Primordial Binaries: I. Dynamical Evolution of
  Isolated Models

abstract:
  In order to interpret the results of complex realistic star cluster
simulations, which rely on many simplifying approximations and assumptions, it
is essential to study the behavior of even more idealized models, which can
highlight the essential physical effects and are amenable to more exact
methods. With this aim, we present the results of N-body calculations of the
evolution of equal-mass models, starting with primordial binary fractions of 0
- 100 %, with values of N ranging from 256 to 16384. This allows us to
extrapolate the main features of the evolution to systems comparable in
particle number with globular clusters. In this range, we find that the
steady-state `deuterium main sequence' is characterized by a ratio of the core
radius to half-mass radius that follows qualitatively the analytical estimate
by Vesperini & Chernoff (1994), although the N dependence is steeper than
expected. Interestingly, for an initial binary fraction f greater than 10%, the
binary heating in the core during the post collapse phase almost saturates
(becoming nearly independent of f), and so little variation in the structural
properties is observed. Thus, although we observe a significantly lower binary
abundance in the core with respect to the Fokker-Planck simulations by Gao et
al. (1991), this is of little dynamical consequence. At variance with the study
of Gao et al. (1991), we see no sign of gravothermal oscillations before 150
halfmass relaxation times. At later times, however, oscillations become
prominent. We demonstrate the gravothermal nature of these oscillations.


title:
Star Clusters with Primordial Binaries: II. Dynamical Evolution of
  Models in a Tidal Field

abstract:
  [abridged] We extend our analysis of the dynamical evolution of simple star
cluster models, in order to provide comparison standards that will aid in
interpreting the results of more complex realistic simulations. We augment our
previous primordial-binary simulations by introducing a tidal field, and
starting with King models of different central concentrations. We present the
results of N-body calculations of the evolution of equal-mass models, starting
with primordial binary fractions of 0 - 100 %, and N values from 512 to 16384.
We also attempt to extrapolate some of our results to the larger number of
particles that are necessary to model globular clusters. We characterize the
steady-state `deuterium main sequence' phase in which primordial binaries are
depleted in the core in the process of `gravitationally burning'. In this phase
we find that the ratio of the core to half-mass radius, r_c/r_h, is similar to
that measured for isolated systems. In addition to the generation of energy due
to hardening and depletion of the primordial binary population, the overall
evolution of the star clusters is driven by a competing process: the tidal
disruption of the system. We find that the depletion of primordial binaries
before tidal dissolution of the system is possible only if the initial number
is below 0.05 N, in the case of a King model with W_0=7 and N=4096 (which is
one of our longest living models). We compare our findings, obtained by means
of direct N-body simulations but scaled, where possible, to larger N, with
similar studies carried out by means of Monte Carlo methods.


title:
Complex small-scale structure in the infrared extinction towards the
  Galactic Centre

abstract:
  A high level of complex structure, or ``granularity'', has been observed in
the distribution of infrared-obscuring material towards the Galactic Centre
(GC), with a characteristic scale of 5arcsec - 15arcsec, corresponding to 0.2 -
0.6pc at a GC distance of 8.5kpc. This structure has been observed in ISAAC
images which have a resolution of 0.6arcsec, significantly higher than that of
previous studies of the GC.
  We have discovered granularity throughout the GC survey region, which covers
an area of 1.6deg x 0.8deg in longitude and latitude respectively (300pc x
120pc at 8.5kpc) centred on Sgr A*. This granularity is variable over the whole
region, with some areas exhibiting highly structured extinction in one or more
wavebands and other areas displaying no structure and a uniform stellar
distribution in all wavebands. The granularity does not appear to correspond to
longitude, latitude or radial distance from Sgr A*. We find that regions
exhibiting high granularity are strongly associated with high stellar
reddening.


title:
Measurement of \Omega_m, \Omega_{\Lambda} from a blind analysis of Type
  Ia supernovae with CMAGIC: Using color information to verify the acceleration
  of the Universe

abstract:
  We present measurements of \Omega_m and \Omega_{\Lambda} from a blind
analysis of 21 high-redshift supernovae using a new technique (CMAGIC) for
fitting the multi-color lightcurves of Type Ia supernovae, first introduced in
Wang et al. (2003). CMAGIC takes advantage of the remarkably simple behavior of
Type Ia supernovae on color-magnitude diagrams, and has several advantages over
current techniques based on maximum magnitudes. Among these are a reduced
sensitivity to host galaxy dust extinction, a shallower luminosity-width
relation, and the relative simplicity of the fitting procedure. This allows us
to provide a cross check of previous supernova cosmology results, despite the
fact that current data sets were not observed in a manner optimized for CMAGIC.
We describe the details of our novel blindness procedure, which is designed to
prevent experimenter bias. The data are broadly consistent with the picture of
an accelerating Universe, and agree with a flat Universe within 1.7\sigma,
including systematics. We also compare the CMAGIC results directly with those
of a maximum magnitude fit to the same SNe, finding that CMAGIC favors more
acceleration at the 1.6\sigma level, including systematics and the correlation
between the two measurements. A fit for w assuming a flat Universe yields a
value which is consistent with a cosmological constant within 1.2\sigma.


title:
The Radius-Luminosity Relationship for Active Galactic Nuclei: The
  Effect of Host-Galaxy Starlight on Luminosity Measurements

abstract:
  We have obtained high resolution images of the central regions of 14
reverberation-mapped active galactic nuclei (AGN) using the Hubble Space
Telescope Advanced Camera for Surveys High Resolution Camera to account for
host-galaxy starlight contamination of measured AGN luminosities. We measure
the host-galaxy starlight contribution to the continuum luminosity at 5100 A
through the typical ground-based slit position and geometry used in the
reverberation-mapping campaigns. We find that removing the starlight
contribution results in a significant correction to the luminosity of each AGN,
both for lower luminosity sources, as expected, but also for the higher
luminosity sources such as the PG quasars. After accounting for the host galaxy
starlight, we revisit the well-known broad-line region radius--luminosity
relationship for nearby AGN. We find the power-law slope of the relationship
for the H beta line to be 0.518 +/- 0.039, shallower than previously reported
and consistent with the slope of 0.5 expected from the naive theoretical
assumption that all AGN have, on average, the same ionizing spectrum and the
same ionization parameter and gas density in the H beta line-emitting region.


title:
Final Results from the BIMA CMB Anisotropy Survey and Search for
  Signature of the SZ effect

abstract:
  We report the final results of our study of the cosmic microwave background
(CMB) with the BIMA array. Over 1000 hours of observation were dedicated to
this project exploring CMB anisotropy on scales between 1' and 2' in eighteen
6.6' FWHM fields. In the analysis of the CMB power spectrum, the visibility
data is divided into two bins corresponding to different angular scales.
Modeling the observed excess power as a flat band of average multipole ell=
5237, we find Delta T_1^2=220_{-120}^{+140} muK^2 at 68% confidence and Delta
T_1^2 >0 muK^2 with 94.7% confidence. In a second band with average multipole
of ell = 8748, we find Delta T_2^2 consistent with zero, and an upper limit 880
muK^2 at 95% confidence. An extensive series of tests and supplemental
observations with the VLA provide strong evidence against systematic errors or
radio point sources being the source of the observed excess power. The dominant
source of anisotropy on these scales is expected to arise from the
Sunyaev-Zel'dovich (SZ) effect in a population of distant galaxy clusters. If
the excess power is due to the SZ effect, we can place constraints on the
normalization of the matter power spectrum sigma_8 = 1.03^{+0.20}_{-0.29} at
68% confidence. The distribution of pixel fluxes in the BIMA images are found
to be consistent with simulated observations of the expected SZ background and
rule out instrumental noise or radio sources as the source of the observed
excess power with similar confidence to the detection of excess power.
Follow-up optical observations to search for galaxy over-densities
anti-correlated with flux in the BIMA images, as might be expected from the SZ
effect, proved to be inconclusive.


title: Universe Evolution in a 5D Ricci-flat Cosmology

abstract:
  We use Wetterich's parameterization equation of state (EOS) of dark energy to
a $5D$ Ricci-flat cosmological solution and we suppose the universe contains
three major components: matter, radiation and dark energy. By using the
relation between the scale factor and the redshift $z$, we show that the two
arbitrary functions contained in the $5D$ solution could be solved out
analytically in terms of the variable $z$. Thus the whole $5D$ solution could
be constructed uniquely if the current values of the three density parameters
$\Omega_{m0}$, ${\Omega_{r0}}$, $\Omega_{x0}$, the EOS $w_{0}$%, and the
bending parameter $b$ contained in the EOS are all known. Furthermore, we find
that all the evolutions of the mass density $\Omega_{m} $, the radiation
density ${\Omega_{r}}$, the dark energy density $\Omega_{x}$, and the
deceleration parameter $q$ depend on the bending parameter $b$ sensitively.
Therefore it is deserved to study observational constraints on the bending
parameter $b$.


title: Dark Energy from Brane-world Gravity

abstract:
  Recent observations provide strong evidence that the universe is
accelerating. This confronts theory with a severe challenge. Explanations of
the acceleration within the framework of general relativity are plagued by
difficulties. General relativistic models require a "dark energy" field with
effectively negative pressure. An alternative to dark energy is that gravity
itself may behave differently from general relativity on the largest scales, in
such a way as to produce acceleration. The alternative approach of modified
gravity also faces severe difficulties, but does provide a new angle on the
problem. This review considers an example of modified gravity, provided by
brane-world models that self-accelerate at late times.


title:
Metallicity Gradient And The Hybrid Formation Scenario For Early-Type
  Galaxies

abstract:
  We present radial gradients of the Lick index Mg2 for 40 early-type galaxies.
In plots of Grad(Mg2) versus mass indicators, such as log(sigma), the lower
boundary of the points distribution may be populated by galaxies which
predominantly formed by monolithic collapse. Galaxies showing flatter gradients
at higher masses could represent objects which suffered important merging
episodes. Thus, our results support a hybrid formation scenario. To remove
possible age effects, we computed metallicity gradients (Grad[Z/H]) using Mg2
and Hbeta indices for an [alpha/Fe]=0.3 single stellar population model. The
conclusions remain the same.


title: Corona of Magnetars

abstract:
  We develop a theoretical model that explains the formation of hot coronae
around strongly magnetized neutron stars -- magnetars. The starquakes of a
magnetar shear its external magnetic field, which becomes non-potential and is
threaded by an electric current. Once twisted, the magnetosphere cannot untwist
immediately because of its self-induction. The self-induction electric field
lifts particles from the stellar surface, accelerates them, and initiates
avalanches of pair creation in the magnetosphere. The created plasma corona
maintains the electric current demanded by curl(B) and regulates the
self-induction e.m.f. by screening. This corona persists in dynamic
equilibrium: it is continually lost to the stellar surface on the
light-crossing time of 10^{-4} s and replenished with new particles. In
essence, the twisted magnetosphere acts as an accelerator that converts the
toroidal field energy to particle kinetic energy. Using a direct numerical
experiment, we show that the corona self-organizes quickly (on a millisecond
timescale) into a quasi-steady state, with voltage ~1 GeV along the magnetic
lines. The heating rate of the corona is ~10^{36} erg/s, in agreement with the
observed persistent, high-energy output of magnetars. We deduce that a static
twist that is suddenly implanted into the magnetosphere will decay on a
timescale of 1-10 yrs. The particles accelerated in the corona impact the solid
crust, knock out protons, and regulate the column density of the hydrostatic
atmosphere of the star. The transition layer between the atmosphere and the
corona is the likely source of the observed 100-keV emission from magnetars.
The corona emits curvature radiation and can supply the observed IR-optical
luminosity. (Abridged)


title: Expansion Parallax for the Compact Planetary Nebula M2-43

abstract:
  We present high quality radio continuum observations made with the Very Large
Array (VLA) at 3.6 cm at two epochs toward the planetary nebula M2-43. The
comparison of the two epochs, obtained with a time separation of 4.07 years,
clearly shows the expansion of the planetary nebula with an angular rate of
0.61 +/- 0.09 mas/year.Assuming that the expansion velocity in the plane of the
sky (determined from these measurements) and the expansion velocity in the line
of sight (determined from optical spectroscopy available in the literature) are
equal, we find a distance to the planetary nebula of 6.9 +/- 1.5 kpc. This is
the largest distance for a planetary nebula measured up to now with this
technique.


title: Stellar Explosions by Magnetic Towers

abstract:
  We propose a magnetic mechanism for the collimated explosion of a massive
star relevant for GRBs, XRFs and asymmetric supernovae. We apply Lynden-Bell's
magnetic tower scenario to the interior of a massive rotating star after the
core has collapsed to form a black hole with an accretion disk or a millisecond
magnetar acting as a central engine. We solve the force-free Grad-Shafranov
equation to calculate the magnetic structure and growth of a tower embedded in
a stellar environment. The pressure of the toroidal magnetic field,
continuously generated by differential rotation of the central engine, drives a
rapid expansion which becomes vertically collimated after lateral force balance
with the surrounding gas pressure is reached. The collimation naturally occurs
because hoop stress concentrates magnetic field toward the rotation axis and
inhibits lateral expansion. This leads to the growth of a self-collimated
magnetic tower. When embedded in a massive star, the supersonic expansion of
the tower drives a strong bow shock behind which an over-pressured cocoon
forms. The cocoon confines the tower by supplying collimating pressure and
provides stabilization against disruption due to MHD instabilities. Because the
tower consists of closed field lines starting and ending on the central engine,
mixing of baryons from the cocoon into the tower is suppressed. The channel
cleared by the growing tower is thus plausibly free of baryons and allows the
escape of magnetic energy from the central engine through the star. While
propagating down the stellar density gradient, the tower accelerates and
becomes relativistic. During the expansion, fast collisionless reconnection
becomes possible resulting in dissipation of magnetic energy which may be
responsible for GRB prompt emission.


title: The problem of what exists

abstract:
  Popular multiverse models such as the one based on the string theory
landscape require an underlying set of unexplained laws containing many
specific features and highly restrictive prerequisites. I explore the
consequences of relaxing some of these prerequisites with a view to discovering
whether any of them might be justified anthropically. Examples considered
include integer space dimensionality, the immutable, Platonic nature of the
laws of physics and the no-go theorem for strong emergence. The problem of why
some physical laws exist, but others which are seemingly possible do not, takes
on a new complexion following this analysis, although it remains an unsolved
problem in the absence of an additional criterion.


title: A Keck/DEIMOS Spectroscopy of Lyman Alpha Blobs at Redshift z=3.1

abstract:
  We present the results of an intermediate resolution (~2 angstrom)
spectroscopy of a sample of 37 candidate Lyman alpha blobs and emitters at
redshift z=3.1 using the DEIMOS spectrograph on the 10 m Keck telescope. The
emission lines are detected for all the 37 objects and have variety in their
line profiles. The Lyman alpha velocity widths (FWHM) of the 28 objects with
higher quality spectra, measured by fitting a single Gaussian profile, are in
the range of 150 - 1700 km/s and correlate with the Lyman alpha spatial
extents. All the 12 Lyman alpha blobs (>16 arcsec^2) have large velocity widths
of > 500 km/s. While there are several possible physical interpretations of the
Lyman alpha velocity widths (motion of gravitationally-bound gas clouds,
inflows, merging of clumps, or outflows from superwinds), the large velocity
widths of the Lyman alpha blobs suggest that they are the sites of massive
galaxy formation. If we assume gravitationally-bound gas clouds, the dynamical
masses of the Lyman alpha blobs are estimated to be ~10^12 - 10^13 Msun. Even
for the case of outflows, the outflow velocities are likely to be the same
order of the rotation velocities as inferred from the observational evidence
for local starburst galaxies.


title: The G-dwarf problem in the Galactic spheroid

abstract:
  Using two alternative [O/H]-[Fe/H] dependences, the empirical oxygen
abundance distribution (EGD) is deduced from two different samples of old
objects, available in the literature. Under the assumption that each
distribution (with the addition of a third one previously known) is typical for
the corresponding subsystem, the EGD of the Galactic spheroid is determined
weighting by mass. A fit to the data is provided by simple models of chemical
evolution implying both homogeneous and inhomogeneous mixing, where star
formation is inhibited during halo formation and enhanced during bulge
formation, with respect to the disk. The theoretical oxygen abundance
distribution (TGD) is first determined for the halo and the bulge separately,
and then for the Galactic spheroid weighting by mass. Simple models implying
inhomogeneous mixing are able to fit an empirical age-metallicity relation
(EAMR) recently determined from a homogeneous sample of globular clusters,
which shows a non monotonic trend characterized by large dispersion. Some
possible implications related to the formation of Galactic spheroid and disk
are also discussed.


title: Disentangling telluric lines in stellar spectra

abstract:
  The use of a method of spectra disentangling for telluric lines is explained
in detail, with a particular emphasis on high-precision radial-velocity
measurements for the search for extrasolar planets. New improvements to the
method are introduced.


title: Catalog Extraction in SZ Cluster Surveys: a matched filter approach

abstract:
  We present a method based on matched multifrequency filters for extracting
cluster catalogs from Sunyaev-Zel'dovich (SZ) surveys. We evaluate its
performance in terms of completeness, contamination rate and photometric
recovery for three representative types of SZ survey: a high resolution single
frequency radio survey (AMI), a high resolution ground-based multiband survey
(SPT), and the Planck all-sky survey. These surveys are not purely flux
limited, and they loose completeness significantly before their point-source
detection thresholds. Contamination remains relatively low at <5% (less than
30%) for a detection threshold set at S/N=5 (S/N=3). We identify photometric
recovery as an important source of catalog uncertainty: dispersion in recovered
flux from multiband surveys is larger than the intrinsic scatter in the Y-M
relation predicted from hydrodynamical simulations, while photometry in the
single frequency survey is seriously compromised by confusion with primary
cosmic microwave background anisotropy. The latter effect implies that
follow-up observations in other wavebands (e.g., 90 GHz, X-ray) of single
frequency surveys will be required. Cluster morphology can cause a bias in the
recovered Y-M relation, but has little effect on the scatter; the bias would be
removed during calibration of the relation. Point source confusion only
slightly decreases multiband survey completeness; single frequency survey
completeness could be significantly reduced by radio point source confusion,
but this remains highly uncertain because we do not know the radio counts at
the relevant flux levels.


title: Light element synthesis in baryon isocurvature models

abstract:
  The prejudice against baryon isocurvature models is primarily because of
their inconsistency with early universe light element nucleosynthesis results.
We propose that incipient low metallicity (Pop II) star forming regions can be
expected to have environments conducive to Deuterium production by spallation,
up to levels observed in the universe.


title: A CO, HCN and CI line survey of Ultra Luminous Infrared Galaxies

abstract:
  Preliminary results from a sensitive survey of the CO J=1--0, 2--1,
  3--2, 4--3, 6--5, HCN J=1--0, 3--2, 4--3, and CI J=1--0 lines of a sample of
30 Ultraluminous Infrared Galaxies (ULIRGs) are presented. These reveal a
tandalizing picture of the physical conditions of the molecular gas in these
extraordinary galaxies ($\rm L_{FIR}>10^{12} L_{\odot}$), with a diffuse phase
dominating the low-J CO lines and a much denser and warmer phase dominating the
CO 4-3 and 6-5 and all the HCN lines. The CI J=1--0 emission was found to be a
robust tracer of their total molecular gas mass under a large range of physical
conditions, a potent alternative to the much weaker emission from the $
^{13}$CO isotopologue, and especially promising as an H$_2$ tracer for similar
objects at high redshifts.


title: Weak gravitational lensing in brane-worlds

abstract:
  We derive the deflection angle of light rays caused by a brane black hole
with mass m and tidal charge q in the weak lensing approach, up to the second
order in perturbation theory. We point out when the newly derived second order
contributions become important.


title:
On the cross-correlation of sub-mm sources and optically-selected
  galaxies

abstract:
  Bright sub-mm galaxies are expected to arise in massive highly-biased haloes,
and hence exhibit strong clustering. We argue that a valuable tool for
measuring these clustering properties is the cross-correlation of sub-mm
galaxies with faint optically-selected sources. We analyze populations of
SCUBA-detected and optical galaxies in the GOODS-N survey area. Using
optical/IR photometric-redshift information, we search for correlations induced
by two separate effects: (1) cosmic magnification of background sub-mm sources
by foreground dark matter haloes traced by optical galaxies at lower redshifts;
and (2) galaxy clustering due to sub-mm and optical sources tracing the same
population of haloes where their redshift distributions overlap. Regarding
cosmic magnification, we find no detectable correlation. Our null result is
consistent with a theoretical model for the cosmic magnification, and we show
that a dramatic increase in the number of sub-mm sources will be required to
measure the effect reliably. Regarding clustering, we find evidence at the
3.5-sigma level for a cross-correlation between sub-mm and optical galaxies
analyzed in identical photometric redshift slices. The data hint that the
sub-mm sources have an enhanced bias parameter compared to the
optically-selected population (with a significance of 2-sigma). The next
generation of deep sub-mm surveys can potentially perform an accurate
measurement of each of these cross-correlations, adding a new set of
diagnostics for understanding the development of massive structure in the
Universe.


title:
Dynamical stability of collisionless stellar systems and barotropic
  stars: the nonlinear Antonov first law

abstract:
  We complete previous investigations on the dynamical stability of barotropic
stars and collisionless stellar systems. A barotropic star that minimizes the
energy functional at fixed mass is a nonlinearly dynamically stable stationary
solution of the Euler-Poisson system. Formally, this minimization problem is
similar to a condition of ``canonical stability'' in thermodynamics. A stellar
system that maximizes an H-function at fixed mass and energy is a nonlinearly
dynamically stable stationary solution of the Vlasov-Poisson system. Formally,
this maximization problem is similar to a condition of ``microcanonical
stability'' in thermodynamics. Using a thermodynamical analogy, we provide a
derivation and an interpretation of the nonlinear Antonov first law in terms of
``ensembles inequivalence'': a spherical stellar system with f=f(epsilon) and
f'(epsilon)<0 is nonlinearly dynamically stable with respect to the
Vlasov-Poisson system if the corresponding barotropic star with the same
equilibrium density distribution is nonlinearly dynamically stable with respect
to the Euler-Poisson system. This is similar to the fact that ``canonical
stability implies microcanonical stability'' in thermodynamics. The converse is
wrong in case of ``ensembles inequivalence'' which is generic for systems with
long-range interactions like gravity. We show that criteria of nonlinear
dynamical stability can be obtained very simply from purely graphical
constructions by using the method of series of equilibria and the turning point
argument of Poincare, as in thermodynamics.


title: Can sterile neutrinos be the dark matter?

abstract:
  We use the Ly-alpha forest power spectrum measured by the SDSS and
high-resolution spectroscopy observations in combination with cosmic microwave
background and galaxy clustering constraints to place limits on a sterile
neutrino as a dark matter candidate in the warm dark matter (WDM) scenario.
Such a neutrino would be created in the early universe through mixing with an
active neutrino and would suppress structure on scales smaller than its free
streaming scale. We ran a series of high-resolution hydrodynamic simulations
with varying neutrino mass to describe the effect of a sterile neutrino on the
Ly-alpha forest power spectrum. We find that the mass limit is m_s >14 keV at
95% c.l. (10keV at 99.9%), which is nearly an order of magnitude tighter
constraint than previously published limits and is above the upper limit
allowed by X-ray constraints, excluding this candidate as dark matter in this
model. The corresponding limit for a neutrino that decoupled early while in
thermal equilibrium is 2.5keV (95% c.l.).


title:
On the Large-Scale Structure of the Universe as given by the Voronoi
  Diagrams

abstract:
  The size distributions of 2D and 3D Voronoi cells and of cells of
$V_p(2,3)$,--2D cut of 3D Voronoi diagram--are explored, with the
single-parameter (re-scaled) gamma distribution playing a central role in the
analytical fitting. Observational evidence for a cellular universe is briefly
reviewed. A simulated $V_p(2,3)$ map with galaxies lying on the cell boundaries
is constructed to compare, as regards general appearance, with the observed CFA
map of galaxies and voids, the parameters of the simulation being so chosen as
to reproduce the largest observed void size.


title:
Large amplitude oscillation of a polar crown filament in the
  pre-eruption phase

abstract:
  We report observation of a large-amplitude filament oscillation followed by
an eruption. This is used to probe the pre-eruption condition and the trigger
mechanism of solar eruptions. We used the EUV images from the
Extreme-Ultraviolet Imaging Telescope on board SOHO satellite and the H-alpha
images from the Flare Monitoring Telescope at Hida Observatory. The observed
event is a polar crown filament that erupted on 15 Oct. 2002. The filament
clearly exhibited oscillatory motion in the slow-rising, pre-eruption phase.
The amplitude of the oscillation was larger than 20 km/s, and the motion was
predominantly horizontal. The period was about 2 hours and seemed to increase
during the oscillation, indicating weakening of restoring force. These results
strongly indicate that, even in the slow-rise phase before the eruption, the
filament retained equilibrium and behaved as an oscillator, and the equilibrium
is stable to nonlinear perturbation. Moreover, the transition from such
nonlinear stability to either instabilities or a loss of equilibrium that leads
to the eruption occurred in the Alfven time scale. This suggests that the onset
of the eruption was triggered by a fast magnetic reconnection that stabilized
the pre-eruption magnetic configuration, rather than by the slow shearing
motion at the photosphere.


title: Issues in Gravitational Clustering and Cosmology

abstract:
  Observations reveal that on large scales the universe is spanned by a
percolating network of superclusters interspersed with large and almost empty
regions -- voids. This thesis reports the construction of a sophisticated
computational algorithm called SURFGEN which is used to determine the
morphological and topological properties of the cosmic web. SURFGEN generates a
triangulated surface from a discrete data set representing (say) the
distribution of galaxies in real (or redshift) space. SURFGEN then determines,
for this surface, the Minkowski functionals which provide us with an excellent
diagnostic of three dimensional shapes of clusters, superclusters and voids.
SURFGEN is applied to N-body simulations, mock galaxy catalogues as well as to
galaxies in the Las Campanas Redshift Survey. In all cases the morphology of
individual superclusters and voids is determined and the connectedness of the
cosmic web is assessed by means of the Genus curve and percolation analysis. We
demonstrate that SURFGEN can successfully discriminate between rival models of
structure formation and is a very useful tool with which to quantify the
geometrical and topological properties of large scale structure.


title: Systematics in the X-ray Cluster Mass Estimators

abstract:
  We examine the systematics affecting the X-ray mass estimators applied to a
set of five simulated galaxy clusters. They have been processed through the
X-ray Map Simulator, X-MAS, to provide Chandra-like long exposures that are
analyzed to reconstruct the gas temperature, density, and mass profiles used as
input. We find that at R_2500 the mass profile obtained via a direct
application of the hydrostatic equilibrium equation is consistent within 1
sigma with the actual mass; although we notice this estimator shows high
statistical errors due to high level of Chandra background. Instead, the
poorness of the beta-model in describing the gas density profile makes the
evaluated masses to be underestimated by \sim 40 per cent with respect to the
true mass, both with an isothermal and a polytropic temperature profile. We
also test ways to recover the mass by adopting an analytic mass model, such as
those proposed by Navarro et al. (1997) and Rasia et al. (2004), and fitting
the temperature profile expected from the hydrostatic equilibrium equation to
the observed one. These methods and the one of the hydrostatic equilibrium
equation provide a more robust mass estimation than the ones based on the
beta-model. In the present work the main limitation for a precise mass
reconstruction is to ascribe to the relatively high level of the background
chosen to reproduce the Chandra one. After artificially reducing it by a factor
of 100, we find that the estimated mass significantly underestimates the true
mass profiles. This is manly due (i) to the neglected contribution of the gas
bulk motions to the total energy budget and (ii) to the bias towards lower
values of the X-ray temperature measurements because of the complex thermal
structure of the emitting plasma.


title:
Discovery of Very High Energy gamma - ray emission from the extreme BL
  Lac object H2356-309 with H.E.S.S

abstract:
  The understanding of acceleration mechanisms in active galactic nuclei (AGN)
jets and the measurement of the extragalactic-background-light (EBL) density
are closely linked and require the detection of a large sample of
very-high-energy (VHE) emitting extragalactic objects at varying redshifts. We
report here on the discovery with the H.E.S.S. (High Energy Stereoscopic
System) atmospheric-Cherenkov telescopes of the VHE Gamma-ray emission from
H2356 - 309, an extreme BL Lac object located at a redshift of 0.165. The
observations of this object, which was previously proposed as a
southern-hemisphere VHE candidate source, were performed between June and
December 2004. The total exposure is 38.9 hours live time, after data quality
selection, which yields the detection of a signal at the level of 9.0$\sigma$
(standard deviations) .


title:
Multi-resolution analysis of the H.E.S.S. Galactic Survey Sources and
  Search for Counterparts in CO and HI data

abstract:
  From May to July 2004, the central radian of the Galactic Plane was scanned
by the H.E.S.S. (High Energy Stereoscopic System) telescopes at energies above
200 GeV. This survey was performed from -$3^o$ to +$3^o$ in latitude, for a
total of 230 hours, revealing eight new VHE sources at a significance level
greater than 6$\sigma$(standard deviations). We present a multi-resolution
analysis of these sources based on a continuous wavelet transformation (CWT).
Using CO and HI data, we investigate the possible associations of the potential
counterparts proposed in [1], with sites of enhanced interstellar matter
density.


title: A powerful hydrodynamic booster for relativistic jets

abstract:
  Velocities close to the speed of light are a robust observational property of
the jets observed in microquasars and AGNs, and are expected to be behind much
of the phenomenology of GRBs. Yet, the mechanism boosting relativistic jets to
such large Lorentz factors is still essentially unknown. Building on recent
general-relativistic, multidimensional simulations of progenitors of short
GRBs, we discuss a new effect in relativistic hydrodynamics which can act as an
efficient booster in jets. This effect is purely hydrodynamical and occurs when
large velocities tangential to a discontinuity are present in the flow,
yielding Lorentz factors $\Gamma \sim 10^2-10^3$ or larger in flows with
moderate initial Lorentz factors. Although without a Newtonian counterpart,
this effect can be explained easily through the most elementary hydrodynamical
flow: i.e., a relativistic Riemann problem.


title: Solar and stellar system tests of the cosmological constant

abstract:
  Some tests of gravity theories - periastron shift, geodetic precession,
change in mean motion and gravitational redshift - are applied in solar and
stellar systems to constrain the cosmological constant. We thus consider a
length scale range from 10^8 to 10^{15} km. Best bounds from the solar system
come from perihelion advance and change in mean motion of Earth and Mars,
Lambda < 10^{-36} km^{-2}. Such a limit falls very short to estimates from
observational cosmology analyses but a future experiment performing radio
ranging observations of outer planets could improve it by four orders of
magnitude. Beyond the solar system, together with future measurements of
periastron advance in wide binary pulsars, gravitational redshift of white
dwarfs can provide bounds competitive with Mars data.


title: Time-Dependent Synchrotron and Compton Spectra from Jets of Microquasars

abstract:
  Jet models for the high-energy emission of Galactic X-ray binary sources have
regained significant interest with detailed spectral and timing studies of the
X-ray emission from microquasars, the recent detection by the HESS
collaboration of very-high-energy gamma-rays from the microquasar LS~5039, and
the earlier suggestion of jet models for ultraluminous X-ray sources observed
in many nearby galaxies. Here we study the synchrotron and Compton signatures
of time-dependent electron injection and acceleration, adiabatic and radiative
cooling, and different jet geometries in the jets of Galactic microquasars.
Synchrotron, synchrotron-self-Compton, and external-Compton radiation processes
with soft photons provided by the companion star and the accretion disk are
treated. An analytical solution is presented to the electron kinetic equation
for general power-law geometries of the jets for Compton scattering in the
Thomson regime. We pay particular attention to predictions concerning the rapid
flux and spectral variability signatures expected in a variety of scenarios,
making specific predictions concerning possible spectral hysteresis, similar to
what has been observed in several TeV blazars. Such predictions should be
testable with dedicated monitoring observations of Galactic microquasars and
ultraluminous X-ray sources using Chandra and/or XMM-Newton.


title: Annihilating dark matter and the galactic positron excess

abstract:
  The possibility that the Galactic dark matter is composed of neutralinos that
are just above half the $Z^o$ mass is examined, in the context of the Galactic
positron excess. In particular, we check if the anomalous bump in the cosmic
ray positron to electron ratio at $10~GeV$ can be explained with the ``decay''
of virtual $Z^o$ bosons produced when the neutralinos annihilate. We find that
the low energy behaviour of our prediction fits well the existing data.
Assuming the neutralinos annihilate primarily in the distant density
concentration in the Galaxy and allowing combination of older, diffused
positrons with young free-streaming ones, produces a fit which is not
satisfactory on its own but is significantly better than the one obtained with
homogeneous injection.


title: Spherical collapse with dark energy

abstract:
  I discuss the work of Maor and Lahav [1], in which the inclusion of dark
energy into the spherical collapse formalism is reviewed. Adopting a
phenomenological approach, I consider the consequences of - a) allowing the
dark energy to cluster, and, b) including the dark energy in the virialization
process. Both of these issues affect the final state of the system in a
fundamental way. The results suggest a potentially differentiating signature
between a true cosmological constant and a dynamic form of dark energy. This
signature is unique in the sense that it does not depend on a measurement of
the value of the equation of state of dark energy.


title:
Chandra Observations of the Highest Redshift Quasars from the Sloan
  Digital Sky Survey

abstract:
  We present new Chandra observations of 21 z>4 quasars, including 11 sources
at z>5. These observations double the number of X-ray detected quasars at z>5,
allowing investigation of the X-ray spectral properties of a substantial sample
of quasars at the dawn of the modern Universe. By jointly fitting the spectra
of 15 z>5 radio-quiet quasars (RQQs), including sources from the Chandra
archive, with a total of 185 photons, we find a mean X-ray power-law photon
index of Gamma=1.95^{+0.30}_{-0.26}, and a mean neutral intrinsic absorption
column density of N_H<~6x10^{22} cm^{-2}. These results show that quasar X-ray
spectral properties have not evolved up to the highest observable redshifts. We
also find that the mean optical-X-ray spectral slope (alpha_ox) of
optically-selected z>5 RQQs, excluding broad absorption line quasars, is
alpha_ox=-1.69+/-0.03, which is consistent with the value predicted from the
observed relationship between alpha_ox and ultraviolet luminosity. Four of the
sources in our sample are members of the rare class of weak emission-line
quasars, and we detect two of them in X-rays. We discuss the implications our
X-ray observations have for the nature of these mysterious sources and, in
particular, whether their weak-line spectra are a consequence of continuum
boosting or a deficit of high-ionization line emitting gas.


title: Strong Infrared Emission from the Extrasolar Planet HD189733b

abstract:
  We report detection of strong infrared thermal emission from the nearby (d=19
pc) transiting extrasolar planet HD189733b, by measuring the flux decrement
during its prominent secondary eclipse. A 6-hour photometric sequence using
Spitzer's infrared spectrograph in peak-up imaging mode at 16-microns shows the
secondary eclipse depth to be 0.551 +/-0.030%, with accuracy limited by
instrumental baseline uncertainties, but with 32-sigma precision (0.017%) on
the detection. The 16-micron brightness temperature of this planet (1117+/-42K)
is very similar to the Spitzer detections of TrES-1 and HD209458b, but the
observed planetary flux (660 micro-Jy) is an order of magnitude greater. This
large signal will allow a detailed characterization of this planet in the
infrared. Our photometry has sufficient signal-to-noise (~400 per point) to
motivate a search for structure in the ingress/egress portions of the eclipse
curve, caused by putative thermal structure on the disk of the planet. We show
that by binning our 6-second sampling down to 6-minute resolution, we detect
the modulation in the intensity derivative during ingress/egress due to the
overall shape of the planet, but our sensitivity is not yet sufficient to
distinguish between realistic models of the temperature distribution across the
planet's disk. We point out the potential for extending Spitzer secondary
eclipse detections down to the regime of transiting hot Neptunes, if such
systems are discovered among nearby lower main sequence stars.


title:
Probing Cosmic Chemical Evolution with Gamma-Ray Bursts: GRB060206 at
  z=4.048

abstract:
  Aim: We present early optical spectroscopy of the afterglow of the gamma-ray
burst GRB 060206 with the aim of determining the metallicity of the GRB
absorber and the physical conditions in the circumburst medium. We also discuss
how GRBs may be important complementary probes of cosmic chemical evolution.
Method: Absorption line study of the GRB afterglow spectrum. Results: We
determine the redshift of the GRB to be z=4.04795+/-0.00020. Based on the
measurement of the neutral hydrogen column density from the damped Lyman-alpha
line and the metal content from weak, unsaturated Sii lines we derive a
metallicity of [S/H] =-0.84+/-0.10. This is one of the highest metallicities
measured from absorption lines at z~4. From the very high column densities for
the forbidden Siii*, Oi*, and Oi** lines we infer very high densities and low
temperatures in the system. There is evidence for the presence of H$_2$
molecules with logN(H_2) ~ 17.0, translating into a molecular fraction of logf
\~ -3.5 with f=2N(H_2)/(2N(H_2)+ N(Hi)). Even if GRBs are only formed by single
massive stars with metallicities below ~0.3Z(solar), they could still be fairly
unbiased tracers of the bulk of the star formation at z>2. Hence, metallicities
as derived for GRB060206 here for a complete sample of GRB afterglows will
directly show the distribution of metallicities for representative star-forming
galaxies at these redshifts.


title: Event Rate for Extreme Mass Ratio Burst Signals in the LISA Band

abstract:
  Stellar mass compact objects in short period orbits about a
$10^{4.5}$--$10^{7.5}$ solar mass massive black hole (MBH) are thought to be a
significant continuous-wave source of gravitational radiation for the ESA/NASA
Laser Interferometer Space Antenna (LISA) gravitational wave detector. However,
these extreme mass-ratio inspiral sources began in long-period, nearly
parabolic orbits that have multiple close encounters with the MBH. The
gravitational radiation emitted during these close encounters may be detectable
by LISA as a gravitational wave burst if the characteristic passage timescale
is less than $10^5$ seconds. Scaling a static, spherical model to the size and
mass of the Milky Way bulge we estimate an event rate of ~ 15 per year for such
burst signals, detectable by LISA with signal-to-noise greater than five,
originating in our galaxy. When extended to include Virgo cluster galaxies our
estimate increases to a gravitational wave burst rate of ~ 18. We conclude that
these extreme mass-ratio burst sources may be a steady and significant source
of gravitational radiation in the LISA data streams.


title: The Low-mass Populations in OB Associations

abstract:
  Low-mass stars 0.1 ~< M ~< 1 Msun) in OB associations are key to addressing
some of the most fundamental problems in star formation. The low-mass stellar
populations of OB associations provide a snapshot of the fossil star-formation
record of giant molecular cloud complexes. Large scale surveys have identified
hundreds of members of nearby OB associations, and revealed that low-mass stars
exist wherever high-mass stars have recently formed. The spatial distribution
of low-mass members of OB associations demonstrate the existence of significant
substructure ("subgroups"). This "discretized" sequence of stellar groups is
consistent with an origin in short-lived parent molecular clouds within a Giant
Molecular Cloud Complex. The low-mass population in each subgroup within an OB
association exhibits little evidence for significant age spreads on time scales
of ~10 Myr or greater, in agreement with a scenario of rapid star formation and
cloud dissipation. The Initial Mass Function (IMF) of the stellar populations
in OB associations in the mass range 0.1 ~< M ~< 1 Msun is largely consistent
with the field IMF, and most low-mass pre-main sequence stars in the solar
vicinity are in OB associations. These findings agree with early suggestions
that the majority of stars in the Galaxy were born in OB associations. The most
recent work further suggests that a significant fraction of the stellar
population may have their origin in the more spread out regions of OB
associations, instead of all being born in dense clusters. (Abridged version).


title: Opacity in the upper atmospheres of active stars II. AD Leonis

abstract:
  We present FUV and UV spectroscopic observations of AD Leonis, with the aim
of investigating opacity effects in the transition regions of late-type stars.
The C III lines in FUSE spectra show significant opacity during both the
quiescent and flaring states of AD Leonis, with up to 30% of the expected flux
being lost during the latter. Other FUSE emission lines tested for opacity
include those of O VI, while C IV, Si IV and N V transitions observed with STIS
are also investigated. These lines only reveal modest amounts of opacity with
losses during flaring of up to 20%. Optical depths have been calculated for
homogeneous and inhomogeneous geometries, giving path lengths of ~20-60 km and
\~10-30 km, respectively, under quiescent conditions. However path lengths
derived during flaring are ~2-3 times larger. These values are in excellent
agreement with both estimates of the small-scale structure observed in the
solar transition region, and path lengths derived previously for several other
active late-type stars.


title: Future Directions in Astronomy Visualisation

abstract:
  Despite the large budgets spent annually on astronomical research equipment
such as telescopes, instruments and supercomputers, the general trend is to
analyse and view the resulting datasets using small, two-dimensional displays.
We report here on alternative advanced image displays, with an emphasis on
displays that we have constructed, including stereoscopic projection, multiple
projector tiled displays and a digital dome. These displays can provide
astronomers with new ways of exploring the terabyte and petabyte datasets that
are now regularly being produced from all-sky surveys, high-resolution computer
simulations, and Virtual Observatory projects. We also present a summary of the
Advanced Image Displays for Astronomy (AIDA) survey which we conducted from
March-May 2005, in order to raise some issues pertitent to the current and
future level of use of advanced image displays.


title: Multiplicity and Optical Excess Across the Substellar Boundary in Taurus

abstract:
  We present the results of a high-resolution imaging survey of 22 brown dwarfs
and very low mass stars in the nearby (~145 pc) young (~1-2 Myr) low-density
star-forming region Taurus-Auriga. We obtained images with the Advanced Camera
for Surveys/High Resolution Channel on HST through the F555W (V), F775W (i'),
and F850LP (z') filters. This survey confirmed the binarity of MHO-Tau-8 and
discovered a new candidate binary system, V410-Xray3, resulting in a binary
fraction of 9+/-5% at separations >4 AU. Both binary systems are tight (<10 AU)
and they possess mass ratios of 0.75 and 0.46, respectively. The binary
frequency and separations are consistent with low-mass binary properties in the
field, but the mass ratio of V410-Xray3 is among the lowest known. We find that
the binary frequency is higher for very low mass stars and high-mass brown
dwarfs than for lower-mass brown dwarfs, implying either a decline in frequency
or a shift to smaller separations for the lowest mass binaries. Combining these
results with multiplicity statistics for higher-mass Taurus members suggests a
gradual decline in binary frequency and separation toward low masses. The
implication is that the distinct binary properties of very low-mass systems are
set during formation and that the formation process is similar to the process
which creates higher-mass stellar binaries, but occurs on a smaller scale. We
show that there are no planets or very low-mass brown dwarfs with mass >3 M_J
at projected separation >40 AU orbiting any of the Taurus members in our
sample. We identify several BDs with significant (>1 mag) V-band excesses. The
excesses appear to be correlated with signatures of accretion, and if
attributed to accretion luminosity, may imply mass accretion rates several
orders of magnitude above those inferred from line-profile analyses. (abridged)


title: Significant primordial star formation at redshifts z ~ 3-4

abstract:
  Four recent observational results have challenged our understanding of
high--redshift galaxies, as they require the presence of far more ultraviolet
photons than should be emitted by normal stellar populations. First, there is
significant ultraviolet emission from Lyman Break Galaxies (LBGs) at
wavelenghts shorter than 912\AA. Second, there is strong Lyman alpha emission
from extended ``blobs'' with little or no associated apparent ionizing
continuum. Third, there is a population of galaxies with unusually strong
Lyman-alpha emission lines. And fourth, there is a strong HeII (1640 \AA)
emission line in a composite of LBGs. The proposed explanations for the first
three observations are internally inconsistent, and the fourth puzzle has
remained hitherto unexplained. Here we show that all four problems are resolved
simultaneously if 10-30 percent of the stars in many galaxies at z ~ 3-4 are
mainly primordial - unenriched by elements heavier than helium ('metals'). Most
models of hierarchical galaxy formation assume efficient intra--galactic metal
mixing, and therefore do not predict metal-free star formation at redshifts
significantly below z ~5. Our results imply that micro-mixing of metals within
galaxies is inefficient on a ~ Gyr time-scale, a conclusion that can be
verified with higher resolution simulations, and future observations of the
HeII emission line.


title: ZZ Ceti Stars: Fractal Analogues of Excited Helium Ions?

abstract:
  Multi-periodic pulsation phenomena of ZZ Ceti variable stars are analyzed
within the context of a fractal cosmological paradigm that emphasizes discrete
self-similarity in nature. A quantitative test comparing relevant stellar and
atomic periods provides preliminary support for the analysis. This paper
completes a 3-part series that explores the possibility of discrete
cosmological self-similarity in variable stars; the first and second papers
discussed RR Lyrae and delta Scuti stars, respectively.


title: A study of multiscale density fluctuation measurements

abstract:
  Intriguing parallels between density fluctuation power versus wavenumber on
small (mm) and large (Mpc) scales are presented. The comparative study is
carried out between fusion plasma measurements and cosmological data. Based on
predictions from classical fluid turbulence theory, we argue that our
observations are consistent with 2D turbulence. The similar dependencies of
density fluctuations on these disparate scales might indicate that primordial
turbulence has been expanded to cosmological proportions.


title:
The Magnetospheric Eternally Collapsing Object (MECO) Model of Galactic
  Black Hole Candidates and Active Galactic Nuclei

abstract:
  The spectral, timing, and jet formation properties of neutron stars in low
mass x-ray binary systems are influenced by the presence of central magnetic
moments. Similar features shown by the galactic black hole candidates (GBHC)
strongly suggest that their compact cores might be intrinsically magnetic as
well. We show that the existence of intrinsically magnetic GBHC is consistent
with a new class of solutions of the Einstein field equations of General
Relativity. These solutions are based on a strict adherence to the Strong
Principle of Equivalence (SPOE) requirement that the world lines of physical
matter must remain timelike in all regions of spacetime. The new solutions
emerge when the structure and radiation transfer properties of the energy
momentum tensor on the right hand side of the Einstein field equations are
appropriately chosen to dynamically enforce this SPOE requirement of timelike
world line completeness. In this context, we find that the Einstein field
equations allow the existence of highly red shifted, Magnetospheric, Eternally
Collapsing Objects (MECO). MECO necessarily possess intrinsic magnetic moments
and they do not have trapped surfaces that lead to event horizons and curvature
singularities. Their most striking features are equipartition magnetic fields,
pair plasma atmospheres and extreme gravitational redshifts. Since MECO
lifetimes are orders of magnitude greater than a Hubble time, they provide an
elegant and unified framework for understanding a broad range of observations
of GBHC and active galactic nuclei. We examine their spectral, timing and jet
formation properties and discuss characteristics that might lead to their
confirmation.


title: Re-Identification of the `Enigmatic' X-ray Source 1RXS J114003.0+124112

abstract:
  The ROSAT X-ray source 1RXS J114003.0+124112 was identified as a starburst
galaxy at redshift 0.177 by He et al. (2001). Meanwhile, the authors also noted
that the source is almost two orders of magnitude brighter in X-ray than the
X-ray-brightest starburst galaxy and it seems to be in a merging system, making
this source an enigmatic system for further observations. This paper reports
the re-identification of 1RXS J114003.0+124112 with the observations on the 2.6
m telescope at Byurakan Astrophysical Observatory, Armenia and with the SDSS
data. The results indicate that the starburst activity is associated with the
brighter object in the system, while the fainter object is a typical Seyfert 1
galaxy at redshift 0.282. Therefore, the two objects are not in a merging
system, and the Seyfert 1 galaxy naturally accounts for the high X-ray flux.
Three more objects reside in the vicinity, but they are all too faint to be
responsible for the high X-ray flux.


title: Results of SPARO 2003: Mapping Magnetic Fields in Giant Molecular Clouds

abstract:
  We present results from the Austral Winter 2003 observing campaign of SPARO,
a 450 micron polarimeter used with a two-meter telescope at South Pole. We
mapped large-scale magnetic fields in four Giant Molecular Clouds (GMCs) in the
Galactic disk: NGC 6334, the Carina Nebula, G333.6-0.2 and G331.5-0.1. We find
a statistically significant correlation of the inferred field directions with
the orientation of the Galactic plane. Specifically, three of the four GMCs
(NGC 6334 is the exception) have mean field directions that are within 15
degrees of the plane. The simplest interpretation is that the field direction
tends to be preserved during the process of GMC formation. We have also carried
out an analysis of published optical polarimetry data. For the closest of the
SPARO GMCs, NGC 6334, we can compare the field direction in the cloud as
measured by SPARO with the field direction in a larger region surrounding the
cloud, as determined from optical polarimetry. For purposes of comparison, we
also use optical polarimetry to determine field directions for other regions of
similar size and distance. Overall, the results from this optical polarimetry
analysis are consistent with our suggestion that field direction tends to be
preserved during GMC formation. Finally, we compare the disorder in our
magnetic field maps with the disorder seen in magnetic field maps derived from
MHD turbulence simulations. We conclude from these comparisons that the
magnetic energy density in our clouds is comparable to the turbulent energy
density.


title:
The dissolving Rosette HH2 jet bathed in harsh UV radiation of the
  Rosette Nebula

abstract:
  Herbig-Haro flows discovered in photoionized medium forms a separate category
and detailed studies of which become one of the key issues to our understanding
of jet production and evolution. The Rosette HH2 jet is the second of such
flows that immersed in the spectacular HII region of the Rosette Nebula.
However, its disconnected jet components are detached from the proposed energy
source, have additional unusual properties and thus a disputable nature. In
this paper, we investigate through high-quality echelle spectrographs the
physical nature of the jet system. The jet shows distinctly different velocity
components. It is believed to be composed of a fast neutral jet with an
approaching velocity of -39.5 km $^{-1}$ as respect to the systemic rest frame,
and likely an extensive, photoevaporated envelope dissolving at roughly the
sound speed. This led us to infer a fast dissipating nature of the jet system
being bathed in the fully photoionized medium of Rosette.
  In addition, time series photometric observations provide evidence that the
energy source is highly variable, with amplitudes of up to ${>}$ 1 mag in R &
I. This is consistent well with an early evolutionary status of the jet driving
star with a red, late type spectrum in the optical.


title:
Magnetohydrodynamic Simulations of A Rotating Massive Star Collapsing to
  A Black Hole

abstract:
  We perform two-dimensional, axisymmetric, magnetohydrodynamic simulations of
the collapse of a rotating star of 40 Msun and in the light of the collapsar
model of gamma-ray burst. Considering two distributions of angular momentum, up
to \sim 10^{17} cm^2/s, and the uniform vertical magnetic field, we investigate
the formation of an accretion disk around a black hole and the jet production
near the hole. After material reaches to the black hole with the high angular
momentum, the disk is formed inside a surface of weak shock. The disk becomes
in a quasi-steady state for stars whose magnetic field is less than 10^{10} G
before the collapse. We find that the jet can be driven by the magnetic fields
even if the central core does not rotate as rapidly as previously assumed and
outer layers of the star has sufficiently high angular momentum. The magnetic
fields are chiefly amplified inside the disk due to the compression and the
wrapping of the field. The fields inside the disk propagate to the polar region
along the inner boundary near the black hole through the Alfv{\'e}n wave, and
eventually drive the jet. The quasi-steady disk is not an advection-dominated
disk but a neutrino cooling-dominated one. Mass accretion rates in the disks
are greater than 0.01 Msun/sec with large fluctuations. The disk is transparent
for neutrinos. The dense part of the disk, which locates near the hole, emits
neutrino efficiently at a constant rate of < 8 \times 10^{51} erg/s. The
neutrino luminosity is much smaller than those from supernovae after the
neutrino burst.


title: Planetary nebulae as tracers of galaxy stellar populations

abstract:
  We address the general problem of the luminosity-specific planetary nebula
(PN) number, defined as alpha = N(PN)/L(gal), and its relationship with age and
metallicity of the parent stellar population. Our analysis relies on population
synthesis models for simple stellar populations and more elaborated galaxy
models along the full star-formation range of the Hubble morphological
sequence. This theoretical framework is compared with the updated census of the
PN population in Local Group galaxies and external ellipticals in the Leo
group, and the Virgo and Fornax clusters.


title: A strong case for fast stellar rotation at very low metallicities

abstract:
  We investigate the effect of new stellar models, which take rotation into
account, computed for a metallicity Z = 10^{-8} on the chemical evolution of
the earliest phases of the Milky Way. These models are computed under the
assumption that the ratio of the initial rotation velocity to the critical
velocity of stars is roughly constant with metallicity. This naturally leads to
faster rotation at lower metallicity, as metal poor stars are more compact than
metal rich ones. We find that the new Z = 10^{-8} stellar yields have a
tremendous impact on the interstellar medium nitrogen enrichment for
log(O/H)+12 < 7 (or [Fe/H]< -3).We show that upon the inclusion of the Z =
10^{-8} stellar yields in chemical evolution models, both high N/O and C/O
ratios are obtained in the very-metal poor metallicity range in agreement with
observations. Our results give further support to the idea that stars at very
low metallicities could have rotational velocities of the order of 600-800 km
s^{-1}.


title: Heavy element nucleosynthesis in a collapsar

abstract:
  We investigate synthesis of heavy elements in a collapsar. We have calculated
detailed composition of magnetically driven jets ejected from a collapsar,
which is based on long-term, magneto-hydrodynamic simulations of a rapidly
rotating massive star of 40Msun during core collapse. We follow evolution of
abundances of about 4000 nuclides from the collapse phase to the ejection phase
through the jet generation phase with use of two large nuclear reaction
networks. We find that the r-process successfully operates in the jets, so that
U and Th are synthesized abundantly when the progenitor has large magnetic
field of 10^{12} G and rapidly rotating core. Abundance pattern inside the jets
is similar compared to that of r-elements in the solar system. Heavy
neutron-rich nuclei \sim 0.01Msun can be ejected from the collapsar. The
detailed abundances depend on nuclear properties of mass model, beta-decay
rate, and fission, for nuclei near the neutron drip line. Furthermore, we find
that p-nuclei are produced without seed nuclei: not only light p-nuclei, such
as Se74, Kr78, Sr84, and Mo92, but also heavy p-nuclei, In113, Sn115, and
La138, can be abundantly synthesized in the jets. The amounts of p-nuclei in
the ejecta are much greater than those in core-collapse supernovae (SNe). In
particular, Mo92, In113, Sn115, and La138 deficient in the SNe, are
significantly produced in the ejecta.


title: Long range correlation in cosmic microwave background radiation

abstract:
  We investigate the statistical anisotropy and Gaussianity of temperature
fluctuations of Cosmic Microwave Background radiation (CMB) data from {\it
Wilkinson Microwave Anisotropy Probe} survey, using the multifractal detrended
fluctuation analysis, rescaled range and scaled windowed variance methods. The
multifractal detrended fluctuation analysis shows that CMB fluctuations has a
long range correlation function with a multifractal behavior. By comparing the
shuffled and surrogate series of CMB data, we conclude that the multifractality
nature of temperature fluctuation of CMB is mainly due to the long-range
correlations and the map is consistent with a Gaussian distribution.


title:
Modified equation of state, scalar field, and bulk viscosity in
  Friedmann universe

abstract:
  A generalized dynamical equation for the scale factor of the universe is
proposed to describe the cosmological evolution, of which the $\Lambda$CDM
model is a special case. It also provides a general example to show the
equivalence of the modified equation of state (EOS) and a scalar field model.
In the mathematical aspect, the EOS, the scalar field potential $V(\phi)$, and
the scale factor $a(t)$ all have possessed analytical solutions. Such features
are due to a simple form invariance of the equation inherited which determines
the Hubble parameter. From the physical point of view, this dynamical equation
can be regarded as the $\Lambda$CDM model with bulk viscosity, an existence
content in the universe. We employ the SNe Ia data with the parameter
$\mathcal{A}$ measured from the SDSS data and the shift parameter $\mathcal{R}$
measured from WMAP data to constrain the parameters in our model. The result is
that the contribution of the bulk viscosity, accumulated as an effective dark
energy responsible for the current cosmic accelerating expansion, is made
approximately ten percent to that of the cosmological constant.


title:
Evolutionary Paths for Galaxies and AGNs: New Insights by the Spitzer
  Space Telescope

abstract:
  We compare the history of the galaxy mass build-up, as inferred from near-IR
observations, and the Star Formation Rate of massive stars in the comoving
volume traced by deep extensive far-IR surveys, both possible now with the
Spitzer Space Telescope. These two independent and complementary approaches to
the history of galaxy formation consistently indicate that a wide interval of
cosmic epochs between z~0.7 to z~2 brackets the main evolutionary phases. The
rate of the integrated galaxy mass growth indicated by the IR-based comoving
SFR appears consistent with the observed decrease of the stellar mass densities
with redshift. There are also indications that the evolution with z of the
total population depends on galaxy mass, being stronger for moderate-mass, but
almost absent up to z=1.4 for high-mass galaxies, thus confirming previous
evidence for a "downsizing" effect in galaxy formation. The most massive
galaxies appear already mostly in place by z~1. Although a precise matching of
this galaxy build-up with the growth of nuclear super-massive black-holes is
not possible with the present data (due to difficulties for an accurate census
of the obscured AGN phenomenon), some preliminary indications reveal a similar
mass/luminosity dependence for AGN evolution as for the hosting galaxies.


title:
The Structure of the Homunculus: I. Shape and Latitude Dependence from
  H2 and [Fe II] Velocity Maps of Eta Carinae

abstract:
  High resolution long-slit spectra obtained with the Phoenix spectrograph on
Gemini South provide our most accurate probe of the three dimensional structure
of the Homunculus around eta Car. The new near-infrared spectra dramatically
confirm the double-shell structure inferred previously from thermal dust
emission, resolving the nebula into a very thin outer shell seen in H2 21218,
and a warmer, thicker inner layer seen in [Fe II] 16435. The thin H2 skin hints
that the most important mass loss during the 19th century eruption had a very
short duration of less than 5 yr. H2 emission traces the majority of the mass
in the nebula, and has an average density of order 10^6.5 cm-3. This emission,
in turn, yields our first definitive picture of the exact shape of the nebula,
plus a distance of 2350pm50 pc and an inclination angle of 41deg (the polar
axis is tilted 49deg from the plane of the sky). The distribution of the H2
emission provides the first measure of the latitude dependence of the speed,
mass loss, and kinetic energy associated with eta Car's 19th century explosion.
Almost 75 percent of the total mass and more than 90 percent of the kinetic
energy in the ejecta were released at high latitudes. This rules out a model
for the bipolar shape wherein an otherwise spherical explosion was pinched at
the waist by a circumstellar torus. Also, the ejecta could not have been
deflected toward polar trajectories by a companion star, since the kinetic
energy of the polar ejecta is greater than the binding energy of the putative
binary system. Instead, most of the mass appears to have been directed poleward
by the explosion itself. [abridged]


title:
Evidence for the Strong Effect of Gas Removal on the Internal Dynamics
  of Young Stellar Clusters

abstract:
  We present detailed luminosity profiles of the young massive clusters M82-F,
NGC 1569-A, and NGC 1705-1 which show significant departures from equilibrium
(King and EFF) profiles. We compare these profiles with those from N-body
simulations of clusters which have undergone the rapid removal of a significant
fraction of their mass due to gas expulsion. We show that the observations and
simulations agree very well with each other suggesting that these young
clusters are undergoing violent relaxation and are also losing a significant
fraction of their stellar mass. That these clusters are not in equilibrium can
explain the discrepant mass-to-light ratios observed in many young clusters
with respect to simple stellar population models without resorting to
non-standard initial stellar mass functions as claimed for M82-F and NGC
1705-1. We also discuss the effect of rapid gas removal on the complete
disruption of a large fraction of young massive clusters (``infant
mortality''). Finally we note that even bound clusters may lose >50% of their
initial stellar mass due to rapid gas loss (``infant weight-loss'').


title: Tracing gas motions in the Centaurus Cluster

abstract:
  We apply the stochastic model of iron transport developed by Rebusco et. al.
(2005) to the Centaurus cluster. Using this model, we find that an effective
diffusion coefficient D in the range 2x10^28 - 4x10^28 cm^2 s^-1 can
approximately reproduce the observed abundance distribution. Reproducing the
flat central profile and sharp drop around 30-70 kpc, however, requires a
diffusion coefficient that drops rapidly with radius so that D > 4x10^28 cm^2
s^-1 only inside about 25 kpc. Assuming that all transport is due to
fully-developed turbulence, which is also responsible for offsetting cooling in
the cluster core, we calculate the length and velocity scales of energy
injection. These length scales are found to be up to a factor of ~ 10 larger
than expected if the turbulence is due to the inflation and rising of a bubble.
We also calculate the turbulent thermal conductivity and find it is unlikely to
be significant in preventing cooling.


title: Neutrino mixing as a source of dark energy

abstract:
  We show that the vacuum condensate due to neutrino mixing in quantum field
theory (QFT) contributes to the dark energy budget of the universe which gives
rise to the accelerated behavior of cosmic flow. The mechanism of neutrino
mixing is therefore a possible candidate to contribute to the cosmological dark
energy.


title: Atmospheres of Extrasolar Giant Planets

abstract:
  The key to understanding an extrasolar giant planet's spectrum--and hence its
detectability and evolution--lies with its atmosphere. Now that direct
observations of thermal emission from extrasolar giant planets are in hand,
atmosphere models can be used to constrain atmospheric composition, thermal
structure, and ultimately the formation and evolution of detected planets. We
review the important physical processes that influence the atmospheric
structure and evolution of extrasolar giant planets and consider what has
already been learned from the first generation of observations and modeling. We
pay particular attention to the roles of cloud structure, metallicity, and
atmospheric chemistry in affecting detectable properties through Spitzer Space
Telescope observations of the transiting giant planets. Our review stresses the
uncertainties that ultimately limit our ability to interpret EGP observations.
Finally we will conclude with a look to the future as characterization of
multiple individual planets in a single stellar system leads to the study of
comparative planetary architectures.


title: Understanding the Stellar Initial Mass Function

abstract:
  The essential features of the stellar Initial Mass Function are, rather
generally, (1) a peak at a mass of a few tenths of a solar mass, and (2) a
power-law tail toward higher masses that is similar to the original Salpeter
function. Recent work suggests that the IMF peak reflects a preferred scale of
fragmentation associated with the transition from a cooling phase of collapse
at low densities to a nearly isothermal phase at higher densities, where the
gas becomes thermally coupled to the dust. The Salpeter power law is plausibly
produced, at least in part, by scale-free accretion processes that build up
massive stars in dense environments. The young stars at the Galactic Center
appear to have unusually high masses, possibly because of a high minimum mass
resulting from the high opacity of the dense star-forming gas.


title:
LISA observations of massive black hole mergers: event rates and issues
  in waveform modelling

abstract:
  The observability of gravitational waves from supermassive and
intermediate-mass black holes by the forecoming Laser Interferometer Space
Antenna (LISA), and the physics we can learn from the observations, will depend
on two basic factors: the event rates for massive black hole mergers occurring
in the LISA best sensitivity window, and our theoretical knowledge of the
gravitational waveforms. We first provide a concise review of the literature on
LISA event rates for massive black hole mergers, as predicted by different
formation scenarios. Then we discuss what (in our view) are the most urgent
issues to address in terms of waveform modelling. For massive black hole binary
inspiral these include spin precession, eccentricity, the effect of high-order
Post-Newtonian terms in the amplitude and phase, and an accurate prediction of
the transition from inspiral to plunge. For black hole ringdown, numerical
relativity will ultimately be required to determine the relative quasinormal
mode excitation, and to reduce the dimensionality of the template space in
matched filtering.


title:
The H alpha Galaxy Survey. III. Constraints on supernova progenitors
  from spatial correlations with H alpha emission

abstract:
  Aims: We attempt to constrain progenitors of the different types of
supernovae from their spatial distributions relative to star formation regions
in their host galaxies, as traced by H alpha + NII line emission.
  Methods: We analyse 63 supernovae which have occurred within galaxies from
our H alpha survey of the local Universe. Three statistical tests are used,
based on pixel statistics, H alpha radial growth curves, and total galaxy
emission-line fluxes.
  Results: Many more type II supernovae come from regions of low or zero
emission line flux than would be expected if the latter accurately traces
high-mass star formation. We interpret this excess as a 40% `Runaway' fraction
in the progenitor stars. Supernovae of types Ib and Ic do appear to trace star
formation activity, with a much higher fraction coming from the centres of
bright star formation regions than is the case for the type II supernovae. Type
Ia supernovae overall show a weak correlation with locations of current star
formation, but there is evidence that a significant minority, up to about 40%,
may be linked to the young stellar population. The radial distribution of all
core-collapse supernovae (types Ib, Ic and II) closely follows that of the line
emission and hence star formation in the their host galaxies, apart from a
central deficiency which is less marked for supernovae of types Ib and Ic than
for those of type II. Core-collapse supernova rates overall are consistent with
being proportional to galaxy total luminosities and star formation rates;
however, within this total the type Ib and Ic supernovae show a moderate bias
towards more luminous host galaxies, and type II supernovae a slight bias
towards lower-luminosity hosts.


title:
Quasi Periodic Oscillations and Strongly Comptonized X-ray emission from
  Holmberg IX X-1

abstract:
  We report the discovery of a 200mHz quasi-periodic oscillation (QPO) in the
X-ray emission from a bright ultra-luminous X-ray source (ULX) Holmberg IX X-1
using a long XMM-Newton observation. The QPO has a centroid at
202.5_{-3.8}^{+4.9}mHz, a coherence Q ~9.3 and an amplitude (rms) of 6% in the
0.2-10keV band. This is only the second detection of a QPO from an ULX, after
M82 X-1, and provides strong evidence against beaming. The power spectrum is
well fitted by a power law with an index of ~0.7. The total integrated power
(rms) is ~9.4% in the 0.001-1Hz range. The X-ray spectrum shows clear evidence
for a soft X-ray excess component that is well described by a multicolor disk
blackbody (kT_in ~ 0.3keV) and a high energy curvature that can be modeled
either by a cut-off power law (Gamma ~ 1; E_cutoff ~9keV) or as a strongly
Comptonized continuum in an optically thick (tau ~7.3) and cool (kT_e ~3keV)
plasma. Both the presence of the QPO and the shape of the X-ray spectrum
strongly suggest that the ULX is not in the high/soft or thermally dominated
state. A truncated disk and inner optically thick corona may explain the
observed X-ray spectrum and the presence of the QPO.


title: The Mass-Metallicity Relation at z~2

abstract:
  We use a sample of 87 rest-frame UV-selected star-forming galaxies with mean
spectroscopic redshift z=2.26 to study the correlation between metallicity and
stellar mass at high redshift. Using stellar masses determined from SED fitting
to 0.3-8 micron photometry, we divide the sample into six bins in stellar mass,
and construct six composite H-alpha+[NII] spectra from all of the objects in
each bin. We estimate the mean oxygen abundance in each bin from the
[NII]/H-alpha ratio, and find a monotonic increase in metallicity with
increasing stellar mass, from 12+log(O/H) < 8.2 for galaxies with <M_star> =
2.7e9 Msun to 12+log(O/H) = 8.6 for galaxies with <M_star> = 1e11 Msun. We use
the empirical relation between star formation rate density and gas density to
estimate the gas fractions of the galaxies, finding an increase in gas fraction
with decreasing stellar mass. These gas fractions combined with the observed
metallicities allow the estimation of the effective yield y_eff as a function
of stellar mass; in constrast to observations in the local universe which show
a decrease in y_eff with decreasing baryonic mass, we find a slight increase.
Such a variation of metallicity with gas fraction is best fit by a model with
supersolar yield and an outflow rate ~4 times higher than the star formation
rate. We conclude that the mass-metallicity relation at high redshift is driven
by the increase in metallicity as the gas fraction decreases through star
formation, and is likely modulated by metal loss from strong outflows in
galaxies of all masses. There is no evidence for preferential loss of metals
from low mass galaxies as has been suggested in the local universe. [Abridged]


title:
HD molecule and search for early structure-formation signatures in the
  Universe

abstract:
  Possible detection of signatures of structure formation at the end of the
'dark age' epoch (z~40-20) is examined. We discuss the spectral-spatial
fluctuations in the CMBR temperature produced by elastic resonant scattering of
CMBR photons on HD molecules located in protostructures moving with peculiar
velocity. Detailed chemical kinematic evolution of HD molecules in the
expanding homogeneous medium is calculated. Then, the HD abundances are linked
to protostructures at their maximum expansion, whose properties are estimated
by using the top-hat spherical approach and the LambdaCDM cosmology. We find
that the optical depths in the HD three lowest pure rotational lines for
high-peak protohaloes at their maximum expansion are much higher than those in
LiH molecule. The corresponding spectral-spatial fluctuation amplitudes however
are probably too weak as to be detected by current and forthcoming
millimeter-telescope facilities. We extend our estimates of spectral-spatial
fluctuations to gas clouds inside collapsed CDM haloes by using results from a
crude model of HD production in these clouds. The fluctuations for the
highest-peak CDM haloes at redshifts ~20-30 could be detected in the future.
Observations will be important to test model predictions of early structure
formation in the universe.


title: Relativistic MHD Winds from Rotating Neutron Stars

abstract:
  We solve for the time-dependent dynamics of axisymmetric, general
relativistic magnetohydrodynamic winds from rotating neutron stars. The mass
loss rate is obtained self-consistently as a solution to the MHD equations,
subject to a finite thermal pressure at the stellar surface. We consider both
monopole and dipole magnetic field geometries and we explore the parameter
regime extending from low magnetization (low-sigma_o), almost thermally-driven
winds to high magnetization (high-sigma_o), relativistic Poynting-flux
dominated outflows. We compute the angular momentum and rotational energy loss
rates as a function of sigma_o and compare with analytic expectations from the
classical theory of pulsars and magnetized stellar winds. In the case of the
monopole, our high-sigma_o calculations asymptotically approach the analytic
force-free limit. If we define the spindown rate in terms of the open magnetic
flux, we similarly reproduce the spindown rate from recent force-free
calculations of the aligned dipole. However, even for sigma_o as high as ~20,
we find that the location of the Y-type point (r_Y), which specifies the radius
of the last closed field line in the equatorial plane, is not the radius of the
light cylinder R_L = c/omega (R = cylindrical radius), as has previously been
assumed in most estimates and force-free calculations. Instead, although the
Alfven radius at intermediate latitudes quickly approaches R_L as sigma_o
exceeds unity, r_Y remains significantly less than R_L. Because r_Y < R_L, our
calculated spindown rates thus exceed the classic ``vacuum dipole'' rate. We
discussthe implications of our results for models of rotation-powered pulsars
and magnetars, both in their observed states and in their hypothesized rapidly
rotating initial state.


title:
Mimicking Dark Energy with Lemaitre-Tolman-Bondi Models: Weak Central
  Singularities and Critical Points

abstract:
  There has been much debate over whether or not one could explain the observed
acceleration of the Universe with inhomogeneous cosmological models, such as
the spherically-symmetric Lemaitre-Tolman-Bondi (LTB) models. It has been
claimed that the central observer in these models can observe a local
acceleration, which would contradict general theorems. We resolve the
contradiction by noting that many of the models that have been explored contain
a weak singularity at the location of the observer which makes them unphysical.
In the absence of this singularity, we show that LTB models must have a
positive central deceleration parameter $q_{0}$, in agreement with the general
theorems. We also show that it is possible to achieve a negative apparent
deceleration parameter at nonzero redshifts in LTB models that do not contain
this singularity. However, we find other singularities that tend to arise in
LTB models when attempting to match luminosity distance data, and these
generally limit the range of redshifts for which these models can mimic
observations of an accelerating Universe. Exceptional models do exist that can
extend to arbitrarily large redshift without encountering these pathologies,
and we show how these may be constructed. These special models exhibit regions
with negative effective equation of state parameter, which may fall below
negative one, but we have failed to find any singularity-free models that agree
with observations. Moreover, models based on dust-filled LTB metrics probably
fail to reproduce observed properties of large scale structure.


title:
Dynamics and Disequilibrium Carbon Chemistry in Hot Jupiter Atmospheres,
  With Application to HD 209458b

abstract:
  Chemical equilibrium considerations suggest that, assuming solar elemental
abundances, carbon on HD 209458b is sequestered primarily as carbon monoxide
(CO) and methane (CH4). The relative mole fractions of CO(g) and CH4(g) in
chemical equilibrium are expected to vary greatly according to variations in
local temperature and pressure. We show, however, that in the p = 1--1000 mbar
range, chemical equilibrium does not hold. To explore disequilibrium effects,
we couple the chemical kinetics of CO and CH4 to a three-dimensional numerical
model of HD 209458b's atmospheric circulation. These simulations show that
vigorous dynamics caused by uneven heating of this tidally locked planet
homogenize the CO and CH4 concentrations at p < 1 bar, even in the presence of
lateral temperature variations of ~500--1000 K. In the 1--1000 mbar pressure
range, we find that over 98% of the carbon is in CO. This is true even in cool
regions where CH4 is much more stable thermodynamically. Our work shows
furthermore that planets 300--500 K cooler than HD 209458b can also have
abundant CO in their upper layers due to disequilibrium effects. We demonstrate
several interesting observational consequences of these results.


title:
Local Voids as the Origin of Large-angle Cosmic Microwave Background
  Anomalies I

abstract:
  We explore the large angular scale temperature anisotropies in the cosmic
microwave background due to expanding homogeneous local voids at redshift z~1.
A compensated spherically symmetric homogeneous dust-filled void with radius
\~3*10^2 h^{-1}Mpc, and density contrast ~-0.3 can be observed as a cold spot
with a temperature anisotropy -1*10^{-5} surrounded by a slightly hotter ring.
We find that a pair of these circular cold spots separated by ~50 degree can
account both for the planarity of the octopole and for the alignment between
the quadrupole and the octopole in the cosmic microwave background (CMB)
anisotropy. The cold spot in the Galactic southern hemisphere which is
anomalous at the ~3sigma level can be explained by such a large void at z~1.
The observed north-south asymmetry in the large-angle CMB power can be
attributed to the asymmetric distribution of these local voids between the two
hemispheres. The statistical significance of the low quadrupole is further
reduced in this interpretation of the large angular scale CMB anomalies.


title:
The Performance of CRTNT Fluorescence Light Detector for Sub-EeV Cosmic
  Ray Observation

abstract:
  Cosmic Ray Tau Neutrino Telescopes (CRTNT) using for sub-EeV cosmic ray
measurement is discussed. Performances of a stereoscope configuration with a
tower of those telescopes plus two side-triggers are studied. This is done by
using a detailed detector simulation driven by Corsika. Detector aperture as a
function of shower energy above 10^17 eV is calculated. Event rate of about 20k
per year for the second knee measurement is estimated. Event rate for cross
calibration with detectors working on higher energy range is also estimated.
Different configurations of the detectors are tried for optimization.


title:
The correlations between BL Lacs and ultra-high-energy cosmic rays
  deflected by using different GMF models

abstract:
  Some studies suggested that a correlation between locations of BL Lacertae
objects (BL Lacs) and the arrival directions of the ultrahigh energy cosmic
rays (UHECRs) exists. Especially by assuming the primary particles charged +1
and using a galactic magnetic field (GMF) model to calculate the deflections of
the UHECRs, the significance of correlation is improved. We construct a new GMF
model by incorporating all progresses in the GMF measurements in recent years.
Based on a thorough study of the deflections of the UHECRs measured by the
AGASA experiment, we study the GFM model dependence of the correlation between
the UHECRs and the selected BL Lacs using the new model together with others.
It turns out that only specific one of those GMF models makes the correlation
significant, even if neither GMF models themselves nor deflections of the
UHECRs are not significantly different. It suggests that the significance of
the correlation, calculated using a method suggested in those studies, is
intensively depending on the GMF model. Great improvement in statistics may
help to suppress the sensitivity to the GMF models.