title: The Era of Reionization

abstract:
  In popular cold dark matter cosmological scenarios, stars may have first
appeared in significant numbers around a redshift of 10 or so, as the gas
within protogalactic halos with virial temperatures in excess of 20,000 K
(corresponding to masses comparable to those of present-day dwarf ellipticals)
cooled rapidly due to atomic processes and fragmented. It is this `second
generation' of subgalactic stellar systems, aided perhaps by an early
population of accreting black holes in their nuclei, which may have generated
the ultraviolet radiation and mechanical energy that ended the cosmic ``dark
ages'' and reheated and reionized most of the hydrogen in the universe by a
redshift of 6. The detailed history of the universe during and soon after these
crucial formative stages depends on the power-spectrum of density fluctuations
on small scales and on a complex network of poorly understood `feedback'
mechanisms, and is one of the missing link in galaxy formation and evolution
studies. The astrophysics of the epoch of first light is recorded in the
thermal state, ionization degree, and chemical composition of the intergalactic
medium, the main repository of baryons at high redshifts.


title:
Turbulent Magnetohydrodynamic Elasticity: I. Boussinesq-like
  Approximations for Steady Shear

abstract:
  We re-examine the Boussinesq hypothesis of an effective turbulent viscosity
within the context of simple closure considerations for models of strong
magnetohydrodynamic turbulence. Reynolds-stress and turbulent Maxwell-stress
closure models will necessarily introduce a suite of transport coefficients,
all of which are to some degree model-dependent. One of the most important
coefficients is the relaxation time for the turbulent Maxwell stress, which
until recently has been relatively ignored. We discuss this relaxation within
the context of magnetohydrodynamic turbulence in steady high Reynolds-number,
high magnetic-Reynolds-number shearing flows. The relaxation time for the
turbulent Maxwell stress is not limited by the shear time scale, in contrast
with Reynolds-stress closure models for purely hydrodynamical turbulence. The
anisotropy of the turbulent stress tensor for magnetohydrodynamic turbulence,
even for the case of zero mean-field considered here, can therefore not be
neglected. This shear-generated anisotropy can be interpreted as being due to
an effective turbulent elasticity, in analogy to the Boussinesq turbulent
viscosity. We claim that this turbulent elasticity should be important for any
astrophysical problem in which the turbulent stress in quasi-steady shear has
been treated phenomenologically with an effective viscosity.


title: Cosmological X-ray Flashes in the Off-Axis Jet Model

abstract:
  The <V/Vmax> of the cosmological X-ray flashes detected by Wide Field Cameras
on BeppoSAX is calculted theoretically in a simple jet model. The total
emission energy from the jet is assumed to be constant. We find that if the jet
opening half-angle is smaller than 0.03 radian, the theoretical <V/Vmax> is
less than ~0.4, which is consistent with the recently reported observational
value of 0.27+/-0.16 at the 1-sigma level. This suggests that the off-axis GRB
jet with the small opening half-angle at the cosmological distance can be
identified as the cosmological X-ray flash.


title: Realizability of stationary spherically symmetric transonic accretion

abstract:
  The spherically symmetric stationary transonic (Bondi) flow is considered a
classic example of an accretion flow. This flow, however, is along a
separatrix, which is usually not physically realizable. We demonstrate, using a
pedagogical example, that it is the dynamics which selects the transonic flow.


title: Cosmic Ray History and its Implications for Galactic Magnetic Fields

abstract:
  There is evidence that cosmic rays were present in galaxies at moderately
high redshift. This suggests that magnetic fields were also present. If cosmic
rays and magnetic fields must always be close to equipartition, as they are to
an order of magnitude within the local universe, this would provide a powerful
constraint on theories of the origin and evolution of magnetic fields in
galaxies. We evaluate current theories of cosmic ray acceleration and
confinement at very low magnetic fieldstrength, and find that the properties of
small scale turbulence are fundamentally changed in the presence of cosmic
rays. As a result, magnetic fields several orders of magnitude weaker than
present galactic fields can accelerate and retain a population of relativistic
cosmic rays, provided that the fields are coherent on lengthscales greater than
a cosmic ray gyroradius.


title: Detecting supersymmetric dark matter in M31 with CELESTE ?

abstract:
  It is widely believed that dark matter exists within galaxies and clusters of
galaxies. Under the assumption that this dark matter is composed of the
lightest, stable supersymmetric particle, assumed to be the neutralino, the
feasibility of its indirect detection via observations of a diffuse gamma-ray
signal due to neutralino annihilation within M31 is examined.


title: Bolometric Light Curves of Supernovae

abstract:
  The thermalized energy from the radioactive decays of 56Ni and 57Ni and their
daughter nuclides power the light curves of supernovae near maximum light. The
bolometric light curve gives us a fundamental understanding of the energy
evolution of a supernova explosion and the amount of radioactive nuclides
produced. In this review, I will discuss the bolometric evolution of the Type
IIp supernova SN1987A, and the general class of bolometric light curves of Type
Ia thermonuclear explosions.


title:
The 2dF Galaxy Redshift Survey: the luminosity function of cluster
  galaxies

abstract:
  We have determined the composite luminosity function (LF) for galaxies in 60
clusters from the 2dF Galaxy Redshift Survey. The LF spans the range
$-22.5<M_{b_{\rm J}}<-15$, and is well-fitted by a Schechter function with
${M_{b_{\rm J}}}^{*}=-20.07\pm0.07$ and $\alpha=-1.28\pm0.03$ ($H_0$=100 km
s$^{-1}$ Mpc$^{-1}$, $\Omega_M$=0.3, $\Omega_\Lambda$=0.7). It differs
significantly from the field LF of \cite{mad02}, having a characteristic
magnitude that is approximately 0.3 mag brighter and a faint-end slope that is
approximately 0.1 steeper. There is no evidence for variations in the LF across
a wide range of cluster properties. However the LF of early-type galaxies in
clusters is both brighter and steeper than its field counterpart. The
differences between the field and cluster LFs for the various spectral types
can be qualitatively explained by the suppression of star formation in the
dense cluster environment, together with mergers to produce the brightest
early-type galaxies.


title:
Dynamical response to supernova-induced gas removal in two-component
  spherical galaxies

abstract:
  We investigate dynamical response on size and velocity dispersion to mass
loss by supernovae in formation of two-component spherical galaxies composed of
baryon and dark matter. Three-dimensional deprojected de Vaucouleurs-like and
exponential-like profiles for baryon, embedded in truncated singular isothermal
and homogeneous profiles for dark matter, are considered. As a more realistic
case, we also consider a dark matter profile proposed by Navarro, Frenk &
  White. For simplicity we assume that dark matter distribution is not affected
by mass loss and that the change of baryonic matter distribution is homologous.
We found that the degree of the response depends on the fraction of dark matter
in the region where baryon is distributed, so that dwarf spheroidal galaxies
would be affected even in a dark halo if they are formed by galaxy mergers in
the envelope of the dark halo. Our results suggest that this scenario, combined
with dynamical response, would make not only the observed trends but the
dispersed characteristics of dwarf spheroidals.


title: Shock breakouts in SNe Ib/c

abstract:
  Numerical modeling of shock breakout in compact presupernovae of type Ib/c is
done by two independent methods. Peak color temperatures reach 4 to 8 million K
for explosion energies 1 to 9 foe with a typical local time-scale of 0.03
seconds. In the obverver's frame the burst is smeared over few seconds due to
light travel time correction R/c.


title: Cosmological consequences of a built-in cosmological constant model

abstract:
  We have analyzed the implications of a phenomenological model of a built-in
cosmological constant of Rastall and Al-Rawaf -Taha type. We have produced the
presently observed cosmic acceleration with the aid of introducing a positive
cosmological constant. We have shown that the cosmological models of the type
$\Lambda\propto\frac{\ddot R}{R}, \Lambda\propto H^2$ or $\Lambda\propto 8\pi
G\rho$ are equivalent to a built-in cosmological constant model of Al-Rawaf and
Taha type. Such models are compatible with the recent observational data and do
not suffer from fine tuning problems. We predict a higher lensing probability
than in Einstein de Sitter and Abdel Rahman models. We also predict a higher
value for the luminosity and angular diameter distances than that of Abdel
Rahman model. The lens distribution peaks at relatively smaller values of the
lens red-shift and occurs at higher red-shift.


title: Dark Energy: Is it Q or Lambda ?

abstract:
  New observations of Cosmic Microwave Background Anisotropies, Supernovae
luminosity distances and Galaxy Clustering are sharpening our knowledge about
dark energy. Here we present the latest constraints.


title:
Lightcurves of thermonuclear supernovae as a probe of the explosion
  mechanism and their use in cosmology

abstract:
  Thermonuclear supernovae are valuable for cosmology but their physics is not
yet fully understood. Modeling the development and propagation of nuclear flame
is complicated by numerous instabilities. The predictions of supernova light
curves still involve some simplifying assumptions, but one can use the
comparison of the computed fluxes with observations to constrain the explosion
mechanism. In spite of great progress in recent years, a number of issues
remains unsolved both in flame physics and light curve modeling.


title:
On the universal X-ray luminosity function of binary X-ray sources in
  galaxies

abstract:
  The empirically determined universal power-law shape of X-ray luminosity
function of high mass X-ray binaries in galaxies is explained by fundamental
mass-luminosity and mass-radius relations for massive stars.


title: Observable Effects of Shocks in Compact and Extended Presupernovae

abstract:
  We simulate shock propagation in a wide range of core-collapsing
presupernovae: from compact WR stars exploding as SNe Ib/c through very
extended envelopes of the narrow-line SNe IIn. We find that the same physical
phenomenon of radiating shocks can produce outbursts of X-ray radiation (with
photon energy $3kT \sim 1$ keV) lasting only a second in SNe Ib/c, as well as a
very high flux of visual light, lasting for months, in SNe IIn.


title: Ion-dominated plasma and the origin of jets in quasars

abstract:
  Low cooling plasmas associated with large kinetic energies are likely to be
the origin of the kpc-extended and well collimated extra-galactic jets. It is
proposed that jets are launched from a layer, governed by a highly diffusive,
super-Keplerian rotating and thermally dominated by virial-hot and magnetized
ion-plasma. The launching layer is located between the accretion disk and the
corona surrounding the nucleus. The matter in the layer is causally connected
to both the disk and to the central engine. Moreover we find that coronae, in
the absence of heating from below, are dynamically unstable to thermal
ion-conduction, and that accretion disks become intrinsically
advection-dominated. We confirm the capability of this multi-layer model to
form jets by carrying out 3D axisymmetric quasi-stationary MHD calculations
with high spatial resolution, and taking into account turbulent and magnetic
diffusion. The new multi-layer topology accommodates several previously
proposed elements for jet-initiation, in particular the ion-torus, the
magneto-centrifugal and the truncated disk - advective tori models.


title:
Brown dwarfs in the Pleiades cluster : clues to the substellar mass
  function

abstract:
  We present the results of a 6.4 square degrees imaging survey of the Pleiades
cluster in the I and Z-bands. The survey extends up to 3 degrees from the
cluster center and is 90% complete down to I~22. It covers a mass range from
0.03 Msun to 0.48 Msun and yields 40 brown dwarf candidates (BDCs) of which 29
are new. The spatial distribution of BDCs is fitted by a King profile in order
to estimate the cluster substellar core radius. The Pleiades mass function is
then derived accross the stellar-substellar boundary and we find that, between
0.03 Msun and 0.48 Msun, it is well represented by a single power-law, dN/dM
\propto M^{-alpha}, with an index alpha=0.60 +/- 0.11. Over a larger mass
domain, however, from 0.03 Msun to 10 Msun, the mass function is better fitted
by a log-normal function. We estimate that brown dwarfs represent about 25% of
the cluster population which nevertheless makes up less than 1.5% of the
cluster mass. The early dynamical evolution of the cluster appears to have had
little effect on its present mass distribution at an age of 120 Myr. Comparison
between the Pleiades mass function and the Galactic field mass function
suggests that apparent differences may be mostly due to unresolved binary
systems.


title: Dense gas clouds and the Unidentified EGRET sources

abstract:
  Cold, dense gas clouds have been proposed as a major component of the
Galactic dark matter; such clouds can be revealed by the gamma-ray emission
which arises from cosmic-rays interacting with the gas. If this dark matter
component is clustered then highly luminous GeV sources result, preferentially
at low to mid Galactic latitudes where they lie within the cosmic-ray disk. The
predicted emission for such clusters is steady, continuum emission with peak
power emerging at several hundred MeV. These sources would not have obvious
counterparts at other wavelengths and are thus of interest in connection with
the UnIDentified (UID) EGRET sources. Here we present a Monte Carlo simulation
of the gamma-ray source population due to cold gas clouds, assuming a
Cold-Dark-Matter-like mass spectrum for the clustering. We find that ~280 EGRET
sources are predicted by this model, with a median Galactic latitude of 12
degrees for the population, and a median angular size of 2.2 degrees. The
latitude and size distributions are consistent with the UID EGRET source data,
but the source counts are clearly overpredicted. On the basis of these results
we propose that clusters of cold gas clouds comprise the majority population of
the observed UID EGRET sources. Our interpretation implies that there should be
microwave counterparts to most of the UID sources, and will thus be strongly
constrained by data from the present generation of microwave anisotropy
experiments.


title:
A theoretician's analysis of the supernova data and the limitations in
  determining the nature of dark energy

abstract:
  Current cosmological observations show a strong signature of the existence of
a dark energy component with negative pressure. The most obvious candidate for
this dark energy is the cosmological constant (with the equation of state
w_X=p/\rho=-1), which, however, raises several theoretical difficulties. This
has led to models for dark energy component which evolves with time. We discuss
certain questions related to the determination of the nature of dark energy
component from observations of high redshift supernova. The main results of our
analysis are: (i) Even if the precise value of w_X is known from observations,
it is not possible to determine the nature of the unknown dark energy source
using only kinematical and geometrical measurements. We have given explicit
examples to show that different types of sources can give rise to a given w_X.
(ii) Although the full data set of supernova observations (which are currently
available) strongly rule out models without dark energy, the high (z>0.25) and
low (z<0.25) redshift data sets, individually, admit decelerating models with
zero dark energy. Any possible evolution in the absolute magnitude of the
supernovae, if detected, might allow the decelerating models to be consistent
with the data. (iii) We have introduced two parameters, which can be obtained
entirely from theory, to study the sensitivity of the luminosity distance on
w_X. Using these two parameters, we have argued that although one can determine
the present value of w_X accurately from the data, one cannot constrain the
evolution of w_X.


title: On the total energy of open Friedmann-Robertson-Walker universes

abstract:
  The idea that the universe has zero total energy when one includes the
contribution from the gravitational field is reconsidered. A Hamiltonian is
proposed as an energy for the exact equations of FRW cosmology: it is then
shown that this energy is constant. Thus open and critically open FRW universes
have the energy of their asymptotic state of infinite dilution, which is
Minkowski space with zero energy. It is then shown that de Sitter space, the
inflationary attractor, also has zero energy, and the argument is generalized
to Bianchi models converging to this attractor.


title: Formation and Evolution of Self-Interacting Dark Matter Halos

abstract:
  We study the formation and evolution of self-interacting dark matter (SIDM)
halos. We find analytical, fully cosmological similarity solutions taking
account of the collisional interaction of SIDM particles. This interaction
results in a thermal conductivity that heats the halo core and flattens its
density profile. These similarity solutions are relevant to galactic and
cluster halo formation in the CDM model. We assume an initial mass profile dM/M
M^{-eps}, as in the familiar secondary infall model. If eps=1/6, SIDM halos
will evolve self-similarly, with a cold, supersonic infall terminated by a
strong accretion shock. Different solutions arise for different values of the
collisionality parameter, Q= sigma rho_b r_s, where sigma is the scattering
cross section, rho_b is the cosmic mean density, and r_s is the shock radius.
For all these solutions, a flat-density, isothermal core is present which grows
in size as a fixed fraction of r_s. We find two different regimes for these
solutions: 1) for Q \leq Q_{th}, the core density decreases and core size
increases as Q increases; 2) for Q \geq Q_{th}, the core density increases and
core size decreases as Q increases. Our similarity solutions are in agreement
with previous N-body simulations of SIDM halos, which correspond to the low-Q
regime, if Q=[8.4e-4 - 4.9e-2]Q_{th} (low-Q), or sigma=[0.56-5.6]cm^2/g. As
Q=\infty, our similarity solution aquires a central density cusp, in agreement
with some simulation results which used an ordinary collisional fluid to
approximate the effects of SIDM collisionality. When Q=[18.6-231]Q_{th} or
sigma=[1.2e4 - 2.71e4]cm^2/g, for which we find flat-density cores comparable
to those of the observationally acceptable low-Q solutions, has not previously
been identified. Further study of this regime is warranted.


title:
Emission Line Galaxies in the STIS Parallel Survey I: Observations and
  Data Analysis

abstract:
  In the first three years of operation STIS obtained slitless spectra of
approximately 2500 fields in parallel to prime HST observations as part of the
  STIS Parallel Survey (SPS). The archive contains almost 300 fields at high
galactic latitude (|b|>30) with spectroscopic exposure times greater than 3000
seconds. This sample contains 220 fields (excluding special regions and
requiring a consistent grating angle) observed between 6 June 1997 and 21
September 2000, with a total survey area of about 160 square arcminutes. At
this depth, the SPS detects an average of one emission line galaxy per three
fields. We present the analysis of these data, and the identification of 131
low to intermediate redshift galaxies detected by optical emission lines. The
sample contains 78 objects with emission lines that we infer to be redshifted
[OII]3727 emission at 0.43<z<1.7. The comoving number density of these objects
is comparable to that of H-alpha emitting galaxies in the NICMOS parallel
observations. One quasar and three probable Seyfert galaxies are detected. Many
of the emission-line objects show morphologies suggestive of mergers or
interactions. The reduced data are available upon request from the authors.


title:
A Hybrid Cosmological Hydrodynamic/N-body Code Based on the Weighted
  Essentially Non-Oscillatory Scheme

abstract:
  We describe a newly developed cosmological hydrodynamics code based on the
weighted essentially non-oscillatory (WENO) schemes for hyperbolic conservation
laws. High order finite difference WENO schemes are designed for problems with
piecewise smooth solutions containing discontinuities, and have been successful
in applications for problems involving both shocks and complicated smooth
solution structures. We couple hydrodynamics based on the WENO scheme with
standard Poisson solver - particle-mesh (PM) algorithm for evolving the
self-gravitating system. A third order total variation diminishing (TVD)
Runge-Kutta scheme has been used for time-integration of the system. We brief
the implementation of numerical technique. The cosmological applications in
simulating intergalactic medium and Ly$\alpha$ forest in the CDM scenario are
also presented.


title:
Point Source Detection using the Spherical Mexican Hat Wavelet on
  simulated all-sky Planck maps

abstract:
  We present an estimation of the point source (PS) catalogue that could be
extracted from the forthcoming ESA Planck mission data. We have applied the
Spherical Mexican Hat Wavelet (SMHW) to simulated all-sky maps that include
CMB, Galactic emission (thermal dust, free-free and synchrotron), thermal
Sunyaev-Zel'dovich effect and PS emission, as well as instrumental white noise.
This work is an extension of the one presented in Vielva et al. (2001a). We
have developed an algorithm focused on a fast local optimal scale
determination, that is crucial to achieve a PS catalogue with a large number of
detections and a low flux limit. An important effort has been also done to
reduce the CPU time processor for spherical harmonic transformation, in order
to perform the PS detection in a reasonable time. The presented algorithm is
able to provide a PS catalogue above fluxes: 0.48 Jy (857 GHz), 0.49 Jy (545
GHz), 0.18 Jy (353 GHz), 0.12 Jy (217 GHz), 0.13 Jy (143 GHz), 0.16 Jy (100 GHz
HFI), 0.19 Jy (100 GHz LFI), 0.24 Jy (70 GHz), 0.25 Jy (44 GHz) and 0.23 Jy (30
GHz). We detect around 27700 PS at the highest frequency Planck channel and
2900 at the 30 GHz one. The completeness level are: 70% (857 GHz), 75% (545
GHz), 70% (353 GHz), 80% (217 GHz), 90% (143 GHz), 85% (100 GHz HFI), 80% (100
GHz LFI), 80% (70 GHz), 85% (44 GHz) and 80% (30 GHz). In addition, we can find
several PS at different channels, allowing the study of the spectral behaviour
and the physical processes acting on them. We also present the basic procedure
to apply the method in maps convolved with asymmetric beams. The algorithm
takes ~ 72 hours for the most CPU time demanding channel (857 GHz) in a Compaq
HPC320 (Alpha EV68 1 GHz processor) and requires 4 GB of RAM memory.


title: Behaviour of Magnetic Tubes in Neutron Star's Interior

abstract:
  It is found from Maxwell's equations that the magnetic field lines are good
analogues of relativistic strings. It is shown that the super-conducting
current in the neutron star's interior causes local rotation of magnetic flux
tubes carrying quantized flux.


title: Molecular Clouds. Formation and Disruption

abstract:
  Molecular clouds (MC) are the densest and coldest component of the
interstellar gas, and the sites of star formation. They are also turbulent and
fractal and their masses and sizes span several orders of magnitude. It is also
generally believed that they are close to Virial equilibrium (VE). Since this
statement has been questioned by a number of authors, with important
implications on molecular clouds' lifetimes, we will review this subject within
the context of a turbulent ISM. In this framework, there is significant
numerical evidence that MCs are not in VE, that there is a strong exchange of
mass, momentum and energy between clouds and their surrounding medium, and that
it is difficult (if not impossible) to form quasistatic cores inside MCs,
suggesting that they must be transient, short-lived phenomena. Thus, their
formation and disruption must be primarily dynamical, and probably not due to
just a single mechanism, but rather to the combination of several processes.
This picture seems consistent with recent estimates of ages of stars in the
solar neighborhood.


title: A Self-Consistent Study of Triaxial Black-Hole Nuclei

abstract:
  We construct models of triaxial galactic nuclei containing central black
holes using the method of orbital superposition, then verify their stability by
advancing N-body realizations of the models forward in time. We assume a
power-law form for the stellar density, rho ~ 1/r and 1/r^2; these correspond
approximately to the nuclear density profiles of bright and faint galaxies
respectively. Equidensity surfaces are ellipsoids with fixed axis ratios. The
central black hole is represented by a Newtonian point mass. We consider three
triaxial shapes: almost prolate, almost oblate and maximally triaxial. Two
kinds of orbital solution are attempted for each mass model: the first
including only regular orbits, the second including chaotic orbits as well. We
find that stable configurations exist in the maximally triaxial and
nearly-oblate cases; however steady-state solutions in the nearly-prolate
geometry could not be found. A large fraction of the mass, of order 50% or
more, could be assigned to the chaotic orbits without inducing evolution. Our
results demonstrate that triaxiality may persist even within the sphere of
influence of the central black hole, and that chaotic orbits may constitute an
important building block of galactic nuclei.


title: Completeness of USNO-B for High Proper-Motion Stars

abstract:
  I test the completeness of USNO-B detections of high proper-motion
(mu>0.18"/yr) stars and the accuracy of its measurements by comparing them to
the revised NLTT (rNLTT) catalog of Salim & Gould. For 14.5<V<18.5, only 6% of
such stars are missing from USNO-B while another 4% have large errors, mostly
too large to be useful. Including both classes, incompleteness is 10%. These
fractions rise toward both brighter and fainter magnitudes. Incompleteness
rises with proper motion to about 30% at mu=1"/yr. It also rises to about 35%
at the Galactic plane, although this is only determined for relatively bright
stars V<~14. For binaries, incompleteness rises from 10% at separations of 30"
to 47% at 10". The proper-motion errors reported internally by USNO-B are
generally correct. However, there is floor of sigma_mu~4mas/yr below which the
reported errors should not be taken at face value. The small number of stars
with relatively large reported errors (sigma_mu>~20mas/yr) may actually have
still larger errors than tabulated.


title:
The Cross-Wavelet Transform and Analysis of Quasiperiodic Behavior in
  the Pearson-Readhead VLBI Survey Sources

abstract:
  We introduce an algorithm for applying a cross-wavelet transform to analysis
of quasiperiodic variations in a time-series, and introduce significance tests
for the technique. We apply a continuous wavelet transform and the
cross-wavelet algorithm to the Pearson-Readhead VLBI survey sources using data
obtained from the University of Michigan 26-m parabloid at observing
frequencies of 14.5, 8.0, and 4.8 GHz. Thirty of the sixty-two sources were
chosen to have sufficient data for analysis, having at least 100 data points
for a given time-series. Of these thirty sources, a little more than half
exhibited evidence for quasiperiodic behavior in at least one observing
frequency, with a mean characteristic period of 2.4 yr and standard deviation
of 1.3 yr. We find that out of the thirty sources, there were about four time
scales for every ten time series, and about half of those sources showing
quasiperiodic behavior repeated the behavior in at least one other observing
frequency.


title: Deconstructing HD 28867

abstract:
  The 3" pair of B9 stars, HD 28867, is one of the brightest X-ray sources in
the Taurus-Auriga star forming region. In this multi-wavelength study, we
attempt to deduce the source of the X-ray emission. We show that the East
component is the X-ray source. The East component has a near-IR excess and
displays narrow absorption lines in the optical, both of which are consistent
with a cool stellar companion. This companion is one of the brightest low mass
pre-main sequence stars in Tau-Aur; at 2 microns it and the B9 star are equally
bright. We see evidence for radial velocity variability in the cool component
of >34 km/s. It is not visible in K band speckle imaging, which constrains the
companion to lie within 14 AU of the B star.
  We also report on a possible fourth member of the group, an M1 star 18" south
of HD 28867.


title:
Emission Line Galaxies in the STIS Parallel Survey II: Star Formation
  Density

abstract:
  We present the luminosity function of [OII]-emitting galaxies at a median
redshift of z=0.9, as measured in the deep spectroscopic data in the STIS
Parallel Survey (SPS). The luminosity function shows strong evolution from the
local value, as expected. By using random lines of sight, the SPS measurement
complements previous deep single field studies. We calculate the density of
inferred star formation at this redshift by converting from [OII] to H-alpha
line flux as a function of absolute magnitude and find rho_dot=0.043 +/- 0.014
Msun/yr/Mpc^3 at a median redshift z~0.9 within the range 0.46<z<1.415 (H_0 =
70 km/s/Mpc, Omega_M=0.3, Omega_Lambda=0.7. This density is consistent with a
(1+z)^4 evolution in global star formation since z~1. To reconcile the density
with similar measurements made by surveys targeting H-alpha may require
substantial extinction correction.


title:
The Sloan Digital Sky Survey: The Cosmic Spectrum and Star-Formation
  History

abstract:
  We present a determination of the `Cosmic Optical Spectrum' of the Universe,
i.e. the ensemble emission from galaxies, as determined from the red-selected
Sloan Digital Sky Survey main galaxy sample and compare with previous results
of the blue-selected 2dF Galaxy Redshift Survey. Broadly we find good agreement
in both the spectrum and the derived star-formation histories. If we use a
power-law star-formation history model where star-formation rate $\propto
(1+z)^\beta$ out to z=1, then we find that $\beta$ of 2 to 3 is still the most
likely model and there is no evidence for current surveys missing large amounts
of star formation at high redshift. In particular `Fossil Cosmology' of the
local universe gives measures of star-formation history which are consistent
with direct observations at high redshift. Using the photometry of SDSS we are
able to derive the cosmic spectrum in absolute units (i.e.$ W \AA$^{-1}$
Mpc$^{-3}$) at 2--5\AA resolution and find good agreement with published
broad-band luminosity densities. For a Salpeter IMF the best fit stellar
mass/light ratio is 3.7--7.5 $\Msun/\Lsun$ in the r-band (corresponding to
$\omstars h = 0.0025$--0.0055) and from both the stellar emission history and
the H$\alpha$ luminosity density independently we find a cosmological
star-formation rate of 0.03--0.04 h $\Msun$ yr$^{-1}$ Mpc$^{-3}$ today.


title:
Review on the Observed and Physical Properties of Core Collapse
  Supernovae

abstract:
  This paper summarizes observed and physical properties of all types of core
collapse supernovae. Despite the great diversity displayed by these objects,
several regularities emerge which suggest that 1) there is a continuum in the
properties of these objects, 2) the mass of the envelope is one of the driving
parameters of the explosion, or it is correlated with some other property of
the core, with the latter determining the outcome of the explosion, and 3) the
physics of the core and explosion mechanism of all core collapse supernovae are
not be fundamentally different, regardless of the external appearance of the
supernova. Far above in energy scale and 56Ni production lies SN 1998bw, the
only supernova firmly associated with a gamma-ray burst.


title: Grain Acceleration by MHD Turbulence: Gyroresonance Mechanism

abstract:
  We discuss a new mechanism of dust acceleration that acts in a turbulent
magnetized medium. The magnetohydrodynamic (MHD) turbulence includes both fluid
motions and magnetic fluctuations. We show that while the fluid motions bring
about grain motions through the drag, the electromagnetic fluctuations, can
accelerate grains through resonant interactions. In this paper we calculate
grain acceleration by gyroresonance in Cold Neutral Medium. We consider both
incompressible and compressible MHD modes. We show that fast modes dominate
grain acceleration. For the parameters chosen, fast modes render supersonic
velocities to grains that may shatter grains and enable efficient absorption of
heavy elements. Since the grains are preferentially accelerated with large
pitch angles, the supersonic grains get aligned with long axes perpendicular to
the magnetic field.


title: The Virgo High-Resolution CO Survey I. CO Atlas

abstract:
  We present the results of the Virgo high-resolution CO survey (ViCS) obtained
with the Nobeyama Millimeter-wave Array (NMA). This survey was made in the
course of a long-term project at Nobeyama from 1999 December through 2002
April. The objects were selected from Virgo cluster members, considering CO
richness from single dish flux, mild inclination, and lack of strong tidal
perturbations. The central 1 arc min regions (4.7 kpc) of 15 spiral galaxies
were observed with resolutions of 2 to 5 arcsec and 10 to 20 km/s, and
sensitivities of 20 mJy/ beam for a 10 km/s channel. The objects lie at the
same distance of the Virgo cluster (16.1 Mpc), which is advantageous for
comparisons among individual galaxies. We describe the details of observations
and data reduction, and present an atlas of integrated CO intensity maps,
velocity fields and position-velocity diagrams along the major axes. The
molecular gas morphology in the Virgo galaxies shows a wealth of variety, not
specifically depending on the Hubble types.


title:
The Virgo High-Resolution CO Survey. II. Rotation Curves and Dynamical
  Mass Distributions

abstract:
  Based on a high-resolution CO survey of Virgo spirals with the Nobeyama
Millimeter-wave Array, we determined the dynamical centers using velocity
fields, and derived position-velocity diagrams (PVDs) along the major axes of
the galaxies across their dynamical centers. We applied a new iteration method
to derive rotation curves (RCs), which reproduce the observed PVDs. The
obtained high-accuracy RCs generally show steep rise in the central 100 to 200
pc regions, followed by flat rotation in the disk. We applied a deconvolution
method to calculate the surface-mass density (SMD) using the RCs based on two
extreme assumptions that the mass distribution is either spherical or thin-disk
shaped. Both assumptions give nearly identical results, agreeing with each
other within a factor of two at any radii. The SMD distributions revealed
central massive cores with peak SMD of 10^4 - 10^5 Msun pc^-2 and total mass
within 200 pc radius of the order of about 10^9 Msun Correlation analysis among
the derived parameters show that the central CO-line intensity is positively
correlated with the central SMD, which suggests that the deeper is the
gravitational potential, the higher is the molecular gas concentration in the
nuclei regardless morphological types.


title: The Virgo High-Resolution CO Survey. III. NGC 4254

abstract:
  We present high-angular-resolution (1".5 - 5") interferometer observations of
the \co emission in the central region of the SA(s)c galaxy NGC 4254. The
observations were obtained using the Nobeyama Millimeter-wave Array (NMA)
during the course of a long-term CO line survey of Virgo spirals. We present
the spectra, channel maps, integrated intensity distributions, velocity fields,
position--velocity diagrams, and compare the data with various optical images.
The rotation velocity is already finite at the nucleus, or at least it rises
steeply to 80 km/s within the central 1", indicating the existence of a massive
core of 10^8 Msun within 1" (80 pc) radius. The CO intensity maps show that the
inner disk has well-developed multiple spiral arms, winding out from a
bar-shaped elongated molecular complex. In addition to the bisymmetric spiral
arms, an asymmetric tightly wound arm with high molecular gas density is found
to wind out from the molecular bar. The molecular spiral arms, particularly the
tightly wound arm, well traces optical dark lanes, and are associated with
H$\alpha$ arms having many H {\sc ii} regions. The inner asymmetric spiral
structures can be explained by ram-pressure distortion of inter-arm low density
regions of the inner disk by the intra-cluster gas wind, and is indeed
reproduced by a hydrodynamical simulation.


title: Dirty Fireballs and Orphan Afterglows: A Tale of Two Transients

abstract:
  Orphan afterglows are transient events that are produced by cosmological
fireballs and resemble gamma ray burst (GRB) afterglows, yet are not
accompanied by gamma rays. Such transients may be produced by jetlike GRBs
observed off-axis, and therefore hold great promise as a test of gamma ray
burst collimation. However, orphans may also be produced by "dirty fireballs,"
i.e., cosmological fireballs whose ejecta carry too many baryons to produce a
GRB.
  A well designed orphan afterglow search can distinguish between on-axis dirty
fireballs and off-axis orphans in at least two ways. First, by combining
real-time triggers from a wide area, multicolor search with deeper followup
observations, the light curve can be tracked for a time exceeding 2*t_1, where
t_1 is the age of the event at first observation. Such a light curve allows
simultaneous fits to t_1 and the time decay slope alpha with sufficient
accuracy to distinguish on- and off-axis orphans. Second, radio followup of
orphan afterglows will show whether the radio flux is falling in time (as
expected for an off-axis orphan) or not (as expected for on-axis events).
Additional tests involving multi-band monitoring of the cooling,
self-absorption, and f_nu peak frequencies are also possible, although much
more observationally demanding.
  A further complication in orphan searches is that dirty fireballs are likely
to also be collimated, and that collimated dirty fireballs viewed off-axis will
individually be practically indistinguishable from off-axis GRB afterglows. To
recognize their presence, orphan afterglow surveys must be sufficiently
extensive to catch at least some dirty fireballs on-axis.


title: The State of the Universe: Cosmological Parameters 2002

abstract:
  In the past decade, observational cosmology has had one of the most exciting
periods in the past century. The precision with which we have been able to
measure cosmological parameters has increased tremendously, while at the same
time, we have been surprised beyond our wildest dreams by the results. I review
here recent measurements of the expansion rate, geometry, age, matter content,
and equation of state of the universe, and discuss the implications for our
understanding of cosmology.


title: A Search for Stellar Obscuration Events due to Dark Clouds

abstract:
  The recent detections of a large population of faint submillimetre sources,
an excess halo gamma-ray background, and the extreme scattering events observed
for extragalactic radio sources have been explained as being due to baryonic
dark matter in the form of small, dark, gas clouds. In this paper we present
the results of a search for the transient stellar obscurations such clouds are
expected to cause. We examine the Macho project light curves of 48 x 10^6 stars
toward the Galactic bulge, LMC and SMC for the presence of dark cloud
extinction events. We find no evidence for the existence of a population of
dark gas clouds with Av > 0.2 and masses between ~ 10^-4 and 10^-2 M_solar in
the Galactic disk or halo. However, it is possible that such dark cloud
populations could exist if they are clustered in regions away from the observed
lines of sight.


title:
Evidence for coupling between the Sagittarius dwarf galaxy and the Milky
  Way warp

abstract:
  Using recent determinations of the mass and orbit of Sagittarius, I calculate
its orbital angular momentum. From the latest observational data, I also
calculate the angular momentum of the Milky Way's warp. I find that both
angular momenta are directed toward l=270, b=0, and have magnitude 2-8x10^12
M_Sun kpc km s^-1, where the range in both cases reflects uncertainty in the
mass. The coincidence of the angular momenta is suggestive of a coupling
between these systems. Direct gravitational torque of Sgr on the disk is ruled
out as the coupling mechanism. Gravitational torque due to a wake in the halo
and the impulsive deposition of momentum by a passage of Sgr through the disk
are still both viable mechanisms pending better simulations to test their
predictions on the observed Sgr-MW system.


title: Boson-fermion stars: exploring different configurations

abstract:
  We use the flexibility of the concept of a fermion-boson star to explore
different configurations, ranging from objects of atomic size and masses of the
order $10^{18}$ g, up to objects of galactic masses and gigantic halos around a
smaller core, with possible interesting applications to astrophysics and
cosmology, particularly in the context of dark matter.


title: Photometric Survey of the Irregular Satellites

abstract:
  We present BVRI colors of 13 Jovian and 8 Saturnian irregular satellites
obtained with the 2.56m Nordic Optical Telescope on La Palma, the 6.5m Magellan
Baade Telescope on La Campanas, and the 6m MMT on Mt. Hopkins. The observations
were performed between December 2001 to March 2002. Nearly all of the known
irregular satellites can be divided into two distinct classes based on their
colors. One, the grey color class, has the similar colors to the C-type
asteroid, and the other, the light red color class, has colors similar to
P/D-type asteroids. We also find at least one object, the Jovian irregular J
XXIII Kalyke, that has colors similar to the red colored Centaurs/TNOs,
although its classification is unsecure. We also find that there is a
correlation between the physical properties and dynamical properties of the
irregular satellites. Most of the dynamical clusters have homogeneous colors,
which points to single homogeneous progenitors being cratered or fragmented as
the source of each individual cluster. The heterogeneous colored clusters are
most easily explained by assuming that there are several dynamical clusters in
the area, rather than just one.


title:
Collective excitations of quantum universe and the problem of dark
  matter and energy

abstract:
  In the present report we make an attempt to give an answer to the question of
modern cosmology about the nature of the dark matter and energy in our
universe. On the basis of our quantum cosmological approach, proposed in
1997-2002, we show that there can be two types of collective states in the
universe. One of them relates to a gravitational field, another is connected
with a matter (scalar) field which fills the universe on all stages of its
evolution. The collective excitations of the scalar field above its true vacuum
reveal themselves mainly in the form of dark matter and energy. Under the
action of the gravitational forces they decay and produce the non-baryonic dark
matter, optically bright and dark baryons. We have calculated the corresponding
energy densities which prove to be in good agreement with the data from the
recent observations.


title:
Intermittent Features of the QSO Ly$\alpha$ Transmitted Flux: Results
  from Hydrodynamic Cosmological Simulations

abstract:
  It has been recently found that the local fluctuations of the QSO's
Ly$\alpha$ absorption spectrum transmitted flux show spiky structures. This
implies that the mass fields of the intergalactic medium (IGM) is intermittent.
This feature cannot be explained by the clustering evolution of cosmic mass
field in the linear regimes and is also difficult to incorporate into the
hierarchical clustering scenario. We calculate the structure functions and
intermittent exponent of the IGM and HI for full hydrodynamical simulation
samples. The result shows the intermittent features of the Ly$\alpha$
transmitted flux fluctuations as well as the mass field of the IGM. We find
that within the error bars of current data, all the intermittent behavior of
the simulation samples are consistent with the observation. This result is
different from our earlier result (Pando et al 2002), which shows that the
intermittent behavior of samples generated by pseudo-hydro simulation cannot be
fitted with observed data. One difference between the pseudo-hydro and full
hydro simulations is in treating the dynamical relation between the IGM (or HI)
and dark matter fields. The former assumes that the IGM density distribution
traces the underlying dark matter point-by-point on scales larger than the
Jeans length in either the linear or nonlinear regimes. However, hydrodynamic
studies have found that a statistical discrepancy between the IGM field and
underlying dark matter in nonlinear regime is possible. We find that the
point-by-point correlation between the IGM density perturbations and dark
matter become weaker on comoving scales less than 2 h$^{-1}$ Mpc (in LCDM
model), which is larger than the IGM Jeans length.


title:
A Catalog of Broad Absorption Line Quasars from the Sloan Digital Sky
  Survey Early Data Release

abstract:
  We present a catalog of 224 broad absorption line quasars (BALQSOs) from the
Sloan Digital Sky Survey's Early Data Release Quasar Catalog, including a
relatively complete and homogeneous subsample of 131 BALQSOs. Since the
identification of BALQSOs is subject to considerable systematic uncertainties,
we attempt to create a complete sample of SDSS BALQSOs by combining the results
of two automated selection algorithms and a by-eye classification scheme. One
of these automated algorithms finds broad absorption line troughs by comparison
with a composite quasar spectrum. We present the details of this algorithm and
compare this method to that which uses a power-law fit to the continuum. The
BALQSOs in our sample are further classified as high-ionization BALQSOs
(HiBALs), low-ionization BALQSOs (LoBALs), and BALQSOs with excited iron
absorption features (FeLoBALs); composite spectra of each type are presented.
We further present a study of the properties of the BALQSOs in terms of the
balnicity distribution, which rises with decreasing balnicity. This
distribution of balnicities suggests that the fraction of quasars with
intrinsic outflows may be significantly underestimated.


title: The BaR-SPOrt Experiment

abstract:
  BaR-SPOrt (Balloon-borne Radiometers for Sky Polarisation Observations) is an
experiment to measure the linearly polarized emission of sky patches at 32 and
90 GHz with sub-degree angular resolution. It is equipped with high sensitivity
correlation polarimeters for simultaneous detection of both the U and Q stokes
parameters of the incident radiation. On-axis telescope is used to observe
angular scales where the expected polarization of the Cosmic Microwave
Background (CMBP) peaks. This project shares most of the know-how and
sophisticated technology developed for the SPOrt experiment onboard the
International Space Station. The payload is designed to flight onboard long
duration stratospheric balloons both in the Northern and Southern hemispheres
where low foreground emission sky patches are accessible. Due to the weakness
of the expected CMBP signal (in the range of microK), much care has been spent
to optimize the instrument design with respect to the systematics generation,
observing time efficiency and long term stability. In this contribution we
present the instrument design, and first tests on some components of the 32 GHz
radiometer.


title: Cosmology with an extra-dimension

abstract:
  I present the main features of the brane cosmology scenario, according to
which our universe is a self-gravitating brane embedded in a five-dimensional
spacetime.


title: Cosmology in a brane-universe

abstract:
  This contribution presents the cosmological models with extra dimensions that
have been recently elaborated, which assume that ordinary matter is confined on
a surface, called brane, embedded in a higher dimensional spacetime.


title: Extended Acceleration in Slot Gaps and Pulsar High-Energy Emission

abstract:
  We revise the physics of primary electron acceleration in the "slot gap" (SG)
above the pulsar polar caps (PCs), a regime originally proposed by Arons and
Scharlemann (1979) in their electrodynamic model of pulsar PCs. We employ the
standard definition of the SG as a pair-free space between the last open field
lines and the boundary of the pair plasma column which is expected to develop
above the bulk of the PC. The rationale for our revision is that the proper
treatment of primary acceleration within the pulsar SGs should take into
account the effect of the narrow geometry of the gap on the electrodynamics
within the gap and also to include the effect of inertial frame dragging on the
particle acceleration. The combination of the effects of frame dragging and
geometrical screening in the gap region naturally gives rise to a regime of
extended acceleration, that is not limited to "favorably curved" field lines as
in earlier models, and the possibility of multiple-pair production by curvature
photons at very high altitudes, up to several stellar radii. The estimated
theoretical high-energy luminosities of the SG cascade radiation are in good
agreement with the corresponding empirical relationships for gamma-ray pulsars.
We illustrate the results of our modeling of the pair cascades and gamma-ray
emission from the high altitudes in the SG for the Crab pulsar. The combination
of the frame-dragging field and high-altitude SG emission enables both
acceleration at the smaller inclination angles and a larger emission beam, both
necessary to produce widely-spaced double-peaked profiles.


title:
First Results From an X-ray, Weak Lensing, and Sunyaev-Zeldovich Effect
  Survey of Nearby Clusters: Abell 3266

abstract:
  As part of a combined Sunyaev-Zeldovich Effect (SZE), X-ray and weak lensing
survey of low redshift (z<0.1) X-ray clusters, we present SZE images of the
z=0.059 X-ray cluster Abell 3266 at three observing frequencies (150, 220, 275
GHz) and after the spectral subtraction of primary Cosmic Microwave Background
(CMB) anisotropies. These images were generated using the ACBAR bolometer array
operated on the Viper telescope at the South Pole. The multi-frequency data
from ACBAR should allow us to overcome one of the main obstacles facing the
analysis of SZE observations of nearby clusters, i.e. contamination from
primary Cosmic Microwave Background (CMB) anisotropies.


title: The Progenitors of Dwarf Spheroidal Galaxies

abstract:
  Dwarf spheroidal (dSph) galaxies present an evolutionary puzzle that we
explore in 40 early- and late-type dwarfs in the Local Group and nearby field.
Although dSphs formed stars over extended periods, today all but one are free
of detectable interstellar matter (ISM), even in the Fornax dSph, where stars
still formed 100 Myr ago. Combining metallicities for red giants with HI data
from the literature, we show that the well-known offset in
luminosity-metallicity (L-Z) relations for dSphs and dwarf irregular (dIrr)
galaxies exists also when comparing only their old stellar populations: dSphs
have higher mean stellar metallicities for a fixed luminosity. Evidently
younger dSphs experienced more efficient enrichment than young dIrrs. Dwarf
galaxies, whose locus in the L-Z diagram is consistent with that of dSphs even
for baryonic luminosities, are the ``transition-type dwarfs'' Phoenix, DDO210,
LGS3, Antlia, and KKR25. They have mixed dIrr/dSph morphologies, low stellar
masses, low angular momentum, and HI contents of less than a few 10^6 solar
masses. Unlike dIrrs, many transition-type dwarfs would closely resemble dSphs
if their gas were removed; they are likely dSph progenitors. As gas removal is
key, we consider the empirical evidence for various gas removal processes. We
suggest that internal gas removal mechanisms are inadequate and favor ram
pressure stripping to make dSphs. A combination of initial conditions and
environment seems to support the formation of dSphs, which appear to form from
small galaxies with active early star formation, whose evolution halts due to
externally induced gas loss. Transition-type dwarfs then are dSphs that kept
their ISM, and therefore should replace dSphs in isolated locations where
stripping is ineffective. (Abridged)


title: Structure Function Scaling in Compressible Super-Alfvenic MHD Turbulence

abstract:
  Supersonic turbulent flows of magnetized gas are believed to play an
important role in the dynamics of star-forming clouds in galaxies.
Understanding statistical properties of such flows is crucial for developing a
theory of star formation. In this letter we propose a unified approach for
obtaining the velocity scaling in compressible and super--Alfv\'{e}nic
turbulence, valid for arbitrary sonic Mach number, \ms. We demonstrate with
numerical simulations that the scaling can be described with the
She--L\'{e}v\^{e}que formalism, where only one parameter, interpreted as the
Hausdorff dimension of the most intense dissipative structures, needs to be
varied as a function of \ms. Our results thus provide a method for obtaining
the velocity scaling in interstellar clouds once their Mach numbers have been
inferred from observations.


title: X-ray emission line gas in the LINER galaxy M81

abstract:
  We present the soft X-ray spectrum of the LINER galaxy M81 derived from a
long observation with the XMM RGS. The spectrum is dominated by continuum
emission from the active nucleus, but also contains emission lines from Fe L,
and H-like and He-like N, O, and Ne. The emission lines are significantly
broader than the RGS point-source spectral resolution; in the cross dispersion
direction the emission lines are detected adjacent to, as well as coincident
with, the active nucleus. This implies that they originate in a region of a few
arc-minutes spatial extent (1 arc-minute ~ 1 kpc in M81). The flux ratios of
the OVII triplet suggest that collisional processes are responsible for the
line emission. A good fit to the whole RGS spectrum is obtained using a model
consisting of an absorbed power law from the active nucleus and a 3 temperature
optically thin thermal plasma. Two of the thermal plasma components have
temperatures of 0.18+-0.04 keV and 0.64+-0.04 keV, characteristic of the hot
interstellar medium produced by supernovae; the combined luminosity of the
plasma at these two temperatures accounts for all the unresolved bulge X-ray
emission seen in the Chandra observation by Tennant et al. (2001). The third
component has a higher temperature (~1.7 keV), and we argue that this, along
with some of the 0.64 keV emission, comes from X-ray binaries in the bulge of
M81.


title: Toward an Understanding of the Progenitors of Gamma-Ray Bursts

abstract:
  The various possibilities for the progenitors of gamma-ray bursts (GRBs)
manifest in differing observable properties. Through deep spectroscopic and
high-resolution imaging observations of some GRB hosts, I demonstrate that
well-localized long-duration GRBs are connected with otherwise normal
star-forming galaxies at moderate redshifts of order unity. I test various
progenitor scenarios by examining the offset distribution of GRBs about their
apparent hosts, making extensive use of ground-based optical data from Keck and
Palomar and space-based imaging from the Hubble Space Telescope. The offset
distribution appears to be inconsistent with the coalescing neutron star binary
hypothesis but statistically consistent with a population of progenitors that
closely traces the ultra-violet light of galaxies. This is naturally explained
by bursts which originate from the collapse of massive stars. This claim is
further supported by the unambiguous detections of emission ''bumps'' which can
be explained as supernovae that occur at approximately the same time as the
associated GRB; if true, GRB 980326 and GRB 011121 provide strong observational
evidence connecting cosmological GRBs to high-redshift supernovae and implicate
massive stars as the progenitors of some long-duration GRBs. Interestingly,
most alternative models of these bumps require wind-stratified circumburst
media; this too, implicates massive stars. In addition to this work, I also
constructed the Jacobs Camera (JCAM), a dual-beam optical camera for the
Palomar 200-inch Telescope designed to follow-up rapid GRB localizations
(abridged).


title: A Low Latitude Halo Stream around the Milky Way

abstract:
  We present evidence for a ring of stars in the plane of the Milky Way,
extending at least from l = 180 deg to l = 227 deg with turnoff magnitude $g
\sim 19.5$; the ring could encircle the Galaxy. We infer that the low Galactic
latitude structure is at a fairly constant distance of R = 18 +/- 2 kpc from
the Galactic Center above the Galactic plane, and has R = 20 +/- 2 kpc in the
region sampled below the Galactic plane. The evidence includes five hundred
SDSS spectroscopic radial velocities of stars within 30 degrees of the plane.
The velocity dispersion of the stars associated with this structure is found to
be 27 km/s at (l,b) = (198, -27), 22 km/s at (l,b) = (225, 28), 30 km/s at
(l,b) = (188, 24), and 30 km/s at (l,b) = (182, 27) degrees. The structure
rotates in the same prograde direction as the Galactic disk stars, but with a
circular velocity of 110+/-25 km/s. The narrow measured velocity dispersion is
inconsistent with power law spheroid or thick disk populations. We compare the
velocity dispersion in this structure with the velocity dispersion of stars in
the Sagittarius dwarf galaxy tidal stream, for which we measure a velocity
dispersion of 20 km/s at (l, b) = (165, -55) deg. We estimate a preliminary
metallicity from the Ca II (K) line and color of the turnoff stars of [Fe/H] =
-1.6 with a dispersion of 0.3 dex and note that the turnoff color is consistent
with that of the spheroid population. We interpret our measurements as evidence
for a tidally disrupted satellite of $2 \times 10^7$ to $5 \times 10^8 \rm
M_\odot$ which rings the Galaxy.


title: High Energy Neutrinos from Gamma Ray Bursts

abstract:
  We treat high-energy neutrino production in GRBs. Detailed calculations of
photomeson neutrino production are presented for the collapsar model, where
internal nonthermal synchrotron radiation is the primary target photon field,
and the supranova model, where external pulsar-wind synchrotron radiation
provides important additional target photons. Detection of > 10 TeV neutrinos
from GRBs with Doppler factors > 200, inferred from gamma-ray observations,
would support the supranova model. Detection of < 10 TeV neutrinos is possible
for neutrinos formed from nuclear production. Only the most powerful bursts at
fluence levels > 3x10^{-4} erg/cm^2 offer a realistic prospect for detection of
muon neutrinos.


title: CMB Lensing Reconstruction on the Full Sky

abstract:
  Gravitational lensing of the microwave background by the intervening dark
matter mainly arises from large-angle fluctuations in the projected
gravitational potential and hence offers a unique opportunity to study the
physics of the dark sector at large scales. Studies with surveys that cover
greater than a percent of the sky will require techniques that incorporate the
curvature of the sky. We lay the groundwork for these studies by deriving the
full sky minimum variance quadratic estimators of the lensing potential from
the CMB temperature and polarization fields. We also present a general
technique for constructing these estimators, with harmonic space convolutions
replaced by real space products, that is appropriate for both the full sky
limit and the flat sky approximation. This also extends previous treatments to
include estimators involving the temperature-polarization cross-correlation and
should be useful for next generation experiments in which most of the
additional information from polarization comes from this channel due to
sensitivity limitations.


title:
The Effect of Angular Structure of Gamma-Ray Burst Outflows on the
  Afterglow Emission

abstract:
  We investigate analytically the effect of an anisotropic distribution of the
kinetic energy within a relativistic fireball on the decay of the afterglow
emission, focusing on axially symmetric fireballs with a uniform core and a
power-law decrease with angle outside the core. The afterglow fall-off steepens
after the core becomes fully visible. For observer directions within the core,
simple formulae are derived for the afterglow decay after the break, while for
off-core observers results are shown graphically. Some criteria for assessing
from observations the necessity of an angular structure and/or collimation are
given. Applying them to several afterglows with light-curve breaks, we find
that jets endowed with structure are required only if the circumburst medium
has a wind-like (r^{-2}) stratification. Numerical fits to the multiwavelength
emission of the afterglows 990510 and 000301c show that, for the former, the
angular distribution of the ejecta kinetic energy is not far from uniformity,
and that, with a standard power-law electron distribution, the sharp steepening
of the R-band light-curve of the latter is better accommodated by a structured
jet than an uniform outflow. Structured outflows may accommodate the shallower
light-curve breaks observed in other afterglows.


title: Multi-Wavelength Observations of 1ES1959+650 in a Flaring State

abstract:
  In May 2002, the BL Lacertae object (BL Lac), 1ES1959+650, was detected in
the Very High Energy (VHE) regime by the VERITAS collaboration using the
Whipple $\gamma$-ray observatory. During the following two months, the VERITAS
collaboration observed episodes of flaring; at times, the nightly average VHE
signal was three times as bright as the Crab Nebula, the standard candle in VHE
astronomy. 1ES1959+650 was also monitored in the optical and X-ray bands. The
X-ray light curve showed periodic behavior and correlation with the VHE and the
optical bands.


title: On the Fractal Dimension of the Visible Universe

abstract:
  Estimates of the fractal dimension $D$ of the set of galaxies in the
universe, based on ever improving data sets, tend to settle on $D\approx 2$.
This result raised a raging debate due to its glaring contradiction with
astrophysical models that expect a homogeneous universe. A recent mathematical
result indicates that there is no contradiction, since measurements of the
dimension of the {\em visible} subset of galaxies is bounded from above by D=2
even if the true dimension is anything between D=2 and D=3. We demonstrate this
result in the context of a simple fractal model, and explain how to proceed in
order to find a better estimate of the true dimension of the set of galaxies.


title: An analytic model for the galactic winds and mass outflows

abstract:
  Galactic winds and mass outflows are observed both in nearby starburst
galaxies and in high-redshift star-forming galaxies. In this paper we develop a
simple analytic model to understand the observed superwind phenomenon. Our
model is built upon the model of McKee & Ostriker (1977) for the interstellar
medium. It allows one to predict how properties of a superwind, such as wind
velocity and mass outflow rate, are related to properties of its star-forming
host galaxy, such as size, gas density and star formation rate. The model
predicts a threshold of star formation rate density for the generation of
observable galactic winds. Galaxies with more concentrated star formation
produce superwinds with higher velocities. The predicted mass outflow rates are
comparable to (or slightly larger than) the corresponding star formation rates.
We apply our model to both local starburst galaxies and high-redshift Lyman
break galaxies, and find its predictions to be in good agreement with current
observations. Our model is simple, and so can be easily incorporated into
numerical simulations and semi-analytical models of galaxy formation.


title: The SU UMa Nature of the Dwarf Nova, DM Lyrae

abstract:
  We carried out time-resolved $V$-band photometry of DM Lyr during long
outbursts in 1996 July and in 1996 February-March at Ouda Station, Kyoto
University and at Osaka Kyoiku University. Since superhumps were clearly
detected in the light curves, DM Lyr was first identified with an SU UMa-type
dwarf nova. The superhump period is 0.0673(2) d, and the superhump excess is
2.8(3) %. The duration of the superoutburst, the outburst amplitude, the
decline rate in the plateau phase, and the superhump excess were typical values
for a usual SU UMa star. According to visual and CCD observations reported to
VSNET, this star has experienced a dramatic change of the outburst pattern from
a superoutburst phase to a normal outburst phase. There may exist mechanisms to
decrease the number of the normal outburst between two successive
superoutbursts and to elongate the recurrence cycle of the superoutburst.


title: Strong gravitational lensing and galactic bulges

abstract:
  Lensing probabilities of quasars with image separations greater than
\Delta\theta and flux density ratios less than q_{\mathrm{r}} are calculated by
foreground dark matter halos in a flat, cosmological constant dominated
(\LambdaCDM) universe . The mass density of the lenses is taken to be the
Navarro-Frenk-White (NFW) profile on all mass scales, plus a central point mass
for low-mass halos with M<M_c=5\times 10^{13}h^{-1}M_{\odot}. We introduce a
quantity M_{\mathrm{eff}}, which is a point mass ranging from 1 to 1000 times
the mass M_{\bullet} of a supermassive black hole (SMBH) inhabiting the center
of each galaxy, to describe the contributions of galactic central SMBHs and
galactic bulges to lensing probabilities. The lensing cross section and thus
the lensing probability are quite sensitive to the flux density ratio
q_{\mathrm{r}} of multiple images in our calculations. It is shown that, to
reproduce the lensing survey results of JVAS/CLASS for q_{\mathrm{r}}<10, about
20% of the bulge mass is needed as a point mass for each galaxy. Since there is
still considerable uncertainty regarding the value of the spectrum
normalization parameter \sigma_8, we investigate the effect of varying this
parameter within its entire observational range (from 0.7 to 1.1), and find
that low \sigma_8 values (\leq 0.7) are ruled out, and the best fit value is
\sigma_8\simeq 1.0.


title: The Cluster Wind from Local Massive Star Clusters

abstract:
  Results of a study of the theoretically predicted and observed X-ray
properties of local massive star clusters are presented, with a focus on
understanding the mass and energy flow from these clusters into the ISM via a
cluster wind. A simple theoretical model, based on the work of Chevalier &
Clegg (1985), is used to predict the theoretical cluster properties, and these
are compared to those obtained from recent Chandra observations. The model
includes the effect of lower energy transfer efficiency and mass-loading. In
spite of limited statistics, some general trends are indicated; the observed
temperature of the diffuse X-ray emission is lower than that predicted from the
stellar mass and energy input rates, but the predicted scaling of X-ray
luminosity with cluster parameters is seen. The implications of these results
are discussed.


title: Extreme Energy Cosmic Rays: Bottom-up vs. Top-down scenarii

abstract:
  We present an overview on extreme energy cosmic rays (EECR) and the
fundamental physics connected with them. The top-down and bottom-up scenarii
are contrasted. We summarize the essential features underlying the top-down
scenarii for EECR, namely, the lifetime and the mass {\bf imposed} to the heavy
relics whatever they be: topological and non-topological solitons, X-particles,
cosmic defects, microscopic black-holes, fundamental strings. An unified
formula for the quantum decay rate of all these objects was provided in
hep-ph/0202249. The key point in the top-down scenarii is the necessity to {\bf
adjust} the lifetime of the heavy object to the age of the universe. The
natural lifetimes of such heavy objects are, however, microscopic times
associated to the GUT energy scale (sim 10^{-28} sec. or shorter); such heavy
objects could have been abundantly formed by the end of inflation and it seems
natural they decayed shortly after being formed. The arguments produced to {\bf
fine tune} the relics lifetime to the age of the universe are critically
analyzed. The annihilation scenario (`Wimpzillas') is analyzed too. Top-down
scenarii based on networks of topological defects are strongly disfavored at
the light of the recent CMB anisotropy observations. We discuss the
acceleration mechanisms of cosmic rays,their possible astrophysical sources and
the main open physical problems and difficulties in the context of bottom-up
scenarii, and we conclude by outlining the expectations from future
observatories like EUSO and where the theoretical effort should be placed.


title: Studying the Evolving Universe with XMM-Newton and Chandra

abstract:
  First indications of the warm/hot intergalactic medium, tracing out the large
scale structure of the universe, have been obtained in sensitive Chandra and
XMM-Newton high resolution absorption line spectroscopy of bright blazars. High
resolution X-ray spectroscopy and imaging also provides important new
constraints on the physical condition of the cooling matter in the centers of
clusters, requiring major modifications to the standard cooling flow models.
XMM-Newton and Chandra low resolution spectroscopy detected significant Fe
K_alpha absorption features in the spectrum of the ultraluminous, high redshift
lensed broad absorption line QSO APM 08279+5255, yielding new insights in the
outflow geometry indicating a supersolar Fe/O ratio. Chandra high resolution
imaging spectroscopy of the nearby ULIRG/obscured QSO NGC 6240 for the first
time gave evidence of two active supermassive black holes in the same galaxy,
likely bound to coalesce in the course of the ongoing major merger in this
galaxy. Deep X-ray surveys have shown that the cosmic X-ray background (XRB) is
largely due to the accretion onto supermassive black holes, integrated over the
cosmic time. These surveys have resolved more than 80% of the X-ray background
into discrete sources. Optical spectroscopic identifications show that the
sources producing the bulk of the X-ray background are a mixture of obscured
(type-2) and unobscured (type-1) AGNs, as predicted by the XRB population
synthesis models. A class of highly luminous type-2 AGN, so called QSO-2s, has
been detected in the deepest Chandra and XMM-Newton surveys. The new Chandra
AGN redshift distribution peaks at much lower redshifts (z~0.7) than that based
on ROSAT data, indicating that the evolution of Seyfert galaxies occurs at
significantly later cosmic time than that of QSOs.


title: Star cluster ecology V: Dissection of an open star cluster--spectroscopy

abstract:
  We have modeled in detail the evolution of rich open star clusters such as
the Pleiades, Praesepe and Hyades, using simulations that include stellar
dynamics as well as the effects of stellar evolution. The dynamics is modeled
via direct N-body integration, while the evolution of single stars and binaries
is followed through the use of fitting formulae and recipes. The feedback of
stellar and binary evolution on the dynamical evolution of the stellar system
is taken into account self-consistently. Our model clusters dissolve in the
tidal field of the Galaxy in a time span on the order of a billion years. The
rate of mass loss is rather constant, about 1Msun per million years. The binary
fraction at first is nearly constant in time, then increases slowly near the
end of a cluster's lifetime. For clusters which are more than about 100 million
years old the fractions of stars in the form of binaries, giants and collision
products in the inner few core radii are considerably higher than in the outer
regions, beyond the cluster's half mass radius. When stars with masses >2Msun
escape from the cluster, they tend to do so with velocities higher than
average....
  <Abstract abbreviated, read manuscript for rest>


title: Implications of 2dFGRS results on cosmic structure

abstract:
  The 2dF Galaxy Redshift Survey is the first to observe more than 100,000
redshifts, making possible precise measurements of many aspects of galaxy
clustering. The spatial distribution of galaxies can be studied as a function
of galaxy spectral type, and also of broad-band colour. Redshift-space
distortions are detected with a high degree of significance, confirming the
detailed Kaiser distortion from large-scale infall velocities, and measuring
the distortion parameter beta = Omega_m^{0.6}/b = 0.49 +- 0.09. The power
spectrum is measured to <10% accuracy for k > 0.02 h Mpc^{-1}, and is well
fitted by a CDM model with Omega_m h =0.18 +- 0.02 and a baryon fraction of
0.17 +- 0.06. A joint analysis with CMB data requires Omega_m = 0.31 +- 0.05
and h = 0.67 +- 0.04, assuming scalar fluctuations. The fluctuation amplitude
from the CMB is sigma_8 = 0.76 +- 0.04, assuming reionization at z < approx 10,
so that the general level of galaxy clustering is approximately unbiased, in
agreement with an internal bispectrum analysis. Luminosity dependence of
clustering is however detected at high significance, and is well described by a
relative bias of b/b^* = 0.85 + 0.15(L/L^*). This is consistent with the
observation that L^* in rich clusters is brighter than the global value by 0.28
+- 0.08 mag.


title: Evolution of CNO abundances in the Universe

abstract:
  After summarizing the most important features of current stellar yields of
CNO elements (including recent results concerning rotating and mass losing
stars) I discuss how these yields may help to interpret relevant observations
in the local Galaxy, the Milky Way disk and extragalactic systems
(extragalactic HII regions and DLAs).


title: Further Discoveries of 12CO in Low Surface Brightness Galaxies

abstract:
  Using the IRAM 30m telescope we have obtained seven new, deep CO J(1-0) and
J(2-1) observations of low surface brightness (LSB) galaxies. Five of the
galaxies have no CO detected to extremely low limits (0.1-0.4 K km/s at
J(1-0)), while two of the galaxies, UGC 01922 and UGC 12289, have clear
detections in both line transitions. When these observations are combined with
all previous CO observations taken of LSB systems, we compile a total of 34
observations, in which only 3 galaxies have had detections of their molecular
gas. Comparing the LSB galaxies with and without CO detections to a sample of
high surface brightness (HSB) galaxies with CO observations indicates that it
is primarily the low density of baryonic matter within LSB galaxies which is
causing their low CO fluxes. Finally, we note that one of the massive LSB
galaxies studied in this project, UGC 06968 (a Malin-1 `cousin'), has upper
limits placed on both M_H2 and M_H2/M_HI which are 10-20 times lower than the
lowest values found for any galaxy (LSB or HSB) with similar global properties.
This may be due to an extremely low temperature and metallicity within UGC
06968, or simply due to the CO distribution within the galaxy being too diffuse
to be detected by the IRAM beam.


title: Implementing TOPbase/Iron Project: Continuous Absorption from Fe II

abstract:
  We discuss implementation of TOPbase and Iron Project opacities for stellar
spectral codes. We use a technique employed by Peach, where a
Boltzmann-averaged cross section is calculated for selected temperatures, and
the opacity obtained from double interpolation in temperature and wavelength.
It is straightforward to include {\it all} levels for which cross sections have
been calculated. Boltzmann-averaged cross sections for Fe II show a local
maximum between 1700 and 2000[A]. We suggest this feature arises from 3d^5 4snl
to 3d^5 4pnl transitions within Fe II. IUE spectra of iron-rich CP stars show
local minima in this region. Theoretical calculations of a representative
stellar continuum demonstrate that Fe II photoionization contributes
significantly to the observed minima.


title:
The Origin of the Dust Arch in the Halo of NGC 4631: An Expanding
  Superbubble?

abstract:
  We study the nature and the origin of the dust arch in the halo of the
edge-on galaxy NGC 4631 detected by Neininger & Dumke (1999). We present CO
observations made using the new On-The-Fly mapping mode with the FCRAO 14m
telescope, and find no evidence for CO emission associated with the dust arch.
Our examination of previously published HI data shows that if previous
assumptions about the dust temperature and gas/dust ratio are correct, then
there must be molecular gas associated with the arch, below our detection
threshold. If this is true, then the molecular mass associated with the dust
arch is between 1.5 x 10^8 M(sun)and 9.7 x 10^8 M(sun), and likely towards the
low end of the range. A consequence of this is that the maximum allowed value
for the CO-to-H_2 conversion factor is 6.5 times the Galactic value, but most
likely closer to the Galactic value. The kinematics of the HI apparently
associated with the dust arch reveal that the gas here is not part of an
expanding shell or outflow, but is instead two separate features (a tidal arm
and a plume of HI sticking out into the halo) which are seen projected together
and appear as a shell. Thus there is no connection between the dust "arch" and
the hot X-ray emitting gas that appears to surround the galaxy Wang et al.
(2001).


title:
A Photometric and Spectroscopic Study of Dwarf and Giant Galaxies in the
  Coma Cluster - IV. The Luminosity Function

abstract:
  A large spectroscopic survey is constructed of galaxies in the Coma cluster.
The survey covers a wide area (1 deg$^2$) to deep magnitudes (R ~ 19.5),
covering both the core (high density) and outskirts (intermediate to low
density) of the cluster. The spectroscopic sample consists of a total of 1191
galaxies, of which, 760 galaxies are confirmed members of the Coma cluster. A
statistical technique is developed to correct the spectroscopic sample for
incompletness. The corrected sample is then used to construct R-band luminosity
function (LF) spanning a range of 7 magnitudes (-23 < M_R < -16) both at the
core and outskirts of the cluster.
  Dependence of the LF on local environment in Coma is explored. The LFs are
found to be the same, within the errors, between the inner and outer regions
and close to those from recent measurements for field galaxies. The total
B-band LF for the Coma cluster, fitted to a Schecter form is also measured and
shows a dip at M(B) = -18 mag., in agreement with previous studies. The
implications of this feature are discussed.
  The LF is studied in B-R color intervals and shows a steep faint-end slope
for red (B-R > 1.35) galaxies, both at the core and outskirts of the cluster.
This population of low luminosity red galaxies has a higher surface density
than the blue (B-R < 1.35) star-forming population, dominating the faint-end of
the Coma cluster LF. It is found that relative number of high surface
brightness galaxies is larger at the cluster core, implying destruction of low
surface brightness galaxies in dense core environment.


title: Mapping Magnetic Fields in the Cold Dust at the Galactic Center

abstract:
  We report the detection of polarized emission in the vicinity of the Galactic
center for 158 positions within eight different pointings of the Hertz
polarimeter operating on the Caltech Submillimeter Observatory. These pointings
include positions 2 arcminutes offset to the E, NE, and NW of M-0.02-0.07;
positions to the SE and NW of the 20 km/s cloud (M-0.13-0.08), CO+0.02-0.02,
M+0.07-0.08, and M+0.11-0.08. We use these data in conjunction with previous
far-infrared and submillimeter polarization results to find that the direction
of the inferred magnetic field is related to the density of the molecular
material in the following way: in denser regions, the field is generally
parallel to the Galactic plane, whereas in regions with lower densities, the
field is generally perpendicular to the plane. This finding is consistent with
a model in which an initially poloidal field has been sheared into a toroidal
configuration in regions that are dense enough such that the gravitational
energy density is greater than the energy density of the magnetic field. Using
this model, we estimate the characteristic strength of the magnetic field in
the central 30 pc of our Galaxy to be a few mG.


title:
The Birmingham-CfA cluster scaling project - I: gas fraction and the M-T
  relation

abstract:
  We have assembled a large sample of virialized systems, comprising 66 galaxy
clusters, groups and elliptical galaxies with high quality X-ray data. To each
system we have fitted analytical profiles describing the gas density and
temperature variation with radius, corrected for the effects of central gas
cooling. We present an analysis of the scaling properties of these systems and
focus in this paper on the gas distribution and M-T relation. In addition to
clusters and groups, our sample includes two early-type galaxies, carefully
selected to avoid contamination from group or cluster X-ray emission. We
compare the properties of these objects with those of more massive systems and
find evidence for a systematic difference between galaxy-sized haloes and
groups of a similar temperature. We derive a mean logarithmic slope of the M-T
relation within R_200 of 1.84+/-0.06, although there is some evidence of a
gradual steepening in the M-T relation, with decreasing mass. We recover a
similar slope using two additional methods of calculating the mean temperature.
Repeating the analysis with the assumption of isothermality, we find the slope
changes only slightly, to 1.89+/-0.04, but the normalization is increased by
30%. Correspondingly, the mean gas fraction within R_200 changes from
(0.13+/-0.01)h70^-1.5 to (0.11+/-0.01)h70^-1.5, for the isothermal case, with
the smaller fractional change reflecting different behaviour between hot and
cool systems. There is a strong correlation between the gas fraction within
0.3*R_200 and temperature. This reflects the strong (5.8 sigma) trend between
the gas density slope parameter, beta, and temperature, which has been found in
previous work. (abridged)


title: Next-generation test of cosmic inflation

abstract:
  The increasing precision of cosmological datasets is opening up new
opportunities to test predictions from cosmic inflation. Here we study the
impact of high precision constraints on the primordial power spectrum and show
how a new generation of observations can provide impressive new tests of the
slow-roll inflation paradigm, as well as produce significant discriminating
power among different slow-roll models. In particular, we consider
next-generation measurements of the Cosmic Microwave Background (CMB)
temperature anisotropies and (especially) polarization, as well as new
Lyman-$\alpha$ measurements that could become practical in the near future. We
emphasize relationships between the slope of the power spectrum and its first
derivative that are nearly universal among existing slow-roll inflationary
models, and show how these relationships can be tested on several scales with
new observations. Among other things, our results give additional motivation
for an all-out effort to measure CMB polarization.


title: High Contrast Imaging of Extrasolar Planets

abstract:
  Gaussian aperture pupil masks (GAPMs) can in theory achieve the contrast
requisite for directly imaging an extrasolar planet. We use lab tests and
simulations to further study their possible place as a high contrast imaging
technique. We present lab comparisons with traditional Lyot coronagraphs and
simulations of GAPMs and other high contrast imaging techniques on HST.


title: A New Transiting Extrasolar Giant Planet

abstract:
  We have measured radial velocities of a star, OGLE-TR-56, which shows a
1.2-day transit-like light curve found photometrically by Udalski et
al.(2002ab). Here we show that the velocity changes we detect are probably
induced by an object of 0.9 Jupiter masses - a very close-in gas-giant planet
only 0.023 AU from its star, with a planetary radius of 1.3 Jupiter radii and a
mean density of 0.5 g/cm3. At its small orbital distance, OGLE-TR-56b is hotter
than any known planet, approaching 1900K, but it is stable against long-term
evaporation or tidal disruption.


title: Low Frequency Coherence Break in The Soft X-ray State of GRS 1915+105

abstract:
  We present results from the analysis of X-ray power density spectra and
coherence when GRS 1915+105 is in soft states. We use three data sets that
belong to $\mu$, $\phi$ and $\delta$ classes in Belloni et al (2000). We find
that the power density spectra appear to be complex, with several features
between 0.01 and 10 Hz. The coherence deviates from unity above a
characteristic frequency. We discuss our results in different models. The
corona size in the sphere-disk model implied by this break frequency is on the
order of 10$^4$ GM/c$^2$, which is unphysical. Our results are more consistent
with the prediction of the model of a planar corona sustained by magnetic
flares, in which the characteristic frequency is associated with the longest
time-scale of an individual flare, which is about eight seconds.


title: Shear calibration biases in weak lensing surveys

abstract:
  We investigate biases induced by the conversion between the observed image
shape to shear distortion in current weak lensing analysis methods. Such
overall calibration biases cannot be detected by the standard tests such as E/B
decomposition or calibration with stars. We find that the non-Gaussianity of
point spread function has a significant effect and can lead to up to 15 per
cent error on the linear amplitude of fluctuations sigma_8 depending on the
method of analysis. This could explain some of the discrepancies seen in recent
amplitude determinations from weak lensing. Using an elliptical Laguerre
expansion method we develop a re-Gaussianization method which reduces the error
to calibration error of order 1 per cent even for poorly resolved galaxies. We
also discuss a new type of shear selection bias which results in up to roughly
8 percent underestimation of the signal. It is expected to scale with redshift,
inducing errors in the growth factor extraction if not properly corrected for.
Understanding and correcting for such effects is crucial if weak lensing is to
become a high precision probe of cosmology.


title:
Three New Long Period X-ray Pulsars Discovered in the Small Magellanic
  Cloud

abstract:
  The Small Magellanic Cloud is increasingly an invaluable laboratory for
studying accreting and isolated X-ray pulsars. We add to the class of compact
SMC objects by reporting the discovery of three new long period X-ray pulsars
detected with the {\it Chandra X-ray Observatory}. The pulsars, with periods of
152, 304 and 565 seconds, all show hard X-ray spectra over the range from 0.6 -
7.5 keV. The source positions of the three pulsars are consistent with known
H-alpha emission sources, indicating they are likely to be Be type X-ray binary
star systems.


title:
Possibly interacting Vorontsov-Velyaminov galaxies. II. The 6m telescope
  spectroscopy of VV 080, 131, 499, 523 and 531

abstract:
  In continuation of the program formulated in Paper I we present results of
long-slit spectroscopy with the Russian 6m telescope of five more objects from
the Vorontsov-Velyaminov Atlas and Catalogue of Interacting galaxies. These are
the galaxies for which the interaction is not evident, although all of them are
classified as multiple systems (usually as ``nests'', ``chains'' and similar
systems). The spectrophotometry data enable us to derive for all galaxies
abundances of O, and for some of them abundances of N, Ne and S. For two of
them chemical abundances are given for the first time. In spectra of three of
the studied galaxies [Oiii]4363 line is measured, and T_e and oxygen abundance
are derived by the classical method. For the two others, empirical methods are
used. For all 5 galaxies, the radial velocity distribution along the slit was
obtained in the Ha-line. The studied galaxies represent a rather mixed sample:
from very low luminosity irregular galaxies, like VV 499 (DDO 053), to rather
bright VV 523 (NGC 3991). Their metallicities vary from Z=1/25 Zo for VV 499 to
1/2 Zo for VV 523. The morphology of these galaxies ranges between typical dIrr
(VV 080) through ring-like (VV 131) to clumpy Irr (VV 523). Position--Velocity
diagrams in the Ha-line along the galaxy body imply the existence of
large-scale ionized gas outflows/supershells around the sites of intense
current and/or recent SF activity. Sizes of supershells vary in the range of
several hundred pc to about 2 kpc. For all studied galaxies we examine their
local environment and indicate the nearest neighbouring objects capable of
inducing the observed enhanced star formation.


title: VLBI Imaging of Seyfert Galaxies

abstract:
  The advent of the Very Long Baseline Array and its phase-referencing
capability have enabled milliarcsecond-scale imaging of radio sources at
sub-millijansky sensitivity, opening the door to high-resolution imaging of
Seyfert galaxies. Over the last few years, this has led to a number of
interesting new results that shed light on the characteristics of the inner
cores of Seyfert galaxies. These include the following: (1) classical Seyfert
galaxies with steep radio spectra have a strong tendency to exhibit radio jets
at milliarcsecond scales, sometimes with considerable curvature in the jets;
(2) apparent speeds of jets imaged at multiple epochs generally are
considerably less than c, often in the vicinity of 0.1c or less, although there
sometimes are faster motions seen after strong outbursts; and (3) lower
luminosity Seyfert galaxies have a much stronger tendency to show flat or
somewhat inverted radio spectra, usually are unresolved on milliarcsecond
scales, and probably are dominated by a combination of low-radiative-efficiency
accretion flows and very compact radio jets. This paper discusses some examples
that illustrate these properties, and summarizes some of what we have learned
about weak active galaxies on milliarcsecond scales.


title: Wavelet Band Powers of the Primordial Power Spectrum from CMB Data

abstract:
  Measuring the primordial matter power spectrum is our primary means of
probing unknown physics in the very early universe. We allow the primordial
power spectrum to be an arbitrary function, and parametrize it in terms of
wavelet band powers. Current cosmological data correspond to 11 such wavelet
bands. We derive constraints on these band powers as well as $H_0$, $\Omega_b
h^2$ and $\Omega_m h^2$ from current Cosmic Microwave Background Anisotropy
(CMB) data using the Markov Chain Monte Carlo (MCMC) technique. Our results
indicate a feature in the primordial power spectrum at $ 0.008 \la k/(h
{Mpc}^{-1}) \la 0.1$. MAP and Planck data should allow us to put tighter
constraints on the primordial power spectrum.


title:
Hubble Space Telescope and Ground-Based Optical and Ultraviolet
  Observations of GRB010222

abstract:
  We report on Hubble Space Telescope WFPC2 optical and STIS near ultraviolet
MAMA observations, and ground-based optical observations of GRB010222, spanning
15 hrs to 71 days. The observations are well-described by a relativistic
blast-wave model with a hard electron-energy distribution, p = 1.57, and a jet
transition at t_j=0.93 days. These values are slightly larger than previously
found as a result of a correction for the contribution from the host galaxy to
the late-time ground-based observations and the larger temporal baseline
provided by the Hubble Space Telescope observations. The host galaxy is found
to contain a very compact core (size <0.25 arcsec) which coincides with the
position of the optical transient. The STIS near ultraviolet MAMA observations
allow for an investigation of the extinction properties along the line of sight
to GRB010222. We find that the far ultraviolet curvature component (c_4) is
rather large. In combination with the low optical extinction A_V =0.11 mag,
when compared to the Hydrogen column inferred from X-ray observations, we
suggest that this is evidence for dust destruction.


title: Massive Quiescent Cores in Orion. I. Temperature Structure

abstract:
  We have mapped four massive cores in Orion using the \ammonia (J,K) = (1,1)
and (J,K) = (2,2) inversion transitions, as part of our effort to study the
pre--protostellar phase of massive star formation. These cores were selected to
be quiescent, i.e. they contain no apparent IR sources and are not associated
with any molecular outflows. These cores are one order of magnitude more
massive than dark cloud cores and have about twice the line width. This paper
focuses on their temperature structure. We find a statistically significant
correlation between the gas kinetic temperature and the gas column density. The
general trend is for the gas to be colder where the column density is higher,
which we interpret to mean that the interiors of these cores are colder than
the regions surrounding them. This is in contrast with dark cloud cores, which
exhibit relatively flat temperature profiles. The temperature gradient within
the massive quiescent Orion cores is consistent with an external radiation
source heating the dust, and dust--gas collisions providing relatively close
coupling between dust and gas temperatures. From linewidth and temperature, we
also obtained the spatial distribution of the turbulence. An anticorrelation is
found between the intensity of emission and the degree of turbulence. Thus, we
suggest that the initial stage of massive pre--protostellar cloud cores is
relatively quiescent condensations which are cooler than their surroundings.


title: The 2001 Astronomy Job Market

abstract:
  An overview of the 2001 astronomy job market is presented, highlighting the
recent hiring trends which prospective PhD students and postdocs might like to
be aware of. Cosmology and extragalactic astronomy continue to dominate the
market, with theory/computational positions now outstripping the number of pure
observational ones. A biased recipe-for-success is presented which students and
postdocs should feel free to discuss, dismiss, or approach the author for
details.


title:
Compressible Magnetohydrodynamic Turbulence: mode coupling, scaling
  relations, anisotropy, new regime and astrophysical implications

abstract:
  We present numerical simulations and explore scalings and anisotropy of
compressible magnetohydrodynamic (MHD) turbulence. Our study covers both gas
pressure dominated (high beta) and magnetically dominated (low beta) plasmas at
different Mach numbers. In addition, we present results for superAlfvenic
turbulence and discuss in what way it is similar to the subAlfvenic turbulence.
We describe a technique of separating different magnetohydrodynamic (MHD) modes
(slow, fast and Alfven) and apply it to our simulations. We show that, for both
high and low beta cases, Alfven and slow modes reveal the Kolmogorov spectrum
(index=-5/3) and scale-dependent Goldreich-Sridhar anisotropy, while fast modes
exhibit spectrum with index=-3/2 and isotropy. We discuss the statistics of
density fluctuations arising from MHD turbulence at different regimes. Our
findings entail numerous astrophysical implications ranging from cosmic ray
propagation to gamma ray bursts and star formation. In particular, we show that
the rapid decay of turbulence reported by earlier researchers is not related to
compressibility and mode coupling in MHD turbulence. In addition, we show that
magnetic field enhancements and density enhancements are marginally correlated.
Addressing the density structure of partially ionized interstellar gas on AU
scales, we show that the new regime of MHD turbulence that we earlier reported
for incompressible flows persists for compressible turbulence and therefore may
provide an explanation for those mysterious structures.


title: The field brown dwarf LP 944-20 and the Castor moving group

abstract:
  A reliable age estimation for the field brown dwarf LP 944-20 is accomplished
through the analysis of its kinematic properties. The space velocities of this
star strongly suggest its membership in the so-called Castor moving group. LP
944-20 can be sensibly assumed to have the group's age, which is estimated to
be ~320 Myr, and metal content, which is found to be roughly solar. With these
new constrains and the available photometry and lithium abundance, current
brown dwarf models are put to a test. Using the IR magnitudes and the lithium
diagnostics, the models are able to provide a reasonable description of the
brown dwarf's properties (to within a few sigma) but yield an age which is
roughly 50% larger than our estimate. Possible reasons for this discrepancy are
discussed.


title: Geometry of weak lensing of CMB polarization

abstract:
  Hu [Phys. Rev. D62 (2000) 043007] has presented a harmonic-space method for
calculating the effects of weak gravitational lensing on the cosmic microwave
background (CMB) over the full sky. Computing the lensed power spectra to first
order in the deflection power requires one to formulate the lensing
displacement beyond the tangent-space approximation. We point out that for CMB
polarization this displacement must undergo geometric corrections on the
spherical sky to maintain statistical isotropy of the lensed fields. Although
not discussed by Hu, these geometric effects are implicit in his analysis.
However, there they are hidden by an overly-compact notation that is both
unconventional and rather confusing. Here we aim to ameliorate this deficiency
by providing a rigorous derivation of the lensed spherical power spectra.