title: Signatures of AGN model for UHECR

abstract:
  We demonstrate that the energy spectra of Ultra High Energy Cosmic rays
(UHECR) as observed by AGASA, Fly's Eye, HiRes and Yakutsk detectors, have the
imprints of UHE proton interaction with the CMB radiation in the form of the
dip at $E\sim 1\times 10^{19}$~ eV, of the beginning of the GZK cutoff, and of
very good agreement with calculated spectrum shape. We argue that these data,
combined with small-angle clustering and correlation with AGN (BL Lacs), point
to the AGN model of UHECR origin at energies $E \lsim 1\times 10^{20}$ eV. The
excess of the events at $E \gsim 1\times 10^{20}$ eV, which is observed by
AGASA (but absent in HiRes data) can be explained by another component of
UHECR, e.g. by UHECR from superheavy dark matter.


title: Benchmark Parameters for CMB Polarization Experiments

abstract:
  The recently detected polarization of the cosmic microwave background (CMB)
holds the potential for revealing the physics of inflation and gravitationally
mapping the large-scale structure of the universe, if so called B-mode signals
below 10^{-7}, or tenths of a uK, can be reliably detected. We provide a
language for describing systematic effects which distort the observed CMB
temperature and polarization fields and so contaminate the B-modes. We identify
7 types of effects, described by 11 distortion fields, and show their
association with known instrumental systematics such as common mode and
differential gain fluctuations, line cross-coupling, pointing errors, and
differential polarized beam effects. Because of aliasing from the small-scale
structure in the CMB, even uncorrelated fluctuations in these effects can
affect the large-scale B modes relevant to gravitational waves. Many of these
problems are greatly reduced by having an instrumental beam that resolves the
primary anisotropies (FWHM << 10'). To reach the ultimate goal of an
inflationary energy scale of 3 \times 10^{15} GeV, polarization distortion
fluctuations must be controlled at the 10^{-2}-10^{-3} level and temperature
leakage to the 10^{-4}-10^{-3} level depending on effect. For example pointing
errors must be controlled to 1.5'' rms for arcminute scale beams or a percent
of the Gaussian beam width for larger beams; low spatial frequency differential
gain fluctuations or line cross-coupling must be eliminated at the level of
10^{-4} rms.


title: A Keplerian disk around the Herbig Ae star HD 34282

abstract:
  We report new millimeter observations of the circumstellar material
surrounding the Herbig Ae A0.5 star HD 34282 performed with the IRAM array in
CO J=2-1 and in continuum at 1.3 mm. These observations have revealed the
existence of a large Keplerian disk around the star. We have analysed
simultaneously the line and continuum emissions to derive the physical
properties of both the gas and the dust. The analysis of our observations also
shows that the Hipparcos distance to the star is somewhat underestimated ; the
actual distance is probably about 400 pc. With this distance the disk around HD
34282 appears more massive and somewhat hotter than the observed disks around
less massive T Tauri stars, but shares the general behaviour of passive disks.


title:
Uncovering Additional Clues to Galaxy Evolution. I. Dwarf Irregulars in
  the Field

abstract:
  In order to recognize environmental effects on the evolution of dwarf
galaxies in clusters of galaxies, it is first necessary to quantify the
properties of objects which have evolved in relative isolation. With oxygen
abundance as the gauge of metallicity, two key diagnostics of the evolution of
dwarf irregular galaxies in the field are re-examined: the
metallicity-luminosity relationship and the metallicity-gas fraction
relationship. Gas fractions are evaluated from the masses of luminous
components only, i.e., constituents of the nucleogenetic pool. Results from new
optical spectroscopy obtained for H II regions in five dwarf irregular galaxies
in the Local Volume are incorporated into a new analysis of field dwarfs with
[O III]4363 detections and good distances. The updated fit to the
metallicity-luminosity relationship is consistent with results reported in the
literature. The fit to the metallicity-gas fraction relation shows an excellent
correlation consistent with expectations of the simple "closed box" model of
chemical evolution. The simplest explanation consistent with the data is that
flow rates are zero, although the observations allow for the possibility of
modest flows. The derived oxygen yield is one-quarter of the value for the
solar neighbourhood.


title: Analytic Lightcurves for Planetary Transit Searches

abstract:
  We present exact analytic formulae for the eclipse of a star described by
quadratic or nonlinear limb darkening. In the limit that the planet radius is
less than a tenth of the stellar radius, we show that the exact lightcurve can
be well approximated by assuming the region of the star blocked by the planet
has constant surface brightness. We apply these results to the HST observations
of HD 209458, showing that the ratio of the planetary to stellar radii is
0.1207+-0.0003. These formulae give a fast and accurate means of computing
lightcurves using limb-darkening coefficients from model atmospheres which
should aid in the detection, simulation, and parameter fitting of planetary
transits.


title:
A qualitative and numerical study or the matter-radiation interaction in
  Kantowski-Sachs cosmologies

abstract:
  We examine, from both a qualitative and a numerical point of view, the
evolution of Kantowski--Sachs cosmological models whose source is a mixture of
a gas of weakly interacting massive particles (WIMP's) and a radiative gas made
up of a ``tightly coupled'' mixture of electrons, baryons and photons from the
end of nucleosynthesis up to the duration of radiative interactions. In this
cosmic era annihilation processes are negligible, while the WIMP's only
interact gravitationally with the radiative gas and the latter behaves as a
single dissipative fluid that can be studied within a hydrodynamical framework.
Applying the full transport equations of Extended Irreversible Thermodynamics,
coupled with the field and balance equations, we obtain a set of governing
equations that becomes an autonomous system of ordinary differential equations
once the shear viscosity relaxation time is specified; assuming the latter to
be proportional to the Hubble time, the qualitative analysis indicates that
models begin in the radiation dominated epoch close to an isotropic equilibrium
point. We show how the relaxation time governs the relaxation of the models
towards an equilibrium photon entropy, leading to ``near-Eckart'' and transient
regimes associated with `abrupt' and `smooth' relaxation processes,
respectively. Assuming the WIMP particle to be a super-symmetric neutralino of
a 100$ GeV, the numerical analysis reveals that a physically plausible
evolution, compatible with a stable equilibrium state and with observed bounds
on CMB anisotropies and neutralino abundance, is only possible for models
characterized by initial conditions associated with nearly zero spatial
curvature and total initial energy density very close to unity.


title:
KISS AGNs in the Soft X-ray Band: Correlation with the ROSAT All-Sky
  Survey

abstract:
  We present a study of the X-ray properties of a volume-limited sample of
optically selected emission-line galaxies. The sample is derived from a
correlation between the KPNO International Spectroscopic Survey (KISS), an
H-alpha-selected objective-prism survey of AGNs and starbursting galaxies, and
the ROSAT All-Sky Survey (RASS). After elimination of all spurious matches, we
identify 18 ROSAT-detected X-ray sources within the KISS sample in the 0.1-2.4
keV band. Due to soft X-ray selection effects, the majority of the ROSAT
sources are Seyfert 1 galaxies. The majority (54%) of the ROSAT-KISS Seyferts
are classified as narrow-line Seyfert 1 objects, a relatively high percentage
compared to previous objective-prism-selected Seyfert galaxy samples. We
estimate the X-ray luminosities of the ROSAT-detected KISS objects and derive
volume emissivities of 6.63 x 10^38 ergs/s/Mpc^3 and 1.45 x 10^38 ergs/s/Mpc^3
for the 30 deg and 43 deg survey strips, respectively. For those KISS AGNs not
detected by RASS, we use the median L_X/L_H-alpha ratio derived from a previous
study to estimate L_X. The total 0.5-2 keV volume emissivity we predict for the
overall KISS AGN sample is sufficient to account for 22.1 +/- 8.9% of the soft
X-ray background (XRB), averaged over both survey strips. The KISS AGN sample
is made up predominantly of intermediate-luminosity Seyfert 2's and LINERs,
which tend to be weak soft X-ray sources. They may, however, represent a much
more significant contribution to the hard XRB.


title: Linear and Circular Polarization Properties of Jets

abstract:
  I discuss the transfer of polarized synchrotron radiation in relativistic
jets. I argue that the main mechanism responsible for the circular polarization
properties of compact synchrotron sources is likely to be Faraday conversion
and that, contrary to common expectation, a significant rate of Faraday
rotation does not necessarily imply strong depolarization. The long-term
persistence of the sign of circular polarization, observed in some sources, is
most likely due to a small net magnetic flux generated in the central engine,
carried along the jet axis and superimposed on a highly turbulent magnetic
field. I show that the mean levels of circular and linear polarizations depend
on the number of field reversals along the line of sight and that the gradient
in Faraday rotation across turbulent regions can lead to "correlation
depolarization''. The model is potentially applicable to a wide range of
synchrotron sources. In particular, I demonstrate how the model can naturally
explain the excess of circular over linear polarization in the Galactic Center
(Sgr A*) and the low-luminosity AGN M81*.


title: Force Free Waves and Black Hole Magnetospheric Causality

abstract:
  The force free approximation is often useful when describing tenuous plasmas
in strong cosmic magnetic fields. Time evolution of any such system is governed
by the information that can be transported along the characteristics of the
plasma modes allowed by the force free constraint. This brief article
elucidates, for the first time, the nature of the information that can be
transported along the characteristics for each of the two plasma modes, the
Alfven and fast modes. It is reassuring that these modes behave as one would
expect if the perfect magnetohydrodynamic (MHD) modes in a magnetically
dominated plasma were evaluated in the limit of zero plasma inertia (i.e., only
allowed to propagate information consistent with the force free constraint).
There are no properties of these waves that do not exist within the MHD theory,
when this additional constraint on the current is imposed. The results of the
characteristic analysis elucidates the nature of the causality violation in
force free black hole magnetospheres. The most significant result from the
standpoint of global causality is that charge and current perturbations can not
be transported along the fast mode short wavelength characteristics in the
force free limit.


title:
Spectroscopy of Low Surface Brightness Galaxies with the Hobby-Eberly
  Telescope

abstract:
  We have obtained low resolution spectra of nineteen red and blue low surface
brightness galaxies, using the Marcario Low Resolution Spectrograph on the 9.2m
Hobby-Eberly Telescope. These galaxies form a very heterogeneous class, whose
spectra qualitatively resemble those of high surface brightness galaxies
covering the full range of spectra seen in galaxies of Hubble types from E to
Irr. We use a combination of emission line (EW(Halpha), NII/Halpha) and
absorption line (Mgb, Hbeta, <Fe>) based diagnostics to investigate the
star-formation and chemical enrichment histories of these galaxies. These are
diverse, with some galaxies having low metallicity and very young mean stellar
ages, and other galaxies showing old, super-solar metallicity stellar
populations. In contrast with some previous studies which found a strong trend
of decreasing metallicity with decreasing central surface brightness, we find a
population of galaxies with low surface brightness and near-solar metallicity.
Correlations between several of the gas phase and stellar population age and
metallicity indicators are used to place contraints on plausible evolutionary
scenarios for LSB galaxies. The redshift range spanned by these galaxies is
broad, with radial velocities from 3400 km/s to more than 65000 km/s. A subset
of the sample galaxies have published HI redshifts and gas masses based on
observations with the Arecibo 305m single-dish radio telescope, which place
these galaxies far off of the mean Tully-Fisher relation. Our new optical
redshifts do not agree with the published HI redshifts for these galaxies. Most
of the discrepancies can be explained by beam confusion in the Arecibo
observations, causing erroneous HI detections for some of the galaxies.


title: Shock-Wave Cosmology Inside a Black Hole

abstract:
  We construct a class of global exact solutions of the Einstein equations that
extend the Oppeheimer-Snyder (OS) model to the case of non-zero pressure, {\em
inside the Black Hole}, by incorporating a shock wave at the leading edge of
the expansion of the galaxies, arbitrarily far beyond the Hubble length in the
Friedmann-Robertson-Walker (FRW) spacetime. Here the expanding FRW universe
emerges behind a subluminous blast wave that explodes outward from the FRW
center at the instant of the Big Bang. The total mass behind the shock
decreases as the shock wave expands, and the entropy condition implies that the
shock wave must weaken to the point where it settles down to an OS interface,
(bounding a {\em finite} total mass), that eventually emerges from the White
Hole event horizon of an ambient Schwarzschild spacetime. The entropy condition
breaks the time symmetry of the Einstein equations, selecting the explosion
over the implosion. These shock wave solutions indicate a new cosmological
model in which the Big Bang arises from a localized explosion occurring inside
the Black Hole of a Schwarzschild spacetime.


title: Component Masses of the Young Spectroscopic Binary UZ Tau E

abstract:
  We report estimates of the masses of the component stars in the
pre-main-sequence spectroscopic binary UZ Tau E. These results come from the
combination of our measurements of the mass ratio, M2/M1=0.28 +/-0.01, obtained
using high resolution H-band spectroscopy, with the total mass of the system,
(1.31 +/-0.08)(D/140pc) M_sun, derived from millimeter observations of the
circumbinary disk (Simon et al. 2000). The masses of the primary and secondary
are (1.016 +/-0.065)(D/140pc) M_sun and (0.294 +/-0.027)(D/140pc) M_sun,
respectively. Using the orbital parameters determined from our six epochs of
observation, we find that the inclination of the binary orbit, 59.8 +/-4.4
degrees, is consistent with that determined for the circumbinary disk from the
millimeter observations, indicating that the disk and binary orbits are
probably coplanar.


title:
Gravitational Lensing Magnification and Time Delay Statistics for
  Distant Supernovae

abstract:
  Strong gravitational lensing of distant supernovae (SNe), particularly Type
Ia's, has some exploitable properties not available when other sorts of
cosmologically distant sources are lensed. One such property is that the
``standard candle'' nature of the SN at peak brightness allows a direct
determination of the lensing magnification factor for each well observed image.
Another is that the duration of an SN event is of the same order as the
differential time delays between the various lens images. The comparable time
scales of the photometric event and the time delay invite a variety of
applications, including high precision measurements of the delay and the
targeting of especially interesting phases of the explosion for intensive
observation when they appear in trailing images. As an initial exploration of
these possibilities we present calculations of SN lensing statistics in a
``concordance cosmology''. We emphasize magnification and time delay effects.
Plausible SN surveys, such as the proposed SNAP space mission, would discover
several to some tens of strongly lensed SNe Ia per year, and at least a few of
these will be at redshifts well beyond those that would be accessible via
unlensed events. The total number of such anomalously high redshift SNe Ia will
be a useful test of high redshift star formation models. SN surveys of finite
duration will, of course, miss the appearance of some images; we quantify this
selection bias. Finally, we investigate how well the appearance of trailing
images can be predicted based on various amounts of available information on
the lensing event. Knowledge of the magnification factor for the leading image
makes it possible to predict the appearance of a trailing image relatively
accurately if the lens redshift is also known. (Abridged)


title: A Model of the Universe including dark Energy

abstract:
  In this work we explore a model of the universe in which dark energy is
modelled explicitely with both a dynamical quintessence field (with a double
exponential self-interaction potential) and a cosmological constant. For a
given region of the parameter space, our results confirm the possibility of a
collapsing universe, which is necessary for an adequate definition of both
perturbative quantum field and string theories. We have also reproduced the
measurements of modulus distance from supernovae with good accuracy.


title:
Systematic effects in the measurement of polarization by the PLANCK
  telescope

abstract:
  We present estimates of the response to polarized signals by the PLANCK
telescope. These estimates are based on a set of simulations, using a physical
optics code (GRASP8), for linearly polarized detectors at different frequencies
and located in different positions of an early design of the PLANCK focal
plane. We show how the optical aberration introduced by the studied focal plane
configuration affects absolute and relative orientation of the sky signals
polarization planes. In addition, we compute the spurious signal introduced by
the telescope optics into a PLANCK-type measurement of the sky polarization.
Our analysis shows that the spurious polarization expected in a PLANCK-like
experiment is typically of the order of 0.2 % of the unpolarized intensity.


title: An improvement of the BeppoSAX LECS and MECS positioning accuracy

abstract:
  We present a study of the source positioning accuracy of the LECS and MECS
instruments on-board BeppoSAX. From the analysis of a sample of archival images
we find that a systematic error, which depends on the spacecraft roll angle and
has an amplitude of ~17'' for the LECS and ~27'' for the MECS, affects the sky
coordinates derived from both instruments. The error is due to a residual
misalignment of the two instruments with respect to the spacecraft Z axis
arisen from the presence of attitude inaccuracies in the observations used to
calibrate the pointing direction of LECS and MECS optical axes. Analytical
formulae to correct LECS and MECS sky coordinates are derived. After the
coordinate correction the 90% confidence level error radii are 16'' and 17''
for LECS and MECS respectively, improving by a factor of ~2 the source location
accuracy of the two instruments. The positioning accuracy improvement presented
here can significantly enhance the follow-up studies at other wavelengths of
the X-ray sources observed with LECS and MECS instruments.


title: The inner structure of Zeldovich' pancakes

abstract:
  The evolution of a planar perturbation in a Einstein-de Sitter Universe is
studied using a previously introduced Lagrangian scheme. An approximate
discrete dynamical system is derived, which describes the mass agglomeration
process qualitatively. Quantitative predictions for the late density profile
are obtained therefrom, and validated by numerical simulations. The main result
is a scaling regime for the density profile of a collapsing object of mass $M$
around cosmological coordinate $r^*$, $\rho(r)\sim
\frac{M}{d}(\frac{|r-r^*|}{d})^{-{1/4}}$. The characteristic scale of the
agglomeration, $d\sim (t/t_0)^{{4/9}}$, is an increasing function of
cosmological time $t$. The major part of the mass hence always lies in a region
with decreasing mass density. This shows that one-dimensional self-gravitating
motion is not sufficient to effectively drive structure formation in an
Einstein-de Sitter Universe. These results are compared with analogous
investigations for the adhesion model (Burgers equation with positive
viscosity), where the agglomeration is faster, and one-dimensional dynamics is
effective. We further study the mutual motion of two mass agglomerations, and
show that they oscillate around each other for long times, like two ``heavy
particles''. Individual particles in the two agglomerations do not mix
effectively on the time scale of the interagglomeration motion.


title: Improving the Accuracy of Cosmic Magnification Statistics

abstract:
  The systematic magnification of background sources by the weak
gravitational-lensing effects of foreground matter, also called cosmic
magnification, is becoming an efficient tool both for measuring cosmological
parameters and for exploring the distribution of galaxies relative to the dark
matter. We extend here the formalism of magnification statistics by estimating
the contribution of second-order terms in the Taylor expansion of the
magnification and show that the effect of these terms was previously
underestimated. We test our analytical predictions against numerical
simulations and demonstrate that including second-order terms allows the
accuracy of magnification-related statistics to be substantially improved. We
also show, however, that both numerical and analytical estimates can provide
only lower bounds to real correlation functions, even in the weak lensing
regime. We propose to use count-in-cells estimators rather than correlation
functions for measuring cosmic magnification since they can more easily be
related to correlations measured in numerical simulations.


title: Black hole masses of BL Lac objects

abstract:
  The correlation between black hole mass M(BH) and the central stellar
velocity dispersion sigma in nearby elliptical galaxies affords a novel way to
determine M(BH) in active galaxies. We report on measurements of sigma from
optical spectra of 7 BL Lac host galaxies. The range of sigma (160 - 290 km/s)
corresponds to estimated M(BH) of 5 x 10^7 - 9 x 10^8 Mo. The average ratio of
M(BH) to the host galaxy mass is 1.4 x 10^-3, consistent with that estimated in
other active and inactive galaxies. The range of sigma and M(BH) of the BL Lacs
are similar to those obtained for low redshift radio galaxies, in good
agreement with the predictions of the unified models for radio-loud active
galaxies.


title:
Constraints on the Neutron Star Magnetic Field of the two X-ray
  Transients SAX J1808.4-3658 and Aql X-1

abstract:
  The recently discovered coherent X-ray pulsations at a frequency of ~400 Hz
in SAX J1808.4-3658, together with a measure of the source luminosity in
quiescence, allow us to put an upper limit on the neutron star magnetic field,
that is B < 5 10^8 Gauss, using simple considerations on the position of the
magnetospheric radius during quiescent periods. Combined with the lower limit
inferred from the presence of X-ray pulsations, this constrains the SAX
J1808.4-3658 neutron star magnetic field in the quite narrow range (1-5) 10^8
Gauss. Similar considerations applied to the case of Aql X-1 give a neutron
star magnetic field lower than ~10^9 Gauss.


title: Internal Shocks and the Blazar Sequence

abstract:
  We consider the internal shock model as the dissipation mechanism responsible
for the emission in blazars. It has been shown that this model is successful in
reproducing the observed spectral energy distribution and the variability
properties of a powerful blazar like 3C 279. However, the blazar family covers
a wide range of spectral characteristics which appear to be correlated and the
whole class can be seen as a sequence: the frequency and the intensity of the
low energy versus high energy peak intensity increase with decreasing
luminosity. We show that the internal shock model can satisfactorily account
also for the properties of the low power blazars like BL Lac and Mkn 421 and it
is successful in reproducing the blazar sequence.


title: Black Hole Binary Dynamics

abstract:
  We discuss a new N-body simulation method for studying black hole binary
dynamics. This method avoids previous numerical problems due to large mass
ratios and trapped orbits with short periods. A treatment of relativistic
effects is included when the associated time-scale becomes small. Preliminary
results with up to N = 240 000 particles are obtained showing systematic
eccentricity growth until the relativistic regime is reached, with subsequent
coalescence in some cases.


title: Phase mixing of a three dimensional magnetohydrodynamic pulse

abstract:
  Phase mixing of a three dimensional magnetohydrodynamic (MHD) pulse is
studied in the compressive, three-dimensional (without an ignorable coordinate)
regime. It is shown that the efficiency of decay of an Alfvenic part of a
compressible MHD pulse is related linearly to the degree of non-planeness of
the pulse in the homogeneous transverse direction. In the developed stage of
phase mixing (for large times), coupling to its compressive part does not alter
the power-law decay of an Alfvenic part of a compressible MHD pulse. The same
applies to the dependence upon the resistivity of the Alfvenic part of the
pulse. All this implies that the dynamics of Alfven waves can still be
qualitatively understood in terms of the previous 2.5D models. Thus, the phase
mixing remains a relevant paradigm for the coronal heating applications in the
realistic 3D geometry and compressive plasma.


title: The Deep Lens Survey

abstract:
  The Deep Lens Survey (DLS) is a deep BVRz' imaging survey of seven 2x2 degree
fields, with all data to be made public. The primary scientific driver is weak
gravitational lensing, but the survey is also designed to enable a wide array
of other astrophysical investigations. A unique feature of this survey is the
search for transient phenomena. We subtract multiple exposures of a field,
detect differences, classify, and release transients on the Web within about an
hour of observation. Here we summarize the scientific goals of the DLS, field
and filter selection, observing techniques and current status, data reduction,
data products and release, and transient detections. Finally, we discuss some
lessons which might apply to future large surveys such as LSST.


title: Wolf-Rayets in IC10: Probing the Nearest Starburst

abstract:
  IC10 is the nearest starburst galaxy, as revealed both by its Halpha surface
brightness and the large number of Wolf-Rayet stars (WRs) per unit area. The
relative number of known WC- to WN-type WRs has been thought to be unusually
high (~2), unexpected for IC10's metallicity. In this Letter we report the
first results of a new and deeper survey for WRs in IC10. We sucessfully
detected all of the spectroscopically known WRs, and based upon comparisons
with a neighboring control field, estimate that the total number of WRs in IC10
is about 100. We present spectroscopic confirmation of two of our WR
candidates, both of which are of WN type. Our photometric survey predicts that
the actual WC/WN ratio is ~0.3. This makes the WC/WN ratio of IC 10 consistent
with that expected for its metallicity, but greatly increases the already
unusually high number of WRs, resulting in a surface density that is about 20
times higher than in the LMC. If the majority of these candidates are
spectroscopically confirmed, IC10 must have an exceptional population of high
mass stars.


title: Weak Lensing Discovery and Tomography of a Cluster at z=0.68

abstract:
  We report the weak lensing discovery, spectroscopic confirmation, and weak
lensing tomography of a massive cluster of galaxies at $z=0.68$, demonstrating
that shear selection of clusters works at redshifts high enough to be
cosmologically interesting. The mass estimate from weak lensing, $11.1 +- 2.8 x
10^{14} (r/Mpc)$ solar masses within projected radius r, agrees with that
derived from the spectroscopy ($\sigma_v = 980 km s^{-1}$), and with the
position of an arc which is likely to be a strongly lensed background galaxy.
The redshift estimate from weak lensing tomography is consistent with the
spectroscopy, demonstrating the feasibility of baryon-unbiased mass surveys.
This tomographic technique will be able to roughly identify the redshifts of
any dark clusters which may appear in shear-selected samples, up to z ~ 1.


title:
Carbon Abundances of Faint Stars in M13 - Evidence for Two Abundance
  Altering Mechanisms

abstract:
  We present an analysis of CH band strengths in Keck LRIS spectra of a sample
of 81 stars in M13 within 2 magnitudes of the main-sequence turnoff. The
subgiants clearly exhibit a substantial (a factor of ~ 6) spread in [C/Fe].
Moreover, the bulk of the subgiants possess C abundances larger than those
found among their more luminous counterparts. The turnoff stars themselves are
too warm for appreciable CH formation, but the relatively small range in the
observed CH band strength for stars just below the turnoff nevertheless
translates into this same spread in [C/Fe]. Still fainter, the sample size is
small, but the same range in [C/Fe] appears to be present. On the basis of
these observations we suggest that a process external to the present stars has
resulted in a substantial star-to-star dispersion in [C/Fe] (and possibly other
light elements) among all stars in M13. In addition, the surface C abundances
among the more luminous stars have been further modified by the operation of an
internal deep-mixing mechanism during red giant branch ascent. The amplitude of
the scatter we find in [C/Fe] at all luminosities may prove difficult to
explain via accretion from intermediate mass AGB stars as the external
"polluting" mechanism.


title:
The oscillation and stability of differentially rotating spherical
  shells: The normal mode problem

abstract:
  An understanding of the dynamics of differentially rotating systems is key to
many areas of astrophysics. We investigate the oscillations of a simple system
exhibiting differential rotation, and discuss issues concerning the role of
corotation points and the emergence of dynamical instabilities. This problem is
of particular relevance to the emission of gravitational waves from oscillating
neutron stars, which are expected to possess significant differential rotation
immediately after birth or binary merger.


title:
Star Formation Rate estimators: [OII]3727 vs. Halpha for local
  star-forming galaxies

abstract:
  The [OII]3727 emission line is frequently used as an indicator of the star
formation rate (SFR) despite its complex dependence on metallicity and
excitation conditions. We have analysed the properties of the [OII] and Halpha
emission lines for a complete sample of local Halpha-selected galaxies, the
Universidad Complutense de Madrid (UCM) survey. We find a large scatter in the
[OII]/Halpha line ratios, although the scatter in the extinction-corrected
[OII]^0/Halpha^0 ratio is considerably smaller. We also find that the
[OII]/Halpha ratios are reasonably well correlated with the absolute B- and
K-band magnitudes and with EW([OII]). However, the extinction-corrected
[OII]^0/Halpha^0 ratio is largely independent of these quantities, indicating
that extinction is the main driver of the correlations. These correlations
allow us to statistically predict--with varying degrees of accuracy--the
observed and extinction-corrected Halpha fluxes from the observed [OII] flux
using the information contained in EW([OII]) and/or the absolute magnitudes,
but extreme caution is needed to make sure that the sample selection effects
are correctly taken into account.


title: Quantum-Gravity Analysis of Gamma-Ray Bursts using Wavelets

abstract:
  In some models of quantum gravity, space-time is thought to have a foamy
structure with non-trivial optical properties. We probe the possibility that
photons propagating in vacuum may exhibit a non-trivial refractive index, by
analyzing the times of flight of radiation from gamma-ray bursters (GRBs) with
known redshifts. We use a wavelet shrinkage procedure for noise removal and a
wavelet `zoom' technique to define with high accuracy the timings of sharp
transitions in GRB light curves, thereby optimizing the sensitivity of
experimental probes of any energy dependence of the velocity of light. We apply
these wavelet techniques to 64 ms and TTE data from BATSE, and also to OSSE
data. A search for time lags between sharp transients in GRB light curves in
different energy bands yields the lower limit $M \ge 6.9 \cdot 10^{15}$ GeV on
the quantum-gravity scale in any model with a linear dependence of the velocity
of light $~ E/M$. We also present a limit on any quadratic dependence.


title: Observations of Neutron-Capture Elements in the Early Galaxy

abstract:
  Neutron-capture elements in low metallicity Galactic halo stars vary widely
both in overall contents and detailed abundance patterns. This review discusses
recent observational results on the n-capture elements, discussing the
implications for early Galactic nucleosynthesis of: (a) the star-to-star
``bulk'' variations in the n-capture/Fe abundance ratios; (b) the distinct
signature of rapid n-capture synthesis events in many (most?) of the lowest
metallicity stars; (c) the existence of metal-poor stars heavily enriched in
the products of slow n-capture synthesis reactions; and (d) the now-routine
detection of radioactive thorium (and even uranium in one and possibly two
cases) in the spectra of metal-poor stars.


title: Dynamics of the Lyman alpha and C IV emitting gas in 3C 273

abstract:
  In this paper we study the variability properties of the Lyman alpha and C IV
emission lines in 3C273 using archival IUE observations. Our data show for the
first time the existence of variability on time scales of several years. We
study the spatial distribution and the velocity field of the emitting gas by
performing detailed analyses on the line variability using correlations, 1D and
2D response functions, and principal component analysis. In both lines we find
evidence for two components, one which has the dynamic properties of gas in
Keplerian motion around a black hole with a mass of the order of 10^9 Mo, and
one which is characterized by high, blue-shifted velocities at large lag. There
is no indication of the presence of optically thick emission medium neither in
the Lya, nor in the Civ response functions. The component characterized by
blue-shifted velocities, which is comparatively much stronger in Civ than in
Lya, is more or less compatible with being the result of gas falling towards
the central black hole with free-fall acceleration. We propose however that the
line emission at high, blue-shifted velocities is better explained in terms of
entrainment of gas clouds by the jet. This gas is therefore probably
collisionally excited as a result of heating due to the intense infrared
radiation from the jet, which would explain the strength of this component in
Civ relative to Lya. This phenomenon might be a signature of disk-jet
interaction.


title:
Our Sun. IV. The Standard Model and Helioseismology: Consequences of
  Uncertainties in Input Physics and in Observed Solar Parameters

abstract:
  Helioseismology provides a powerful tool to explore the deep interior of the
Sun: for example, the adiabatic sound speed can be inferred with an accuracy of
a few parts in 10,000. This has become a serious challenge to theoretical
models of the Sun. Therefore, we have undertaken a self-consistent, systematic
study of sources of uncertainties in the standard solar model, which must be
understood before the helioseismic observations can be used as constraints on
theory. We find that the largest uncertainty in the sound speed in the solar
interior, namely, 3 parts in 1000, arises from uncertainties in the observed
photospheric abundances of the elements; uncertainties of 1 part in 1000 arise
from (1) the 4% uncertainty in the OPAL opacities, (2) the 5% uncertainty in
the basic pp nuclear reaction rate, (3) the 15% uncertainty in the diffusion
constants for the gravitational settling of helium, and (4) the 50%
uncertainties in diffusion constants for the heavier elements. (Other
investigators have shown that similar uncertainties arise from uncertainties in
the interior equation of state and in rotation-induced turbulent mixing.) The
predicted pre-main-sequence solar lithium depletion is a factor of order 20 (an
order of magnitude larger than that predicted by earlier models that neglected
gravitational settling and used older opacities), and is uncertain by a factor
of 2. The predicted neutrino capture rate is uncertain by 30% for the Cl-37
experiment and by 3% for the Ga-71 experiments (not including uncertainties in
the capture cross sections), while the B-8 neutrino flux is uncertain by 30%.


title:
Our Sun. V. A Bright Young Sun Consistent with Helioseismology and Warm
  Temperatures on Ancient Earth and Mars

abstract:
  The relatively warm temperatures required on early Earth and Mars have been
difficult to account for via warming from greenhouse gases. We tested whether
this problem can be resolved for both Earth and Mars by a young Sun that is
brighter than predicted by the standard solar model. We computed high-precision
solar evolutionary models with slightly increased initial masses of M_i = 1.01
to 1.07 M_sun; for each mass, we considered three different mass loss
scenarios. We then tested whether these models were consistent with the current
high-precision helioseismic observations. The relatively modest mass loss rates
in these models are consistent with observational limits from young stars and
estimates of the past solar wind obtained from lunar rocks, and do not
significantly affect the solar lithium depletion. For appropriate initial
masses, all three mass loss scenarios are capable of yielding a solar flux 3.8
Gyr ago high enough to be consistent with water on ancient Mars. We find that
all of our mass-losing solar models are consistent with the helioseismic
observations. The early solar mass loss of a few percent does indeed leave a
small fingerprint on the Sun's internal structure. However, for helioseismology
to significantly constrain early solar mass loss would require higher accuracy
in the observed solar parameters and input physics, namely, by a factor of
about 3 for the observed solar surface composition, and a factor of 2 for the
solar interior opacities, the pp nuclear reaction rate, and the diffusion
constants for gravitational settling.


title:
Measuring Distances and Probing the Unresolved Stellar Populations of
  Galaxies Using Infrared Surface Brightness Fluctuations

abstract:
  To empirically calibrate the IR surface brightness fluctuation (SBF) distance
scale and probe the properties of unresolved stellar populations, we measured
fluctuations in 65 galaxies using NICMOS on the Hubble Space Telescope. The
early-type galaxies in this sample include elliptical and S0 galaxies and
spiral bulges in a variety of environments. Absolute fluctuation magnitudes in
the F160W (1.6 micron) filter were derived for each galaxy using
previously-measured I-band SBF and Cepheid variable star distances. F160W SBFs
can be used to measure distances to early-type galaxies with a relative
accuracy of ~10% provided that the galaxy color is known to ~0.035 mag or
better. Near-IR fluctuations can also reveal the properties of the most
luminous stellar populations in galaxies. Comparison of F160W fluctuation
magnitudes and optical colors to stellar population model predictions suggests
that bluer elliptical and S0 galaxies have significantly younger populations
than redder ones, and may also be more metal-rich. There are no galaxies in
this sample with fluctuation magnitudes consistent with old, metal-poor (t>5
Gyr, [Fe/H]<-0.7) stellar population models. Composite stellar population
models imply that bright fluctuations in the bluer galaxies may be the result
of an episode of recent star formation in a fraction of the total mass of a
galaxy. Age estimates from the F160W fluctuation magnitudes are consistent with
those measured using the H-beta Balmer line index. The two types of
measurements make use of completely different techniques and are sensitive to
stars in different evolutionary phases. Both techniques reveal the presence of
intermediate-age stars in the early-type galaxies of this sample.


title: Fireball Heated by Neutrinos

abstract:
  The fireball, the promising model of the gamma-ray burst (GRB), is an opaque
radiation plasma, whose energy is significantly greater than its rest mass. We
numerically simulate the evolution of the fireball heated by the
neutrino-antineutrino annihilation process for the spherically symmetric case.
We also derive analytical energy and momentum deposition rates via neutrino
scattering with thermalized electron-positron pairs in the fireball. In our
simulation the matter is provided around the neutrinosphere before neutrinos
start to be emitted, and the energy is injected during a finite period of time
$t_{\rm dur}$. In the acceleration regime the matter shell is pushed from
behind by radiation pressure. The Lorentz factor of the shell reaches the
maximum value $\eta$ at $r \simeq \eta^2 c t_{\rm dur}$. After the fireball
enters the coasting regime, the velocity distribution in the shell becomes very
flat. The shell expansion rate $d W/dr$ can be much smaller than $\eta^{-2}$.
The runaway of temperature of the fireball due to neutrino scattering with
electron-positron pairs does not occur in most cases. The energy deposition due
to scattering is not so significant.


title:
Formation and Migration of Trans-Neptunian Objects - Proceedings of the
  conference "Scientific Frontiers in Research of Extrasolar Planets"

abstract:
  Some large trans-Neptunian objects could be formed by the compression of
rarefied dust condensations, but not by the accumulation of smaller
planetesimals. A considerable portion of near-Earth objects could have come
from the trans-Neptunian region. Our runs of the evolution of thousands orbits
of Jupiter-family comets under the gravitational influence of planets showed
that former Jupiter-family comets collide with the terrestrial planets mostly
from orbits with aphelia located deep inside Jupiter's orbit.


title:
Small Scale Clustering in the Isotropic Arrival Distribution of
  Ultra-High Energy Cosmic Rays and Implications for Their Source Candidates

abstract:
  We present numerical simulations on the propagation of UHE protons with
energies of $(10^{19.5}-10^{22})$ eV in extragalactic magnetic fields over 1
Gpc. We use the ORS galaxy sample, which allow us to accurately quantify the
contribution of nearby sources to the energy spectrum and the arrival
distribution, as a source model. We calculate three observable quantities,
cosmic ray spectrum, harmonic amplitude, and two point correlation function
from our data of numerical simulations. With these quantities, we compare the
results of our numerical calculations with the observation. We show that the
three observable quantities including the GZK cutoff of the energy spectrum can
be reproduced in the case that the number fraction $\sim 10^{-1.7}$ of the ORS
galaxies more luminous than -20.5 mag is selected as UHECR sources. In terms of
the source number density, this constraint corresponds to $10^{-6}$ Mpc$^{-3}$.
However, since mean number of sources within the GZK sphere is only $\sim 0.5$
in this case, the AGASA 8 events above $10^{20.0}$ eV, which do not constitute
the clustered events with each other, can not be reproduced. On the other hand,
if the cosmic ray flux measured by the HiRes, which is consistent with the GZK
cutoff, is correct and observational features about the arrival distribution of
UHECRs are same as the AGASA, our source model can explain both the arrival
distribution and the flux at the same time. Thus, we conclude that large
fraction of the AGASA 8 events above $10^{20}$ eV might originate in the
topdown scenarios, or that the cosmic ray flux measured by the HiRes experiment
might be better. We also discuss the origin of UHECRs below $10^{20.0}$ eV
through comparisons between the number density of astrophysical source
candidates and our result ($\sim 10^{-6}$ Mpc$^{-3}$).


title: On the central structure of M15

abstract:
  We present a detailed comparison between the latest observational data on the
kinematical structure of the core of M15, obtained with the Hubble STIS and
WFPC2 instruments, and the results of dynamical simulations carried out using
the special-purpose GRAPE-6 computer. The observations imply the presence of a
significant amount of dark matter in the cluster core. In our dynamical
simulations, neutron stars and/or massive white dwarfs concentrate to the
center through mass segregation, resulting in a sharp increase in $M/L$ toward
the center. While consistent with the presence of a central black hole, the
Hubble data can also be explained by this central concentration of stellar-mass
compact objects. The latter interpretation is more conservative, since such
remnants result naturally from stellar evolution, although runaway merging
leading to the formation of a black hole may also occur for some range of
initial conditions. We conclude that no central massive object is required to
explain the observational data, although we cannot conclusively exclude such an
object at the level of $\sim500-1000$ solar masses. Our findings are unchanged
when we reduce the assumed neutron-star retention fraction in our simulations
from 100% to 0%.


title: Constraining dark energy from the abundance of weak gravitational lenses

abstract:
  We examine the prospect of using the observed abundance of weak gravitational
lenses to constrain the equation-of-state parameter w of the dark energy. Here
we solve the spherical-collapse model with dark energy, clarifying some
ambiguities found in the literature, and provide fitting formulas for the
overdensity at virialization and the linear-theory overdensity at collapse. We
then compute the variation in the predicted weak-lens abundance with w. We find
that the predicted redshift distribution and number count of weak lenses are
highly degenerate in w and \Omega_0. If we fix \Omega_0 the number count for
w=-2/3 is a factor of 2 smaller than for the \LambdaCDM model. However, if we
allow \Omega_0 to vary with w such that the amplitude of the matter power
spectrum as measured by COBE matches that obtained from the X-ray cluster
abundance, the decrease in the predicted lens abundance is less than 25% for -1
< w < -0.4. We show that a more promising method for constraining the dark
energy---one that is largely unaffected by the \Omega_0 - w degeneracy as well
as uncertainties in observational noise---is to compare the relative abundance
of virialized X-ray lensing clusters with the abundance of non-virialized,
X-ray underluminous, lensing halos. For aperture sizes of 15 arcmin, the
predicted ratio of the non-virialized to virialized lenses is greater than 40%
and varies by 20% between w=-1 and w=-0.6. Overall, if all other weak lensing
parameters are fixed, a survey must cover > 40 degree^2 in order for the number
count to differentiate a \LambdaCDM cosmology from a w=-0.9 model to 3\sigma.
However, given uncertainties in the lensing parameters, the non-virialized lens
fraction provides the most robust constraint on w, requiring 50 degree^2 of sky
coverage in order to differentiate w=-1 from w=-0.6 to 3\sigma.


title: Properties of the background of EPIC-pn onboard XMM-Newton

abstract:
  We have investigated the background properties of EPIC-pn onboard XMM-Newton
to establish the background subtraction method. Count rates of the background
vary violently by two orders of magnitude at the maximum, while during the most
quiet period, these are stable within 8 % at a 1 $\sigma$ level. The overall
spectrum is dominated by particle events above 5 keV, and its spatial variation
is also found. The long-term variation of the background is also investigated
with CAL CLOSED data, where the filter wheel was in closed position with the
internal calibration source illuminating the sensitive area. The average
background count rate decreased by 20 % from March 2000 to January 2001, but it
regained in February 2001. For the modeling of the background spectrum, we
investigate relations between the 2.0--7.0 keV count rate and some
characteristic parameters. The 2.0--7.0 keV background count rate shows a good
correlation with the count rate of events outside the field of view. This
correlation is usable for the modeling of the background.


title:
Measuring the Geometry and Topology of Large Scale Structure using
  SURFGEN: Methodology and Preliminary Results

abstract:
  We present a new ansatz which can successfully be used to determine the
morphological properties of the supercluster-void network. The ansatz is based
on a surface modelling scheme SURFGEN, which generates a triangulated surface
from a discrete data set representing (say) the distribution of galaxies in
real (or redshift) space. Four Minkowski functionals -- surface area, volume,
extrinsic curvature and genus -- describe the geometry and topology of the
supercluster-void network. Ratio's of Minkowski functionals -- Shapefinders --
provide us with an excellent diagnostic of three dimensional shapes of
clusters, superclusters and voids. Minkowski functionals and Shapefinders are
determined for a triangulated iso-density surface using SURFGEN. SURFGEN is
tested against both simply and multiply connected eikonal surfaces such as
triaxial ellipsoids and tori. Remarkably, the first three Minkowski functionals
are computed to better than 1% accuracy while the fourth (genus) is known
exactly. SURFGEN also gives excellent results when applied to Gaussian random
fields. Our results indicate that the surface modelling scheme SURFGEN is
accurate and robust and can successfully be used to quantify the topology and
morphology of the supercluster-void network in the universe. We apply SURFGEN
to three cosmological models, $\L$CDM, $\T$CDM and SCDM and obtain interesting
new results pertaining to the geometry, morphology and topology of large scale
structure.


title: Hydrodynamical Simulations of the IGM at High Mach Numbers

abstract:
  We present a new approach to doing Eulerian computational fluid dynamics that
is designed to work at high Mach numbers encountered in hydrodynamical
simulations of the IGM. In conventional Eulerian CFD, the thermal energy is
poorly tracked in supersonic bulk flows where local fluid variables cannot be
accurately separated from the much larger bulk flow components. We described a
method in which local fluid quantities can be directly tracked and the Eulerian
fluid equations solved in a local frame moving with the flow. The new algorithm
has been used to run large hydrodynamical simulations on a 1024^3 grid to study
the kinetic SZ effect. The KSZ power spectrum is broadly peaked at l~10^4 with
temperature fluctuations on micro Kelvin levels.


title:
Spiral-like Light Profiles but Elliptical-like Kinematics in Mergers of
  Galaxies

abstract:
  It is commonly accepted that a merger of two spiral galaxies results in a
remnant with an elliptical-like surface-brightness profile. Surprisingly, our
recent study (Chitre & Jog 2002) of the 2MASS data for twenty-seven advanced
mergers of galaxies has shown that half of these have a light distribution that
decreases exponentially with radius. Such a distribution normally characterizes
a rotationally supported disk in a spiral galaxy. Here we show from kinematic
data for two of these mergers, Arp 224 and Arp 214, that the main support
against gravitational collapse comes from pressure due to random motion of
stars as seen in an elliptical galaxy rather than from rotation. The origin of
the unusual combination of properties seen here is a puzzle. The standard
theoretical N-body models in the literature cannot account for these systems.
Further observational and dynamical studies of this new class of merger
remnants are needed, and would be important for understanding merger dynamics
and galaxy evolution.


title: New Energy Source Controlled by Gravity Alone?

abstract:
  I present a theoretical and numerical (Monte Carlo) N-particle analysis of
Penrose scattering processes in the ergosphere of a supermassive Kerr black
hole. These GR model calculations reveal that the observed high energies and
luminosities of quasars and other active galactic nuclei, the collimated jets
about the polar axis, and the asymmetrical jets (which can be enhanced by
relativistic Doppler beaming effects) all are inherent properties of rotating
black holes. The Penrose scattered escaping relativistic particles exhibit
tightly wound coil-like cone distributions (highly collimated vortical jet
distributions) about the polar axis, with helical polar angles of escape
varying from 0.5-30 deg for the highest energy particles. The gravitomagnetic
field exerts a force acting on the momentum vectors of the incident and
scattered particles, causing asymmetrical particle jet emission above and below
the equatorial plane. When the accretion disk is assumed to be an ADAF,
energies as high as 54 GeV can be attained by these Penrose processes alone;
and when relativistic beaming is included, energies in the TeV range can be
achieved, agreeing with observations of some BL Lac objects. This
energy-momentum extraction model can be applied to any size black hole. When
this model is applied specifically to quasars 3C 279, 3C 273, Seyfert 1 galaxy
MCG--60-30-15, and galactic black hole source Cygnus X-1, their observed high
energy luminosity spectra in general can be explained. The consistency of these
Penrose model calculations with observations suggests that the external
magnetic field of the accretion disk plays a negligible role in the extraction
of energy-momentum from a rotating black hole, close to the event horizon,
where gravitational forces appear to be dominant.


title:
Serendipitous AGN in the XMM-Newton fields of Markarian 205 and QSO
  0130-403

abstract:
  The X-ray spectra of serendipitously observed AGN in the XMM-Newton fields of
Mrk 205 and QSO 0130-403 are analysed. The sample consists of 23 objects, none
of which is detected at radio frequencies, with a median X-ray luminosity of ~
4 x 10^44 erg s^-1 and redshifts ranging from ~0.1 to just over 3. The mean
photon index was found to be 1.89 +/- 0.04. In contrast to past ASCA and ROSAT
observations of high-redshift radio-loud quasars, we find little evidence for
excess intrinsic absorption in these radio-quiet objects, with only three
sources requiring a column density in excess of the Galactic value. Comparing
the measured spectral indices over the redshift range, we also find there is no
X-ray spectral evolution of QSOs with time, up to redshift 3. Within the sample
there is no evidence for evolution of the optical to X-ray spectral index,
alpha-ox, with redshift, the mean value being -1.66 +/- 0.04. However, upon
comparing the values from the Bright Quasar Survey at low redshift (z < 0.5)
and high redshift QSOs detected by Chandra (z > 4), a slight steepening of
alpha-ox is noted for the more distant objects. In most of the sources there is
no significant requirement for a soft excess, although a weak thermal component
(< 10% of Lx) cannot be excluded. There is an indication of spectral flattening
(by delta gamma=0.2) at higher energies (> 3 keV, QSO rest frame) for the
sample as a whole. This is consistent with the presence of a Compton reflection
component in these radio-quiet AGN, with the scattering medium (such as an
accretion disc or molecular torus) occupying a solid angle of 2 pi steradians
to the X-ray source.


title:
Galaxy formation using halo merger histories taken from N-body
  simulations

abstract:
  We develop a hybrid galaxy formation model which uses outputs from an N-body
simulation to follow the merger histories (or ``merger trees'') of dark matter
halos and treats baryonic processes, such as the cooling of gas within halos
and subsequent star formation, using the semi-analytic model of Cole et al. We
compare this hybrid model to an otherwise identical model which utilises merger
tree realisations generated by a Monte-Carlo algorithm and find that, apart
from the limited mass resolution imposed by the N-body particle mass, the only
significant differences between the models are due to the known discrepancy
between the distribution of halo progenitor masses predicted by extended Press
Schechter theory and that found in N-body simulations. We investigate the
effect of limited mass resolution on the hybrid model by comparing to a purely
semi-analytic model with greatly improved mass resolution. We find that the
mass resolution of the simulation we use, which has a particle mass of
1.4x10^10 Msolar/h, is insufficient to produce a reasonable luminosity function
for galaxies with magnitudes in the b_J band fainter than -17.


title: Cosmic Magnification

abstract:
  I present the current status of the cosmic magnification produced by
systematic amplification of background sources by large-scale structures. After
introducing its principle, I focus on its interests for cosmology and underline
its complementary aspect to cosmic shear and galaxy auto-correlations. I
finally discuss recent investigations using higher-order statistics.


title:
The Low Mass X-ray Binary-Globular Cluster Connection II: NGC 4472 X-ray
  Source Properties and Source Catalogs

abstract:
  We present the results of a Chandra/HST study of the point sources of the NGC
4472. We identify 144 X-ray sources, 72 with HST matches. The optical data show
1102 sources, 829 with globular cluster colors. Thirty matches are found -
likely to be low mass X-ray binaries in globular clusters, while 42 have no
optical counterparts to V~25 and I~24 - likely predominantly LMXBs in the field
star population. Thus approximately 40% of the X-ray sources are in globular
clusters and ~4% of the globular clusters contain X-ray sources. The blue GC
sources may have harder X-ray spectra than the red GC sources. No significant
differences are found between the X-ray properties of the field sources and of
the GC sources. This study, along with our previous result from Paper I in this
series on the similarity of the spatial profile of the field LMXBs, globular
cluster LMXBs, and the globular clusters themselves suggest that a significant
fraction of the observed low mass X-ray binaries in the field may be created in
a globular cluster then ejected into the field by stellar interaction s;
however, by comparing the results for NGC 4472 with those in several other
galaxies, we find tentative evidence for a correlation be tween the globular
cluster specific frequency and the fraction of LMXBs in globular clusters, a
correlation which would be most easily explained if some of the field sources
were generated in situ. We show that isolated accreting very massive black
holes are unlikely to be observable with current X-ray instrumentation and that
these sources hence do not contaminate the LMXB population. We discuss the
possibility that several equatorial point sources may indicate the presence of
a disk wind responsible for the low radiative efficiency observed in the
nucleus of this source. (abridged)


title: A high-sensitivity OH 5-cm line survey in late-type stars

abstract:
  We have undertaken a comprehensive search for 5-cm excited OH maser emission
from evolved stars representative of various stages of late stellar evolution.
Observed sources were selected from known 18-cm OH sources. This survey was
conducted with the 100-m Effelsberg telescope to achieve high signal to noise
ratio observations and a sensitivity limit of about 0.05 to 0.1 Jy. A total of
64 stellar sources were searched for both main line and satellite line
emission. We confirm the previous detection of 5 cm OH in Vy 2-2, do not
confirm emission from NML-Cyg and do not report any other new detection within
the above sensitivity limit.
  Implications of these results on the pumping mechanism of the OH radical in
circumstellar envelopes are briefly discussed.


title: The dust disk of HR4049

abstract:
  We present the Spectral Energy Distribution of HR 4049 based on literature
data and new continuum measurements at 850 micron. The SED shows variable
absorption in the UV, and a large IR excess, both caused by circumstellar dust.
The shape of the IR excess from 1 micron all the way down to 850 micron can be
nearly perfectly fitted with a single blackbody function at T ~ 1150 K or
alternatively with a sum of blackbodies in a narrow temperature range. The
energy emitted in this IR continuum radiation is about one-third of the stellar
luminosity. We show that this blackbody radiation must be due to the presence
of a circumbinary disk with a large height. This disk must also be gas-rich, in
agreement with the observations of molecular bands in the ISO-SWS spectrum. We
present two possible scenario's for explaining the shape and the intensity of
the IR excess. The first scenario involves large grains (a >1 mm) that each
radiate like a blackbody. The second scenario argues that the blackbody
radiation is due to a very optically thick circumbinary disk. We investigate if
such a disk would indeed produce blackbody radiation by presenting results from
radiative transfer calculations. We further quantify the properties of such a
disk and its stability in the framework of (hydro)dynamics, grain settling,
radiation pressure and grain drift. The virtues and shortcomings of both models
for the origin of the IR blackbody are discussed by contrasting them with other
observations and assessing them in the framework of (binary) (post-)AGB
evolution.


title: A VLT/FORS2 spectroscopic survey in the HDF-S

abstract:
  We report on low-resolution multi-object spectroscopy of 65 objects from
I(AB) ~= 20 to I(AB) ~= 25 in the HDF-S obtained with the VLT Focal Reducer/low
dispersion Spectrograph (FORS2). 18 objects belong to the HDF-S proper, i.e.
the WFPC2 deep area. 15 high-redshift galaxies with 2.0 < z < 3.5 (10 in the
HDF-S proper) have been identified. The spectroscopic redshifts are in good
agreement with the photometric ones derived from a chi^{2} minimization
technique comparing the observed spectral energy distribution with synthetic
libraries and with a new neural network (NN) approach. The dispersion with the
former method is sigma_z=0.16 whereas the latter provides sigma_z=0.13. No
"catastrophic" difference is encountered. The inferred star formation rates of
the individual objects range from tens to a few hundreds of M_{\odot} yr^{-1}
and the global star formation rate of the Universe at <z>=~2.4 is estimated to
be 0.15 M_{\odot} yr^{-1} Mpc^{-3} with a statistical error of 0.04. Evidence
for large scale structure is found with two groups' redshifts observed at z ~=
2.1 and z ~= 2.7 and a pronounced low redshift peak around z ~= 0.58. An
elliptical galaxy lensing a background object turns out to be at a redshift
z=0.577.


title:
The diffuse radio emission from the Coma cluster at 2.675 GHz and 4.85
  GHz

abstract:
  We present new measurements of the diffuse radio halo emission from the Coma
cluster of galaxies at 2.675 GHz and 4.85 GHz using the Effelsberg 100--m
telescope. After correction for the contribution from point sources we derive
the integrated flux densities for the halo source (Coma C), $S_{2.675
GHz}=(107\pm 28)mJy$ and $S_{4.85 GHz}=(26\pm 12)mJy$. These values verify the
strong steepening of the radio spectrum of Coma C at high frequencies. Its
extent strongly depends on frequency, at 4.85 GHz it is only marginally
visible. The measurement at 4.85 GHz is the first flux density determination
for Coma C at this high frequency. In order to quantify the spectral steepening
we compare the expectations for the spectrum of Coma C with the observations,
resorting to basic models for radio halo formation. The in--situ acceleration
model provides the best fit to the data. From equipartition assumptions we
estimate a magnetic field strength $B_{eq}=0.57 (1+k)^{0.26}\mu G$ in the
intracluster medium of Coma, where k is the energy ratio of the positively and
negatively charged particles.
  As a by--product of the 2.675 GHz observation we present a new flux density
for the diffuse emission of the extended source 1253+275 ($S_{2.675GHz}=112\pm
10$). This measurement provides a smaller error range for the power--law fit to
the spectrum ($\alpha=1.18\pm 0.02$) compared to previous investigations and
yields an equipartition magnetic field strength of $B_{eq}=0.56 (1+k)^{0.24}\mu
G$.


title:
Gravitational Waves Probe the Coalescence Rate of Massive Black Hole
  Binaries

abstract:
  We calculate the expected nHz--$\mu$Hz gravitational wave (GW) spectrum from
coalescing Massive Black Hole (MBH) binaries resulting from mergers of their
host galaxies. We consider detection of this spectrum by precision pulsar
timing and a future Pulsar Timing Array. The spectrum depends on the merger
rate of massive galaxies, the demographics of MBHs at low and high redshift,
and the dynamics of MBH binaries. We apply recent theoretical and observational
work on all of these fronts. The spectrum has a characteristic strain
$h_c(f)~10^{-15} (f/yr^{-1})^{-2/3}$, just below the detection limit from
recent analysis of precision pulsar timing measurements. However, the amplitude
of the spectrum is still very uncertain owing to approximations in the
theoretical formulation of the model, to our lack of knowledge of the merger
rate and MBH population at high redshift, and to the dynamical problem of
removing enough angular momentum from the MBH binary to reach a GW-dominated
regime.


title: Galactic Cosmic Rays from PBHs and Primordial Spectra with a Scale

abstract:
  We consider the observational constraints from the detection of antiprotons
in the Galaxy on the amount of Primordial Black Holes (PBH) produced from
primordial power spectra with a bumpy mass variance. Though essentially
equivalent at the present time to the constraints from the diffuse $\gamma$-ray
background, they allow a widely independent approach and they should improve
sensibly in the nearby future. We discuss the resulting constraints on
inflationary parameters using a Broken Scale Invariance (BSI) model as a
concrete example.


title: Cluster cores and cooling flows

abstract:
  The gas temperature in the cores of many clusters of galaxies drops inward by
about a factor of three or more within the central 100 kpc radius. The
radiative cooling time drops over the same region from 5 or more Gyr down to
below a few 10^8yr. Although it would seem that cooling flows are taking place,
XMM-Newton spectra show no evidence for strong mass cooling rates of gas below
1--2 keV. Chandra images show holes coincident with radio lobes and cold fronts
indicating that the core regions are complex. The observational situation is
reviewed. It is likely that some form of heating is important in reducing the
mass cooling rates by a factor of up to ten. Conduction of heat from the hot
outer gas or heating from a central radio source are discussed, together with
possible ways in which continued cooling might occur. Parallels with the
formation of the baryonic part of galaxies are explored.


title:
Swing wave-wave interaction: Coupling between fast magnetosonic and
  Alfv{\'e}n waves

abstract:
  We suggest a mechanism of energy transformation from fast magnetosonic waves
propagating across a magnetic field to Alfv{\'e}n waves propagating along the
field. The mechanism is based on {\it swing wave-wave interaction} [T.V.
Zaqarashvili, Astrophys. J. Lett. {\bf 552}, 107 (2001)]. The standing fast
magnetosonic waves cause a periodical variation in the Alfv{\'e}n speed, with
the amplitude of an Alfv{\'e}n wave being governed by Mathieu's equation.
Consequently, sub-harmonics of Alfv{\'e}n waves with a frequency half that of
magnetosonic waves grow exponentially in time. It is suggested that the energy
of nonelectromagnetic forces, which are able to support the magnetosonic
oscillations, may be transmitted into the energy of purely magnetic
oscillations. Possible astrophysical applications of the mechanism are briefly
discussed.


title:
The Central Mass Distribution in Dwarf and Low Surface Brightness
  Galaxies

abstract:
  We present Halpha rotation curves for a sample of 15 dwarf and LSB galaxies.
  From these, we derive limits on the slopes of the central mass distributions.
Assuming the density distributions of dark matter halos follow a power-law at
small radii, rho(r)~r^(-alpha), we find inner slopes in the range 0<alpha<1 for
most galaxies. In general, halos with constant density cores (\alpha=0) provide
somewhat better fits, but the majority of our galaxies (~75%) are also
consistent with alpha=1, provided that the R-band mass-to-light ratios are
smaller than about 2. Halos with alpha=1.5, however, are ruled out in virtually
every case. To investigate the robustness of these results we discuss and model
several possible causes of systematic errors including non-circular motions,
slit width, seeing, and slit alignment errors. Taking the associated
uncertainties into account, we conclude that even for the 25% of the cases
where alpha=1 seems inconsistent with the rotation curves, we cannot rule out
cusp slopes this steep. Inclusion of literature samples similar to the one
presented here leads to the same conclusion when possible systematic errors are
taken into account. In the ongoing debate on whether the rotation curves of
dwarf and LSB galaxies are consistent with predictions for a CDM universe, we
argue that our sample and the literature samples discussed in this paper
provide insufficient evidence to rule out halos with alpha=1. At the same time,
we note that none of the galaxies in these samples require halos with steep
cusps, as most are equally well or better explained by constant density cores.
(abridged)


title:
Chemical Abundances in Broad Emission Line Regions: The "Nitrogen-Loud"
  QSO 0353-383

abstract:
  The intensity of the strong N V 1240 line relative to C IV 1549 or to He II
1640 has been proposed as an indicator of the metallicity of QSO broad emission
line regions, allowing abundance measurements in a large number of QSOs out to
the highest redshifts. Previously, it had been shown that the (normally) much
weaker lines N III] 1750 and N IV] 1486 could be used in the same way. The
redshift 1.96 QSO 0353-383 has long been known to have N III] and N IV] lines
that are far stronger relative to Ly-alpha or C IV than in any other QSO.
Because in this particular case these intercombination lines can be easily
measured, this unusual object provides an ideal opportunity for testing whether
the N V line is a valid abundance indicator. Using new observations of
Q0353-383 made both with HST in the ultraviolet and from the ground in the
visible passband, we find that intensity ratios involving the strengths of N V,
N IV] and N III] relative to lines of He, C and O all indicate that nitrogen is
overabundant relative to oxygen in Q0353-383 by a factor of ~15 compared to
solar ratios. This agreement among the diagnostics supports the use of these
lines for measuring BLR chemical abundances. If nitrogen behaves like a
secondary element, such that N/O is proportional to O/H, then the extreme
nitrogen enhancement in Q0353-383 implies a metallicity of ~15 times the solar
value. Even if Q0353-383 represents an extreme outlier in the N/O proportional
to O/H relation, the overall metallicity should still be at least five times
solar. Unusually high metallicities in Q0353-383 might imply that we caught
this object just as the gas-phase metallicity in the central part of its host
galaxy has peaked, at a time when the interstellar gas supply is nearly
exhausted and hence the fuel source for the central QSO is ready to shut off.


title:
Dust and molecules in the Local Group galaxy NGC 6822. III. The
  first-ranked HII region complex Hubble V

abstract:
  We present maps of the first-ranked HII region complex Hubble V in the
metal-poor Local Group dwarf galaxy NGC 6822 in the first four transitions of
CO, the 158 micron transition of C+, the 21-cm line of HI, the Pa-beta line of
HII, and the continuum at 21 cm and 2.2 micron wavelengths. We have also
determined various integrated intensities, notably of HCO+ and near-IR H2
emission. Although Hubble X is located in a region of relatively strong HI
emission, our mapping failed to reveal any significant CO emission from it. The
relatively small CO cloud complex associated with Hubble V is comparable in
size to the ionized HII region. The CO clouds are hot (Tkin) = 150 K) and have
high molecular gas densities (n(H2) = 10**4 cm**-3) Molecular hydrogen probably
extends well beyond the CO boundaries. C+ column densities are more than an
order of magnitude higher than those of CO. The total mass of the complex is
about 10**6 M(sun) and molecular gas account for more than half of this. The
complex is excited by luminous stars reddened or obscured at visual, but
apparent at near-infrared wavelengths. The total embedded stellar mass may
account for about 10% of the total mass, and the mass of ionized gas for half
of that. Hubble V illustrates that modest star formation efficiencies may be
associated with high CO destruction efficiencies in low-metallicity objects.
The analysis of the Hubble V photon-dominated region (PDR) confirms in an
independent manner the high value of the CO-to-H2 conversion factor X found
earlier, characteristic of starforming low-metallicity regions.


title: Search for double degenerate progenitors of supernovae type Ia with SPY

abstract:
  We report on a large survey for double degenerate (DD) binaries as potential
progenitors of type Ia supernovae with the UVES spectrograph at the ESO VLT
(ESO SN Ia Progenitor surveY - SPY).


title: Brane universes tested by supernovae

abstract:
  We discuss observational constrains coming from supernovae Ia
\cite{Perlmutter99} imposed on the behaviour of the Randall-Sundrum models. In
the case of dust matter on the brane, the difference between the best-fit
general relativistic model with a $\Lambda$-term \cite{Perlmutter99} and the
best-fit brane models becomes detectable for redshifts $z > 0.6$. It is
interesting that brane models predict brighter galaxies for such redshifts
which is in agreement with the measurement of the $z = 1.7$ supernova
\cite{Riess01} and with the New Data from the High Z Supernovae Search Team
\cite{schmit02}. We also demonstrate that the fit to supernovae data can also
be obtained, if we admit the "super-negative" dark energy $p = - (4/3) \varrho$
on the brane, where the dark energy in a way mimics the influence of the
cosmological constant. It also appears that the dark energy enlarges the age of
the universe which is demanded in cosmology. Finally, we propose to check for
dark radiation and brane tension by the application of the angular diameter of
galaxies minimum value test.


title: A Grid of NLTE Line-Blanketed Model Atmospheres of O-type Stars

abstract:
  We have constructed a comprehensive grid of 690 metal line-blanketed, NLTE,
plane-parallel, hydrostatic model atmospheres for the basic parameters
appropriate to O-type stars. The OSTAR2002 grid considers 12 values of
effective temperatures, 27500K < Teff < 55000K with 2500K steps, 8 surface
gravities, 3.0 < log g< 4.75 with 0.25 dex steps, and 10 chemical compositions,
from metal-rich relative to the Sun to metal-free. The lower limit of log g for
a given effective temperature is set by an approximate location of the
Eddington limit. The selected chemical compositions have been chosen to cover a
number of typical environments of massive stars: the galactic center, the
Magellanic Clouds, Blue Compact Dwarf galaxies like I Zw 18, and galaxies at
high redshifts. The paper contains a description of the OSTAR2002 grid and some
illustrative examples and comparisons. The complete OSTAR2002 grid is available
at our website at http://tlusty.gsfc.nasa.gov.


title:
Addendum: "Hubble Space Telescope Evidence for an Intermediate-Mass
  Black Hole in the Globular Cluster M15: II. Kinematical Analysis and
  Dynamical Modeling"

abstract:
  It has been reported that there is an error in the figure in Dull et al.
(1997, D97) that shows the radial M/L profile in Fokker-Planck models of M15.
We discuss how this modifies the interpretation of our kinematical data. These
imply the existence of a dark and compact mass component near the center of
M15, either a single black hole (BH) or a collection of dark remnants that have
sunk to the cluster center due to mass segregation. We previously showed that
the latter interpretation is in conflict with the D97 M/L profile, which
supported the BH interpretation. We repeat our analysis here with the corrected
D97 profile. Models without a BH are now found to be statistically acceptable
(within 1-sigma), although inclusion of a BH still provides a marginally better
fit. It does not necessarily follow that dark remnants are now the preferred
interpretation of the data. The D97 models, as well as N-body models by
Baumgardt et al. (2002), assume that all neutron stars are retained during
cluster evolution. This conflicts with predictions of the neutron-star
retention rate (typically below 10 per cent) based on pulsar kick velocities.
The presence of a single BH therefore continues to be a viable interpretation
of the data. The best fit BH mass with the corrected D97 M/L profile is M_BH =
1.7^{+2.7}_{-1.7} x 10^3 solar masses, and with a constant M/L it is M_BH =
3.2^{+2.2}_{-2.2} x 10^3 solar masses. A model that includes both neutron star
escape and mass segregation would probably yield a value between these numbers.
This agrees with the correlation between velocity dispersion and BH mass
inferred for galaxies. However, with the presently available models and data it
is neither uniquely implied nor ruled out that M15 has an intermediate-mass BH.


title:
Velocity statistics from spectral line data: effects of density-velocity
  correlations, magnetic field, and shear

abstract:
  In a previous work Lazarian and Pogosyan suggested a technique to extract
velocity and density statistics, of interstellar turbulence, by means of
analysing statistics of spectral line data cubes. In this paper we test that
technique, by studying the effect of correlation between velocity and density
fields, providing a systematic analysis of the uncertainties arising from the
numerics, and exploring the effect of a linear shear. We make use of both
compressible MHD simulations and synthetic data to emulate spectroscopic
observations and test the technique. With the same synthetic spectroscopic
data, we also studied anisotropies of the two point statistics and related
those anisotropies with the magnetic field direction. This presents a new
technique for magnetic field studies. The results show that the velocity and
density spectral indices measured are consistent with the analytical
predictions. We identified the dominant source of error with the limited number
of data points along a given line of sight. We decrease this type of noise by
increasing the number of points and by introducing Gaussian smoothing. We argue
that in real observations the number of emitting elements is essentially
infinite and that source of noise vanishes.


title: UV properties and evolution of high-redshift galaxies

abstract:
  I assess the problem of morphological and photometric evolution of
high-redshift galaxies in the ultraviolet wavelength range. My discussion will
partly rely on a new set of template galaxy models, in order to infer the
expected changes along the Hubble morphological sequence at the different
cosmic epochs. The impact of evolution on the faint-end galaxy luminosity
function at z~1 and beyond will also be evaluated and briefly discussed. See
http://www.merate.mi.astro.it/~eps/home.html for more info and model retrieval.


title:
Reliability in the Face of Complexity; The Challenge of High-End
  Scientific Computing

abstract:
  This conference centers on photoionized plasmas, and the tools necessary to
understand them. One of the major goals of meetings held between developers of
plasma codes is to identify sources of differences between various codes, and
resolve them. Very often these differences are caused by bugs. This
contribution outlines some practical aspects of developing bug-free codes, and
is based on my experience creating the plasma simulation code Cloudy.
  Computers present nothing less than a new way to understand the universe. We
can do any numerical experiment we can imagine. But machines are growing faster
far more quickly than people are getting smarter. Harnessing the power of
future machines in a reliable way will present an ever greater intellectual
challenge. More powerful machines allow a more complete and complex simulation
of physical processes, and so offers a far greater opportunity for errors.
Industrial standards of quality control, and the associated code development
techniques, can play a major role in developing reliable simulations.


title: Ripples and tails in the compact group of galaxies Hickson 54

abstract:
  HCG 54 has been classified as a compact galaxy group by Hickson, but its
nature is uncertain because of its unusual properties. We present here a study
of HCG~54 based on deep optical images and spectroscopy as well as high spatial
and spectral resolution HI observations obtained at the VLA. Both optical and
radio data indicate clearly that HCG~54 is a product of a recent merger
involving at least two galaxies. Our optical images have revealed a blue
elongated structure associated with HCG 54a embedded in a rounder and redder
stellar envelope. Several ripples or shells whose center is located near HCG
54a and b are also detected. These observed features are similar to those found
in the numerical simulations of tidal interactions involving two equal mass
disk galaxies. This system is embedded in an HI cloud 12 kpc in diameter, and a
20 kpc HI tidal tail emerges from its western edge. Both the HI distribution
and kinematics are consistent with a recent history of a deeply penetrating
interaction or a merger. Based on the analysis of our new data we propose that
HCG 54 is the remnant of a merger in an advanced stage, whose main body is what
has been called HCG 54a, while HCG 54b marks the location of a strong starburst
induced by the interaction, as evidenced by the Wolf Rayet stellar population
that we detect. Optical spectra of HCG 54c and d show HII region features and
are interpreted as tidal debris of the collision undergoing active star
formation.


title: Rotation and abundance anomalies in blue horizontal-branch stars

abstract:
  To address the puzzling photometric properties of horizontal branch stars in
Galactic GCs, several different groups have undertaken detailed spectroscopic
analyses of individual blue HB stars. Hotter BHB stars show strong metal
enhancement and helium depletion, likely due to atomic diffusion, and slow
rotation velocities, in contrast to the cooler BHB stars, which have a bimodal
distribution of rotation speeds -- some of them much faster than expected --
but no anomalous abundances. I review the observational results to date, and
discuss possible explanations and ramifications of these abundance and rotation
characteristics.


title:
Study of the Interstellar Medium and Star Formation of a complete sample
  of 760 isolated galaxies

abstract:
  A key problem in astronomy involves the role of the environment in the
formation and evolution of galaxies. In order to answer this question it is
necessary to characterize a reference sample with minimum influence from the
environment, so that its evolution is completeley determined by nature. The aim
of this project is to provide such reference, quantifying the ISM properties of
a well defined and statistically significant sample of 760 isolated galaxies.
Based on optical, Halpha and infrared luminosities, radiocontinuum emission,
molecular and atomic gas content, compiled from the bibliography or observed by
ourselves, together with POSS-II digitized images, we will perform a
statistical study of the Interstellar Medium (ISM) properties as a function of
isolation, and its relation to star formation, morphology and luminosities, as
well as nuclear activity frequency. This sample will be different from previous
studies by three essential characteristics: a) strict definition of isolation,
b) statistical significance, and c) complete multiwavelength information
concerning the ISM. It will serve to evaluate the properties of interacting
galaxies, which will be of special interest to analyse the large amount of data
that will be generated during the next decade for high z galaxies, with the new
instruments to come. Once the analysis will be finished, the data will become
public by means of a database with free internet acces via a simple and
efficient WEB interface.


title: Aspects of the Cosmic Microwave Background Dipole

abstract:
  Cosmic microwave background (CMB) experiments generally infer a temperature
fluctuation from a measured intensity fluctuation through the first term in the
Taylor expansion of the Planck function, the relation between the intensity in
a given frequency and the temperature. However, with the forthcoming Planck
satellite, and perhaps even with the Microwave Anisotropy Probe, the CMB-dipole
amplitude will be large enough to warrant inclusion of the next higher order
term. To quadratic order in the dipole amplitude, there is an intensity
quadrupole induced by the dipole with a frequency dependence given by the
second derivative of the Planck function. The Planck satellite should be able
to detect this dipole-induced intensity quadrupole and distinguish it through
its frequency depdendence from the intrinsic CMB temperature and foreground
quadrupoles. This higher-order effect provides a robust pre-determined target
that may provide tests of Planck's and MAP's large-angle-fluctuation
measurements and of their techniques for multi-frequency foreground
subtraction.


title:
Calculation of an optimized telescope apodizer for Terrestrial Planet
  Finder coronagraphic telescope

abstract:
  One of two approaches to implementing NASA's Terrestrial Planet Finder is to
build a space telescope that utilizes the techniques of coronagraphy and
apodization to suppress diffraction and image exo-planets. We present a method
for calculation of a telescope's apodizer which suppresses the side lobes of
the image of a star so as to optimally detect an Earth-like planet. Given the
shape of a telescope's aperture and given a search region for a detector, we
solve an integral equation to determine an amplitude modulation (an apodizer)
which suppresses the star's energy in the focal plane search region. The method
is quite general and yields as special cases the product apodizer reported by
Nisenson and Papaliolios (2001) and the Prolate spheroidal apodizer of Kasdin
et al (2002), and Aime et al (2002). We show computer simulations of the
apodizers and the corresponding point spread functions for various
aperture-detector configurations.


title: Angular Size Measurements Of Mira Variable Stars At 2.2 Microns. II

abstract:
  We present angular size measurements of 22 oxygen-rich Mira variable stars.
These data are part of a long term observational program using the Infrared
Optical Telescope Array (IOTA) to characterize the observable behavior of these
stars. Complementing the infrared angular size measurements, values for
variable star phase, spectral type, bolometric flux and distance were
established for stars in the sample; flux and distance led to values for
effective temperature, and linear radius, respectively. Additionally, values
for the K-[12] color excess were established for these stars, which is
indicative of dusty mass loss. Stars with higher color excess are shown to be
systematically 120 solar radii larger than their low color excess counterparts,
regardless of period. This analysis appears to present a solution to a
long-standing question presented by the evidence that some Mira angular
diameters are indicative of first overtone pulsation, while other diameters are
more consistent with fundamental pulsation. A simple examination of the
resultant sizes of these stars in the context of pulsation mode is consistent
with at least some of these objects pulsating in the fundamental mode.


title:
Interferometric Phase Calibration Sources in the Declination Range 0deg
  to -30deg

abstract:
  We present a catalog of 321 compact radio sources in the declination range
0deg > delta > -30deg. The positions of these sources have been measured with a
two-dimensional rms accuracy of 35 milliarcseconds using the NRAO Very Large
Array. Each source has a peak flux density >50 mJy at 8.4 GHz. We intend for
this catalog to be used mainly for selection of phase calibration sources for
radio interferometers, although compact radio sources have other scientific
uses.


title: A Keck Adaptive Optics Search for Young Extrasolar Planets

abstract:
  Adaptive optics, large primary mirrors, and careful selection of target stars
are the keys to ground-based imaging of extrasolar planets. Our near-IR survey
is capable of identifying exoplanets of 1-10 M${_J}$ within 100 AU of young
(t$<$60 Myr), nearby (d$<$60 pc) stars. For very young and proximate targets
such as GJ 803 (12 Myr, 10 pc) we are able to detect exoplanets with parameters
approaching those of planets our solar system (1 M${_J}$ at 19 AU, 2 M${_J}$ at
9 AU; 5 M${_J}$ at 5 AU). We have thus far imaged over 100 stars with Keck AO.
Here we report on our progress, discuss specific observing strategies, and
present detailed sensitivity limits.


title: The Large Scale Distribution of Neutral Hydrogen in the Fornax Region

abstract:
  Using HIPASS data, we have searched for HI in a ~25x25 sq.deg. region centred
on the Fornax cluster. Within a velocity search range of 300 - 3700 km/s and a
lower flux limit of ~40 mJy, 110 galaxies with HI emission were detected, one
of which is previously uncatalogued. None of the detections has early-type
morphology. Previously unknown velocities for 14 galaxies have been determined,
with a further 4 velocity measurements being significantly dissimilar to
published values. Identification of an optical counterpart is relatively
unambiguous for more than ~90% of our HI galaxies. The galaxies appear to be
embedded in a sheet at the cluster velocity which extends for more than 30 deg
across the search area. At the nominal cluster distance of ~20 Mpc, this
corresponds to an elongated structure more than 10 Mpc in extent. A velocity
gradient across the structure is detected, with radial velocities increasing by
\~500 km/s from SE to NW. The clustering of galaxies evident in optical surveys
is only weakly suggested in the spatial distribution of our HI detections. Our
results suggest a considerable deficit of HI-rich galaxies in the centre of the
cluster. However, relative to the field, there is a 3(+/-1)-fold excess of
HI-rich galaxies in the outer parts of the cluster where galaxies may be
infalling towards the cluster for the first time.


title:
Peculiar, Low Luminosity Type II Supernovae: Low Energy Explosions in
  Massive Progenitors?

abstract:
  A number of supernovae, classified as Type II, show remarkably peculiar
properties such as an extremely low expansion velocity and an extraordinarily
small amount of $^{56}$Ni in the ejecta. We present a joint analysis of the
available observations for two of these peculiar Type II supernovae, SN 1997D
and SN 1999br, using a comprehensive semi-analytic method that can reproduce
the light curve and the evolution of the line velocity and continuum
temperature. We find that these events are under-energetic with respect to a
typical Type II supernova and that the inferred mass of the ejecta is
relatively large. We discuss the possibility that these supernovae originate
from the explosion of a massive progenitor in which the rate of early infall of
stellar material on the collapsed core is large. Events of this type could form
a black hole remnant, giving rise to significant fallback and late-time
accretion.


title: The WINGS Survey: a progress report

abstract:
  A two-band (B and V) wide-field imaging survey of a complete, all-sky X-ray
selected sample of 78 clusters in the redshift range z=0.04-0.07 is presented.
The aim of this survey is to provide the astronomical community with a complete
set of homogeneous, CCD-based surface photometry and morphological data of
nearby cluster galaxies located within 1.5 Mpc from the cluster center. The
data collection has been completed in seven observing runs at the INT and
ESO-2.2m telescopes. For each cluster, photometric data of about 2500 galaxies
(down to V~23) and detailed morphological information of about 600 galaxies
(down to V~21) are obtained by using specially designed automatic tools.
  As a natural follow up of the photometric survey, we also illustrate a long
term spectroscopic program we are carrying out with the WHT-WYFFOS and AAT-2dF
multifiber spectrographs. Star formation rates and histories, as well as
metallicity estimates will be derived for about 350 galaxies per cluster from
the line indices and equivalent widths measurements, allowing us to explore the
link between the spectral properties and the morphological evolution in high-
to low-density environments, and across a wide range in cluster X-ray
luminosities and optical properties.


title:
Large Velocity Gradients in the Tidal Tails of the Interacting Galaxy AM
  1353-272 ("The Dentist's Chair")

abstract:
  We present VLT observations of the interacting system AM 1353-272. Using the
FORS2 instrument, we studied the kinematics of the ionized gas along its
prominent tidal tails and discovered strikingly large velocity gradients
associated with seven luminous tidal knots. These kinematical structures cannot
be caused by streaming motion and most likely do not result from projection
effects. More probably, instabilities in the tidal tails have lead to the
formation of kinematically decoupled objects which could be the progenitors of
self-gravitating Tidal Dwarf Galaxies.


title: Spectral variability of the nucleus of M33 in a Chandra-ACIS observation

abstract:
  We have analyzed a 90 ksec long observation of the bright nucleus of M33 made
with Chandra/ACIS. We detected low-amplitude (~sim10%) highly significant
variability on timescales of ~5000 sec. We also find associated spectral
variability. The two main spectral components (a power-law with \Gamma~2 and a
multicolor disk -MCD- with kT~0.9-1.2 keV) vary in relative flux. The MCD
temperature also increases with increasing MCD flux. The pattern of variability
is reminiscent of (but not identical to) galactic black hole binaries. A ~5
M$_{\odot}$ accreting black hole may explain this source.


title:
The Crustal Rigidity of a Neutron Star, and Implications for PSR 1828-11
  and other Precession Candidates

abstract:
  We calculate the crustal rigidity parameter, b, of a neutron star (NS), and
show that b is a factor 40 smaller than the standard estimate due to Baym &
Pines (1971). For a NS with a relaxed crust, the NS's free-precession frequency
is directly proportional to b. We apply our result for b to PSR 1828-11, a 2.5
Hz pulsar that appears to be precessing with period 511 d. Assuming this 511-d
period is set by crustal rigidity, we show that this NS's crust is not relaxed,
and that its reference spin (roughly, the spin for which the crust is most
relaxed) is 40 Hz, and that the average spindown strain in the crust is 5
\times 10^{-5}. We also briefly describe the implications of our b calculation
for other well-known precession candidates.


title:
The high energy gamma-ray emission expected from Tycho's supernova
  remnant

abstract:
  A nonlinear kinetic model of cosmic ray (CR) acceleration in supernova
remnants (SNRs) is used to describe the properties of Tycho's SNR. Observations
of the expansion characteristics and of the nonthermal radio and X-ray emission
spectra, assumed to be of synchrotron origin, are used to constrain the overall
dynamical evolution and the particle acceleration parameters of the system, in
addition to what is known from independent estimates of the distance and
thermal X-ray observations. It is shown that a very efficient production of
nuclear cosmic rays, leading to strong shock modification, and a large
downstream magnetic field strength B_d approx 240muG are required to reproduce
the observed synchrotron emission from radio to X-ray frequencies. This field
strength is still well within the upper bound for the effective magnetic field,
consistent with the acceleration process. The pi^0-decay gamma-ray flux turns
out to be somewhat greater than the inverse Compton (IC) flux off the Cosmic
Microwave Background at energies below 1 TeV, dominating it strongly at 10 TeV.
The predicted TeV gamma-ray flux is consistent with but close to the very low
upper limit recently obtained by HEGRA. A future detection at E_gamma ~ 10 TeV
would clearly indicate hadronic emission.


title: Accelerating universe without event horizon

abstract:
  It is shown that if a small negative cosmological constant is added to
quintessence models with equation of state $p=\omega\rho$ on the range $-1
<\omega < -1/3$, the resulting scenarios could not contain any future event
horizons. Therefore, such cosmological accelerating scenarios could not present
the kind of obstacles recently pointed out to define a set of observable
quantities analogous to an S-matrix needed by predictive M and string theories
in an accelerating universe driven by dark energy. These scenarios become
accelerating only at early times after coincidence time, and lead finally to
re-collapse.


title: Blue Horizontal-Branch Stars and Simple Stellar Populations

abstract:
  The effects of blue horizontal-branch (HB) stars on the integrated
spectrophotometric indices of simple stellar populations (SSPs) are addressed.
Synthetic spectra are drawn from a grid of simulated globular clusters,
constructed so as to reproduce the observed range of HB morphologies in the
Milky Way system. Our models indicate that the Hbeta line index increases by as
much as 0.75A and the integrated B-V colour becomes bluer by upwards of 0.15mag
because of the contribution from blue HB stars. We discuss the importance of
both optical and far-UV colours as age discriminants for SSPs, in particular
for high metallicities. We suggest that relative age differences (and
consequently their differing HB morphologies) result in non-linear
colour-metallicity relations.