title: Ionizing Photons and EUV Excesses in Clusters of Galaxies

abstract:
  Observations with the Extreme Ultraviolet Explorer satellite are purported to
show extreme ultraviolet (EUV) and soft X-ray excesses in several clusters of
galaxies (Bonamente, Lieu & Mittaz 2001). If interpreted as thermal emission,
this would imply the presence of warm (T\sim 10^6 K) gas in these clusters with
a mass comparable to that of gas at coronal temperatures. If true, this would
have profound implications for our understanding of galaxy clusters and the
distribution of baryons in the universe. Here we show that because of the large
ionizing photon emissivities of gas at such low temperatures, the ionizing
photon fluxes seen by disk galaxies in the observed clusters can be very large,
resulting in minimum emission measures from neutral gas in such disks as high
as 100 cm^(-6) pc. This result is essentially independent of the mechanism
actually responsible for producing the alleged EUV excesses. The predicted
emission measures in Abell 1795 (z=0.063) are about an order of magnitude
larger than seen in the Reynolds layer of the Galaxy, providing a
straightforward observational test of the reality of the EUV excess. New
tunable filter H alpha images and WFPC images from the Hubble Space Telescope
archive do not support the existence of the claimed EUV excess.


title: Black Holes and Galaxy Metamorphosis

abstract:
  Supermassive black holes can be seen as an agent of galaxy transformation. In
particular, a supermassive black hole can cause a triaxial galaxy to evolve
toward axisymmetry by inducing chaos in centrophilic orbit families. This is
one way in which a single supermassive black hole can induce large-scale
changes in the structure of its host galaxy -- changes on scales far larger
than the Schwarzschild radius ($O(10^{-5}) \rm{pc}$) and the radius of
influence of the black hole ($O(1)-O(100) \rm{pc}$). We will discuss the
transformative power of supermassive black holes in light of recent high
resolution N-body realizations of cuspy triaxial galaxies.


title:
Nucleosynthesis and mixing on the Asymptotic Giant Branch. III.
  Predicted and observed s-process abundances

abstract:
  We present the results of s-process nucleosynthesis calculations for AGB
stars of different metallicities and initial masses. The computations were
based on previously published stellar evolutionary models that account for the
III dredge up phenomenon occurring late on the AGB. Neutron production is
driven by the 13C(alpha,n)16O reaction during the interpulse periods in a tiny
layer in radiative equilibrium at the top of the He- and C-rich shell. The
s-enriched material is subsequently mixed with the envelope by the III dredge
up, and the envelope composition is computed after each thermal pulse. We
follow the changes in the photospheric abundance of the Ba-peak elements (heavy
s, or `hs') and that of the Zr-peak ones (light s, or `ls'), whose logarithmic
ratio [hs/ls] has often been adopted as an indicator of the s-process
efficiency. The theoretical predictions are compared with published abundances
of s elements for Galactic AGB giants of classes MS, S, SC, post-AGB
supergiants, and for various classes of binary stars. The observations in
general confirm the complex dependence of n captures on metallicity. They
suggest that a moderate spread exists in the abundance of 13C that is burnt in
different stars. Although additional observations are needed, a good
understanding has been achieved of s-process operation in AGB. The detailed
abundance distribution including the light elements (CNO) of a few s-enriched
stars at different metallicity are examined.


title:
A Comparison of Independent Star Formation Diagnostics for a UV-Selected
  Sample of Nearby Galaxies

abstract:
  We present results from a decimetric radio survey undertaken with the Very
Large Array as part of a longer term goal to inter-compare star formation and
dust extinction diagnostics, on a galaxy by galaxy basis, for a representative
sample of nearby galaxies. For our survey field, Selected Area 57, star
formation rates derived from 1.4GHz luminosities are compared with earlier
nebular emission line and ultraviolet (UV) continuum diagnostics. We find broad
correlations, over several decades in luminosity, between H-alpha, the UV
continuum and 1.4GHz diagnostics. However, the scatter in these relations is
found to be larger than observational errors, with offsets between the observed
relations and those expected assuming constant star-formation histories and
luminosity-independent extinction models. We investigate the physical origin of
the observed relations, and conclude the discrepancies between different
star-formation diagnostics can only be partly explained by simple models of
dust extinction in galaxies. These models cannot by themselves explain all the
observed differences, introducing the need for temporally varying
star-formation histories and/or more complex models of extinction, to explain
the entire dataset.


title: Magnetic Deformation of Atoms in the Crust of Magnetars

abstract:
  Some special features of magnetically deformed multi-electron atoms in the
crustal region of strongly magnetized neutron stars (magnetars) are studied
with the relativistic version of semi-classical Thomas-Fermi model. An
analytical solution of Poisson's equation with cylindrical symmetry is
obtained. The variation of atomic dimension with magnetic field strength is
also studied. An expression for atomic quadrupole moment, appears because of
magnetic deformation is derived. The effect of atomic quadrupole-quadrupole
interaction in the equation of state of crustal matter of magnetar is briefly
discussed.


title:
Near-infrared template spectra of normal galaxies: k-corrections, galaxy
  models and stellar populations

abstract:
  We have observed 28 local galaxies in the wavelength range between 1 and 2.4
mic in order to define template spectra of the normal galaxies along the Hubble
sequence. Five galaxies per morphological type were observed in most cases, and
the resulting RMS spread of the normalized spectra of each class, including
both intrinsic differences and observational uncertainties, is about 1% in K,
2% in H and 3% in J. Many absorption features can be accurately measured. The
target galaxies and the spectroscopic aperture (7"x53") were chosen to be
similar to those used by Kinney et al. (1996) to define template UV and optical
spectra. The two data sets are matched in order to build representative spectra
between 0.1 and 2.4 mic. The continuum shape of the optical spectra and the
relative normalization of the near-IR ones were set to fit the average
effective colours of the galaxies of the various Hubble classes. The resulting
spectra are used to compute the k-corrections of the normal galaxies in the
near-IR bands and to check the predictions of various spectral synthesis
models: while the shape of the continuum is generally well predicted, large
discrepancies are found in the absorption lines. Among the other possible
applications, here we also show how these spectra can be used to place
constraints on the dominant stellar population in local galaxies. Spectra and
k-corrections are publicly available and can be downloaded from the web site
http://www.arcetri.astro.it/~filippo/spectra.


title: Echoes in X-ray binaries; mapping the accretion flow

abstract:
  In X-ray binaries much of the optical/UV emission arises from X-rays
reprocessed by material in the accretion disk, stream and the companion star.
The resulting reprocessed variability will be delayed in time with respect to
the X-ray variability by an amount depending on the position of the
reprocessing regions. We can determine a range of time-delays present in the
system. This time-delay transfer function can be used to `echo-map' the
geometry of the reprocessing regions in the binary system.
  We present our modeling of this transfer function and show results from our
echo-mapping campaign using X-ray lightcurves from RXTE, simultaneous with HST.
In the X-ray transient, GRO j1655-40, shortly after the 1996 outburst, we find
evidence for reprocessing in the outer regions of a thick accretion disk.


title: M82-F: A Doomed Super Star Cluster?

abstract:
  We present high dispersion echelle spectroscopy of the very luminous, young
super star cluster (SSC) `F' in M82, obtained with the 4.2-m William Herschel
Telescope (WHT), for the purpose of deriving its dynamical mass and assessing
whether it will survive to become an old globular cluster. We measure a stellar
velocity dispersion of 13.4 +/- 0.7 km/s, a projected half-light radius of 2.8
+/- 0.3 pc from archival HST/WFPC2 images, and derive a dynamical mass of 1.2
+/- 0.1 x 10^6 solar masses, demonstrating that M82-F is a very massive,
compact cluster. We determine that the current visual luminosity-to-mass ratio
for M82-F is 45 +/- 13. Comparison with spectral synthesis models shows that
the visual luminosity-to-mass ratio is a factor of 5 higher than that predicted
for a standard Kroupa (2001) initial mass function (IMF) at the well-determined
age for M82-F of 60 +/- 20 Myr. This high value of the visual
luminosity-to-mass ratio indicates a deficit of low mass stars in M82-F; the
current mass function (MF) evidently is `top-heavy'. We find that a lower mass
cutoff of 2-3 solar masses is required to match the observations for a MF with
a slope of 2.3. Since the cluster apparently lacks long-lived low mass stars,
it will not become an old globular cluster. We also derive up-dated
luminosity-to-mass ratios for the younger SSCs NGC 1569A and NGC 1705-1. We
discuss the implications of our findings in the context of large scale IMF
variations; with the present data the top-heavy MF could reflect a local mass
segregation effect during the birth of the cluster.


title:
Comparing the SFI Peculiar Velocities with the PSCz Gravity Field: a
  VELMOD analysis

abstract:
  We compare the peculiar velocities derived from the I-band Tully-Fisher (TF)
relation for 989 field spiral galaxies in the SFI catalogue with the predicted
velocity field derived from the IRAS PSCz galaxy redshift survey. We assume
linear gravitational instability theory and apply the maximum likelihood
technique, VELMOD, to SFI galaxies within cz<6000 km/s. The resulting
calibration of the TF relation is consistent with a previous, independent
calibration for a similar sample of spirals residing in clusters. Our analysis
provides an accurate estimate of the quantity beta. Using the forward TF
relation and smoothing the predicted velocity field with a Gaussian filter of
radius 300 km/s, we obtain beta = 0.42 +/- 0.04 (1 sigma uncertainty). This
value, as well as other parameters in the fit, are robust to varying the
smoothing radius to 500 km/s and splitting the sample into spherical shells in
redshift space. The one exception is the small-scale velocity dispersion,
sigma_v, which varies from 200 km/s within cz= 4000 km/s 500 km/s at larger
distance. For beta = 0.42, the residuals between the TF data and the PSCz
gravity field are uncorrelated, indicating that the model provides a good fit
to the data. More generally, a chi^2 statistic indicates that the PSCz model
velocity field provides an acceptable (3 sigma) fit to the data for 0.3 < beta
< 0.5.


title:
Low-excitation CO in HR10: implications for measuring metal-rich H2 mass
  at high redshifts

abstract:
  We examine the physical conditions of the molecular gas in the extremely red
object (ERO), HR10 at z=1.44, as constrained by the recent detection of CO J+1
-> J, J=1, 4 lines. The line ratios of such widely spaced CO transitions are
extremely sensitive probes of gas excitation; in the case of the HR10, they
provide a rare opportunity to study the state of the molecular gas in a
gas-rich starburst at a cosmologically significant distance. Contrary to
earlier claims, we find the CO J=5-4 transition to be of low excitation. The
brightness temperature ratio of (5-4)/(2-1) ~ 0.15. This has serious
consequences for estimates of H2 gas mass and the detectability of high-J CO
lines from similar objects at high redshifts (z>~3).


title:
On disc driven inward migration of resonantly coupled planets with
  application to the system around GJ876

abstract:
  We consider two protoplanets gravitationally interacting with each other and
a protoplanetary disc. The two planets orbit interior to a tidally maintained
disc cavity while the disc interaction indices inward migration. When the
migration is slow enough, the more rapidly migrating outer protoplanet
approaches and becomes locked in a 2:1 commensurability with the inner one.
This is maintained in subsequent evolution. We study this evolution using a
simple anaytic model, full hydrodynamic 2D simulations of the disc planet
system and longer time N body integrations incorporating simple prescriptions
for the effect of the disc on the planet orbits. The eccentricity of the
protoplanets are found to be determined by the migration rate induced in the
outer planet orbit by the external disc. We apply our results to the recently
discovered resonant planets around GJ876. Simulation shows that a disc with
parameters expected for protoplanetary discs causes trapping in the 2:1
commensurability when the planets orbit in an inner cavity and that
eccentricities in the observed range may be obtained.


title:
The Spatial Distribution and Kinematics of Stellar Populations in E+A
  Galaxies

abstract:
  We use long-slit spectroscopic observations of the sample of E+A galaxies
described by Zabludoff et al. to constrain the nature of the progenitors and
remnants of the E+A phase of galaxy evolution. We measure spatially-resolved
kinematic properties of the young (<~1 Gyr) and old (> few Gyr) stellar
populations. The young stellar populations are more centrally concentrated than
the older populations, but they are not confined to the galaxy core (radius <~
1 kpc). The kinematics of the old stellar population place 16 of 20 of our E+As
on a trend parallel to the Faber-Jackson relation that is offset by $\sim$ 0.6
mag in R. Eighteen of 20 E+As have v/sigma < 1. As the young stars in these
systems evolve, the luminosity offset will disappear and the remnants will be
pressure-supported systems that lie on the Faber-Jackson relation. Although
Zabludoff et al. spectroscopically selected the most extreme E+A galaxies in
the local volume, the sample is kinematically diverse: velocity dispersions
range from <~ 30 km/s to ~ 200 km/s over a luminosity range of M_R = -19 to -22
+ 5 log h. Combining these results with an estimate of the number of galaxies
that experience an E+A phase, we conclude that the E+A phase of galaxy
evolution is important in the development of a large fraction of
spheroid-dominated galaxies over a wide range of luminosities and masses. Our
kinematic observations, together with evidence that E+As have recently evolved
from a vigorous star forming phase to a quiescent phase (e.g. Couch and
Sharples, Caldwell et al.) and that many have tidal features consistent with
disk-like progenitors (Zabludoff et al.), indicate that these galaxies are
undergoing a transformation from star-forming, disk-dominated galaxies into
quiescent, spheroid-dominated galaxies.


title:
Near-Infrared Imaging of the Central Regions of Metal-Poor Inner
  Spheroid Globular Clusters

abstract:
  JHK images obtained with the Canada-France-Hawaii Telescope (CFHT) Adaptive
Optics Bonnette (AOB) are used to investigate the near-infrared photometric
properties of red giant branch (RGB) and horizontal branch (HB) stars in eight
metal-poor globular clusters with R_GC < 2 kpc. The slope of the RGB on the (K,
J-K) CMDs confirms the metal-poor nature of these clusters, four of which
appear to have metallicities comparable to M92. The luminosity functions of RGB
stars in inner spheroid and outer halo clusters have similar slopes, although
there is a tendency for core-collapsed clusters to have slightly flatter
luminosity functions than non-collapsed clusters. The distribution of red HB
stars on the (K, J-K) CMDs of inner spheroid clusters with [Fe/H] ~ -1.5 is
very different from that of clusters with [Fe/H] ~ -2.2, suggesting that
metallicity is the main parameter defining HB content among these objects. The
RGB-bump is detected in four of the inner spheroid clusters, and this feature
is used to compute distances to these objects. Finally, the specific frequency
of globular clusters in the inner Galaxy is discussed in the context of the
early evolution of the bulge. If the globular cluster formation efficiency for
the inner Galaxy is similar to that measured in other spheroidal systems, then
the main body of the bulge could have formed from gas that was chemically
enriched in situ.


title:
Cosmological Difficulties with Modified Newtonian Dynamics (or: La Fin
  du MOND?)

abstract:
  The cold dark matter paradigm has been extremely successful for explaining a
wide range of cosmological phenomena. Nevertheless, since evidence for
non-baryonic dark matter remains indirect, all reasonable alternatives should
be explored. One proposed idea, involving a fundamental acceleration scale a_0
= 1-2e-10 m/s^2, is called MOdified Newtonian Dynamics or MOND. MOND was
suggested to explain the flat rotation curves of galaxies without the need for
dark matter. Whether or not it can adequately fit the available data has been
debated for almost 20 years (and we summarise many of these studies), but only
recently have there been attempts to extend MOND to larger scale regimes. We
discuss how the basic properties of MOND make it at best ambiguous to apply
these ideas to cosmological scales. We emphasize the difficulties inherent in
developing a full theory in which to embed MOND. Without such a theory there is
no obviously consistent way to discuss the early Universe and the growth of
perturbations. Recent claims that MONDian cosmology works very well are
therefore not supportable. We also provide an argument for why a_0~cH_0
naturally, a coincidence which is often suggested as a motivation for taking
MOND seriously. We discuss other alternative theories of gravity concluding, as
others have, that no metric theory extensions appear workable for explaining
rotation curves as well as other observed phenomena. The whole premise of many
of these attempts is fatally flawed - galaxies are not pre-selected, discrete,
isolated regions which formed monolithically and around which one can construct
an axially-symmetric dynamical model in order to remove the need for dark
matter. In the modern view, galaxies are part of a dynamic continuum of objects
which collectively make up the evolving large-scale structure of the universe.


title:
The Detection of Bright Asymptotic Giant Branch Stars in the Nearby
  Elliptical Galaxy Maffei 1

abstract:
  We have used the adaptive optics system on the Canada-France-Hawaii Telescope
to study a field 6 arcmin from the center of the heavily obscured elliptical
galaxy Maffei 1. Our near diffraction-limited H and K' images reveal an excess
population of objects with respect to a background field, and we conclude that
the asymptotic giant branch tip (AGB-tip) in Maffei 1 occurs at K = 20 +/-
0.25. Assuming that stars at the AGB-tip in Maffei 1 have the same intrinsic
luminosity as those in the bulge of M31, then the actual distance modulus of
Maffei 1 is 28.2 +/- 0.3 if A_V = 5.1, which corresponds to a distance of 4.4
(+0.6, -0.5) Mpc. This is in excellent agreement with the distance estimated
from surface brightness flucuations in the infrared, and confirms that Maffei 1
is too distant to significantly affect the dynamics of the Local Group.


title: Subarcsecond Mid-IR Structure of the Dust Shell around IRAS 22272+5435

abstract:
  We report sub-arcsecond imaging of extended mid-infrared emission from a
proto-planetary nebula (PPN), \iras 22272+5435, performed at the MMT
observatory with its newly upgraded 6.5 m aperture telescope and at the Keck
observatory. The mid-infrared emission structure is resolved into two emission
peaks separated by $0\arcsec.5 - 0\arcsec.6$ in the MMT 11.7 $\um$ image and in
the Keck 7.9, 9.7, and 12.5 $\um$ images, corroborating the predictions based
on previous multi-wavelength morphological studies and radiative transfer
calculations. The resolved images show that the PPN dust shell has a toroidal
structure with the $0\arcsec.5$ inner radius. In addition, an unresolved mid-IR
excess appears at the nebula center. Radiative transfer model calculations
suggest that the highly equatorially-enhanced ($\rho_{\rm eq}/\rho_{\rm pole} =
9$) structure of the PPN shell was generated by an axisymmetric superwind with
${\dot M}_{\rm sw} = 4 \times 10^{-6} M_{\odot}$ yr$^{-1}$, which was preceded
by a spherical asymptotic giant branch (AGB) wind with ${\dot M}_{\rm AGB} = 8
\times 10^{-7} M_{\odot}$ yr$^{-1}$. These model calculations also indicate
that the superwind shell contains larger dust grains than the AGB wind shell.
The unresolved mid-infrared excess may have been produced by a post-AGB mass
loss at a rate of $2 - 6 \times 10^{-7} M_{\odot}$ yr$^{-1}$. While the central
star left the AGB about 380 years ago after the termination of the superwind,
the star seems to have been experiencing an ambient post-AGB mass loss with a
sudden, increased mass ejection about 10 years ago.


title: The Mass Dependence of Stellar Rotation in the Orion Nebula Cluster

abstract:
  We have determined new rotation periods for 404 stars in the Orion Nebula
Cluster using the Wide Field Imager attached to the MPG/ESO 2.2 m telescope on
La Silla, Chile. Mass estimates are available for 335 of these and most have M
< 0.3 M_sun. We confirm the existence of a bimodal period distribution for the
higher mass stars in our sample and show that the median rotation rate
decreases with increasing mass for stars in the range 0.1 < M <0.4 M_sun. While
the spread in angular momentum (J) at any given mass is more than a factor of
10, the majority of lower mass stars in the ONC rotate at rates approaching 30%
of their critical break-up velocity, as opposed to 5-10% for solar-like stars.
This is a consequence of both a small increase in observed specific angular
momentum (j=J/M) and a larger decrease in the critical value of j with
decreasing mass. Perhaps the most striking fact, however, is that j varies by
so little - less than a factor of two - over the interval 0.1-1.0 M_sun. The
distribution of rotation rates with mass in the ONC (age ~ 1 My) is similar in
nature to what is found in the Pleiades (age ~ 100 My). These observations
provide a significant new guide and test for models of stellar angular momentum
evolution during the proto-stellar and pre-main sequence phases.


title:
Host Galaxies, Obscuration and Nuclear Structure of Three Nearby Compact
  Symmetric Objects

abstract:
  We present 3-band HST imaging of three z</=0.1 compact symmetric objects
(CSOs): 4C 31.04, 1946+708 and 1146+596. These objects were chosen on the basis
of proximity to Earth as well as HI 21 cm absorption. The inner H-band
isophotes of these galaxies are well fit by "nuker" models, typical of nearby
ellipticals. Each shows a significant flattening in the isophotal profile at
radii ~0.5", as well as variations in ellipticity and PA. However, neither is
uncommon for elliptical galaxies. All three show modest departures from nuker
models at radii of 1-5 $h_{60}^{-1}$ kpc. Each shows large, well distributed
dust features, which are somewhat concentrated in the nuclear regions in
features which resemble disks or tori. The amount of dust in these galaxies is
about 10 times higher than normal for ellipticals and radio galaxy hosts. The
nuclear dust disks tend to be oriented roughly perpendicular to the radio axis.
One galaxy, 4C31.04, exhibits bright nuclear regions well-aligned with the
radio axis, while another, 1146+596, shows a significant near-IR excess
resembling a stellar bar along its dust disk. The combination of outwardly
normal isophotal profiles with significant variations in PA and ellipticity is
consistent with the host galaxies being relatively recent merger remnants, with
the mergers having occurred >/= 10^8 years ago. Such a merger could have
"triggered" the current activity in these objects, but our data require a
significant time delay between the merger and the onset of nuclear activity.
However, these data are also consistent with the hypothesis that the onset of
nuclear activity in radio galaxies is due to relatively minor "feeding" events
and/or the formation of "bars within bars", which would disturb the internal
kinematics only slightly.


title: Seeing double: strong gravitational lensing of high-redshift supernovae

abstract:
  With the advent of large, deep surveys, the observation of a strongly
gravitationally lensed supernova becomes increasingly likely. High-redshift
surveys continue apace, with a handful of type Ia supernovae observed to date
at redshifts of one or greater. In addition, a satellite (the
Supernova/Acceleration Probe [SNAP]) has been proposed dedicated to observing
thousands of supernovae per year out to a redshift of 1.7. Although it is
exceedingly unlikely that we will see a multiply-imaged supernova from ongoing
surveys, we find that SNAP would observe at least eight such events per year.
Since having a standard candle is inessential to most lensing studies, SNAP's
large sample of type II supernovae contributes to this rate. Each case of
strong lensing allows for a precise determination of time delays, image
separations, and relative image magnifications, and the SNAP strong-lensing
database will offer measures of $\Omega_m$, $\Omega_\Lambda$, and $H_0$,
independent of SNAP's primary goal of establishing the distance-redshift
relation. These systems also constrain models for the matter density profiles
of galaxies and clusters. Furthermore, lensed type Ia supernovae afford the
opportunity to break the mass-sheet degeneracy found in many lensing
measurements.


title: What is the real nature of HD 108 ?

abstract:
  Since the beginning of the past century, the nature of HD 108 has been a
subject of intense debate. One after another, astronomers explored its
variability and attributed it either to binarity, or to changes in the stellar
wind of a single star. In this article, we analyse a 30 years long campaign of
spectroscopic observations of this star with special emphasis on the last 15
years during which photographic plates have been replaced by CCD detectors. Our
investigation of the radial velocities of HD 108 yields no significant short-
or long-term period and does not confirm the published periodicities either.
Though the radial velocity of HD 108 appears clearly variable, the variations
cannot be explained by the orbital motion in a spectroscopic binary. However,
our data reveal spectacular changes in the H I Balmer lines and some He I
profiles over the years. These lines continuously evolved from P Cygni profiles
to `pure' absorption lines. A similar behaviour was already observed in the
past, suggesting that these changes are recurrent. HD 108 seems to share
several characteristics of Oe stars and we discuss different hypotheses for the
origin of the observed long-term variations. As we are now in a transition
period, a continuous monitoring of HD 108 should be considered for the next few
years.


title: The Cosmic Baryon Fraction and the Extragalactic Ionizing Background

abstract:
  We reassess constraints on the cosmological baryon density from observations
of the mean decrement and power spectrum of the Lyman-alpha forest, taking into
account uncertainties in all free parameters in the simplest gravitational
instability model. The uncertainty is dominated by that of the photoionizing
background, but incomplete knowledge of the thermal state of the intergalactic
medium also contributes significantly to the error-budget. While current
estimates of the baryon fraction from the forest do prefer values that are
somewhat higher than the big bang nucleosynthesis value of \Omega_b h^2 = 0.02
\pm 0.001, the discrepancy is at best about 3 \sigma. For instance, assuming
the highest estimate of the ionizing background, as indicated by recent
measurements of a large escape fraction from Lyman-break galaxies by Steidel,
Pettini & Adelberger, we find \Omega_b h^2 = 0.045 \pm 0.008. A recent
measurement of the ionizing background from the proximity effect by Scott et
al., on the other hand, implies \Omega_b h^2 = 0.03 \pm 0.01. We provide an
expression from which future likelihoods for \Omega_b h^2 can be derived as
measurements of the ionizing background improve -- consistency among
constraints from the forest, nucleosynthesis and the microwave background will
provide a powerful test of the gravitational instability model. We also develop
a formalism which treats lower bounds on the baryon density in a statistical
manner, which is appropriate if only a lower bound on the ionizing background
is known. Finally, we discuss the implications of the escape fraction
measurement for the age, structure and stellar content of Lyman-break galaxies.


title: CMB Power Spectrum Estimation via Hierarchical Decomposition

abstract:
  We have developed a fast, accurate and generally applicable method for
inferring the power spectrum and its uncertainties from maps of the cosmic
microwave background (CMB) in the presence of inhomogeneous and correlated
noise. For maps with 10 to 100 thousand pixels, we apply an exact power
spectrum estimation algorithm to submaps of the data at various resolutions,
and then combine the results in an optimal manner. To analyze larger maps
efficiently one must resort to sub-optimal combinations in which cross-map
power spectrum error correlations are only calculated approximately. We expect
such approximations to work well in general, and in particular for the
megapixel maps to come from the next generation of satellite missions.


title: Kinematic dynamo wave in the vicinity of the solar poles

abstract:
  We consider a dynamo wave in the solar convective shell for the kinematic
$\alpha\omega$-dynamo model. The spectrum and eigenfunctions of the
corresponding equations are derived analytically with the aid of the WKB
method. Our main aim here is to investigate the dynamo wave behavior in the
vicinity of the solar poles. Explicit expressions for the incident and
reflected waves are obtained. The reflected wave is shown to be relatively weak
in comparison to the incident wave. The phase shifts and the ratio of
amplitudes of the two waves are found.


title: Evidence for dust grain growth in young circumstellar disks

abstract:
  Hundreds of circumstellar disks in the Orion nebula are being rapidly
destroyed by the intense ultraviolet radiation produced by nearby bright stars.
These young, million-year-old disks may not survive long enough to form
planetary systems. Nevertheless, the first stage of planet formation -- the
growth of dust grains into larger particles -- may have begun in these systems.
Observational evidence for these large particles in Orion's disks is presented.
A model of grain evolution in externally irradiated protoplanetary disks is
developed and predicts rapid particle size evolution and sharp outer disk
boundaries. We discuss implications for the formation rates of planetary
systems.


title: GRBs, Fireballs and Precessing Gamma Jets

abstract:
  Fireballs are huge isotropic explosions models widely believed to explain
Gamma Ray Burst, GRBs (Piran,1999); ever-new versions consider wide beamed
(10^o) Jet explosions hitting external shells. On the contrary, since
1994-1998, we argued (Fargion 1995-2000; see also Blackman et all.1996) that
GRBs (as well as Soft Gamma Repeaters SGR) are spinning and precessing Gamma
Jets, produced by collimated e^+,e^- Jet via Inverse Compton Scattering, in a
very narrow (0.1^o) angles, blazing and flashing the observer. The Jet arises
in Super-Nova (SN) explosions; its energy decays slowly from earliest SN powers
(corresponding to GRB) toward lower stable power as Soft Gamma Repeaters (SGR)
regimes. GRBs and SGRs shared (sometimes) same spectra and time structure: then
SGRs are low-power GRBs, but without SN relics (or GRB afterglows, signatures
of Jets in SN-GRBs). Moreover weak isolated X-ray precursor signals,(such as
GRB980519, GRB981226,GRB000131), corresponding to huge isotropic, sim 10^{47}
erg s^{-1}, followed by the extreme GRB, sim {10^{52}} erg s^{-1} powers,
disagree with any Fireball explosive scenarios. We naturally interpret these
X-Ray precursors as rare earliest marginal blazes of outlying X conical
precessing Jet tails, surrounding the gamma Jet, later hitting in-axis as a
GRB.


title:
Chandra and ASCA X-ray Observations of the Radio Supernova SN1979C IN
  NGC 4321

abstract:
  We report on the X-ray observation of the radio selected supernova SN1979C
carried out with ASCA in 1997 December and serendipitously available from a
Chandra Guaranteed Time Observation in 1999 November. The supernova, of type SN
II-Linear (SN IIL), was first observed in the optical and occurred in the
weakly barred, almost face on spiral galaxy NGC 4321 (M100). The galaxy, a
member of the Virgo S cluster, is at a distance of 17.1 Mpc, and contains at
least three other supernovae discovered in this century. The useful exposure
time was ~25 ks for the Solid-State Imaging Spectrometer (SIS), ~28 ks for the
Gas Scintillation Imaging Spectrometer (GIS), and ~2.5 ks for Chandra's
Advanced CCD Imaging Spectrometer (ACIS). No point source was detected at the
radio position of SN1979C in a 3' diameter half power response circle in the
ASCA data. The background and galaxy subtracted SN signal had a 3sigma upper
limit to the flux of 6.3x10^-14 ergs/s/cm^-2 in the full ASCA SIS band
(0.4-10.0 keV) and a 3sigma upper limit of <3-4x10^-14 erg/s/cm^2 in the 2-10
keV band. In the Chandra data, a source at the position of SN1979C is
marginally detected at energies below 2 keV at a flux consistent with the ROSAT
HRI detection in 1995. At energies above 2 keV, no source is detected with an
upper limit of ~3x10^-14 erg/s/cm^-2. These measurements give the first ever
x-ray flux limit of a Type IIL SN above 2 keV which is an important diagnostic
of the outgoing shock wave ploughing through the circumstellar medium.


title:
First Measurement of Uranium/Thorium ratio in a very old Star:
  Implications for the age of the Galaxy

abstract:
  During an ESO-VLT large program devoted to high-resolution spectroscopy of
extremely metal-poor stars selected from the H&K survey of Beers and
colleagues, a [Fe/H] giant star was found to be as enriched in neutron-capture
r-process elements as CS 22892-052, but with a much reduced masking by
molecular lines. This allowed the detection and the measurement of the uranium
line at 3859 A, for the first time in an extremely old star. Making use of the
short 238U decay time (4.47 Gyr) we obtained a radioactive dating of the
formation of U and Th in of this star, born in the early days of the Galaxy.


title: Jet Formation from Rotating Magnetized Objects

abstract:
  Jet formation is connected most probably with matter acceleration from the
vicinity of rotating magnetized bodies. It is usually related to the mass
outflows and ejection from accretion disks around black holes. Problem of jet
collimation is discussed. Collapse of a rotating magnetized body during star
formation or supernovae explosion may lead to a jet-like mass ejection for
certain angular velocity and magnetic field distributions at the beginning of
the collapse. Jet formation during magnetorotational explosion is discussed
basing on the numerical simulation of collapse of magnetized bodied with
quasi-dipole field.


title: One Mass-Radius relation for Planets, White Dwarfs and Neutron Stars

abstract:
  We produce the simple formula for the radius R of a cold body of mass M,
  (4 pi rho/3)^{1/3} R = I.M^{1/3} / [1+ (M/Mp)^{2/3}], where I is one for
white dwarfs with non-relativistic electrons, but depends on the ratio of the
total mass to Mch, the Chandrasekhar mass. Mp is the mass of the planet of
maximum radius and rho is the density of the material at low pressure. Mp and
rho are derived in terms of fundamental constants and Mp/Mch is basically given
by the three halves power of the fine structure constant. The aim of the
discussion is to emphasise physical principles and to connect the masses
derived to the fundamental constants, so mathematical niceties are sacrificed
and replaced by interpolations between simple exact limits.


title: The giant radio halo in Abell 2163

abstract:
  New radio data is presented for the rich cluster Abell 2163. The cluster
radio emission is characterized by the presence of a radio halo, which is one
of the most powerful and extended halos known so far. In the NE peripheral
cluster region, we also detect diffuse elongated emission, which we classify as
a cluster relic. The cluster A2163 is very hot and luminous in X-ray. Its
central region is probably in a highly non relaxed state, suggesting that this
cluster is likely to be a recent merger. The existence of a radio halo in this
cluster confirms that halos are associated with hot massive clusters, and
confirms the connection between radio halos and cluster merger processes. The
comparison between the radio emission of the halo and the cluster X-ray
emission shows a close structural similarity. A power law correlation is found
between the radio and X-ray brightness, with index = 0.64. We also report the
upper limit to the hard X-ray emission, obtained from a BeppoSAX observation.
We discuss the implications of our results.


title: Tau Neutrinos in the Auger Observatory : A New Window to UHECR Sources

abstract:
  The cosmic ray spectrum has been shown to extend well beyond 10^{20}eV. With
nearly 20 events observed in the last 40 years, it is now established that
particles are accelerated or produced in the universe with energies near
10^{21}eV. In all production models neutrinos and photons are part of the
cosmic ray flux. In acceleration models (bottom-up models), they are produced
as secondaries of the possible interactions of the accelerated charged
particle; in direct production models (top-down models) they are a dominant
fraction of the decay chain. In addition, hadrons above the GZK threshold
energy will also produce, along their path in the Universe, neutrinos and
photons as secondaries of the pion photo-production processes. Therefore,
photons and neutrinos are very distinctive signatures of the nature and
distribution of the potential sources of ultra high energy cosmic rays. In the
following we describe the tau neutrino detection and identification
capabilities of the Auger observatory. We show that in the range
3x10^{17}-3x10^{20}eV the Auger effective apperture reaches a few tenths of
km^2.sr, making the observatory sensitive to fluxes as low as a few tau
neutrinos per km^2.sr.year. In the hypothesis of nu_mu <-->nu_tau oscillations
with full mixing, this sensitivity allows to probe the GZK cutoff as well as to
provide model independent constraints on the mechanisms of production of ultra
high energy cosmic rays.


title:
Chandra Detects a Rapid Flare in the Gravitationally Lensed Mini-BALQSO
  RX J0911.4+0551

abstract:
  The mini Broad Absorption Line (BAL) quasar RX J0911.4+0551 was observed with
the Advanced CCD Imaging Spectrometer (ACIS) of the Chandra X-ray Observatory
for ~ 29 ks as part of a gravitational lens (GL) survey aimed at measuring
time-delays. Timing analysis of the light-curve of the lensed image A2 shows a
rapid flux variation with a duration of about 2000s. A Kolmogorov-Smirnov test
shows that the probability that a constant-intensity source would produce the
observed variability is less than ~ 0.2 percent. We discuss possible origins
for the observed short-term X-ray variability. Our gravitational lens models
for the RX J0911.4+0551 GL system predict a time-delay of less than a day
between images A1 and A2. The rapid variability combined with the predicted
short-time delay make RX J0911.4+0551 an ideal system to apply the GL method
for estimating the Hubble constant. We describe the prospects of measuring H_0
within single X-ray observations of GL systems with relatively short time
delays. Modeling of the spectrum of the mini-BAL quasar RX J0911.4+0551
suggests the presence of an intrinsic absorber. Partial covering models are
slightly preferred over models that contain absorption due to intrinsic ionized
or neutral gas.


title: Constraints on Cosmological and Biasing models using AGN clustering

abstract:
  We attempt to put constraints on different cosmological and biasing models by
combining the recent clustering results of X-ray sources in the local ($z\le
0.1$) and distant universe ($z\sim 1$). To this end we compare the measured
angular correlation function for bright (Akylas et al. 2000) and faint
(Vikhlinin & Forman 1995) {\em ROSAT} X-ray sources respectively with those
expected in three spatially flat cosmological models. Taking into account the
different functional forms of the bias evolution, we find that there are two
cosmological models which performs well the data. In particular,
low-$\Omega_{\circ}$ cosmological models
($\Omega_{\Lambda}=1-\Omega_{\circ}=0.7$) which contain either (i) high
$\sigma_{8}^{\rm mass}=1.13$ value with galaxy merging bias, $b(z) \propto
(1+z)^{1.8}$ or (ii) low $\sigma_{8}^{\rm mass}=0.9$ with non-bias, $b(z)
\equiv 1$ best reproduce the AGN clustering results. While $\tau$CDM models
with different bias behaviour are ruled out at a high significance level.


title:
The Farthest Known Supernova: Support for an Accelerating Universe and a
  Glimpse of the Epoch of Deceleration

abstract:
  We present photometric observations of an apparent Type Ia supernova (SN Ia)
at a redshift of ~1.7, the farthest SN observed to date. SN 1997ff, was
discovered in a repeat observation by the HST of the HDF-), and serendipitously
monitored with NICMOS on HST throughout the GTO campaign. The SN type can be
determined from the host galaxy type:an evolved, red elliptical lacking enough
recent star formation to provide a significant population of core-collapse SNe.
The class- ification is further supported by diagnostics available from the
observed colors and temporal behavior of the SN, both of which match a typical
SN Ia. The photo- metric record of the SN includes a dozen flux measurements in
the I, J, and H bands spanning 35 days in the observed frame. The redshift
derived from the SN photometry, z=1.7+/-0.1, is in excellent agreement with the
redshift estimate of z=1.65+/-0.15 derived from the
U_300,B_450,V_606,I_814,J_110,J_125,H_160, H_165,K_s photometry of the galaxy.
Optical and near-infrared spectra of the host provide a very tentative
spectroscopic redshift of 1.755. Fits to observations of the SN provide
constraints for the redshift-distance relation of SNe~Ia and a powerful test of
the current accelerating Universe hypothesis. The apparent SN brightness is
consistent with that expected in the decelerating phase of the preferred
cosmological model, Omega_M~1/3, Omega_Lambda~2/3. It is inconsistent with grey
dust or simple luminosity evolution, candidate astro- physical effects which
could mimic past evidence for an accelerating Universe from SNe Ia at z~0.5.We
consider several sources of possible systematic error including lensing, SN
misclassification, selection bias, and calibration errors. Currently, none of
these effects appears likely to challenge our conclusions.


title: Abundances in the Uranium-Rich Star CS 31082-001

abstract:
  The recent discovery by Cayrel et al. of U in CS 31082-001 along with Os and
Ir at greatly enhanced abundances but with [Fe/H]=-2.9 strongly reinforces the
argument that there are at least two kinds of SNII sources for r-nuclei. One
source is the high-frequency H events responsible for heavy r-nuclei (A>135)
but not Fe. The H-yields calculated from data on other ultra-metal-poor stars
and the sun provide a template for quantitatively predicting the abundances of
all other r-elements. In CS 31082-001 these should show a significant
deficiency at A<135 relative to the solar r-pattern. It is proposed that CS
31082-001 should have had a companion that exploded as an SNII H event. If the
binary survived the explosion, this star should now have a compact companion,
most likely a stellar-mass black hole. Comparison of abundance data with
predicted values and a search for a compact companion should provide a
stringent test of the proposed r-process model. The U-Th age determined by
Cayrel et al. for CS 31082-001 is, to within substantial uncertainties, in
accord with the r-process age determined from solar system data. The time gap
between Big Bang and onset of normal star formation only allows r-process
chronometers to provide a lower limit on the age of the universe.


title:
Cold Gas Kinematics in an L* Spiral Galaxy at z=0.437: The Nature of
  Damped Lyman-alpha Absorbers

abstract:
  Westerbork Radio Synthesis Telescope observations of the redshifted 21cm line
absorber against the z_em = 0.871 double lobed quasar 3C196 show that the
intervening absorber is an L approximately equal L* spiral galaxy (3C196-G1)
and that the absorbing layer of cold gas extends to radii of at least 30
h_50^-1 kpc. The new data solve several long standing puzzles about this system
by (1) discovering a second 21cm absorption feature, corresponding to
absorption against the NE lobe of the background radio source and (2) spatially
``resolving'' the two absorption features to isolate the absorption along the
two lines of sight to the opposing radio lobes. These findings resolve the
disagreement in redshift between the UV metal and 21cm lines, and as well as
demonstrating that the neutral layer does absorb both lobes of the background
radio source. Simple kinematic models with an inclined, rotating gas disk match
the observed 21cm profile and are also compatible with both the redshift and
velocity spread of the absorption measured in UV resonance lines along a third,
independent line of sight to the quasar nucleus and with the lack of 21cm
absorption in as earlier VLBI experiment that was sensitive to opacity against
the hot spot in the northern lobe. The inferred rotation speed and luminosity
for the galaxy are compatible with the z approximately 0 Tully-Fisher Relation.
  This system illustrates well how 21cm absorption against extended background
radio sources is a powerful tool in determining the nature of the damped
Lyman-alpha class of QSO absorption line system.


title:
Caltech Faint Galaxy Redshift Survey XV: Classification of Galaxies with
  0.2 < z < 1.1 in the Hubble Deep Field (North) and its Flanking Fields

abstract:
  To circumvent the spatial effects of resolution on galaxy classification, the
images of 233 objects of known redshift in the Hubble Deep Field (HDF) and its
Flanking Fields (FF) that have redshifts in the range 0.20 < z < 1.10 were
degraded to the resolution that they would have had if they were all located at
a redshift z= 1.00. As in paper XIV of the present series, the effects of
shifts in rest wavelength were mitigated by using R-band images for the
classification of galaxies with 0.2 < z < 0.6 and I-band images for objects
with redshifts 0.6 < z < 1.1. A special effort was made to search for bars in
distant galaxies. The present data strongly confirm the previous conclusion
that the Hubble tuning fork diagram only provides a satisfactory framework for
the classification of galaxies with z ~< 0.3. More distant disk galaxies are
often difficult to shoehorn into the Hubble classification scheme. The paucity
of barred spirals and of grand-design spirals at large redshifts is confirmed.
It is concluded that the morphology of disk galaxies observed at look-back
times smaller than 3--4 Gyr differs systematically from that of more distant
galaxies viewed at look-back times of 4--8 Gyr. The disks of late-type spirals
at z >0.5 are seen to be more chaotic than those of their nearer counterparts.
Furthermore the spiral structure in distant early-type spirals appears to be
less well-developed than it is in nearby early-galaxies.


title:
A High Spatial Resolution Analysis of the MAXIMA-1 Cosmic Microwave
  Background Anisotropy Data

abstract:
  We extend the analysis of the MAXIMA-1 cosmic microwave background (CMB) data
to smaller angular scales. MAXIMA, a bolometric balloon experiment, mapped a
124 deg$^2$ region of the sky with 10\arcmin resolution at frequencies of 150,
240 and 410 GHz during its first flight. The original analysis, which covered
the multipole range $36 \leq \ell \leq 785$, is extended to $\ell = 1235$ using
data from three 150 GHz photometers in the fully cross-linked central 60
deg$^2$ of the map. The main improvement over the original analysis is the use
of 3\arcmin square pixels in the calculation of the map. The new analysis is
consistent with the original for $\ell < 785$. For $\ell > 785$, where
inflationary models predict a third acoustic peak, the new analysis shows power
with an amplitude of $56 \pm 7$ \microk at $\ell \simeq 850$ in excess to the
average power of $42 \pm 3$ \microk in the range $441 < \ell < 785$.


title:
A measurement by BOOMERANG of multiple peaks in the angular power
  spectrum of the cosmic microwave background

abstract:
  This paper presents a measurement of the angular power spectrum of the Cosmic
Microwave Background from l=75 to l=1025 (~10' to 5 degrees) from a combined
analysis of four 150 GHz channels in the BOOMERANG experiment. The spectrum
contains multiple peaks and minima, as predicted by standard
adiabatic-inflationary models in which the primordial plasma undergoes acoustic
oscillations. These results significantly constrain the values of Omega_tot,
Omega_b h^2, Omega_c h^2 and n_s.


title:
Prediction of supersoft X-ray phase, helium enrichment, and turn-off
  time in recurrent nova CI Aquilae 2000 outburst

abstract:
  Recurrent nova CI Aquilae is still bright 300 days after the optical maximum,
showing the slowest evolution among recurrent novae. We predict the turn-off
time of CI Aql 2000 outburst coming in August 2001 after a supersoft X-ray
source (SSS) phase lasts 250 days. We also predict helium enrichment of ejecta,
He/H = 0.25 by number. Observational confirmations are urgently required. Based
on the optically thick wind mass-loss theory of the thermonuclear runaway
model, we have also estimated the WD mass to be 1.2 +- 0.05 Msun by fitting our
theoretical light curves with the 1917 and 2000 outbursts. The mass of the
hydrogen-rich envelope on the WD is also estimated to be 6 x 10^{-6} Msun at
the optical maximum, indicating an average mass accretion rate of 0.7 x 10^{-7}
Msun/yr during the quiescent phase between the 1917 and 2000 outbursts. Using
these obtained values, we have consistently reproduced the light curve in
quiescence as well as the two outburst phases. Thus, we predict the turn-off
time to be in August 2001 for the 2000 outburst. We strongly recommend soft
X-ray observations to detect SSS until August 2001 because the massive wind
phase have already ended in December 2000 followed by an SSS phase that very
likely lasts until August 2001.


title: Nuclear astrophysics researches in an ion trap apparatus

abstract:
  At low energies, far below Coulumb barrier, fusion nuclear reactions are very
sensitive to its shape, which is usually in experiments modified by atomic
electrons of targer or both projectile and target particles. This article
describes proposal on construction of an installation and measurements of
excitation functions for d(d,p)t reaction in the region 1.5<E_{cm}<12.0 keV for
3^He(d,p)4^He reaction in the region 6.5<E_{cm}<15.0 keV center of mass energy
in the conditions when the both beam and target particles would be in bare
nuclear states. The technology of Electron Beam Ion Sources and Traps can
provide such experimental conditions. Possibilities to study some other
reactions are also considered.


title:
Mass-Metallicity Relation for the Local Group Dwarf Spheroidal Galaxies:
  A New Picture for the Chemical Enrichment of Galaxies in the Lowest Mass
  Range

abstract:
  The virial mass ($M_{\rm vir}$)-metallicity relation among the Local Group
dwarf spheroidal galaxies (dSphs) is examined. Hirashita, Takeuchi, & Tamura
showed that the dSphs can be divided into two distinct classes with respect to
the relation between their virial masses and luminosities: low-mass ($M_{\rm
vir} \la 10^8 M_\odot$) and high-mass ($M_{\rm vir} \ga 10^8 M_\odot$) groups.
We see that both the mass-metallicity and the mass-luminosity relations of the
high-mass dSphs are understood as a low-mass extension of giant ellipticals. On
the contrary, we find that the classical galactic-wind model is problematic to
apply to the low-mass dSphs, whose low binding energy is comparable to that
released by several supernova explosions. A strongly regulated star formation
in their formation phase is required to reproduce their observed metallicity.
Such regulation is naturally expected in a gas cloud with the primordial
elemental abundance according to Nishi & Tashiro. A significant scatter in the
mass-metallicity relation for the low-mass dSphs is also successfully explained
along with the scenario of Hirashita and coworkers. We not only propose a new
picture for a chemical enrichment of the dSphs, but also suggest that the
mass-metallicity and the mass-luminosity relations be understood in a
consistent context.


title: Perturbation evolution with a non-minimally coupled scalar field

abstract:
  We recently proposed a simple dilaton-derived quintessence model in which the
scalar field was non-minimally coupled to cold dark matter, but not to
`visible' matter. Such couplings can be attributed to the dilaton in the low
energy limit of string theory, beyond tree level. In this paper we discuss the
implications of such a model on structure formation, looking at its impact on
matter perturbations and CMB anisotropies. We find that the model only deviates
from $\Lambda$CDM and minimally coupled theories at late times, and is well
fitted to current observational data. The signature left by the coupling, when
it breaks degeneracy at late times, presents a valuable opportunity to
constrain non-minimal couplings given the wealth of new observational data
promised in the near future.


title: Luminous and Dark Matter in the Milky Way

abstract:
  (Abridged) Axisymmetric models of the Milky Way exhibit strong interrelations
between the Galactic constants (R_0 and T_0), the stellar columndensity (S_*)
and the shape of the dark matter (DM) halo. Here we present analytical
relations that can be used to investigate the effects of the uncertain gaseous
velocity dispersion on the HI flaring constraints. The contribution of cosmic
rays and magnetic fields to the pressure gradients is small. A significantly
flattened dark matter halo is only possible if R_0 <~ 6.8 kpc.
  If R_0 is larger than ~7 kpc, or T_0 >~ 170 km/s, we can rule out two DM
candidates that require a highly flattened DM halo: 1) decaying massive
neutrinos; and 2) a disk of cold molecular hydrogen.
  It is only possible to construct self-consistent models of the Galaxy based
on the IAU-recommended values for the Galactic constants in the unlikely case
that the the stellar columndensity is smaller than ~18 M_sun/pc^2. If we assume
that the halo is oblate and S_* = 35 +/- 5 M_sun/pc^2, R_0 <~ 8 kpc and T_0 <~
200 km/s.
  Combining the best kinematical and star-count estimates of S_*, we conclude
that: 25 <~ S_* <~ 45 M_sun/pc^2. Kuijken & Gilmore's (1991) determination of
the columndensity of matter with |z|<=1.1 kpc is robust and valid over a wide
range of Galactic constants.
  Our mass models show that the DM density in the Galactic centre is uncertain
by a factor 1000. In the Solar neighbourhood we find: rho_DM ~0.42 GeV/c^2/cm^3
or (11 +/- 5) mM_sun/pc^3 -- roughly 15% of rho_tot.


title: The First Detection of Co in a Damped Lyman Alpha System

abstract:
  The study of elemental abundances in Damped Lyman Alpha systems (DLAs) at
high redshift represents one of our best opportunities to probe galaxy
formation and chemical evolution at early times. By coupling measurements made
in high z DLAs with our knowledge of abundances determined locally and with
nucleosynthetic models, we can start to piece together the star formation
histories of these galaxies. Here, we discuss the clues to galactic chemical
evolution that may be gleaned from studying the abundance of Co in DLAs. We
present high resolution echelle spectra of two QSOs, Q2206-199 and Q1223+17,
both already known to exhibit intervening damped systems. These observations
have resulted in the first ever detection of Co at high redshift, associated
with the z= 1.92 DLA in the sightline towards Q2206-199. We find that the
abundance of Co is approximately 1/4 solar and that there is a clear
overabundance relative to iron, [Co/Fe] = +0.31 +/- 0.05. From the abundance of
Zn, we determine that this is a relatively metal-rich DLA, with a metallicity
approximately 1/3 solar. Therefore, this first detection of Co is similar to
the marked overabundance relative to Fe seen in Galactic bulge and thick disk
stars.


title:
Modelling The First Probable Two Plane Lens System B2114+022:
  Reproducing Two Compact Radio Cores A, D

abstract:
  We test possible lensing scenarios of the JVAS system B2114+022, in which two
galaxies at different redshifts (``G1'' at $z_1 = 0.3157$ and ``G2'' at $z_2 =
0.5883$) are found within 2 arcseconds of quadruple radio sources. For our
investigation, we use possible lensing constraints derived from a wealth of
data on the radio sources obtained with VLA, MERLIN, VLBA and EVN as well as
HST imaging data on the two galaxies, which are presented in Augusto et al. In
the present study, we focus on reproducing the widest separated,
observationally similar radio components A and D as lensed images. We first
treat G2 (which is the more distant one from the geometric centre) as a shear
term, and then consider two plane lensing explicitly including G2's potential
at the $z_2$ plane as the first case of two plane lens modelling. Our modelling
results not only support the hypothesis that the system includes
gravitationally lensed images of a higher redshift extragalactic object, but
they also show that the explicit inclusion of G2's potential at the second lens
plane is necessary in order to fit the data with astrophysically plausible
galaxy parameters. Finally, we illustrate a natural consequence of a two-plane
lens system, namely the prediction of distortion as well as shift and
stretching of G2's isophotes by G1's potential, which can in principle be
measured by subtracting out G1's light distribution in a high S/N and good
angular resolution image, especially a multi-colour one.


title: Discovery of a 75 day orbit in XTE J1543-568

abstract:
  Dedicated monitoring of the transient X-ray pulsar XTE J1543-568 during the
first year after its discovery has revealed the unambiguous detection of a
binary orbit. The orbital period is 75.56+/-0.25 d, and the projected
semi-major axis 353+/-8 lt-sec. The mass function and position in the pulse
period versus orbital period diagram are consistent with XTE J1543-568 being a
Be X-ray binary. The eccentricity of less than 0.03 (2 sigma) is among the
lowest for the 12 Be X-ray binaries whose orbits have now been measured. This
confirms the suspicion that small kick velocities of neutron stars during
supernovae are more common than expected. The distance is estimated to be
larger than 10 kpc, and the luminosity at least 1E37 erg/s.


title: Radio flares and plasmon size in Cygnus X-3

abstract:
  We have observed a number of minor radio flares in Cyg X-3 using the MERLIN
array. Photometric observations show the system to be highly active with
multiple flares on hourly timescales over the one month observing programme.
Analysis of the source's power spectrum show no persistent periodicities in
these data, and no evidence of the 4.8 hr orbital period. An upper limit of 15
mJy can be placed on the amplitude of any sinusoidal varaition of source flux
at the orbital period. The brightness temperature of a flare is typically T >
10^{9}- 10^{10} K, with a number of small flares of 5 minute duration having
brightness temperatures of T > few x 10^{11} K. For such a change in flux to
occur within a typical 10 minute timescale, the radiation must originate from
plasmons with a size < 1.22 AU. This emission is unlikely to originate close to
the centre of the system as both the jets and compact object are buried deep
within an optically thick stellar wind. Assuming a spherically symmetric wind,
plasmons would become visible at distances ~ 13 AU from the core.


title: X-ray emission from middle-aged pulsars

abstract:
  We present a simple, unified model which accounts for properties of the X-ray
emission from the three middle-aged pulsars PSR 1055-52, PSR 0656+14 and PSR
0630+18 (Geminga). The X-ray radiation from these objects is pulsed more
strongly at energies above a transition point around 0.5 keV. In addition, the
phase of the pulses shifts by about 80-100 degrees around the same point.
Geminga also has the peculiarity that its pulsed fraction decreases in the
0.3-0.5 keV energy range, attaining a minimum near 0.5 keV. We show that a
two-component hydrogen atmosphere is able to account for these disparate
features. In our model, the hotter component is powered by particle bombardment
and is restricted to the polar regions, while the cooler one covers the entire
stellar surface. The two components also differ in their emission patterns,
with the hard and soft contributions coming from areas radiating into fan and
pencil beams, respectively.


title: Gamma-ray Burst Remnants: How can we find them?

abstract:
  By now there is substantial evidence that Gamma-Ray Bursts (GRBs) originate
at cosmological distances from very powerful explosions. The interaction
between a GRB and its surrounding environment has dramatic consequences on the
environment itself. At early times, the strong X-ray UV afterglow flux
photoionizes the medium on distance scales on the order of 100 pc or more. Here
I discuss the long-term effects resulting from the interaction between a GRB
and its environment, and in particular the signatures of the emission spectrum
produced while the heated and ionized gas slowly cools and recombines. Besides
photoionizing the medium with its afterglow, a GRB explosion drives a blast
wave which is expected to have a very long lifetime. I discuss possible
candidates for such GRB remnants in our own and in nearby galaxies, and ways to
distinguish them from remnants due to other phenomena, such as multiple
supernova (SN) explosions.


title: JHK Spectroscopy of the z=2.39 Radio Galaxy 53W002 and Its Companions

abstract:
  We present low-resolution, near-IR JHK spectra of the weak z=2.39 radio
galaxy 53W002 and its companion objects #18 and #19, obtained with OHS/CISCO on
the Subaru Telescope. They cover rest-frame wavelengths of 3400-7200A, and many
rest-optical emission lines are detected. Contributions to the broad-band flux
from these emission lines are found to be very large, up to 40% in the H and
K'-bands and 30% in the J-band.


title: JHK Spectra of the z=2.39 Radio Galaxy 53W002

abstract:
  We present low-resolution, near-IR JHK spectra of the weak z=2.39 radio
galaxy 53W002, obtained with the OH-airglow Suppressor spectrograph (OHS) and
Cooled Infrared Spectrograph and Camera for OHS (CISCO) on the Subaru
Telescope. They cover rest-frame wavelengths of 3400-7200 A, and the emission
lines of [O II]3727, Hb, [O III]4959, 5007, Ha, [N II]6548, 6583 and [S
II]6716, 6731 were detected. Using the Ha/Hb line ratio, we find an extinction
of E(B-V)=0.14. The emission-line ratios are reproduced by a cloud of electron
density n_e=1x10^{3-4}(/cm3) with solar metallicity, ionized by an alpha=-0.7
power-law continuum with ionizing parameter U=1x10^-3. In addition to these
emission lines, we make the first spectroscopic confirmation of the Balmer
discontinuity in a high-z radio galaxy. Together with rest-frame UV photometry
from the literature, we show that at least 1/3 of the present stellar mass was
formed in the current starburst. The stellar mass was estimated to be
(1-1.4)x10^11 M_sol by one-component model fitting, which is smaller than that
of typical z~1 B2/6C radio galaxies. We suggest that 53W002 is currently
assembling a large part of its stellar mass through merger events with the
surrounding sub-galactic clumps, some of which can be identified with the Lya
emitters detected in narrow-band imaging. After a few such events over the next
few Gyr, 53W002 will evolve into a massive elliptical galaxy.


title:
A New Measurement of the Primordial Abundance of Deuterium: Toward
  Convergence with the Baryon Density from the CMB?

abstract:
  From the analysis of the near-UV spectrum of the QSO 2206-199, obtained with
a long series of exposures with STIS on the HST, we deduce a value (D/H) =
(1.65 +/- 0.35) x 10(-5) (1 sigma error) for the abundance of deuterium in the
z(abs) = 2.0762 damped Lyman alpha system (DLA) along this sight-line. The
velocity structure of this absorber is very simple and its neutral hydrogen
column density, N(H I), is accurately known; the error in D/H is mostly due to
the limited signal-to-noise ratio of the spectrum. Since this is also one of
the most metal-poor DLAs, with metal abundances of about 1/200 of solar, the
correction due to astration of D is expected to be insignificant and the value
we deduce should be essentially the primordial abundance of deuterium. When all
(six) available measurements of D/H in high redshift QSO absorbers are
considered, we find that the three DLAs---where N(H I) is measured most
reliably---give consistently lower values than the three Lyman limit systems.
We point out that the weighted mean of the DLA measurements, D/H = (2.2 +/-
0.2) x 10(-5), yields a baryon density Omega_B h^2 = 0.025 +/- 0.001 which is
within 1 sigma of the value deduced from the analysis of the CMB angular power
spectrum, and is still consistent with the present-day D/H and models of
Galactic chemical evolution. Future observations of D I absorption in other
DLAs are needed to establish whether our finding reflects a real advantage of
DLAs over other classes of QSO absorbers for the measurement of D, or is just a
statistical fluctuation.


title: Eccentricity Evolution of Resonant Migrating Planets

abstract:
  We examine the eccentricity evolution of a system of two planets locked in a
mean motion resonance, in which the outer planet loses energy and angular
momentum. The sink of energy and angular momentum could be either a gas or
planetesimal disk. We show that the eccentricity of both planetary bodies can
grow to large values, particularly if the inner body does not directly exchange
energy or angular momentum with the disk. We analytically calculate the
eccentricity damping rate in the case of a single planet migrating through a
planetesimal disk. We present the results of numerical integrations of two
resonant planets showing rapid growth of eccentricity. We also present
integrations in which a Jupiter-mass planet is forced to migrate inward through
a system of 5-10 roughly Earth mass planets. The migrating planet can eject or
accrete the smaller bodies; roughly 5% of the mass (averaged over all the
integrations) accretes onto the central star. The results are discussed in the
context of the currently known extrasolar planetary systems.


title:
Detection of Pulsed X-ray Emission from The Fastest Millisecond Pulsar
  PSR B1937+21 with ASCA

abstract:
  We have detected pulsed X-ray emission from the fastest millisecond pulsar
known, PSR B1937+21 (P=1.558 msec), with ASCA. The pulsar is detected as a
point source above $\sim 1.7$ keV, with no indication of nebulosity. The source
flux in the 2--10 keV band is found to be $f = (3.7\pm 0.6) \times 10^{-13}$
erg s$^{-1}$ cm$^{-2}$, which implies an isotropic luminosity of $L_{\rm x} = 4
\pi D^2 f \sim (5.7\pm 1.0) \times 10^{32} ~(D/3.6 {\rm kpc})^2$ erg s$^{-1}$,
where D is the distance, and an X-ray efficiency of $\sim 5 \times 10^{-4}$
relative to the spin-down power of the pulsar.
  The pulsation is found at the period predicted by the radio ephemeris with a
very narrow primary peak, the width of which is about 1/16 phase ($\sim 100
\mu$s), near the time resolution limit ($61 \mu$s) of the observation. The
instantaneous flux in the primary peak (1/16 phase interval) is found to be
($4.0\pm 0.8) \times 10^{-12}$ erg s$^{-1}$ cm$^{-2}$. Although there is an
indication for the secondary peak, we consider its statistical significance too
low to claim a definite detection.
  The narrow pulse profile and the detection in the 2--10 keV band imply that
the X-ray emission is caused by the magnetospheric particle acceleration.
Comparison of X-ray and radio arrival times of pulses indicates, within the
timing errors, that the X-ray pulse is coincident with the radio interpulse.


title:
VLT Spectroscopy of Galaxies Lensed by Abell AC114: Implication for the
  Mass Model and the Study of Low-Luminosity Galaxies at High-Redshift

abstract:
  We present the first results of a spectroscopic survey of faint lensed
galaxie s in the core of the galaxy cluster AC114 (z=0.312) obtained from
observations w ith the FORS1 spectrograph mounted on the VLT-Antu. The galaxies
were chose n in areas close to the high-z critical lines predicted by the
gravitational lens model of Natarajan et al (NKSE, 1998) for this cluster,
according to both lensing and photometric redshift criteria. All the target
galaxies are found to correspond to background galaxies with redshifts values
in the [0.7, 3.5] interval. Our spectroscopic observations confirm the
predicted lensing redshifts for 3 of the multiple-image galaxies, and together
with predictions of the NKSE model led to the discovery of a new 5-image
configuration at redshift z=3.347. A revised NKSE model, compatible with the
redshift of this new multiple-image system, was generated and employed to
calculate the gravitational amplifications of all the observed galaxies. The
galaxies corresponding to the multiple-image systems are found to be
intrinsically fainter, between 0.5 and 1.5 magnitudes, than the limiting
magnitudes of existing blank field studies. When all the observed background
galaxies are considered, the resulting intrinsic absolute magnitudes range from
M_B~-22 to -19. Therefore, a large gain in sensitivity towards low luminosity
high-z objects can actually be obtained, in agreement with theoretical
expectations. This method can be used advantageously to probe the high redshift
Universe and, in particular, its application to an ensemble of massive cluster
cores could constraint the faint end of luminosity function of high redshift
galaxies.


title: Low Albedos Among Extinct Comet Candidates

abstract:
  We present radiometric effective radii and visual geometric albedos for six
asteroids in comet-like orbits. Our sample has three of the four known
retrograde asteroids (1999 LE31, 2000 DG8, and 2000 HE46) and three objects
((18916) 2000 OG44, 2000 PG3, and 2000 SB1) on prograde but highly elliptical
orbits. These measurements more than double the number of known albedos for
asteroids with a Tisserand invariant in the cometary regime. We find that all
six of our objects, and nine of the ten now known, have albedos that are as low
as those of active cometary nuclei, which is consistent with their supposed
evolutionary connection to that group. This albedo distribution is distinct
from that of the whole near-Earth and unusual asteroid population, and the
strong correlation between Tisserand invariant and albedo suggests there is a
significant cometary contribution to this asteroid population.


title: H2 Formation in Low Metallicity Galaxies

abstract:
  A possible formation mechanism of hydrogen molecules on a galactic scale is
examined. We are interested especially in the role of hydrogen molecules for
formation and evolution of primordial galaxies. Then, formation process of
hydrogen molecules in a very low-metallicity galaxy (I Zw 18; the most typical
metal-deficient galaxy) is studied. Adopting a recent observational result of
absorption lines of hydrogen molecule in I Zw 18, we obtain the upper limit for
the ionization degree in the case where hydrogen molecules can form via the
H$^{-}$-process, although they are generally believed to form on the surface of
dust grains. Furthermore, we present a critical ionization degree, above which
H$^{-}$-process can be dominant over the formation process on the surface of
grains. Interestingly, this critical ionization degree is comparable to the
upper limit of the ionization degree for I Zw 18. For determination of the
formation process of hydrogen molecules, future observational facilities can be
useful. Thus, we examine the detectability in some wavelengths for the metal
deficient galaxies. According to our estimate, near-infrared line emission of
hydrogen molecule is observable in the level of 10 $\mu$Jy, the free-free radio
emission is in the level of mJy, and the far-infrared emission from the dust on
which hydrogen molecules form can also be detected with 10-mJy level with its
temperature of 16 K. The near-infrared line and the far-infrared continuum are
feasible for ASTRO-F observations.


title:
On the Possibility of Observing H2 Emission from Primordial Molecular
  Cloud Kernels

abstract:
  We study the prospects for observing H$_2$ emission during the assembly of
primordial molecular cloud kernels. The primordial molecular cloud cores, which
resemble those at the present epoch, can emerge around $1+z=20$ according to
recent numerical simulations. The kernels form inside the cores, and the first
stars will appear inside the kernels. A kernel typically contracts to form one
of the first generation stars with an accretion rate that is as large as $\sim
0.01 M_\odot$ year$^{-1}$. This occurs due to the primordial abundances that
result in a kernel temperature of order 1000K, and the collapsing kernel emits
H$_2$ line radiation at a rate $\sim 10^{35}$ erg sec$^{-1}$. Principally
$J=5-3$ (v=0) rotational emission of H$_2$ is expected. At redshift $1+z=20$,
the expected flux is $\sim 0.01~\mu$Jy for a single kernel. While an individual
object is not observable by any facilities available in the near future, the
expected assembly of primordial star clusters on sub-galactic scales can result
in fluxes at the sub-mJy level. This is marginally observable with ASTRO-F. We
also examine the rotational $J=2-0$ (v=0) and vibrational $\delta v = 1$
emission lines. The former may possibly be detectable with ALMA.


title:
Different Types of X-ray Variability Observed in Micro-Quasar GRS
  1915+105 with the IXAE

abstract:
  The galactic micro-quasar source GRS 1915+105 has been observed with the
Indian X-ray Astronomy Experiment (IXAE) several times over a period extending
from 1996 to 2000. The source has been observed in different luminosity states
and exhibits a rich variety of random and regular X-ray variability over a wide
range of time scales. It also shows a unique variability characteristic namely
the occurrence of quasi-regular X-ray bursts with period ranging from 20 s to
about 100 s which have slow rise and fast decay. The X-ray spectrum of these
bursts is hardest near the end of decay. In the low-hard state and bright-soft
state with rapid variability, the source exhibits quasi-periodic oscillations
(QPOs) with variable frequency which is luminosity dependent. Regular X-ray
intensity dips have been detected coincident with the occurrence of a giant
radio outburst. The source made a transition from a low-state to a high-state
in 1999 in less than a day and from a soft-bright state to a hard-low state in
2000 in less than 100 minutes during the IXAE observations. Details of these
and other variability characteristics of the source are presented in this
paper.


title: Conference Summary - 20th Texas Symposium on Relativistic Astrophysics

abstract:
  This is the written version of the summary talk given at the 20th Texas
Symposium on Relativistic Astrophysics in Austin, Texas, on December 15, 2000.
After a brief summary of some of the highlights at the conference, comments are
offered on three special topics: theories with large additional spatial
dimensions, the cosmological constant problems, and the analysis of
fluctuations in the cosmic microwave background.


title:
The photometric-amplitude and mass-ratio distributions of contact binary
  stars

abstract:
  The distribution of the light-variation amplitudes, A(a), in addition to
determining the number of undiscovered contact binary systems falling below
photometric detection thresholds and thus lost to statistics, can serve as a
tool in determination of the mass-ratio distribution, Q(q), which is very
important for understanding of the evolution of contact binaries. Calculations
of the expected A(a) show that it tends to converge to a mass-ratio dependent
constant value for a->0. Strong dependence of A(a) on Q(q) can be used to
determine the latter distribution, but the technique is limited by the presence
of unresolved visual companions and by blending in crowded areas of the sky.
The bright-star sample to 7.5 magnitude is too small for an application of the
technique while the the Baade's Window sample from the OGLE project may suffer
stronger blending; thus the present results are preliminary and illustrative
only. Estimates based on the Baade's Window data from the OGLE project, for
amplitudes a>0.3 mag. where the statistics appear to be complete allowing
determination of Q(q) over 0.12<q<1, suggest a steep increase of Q(q) with
q->0. The mass-ratio distribution can be approximated by a power law, either
Q(q)~(1-q)^a1 with a1=6+/-2 or Q(q)~q^b1, with b1=-2+/-0.5, with a slight
preference for the former form. Both forms must be modified by the
theoretically expected cut-off caused by a tidal instability at about q_min
0.07-0.1. An expected maximum in Q(q), is expected to be mapped into a local
maximum in A(a) around 0.2-0.25 mag.


title:
A re-analysis of the optical light curves of XTE~J2123-058: the mass of
  the binary components and the outburst mechanism

abstract:
  Rejected by MNRAS due to irregularites in the text. The first author is
solely resposible for this.


title:
Specifying the Environments around GRB, Explaining the Fe line in the
  X-Ray Afterglow of GRB000214

abstract:
  We present a model explaining the Fe K alpha line and the continuum in the
afterglow of GRB000214. We pose the importance to seek the physically natural
environment around GRB000214. For the reproduction of the observation, we need
the ring-like remnant around the progenitor like that of SN 1987A produced by
the mass-loss of the progenitor and the fireball spread over in every
directions. The observation of GRB000214, in which the continuum power law
spectrum decreased faster than the line, motivated us to consider the two
independent systems for the line emission and the continuum spectrum. At first,
the continuum spectrum can be fitted by the afterglow emission of the fireball
pointing toward the observer which does not collide with the ring because the
emission of GRB and the afterglow are highly collimated to the observer by the
relativistic beaming effect. Secondly, the line can be fitted by the
fluorescence of the Fe atoms in the ring illuminated by the X-ray afterglow.
The significance of this study is that our model may constrain strongly the GRB
model. Although the Supranova model assumes the extreme-ring-like remnant
produced by the usual supernova explosion, this may not be probable. It is
because the supernova remnants are known to be shell-like. The model also
assumes two steps of explosions, on the other hand, we need only one explosion
of the progenitor. In this sense, our scenario is more natural. Moreover, in
the numerical simulations of Hypernova, the jet of the opening angle of only 1
degree is generated. In our model, the fireball which spreads over in every
directions reconciles with the observation of 1 percent of the polarization in
the observation of SN1998bw which showed the explosion might not be so
collimated.


title: The Location of CMB Peaks in a Universe with Dark Energy

abstract:
  The locations of the peaks of the CMB spectrum are sensitive indicators of
cosmological parameters, yet there is no known analytic formula which
accurately describes their dependence on them. We parametrize the location of
the peaks as l_m = l_A(m - \phi_m), where l_A is the analytically calculable
acoustic scale and m labels the peak number. Fitting formulae for the phase
shifts \phi_m for the first three peaks and the first trough are given. It is
shown that in a wide range of parameter space, the acoustic scale l_A can be
retrieved from actual CMB measurements of the first three peaks within one
percent accuracy. This can be used to speed up likelihood analysis. We describe
how the peak shifts can be used to distinguish between different models of dark
energy.


title: Discovery of a 450 Hz QPO from the Microquasar GRO J1655-40 with RXTE

abstract:
  We report the discovery with the proportional counter array (PCA) onboard the
Rossi X-ray Timing Explorer (RXTE) of a 450 Hz quasiperiodic oscillation (QPO)
in the hard X-ray flux from the galactic microquasar GRO J1655-40. This is the
highest frequency QPO modulation seen to date from a black hole. The QPO is
detected only in the hard X-ray band above 13 keV. It is both strong and
narrow, with a typical rms amplitude of 4.5 % in the 13 - 27 keV range, and a
width of 40 Hz (FWHM). For two observations in which we detect the 450 Hz QPO a
previously known 300 Hz QPO is also observed in the 2 - 13 keV band. We show
that these two QPO sometimes appear simultaneously, thus demonstrating the
first detection of a pair of high frequency QPO in a black hole system. Prior
to this, pairs of high frequency QPO have only been detected in neutron star
systems. GRO J1655-40 is one of only a handful of black hole systems with a
good dynamical mass constraint. For a non-rotating black hole with mass between
5.5 - 7.9 solar masses, the innermost stable circular orbit (ISCO) ranges from
45 - 70 km. For any mass in this range the radius at which the orbital
frequency reaches 450 Hz is less than the ISCO radius, indicating that if the
modulation is caused by Kepler motion, the black hole must have appreciable
spin. If the QPO frequency is set by the orbital frequency of matter at the
ISCO then for this mass range the dimensionless angular momentum lies between
0.15 < j < 0.5. Moreover, if the modulation is caused by oscillation modes in
the disk or Lense-Thirring precession, then this would also require a rapidly
rotating hole. We briefly discuss the implications of our findings for models
of X-ray variability in black holes and neutron stars.


title:
Experiment Design and First Season Observations with the Degree Angular
  Scale Interferometer

abstract:
  We describe the instrumentation, experiment design and data reduction for the
first season of observations with the Degree Angular Scale Interferometer
(DASI), a compact microwave interferometer designed to measure anisotropy in
the Cosmic Microwave Background (CMB) on degree and sub-degree scales
(l=100--900). The telescope was deployed at the Amundsen-Scott South Pole
research station during the 1999--2000 austral summer and conducted
observations of the CMB throughout the following austral winter. In its first
season of observations, DASI has mapped CMB fluctuations in 32 fields, each 3.4
deg across, with high sensitivity.


title:
DASI First Results: A Measurement of the Cosmic Microwave Background
  Angular Power Spectrum

abstract:
  We present measurements of anisotropy in the Cosmic Microwave Background
(CMB) from the first season of observations with the Degree Angular Scale
Interferometer (DASI). The instrument was deployed at the South Pole in the
austral summer 1999--2000, and made observations throughout the following
austral winter. We have measured the angular power spectrum of the CMB in the
range 100<l<900 with high signal-to-noise. In this paper we review the
formalism used in the analysis, in particular the use of constraint matrices to
project out contaminants such as ground and point source signals, and to test
for correlations with diffuse foreground templates. We find no evidence of
foregrounds other than point sources in the data, and find a maximum likelihood
temperature spectral index beta = -0.1 +/- 0.2 (1 sigma), consistent with CMB.
We detect a first peak in the power spectrum at l approx 200, in agreement with
previous experiments. In addition, we detect a peak in the power spectrum at l
approx 550 and power of similar magnitude at l approx 800 which are consistent
with the second and third harmonic peaks predicted by adiabatic inflationary
cosmological models.


title:
Cosmological Parameter Extraction from the First Season of Observations
  with DASI

abstract:
  The Degree Angular Scale Interferometer (\dasi) has measured the power
spectrum of the Cosmic Microwave Background anisotropy over the range of
spherical harmonic multipoles 100<l<900. We compare this data, in combination
with the COBE-DMR results, to a seven dimensional grid of adiabatic CDM models.
Adopting the priors h>0.45 and 0.0<=tau_c<=0.4, we find that the total density
of the Universe Omega_tot=1.04+/-0.06, and the spectral index of the initial
scalar fluctuations n_s=1.01+0.08-0.06, in accordance with the predictions of
inflationary theory. In addition we find that the physical density of baryons
Omega_b.h^2=0.022+0.004-0.003, and the physical density of cold dark matter
Omega_cdm.h^2=0.14+/-0.04. This value of Omega_b.h^2 is consistent with that
derived from measurements of the primordial abundance ratios of the light
elements combined with big bang nucleosynthesis theory. Using the result of the
HST Key Project h=0.72+/-0.08 we find that Omega_t=1.00+/-0.04, the matter
density Omega_m=0.40+/-0.15, and the vacuum energy density
Omega_lambda=0.60+/-0.15. (All 68% confidence limits.)


title:
The X-ray Source SLX 1732-304 in the Globular Cluster Terzan 1: The
  Spectral States and an X-ray Burst

abstract:
  The results of ART-P/Granat observations of the X-ray burster SLX1732-304 in
the globular cluster Terzan 1 are presented. The X-ray (3-20 keV) fluxes from
the source differed by more than a factor of 4 during the observing sessions on
September 8 ($F_{\rm X}\simeq6.95\times10^{-10}$ erg cm$^{-2}$ s$^{-1}$) and
October 6, 1990 ($F_{\rm X}\simeq1.64\times10^{-10}$ erg cm$^{-2}$ s$^{-1}$).
The intensity variations of SLX1732-304 were apparently accompanied by
variations in its hardness: whereas the source in its high state had the
spectrum with a distinct exponential cutoff typical of bright low-mass X-ray
binaries, its low-state spectrum could be satisfactorily described by a simple
power law with a photon index $\alpha\simeq1.7$. During the ART-P observation
on September 8, a type I X-ray burst was detected from SLX1732-304.


title:
Low State of the X-ray Burster SLX 1732-304 in the Globular Cluster
  Terzan 1 According to RXTE Data

abstract:
  Observations of the X-ray burster SLX 1732-304 in the globular cluster Terzan
1 with the PCA/RXTE instrument in April 1997 are presented. The source was in a
low state; its flux in the standard X-ray band was half the flux recorded by
the ART-P/Granat telescope also during its low state. At the same time, its
spectrum was softer than the ART-P spectrum; it was well described by a power
law with a photon index of 2.3 without any evidence of a high-energy cutoff.


title: Small-Scale Variations of HI Spectra from Interstellar Scintillatio

abstract:
  I suggest that radio-wave scattering by the interstellar plasma, in
combination with subsonic gradients in the Doppler velocity of interstellar HI,
is responsible for the observed small-scale variation in HI absorption spectra
of pulsars. Velocity gradients on the order of 0.05 to 0.3 km/s across 1 AU can
produce the observed variations. I suggest observational tests to distinguish
between this model and the traditional picture of small-scale opacity
variations from cloudlets.


title:
The Physics of Protoneutron Star Winds: Implications for r-Process
  Nucleosynthesis

abstract:
  We solve the general-relativistic steady-state eigenvalue problem of
neutrino-driven protoneutron star winds, which immediately follow core-collapse
supernova explosions. We provide velocity, density, temperature, and
composition profiles and explore the systematics and structures generic to such
a wind for a variety of protoneutron star characteristics. Furthermore, we
derive the entropy, dynamical timescale, and neutron-to-seed ratio in the
general relativistic framework essential in assessing this site as a candidate
for $r$-process nucleosynthesis. Generally, we find that for a given mass
outflow rate ($\dot{M}$), the dynamical timescale of the wind is significantly
shorter than previously thought. We argue against the existence or viability of
a high entropy ($\gtrsim300$ per k$_{B}$ per baryon), long dynamical timescale
$r$-process epoch. In support of this conclusion, we model the protoneutron
star cooling phase, calculate nucleosynthetic yields in our steady-state
profiles, and estimate the integrated mass loss. We find that transonic winds
enter a high entropy phase only with very low $\dot{M}$
($\lesssim1\times10^{-9}$ M$_\odot$ s$^{-1}$) and extremely long dynamical
timescale ($\tau_\rho\gtrsim0.5$ seconds). Our results support the possible
existence of an early $r$-process epoch at modest entropy ($\sim150$) and very
short dynamical timescale, consistent in our calculations with a very massive
or very compact protoneutron star that contracts rapidly after the preceding
supernova. We explore possible modifications to our models, which might yield
significant $r$-process nucleosynthesis generically. Finally, we speculate on
the effect of fallback and shocks on both the wind physics and nucleosynthesis.


title: Accelerating Universe and Event Horizon

abstract:
  It has been argued in the literature that if a universe is expanding with an
accelerating rate indefinitely, it presents a challenge to string theories due
to the existence of event horizons. We study the fate of a currently
accelerating universe. We show that the universe will continue to accelerate
indefinitely if the parameter $\omega = p/\rho$ of the equation of state is a
constant, no matter how many different types of energy (matter, radiation,
quintessence, cosmological constant and etc) are contained in the universe.
This type of universe will always exhibit an event horizon indicating that such
a universe may not be derived from string theories. We also comment on some
related issues.


title: The Distance to SN 1999em from the Expanding Photosphere Method

abstract:
  We present optical and IR spectroscopy of the first two months of evolution
of the Type II SN 1999em. We combine these data with high-quality optical/IR
photometry beginning only three days after shock breakout, in order to study
the performance of the ``Expanding Photosphere Method'' (EPM) in the
determination of distances. With this purpose we develop a technique to measure
accurate photospheric velocities by cross-correlating observed and model
spectra. The application of this technique to SN 1999em shows that we can reach
an average uncertainty of 11% in velocity from an individual spectrum. Our
analysis shows that EPM is quite robust to the effects of dust. In particular,
the distances derived from the VI filters change by only 7% when the adopted
visual extinction in the host galaxy is varied by 0.45 mag. The superb time
sampling of the BVIZJHK light-curves of SN 1999em permits us to study the
internal consistency of EPM and test the dilution factors computed from
atmosphere models for Type II plateau supernovae. We find that, in the first
week since explosion, the EPM distances are up to 50% lower than the average,
possibly due the presence of circumstellar material. Over the following 65
days, on the other hand, our tests lend strong credence to the atmosphere
models, and confirm previous claims that EPM can produce consistent distances
without having to craft specific models to each supernova. This is particularly
true for the VI filters which yield distances with an internal consistency of
4%. From the whole set of BVIZJHK photometry, we obtain an average distance of
7.5+/-0.5 Mpc, where the quoted uncertainty (7%) is a conservative estimate of
the internal precision of the method obtained from the analysis of the first 70
days of the supernova evolution.


title:
How accurately can the SZ effect measure peculiar cluster velocities and
  bulk flows?

abstract:
  The Sunyaev-Zel'dovich effect is a powerful tool for cosmology that can be
used to measure the radial peculiar velocities of galaxy clusters, and thus to
test, and constrain, theories of structure formation and evolution. This
requires, in principle, an accurate measurement of the effect, a good
separation between the Sunyaev-Zel'dovich components, and a good understanding
of the sources contributing to the signal and their effect on the measured
velocity. In this study, we evaluate the error in the individual radial
peculiar velocities determined with Sunyaev-Zel'dovich measurements. We
estimate, for three cosmological models, the errors induced by the major
contributing signals (primary Cosmic Microwave Background anisotropies,
Sunyaev-Zel'dovich effect due to the background cluster population, residuals
from component separation and instrumental noise). We generalise our results to
estimate the error in the bulk velocity on large scales. In this context, we
investigate the limitation due to the Sunyaev-Zel'dovich source (or spatial)
confusion in a Planck-like instrumental configuration. Finally, we propose a
strategy based on the future all-sky Sunyaev-Zel'dovich survey, that will be
provided by the Planck mission, to measure accurately the bulk velocities on
large scales up to redshift 1, or more.


title: On the Distribution of Haloes, Galaxies and Mass

abstract:
  The stochasticity in the distribution of dark haloes in the cosmic density
field is reflected in the distribution function $P_V(N_h|\delta_m)$ which gives
the probability of finding $N_h$ haloes in a volume $V$ with mass density
contrast $\delta_m$. We study the properties of this function using
high-resolution $N$-body simulations, and find that $P_V(N_n|\delta_m)$ is
significantly non-Poisson. The ratio between the variance and the mean goes
from $\sim 1$ (Poisson) at $1+\delta_m\ll 1$ to $<1$ (sub-Poisson) at
$1+\delta_m\sim 1$ to $>1$ (super-Poisson) at $1+\delta_m\gg 1$. The mean bias
relation is found to be well described by halo bias models based on the
Press-Schechter formalism. The sub-Poisson variance can be explained as a
result of halo-exclusion while the super-Poisson variance at high $\delta_m$
may be explained as a result of halo clustering. A simple phenomenological
model is proposed to describe the behavior of the variance as a function of
$\delta_m$. Galaxy distribution in the cosmic density field predicted by
semi-analytic models of galaxy formation shows similar stochastic behavior. We
discuss the implications of the stochasticity in halo bias to the modelling of
higher-order moments of dark haloes and of galaxies.


title: Russell Lecture: Dark Star Formation and Cooling Instability

abstract:
  Optically thin cooling gas at most temperatures above 30K will make
condensations by pressure pushing material into cool dense regions. This works
without gravity. Cooling condensations will flatten and become
planar/similarity solutions. Most star formation may start from cooling
condensations - with gravity only important in the later stages. The idea that
some of the dark matter could be pristine white dwarfs that condensed slowly on
to planetary sized seeds without firing nuclear reactions is found lacking.
However, recent observations indicate fifty times more halo white dwarfs than
have been previously acknowledged; enough to make the halo fraction observed as
MACHOS.
  A cosmological census shows that only 1% of the mass of the Universe is of
known constitution.


title:
Interpreting CMB Anisotropy Observations: Trying to Tell the Truth with
  Statistics

abstract:
  A conflict has been reported between the baryon density inferred from
deuterium observations and that found from recent CMB observations by BOOMERanG
and MAXIMA. Despite the flurry of papers that attempt to resolve this conflict
by adding new physics to the early universe, we will show that it can instead
be resolved via a more careful usage of statistics. Indeed, the Bayesian
analyses that produce this conflict are by their nature poorly suited for
drawing this type of conclusion. A properly defined frequentist analysis can
address this question directly and appears not to find a conflict. Finally, a
conservative accounting of systematic uncertainties in measuring the deuterium
abundance could reduce what is nominally a 3 sigma conflict to 1 sigma.


title: RX J0848+4456: Disentangling a Moderate Redshift Cluster

abstract:
  We present a multi-wavelength study of RX J0848+4456, a cluster of galaxies
discovered through X-ray emission in the ROSAT Deep Cluster Survey. Our
observations consist of WFPC2 imaging, optical spectra, and X-ray data
collected with the Chandra observatory. We find that RX J0848+4456 consists of
an X-ray emitting cluster of galaxies at a redshift of z=0.570 and a group at
slightly lower redshift, z=0.543, with little X-ray emission. This lower
redshift system, however, is a gravitational lens, with the lensed galaxy an
unusual AGN or star-forming system at z=3.356.
  The cluster has an X-ray temperature of kT = 3.6 +/- 0.4 keV, a bolometric
luminosity of 1.0e44 +/- 0.3e44 erg/s and a velocity dispersion of 670 +/- 50
km/s. These values all agree with the low redshift correlations for clusters of
galaxies, implying a relaxed system with the ICM in equilibrium with the dark
matter potential. The lower redshift group of galaxies at z=0.543 has, at most
1/5, more likely 1/10, of the X-ray luminosity of RX J0848+4456. Despite being
a gravitational lens, this is a low mass system, with an X-ray temperature of
kT = 2.3 +0.5 -0.4 keV and a velocity dispersion of only 430 +/- 20 km/s. Our
observations show the importance of detailed studies of clusters of galaxies
when using them as probes of cosmological mass functions.