title: System parameters of the long-period polar V1309 Ori

abstract:
  Based on high-resolution optical spectroscopy in the blue and the near
infra-red spectral range, we derived velocity images (Doppler tomograms) of the
mass-donating secondary star and the accretion stream of the long-period
eclipsing polar V1309 Ori (RX J0515.41+0104.6). Combined with HST-spectroscopy
of high time resolution and optical photometry we were able to derive the main
system parameters and to determine the accretion geometry of the binary. The
length of the eclipse of the white dwarf is Delta t_{ecl} = 2418 +/- 60 s, the
mass ratio Q = 1.37 - 1.63, and the orbital inclination i=76.6 - 78.9 degrees.
The surface of the secondary star could be resolved in the Doppler image of NaI
absorption lines, where it shows a marked depletion on the X-ray irradiated
side. The accretion geometry proposed by us with a nearly aligned rotator,
co-latitude delta ~ 10 degrees, tilted away from the ballistic stream, azimuth
chi ~ -35 degrees, explains the shape of the emission-line Doppler tomograms
and the shape of optical/UV eclipse light curves.


title: The Role of Dust in Producing the Cosmic Infrared Background

abstract:
  The extragalactic background light (EBL), exclusive of the cosmic microwave
background, consists of the cumulative radiative output from all energy sources
in the universe since the epoch of recombination. Most of this energy is
released at ultraviolet and optical wavelengths. However, observations show
that a significant fraction of the EBL falls in the 10 to 1000 micron
wavelength regime. This provides conclusive evidence that we live in a dusty
universe, since only dust can efficiently absorbs a significant fraction of the
background energy and reemit it at infrared wavelengths. The general role of
dust in forming the cosmic infrared background (CIB) is therefore obvious.
However, its role in determining the exact spectral shape of the CIB is quite
complex. The CIB spectrum depends on the microscopic physical properties of the
dust, its composition, abundance, and spatial distribution relative to the
emitting sources, and its response to evolutionary processes that can modify
all the factors listed above. This paper will present a brief summary of the
many ways dust affects the intensity and spectral shape of the cosmic infrared
background. In an Appendix we present new limits on the mid-infrared intensity
of the CIB using TeV gamma-ray observations of Mrk 501.


title: A geometric interpretation of integrable motions

abstract:
  Integrability, one of the classic issues in galactic dynamics and in general
in celestial mechanics, is here revisited in a Riemannian geometric framework,
where newtonian motions are seen as geodesics of suitable ``mechanical''
manifolds. The existence of constants of motion that entail integrability is
associated with the existence of Killing tensor fields on the mechanical
manifolds. Such tensor fields correspond to hidden symmetries of non-Noetherian
kind. Explicit expressions for Killing tensor fields are given for the N=2 Toda
model, and for a modified Henon-Heiles model, recovering the already known
analytic expressions of the second conserved quantity besides energy for each
model respectively.


title: Three-Dimensional Magnetohydrodynamic Simulations of Spherical Accretion

abstract:
  We present three-dimensional numerical magnetohydrodynamic simulations of
radiatively inefficient spherical accretion onto a black hole. The simulations
are initialized with a Bondi flow, and with a weak, dynamically unimportant,
large-scale magnetic field. The magnetic field is amplified as the gas flows
in. When the magnetic pressure approaches equipartition with the gas pressure,
the field begins to reconnect and the gas is heated up. The heated gas is
buoyant and moves outward, causing line stretching of the frozen-in magnetic
field. This leads to further reconnection, and more heating and
buoyancy-induced motions, so that the flow makes a transition to a state of
self-sustained convection. The radial structure of the flow changes
dramatically from its initial Bondi profile, and the mass accretion rate onto
the black hole decreases significantly. Motivated by the numerical results, we
develop a simplified analytical model of a radiatively inefficient spherical
flow in which convective transport of energy to large radii plays an important
role. In this "convection-dominated Bondi flow" the accretion velocity is
highly subsonic and the density varies with radius as ~R^{-1/2} rather than the
standard Bondi scaling ~R^{-3/2}. We estimate that the mass accretion rate onto
the black hole is significantly less than the Bondi accretion rate.
Convection-dominated Bondi flows may be relevant for understanding many
astrophysical phenomena, e.g. post-supernova fallback and radiatively
inefficient accretion onto supermassive black holes, stellar-mass black holes
and neutron stars.


title:
Reconciliation of the Surface Brightness Fluctuations and Type Ia
  Supernovae Distance Scales

abstract:
  We present Hubble Space Telescope measurements of surface brightness
fluctuations (SBF) distances to early-type galaxies that have hosted Type Ia
supernovae (SNIa). The agreement in the relative SBF and SNIa multicolor light
curve shape and delta-m_15 distances is excellent. There is no systematic scale
error with distance, and previous work has shown that SBF and SNIa give
consistent ties to the Hubble flow. However, we confirm a systematic offset of
about 0.25 mag in the distance zero points of the two methods, and we trace
this offset to their respective Cepheid calibrations. SBF has in the past been
calibrated with Cepheid distances from the H_0 Key Project team, while SNIa
have been calibrated with Cepheid distances from the team composed of Sandage,
Saha, and collaborators. When the two methods are calibrated in a consistent
way, their distances are in superb agreement. Until the conflict over the
``long'' and ``short'' extragalactic Cepheid distances among many galaxies is
resolved, we cannot definitively constrain the Hubble constant to better than
about 10%, even leaving aside the additional uncertainty in the distance to the
Large Magellanic Cloud, common to both Cepheid scales. However, recent
theoretical SBF predictions from stellar population models favor the Key
Project Cepheid scale, while the theoretical SNIa calibration lies between the
long and short scales. In addition, while the current SBF distance to M31/M32
is in good agreement with the RR Lyrae and red giant branch distances,
calibrating SBF with the longer Cepheid scale would introduce a 0.3 mag offset
with respect to the RR Lyrae scale.


title: Structure and conditions in massive star forming giant molecular clouds

abstract:
  Massive stars form in clusters within self-gravitating molecular clouds. The
size scale of these clusters is sufficiently large that non-thermal, or
turbulent, motions of the gas must be taken into account when considering their
formation. Millimeter wavelength radio observations of the gas and dust in
these clouds reveal a complex, self-similar structure that reflects the
turbulent nature of the gas. Differences are seen, however, towards dense bound
cores in proto-clusters. Examination of the kinematics of gas around such cores
suggests that dissipation of turbulence may be the first step in the star
formation process. Newly formed stars, on the other hand, replenish turbulence
through their winds and outflows. In this way, star formation may be
self-regulated. Observations and simulations are beginning to demonstrate the
key role that cloud turbulence plays in the formation and evolution of stellar
groups.


title:
Hard pomeron enhancement of ultrahigh-energy neutrino-nucleon
  cross-sections

abstract:
  An unknown small-x behavior of nucleon structure functions gives appreciable
uncertainties to high-energy neutrino-nucleon cross-sections. We construct
structure functions using at small x Regge inspired description by A. Donnachie
and P. V. Landshoff with soft and hard pomerons, and employing at larger x the
perturbative QCD expressions. The smooth interpolation between two regimes for
each Q^2 is provided with the help of simple polynomial functions. To obtain
low-x neutrino-nucleon structure functions $F_2^{\nu N, \bar \nu N}(x,Q^2)$ and
singlet part of $F_{3}^{\nu N,\bar \nu N}(x,Q^2)$ from Donnachie-Landshoff
function $F_2^{ep}(x,Q^2)$, we use the Q^2-dependent ratios R_2(Q^2) and
R_3(Q^2) derived from perturbative QCD calculations. Non-singlet part of F_3 at
low x, which is very small, is taken as power-law extrapolation of perturbative
function at larger x. This procedure gives a full set of smooth
neutrino-nucleon structure functions in the whole range of x and Q^2 at
interest.
  Using these structure functions, we have calculated the neutrino-nucleon
cross-sections and compared them with some other cross-sections known in
literature. Our cross-sections turn out to be the highest among them at the
highest energies, which is explained by contribution of the hard pomeron.


title: Pre-Existing Superbubbles as the Sites of Gamma-Ray Bursts

abstract:
  According to recent models, gamma-ray bursts apparently explode in a wide
variety of ambient densities ranging from ~ 10^{-3} to 30 cm^{-3}. The lowest
density environments seem, at first sight, to be incompatible with bursts in or
near molecular clouds or with dense stellar winds and hence with the
association of gamma-ray bursts with massive stars. We argue that low ambient
density regions naturally exist in areas of active star formation as the
interiors of superbubbles. The evolution of the interior bubble density as a
function of time for different assumptions about the evaporative or
hydrodynamical mass loading of the bubble interior is discussed. We present a
number of reasons why there should exist a large range of inferred afterglow
ambient densities whether gamma-ray bursts arise in massive stars or some
version of compact star coalescence. We predict that many gamma-ray bursts will
be identified with X-ray bright regions of galaxies, corresponding to
superbubbles, rather than with blue localized regions of star formation.
Massive star progenitors are expected to have their own circumstellar winds.
The lack of evidence for individual stellar winds associated with the
progenitor stars for the cases with afterglows in especially low density
environments may imply low wind densities and hence low mass loss rates
combined with high velocities. If gamma-ray bursts are associated with massive
stars, this combination might be expected for compact progenitors with
atmospheres dominated by carbon, oxygen or heavier elements, that is,
progenitors resembling Type Ic supernovae.


title: A Straight and Narrow Ionized Filament

abstract:
  We report the discovery of a extremely narrow, extremely linear, ionized
filament. The filament is 2.5 degrees long and has an H$\alpha$ surface
brightness of 0.5 rayleighs. The filament is approximately ``Y'' shaped. The
widest separation of the two diagonal segments is 5 arcminutes. We discuss four
possible origins for this feature: (1) an extremely low density, nearby jet,
(2) an unusually linear filament associated with some large-scale nearby
nebula, perhaps even the Local Bubble, (3) an ionized trail left by mechanical
input from a star or compact object moving through the ISM, or (4) an ionized
trail left by photoionization (``Fossil \stromgren Trail'') from a star or
compact object. We favor this last hypothesis, and derive some of the basic
properties for an ionized trail. Regardless of whether this latter hypothesis
applies to this specific filament, the basic properties of such a trail, its
length, width, and brightness, are interesting, predictable, and should be
observable behind some white dwarfs. We suggest future tests for ascertaining
the origin of this filament, and discuss how this structure might be useful to
constrain the thermal and velocity structure of the nearby interstellar medium.


title:
High Frequency Quasi-Periodic Oscillations in the 2000 Outburst of the
  Galactic Microquasar XTE J1550-564

abstract:
  We present an analysis of the high frequency timing properties of the
April-May 2000 outburst of the black hole candidate and Galactic microquasar
XTE J1550-564, measured with the Rossi X-ray Timing Explorer. The rapid X-ray
variability we measure is consistent with the source being in either the ``very
high'' or ``intermediate'' black hole state. Strong (5-8% rms) quasi-periodic
oscillations (QPOs) are found between 249-276 Hz; this represents the first
detection of the same high frequency QPO in subsequent outbursts of a transient
black hole candidate. We also present evidence for lower-frequency QPOs at
approximately 188 Hz (3.5 sigma, single trial), also reported previously and
likely present simultaneously with the higher-frequency QPOs. We discuss these
findings within the context of the 1998 outburst of XTE J1550-564, and comment
on implications for models of QPOs, accretion flows, and black hole spin.


title: Constraints on Thermal Emission Models of Anomalous X-ray Pulsars

abstract:
  Thermal emission from the surface of an ultramagnetic neutron star is
believed to contribute significantly to the soft X-ray flux of the Anomalous
X-ray Pulsars. We compare the detailed predictions of models of the surface
emission from a magnetar to the observed properties of AXPs. In particular, we
focus on the combination of their luminosities and energy-dependent pulsed
fractions. We use the results of recent calculations for strongly magnetized
atmospheres to obtain the angle- and energy-dependence of the surface emission.
We include in our calculations the effects of general relativistic photon
transport and interstellar extinction. We find that the combination of the
large pulsed fractions and the high luminosities of AXPs cannot be accounted
for by surface emission from a magnetar with two antipodal hot regions or a
temperature distribution characteristic of a magnetic dipole. This result is
robust for reasonable neutron star radii, for the range of magnetic field
strengths inferred from the observed spin down rates, and for surface
temperatures consistent with the spectral properties of AXPs. Models with a
single hot emitting region can reproduce the observations, provided that the
distance to one of the sources is ~30% less than the current best estimate, and
allowing for systematic uncertainties in the spectral fit of a second source.
Finally, the thermal emission models with antipodal emission geometry predict a
characteristic strong increase of the pulsed fraction with photon energy, which
is apparently inconsistent with the current data. The energy-dependence of the
pulsed fraction in the models with one hot region shows a wider range of
behavior and can be consistent with the existing data. Upcoming high-resolution
observations with Chandra and XMM-Newton will provide a conclusive test.


title:
Statistical Properties of Radio Emission from the Palomar Seyfert
  Galaxies

abstract:
  We have carried out an analysis of the radio and optical properties of a
statistical sample of 45 Seyfert galaxies from the Palomar spectroscopic survey
of nearby galaxies. We find that the space density of bright galaxies (-22 mag
<= M_{B_T} <= -18 mag) showing Seyfert activity is (1.25 +/- 0.38) X 10^{-3}
Mpc^{-3}, considerably higher than found in other Seyfert samples. Host galaxy
types, radio spectra, and radio source sizes are uncorrelated with Seyfert
type, as predicted by the unified schemes for active galaxies. Approximately
half of the detected galaxies have flat or inverted radio spectra, more than
expected based on previous samples. Surprisingly, Seyfert 1 galaxies are found
to have somewhat stronger radio sources than Seyfert 2 galaxies at 6 and 20 cm,
particularly among the galaxies with the weakest nuclear activity. We suggest
that this difference can be accommodated in the unified schemes if a minimum
level of Seyfert activity is required for a radio source to emerge from the
vicinity of the active nucleus. Below this level, Seyfert radio sources might
be suppressed by free-free absorption associated with the nuclear torus or a
compact narrow-line region, thus accounting for both the weakness of the radio
emission and the preponderance of flat spectra. Alternatively, the flat spectra
and weak radio sources might indicate that the weak active nuclei are fed by
advection-dominated accretion disks.


title: Mapping the gravitational wave background

abstract:
  The gravitational wave sky is expected to have isolated bright sources
superimposed on a diffuse gravitational wave background. The background
radiation has two components: a confusion limited background from unresolved
astrophysical sources; and a cosmological component formed during the birth of
the universe. A map of the gravitational wave background can be made by
sweeping a gravitational wave detector across the sky. The detector output is a
complicated convolution of the sky luminosity distribution, the detector
response function and the scan pattern. Here we study the general
de-convolution problem, and show how LIGO (Laser Interferometric Gravitational
Observatory) and LISA (Laser Interferometer Space Antenna) can be used to
detect anisotropies in the gravitational wave background.


title:
Amplification, Saturation, and Q Thresholds for Runaway: Growth of
  Self-Gravitating Structures in Models of Magnetized Galactic Gas Disks

abstract:
  We investigate the susceptibility of gaseous, magnetized galactic disks to
formation of self-gravitating condensations using two-dimensional, local
models. We focus on two issues: (1) determining the threshold condition for
gravitational runaway, taking into account nonlinear effects, and (2)
distinguishing the magneto-Jeans instability (MJI) that arises under
inner-galaxy rotation curves from the modified swing amplification (MSA) that
arises under outer-galaxy rotation curves. For axisymmetric density
fluctuations, instability is known to require a Toomre parameter Q<1. For
nonaxisymmetric fluctuations, any nonzero shear $q \equiv -d\ln \Omega /d \ln
R$ winds up wavefronts such that in linear theory amplification saturates. Any
Q threshold for nonaxisymmetric gravitational runaway must originate from
nonlinear effects. We use numerical magnetohydrodynamic simulations to
demonstrate the anticipated threshold phenomenon, to analyze the nonlinear
processes involved, and to evaluate the critical value $Q_c$ for stabilization.
We find $Q_c \sim 1.2-1.4$ for a wide variety of conditions, with the largest
values corresponding to nonzero but subthermal mean magnetic fields. Our
findings for $Q_c$ are similar to those inferred from thresholds for active
star formation in the outer regions of spiral galaxies. MJI is distinct from
MSA in that opposition to Coriolis forces by magnetic tension, rather than
cooperation of epicyclic motion with kinematic shear, enables nonaxisymmetric
density perturbations to grow. We suggest that under low-shear inner-disk
conditions, $Q_c$ will be larger than that in outer disks by a factor $\sim
(v_A/q c_s)^{1/2}$, where $v_A$ and $c_s$ are the respective Alfven and sound
speeds.


title:
Impacts of a power-law non-thermal electron tail on the ionization and
  recombination rates

abstract:
  We have investigated the effects of a non-thermal electron population on the
ionization and recombination rates. The considered electron distribution is
defined as a Maxwellian function below a break energy E_b and as a power-law
function of index alpha above this energy. We have calculated the collisional
(direct and excitation autoionization) ionization coefficient rates as well as
the (radiative and dielectronic) recombination rates. Practical methods are
given to calculate these rates in order to be easily included in a computer
code. The ionization rates are very sensitive to the non-thermal electron
population and can be increased by several orders of magnitude depending on the
temperature and parameters of the power-law function (E_b and alpha). The
non-thermal electrons have a much weaker effect on the (radiative and
dielectronic) recombination rates. We have determined the mean electric charge
of elements C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe and Ni for different values of
the break energy and power-law index. The ionization balance is affected
significantly, whereas the effect is smaller in ionizing plasmas.


title: Search for Spatial Variability in the Solar Acoustic Spectrum

abstract:
  Motivated by the various examples of spatial variability in the power of the
acoustic spectrum, we attempted to look for spatial variability in the peak
frequency of the spectrum. However, the determination of this peak frequency on
a spatial scale of a single pixel (8 arc seconds for the GONG data) is limited
by the stochastic variations in the power spectrum presumably caused by the
stochastic nature of the excitation process. Averaging over a large number of
spectra (100 spectra from a 10 $\times$ 10 pixels area) produced stabler
spectra. The peak frequencies of 130 such locations were found to be
distributed with a FWHM of about 130 $\mu$Hz. A map of the spatial variation of
this peak frequency did not show any strong feature with statistically
significant deviation from the mean of the distribution. Likewise, the scatter
in the peak frequencies masked the detection of magnetic field induced changes
in the peak frequency. On a much larger scale, the N latitudes showed a
slightly lower value of the peak frequency as compared to the S latitudes,
although the difference (25 $\mu$Hz) is barely larger than the {\it rms} spread
(20 $\mu$Hz).


title: A Giant Air Shower Array in Nord Rhein Westfalen

abstract:
  A proposal is presented to construct a very large air shower array in the
densely populated central area of Nord-Rhein-Westfalen (NRW). The aim would be
to reach a size of approximately 4000 km$^2$ to study the highest energy end of
the all particle cosmic ray spectrum, as it is accessible in the northern
hemisphere.


title:
Metal-rich and metal-poor globular clusters in ellipticals: Did we learn
  anything? or Constraints on galaxy formation and evolution from globular
  cluster sub-populations

abstract:
  A brief review on globular cluster sub-populations in galaxies, and their
constraints on galaxy formation and evolution is given. The metal-poor and
metal-rich sub-populations are put in a historical context, and their
properties, as known to date, are summarized. We review why the study of these
sub-populations is extremely useful for the study of galaxy formation and
evolution, but highlight a few caveats with the current interpretations. We
re-visit the current globular cluster system formation scenarios and show how
they boil down to a single scenario for the metal-poor clusters (namely the
formation in ``universal'', small fragments at high $z$) and that a
hierarchical formation seems favored for the metal-rich clusters.


title: On the clustering phase transition in self-gravitating N-body systems

abstract:
  The thermodynamic behaviour of self-gravitating $N$-body systems has been
worked out by borrowing a standard method from Molecular Dynamics: the time
averages of suitable quantities are numerically computed along the dynamical
trajectories to yield thermodynamic observables. The link between dynamics and
thermodynamics is made in the microcanonical ensemble of statistical mechanics.
The dynamics of self-gravitating $N$-body systems has been computed using two
different kinds of regularization of the newtonian interaction: the usual
softening and a truncation of the Fourier expansion series of the two-body
potential. $N$ particles of equal masses are constrained in a finite three
dimensional volume. Through the computation of basic thermodynamic observables
and of the equation of state in the $P - V$ plane, new evidence is given of the
existence of a second order phase transition from a homogeneous phase to a
clustered phase. This corresponds to a crossover from a polytrope of index
$n=3$, i.e. $p=K V^{-4/3}$, to a perfect gas law $p=K V^{-1}$, as is shown by
the isoenergetic curves on the $P - V$ plane. The dynamical-microcanonical
averages are compared to their corresponding canonical ensemble averages,
obtained through standard Monte Carlo computations. A major disagreement is
found, because the canonical ensemble seems to have completely lost any
information about the phase transition. The microcanonical ensemble appears as
the only reliable statistical framework to tackle self-gravitating systems.
Finally, our results -- obtained in a ``microscopic'' framework -- are compared
with some existing theoretical predictions -- obtained in a ``macroscopic''
(thermodynamic) framework: qualitative and quantitative agreement is found,
with an interesting exception.


title:
The Influence of the Gravitational Acceleration on the Supernova-Driven
  P arker Instability

abstract:
  Within a framework of 2D MHD simulations, we explore the dynamical regimes
initi ated by a supernova explosion in a magnetized stratified ISM. We
concentrate on the formation of large scale magnetic structures and outflows
connected with the Parker instability. For the sake of simplicity we show only
models with a fixed explosion energy corresponding to a single SN occuring in
host galaxies with different fixed values of the gravitational acceleration $g$
and different ratios of specific heats. We show that in general depending on
these two parameters, three different regimes are possible: a) a slowly growing
Parker instability on time scales much longer than the galac tic rotation
period for small $g$, b) the Parker instability growing at roughly the rotation
period, which for ratios of specific heats larger than 1 is accompanied byan
outflow resulting from the explosion for intermediate $g$, and c) a rapidly g
rowing instability and a strong blowout flow for large $g$. By means of
numerical simul ations and analytical estimates we show that the explosion
energy and gravitational acceleration which separate the three regimes scale as
$Eg^2\sim $const in the 2D case. We expect that in the 3D case this scaling law
is $Eg^3\sim $const. Our simulations demonstrate furthermore, that a single SN
explosion can lead to the growth of multiple Parker loops in the disc and large
scale magnetic field loops in the halo, extending over 2-3 kpc horizontally and
up to 3 kpc vertically abov e the midplane of the disc.


title: Testing Cosmological Models with Negative Pressure

abstract:
  There is now strong evidence that the main contribution to the cosmic energy
density is not due to matter, but to another component with negative pressure.
Its nature is still unknown: it could be the vacuum energy, manifesting itself
as a positive cosmological constant with $w \equiv P/\rho c^2 = -1$
($\Lambda$CDM model), a spatially inhomogeneous and dynamically evolving form
of energy with $-1 < w < 0$ (quintessence, QCDM model), or a dark energy
component with $w < -1$, such as a quantized free scalar field (VCDM model).
After presenting simple redshift--distance formulae, which are useful for
comparing observations with theoretical predictions without numerical
integration, I discuss the behaviour of different $w < 0$ models in the context
of the Alcock--Paczy\'nski geometric test and the statistics of gravitational
lensing.


title: Redshift Evolution of the Merger Fraction of Galaxies in CDM Cosmologies

abstract:
  We use semi-analytical modelling of galaxy formation to study the redshift
evolution of the galaxy merger fractions and merger ratesin Lambda CDM and
quintessence (QCDM) cosmologies, their dependence on physical parameters as the
environment, the merger timescale, the way major mergers are defined, and the
minimum mass of objects taken into account. We find that for a given final halo
mass the redshift dependence of the merger fraction F_mg and the resulting
merger rate can be fitted well by a power law for redshifts z <= 1. The
normalization F_{mg}(0) and the slope m depend on the final halo mass. For a
given merger timescale t_merg and an assumed maximum mass ratio R_major for
major mergers, F_mg(0) and m depend exponentially on each other. The slope m
depends logarithmically on the ratio of the final halo mass and the minimum
halo mass taken into account. In addition, the local normalization F_{mg}(0)
increases for larger R_{major} while m decreases. We compare the predicted
merger fractionwith recent observations and find that the model cannot
reproduce both the merger index and the normalization at the same time. In
general the model underestimates F_{mg}(0) and m by a factor of 2.


title:
How old is the Universe ? Setting new constraints on the age of the
  Universe

abstract:
  There are three independent techniques for determining the age of the
universe: via cosmochronology of long-lived radioactive nuclei, via stellar
modelling and population synthesis of the oldest stellar populations, and via
the precision cosmology that has become feasible with the mapping of the
acoustic peaks in the cosmic microwave background. We demonstrate that all
three methods give completely consistent results, and enable us to set rigorous
bounds on the maximum and minimum ages that are allowed for the universe. We
present new constraints on the age of the universe by performing a multiband
colour analysis of bright cluster ellipticals over a large redshift range
(0.3<z<0.9), which allows us to infer the ages of their stellar populations
over a wide range of possible formation redshifts and metallicities. Applying a
conservative prior to Hubble's constant of H0=70+-15 km/s/Mpc, we find the age
of the universe to be 13.2(+3.6 -2.0) Gyr (1-sigma), in agreement both with the
estimates from type Ia supernovae, as well as with the latest uranium decay
estimates. Without the assumption of any priors, universes older than 18 Gyr
are ruled out by the data at the 90 % confidence level.


title: Constraining neutrino physics with BBN and CMBR

abstract:
  We perform a likelihood analysis of the recent results on the anisotropy of
Cosmic Microwave Background Radiation from the BOOMERanG and DASI experiments
to show that they single out an effective number of neutrinos in good agreement
with standard Big Bang Nucleosynthesis. We also consider degenerate Big Bang
Nucleosynthesis to provide new bounds on effective relativistic degrees of
freedom $N_\nu$ and, in particular, on neutrino chemical potential
$\xi_\alpha$. When including Supernova Ia data we find, at $2\sigma$, $N_\nu
\leq 7$ and $-0.01 \leq \xi_e \leq 0.22$, $|\xi_{\mu,\tau}|\leq 2.6$.


title: X-ray bursts at extreme mass accretion rates from GX 17+2

abstract:
  (abridged version) We report on ten type I X-ray bursts from GX 17+2 in data
obtained with the RXTE/PCA in 1996--2000. Three bursts were short in duration
(~10 s), whereas the others lasted for ~6-25 min. Five of the long bursts
showed evidence for radius expansion of the neutron star photosphere. No
correlations o f the burst properties with respect to the persistent X-ray
spectral properties are seen, suggesting no correlation with inferred
persistent mass accretion rate. The presence of short bursts in GX 17+2 (and
similar bright X-ray sources) is not accounted for in the current X-ray bursts
theories at the high mass accretion rates encountered in these sources. We find
that in contrast to previous suggestions the persistent black-body emission
does NOT arise from the same site as the burst emission. The black-body
component of the persistent emission is consistent with arising in an expanded
boundary layer, as indicated by recent theoretical work. The total persistent
flux just before and after the radius expansion bursts is inferred to be up to
a factor of 2 higher than the net peak flux of the burst. If both the burst and
persistent emission are radiated isotropically, this would imply that the
persistent emission is up to a factor of 2 higher than the Eddington
luminosity. This is unlikely and we suggest that the persistent luminosity is
close to the Eddington luminosity and that the burst emission is (highly)
anisotropic. Assuming that the net burst peak fluxes equal the Eddington limit,
applying standard burst parameters (1.4 M_sun neutron star, cosmic composition,
electron scattering opacity appropriate for high temperatures), and taking into
account gravitational redshift and spectral hardening, we derive a distance to
GX 17+2 of ~8 kpc, with an uncertainty of up to ~30%.


title:
Combining maximum-entropy and the mexican hat wavelet to reconstruct the
  microwave sky

abstract:
  We present a maximum-entropy method (MEM) and `Mexican Hat' wavelet (MHW)
joint analysis to recover the different components of the microwave sky from
simulated observations by the ESA Planck satellite in a small patch of the sky.
This combined method allows one to improve the CMB, Sunyaev-Zel'dovich and
Galactic foregrounds separation achieved by the MEM technique alone. In
particular, the reconstructed CMB map is free from any bright point source
contamination. The joint analysis also produces point source catalogues at each
Planck frequency which are more complete and accurate than those obtained by
each method on its own. The results are especially improved at high frequencies
where infrared galaxies dominate the point source contribution. Although this
joint technique has been performed on simulated Planck data, it could be easily
applied to other multifrequency CMB experiments, such as the forthcoming NASA
MAP satellite or the recently performed Boomerang and MAXIMA experiments.


title:
Tidal torques dynamical friction and the structure of clusters of
  galaxies

abstract:
  We study the joint effect of tidal torques and dynamical friction on the
collapse of density peaks solving numerically the equations of motion of a
shell of barionic matter falling into the central regions of a cluster of
galaxies. We calculate the evolution of the expansion parameter, a(t), of the
perturbation using a coefficient of dynamical friction eta_{cl} obtained from a
clustered system and taking into account the gravitational interaction of the
quadrupole moment of the system with the tidal field of the matter of the
neighboring proto-galaxies. We show that within high-density environments, such
as rich clusters of galaxies, tidal torques and dynamical friction slow down
the collapse of low-nu peaks producing an observable variation of the parameter
of expansion of the shell. As a consequence a bias of dynamical nature arises
because high-density peaks preferentially collapse to form halos within which
visible objects eventually will condense. For a standard Cold Dark Matter model
this dynamical bias can account for a substantial part of the total bias
required by observations on cluster scales.


title:
Are There Blue, Massive E/S0s at z < 1 ?: Kinematics of Blue Spheroidal
  Galaxy Candidates

abstract:
  Several recent studies find that 10 - 50% of morphologically selected field
early-type galaxies at redshifts z <= 1 have blue colors indicative of recent
star formation. Such ``blue spheroids''might be massive early-type galaxies
with active star formation, perhaps induced by recent merger events.
  Alternatively, they could be starbursting, low-mass spheroids. To distinguish
between these two choices, we have selected 10 ``Blue Spheroid Candidates''
  (hereafter, BSCs) from a quantitatively selected E/S0 sample and studied
their properties, including kinematics from Keck spectra obtained as part of
the DEEP Groth Strip Survey (GSS). Most BSCs (70%) turn out to belong to two
broad categories, while the remaining objects are likely to be misclassified
objects. Type-1 BSCs have underlying red stellar components with bluer inner
components. Type-2 BSCs do not show an obvious sign of the underlying red
stellar component, and their overall colors are quite blue ((U-B)_rest < 0).
  Both Type-1 and Type-2 BSCs have internal velocity dispersions measured from
emission lines sigma < 80$ km/sec and estimated dynamical masses of only a few
times 10^10 M_sun or less. For Type-1 BSCs, we estimate sigma of the red
component using the fundamental plane relation of distant field absorption-line
galaxies and find that these sigma estimates are similar to the sigma measured
from emission lines. Overall, we conclude that our Type-1 and Type-2 BSCs are
more likely to be star-forming low mass spheroids than star-forming, massive,
early-type galaxies.


title:
Central Structural Parameters of Early-Type Galaxies as Viewed with
  HST/NICMOS

abstract:
  We present surface photometry for the central regions of a sample of 33
early-type (E, S0, and S0/a) galaxies observed at 1.6 microns (H band) using
the Hubble Space Telescope (HST). We employ a new technique of two-dimensional
fitting to extract quantitative parameters for the bulge light distribution and
nuclear point sources, taking into consideration the effects of the
point-spread function. Parameterizing the bulge profile with a ``Nuker'' law,
we confirm that the central surface-brightness distributions largely fall into
two categories, each of which correlates with the global properties of the
galaxies. ``Core'' galaxies tend to be luminous ellipticals with boxy or pure
elliptical isophotes, whereas ``power-law'' galaxies are preferentially lower
luminosity systems with disky isophotes. Unlike most previous studies, however,
we do not find a clear gap in the distribution of inner cusp slopes; several
objects have inner cusp slopes (0.3 < gamma < 0.5) which straddle the regimes
conventionally defined for core and power-law type galaxies. The nature of
these intermediate objects is unclear. We draw attention to two objects in the
sample which appear to be promising cases of galaxies with isothermal cores
that are not the brightest members of a cluster. Unresolved nuclear point
sources are found in about 50% of the sample galaxies, roughly independent of
profile type, with magnitudes in the range m^{nuc}_H = 12.8 to 17.4 mag, which
correspond to M_H^{nuc} = -12.8 to -18.4 mag. (Abridged)


title:
The Nature of the Red Giant Branches in the Ursa Minor and Draco Dwarf
  Spheroidal Galaxies

abstract:
  Spectra for stars located redward of the fiducial red giant branches of the
Ursa Minor and Draco dwarf spheroidal galaxies have been obtained with the
Hobby-Eberly telescope and the Marcario Low Resolution Spectrometer. From a
comparison of our radial velocities with those reported in previous
medium-resolution studies, we find an average difference of 10 km/s with a
standard deviation of 11 km/s. On the basis of these radial velocities, we
confirm the membership of five stars in Ursa Minor, and find two others to be
nonmembers. One of the confirmed members is a known carbon star which lies
redward of RGB; three others are previously unidentified carbon stars. The
fifth star is a red giant which was found previously by Shetrone et al. (2001)
to have [Fe/H] =-1.68+/-0.11 dex. In Draco, we find eight nonmembers, confirm
the membership of one known carbon star, and find two new members. One of these
stars is a carbon star, while the other shows no evidence for C2 bands or
strong atomic bands, although the signal-to-noise ratio of the spectrum is low.
Thus, we find no evidence for a population of stars more metal-rich than [Fe/H]
\~ -1.45 dex in either of these galaxies. Indeed, our spectroscopic survey
suggests that every candidate suspected of having a metallicity in excess of
this value based on its position in the color-magnitude diagram is, in
actuality, a carbon star. Based on the census of 13 known carbon stars in these
two galaxies, we estimate of the carbon star specific frequency to be e(dSph) ~
2.4E-5/Lsolarv, 25-100 times higher than that of Galactic globular clusters.


title: A self-regulated model of galactic spiral structure formation

abstract:
  The presence of spiral structure in isolated galaxies is a problem that has
only been partially explained by theoretical models. Because the rate and
pattern of star formation in the disk must depend only on mechanisms internal
to the disk, we may think of the spiral galaxy as a self-regulated system far
from equilibrium. This paper uses this idea to look at a reaction-diffusion
model for the formation of spiral structures in certain types of galaxies. In
numerical runs of the model, spiral structure forms and persists over several
revolutions of the disk, but eventually dies out.


title:
A convection zone dynamo including the effects of magnetic buoyancy and
  downward flows

abstract:
  A magnetic flux tube may be considered both as a separate body and as a
confined field. As a field, it is affected both by the cyclonic convection
($\alpha$-effect) and differential rotation ($\Omega$-effect). As a body, the
tube experiences not only a buoyant force, but also a dynamic pressure due to
downflows above the tube. When these two dynamic effects are incorporated into
the $\alpha\Omega$ dynamo equations, we obtain a dynamo operating in the
convection zone. We analyze and solve the extended dynamo equations in the
linear approximation by using observed solar internal rotation and assuming a
downflow suggested by numerical simulations of the solar convection zone. The
results produce: (i) the 22-year cycle period; (ii) the extended butterfly
diagram; (iii) the confinement of strong activity to low heliographic latitudes
$|\Phi|\le 35^\circ$; (iv) at low latitudes the radial field is in an
approximately $\pi$ phase lag compared to the toroidal field at the same
latitude; (v) the poleward branch is in a $\pi/2$ phase lag with respect to the
equatorward branch; (vi) most of the magnetic flux is present in a strongly
intermittent form, concentraed into strong flux tubes; (vii) the magnetic field
peaks at a depth of $r=0.96 R_{\sun}$; (viii) total solar irradiance varies in
phase with the solar cycle activity, having an amplitude of 0.1%; (ix) solar
effective temperature varies in phase with the solar cycle activity, having an
amplitude of 1.5 $^\circ C$; and (x) solar radius also varies in phase with the
solar cycle activity, having an amplitude of 20 mas. All these results are in
agreement with the corresponding observations.


title:
X-Ray Observations of XTE J1550-564 During the Decay of the 2000
  Outburst - I. Chandra and RXTE Energy Spectra

abstract:
  We report on the evolution of the X-ray energy spectrum for the black hole
candidate (BHC) X-ray transient XTE J1550-564 during the decay of the 2000
outburst. The Rossi X-ray Timing Explorer (RXTE) and Chandra observations span
nearly five orders of magnitude in luminosity. The RXTE spectra are dominated
by a power-law component and a comparatively weak soft component was also
detected for the first two observations. The source made a transition to the
canonical hard state near a luminosity of 9E36 erg/s over several observations
as evidenced by a drop in the flux of the soft component in the RXTE energy
band and a hardening of the power-law component to a photon index near 1.6. The
power-law did not exhibit this behavior for the previous XTE J1550-564
outburst. For some observations, we detect a high energy cutoff and find that
the cutoff is more significant and at lower energy during the transition than
in the hard state. The cutoff in the hard state is at higher energy than has
been seen for most previous accreting BHCs. The Chandra spectrum provides
evidence for spectral evolution after the hard state transition. It is well,
but not uniquely, described by a power-law with a photon index of
2.30^{+0.41}_{-0.48} (90% confidence) and interstellar absorption.
Advection-dominated accretion flow models predict gradual spectral softening as
the luminosity drops, but our observations do not allow us to determine if the
spectral evolution is gradual or sudden. The lowest luminosity we measure for
XTE J1550-564 with Chandra is 5E32 erg/s (0.5-7 keV, for a distance of 4 kpc).
Although this is probably not the true quiescent luminosity, it represents a
useful upper limit on this quantity.


title:
X-Ray Observations of XTE J1550-564 During the Decay of the 2000
  Outburst - II. Timing

abstract:
  We investigate the timing behavior of XTE J1550-564 with the Rossi X-ray
Timing Explorer (RXTE) as the source made a transition to the hard state during
the decay of the 2000 outburst. We detect a high frequency QPO at 65 Hz in one
observation with a fractional rms amplitude of 4.9%. This is the first time
that a high frequency QPO has been detected in a transition to the hard state
during outburst decay. We also observe low frequency QPOs in the 0.36-4.1 Hz
range and rich aperiodic variability. The changes in the temporal properties
during the decay are very similar to the state transitions observed for other
sources. We find a correlation between the QPO frequency and the break
frequency in the continuum power spectra. We investigate the energy dependence
of rms amplitudes of the QPOs. We compare these timing properties with those
previously observed for XTE J1550-564 and other Galactic black hole candidates
and discuss the implications for QPO models and black hole accretion.


title:
Constraints on Omega_m, Omega_L, and Sigma_8, from Galaxy Cluster
  Redshift Distributions

abstract:
  We show that the counts of galaxy clusters in future deep cluster surveys can
place strong constraints on the matter density, Omega_m, the vacuum energy
density, Omega_L, and the normalization of the matter power spectrum, sigma_8.
Degeneracies between these parameters are different from those in studies of
either high--redshift type Ia Supernovae (SNe), or cosmic microwave background
(CMB) anisotropies. Using a mass threshold for cluster detection expected to be
typical for upcoming SZE surveys, we find that constraints on Omega_m and
sigma_8 at the level of roughly 5% or better can be expected, assuming redshift
information is known at least to z=0.5 and in the absence of significant
systematic errors. Without information past this redshift, Omega_L is
constrained to 25%. With complete redshift information, deep (M_{lim}=
10^{14}h^{-1}{M_sun}), relatively small solid angle (roughly 12 {deg}^2)
surveys can further constrain Omega_L to an accuracy of 15%, while large solid
angle surveys with ground-based large-format bolometer arrays could measure
Omega_L to a precision of 4% or better.


title:
Primordial Nucleosynthesis with CMB Inputs: Probing the Early Universe
  and Light Element Astrophysics

abstract:
  Cosmic microwave background (CMB) determinations of the baryon-to-photon
ratio $\eta \propto \Omega_{\rm baryon} h^2$ will remove the last free
parameter from (standard) big bang nucleosynthesis (BBN) calculations. This
will make BBN a much sharper probe of early universe physics, for example,
greatly refining the BBN measurement of the effective number of light neutrino
species, $N_{\nu,eff}$. We show how the CMB can improve this limit, given
current light element data. Moreover, it will become possible to constrain
$N_{\nu,eff}$ independent of \he4, by using other elements, notably deuterium;
this will allow for sharper limits and tests of systematics. For example, a 3%
measurement of $\eta$, together with a 10% (3%) measurement of primordial D/H,
can measure $N_{\nu,eff}$ to a 95% confidence level of $\sigma_{95%}(N_\nu) =
1.8$ (1.0) if $\eta \sim 6.0\times 10^{-10}$. If instead, one adopts the
standard model value $N_{\nu,eff}=3$, then one can use $\eta$ (and its
uncertainty) from the CMB to make accurate predictions for the primordial
abundances. These determinations can in turn become key inputs in the
nucleosynthesis history (chemical evolution) of galaxies thereby placing
constraints on such models.


title:
Order and chaos in the local disc stellar kinematics induced by the
  Galactic bar

abstract:
  (Abridged) The Galactic bar causes a characteristic splitting of the disc
phase space into regular and chaotic orbit regions which is shown to play an
important role in shaping the stellar velocity distribution in the Solar
neighbourhood. A detailed orbital analysis within an analytical 2D rotating
barred potential reveals that this splitting is mainly dictated by the value of
the Hamiltonian H and the bar induced resonances. Test particle and N-body
simulations reveal how the decoupled evolution of the disc distribution
function in the two kind of regions and the process of chaotic mixing lead to
overdensities in the H>H_12 chaotic part of the u-v velocity distributions
outside corotation, where H_12 is the effective potential at the Lagrangian
points L_1/2. In particular, for realistic space positions of the Sun near or
slightly beyond the outer Lindblad resonance and if u is defined positive
towards the anti-centre, the eccentric quasi-periodic orbits trapped around the
stable x1(1) orbits - i.e. the bar-aligned closed orbits which asymptotically
become circular at larger distances - produce a broad u<0 regular arc in
velocity space extending within the H>H_12 zone, whereas the corresponding u>0
region appears as an overdensity of chaotic orbits forced to avoid that arc.
This chaotic overdensity provides an original interpretation, distinct from the
anti-bar elongated quasi-periodic orbit interpretation proposed by Dehnen
(2000), for the prominent stream of high asymmetric drift and predominantly
outward moving stars clearly emerging from the Hipparcos data. The effects of
spiral arms and of molecular clouds are also briefly discussed within this
context.


title:
Probing the faint end of the Galaxy luminosity function at z=3 with
  Ly-alpha emission

abstract:
  We present spectroscopic observations obtained with the ESO Very Large
Telecope (VLT) of seven candidate Ly-alpha emitting galaxies in the field of
the radio quiet Q1205-30 at z=3.04 previously detected with deep narrow band
imaging. Based on equivalent widths and limits on line ratios we confirm that
all seven objects are Ly-alpha emitting galaxies. Deep images also obtained
with the VLT in the B and I bands show that five of the seven galaxies have
very faint continuum fluxes (I(AB) approx. 26.8 and B(AB) approx. 27.3). The
star formation rates of these seven galaxies estimated from the rest-frame UV
continuum around 2000AA, as probed by the I-band detections, as well as from
the Ly-alpha luminosities, are 1-4 M_sun yr^{-1}. This is 1-3 orders of
magnitude lower than for other known populations of star-forming galaxies at
similar redshifts (the Lyman-Break galaxies and the sub-mm selected sources).
The inferred density of the objects is high, 16+-4 per arcmin^2 per unit
redshift. This is consistent with the integrated luminosity function for
Lyman-Break galaxies down to R=27 if the fraction of Ly-alpha emitting galaxies
is approx. 70% at the faint end of the luminosity function. However, if this
fraction is 20% as reported for the bright end of the luminosity function then
the space density in this field is significantly larger (by a factor of 3.5)
than expected from the luminosity function for Lyman-Break galaxies in the
HDF-North. This would be an indication that at least some radio quiet QSOs at
high redshift reside in overdense environments or that the faint end slope of
the high redshift luminosity function has been underestimated. These
observations show that Ly-alpha emission is an efficient method by which to
probe the faint end of the luminosity function at high redshifts.


title: A few things we do not know about stars and model atmospheres

abstract:
  We list a few things that we do not understand about stars and that most
people ignore. These are all hard problems. We can learn more cosmology by
working on them to reduce the systematic errors they introduce than by trying
to derive cosmological results that are highly uncertain.


title: Statistical Properties of Bright Galaxies in the SDSS Photometric System

abstract:
  We investigate the photometric properties of 456 bright galaxies using
imaging data recorded during the commissioning phase of the Sloan Digital Sky
Survey (SDSS). Morphological classification is carried out by correlating
results of several human classifiers. Our purpose is to examine the statistical
properties of color indices, scale lengths, and concentration indices as
functions of morphology for the SDSS photometric system. We find that $u'-g'$,
$g'-r'$, and $r'-i'$ colors of SDSS galaxies match well with those expected
from the synthetic calculation of spectroscopic energy distribution of template
galaxies and with those transformed from $UBVR_CI_C$ color data of nearby
galaxies. The agreement is somewhat poor, however, for $i'-z'$ color band with
a discrepancy of $0.1-0.2$ mag. With the aid of the relation between surface
brightness and radius obtained by Kent (1985), we estimate the averages of the
effective radius of early type galaxies and the scale length of exponential
disks both to be 2.6 kpc for $L^*$ galaxies. We find that the half light radius
of galaxies depends slightly on the color bands, consistent with the expected
distribution of star-forming regions for late type galaxies and with the known
color gradient for early type galaxies. We also show that the (inverse)
concentration index, defined by the ratio of the half light Petrosian radius to
the 90% light Petrosian radius, correlates tightly with the morphological type;
this index allows us to classify galaxies into early (E/S0) and late (spiral
and irregular) types, allowing for a 15-20% contamination from the opposite
class compared with eye-classified morphology.


title:
ISO/SWS observations of SN 1987A: II. A refined upper limit on the mass
  of Ti-44 in the ejecta of SN 1987A

abstract:
  ISO/SWS observations of SN 1987A on day 3425 show no emission in [Fe I] 24.05
microns and [Fe II] 25.99 microns down to the limits of roughly 0.39 Jy and
0.64 Jy, respectively. Assuming a homogeneous distribution of Ti-44 inside 2000
km/s and negligible dust cooling, we have made time dependent theoretical
models to estimate an upper limit on the mass of ejected Ti-44. Assessing
various uncertainties of the model, and checking the late optical emission it
predicts, we obtain an upper limit of 1.1EE-4 solar masses. This is lower than
in our previous estimate using other ISO data, and we compare our new result
with other models for the late emission, as well as with expected yields from
explosion models. We also show that steady-state models for the optical
emission are likely to overestimate the mass of ejected Ti-44. The low limit we
find for the mass of ejected Ti-44 could be higher if dust cooling is
important. A direct check on this is provided by the gamma-ray emission at
1.157 Mev as a result of the radioactive decay of Ti-44.


title:
On possible observational evidences of spiral shocks in accretion disks
  of CVs

abstract:
  The results of three-dimensional numerical simulations of mass transfer in
binaries with spiral shocks are presented. It is shown that the mass transfer
rate variation disturbs the equilibrium state of accretion disk and results in
formation of the blob. This dense formation moves on the disk with variable
velocity. The results of our simulations show that the blob lives long enough
and retains its main characteristics for the time of order of tens orbital
periods. Analysis of the results shows that the action of dissipation is
negligible on these timescales and the blob smearing out due to differential
rotation of the disk is stopped by its interaction with spiral shocks.
  Light curves of some CVs show periodic or quasi-periodic photometric
modulations with typical period 0.1-0.2P_orb. We suggest to consider the
formation of the blob in binaries with spiral shocks as a possible reason for
these modulations. The efficiency of this mechanism is confirmed by good
qualitative (and, in part, quantitative) agreement between the results of our
simulations and observations of binaries IP Peg and EX Dra.


title: Distance measurements as a probe of cosmic acceleration

abstract:
  A major recent evelopment in observational cosmology has been an accurate
measurement of the luminosity distance-redshift relation out to redshifts z=0.8
from Type Ia supernova standard candles. The results have been argued as
evidence for cosmic acceleration. It is well known that this assertion depends
on the assumption that we know the equation of state for all mass-energy other
than normal pressureless matter; popular models are based on either the
cosmological constant or on the more general quintessence formulation. But this
assertion also depends on a number of other assumptions, implicit in the
derivation of the standard cosmological field equations: large-scale isotropy
and homogeneity, the flatness of the Universe, and the validity of general
relativity on cosmological scales (where it has not been tested). A detailed
examination of the effects of these assumptions on the interplay between the
luminosity distance-redshift relation and the acceleration of the Universe is
not possible unless one can define the precise nature of the failure of any
particular assumption. However a simple quantitative investigation is possible
and reveals a number of considerations about the relative importance of the
different assumptions. In this paper we present such an investigation. We find
that the relationship between the distant-redshift relation and the sign of the
deceleration parameter is fairly robust and is unaffected if only one of the
assumptions that we investigate is invalid so long as the deceleration
parameter is not close to zero (it would not be close to zero in the
currently-favored Omega_Lambda = 1 - Omega_matter = 0.7 or 0.8 Universe, for
example). Failures of two or more assumptions in concordance may have stronger
effects.


title:
Identification of A Transient Neutron Star in Quiescence in the Globular
  Cluster NGC 5139

abstract:
  Using the Chandra/ACIS-I detector, we have identified an X-ray source (CXOU
132619.7-472910.8) in the globular cluster NGC 5139 with a thermal spectrum
identical to that observed from transiently accreting neutron stars in
quiescence. The absence of intensity variability on timescales as short as 4
seconds (< 25% rms variability) and as long as 5 years (<50% variability)
supports the identification of this source as a neutron star, most likely
maintained at a high effective temperature (approximately 1e6 K) by transient
accretion from a binary companion. The ability to spectrally identify quiescent
neutron stars in globular clusters (where the distance and interstellar column
densities are known) opens up new opportunities for precision neutron star
radius measurements.


title: Milliarcsecond structure of methanol masers in L1206 and GL2789

abstract:
  We report results of EVN interferometric study of two star-forming regions
L1206 and GL2789 in the brightest methanol maser line at 6.7 GHz. Using
measured absolute positions both methanol masers were identified with
protostars which are sources of bipolar outflows. Both masers consist of
several maser spots, with some of them being aligned in a linear structure with
velocity gradient probably delineating edge-on circumstellar disks. We
estimated the radii of such disks to be 140 AU and 280 AU (or 700 AU for the
whole structure treated as a disk) for L1206 and GL2789 respectively. The
brightness temperatures of the most intense features in L1206 and GL2789 are at
least 1.1x10^10 K and 1.4x10^9 K respectively.


title: Space-VLBI observations of OH masers

abstract:
  We report on the first space-VLBI observations of the OH masers in two
main-line OH transitions at 1665 and 1667 MHz. The observations involved the
space radio telescope on board the Japanese satellite HALCA and an array of
ground radio telescopes. The maps of the maser region and images of individual
maser spots were produced with an angular resolution of 1 mas, which is several
times higher than the angular resolution available on the ground. The maser
spots were only partly resolved and a lower limit to the brightness temperature
6x10^12 K was obtained. The masers seem to be located in the direction of low
interstellar scattering.


title: Difficulty of a spinning complex scalar field to be dark energy

abstract:
  We comment on the possibility of a spinning complex scalar field to be dark
energy. We show that it deforms (almost) completely into a nontopological
soliton state, a Q ball, and the equation of state becomes that of the matter
or radiation, depending on the fate of the Q ball. Thus, the spinning complex
scalar field is usually very difficult to play the role of the dark energy. We
also show the general condition that the spinning complex scalar field can
successfully be the dark energy.


title: Spectral classification of stars using synthetic model atmospheres

abstract:
  We devised a straightforward procedure to derive the atmosphere fundamental
parameters of stars across the different MK spectral types by comparing
mid-resolution spectroscopic observations with theoretical grids of synthetic
spectra.The results of a preliminary experiment, by matching the Gunn and
Stryker and Jacoby et al. spectrophotometric atlases with the Kurucz models,
are briefly discussed. For stars in the A-K spectral range, effective
temperature is obtained within a 1-2% relative uncertainty (at 2 sigma
confidence level). This value raises to 4-5% for the hottest stars in the
samples (O-B spectral types). A poorer fit is obtained throughout for stars
cooler than 4000 K mainly due to the limiting input physics in the Kurucz
models.


title: On the helium flash in low-mass Population III Red Giant stars

abstract:
  We investigate the evolution of initially metal-free, low-mass Red Giant
stars through the He core flash at the tip of the Red Giant Branch. The low
entropy barrier between the helium- and hydrogen-rich layers enables a
penetration of the helium flash driven convective zone into the inner tail of
the extinguishing H-burning shell. As a consequence, protons are mixed into
high-temperature regions triggering a H-burning runaway. The subsequent
dredge-up of matter processed by He and H burning enriches the stellar surface
with large amounts of helium, carbon and nitrogen. Extending previous results
by Hollowell et al. (1990) and Fujimoto et al. (2000), who claimed that the
H-burning runaway is an intrinsic property of extremely metal-poor low-mass
stars, we found that its occurrence depends on additional parameters like the
initial composition and the treatment of various physical processes.
  We perform some comparisons between predicted surface chemical abundances and
observational measurements for extremely metal-deficient stars. As in previous
investigations, our results disclose that although the described scenario
provides a good qualitative agreement with observations, considerable
discrepancies still remain. They may be due to a more complex evolutionary path
of `real' stars, and/or some shortcomings in current evolutionary models.
  In addition, we analyze the evolutionary properties after the He core flash,
during both the central and shell He-burning phases, allowing us to deduce some
interesting differences between models whose Red Giant Branch progenitor has
experienced the H-flash and canonical models. In particular, the Asymptotic
Giant Branch evolution of extremely metal-deficient stars and the occurrence of
thermal pulses are strongly affected by the previous RGB evolution.


title:
Gravitational lensing potential reconstruction in quadruply imaged
  systems

abstract:
  We develop a semi - analytical method to reconstruct the lensing potential in
quadruply imaged gravitational lens systems. Assuming that the potential
belongs to a broad class of boxy non - elliptical models, we show how it is
possible to write down a system of equations which can be numerically solved to
recover the potential parameters directly from image positions and using
physical constraints. We also describe a code developed to search for solutions
of the system previously found and test it on simulated cases. Finally, we
apply the method to the quadruple lens PG1115+080 which allows us to get also
an estimate of the Hubble constant H_0 from the measured time delay as H_0 =
56_{-11}^{+17} km/s/Mpc.


title:
Eclipses by a Circumstellar Dust Feature in the Pre-Main Sequence Star
  KH15D

abstract:
  Photometry and spectroscopy of the unique pre-main sequence eclipsing object
KH15D in the young cluster NGC 2264 are presented. The orbital period is 48.34
days and both the length (~16 d) and depth (~3 mag) of the eclipse have
increased with time. A brightening near the time of central eclipse is
confirmed in the recent data but at a much smaller amplitude than was
originally seen. Spectra taken when the star is bright show that the primary is
a weak T Tauri star of spectral type K7. During eclipse there is no detectable
change in spectral type or reddening, indicating that the obscuration is caused
by rather large dust grains and/or macroscopic objects. Evidently the star is
eclipsed by an extended feature in its circumstellar disk orbiting with a
semi-major axis of ~0.2 AU. Continued photometric monitoring should allow us to
probe the disk structure with a spatial resolution of ~3 x 10^6 km or better.


title:
Type Ia Supernovae, the Hubble Constant, the Cosmological Constant, and
  the Age of the Universe

abstract:
  The age of the Universe depends on both the present-day Hubble Constant and
on the history of cosmic expansion. For decelerating cosmologies such as
Omega_m= 1, the dimensionless product H_0,t_0<1 and modestly high values of the
Hubble constant H_0 > 70 would be inconsistent with a cosmic age t_0 larger
than 12 Gyr. But if Omega_Lambda > 0, then H_0,t_0 can take on a range of
values. Evidence from the Hubble diagram for high redshift Type Ia supernovae
favors Omega_Lambda~0.7 and H_0,t_0 ~ 1. Then, if H_0 lies in the range 65--73,
the age of the Universe, t_0, is 14+/-1.6 Gyr.


title: Structural evolution in elliptical galaxies: the age-shape relation

abstract:
  We test the hypothesis that the apparent axis ratio of an elliptical galaxy
is correlated with the age of its stellar population. We find that old
ellipticals (with estimated stellar ages t > 7.5 Gyr) are rounder on average
than younger ellipticals. The statistical significance of this shape difference
is greatest at small radii; a Kolmogorov-Smirnov test comparing the axis ratios
of the two populations at R = Re/16 yields a statistical significance greater
than 99.96 percent. The relation between age and apparent axis ratio is linked
to the core/powerlaw surface brightness profile dichotomy. Core ellipticals
have older stellar populations, on average, than powerlaw ellipticals and are
rounder in their inner regions. Our results are consistent with a scenario in
which powerlaw ellipticals are formed in gas-rich mergers while core
ellipticals form in dissipationless mergers, with cores formed and maintained
by the influence of a binary black hole.


title:
Squared temperature-temperature power spectrum as a probe of the CMB
  bispectrum

abstract:
  It is now well known that mode-coupling effects associated with certain
secondary effects generate higher order correlations in cosmic microwave
background (CMB) temperature anisotropies, beyond the two-point function. In
order to extract the non-Gaussian signal at the three-point level, we suggest a
two-point statistic in the form of an angular power spectrum involving
correlations between squared temperature and temperature anisotropies. This
power spectrum contains compressed information from the bispectrum and can be
easily measured in data with the same techniques that have been considered for
the measurement of the usual temperature-temperature anisotropy power spectrum.
We study the proposed power spectrum resulting from the non-Gaussian signal
generated by correlations involved with gravitational lensing angular
deflections in CMB and the Sunyave-Zel'dovich (SZ) effect due to large scale
pressure fluctuations. Using the Planck frequency cleaned CMB and SZ maps, the
CMB^2-SZ power spectrum provides a direct estimate of the cross-power between
lensing angular deflections and the SZ effect. Through an optimal filter
applied to the squared CMB map, the proposed statistic allows one to obtain all
information from the lensing-SZ bispectrum. The observational measurement of
the lensing-SZ cross-correlation is useful to understand the relation between
large scale structure pressure and dark matter fluctuations.


title: A Re-examination of the Distribution of Galactic Free Electrons

abstract:
  We present a list of 109 pulsars with independent distance information
compiled from the literature. Since the compilation of Frail & Weisberg, there
are 35 pulsars with new distance estimate and 25 pulsars for which the distance
or distance uncertainty have been revised. We used this data to fit a smooth,
axisymmetric, two disk model of the distribution of galactic electrons. The two
exponential model components have mean local midplane densities at the solar
circle of 2.03e-2 cm^-3 and 0.71e-2 cm^-3, and scale heights of 1.07 and 0.053
kpc. The thick component shows very little radial variation, while the second
has a radial scale length of only a few kiloparsecs. We also examined a model
which varies as sech^2(x), rather than exp(-x), in both the radial and vertical
direction. We prefer this model with no midplane cusp, but find that the fit
parameters essentially describe the same electron distribution. The distances
predicted by this distribution have a similar scatter as the more complex model
of Taylor & Cordes. We examine the pulsars that deviate strongly from this
model. There are two regions of enhanced dispersion measure, one of which
correlates well with the Sagittarius-Carina spiral arm. We find that the
scatter of the observed dispersion measure from the model is not fit well by
either a normal or log-normal distribution of lump sizes, but may be caused
instead by the uncertainties in the distances.


title: On the orbital period of the cataclysmic variable RZ Leonis

abstract:
  In this research note we present a time-resolved study of the Balmer emission
lines of RZ Leo. From the analysis of the radial velocities we find an orbital
period of 0.07651(26) d. This is in excellent agreement with the
photometrically determined periods in quiescence and during the early stages of
superoutburst. A comparison of the recently determined superhump period gives
an excess of ~0.03, which is a typical value for an SU UMa star of this period.


title: The Physics of Cluster Mergers

abstract:
  Clusters of galaxies generally form by the gravitational merger of smaller
clusters and groups. Major cluster mergers are the most energetic events in the
Universe since the Big Bang. Some of the basic physical properties of mergers
will be discussed, with an emphasis on simple analytic arguments rather than
numerical simulations. Semi-analytic estimates of merger rates are reviewed,
and a simple treatment of the kinematics of binary mergers is given. Mergers
drive shocks into the intracluster medium, and these shocks heat the gas and
should also accelerate nonthermal relativistic particles. X-ray observations of
shocks can be used to determine the geometry and kinematics of the merger. Many
clusters contain cooling flow cores; the hydrodynamical interactions of these
cores with the hotter, less dense gas during mergers are discussed. As a result
of particle acceleration in shocks, clusters of galaxies should contain very
large populations of relativistic electrons and ions. Electrons with Lorentz
factors gamma~300 (energies E = gamma m_e c^2 ~ 150 MeV) are expected to be
particularly common. Observations and models for the radio, extreme
ultraviolet, hard X-ray, and gamma-ray emission from nonthermal particles
accelerated in these mergers are described.


title: Fossil Disks and Propellor Spindown of SGR/AXPs

abstract:
  We have shown that the interstellar media which surround the progenitors of
SGRs and AXPs were unusually dense compared to the environments around most
young radio pulsars. This environmental correlation argues strongly against the
current magnetar model for SGRs and AXPs. We suggest instead that they are
neutron stars with sub-critical magnetic fields and are spun down rapidly by
``propeller'' torques from fossil disks formed from the fallback of supernova
ejecta. We show that this hypothesis is consistent with the observed properties
of these enigmatic objects, and we compare the propeller and magnetar models
for SGR and AXPs.


title:
Observations of the Optical Counterpart to XTE J1118+480 During Outburst
  by the ROTSE-I Telescope

abstract:
  The X-ray nova XTE J1118+480 exhibited two outbursts in the early part of
2000. As detected by the Rossi X-ray Timing Explorer (RXTE), the first outburst
began in early January and the second began in early March. Routine imaging of
the northern sky by the Robotic Optical Transient Search Experiment (ROTSE)
shows the optical counterpart to XTE J1118+480 during both outbursts. These
data include over 60 epochs from January to June 2000. A search of the ROTSE
data archives reveal no previous optical outbursts of this source in selected
data between April 1998 and January 2000. While the X-ray to optical flux ratio
of XTE J1118+480 was low during both outbursts, we suggest that they were full
X-ray novae and not mini-outbursts based on comparison with similar sources.
The ROTSE measurements taken during the March 2000 outburst also indicate a
rapid rise in the optical flux that preceded the X-ray emission measured by the
RXTE by approximately 10 days. Using these results, we estimate a pre-outburst
accretion disk inner truncation radius of 1.2 x 10^4 Schwarzschild radii.


title:
Very low luminosities from the accretion-driven millisecond X-ray pulsar
  SAX J1808.4-3658 during quiescence

abstract:
  We have observed the millisecond X-ray pulsar SAX J1808.4-3658 on three
occasions during its 2000 outburst with the BeppoSAX satellite. The source was
highly variable and erratic during this outburst, and by coincidence we
obtained data only during times when the source had very low luminosities.
During our observations, we detected four faint sources. The source closest to
the position of SAX J1808.4-3658 is still ~1.6' away. This source can only be
identified with SAX J1808.4-3658 if we assume that the BeppoSAX positional
reconstruction is not completely understood. We also reanalyzed a BeppoSAX
observation taken in March 1999 when the source was in quiescence and during
which the source was thought to have been detected (Stella et al. 2000). Based
on the similarities (position and luminosity) of this source with the above
mentioned source ~1.6' away from SAX J1808.4-3658, it is possible that they are
the same source. If this source is not the millisecond pulsar, then during all
BeppoSAX observations of SAX J1808.4-3658 (the 2000 outburst ones and the 1999
quiescent one), the millisecond pulsar was not detected. A reanalysis of the
ASCA quiescent data of SAX J1808.4-3658 (Dotani, Asai, & Wijnands 2000)
confirms that during this observation the source was securely detected in
quiescence. We discuss our results for SAX J1808.4-3658 in the context of the
quiescent properties of low-mass X-ray binary transients.


title: Propagation of Magnetized Neutron Stars Through the Interstellar Medium

abstract:
  This work investigates the propagation of magnetized, isolated old neutron
stars through the interstellar medium. We performed axisymmetric non
relativistic magnetohydrodynamic (MHD) simulations of the propagation of a
non-rotating star with dipole magnetic field aligned with its velocity through
the interstellar medium (ISM). Effects of rotation will be discussed in a
subsequent work. We consider two cases: (1) where theaccretion radius $R_{acc}$
is comparable to the magnetic standoff distance or Alfv\'en radius $R_A$ and
gravitational focusing is important; and (2) where $R_{acc}<< R_A$ and the
magnetized star interacts with the ISM as a ``magnetic plow'', without
significant gravitational focusing. For the first case simulations were done at
a low Mach number ${\cal M}=3$ for a range of values of the magnetic field
$B_*$. For the second case, simulations were done for higher Mach numbers,
${\cal M}=10,$ 30, and 50. In both cases, the magnetosphere of the star
represents an obstacle for the flow, and a shock wavestands in front of the
star. Magnetic field lines are stretched downwind from the star and form a
hollow elongated magnetotail. Reconnection of the magnetic field is observed in
the tail which may lead to acceleration of particles. Similar powers are
estimated to be released in the bow shock wave and in the magnetotail. The
estimated powers are, however, below present detection limits. Results of our
simulations maybe applied to other strongly magnetized stars, for example,
white dwarfs and magnetic Ap stars. Future more sensitive observations may
reveal long magnetotails of magnetized stars moving through the ISM.


title: Acoustic Oscillations in the Early Universe and Today

abstract:
  During its first ~100,000 years, the universe was a fully ionized plasma with
a tight coupling by Thompson scattering between the photons and matter. The
trade--off between gravitational collapse and photon pressure causes acoustic
oscillations in this primordial fluid. These oscillations will leave
predictable imprints in the spectra of the cosmic microwave background and the
present day matter-density distribution. Recently, the BOOMERANG and MAXIMA
teams announced the detection of these acoustic oscillations in the cosmic
microwave background (observed at redshift ~1000). Here, we compare these CMB
detections with the corresponding acoustic oscillations in the matter-density
power spectrum (observed at redshift ~0.1). These consistent results, from two
different cosmological epochs, provide further support for our standard Hot Big
Bang model of the universe.


title: Mapping the Dark Matter through the CMB Damping Tail

abstract:
  The lensing of CMB photons by intervening large-scale structure leaves a
characteristic imprint on its arcminute-scale anisotropy that can be used to
map the dark matter distribution in projection on degree scales or ~100 Mpc/h
comoving. We introduce a new algorithm for mass reconstruction which optimally
utilizes information from the weak lensing of CMB anisotropies in the damping
tail. It can ultimately map individual degree scale mass structures with high
signal-to-noise. To achieve this limit an experiment must produce a high
signal-to-noise, foreground-free CMB map of arcminute scale resolution,
specifically with a FWHM beam of < 5' and a noise level of < 15 (10^-6-arcmin)
or 41 (uK-arcmin).


title: Transport of Magnetic Fields in Convective, Accreting Supernova Cores

abstract:
  We consider the amplification and transport of a magnetic field in the
collapsed core of a massive star, including both the region between the
neutrinosphere and the shock, and the central, opaque core. An analytical
argument explains why rapid convective overturns persist within a newly formed
neutron star for roughly 10 seconds ($> 10^3$ overturns), consistent with
recent numerical models. A dynamical balance between turbulent and magnetic
stresses within this convective layer corresponds to flux densities in excess
of $10^{15}$G. Material accreting onto the core is heated by neutrinos and also
becomes strongly convective. We compare the expected magnetic stresses in this
convective `gain layer' with those deep inside the neutron core.
  Buoyant motions of magnetized fluid are greatly aided by the intense neutrino
flux. We calculate the transport rate through a medium containing free neutrons
protons, and electrons, in the limiting cases of degenerate or non-degenerate
nucleons. Fields stronger than $\sim 10^{13}$ G are able to rise through the
outer degenerate layers of the neutron core during the last stages of
Kelvin-Helmholtz cooling (up to 10 seconds post-collapse), even though these
layers have become stable to convection. We also find the equilibrium shape of
a thin magnetic flux rope in the dense hydrostatic atmosphere of the neutron
star, along with the critical separation of the footpoints above which the rope
undergoes unlimited expansion against gravity. The implications of these
results for pulsar magnetism are summarized, and applied to the case of late
fallback over the first 1,000-10,000 s of the life of a neutron star


title: Observational Evidence for Strong Disk Comptonization in GRO J1655-40

abstract:
  Analysis was made of the multiple XTE/PCA data on the promised black hole
candidate with superluminal jet, GRO J1655-40, acquired during its 1996--1997
outburst. The X-ray spectra can be adequately described by the sum of an
optically thick disk spectrum and a power-law. When the estimated 1--100 keV
power-law luminosity exceeds 1E37 erg/s (assuming a distance of 3.2 kpc), the
inner disk radius and the maximum color temperature derived from a simple
accretion disk model (a multi-color disk model) vary significantly with time.
These results reconfirm the previous report by Sobczak et al. (1999). In this
strong power-law state (once called ``very high state''), the disk luminosity
decreases with temperature, in contradiction to the prediction of the standard
Shakura-Sunyaev model. In the same state, the intensity of the power-law
component correlates negatively with that of the disk component, and positively
with the power-law photon index, suggesting that the strong power-law is simply
the missing optically thick disk emission. One possible explanation for this
behavior is inverse-Compton scattering in the disk. By re-fitting the same data
incorporating a disk Comptonization, the inner radius and temperature of the
underlying disk are found to become more constant. These results provide one of
the first observational confirmations of the scenario of disk Comptonization in
the strong power-law state. This strong power-law state seems to appear when
color temperature of the disk exceeds the certain threshold, 1.2 -- 1.3 keV.


title: The gas content of peculiar galaxies: counterrotators and polar rings

abstract:
  This paper studies the global ISM content in a sample of 104 accreting
galaxies, including counterrotators and polar rings, which spans the entire
Hubble sequence. The molecular, atomic and hot gas content of accretors is
compared to a newly compiled sample of normal galaxies. We present results of a
small survey of the J=1--0 line of {12}CO with the 15m SEST telescope on a
sample of 11 accretors (10 counterrotators and 1 polar ring). The SEST sample
is enlarged with published data from 48 galaxies, for which observational
evidence of counterrotation in the gas and/or the stars has been found.
Furthermore, the available data on a sample of 46 polar ring galaxies has been
compiled. It was found that the normalized content of cold gas (M_gas/L_B) in
polar rings is ~1 order of magnitude higher than the reference value derived
for normal galaxies. The inferred gas masses are sufficient to stabilize polar
rings through self-gravity. In contrast, it was found that the cold gas content
of counterrotators is close to normal for all galaxy types. Although
counterrotators and polar rings probably share a common origin, the gas masses
estimated here confirm that light gas rings accreted by future counterrotators
may have evolved faster than the self-gravitating structures of polar rings. In
this scenario, the transformation of atomic into molecular gas could be
enhanced near the transition region between the prograde and the retrograde
disks, especially in late-type accretors characterized by a high content of
primordial gas. This is tentatively confirmed in this work: the measured H_2/HI
ratio seems larger in counterrotators than in normal or polar ring galaxies for
types later than S0s.


title:
The dusty SF history of high-z galaxies, modelling tools and future
  prospects

abstract:
  We summarize recent advances in the determination of the cosmic history of
star formation and other properties of high-z galaxies, and the relevance of
this information in our understanding of the formation of structures. We
emphasize the importance of dust reprocessing in the high--z universe, as
demonstrated in particular by IR and sub-mm data. This demand a panchromatic
approach to observations and suitable modelling tools. We spend also some words
on expectations from future instruments.


title: Calorimetry of gamma-ray bursts: echos in gravitational waves

abstract:
  Black holes surrounded by a disk or torus may drive the enigmatic
cosmological gamma-ray bursts (GRBs). Equivalence in poloidal topology to
pulsar magnetospheres shows a high incidence of the black hole-luminosity $L_H$
into the surrounding magnetized matter. We argue that this emission is
re-radiated into gravitational waves at $L_{GW}\simeq L_H/3$ in frequencies of
order 1kHz, winds and, potentially, MeV neutrinos. The total energy budget and
input to the GRB from baryon poor jets are expected to be standard in this
scenario, consistent with recent analysis of afterglow data. Collimation of
these outflows by baryon rich disk or torus winds may account for the observed
spread in opening angles up to about $35^o$. This model may be tested by future
LIGO/VIRGO observations.


title: Clusters of galaxies among ROSAT blank field sources

abstract:
  We present here an efficient method for selecting high luminosity and massive
high redshift clusters of galaxies, crucially important tools in cosmology. By
selecting bright and extremely X-ray loud (high F(X)/F(V)) sources, we were
able to identify 2 high redshift (z=0.45 and z=0.89) clusters so far and we
have evidence for at least one more candidate at 0.4<z<1.1 out of a total of 16
selected sources.


title:
XMM-Newton Observations of Galaxy Clusters: The Radial Temperature
  Profile of A2163

abstract:
  XMM-Newton, with its high throughput and excellent spatial and spectral
resolution, is an ideal instrument for spectro-imaging observation of clusters.
Presented here is an XMM-Newton mosaic observation of A2163, from which a new
radial temperature profile is derived. The issue of background subtraction is
addressed in some detail as a proper treatment of the background is essential
for the derivation of correct temperatures, and thus, of the correct total
cluster mass.


title: All-sky component separation for the Planck mission

abstract:
  An harmonic-space maximum-entropy method (MEM) is presented for separating
the emission from different physical components in all-sky observations by the
forthcoming Planck satellite. The analysis is performed at full Planck
resolution, with a pixel size of 1.7 arcmin, which corresponds to a maximum
multipole of around 6000. The simulated Planck data include emission from the
CMB, the kinetic and thermal Sunyaev-Zel'dovich (SZ) effects from galaxy
clusters, as well as Galactic dust, free-free and synchrotron emission. Our
simulations also assume homogeneous, uncorrelated pixel noise, although this is
not a requirement of the method. We find that the MEM technique produces
faithful reconstructions of the main input components over the whole sky,
without the need to perform a Galactic cut. The CMB power spectrum is
accurately recovered up to a multipole of around 2000. The algorithm is
parallelised so that the entire reconstruction can be performed in around 6 hr
using 30 R10000 processors on an SGI Origin 2000 supercomputer and requires 14
Gb of memory.


title: A Dual Frequency, Multi-Year Monitoring Program of Compact Radio Sources

abstract:
  We present light curves for 149 sources monitored with the Green Bank
Interferometer. The light curves are at two radio frequencies (approximately
2.5 and 8.2 GHz) and range from 3 to 15 yrs in length, covering the interval
1979--1996, and have a typical sampling of one flux density measurement every 2
days. We have used these light curves to conduct various variability analysis
(rms flux density variations and autoregressive, integrated, moving average
modeling) of these sources. We find suggestive, though not unambiguous
evidence, that these sources have a common, broadband mechanism for intrinsic
variations, in agreement with previous studies of a subset of these source. We
also find that the sources generally display a short-term variability (~ 10 d)
that arises from radio-wave scattering in an extended medium. These conclusions
extend those of Fiedler et al. (1987) who used a sub-sample of these data. The
primary motivation for this monitoring program was the identification of
extreme scattering events. In an effort to identify ESEs in a systematic
manner, we have taken the wavelet transform of the light curves. We find 15
events in the light curves of 12 sources that we classify as probable ESEs.
However, we also find that five ESEs previously identified from these data do
not survive our wavelet selection criteria. Future identification of ESEs will
probably continue to rely on both visual and systematic methods. Instructions
for obtaining the data are also presented.


title:
NICS-TNG infrared spectroscopy of trans-neptunian objects 2000 EB173 and
  2000 WR106

abstract:
  We report complete near-infrared (0.9-2.4 $\mu$m) spectral observations of
trans-neptunian objects (TNOs) 2000 EB173 and 2000 WR106 collected using the
new Near Infrared Camera Spectrometer (NICS) attached to the 3.56m Telescopio
Nazionale Galileo (TNG). Both spectra are very red and with a quite strong and
broad drop extending throughout the K band. However, while 2000 EB173 does not
show any evidence of narrow absorption features, the spectrum of 2000 WR106 has
quite deep water ice absorption at 1.5 and 2.0 $\mu$m. Moreover, the latter
object is significantly less red than the former indicating, therefore, that
the surface of 2000 WR106 is ``cleaner'' (i.e. less processed by particle
irradiation) than that of 2000 EB173.


title: Cold gas in elliptical galaxies

abstract:
  We explore the evolution of the cold gas (molecular and neutral hydrogen) of
elliptical galaxies and merger remnants ordered into a time sequence on the
basis of spectroscopic age estimates. We find that the fraction of cold gas in
early merger remnants decreases significantly for ~1-2 Gyr, but subsequent
evolution toward evolved elliptical systems sees very little change. This trend
can be attributed to an initial gas depletion by strong star-formation which
subsequently declines to quiescent rates. This explanation is consistent with
the merger picture for the formation of elliptical galaxies. We also explore
the relation between HI-to-H2 mass ratio and spectroscopic galaxy age, but find
no evidence for a statistically significant trend. This suggests little net HI
to H2 conversion for the systems in the present sample.


title:
The fine spatial structure of methanol masers as an evidence in support
  of their connection with bipolar outflows

abstract:
  We studied class I methanol masers in the transition 7_0-6_1 A+ at the
frequency 44 GHz with the VLA. The observations on the VLA were made with the
angular resolution 0''.1, which was the highest at the moment. It was shown
that the masers consist of chains of unresolved spots located on curved lines
or arcs. The length of such arcs is from 20 to 1000 AU and the brightness
temperature of the strongest masers exceeds 3.6x10^8 K. The observed location
of maser spots is in agreement with their position at the border line between
molecular outflows and surrounding molecular clouds. The high brightness
temperature implies that the maser condensations have enhanced abundance of
methanol due to evaporation of methanol from the surface of dust grains. The
mass of maser condensations is less than 4x10^-5 solar mass and corresponds to
planetary masses.


title: Proper Motion of Water Masers Near NGC1333-SVS13

abstract:
  VLBA observations of water masers toward the region of NGC1333 near SVS13,
the driving source for the well-known Herbig-Haro objects HH7-11, are reported.
Maser emission was observed over four epochs spaced by three weeks during late
1998. SVS13 is associated with the millimeter continuum SED Class I source
SSV13A1. High resolution CO observations have secured the association of the
flow with the continuum object on arc-second scales. A 1998 Aug 12 VLA
observation places the blueshifted masers within 80 AU (0''.2) of the 2.7 mm
position for A1 reported from BIMA. We report observations of two groups of
masers, one redshifted by about 6 km s-1 and one blueshifted by about 2-3 km
s-1, separated by about 100 AU in projected distance along position angle 21
degrees. Redshifted masers were present only in the latter two epochs. During
all epochs, an arclike structure was present with similar morphology; over time
this structure moved relative to the southernmost blue maser toward the
southeast, roughly along the position angle defined by the Herbig-Haro objects,
with a proper motion of about 13 km s-1. Both redshifted and blueshifted masers
are clearly part of the same lobe of the flow; their observed Doppler shifts
are artifacts of the opening angle of the flow. Our data suggest that the
opening angle is about 10 degrees. We measure lower expansion velocities and a
wider opening angle than has been found in some other flows near Class 0 SED
objects, perhaps indicating that the flows open and slow as they age.


title:
Clouds and Chemistry: Ultracool Dwarf Atmospheric Properties from
  Optical and Infrared Colors

abstract:
  The optical and infrared colors of L and T dwarfs are sensitive to cloud
sedimentation and chemical equilibrium processes in their atmospheres. The
i'-z' vs. J-K color-color diagram provides a window into diverse atmospheric
processes mainly because different chemical processes govern each color, and
cloud opacity largely affects J-K but not i'-z'. Using theoretical atmosphere
models that include for the first time a self-consistent treatment of cloud
formation, we present an interpretation of the i'-z' vs. J-K color trends of
known L and T dwarfs. We find that the i'-z' color is extremely sensitive to
chemical equilibrium assumptions: chemical equilibrium models accounting for
cloud sedimentation predict redder i'-z' colors--by up to 2 magnitudes--than
models that neglect sedimentation. We explore the previously known J-K color
trends where objects first become redder, then bluer with decreasing effective
temperature. Only models that include sedimentation of condensates are able to
reproduce these trends. We find that the exact track of a cooling brown in J-K
(and i'-z') is very sensitive to the details of clouds, in particular to the
efficiency of sedimentation of condensates in its atmosphere. We also find that
clouds still affect the strength of the J, H, and K band fluxes of even the
coolest T dwarfs. In addition, we predict the locus in the i'-z' vs. J-K
color-color diagram of brown dwarfs cooler than yet discovered.


title: Stellar Mixing and the Primordial Lithium Abundance

abstract:
  We compare the properties of recent samples of the lithium abundances in halo
stars to one another and to the predictions of theoretical models including
rotational mixing, and we examine the data for trends with metal abundance. We
find from a KS test that in the absence of any correction for chemical
evolution, the Ryan, Norris, & Beers (1999} sample is fully consistent with
mild rotational mixing induced depletion and, therefore, with an initial
lithium abundance higher than the observed value. Tests for outliers depend
sensitively on the threshold for defining their presence, but we find a
10$--$45% probability that the RNB sample is drawn from the rotationally mixed
models with a 0.2 dex median depletion (with lower probabilities corresponding
to higher depletion factors). When chemical evolution trends (Li/H versus Fe/H)
are treated in the linear plane we find that the dispersion in the RNB sample
is not explained by chemical evolution; the inferred bounds on lithium
depletion from rotational mixing are similar to those derived from models
without chemical evolution. We find that differences in the equivalent width
measurements are primarily responsible for different observational conclusions
concerning the lithium dispersion in halo stars. The standard Big Bang
Nucleosynthesis predicted lithium abundance which corresponds to the deuterium
abundance inferred from observations of high-redshift, low-metallicity QSO
absorbers requires halo star lithium depletion in an amount consistent with
that from our models of rotational mixing, but inconsistent with no depletion.


title:
Applications of Halo Approach to Non-Linear Large Scale Structure
  Clustering

abstract:
  We present astrophysical applications of the recently popular halo model to
describe large scale structure clustering. We formulate the power spectrum,
bispectrum and trispectrum of dark matter density field in terms of
correlations within and between dark matter halos. The halo approach uses
results from numerical simulations and involves a profile for dark matter, a
mass function for halos, and a description of halo biasing with respect to the
linear density field. This technique can easily be extended to describe
clustering of any property of the large scale structure, such as galaxies,
baryons and pressure, provided that one formulate the relationship between such
properties and dark matter. In detail, we discuss applications of the halo
model for several observational probes of the local universe involving weak
gravitational lensing, thermal Sunyaev-Zel'dovich (SZ) effect and the kinetic
SZ effect. We also propose a new cosmological test using the redshift evolution
of the angular power spectrum of halos and using a calibrated linear power
spectrum, which acts as an effective standard ruler (Summary).