title: Solar Wakes of Dark Matter Flows

abstract:
  We analyze the effect of the Sun's gravitational field on a flow of cold dark
matter (CDM) through the solar system in the limit where the velocity
dispersion of the flow vanishes. The exact density and velocity distributions
are derived in the case where the Sun is a point mass. The results are extended
to the more realistic case where the Sun has a finite size spherically
symmetric mass distribution. We find that regions of infinite density, called
caustics, appear. One such region is a line caustic on the axis of symmetry,
downstream from the Sun, where the flow trajectories cross. Another is a
cone-shaped caustic surface near the trajectories of maximum scattering angle.
The trajectories forming the conical caustic pass through the Sun's interior
and probe the solar mass distribution, raising the possibility that the solar
mass distribution may some day be measured by a dark matter detector on Earth.
We generalize our results to the case of flows with continuous velocity
distributions, such as that predicted by the isothermal model of the Milky Way
halo.


title:
The Effect of Vacuum Polarization and Proton Cyclotron Resonances on
  Photon Propagation in Strongly Magnetized Plasmas

abstract:
  We consider the effects of vacuum polarization and proton cyclotron
resonances on the propagation of radiation through a strongly magnetized
plasma. We analyze the conditions under which the photons evolve adiabatically
through the resonant density and find that the adibaticity condition is
satisfied for most photon energies of interest, allowing for a normal-mode
treatment of the photon propagation. We then construct radiative equilibrium
atmosphere models of strongly magnetized neutron stars that includes these
effects, employing a new numerical method that resolves accurately the sharp
changes of the absorption and mode-coupling cross sections at the resonant
densities. We show that the resulting spectra are modified by both resonances
and are harder at all field strengths than a blackbody at the effective
temperature. We also show that the narrow absorption features introduced by the
proton cyclotron resonance have small equivalent widths. We discuss the
implications of our results for properties of thermal emission from the
surfaces of young neutron stars.


title:
Are X-ray Clusters Cooled by Heat Conduction to the Surrounding
  Intergalactic Medium?

abstract:
  We show that X-ray clusters would have cooled substantially over a Hubble
time by transport of heat from their hot interior to the their envelope, if the
heat conductivity had not been heavily suppressed relative to the Spitzer value
due to magnetic fields. The suppression is required in order for the observed
abundance of hot X-ray clusters to be consistent with predictions from popular
cosmological models. If a similar or stronger suppression factor applies to
cluster cores, then thermal conduction can not be the mechanism that prevents
cooling flows there.


title:
Mass-Loss Rate Determination for the Massive Binary V444 Cyg using 3-D
  Monte-Carlo Simulations of Line and Polarization Variability

abstract:
  A newly developed 3-D Monte Carlo model is used, in conjunction with a
multi-line non-LTE radiative transfer model, to determine the mass-loss rate of
the Wolf-Rayet (W-R) star in the massive binary \object{V444 Cyg} (WN5+O6).
This independent estimate of mass-loss rate is attained by fitting the observed
\HeI (5876) \AA and \HeII (5412) \AA line profiles, and the continuum light
curves of three Stokes parameters ((I, Q, U)) in the (V) band simultaneously.
The high accuracy of our determination arises from the use of many
observational constraints, and the sensitivity of the continuum polarization to
the mass-loss rate. Our best fit model suggests that the mass-loss rate of the
system is (\dot{M}_{\WR}=0.6(\pm 0.2) \times 10^{-5} M_{\sun} \mathrm{yr}^{-1}
), and is independent of the assumed distance to \object{V444 Cyg}. The fits
did not allow a unique value for the radius of the W-R star to be derived. The
range of the volume filling factor for the W-R star atmosphere is estimated to
be in the range of 0.050 (for $R_{\WR}=5.0 R_{\sun}$) to 0.075 (for
$R_{\WR}=2.5 R_{\sun}$). We also found that the blue-side of \HeI (5876 ) \AA
and \HeII (5412) \AA lines at phase 0.8 is relatively unaffected by the
emission from the wind-wind interaction zone and the absorption by the O-star
atmosphere; hence, the profiles at this phase are suitable for spectral line
fittings using a spherical radiative transfer model.


title: Supersonic turbulence and structure of interstellar molecular clouds

abstract:
  The interstellar medium (ISM) provides a unique laboratory for highly
supersonic, driven hydrodynamics turbulence. We present a theory of such
turbulence, confirm it by numerical simulations, and use the results to explain
observational properties of interstellar molecular clouds, the regions where
stars are born.


title: The mode trapping properties of full DA white dwarf evolutionary models

abstract:
  An adiabatic, non-radial pulsation study of a 0.563 M_sun DA white dwarf
model is presented on the basis of new evolutionary calculations performed in a
self-consistent way with the predictions of time dependent element diffusion,
nuclear burning and the history of the white dwarf progenitor. Emphasis is
placed on the role played by the internal chemical stratification of these new
models in the behaviour of the eigenmodes, and the expectations for the full
g-spectrum of periods. The implications for the mode trapping properties are
discussed at length. In this regard, we find that, for high periods, the
viability of mode trapping as a mode selection mechanism is markedly weaker for
our models, as compared with the situation in which the hydrogen-helium
transition region is treated assuming equilibrium diffusion in the trace
element approximation.


title: New Members of the Cluster Family in Nearby Lenticulars

abstract:
  Using spectra obtained with the Keck I telescope we have demonstrated
conclusively that the faint (23<V<24 mag.) and unusually extended objects we
discovered in HST images of the lenticular galaxies, NGC 1023 and NGC 3384, are
star clusters associated with their respective galaxies. In the case of NGC
1023 we were further able to establish that these objects are old (>7--8 Gyr),
moderately metal-rich ([Fe/H]=-0.58+/-0.24) and, having a system rotation curve
which is very similar to that of the host galaxy, are associated with the
lenticular disk. Alpha-element to iron abundance ratios are highly supersolar
with [alpha/Fe] between +0.3 and +0.6. With moderately high metallicities and
luminosities, and effective radii in the range 7--15 pc (compared to the 2--3
pc sizes typical of normal globular and open clusters), this population of
clusters has no known analog in the Milky Way or elsewhere in the Local Group.


title: A Coronagraph with a Band-Limited Mask for Finding Terrestrial Planets

abstract:
  Several recent designs for planet-finding telescopes use coronagraphs
operating at visible wavelengths to suppress starlight along the telescope's
optical axis while transmitting any off-axis light from circumstellar material.
We describe a class of graded coronagraphic image masks that can, in principle,
provide perfect elimination of on-axis light, while simultaneously maximizing
the Lyot stop throughput and angular resolution. These ``band-limited'' masks
operate on the intensity of light in the image plane, not the phase. They can
work with almost any entrance pupil shape, provided that the entrance pupil
transmissivity is uniform, and can be combined with an apodized Lyot stop to
reduce the sensitivity of the coronagraph to imperfections in the image mask.
We discuss some practical limitations on the dynamic range of coronagraphs in
the context of a space-based terrestrial planet finder (TPF) telescope, and
emphasize that fundamentally, the optical problem of imaging planets around
nearby stars is a matter of precision fabrication and control, not Fraunhofer
diffraction theory.


title:
Spectroscopic Properties of QSOs Selected from Ultraluminous Infrared
  Galaxy Samples

abstract:
  We performed spectroscopic observations for a large infrared QSO sample with
a total of 25 objects. The sample was compiled from the QDOT redshift survey,
the 1 Jy ULIRGs survey and a sample obtained by a cross-correlation study of
the IRAS Point Source Catalogue with the ROSAT All Sky Survey Catalogue.
Statistical analyses of the optical spectra show that the vast majority of
infrared QSOs have narrow permitted emission lines (with FWHM of Hbeta less
than 4000 km/s) and more than 60% of them are luminous narrow line Seyfert 1
galaxies. Two of the infrared QSOs are also classified as low ionization BAL
QSOs. More than 70% of infrared QSOs are moderately or extremely strong Fe II
emitters. This is the highest percentage of strong Fe II emitters in all
subclasses of QSO/Seyfert 1 samples. We found that the Fe II to Hbeta, line
ratio is significantly correlated with the [OIII]5007 peak and Hbeta blueshift.
Soft X-ray weak infrared QSOs tend to have large blueshifts in permitted
emission lines and significant Fe II48,49 (5100--5400 A) residuals relative to
the Boroson & Green Fe II template. If the blueshifts in permitted lines are
caused by outflows, then they appear to be common in infrared QSOs. As the
infrared-selected QSO sample includes both luminous narrow line Seyfert 1
galaxies and low ionization BAL QSOs, it could be a useful laboratory to
investigate the evolutionary connection among these objects.


title: The Intriguing Distribution of Dark Matter in Galaxies

abstract:
  We review the most recent evidence for the amazing properties of the density
distribution of dark matter around spiral galaxies. Their rotation curves,
coadded according to the galaxy luminosity, conform to an universal profile
which can be represented as the sum of an exponential thin disk plus a
spherical halo with a flat density core. From dwarfs to giants, these halos
feature an inner constant density region. The fine structure of dark matter
halos is obtained from the kinematics of a number of suitable low-luminosity
disk galaxies. The halo circular velocity increases linearly with radius out to
the edge of the stellar disk, implying a constant dark halo density over the
entire disk region. The properties of halos around normal spirals provide
substantial evidence of a discrepancy between the mass distributions predicted
in the Cold Dark Matter scenario and those actually detected around galaxies.


title:
Corotation: its influence on the chemical abundance pattern of the
  Galaxy

abstract:
  A simple theory for the chemical enrichment of the Galaxy which takes into
account the effects of spiral arms on heavy elements output was developed. In
the framework of the model with the corotation close to the position of the Sun
in the Galaxy the observed abundance features are explained.


title: Hydromagnetic instabilities in protoneutron stars

abstract:
  The stability properties of newly born neutron stars, or proto--neutron
stars, are considered. We take into account dissipative processes, such as
neutrino transport and viscosity, in the presence of a magnetic field. In order
to find the regions of the star subject to different sorts of instability, we
derive the general instability criteria and apply it to evolutionary models of
PNSs. The influence of the magnetic field on instabilities is analyzed and the
critical magnetic field stabilizing the star is obtained. In the light of our
results, we estimate of the maximum poloidal magnetic field that might be
present in young pulsars or magnetars.


title: Radiation Driven Implosion of Molecular Cloud Cores

abstract:
  We present the first three-dimensional calculations of Radiation Driven
Implosion of Molecular Clouds including self-gravity and ionization. We discuss
the effects of initial density perturbations on the dynamics of ionizing
globules and show that the onset of gravitational collapse can be significantly
delayed for a multiple of the implosion timescale. We demonstrate that
Radiation Driven Implosion could be an efficient process for injecting
disordered kinetic energy into molecular clouds in the vicinity of massive
stars.


title:
Early-type variables in the Magellanic Clouds. I. Beta Cephei stars in
  the LMC bar

abstract:
  A thorough analysis of the OGLE-II time-series photometry of the Large
Magellanic Cloud bar supplemented by similar data from the MACHO database led
us to the discovery of three Beta Cephei-type stars. These are the first known
extragalactic Beta Cephei-type stars. Two of the three stars are multiperiodic.
Two stars have inferred masses of about 10 Mo while the third is about 2 mag
brighter and at least twice as massive. All three variables are located in or
very close to the massive and young LMC associations (LH 41, 59 and 81). It is
therefore very probable that the variables have higher than average
metallicities. This would reconcile our finding with theoretical predictions of
the shape and location of the Beta Cephei instability strip in the H-R diagram.
The low number of Beta Cephei stars found in the LMC is another observational
confirmation of strong dependence of the mechanism driving pulsations in these
variables on metallicity. Follow-up spectroscopic determination of the
metallicities in the discovered variables will provide a good test for the
theory of pulsational stability in massive main-sequence stars.


title:
The extreme r-element rich, iron-poor halo giant CS31082-001:
  Implications for the r-process site(s) and radioactive cosmochronology

abstract:
  We present a high-resolution spectroscopic analysis of the bright (V=11.7),
extreme halo giant CS31082-001 ([Fe/H] = -2.9), obtained in an ESO-VLT Large
Programme dedicated to very metal-poor stars. We find CS31082-001 to be
extremely rich in r-process elements, comparable in this respect only to the
similarly metal-poor, but carbon-enriched, giant CS22892-052. As a result of
the extreme overabundance of the heaviest r-process elements, and negligible
blending from CH and CN molecular lines, a reliable measurement is obtained of
the U II line at 386 nm, for the first time in a halo star, along with numerous
lines of Th II, as well as lines of 25 other r-process elements. Abundance
estimates for a total of 43 elements are reported in CS31082-001, almost half
of the entire periodic table. All elements with 56 \leq Z \leq 72 follow the
Solar r-element pattern, reduced by about 1.25 dex ([r/Fe]=+1.7 dex, a factor
50). Pb, in contrast, seems to be below the shifted Solar r-process
distribution, possibly indicating an error in the latter, while thorium is more
enhanced than the lighter nuclides. Thus, while a universal production ratio
for the r-process elements seems to hold in the interval 56 \leq Z \leq 72, it
breaks down in the actinide region. When available, the U/Th is thus preferable
to Th/Eu for radioactive dating: (i) because of its faster decay rate and
smaller sensitivity to observational errors, and (ii) because the inital
production ratio of the neighboring nuclides 238U and 232Th is more robustly
predicted than the 151Eu/232Th ratio. Our current best estimate for the age of
CS31082-001 is 14.0+/-2.4 Gyr.


title:
Using the High Resolution X-ray Spectrum of PSR B0656+14 to Constrain
  the Chemical Composition of the Neutron Star Atmosphere

abstract:
  Observations of PSR B0656+14 using the Chandra Low Energy Transmission
Grating Spectrometer are presented. The zeroth order events are pulsed at an
amplitude of 10 +/- 2% and the image may be slightly extended. The extended
emission is modelled as a Gaussian with a FWHM of about 0.75", for a linear
size (at a distance of 760 pc) of 8.5e15 cm. In the absence of systematic
errors in the detector point spread function, the extended emission comprises
<~ 50% of the observed flux in the 0.2-2.0 keV band, for a luminosity of <~
3e32 erg/s. The spectrum is well modelled by a dominant blackbody with T =
8.0e5 +/- 3e4 K and a size of 22.5 +/- 2.1 km in addition to a harder component
that is modelled as a hotter and much smaller blackbody. No significant
absorption features are found in the spectrum that might be expected from
ionization edges of H or He or bound-bound transitions of Fe in magnetized
atmospheres. Such features are expected to be deep but could vary in position
or strength with rotation phase. There are no strong absorption features in the
pulse-phased spectra, however, so we conclude that the atmosphere is not
dominated by Fe or other heavy elements that would be partially ionized at a
temperature of 1e6 K.


title:
The luminosity functions and stellar masses of galactic disks and
  spheroids

abstract:
  We present a method to obtain quantitative measures of galaxy morphology and
apply it to a spectroscopic sample of field galaxies in order to determine the
luminosity and stellar mass functions of galactic disks and spheroids. We
estimate, for each galaxy, the bulge-to-disk luminosity ratio in the I-band
using a two-dimensional image fitting procedure. Monte Carlo simulations
indicate that reliable determinations are only possible for galaxies
approximately two magnitudes brighter than the photometric completeness limit,
leaving a sample of 90 galaxies with well determined bulge-to-total light
ratios. We construct the luminosity functions of disks and spheroids and, using
a stellar population synthesis model, we estimate the stellar mass functions of
each of these components. The disk and spheroid luminosity functions are
remarkably similar. We do, however, find evidence in the bi-variate luminosity
function that spheroid-dominated galaxies occur only among the brightest
spheroids, while disk-dominated galaxies span a much wider range of disk
luminosities. Remarkably, the total stellar mass residing in disks and
spheroids is approximately the same. For our sample, we find the ratio of
stellar masses in disks and spheroids to be 1.3+/-0.2. Ongoing large
photometric and redshift surveys will lead to a large increase in the number of
galaxies to which our techniques can be applied and thus to an improvement in
the current estimates. (abridged)


title: The Spectrum of Earthshine: A Pale Blue Dot Observed from the Ground

abstract:
  We report the visible reflection spectrum of the integrated Earth,
illuminated as it would be seen as an spatially-unresolved extrasolar planet.
The spectrum was derived from observation of lunar earthshine in the range 4800
to 9200 Angstrom at a spectral resolution of about 600. We observe absorption
features of ozone, molecular oxygen and water. We see enhanced reflectivity at
short wavelengths from Rayleigh scattering, and apparently negligible
contributions from aerosol and ocean water scattering. We also see enhanced
reflectivity at long wavelengths starting at about 7300 Angstrom, corresponding
to the well-known red reflectivity edge of vegetation due to its chlorophyll
content; however this signal is not conclusive, due to the breakdown of our
simple model at wavelengths beyond 7900 Angstrom.


title:
Two emission line objects with z>0.2 in the optical filament apparently
  connecting the Seyfert galaxy NGC 7603 to its companion

abstract:
  We present new spectroscopic observations of an old case of anomalous
redshift--NGC 7603 and its companion. The redshifts of the two galaxies which
are apparently connected by a luminous filament are z=0.029 and z=0.057
respectively. We show that in the luminous filament there are two compact
emission line objects with z=0.243 and z=0.391. They lie exactly on the line
traced by the filament connecting the galaxies. As far as we are aware, this is
the most impressive case of a system of anomalous redshifts discovered so far.


title: GRB 011121: A Massive Star Progenitor

abstract:
  Of the cosmological gamma-ray bursts, GRB 011121 has the lowest redshift,
z=0.36. More importantly, the multi-color excess in the afterglow detected in
the Hubble Space Telescope (HST) light curves is compelling observational
evidence for an underlying supernova. Here we present near-infrared and radio
observations of the afterglow. We undertake a comprehensive modeling of these
observations and those reported in the literature and find good evidence
favoring a wind-fed circumburst medium. In detail, we infer the progenitor had
a mass loss rate of Mdot ~ 10^-7 / v_w3 Mo/yr where v_w3 is the speed of the
wind from the progenitor in units of 10^3 km/s. This mass loss rate is similar
to that inferred for the progenitor of SN 1998bw which has been associated with
GRB 980425. Our data, taken in conjunction with the HST results of Bloom et al.
(2002), provide a consistent picture: the long duration GRB 011121 had a
massive star progenitor which exploded as a supernova at about the same time as
the GRB event.


title: The slope of the black-hole mass versus velocity dispersion correlation

abstract:
  Observations of nearby galaxies reveal a strong correlation between the mass
of the central dark object M and the velocity dispersion sigma of the host
galaxy, of the form log(M/M_sun) = a + b*log(sigma/sigma_0); however, published
estimates of the slope b span a wide range (3.75 to 5.3). Merritt & Ferrarese
have argued that low slopes (<4) arise because of neglect of random measurement
errors in the dispersions and an incorrect choice for the dispersion of the
Milky Way Galaxy. We show that these explanations account for at most a small
part of the slope range. Instead, the range of slopes arises mostly because of
systematic differences in the velocity dispersions used by different groups for
the same galaxies. The origin of these differences remains unclear, but we
suggest that one significant component of the difference results from Ferrarese
& Merritt's extrapolation of central velocity dispersions to r_e/8 (r_e is the
effective radius) using an empirical formula. Another component may arise from
dispersion-dependent systematic errors in the measurements. A new determination
of the slope using 31 galaxies yields b=4.02 +/- 0.32, a=8.13 +/- 0.06, for
sigma_0=200 km/s. The M-sigma relation has an intrinsic dispersion in log M
that is no larger than 0.3 dex. In an Appendix, we present a simple model for
the velocity-dispersion profile of the Galactic bulge.


title:
Beyond the Bulge: a Fundamental Relation Between Supermassive Black
  Holes and Dark Matter Halos

abstract:
  The possibility that the masses of supermassive black holes (SBHs) correlate
with the total gravitational mass of their host galaxy, or the mass of the dark
matter halo in which they presumably formed, is investigated using a sample of
16 spiral and 20 elliptical galaxies. The bulge velocity dispersion, typically
defined within an aperture of size less than 0.5 kpc, is found to correlate
tightly with the galaxy's circular velocity, the latter measured at distances
from the galactic center at which the rotation curve is flat, 20 to 80kpc. By
using the well known M-sigma relation for SBHs, and a prescription to relate
the circular velocity to the mass of the dark matter halo in a standard CDM
cosmology, the correlation between velocity dispersion and circular velocity is
equivalent to one between SBH and halo masses. Such a correlation is found to
be nonlinear, with the ratio between the two masses decreasing from 2X10^-4 for
halos of 10^14 solar masses, to 10^-5 for halos of 10^12 solar masses.
Preliminary evidence suggests that halos smaller than ~5X10^11 solar masses are
increasingly less efficient -- perhaps unable -- at forming SBHs.


title: Diffraction-limited CCD imaging with faint reference stars

abstract:
  By selecting short exposure images taken using a CCD with negligible readout
noise we obtained essentially diffraction-limited 810 nm images of faint
objects using nearby reference stars brighter than I=16 at a 2.56 m telescope.
The FWHM of the isoplanatic patch for the technique is found to be 50
arcseconds, providing ~20% sky coverage around suitable reference stars.


title: Structure, Kinematics, and Dynamics of Bulges

abstract:
  A historical review of our understanding of bulges is first presented,
highlighting similarities and differences between bulges and ellipticals. Then,
some topics of current interest are reviewed, bypassing stellar population
questions and focusing on structural and dynamical issues relating bulges and
disks. The topics are: i) the fundamental plane; ii) the evidence for two
classes of bulges, R^1/4 and exponential, and its significance for bulge
formation; iii) the three-dimensional structure of bulges, in particular the
relation between boxy/peanut-shaped bulges and bars; iv) the nuclear properties
of bulges, and their possible effects on bulge dynamics and secular evolution;
and v) the large-scale mass distribution and evidence for dark matter in
bulges. To conclude, new prospects offered by wide-field integral-field
spectroscopy and other instrument developments (space and ground-based) are
discussed.


title: The Cosmic Radio and Infrared Backgrounds Connection

abstract:
  We use the radio-infrared (IR) flux correlation bet ween star-forming
galaxies in the local universe to derive a simple analytical expression between
the intensity of the IR background and the brightness t emperature of the radio
background. This relation i s insensitive to the star formation history of the
galaxies that produce the cosmic IR background (CIB). We use the observed CIB
intensity to constrain t he cosmic star formation history, and the relation
between the CIB and the cosmic radio background (CR B) to constrain the
relative contribution of star-f orming galaxies to the CRB. Current limits on
the C IB intensity predict a 178 MHz brightness temperature of ~18+-9 K, about
half of the 37+-8 K inferred for an isotropic radio component. This suggests
that s tar-forming galaxies and AGN contribute about equal ly to the CRB
intensity at that frequency.


title:
Evidence for the evolutionary sequence of blazars: different types of
  accretion flows in BL Lac objects

abstract:
  The limits on the mass of the black hole in 23 BL Lac objects are obtained
from their luminosities of the broad emission line H\beta on the assumption
that broad emission lines are emitted from clouds ionized by the radiation of
the accretion disk surrounding a black hole. The distribution of line
luminosity L_{H\beta} of all these BL Lac objects suggests a bimodal nature,
although this cannot be statistically proven on the basis of the present,
rather small sample. We found that standard thin disks are probably in the
sources with L_{H\beta}>10^{41} erg s^{-1}. The central black holes in these
sources have masses of 10^{8-10} M_\odot, if the matter is accreting at the
rate of 0.025 {\dot M}_{\rm Edd}. For the sources with L_{H\beta}<10^{41} erg
s^{-1}, the accretion flows have transited from standard thin disk type to the
ADAF type. The lower limits on the mass of the black hole in these sources are
in the range of 1.66-24.5\times 10^{8} M_\odot. The results support the
evolutionary sequence of blazars: FSRQ\to LBL\to HBL.


title:
Moderate Temperature Clusters of Galaxies from the RDCS and the High
  Redshift Luminosity-Temperature Relation

abstract:
  We present our discovery observations and analysis of RDCS1317+2911, z =
0.805, and RDCS1350+6007, z= 0.804, two clusters of galaxies identified through
X-ray emission in the ROSAT Deep Cluster Survey (RDCS). We find a temperature
of 3.7 +1.5 -0.9 keV and a bolometric luminosity of 8.2e43 +1.7e43 -1.6e43
erg/s for RDCS1317+2911, and a temperature of 4.9 +1.3 -0.9 keV and a
bolometric luminosity of 4.1e44 +0.5e44 -0.4e44 erg/s for RDCS1350+6007. Our
weak lensing analysis of RDCS1350+6007 confirms the general shape of the inner
density profile but predicts twice the mass of the model based on the X-ray
profile. We combine the X-ray luminosities and temperatures for RDCS clusters
of galaxies with such measurements of other clusters at high redshift (z>0.7)
and fit the luminosity-temperature relation. We find no statistically
significant evolution in the slope or zero-point of this relation at a median
of z=0.83. This result is in agreement with models of intracluster medium
evolution with significant pre-heating or high initial entropy values. We
discuss how low temperature, high redshift clusters of galaxies will allow us
to improve on this result and announce the discovery of two such objects, CXOU
J0910.1+5419 and CXOU J1316.9+2914.


title:
XMM-Newton observations of variability in the X-ray binaries of M31:
  flares dips and a burst

abstract:
  The XMM-Newton satellite has made four observations of the core of M31 as
part of a survey that will span the entire galaxy. The majority of the X-ray
emission is contributed by point sources, chiefly X-ray Binaries (XB). Exciting
early results from a survey of time variability in three XMM exposures of the
M31 core reveal XB exhibiting Sco X-1 like flaring, dips and a burst. The
flaring source in M31 also exhibits variability in intensity and spectral
hardness that is characteristic of a Z-source.


title: Binary Lenses in OGLE-II 1997-1999 Database. A Preliminary Study

abstract:
  We present 18 binary lens candidates from OGLE-II database for seasons
1997-1999. The candidates have been selected by visual light curves inspection
from the subsample of strong transient events; the same procedure gives 215
single lens candidates. Among the double lenses there are 12 cases interpreted
as caustic crossing events. We compare the mass ratio and separation
distributions obtained for binary lenses with the predictions based on stellar
double systems observations. We take into account the selection bias, which
causes over-representation of binary lenses of similar mass and separation
close to the Einstein radius. There is no strong discrepancy between the
expected and observed distributions of the mass ratio or the binary
separations. We find two cases of binary lens candidates, SC20_1793 and
SC20_3525, with extreme mass ratios, which may suggest presence of planets or
brown dwarf companions. Unfortunately, neither case is very strong, as
alternative solutions give fits to the data which are only unsubstantially
worse. Binary lenses provide a modest contribution to overall optical depth to
microlensing.


title:
Problems with the Pulsation Mode Selection Mechanism in the Lower
  Instability Strip (Observations and Therory)

abstract:
  We examine the severe disagreement between the number of predicted and
observed pulsation modes for Delta Scuti stars. The selection of nonradial
modes trapped in the outer envelope is considered on the basis of kinetic
energy arguments. The trapped l=1 modes for the star 4 CVn are in good, but not
perfect agreement with the observations. The trapping of the l=2 modes is
weaker, so that this simple rule of mode selection may apply to l=1, and
possibly not to l=2 modes.


title: Clusters of EAS with electron number >~ 10^4

abstract:
  We perform cluster analysis of arrival times of extensive air showers (EAS)
registered with the EAS-1000 Prototype array in the period from August, 1997
till February, 1999. We present twenty cluster events each consisting of one or
several EAS clusters, study the dynamics of their development, and analyze the
angular distribution of EAS in clusters. We find that there may be certain
correlation between EAS clusters with mean electron number $\sim10^5$ on the
one hand and gamma-ray bursts and ultrahigh energy cosmic rays on the other.


title: Close frequency pairs in Delta Scuti stars

abstract:
  The majority of the well-studied Delta Scuti stars show frequency pairs in
the power spectra with frequency separations less than 0.06 c/d(0.7 microHz) as
well as amplitude variability. We examine the interpretation in terms of
separate excited stellar pulsation modes,single modes with variable amplitudes,
and observational problems. The variable-phase technique, which examines the
phase jumps near the times of minimum amplitude of an assumed single frequency,
is applied to the extensive data of the star BI CMi, which shows some of the
most extreme behavior. The following results are found for the 5 features in
the power spectrum which could be explained as single modes with variable
amplitudes or as double modes: for three features it can be shown that these
are indeed pairs of separate pulsation modes beating with each other: at times
of minimum amplitude the phase jumps are observed and both the observed
amplitude and phase variations can be predicted correctly by assuming two
separate modes of nearly equal frequencies. Artifacts caused by observational
error,insufficient frequency resolution or variable amplitudes can be ruled
out. A fourth pair has a probable origin in two excited modes, while a 5th case
is inconclusive due to long time scales of variability and small amplitudes.The
existence of close frequencies need to be taken into account in planning the
lengths of earth-based as well as space campaigns so that sufficient frequency
resolution is obtained. Possible reasons for the existence of close frequencies
in Delta Scuti stars are considered.They include the dense frequency spacing
caused by the presence of mixed modes, rotational splitting as well as
near-coincidence of the frequencies of modes with different l values (the
so-called Small Spacing).


title: Why Do Disks Form Jets?

abstract:
  It is argued that jet modelers have given insufficient study to the natural
magneto-static configurations of field wound up in the presence of a confining
general pressure. Such fields form towers whose height grows with each twist at
a velocity comparable to the circular velocity of the accretion disk that turns
them. A discussion of the generation of such towers is preceded by a brief
history of the idea that quasars, active galaxies, and galactic nuclei contain
giant black holes with accretion disks.


title:
Gamma-Ray Burst Neutrino Background and Star Formation History in the
  Universe

abstract:
  We estimate the flux of the GRB neutrino background and compute the event
rate at SK and TITAND in the collapsar model, assuming that GRB formation rate
is proportional to the star formation rate. We find that the flux and the event
rate depend sensitively on the mass-accretion rate. Although the detection of
signals from GRBs seems to be difficult by SK, we find that we can detect them
by TITAND (optimistically about 20 events per year in the energy range where
the energy of anti-electron neutrino is larger than 50 MeV). Therefore, we show
that we will obtain the informations on the mass-accretion rate of collapsar by
observing the GRB neutrino background, which, in turn, should give us
informations on the total explosion energy of GRBs.


title:
Time-resolved optical spectroscopy of the pulsating DA white dwarf HS
  0507+0434B: New constraints on mode identification and pulsation properties

abstract:
  We present a detailed analysis of time-resolved optical spectra of the ZZ
Ceti white dwarf, HS 0507+0434B. Using the wavelength dependence of observed
mode amplitudes, we deduce the spherical degree, l, of the modes, most of which
have l=1. The presence of a large number of combination frequencies (linear
sums or differences of the real modes) enabled us not only to test theoretical
predictions but also to indirectly infer spherical and azimuthal degrees of
real modes that had no observed splittings. In addition to the above, we
measure line-of-sight velocities from our spectra. We find only marginal
evidence for periodic modulation associated with the pulsation modes: at the
frequency of the strongest mode in the lightcurve, we measure an amplitude of
2.6+/-1.0 km/s, which has a probability of 2% of being due to chance; for the
other modes, we find lower values. Our velocity amplitudes and upper limits are
smaller by a factor of two compared to the amplitudes found in ZZ Psc. We find
that this is consistent with expectations based on the position of HS
0507+0434B in the instability strip. Combining all the available information
from data such as ours is a first step towards constraining atmospheric
properties in a convectionally unstable environment from an observational
perspective.


title: Possible Commensurabilities Among Pairs of Extrasolar Planets

abstract:
  We investigate the possible commensurabilities to be expected when two
protoplanets in the Jovian mass range, gravitationally interacting with each
other and an external protoplanetary disc, are driven by disc induced orbital
migration of the outer protoplanet into a commensurability which is then
maintained in subsequent evolution. We find that for a variety of protoplanet
masses and typical protoplanetary disc properties, as well as the setting up of
2:1 commensurabilities of the type recently observed in GJ876, 3:1
commensurabilities are often formed, in addition to 4:1, 5:1, and 5:2
commensurabilities which occur less frequently. The higher order
commensurabilites are favoured when either one of the planets is massive, or
the inner planet begins with a significant orbital eccentricity. Detection of
such commensurabilities could yield important information relating to the
operation of protoplanet disc interactions during and shortly post formation.


title: The Crab Nebula: interpretation of CHANDRA observations

abstract:
  We interpret the observed X-ray morphology of the central part of the Crab
Nebula (torus + jets) in terms of the standard theory by Kennel and Coroniti
(1984). The only new element is the inclusion of anisotropy in the energy flux
from the pulsar in the theory. In the standard theory of relativistic winds,
the Lorentz factor of the particles in front of the shock that terminates the
pulsar relativistic wind depends on the polar angle as
$\gamma=\gamma_0+\gamma_m\sin^2\theta$, where $\gamma_0 \sim 200$ and $\gamma_m
\sim 4.5\times 10^6$. The plasma flow in the wind is isotropic. After the
passage of the pulsar wind through the shock, the flow becomes subsonic with a
roughly constant (over the plerion volume) pressure $P={1\over 3}n\epsilon$,
where $n$ is the plasma particle density and $\epsilon$ is the mean particle
energy. Since $\epsilon \sim \gamma mc^2$, a low-density region filled with the
most energetic electrons is formed near the equator. A bright torus of
synchrotron radiation develops here. Jet-like regions are formed along the
pulsar rotation axis, where the particle density is almost four orders of
magnitude higher than that in the equatorial plane, because the particle energy
there is four orders of magnitude lower. The energy of these particles is too
low to produce detectable synchrotron radiation. However, these quasi-jets
become comparable in brightness to the torus if additional particle
acceleration takes place in the plerion. We also present the results of our
study of the hydrodynamic interaction between an anisotropic wind and the
interstellar medium. We compare the calculated and observed distributions of
the volume intensity of X-ray radiation.


title:
Point source detection and extraction from simulated Planck TOD using
  optimal adaptive filters

abstract:
  Wavelet-related techniques have proven useful in the processing and analysis
of one and two dimensional data sets (spectra in the former case, images in the
latter). In this work we apply adaptive filters, introduced in a previous work
(Sanz et al. 2001), to optimize the detection and extraction of point sources
from a one-dimensional array of time-ordered data such as the one that will be
produced by the future 30 GHz LFI28 channel of the ESA Planck mission. At a
$4\sigma$ detection level 224 sources over a flux of 0.88 Jy are detected with
a mean relative error (in absolute value) of 21% and a systematic bias of
-7.7%. The position of the sources in the sky is determined with errors
inferior to the size of the pixel. The catalogue of detected sources is
complete at fluxes $\geq$ 4.3 Jy. The number of spurious detections is less
than a 10% of the true detections. We compared the results with the ones
obtained by filtering with a Gaussian filter and a Mexican Hat Wavelet of width
equal to the scale of the sources. The adaptive filter outperforms the other
filters in all considered cases. We conclude that optimal adaptive filters are
well suited to detect and extract sources with a given profile embedded in a
background of known statistical properties. In the Planck case, they could be
useful to obtain a real-time preliminary catalogue of extragalactic sources,
which would have a great scientific interest, e. g. for follow-up observations.


title:
Filtering techniques for the detection of Sunyaev-Zel'dovich clusters in
  multifrequency CMB maps

abstract:
  The problem of detecting Sunyaev-Zel'dovich (SZ) clusters in multifrequency
CMB observations is investigated using a number of filtering techniques. A
multifilter approach is introduced, which optimizes the detection of SZ
clusters on microwave maps. An alternative method is also investigated, in
which maps at different frequencies are combined in an optimal manner so that
existing filtering techniques can be applied to the single combined map. The SZ
profiles are approximated by the circularly-symmetric template $\tau (x) = [1
+(x/r_c)^2]^{-\lambda}$, with $\lambda \simeq \tfrac{1}{2}$ and $x\equiv
|\vec{x}|$, where the core radius $r_c$ and the overall amplitude of the effect
are not fixed a priori, but are determined from the data. The background
emission is modelled by a homogeneous and isotropic random field, characterized
by a cross-power spectrum $P_{\nu_1 \nu_2}(q)$ with $q\equiv |\vec{q}|$. The
filtering methods are illustrated by application to simulated Planck
observations of a $12.8^\circ \times 12.8^\circ$ patch of sky in 10 frequency
channels. Our simulations suggest that the Planck instrument should detect
$\approx 10000$ SZ clusters in 2/3 of the sky. Moreover, we find the catalogue
to be complete for fluxes $S > 170$ mJy at 300 GHz.


title: Chandra Discovery of Luminous Supersoft X-Ray Sources in M81

abstract:
  A Chandra ACIS-S imaging observation of the nearby galaxy M81 (NGC 3031)
reveals 9 luminous soft X-ray sources. The local environments, X-ray spectral
properties, and X-ray light curves of the sources are presented and discussed
in the context of prevailing physical models for supersoft sources. It is shown
that the sample falls within expectations based on population synthesis models
taken from the literature though the high observed luminosities (L~2.0e36 to
\~3.0e38 erg/s in the 0.2-2.0 keV band) and equivalent blackbody temperatures
T~40 to 80 eV) place the brightest detected M81 objects at the high luminosity
end of the class of supersoft sources defined by previous ROSAT and Einstein
studies of nearby galaxies. This is interpreted as a natural consequence of the
higher sensitivity of Chandra to hotter and more luminous systems. Most of the
sources can be explained as canonical \ssss, accreting white dwarfs powered by
steady surface nuclear burning, with X-ray spectra well-fit by hot white dwarf
local thermodynamic equilibrium atmosphere models. An exceptionally bright
source is scrutinized in greater detail as its estimated bolometric luminosity,
L~1.5e39 erg/s, greatly exceeds theoretical estimates for supersoft sources.
This source may be beyond the stability limit and undergoing a phase of mass
outflow under extreme conditions. Alternatively, a model in which the observed
X-ray spectrum arises from an accretion disk around a blackhole of mass
\~1200/sqrt(cos(i)) solar masses (viewed at an inclination angle i) cannot be
excluded.


title: Annihilation Radiation from a Dark Matter Spike at the Galactic Centre

abstract:
  We study annihilation radiation of neutralinos in the Galactic centre,
assuming the existence of a 'spike' in the dark matter density profile, due to
adiabatic accretion onto the massive black hole lying at the Galactic centre.
Under this assumption we find that it is possible to reproduce the observed
SgrA* emission at radio and gamma-ray frequencies in a consistent scenario with
a magnetic field close to the equipartition strength and with values of
$\gamma$ (the density profile power law index) around 0.1.


title: Where have all the black holes gone?

abstract:
  We have calculated stationary models for accretion disks around super-massive
black holes in galactic nuclei. Our models show that below a critical mass flow
rate of ~3 10**-3 M_Edd advection will dominate the energy budget while above
that rate all the viscously liberated energy is radiated. The radiation
efficiency declines steeply below that critical rate. This leads to a clear
dichotomy between AGN and normal galaxies which is not so much given by
differences in the mass flow rate but by the radiation efficiency. At very low
mass accretion rates below 5 10**-5 M_Edd synchrotron emission and
Bremsstrahlung dominate the SED, while above 2 10**-4 M Edd the inverse Compton
radiation from synchrotron seed photons produce flat to inverted SEDs from the
radio to X-rays. Finally we discuss the implications of these findings for AGN
duty cycles and the long-term AGN evolution.


title: 2MASS observations of spectroscopically identified extragalactic C stars

abstract:
  We matched spectroscopically identified C stars (from low resolution
objective prism surveys) in the Magellanic Clouds with 2MASS sources. We
confirm that C stars show a large spread in absolute magnitudes, even in the Ks
band. We show that the I and Ks magnitude distributions of a population of C
stars (in the LMC) have a similar narrow dispersion if the C stars are selected
in a well defined color range. Using magnitude and color criteria, we employ
the 2MASS data to identify 26 C stars in the the Fornax dwarf spheroidal
galaxy.
  The mean Ks magnitude and the mean bolometric magnitude of C stars are found
to be slightly brighter in the LMC and SMC when compared to those of the Fornax
dwarf spheroidal galaxy. The difference could be explained by ages or/and
abundance differences.


title: Optical and Infrared Spectroscopy of SN 1999ee and SN 1999ex

abstract:
  We report optical and infrared spectroscopic observations of the Type Ia SN
1999ee and the Type Ib/c SN 1999ex, both of which were hosted by the galaxy IC
5179. For SN 1999ee we obtained a continuous sequence with an unprecedented
wavelength and temporal coverage beginning 9 days before maximum light and
extending through day 42. Before maximum light SN 1999ee displayed a normal
spectrum with a strong Si II 6355 absorption, thus showing that not all
slow-declining SNe are spectroscopically peculiar at these evolutionary phases.
A comparative study of the infrared spectra of SN 1999ee and other Type Ia
supernovae shows that there is a remarkable homogeneity among the Branch-normal
SNe Ia during their first 60 days of evolution. SN 1991bg-like objects, on the
other hand, display spectroscopic peculiarities at infrared wavelengths. SN
1999ex was characterized by the lack of hydrogen lines, weak optical He I
lines, and strong He I 10830,20581, thus providing an example of an
intermediate case between pure Ib and Ic supernovae. We conclude therefore that
SN 1999ex provides first clear evidence for a link between the Ib and Ic
classes and that there is a continuous spectroscopic sequence ranging from the
He deficient SNe Ic to the SNe Ib which are characterized by strong optical He
I lines.


title: Formation of Galactic Disks

abstract:
  We review progress in understanding the formation of galactic disks in the
standard cosmogonic scenario involving gravitational clustering of baryons and
dark matter and dissipative collapse of the baryons. This scenario accounts
remarkably well for the observed properties of galactic disks if they have
retained most of the specific angular momentum they acquired by tidal torques.
Early simulations, which included cooling of the gas but not star formation and
the associated feedback, indicated instead that most of the angular momentum of
the baryons would be transferred to the dark matter. Recent simulations
indicate that this angular-momentum problem can be solved partially, and in
some cases entirely, by feedback and other effects.


title: Core-collapse supernova simulations: Variations of the input physics

abstract:
  Spherically symmetric simulations of stellar core collapse and post-bounce
evolution are used to test the sensitivity of the supernova dynamics to
different variations of the input physics. We consider a state-of-the-art
description of the neutrino-nucleon interactions, possible lepton-number
changing neutrino reactions in the neutron star, and the potential impact of
hydrodynamic mixing behind the supernova shock.


title:
Massive Star Formation in Luminous Infrared Galaxies: Giant HII Regions
  and their relation to Super Star Clusters

abstract:
  We have used HST/NICMOS H-band narrow-band Pa-alpha (at rest 1.87micron)
images to identify star clusters and HII regions respectively in a sample of 8
luminous infrared galaxies (LIRGs). These observations have revealed the
presence of a large population of super star clusters (SSC) and bright HII
regions. A significant fraction of the HII regions shows H-alpha luminosities
above that of 30 Doradus, the prototypical giant HII region. The excess of
extremely luminous HII regions in LIRGs has been confirmed by comparison with
normal galaxies observed at similar spatial resolutions. Despite the large
numbers of identified star clusters and HII regions in LIRGs, we only find a
small fraction of coincidences, between 4% and 30%. Using synthesis models we
have reproduced the relative fractions of young HII regions, intermediate and
old star clusters observed in Arp299 and the central region NGC3256 using a
Salpeter IMF and instantaneous star formation. HII regions with no detected
near-infrared cluster counterpart (25-39%) represent the youngest sites of star
formation, with ages of up to approximately 5Myr and mostly intermediate mass
(~10^5Msun) ionizing clusters. For these two galaxies, and within the present
detection threshold we can only detect coincidences (4-10%) between an HII
region and a near-infrared star cluster for the most massive star clusters
(~10^6Msun) during the first 7Myr of their evolution. The identified
near-infrared SSCs with no detectable Pa-alpha emission represent the ``old''
population (53-66% of the detected sources), with ages of between 7 and
20-40Myr. Older clusters possibly created in this or previous episodes of star
formation are likely to exist in these systems but cannot be identified with
the present detection threshold. (Abridged)


title: Are there MACHOs in the Milky Way halo?

abstract:
  Microlensing searches aim to detect compact halo dark matter via its
gravitational lensing effect on stars within the Large Magellanic Cloud. The
most recent results have led to the claim that roughly one fifth of the
galactic halo dark matter may be in the form of compact, solar-mass objects. We
analyze this hypothesis by considering the goodness-of-fit of the best-fit halo
dark matter solutions to the observational data. We show that the distribution
of the durations of the observed microlensing events is narrower than that
expected to result from a standard halo lens population at 90 to 95%
confidence. Only when the fraction of expected background (non-halo) events is
significantly increased does the discrepancy between the observed and
theoretical event duration distributions disappear. This indicates that it is
possible that most of the lenses responsible for the observed microlensing
events are not located within the Milky Way halo.


title: Powerful Water Masers in Active Galactic Nuclei

abstract:
  Luminous water maser emission in the 6_(16)-5_(23) line at 22 GHz has been
detected from two dozen galaxies. In all cases the emission is confined to the
nucleus and has been found only in AGN, in particular, in Type 2 Seyferts and
LINERs. I argue that most of the observed megamaser sources are powered by
X-ray irradiation of dense gas by the central engine. After briefly reviewing
the physics of these X-Ray Dissociation Regions, I discuss in detail the
observations of the maser disk in NGC 4258, its implications, and compare
alternative models for the maser emission. I then discuss the observations of
the other sources that have been imaged with VLBI to date, and how they do or
do not fit into the framework of a thin, rotating disk, as in NGC 4258.
Finally, I briefly discuss future prospects, especially the possibility of
detecting other water maser transitions.


title: A Wavelet Analysis of Solar Climate Forcing: I) Solar Cycle Timescales

abstract:
  We use the technique of wavelet analysis to quantitatively investigate the
role of solar variability in forcing terrestrial climate change on solar cycle
timescales (roughly 11 years). We examine the connection between mean annual
solar irradiance, as reconstructed from sunspot and isotope records, and the
climate, as proxied by two Northern Hemisphere surface air temperature
reconstructions. By applying wavelet transforms to these signals, we are able
to analyze both the frequency content of each signal, and also the time
dependence of that content. After computing wavelet transforms of the data, we
perform correlation analyses on the wavelet transforms of irradiance and
temperature via two techniques: the Pearson's method and the conditional
probability method. We thus track the correlation between individual frequency
components of both signals as a function of time. A nonzero correlation between
the irradiance and temperature wavelet spectra requires a phase lag between the
two data sets (i.e., terrestrial response to solar output is not
instantaneous). We search for the optimal phase lag that maximizes the
correlation. By choosing an appropriate phase for each year, we find a
significant, positive sun-climate correlation for most of the period AD
1720-1950. We find that this phase-optimized correlation varies in time,
oscillating between 0.12 and 0.71 throughout the past 400 years. We find that
the phase lag varies from 0-10 years. We also present a test to determine
whether terrestrial response to solar output is enhanced via stochastic
resonance, wherein the weak periodic solar signal is amplified by terrestrial
noise.


title: Optical and Near-Infrared Photometry of Distant Galaxy Clusters

abstract:
  We present optical and near-infrared photometry of 45 clusters of galaxies at
0.1 < z < 1.3. Galaxy catalogs in each cluster were defined at the longest
wavelenth available, generally the K-band, down to approximately two magnitudes
below M*. We include finding chart images of the band used for catalog
definition. The photometry has been used in previously published papers to
examine the origin and evolution of galaxies in distant clusters.


title:
The Palomar/MSU Nearby Star Spectroscopic Survey III: Chromospheric
  Activity, M-dwarf Ages and the Local Star Formation History

abstract:
  We present high-resolution echelle spectroscopy of 676 nearby M dwarfs. Our
measurements include radial velocities, equivalent widths of important
chromospheric emission lines, and rotational velocities for rapidly rotating
stars. We identify several distinct groups by their H alpha properties, and
investigate variations in chromospheric activity amongst early (M0-M2.5) and
mid (M3-M6) dwarfs. Using a volume-limited sample together with a relationship
between age and chromospheric activity, we show that the rate of star formation
in the immediate Solar Neighbourhood has been relatively constant over the last
4 Gyr. In particular our results are inconsistent with recent large bursts of
star formation. We use the correlation between H alpha activity and age as a
function of colour to set constraints on the properties of L and T dwarf
secondary components in binary systems. We also identify a number of
interesting stars, including rapid rotators, radial velocity variables, and
spectroscopic binaries.


title:
Exclusion limits on the WIMP-nucleon cross-section from the Cryogenic
  Dark Matter Search

abstract:
  The Cryogenic Dark Matter Search (CDMS) employs low-temperature Ge and Si
detectors to search for Weakly Interacting Massive Particles (WIMPs) via their
elastic-scattering interactions with nuclei while discriminating against
interactions of background particles. For recoil energies above 10 keV, events
due to background photons are rejected with >99.9% efficiency, and surface
events are rejected with >95% efficiency. The estimate of the background due to
neutrons is based primarily on the observation of multiple-scatter events that
should all be neutrons. Data selection is determined primarily by examining
calibration data and vetoed events. Resulting efficiencies should be accurate
to about 10%. Results of CDMS data from 1998 and 1999 with a relaxed
fiducial-volume cut (resulting in 15.8 kg-days exposure on Ge) are consistent
with an earlier analysis with a more restrictive fiducial-volume cut.
Twenty-three WIMP candidate events are observed, but these events are
consistent with a background from neutrons in all ways tested. Resulting limits
on the spin-independent WIMP-nucleon elastic-scattering cross-section exclude
unexplored parameter space for WIMPs with masses between 10-70 GeV c^{-2}.
These limits border, but do not exclude, parameter space allowed by
supersymmetry models and accelerator constraints. Results are compatible with
some regions reported as allowed at 3-sigma by the annual-modulation
measurement of the DAMA collaboration. However, under the assumptions of
standard WIMP interactions and a standard halo, the results are incompatible
with the DAMA most likely value at >99.9% CL, and are incompatible with the
model-independent annual-modulation signal of DAMA at 99.99% CL in the
asymptotic limit.


title: LIFTS: an Imaging Fourier Transform Spectrograph for Astronomy

abstract:
  We present the first astronomical observations of the Livermore Imaging
Fourier Transform Spectrograph for visible-band astronomy using the 3.5-meter
Apache Point Observatory.


title: The effects of similarity breaking on the intracluster medium

abstract:
  We construct a family of simple analytical models of galaxy clusters at the
present epoch and compare its predictions with observational data. We explore
two processes that break the self-similarity of galaxy clusters: systematic
variation in the dark matter halo concentration and energy injection into the
intracluster gas, through their effects on the observed cluster properties.
Three observed relations between cluster properties and temperature are
employed to constrain the model; mass, slope of gas density profile (beta) and
luminosity. The slope of the mass-temperature relation is found to be
reproduced by our model when the observed variation in concentration is
included, raising the slope from the self-similar prediction of 1.5, to that of
the observed relation, ~ 2. Heating of the gas is observed to have little
effect on the mass-temperature relation. The mean trend in the beta-temperature
relation is reproduced by energy injection of 0.5-0.75 keV per particle, while
concentration variation has only a small effect. Excess energies calculated for
individual systems from the beta-temperature relation suggest that the lowest
mass systems may have excess energies that are biased to lower values by
selection effects. The observed properties of the luminosity-temperature
relation are reproduced by the combined effects of excess energy and a trend in
the dark matter concentration. At high masses the observed variation in dark
matter concentration results a slope of ~ 2.7 compared to recent observations
in the range 2.6-2.9, whilst the observed steepening in galaxy groups is
predicted when heating of 0.5-0.75 keV per particle is included. Hence a
combination of energy injection and dark matter concentration variation appears
able to account for the mean trends in the observed relations.


title:
Evolution of the Correlation Function for a Class of Processes involving
  Non Local Self - Replication

abstract:
  A large class of evolutionary processes can be modeled by a rule which
involves self-replication of some physical quantity with a non local rescaling.
I show that a class of such models are exactly solvable -- in the discrete as
well as continuum limit -- and can represent several physical situations as
varied from the formation of galaxies in some cosmological models to growth of
bacterial cultures.
  This class of models, in general, has no steady state solution and evolve
unstably as $t \to \infty$ for generic initial conditions. They can however
exhibit (unstable) power law correlation function in the continuum limit, for
an intermediate range of times and length scales.


title: Pulsar bow-shock nebulae. II. Hydrodynamical simulation

abstract:
  We present hydrodynamical simulations, using a 2-D two component model
(ambient medium and pul sar wind have different specific heat ratios), of bow
shocks in a representative regime for pu lsar wind driven bow-shock nebulae. We
also investigate the behaviour of a passive toroidal ma gnetic field wound
around the pulsar velocity direction. Moreover we estimate the opacity of t he
bow-shock to penetration of ISM neutral hydrogen: this quantity affects
observable properti es of the nebula, like its size, shape, velocity and
surface brightness distribution. Finally we compare these numerical results
with those from an analytical model. The development of mor e realistic models
is needed in order to tune the criteria for searches of new such objects, a s
well as to interpret data on the known objects.


title: Contribution of the Large Magellanic Cloud to the Galactic Warp

abstract:
  Multi-scale interaction between the LMC, Galactic halo, and the disk is
examined with N-body simulations, and precise amplitudes of the Galactic warp
excitation are obtained. The Galactic models are constructed most realistically
to satisfy available observational constraints on the local circular velocity,
the mass, surface density and thickness of the disk, the mass and size of the
bulge, the local density of the halo matter at the solar radius, and the mass
and orbit of the LMC. By using hybrid algorithm (SCF-TREE) I have succeeded to
follow the evolution with millions of particles. The orbiting satellite excites
density enhancement as a wake, and the wake exerts a tidal force on the disk.
Because of the additional torque from the wakes in the halo, the amplitudes of
the induced warps are much larger than the classical estimate by [hunt1969],
who considered only the direct torque from the LMC. The obtained amplitudes of
m=0, 1, 2 warps in the larger halo model show very good agreement with the
observed amplitude in the Milky Way. This result revives the LMC as a possible
candidate of the origin of the Galactic warp. Our smaller halo model, however,
yield only weak warps in all the harmonic modes. Therefore the halo still has
significant influence on excitation of warp even in the interaction scenario
for excitation of warps.


title:
Chemical evolution in a model for the joint formation of quasars and
  spheroids

abstract:
  Direct and indirect pieces of observational evidence point to a strong
connection between high-redshift quasars and their host galaxies. In the
framework of a model where the shining of the quasar is the episode that stops
the formation of the galactic spheroid inside a virialized halo, it has been
proven possible to explain the submillimetre source counts together with their
related statistics and the local luminosity function of spheroidal galaxies.
The time delay between the virialization and the quasar manifestation required
to fit the counts is short and incresing with decresing the host galaxy mass.
In this paper we compute the detailed chemical evolution of gas and stars
inside virialized haloes in the framework of the same model, taking into
account the combined effects of cooling and stellar feedback. Under the
assumption of negligible angular momentum, we are able to reproduce the main
observed chemical properties of local ellipticals. In particular, by using the
same duration of the bursts which are required in order to fit the
submillimetre source counts, we recover the observed increase of the Mg/Fe
ratio with galactic mass. Since for the most massive objects the assumed
duration of the burst is Tburst < 0.6 Gyr, we end up with a picture for
elliptical galaxy formation in which massive spheroids complete their assembly
at early times, thus resembling a monolithic collapse, whereas smaller galaxies
are allowed for a more prolonged star formation, thus allowing for a more
complicated evolutionary history.


title: Evolution of cosmological dark matter perturbations

abstract:
  We discuss the propagation of dark matter perturbations with non-zero
velocity dispersion in cosmological models. In particular a non-zero massive
neutrino component may well have a significant effect on the matter power
spectrum and cosmic microwave background anisotropy. We present a covariant
analysis of the evolution of a dark matter distribution via a two-dimensional
momentum-integrated hierarchy of multipole equations. This can be expanded in
the velocity weight to provide accurate approximate equations if the matter is
non-relativistic, and we also perform an expansion in the mass to study the
propagation of relativistic matter perturbations. We suggest an approximation
to the exact hierarchy that can be used to calculate efficiently the effect of
the massive neutrinos on the CMB power spectra. We implement the corresponding
scalar mode equations numerically achieving a considerable reduction in
computation time compared with previous approaches.


title: Possible Recovery of SN 1961V In Hubble Space Telescope Archival Images

abstract:
  SN 1961V in NGC 1058 was originally classified by Fritz Zwicky as a ``Type
V'' supernova. However, it has been argued that SN 1961V was not a genuine
supernova, but instead the superoutburst of an eta Carinae-like luminous blue
variable star. In particular, Filippenko et al. (1995, AJ, 110, 2261) used
pre-refurbishment HST WFPC images and the known radio position of SN 1961V to
conclude that the star survived the eruption and is likely coincident with a V
\~ 25.6 mag, V-I ~ 1.9 mag object. Recently, Stockdale et al. (2001, AJ, 122,
283) recovered the fading SN 1961V at radio wavelengths and argue that its
behavior is similar that of some Type II supernovae. We have analyzed
post-refurbishment archival HST WFPC2 data and find that the new radio position
is still consistent with the Filippenko et al. object, which has not changed in
brightness or color, but is also consistent with an adjacent, fainter (I ~ 24.3
mag) and very red (V-I > 1.0 mag) object. We suggest that this fainter object
could be the survivor of SN 1961V. Forthcoming HST observations may settle this
issue.


title: The Photometric Plane of Elliptical Galaxies

abstract:
  The Sersic r^(1/n) index n of an elliptical galaxy (or bulge) has recently
been shown to correlate strongly (r=0.8) with a galaxy's central velocity
dispersion. This index could therefore prove extremely useful and
cost-effective (in terms of both telescope time and data reduction) for many
fields of extragalactic research. It is a purely photometric quantity which
apparently not only traces the mass of a bulge but has additionally been shown
to reflect the degree of bulge concentration. This paper explores the affect of
replacing the central velocity dispersion term in the Fundamental Plane with
the Sersic index n. Using a sample of early-type galaxies from the Virgo and
Fornax clusters, various (B-band) `Photometric Planes' were constructed and
found to have a scatter of 0.14-0.17 dex in log(r_e), or a distance error of
38-48% per galaxy (the higher values arising from the inclusion of the S0
galaxies). The corresponding Fundamental Plane yielded a 33-37% error in
distance for the same galaxy (sub-)samples (i.e. ~15-30% less scatter). The
gains in using a hyperplane (i.e. adding the Sersic index to the Fundamental
Plane as a fourth parameter) were small, giving a 27-33% error in distance,
depending on the galaxy sample used. The Photometric Plane has been used here
to estimate the Virgo-Fornax distance modulus; giving a value of
\Delta\mu=0.62(+/-0.30) mag (cf. 0.51(+/-0.21), HST Key Project on the
Extragalactic distance Scale). The prospects for using the Photometric Plane at
higher redshift appears promising. Using published data on the intermediate
redshift cluster Cl 1358+62 (z=0.33) gave a Photometric Plane distance error of
35-41% per galaxy.


title: Radial Mixing in Galactic Discs

abstract:
  We show that spiral waves in galaxy discs churn the stars and gas in a manner
that largely preserves the overall angular momentum distribution and leads to
little increase in random motion. Changes in the angular momenta of individual
stars are typically as large as ~50% over the lifetime of the disk. The changes
are concentrated around the corotation radius for an individual spiral wave,
but since transient waves with a wide range of pattern speeds develop in rapid
succession, the entire disk is affected. This behaviour has profound
consequences for the metallicity gradients with radius in both stars and gas.
The ISM is also stirred by the same mechanism. We find observational support
for stirring, propose a simple model for the distribution of stars over
metallicity and age, and discuss other possible consequences.


title:
Chandra and XMM-Newton Observations of the Highest Redshift Quasars:
  X-rays from the Dawn of the Modern Universe

abstract:
  We review X-ray studies of the highest redshift (z > 4) quasars, focusing on
recent advances enabled largely by the capabilities of Chandra and XMM-Newton.
Included are discussions of basic X-ray population studies, X-ray spectroscopy,
high-redshift AGN in X-ray surveys, and future prospects.


title: Scattering of Stars by Transient Spiral Waves

abstract:
  Transient spiral waves of moderate amplitude cause substantial changes to the
angular momenta of many stars in a galaxy disk. Stars near to corotation are
affected most strongly: for a wave of ~20% overdensity, the rms change for
particles near to corotation is ~18% of their initial angular momenta. Yet
these changes produce no increase in random motion near corotation, while the
same wave causes mild heating near its Lindblad resonances. The direction of
radial migration depends both on initial location relative to corotation and on
azimuth. Streamlines of cold gas become very significantly distorted before
they cross, suggesting that gas is also mixed radially by this mechanism. Such
continuous churning of the disk has profound implications for abundance
gradients in galaxies. Furthermore, it is quite possible that the Sun has
migrated significantly from its radius of birth, consistent with the claims of
Wielen et al.


title:
The Metal Content of Dwarf Starburst Winds: Results from Chandra
  Observations of NGC 1569

abstract:
  (Abridged) We present deep, Chandra spectral imaging of the dwarf starburst
galaxy NGC 1569. The unprecedented spatial resolution allows us to spatially
identify the components of the integrated \x spectrum. Fitted spectral models
require an intrinsic absorption component and higher metal abundances than
previous studies indicated. Our results provide the first direct evidence for
metal-enriched winds from dwarf starburst galaxies.


title: Double Bars, Inner Disks, and Nuclear Rings in Early-Type Disk Galaxies

abstract:
  We present results from an imaging survey of an unbiased sample of
thirty-eight early-type (S0--Sa), low-inclination, optically barred galaxies in
the field. Our goal was to find and characterize central stellar and gaseous
structures: secondary bars, inner disks, and nuclear rings. Bars inside bars
are surprisingly common: at least one quarter of the sample galaxies (possibly
as many as 40%) are double-barred, with no preference for Hubble type or the
strength of the primary bar. A typical secondary bar is ~12% of the size of its
primary bar and 240--750 pc in radius. We see no significant effect of
secondary bars on nuclear activity. We also find kiloparsec-scale inner disks
in at least 20% of our sample, almost exclusively in S0 galaxies. These disks
are on average 20% the size of their host bar, and show a wider range of
relative sizes than do secondary bars. Nuclear rings are present in about a
third of our sample. Most are dusty, sites of current or recent star formation,
or both; such rings are preferentially found in Sa galaxies. Three S0 galaxies
(15% of the S0's) appear to have purely stellar nuclear rings, with no evidence
for dust or recent star formation. The fact that these central stellar
structures are so common indicates that the inner regions of early-type barred
galaxies typically contain dynamically cool and disklike structures. This is
especially true for S0 galaxies, where secondary bars, inner disks, and/or
stellar nuclear rings are present at least two thirds of the time. (abridged)


title: A New Way to Resolve Cepheid Binaries

abstract:
  We have measured the centroid shift of low resolution HST FOC spectra as the
dominant star changes from the Cepheid to the hot companion. With this approach
we have resolved the AW Per system and marginally resolved the U Aql system.


title:
Megachannel Extraterrestrial Assay Candidates: No Transmissions from
  Intrinsically Steady Sources

abstract:
  This paper reports new, more sensitive observations of nine of the eleven
extrastatistical signals in the Megachannel Extraterrestrial Assay (META).
These extrastatistical signals had all of the expected characteristics of a
transmission from an extraterrestrial transmitter, except that they did not
repeat. Cordes, Lazio, & Sagan showed that this lack of repeatability could be
explained by the high detection thresholds used in the reobservations of these
candidates combined with interstellar scintillation of intrinsically steady
sources. We use the Cordes, Lazio, & Sagan methodology, correcting an error in
the original presentation, and our new observations to rule out this
scintillation hypothesis at a confidence level of at least 97.8% (for the case
of an intrinsically weak source) to a level in excess of 99% (if the source
strengths are comparable to that favored by Cordes, Lazio, & Sagan. We also
demonstrate that gravitational microlensing cannot account for the initial
detection of these candidate signals nor is gravitational lensing likely to
play a role in future SETI programs. We conclude that the META candidates do
not reflect a large population of powerful, strong beacons.


title: Counterclockwise magnetic fields in the Norma spiral arm

abstract:
  Pulsars provide unique probes of the large-scale interstellar magnetic field
in the Galactic disk. Up to now, the limited Galactic distribution of the known
pulsar population has restricted these investigations to within a few
kiloparsec of the Sun. The Parkes multibeam pulsar survey has discovered many
more-distant pulsars which enables us for the first time to explore the
magnetic field in most of the nearby half of the Galactic disk. Here we report
the detection of counterclockwise magnetic fields in the Norma spiral arm using
pulsar rotation measures. The fields are coherent in direction over a linear
scale of $\sim 5$ kpc along the arm and have a strength of $-4.4\pm0.9$ $\mu$G.
The magnetic field between the Carina-Sagittarius and Crux-Scutum arms is
confirmed to be coherent from $l\sim45\degr$ to $l\sim305\degr$ over a length
of $\sim 10$ kpc. These results strengthen arguments for a bisymmetric spiral
model for the field configuration in the Galactic disk.


title: Stellar Atmospheres of Nearby Young Solar Analogs

abstract:
  High-resolution (R ~ 90,000) spectra of 34 nearby, young Sun-like stars were
analyzed using stellar atmosphere models to estimate effective photosphere
temperatures, surface gravities, and the abundance of certain heavy elements
(C, Na, Mg, Si, S, Ca, Ti, Fe, and Ni). The effective temperatures derived from
spectroscopy were compared with temperatures estimated using optical and
near-infrared photometry. In many cases the spectroscopic temperatures are
significantly higher than the photometric estimates, possibly as a result of
spottedness or chromospheric activity on these active stars. Values of
effective temperature, surface gravity, and luminosity were compared to
theoretical stellar evolution tracks and the evolutionary status of these
objects was evaluated. The correlation between heavy element abundance patterns
and kinematics (space motion) was also examined. Two nearby stars that were
tentatively assigned to the Hyades cluster based on kinematics have Fe
abundances that are also consistent with membership in that cluster. Members of
the Ursa Major kinematic group exhibit a range of [Fe/H] values but have
monotonic [Si/Fe]. These two observations suggest that heterogeneous
incorporation of the heavy elements into protostars is creating the variation
in metallicity. Local Association members have a distinctly different Si/Fe
that probably reflects their distinct origin and chemical inheritance.


title: PG1115+166 - a long period DA+DB binary

abstract:
  We present spectra of the DAB white dwarf PG1115+166. Radial velocity
measurements of the Balmer lines and the HeI6678 line show that this is a
binary white dwarf with a period of 30.09d in which the Balmer lines move in
anti-phase to the HeI line, i.e., PG1115+166 is a DA+DB binary. The minimum
masses of the stars are M_DA=0.43+-0.15 solar masses and M_DB=0.52+-0.12 solar
masses. The separation of the stars is about 45 solar radii which is much
smaller than a typical AGB progenitor of a white dwarf, implying that there has
been at least one common envelope phase in this binary. Indeed, it is possible
that this binary may have suffered up to three mass transfer episodes - two
associated with the red giant phase prior to the formation of each white dwarf
and a third associated with the ``born-again'' red giant phase of the DB white
dwarf. PG1115+166 has the longest orbital period of any post common envelope
white dwarf - white dwarf binary found to date. Published models for the
formation of white dwarf - white dwarf binaries do not predict any white dwarfs
with the combination of long orbital period and high mass found in PG1115+166.
We conclude that PG1115+166 is a key object for testing models of binary star
evolution and it may also be a key object for our understanding of the
formation of DB white dwarfs. We outline the observational tests which can be
applied to scenarios for the formation of PG1115+166 and apply them to the
simplest case of a single common envelope phase. This suggests that some part
of the internal energy stored in the envelope of the AGB star, e.g., as ionized
hydrogen, may have contributed to the ejection of the common envelope, but
there are several unanswered questions concerning this simple scenario.


title: Can Primordial Black Holes be a Significant Part of Dark Matter ?

abstract:
  The computation of PBH (primordial black hole) production from primordial
perturbations has recently been improved by considering a more accurate
relation between the primordial power spectrum and the PBH mass variance. We
present here exact expressions which are valid for primordial spectra of
arbitrary shape and which allow accurate numerical calculations. We then
consider the possibility to have a significant part of dark matter in the form
of PBHs produced by a primordial spectrum of inflationary origin possessing a
characteristic scale. We show that in this model the relevant PBH mass is
constrained to lie in the range $5\times 10^{15} {\rm g}\lesssim M \lesssim
10^{21} {\rm g}$. This is much less than the mass range coming from the QCD
phase transition, allowing the two mechanisms to be easily distinguished.


title:
On the accuracy of the S/N estimates obtained with the exposure time
  calculator of the Wide Field Planetary Camera 2 on board the Hubble Space
  Telescope

abstract:
  We have studied the accuracy and reliability of the exposure time calculator
(ETC) of the Wide Field Planetary Camera 2 (WFPC2) on board the Hubble Space
Telescope (HST) with the objective of determining how well it represents actual
observations and, therefore, how much confidence can be invested in it and in
similar software tools. We have found, for example, that the ETC gives, in
certain circumstances, very optimistic values for the signal-to-noise ratio
(SNR) of point sources. These values overestimate by up to a factor of 2 the
HST performance when simulations are needed to plan deep imaging observations,
thus bearing serious implications on observing time allocation. For this
particular case, we calculate the corrective factors to compute the appropriate
SNR and detection limits and we show how these corrections vary with field
crowding and sky background. We also compare the ETC of the WFPC2 with a more
general ETC tool, which takes into account the real effects of pixel size and
charge diffusion. Our analysis indicates that similar problems may afflict
other ETCs in general showing the limits to which they are bound and the
caution with which their results must be taken.


title:
Results of investigation of radio galaxies of the survey "Cold":
  photometry, colour redshifts and the age of the stellar population

abstract:
  BVRI data for the majority of the objects of the RC catalogue with steep
spectra and $m_R<24^m$ are presented. These data have been used to estimate
colour redshifts and the age of stellar systems of host galaxies. By way of
example of distant radio galaxies it is shown that this approach gives an
accuracy of redshift estimates close to that for field galaxies ($\sim20$ %).
The age estimates are less confident, however, the lower age limit for not too
distant ($z<1.5$) objects is determined quite reliably. Several galaxies have
been detected that have an age above that of the Universe at the given $z$ in a
simple CDM model of the Universe. A possibility of using such objects to
specify the part played by ``dark energy'' is discussed. This paradox
disappears in a model with the $\Lambda$-term equal to 0.6--0.8.


title:
The shape of the relativistic iron K-alpha line from MCG6--6-30-15
  measured with the Chandra HETGS and RXTE

abstract:
  We confirm the detection of the relativistically broadened iron K-alpha
emission at 6.4 keV with simultaneous Chandra HETGS and RXTE PCA observations.
Heavily binned HETGS data show a disk line profile with parameters very similar
to those previously seen by ASCA. We observe a resolved narrow component with a
velocity width ~4700 km/s (FWHM ~ 11,000 km/s), that is most prominent, and
narrower (FWHM ~ 3600 km/s) when the continuum flux is high. It plausibly is
just the blue wing of the broad line. We obtain a stringent limit on the
equivalent width of an intrinsically narrow line in the source of 16 eV,
indicating little or no contribution due to fluoresence from distant material
such as the molecular torus. Variability studies of the narrow component show a
constant iron line flux and variable width indicating the line may be
originating from different kinematic regions of the disk.


title:
Metallicity Evolution of Damped Lyman Alpha Systems In Lambda CDM
  Cosmology

abstract:
  Utilizing a new, high mass resolution hydrodynamic simulation we compute the
metallicity evolution of damped Lyman alpha systems (DLAs) and find a
reasonable agreement with observations. In particular, the observed slow
evolution of the DLA metallicity occurs naturally in the simulation due to the
combined effects of physical and observational selection. The slow metallicity
evolution is caused by the steady transformation, with increasing time, of the
highest metallicity systems to "galaxies", thus depleting this category, while
all the lower metallicity systems show, individually, an increase in
metallicity. Although the trend of DLA metallicity with redshift is in good
agreement with observations, it appears that the average metallicity of
simulated DLAs is higher than observed by 0.3-0.5 dex in the probed redshift
range (z=0-5). Our study indicates that this difference may be attributed to
observational selection effects due to dust obscuration. If we allow for a dust
obscuration effect, our model reproduces the observed metallicity evolution in
both amplitude and slope. We find that DLAs are not a simple population but
probe a range of different systems and the mix changes with redshift. About 50%
of all metals in the gaseous phase is in DLAs at all times from z=5 to z=1,
making a rapid downturn at z\le 1 to ~20% by z=0, as metals are swept into the
hotter components of the IGM as well as locked up in stars. While not the
primary focus of this study, we find that the model provides good matches to
observations with respect to column density distribution and evolution of
neutral gas content, if the same dust obscuration is taken into account. We
find Omega_{DLA,comp}=(1-3)E-3, depending on the effect of dust obscuration.


title:
Predictions for the frequency and orbital radii of massive extrasolar
  planets

abstract:
  We investigate the migration of massive extrasolar planets due to
gravitational interaction with a viscous protoplanetary disc. We show that a
model in which planets form at 5 AU at a constant rate, before migrating, leads
to a predicted distribution of planets that is a steeply rising function of log
(a), where a is the orbital radius. Between 1 AU and 3 AU, the expected number
of planets per logarithmic interval in orbital radius roughly doubles. We
demonstrate that, once selection effects are accounted for, this is consistent
with current data, and then extrapolate the observed planet fraction to masses
and radii that are inaccessible to current observations. In total, about 15
percent of stars targeted by existing radial velocity searches are predicted to
possess planets with masses 0.3 M_Jupiter < M_p sin (i) < 10 M_Jupiter, and
radii 0.1 AU < a < 5 AU. A third of these planets (around 5 percent of the
target stars) lie at the radii most amenable to detection via microlensing. A
further 5-10 percent of stars could have planets at radii of 5 AU < a < 8 AU
that have migrated outwards. We discuss the probability of forming a system
(akin to the Solar System) in which significant radial migration of the most
massive planet does not occur. About 10-15 percent of systems with a surviving
massive planet are estimated to fall into this class. Finally, we note that a
smaller fraction of low mass planets than high mass planets is expected to
survive without being consumed by the star. The initial mass function for
planets is thus predicted to rise more steeply towards small masses than the
observed mass function.


title: A Catalog of Candidate Intermediate-luminosity X-ray Objects

abstract:
  ROSAT, and now Chandra, X-ray images allow studies of extranuclear X-ray
point sources in galaxies other than our own. X-ray observations of normal
galaxies with ROSAT and Chandra have revealed that off-nuclear, compact,
Intermediate-luminosity (Lx[2-10 keV] >= 1e39 erg/s) X-ray Objects (IXOs,
a.k.a. ULXs [Ultraluminous X-ray sources]) are quite common. Here we present a
catalog and finding charts for 87 IXOs in 54 galaxies, derived from all of the
ROSAT HRI imaging data for galaxies with cz <= 5000 km/s from the Third
Reference Catalog of Bright Galaxies (RC3). We have defined the cutoff Lx for
IXOs so that it is well above the Eddington luminosity of a 1.4 Msun black hole
(10^38.3 erg/s), so as not to confuse IXOs with ``normal'' black hole X-ray
binaries. This catalog is intended to provide a baseline for follow-up work
with Chandra and XMM, and with space- and ground-based survey work at
wavelengths other than X-ray. We demonstrate that elliptical galaxies with IXOs
have a larger number of IXOs per galaxy than non-elliptical galaxies with IXOs,
and note that they are not likely to be merely high-mass X-ray binaries with
beamed X-ray emission, as may be the case for IXOs in starburst galaxies.
Approximately half of the IXOs with multiple observations show X-ray
variability, and many (19) of the IXOs have faint optical counterparts in DSS
optical B-band images. Follow-up observations of these objects should be
helpful in identifying their nature.


title: Hydromagnetic Stability of a Slim Disk in a Stationary Geometry

abstract:
  The magnetorotational instability originates from the elastic coupling of
fluid elements in orbit around a gravitational well. Since inertial
accelerations play a fundamental dynamical role in the process, one may expect
substantial modifications by strong gravity in the case of accretion on to a
black hole. In this paper, we develop a fully covariant, Lagrangian
displacement vector field formalism with the aim of addressing these issues for
a disk embedded in a stationary geometry with negligible radial flow. This
construction enables a transparent connection between particle dynamics and the
ensuing dispersion relation for MHD wave modes. The MRI--in its incompressible
variant-- is found to operate virtually unabated down to the marginally stable
orbit; the putative inner boundary of standard accretion disk theory. To get a
qualitative feel for the dynamical evolution of the flow below $r_{\rm ms}$, we
assume a mildly advective accretion flow such that the angular velocity profile
departs slowly from circular geodesic flow. This exercise suggests that the
turbulent eddies will occur at spatial scales approaching the radial distance
while tracking the surfaces of null angular velocity gradients. The implied
field topology, namely large-scale horizontal field domains, should yield
strong mass segregation at the displacement nodes of the non-linear modes when
radiation stress dominates the local disk structure (an expectation supported
by quasi-linear arguments and by the non-linear behavior of the MRI in a
non-relativistic setting). Under this circumstance, baryon-poor flux in
horizontal field domains will be subject to radial buoyancy and to the Parker
instability, thereby promoting the growth of poloidal field.


title: P-Cygni Type Lya from Starburst Galaxies

abstract:
  P-Cygni type Lya profiles exhibited in nearly half of starburst galaxies,
both nearby and high-z, are believed to be formed by an expanding supershell
surrounding a star-forming region. We apply the Monte Carlo code which was
developed previously for static and plane-parallel medium to calculate the Lya
line transfer in a supershell of neutral hydrogen which are expanding radially
in a spherical bulk flow. We consider typical cases that the supershell has the
Lya line-centre optical depth of $\tau_0=10^5-10^7$, a radial expansion
velocity of $V_exp = 300 km/s, and the turbulence of b=40 km/s. We find that
there appear a few emission peaks at the frequencies corresponding to (2N-1)
V_exp, where the order of back scatterings N > 1. As V_exp -> b, the emergent
profiles become similar to those for the static medium and the peaks are less
prominent. We also investigate the effects of column density of the supershell
on the emergent Lya profiles. We find that the number and the flux ratios of
emission peaks are determined by interplay of $\tau_0$ and V_exp of the
supershell. We discuss the effects of dust extinction and the implication of
our works in relation to recent spectroscopic observations of starburst
galaxies.


title: Lya Polarisation in Thick H I Media

abstract:
  We have investigated the linear polarisation of Lya transferred in a static,
dustless, and thick plane-parallel slab that is uniformly filled with neutral
hydrogen. Because the scattering phase function is characterised by the dipole
type for wing scatterings of Lya, which is in high contrast with more isotropic
scattering phase function associated with resonant scatterings, the
polarisation of the emergent Lya is dominantly controlled by the number of wing
scatterings before escape from the slab. When the scattering medium is
extremely thick, photons emergent in the grazing direction are polarised in the
direction perpendicular to the slab normal up to 12%, which coincides with the
limit attained by the Thomson scattered radiation in a semi-infinite thick
medium investigated by Chandrasekhar in 1960. The number of wing scatterings
before escape is sensitively dependent on the product of the Voigt parameter
$a$ and the line-centre optical depth $\tau_0$, with which the variation of the
degree of polarisation can also be explained in comparison with the Thomson
scattering case. The polarisation direction is parallel to the slab normal when
$a\tau_0<10^3$, while it is perpendicular when $a\tau_0>10^3$. Our simulated
spectropolarimetry of Lya from a highly thick medium is characterised by
negligible polarisation around the line centre, parallel polarisation in the
near wing parts and perpendicular polarisation in the far wing parts, where the
polarisation direction is measured with respect to the slab normal. The
polarisation flip naturally reflects the diffusive nature of the Lya transfer
process in both real space and frequency space. We also discuss the beaming
effect that is associated with the parallel polarisation in the near wing parts
of the emission.


title:
Position-velocity diagrams of ionized gas in the inner regions of disk
  galaxies

abstract:
  We use long-slit spectroscopy along the major axis of a sample of 23 nearby
disk galaxies to study the kinematic properties of the ionized-gas component in
their inner regions. For each galaxy, we derive the position-velocity diagram
of the ionized gas from its emission lines. We discuss the variety of shapes
observed in such position-velocity diagrams by comparing the gas velocity
gradient, velocity dispersion and integrated flux measured in the inner (r
+/-1'') and outer regions (r +/-4''). This kind of analysis allows the
identification of galaxies which are good candidates to host a circumnuclear
Keplerian gaseous disk rotating around a central mass concentration, and to
follow up with Hubble Space Telescope observations.


title: The Type Ic Hypernova SN 2002ap

abstract:
  Photometric and spectroscopic data of the energetic Type Ic supernova (SN)
2002ap are presented, and the properties of the SN are investigated through
models of its spectral evolution and its light curve. The SN is
spectroscopically similar to the "hypernova" SN 1997ef. However, its kinetic
energy [$\sim (4-10) \times 10^{51}$ erg] and the mass ejected (2.5-5
$M_{\odot}$) are smaller, resulting in a faster-evolving light curve. The SN
synthesized $\sim 0.07 M_{\odot}$ of $^{56}$Ni, and its peak luminosity was
similar to that of normal SNe. Brightness alone should not be used to define a
hypernova, whose defining character, namely very broad spectral features, is
the result of a high kinetic energy. The likely main-sequence mass of the
progenitor star was 20-25 $M_{\odot}$, which is also lower than that of both
hypernovae SNe 1997ef and 1998bw. SN 2002ap appears to lie at the low-energy
and low-mass end of the hypernova sequence as it is known so far. Observations
of the nebular spectrum, which is expected to dominate by summer 2002, are
necessary to confirm these values.


title: Supernova 2002ap - The First Month

abstract:
  Supernova (SN) 2002ap in M74 was discovered on January 29, 2002. Being one of
the nearest (10 Mpc) SN events in the last decades, and spectroscopically
similar to the so-called ``hypernovae'' 1997ef and 1998bw, both possibly
associated with gamma-ray bursts (GRBs), it is of great interest. Shortly after
its discovery, we launched an intensive photometric and spectroscopic
monitoring campaign of this event, and here we report the results of the first
month of observations. We use our UBVRI photometry to estimate the magnitudes
at, and dates of, peak brightness. Our data suggest that this object reached
its peak B-band luminosity on Feb. 7.1(-1.3)(+2) UT. Based on its similarity to
SN 1998bw, we estimate the range of possible dates for a GRB that may have been
associated with SN 2002ap. We find that it may include dates outside the time
frame for which all available gamma-ray data have been intensively scanned,
according to recent reports. The absolute magnitude at peak brightness of SN
2002ap (M_B = -16.9) shows that it was significantly fainter than SN 1998bw, or
normal type-Ia SNe, but similar to SN 1997ef. Our spectroscopic observations
confirm that SN 2002ap is strikingly similar to SNe 1998bw and 1997ef. We
briefly describe the spectral evolution of this object. To assist other
observers and to stimulate theoretical models, we make our entire data set
publicly available in digital form.


title:
JHK' Imaging Photometry of Seyfert 1 AGNs and Quasars I: Multi-Aperture
  Photometry

abstract:
  Near-infrared $JHK'$ imaging photometry was obtained of 331 AGNs consisting
mainly of Seyfert 1 AGNs and quasars (QSOs). This sample was selected to cover
a range of radio emission strength, redshift from $z=0$ to 1, and absolute
$B$-magnitude from $M_B=-29$ mag to -18 mag. Among low-$z$ AGNs with $z<0.3$,
Seyfert $1-1.5$ AGNs are distributed over a region from a location typical of
``galaxies'' to a location typical of ``QSOs'' in the two-color $J-H$ to $H-K'$
diagram, but Seyfert $1.8-2$ AGNs are distributed around the location of
``galaxies''. Moreover, bright AGNs with respect to absolute $B$-magnitude are
distributed near the location of ``QSOs'', while faint AGNs are near the
location of ``galaxies''. The distribution of such low-$z$ AGNs in this diagram
was found to have little dependence on their 6 cm radio flux. The near-infrared
colors of the AGNs observed with an aperture of 7 pixels ($7.49''$) are more
QSO-like than those observed with larger apertures up to 15 pixels ($16.1''$).
This aperture effect may be explained by contamination from the light of host
galaxies within larger apertures. This effect is more prominent for less
luminous AGNs.