title:
A search for previously unrecognised metal-poor subdwarfs in the
  Hipparcos astrometric catalogue

abstract:
  We have identified 317 stars included in the Hipparcos astrometric catalogue
which have parallaxes measured to a precision of better than 15%, and whose
location in the (M_V, (B-V)_T) diagram implies a metallicity comparable to or
less than that of the intermediate-abundance globular cluster, M5. We have
undertaken an extensive literature search to locate Stromgren, Johnson/Cousins
and Walraven photometry for over 120 stars. In addition, we present new UBVRI
photometry of 201 of these candidate halo stars, together with similar data for
a further 14 known metal-poor subdwarfs. Those observations provide the first
extensive dataset of RI photometry of metal-poor, main-sequence stars with
well-determined trigonometric parallaxes. Finally, we have obtained
intermediate-resolution optical spectroscopy of 175 stars. We are able to
estimate abundances for 270 stars. The overwhelming majority have near-solar
abundance, with their inclusion in the present sample stemming from errors in
the colours listed in the Hipparcos catalogue. Only 44 stars show consistent
evidence of abundances below [Fe/H]= -1.0. Nine are additions to the small
sample of metal-poor subdwarfs with accurate photometry. We consider briefly
the implication of these results for cluster main-sequence fitting.


title: Canonical elements for collision orbits

abstract:
  I derive a set of canonical elements that are useful for collision orbits
(perihelion distance approaching zero at fixed semimajor axis). The coordinates
are the mean anomaly and the two spherical polar angles at aphelion.


title: "Signature" neutrinos from photon sources at high redshift

abstract:
  The temperature of the cosmic microwave background increases with redshift;
at sufficiently high redshift it becomes possible for ultrahigh-energy photons
and electrons to produce muons and pions through interactions with background
photons. At the same time, energy losses due to interactions with radio
background and intergalactic magnetic fields are negligible. The energetic
muons and pions decay, yielding a flux of ``signature'' neutrinos with energies
$E_\nu \sim 10^{17}$eV. Detection of these neutrinos can help understand the
origin of ultrahigh-energy cosmic rays.


title:
Stellar and nuclear-physics constraints on two r-process components in
  the early Galaxy

abstract: Proceedings of "Nuclei in the Cosmos 2000", Aarhus, Danmark


title: Measurements of r-process nuclei

abstract:
  Progress in the astrophysical understanding of r-process nucleosynthesis also
depends on the knowledge of nuclear-physics quantities of extremely
neutron-rich isotopes. In this context, experiments at CERN-ISOLDE have played
a pioneering role in exploring new shell-structure far from stability. Possible
implications of new nuclear-data input on the reproduction of r-abundance
observations are presented.


title: AMiBA: Array for Microwave Background Anisotropy

abstract:
  As part of a 4-year Cosmology and Particle Astrophysics (CosPA) Research
Excellence Initiative in Taiwan, AMiBA $-$ a 19-element dual-channel 85-105 GHz
interferometer array is being specifically built to search for high redshift
clusters of galaxies via the Sunyaev-Zeldovich Effect (SZE). In addition, AMiBA
will have full polarization capabilities, in order to probe the polarization
properties of the Cosmic Microwave Background. AMiBA, to be sited on Mauna Kea
in Hawaii or in Chile, will reach a sensitivity of $\sim 1$ mJy or 7$\mu$K in 1
hour. The project involves extensive international scientific and technical
collaborations. The construction of AMiBA is scheduled to starting operating in
early 2004.


title:
Relativistic Corrections to the Sunyaev-Zel'dovich Effect for Clusters
  of Galaxies. V. Precision Analytic Fitting Formula for the Crossover
  Frequency Region

abstract:
  We have succeeded in obtaining a precision analytic fitting formula for the
exact numerical results of the relativistic corrections to the thermal
Sunyaev-Zeldovich effect for clusters of galaxies which has a 1% accuracy for
the crossover frequency region where the thermal thermal Sunyaev-Zeldovich
effect signal changes from negative to positive sign. The fitting has been
carried out for the ranges 0.020 < theta < 0.035 and 0 < X < 15, where theta=
kTe/mc^{2}, X = omega/kT0, Te is the electron temperature, omega is the angular
frequency of the photon, and T0 is the temperature of the cosmic microwave
background radiation. The overall accuracy of the fitting is better than 0.1%.
The present analytic fitting formula will be useful for accurate analyses of
the thermal Sunyaev-Zeldovich effect for clusters of galaxies.


title:
Evidence for an inflationary phase transition from the LSS and CMB
  anisotropy data

abstract:
  In the light of the recent Boomerang and Maxima observations of the CMB which
show an anomalously low second acoustic peak, we reexamine the prediction by
Adams et al (1997) that this would be the consequence of a 'step' in the
primordial spectrum induced by a spontaneous symmetry breaking phase transition
during primordial inflation. We demonstrate that a deviation from
scale-invariance around $k\sim0.1h$~Mpc$^{-1}$ can simultaneously explain both
the feature identified earlier in the APM galaxy power spectrum as well the
recent CMB anisotropy data, with a baryon density consistent with the BBN
value. Such a break also allows a good fit to the data on cluster abundances
even for a critical density matter-dominated universe with zero cosmological
constant.


title: WIMP searches with AMANDA-B10

abstract:
  We report on the search for nearly vertical up-going muon neutrinos from WIMP
annihilations in the center of the Earth with the AMANDA-B10 detector. The
whole data sample collected in 1997, 10^9 events, has been analyzed and a final
sample of 15 up-going events is found in a restricted zenith angular region
where a signal from WIMP annihilations is expected. A preliminary upper limit
at 90% confidence level on the annihilation rate of WIMPs in the center of the
Earth is presented.


title:
In-Orbit Performance of the Space Telescope NINA and GCR Flux
  Measurements

abstract:
  The NINA apparatus, on board the Russian satellite Resurs-01 n.4, has been in
polar orbit since 1998 July 10, at an altitude of 840 km. Its main scientific
task is to study the galactic, solar and anomalous components of cosmic rays in
the energy interval 10--200 MeV/n. In this paper we present a description of
the instrument and its basic operating modes. Measurements of Galactic Cosmic
Ray spectra will also be shown.


title: A radio supernova remnant associated with the young pulsar J1119-6127

abstract:
  We report on Australia Telescope Compact Array observations in the direction
of the young high magnetic-field pulsar J1119-6127. In the resulting images we
identify a non-thermal radio shell of diameter 15', which we classify as a
previously uncatalogued young supernova remnant, G292.2-0.5. This supernova
remnant is positionally coincident with PSR J1119-6127, and we conclude that
the two objects are physically associated. No radio emission is detected from
any pulsar wind nebula (PWN) associated with the pulsar; our observed upper
limits are consistent with the expectation that high magnetic-field pulsars
produce radio nebulae which fade rapidly. This system suggests a possible
explanation for the lack of an associated radio pulsar and/or PWN in many
supernova remnants.


title: XMM-Newton observation of the Tycho Supernova Remnant

abstract:
  We present the observation of the Tycho supernova remnant obtained with the
EPIC and RGS instruments onboard the XMM-Newton satellite. We compare images
and azimuthally averaged radial profiles in emission lines from different
elements (silicon and iron) and different transition lines of iron (Fe L and Fe
K). While the Fe XVII L line and Si XIII K line images are globally spatially
coincident, the Fe K emission clearly peaks at a smaller radius, indicating a
higher temperature toward the reverse shock. This is qualitatively the profile
expected when the reverse shock, after travelling through the outer power-law
density profile, has entered the central plateau of the ejecta. The high energy
continuum map has an overall smooth distribution, with a similar extent to the
radio emission. Its radial profile peaks further out than the lines emission.
Brighter and harder continuum regions are observed with a rough bipolar
symmetry in the eastern and western edges. The spectral analysis of the
southeastern knots supports spatial variations of the relative abundance of
silicon and iron, which implies an incomplete mixing of the silicon and iron
layers.


title:
Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) -
  Third Edition - Comments and Statistics

abstract:
  The Catalogue, available at the Centre de Donn\'ees Stellaires de Strasbourg,
consists of 13573 records concerning the results obtained from different
methods for 7778 stars, reported in the literature. The following data are
listed for each star: identifications, apparent magnitude, spectral type,
apparent diameter in arcsec, absolute radius in solar units, method of
determination, reference, remarks. Comments and statistics obtained from CADARS
are given.


title: Gamma Rays from Molecular Clouds

abstract:
  I discuss the spectral features of pi-0 decay gamma-radiation from
clouds/targets located in proximity of relatively young proton accelerators,
and speculate that such ``accelerator+target'' systems in our Galaxy can be
responsible for a subset of unidentified EGRET sources. Also, I argue that the
recent observations of high energy gamma-rays from the Orion complex contain
evidence that the level of the ``sea'' of galactic cosmic rays may differ
significantly from the flux and the spectrum of local (directly detected)
particles.


title: Primordial Nucleosynthesis, Cosmic Microwave Background and Neutrinos

abstract:
  We report the results of a recent likelihood analysis combining the
primordial nucleosynthesis and the BOOMERanG and MAXIMA-1 data on cosmic
microwave background radiation anisotropies. We discuss the possible
implications for relic neutrino background of a high value for the baryonic
matter content of the universe, larger than what is expected in a standard
nucleosynthesis scenario.


title: Cold H2O and CO ice and gas toward the Galactic Center

abstract:
  We present observations of CO, 13CO and of H2O in the middle and far-infrared
taken with the ISO-SWS and ISO-LWS spectrometers toward two positions in the
Galactic Center region (Sgr A* and GCS-3). Both ice and gas phase molecules are
detected. The ISO data have been complemented with observations of the J=3-2
and J=7-6 lines of CO carried out at the Caltech Submillimeter Observatory. The
ISO and CSO data indicate that the absorbing gas is extremely cold, T_K ~ 10 K,
suggesting that it is located in the dark clouds of the different spiral arms
that intersect the line of sight towards the Galactic Center. From the analysis
of the CO absorption we derive 13CO gas phase column densities of 1.1 and
0.7E17 cm-2 towards Sgr A* and GCS-3, respectively. The H2O gas column density
in the direction of Sgr A* is ~ 2E16 cm-2. The derived CO/H2O and gas/solid
abundance ratios corresponding to these cold clouds are remarkably similar
along the two lines of sight. We find that nearly all the CO is in the gas
phase, while the H2O is almost entirely frozen onto the surfaces of cold dust
grains. Finally, the N_{gas+ice}(CO)/N_{gas+ice}(H2O) abundance ratio is ~5
implying that H2O formation processes are highly efficient.


title:
AGN and starbursts at high redshift: High resolution EVN radio
  observations of the Hubble Deep Field

abstract:
  We present deep, wide-field European VLBI Network (EVN) 1.6 GHz observations
of the Hubble Deep Field (HDF) region with a resolution of 0.025 arcseconds.
Above the 210 microJy/beam (5sigma) detection level, the EVN clearly detects
two radio sources in a field that encompasses the HDF and part of the Hubble
Flanking Fields (HFF). The sources detected are: VLA J123644+621133 (a z=1.013,
low-luminosity FR-I radio source located within the HDF itself) and VLA
J123642+621331 (a dust enshrouded, optically faint, z=4.424 starburst system).
A third radio source, J123646+621404, is detected at the 4sigma level. The VLBI
detections of all three sources suggest that most of the radio emission of
these particular sources (including the dusty starburst) is generated by an
embedded AGN.


title:
Reddening Independent Quasar Selection from a Wide Field Optical and
  Near-IR Imaging Survey

abstract:
  We present preliminary results from a wide field near-IR imaging survey that
uses the Cambridge InfraRed Survey Instrument (CIRSI) on the 2.5m Isaac Newton
Telescope (INT). CIRSI is a JH-band mosaic imager that contains 4 Rockwell
1024$^{2}$ HgCdTe detectors (the largest IR camera in existence), allowing us
to survey approximately 4 deg^2 per night to H ~ 19. Combining CIRSI
observations with the deep optical imaging from the INT Wide Field Survey, we
demonstrate a reddening independent quasar selection technique based on the (g
- z) / (z - H) color diagram.


title:
ISO spectroscopy of circumstellar dust in 14 Herbig Ae/Be systems:
  towards an understanding of dust processing

abstract:
  We present Infrared Space Observatory (ISO) spectra of fourteen isolated
Herbig Ae/Be (HAEBE) stars, to study the characteristics of their circumstellar
dust. These spectra show large star-to-star differences, in the emission
features of both carbon-rich and oxygen-rich dust grains. The IR spectra were
combined with photometric data ranging from the UV through the optical into the
sub-mm region. We defined two key groups, based upon the spectral shape of the
infrared region. The derived results can be summarized as follows: (1) the
continuum of the IR to sub-mm region of all stars can be reconstructed by the
sum of a power-law and a cool component, which can be represented by a black
body. Possible locations for these components are an optically thick,
geometrically thin disc (power-law component) and an optically thin flared
region (black body); (2) all stars have a substantial amount of cold dust
around them, independent of the amount of mid-IR excess they show; (3) also the
near-IR excess is unrelated to the mid-IR excess, indicating different
composition/location of the emitting material; (4) remarkably, some sources
lack the silicate bands; (5) apart from amorphous silicates, we find evidence
for crystalline silicates in several stars, some of which are new detections;
(6) PAH bands are present in at least 50% of our sample, and their appearance
is slightly different from PAHs in the ISM; (7) PAH bands are, with one
exception, not present in sources which only show a power-law continuum in the
IR; their presence is unrelated to the presence of the silicate bands; (8) the
dust in HAEBE stars shows strong evidence for coagulation; this dust processing
is unrelated to any of the central star properties (such as age, spectral type
and activity).


title:
Compton scattering sequence reconstruction algorithm for the liquid
  xenon gamma-ray imaging telescope (LXeGRIT)

abstract:
  The Liquid Xenon Gamma-Ray Imaging Telescope (LXeGRIT) is a balloon born
experiment sensitive to \g -rays in the energy band of 0.2-20 MeV. The main
detector is a time projection chamber filled with high purity liquid xenon
(LXeTPC), in which the three-dimensional location and energy deposit of
individual \g -ray interactions are accurately measured in one homogeneous
volume. To determine the \g -ray initial direction (Compton imaging), as well
as to reject background, the correct sequence of interactions has to be
determined. Here we report the development and optimization of an algorithm to
reconstruct the Compton scattering sequence and show its performance on Monte
Carlo events and LXeGRIT data.


title:
Spectroscopy and Imaging Performance of the Liquid Xenon Gamma-Ray
  Imaging Telescope (LXeGRIT)

abstract:
  LXeGRIT is a balloon-borne Compton telescope based on a liquid xenon time
projection chamber (LXeTPC) for imaging cosmic \g-rays in the energy band of
0.2-20 MeV. The detector, with 400 cm$^2$ area and 7 cm drift gap, is filled
with high purity LXe. Both ionization and scintillation light signals are
detected to measure the energy deposits and the three spatial coordinates of
individual \g -ray interactions within the sensitive volume. The TPC has been
characterized with repeated measurements of its spectral and Compton imaging
response to \g -rays from radioactive sources such as \na, \cs, \yt and Am-Be.
The detector shows a linear response to \g -rays in the energy range 511 keV
-4.4 MeV, with an energy resolution (FWHM) of $ \Delta E/E=8.8% \: \sqrt{1\MeV
/E}$. Compton imaging of \yt \g -ray events with two detected interactions is
consistent with an angular resolution of $\sim$ 3 degrees (RMS) at 1.8 MeV.


title: Towards a model of Quintessential Inflation

abstract:
  A model of quintessential inflation is presented, which manages to achieve
the requirements of both inflation and quintessence with natural values of the
mass-scales and parameters.


title:
Local clouds: ionization, temperatures, electron densities and
  interfaces, from GHRS and IMAPS spectra of epsilon Canis Majoris

abstract:
  The composition and physical properties of several local clouds, including
the Local Interstellar Cloud (LIC) in which the Sun is embedded, are derived
from absorption features in the UV spectrum of the star epsilon CMa.
  We derive temperatures and densities for three components by combining our
interpretations of the ionization balance of magnesium and the relative
population of C II in an excited fine-structure level. We find that for the LIC
n(e) = 0.12 +/-0.05 cm-3 and T = 7000 +/-1200 K.
  We derive the ionization fractions of hydrogen and discuss the ionizing
processes. In particular the hydrogen and helium ionizations in the LIC are
compatible with photoionization by the local EUV radiation fields from the hot
stars and the cloud interface with the hot gas.
  We confirm the detection of high ionization species : Si III is detected in
all clouds and C IV in two of them, including the LIC, suggesting the presence
of ionized interfaces around the local clouds.


title: Type Ia Supernovae: Toward the Standard Model?

abstract:
  In this short review I suggest that recent developments support the
conjecture that Type Ia supernovae (SNe Ia) are the complete disruptions of
Chandrasekhar-mass carbon-oxygen white dwarfs in single-degenerate binary
systems. The causes of the observational diversity of SNe Ia within the context
of this standard model, and the implications of the model for young remnants of
SNe Ia, are briefly discussed.


title:
Irregular Magnetic Fields in Interstellar Clouds and the Linear
  Polarization of Starlight

abstract:
  Calculations are performed for the linear polarization of starlight due to
extinction by aligned dust grains when the starlight traverses a medium with
irregular magnetic fields. This medium is intended to represent the optically
thick components of interstellar clouds which are observed to make little, if
any, contribution to the polarization of starlight. In agreement with the
observations, we find that the polarization properties of the starlight---the
average fractional polarization and the dispersion in position angles---can be
essentially unchanged. For this, the rms of the irregular component must be
greater than the average magnetic field, which in turn tends to imply that the
turbulent velocities in these interstellar clouds are super-Alfvenic.


title: The Southern Galactic Plane Survey: The Test Region

abstract:
  The Southern Galactic Plane Survey (SGPS) is a project to image the HI line
emission and 1.4 GHz continuum in the fourth quadrant of the Milky Way at high
resolution using the Australia Telescope Compact Array (ATCA) and the Parkes
Radio Telescope. In this paper we describe the survey details and goals,
present lambda 21-cm continuum data, and discuss HI absorption and emission
characteristics of the SGPS Test Region (325.5 deg < l < 333.5 deg; -0.5 deg <
b < +3.5 deg). We explore the effects of massive stars on the interstellar
medium (ISM) through a study of HI shells and the HI environments of HII
regions and supernova remnants. We find an HI shell surrounding the HII region
RCW 94 which indicates that the region is embedded in a molecular cloud. We
give lower limits for the kinematic distances to SNRs G327.4+0.4 and G330.2+1.0
of 4.3 kpc and 4.9 kpc, respectively. We find evidence of interaction with the
surrounding HI for both of these remnants. We also present images of a possible
new SNR G328.6-0.0. Additionally, we have discovered two small HI shells with
no counterparts in continuum emission.


title: Multi-Color Observations of the GRB000926 Afterglow

abstract:
  We present multi-color light-curves of the optical afterglow of GRB 000926.
Beginning ~1.5 days after the burst, the light-curves of this GRB steepen
measurably. The existence of such achromatic breaks are usually taken to be an
important observational signature that the ejecta are not expanding
isotropically, but rather have a collimated jet-like geometry. If we interpret
the data in this context, we derive an opening angle of 5 degrees, which
reduces the energy release compared to an isotropic model by a factor of ~275,
to 1.7 x 10^51 erg. To fit the data with a simple jet model requires extinction
along the line of sight. The derived A_V is in the range 0.11 - 0.82 mag,
depending on the adopted extinction law and whether the electrons giving rise
to the optical emission are undergoing synchrotron cooling or not. Since this
is in excess of the expected extinction from our Galaxy, we attribute this to
the GRB host. We note that this extinction is typical of a galactic disk, and
therefore the event likely took place in the disk of its host.


title: The ASCA Catalog of Potential X-Ray Counterparts of GeV Sources

abstract:
  We present a catalog of 2-10 keV ASCA Gas Imaging Spectrometer images of
fields containing bright sources of GeV emission. The images cover $\sim 85%$
of the 95% confidence position contour for 28 of the 30 sources with $> 1$ GeV
fluxes above $4\times 10^{-8}$ ph ${\rm cm}^{-2} {\rm s}^{-1}$. We find an
excess of hard X-ray sources with $F_{2-10 keV} \ga 10^{-12}$ ergs ${\rm
cm}^{-2} {\rm s}^{-1}$ positionally coincident with unidentified sources of GeV
emission. We comment on radio-loud and radio-quiet pulsar candidates, as well
as several SNR and massive binaries as possible sources of the GeV emission. We
also find evidence for a class of variable $\gamma-$ray sources associated with
extended regions of hard X-ray emission, and propose that for these sources, a
significant percentage of the $\gamma-$ray emission is generated in synchrotron
nebulae surrounding fast, young pulsars.


title:
The Dynamics of Sinking Satellites Around Disk Galaxies: A Poor Man's
  Alternative to High-Resolution Numerical Simulations

abstract:
  We have developed a simple yet surprisingly accurate analytic scheme for
tracking the dynamical evolution of substructure within larger dark halos. The
scheme incorporates the effects of dynamical friction, tidal mass loss and
tidal heating via physically motivated approximations. Using our scheme, we can
predict the orbital evolution and mass-loss history of individual subhalos in
detail. We are also able to determine the impact and importance of the
different physical processes on the dynamical evolution of the subhalos. To
test and calibrate this model, we compare it with a set of recent
high-resolution numerical simulations of mergers between galaxies and small
companions. We find that we can reproduce the orbits and mass-loss rates seen
in all of these simulations with considerable accuracy, using a single set of
values for the three free parameters in our model. Computationally, our scheme
is more than 1000 times faster than the simplest of the high-resolution
numerical simulations. This means that we can carry out detailed and
statistically meaningful investigations into the characteristics of the subhalo
population in different cosmologies, the stripping and disruption of the
subhalos, and the interactions of the subhalos with other dynamical structures
such as a thin disk. This last point is of particular interest given the
ubiquity of minor mergers in hierarchical models. In this regard, our method's
simplicity and speed makes it particularly attractive for incorporation into
semi-analytic models of galaxy formation.


title: Thermal Relaxation in Young Neutron Stars

abstract:
  The internal properties of the neutron star crust can be probed by observing
the epoch of thermal relaxation. After the supernova explosion, powerful
neutrino emission quickly cools the stellar core, while the crust stays hot.
The cooling wave then propagates through the crust, due to its finite thermal
conductivity. When the cooling wave reaches the surface (age 10-100 yr), the
effective temperature drops sharply from 250 eV to 30 or 100 eV, depending on
the cooling model. The crust relaxation time is sensitive to the (poorly known)
microscopic properties of matter of subnuclear density, such as the heat
capacity, thermal conductivity, and superfluidity of free neutrons. We
calculate the cooling models with the new values of the electron thermal
conductivity in the inner crust, based on a realistic treatment of the shapes
of atomic nuclei. Superfluid effects may shorten the relaxation time by a
factor of 4. The comparison of theoretical cooling curves with observations
provides a potentially powerful method of studying the properties of the
neutron superfluid and highly unusual atomic nuclei in the inner crust.


title: Mapping the Galactic Halo III. Simulated Observations of Tidal Streams

abstract:
  We have simulated the evolution of tidal debris in the Galactic halo in order
to guide our ongoing survey to determine the fraction of halo mass accreted via
satellite infall. Contrary to naive expectations that the satellite debris will
produce a single narrow velocity peak on a smooth distribution, there are many
different signatures of substructure, including multiple peaks and broad but
asymmetrical velocity distributions. Observations of the simulations show that
there is a high probability of detecting the presence of tidal debris with a
pencil beam survey of 100 square degrees. In the limiting case of a single 10^7
Msun satellite contributing 1% of the luminous halo mass the detection
probability is a few percent using just the velocities of 100 halo stars in a
single 1 square degree field. The detection probabilities scale with the
accreted fraction of the halo and the number of fields surveyed. There is also
surprisingly little dependence of the detection probabilities on the time since
the satellite became tidally disrupted, or on the initial orbit of the
satellite, except for the time spent in the survey volume.


title:
Gas fueling and nuclear disk formation in merging between a central
  black hole and a gas clump

abstract:
  We numerically investigate dynamical evolution of a merger between a central
massive black hole (MBH) and a gas clump with the mass of $10^6$ $-$ $10^7$
$M_{\odot}$ in the central tens pc of a galactic bulge. We found that strong
tidal gravitational field of the MBH transforms the initial spherical clump
into a moderately thick gaseous disk (or torus) around the MBH. The developed
disk is also found to show rotation, essentially because the tidal field
changes efficiently the orbital angular momentum of the clump into intrinsic
angular momentum of the disk. Furthermore about a few percent of gas mass
(corresponding to a few $10^5$ $M_{\odot}$) in the clump is found to be
transferred to the central sub-parsec region around the MBH within an order of
$10^6$ yr. We thus suggest that successive merging of gas clumps onto a MBH can
not only be associated closely with the formation of nuclear disk around the
MBH but also can provide gas fuel for the MBH.


title: Extended SZ map of the most luminous X-ray cluster, RXJ1347-1145

abstract:
  We present in this letter a high resolution (22'' FWHM) extended map at 2.1mm
of the Sunyaev-Zel'dovich effect toward the most luminous X-ray cluster,
RXJ1347-1145. These observations have been performed with the DIABOLO
photometer working at the focus of the 30m IRAM radiotelescope. We have derived
a projected gas mass of $(1.1 \pm 0.1)\times 10^{14} h_{50}^{-5/2}$M$_{\odot}$
within an angular radius of $\theta=74''$ (ie: projected radius of 0.6Mpc,
$H_{0}=50$km/s/Mpc, $\Omega_m=0.3$, $\Omega_\Lambda=0.7$). This result matches
very well the expected gas mass from the cluster models of X-ray data. With an
unprecedented sensitivity level our measurement does not show significant
departure from a spherical distribution. The data analysis also allows us to
characterize the 2.1mm flux of a well known radio source lying in the center of
the cluster: $F_{RS}(2.1\textrm{mm})=5.7\pm 1.6$mJy.


title:
ASCA Discovery of Diffuse 6.4 keV Emission Near the Sgr C Complex: A New
  X-ray Reflection Nebula

abstract:
  We present an ASCA discovery of diffuse hard X-ray emission from the Sgr C
complex with its peak in the vicinity of the molecular cloud core. The X-ray
spectrum is characterized by a strong 6.4-keV line and large absorption. These
properties suggest that Sgr C is a new X-ray reflection nebula which emits
fluorescent and scattered X-rays via irradiation from an external X-ray source.
We found no adequately bright source in the immediate Sgr C vicinity to fully
account for the fluorescence. The irradiating source may be the Galactic
nucleus Sgr A*, which was brighter in the past than it is now as is suggested
from observations of the first X-ray reflection nebula Sgr B2.


title:
Detection of massive tidal tails around the globular cluster Pal 5 with
  SDSS commissioning data

abstract:
  We report the discovery of two well-defined tidal tails emerging from the
sparse remote globular cluster Palomar 5. These tails stretch out symmetrically
to both sides of the cluster in the direction of constant Galactic latitude and
subtend an angle of 2.6 degrees on the sky. The tails have been detected in
commissioning data of the Sloan Digital Sky Survey (SDSS), providing deep
five-color photometry in a 2.5 degrees wide band along the equator. The stars
in the tails make up a substantial part (~1/3) of the current total population
of cluster stars in the magnitude interval 19.5 < i* < 22.0. This reveals that
the cluster is subject to heavy mass loss. The orientation of the tails
provides an important key for the determination of the cluster's Galactic
orbit.


title: ALMA and high redshift dusty starburst mergers

abstract:
  By using a new numerical code for deriving the spectral energy distributions
of galaxies, we have investigated the time evolution of morphological
properties, the star formation rate, and the submillimeter flux at 850 $\mu$m
in high-redshift ($z$) dusty starburst mergers with mass ratio ($m_{2}$) of two
disks ranging from 0.1 (minor merger) to 1.0 (major one). We found that the
maximum star-formation rate, the degree of dust extinction, and the 850 $\mu$m
flux are larger for mergers with larger $m_{2}$. The 850 $\mu$m flux from
mergers at 1.5 $\le z \le$ 3.0 in the observer frame is found to be a few mJy
for major merger cases, and at most $\sim$ 100 $\mu$Jy for minor ones. This
result suggests that only high-redshift major mergers are now detected by SCUBA
with the current 850 $\mu m$ detection limit of a few mJy. These results imply
that LMSA (ALMA) with the expected detection limit of the order of 10 $\mu$Jy
at 850 $\mu m$ can be used to study high-redshift mergers with variously
different $m_2$, and thus provide an important clue to the formation of
galaxies in a high-redshift universe.


title: Brane Quintessence

abstract:
  We propose a new quintessence scenario in the brane cosmology, assuming that
a quintessence field $Q$ is confined in our 3-dimensional brane world. With a
potential $V(Q)= \mu^{\alpha+4} Q^{-\alpha}~(\alpha\geq 2)$, we find that the
density parameter of the scalar field decreases as $\Omega_Q \sim
a^{-4(\alpha-2)/(\alpha+2)}$ in the epoch of quadratic energy density
dominance, if $\alpha\leq 6$. This attractor solution is followed by the usual
tracking quintessence scenario after a conventional Friedmann universe is
recovered. With an equipartition of initial energy density, we find a natural
and successful quintessence model for $\alpha\gsim 4$.


title: UHECR Production by a Compact Black-Hole Dynamo: Application to Sgr A*

abstract:
  The possibility that the excess cosmic ray (CR) flux near 10$^{18}$ eV,
reported recently by the AGASA group, is due to a compact black hole dynamo
associated with the Sgr A* source is considered. Under the assumption that the
Galactic center black hole rotates with nearly maximal spin, and that the
magnetic field threading the horizon is in rough equipartition with matter
accreted by the hole, the spectra and total fluxes of accelerated CRs and their
associated curvature emission depend only on accretion rate. For the accretion
rate estimated on the basis of observations of stellar winds near Sgr A* ($\sim
10^{-3}$ Eddington), the maximum proton energy achievable by this mechanism is
of the order of $10^{18}$ eV, and the corresponding CR power is $\sim
10^{41}\alpha_{CR}$ erg s$^{-1}$, where $\alpha_{CR}<<1$ is the CR production
efficiency. The corresponding spectrum of curvature photons peaks at around a
hundred GeV, with a total luminosity comparable to the CR power released. For
much lower accretion rates both the CR and gamma-ray fluxes predicted are
completely insignificant. Upcoming gamma-ray experiments, such as CANGAROO,
HESS and GLAST, can be used to probe the parameters of this system.


title: A cloudy model for the Circumnuclear Disk in the Galactic Centre

abstract:
  We present a first attempt to construct an analytic model for a clumped gas
and dust disk and apply it to the Galactic Centre. The clumps are described as
isothermal spheres partially ionized by the external UV radiation field. The
disk structure formed by the clouds is described as a quasi standard continuous
accretion disk using adequately averaged parameters of the discrete cloud
model. The viscosity in the Circumnuclear Disk is due to partially inelastic
cloud-cloud collisions. We find two different solutions for the set of
equations corresponding to two stable cloud regimes: (i) the observed molecular
clouds and (ii) much lighter and smaller clouds which correspond to the
stripped cores of the observed clouds. It is shown that the resulting physical
characteristics of the heavy clouds and the disk are in very good agreement
with all comparable observations at multiple wavelengths. A mass accretion rate
of approx. 10^-4 M_solar/yr for the isolated Circumnuclear Disk is inferred. We
propose that the Circumnuclear Disk has a much longer lifetime (approx. 10^7
yr) than previously assumed.


title: Coulomb plasmas in outer envelopes of neutron stars

abstract:
  Outer envelopes of neutron stars consist mostly of fully ionized, strongly
coupled Coulomb plasmas characterized by typical densities about 10^4-10^{11}
g/cc and temperatures about 10^4-10^9 K. Many neutron stars possess magnetic
fields about 10^{11}-10^{14} G. Here we briefly review recent theoretical
advances which allow one to calculate thermodynamic functions and electron
transport coefficients for such plasmas with an accuracy required for
theoretical interpretation of observations.


title: Optical and X-ray monitoring of the NLS1 galaxy Ark 564

abstract:
  The Narrow-line Seyfert galaxy Ark 564 was monitored between June 04, 2000
and June 24, 2000 from Skinakas Observatory. The B,V,R and I band light curves
show night to night variations of 0.1 mag. Comparison with X-ray data from a
simultaneous ASCA observation shows that the X-ray variations are more
pronounced than in the optical band. Cross correlation analysis yields a time
lag of ~ 0.8 days in the sense that the X-rays are leading the optical but with
low statistical significance. We discuss possible implications of our results
to current physical models of AGN.


title:
Discovery of a Transient Absorption Edge in the X-ray Spectrum of GRB
  990705

abstract:
  We report the discovery of a transient equivalent hydrogen column density
with an absorption edge at ~3.8 kiloelectron volts in the spectrum of the
prompt x-ray emission of gamma-ray burst (GRB) 990705. This feature can be
satisfactorily modeled with a photoelectric absorption by a medium located at a
redshift of ~0.86 and with an iron abundance of ~75 times the solar one. The
transient behavior is attributed to the strong ionization produced in the
circumburst medium by the GRB photons. The high iron abundance points to the
existence of a burst environment enriched by a supernova along the line of
sight. The supernova explosion is estimated to have occurred about 10 years
before the burst. Our results agree with models in which GRBs originate from
the collapse of very massive stars and are preceded by a supernova event


title:
Estimation of Signal and Noise Parameters from CMB Polarization
  Observations

abstract:
  We propose a technique for determination of the spectral parameters of the
cosmological signal and pixel noise using observational data on CMB
polarization without any additional assumptions. We introduce the notion of so
called crossing points in the observational maps and derive the theoretical
dependence of the total number of crossing points at different level of the
polarization. Finally, we use the statistics of the signal in the vicinities of
the singular points, where the polarization of the pure CMB vanishes to correct
the final result.


title:
Observational Matter Power Spectrum and the Height of the Second
  Acoustic Peak

abstract:
  We show that the amplitude of the second acoustic peak in the newly released
BOOMERANG-98 and MAXIMA-I data is compatible with the standard primordial
nucleosynthesis and with the locally broken-scale-invariant matter power
spectrum suggested by recent measurements of the power spectrum in the range
$20 - 200$ Mpc. If the slope of matter density perturbations on large scales is
$n \approx 1$, the Hubble constant is $0.5< h < 0.75$, and r.m.s. mass
fluctuations at 8 Mpc are $0.65 \le \sigma_8 \le 0.75$, then for a Universe
approximately 14 Gyr old our best fit within the nucleosynthesis bound
$\Omega_Bh^2= 0.019 \pm 0.0024$ requires $0.3 \le \Omega_m \le 0.5$. Cluster
abundances further constraint the matter density to be $\Omega_m \approx 0.3$.
The CMB data alone are not able to determine the detailed form of the matter
power spectrum in the range $0.03<k<0.06$ \hmpc where deviations from the
scale-invariant spectrum are expected to be most significant, but they do not
contradict the existence of the previously claimed peak at $k\sim 0.05$ \hmpc,
and a depression at $k\sim 0.035$ \hmpc.


title:
On the minimum and maximum mass of neutron stars and the delayed
  collapse

abstract:
  The minimum and maximum mass of protoneutron stars and neutron stars are
investigated. The hot dense matter is described by relativistic (including
hyperons) and non-relativistic equations of state. We show that the minimum
mass ($\sim$ 0.88 - 1.28 $M_{\sun}$) of a neutron star is determined by the
earliest stage of its evolution and is nearly unaffected by the presence of
hyperons. The maximum mass of a neutron star is limited by the protoneutron
star or hot neutron star stage. Further we find that the delayed collapse of a
neutron star into a black hole during deleptonization is not only possible for
equations of state with softening components, as for instance, hyperons, meson
condensates etc., but also for neutron stars with a pure nucleonic-leptonic
equation of state.


title: Are There ADAFs in Nearby Giant Elliptical Galaxies?

abstract:
  Recently it has been suggested that the hard x-ray power-law tails exhibited
in the ASCA spectra of several nearby giant elliptical galaxies are caused by
low-radiative efficiency accretion flows (ADAFs) onto a massive black hole in
the centers of the galaxies. The estimated fluxes from these central ADAFs as
derived from the ASCA x-ray spectral analyses indicate that they may be visible
as x-ray point sources. We analyze archival ROSAT HRI images of three such
galaxies, NGCs 1399, 4636, and 4696, to determine whether point x-ray sources
consistent with ASCA-derived fluxes are present in the centers of the galaxies.
We find that the upper limit for the flux of a central point x-ray source in
each of these galaxies as determined by the ROSAT HRI data is only marginally
consistent with the predicted flux inferred from the ASCA spectra. We suggest
that although a central point source, such as a ADAF associated with a massive
black hole, cannot be completely ruled out, they can only account for a
fraction of the flux of the observed hard x-ray power law components.


title:
Physical conditions in QSO absorbers from fine-structure absorption
  lines

abstract:
  We calculate theoretical population ratios of the ground fine-structure
levels of some atoms/ions which typically exhibit UV lines in the spectra of
QSO absorbers redward the Ly-alpha forest: C0, C+, O0, Si+ and Fe+. The most
reliable atomic data available is employed and a variety of excitation
mechanisms considered: collisions with several particles in the medium, direct
excitation by photons from the cosmic microwave background radiation (CMBR) and
fluorescence induced by a UV field present.
  The theoretical population ratios are confronted with the corresponding
column density ratios of C I and C II lines observed in damped Ly-alpha (DLA)
and Lyman Limit (LL) systems collected in the recent literature to infer their
physical conditions.
  The volumetric density of neutral hydrogen in DLA systems is constrained to
be lower than tens of cm^-3 (or a few cm^-3 in the best cases) and the UV
radiation field intensity must be lower than two orders of magnitude the
radiation field of the Galaxy (one order of magnitude in the best cases). Their
characteristic sizes are higher than a few pc (tens of pc in the best cases)
and lower limits for their total masses vary from 10^0 to 10^5 solar masses.
  For the only LL system in our sample, the electronic density is constrained
to be n_e<0.15 cm^-3. We suggest that the fine-structure lines may be used to
discriminate between the current accepted picture of the UV extragalatic
background as the source of ionization in these systems against a local origin
for the ionizing radiation as supported by some authors.
  We also investigate the validity of the temperature-redshift relation of the
CMBR predicted by the standard model and study the case for alternative models.


title:
Towards a Precise Measurement of Matter Clustering: Lyman-alpha Forest
  Data at Redshifts 2-4

abstract:
  We measure the filling factor, correlation function, and power spectrum of
transmitted flux in a large sample of Lya forest spectra, comprised of 30 Keck
HIRES spectra and 23 Keck LRIS spectra. We infer the linear matter power
spectrum P(k) from the flux power spectrum P_F(k), using an improved version of
the method of Croft et al. (1998) that accounts for the influence of z-space
distortions, non- linearity, and thermal broadening on P_F(k). The evolution of
the shape and amplitude of P(k) over the range z= 2-4 is consistent with
gravitational instability, implying that non-gravitational fluctuations do not
make a large contribution. Our fiducial measurement of P(k) comes from data
with <z> = 2.72. It has amplitude Delta^2(k_p)=0.74^0.20_-0.16 at wavenumber
k_p=0.03 (km/s)^-1 and is well described by a power-law of index -2.43 +/- 0.06
or by a CDM-like power spectrum with shape parameter Gamma'=1.3^+0.7_-0.5*10^-3
(km/s) at z=2.72. For Omega_m=0.4, Omega_Lam=0.6, the best-fit Gamma =0.16
(h^-1mpc)^-1, in good agreement with the 2dF Galaxy Redshift Survey, and the
best-fit sigma_8=0.82 (Gamma/0.15)^-0.44. Matching the observed cluster mass
function and our Delta^2(k_p) in spatially flat models requires
Omega_m=0.38^+0.10_-0.08 + 2.2 (Gamma-0.15). Matching Delta^2(k_p) in
COBE-normalized, flat CDM models with no tensor fluctuations requires Omega_m =
(0.29 +/-0.04) n^-2.89 h_65^-1.9. The Lya forest complements other probes of
P(k) by constraining a regime of redshift and lengthscale not accessible by
other means, and the consistency of these inferred parameters with independent
estimates provides further support for inflation, cold dark matter, and vacuum
energy (abridged).


title: The Brown Dwarf Mass Function from Pixel Microlensing

abstract:
  We argue that gravitational microlensing is a feasible technique for
measuring the mass function of brown dwarf stars in distant galaxies.
Microlensing surveys of the bulge of M31, and of M87 in the Virgo cluster, may
provide enough events to differentiate the behaviour of the mass function of
lenses below the hydrogen burning limit (though we find that M87 is a more
favourable target). Such objects may provide a significant supply of baryonic
dark matter, an interesting possibility for the study of galactic dynamics.
Furthermore, these systems have different metallicities than the solar
neighbourhood, which may affect the mass function. These considerations are
relevant in the context of star formation studies.


title:
Tunable-filter imaging of quasar fields at z~1. I. A cluster around MRC
  B0450-221

abstract:
  Using a combination of multicolour broad- and narrow-band imaging techniques
and follow-up spectroscopy, we have detected an overdensity of galaxies in the
field of quasar MRC B0450-221, whose properties are consistent with a cluster
at the quasar redshift z=0.9. An excess of red galaxies (V-I>2.2, I-K'>3.8) is
evident within 1' of the quasar, with the colours expected for galaxies at
z=0.9 that have evolved passively for 3 Gyr or more. A number of line-emitting
galaxies (nine candidates with equivalent widths EW>70A) are also detected in
the field using the TAURUS Tunable Filter (TTF). Three have been confirmed
spectroscopically to indeed lie at z=0.9. The TTF candidates with the strongest
[O II] line emission cluster in a group which lies 200-700 kpc away from the
quasar and the red galaxy excess, and therefore most likely on the outskirts of
the cluster. These observations are the first in a series probing quasar
environments at z~1 with TTF.


title: A Balloon-borne Large Aperture Submillimeter Telescope

abstract:
  A new generation of sub-orbital platforms will be operational in the next few
years. These new telescopes will operate from airborne and balloon-borne
platforms where the atmosphere is transparent enough to allow sensitive
measurements to be made in the submillimeter bands. The telescopes will take
advantage of state-of-the-art instrumentation including large format bolometer
arrays and spectrometers. Other papers in this volume will deal specifically
with the potential of these bands. In this paper will review the capabilities
the BLAST balloon-borne telescope.


title:
A Large-Scale Jet and FR I Radio Source in a Spiral Galaxy: The Host
  Properties and External Environment

abstract:
  We have identified a large (~200 kpc), powerful double radio source whose
host galaxy is clearly a disk and most likely a spiral. This FR I radio galaxy
is located very near the center of the RC 0 cluster Abell 428. The existence of
such an object violates a fundamental paradigm for radio loud AGN. In paper I,
we showed that this object was most likely a spiral host with optical line
ratios and colors consistent with an AGN. In this paper, we present new, higher
resolution radio imaging, a radio/mm continuum spectrum for the nucleus, a
detection of HI absorption against the bright radio core, an upper-limit to CO
and the gas mass, and 70 optical redshifts. We confirm the existence of a radio
jet at 20cm extending 42 kpc into the southern lobe. At 3.6cm, we also detect a
nuclear jet similar in length to that in M87 but 10 times weaker. We believe
that this is the first detection of a radio jet on these scales in a disk or
spiral host galaxy. The nuclear radio spectrum is similar to many blazar or QSO
like objects, suggesting that the galaxy harbors an imbedded and obscured AGN.
We model a turnover in the spectrum at low frequencies as Free-Free absorption.
We detect very strong and narrow HI absorption with nearly the entire 20 cm
core continuum absorbed, implying an unusually large optical depth (tau~1). We
suggest that the nucleus is seen through a disk-like distribution of ISM gas,
possibly through a spiral arm or a warp to account for the high column density.
  From the radial velocities, we find that A428 is in fact made up of at least
2 clumps of galaxies separated by 3300 km/s, which are imbedded in a nearly
continuous distribution of galaxies over 13000 km/s in velocity. Thus, the
environment resembles a poor group within a filament viewed end-on.


title:
Far Ultraviolet Spectroscopy of a Nonradiative Shock in the Cygnus Loop:
  Implications for the Postshock Electron-Ion Equilibration

abstract:
  We present far ultraviolet spectra of a fast (~ 300 km/s) nonradiative shock
in the Cygnus Loop supernova remnant. Our observations were performed with the
Far Ultraviolet Spectroscopic Explorer (FUSE) satellite, covering the
wavelength range 905-1187 Angstroms. The purpose of these observations was to
estimate the degree of electron-ion equilibration by (1) examining the
variation of O VI 1032, 1038 intensity with position behind the shock, and (2)
measuring the widths of the O VI lines. We find significant absorption near the
center of the O VI 1032 line, with less absorption in O VI 1038. The absorption
equivalent widths imply an O VI column density greatly exceeding that of
interstellar O VI along the Cygnus Loop line of sight. We suggest that the
absorption may be due to resonant scattering by O VI ions within the shock
itself. The widths of the O VI emission lines imply efficient ion-ion
equilibration, in agreement with predictions from Balmer-dominated spectra of
this shock.


title: Scaling of N-body calculations

abstract:
  We report results of collisional N-body simulations aimed to study the
N-dependance of the dynamical evolution of star clusters. Our clusters consist
of equal-mass stars and are in virial equilibrium. Clusters moving in external
tidal fields and clusters limited by a cut-off radius are simulated. Our main
focus is to study the dependence of the lifetimes of the clusters on the number
of cluster stars and the chosen escape condition.
  We find that star clusters in external tidal fields exhibit a scaling problem
in the sense that their lifetimes do not scale with the relaxation time.
Isolated clusters show a similar problem if stars are removed only after their
distance to the cluster centre exceeds a certain cut-off radius. If stars are
removed immediately after their energy exceeds the energy necessary for escape,
the scaling problem disappears.
  We show that some stars which gain the energy necessary for escape are
scattered to lower energies before they can leave the cluster. Since the
efficiency of this process decreases with increasing particle number, it causes
the lifetimes not to scale with the relaxation time. Analytic formulae are
derived for the scaling of the lifetimes in the different cases.


title: New Perspectives on Cooling Flows and Cluster Radio Sources

abstract:
  We discuss new results from the Chandra X-ray Observatory and XMM-Newton on
cluster cooling flows, emphasizing early results from our Chandra programs. We
find cooling rates reduced by factors of 5-10 compared to those from earlier
missions. Nevertheless, substantial amounts of keV gas appear to be cooling and
fueling star formation in central dominant cluster galaxies (CDGs). The
structure of the keV thermal gas is remarkably complex, particularly in regions
surrounding the the radio source and sites of star formation in CDGs. The radio
sources are displacing the thermal gas leaving cavities filled with radio
emission. The cavities are apparently supported against the local gas pressure
by magnetic fields and cosmic rays. In addition, radio-faint, ``ghost''
cavities are seen in some clusters. They may be relics of earlier radio
outbursts rising buoyantly in the intracluster medium. The radio sources may
reduce the mass deposition rates by mechanical heating, and by inducing
convective currents that move cool material outward.


title: The COMPTEL instrumental line background

abstract:
  The instrumental line background of the Compton telescope COMPTEL onboard the
Compton Gamma-Ray Observatory is due to the activation and/or decay of many
isotopes. The major components of this background can be attributed to eight
individual isotopes, namely 2D, 22Na, 24Na, 28Al, 40K, 52Mn, 57Ni, and 208Tl.
The identification of instrumental lines with specific isotopes is based on the
line energies as well as on the variation of the event rate with time,
cosmic-ray intensity, and deposited radiation dose during passages through the
South-Atlantic Anomaly. The characteristic variation of the event rate due to a
specific isotope depends on its life-time, orbital parameters such as the
altitude of the satellite above Earth, and the solar cycle. A detailed
understanding of the background contributions from instrumental lines is
crucial at MeV energies for measuring the cosmic diffuse gamma-ray background
and for observing gamma-ray line emission in the interstellar medium or from
supernovae and their remnants. Procedures to determine the event rate from each
background isotope are described, and their average activity in spacecraft
materials over the first seven years of the mission is estimated.


title: Fast Algorithms and Efficient Statistics: N-point Correlation Functions

abstract:
  We present here a new algorithm for the fast computation of N-point
correlation functions in large astronomical data sets. The algorithm is based
on kdtrees which are decorated with cached sufficient statistics thus allowing
for orders of magnitude speed-ups over the naive non-tree-based implementation
of correlation functions. We further discuss the use of controlled
approximations within the computation which allows for further acceleration. In
summary, our algorithm now makes it possible to compute exact, all-pairs,
measurements of the 2, 3 and 4-point correlation functions for cosmological
data sets like the Sloan Digital Sky Survey (SDSS; York et al. 2000) and the
next generation of Cosmic Microwave Background experiments (see Szapudi et al.
2000).


title: Dark Halo and Disk Galaxy Scaling Laws

abstract:
  I highlight recent progress in our understanding of the origin of disk galaxy
scaling laws in a hierarchically clustering universe. Numerical simulations of
galaxy formation in Cold Dark Matter (CDM) dominated universes indicate that
the slope and scatter of the I-band Tully-Fisher (TF) relation are well
reproduced in this model, although not, as proposed in recent work, because of
the cosmological equivalence between halo mass and circular velocity, but
rather as a result of the dynamical response of the halo to the assembly of the
luminous component of the galaxy. The zero-point of the TF relation is
determined mainly by the stellar mass-to-light ratio ($\Upsilon_I$) as well as
by the concentration ($c$) of the dark halo. For $c \sim 10$, as is typical of
halos formed in the ``concordance'' $\Lambda$CDM model, we find that this
requires $\Upsilon_I \sim 1.5$, in reasonable agreement with the mass-to-light
ratios expected of stellar populations with colors similar to those of TF
galaxies. This conclusion supersedes that of Navarro & Steinmetz (2000a,b), who
claimed the $\Lambda$CDM halos were too concentrated to be consistent with the
observed TF relation. The disagreement can be traced to inconsistencies in the
normalization of the power spectrum used in that work. Our new results show
that simulated disk galaxies in the $\Lambda$CDM scenario are not clearly
inconsistent with the observed I-band Tully-Fisher relation. On the other
hand,their angular momenta is much lower than observed. Accounting
simultaneously for the spin, size and luminosity of disk galaxies remains a
challenge for hierarchical models of galaxy formation.


title:
Feedback from Galaxy Formation: Production and Photodissociation of
  Primordial Molecular Hydrogen

abstract:
  We use one-dimensional radiative transfer simulations to study the evolution
of H_2 gas-phase (H^- catalyzed) formation and photo-dissociation regions in
the primordial universe. We find a new positive feedback mechanism capable of
producing shells of H_2 in the intergalactic medium, which are optically thick
in some Lyman-Werner bands. While these shells exist, this feedback effect is
important in reducing the H_2 dissociating background flux and the size of
photo-dissociation spheres around each luminous object. The maximum background
opacity of the IGM in the H_2 Lyman-Werner bands is \tau_{H_2} ~ 1-2 for a
relic molecular fraction x_{H_2}=2 x 10^{-6}, about 6 times greater than found
by Haiman, Abel & Rees. Therefore, the relic molecular hydrogen can decrease
the photo-dissociation rate by about an order of magnitude. The problem is
relevant to the formation of small primordial galaxies with masses M_{DM} <
10^8 M_\odot, that rely on molecular hydrogen cooling to collapse.
Alternatively, the universe may have remained dark for several hundred million
years after the birth of the first stars, until galaxies with virial
temperature T_{vir} > 10^4 K formed.


title:
Discriminating weak lensing from intrinsic spin correlations using the
  curl-gradient decomposition

abstract:
  The distortion field defined by the ellipticities of galaxy shapes projected
on the sky can be uniquely decomposed into a gradient and a curl component. If
the observed ellipticities are induced by weak gravitational lensing, then the
distortion field is curl free. Here we show that, in contrast, the distortion
field resulting from intrinsic spin alignments is not curl free. This provides
a powerful discriminant between lensing and intrinsic contributions to observed
ellipticity correlations. We also show how these contributions can be
disentangled statistically from the ellipticity correlations or computed
locally from circular integrals of the ellipticity field. This allows for an
unambiguous detection of intrinsic galaxy alignments in the data. When the
distortions are dominated by lensing, as occurs at high redshifts, the
decomposition provides a valuable tool for understanding properties of the
noise and systematic errors. These techniques can be applied equally well to
the polarization of the microwave background, where it can be used to separate
curl-free scalar perturbations from those produced by gravity waves or defects.


title: The Power Spectrum Dependence of Dark Matter Halo Concentrations

abstract:
  High-resolution N-body simulations are used to examine the power spectrum
dependence of the concentration of galaxy-sized dark matter halos. It is found
that dark halo concentrations depend on the amplitude of mass fluctuations as
well as on the ratio of power between small and virial mass scales. This
finding is consistent with the original results of Navarro, Frenk & White
(NFW), and allows their model to be extended to include power spectra
substantially different from Cold Dark Matter (CDM). In particular, the
single-parameter model presented here fits the concentration dependence on halo
mass for truncated power spectra, such as those expected in the warm dark
matter scenario, and predicts a stronger redshift dependence for the
concentration of CDM halos than proposed by NFW. The latter conclusion confirms
recent suggestions by Bullock et al., although this new modeling differs from
theirs in detail. These findings imply that observational limits on the
concentration, such as those provided by estimates of the dark matter content
within individual galaxies, may be used to constrain the amplitude of mass
fluctuations on galactic and subgalactic scales. The constraints on
$\Lambda$CDM models posed by the dark mass within the solar circle in the Milky
Way and by the zero-point of the Tully-Fisher relation are revisited, with the
result that neither dataset is clearly incompatible with the `concordance'
($\Omega_0=0.3$, $\Lambda_0=0.7$, $\sigma_8=0.9$) $\Lambda$CDM cosmogony. This
conclusion differs from that reached recently by Navarro & Steinmetz, a
disagreement that can be traced to inconsistencies in the normalization of the
$\Lambda$CDM power spectrum used in that work.


title: Recent results from the Tokyo axion helioscope experiment

abstract:
  We have searched for axions which could have been produced in the solar core
using an axion helioscope with a 2.3m-long 4T superconducting magnet. Axion
mass region up to m_a=0.26eV was newly explored by introducing
dispersion-matching gas. Preliminary analysis sets a limit on axion-photon
coupling constant to be less than (6.4--9.6)e-10 GeV^{-1} (95%CL) for this mass
region from the absence of the axion signal. This is more stringent than the
limit inferred from the solar age consideration and also more stringent than
the recent helioseismological bound.


title:
The determination of mass of stellar disks of galaxies from the
  kinematic data

abstract:
  Different ways of the determination of masses of galactic disks, based on the
kinematic data, are briefly discussed. The analysis of the rotation curves
which reach maximum inside of a disk, and N-body modeling, reproducing the
rotation curves and stellar velocity dispersion of real galaxies, enable to
conclude that the mass of a disk is usually significantly less than the total
mass of spherical components (bulge + dark halo) inside of optical borders of a
galaxy, although the exceptions also exist.


title:
New Evidence for the Unified Scheme of BL Lac Objects and Fri Radio
  Galaxies

abstract:
  In this paper, we collect radio and X-ray observations for most
Fanaroff-Riley I (FRI) radio galaxies in the Zirbel-Baum radio galaxy sample,
and investigate the distribution of the radio-to-X-ray effective spectral
index, $\alpha_{rx}$, to test the unified scheme of BL Lac objects and FRI
radio galaxies. It is found that the range of $\alpha_{rx}$ for FRI radio
galaxies is almost the same as that for BL Lac objects, that the distribution
of $\alpha_{rx}$ probably peaks at the same position as BL Lac objects, and
that the distribution of $\alpha_{rx}$ for FRIs is similar to that for BL Lac
objects. These suggest that there exist two subclasses of FRI radio galaxies:
one is HBL-like, and the other is LBL-like, corresponding to high-energy-peaked
(HBL) and low--energy-peaked (LBL) BL Lac objects, respectively. This result is
consistent with previous VLA observations, and supports the unified scheme of
BL Lac objects and FRI radio galaxies.


title: Shocked Molecular Gas in the Supernova Remnant HB 21

abstract:
  We report the discovery of the shocked molecular gas in the supernova remnant
HB 21. We derive the physical parameters of the shocked gas from CO J=1-0 and
J=2-1 line observations. We discuss the correlation of the shocked molecular
gas with the previously detected, shocked atomic gas and the associated
infrared emission.


title:
Discovery of a 9-s X-Ray Pulsar, AX J0049-732, in the Small Magellanic
  Cloud

abstract:
  We report the ASCA discovery of a new X-ray pulsar, AX J0049-732, in the
Small Magellanic Cloud (SMC). The pulse shape is sinusoidal with a barycentric
period of 9.1320 +/- 0.0004 s. The X-ray spectrum was fitted by an absorbed
power-law model with a photon index of ~0.6 and a column density of ~1.3e22
cm^-2. An unabsorbed flux in the 0.7-10.0 keV was estimated to be ~8e-13 erg
cm^-2 s^-1 corresponding to the X-ray luminosity of ~4e35 erg s^-1 at the SMC
distance of 62 kpc.


title: The Luminosity Function Of Field Galaxies And Its Evolution Since z=1

abstract:
  We present the B-band luminosity function and comoving space and luminosity
densities for a sample of 2779 I-band selected field galaxies based on
multi-color data from the CADIS survey. The sample is complete down to I_815 =
22 without correction and with completeness correction extends to I_815=23.0.
By means of a new multi-color analysis the objects are classified according to
their spectral energy distributions (SEDs) and their redshifts are determined
with typical errors of delta z <= 0.03. We have split our sample into four
redshift bins between z=0.1 and z=1.04 and into three SED bins E-Sa,Sa-Sc and
starbursting (emission line) galaxies. The evolution of the luminosity function
is clearly differential with SED. The normalization phi* of luminosity function
for the E-Sa galaxies decreases towards higher redshift, and we find evidence
that the comoving galaxy space density decreases with redshift as well. In
contrast, we find phi* and the comoving space density increasing with redshift
for the Sa-Sc galaxies. For the starburst galaxies we find a steepening of the
luminosity function at the faint end and their comoving space density increases
with redshift.


title: UVES-VLT Observations of the OIII Bowen Lines in RR Tel

abstract:
  The exceptional resolution of UVES has allowed the detection of weak spectral
features and the separation of components in blended lines. The intensities of
all of the OIII fluorescence lines produced by the O1, O3 and other channels,
including the 5592 Angstrom charge-exchange line, have been measured and their
ratios compared with models.


title: Magnetic tension and the geometry of the universe

abstract:
  The vector nature of magnetic fields and the geometrical interpretation of
gravity introduced by general relativity, guarantee a special coupling between
magnetism and spacetime curvature. This magneto-geometrical interaction
effectively transfers the tension properties of the field into the spacetime
fabric, triggering a variety of effects with profound implications. Given the
ubiquity of magnetic fields in the universe, these effects could prove
critical. We discuss the nature of the magneto-curvature coupling and
illustrate some of its potential implications for cosmology.


title: Neutralino Gamma-ray Signals from Accreting Halo Dark Matter

abstract:
  There is mounting evidence that a self-consistent model for particle cold
dark matter has to take into consideration spatial inhomogeneities on
sub-galactic scales seen, for instance, in high-resolution N-body simulations
of structure formation. Also in more idealized, analytic models, there appear
density enhancements in certain regions of the halo. We use the results from a
recent N-body simulation of the Milky Way halo and investigate the gamma-ray
flux which would be produced when a specific dark matter candidate, the
neutralino, annihilates in regions of enhanced density. The clumpiness found on
all scales in the simulation results in very strong gamma-ray signals which
seem to already rule out some regions of the supersymmetric parameter space,
and would be further probed by upcoming experiments, such as the GLAST
gamma-ray satellite. As an orthogonal model of structure formation, we also
consider Sikivie's simple infall model of dark matter which predicts that there
should exist continuous regions of enhanced density, caustic rings, in the dark
matter halo of the Milky Way. We find, however, that the gamma-ray signal from
caustic rings is generally too small to be detectable.


title: Why did Supernova 1054 shine at late times?

abstract:
  The Crab nebula is the remnant of supernova 1054 (SN 1054). The progenitor of
this supernova has, based on nucleosynthesis arguments, been modeled as an 8-10
solar mass star. Here we point out that the observations of the late light
curve of SN 1054, from the historical records, are not compatible with the
standard scenario, in which the late time emission is powered by the
radioactive decay of small amounts of Ni-56. Based on model calculations we
quantify this discrepancy. The rather large mass of Ni-56 needed to power the
late time emission, 0.06[-0.03,+0.02] solar masses, seems inconsistent with
abundances in the Crab nebula. The late light curve may well have been powered
by the pulsar, which would make SN 1054 unique in this respect. Alternatively,
the late light curve could have been powered by circumstellar interaction, in
accordance with scenarios in which 8-10 solar mass stars are progenitors to
`dense wind' supernovae.


title: M31's molecular arms at all scales to below 10pc

abstract:
  I present a unique data set for the study of molecular gas in galaxies: a
complete, high-resolution survey of the CO in M31 and additional local studies.
The fully sampled survey has an angular resolution of 23" FWHM and the
interferometric data attain the pc-scale with sub-arcsecond resolution. For the
first time it is now possible to study large and small scales in conjunction.
Thus we are able to derive the global structure and study the links down to the
individual cloud complexes and star formation regions.


title: The outer ejecta of Eta Carinae

abstract:
  The nebula around Eta Carinae consists of an inner bipolar structure,
historically called the Homunculus, and the outer ejecta consisting mainly of a
variety of knots of different sizes.They reach out to distances of up to 30"
or0.3pc from Eta Car. With high-resolution long-slit observations we mapped the
outer nebula in order to analyze the global expansion pattern and to model the
three dimensional structure of the ejecta. We find very different expansion
velocities for the knots of the outer ejecta. In some cases they reach up to
values as high as 2000km/s. Typical expansion velocities lie at considerably
lower values around 400-600km/s, i.e., they are comparable to the expansion
velocities found in the Homunculus. Remarkably, the expansion of the outer
ejecta reveals a bidirectional motion pattern, which is consistent with the
bipolar structure of the inner nebula. A general overview of the morphology and
kinematics of the outer ejecta is given and put into context with the structure
and kinematics of the inner part of the nebula, the Homunculus.


title: The X-ray emission of 3C 346 and its environment

abstract:
  We present a detailed spectral and spatial analysis of the X-ray properties
of the compact and unusual radio galaxy 3C 346, combining information from
ROSAT and ASCA. The dominant component of X-ray emission (~ 10^44 ergs/s in
each of the 0.5-3 keV and 2-10 keV bands) is unresolved and not heavily
absorbed (intrinsic N_H ~< 2 10^21 cm^-2), with evidence for variability of 32
+/- 13% over 18 months. We relate the X-ray emission to radio structures on
both milliarcsecond scales and the arcsecond scales which Chandra can resolve.
The absence of X-ray absorption, and the radio/optical/X-ray colors, when
combined with previous radio evidence that the source is a foreshortened FRII,
suggest that the radio jets are seen at an angle to the line of sight of about
30 degrees, intermediate between the radio-galaxy and quasar classes. Roughly a
third of the soft X-ray emission is from a cluster atmosphere, for which we
measure a temperature of 1.9 (+1.3, -0.7) keV, making this the second
low-redshift (z < 0.2) powerful radio galaxy, after Cygnus A, with a measured
cluster temperature. At a jet angle of ~ 30 degrees, all the radio structures
lie within the core radius of the cluster, for which the cooling time is
sufficiently long that there is no reason to expect the presence of a cooling
flow. The radio lobes of 3C 346 are roughly in pressure balance with the
external medium under the assumptions that the energy densities in the magnetic
field and radiating particles balance and that a source of excess pressure in
the radio lobes, commonly invoked in other radio galaxies, is absent here.


title: Mixing, Enhanced Helium and Blue Tails in Globular Clusters

abstract:
  We investigate the consequences of an increase in the envelope helium
abundance of pre-helium flash red giants in globular clusters. Comparing
predictions with the CM diagrams of a few crucial GC, one finds no evidence for
a substantial increase in the surface helium content of HB members of these
clusters, at least for objects in the RR Lyrae region or close to it. The
possibility that the most peculiar giants belong to the asymptotic giant branch
is discussed. The consequences of a delay in the helium flash are briefly
examined.


title: Associated HI in Absorbers at High Redshift

abstract:
  WSRT observations have provided a first inventory of the incidence of HI 21
cm line absorption associated with AGN at redshifts up to z=1.0. There is a
large range in line depths, from tau=0.44 to tau less than 0.001, and a
substantial variety of line profiles, from Gaussians of less than ten km/s to
more typically a few hundred km/s, as well as irregular and multi-peaked
absorption, sometimes spanning many hundreds of km/s. The chance to detect
appreciable HI absorption is greatest in the most compact radio sources, GPSs
and CSOs, where it can occur in circumnuclear ``disks'' or ``tori'', as well as
in gas enveloping jets and hot spots; inferred densities range at least between
10 per cubic cm and 10000 per cubic cm. But HI absorption occurs also in some
CSSs, perhaps associated with jet-cloud interaction regions, and in quasars
with a large optical reddening. VLBI observations at the unusual UHF
frequencies of redshifted HI 21 cm can give unique ``sight''lines into the
physics and evolution of young radio sources and their inner galactic medium.


title: Spiral waves in accretion discs - observations

abstract:
  I review the observational evidence for spiral structure in the accretion
discs of cataclysmic variables (CVs). Doppler tomography is ideally suited to
resolve and map such co-rotating patterns and allows a straightforward
comparison with theory. The dwarf nova IP Pegasi presents the best studied
case, carrying two spiral arms in a wide range of emission lines throughout its
outbursts. Both arms appear at the locations where tidally driven spiral waves
are expected, with the arm closest to the gas stream weaker in the lines
compared to the arm closest to the companion. Eclipse data indicates
sub-Keplerian velocities in the outer disc. The dramatic disc structure changes
in dwarf novae on timescales of days to weeks, provide unique opportunities for
our understanding of angular momentum transport and the role of density waves
on the structure of accretion discs.
  I present an extension to the Doppler tomography technique that relaxes one
of the basic assumptions of tomography, and is able to map modulated emission
sources. This extension allows us to fit anisotropic emission from, for
example, spiral shocks, the irradiated companion star and disc-stream
interaction sites.


title:
The Interstellar Medium of Star-forming Irregular Galaxies: The View
  with ISO

abstract:
  We present mid-infrared imaging and far-infrared (FIR) spectroscopy of 5 IBm
galaxies observed by ISO as part of our larger study of the inter- stellar
medium of galaxies. Most of the irregulars in our sample are very actively
forming stars. The mid-infrared imaging was in a band centered at 6.75 microns
that is dominated by polycyclic aromatic hydrocarbons (PAHs) and in a band
centered at 15 microns that is dominated by small dust grains. The spectroscopy
of 3 of the galaxies includes [CII]158 microns and [OI]63 microns, important
coolants of photodissociation regions (PDRs), and [OIII]88 microns and [NII]122
microns, which come from ionized gas. [OI]145 microns and [OIII]52 microns were
measured in one galaxy as well. These data are combined with PDR and HII region
models to deduce properties of the interstellar medium of these galaxies.


title: Deep Blazar Surveys

abstract:
  I address the need for deep blazar surveys by showing that our current
understanding of blazars is based on a relatively small number of intrinsically
luminous sources. I then review the on-going deeper surveys, addressing in
particular their limits and limitations. Finally, I present some preliminary
results on the evolutionary properties of faint blazars as derived from the
Deep X-ray Radio Blazar Survey (DXRBS).


title: The Deep X-ray Radio Blazar Survey (DXRBS). II. New Identifications

abstract:
  We have searched the archived, pointed ROSAT Position Sensitive Proportional
Counter data for blazars by correlating the WGACAT X-ray database with several
publicly available radio catalogs, restricting our candidate list to
serendipitous X-ray sources with a flat radio spectrum (alpha_r <= 0.70). This
makes up the Deep X-ray Radio Blazar Survey (DXRBS). Here we present new
identifications and spectra for 106 sources, including 86 radio-loud quasars,
11 BL Lacertae objects, and 9 narrow-line radio galaxies. Together with our
previously published objects and already known sources, our sample now contains
298 identified objects: 234 radio-loud quasars (181 flat-spectrum quasars: FSRQ
[alpha_r <= 0.50] and 53 steep-spectrum quasars: SSRQ), 36 BL Lacs, and 28
narrow-line radio galaxies. Redshift information is available for 96% of these.
Thus our selection technique is ~ 90% efficient at finding radio-loud quasars
and BL Lacs. Reaching 5 GHz radio fluxes ~ 50 mJy and 0.1-2.0 keV X-ray fluxes
a few x 10^-14 erg/cm^2/s, DXRBS is the faintest and largest flat-spectrum
radio sample with nearly complete (~ 85%) identification. We review the
properties of the DXRBS blazar sample, including redshift distribution and
coverage of the X-ray-radio power plane for quasars and BL Lacs. Additionally,
we touch upon the expanded multiwavelength view of blazars provided by DXRBS.
By sampling for the first time the faint end of the radio and X-ray luminosity
functions, this sample will allow us to investigate the blazar phenomenon and
the validity of unified schemes down to relatively low powers.


title: Mining the Blazar Sky

abstract:
  We present the results of our methods to "mine" the blazar sky, i.e., select
blazar candidates with very high efficiency. These are based on the
cross-correlation between public radio and X-ray catalogs and have resulted in
two surveys, the Deep X-ray Radio Blazar Survey (DXRBS) and the "Sedentary" BL
Lac survey. We show that data mining is vital to select sizeable, deep samples
of these rare active galactic nuclei and we touch upon the identification
problems which deeper surveys will face.


title: Ultraviolet Line Spectra of Metal-Poor Star-Forming Galaxies

abstract:
  We present synthetic ultraviolet spectra of metal-poor star-forming galaxies
which were calculated with the Starburst99 package. A new spectral library was
generated from HST observations of O stars in the Large and Small Magellanic
Clouds. The corresponding mean metallicity of the synthetic spectra is
approximately 1/4\Zs. The spectra have a resolution of 1\AA and cover the
spectral range 1200-1600\AA. A set of model spectra was calculated for a
standard initial mass function and star-formation history and is compared to
synthetic spectra at solar metallicity. We find that the spectral lines are
generally weaker at lower metallicity, as expected from the lower elemental
abundances. Stellar-wind lines, however, show a more complex behavior: the
metallicity dependence of the ionization balance can be important in trace
ions, like N$^{4+}$ and Si$^{3+}$. Therefore the strength of \nv and \siiv does
not scale monotonically with metallicity. We compare our new models to
ultraviolet spectra of NGC 5253 and \cB, two star-forming galaxies with 1/4
solar metallicity at low and high redshift, respectively. The new library
provides significantly better fits to the observations than earlier models
using the \Zs library. We discuss the potential of utilizing stellar
photospheric and wind lines to estimate the chemical composition of
star-forming galaxies. The new metal-poor synthetic spectra are available via
the Starburst99 website.


title: HI Emission and Absorption in the Southern Galactic Plane Survey

abstract:
  We present preliminary results from the Southern Galactic Plane Survey (SGPS)
Test Region and Parkes data. As part of the pilot project for the Southern
Galactic Plane Survey, observations of a Test Region (325.5 deg < l < 333.5
deg; -0.5 deg < b < 3.5 deg) were completed in December 1998. Single dish
observations of the full survey region (253 deg < l < 358 deg; |b| <1 deg) with
the Parkes Radio Telescope were completed in March 2000. We present a sample of
SGPS HI data with particular attention to the smallest and largest scale
structures seen in absorption and emission, respectively. On the large scale,
we detect many prominent HI shells. On the small scale, we note extremely
compact, cold clouds seen in HI self-absorption. We explore how these two
classes of objects probe opposite ends of the HI spatial power spectrum.


title: Super-Eddington Atmospheres that Don't Blow Away

abstract:
  We show that magnetized, radiation dominated atmospheres can support steady
state patterns of density inhomogeneity that enable them to radiate at far
above the Eddington limit, without suffering mass loss. The inhomogeneities
consist of periodic shock fronts bounding narrow, high-density regions,
interspersed with much broader regions of low density. The radiation flux
avoids the regions of high density, which are therefore weighed down by
gravity, while gas in the low-density regions is slammed upward into the shock
fronts by radiation force. As the wave pattern moves through the atmosphere,
each parcel of matter alternately experiences upward and downward forces, which
balance on average. Magnetic tension shares the competing forces between
regions of different densities, preventing the atmosphere from blowing apart.
We calculate the density structure and phase speed of the wave pattern, and
relate these to the wavelength, the density contrast, and the factor by which
the net radiation flux exceeds the Eddington limit. In principle, this factor
can be as large as the ratio of magnetic pressure to mean gas pressure, or the
ratio of radiation pressure to gas pressure, whichever is smaller. Although the
magnetic pressure must be large compared to the mean gas pressure in order to
support a large density contrast, it need not be large compared to the
radiation pressure. These highly inhomogeneous flows could represent the
nonlinear development of the "photon bubble" instability discovered by Gammie.
We briefly discuss the applicability of these solutions to astrophysical
systems.


title: The New Paradigm: Novel, Virtual Observatory Enabled Science

abstract:
  A virtual observatory will not only enhance many current scientific
investigations, but it will also enable entirely new scientific explorations
due to both the federation of vast amounts of multiwavelength data and the new
archival services which will, as a necessity, be developed. The detailing of
specific science use cases is important in order to properly facilitate the
development of the necessary infrastructure of a virtual observatory. The
understanding of high velocity clouds is presented as an example science use
case, demonstrating the future synergy between the data (either catalog or
images), and the desired analysis in the new paradigm of a virtual observatory.


title: Plerions and pulsar-powered nebulae

abstract:
  In this brief review, I discuss recent developments in the study of
pulsar-powered nebulae ("plerions"). The large volume of data which has been
acquired in recent years reveals a diverse range of observational properties,
demonstrating how differing environmental and pulsar properties manifest
themselves in the resulting nebulae.


title: Starbursts in multiple galaxy mergers

abstract:
  We numerically investigate stellar and gaseous dynamical evolution of mergers
between five identical late-type disk galaxies with the special emphasis on
star formation history and chemical evolution of multiple galaxy mergers. We
found that multiple encounter and merging can trigger repetitive massive
starbursts (typically $\sim$ 100 $M_{\odot}$ ${\rm yr}^{-1}$) owing to the
strong tidal disturbance and the resultant gaseous dissipation during merging.
The magnitude of the starburst is found to depend on initial virial ratio
(i.e., the ratio of total kinematical energy to total potential energy) such
that the maximum star formation rate is larger for the merger with smaller
virial ratio. Furthermore we found that the time interval between the epochs of
the triggered starbursts is longer for the merger with the larger virial ratio.
The remnant of a multiple galaxy merger with massive starbursts is found to
have metal-poor gaseous halo that is formed by tidal stripping during the
merging. We accordingly suggest that metal-poor gaseous halo in a field
elliptical galaxy is a fossil record of the past multiple merging events for
the galaxy.


title: Ultra-Relativistic Blast Wave: Stability and Strong Non-Universality

abstract:
  Linear eigenmodes of a spherically symmetrical ultra-relativistic blast wave
(the Blandford-McKee, BMK, solution) are calculated. The BMK solution is shown
to be stable and strongly non-universal. It is stable because all the
eigenmodes decay. Non-universality of the BMK solution (BMK is not an
intermediate asymptotic) is a consequence of causality. In terms of eigenmodes
-- some eigenmodes decay too slowly. For each degree l, there exists an
eigenmode which decays at the smallest rate. The amplitude of this eigenmode,
defined as relative perturbation of energy behind the shock front, is constant
at early time. Later, when the blast wave slows down to Gamma = l/10, an
oscillatory decay commences, and the amplitude drops to less than 10% of the
initial value at Gamma = l/100. The non-universality is surprisingly strong.
Near the end of the ultra-relativistic stage, perturbations with l<200, that is
more than 10,000 different harmonics, are suppressed by less than a factor of
10. Spherical symmetry is only reached by the time the blast wave slows down to
non-relativistic velocities, when the Sedov/Taylor/von Neumann solution sets
in.


title:
Photometric evolution of dusty starburst mergers:On the nature of
  ultra-luminous infrared galaxies

abstract:
  By performing N-body simulations of chemodynamical evolution of galaxies with
dusty starbursts, we investigate photometric evolution of gas-rich major
mergers in order to explore the nature of ultraluminous infrared galaxies
(ULIRGs) with the total infrared luminosity ($L_{\rm IR}$ for $8\sim 1000$
$\mu$m) of $\sim$ $10^{12}$ $L_{\odot}$. Main results are the following three.
(1) Global colors and absolute magnitudes the during dusty starburst of a major
merger do not change with time significantly, because interstellar dust heavily
obscures young starburst populations that could cause rapid evolution of
photometric properties of the merger. (2) Dust extinction of stellar
populations in a galaxy merger with large infrared luminosity ($L_{\rm IR}$ $>$
$10^{11}$ $L_{\odot}$) is selective in the sense that younger stellar
populations are preferentially obscured by dust than old ones. This is because
younger populations are located in the central region where a larger amount of
dusty interstellar gas can be transferred from the outer gas-rich regions of
the merger. (3) Both $L_{\rm IR}$ and the ratio of $L_{\rm IR}$ to $B$ band
luminosity $(L_{\rm B}$) increases as the star formation rate increase during
the starburst of the present merger model, resulting in the positive
correlation between $L_{\rm IR}$ and $L_{\rm IR}/L_{\rm B}$.


title: Formation and evolution of E+A galaxies in dusty starburst galaxies

abstract:
  The formation and evolution of the ``E+A'' (also named ``k+a'' and ``a+k''
types by Dressler et al. 1999) galaxies found in significant numbers in the
cores of intermediate redshift clusters has been extensively discussed by many
authors. In this paper, we model the spectral, dynamical and morphological
evolution of a prime candidate for producing this spectral signature: a dusty
starburst associated with a major galaxy merger. We show that as this system
evolves dynamically, its spectral type changes from and ``e(a)'' type
(exhibiting strong H$\delta$ absorption and modest [OII] emission -- the
identifying features of local dusty starburst galaxies) to a k+a type and then
finally to a passive ``k'' type. This result shows that galaxies with an e(a)
spectral type can be precursors to the k+a systems and that dynamical evolution
greatly controls the spectral evolution in these merger cases. Our simulations
also show that a merger with very high infrared luminosity ($L_{\rm IR}$ $>$
$10^{11}$ $L_{\odot}$) is more likely to show an e(a) spectrum, which implies
that spectral types can be correlated with infrared fluxes in dusty starburst
galaxies. Based on these results, we discuss the origin of the evolution of
k+a/a+k galaxies in distant clusters and the role merging is likely to have.


title:
Merging between a Central Massive Black Hole and a Compact Stellar
  System: A Clue to the Origin of M31'S Nucleus

abstract:
  The central bulge of M31 is observed to have two distinct brightness peaks
with the separation of $\sim$ 2 pc. Tremaine (1995) recently proposed a new
idea that the M31's nucleus is actually a single thick eccentric disk
surrounding the central super-massive black hole. In order to explore the
origin of the proposed eccentric disk, we numerically investigate the dynamical
evolution of a merger between a central massive black hole with the mass of
$\sim$ $10^7$ $M_{\odot}$ and a compact stellar system with the mass of $\sim$
$10^6$ $M_{\odot}$ and the size of a few pc in the central 10 pc of a galactic
bulge. We found that the stellar system is destroyed by strong tidal field of
the massive black hole and consequently forms a rotating nuclear thick stellar
disk. The orbit of each stellar component in the developed disk is rather
eccentric with the mean eccentricity of $\sim$ 0.5. These results imply that
the M31's nuclear eccentric disk proposed by Tremaine (1995) can be formed by
merging between a central massive black hole and a compact stellar system. We
furthermore discuss when and how a compact stellar system is transferred into
the nuclear region around a massive black hole.


title: The deceleration of Giant Herbig-Haro Flows

abstract:
  It has been recently discovered that spatially separated Herbig-Haro objects,
once considered unrelated, are linked within a chain that may extend for
parsecs in either direction of the embedded protostar forming a "giant
Herbig-Haro jet". Presently, several dozen of these giant flows have been
detected and the best documented example, the HH~34 system, shows a systematic
velocity decrease with distance on either side of the source. In this paper, we
have modeled giant jets by performing fully three-dimensional simulations of
overdense, radiatively cooling jets modulated with long-period
  (P $\sim$ several hundred years) and large amplitude sinusoidal velocity
variability at injection ($\Delta v \sim$ mean jet flow velocity). Allowing
them to travel over a distance well beyond the source, we have found that
multiple travelling pulses develop and their velocity indeed falls off smoothly
and systematically with distance. This deceleration is fastest if the jet is
pressure-confined, in which case the falloff in velocity is roughly consistent
with the observations. The deceleration occurs as momentum is transferred by
gas expelled sideways from the traveling pulses. The simulation of a
pressure-confined, steady-state jet with similar initial conditions to those of
the pulsed jet shows that the flow in this case experiences $acceleration$.
This result is thus an additional indication that the primary source of
deceleration in the giant flows $cannot$ be attributed to braking of the jet
head against the external medium.


title: Detailed abundance analysis of 8 super-metal-rich star candidates

abstract:
  We provide detailed abundance analyses of 8 candidate super-metal-rich stars.
Five of them are confirmed to have [Fe/H] > 0.2 dex, the generally-accepted
limit for super-metal-richness. Furthermore, we derive abundances of several
elements and find that the stars follow trends seen in previous studies of
metal-rich stars. Ages are estimated from isochrones and velocities calculated.
We find that there do exist very metal-rich stars that are older than 10 Gyr.
This is contrary to what is found in several recent studies of the galactic
age-metallicity relation. This is tentative evidence that there might not exist
a one-to-one relation between age and metallicity for all stars. This is not
surprising considering the current models of the independent evolution of the
different galactic components. We also find that one star, HD 182572, could
with ~ 75 % chance be a thick disk star with, for the thick disk, an extremely
high metallicity at 0.34 dex. This star is, intriguingly, also somewhat
enhanced in the alpha-elements.


title:
Size determination of the Centaur Chariklo from millimeter-wavelength
  bolometer observations

abstract:
  Using the Max-Planck Millimeter Bolometer Array (MAMBO) at the IRAM 30m
telescope we detected emission at 250 GHz from the Centaur Chariklo (1997
CU26). The observed continuum flux density implies a photometric diameter of
273 km. The resulting geometric albedo is 0.055, somewhat higher than expected
from a comparison with most of the other few Centaurs and cometary nuclei for
which such data are available.


title:
Comparison of the H-alpha circumstellar disks in Be/X-ray binaries and
  Be stars

abstract:
  We present a comparative study of the circumstellar disks in Be/X-ray
binaries and isolated Be stars based upon the H-alpha emission line. From this
comparison it follows that the overall structure of the disks in the Be/X-ray
binaries is similar to the disks of other Be stars, i.e. they are axisymmetric
and rotationally supported. The factors for the line broadening (rotation and
temperature) in the disks of the Be stars and the Be/X-ray binaries seem to be
identical.
  However, we do detect some intriguing differences between the envelopes. On
average, the circumstellar disks of the Be/X-ray binaries are twice as dense as
the disks of the isolated Be stars. The different distribution of the Be/X-ray
binaries and the Be stars seen in the full width at half maximum (FWHM) versus
peak separation diagram indicates that the disks in Be/X-ray binaries have on
average a smaller size, probably truncated by the compact object.


title: Stellar spectroscopy far beyond the Local Group

abstract:
  Multi-object spectroscopic observations of blue supergiants in NGC 3621, a
spiral galaxy at a distance of 6.7 Mpc, carried out with the ESO VLT and FORS
are presented. We demonstrate the feasibility of quantitative stellar
spectroscopy at distances approaching a ten-fold increase over previous
investigations by determining chemical composition, stellar parameters,
reddening, extinction and wind properties of one of our targets, a supergiant
of spectral type A1 Ia located in the outskirts of NGC 3621. The metallicity
(determined from iron group elements) is reduced by a factor of two relative to
the sun in qualitative agreement with results from previous abundance studies
based on H II region oxygen emission lines. Reddening and extinction are E(B-V)
= 0.12 and Av = 0.37, respectively, mostly caused by the galactic foreground.
Comparing stellar wind momentum and absolute V magnitude with galactic and M31
counterparts we confirm the potential of the wind momentum-luminosity
relationship as an alternative tool to estimate extragalactic distances.


title:
VLA and MERLIN monitoring observations of the gravitational lens system
  B1030+074

abstract:
  We present VLA and MERLIN monitoring data of the JVAS gravitational lens
system B1030+074. The system was monitored with the VLA from February 1998 to
October 1998 at 8.4-GHz during which the VLA was at its A, BnA and B
configuration. The 47 epochs of observations have an average spacing of
approximately 5 days. Ten MERLIN snapshots were obtained in the L-band (1.7
GHz) during the months of April, May and June 1998. Preliminary light curves of
the two components of the lens system obtained from the VLA data indicate that
during the period of the monitoring the A flux density showed a steady
decrease. No changes are observed in the B light curve.


title: Current Problems for X-ray Emission from Radio Jets

abstract:
  A list is presented of known extragalactic radio jets which also have
associated X-ray emission. The canonical emission processes for the production
of X-rays are reviewed and the sources are categorized on the basis of our
current understanding. Although it seems clear that the X-ray emission is
non-thermal, the two competing processes, synchrotron and inverse Compton
emissions, arise from extremely high energy (synchrotron) or extremely low
energy (beaming models with IC emission), relativistic electrons. Only
synchrotron self-Compton emission from a few hotspots provides information on
the `normal' energy range of the electrons responsible for the observed radio
emission.