title: Maximum Feedback and Dark Matter Profiles of Dwarf Galaxies

abstract:
  The observed rotation curves of dark matter-dominated dwarf galaxies indicate
low density cores, contrary to the predictions of CDM models. A possible
solution of this problem involves stellar feedback. A strong baryonic wind
driven by vigorous star formation can remove a large fraction of the gas,
causing the dark matter to expand. We explore the maximum effect of the
feedback with an instantaneous removal of the gaseous disk. The energy input
depends on the compactness of the disk, hence the specific angular momentum of
the disk. For the plausible cosmological parameters and a large range of the
disk angular momentum, the feedback is insufficient to destroy the central halo
cusp, while the inner density is lowered only by a modest factor of 2 to 6. Any
realistic modeling of the feedback would have even lesser impact on dark
matter. We find that no star formation effect can resolve the problems of CDM
cusps.


title: X-Ray Observations on the Galactic Center Region

abstract:
  This paper reports on the early Chandra view of the Galactic center (GC)
activities. The massive black hole Sgr A* is extremely faint, while more bright
diffuse X-ray emission is prevailing in the circumnuclear disk. Another high
temperature plasma is found in the Sgr A East shell. This may indicate that Sgr
A East is a supernova remnant, although no clear X-ray shell is found. A hint
of non-thermal X-ray filaments is found, suggesting the presence of an
acceleration site of extremely high-energy cosmic rays. The giant molecular
cloud Sgr B2 is established to be an X-ray reflection nebula, possibly arising
from the past Sgr A activities. Chandra further discovered high temperature
shells, suggesting multiple supernova explosions near the GC region.


title: Sub-parsec to Mega-parsec jet emission and power

abstract:
  Relativistic jets carry a significant fraction of the total energy budget of
a radio source, rivaling the power that is extracted through accretion. A minor
part of this bulk kinetic power is transformed to radiation, possibly through
internal shocks if the plasma is accelerated, at the base of the jet, to a
velocity which changes in time. In this way we can understand why some
radiation is produced all along the jet even if most of it originates at a
preferred location, and why the efficiency of conversion of bulk to random
energy is small. The recent observations by Chandra of intense jet X-ray
emission at large scales suggest that at least the "spine" of jets continues to
be highly relativistics even up to hundreds of kiloparsecs away from the
nucleus and give tight lower limits on the jet bulk kinetic power.


title:
Long-term Multi-wavelength Observations of GRS 1758-258 and the ADAF
  Model

abstract:
  We present a long-term multi-wavelength light curve of Galactic black hole
candidate GRS 1758-258 by combining previously published and archival data from
GRANAT, ROSAT, CGRO, RXTE, SAX, ASCA, EXOSAT, and the VLA. In addition we
include first spectral results from the balloon-borne Gamma-ray Arcminute
Telescope Imaging System (GRATIS). In light of divergent analyses of the
1991-1993 ROSAT observations, we have re-analyzed these data; we find the soft
X-rays track the hard X-rays, and that the fits require no black-body
component-- indicating that GRS 1758-258 did not go to the high state in 1993.
We offer an interpretation based on the ADAF model for a system with mdot
\ltsim mdot_crit. We find the 1990-1993 coeval hard and soft X-ray observations
support the ADAF predictions. We discuss a new way to constrain black-hole mass
with spectral data and the ADAF theory, and apply this technique to GRS
1758-258 to find M_1 \gtsim 8--9 M_sol at an assumed distance of 8.5 kpc.
Further investigations of the ADAF model allow us to evaluate the model
critically against the data and flux-flux diagram of Barret, McClintock &
Grindlay (1996) and to understand the limits of the latter's ``X-ray burster
box.''


title: Monitoring Variability of the Sky

abstract:
  Variability in the sky has been known for centuries, even millennia, but our
knowledge of it is very incomplete even at the bright end. Current technology
makes it possible to built small, robotic optical instruments, to record images
and to process data in real time, and to archive them on-line, all at a low
cost. In addition to obtaining complete catalogs of all kinds of variable
objects, spectacular discoveries can be made, like the optical flash associated
with GRB 990123 and a planetary transit in front of HD 209458. While prototypes
of such robotic instruments have been in operation for several years, it is not
possible to purchase a complete system at this time. I expect (hope) that
complete systems will become available `off the shelf' in the near future, as
monitoring bright sky for variability has a great scientific, educational and
public outreach potential.


title:
Supernova SN1987A Bound on Neutrino Spectra for R-Process
  Nucleosynthesis

abstract:
  The neutrino driven wind during a core collapse supernova is an attractive
site for r-process nucleosynthesis. The electron fraction $Y_e$ in the wind
depends on observable neutrino energies and luminosities. The mean antineutrino
energy is limited by supernova SN1987A data while lepton number conservation
constrains the ratio of antineutrino to neutrino luminosities. If $Y_e$, in the
wind, is to be suitable for rapid neutron capture nucleosynthesis, then the
mean electron neutrino energy may be significantly lower then that predicted in
present supernova simulations, or there may be new neutrino physics such as
oscillations to sterile neutrinos.


title: Chandra Observations of NGC 4636 - An Elliptical Galaxy in Turmoil

abstract:
  Chandra images show symmetric, 8 kpc long, arm-like features in the X-ray
halo surrounding NGC 4636. The leading edges of these features are sharp and
are accompanied by temperature increases of ~30%. These properties, along with
their scale and symmetry, suggest that the arm-like structures are produced by
nuclear outburst driven shocks. We interpret these observations as part of a
cycle in which cooling gas originally fueled a nuclear outburst about 3 X
10^{6} years ago leading to shocks that reheat the cooling gas, thus preventing
the accumulation of significant amounts of cooled gas in the galaxy center and
temporarily starving the central AGN.


title:
Toward a National Virtual Observatory: Science Goals, Technical
  Challanges, and Implementation Plan

abstract:
  The National Academy of Science Astronomy and Astrophysics Survey Committee,
in its new Decadal survey entitled Astronomy and Astrophysics in the New
Millennium, recommends, as a first priority, the establishment of a National
Virtual Observatory. The NVO would link the archival data sets of space- and
ground-based observatories, the catalogs of multi-wavelength surveys, and the
computational resources necessary to support comparison and cross-correlation
among these resources. This White Paper describes the scientific opportunities
and technical challenges of an NVO, and lays out an implementation strategy
aimed at realizing the goals of the NVO in cost-effective manner. The NVO will
depend on inter-agency cooperation, distributed development, and distributed
operations. It will challenge the astronomical community, yet provide new
opportunities for scientific discovery that were unimaginable just a few years
ago.


title: Constraints on Galaxy Formation from Stars in the Far Outer Disk of M31

abstract:
  Numerical simulations of galaxy formation within the cold dark matter (CDM)
hierarchical clustering framework are unable to produce large disk galaxies
without invoking some form of feedback to suppress gas cooling and collapse to
a redshift of unity or below. An important observational consequence of
delaying the epoch of disk formation until relatively recent times is that the
stellar populations in the extended disk should of be predominantly
young-to-intermediate age. We use a deep HST/WFPC2 archival pointing to
investigate the mean age and metallicity of the stellar population in a
disk-dominated field at 30 kpc along the major axis of M31. Our analysis of the
color-magnitude-diagram reveals the dominant population to have significant
mean age (>~8 Gyr) and a moderately-high mean metallicity ([Fe/H]~-0.7);
tentative evidence is also presented for a trace population of ancient (>10
Gyr) metal-poor stars. These characteristics are unexpected in CDM models and
we discuss the possible implications of this result, as well as alternative
interpretations.


title:
Was the Cosmic Web of Protogalactic Material Permeated by Lobes of Radio
  Galaxies During the Quasar Era?

abstract:
  Evidence for extended active lifetimes (> 10^8 yr) for radio galaxies implies
that many large radio lobes were produced during the `quasar era', 1.5 < z < 3,
when the comoving density of radio sources was 2 -- 3 dex higher than the
present level. However, inverse Compton losses against the intense microwave
background substantially reduce the ages and numbers of sources that are
detected in flux-limited surveys. The realization that the galaxy forming
material in those epochs was concentrated in filaments occupying a small
fraction of the total volume then leads to the conclusion that radio lobes
permeated much of the volume occupied by the protogalactic material during that
era. The sustained overpressure in these extended lobes is likely to have
played an important role in triggering the high inferred rate of galaxy
formation at z > 1.5 and in the magnetization of the cosmic network of
filaments.


title:
Consequences on some dark energy-candidates from the type Ia supernova
  SN 1997ff

abstract:
  We examine the status of various dark energy-models in light of the recently
observed SN 1997ff at z \approx 1.7. The modified data still fit a pure
cosmological constant \Lambda or a quintessence with an equation of state
similar to that of \Lambda. The kinematical \Lambda-models, \Lambda\sim S^{-2}
and \Lambda\sim H^2, also fit the data reasonably well and require less dark
energy density than is required by the constant \Lambda-model. However, the
model \Lambda\sim S^{-2} with low energy density becomes unphysical as it
cannot accommodate higher redshift objects. We also examine an alternative
explanation of the data, viz., the absorption by the intervening whisker-like
dust and find that the quasi-steady state model and the FRW model \Omega_{\rm
m0}=0.33, {\it without any dark energy} also fit the data reasonably well. We
notice that the addition of SN 1997ff to the old data has worsened the fit to
most of the models, except a closed FRW model with a constant \Lambda and a
closed quintessence-model with \omega_\phi=-0.82, and the models have started
departing from each other as we go above z=1. However, to make a clear
discrimination possible, a few more supernovae with z>1 are required. We have
also calculated the age of the universe in these models and find that, in the
models with a constant \Lambda, the expansion age is uncomfortably close to the
age of the globular clusters. Quintessence-models show even lower age. The
kinematical \Lambda-models are, however, interesting in this connection
(especially the model \Lambda\sim H^2), which give remarkably large age of the
universe.


title: Heavy Element Diffusion in Metal Poor Stars

abstract:
  Stellar evolution models which include the effect of helium and heavy element
diffusion have been calculated for initial iron abundances of [Fe/H] = -2.3,
-2.1, -1.9 and -1.7. These models were calculated for a large variety of masses
and three separate mixing lengths, \alpha = 1.50, 1.75 and 2.00 (with \alpha =
1.75 being the solar calibrated mixing length). The change in the surface iron
abundance for stars of different masses was determined for the ages 11, 13 and
15 Gyr. Iron settles out of the surface convection zone on the main sequence;
this iron is dredged back up when the convection zone deepens on the giant
branch. In all cases, the surface [Fe/H] abundance in the turn-off stars was at
least 0.28 dex lower than the surface [Fe/H] abundance in giant-branch stars of
the same age. However, recent high dispersion spectra of stars in the globular
cluster NGC 6397 found that the turn-off and giant branch stars had identical
(within a few percent) iron abundances of [Fe/H] =-2.03 (Gratton et al. 2001).
These observations prove that heavy element diffusion must be inhibited in the
surface layers of metal-poor stars. When diffusion is inhibited in the outer
layers of a stellar model, the predicted temperatures of the models are similar
to models evolved without diffusion, while the predicted lifetimes are similar
to stars in which diffusion is not inhibited. Isochrones constructed from the
models in which diffusion is inhibited fall half-way between isochrones without
diffusion, and isochrones with full diffusion. As a result, absolute globular
cluster ages which are based upon the absolute magnitude of the turn-off are 4%
larger than ages inferred from full diffusion isochrones, and 4% smaller than
ages inferred from no diffusion isochrones.


title: Chandra localization of KS1731--260

abstract:
  We present the analysis of the Chandra image of KS 1731-260. The improvement
of the source localization (down to ~0.6'') allowed us to rule out 12 of 13
infrared companion candidates proposed by Barret et al. (1998). The remaining
possible infrared counterpart of KS 1731-260 (angular distance between sources
~1.45'', or ~2\sigma) has the brightness m_{J}~16 in the J band. If this star
is really the counterpart of KS 1731-260, the lower limit on its luminosity is
L_{tot}>L_{J,H}~10L_{\odot}. The strong drop of the X-ray flux from the source
allow us to propose the additional check of whether the decribed star is the
real counterpart of KS1731-260. If the optical and infrared brightness of the
binary system is partially caused by the reprocessing of X-rays, as it is usual
for the low mass binary systems, the infrared brightness of real counterpart
should strongly reduce in 2001, when the X-ray flux from KS1731-260 turned off
(Wijnands et al. 2001)


title:
DDO Photometry of M71: Carbon and Nitrogen Patterns Among Evolving
  Giants

abstract:
  We present V, B-V, and DDO C(41-42) and C(42-45) photometry for a sample of
75 red giants down to M_V = +2 in the relatively metal-rich Galactic globular
cluster M71. The C(41-42) colors reveal a bimodal distribution of CN band
strengths generally anticorrelated with CH band strength as measured by the
C(42-45) color. Both DDO colors agree well with those found in 47 Tucanae -- a
nearby globular cluster of similar metallicity -- and suggest nearly identical
C and N abundance patterns among the giants of both clusters. A comparison with
synthetic DDO colors demonstrates that little change in surface C or N
abundance is required to match the colors of the M71 giants over the entire
luminosity range observed. Apparently like 47 Tuc (a cluster of much greater
mass and central concentration), M71 exhibits an abundance pattern which cannot
be solely the result of internal mixing.


title:
Coupled spheroid and black-hole formation, and the multifrequency
  detectability of active galactic nuclei and submillimetre sources

abstract:
  We use a simple model of spheroid formation to explore the relationship
between the creation of stars and dust in a massive proto galaxy and the growth
of its central black hole. This model predicts that sub-mm luminosity peaks
after only ~ 0.2 Gyr. However, without a very massive seed black hole,
Eddington-limited growth means that a black hole mass of 10^9 solar masses, and
hence very luminous AGN activity, cannot be produced until > 0.5 Gyr after the
formation of the first massive stars in the halo. The model thus predicts a
time-lag between the peak of sub-mm luminosity and AGN luminosity in a massive
proto-elliptical of a few times 10^8 years. For a formation redshift z = 5,
this means that powerful AGN activity is delayed until z = 3.5, by which time
star formation in the host is 90% complete, and sub-mm luminosity has declined
to ~ 25% of its peak value. This provides a natural explanation for why
successful sub-mm detections of luminous radio galaxies are largely confined to
z > 2.5. Conversely the model also predicts that while all high-redshift
luminous sub-mm-selected sources should contain an active (and growing) black
hole, the typical luminosity of the AGN in such objects is ~1000 times smaller
than that of the most powerful AGN. This is consistent with the almost complete
failure to detect sub-mm selected galaxies with existing X-ray surveys. Finally
the model yields a black-hole:spheroid mass ratio which evolves rapidly in the
first Gyr, but asymptotes to ~ 0.001-0.003 in agreement with results at low
redshift. This ratio arises not because the AGN terminates star formation, but
because fueling of the massive black hole is linked to the total mass of gas
available for star formation in the host.


title: Density Variations over Subparsec Scales in Diffuse Molecular Gas

abstract:
  We present high-resolution observations of interstellar CN, CH, CH^{+},
\ion{Ca}{1}, and \ion{Ca}{2} absorption lines toward the multiple star systems
HD206267 and HD217035. Substantial variations in CN absorption are observed
among three sight lines of HD206267, which are separated by distances of order
10,000 AU; smaller differences are seen for CH, CH^{+}, and \ion{Ca}{1}. Gas
densities for individual velocity components are inferred from a chemical
model, independent of assumptions about cloud shape. While the component
densities can differ by factors of 5.0 between adjacent sightlines, the
densities are always less than 5000 cm^{-3}. Calculations show that the derived
density contrasts are not sensitive to the temperature or reaction rates used
in the chemical model. A large difference in the CH^{+} profiles (a factor of 2
in column density) is seen in the lower density gas toward HD217035.


title:
Polarimetric variations of binary stars. II. Numerical simulations for
  circular and eccentric binaries in Mie scattering envelopes

abstract:
  We present numerical simulations of the periodic polarimetric variations
produced by a binary star placed at the center of an empty spherical cavity
inside a circumbinary ellipsoidal and optically thin envelope made of dust
grains. Mie single-scattering is considered along with pre- and post-scattering
extinction factors which produce a time-varying optical depth and affect the
morphology of the periodic variations. We are interested in the effects that
various parameters will have on the average polarization, the amplitude of the
polarimetric variations, and the morphology of the variability. We show that
the absolute amplitudes of the variations are smaller for Mie scattering than
for Thomson scattering. Among the four grain types that we have studied, the
highest polarizations are produced by grains with sizes in the range 0.1-0.2
micron. In general, the variations are seen twice per orbit. In some cases,
because spherical dust grains have an asymmetric scattering function, the
polarimetric curves produced also show variations seen once per orbit.
Circumstellar disks produce polarimetric variations of greater amplitude than
circumbinary envelopes.
  Another goal of these simulations is to see if the 1978 BME (Brown, McLean, &
Emslie, ApJ, 68, 415) formalism, which uses a Fourier analysis of the
polarimetric variations to find the orbital inclination for Thomson-scattering
envelopes, can still be used for Mie scattering. We find that this is the case,
if the amplitude of the variations is sufficient and the true inclinations is
i_true > 45 deg. For eccentric orbits, the first-order coefficients of the
Fourier fit, instead of second-order ones, can be used to find almost all
inclinations.


title:
Crustal Emission and the Quiescent Spectrum of the Neutron Star in KS
  1731-260

abstract:
  (Abridged). The type-I X-ray bursting low mass X-ray binary KS 1731-260 was
recently detected for the first time in quiescence by Wijnands et al.,
following an approximately 13 yr outburst which ended in Feb 2001. Unlike all
other known transient neutron stars, the duration of this recent outburst is as
long as the thermal diffusion time of the crust. The large amount of heat
deposited by reactions in the crust will have heated the crust to temperatures
much higher than the equilibrium core temperature. As a result, the thermal
luminosity currently observed from the neutron star is dominated not by the
core, but by the crust. Moreover, the level and the time evolution of quiescent
luminosity is determined mostly by the amount of heat deposited in the crust
during the most recent outburst. Using estimates of the outburst mass accretion
rate, our calculations of the quiescent flux immediately following the end of
the outburst agree with the observed quiescent flux to within a factor of a
few. We present simulations of the evolution of the quiescent lightcurve for
different scenarios of the crust microphysics, and demonstrate that monitoring
observations (with currently flying instruments) spanning from 1--30 yr can
measure the crust cooling timescale and the total amount of heat stored in the
crust. These quantities have not been directly measured for any neutron star.


title:
A Shock-Induced Pair of Superbubbles in the High-Redshift Powerful Radio
  Galaxy MRC 0406-244

abstract:
  We present new optical spectroscopy of the high-redshift powerful radio
galaxy MRC 0406$-$244 at redshift of 2.429. We find that the two extensions
toward NW and SE probed in the rest-frame ultraviolet image are heated mainly
by the nonthermal continuum of the active galactic nucleus. However, each
extension shows a shell-like morphology, suggesting that they are a pair of
superbubbles induced by the superwind activity rather than by the interaction
between the radio jet and the ambient gas clouds. If this is the case, the
intense starburst responsible for the formation of superbubbles could occur
$\sim 1 \times 10^9$ yr ago. On the other hand, the age of the radio jets may
be of the order of $\sim 10^6$ yr, being much shorter than the starburst age.
Therefore, the two events, i.e., the starburst and the radio-jet activities,
are independent phenomena. However, their directions of the expanding motions
could be governed by the rotational motion of the gaseous component in the host
galaxy. This idea appears to explain the alignment effect of MRC 0406$-$244.


title:
Resonant Conversion of Photon Modes Due to Vacuum Polarization in a
  Magnetized Plasma: Implications for X-Ray Emission from Magnetars

abstract:
  It is known that vacuum polarization can modify the photon propagation modes
in the atmospheric plasma of a strongly magnetized neutron star. A resonance
occurs when the effect of vacuum polarization on the photon modes balances that
of the plasma. We show that a photon (with energy $E\go$ a few keV) propagating
outward in the atmosphere can convert from one polarization mode into another
as it traverses the resonant density, $\rho_{res}\simeq
Y_e^{-1}\eta^{-2}(B/10^{14} G)^2(E/1 keV)^2$ g cm$^{-3}$, where $Y_e$ is the
electron fraction, and $\eta\sim 1$ is a slowly varying function of the
magnetic field $B$. The physics of this mode conversion is analogous to the
Mikheyev-Smirnov-Wolfenstein mechanism for neutrino oscillation. Because the
two photon modes have vastly different opacities in the atmosphere, this
vacuum-induced mode conversion can significantly affect radiative transport and
surface emission from strongly magnetized neutron stars.


title: Cluster X-ray Luminosity Evolution

abstract:
  Whether the X-ray luminosities of clusters of galaxies evolve has been a
contentious issue for over ten years. However, the data available to address
this issue have improved dramatically as cluster surveys from the ROSAT archive
near completion. There are now three samples of nearby clusters and seven
distant cluster samples. We present a uniform analysis of four of the distant
cluster samples. Each exhibits highly statistically significant luminosity
evolution. We combine three of these samples to measure the high redshift
cluster X-ray luminosity function with good statistics that shows the nature of
the evolution.


title: Low Redshift Lyman Alpha absorbers and their Connection with Galaxies

abstract:
  We review the ongoing debate about the relationship between low redshift
Lyman Alpha absorbers and luminous galaxies. In particular, we discuss the
difficulty of `assigning' a particular absorber to a particular galaxy, and
consider methods of circumventing this problem. We also provide a status report
on an ongoing project collecting more data to address this issue, and show some
results for a close together pair of QSOs providing two adjacent lines of sight
through the inter-galactic medium.


title: A Million Element Integral Field Unit (MEIFU)

abstract:
  We describe an instrument concept that will provide simultaneous spectra for
a million spatial samples on the sky. With the proposed field of view and
spectral resolution, it will be able to measure redshifts and line strengths
for around 2-4000 z~3-7 galaxies in a 16 night campaign. The main science
driver is to obtain a complete census of the star formation properties of
galaxies with 2.5<z<6.7 as a function of luminosity, environment, morphology
and redshift. This survey will also allow us to study the evolution of the 3
dimensional power spectrum and test the connection between these early galaxies
and the large scale structure of the Lyman Alpha forest. Additional science
drivers include [OII] emitters with 0.13<z<1.52, abundance gradients in nearby
galaxies, searches for planetary nebulae in nearby galaxy groups and clusters,
lensed emission line objects, and spectroscopic searches for objects with
continuum breaks. We expect that this instrument will make an ideal partner to
the HST ACS, where ACS morphology and broadband colour information can
complement the MEIFU spectroscopy and help remove any degeneracies in line
identification.


title: The extended counterpart of submm source Lockman850.1

abstract:
  The IRAM Plateau de Bure mm interferometer and deep K-band imaging have been
used to identify the brightest submm source detected in the Lockman field of
the UK 8mJy SCUBA survey. The near infrared counterpart is an extended
(20-30kpc), clumpy, and extremely red object. The spectral energy distribution
suggests it to be a dusty star forming object at a redshift of about 3 (2-4).
Its star formation rate and near-infrared properties are consistent with
Lockman850.1 being a massive elliptical in formation.


title:
Observational Prospects for Afterglows of Short Duration Gamma-ray
  Bursts

abstract:
  If the efficiency for producing $\gamma$-rays is the same in short duration
($\siml 2$ s) Gamma-Ray Bursts (GRBs) as in long duration GRBs, then the
average kinetic energy of short GRBs must be $\sim 20$ times less than that of
long GRBs. Assuming further that the relativistic shocks in short and long
duration GRBs have similar parameters, we show that the afterglows of short
GRBs will be on average 10--40 times dimmer than those of long GRBs. We find
that the afterglow of a typical short GRB will be below the detection limit
($\siml 10 \microJy$) of searches at radio frequencies. The afterglow would be
difficult to observe also in the optical, where we predict $R \simg 23$ a few
hours after the burst. The radio and optical afterglow would be even fainter if
short GRBs occur in a low-density medium, as expected in NS-NS and NS-BH merger
models. The best prospects for detecting short-GRB afterglows are with early
($\siml 1$ day) observations in X-rays.


title: Angular Momentum Transfer in Protolunar Disk

abstract:
  We numerically calculated angular momentum transfer processes in a dense
particulate disk within Roche limit by global $N$-body simulations, up to
$N=10^5$, for parameters corresponding to a protolunar disk generated by a
giant impact on a proto-Earth. In the simulations, both self-gravity and
inelastic physical collisions are included. We first formalized expressions for
angular momentum transfer rate including self-gravity and calculated the
transfer rate with the results of our $N$-body simulations. Spiral structure is
formed within Roche limit by self-gravity and energy dissipation of inelastic
collisions, and angular momentum is effectively transfered outward. Angular
momentum transfer is dominated by both gravitational torque due to the spiral
structure and particles' collective motion associated with the structure. Since
formation and evolution of the spiral structure is regulated by the disk
surface density, the angular momentum transfer rate depends on surface density,
but not on particle size or number, so that the time scale of evolution of a
particulate disk is independent on the number of particles ($N$) that is used
to represent the disk, if $N$ is large enough to represent the spiral
structure. With $N=10^5$, the detailed spiral structure is resolved while it is
only poorly resolved with $N=10^3$, however, we found that calculated angular
momentum transfer does not change as long as $N \gtrsim 10^3$.


title: On high proper motion white dwarfs from photographic surveys

abstract:
  The interpretation of high proper motion white dwarfs detected by Oppenheimer
et al (2001) was the start of a lively controversy. While the discoverers
identify a large fraction of their findings as dark halo members, others
interpret the same sample as essentially made of disc and/or thick disc stars.
We use the comprehensive description of Galactic stellar populations provided
by the "Besancon" model to produce a realistic simulation of Oppenheimer et al.
data, including all observational selections and calibration biases. The
conclusion is unambiguous: Thick disc white dwarfs resulting from ordinary
hypotheses on the local density and kinematics are sufficient to explain the
observed objects, there is no need for halo white dwarfs. This conclusion is
robust to reasonable changes in model ingredients. The main cause of the
misinterpretation seems to be that the velocity distribution of a proper motion
selected star sample is severely biased in favour of high velocities. This has
been neglected in previous analyses. Obviously this does not prove that no such
objects like halo white dwarfs can exist, but Oppenheimer et al. observations
drive their possible contribution in the dark matter halo down to an extremely
low fraction.


title:
The origin of the ionization of the diffuse interstellar medium in
  spiral galaxies. II. Modelling the distribution of ionizing radiation in NGC
  157

abstract:
  In this paper we make a quantitative study of the hypothesis that the diffuse
H-alpha emitted from the discs of spiral galaxies owes its origin to the
ionizing photons escaping from HII regions. We use the H-alpha measurements of
the complete set of HII regions in the spiral NGC 157, for which an HI density
map was available, to derive a family of models which predict the ionizing
photon distribution in the disc of this galaxy. The predicted diffuse H-alpha
surface brightness distributions from our models were compared with the
observed distributions showing that, in general terms, the hypothesis of
density bounding for the HII regions allows us to predict well the spatial
distribution of the diffuse ionized gas. In the model yielding the best fit to
the data, the regions of lower luminosity lose a constant fraction of their
ionizing flux to their surroundings, while for HII region luminosities above a
specific transition value the ionizing escape fraction is a rising function of
the Ha luminosity.


title:
Physical vs. Observational Properties of Clouds in Turbulent Molecular
  Cloud Models

abstract:
  We examine how well the physical properties of clumps in turbulent molecular
clouds can be determined by measurements of observed clump structures. We
compare simulated observations of three-dimensional numerical models of
isothermal, magnetized, supersonic turbulence to the actual physical structure
of the models. We determine how changing the parameters of turbulence changes
the structure of the simulations. Stronger driving produces greater density
fluctuations, and longer wavelength driving produces larger structures.
Magnetic fields have a less pronounced effect on structure, and one that is not
monotonic with field strength. Aligned structures are seen only with
low-density tracers, and when the intensity of the field is large. Comparing
different regions with the same tracers (or the same region with different
tracers) can give information about physical conditions: different density
tracers can help determine the size of the density fluctuations and thus the
strength of the driving. Nevertheless, velocity superposition of multiple
physical clumps can fully obscure the physical properties of those clumps, and
short wavelength driving worsens this effect. Regarding Larson's relationships,
we confirm previous claims that the mean density-size relationship is an
artifact of the observations; and the velocity dispersion-size relationship, is
consistent with observations. Regarding the mass spectra, we show that, when we
look for clumps with high enough resolution, they converge to a log-normal
function, rather than the power-law obtained in the literature.


title: Relation between $M_{BH}$ and $M_{bulge}$: A simulation study

abstract:
  The dynamical evolution of super star clusters (SSCs) moving in the
background of dark matter halo has been investigated as a possible event
causing the observed correlation between the mass of galactic bulge,
$M_{bulge}$, and the mass of its central black hole, $M_{BH}$. The involved
physical processes are the sinking of SSCs due to the dynamical friction, and
the stripping of SSCs on their way to the center. Model calculations show that
only sinking of circumnuclear SSCs contribute to both the growth of the central
object and the formation of the galactic bulge at the early stage. On the
assumption of a universal density profile for the dark matter halo, and an
isothermal model for the SSCs, our simulations have yielded the mass ratio of
the central objects to the bulges formed this way to be about a few times
$10^{-4}$, less than the observed median value for early type galaxies. It is,
however, consistent with the observed mass ratio for disk spirals, implying
that the proposed scenario might be a possible event for the formation of
bulges and central black holes of late type galaxies and for $M_{BH} -
M_{bulge}$ correlation of disk galaxies.


title: High redshift ellipticals: prospects for the VLT

abstract:
  The results and the present limits of the observations of high-z ellipticals
are discussed in the framework of VLT imminent and future instruments.


title: BeppoSAX survey of Be/X-ray binary candidates

abstract:
  We present a BeppoSAX survey of five Be/X-ray binary candidates. We report on
the identification of two of them, HD 110432 and HD 141926, as low luminosity
Be/X-ray binaries. For HD 110432 we report on the detection of a pulsation
period of ~14 ks. Because the luminosity of these sources is low and their
spectra do not require non-thermal emission models, these systems are good
Be+White Dwarf candidates. If the pulsation period for HD 110432 is confirmed,
this system would be the most firm Be+WD candidate found up to date. The other
three objects HD 65663, HD 249179 and BD+53 2262 did not show detectable X-ray
emission. We argue that, while the properties of BD+53 2262 are still
consistent with a quiescent Be+Neutron Star scenario, the lack of detection for
the other two objects implies that they are most probably not X-ray binaries.


title: Spectroscopy of Globular Clusters in NGC 1399 - A Progress Report

abstract:
  We performed spectroscopy of globular clusters associated with NGC 1399 and
measured radial velocities of more than 400 clusters, the largest sample ever
obtained for dynamical studies. In this progress report, we present the sample
and the first preliminary results. Red and blue clusters have slightly
different velocity dispersions in accordance with their different density
profiles. Their velocity dispersions remain constant with radial distance,
which differs from earlier work.


title:
The Evolution of Neutral Gas in the Universe as Traced by Damped Lyman
  Alpha Systems

abstract:
  We discuss our recent results on the statistical properties of damped Lyman
alpha systems (DLAs) at low redshift (z<1.65) (Rao & Turnshek 2000). Contrary
to expectations, we found that the cosmological neutral gas mass density as
traced by DLAs, $\Omega_{DLA}$, does not evolve from redshifts $z \approx 4$ to
$z \approx 0.5$ and that extrapolation to z=0 results in a value that is a
factor of ~6.5 times higher than what is derived from galaxies at the current
epoch using HI 21 cm emission measurements. We review the current status of HI
measurements at low redshift and at the current epoch, and discuss possible
causes of this discrepancy.


title: A Comparative Study of Damped Lyman Alpha Galaxies

abstract:
  We compare the properties of a sample of local (z=0) gas-rich galaxies
studied in 21 cm emission to a sample of 13 low-redshift (z < 1) damped Lyman
alpha (DLA) galaxies identified as the counterparts of low-redshift DLA systems
found in QSO absorption-line surveys. This absorption-selected sample has
average redshift <z> = 0.5. We find that many of the properties of the two
samples are comparable. However, consideration of the statistical results on
all known low-redshift DLA systems indicates that there is: (1) a somewhat
higher incidence and cosmological mass density for the low-redshift DLA systems
in comparison to expectations at z=0 and (2) an unexpectedly high rate of
occurrence of very large column density [N(HI) > 1E21 atoms/cm^2] low-redshift
DLA systems; both of these results are discussed by Rao & Turnshek in these
proceedings. These differences, coupled with imaging studies, suggest that
there may be an excess of low-redshift DLA galaxies in the form of dwarf and/or
low surface brightness galaxies. Some examples of low-redshift DLA galaxies are
shown by Nestor et al. in these proceedings.


title:
Stationary dark energy with a baryon-dominated era: solving the
  coincidence problem with a linear coupling

abstract:
  We show that all cosmological models with an accelerated stationary global
attractor reduce asymptotically to a dark energy field with an exponential
potential coupled linearly to a perfect fluid dark matter. In such models the
abundance of the dark components reaches a stationary value and therefore the
problem of their present coincidence is solved. The requirement of a vanishing
coupling of the baryons in order to pass local gravity experiments induces the
existence of an intermediate baryon-dominated era. We discuss in detail the
properties of these models and show that to accomodate standard nucleosynthesis
they cannot produce a microwave background consistent with observations. We
conclude that, among stationary models, only a time-dependent coupling or
equation of state might provide a realistic cosmology.


title:
Are the hotspots of radio galaxies the sites of in-situ acceleration of
  relativistic particles?

abstract:
  Using a large set of optically detected hotspots in powerful extragalactic
double radio sources, we examine the basic question of whether the detection of
optical synchrotron radiation requires in-situ acceleration of relativistic
electrons within the hotspots/lobes. For this, we take into account the jet's
bulk relativistic motion, as well as its likely misalignment from the plane of
the sky. Together, both these factors can drastically reduce the apparent range
of the ultra-relativistic electrons ejected from the nucleus in the form of a
jet. The conventionally adopted parameter space for the fundamental variables,
namely, the hotspot magnetic field, radio source orientation angle relative to
the line-of-sight and the bulk speed of the jet plasma, is considered. We find
that the observed optical/near-IR synchrotron emission of the hotspots can be
explained even if the radiating relativistic electrons were accelerated
exclusively within the nuclear region, provided the energy losses incurred by
the electrons during their transport down the jet are dominated by inverse
Compton upscatterings of the cosmic microwave background photons. Under this
circumstance, in-situ acceleration of relativistic electrons inside the
hotspots or lobes is not found to be mandated by their reported
optical/near-infrared detections.


title:
Hyper Extremely Red Objects in the Subaru Deep Field: Evidence for
  Primordial Elliptical Galaxies in the Dusty Starburst Phase

abstract:
  We report observational analyses and theoretical interpretations of unusually
red galaxies in the Subaru Deep Field (SDF). A careful analysis of the SDF data
revealed a population with unusually red near-infrared (NIR) colors of J - K >~
3-4, with higher confidence than the previous SDF result. Their surface number
density drastically increases at K >~ 22 and becomes roughly the same with that
of dusty starburst galaxies detected by submillimeter observations in recent
years. These colors are even redder than the known population of the extremely
red objects (EROs), and too red to explain by passively evolving elliptical
galaxies which are the largest population of EROs. Hence these hyper extremely
red objects (HEROs) should be considered as a distinct population from EROs. We
discuss several possible interpretations of these enigmatic objects, and we
show that these red NIR colors, K-band and sub-mm flux, and surface number
density are quantitatively best explained by primordial elliptical galaxies
reddened by dust, still in the starburst phase of their formation at z ~ 3.


title: Properties of Low-Redshift Damped Lyman Alpha Galaxies

abstract:
  Images of five QSO fields containing six damped Lyman alpha (DLA) systems at
redshifts 0.09<z<0.53 are presented. Identifications for the DLA galaxies
giving rise to the DLA systems are made. The observed and modeled
characteristics of the DLA galaxies are discussed. The DLA galaxies have impact
parameters ranging from < 4 kpc to \approx 34 kpc and luminosities in the range
\approx 0.03L* to \approx 1.3L*. Their morphologies include amorphous low
surface brightness systems, a probable dwarf spiral, and luminous spirals.


title:
ZEPLIN IV: A 1-Ton Very Sensitive ZEPLIN II Extension for SUSY Dark
  Matter

abstract:
  We present a concept of a one ton two-phase liquid Xenon detector based on
the concept of the ZEPLIN II detector currently under construction by a
UCLA/Torino/UKDM team. The ZEPLIN II detector may be installed in the Boulby
laboratory early in 2002. The one ton detector design will benefit from the
initial operations of ZEPLIN II.


title: Precision Neutrino Counting

abstract:
  In the framework of the standard, hot big bang cosmological model the
dynamics of the early evolution of the universe is controlled by the energy
density of relativistic particles, among which neutrinos play an important
role. In equilibrium, the energy density contributed by one flavor of
relativistic neutrinos is 7/8 of that of the cosmic background radiation (CBR)
photons. As the universe expands and cools, neutrinos decouple and their
subsequent contribution to the energy density is modified by the relative
heating of the CBR photons when electron-positron pairs annihilate. The small
corrections to the post-annihilation energy density of the standard model
neutrinos due to incomplete decoupling and finite-temperature QED effects are
reviewed (correcting an error in the literature) and extended to account for
possible additional relativistic degrees of freedom whose presence might modify
the predictions of primordial nucleosynthesis and of the predicted CBR
anisotropies.


title:
Optical and Ultraviolet Spectroscopy of SN 1995N: Evidence for Strong
  Circumstellar Interaction

abstract:
  Optical and ultraviolet observations of the Type IIn supernova 1995N at
epochs between 321 and 1799 days after the explosion show three distinct
velocity components. The narrow lines come from circumstellar gas and show both
low and high ionization. This component has a low filling factor, and is
photoionized by X-rays from the shock. The intermediate component, which is
dominated by newly processed oxygen, originates in a shell with velocity of
2500-5000 km/s, and most likely comes from the ejecta. The hydrogen- and
helium-dominated gas has a low ionization, a high density, and velocities that
extend out to ~10,000 km/s. Strong signatures of Ly-alpha-pumped fluorescence
lines of Fe II are seen in the near-infrared and ultraviolet. The He/H ratio, ~
0.3 by number, and the nitrogen overabundance provide strong evidence for CNO
burning products. The fluxes of the broad hydrogen and helium lines decrease
considerably faster than the oxygen lines. The H-alpha line profile shows
strong evolution, with the red wing decreasing faster than the blue. Possible
scenarios, involving either a clumpy circumstellar medium, or an aspherical
distribution of the surrounding gas, are discussed based on the line profiles
and physical conditions. Finally, we propose that Type IIn supernovae have
their origin in red supergiants in a superwind phase.


title: The compact central source in the RX J0852-4622 supernova remnant

abstract:
  The central region of the recently discovered supernova remnant RX
J0852.0-4622 was observed with the ACIS detector aboard the Chandra X-ray
Observatory. We found only one relatively bright source, about 4' north of the
SNR center, with a flux of $\sim 2\times 10^{-12}$ erg s$^{-1}$ cm$^{-2}$ in
the 0.5--10 keV band. The position of this point-like source, CXOU
J085201.4-461753, rules out its association with the two bright stars in the
field, HD 76060 and Wray 16-30. Observations of the field with the CTIO 0.9-m
telescope show a star ($R\approx 17$, $B\approx 19$) at about 2\farcs4 from the
nominal X-ray position. We consider association of this star with the X-ray
source unlikely and estimate a limiting magnitude of the optical counterpart as
$B \ge 22.5$ and $R \ge 21.0$. Based on the X-ray-to-optical flux ratio, we
argue that the X-ray source is likely the compact remnant of the supernova
explosion that created the RX J0852.0-4622 SNR. The observed X-ray spectrum of
the source is softer than spectra of magnetospheric radiation of
rotation-powered pulsars, but it is harder than spectra of cooling neutron
stars emitting thermal radiation from the entire surface, similar to the
central compact source of the Cas A SNR. We suggest that CXOU J085201.4-461753
belongs to the growing family of radio-quiet compact central sources,
presumably neutron stars, recently discovered in a number of SNRs.


title: Concentrations of Dark Halos from their Assembly Histories

abstract:
  (abridged) We study the relation between the density profiles of dark matter
halos and their mass assembly histories, using a statistical sample of halos in
a high-resolution N-body simulation of the LCDM cosmology. For each halo at
z=0, we identify its merger-history tree, and determine concentration
parameters c_vir for all progenitors, thus providing a structural merger tree
for each halo. We fit the mass accretion histories by a universal function with
one parameter, the formation epoch a_c, defined when the log mass accretion
rate dlogM/dloga falls below a critical value S. We find that late forming
galaxies tend to be less concentrated, such that c_vir ``observed'' at any
epoch a_o is strongly correlated with a_c via c_vir=c_1*a_o/a_c. Scatter about
this relation is mostly due to measurement errors in c_v and a_c, implying that
the actual spread in c_vir for halos of a given mass can be mostly attributed
to scatter in a_c. We demonstrate that this relation can also be used to
predict the mass and redshift dependence of c_v, and the scatter about the
median c_vir(M,z), using accretion histories derived from the Extended
Press-Schechter (EPS) formalism, after adjusting for a constant offset between
the formation times as predicted by EPS and as measured in the simulations;this
new ingredient can thus be easily incorporated into semi-analytic models of
galaxy formation. The correlation found between halo concentration and mass
accretion rate suggests a physical interpretation: for high mass infall rates
the central density is related to the background density; when the mass infall
rate slows, the central density stays approximately constant and the halo
concentration just grows as R_vir. The tight correlation demonstrated here
provides an essential new ingredient for galaxy formation modeling.


title: Brightest Cluster Galaxies and the Las Campanas Distant Cluster Survey

abstract:
  We present our study of the evolution of brightest cluster galaxies based on
data from the Las Campanas Distant Cluster Survey (Gonzalez et al. 2001) and
HST optical and IR imaging. We briefly discuss the technique that enabled us to
use short (~ 3 min) exposures and a small (1m) telescope to efficiently survey
about 130 sq. deg. of sky for high-z galaxy clusters. Follow-up imaging is used
to construct a sample of several tens of BCGs at 0.3 < z < 0.9 with which to
explore their evolution. In particular, we examine the luminosity and color
evolution of these galaxies. We confirm the previous results that 1) BCGs in
different environments evolve differently (eg. Burke et al 2000), 2) BCGs,
particularly those in low-mass clusters, must be accreting significantly since
z ~ 1 (Aragon-Salamanca et al. 1998). From measurments of the colors vs.
redshift, we conclude that this accretion must consist of old stellar
populations. Using HST NICMOS and WFPC2 images, we find preliminary evidence
for evolution in the sizes of BCGs that is consistent with the accretion model
presented in standard hierarchical models (Aragon-Salamanca et al. 1998), but
puzzling differences between NICMOS and WFPC2 scale lengths precludes a
definitive conclusion.


title:
Spectroscopic Target Selection for the Sloan Digital Sky Survey: The
  Luminous Red Galaxy Sample

abstract:
  We describe the target selection and resulting properties of a spectroscopic
sample of luminous, red galaxies (LRG) from the imaging data of the Sloan
Digital Sky Survey (SDSS). These galaxies are selected on the basis of color
and magnitude to yield a sample of luminous, intrinsically red galaxies that
extends fainter and further than the main flux-limited portion of the SDSS
galaxy spectroscopic sample. The sample is designed to impose a
passively-evolving luminosity and rest-frame color cut to a redshift of 0.38.
Additional, yet more luminous, red galaxies are included to a redshift of 0.5.
Approximately 12 of these galaxies per square degree are targeted for
spectroscopy, so the sample will number over 100,000 with the full survey. SDSS
commissioning data indicate that the algorithm efficiently selects luminous
(M_g=-21.4), red galaxies, that the spectroscopic success rate is very high,
and that the resulting set of galaxies is approximately volume-limited out to
z=0.38. When the SDSS is complete, the LRG spectroscopic sample will fill over
1h^-3 Gpc^3 with an approximately homogeneous population of galaxies and will
therefore be well suited to studies of large-scale structure and clusters out
to z=0.5.


title:
Are Simulations of CDM Consistent with Galactic-Scale Observations at
  High Redshift?

abstract:
  We compare new observations on the kinematic characteristics of the damped
Lya systems against results from numerical SPH simulations to test the
predictions of hierarchical galaxy formation. This exercise is particularly
motivated by recent numerical results on the cross-section of damped Lya
systems. Our analysis focuses on the velocity widths of ~50 low-ion absorption
profiles from our sample of z>1.5 damped Lya systems. The results indicate that
current numerical simulations fail to match the damped Lya observations at high
confidence levels (>99.9%). Although we do not believe that our results present
an insurmountable challenge to the paradigm of hierarchical cosmology, the
damped Lya observations suggest that current numerical SPH simulations overlook
an integral aspect of galaxy formation.


title:
A Tunable Lyot Filter at Prime Focus: a Method for Tracing Supercluster
  Scales at z ~ 1

abstract:
  Tunable narrow-band, emission-line surveys have begun to show the ease with
which star forming galaxies can be identified in restricted redshift intervals
to z ~ 5 with a 4m class telescope. These surveys have been carried out with
imaging systems at the Cassegrain or Nasmyth focus and are therefore restricted
to fields smaller than 10 arcmin. We now show that tunable narrowband imaging
is possible over a 30 arcmin field with a high-performance Lyot filter placed
directly in front of a CCD mosaic at the prime focus. Our design is intended
for the f/3.3 prime focus of the AAT 3.9m, although similar devices can be
envisaged for the Subaru 8m (f/2), Palomar 5m (f/3.4), VISTA 4m (f/6), Mayall
4m (f/2.6) or CFHT 3.6m (f/4). A modified Wynne doublet ensures sub-arcsecond
performance over the field. In combination with the new Wide-Field Imaging 8K x
8K mosaic (WFI) at the AAT, the overall throughput (35%) of the system to
unpolarised light is expected to be comparable to the TAURUS Tunable Filter
(TTF). Unlike the TTF, the field is fully monochromatic and the instrumental
profile has much better wing suppression. For targetted surveys of
emission-line sources at z ~ 1, a low-resolution (R ~ 150 at 550nm) Lyot filter
on a 4m telescope is expected to be comparable or superior to current
instruments on 8-10m class telescopes. We demonstrate that the 30 arcmin field
is well matched to superclusters at these redshifts such that large-scale
structure should be directly observable.


title:
Strong Evidence for a Buried AGN in UGC 5101: Implications for
  LINER-Type Ultra-Luminous Infrared Galaxies

abstract:
  We report on the results of 3--4 $\mu$m spectroscopy of the ultra-luminous
infrared galaxy (ULIRG) UGC 5101. It has a cool far-infrared color and a
LINER-type optical spectrum, and so, based on a view gaining some currency,
would be regarded as dominated by star formation. However, we find that it has
strong 3.4 $\mu$m carbonaceous dust absorption, low-equivalent-width 3.3 $\mu$m
polycyclic aromatic hydrocarbon (PAH) emission, and a small 3.3 $\mu$m PAH to
far-infrared luminosity ratio. This favors an alternative scenario, in which an
energetically dominant AGN is present behind obscuring dust. The AGN is
plausibly obscured along all lines of sight (a `buried AGN'), rather than
merely obscured along our particular line of sight. Such buried AGNs have
previously been found in thermal infrared studies of the ULIRGs IRAS 08572+3915
and IRAS F00183$-$7111, both classified optically as LINERs. We argue that
buried AGNs can produce LINER-type optical spectra, and that at least some
fraction of LINER-type ULIRGs are predominantly powered by buried AGNs.


title:
Properties of Planet-induced Deviations in the Astrometric Microlensing
  Centroid Shift Trajectory

abstract:
  In this paper, we investigate the properties of the planet-induced deviations
in the trajectory of the microlensed source star centroid motion (astrometric
curve) and the correlations between the astrometric and photometric deviations.
For this, we construct vector field maps of excess centroid shifts. Fromthe
investigation of the maps, we find that the astrometric deviation is closely
correlated with the photometric one. The astrometric deviation increases as the
photometric deviation increases and $\Delta\deltavec$ is directed towards the
planet when the light curve has positive deviation and vice versa. We also
present excess centroid shift maps for lens systems with various values of the
planetary separation, planet/primary mass ratio, and source size to show the
changes in the pattern of excess centroid shifts with these parameters.


title:
On the dispersion in lithium and potassium among late-type stars in
  young clusters: IC 2602

abstract:
  We have measured the equivalent width (EW) of the K I 7699 A line in a sample
of G and K-type members of the ~35 Myr old cluster IC 2602 for which a
dispersion in Li EWs had been reported by previous studies. Active cluster
stars with 0.75 < (B-V)o < 1 are characterized by a dispersion in the EW of the
K I 7699 A, while earlier and later-type stars do not show any significant
scatter. Cluster stars at all colors show potassium EW excesses with respect to
field inactive stars; furthermore, a statistically significant relationship is
found between differential potassium EWs and log Lx/Lbol ratios, indicating
that the EWs of the potassium feature are altered by activity. Our results
suggest that the dispersion in Li EWs observed among cluster stars later than
(B-V)o ~ 1 cannot be fully explained by the effects of activity. No final
conclusion can instead be drawn for earlier-type stars.


title:
The Star Formation History and the Morphological Evolution of the Draco
  Dwarf Spheroidal Galaxy

abstract:
  The photometric and morphological properties, as well as the star formation
history, of the Draco dwarf spheroidal galaxy are analyzed on the basis of wide
field, CCD photometry of the resolved stars covering about 1deg^2. No
metallicity gradient is detected. The star surface density distribution can be
fitted by a single exponential law of scale-length a=5'.0+/-0'.1. The central
surface magnitude is mu_V=24.4+/-0.5 and the core radius r_c=7'.5+/- 0.'3
(equivalent to r_c=175+/-7 pc). Within errors, the same scale-lengths are found
for the density profiles along the semi-major axis and the semi-minor axis
(re-scaled to semi-major axis units, using the ellipticity of the galaxy) of
Draco. There are hence no evidences of a tidal-tail associated to Draco. The
tidal radius of the galaxy is found to be r_t~42' (~1 kpc). The possibility
that the large mass-to-light relation in Draco could be accounted for by a
convenient spatial orientation is rejected, which implies that other mechanisms
(e.g., dark matter) are required.
  The stellar population of Draco is mainly old. Although some intermediate-age
population is present in Draco, most of the star formation (up to 90%) took
place before ~10 Gyr ago. No significant star formation activity is detected in
the last ~2 Gyr. Two methods ("partial model" and "subgiant") have been used to
investigate the star formation history of Draco.


title: Dynamical Probes of The Halo Mass Function

abstract:
  We explore the relationship between the mass function of CDM halos and
dynamical probes of the mass function such as the distribution of gravitational
lens separations and the local velocity function. The compression of galactic
halos by the cooling baryons, a standard component of modern models, leads to a
feature in the distribution of lens separations near 3 arcsec or in the
velocity function near 400 km/s. The two probes of the mass function, lens
separations and the local velocity function, are mutually consistent. Producing
the observed velocity function of galaxies or the separation distribution using
standard adiabatic compression models requires more cold baryons, an equivalent
cosmological density of Omega_b=0.02 compared to a total cosmological
Omega_b=0.04, than are observed in standard accountings of the baryonic content
of galaxies, Omega_b=0.006$, or our Galaxy, Omega_b<0.015. The requirement for
a higher cold baryon density than is usually assigned to galaxies appears to be
generic to models which use the standard adiabatic compression models for the
transformation of the CDM halo by the cooling baryons. If real, this dynamical
baryon discrepancy suggests either that we are neglecting half of the cold
baryonic mass in standard galactic models (e.g. a MACHO, cold molecular or warm
gas component), or that there is a problem with standard adiabatic compression
models.


title: Probing the evolution of galaxies using redshifted H-alpha emission

abstract:
  In this paper we review the present status and implications of H-alpha
surveys at various redshifts. With the advent of sensitive wide-format
near-infrared detectors on large telescopes, deep and extensive H-alpha surveys
are now feasible to redshift z~2.5. The cosmic star formation history can
therefore be traced out to this redshift using H-alpha alone, avoiding
complications arising from the comparison of different tracers at different
redshifts. The H-alpha surveys to date confirm the rapid increase in luminosity
density from z=0 out to z=1, and show that this increase flattens off at higher
redshifts, remaining approximately constant out to at least z~2.2. We also
discuss the prospects for determining the masses of high redshift galaxies
based on emission lines. A set of high-quality H-alpha rotation curves of
samples of disk galaxies at a number of different redshifts would allow a study
of the evolution of the Tully-Fisher relation and address fundamental issues in
disk galaxy formation. Such a program remains challenging even with present-day
large telescopes.


title: Rapid Calculation of Equatorial Rotation Curves

abstract:
  We derive a simple, fast one-dimensional integral for the equatorial rotation
curve of a thin disk with surface density Sigma(R) modeled as a spheroid with
axis ratio q. The result is simpler than standard expressions even in the limit
of an infinitely thin disk (q-->0).


title:
UBV stellar photometry of bright stars in GC M5. II. Physical parameters
  of HB stars

abstract:
  The physical parameters of the stars in the central region of the globular
cluster M5 (NGC 5904) were determined from UBV photometry using Kurucz (1992)
synthetic flux distributions and some empirical relations. It is found that the
bluest horizontal branch stars have higher luminosities than predicted by
canonical zero-age horizontal branch models. Parameters of the mass
distribution on the HB stars are determined. It is shown that the gap in the
blue HB previously reported (Markov et al. 1999) is probably a statistical
fluctuation.


title:
Dependence of kHz QPO Properties on Normal-Branch Oscillation Phase in
  Scorpius X-1

abstract:
  We analysed RXTE data of Sco X-1 which show kHz quasi-periodic oscillations
(QPOs) and the $\sim$6--8 Hz normal-branch oscillation (NBO) simultaneously.
Using power spectra of 0.03--0.5 s data segments, we find that both the upper
kHz QPO frequency $\nu_2$ and the ratio of lower to upper kHz QPO amplitude are
anticorrelated to variations in the X-ray count-rate taking place on the NBO
time scale. The frequency dependence is similar to (but probably weaker than)
that found on longer time scales, but the power ratio dependence is opposite to
it. A model where radiative stresses on the disk material, modulated at the NBO
frequency, lead to changes in $\nu_2$ can explain the data; this implies some
of the NBO flux changes originate from inside the inner disk radius. We discuss
how these findings affect our understanding of kHz QPOs and of the
low-frequency variability of low-mass X-ray binaries.


title:
Optical and radio variability of the BL Lac object AO 0235+16: a
  possible 5-6 year periodicity

abstract:
  New optical and radio data on the BL Lacertae object AO 0235+16 have been
collected in the last four years by a wide international collaboration, which
confirm the intense activity of this source. The optical data also include the
results of the Whole Earth Blazar Telescope (WEBT) first-light campaign
organized in November 1997. The optical spectrum is observed to basically
steepen when the source gets fainter. We have investigated the existence of
typical variability time scales and of possible correlations between the
optical and radio emissions by means of visual inspection, Discrete Correlation
Function analysis, and Discrete Fourier Transform technique. The major radio
outbursts are found to repeat quasi-regularly with a periodicity of about 5.7
years; this period is also in agreement with the occurrence of some of the
major optical outbursts, but not all of them.


title: Chandra X-ray Observation of NGC 4151

abstract:
  We present Chandra X-ray observations of the nearby Seyfert 1.5 galaxy NGC
4151. The images show the extended soft X-ray emission on the several hundreds
of pc scale with better sensitivity than previously obtained. The spectrum of
the unresolved nuclear source may be described by a heavily absorbed (N_{H}
\simeq 3 \times 10^{22} cm^-2), hard power-law (\Gamma \simeq 0.3) plus soft
emission from either a power-law (\Gamma \simeq 2.6) or a thermal (kT \simeq
0.6 keV) component. The flux of the high energy component has decreased from
that observed by ASCA in 1993 and the spectrum is much harder.The large
difference between the soft and hard spectral shapes does not favor the partial
covering or scattering model of the ``soft excess''. Instead, it is likely that
the hard and soft nuclear components represent intrinsically different X-ray
sources. Spectra of the extended emission to almost 1 kpc NE and SW of the
nucleus have also been obtained. The spectra of these regions may be described
by either thermal bremsstrahlung (kT \simeq 0.4-0.7 keV) or power-law (\Gamma
\simeq 2.5-3.2) continua plus 3 emission lines. There is an excellent
correlation between the extended X-ray and [O III]\lambda 5007 line emissions.
We discuss the nature of the extended X-ray emission. Upper limit to the
electron scattering column was obtained. This upper limit is much too low for
the soft X-rays to be electron scattered nuclear radiation.


title: Neutrinos in a vacuum dominated cosmology

abstract:
  We explore the dynamics of neutrinos in a vacuum dominated cosmology. First
we show that such a geometry will induce a phase change in the eigenstates of a
massive neutrino and we calculate the phase change. We also calculate the delay
in the neutrino flight times in this geometry. Applying our results to the
presently observed background vacuum energy density, we find that for neutrino
sources further than $1.5 Gpc$ away both effects become non-trivial, being of
the order of the standard relativistic corrections. Such sources are within the
obsevable Hubble Deep Field. The results which are theoretically interesting
are also potentially useful, in the future, as detection techniques improve.
For example such effects on neutrinos from distant sources like supernovae
could be used, in an independent method alternative to standard candles, to
constrain the dark energy density and the deceleration parameter. The
discussion is extended to investigate Caianiello's inertial or maximal
acceleration (MA) effects of such a vacuum dominated spacetime on neutrino
oscillations. Assuming that the MA phenomenon exists, we find that its form as
generated by the presently observed vacuum energy density would still have
little or no measurable effect on neutrino phase evolution.


title:
Heating and Ionization of the Intergalactic Medium by an Early X-Ray
  Background

abstract:
  Observational studies indicate that the intergalactic medium (IGM) is highly
ionized up to redshifts just over 6. A number of models have been developed to
describe the process of reionization and the effects of the ionizing photons
from the first luminous objects. In this paper, we study the impact of an X-ray
background, such as high-energy photons from early quasars, on the temperature
and ionization of the IGM prior to reionization, before the fully ionized
bubbles associated with individual sources have overlapped. X-rays, which have
large mean free paths relative to EUV photons, and their photoelectrons can
have significant effects on the thermal and ionization balance. We find that
hydrogen ionization is dominated by the X-ray photoionization of neutral helium
and the resulting secondary electrons. Thus, the IGM may have been warm and
weakly ionized prior to full reionization. We examine several related
consequences, including the filtering of the baryonic Jeans mass scale,
signatures in the cosmic microwave background, and the H$^{-}$-catalyzed
production of molecular hydrogen.


title:
Resolving the Structure of Ionized Helium in the Intergalactic Medium
  with the Far Ultraviolet Spectroscopic Explorer

abstract:
  The neutral hydrogen and the ionized helium absorption in the spectra of
quasars are unique probes of structure in the early universe. We present
Far-Ultraviolet Spectroscopic Explorer observations of the line of sight to the
quasar HE2347-4342 in the 1000-1187 A band at a resolving power of 15,000. We
resolve the He II Ly alpha absorption as a discrete forest of absorption lines
in the redshift range 2.3 to 2.7. About 50 percent of these features have H I
counterparts with column densities log N(HI) > 12.3 that account for most of
the observed opacity in He II Ly alpha. The He II to H I column density ratio
ranges from 1 to >1000 with an average of ~80. Ratios of <100 are consistent
with photoionization of the absorbing gas by a hard ionizing spectrum resulting
from the integrated light of quasars, but ratios of >100 in many locations
indicate additional contributions from starburst galaxies or heavily filtered
quasar radiation. The presence of He II Ly alpha absorbers with no H I
counterparts indicates that structure is present even in low-density regions,
consistent with theoretical predictions of structure formation through
gravitational instability.


title:
The Las Campanas IR Survey: Early Type Galaxy Progenitors Beyond
  Redshift One

abstract:
  (Abridged) We have identified a population of faint red galaxies from a 0.62
square degree region of the Las Campanas Infrared Survey whose properties are
consistent with their being the progenitors of early-type galaxies. The optical
and IR colors, number-magnitude relation and angular clustering together
indicate modest evolution and increased star formation rates among the
early-type field population at redshifts between one and two. The counts of red
galaxies with $H$ magnitudes between 17 and 20 rise with a slope that is much
steeper than that of the total H sample. The surface density of red galaxies
drops from roughly 3000 per square degree at H = 20.5, I-H > 3 to ~ 20 per
square degree at H = 20, I-H > 5. The V-I colors are approximately 1.5
magnitudes bluer on average than a pure old population and span a range of more
than three magnitudes. The colors, and photometric redshifts derived from them,
indicate that the red galaxies have redshift distributions adequately described
by Gaussians with sigma_z ~ 0.2$ centered near redshift one, with the exception
that galaxies having $V-I<1.6$ and $I-H>3$ are primarily in the 1.5 < z < 2
range. We find co-moving correlation lengths of 9-10 Mpc at z ~ 1, comparable
to, or larger than, those found for early-type galaxies at lower redshifts. A
simple photometric evolution model reproduces the counts of the red galaxies,
with only a ~ 30% decline in the underlying space density of early-type
galaxies at z ~ 1.2. We suggest on the basis of the colors, counts, and
clustering that these red galaxies are the bulk of the progenitors of present
day early-type galaxies.


title:
The Las Campanas Infrared Survey. III. The H-band Imaging Survey and the
  Near-Infrared and Optical Photometric Catalogs

abstract:
  (Abridged) The Las Campanas Infrared Survey, based on broad-band optical and
near-infrared photometry, is designed to robustly identify a statistically
significant and representative sample of evolved galaxies at redshifts z>1. We
have completed an H-band imaging survey over 1.1 square degrees of sky in six
separate fields. The average 5 sigma detection limit in a four arcsecond
diameter aperture is H ~ 20. Here we describe the design of the survey, the
observation strategies, data reduction techniques, and object identification
procedures. We present sample near-infrared and optical photometric catalogs
for objects identified in two survey fields. We perform object detection in all
bandpasses and identify ~ 54,000 galaxies over 1,408 square arcminutes of sky
in the two fields. Of these galaxies, ~ 14,000 are detected in the H-band and ~
2,000 have the colors of evolved galaxies, I - H >3, at z > 1. We find that (1)
the differential number counts N(m) for the H-band detected objects has a slope
of 0.44 at H < 19 and 0.27 for H > 19. In addition, we find that (2) the
differential number counts for the H detected red objects has a slope of 0.85
at H < 20 and 0.32 at H > 20, with a mean surface density ~ 3,000 degree^{-2}
mag^{-1} at H=20. Finally, we find that (3) galaxies with red optical to
near-IR colors (I-H > 3) constitute ~ 20% of the H detected galaxies at H ~ 21,
but only 2% at H = 19. We show that red galaxies are strongly clustered, which
results in a strong field to field variation in their surface density.
Comparisons of observations and predictions based on various formation
scenarios indicate that these red galaxies are consistent with mildly evolving
early-type galaxies at z ~ 1, although with a significant amount of on-going
star formation as indicated by the large scatter in their V-I colors.


title: Gravitino Warm Dark Matter with Entropy Production

abstract:
  Gravitinos with a mass in the keV range are an interesting candidate for warm
dark matter. Recent measurements of the matter density of the universe and of
cosmic structures at the dwarf galaxy scale rule out the simplest gravitino
models with thermal freeze-out. We construct a model where the decay of the
messenger particles that transmit the supersymmetry breaking to the observable
sector generates the required entropy to dilute the gravitino relic density by
the required factor of a few to come in line with observations. The model is
natural, and requires only that the coupling of the messenger sector to the
standard model be set so that the decay happens at the appropriate time.


title: Molecular and Ionic shocks in the Supernova Remnant 3C391

abstract:
  New observations of the supernova remnant 3C391 are in the H2 2.12 micron and
[Fe II] 1.64 micron narrow-band filters at the Palomar 200-inch telescope, and
in the 5-15 micron CVF on ISOCAM. Shocked H2 emission was detected from the
region 3C391:BML, where broad millimeter CO and CS lines had previously been
detected. A new H2 clump was confirmed to have broad CO emission, demonstrating
that the near-infrared H2 images can trace previously undetected molecular
shocks. The [Fe II] emission has a significantly different distribution, being
brightest in the bright radio bar, at the interface between the supernova
remnant and the giant molecular cloud, and following filaments in the radio
shell. The near-infrared [Fe II] and the mid-infrared 12-18 micron filter
images are the first images to reveal the radiative shell of 3C391. The
mid-infrared spectrum is dominated by bright ionic lines and H2 S(2) through
S(7). There are no aromatic hydrocarbons associated with the shocks, nor is
their any mid-infrared continuum, suggesting that macromolecules and very small
grains are destroyed. Comparing 3C391 to the better-studied IC443, both
remnants have molecular- and ionic-dominated regions; for 3C391, the
ionic-dominated region is the interface into the giant molecular cloud, showing
that the main bodies of giant molecular clouds contain significant regions with
densities 100 to 1000/cm^3 and a small filling factor with higher-density. The
molecular shocked region resolves into 16 clumps of H2 emission, with some
fainter diffuse emission but with no associated near-infrared continuum
sources. One of the clumps is coincident with a previously-detected OH 1720 MHz
maser. These clumps are interpreted as a cluster of pre-stellar, dense
molecular cores that are presently being shocked by the supernova blast wave.


title:
Detection of X-ray Emission from the Arches Cluster Near the Galactic
  Center

abstract:
  The Arches cluster is an extraordinarily compact massive star cluster with a
core radius of about 10$''$ ($\sim$0.4 pc) and consisting of more than 150 O
star candidates with initial stellar masses greater than 20~M$_\odot$ near
G0.12-0.02. X-ray observations of the radio Arc near the Galactic center at
l$\sim0.2^0$ which contains the Arches cluster have been carried out with the
Advanced CCD Imaging Spectrometer (ACIS) on board Chandra X-ray Observatory. We
report the detection of two X-ray sources from the Arches cluster embedded
within a bath of diffuse X-ray emission extending beyond the edge of the
cluster to at least 90$''\times60''$ (3.6 pc $\times$ 2.4 pc). The brightest
component of the X-ray emission coincides with the core of the cluster and can
be fitted with two-temperature thermal spectrum with a soft and hard component
of 0.8 and 6.4 keV, respectively. The core of the cluster coincides with
several ionized stellar wind sources that have previously been detected at
radio wavelengths, suggesting that the X-ray emission from the core arises from
stellar wind sources. The diffuse emission beyond the boundary of the cluster
is discussed in the context of combined shocked stellar winds escaping from the
cluster. We argue that the expelled gas from young clusters such as the Arches
cluster may be responsible for the hot and extended X-ray emitting gas detected
throughout the inner degree of the Galactic center.


title:
Optical second harmonic generation near a black hole horizon as possible
  source of experimental information on quantum gravitational effects

abstract:
  Optical second harmonic generation near a black hole horizon is suggested as
a source of experimental information on quantum gravitational effects. While
absent in the framework of general relativity, second harmonic generation
appears in the toy models of sonic and electromagnetic black holes, where
spatial dispersion at high frequencies for waves boosted towards the horizon is
introduced. Localization effects in the light scattering from random
fluctuations of matter fields and space-time metric near the black hole horizon
produce a pronounced peak in the angular distribution of second harmonics of
light in the direction normal to the horizon. Such second harmonic light has
the best chances to escape the vicinity of the black hole. This phenomenon is
similar to the well-known strong enhancement of diffuse second harmonic
emission from a randomly rough metal surface in the direction normal to the
surface.


title: Reionization of an Inhomogeneous Universe

abstract:
  Full radiative transfer in 3D space has been solved to pursue the
reionization history in an inhomogeneous universe. It has been shown that the
reionization of an inhomogeneous universe is not a prompt event, but a fairly
slow process. Also, QSO absorption line systems are simulated with using the
results of radiative transfer calculations. Ly$\alpha$ continuum depression
implies that the metagalactic UV intensity decreases rapidly with $z$ at $z>5$,
and the reionization must have taken place between $z=6$ and 10. Finally, it is
stressed that H$\alpha$ forest is a more powerful tool to probe the
reionization history and the density fluctuations in the universe at $z>5$.


title: Cosmic Reionization and Galaxy Formation

abstract:
  Using 3D radiative transfer calculations on the reionization of an
inhomogeneous universe, QSO absorption line systems are simulated and they are
compared with observations of Ly$\alpha$ continuum depression at high
redshifts. By this comparison, it is found that the metagalactic UV intensity
decreases rapidly with $z$ at $z>4$ as $I_{21}=0.5\exp [3(4-z)]$, and the
reionization must have taken place between $z=6$ and 10. Based on this
time-dependence of UV background intensity, we explore the collapse of
pregalactic clouds in the UV background, and find that the self-shielding is
prominent above a mass scale as $ M_{BIF}=3.0\times 10^{11} M_\odot
[(1+z_c)/5]^{-4.2}(I_{21}/0.5)^{0.6}. $ This mass scale predicts the
bifurcation of galactic morphology, and by confrontation with observations it
turns out that the bifurcation mass successfully discriminates between
elliptical and spiral galaxies.


title:
Resolving gravitational microlensing events with long-baseline optical
  interferometry. Prospects for the ESO Very Large Telescope Interferometer

abstract:
  Until now, the detailed interpretation of the observed microlensing events
has suffered from the fact that the physical parameters of the phenomenon
cannot be uniquely determined from the available astronomical measurements,
i.e. the photometric lightcurves. The situation will change in the near-future
with the availability of long-baseline, sensitive optical interferometers,
which should be able to resolve the images of the lensed objects into their
components. For this, it will be necessary to achieve a milliarcsecond
resolution on sources with typical magnitudes K $\ga 12$. Indeed, brighter
events have never been observed up to now by micro-lensing surveys. We discuss
the possibilities opened by the use of long baseline interferometry in general,
and in particular for one such facility, the ESO VLT Interferometer, which will
attain the required performance. We discuss the expected accuracy and limiting
magnitude of such measurements. On the basis of the database of the events
detected by the OGLE experiment, we estimate the number of microlenses that
could be available for measurements by the VLTI. We find that at least several
tens of events could be observed each year. In conjunction with the photometric
data, our ability to measure the angular separation between the microlensed
images will enable a direct and unambiguous determination of both their masses
and locations.


title: Dark energy and cosmic microwave background bispectrum

abstract:
  We compute the cosmic microwave background bispectrum arising from the
cross-correlation of primordial, lensing and Rees-Sciama signals. The amplitude
of the bispectrum signal is sensitive to the matter density parameter, Omega_0,
and the equation of state of the dark energy, which we parameterize by w_Q. We
conclude that the dataset of the Atacama Cosmology Telescope, combined with MAP
2-year data or the Planck data set alone will allow us to break the degeneracy
between Omega_0 and w_Q that arises from the analysis of CMB power spectrum. In
particular a joint measurement of Omega_0 and w_Q with 10% and 30% error on the
two parameters respectively, at the 90% confidence level can realistically be
achieved.


title: Time is Life

abstract:
  The affirmative statement of the existence of extraterrestrial life is
tentatively raised to the status of a principle. Accordingly, Fermi's question
is answered and the anthropic principle is shown to be falsifiable. The
time-scale for the development of life on Earth and the age of the universe are
the fundamental quantities upon which the arguments are framed.


title: A Catalogue and Analysis of X-ray luminosities of Early-type galaxies

abstract:
  We present a catalogue of X-ray luminosities for 401 early-type galaxies, of
which 136 are based on newly analysed ROSAT PSPC pointed observations. The
remaining luminosities are taken from the literature and converted to a common
energy band, spectral model and distance scale. Using this sample we fit the
L_X:L_B relation for early-type galaxies and find a best fit slope for the
catalogue of ~2.2. We demonstrate the influence of group-dominant galaxies on
the fit and present evidence that the relation is not well modeled by a single
powerlaw fit. We also derive estimates of the contribution to galaxy X-ray
luminosities from discrete sources and conclude that they provide
L_discrete/L_B = 29.5 erg/s/L_solar. We compare this result to luminosities
from our catalogue. Lastly, we examine the influence of environment on galaxy
X-ray luminosity and on the form of the L_X:L_B relation. We conclude that
although environment undoubtedly affects the X-ray properties of individual
galaxies, particularly those in the centres of groups and clusters, it does not
change the nature of whole populations.


title:
The Las Campanas IR Survey. II. Photometric redshifts, comparison with
  models and clustering evolution

abstract:
  The LCIR Survey, using the Cambridge IR Survey Instrument (CIRSI), reaches H
\~ 20-21 over ~1 deg^2. We present results for 744 arcmin^2 in which public
UBVRI data exist. We compare optical-IR colours with predictions of a
semi-analytic hierarchical model (SAM) and find reasonable agreement. We also
determine photometric redshifts, finding a median z of z_m ~ 0.55. We compare
N(z) of different spectral types with models, showing that the observations are
inconsistent with simple PLE models while the SAM provides a reasonable fit to
the total N(z) but underestimates the number of z ~ 1 red spectral types. We
also present N(z) for samples of red objects (EROs). We find that EROs with R -
H > 4 and H < 20.5 have z_m ~ 1; redder EROs have higher z_m. For 19 < H < 20,
EROs with R - H > 4 comprise ~18% of the observed galaxy population while in
the SAM they contribute only ~4%. We also determine the angular correlation
function w(theta) for magnitude, colour, spectral type and photo-z selected
samples and use the estimated N(z) to derive the spatial clustering xi(r).
Parametrizing xi(r) by xi(r_c,z)=(r_c/r_*(z))^(-1.8) (r_c comoving), we find
that r_*(z) increases by ~1.5-2 times from z = 0 to z ~ 1.2. We interpret this
as a selection effect - the galaxies selected at z ~ 1.2 are intrinsically very
luminous. When galaxies are selected by absolute magnitude we find no evidence
for evolution in r_* over this z range. Extrapolated to z = 0, we find r_*(0) ~
6.5 h^-1Mpc for red galaxies and r_*(0) ~ 2-4 h^-1Mpc for blue galaxies. We
also find that while the angular clustering amplitude of EROs with R - H > 4 or
I - H > 3 is up to four times that of the whole galaxy population, the spatial
clustering length r_*(z=1) is ~7.5-10.5 h^-1Mpc which is only a factor of ~1.7
times r_* for non-EROs lying in a similar z and luminosity range.


title:
Interferometric array design: optimizing the locations of the antenna
  pads

abstract:
  The design of an interferometric array should allow optimal instrumental
response regarding all possible source positions, times of integration and
scientific goals. It should also take into account constraints such as
forbidden regions on the ground due to impracticable topography. The complexity
of the problem requires one to proceed by steps. A possible approach is to
first consider a single observation and a single scientific purpose. A new
algorithm is introduced to solve efficiently this particular problem called the
configuration problem. It is based on the computation of pressure forces
related to the discrepancies between the model (as determined by the scientific
purpose) and the actual distribution of Fourier samples. The flexibility and
rapidity of the method are well adapted to the full array design. A software
named APO that can be used for the design of new generation interferometers
such as ALMA and ATA has been developed.


title: Warm Ionized Gas on the Outskirts of Active and Star-Forming Galaxies

abstract:
  The preliminary results from a deep emission-line search for warm ionized
material in the halos of nearby active and star-forming galaxies are presented.
The origin of this gas is discussed in the context of galaxy formation and
evolution.


title: VLBA observations of GHz-Peaked-Spectrum radio sources at 15 GHz

abstract:
  We present VLBA observations at 15 GHz of ten GHz Peaked Spectrum (GPS) radio
sources. The cores are often difficult or impossible to locate. When likely
cores are found, they account for a small fraction of the flux density in GPS
galaxies - around or below 2%, while in GPS quasars they can account for more
than 20% of the total flux density. We detect low polarization in the GPS
sources -- i.e., typically less than a few percent and often less than one
percent. This establishes that low polarization in the parsec scale structure
is an important defining characteristic of the GPS sources. The dichotomy in
the radio morphology versus optical identification, i.e., galaxies are
symmetric and quasars are not, is basically confirmed from these new data,
which also indicate that the radio emission from GPS quasars is dominated by a
jet, with often a weak or hidden core, suggesting they are at moderate angles
to the line of sight, and so are only moderately beamed.


title: The Properties of Brightest Cluster Galaxies in X-Ray Selected Clusters

abstract:
  We present the K-band Hubble diagram for 162 brightest cluster galaxies
(BCGs) in X-ray selected clusters, 0.01<z<0.83. The sample incorporates that of
Burke, Collins, & Mann (2000) and includes additional infrared data from the
2MASS extended source catalogue. We show that below z=0.1 the BCGs show no
correlation with their environment, however, above z=0.1 BCGs in more X-ray
luminous clusters are more uniform in their photometric properties. This
suggests that there may be two populations of BCGs which have different
evolutionary histories.


title: Comet Hazard to the Earth

abstract:
  Migration of trans-Neptunian objects to the Earth is considered. Due to the
gravitational influence of large trans-Neptunian objects and mutual collisions,
some objects can get such orbits, from which they can be moved inside the Solar
System under the gravitational influence of planets. About 10-20% or even more
1-km Earth-crossers could have come from the Edgeworth-Kuiper belt and can move
in Jupiter-crossing orbits. The number of former trans-Neptunian objects that
cross the Earth's orbit moving in orbits with aphelia inside Jupiter's orbit
can be of the same order of magnitude. A total mass of icy planetesimals
delivered to the Earth during formation of the giant planets can be about the
mass of the Earth's oceans.


title: Further evidences for a generic Universe

abstract:
  Recently it was argued that an inflationary potential yielding power spectra
characterized by a scale-invariant tensorial spectral index and a weakly
scale-dependent scalar spectral index might account for a generic large-scale
structure formation in the multiverses scenario of eternal inflation. Here it
is shown that this statement remains true if the tensorial index is allowed to
slowly vary in a wide range of angular scales. In the cases analyzed in this
paper, the scalar index also slightly depends on the scales. Therefore, the
production of closely resembling each other universes seems to be a common
feature of inflationary scenarios with weakly scale-dependent spectral indices.
With power-law inflation as the extreme case, this is the class of scenarios
which may give the best fit to near future CMB observations.


title: Disk Diffusion Propagation Model for the Outburst of XTE J1118+480

abstract:
  We present a linear diffusion model for the evolution of the double-peaked
outburst in the transient source XTEJ1118+480. The model treats the two
outbursts as episodic mass deposition at the outer radius of the disk followed
by evolution of disk structure according to a diffusion process. We demonstrate
that light curves with fast-rise, exponential decay profile are a general
consequence of the diffusion process. Deconvolution of the light curve proves
to be feasible and gives an input function specifying mass deposition at the
outer disk edge as well as the total mass of the disk, both as functions of
time. The derived evolution of total disk mass can be correlated with the
observed evolution of the ~0.1 Hz QPO in the source reported in Wood et al.
(2000).


title: Luminosity Function of GRBs

abstract:
  We attempt to constrain the luminosity function of Gamma Ray Bursts (GRBs)
from the observed number count--flux relation and the afterglow redshift data.
We assume three classes of luminosity functions for our analysis: (a)
Log-normal distribution, (b) Schechter distribution, and (c) Scale-free
distribution. We assume several models of the evolution of the GRB population
for each luminosity function. Our analysis shows that: (a) log-normal is the
only luminosity function that is compatible with both the observations. This
result is independent of the GRB evolution model, (b) for log-normal function,
the average photon luminosity $L_0$ and the width of the luminosity function
$\sigma$ that are compatible with both the observations fall in the range:
$10^{55} sec^{-1} \la L_0 \la 10^{56} sec^{-1}$ and $2 \la \sigma \la 3$, (c)
the agreement of observations with other luminosity functions requires the GRB
population to evolve more strongly than the evolution of the star-formation
rate of the universe.


title: The solar neighbourhood age-metallicity relation - does it exist?

abstract:
  We derive stellar ages, from evolutionary tracks, and metallicities, from
Stromgren photometry, for a sample of 5828 dwarf and sub-dwarf stars from the
Hipparcos Catalogue. This stellar disk sample is used to investigate the
age-metallicity diagram in the solar neighbourhood. Such diagrams are often
used to derive a so called age-metallicity relation. Because of the size of our
sample, we are able to quantify the impact on such diagrams, and derived
relations, due to different selection effects. Some of these effects are of a
more subtle sort, giving rise to erroneous conclusions. In particular we show
that [1] the age-metallicity diagram is well populated at all ages and
especially that old, metal-rich stars do exist, [2] the scatter in metallicity
at any given age is larger than the observational errors, [3] the exclusion of
cooler dwarf stars from an age-metallicity sample preferentially excludes old,
metal-rich stars, depleting the upper right-hand corner of the age-metallicity
diagram, [4] the distance dependence found in the Edvardsson et al. sample by
Garnett & Kobulnicky is an expected artifact due to the construction of the
original sample. We conclude that, although some of it can be attributed to
stellar migration in the galactic disk, a large part of the observed scatter is
intrinsic to the formation processes of stars.


title:
Direct multi-wavelength limb-darkening measurements of three late-type
  giants with the Navy Prototype Optical Interferometer

abstract:
  We present direct measurements of the limb-darkened intensity profiles of the
late-type giant stars HR5299, HR7635, and HR8621 obtained with the Navy
Prototype Optical Interferometer (NPOI) at the Lowell Observatory. A triangle
of baselines with lengths of 18.9 m, 22.2 m, and 37.5 m was used. We utilized
squared visibility amplitudes beyond the first minimum, as well as triple
amplitudes and phases in up to 10 spectral channels covering a wavelength range
of ~650 nm to ~850 nm. We find that our data can best be described by
featureless symmetric limb-darkened disk models while uniform disk and fully
darkened disk models can be rejected. We derive high-precision angular
limb-darkened diameters for the three stars of 7.44 mas +/- 0.11 mas, 6.18 mas
+/- 0.07 mas, and 6.94 mas +/- 0.12 mas, respectively. Using the HIPPARCOS
parallaxes, we determine linear limb-darkened radii of 114 R$_\odot \pm $13
R$_\odot$, 56 R$_\odot \pm $4 R$_\odot$, and 98 R$_\odot \pm $9 R$_\odot$,
respectively. We compare our data to a grid of Kurucz stellar model
atmospheres, with them derive the effective temperatures and surface gravities
without additional information, and find agreement with independent estimates
derived from empirical calibrations and bolometric fluxes. This confirms the
consistency of model predictions and direct observations of the limb-darkening
effect.


title: Hubble Space Telescope WFPC-2 Imaging of Cassiopeia A

abstract:
  The young SNR Cassiopeia A was imaged with WFPC-2 through four filters
selected to capture the complete velocity range of the remnant's main shell in
several important emission lines. Primary lines detected were [O III]
4959,5007, [N II] 6583, [S II] 6716,6731 + [O II] 7319,7330 + [O I] 6300,6364,
and [S III] 9069,9532. About 3/4th of the remnant's main shell was imaged in
all four filters. Considerable detail is observed in the reverse-shocked ejecta
with typical knot scale lengths of 0.2"-0.4" (1 - 2 x 10^16 cm). Both bright
and faint emission features appear highly clumped. Large differences in [S III]
and [O III] line intensities indicating chemical abundance differences are also
seen, particularly in knots located along the bright northern limb and near the
base of the northeast jet. A line of curved overlapping filament in the
remnant's northwestern rim appears to mark the location of the remnant's
reverse shock front in this region. Finger-like ejecta structures elsewhere
suggest cases where the reverse shock front is encountering the remnant's
clumped ejecta. Narrow-band [N II] images of the remnant's circumstellar knots
("QSFs") reveal them to be 0.1"-0.6" thick knots and filaments, often with
diffuse edges facing away from the center of expansion. Three color composite
images of the whole remnant and certain sections along with individual filter
enlargements of selected regions of the bright optical shell are presented and
discussed.


title:
A Synthesis of Data from Fundamental Plane and Surface Brightness
  Fluctuation Surveys

abstract:
  We perform a series of comparisons between distance-independent photometric
and spectroscopic properties used in the surface brightness fluctuations (SBF)
and fundamental plane (FP) methods of early-type galaxy distance estimation.
The data are taken from two recent surveys: the SBF Survey of Galaxy Distances
and the Streaming Motions of Abell Clusters (SMAC) FP survey. We derive a
relation between V-I colour and Mg_2 index using nearly 200 galaxies and
discuss implications for Galactic extinction estimates and early-type galaxy
stellar populations. We find that the reddenings from Schlegel et al (1998) for
galaxies with $E(B{-}V) \gta 0.2$ mag appear to be overestimated by 5--10%, but
we do not find significant evidence for large-scale dipole errors in the
extinction map. In comparison to stellar population models having solar
elemental abundance ratios, the galaxies in our sample are generally too blue
at a given Mg_2; we ascribe this to the well-known enhancement of the
$\alpha$-elements in luminous early-type galaxies. We confirm a tight relation
between stellar velocity dispersion $\sigma$ and the SBF `fluctuation count'
parameter \Nbar, which is a luminosity-weighted measure of the total number of
stars in a galaxy. The correlation between \Nbar and $\sigma$ is even tighter
than that between Mg_2 and $\sigma$. Finally, we derive FP photometric
parameters for 280 galaxies from the SBF survey data set. Comparisons with
external sources allow us to estimate the errors on these parameters and derive
the correction necessary to bring them onto the SMAC system. The data are used
in a companion paper which compares the distances derived from the FP and SBF
methods.