title: A database of high and medium-resolution stellar spectra

abstract:
  We present a database of 908 spectra of 709 stars obtained with the ELODIE
spectrograph at Observatoire de Haute-Provence. 52 orders of the echelle
spectra have been carefully fitted together to provide continuous,
high-resolution spectra in the wavelength range 410 nm - 680 nm. The archive
provides a large coverage of the space of atmospheric parameters : Teff from
3700 K to 13600 K, logg from 0.03 to 5.86 and [Fe/H] from -2.8 to +0.7. At the
nominal resolution, R=42000, the mean signal-to-noise ratio is 150 per pixel.
The spectra given at this resolution are normalized to their pseudo-continuum
and are intended to serve for abundance studies, spectral classification and
tests of stellar atmosphere models. A lower resolution version of the archive,
at R=10000, is calibrated in physical flux with a broad-band photometric
precision of 2.5% and narrow-band precision of 0.5%. It is scoped for stellar
population synthesis of galaxies and clusters, and for kinematical
investigations of stellar systems.


title: Future directions in astroparticle physics and the AUGER experiment

abstract:
  The observation of cosmic ray particles with unexpected high energies is
pushing astroparticle physics into a period of rapid progress both
theoretically and experimentally. Different proposed models for the generation
of these particles are constrained by the absence of the predicted GZK cutoff
in the cosmic ray spectrum and by the composition and the distribution of
arrival directions observed. The database increase due to the Pierre Auger
Observatory will provide a clearer picture of the spectral anisotropy and
properties of such high energy particles, enabling tests of their origin and
nature.


title: Modeling Flares Produced in Blazars

abstract:
  We model light curves of flares observed in blazars, assuming that they are
produced by relativistic electrons/positrons injected by forward-reverse shocks
traveling down the jet with relativistic speeds. We approximate the radiating
region as a thin shell enclosed between the two shock fronts. In addition to
the conventional radiation processes such as synchrotron radiation and its
Comptonization, we take into account Comptonization of light originating in the
broad emission line region, and Comptonization of IR radiation from hot dust.
We demonstrate that flares produced in the adiabatic regime decay much slower
than flares produced in the radiative regime. The lack of such a difference
between the X-ray and $\gamma$-ray flares in 3C279 strongly supports the
synchrotron-self Compton (SSC) mechanism as responsible for X-ray production in
this object. Finally, we discuss a possible scenario which can explain the
`cooling' nature of the MeV peak in blazars by comparing the flares produced in
soft $\gamma$-ray band and above 100 MeV.


title: Jets in Quasars

abstract:
  In my review of jet phenomena in quasars, I focus on the following questions:
How powerful are jets in radio-loud quasars? What is their composition? How are
they launched? And why, in most quasars, are they so weak? I demonstrate the
exceptional role that blazar studies can play in exploring the physics and
structure of the innermost parts of quasar jets.


title: Blazars

abstract:
  In our review of the blazar phenomenon, we discuss blazar models, with a
focus on the following issues: sub-parsec jets and their environment; energy
dissipation and particle acceleration; and radiative processes.


title: The p- and r-processes: reviews and other views

abstract:
  A review is presented of the p-process in Type II supernovae, one of its
goals being to enlighten the changes in views on this nucleosynthesis mechanism
since the work of Jean and Jim on the subject in 1975. Specific discussions are
also devoted to cases of particular interest, like the light Mo and Ru stable
isotopes, the rare nuclide 138La or the radionuclide 146Sm. Some comments of
diverse natures are also made on the r-process. These considerations do not aim
at really providing an exhaustive review of the many nuclear physics and
astrophysics intricacies of this process. In contrast, they are hoped to
complement or to put in perspective other views that are often expressed in
relation with this nucleosynthesis mechanism


title: The Initial Mass Function of the Most Massive Starforming Regions

abstract:
  The stellar initial mass function (IMF) describes how many stars form at
which mass. Despite recent observational progress, many fundamental properties
of the IMF are still unknown. Specifically the question, whether starbursts are
biased towards the formation of more massive stars, is controversially
discussed in the literature. This presentation gives an overview of how the
Large Binocular Telescope (LBT) will contribute to answering this question. I
will present (a) the status quo of the IMF research in starbursts, (b) the
importance of direct star counts in nearby templates, (c) the need for
spectroscopy, (d) the advantage of the LBT over its competitors, and (e) what
additional instrumentation I would like to see at the LBT for the proper
investigation of the most massive starforming regions.


title:
Australia Telescope Compact Array Observations of the OH Star Roberts
  22: Resolved Images of OH Emission

abstract:
  We have imaged the unusual OH/IR object G 284-0.8 (Roberts 22) in the OH
transitions at 1612, 1665 and 1667 MHz using the Australia Telescope Compact
Array in Narrabri, NSW, Australia. The angular resolution of the OH images we
present here is 6 arcsec (12000 AU at a distance of 2 kpc). We find OH
emission, of extent 1.5 arcsec (2800 AU), located inside the optical bipolar
flow region (size 8 arcsec) discovered by Allen et al. (1980) and imaged
recently by Sahai et al. (1999) with the Hubble Space Telescope. We present
astrometry of Roberts 22, providing registration of the OH and Hubble Space
Telescope images to within ~0.35 arcsec. We describe the OH velocity field in
Roberts 22 and discuss the kinematic properties of the source and its
evolutionary status.


title: How Does CMB + BBN Constrain New Physics?

abstract:
  Recent cosmic microwave background (CMB) results from BOOMERANG, MAXIMA, and
DASI provide cosmological constraints on new physics that can be competitive
with those derived from Big Bang Nucleosynthesis (BBN). In particular, both CMB
and BBN can be used to place limits on models involving neutrino degeneracy and
additional relativistic degrees of freedom. However, for the case of the CMB,
these constraints are, in general, sensitive to the assumed priors. We examine
the CMB and BBN constraints on such models and study the sensitivity of ``new
physics" to the assumed priors. If we add a constraint on the age of the
universe ($t_0 \ga 11$ Gyr), then for models with a cosmological constant, the
range of baryon densities and neutrino degeneracy parameters allowed by the CMB
and BBN is fairly robust: $\eta_{10} = 6.0 \pm 0.6$, \deln $\la 6$, $\xi_e \la
0.3$. In the absence of new physics, models without a cosmological constant are
only marginally compatible with recent CMB observations (excluded at the 93%
confidence level).


title: Hydrostatic equilibrium in a magnetized, warped Galactic disc

abstract:
  Hydrostatic equilibrium of the multiphase interstellar medium in the solar
vicinity is reconsidered, with the regular and turbulent magnetic fields
treated separately. The regular magnetic field strength required to support the
gas is consistent with independent estimates provided energy equipartition is
maintained between turbulence and random magnetic fields. Our results indicate
that a midplane value of $B_{0}=4\mkG$ for the regular magnetic field near the
Sun leads to more attractive models than $B_{0}=2\mkG$. The vertical profiles
of both the regular and random magnetic fields contain disc and halo components
whose parameters we have determined. The layer at $1\la|z|\la4\kpc$ can be
overpressured and an outflow at a speed of about $50\kms$ may occur there,
presumably associated with a Galactic fountain flow, if $B_{0}\simeq 2\mkG$. We
show that hydrostatic equilibrium in a warped disc must produce asymmetric
density distributions in $z$, in rough agreement with \HI observations in the
outer Galaxy. This asymmetry may be a useful diagnostic of the details of the
warping mechanism in the Milky Way and other galaxies. We find indications that
gas and magnetic field pressures are different above and below the warped
midplane in the outer Galaxy and quantify the difference in terms of turbulent
velocity and/or magnetic field strength.


title:
Spectral Evolution of the Continuum and Disc Line in Dipping in GRO
  J1655-40

abstract:
  The discovery is reported of emission features in the X-ray spectrum of GRO
J1655-40 obtained using Rossi-XTE on 1997, Feb 26. The features have been
fitted firstly by two Gaussian lines, which in four spectra have average
energies of 5.85+/-0.08 keV and 7.32+/-0.13 keV, strongly suggestive that these
are the red- and blueshifted wings of an iron disc line from material with
velocity ~0.33 c. The blue wing is apparently less bright than expected for a
disc line subject to Doppler boosting, however, known absorption in the
spectrum of GRO J1655-40 at energies between ~7 and 8 keV can reduce the
apparent brightness of the blue wing. The spectra have also been fitted well
using the full relativistic disc line model of Laor, plus an absorption line.
This gives a restframe energy between 6.4 and 6.8 keV indicating that the line
is from highly ionized iron K_alpha. The Laor model also shows that the line
originates at radii extending from ~10 Schwarzschild radii (r_S) outwards. The
line is direct evidence for the black hole nature of the compact object. The
continuum is well described by dominant disc blackbody emission plus
Comptonized emission. During dipping, spectral evolution is well modelled by
allowing progressive covering of the disc blackbody and simple absorption of
the Comptonized emission showing that the thermal emission is more extended.
Acceptable fits are only obtained by including the disc line in the covering
term, indicating that it originates in the same inner disc region as the
thermal continuum. Dip ingress times and durations are used to provide the
radius of the disc blackbody emitter as 170-370 r_S, and the radius of the
absorber.


title: Populating Stellar Orbits Inside a Rotating, Gaseous Bar

abstract:
  In an effort to better understand the formation and evolution of barred
galaxies, we have examined the properties of equatorial orbits in the effective
potential of one model of a rapidly rotating, steady-state gas-dynamical bar
that has been constructed via a self-consistent hydrodynamical simulation.
Using a ``Restriction Hypothesis'' to determine initial conditions, we find
that a significant fraction of orbits in this potential are quasi-ergodic and
that regular orbits have a ``bowtie'' shape in contrast to the more typical x1
orbits. This bowtie orbit should give a boxy-peanut shape to such systems.


title: Formation of optical lines in black-hole binaries

abstract:
  The HI Balmer emission lines of black-hole binaries show double-peaked
profiles during the high-soft state and the quiescent state. In the high-soft
state the profiles are asymmetric with a stronger red peak, but the profiles
are symmetric in the quiescent state. We suggest that in the high-soft state
the emission lines originate from the temperature-inversion layer caused by
irradiative heating of an optically thick accretion disk. Irradiative heating
also causes the formation of a disk wind, which mildly absorbs the blue peak of
the lines. The double-peaked lines seen in the quiescent state arise from an
optically thin disk. In the absence of a disk wind, the lines are unabsorbed
and so the symmetry of the line profiles is preserved.


title: IR spectra of the microquasar GRS 1915+105 during a low state

abstract:
  There is controversy regarding the nature of the suspected donor star to the
microquasar GRS 1915+105, and hence whether GRS 1915+105 is a high mass X-ray
binary (HMXB) or a low-mass X-ray binary (LMXB). In order to clarify this
issue, we obtained an infrared (J, H and K) spectrum of GRS 1915+105 in its low
state which shows a steeper continuum than the prototype X-ray binary Sco X-1.
We did not detect any HeII emission at 2.189 microns from GRS 1915+105 in our
quiescent spectrum, indicating that the line is transient and is only observed
during episodes of high X-ray activity. For our instrument configuration, there
is no detection of the 12CO lines which are characteristic of late-type stars
either in GRS1915+105 or Sco X-1.


title: Strange Cepheids and RR Lyrae

abstract:
  Strange modes can occur in radiative classical Cepheids and RR Lyrae models.
These are vibrational modes that are trapped near the surface as a result of a
'potential barrier' caused by the sharp hydrogen partial ionization region.
Typically the modal number of the strange mode falls between the 7th and 12th
overtone, depending on the astrophysical parameters of the equilibrium stellar
models (L, M, \Teff, X, Z). Interestingly these modes can be linearly unstable
outside the usual instability strip, in which case they should be observable as
new kinds of variable stars, 'strange Cepheids' or 'strange RR Lyrae' stars.
The present paper reexamines the linear stability properties of the strange
modes by taking into account the effects of an isothermal atmosphere, and of
turbulent convection. It is found that the linear vibrational instability of
the strange modes is resistant to both of these effects. Nonlinear hydrodynamic
calculations indicate that the pulsation amplitude of these modes is likely to
saturate at the millimagnitude level. These modes should therefore be
detectable albeit not without effort.


title:
Large X-ray Flares from LMC X-4: Discovery of Milli-hertz Quasi-periodic
  Oscillations and QPO-modulated Pulsations

abstract:
  We report the discovery of milli-hertz (mHz) quasi-periodic oscillations
(QPOs) and QPO-modulated pulsations during large X-ray flares from the
high-mass X-ray binary pulsar LMC X-4 using data from the Rossi X-Ray Timing
Explorer (RXTE). The lightcurves of flares show that, in addition to ~74 mHz
coherent pulsations, there exist two more time-varying temporal structures at
frequencies of ~0.65-1.35 and ~2-20 mHz. These relatively long-term structures
appear in the power density spectra as mHz QPOs and as well-developed sidebands
around the coherent pulse frequency as well, indicating that the amplitudes of
the coherent pulsation is modulated by those of the mHz QPOs. One interesting
feature is that, while the first flare shows symmetric sidebands around the
coherent pulse frequency, the second flare shows significant excess emission in
the lower-frequency sidebands due to the ~2-20 mHz QPOs. We discuss the origin
of the QPOs using a combination of the beat-frequency model and a modified
version of the Keplerian-frequency model. According to our discussion, it seems
to be possible to attribute the origin of the ~0.65-1.35 and ~2-20 mHz QPOs to
the beating between the rotational frequency of the neutron star and the
Keplerian frequency of large accreting clumps near the corotation radius and to
the orbital motion of clumps at Keplerian radii of 2-10 times 10^9 cm,
respectively.


title: Fabry Perot Halpha Observations of the Barred Spiral NGC 3367

abstract:
  We report the gross properties of the velocity field of the barred spiral
galaxy NGC 3367. The following values were found: inclination with respect to
the plane of the sky, i=30 deg; position angle (PA) of receding semi major axis
PA=51 and systemic velocity V(sys)=3032 km/s. Large velocity dispersion are
observed of upt o 120 km/s in the nuclear region, of up to 70 km/s near the
eastern bright sources just beyond the edge of the stellar bar where three
spiral arms seem to start and in the western bright sources at about 10 kpc.
Deviations from normal circular velocities are observed from all the disk but
mainly from the semi circle formed by the string of south western Halpha
sources. An estimate of the dynamical mass is M(dyn)=2x10^11 Msolar.


title:
Using the Supernova / Acceleration Probe (SNAP) to Search for
  Microlensing Events Towards the LMC

abstract:
  Microlensing experiments today have a tantalizing result; they have detected
an excess of microlensing events beyond what is expected from known stellar
populations. These events could be due to a possible form of Halo dark matter.
However, study of these events is limited by their small number and poor
photometric precision. The SNAP satellite, which has been proposed to search
for supernovae, would be an ideal instrument to search for microlensing events
towards the LMC. Due in part to its larger mirror, and largely to its superb
space-based seeing and low background, with a modest program SNAP will be able
to detect $\sim 250$ microlensing events per year. In addition, SNAP will
generate $\sim 16$ high quality events per year with 1% photometric resolution.
These data should break the microlensing degeneracy, and determine whether the
events are indeed due to dark matter lenses in the Galactic Halo. Side benefits
of such a program will include a never before equaled catalog of variable stars
in the LMC. On of the most intriguing possibilities is a direct measurement of
the distance to the LMC. Such a measurement will determine what is today the
most uncertain rung on the distance ladder and thus lock down the Hubble
constant.


title:
HEXTE Studies of Sco X-1 Spectra: Detections of Hard X-Ray Tails Beyond
  200 keV

abstract:
  Using the HEXTE experiment on-board the RXTE satellite, we performed a search
for hard X-ray tails in Sco X-1 spectra. We found strong evidence for the
presence of such a non-thermal component on several occasions. Using the
PCA/RXTE we were able to track the position of the source along the Z diagram,
and we observed that the presence of the hard X-ray tail is not confined to a
particular region. However, we found a correlation between the power law index
of the non-thermal component and the position of the source in the Z diagram,
suggesting that the hard X-ray spectrum (i.e., E > 50 keV) becomes flatter as
the mass accretion rate increases. We were also able to study the temporal
variation of the appearance/absence of the hard X-ray component. With our
derived luminosities, we were also able to test the idea that X-ray
luminosities can be used to distinguish between X-ray binary systems containing
neutron stars and black holes.


title:
Turbulent dissipation in the ISM: the coexistence of forced and decaying
  regimes and implications for galaxy formation and evolution

abstract:
  We discuss the dissipation of turbulent kinetic energy Ek in the global ISM
by means of 2-D, MHD, non-isothermal simulations in the presence of model
radiative heating and cooling. We argue that dissipation in 2D is
representative of that in three dimensions as long as it is dominated by shocks
rather than by a turbulent cascade. Energy is injected at a few isolated sites
in space, over relatively small scales, and over short time periods. This leads
to the coexistence of forced and decaying regimes in the same flow. We find
that the ISM-like flow dissipates its turbulent energy rapidly. In simulations
with forcing, the input parameters are the radius l_f of the forcing region,
the total kinetic energy e_k each source deposits into the flow, and the rate
of formation of those regions, sfr_OB. The global dissipation time t_d depends
mainly on l_f. In terms of measurable properties of the ISM, t_d >= Sigma_g
u_rms^2/(e_k sfr_OB), where Sigma_g is the average gas surface density and
u_rms is the rms velocity dispersion. For the solar neighborhood, t_d >=
1.5x10^7 yr. The global dissipation time is consistently smaller than the
crossing time of the largest energy-containing scales. In decaying simulations,
Ek decreases with time as t^-n, where n~0.8-0.9. This suggests a decay with
distance d as Ek\propto d^{-2n/(2-n)} in the mixed forced+decaying case. If
applicable to the vertical direction, our results support models of galaxy
evolution in which stellar energy injection provides significant support for
the gas disk thickness, but not models of galaxy formation in which this energy
injection is supposed to reheat an intra-halo medium at distances of up to
10-20 times the optical galaxy size, as the dissipation occurs on distances
comparable to the disk height.


title:
Extragalactic radio source evolution & unification: clues to the
  demographics of blazars

abstract:
  In this paper we discuss the demographics of the radio blazar population: (i)
what are their parent (`unbeamed') sources and (ii) what magnitude and/or type
of evolution have they undergone ? The discussion is based on models of radio
source evolution and beaming based on a `dual population' unification paradigm.
These models, developed from radio blazar properties in bright samples, predict
blazar demographic trends at the lower flux-density levels; samples from deep
mJy-level surveys (e.g. NVSS and FIRST) may now provide direct tests of these
predictions.


title: The spectral characteristics of the 2dFGRS-NVSS galaxies

abstract:
  We have analysed the 2dF spectra of a sample of galaxies common to the 2dF
galaxy redshift survey (2dFGRS, Colless 1999) and the NRAO VLA sky survey
(NVSS, Condon et al. 1998). Our sample comprises 88 galaxies selected by Sadler
et al. (1999) from 30 2dFGRS fields observed in 1998. In this paper we discuss
how this and future, much larger, samples of 2dFGRS-NVSS galaxies can be
interpreted via analysis of those galaxies with strong narrow emission lines.
Using diagnostic line ratio measurements we confirm the majority of the eyeball
classifications of Sadler et al. (1999), although many galaxies show evidence
of being `composite' galaxies - a mixture of AGN plus starburst components.


title: General Relativistic Effects in the Core Collapse Supernova Mechanism

abstract:
  We apply our recently developed code for spherically symmetric, fully general
relativistic (GR) Lagrangian hydrodynamics and multigroup flux-limited
diffusion neutrino transport to examine the effects of GR on the hydrodynamics
and transport during collapse, bounce, and the critical shock reheating phase
of core collapse supernovae. Comparisons of models computed with GR versus
Newtonian hydrodynamics show that collapse to bounce takes slightly less time
in the GR limit, and that the shock propagates slightly farther out in radius
before receding. After a secondary quasistatic rise in the shock radius, the
shock radius declines considerably more rapidly in the GR simulations than in
the corresponding Newtonian simulations. During the shock reheating phase, core
collapse computed with GR hydrodynamics results in a substantially more compact
structure from the center out to the stagnated shock. The inflow speed of
material behind the shock is also increased. Comparisons also show that the
luminosity and rms energy of any neutrino flavor during the shock reheating
phase increases when switching from Newtonian to GR hydrodynamics, and
decreases when switching from Newtonian to GR transport. This latter decrease
in neutrino luminosities and rms energies is less in magnitude than the
increase that arise when switching from Newtonian to GR hydrodynamics, with the
result that a fully GR simulation gives higher neutrino luminosities and harder
neutrino spectra than a fully Newtonian simulation of the same precollapse
model.


title: Galaxy mass distributions for some extreme orbital-speed Profiles

abstract:
  Extreme speed profiles, that are impossible to anayze correctly using the
usual methods, are shown to be easily handled using the methods developed
previously by Nicholson (astro-ph/0006330). These profiles are constant orbital
speeds with sharp and smooth ramps at the origin, and constant angular velocity
with speeds increasing linearly to the galaxy rim. Also an example using
measured data for a real galaxy is shown for NGC 3198. A new format is
presented to show results in dimensionless form, that includes a way to show
SMD results so they are easily compared. Based on repeated trials for accuracy,
the rod representing the mass of a fundamental segment is now placed at
0.575*dr at the center ring of a galaxy.


title: HI 21cm absorption in low z damped lyman-alpha systems

abstract:
  We report Giant Metrewave Radio Telescope (GMRT) 21cm observations of two
confirmed and one candidate low redshift damped Lyman-alpha systems (DLAS). HI
absorption was detected in the two confirmed systems, at z=0.2378 and z=0.5247,
with spin temperatures (Ts) of 2050 +- 200 K and 330 +- 70 K respectively. The
non-detection of absorption in the third (candidate) system places an upper
limit on its optical depth, which in turn implies a 3sigma lower limit of 850 K
on its spin temperature. Ground based K-band imaging observations (Turnshek et
al. 2000) have identified the low Ts absorber with a spiral galaxy while the
high Ts system appears to be an LSB galaxy. This continues the trend noted
earlier by Chengalur and Kanekar (2000) of low spin temperatures for DLAS
associated with spiral galaxies and high spin temperatures for those with no
such association.
  Combining these new results with 21cm observations from the published
literature, we find that (1)The 21 cm equivalent width (EW21) of DLAS increases
with increasing column density (NHI). Further, absorbers associated with spiral
galaxies have systematically higher EW21 at the same NHI than DLAS with no such
association, (2)DLAS at high redshift (z > 2) have small velocity spreads
(DeltaV), while, at low redshift (z < 2), both large and small DeltaV are
observed. These trends are in qualitative agreement with hierarchical models of
galaxy formation.


title: ISO Observations of Star-forming Galaxies

abstract:
  The Infrared Space Observatory (ISO) is used to carry out mid-IR (7 and 15
micron) and far-IR (90 micron) observations of a sample of star-forming sub-mJy
radio sources. By selecting the sample at radio wavelengths, one avoids biases
due to dust obscuration. It is found that the mid-IR luminosities, covering the
PAH features, measure the star formation rate for galaxies with $P_{1.4 GHz} <
10^{23}$ W Hz$^{-1}$. This is further confirmed using the H$\alpha$
luminosities. The far-IR emission is also found to trace the SFR over the whole
range of radio and H$\alpha$ luminosities. The implication of the mid-IR
measurements in estimating the SFRs from the future infrared space missions
(SIRTF and ASTRO-F) is discussed.


title: The Ursa Major Cluster of Galaxies. IV ; HI synthesis observations

abstract:
  In this data paper we present the results of an extensive 21cm-line synthesis
imaging survey of 43 spiral galaxies in the nearby Ursa Major cluster using the
Westerbork Synthesis Radio Telescope. Detailed kinematic information in the
form of position-velocity diagrams and rotation curves is presented in an atlas
together with HI channel maps, 21cm continuum maps, global HI profiles, radial
HI surface density profiles, integrated HI column density maps, and HI velocity
fields. The relation between the corrected global HI linewidth and the
rotational velocities Vmax and Vflat as derived from the rotation curves is
investigated. Inclination angles obtained from the optical axis ratios are
compared to those derived from the inclined HI disks and the HI velocity
fields. The galaxies were not selected on the basis of their HI content but
solely on the basis of their cluster membership and inclination which should be
suitable for a kinematic analysis. The observed galaxies provide a
well-defined, volume limited and equidistant sample, useful to investigate in
detail the statistical properties of the Tully-Fisher relation and the dark
matter halos around them.


title:
On The Linearity of The Black Hole - Bulge Mass Relation in Active and
  in Nearby Galaxies

abstract:
  Analysis of PG quasar observations suggests a nonlinear relation between the
black hole mass, M_BH, and the bulge mass, M_bulge, although a linear relation,
as proposed for nearby galaxies, cannot be ruled out. New M_BH values for
nearby galaxies from Gebhardt et al., and L_bulge measurements for Seyfert 1
galaxies from Virani et al., are used here to obtain a more accurate value for
the slope of the M_BH-M_bulge relation. The combined sample of 40 active and
non-active galaxies suggests a significantly nonlinear relation, M_BH\propto
M_bulge^{1.53\pm 0.14}. Further support for a nonlinear relation is provided by
the slope of the M_BH-stellar velocity dispersion relation found recently, and
by the low M_BH found in late type spiral galaxies. The mean M_BH/M_bulge ratio
is therefore not a universal constant, but rather drops from ~0.5% in bright
(M_V ~ -22) ellipticals, to ~0.05% in low luminosity (M_V ~ -18) bulges. Hubble
Space Telescope determinations of M_BH in late type spirals, and of the bulge
magnitude in narrow line Seyfert 1 galaxies (both predicted to have low M_BH),
can further test the validity of the nonlinear M_BH-M_bulge relation.


title: Enhancement of superhorizon scale inflationary curvature perturbations

abstract:
  We show that there exists a simple mechanism which can enhance the amplitude
of curvature perturbations on superhorizon scales during inflation, relative to
their amplitude at horizon crossing. The enhancement may occur even in a
single-field inflaton model, and occurs if the quantity $a\dot\phi/H$ becomes
sufficiently small, as compared to its value at horizon crossing, for some time
interval during inflation. We give a criterion for this enhancement in general
single-field inflation models.


title: Chemical Evolution and Starbursts

abstract:
  The first part of this paper deals with the impact of nonsolar and - for
late-type, dwarf, and high redshift galaxies - generally subsolar abundances on
the interpretation of observational data for starburst galaxies. It points out
the differences in colors, luminosities, emission lines, etc. obtained from a
model using low metallicity input physics for a starburst on top of the stellar
population of a galaxy as compared to an otherwise identical model using solar
metallicity input physics only.
  The second part deals with the chemical evolution during a starburst and
contrasts model predictions with observational clues.


title:
Diffraction-limited 800nm imaging with the 2.56m Nordic Optical
  Telescope

abstract:
  A quantitative assessment is presented of diffraction-limited stellar images
with Strehl ratios of 0.25-0.30 obtained by selection of short-exposure CCD
images of stars brighter than +6m at 810nm with the Nordic Optical Telescope.


title: Sub-electron read noise at MHz pixel rates

abstract:
  A radically new CCD development by Marconi Applied Technologies has enabled
substantial internal gain within the CCD before the signal reaches the output
amplifier. With reasonably high gain, sub-electron readout noise levels are
achieved even at MHz pixel rates. This paper reports a detailed assessment of
these devices, including novel methods of measuring their properties when
operated at peak mean signal levels well below one electron per pixel. The
devices are shown to be photon shot noise limited at essentially all light
levels below saturation. Even at the lowest signal levels the charge transfer
efficiency is good. The conclusion is that these new devices have radically
changed the balance in the perpetual trade-off between readout noise and the
speed of readout. They will force a re-evaluation of camera technologies and
imaging strategies to enable the maximum benefit to be gained from these
high-speed, essentially noiseless readout devices. This new LLLCCD technology,
in conjunction with thinning (backside illumination) should provide detectors
which will be very close indeed to being theoretically perfect.


title: RX J2217.9--5941: A highly X-ray variable Narrow-Line Seyfert1 galaxy

abstract:
  We report the discovery of a highly X-ray variable AGN, RX J2217.9-5941. This
object was bright during the ROSAT All-Sky Survey (RASS), during which a
decrease in the count rate by a factor of 12 was observed. It was found to be
much fainter in follow-up HRI observations and is therefore an X-ray transient
AGN candidate. On long time scales of years, its count rate decreased by a
factor of about 30 between the RASS and the ROSAT HRI and ASCA observations in
1998. Analysis of the ASCA data, complicated by source confusion and poor
statistics, tentatively indicates a steep spectrum in the faint state. There is
no evidence for variability among 5 optical observations of the object obtained
between 1992 and 1998. We discuss the variability of RX J2217.9-5941 and its
possible X-ray transient nature.


title: Finding Galaxy Clusters using Voronoi Tessellations

abstract:
  We present an objective and automated procedure for detecting clusters of
galaxies in imaging galaxy surveys. Our Voronoi Galaxy Cluster Finder (VGCF)
uses galaxy positions and magnitudes to find clusters and determine their main
features: size, richness and contrast above the background. The VGCF uses the
Voronoi tessellation to evaluate the local density and to identify clusters as
significative density fluctuations above the background. The significance
threshold needs to be set by the user, but experimenting with different choices
is very easy since it does not require a whole new run of the algorithm. The
VGCF is non-parametric and does not smooth the data. As a consequence, clusters
are identified irrispective of their shape and their identification is only
slightly affected by border effects and by holes in the galaxy distribution on
the sky. The algorithm is fast, and automatically assigns members to
structures.


title: Temperature and total mass profiles of the A3571 cluster of galaxies

abstract:
  We present BeppoSAX results of a spatially resolved spectral analysis of
A3571, a relaxed nearby cluster of galaxies. In the central 2' (130/h_50 kpc)
radius the metal abundance is 0.49 +- 0.08 solar and the absorption (1.13
+-0.28) x 10^21 atom/cm^2 whereas elsewhere within an 8'(520/h_50 kpc) radius
the abundance is 0.32 \+- 0.05 solar and the absorption consistent with the
galactic value of 4.4 x 10^20 atom/cm2. The significant central metal abundance
enhancement is consistent with the supernova enrichment scenario. The excess
absorption may be attributed to the cooling flow, whose mass flow rate is 80 +-
40 M_Sun/yr from our spectral fit. The BeppoSAX and ASCA radial temperature
profiles agree over the entire overlapping radial range r < 25' = 1.6/h_50 Mpc.
The combined BeppoSAX and ASCA temperature profile exhibits a constant value
out to a radius of 10' (650/h_50 kpc) and a significant decrease (T propto
r^-0.55, corresponding to gamma=1.28) at larger radii. These temperature data
are used to derive the total mass profile. The best fit NFW dark matter density
model results in a temperature profile that is not convectively stable, but the
model is acceptable within the uncertainties of the data. The temperature
profile is acceptably modeled with a ``core'' model for the dark matter
density, consisting of a core radius with a constant slope at larger radii.
With this model the total mass and formal 90% confidence errors within the
virial radius r_178 (2.5/h_50 Mpc) are 9.1+3.6-1.5 x 10^14 h_50^-1 M_Sun, by a
factor of 1.4 smaller than the isothermal value. The gas mass fraction
increases with radius, reaching f_gas(r_178) = 0.26+0.05-0.10 x h_50^-3/2.
Assuming that the measured gas mass fraction is the lower limit to the
primordial baryonic fraction gives Omega_m < 0.4 at 90% confidence.


title: CMB Constraints on a Baryonic Dark Matter-Dominated Universe

abstract:
  In recent years, upper limits on the cosmic microwave background (CMB)
anisotropies combined with predictions made by theories of galaxy formation,
have been extremely powerful in ruling out purely baryonic dark matter (BDM)
universes. However, it has recently been argued that the absence of a prominent
second peak in the anisotropy spectrum measured by the BOOMERanG-98 and
MAXIMA-1 experiments seems to favour a $\Lambda$BDM model when combined with
standard Big Bang Nucleosynthesis (BBN) constraints. In this {\it Letter}, we
further investigate this result showing that, using the CMB data {\it alone}, a
purely baryonic adiabatic model of structure formation seems unlikely if the
universe is flat ($\Omega=1$). Combining the CMB data with supernova type Ia
(SNIa) data renders purely baryonic models inconsistent with flatness at high
significance and more than $3 \sigma$ away from both the BBN constraints and
the HST key project result $h=0.72 \pm 0.08$. These results indicate that only
a radical revision of cosmology with {\it ad hoc} properties could bring
baryonic models such as those advocated by MOND enthusiasts back into agreement
with current observations.


title: Detailed Chemical Analysis of Two Giants in the SGR DSPH

abstract:
  The 8m class telescopes allow for the first time to study stars of external
galaxies with the same resolution and S/N ratio which has been so far used for
Galactic stars. It is quite likely that this study will shake some of our
current beliefs. In this poster we highlight some of the results which have
been obtained for two giants in the Sgr dSph thanks to the UVES spectrograph on
the ESO 8.2m Kueyen telescope. Further details on the observations and data
analysis may be found in Bonifacio et al (2000).


title: VLT/Uves Observations of the Dla at Z=3.39 towards QSO 0000-2621

abstract:
  UVES observations at ESO/VLT of the DLA at z=3.39 towards QSO 0000-2621
provided refined abundances for Fe, Si, N, Ni, and new abundances for O, Ar, P,
Zn, Cr, H2. These determinations confirm that the system has remarkable
properties with the lowest metallicity, a very low H2 molecular fraction and it
has no detectable presence of dust. The [alpha/Fe-peak] ratio is ~ 0.1
challenging current models of chemical evolution. The O/Ar and O/S ratios are
the same as those observed in BCGs, suggesting a universal IMF.


title:
A study of the core of the Shapley Concentration: VI. Spectral
  properties of galaxies

abstract:
  We present the results of a study of the spectral properties of galaxies in
the central part of the Shapley Concentration, covering an extremely wide range
of densities, from the rich cluster cores to the underlying supercluster
environment. Our sample is homogeneous, in a well defined magnitude range
(17=<b_J=<18.8) and contains ~1300 spectra of galaxies at the same distance,
covering an area of ~26 sq.deg. These characteristics allowed an accurate
spectral classification, that we performed using a Principal Components
Analysis technique.
  This spectral classification, together with the [OII] equivalent widths and
the star formation rates, has been used to study the properties of galaxies at
different densities: cluster, intercluster (i.e. galaxies in the supercluster
but outside clusters) and field environment.
  No significant differences are present between samples at low density regimes
(i.e. intercluster and field galaxies). Cluster galaxies, instead, not only
have values significantly different from the field ones, but also show a
dependence on the local density. Moreover, a well defined morphology-density
relation is present in the cluster complexes, although these structures are
known to be involved in major merging events. Also the mean equivalent width of
[OII] shows a trend with the local environment, decreasing at increasing
densities, even if it is probably induced by the morphology-density relation.
  Finally we analyzed the mean star formation rate as a function of the
density, finding again a decreasing trend (at ~ 3sigma significance level). Our
analysis is consistent with the claim of Balogh et al. (1998) that the star
formation in clusters is depressed.


title: Atmospheric reflection during an anomalous low-state of Hercules X-1

abstract:
  We present RXTE observations of the eclipsing X-ray binary Hercules X-1
conducted during an anomalous low state. Data reduction reveals a light curve
over 2.7 orbital cycles remarkably similar to optical and UV light curves which
are dominated by the companion star. Count rates are modulated close to the
orbital period, attaining a maximum when the inner face of the companion star,
irradiated by X-rays from the compact source, is most-visible. Cold reflection
provides an acceptable fit to the energy spectrum. Employing binary geometry to
scale the model and assuming companion star reflection, we are able to
reconstruct the incident X-rays which are removed from our direct line-of-sight
(presumably by the accretion disk). We find the flux of the hidden source to be
identical to the observed flux of Her X-1 at the peak of its main-high state.
Consequently, Her X-1 is emitting a reflected spectrum, largely uncontaminated
by direct X-rays in the anomalous low-state. The spectral energy distribution,
period, amplitude and phasing of the modulation are all consistent with a
companion star origin. Since this source occurs in a well-understood binary
environment, it provides an excellent case study for more sensitive experiments
in the future.


title:
A Comparison of Radio and X-Ray Morphologies of Four Clusters of
  Galaxies Containing Radio Halos

abstract:
  Clusters of galaxies may contain cluster-wide, centrally located, diffuse
radio sources, called halos. They have been found to show morphologies similar
to those of the X-ray emission. To quantify this qualitative statement we
performed a point-to-point comparison of the radio and the X-ray emission for
four clusters of galaxies containing radio halos: Coma, Abell 2255, Abell 2319,
Abell 2744. Our study leads to a linear relation between the radio and the
X-ray surface brightness in two clusters, namely Abell 2255 and Abell 2744. In
Coma and A2319 the radio and the X-ray brightnesses seem to be related with a
sub-linear power law. Implications of these findings within simple radio halo
formation models are briefly discussed.


title:
The Statistical and Physical Properties of the Low Redshift Lyman Alpha
  Forest Observed with HST/STIS

abstract:
  We examine the Ly-alpha absorber population at z<0.3 detected in spectra of
the QSOs PG0953+415 and H1821+643 taken with the Space Telescope Imaging
Spectrograph aboard the Hubble Space Telescope. We compare their statistical
properties to those in carefully-constructed mock quasar spectra drawn from a
cosmological hydrodynamic simulation of a Lambda-CDM universe. We find very
good agreement in the column density and b-parameter distributions, down to the
smallest observable absorbers with N_HI\approx 10^{12.3} cm^-2. The observed
absorber population is complete for N_HI\ga 10^{13} cm^-2, with a column
density distribution slope of \beta=2.04\pm 0.23 and a median b-parameter of 21
km/s above this limit. The intergalactic gas giving rise to these weak
absorbers is analogous to that at high redshift, located in diffuse large-scale
structures that are highly photoionized by the metagalactic UV flux, though a
greater number arise within shock-heated warm gas. The density, temperature,
and column density of these absorbers follow similar relationships to those at
high redshift, though with substantially larger scatter due to the shock-heated
gas. The b-parameters typically have a significant contribution from thermal
broadening, which facilitates a measurement of the low-z IGM temperature as
traced by Ly-alpha absorbers. From our simulation we estimate T_IGM\sim 5000 K,
with an upper limit of 10^4 K, at the mean density. The agreement in predicted
and observed amplitude of the column density distributions allows us to measure
the HI photoionization rate at z=0.17 to be 10^{-13.3\pm 0.7} s^{-1} (estimated
modeling uncertainty), close to predictions based on quasar properties.


title: The SDSS Imaging Pipelines

abstract:
  We summarise the properties of the Sloan Digital Sky Survey (SDSS) project,
discuss our software infrastructure, and outline the architecture of the SDSS
image processing pipelines.
  We then discuss two of the algorithms used in the SDSS image processing; the
KL-transform based modelling of the spatial variation of the PSF, and the use
of galaxy models in star/galaxy separation.
  We conclude with the first author's personal opinions on the challenges that
the astronomical community faces with major software projects.


title: A Black Hole of > 6 Solar Masses in the X-ray Nova XTE J1118+480

abstract:
  Observations of the quiescent X-ray nova XTE J1118+480 with the new 6.5-m MMT
have revealed that the velocity amplitude of the dwarf secondary is 698 +/- 14
km/s and the orbital period of the system is 0.17013 +/- 0.00010 d. The implied
value of the mass function, f(M) = 6.00 +/- 0.36 solar masses, provides a hard
lower limit on the mass of the compact primary that greatly exceeds the maximum
allowed mass of a neutron star. Thus we conclude that the compact primary is a
black hole. Among the eleven dynamically established black-hole X-ray novae,
the large mass function of XTE J1118+480 is rivaled only by that of V404 Cyg.
We estimate that the secondary supplies 34% +/- 8% of the total light at 5900A
and that its spectral type is in the range K5V to M1V. A double-humped I-band
light curve is probably due to ellipsoidal modulation, although this
interpretation is not entirely secure because of an unusual 12-minute offset
between the spectroscopic and photometric ephemerides. Assuming that the light
curve is ellipsoidal, we present a provisional analysis which indicates that
the inclination of the system is high and the mass of the black hole is
correspondingly modest. The broad Balmer emission lines (FWHM = 2300-2900 km/s)
also suggest a high inclination. For the range of spectral types given above,
we estimate a distance of 1.8 +/- 0.6 kpc.


title: Chandra X-ray Observations of Cygnus A and Pictor A

abstract:
  We describe observations of the two nearest, powerful radio galaxies with the
Chandra X-ray Observatory: Cygnus A (z = 0.0562) and Pictor A (z = 0.035).
Since the early results from these observations are published elsewhere
(Wilson, Young & Shopbell 2000, 2001), we here confine ourselves to a summary
of the main conclusions and a few remarks about other aspects of the results on
Cygnus A, which will be amplified in a future paper.


title: Short-Term Dynamical Interactions Among Extrasolar Planets

abstract:
  We show that short-term perturbations among massive planets in multiple
planet systems can result in radial velocity variations of the central star
which differ substantially from velocity variations derived assuming the
planets are executing independent Keplerian motions. We discuss two alternate
fitting methods which can lead to an improved dynamical description of multiple
planet systems. In the first method, the osculating orbital elements are
determined via a Levenberg-Marquardt minimization scheme driving an N-body
integrator. The second method is an improved analytic model in which orbital
elements are allowed to vary according to a simple model for resonant
interactions between the planets. Both of these methods can determine the true
masses for the planets by eliminating the sin(i) degeneracy inherent in fits
that assume independent Keplerian motions. We apply our fitting methods to the
GJ876 radial velocity data (Marcy et al. 2001), and argue that the mass factors
for the two planets are likely in the 1.25-2.0 range


title:
The X-ray view of the quasar MR2251-178 and its host cluster:
  variability, absorption, and intracluster gas emission

abstract:
  (abridged) MR2251-178 was the first quasar initially discovered in X-rays,
and the first one found to host a warm absorber. The quasar turned out to be an
outstanding object in many respects. It has a high ratio of X-ray/optical
luminosity, is surrounded by the largest quasar emission-line nebula known, and
is located in the outskirts of a cluster of galaxies. Here, we present results
from an analysis of the X-ray spectral, temporal, and spatial properties of
this source and its environment based on deep ROSAT observations.
  Remarkably, we do not detect any excess X-ray cold absorption expected to
originate from the giant gas nebula surrounding MR2251-178. This excludes the
presence of a huge HI envelope around the quasar. The X-ray spectrum of
MR2251-178 is best fit by a warm-absorbed powerlaw with an ionization parameter
log U = 0.5 and a column density log N_w = 22.6 which, however, cannot be the
same material as the giant optical emission line nebula. The mean (0.1--2.4)keV
X-ray luminosity amounts to 10^{45} erg/s.
  A spatial analysis shows that the bulk of the X-ray emission from the quasar
is consistent with a point source, as expected in view of the powerlaw-shaped
X-ray spectrum and the rapid X-ray variability we detect. In addition, extended
emission appears at weak emission levels, including a bridge between the quasar
and the cD galaxy of the cluster.
  The X-ray emission from the intra-cluster medium is weak or absent. None of
the other member galaxies of the cluster to which MR 2251-178 belongs, are
detected in X-rays. However, east of the quasar there is a significant excess
of X-ray sources, several of them without optical counterparts on the UK
Schmidt plates.


title:
Detection of the optical afterglow of GRB 000630: Implications for dark
  bursts

abstract:
  We present the discovery of the optical transient of the long-duration
gamma-ray burst GRB000630. The optical transient was detected with the Nordic
Optical Telescope 21.1 hours after the burst. At the time of discovery the
magnitude of the transient was R = 23.04+-0.08. The transient displayed a
power-law decline characterized by a decay slope of alpha = -1.035+-0.097. A
deep image obtained 25 days after the burst shows no indication of a
contribution from a supernova or a host galaxy at the position of the
transient. The closest detected galaxy is a R=24.68+-0.15 galaxy 2.0 arcsec
north of the transient.
  The magnitudes of the optical afterglows of GRB980329, GRB980613 and
GRB000630 were all R>=23 less than 24 hours from the burst epoch. We discuss
the implications of this for our understanding of GRBs without detected optical
transients. We conclude that i) based on the gamma-ray properties of the
current sample we cannot conclude that GRBs with no detected OTs belong to
another class of GRBs than GRBs with detected OTs and ii) the majority (>75%)
of GRBs for which searches for optical afterglow have been unsuccessful are
consistent with no detection if they were similar to bursts like GRB000630 at
optical wavelengths.


title:
Multi-Conjugate Adaptive Optics with two Deformable Mirrors -
  Requirements and Performance

abstract:
  In order to increase the corrected field of view of an adaptive optics (AO)
system, several deformable mirrors (DM) have to be placed in the conjugate
planes of the dominant turbulent layers (multi-conjugate adaptive optics, MCAO
[Beckers et al.]). The performance of MCAO systems depends on the quality of
the wavefront sensing of the individual layers and on the number of corrected
modes in each individual layer as in single layer AO systems. In addition, the
increase in corrected field of view depends on the number of guide stars
providing information about the turbulence over a sufficiently large area in
each turbulent layer. In this paper, we investigate these points and provide
formulae for calculating the increased field of view with a new approach using
the spatial correlation functions of the applied polynomials (e.g. Zernike). We
also present a new scheme of measuring the individual wavefront distortion of
each of the dominant layers with a Shack-Hartmann-Curvature Sensor using
gradient information as well as scintillation. An example for the performance
of a two layer MCAO system is given for the 3.5-m telescope of the Calar Alto
Observatory, Spain, using a measured Cn2-profile. The corrected field of view
in K-band (2.2 Microns) can be as large as 3 arcmin with a Strehl ratio above
60%.


title: Spectral Modeling of GRB Pulses

abstract:
  The energy spectra of pulses of GRBs are modeled for synchrotron and multiple
self-inverse Compton scatterings from a population of thermal and non-thermal
$e^-$s. The contribution from pairs that result from annihilation is also taken
into account. A high particle density (enhanced by the pairs) will increase
absorption but, if the pairs are not accelerated, the absorption frequency
cannot lie in the BATSE window. Pairs will contribute in upscattering and will
most likely increase the population of cold particles that will downscatter
hard photons and thus suppress hard (e.g., above 300 keV) emission.


title:
Automated spectral extraction for high multiplexing MOS and IFU
  observations

abstract:
  VIMOS main distinguishing characteristic is its very high multiplex
capability: in MOS mode up to 800 spectra can be acquired simultaneously, while
the Integral Field Unit produces 6400 spectra to obtain integral field
spectroscopy of an area approximately 1x1 arcmin in size. To successfully
exploit the capabilities of such an instrument it is necessary to expedite as
much as possible the analysis of the very large volume of data that it will
produce, automating almost completely the basic data reduction and the related
bookkeeping process. The VIMOS Data Reduction Software (DRS) has been designed
specifically to satisfy these two requirements. A complete automation is
achieved using a series of auxiliary tables that store all the input
information needed by the data reduction procedures, and all the output
information that they produce. We expect to achieve a satisfactory data
reduction for more than 90% of the input spectra, while some level of human
intervention might be required for a small fraction of them to complete the
data reduction. The DRS procedures can be used as a stand-alone package, but
are also being incorporated within the VIMOS pipeline under development at the
European Southern Observatory.


title: Emission altitudes in young and old radio pulsars

abstract:
  The paper presents a comparison of emission altitudes in very young and very
old radio pulsars. The author confirmes that altitudes at which radio emission
at a given frequency is generated depend on pulsar period and on pulsar age,
although the latter dependence is quite weak.


title:
Gravitational lensing: effects of cosmology and of lens and source
  profiles

abstract:
  We present detailed calculations of the magnification distribution, including
both weak and strong lensing, using very recent solutions of the Dyer-Roeder
(1973) equation for light propagation in a inhomogeneous universe with a
cosmological constant and up-to-date models for the evolving cosmological
distribution of dark matter halos. We address in particular the effect of a
non-zero cosmological constant, of different density profiles of lenses, and of
finite sizes of lensed sources.
  We show that, if dark matter fluctuations are normalized to the local cluster
abundance, in the presence of a cosmological constant the optical depth for
lensing {\em decreases} compared to the case of an Einstein-de Sitter universe,
because halos in the relevant mass range are less abundant over a large
redshift interval. We also discuss the differences in the magnification
probability distributions produced by Navarro, Frenk & White (NFW) and by
Singular Isothermal Sphere (SIS) density profiles of lenses. We find that the
NFW lens is more efficient for moderate magnifications ($2\lsim A\lsim 4$), and
less efficient for larger magnifications. Moreover, we discuss quantitatively
the maximum magnification, $A_{\rm max}$, that can be achieved in the case of
extended sources (galaxies) with realistic luminosity profiles, taking into
account the possible ellipticity of the lens potential. Finally, we apply our
results to a class of sources following the luminosity evolution typical for a
unified scheme of QSO formation. We find that the lensed source counts at $850
\mu$m can be larger than the unlensed ones by several orders of magnitude at
flux densities $\gta100 $mJy.


title:
Infrared constraints on the dark mass concentration observed in the
  cluster Abell 1942

abstract:
  We present a deep H-band image of the region in the vicinity of the cluster
Abell 1942 containing the puzzling dark matter concentration detected in an
optical weak lensing study by Erben et al. (2000). We demonstrate that our
limiting magnitude, H=22, would be sufficient to detect clusters of appropriate
mass out to redshifts comparable with the mean redshift of the background
sources. Despite this, our infrared image reveals no obvious overdensity of
sources at the location of the lensing mass peak, nor an excess of sources in
the I-H vs. H colour-magnitude diagram. We use this to further constrain the
luminosity and mass-to-light ratio of the putative dark clump as a function of
its redshift. We find that for spatially-flat cosmologies, background lensing
clusters with reasonable mass-to-light ratios lying in the redshift range 0<z<1
are strongly excluded, leaving open the possibility that the mass concentration
is a new type of truly dark object.


title: Issues of LiBeB, Oxygen and Iron Evolution

abstract:
  We discuss the highlights of our recent research, specifically the refractory
vs. volatile interpretation of the rise of [O/Fe] with decreasing [Fe/H], and
the issue of primary vs. secondary evolution of Be.


title: The quasar 3C345 at the highest resolution with mm- and space-VLBI

abstract:
  The quasar 3C345 is one of the best examples of extragalactic jet with
superluminal components moving on helical paths. To get better constraints on
the jet physics, we have imaged the source at the highest possible resolution,
using mm-VLBI and space-VLBI observations. We observed 3C345 at 5 different
epochs so far (1 epoch with 3-mm ground VLBI, and 4 epochs with space VLBI at
6cm and 18cm). These measurements expand significantly our ongoing monitoring
of 3C345. In this contribution, we discuss the properties of the jet and its
moving components in the immediate vicinity of the core (<3mas).


title: Precession Interpretation of the Isolated Pulsar PSR B1828-11

abstract:
  Pulse timing of the isolated pulsar PSR B1882-11 shows strong Fourier power
at periods ~1000, 500 and 250 d, correlated with changes in the pulse profile
(Stairs, Lyne & Shemar 2000). We study the extent to which these data can be
explained by precession of the star's rigid crust coupled to the magnetic
dipole torque. We find that the correlated changes in the pulse duration and
spin period derivative can be explained as precession at a period of ~500 d
with a wobble angle of ~3 deg if the star's dipole moment is nearly orthogonal
to its symmetry axis. The dipole torque produces a harmonic at ~250 d.
Comparison of the predicted spin dynamics with the observed pulse durations
requires the radio beam to have a non-standard ``hour-glass'' shape. We make
predictions of variations in beam polarization and pulse profile with which to
test this interpretation. The precession interpretation of PSR B1828-11
seriously challenges the current understanding of the liquid interior of the
neutron star. In particular, if the internal liquid is in a superfluid state,
its rotational vortices cannot be significantly pinned to the crust.


title: Disks around Hot Stars in the Trifid Nebula

abstract:
  We report on mid-IR observations of the central region in the Trifid nebula,
carried out with ISOCAM in several broad-band infrared filters and in the low
resolution spectroscopic mode provided by the circular variable filter.
Analysis of the emission indicates the presence of a hot dust component (500 to
1000 K) and a warm dust component at lower temperatures (150-200 K) around
several members of the cluster exciting the HII region, and other stars
undetected at optical wavelengths. Complementary VLA observations suggest that
the mid-IR emission could arise from a dust cocoon or a circumstellar disk,
evaporated under the ionization of the central source and the exciting star of
the nebula. In several sources the $9.7\mu m$ silicate band is seen in
emission. One young stellar source shows indications of crystalline silicates
in the circumstellar dust.


title: Photometry and the Metallicity Distribution of the Outer Halo of M31

abstract:
  We have conducted a wide-field CCD-mosaic study of the resolved red-giant
branch (RGB) stars of M31, in a field located 20 kpc from the nucleus along the
SE minor axis. In our (I, V-I) color-magnitude diagram, RGB stars in the top
three magnitudes of the M31 halo are strongly present. Photometry of a more
distant control field to subtract field contamination is used to derive the
`cleaned' luminosity function and metallicity distribution function (MDF) of
the M31 halo field. From the color distribution of the foreground Milky Way
halo stars, we find a reddening E(V-I)= 0.10 +/- 0.02 for this field, and from
the luminosity of the RGB tip, we determine a distance modulus (m-M)_o = 24.47
+/- 0.12 (= 783 +/- 43 kpc). The MDF is derived from interpolation within an
extensive new grid of RGB models (Vandenberg et al. 2000). The MDF is dominated
by a moderately high-metallicity population ([m/H]~ -0.5) found previously in
more interior M31 halo/bulge fields, and is much more metal-rich than the
[m/H]~ -1.5 level in the Milky Way halo. A significant (~30% - 40%, depending
on AGB star contribution) metal-poor population is also present. To first
order, the shape of the MDF resembles that predicted by a simple,
single-component model of chemical evolution starting from primordial gas with
an effective yield y=0.0055. It strongly resembles the MDF recently found for
the outer halo of the giant elliptical NGC 5128 (Harris et al. 2000), though
NGC 5128 has an even lower fraction of low-metallicity stars. Intriguingly, in
both NGC 5128 and M31, the metallicity distribution of the globular clusters in
M31 does not match the halo stars; the clusters are far more heavily weighted
to metal-poor objects. We suggest similarities in the formation and early
evolution of massive, spheroidal stellar systems.


title: The BMW Deep X-ray Cluster Survey

abstract:
  We briefly describe the main features of the Brera Multi-Wavelet (BMW) survey
of serendipitous X-ray clusters, based on the still unexploited ROSAT-HRI
archival observations. Cluster candidates are selected from the general BMW
catalogue of 20,000 sources based exclusively on their X-ray extension.
Contrary to common wisdom, a clever selection of the HRI energy channels allows
us to significantly reduce the background noise, thus greatly improving the
ability to detect low surface-brightness sources as clusters. The resulting
sample of ~250 candidates shows a very good sky coverage down to a flux
\~3x10^-14 erg/s/cm^2 ([0.5-2.0] keV band), i.e comparable to existing
PSPC-based deep survey, with a particularly interesting area of ~100 sq.deg.
around fluxes ~10^-13 erg/s/cm^2, i.e. where highly-luminous, rare systems at
z~0.6-1 can be detected. At the same time, the superior angular resolution of
the instrument should avoid biases against intrinsically small systems, while
easing the identification process (e.g. by spotting blends and AGN
contaminants). While about 20% of the candidates are already identified with
groups/clusters at z<0.3 on the DSS2 images, we have started a deep CCD imaging
campaign to observe all sources associated to "blank fields". First results
from these observations reveal a distant (z>0.5) bonafide cluster counterpart
for ~80% of the targets.


title: Nuclear Chronometers

abstract:
  Observations of metal-poor Galactic halo stars indicate that the abundance
pattern of the (heaviest) neutron-capture elements is consistent with the
scaled solar system r-process abundances. Utilizing the radioactive (r-process)
element thorium, age determinations have been made for several of these same
stars, placing constraints on both Galactic and cosmological age estimates.


title: Neutron-Capture Element Trends in the Halo

abstract:
  In a brief review of abundances neutron-capture elements (Z > ~30) in
metal-poor halo stars, attention is called to their star-to-star scatter, the
dominance of r-process synthesis at lowest metallicities, the puzzle of the
lighter members of this element group, and the possibility of a better
r-/s-process discriminant.


title: Halo Star Abundances and r-Process Synthesis

abstract:
  We review recent observational studies of heavy element abundances in low
metallicity stars and explore some implications of these results for
nucleosynthesis and early Galactic chemical evolution.


title: 3C236: Radio Source, Interrupted?

abstract:
  We present new HST STIS/MAMA near-UV images and archival WFPC2 V and R band
images which reveal the presence of four star forming regions in an arc along
the edge of the dust lane in the giant (4 Mpc) radio galaxy 3C236. Two of the
star forming regions are relatively young with ages of order 1E7 yr, while the
other two are older with ages of order 1E8 - 1E9 yr which is comparable to the
estimated age of the giant radio source. Based on dynamical and spectral aging
arguments, we suggest that the fuel supply to the AGN was interrupted for 1E7
yr and has now been restored, resulting in the formation of the inner 2 kpc
scale radio source. This time scale is similar to that of the age of the
youngest of the star forming regions. We suggest that the transport of gas in
the disk is non-steady and that this produces both the multiple episodes of
star formation in the disk as well as the multiple epochs of radio source
activity. If the inner radio source and the youngest star forming region are
related by the same event of gas transport, the gas must be transported from
the hundreds of pc scale to the sub-parsec scale on a time scale of 1E7 yr,
which is similar to the dynamical time scale of the gas on the hundreds of pc
scales.


title: Hidden BL Lacertae Objects Near and Far

abstract:
  I describe two difficulties with current research into the cosmic evolution
of BL Lacertae Objects: (1). Possible sample incompleteness due to unrecognized
(i.e., ``hidden'') BL Lacs; and (2). The absence of a viable physical model of
the evolution, to which current and future observations can be compared.


title: Accretion Disks Around Young Objects. III. Grain Growth

abstract:
  We present detailed models of irradiated T Tauri disks including dust grain
growth with power-law size distributions. The models assume complete mixing
between dust and gas and solve for the vertical disk structure
self-consistentlyincluding the heating effects of stellar irradiation as well
as local viscous heating. For a given total dust mass, grain growth is found to
decrease the vertical height of the surface where the optical depth to the
stellar radiation becomes unit and thus the local irradiation heating, while
increasing the disk emission at mm and sub-mm wavelengths. The resulting disk
models are less geometrically thick than our previous models assuming
interstellar medium dust, and agree better with observed spectral energy
distributions and images of edge-on disks, like HK Tau/c and HH 30. The
implications of models with grain growth for determining disk masses from
long-wavelength emission are considered.


title: Chandra Reveals the X-ray Glint in the Cat's Eye

abstract:
  We have obtained Chandra ACIS-S observations of NGC 6543, the Cat's Eye
Nebula. The X-ray emission from NGC 6543 is clearly resolved into a point
source at the central star and diffuse emission confined within the central
elliptical shell and two extensions along the major axis. Spectral analysis of
the diffuse component shows that the abundances of the X-ray-emitting gas are
similar to those of the fast (1,750 km/s) stellar wind but not those of the
nebula. Furthermore, the temperature of this gas is ~1.7 million K, which is
100 times lower than the expected post-shock temperature of the fast stellar
wind. The combination of low temperature and wind abundances is puzzling. The
thermal pressure of this hot gas is about twice the pressure in the cool
nebular shell; thus, the hot gas plays an essential role in the ongoing
evolution of the nebula.


title:
A critical appraisal of the SED fitting method to estimate photometric
  redshifts

abstract:
  We discuss the stability of the photometric redshift estimate obtained with
the SED fitting method with respect to the choice of the galaxy templates.
Within the observational uncertainty and photometric errors, we find
satisfactory agreement among different sets of theoretical and empirical
templates using the Hubble Deep Field North as a target galaxy sample. Our
results suggest that, especially at high redshift, the description of the
physical processes of photon absorption in the interstellar and intergalactic
medium plays a dominant role in the redshift estimate. The specific choice of
the template set, as long as this includes both normal and starburst galaxies,
is in comparison a minor issue.


title:
On the oxygen abundance determination in HII regions: High - metallicity
  regions

abstract:
  This is our second paper devoted to the problem of line intensity - oxygen
abundance calibration starting from the idea of McGaugh (1991) that the strong
oxygen lines contain the necessary information to determine accurate abundances
in HII regions. The high-metallicity HII regions are considered.
  A relation of the type O/H=f(P,R23) between oxygen abundance and the value of
abundance index R23 introduced by Pagel et al. (1979) and the excitation
parameter P (which is defined here as the contribution of the radiation in
[OIII]4959,5007 lines to the "total" oxygen radiation) has been derived
empirically using the available oxygen abundances determined via measurement of
a temperature-sensitive line ratio [OIII]4959,5007/[OIII]4363 (Te - method). By
comparing oxygen abundances derived with the Te - method and those derived with
the suggested relations (P - method), it was found that the precision of oxygen
abundance determination with the P - method is around 0.1 dex and is comparable
to that of the Te - method.
  A relation of the type Te=f(P,R23) between electron temperature and the
values of abundance index R23 and the excitation parameter P was derived
empirically using the available electron temperatures determined via
measurement of temperature-sensitive line ratios. The mean difference between
electron temperatures derived through the Te=f(P,23 relation and determined via
measurement of the temperature-sensitive line ratio is around 500K.


title: An Integrated Procedure for Tree-Nbody Simulations: FLY and AstroMD

abstract:
  We present a code allowing to evolve three-dimensional self-gravitating
collisionless systems with a large number of particles N >= 10^7. FLY (Fast
Level-based N-bodY code) is a fully parallel code based on a tree algorithm. It
adopts periodic boundary conditions implemented by means of the Ewald summation
technique. FLY is based on the one-side communication paradigm and was
originally developed on a CRAY T3E system using the SHMEM library and it was
ported on SGI ORIGIN 2000 and on IBM SP. FLY (http://www.ct.astro.it/fly/)
version 1.1 is an open source freely available code. FLY data output can be
analysed with AstroMD, an analysis and visualization tool specifically designed
to deal with the visualization and analysis of astrophysical data. AstroMD can
manage different physical quantities. It can find out structures without well
defined shape or symmetries, and perform quantitative calculations on selected
regions. AstroMD (http://www.cineca.it/astromd) is a freely available code.


title: Recycling the universe using scalar fields

abstract:
  We examine the behaviour of a closed oscillating universe filled with a
homogeneous scalar field and find that, contrary to naive expectations, such a
universe expands to larger volumes during successive expansion epochs. This
intriguing behaviour introduces an arrow of time in a system which is
time-reversible. The increase in the maximum size of the universe is closely
related to the work done on/by the scalar field during one complete oscillatory
cycle which, in turn, is related to the asymmetry in the scalar field equation
of state during expansion and collapse. Our analysis shows that scalar fields
with polynomial potentials $V(\phi) = \lambda \phi^q$, $q > 1$ lead to a
growing oscillation amplitude for the universe: the increase in amplitude
between successive oscillations is more significant for smaller values of $q$.
Such behaviour allows for the effective recycling of the universe. A recycled
universe can be quite old and can resolve the flatness problem. These results
have strong bearing on cosmological models in which the role of dark matter is
played by a scalar field. They are also relevant for chaotic inflationary
models of the early universe since they demonstrate that, even if the universe
fails to inflate the first time around, it will eventually do so during future
oscillatory cycles. Thus, the space of initial conditions favourable for
chaotic inflation increases significantly.


title:
Lensing-induced Non-Gaussian Signatures in the Cosmic Microwave
  Background

abstract:
  We propose a new method for extracting the non-Gaussian signatures on the
isotemperature statistics in the cosmic microwave background (CMB) sky, which
is induced by the gravitational lensing due to the intervening large-scale
structure of the universe. To develop the method, we focus on a specific
statistical property of the intrinsic Gaussian CMB field; a field point in the
map that has a larger absolute value of the temperature threshold tends to have
a larger absolute value of the curvature parameter defined by a trace of second
derivative matrix of the temperature field, while the ellipticity parameter
similarly defined is uniformly distributed independently of the threshold
because of the isotropic nature of the Gaussian field. The weak lensing then
causes a stronger distortion effect on the isotemperature contours with higher
threshold and especially induces a coherent distribution of the ellipticity
parameter correlated with the threshold as a result of the coupling between the
CMB curvature parameter and the gravitational tidal shear in the observed map.
These characteristic patterns can be statistically picked up by considering
three independent characteristic functions, which are obtained from the
averages of quadratic combinations of the second derivative fields of CMB over
isotemperature contours with each threshold. Consequently, we find that the
lensing effect generates non-Gaussian signatures on those functions that have a
distinct functional dependence of the threshold. We test the method using
numerical simulations of CMB maps and show that the lensing signals can be
measured definitely, provided that we use CMB data with sufficiently low noise
and high angular resolution.


title: Orbital motion in T Tauri binary systems

abstract:
  Using speckle-interferometry we have carried out repeated measurements of
relative positions for the components of 34 T Tauri binary systems. The
projected separation of these components is low enough that orbital motion is
expected to be observable within a few years. In most cases orbital motion has
indeed been detected. The observational data is discussed in a manner similar
to Ghez et al. (1995). However, we extend their study to a larger number of
objects and a much longer timespan. The database presented in this paper is
valuable for future visible orbit determinations. It will yield empirical
masses for T Tauri stars that now are only poorly known. The available data is
however not sufficient to do this at the present time. Instead, we use short
series of orbital data and statistical distributions of orbital parameters to
derive an average system mass that is independent of theoretical assumptions
about the physics of PMS stars. For our sample this mass is 2.0 solar masses
and thus in the order of magnitude one expects for the mass sum of two T Tauri
stars. It is also comparable to mass estimates obtained for the same systems
using theoretical PMS evolutionary models.


title:
Trans-Planckian dispersion and scale-invariance of inflationary
  perturbations

abstract:
  We investigate the insensitivity of the predictions of inflationary models
with respect to modifications of Planck energy physics. The modification we
consider consists in replacing the usual dispersion relation by nonlinear ones.
This way of addressing the problem has recently recieved attention and
contradictory results were found. Our main result is to show that the
adiabaticity of the mode propagation and the separation of two scales of
interest, the Planck scale and the cosmological horizon scale, are sufficient
conditions for the predictions to be unchanged. We then show that almost all
models satisfy the first condition if the second is met. Therefore the
introduction of a nonlinear dispersion is unlikely to have any discernable
effects on the power spectrum of cosmological perturbations.


title: An All-sky Advanced X-ray Monitor (AXM) Mission

abstract:
  A concept for an all-sky monitor mission substantially more powerful than the
RXTE ASM is presented in brief. It makes use of 31 Gas Electron Multiplier
(GEM) proportional counters to provide continuous monitoring of the entire
x-ray sky, except for earth occultations and a small region around the sun.
This coverage would allow the study of a wide variety of short duration cosmic
outbursts. At time scales longer than a few minutes, the sensitivity for the
monitoring of x-ray sources (1.5 - 15 keV) would be greatly improved over the
RXTE ASM, a factor of 6 in one day. This mission concept, the Advanced X-ray
Monitor (AXM), is described in more detail in Remillard et al. (2000).


title: CMB Bispectrum from Active Models of Structure Formation

abstract:
  We propose a new method for a numerical computation of the angular bispectrum
of the CMB anisotropies arising from active models such as cosmic topological
defects, using a modified Boltzmann code based on CMBFAST. The method does not
use CMB sky maps and requires moderate computational power. As a first
implementation, we apply our method to a recently proposed model of simulated
cosmic strings and estimate the observability of the non-Gaussian bispectrum
signal. A comparison with the cosmic variance of the bispectrum estimator shows
that the bispectrum for the simulated string model we used is not observable.


title: The EDELWEISS Experiment : Status and Outlook

abstract:
  The EDELWEISS Dark Matter search uses low-temperature Ge detectors with heat
and ionisation read- out to identify nuclear recoils induced by elastic
collisions with WIMPs from the galactic halo. Results from the operation of 70
g and 320 g Ge detectors in the low-background environment of the Modane
Underground Laboratory (LSM) are presented.


title: Collapse, Expansion, and a Variable Speed of Light

abstract:
  This paper presents an information-theoretic view of how an observer within a
quantum system will perceive his world. It is argued that because of the
indistinguishability of quantum particles, a coherent state will appear to an
observer within the system like a singularity. As superposition is lost, space
appears to expand, although to the outsider it is merely the collapse of the
wave function. Implications of these ideas to cosmology are considered. The
superluminal expansion of space provides a basis to understand inflationary
cosmologies. This expansion may be taken to be equivalent to a much faster
speed of light during the inflationary period. These ideas can be tested by
checking for `higher' speed of light from photons emitted by decohering atoms.


title: A tidal extension in the Ursa Minor dwarf spheroidal galaxy

abstract:
  We report the detection of main-sequence and blue horizontal-branch stars of
the Ursa Minor dwarf spheroidal galaxy beyond its tidal radius, indicating the
existence of a possible tidal extension in this satellite of the Milky Way.
This tidal extension could spread out well beyond the area covered in our
survey (R>80 arcmin),as suggested by the presence of a ``break'' to a shallower
slope observed in its density profile. The V-band surface brightness for this
possible tidal extension range from 29.8 to 31.5 mag arcsec^-2. The area
covered in our survey (~1.65 deg^2) is not enough to discriminate if this
extra-tidalpopulation is part of a tidal tail or an extended halo around the
galaxy.
  The existence of this tidal extension in Ursa Minor indicates that this
satellite is currently undergoing a tidal disruption process by the Milky Way.
We discuss the possibility of a tidal origin for the high mass-to-light ratio
observed in this galaxy on the basis on our result and recent theoretical
simulations of the tidal disruption of dwarf satellites in the Galactic halo.


title:
The evidence for jet-cloud interactions in a sample of
  high/intermediate-redshift radio galaxies

abstract:
  We present the result obtained from a study, based on long-slit spectroscopy,
of the kinematics and ionization mechanisms of the line-emitting gas for a
sample of four high/intermediate-redshift radio galaxies. In two of the
galaxies (3C352 and 3C435A) the radio sources are of the same scale as the
emission-line regions, whereas in the other two (3C34 and 3C330) the radio
sources are extended on a larger scale than the emission-line structures. We
see evidence for shock-acceleration of the emission-line gas in the extended
regions of all the galaxies, even in the largest radio sources of our sample,
in which the radio hot spots have passed the extended gas of the galaxies. The
extended regions present highly disturbed kinematics (line-splitting and/or
underlying broad components), which are difficult to explain if we do not
consider a strong interaction between the radio-emitting components and the
ambient gas. However, the dominant ionization mechanism of the line-emitting
gas remains uncertain. We have compared the optical diagnostic line ratios of
the galaxies in our sample with both AGN-photoionization and shock-ionization
models. We find a lack of consistency in explaining the main ionization
mechanism of the emission-line gas. This suggest that, if the extended regions
are shock-ionized, some of the assumptions implicit in the shock models may
need to be reconsidered. In addition, we have investigated the nebular
continuum cointribution to the UV excess in the galaxies of our sample. We find
a substantial nebular emission contribution to the UV continuum in all the
cases. However, after the subtraction iof the nebular component, a significant
UV excess remains in the extended nebulae of most of the objects.


title: Gas Mass Fractions and the Evolution of LSB Dwarf Galaxies

abstract:
  The optical and HI properties for a sample of low surface brightness (LSB)
dwarf galaxies, cataloged from the Second Palomar Sky Survey, is presented. Gas
mass fractions for LSB dwarfs reach the highest levels of any know galaxy type
(f_g=95%) confirming that their low stellar densities are due to inefficient
conversion of gas mass into stellar mass. Comparison with star formation models
indicates that the blue optical colors of LSB dwarfs is not due to low
metallicity or recent star formation and can only be explained by a dominant
stellar population that is less than 5 Gyrs in mean age. If star formation
occurs in OB complexes, similar to normal galaxies, then LSB dwarfs must
undergo weak bursts traveling over the extent of the galaxy to maintain their
LSB nature, which contributes to their irregular morphological appearance.


title:
Evolution of Iron K$_{\alpha}$ Line Emission in the Black Hole Candidate
  GX 339-4

abstract:
  GX 339-4 was regularly monitored with RXTE during a period (in 1999) when its
X-ray flux decreased significantly (from 4.2$\times 10^{-10}$ erg cm$^{-2}
s^{-1}$ to 7.6$\times 10^{-12}$ erg cm$^{-2}$s$^{-1}$ in the 3--20 keV band),
as the source settled into the ``off state''. Our spectral analysis revealed
the presence of a prominent iron K$_{\alpha}$ line in the observed spectrum of
the source for all observations. The line shows an interesting evolution: it is
centered at $\sim$6.4 keV when the measured flux is above 5$\times 10^{-11}$
erg cm$^{-2} s^{-1}$, but is shifted to $\sim$6.7 keV at lower fluxes. The
equivalent width of the line appears to increase significantly toward lower
fluxes, although it is likely to be sensitive to calibration uncertainties.
While the fluorescent emission of neutral or mildly ionized iron atoms in the
accretion disk can perhaps account for the 6.4 keV line, as is often invoked
for black hole candidates, it seems difficult to understand the 6.7 keV line
with this mechanism, because the disk should be less ionized at lower fluxes
(unless its density changes drastically). On the other hand, the 6.7 keV line
might be due to recombination cascade of hydrogen or helium like iron ions in
an optically thin, highly ionized plasma. We discuss the results in the context
of proposed accretion models.


title: Radio Continuum Imaging of the Spiral Galaxy NGC 4258

abstract:
  We analyze 3."5 resolution, high sensitivity radio continuum images of the
nearby spiral galaxy NGC 4258 at 6 and 20 cm derived from multiple observations
used to monitor the radio supernova SN 1981K (Van Dyk et al. 1992, [ApJ, 396,
1995]). Seven bright H II region and five supernova remnant candidates are
identified. Extinctions to the H II regions are estimated for the first time
from a comparison of radio flux densities to new optical fluxes derived from
H-alpha observations by Dutil & Roy (1999, [ApJ, 516, 62]). The bright end of
the H II region luminosity function is established at each wavelength. The
luminosity functions are best fit by power laws consistent with the shape of
previously published radio and optical luminosity functions for a number of
galaxies. The supernova remnants are all about 2--3 times the radio luminosity
of Cas A. In addition, the galaxy's nucleus is shown to have been variable over
the SN 1981K monitoring period. The spectral index (alpha) distribution of the
anomalous radio arms is investigated and found to be relatively uniform at
alpha = -0.65 +/- 0.10.


title: Redshifts and Luminosities for 112 Gamma Ray Bursts

abstract:
  Two different luminosity indicators have recently been proposed for Gamma Ray
Bursts that use gamma-ray observations alone. They relate the burst luminosity
(L) with the time lag between peaks in hard and soft energies, and the
spikiness or variability of the burst's light curve (V). These relations are
currently justified and calibrated with only 6 or 7 bursts with known red
shifts. We have examined BATSE data for the lag and V for 112 bursts. (1) A
strong correlation between the lag and V exists, and it is exactly as predicted
from the two proposed relations. This is proof that both luminosity indicators
are reliable. (2) GRB830801 is the all-time brightest burst, yet with a small V
and a large lag, and hence is likely the closest known event being perhaps as
close as 3.2 Mpc. (3) We have combined the luminosities as derived from both
indicators as a means to improve the statistical and systematic accuracy when
compared with the accuracy from either method alone. The result is a list of
112 bursts with good luminosities and hence red shifts. (4) The burst averaged
hardness ratio rises strongly with the luminosity of the burst. (5) The burst
luminosity function is a broken power law, with the break at L = 2x10^{52}
erg/s. The luminosity function has power law indices of -2.8+-0.2 above the
break and -1.7+-0.1 below the break. (6) The number density of GRBs varies with
red shift roughly as (1+z)^(2.5+-0.3) between 0.2<z<5. Excitingly, this result
also provides a measure of the star formation rate out to z~5 with no effects
from reddening, and the rate is rising uniformly for red shifts above 2.


title:
Explaining the Gamma Ray Burst Lag/Luminosity and Variability/Luminosity
  Relations

abstract:
  Two different luminosity indicators have been recently proposed for Gamma Ray
Bursts that use the lag between light curve peaks with hard and soft photons as
well as the variability ('spikiness') of the burst light curve. Schaefer, Deng,
& Band have proven that both of these luminosity indicators are valid by
finding a lag/variability relation for 112 BATSE bursts. Here, I provide simple
and general explanations for both indicators. The lag/luminosity relation is a
consequence of conservation of energy when radiative cooling dominates. High
luminosity bursts cool rapidly so the lag between when hard and soft photons
peak is short, while low luminosity bursts cool slowly so the lag is long. The
variability/luminosity relation arises within internal shock models because the
luminosity and variability both scale as strong functions of the bulk
relativistic motion of the jet, Gamma. With luminosity roughly proportional to
Gamma^5 and variability scaling as Gamma^2, we get the luminosity being
correlated to variability just as the observed power law.


title: Color Transformations for the 2MASS Second Incremental Data Release

abstract:
  Transformation equations are presented to convert colors and magnitudes
measured in the AAO, ARNICA, CIT, DENIS, ESO, LCO (Persson standards), MSSSO,
SAAO, and UKIRT photometric systems to the photometric system inherent to the
2MASS Second Incremental Data Release. The transformations have been derived by
comparing 2MASS photometry with published magnitudes and colors for stars
observed in these systems. Transformation equations have also been derived
indirectly for the Bessell & Brett (1988) and Koornneef (1983) homogenized
photometric systems.


title:
Molecular Gas and Star Formation in the Nucleus of IC 342:C$^{18}$O and
  Millimeter Continuum Imaging

abstract:
  We present high resolution maps ($\sim 2^{''}$) maps of the J=1-0 and J=2-1
transitions of C$^{18}$O in the central $\sim 150$ pc of the gas-rich nucleus
of IC 342, made with the Owens Valley Millimeter Array. From the C$^{18}$O maps
we are able to obtain the most accurate map of N$_{H_{2}}$ to date for IC 342.
Due to their low opacities, the transitions of C$^{18}$O give a more reliable
estimate of the true molecular gas column density distribution than the more
common $^{12}$CO and $^{13}$CO isotopomers. The morphology of the C$^{18}$O
emission in the nucleus is a mini-spiral similar to that of the main
isotopomer, $^{12}$CO, except it is more symmetric, lacking the enhancements to
north. We suggest that the asymmetries present in $^{12}$CO images may reflect
the viewing perspective of the starburst region biased by the high optical
depths of $^{12}$CO, rather than true asymmetries in the amount of molecular
gas present. The giant molecular clouds seen in C$^{18}$O appear to be
nonspherical, probably due to tidal arm shearing. Column densities determined
from C$^{18}$O observations, 1.3 mm dust continuum, and the virial theorem
indicate that the standard Galactic conversion factor, X$_{CO}$, overestimates
the amount of molecular gas in the center of IC 342 by a factor of $\sim$2-3 at
the molecular cloud peaks, and by $>$3 in the diffuse gas away from the
starburst. Revised molecular masses based on this conversion factor imply that
star formation efficiencies in the starburst region are very high. From the
distribution of gas and star formation it appears that the sites of star
formation are dynamically determined, rather than driven by density peaks. Near
the central star-forming region, evidence is seen for chemical enrichment of
C$^{18}$O due to massive stars.


title: CO Detections of Edge-On Low Surface Brightness Galaxies

abstract:
  We have obtained deep CO(1-0) observations of 8 nearby, edge-on, low surface
brightness (LSB) spiral galaxies using the NRAO 12-m telescope. We report
detections of 3 of our targets at >4 sigma level as well as one marginal (~3
sigma) detection. These are among the first direct detections of molecular gas
in late-type, LSB spirals. Using a Galactic CO-to-H2 conversion factor, we
derive MH2~1.4-3.5 x 10^{7}Msun and MH2/MHI~0.010-0.055 for the detected
sources, with 3-sigma upper limits of MH2<0.7-5.7 x 10^{7}Msun and
MH2/MHI<0.006-0.029 for the undetected objects.


title: On the Distribution of X-ray Surface Brightness from Diffuse Gas

abstract:
  Hot intergalactic gas in clusters, groups, and filaments emanates a
continuous background of 0.5-2.0 keV X-rays that ought to be detectable with
the new generation of X-ray observatories. Here we present selected results
from a program to simulate the surface-brightness distribution of this
background with an adaptive-mesh cosmological hydrodynamics code. We show that
the bright end of this distribution is well approximated by combining the
cluster temperature function with a beta-model for surface brightness and
appropriate luminosity-temperature and core radius-luminosity relations. Our
simulations verify that the X-ray background from hot gas vastly exceeds
observational limits if non-gravitational processes do not modify the
intergalactic entropy distribution. An entropy floor of ~100 keV cm^2, which
could be established by either heating or cooling, appears necessary to
reconcile the simulated background with observations. Because the X-ray
background distribution is so sensitive to the effects of non-gravitational
processes, it offers a way to constrain the thermal history of the
intergalactic medium that is independent of the uncertainties associated with
surveys of clusters and groups.


title: The X-ray surface brightness distribution from diffuse gas

abstract:
  We use simulations to predict the X-ray surface brightness distribution
arising from hot, cosmologically distributed diffuse gas. The distribution is
computed for two bands: 0.5-2 keV and 0.1-0.4 keV, using a
cosmological-constant dominated cosmology that fits many other observations. We
examine a number of numerical issues such as resolution, simulation volume and
pixel size and show that the predicted mean background is sensitive to
resolution such that higher resolution systematically increases the mean
predicted background. Although this means that we can compute only lower bounds
to the predicted level, these bounds are already quite restrictive. Since the
observed extra-galactic X-ray background is mostly accounted for by compact
sources, the amount of the observed background attributable to diffuse gas is
tightly constrained. We show that without physical processes in addition to
those included in the simulations (such as radiative cooling or
non-gravitational heating), both bands exceed observational limits. In order to
examine the effect of non-gravitational heating we explore a simple modeling of
energy injection and show that substantial amounts of heating are required
(i.e. 5 keV per particle when averaged over all baryons). Finally, we also
compute the distribution of surface brightness on the sky and show that it has
a well-resolved characteristic shape. This shape is substantially modified by
non-gravitational heating and can be used as a probe of such energy injection.


title: Morphological Evolution and the Ages of Early-Type Galaxies in Clusters

abstract:
  Morphological and spectroscopic studies of high redshift clusters indicate
that a significant fraction of present-day early-type galaxies was transformed
from star forming galaxies at z<1. On the other hand, the slow luminosity
evolution of early-type galaxies and the low scatter in their color-magnitude
relation indicate a high formation redshift of their stars. In this paper we
construct models which reconcile these apparently contradictory lines of
evidence, and we quantify the effects of morphological evolution on the
observed photometric properties of early-type galaxies in distant clusters. We
show that in the case of strong morphological evolution the apparent luminosity
and color evolution of early-type galaxies are similar to that of a single age
stellar population formed at z=infinity, irrespective of the true star
formation history of the galaxies. Furthermore, the scatter in age, and hence
the scatter in color and luminosity, is approximately constant with redshift.
These results are consequences of the ``progenitor bias'': the progenitors of
the youngest low redshift early-type galaxies drop out of the sample at high
redshift. We construct models which reproduce the observed evolution of the
number fraction of early-type galaxies in rich clusters and their color and
luminosity evolution simultaneously. Our modelling indicates that approx. 50%
of early-type galaxies were transformed from other galaxy types at z<1, and
their progenitor galaxies may have had roughly constant star formation rates
prior to morphological transformation. After correcting the observed evolution
of the mean M/L_B ratio for the maximum progenitor bias we find that the mean
luminosity weighted formation redshift of stars in early-type galaxies
z_*=2.0^{+0.3}_{-0.2} for Omega_m=0.3 and Omega_Lambda=0.7. [ABRIDGED]


title: Hypernova Nucleosynthesis and Implications for Cosmic Chemical Evolution

abstract:
  We examine the characteristics of nucleosynthesis in 'hypernovae', i.e.,
supernovae with very large explosion energies ($\gsim 10^{52}$ ergs).
Implications for the cosmic chemical evolution and the abundances in M82 are
discussed.