title: Galaxy and star formation up to z ~ 1

abstract:
  Star formation history shows a gradual decline since the last 8-9 Gyr (z=1).
The bulk of present-day stellar mass and metal content was formed at redshifts
lower than 2-3, which is consistent with a hierarchical scenario of galaxy
formation. Observations of galaxy evolution during the last 2/3 of the Universe
age could be done in great details, and provide numerous insights on the origin
of the Hubble diagram. To some extent, the evolution and formation of
present-day elliptical and spiral galaxies could be related to the most rapidly
evolving galaxy populations at z ~ 1, namely the luminous IR galaxies and the
luminous compact galaxies.


title:
A Possible X-Ray Periodicity at Several Tens Hours of a Ultra-Luminous
  Compact X-Ray Source in IC 342

abstract:
  A long (155 hours) ASCA observation was performed of two ultra luminous
compact X-ray sources, Source 1 and Source 2, in the spiral galaxy IC 342.
While Source 1 that was in a hard spectral state varied little, Source 2 that
was in its soft spectral state varied significantly on a time scale of about
one day. The rms variation amplitude amounts to 5% in the 2-10 keV band, but is
less than 4% in 0.7-2 keV. The variation involves statistically significant
changes in the parameters describing multi-color disk blackbody emission from
this source. The variation is possibly periodic, with a period of either 31
$\pm$ 2, hours or 41 $\pm$ 3 hours. Both are consistent with the orbital period
of a semi-detached binary formed by a black hole and a main-sequence star of
several tens solar masses. These results reinforce the interpretation of these
X-ray objects in terms of accreting massive stellar black holes.


title: Binary Population Synthesis: Low- and Intermediate-Mass X-Ray Binaries

abstract:
  As has only recently been recognized, X-ray binaries with intermediate-mass
secondaries are much more important than previously believed. To assess the
relative importance of low- and intermediate-mass X-ray binaries (LMXBs and
IMXBs), we have initiated a systematic study of these systems consisting of two
parts: an exploration of the evolution of LMXBs and IMXBs for a wide range of
initial masses and orbital periods using detailed binary stellar evolution
calculations, and an integration of these results into a Monte-Carlo binary
population synthesis code. Here we present some of the main results of our
binary calculations and some preliminary results of the population synthesis
study for a ``standard'' reference model. While the inclusion of IMXBs improves
the agreement with the observed properties of ``LMXBs'', several significant
discrepancies remain, which suggests that additional physical processes need to
be included in the model.


title:
XMM-Newton observations of the cluster of galaxies Abell496
  -Measurements of the elemental abundances in the intracluster medium-

abstract:
  The results from XMM-Newton observations of the relaxed cluster of galaxies
Abell~496 are presented. The spatially-resolved X-ray spectra taken by the
European Photon Imaging Cameras show a temperature drop and a Fe abundance
increase in the intra-cluster medium (ICM) towards the cD galaxy at the cluster
center. The abundances of Si and S also show a central enhancement. High
resolution soft X-ray spectra obtained with the Reflection Grating
Spectrometers provides a strong constraint on the temperature structure in the
central cool plasma. Furthermore, the O abundance at the cluster core is
accurately measured based on the OVIII Ly alpha line detected with the RGS.
Contrary to the Si, S, and Fe abundances, the O abundance is radially constant
over the cluster.


title: Classicality of primordial fluctuations and Primordial Black Holes

abstract:
  The production of Primordial Black Holes (PBH) from inflationary
perturbations provides a physical process where the effective classicality of
the fluctuations does not hold for certain scales. For adiabatic perturbations
produced during inflation, this range of scales corresponds to PBH with masses
$M\ll 10^{15}$ g. For PBH with masses $M\sim M_H(t_e)$, the horizon mass at the
end of inflation, the generation process during the preheating stage could be
classical as well, in contrast to the formation of PBH on these scales by
adiabatic inflationary perturbations. For the non evaporated PBH, the
generation process is essentially classical.


title:
A Chandra HETG Observation of the Quasar H 1821+643 and Its Surrounding
  Cluster

abstract:
  We present the high-resolution X-ray spectrum of the low-redshift quasar H
1821+643 and its surrounding hot cluster observed with the Chandra High Energy
Transmission Grating Spectrometer (HETGS). An iron emission line attributed to
the quasar at ~6.43 keV (rest frame) is clearly resolved, with an equivalent
width of ~100 eV. Although we cannot rule out contributions to the line from a
putative torus, the diskline model provides an acceptable fit to this iron
line. We also detect a weak emission feature at ~6.9 keV (rest frame). We
suggest that both lines could originate in an accretion disk comprised of a
highly ionized optically thin atmosphere sitting atop a mostly neutral disk. We
search for absorption features from a warm/hot component of the intergalactic
medium along the ~1.5Gpc/h line of sight to the quasar. No absorption features
are detected at or above the 3 sigma level while a total of six OVI intervening
absorption systems have been detected with HST and FUSE. Based on the lack of
OVII and OVIII absorption lines and by assuming collisionally ionization, we
constrain the gas temperature of a typical OVI absorber to 10^5 < T < 10^6 K,
which is consistent with the results from hydrodynamic simulations of the
intergalactic medium. The zeroth order image reveals the extended emission from
the surrounding cluster. We have been able to separate the moderate CCD X-ray
spectrum of the surrounding cluster from the central quasar and find that this
is a hot cluster with a temperature of ~10 keV and a metal abundance of ~0.3
Zo. We also independently obtain the redshift of the cluster, which is
consistent with the optical results. We estimate that the cluster makes
negligible contributions to the 6.9 keV iron K line flux.


title:
Near-Infrared Spectroscopy of Brown Dwarfs: Methane and the Transition
  between the L and T Spectral Types

abstract:
  We report the possible identification of weak methane spectral features in
the near-infrared K band in two late L dwarfs, DENIS 0205-11 (L7) and 2MASS
1523+30 (L8). New, high signal-to-noise ratio flux-calibrated spectra, spanning
the wavelength interval 1.10 - 2.35 microns with an average resolving power R =
1800 were obtained using NIRSPEC on the Keck II telescope. Results are reported
and compared for three late L dwarfs (L5, L7, and L8) and two T dwarfs (T1 and
T6). The spectra, which are continuous through the atmospheric absorption
bands, show the development of deep steam bands and the weakening of iron
hydride features through the L dwarfs and the emergence of strong methane bands
in the T dwarfs. A detailed comparison of the K band regions with synthetic
spectra suggests that the weak features seen in the L7 and L8 dwarfs at 2.20
microns are likely to be methane. We see no evidence for methane in the H band.
At the R = 1800 resolution, significant differences are evident between the
spectral signatures of the L8 and the T1, leaving room for additional
transition objects (L9 or T0).


title: Observations of Galaxies with Chandra

abstract:
  This talk discusses the growing impact of Chandra observations on the study
of galaxies. In particular, we address progress in the study of X-ray source
populations in diverse galaxies and in the study of the hot ISM.


title: Dark Matter Properties and Halo Central Densities

abstract:
  Using an analytic model calibrated against numerical simulations, we
calculate the central densities of dark matter halos in a ``conventional'' cold
dark matter model with a cosmological constant (LCDM) and in a ``tilted'' model
(TLCDM) with slightly modified parameters motivated by recent analyses of
Ly-alpha forest data. We also calculate how warm dark matter (WDM) would modify
these predicted densities by delaying halo formation and imposing phase space
constraints. As a measure of central density, we adopt the quantity D_{V/2},
the density within the radius R_{V/2} at which the halo rotation curve falls to
half of its maximum value, in units of the critical density. We compare the
theoretical predictions to values of D_{V/2} estimated from the rotation curves
of dark matter dominated disk galaxies. Assuming that dark halos are described
by NFW profiles, our results suggest that the conventional LCDM model predicts
excessively high dark matter densities, unless there is some selection bias in
the data toward the low-concentration tail of the halo distribution. A WDM
model with particle mass 0.5-1 keV provides a better match to the observational
data. However, the modified cold dark matter model, TLCDM, fits the data
equally well, suggesting that the solution to the ``halo cores'' problem might
lie in moderate changes to cosmological parameters rather than radical changes
to the properties of dark matter. If CDM halos have the steeper density
profiles found by Moore et al., then neither conventional LCDM nor TLCDM can
reproduce the observed central densities.


title:
Infrared Properties of Cataclysmic Variables from 2MASS: Results from
  the 2nd Incremental Data Release

abstract:
  Because accretion-generated luminosity dominates the radiated energy of most
cataclysmic variables, they have been ``traditionally'' observed primarily at
short wavelengths. Infrared observations of cataclysmic variables contribute to
the understanding of key system components that are expected to radiate at
these wavelengths, such as the cool outer disk, accretion stream, and secondary
star. We have compiled the J, H, and Ks photometry of all cataclysmic variables
located in the sky coverage of the 2 Micron All Sky Survey (2MASS) 2nd
Incremental Data Release. This data comprises 251 systems with reliably
identified near-IR counterparts and S/N > 10 photometry in one or more of the
three near-IR bands.


title:
Group Scaling Relations From a Cosmological Hydrodynamic Simulation: No
  Pre-heating Required?

abstract:
  We investigate the X-ray vs. optical scaling relations of poor groups to
small clusters (sigma~100-700 km/s) identified in a cosmological hydrodynamic
simulation of a Lambda-CDM universe, with cooling and star formation but no
pre-heating. We find that the scaling relations between X-ray luminosity, X-ray
temperature, and velocity dispersion show significant departures from the
relations predicted by simple hydrostatic equilibrium models or simulations
without cooling, having steeper L_X-sigma and L_X-T_X slopes and a "break" at
\~200 km/s (~0.3 keV). These departures arise because the hot (X-ray emitting)
gas fraction varies substantially with halo mass in this regime. Our
predictions roughly agree with observations. Thus radiative cooling is a
critical physical process in modeling galaxy groups, and may present an
alternative to ad hoc models such as pre-heating or entropy floors for
explaining X-ray group scaling relations.


title: Chemical abundances in an UV-selected sample of galaxies

abstract:
  We discuss the chemical properties of a sample of UV-selected
intermediate-redshift (0 < z < 0.4) galaxies in the context of their physical
nature and star formation history. This work represents an extension of our
previous studies (Treyer et al. 1998; Sullivan et al. 2000, 2001) on
UV-selected galaxies. We revisit the optical spectra of these galaxies and
perform further emission-line measurements restricting the analysis to those
spectra with the full set of emission lines required to derive chemical
abundances. Our final sample consists of 68 galaxies with heavy element
abundance ratios and both UV and CCD B-band photometry. Diagnostics based on
emission-line ratios show that all but one of the galaxies in our sample are
powered by hot, young stars rather than by an AGN. Oxygen-to-hydrogen (O/H) and
nitrogen-to-oxygen (N/O) abundance ratios are compared to those for various
local and intermediate-redshift samples. Our UV-selected galaxies span a wide
range of oxygen abundances, from 0.1 Zsun to solar, intermediate between
low-mass HII galaxies and massive starburst nuclei. For a given oxygen
abundance, most have strikingly low N/O values. Moreover, UV-selected and HII
galaxies systematically deviate from the usual metallicity-luminosity relation
in the sense of being more luminous by 2-3 magnitudes. Adopting the
"delayed-release" chemical evolution model, we propose our UV-selected sources
are observed at a special stage in their evolution, following a powerful
starburst which enriched their ISM in oxygen and temporarily lowered their
mass-to-light ratios. We discuss briefly the implications of our conclusions on
the nature of similarly-selected high-redshift galaxies.


title:
Chemical Properties of Starburst Galaxies Near and Far: Clues to Galaxy
  Evolution

abstract:
  The determination of chemical abundances in star-forming galaxies and the
study of their evolution on cosmological timescales are powerful tools for
understanding galaxy formation and evolution. This contribution presents the
latest results in this domain. We show that detailed studies of chemical
abundances in UV-selected, HII and starburst nucleus galaxies, together with
the development of new chemical evolution models, put strong constraints on the
evolutionary stage of these objects in terms of star formation history.
Finally, we summarize our current knowledge on the chemical properties of
intermediate- and high-redshift galaxies. Although the samples are still too
small for statistical studies, these results give insight into the nature and
evolution of distant star-forming objects and their link with present-day
galaxies.


title: Dwarf Nova Oscillations: New Results

abstract:
  New and archived observations of VW Hyi in outburst show the occasional
presence of optical Dwarf Nova Oscillations (DNOs) over the range of 18 - 40 s.
There is a rapid increase in period near the end of outburst, at the same time
that the EUV falls almost to zero, which we attribute to propellering. The DNOs
return to a shorter period after this phase, but are very incoherent. The DNOs
show some modulation by the Quasi-Periodic Oscillations (QPOs) that are also
occasionally present in the light curve. We interpret the QPOs as a prograde
travelling wave in the inner disc, which obscures and/or reprocesses radiation
from the central region. The model is applied to observations of OY Car and WZ
Sge.


title: Infrared Spectroscopy of Atomic Lines in Gaseous Nebulae

abstract:
  Spectroscopy in the infrared provides a means to assess important properties
of the plasma in gaseous nebulae. We present some of our own work that
illustrates the need for interactions between the themes of this conference -
astronomical data, atomic data, and plasma simulations. We undertook Infrared
Space Observatory (ISO) observations with the intent of better understanding
the effects of density variations in nebulae, particularly planetary nebulae
(PNs), by determining average electron densities from the flux ratios of
several fine-structure, IR emission lines. Instead, we are able to ascertain
only minor density information because of several instances of the observed
line flux ratios being out of range of the theoretical predictions using
current atomic data. In these cases, the ISO data cannot presently be used to
derive electron density, but rather provide direction for needed improvements
in the atomic collision strengths.
  We have detected an unidentified (uid) strong emission line in an ISO/SWS
spectrum of the Orion Nebula. The line has a rest wavelength
2.89350$\pm$0.00003 $\mu$m. A long-slit UKIRT observation confirms the presence
of this line and shows that the emission is spatially extended and appears to
be coincident with the brightest part of the ionized region. We do not detect
the uid line in our SWS02 spectra of any of the several bright PNs which we
observed for a comparable time. The need for basic atomic data, in this case
wavelengths to aid species identification, is paramount for future progress.
  We look toward the future with a brief synopsis of upcoming or planned IR
missions.


title:
Einstein's Biggest Blunder? High-Redshift Supernovae and the
  Accelerating Universe

abstract:
  Nearly 4 years ago, two teams of observational astronomers reported that
high-redshift Type Ia supernovae are fainter than expected in a decelerating or
freely coasting universe. The radical conclusion that the universe has been
accelerating in the past few billion years, possibly because of a nonzero value
for Einstein's cosmological constant, has gripped the worlds of astronomy and
physics, causing a flurry of new research. Having participated on both teams
(but much more closely with one than the other), here I provide a personal,
historical account of the story.


title: Did Very Massive Stars Pre-enrich and Reionize the Universe?

abstract:
  Recent studies of heavy r-process elements in low [Fe/H] halo stars have
suggested that an initial population of metal-free very massive stars (VMSs)
may be required to provide early Fe enrichment without coproducing heavy r
nuclei. We find similar abundance trends in alpha-elements (which should be
copiously produced by VMSs), but not in other elements such as carbon (which
should not), in agreement with this hypothesis. We then combine the
corresponding level of prompt initial enrichment with models of VMS
nucleosynthetic yields and spectra to estimate the corresponding ionizing
fluxes. The result suggests that there may have been enough VMS activity to
reionize the universe. The unusually hard spectrum of VMSs would imply a
different reionization history from canonical models. HeII could have been
reionized at high redshift, only to recombine as a subsequent generation of
stars formed with a ``normal'' initial mass function.


title: 900 ks exposure of NGC 3783 with Chandra/HETGS: no accretion disk lines

abstract:
  We present preliminary results from a 900 ks exposure of NGC 3783 with the
Chandra/HETGS. This is the best combination of signal-to-noise and resolution
ever obtained for an Active Galactic Nucleus (AGN). We resolve the narrow Fe
K\alpha line to have FWHM of 1720+/-360 km/s which, under the simple assumption
of virialized system, suggest that this narrow line is emitted between the
broad line region and the narrow line region. We do not detect any broad
component for the Fe K\alpha line though such component was observed in
previous ASCA observations of this object. Our results suggest an evolution in
the broad Fe K\alpha line that took place from the observations in 1996 to the
observations in 2000/2001.
  The high resolution X-ray spectrum of NGC 3783 shows more than a hundred
absorption lines and several dozen emission lines from the H-like and He-like
ions of N, O, Ne, Mg, Al, Si, and S as well as from Fe_XVII to Fe_XXIV L-shell
transitions. All these features can be modeled by a multi-component,
outflowing, photoionized absorber. There is no evidence (or need in the model)
for soft X-ray emission lines from a relativistic accretion disk as have been
proposed to be seen in a few other AGNs.


title: The University of Cape Town CCD CV Survey

abstract:
  Some results from a high speed photometric survey of faint southern
Cataclysmic Variables are presented, including 7 new orbital periods.


title: The Three-Dimensional Power Spectrum Measured from 2MASS

abstract:
  We present the three-dimensional power spectrum of galaxy clustering using
measurements of the angular correlation function from the second incremental
release of the Two-Micron All Sky Survey (2MASS). The angular positions of
galaxies out to a limiting magnitude of K_s <= 14.0 (508,054 galaxies)
determine the correlation function. We consider a variety of estimators of the
catalog's angular correlation function, and we find the Landy and Szalay (LS)
estimator to be the most reliable choice. Using the LS estimator, we find that
the angular correlation function takes the form of a power law with a break.
The angular correlation function is then used in combination with the selection
function to determine the power spectrum by inverting Limber's equation. We
find good agreement with previous measurements of the power spectrum for 0.04 <
k < 0.1 h Mpc^-1, and evidence for a peak in the power spectrum around k = 0.03
h Mpc^-1. For k > 0.1 h Mpc^-1 we find that the power spectrum is biased higher
than other surveys, which can be understood as a color-based selection effect.


title:
Primordial Black Holes from inflationary models with and without Broken
  Scale Invariance

abstract:
  We review the formalism of primordial black holes (PBHs) production and show
that the mass variance at horizon crossing has been systematically
overestimated in previous studies. We derive the correct expression. The
difference is maximal at the earliest formation times and still very
significant for PBH masses $\sim 10^{15}$g, an accurate estimate requiring
numerical calculations. In particular, this would lead to weaker constraints on
the spectral index $n$. We then derive constraints on inflationary models from
the fact that primordial black holes must not overclose the Universe. This is
done both for the scale-free case of the power spectrum studied earlier and for
the case where a step in the mass variance is superimposed. In the former case
we find various constraints on $n$, depending on the parameters. In the latter
case these limits can be much more strengthened, so that one could find from an
observational limit on $n$ a constraint on the allowed height of the step.


title: Optical/Near-Infrared Imaging of Infrared-Excess Palomar-Green QSOs

abstract:
  Ground-based high spatial-resolution (FWHM < 0.3-0.8") optical and
near-infrared imaging (0.4-2.2um) is presented for a complete sample of
optically selected Palomar-Green QSOs with far-infrared excesses at least as
great as those of "warm" AGN-like ultraluminous infrared galaxies
(L_ir/L_big-blue-bump > 0.46). In all cases, the host galaxies of the QSOs were
detected and most have discernable two-dimensional structure. The QSO host
galaxies and the QSO nuclei are similar in magnitude at H-band. H-band
luminosities of the hosts range from 0.5-7.5 L* with a mean of 2.3 L*, and are
consistent with those found in ULIGs. Both the QSO nuclei and the host galaxies
have near-infrared excesses, which may be the result of dust associated with
the nucleus and of recent dusty star formation in the host. These results
suggest that some, but not all, optically-selected QSOs may have evolved from
an infrared-active state triggered by the merger of two similarly-sized L*
galaxies, in a manner similar to that of the ultraluminous infrared galaxies.


title:
Stellar populations in NGC 5128 with the VLT: evidence for recent star
  formation

abstract:
  We resolve stars of the nearest giant elliptical galaxy NGC 5128 using VLT
with FORS1 and ISAAC. We construct deep U, V and Ks color-magnitude and
color-color diagrams in two different halo fields (in the halo and in the
north-eastern diffuse shell). In the outer, shell field, at ~14 kpc from the
center of the galaxy, there is a significant recent star formation with stars
as young as 10 Myr, approximately aligned with the prominent radio and x-ray
jet from the nucleus of the host AGN. Ionized gas filaments are evident in
ultraviolet images near the area where neutral HI and CO molecular gas was
previously observed. The underlying stellar population of the halo of the giant
elliptical is predominantly old with a very broad metallicity distribution. The
presence of an extended giant branch reaching M_bol=-5 mag suggests the
existence of a significant intermediate-age AGB population in the halo of this
galaxy.


title:
The radio/optical alignment and the recent star formation associated
  with ionized filaments in the halo of NGC 5128 (Centaurus A)

abstract:
  We used the direct CCD camera at the Magellan I telescope at Las Campanas
Observatory and FORS1 at Antu VLT at ESO Paranal Observatory to image fields
centered on the inner and outer optical filaments in the halo of NGC 5128. In
the V vs. U-V color-magnitude diagrams we have identified young blue
supergiants associated with these line-emitting filaments located between the
inner radio lobe and the northern middle lobe. Around the outer filament stars
as young as 10 Myr were detected. They are principally aligned with the
direction of the radio jet, but a vertical north-east alignment along the edge
of the HI cloud is also present. Young stars in the inner filament field are
found inside the bright knots of photoionized gas and are strongly aligned in
the direction towards the center of the galaxy at the same position angle as
the inner radio jet. Fitting the Padova isochrones on UV color-magnitude
diagrams we find that the blue stars around the inner filaments have ages
similar to the ones around the outer filaments ~10-15 Myr and the same
abundance of Z=0.004. The presence of young blue supergiants clearly shows that
the bright blue knots in the north-eastern halo of NGC 5128 are associations of
young stars with photoionized gas. The temperature of the brightest stars is T
\~ 12000-16000 K, insufficient to account alone for the high excitation lines
observed in the surrounding ionized gas. Thus the optical emission jet is
principally seen due to its alignment with the radio structure of the AGN. The
highly collimated star formation is present only in the north eastern halo of
the galaxy, suggesting the interaction of the jet with the gas clouds deposited
during the last accretion event as the preferred triggering mechanism.
(abridged)


title:
Dynamics of gravitational clustering V. Subleading corrections in the
  quasi-linear regime

abstract:
  We investigate the properties of the standard perturbative expansions which
describe the early stages of the dynamics of gravitational clustering. We show
that for hierarchical scenarios with no small-scale cutoff perturbation theory
always breaks down beyond a finite order $q_+$. Besides, the degree of
divergence increases with the order of the perturbative terms so that
renormalization procedures cannot be applied. Nevertheless, we explain that
despite the divergence of these subleading terms the results of perturbation
theory are correct at leading order because they can be recovered through a
steepest-descent method which does not use such perturbative expansions.
Finally, we investigate the simpler cases of the Zel'dovich and Burgers
dynamics. In particular, we show that the standard Burgers equation exhibits
similar properties. This analogy suggests that the results of the standard
perturbative expansions are valid up to the order $q_+$ (i.e. until they are
finite). Moreover, the first ``non-regular'' term of a large-scale expansion of
the two-point correlation function should be of the form $R^{-2} \sigma^2(R)$.
At higher orders the large-scale expansion should no longer be over powers of
$\sigma^2$ but over a different combination of powers of 1/R. However, its
calculation requires new non-perturbative methods.


title: SAURON: An Innovative Look at Early-Type Galaxies

abstract:
  A summary of the SAURON project and its current status is presented. SAURON
is a panoramic integral-field spectrograph designed to study the stellar
kinematics, gaseous kinematics, and stellar populations of spheroids. Here, the
sample of galaxies and its properties are described. The instrument is detailed
and its capabilities illustrated through observational examples. These includes
results on the structure of central stellar disks, the kinematics and
ionization state of gaseous disks, and the stellar populations of galaxies with
decoupled cores.


title: Multiwavelenght analysis of Gl 355 (LQ Hya)

abstract:
  We discuss ROSAT, ASCA, {\it Beppo}SAX and optical observations of the young
active star Gl 355. During the ROSAT observation a strong flare was detected
with a peak flux more than an order of magnitude larger than the quiescent
level. Spectral analysis of the data allows us to study the temperature and
emission measure distribution, and the coronal metal abundance, for the
quiescent phase and, in the case of ROSAT, also during the evolution of the
flare. We have modeled the flare and derived a loop semi--length of the order
of $\sim 1.5$ stellar radii. ROSAT, ASCA and {\it Beppo}SAX data suggest that
the coronal abundance of Gl 355 is subsolar, in the range $0.1 \div 0.3
Z/Z_\odot$. A preliminary analysis of optical spectra allows us to compare the
photospheric and coronal metal abundances.


title: REM - Rapid Eye Mount. A fast slewing robotized infrared telescope

abstract:
  The main goal of the REM project is the observation of prompt afterglow of
Gamma-Ray Burst (GRB) events. Such observations at Near InfraRed (NIR)
wavelengths are even very promising, since they allow to monitor high-z
Ly-$\alpha$ absorbed bursts as well as events occurring in dusty star-forming
regions. In addition to GRB science, a large amount of time ($\sim 40%$) will
be available for different scientific targets: among these the study of
variability of stellar objects open exciting new perspectives.


title: Inflaton potential reconstruction in the braneworld scenario

abstract:
  We consider inflaton potential reconstruction in the context of the simplest
braneworld scenario, where both the Friedmann equation and the form of scalar
and tensor perturbations are modified at high energies. We derive the
reconstruction equations, and analyze them analytically in the high-energy
limit and numerically for the general case. As previously shown by Huey and
Lidsey, the consistency equation between scalar and tensor perturbations is
unchanged in the braneworld scenario. We show that this leads to a perfect
degeneracy in reconstruction, whereby a different viable potential can be
obtained for any value of the brane tension $\lambda$. Accordingly, the initial
perturbations alone cannot be used to distinguish the braneworld scenario from
the usual Einstein gravity case.


title: The joint XMM-Newton and Chandra view of YY Gem

abstract:
  We have observed the flare star YY Gem simultaneously with XMM-Newton and
Chandra as part of a multi-wavelength campaign aiming at a study of variability
related to magnetic activity in this short-period eclipsing binary. Here we
report on the first results from the analysis of the X-ray spectrum. The
vicinity of the star provides high enough S/N in the CCD cameras onboard
XMM-Newton to allow for time-resolved spectroscopy. Since the data are acquired
simultaneously they allow for a cross-calibration check of the performance of
the XMM-Newton RGS and the LETGS on Chandra.


title: The Behaviour of Varying-Alpha Cosmologies

abstract:
  We determine the behaviour of a time-varying fine structure 'constant'
$\alpha (t)$ during the early and late phases of universes dominated by the
kinetic energy of changing $\alpha (t)$, radiation, dust, curvature, and
lambda, respectively. We show that after leaving an initial vacuum-dominated
phase during which $\alpha$ increases, $\alpha$ remains constant in universes
like our own during the radiation era, and then increases slowly, proportional
to a logarithm of cosmic time, during the dust era. If the universe becomes
dominated by negative curvature or a positive cosmological constant then
$\alpha$ tends rapidly to a constant value. The effect of an early period of de
Sitter or power-law inflation is to drive $\alpha$ to a constant value. Various
cosmological consequences of these results are discussed with reference to
recent observational studies of the value of $\alpha$ from quasar absorption
spectra and to the existence of life in expanding universes.


title: FLASH redshift survey - I. Observations and Catalogue

abstract:
  The FLAIR Shapley-Hydra (FLASH) redshift survey catalogue consists of 4613
galaxies brighter than $\bJ = 16.7$ (corrected for Galactic extinction) over a
605 sq. degree region of sky in the general direction of the Local Group
motion. The survey region is an approximately $60\degr \times 10\degr$ strip
spanning the sky from the Shapley Supercluster to the Hydra cluster, and
contains 3141 galaxies with measured redshifts. Designed to explore the effect
of the galaxy concentrations in this direction (in particular the Supergalactic
plane and the Shapley Supercluster) upon the Local Group motion, the 68%
completeness allows us to sample the large-scale structure better than similar
sparsely-sampled surveys. The survey region does not overlap with the areas
covered by ongoing wide-angle (Sloan or 2dF) complete redshift surveys. In this
paper, the first in a series, we describe the observation and data reduction
procedures, the analysis for the redshift errors and survey completeness, and
present the survey data.


title:
Energy Balance in the Solar Transition Region. IV. Hydrogen and Helium
  Mass Flows With Diffusion

abstract:
  In this paper we have extended our previous modeling of energy balance in the
chromosphere-corona transition region to cases with particle and mass flows.
The cases considered here are quasi-steady, and satisfy the momentum and energy
balance equations in the transition region. We include in all equations the
flow velocity terms and neglect the partial derivatives with respect to time.
We present a complete and physically consistent formulation and method for
solving the non-LTE and energy balance equations in these situations, including
both particle diffusion and flows of H and He. Our results show quantitatively
how mass flows affect the ionization and radiative losses of H and He, thereby
affecting the structure and extent of the transition region. Also, our
computations show that the H and He line profiles are greatly affected by
flows. We find that line shifts are much less important than the changes in
line intensity and central reversal due to the effects of flows. In this paper
we use fixed conditions at the base of the transition region and in the
chromosphere because our intent is to show the physical effects of flows and
not to match any particular observations. However, we note that the profiles we
compute can explain the range of observed high spectral and spatial resolution
Lyman alpha profiles from the quiet Sun. We suggest that dedicated modeling of
specific sequences of observations based on physically consistent methods like
those presented here will substantially improve our understanding of the energy
balance in the chromosphere and corona.


title:
An XMM-Newton study of the X-ray binary MXB1659-298 and the discovery of
  narrow X-ray absorption lines

abstract:
  We report the discovery of narrow X-ray absorption lines from the low-mass
X-ray binary MXB1659-298 during an XMM-Newton observation in 2001 February. The
7.1 hr orbital cycle is clearly evident with narrow X-ray eclipses preceded by
intense dipping activity. A sinusoid-like OM $B$-band modulation with a
peak-to-peak modulation of 0.5 magnitude and a minimum coincident with the
X-ray eclipse is visible. EPIC and RGS spectra reveal the presence of narrow
resonant absorption features identified with OVIII 1s-2p, 1s-3p and 1s-4p, NeX
1s-2p, FeXXV 1s-2p, and FeXXVI 1s-2p transitions, together with a broad Fe
emission feature at ~6.5 keV. The EWs of the Fe absorption features show no
obvious dependence on orbital phase, even during dipping intervals. Previously,
the only X-ray binaries known to exhibit narrow X-ray absorption lines were two
superluminal jet sources and it had been suggested that these features are
related to the jet formation mechanism. This now appears unlikely, and instead
their presence may be related to the viewing angle of the system. The
MXB1659-298 0.6--12 keV continuum is modeled using absorbed cutoff power-law
and blackbody components. During dips the blackbody is more strongly absorbed
than the power-law. The spectral shape of the 3.6% of 0.5--10 keV emission that
remains during eclipses is consistent with that during non-dipping intervals.


title:
Rotational Velocities and Radii of Pre-Main-Sequence Stars in the Orion
  Nebula Cluster

abstract:
  We have obtained high-dispersion spectra for 256 pre-main-sequence stars in
the Orion Nebula Cluster in order to measure their projected rotational
velocities and study the rotational evolution and physical properties of young,
low-mass stars. Half the stars were chosen because they had known photometric
periods and half were selected as a control sample of similar objects without
known periods. More than 90% of the spectra yielded vsin(i) measurements,
although one-third are upper limits. We find strong evidence confirming the
assumption that the periodic light variations of T Tauri stars are caused by
rotation of surface spots. We find no significant difference between the
vsin(i) distributions of the periodic and control samples, indicating that
there is no strong bias in studying the rotation of young stars using periodic
variables. Likewise, the classical and weak T Tauri stars exhibit vsin(i)
distributions that are statistically the same. For stars with known period and
vsin(i), the mean value of sin(i) is lower than expected for a random
distribution of rotation axes. This could be due to errors in the quantities
that contribute to the sin(i) calculation or to a real physical effect. We find
that mean sin(i) has the expected value if we increase the stars' Teff values
by 400-600 K. Finally, we have calculated minimum radii for stars with vsin(i)
and period, and average radii for stars grouped by location in the H-R diagram.
We find evidence at the 3-sigma level that the radii of stars on similar mass
tracks are decreasing as the stars move closer to the ZAMS. [abridged]


title: Extragalactic H2O Masers

abstract:
  Study of extragalactic H2O masers has progressed significantly in the 25
years since their discovery. Existing in star forming regions and in the
accretion disks supermassive black holes, they are familiar and unfamiliar at
the same time. A review of how our understanding has grown, up to the present
day, is followed by comments on future prospects.


title: Chandra Observations of Cold Fronts in Cluster of Galaxies

abstract:
  High-resolution Chandra images of several clusters of galaxies reveal sharp,
edge-like discontinuities in their gas density. The gas temperature is higher
in front of the edge where the density is low, corresponding to approximately
continuous pressure across the edge. This new phenomenon was called ``cold
fronts'', to contrast it to shock fronts that should look similar in X-ray
images but where the temperature should jump in the opposite direction. The
first cold fronts were discovered in merging clusters, where they appear to
delineate the boundaries of dense cool subcluster remnants moving through and
being stripped by the surrounding shock-heated gas. Later, Chandra revealed
cold fronts in the central regions of several apparently relaxed clusters. To
explain the gas bulk motion in these clusters, we propose either a peculiar
cluster formation history that resulted in an oscillating core, or gas sloshing
(without the involvement of the underlying dark matter peak) caused by past
subcluster infall or central AGN activity. We review these observations and
discuss their implications for the X-ray cluster mass estimates.


title: Narrowband CCD Photometry of Giant HII Regions

abstract:
  We have obtained accurate CCD narrow band H_beta and H_alpha photometry of
Giant HII Regions in M 33, NGC 6822 and M 101. Comparison with previous
determinations of emission line fluxes show large discrepancies; their probable
origins are discussed. Combining our new photometric data with global velocity
dispersion (sigma) derived from emission line widths we have reviewed the
L(H_beta)-sigma relation. A reanalysis of the properties of the GEHRs included
in our sample shows that age spread and the superposition of components in
multiple regions introduce a considerable spread in the regression. Combining
the information available in the literature regarding ages of the associated
clusters, evolutionary footprints on the interstellar medium, and kinematical
properties of the knots that build up the multiple GEHRs, we have found that a
subsample - which we refer to as young and single GEHRs - do follow a tight
relation in the L-sigma plane.


title: The Spectra and Classification of L and T Dwarfs

abstract:
  In this contribution, I discuss some of the salient features of L and T dwarf
spectra in both the red optical (6300--10000 {\AA}) and near-infrared (1--2.5
$\micron$) wavelength regimes. Important absorption bands and lines, including
those of H$_2$O, CH$_4$, FeH, CrH, CO, and the alkali metal lines, are
identified, and the development of recent classification schemes based on these
features are discussed. I briefly point out future work required in these
wavelength regions and in the mid-infrared that are required to garner a
complete picture of these low-luminosity dwarfs.


title: Chandra and RXTE Observations of X-ray Novae

abstract:
  We discuss new observations of X-ray novae with Chandra which provide strong
evidence that black holes have event horizons. The evidence is based on the
finding that black hole X-ray novae in quiescence are approximately 100 times
fainter than equivalent neutron star X-ray novae. The advection-dominated
accretion flow model provides a natural explanation for this difference. RXTE
observations of XTE J1550-564 in the very high state, which were obtained
during the 1998-1999 outburst of the source, reveal an extraordinarily tight
correlation between the central frequency of the low frequency QPO and the
soft, non-power-law flux in the 2-20 keV band. We discuss the nature of this
soft spectral component and suggest the importance of obtaining direct
observations of it at low energies (E < 2 keV) at the first available
opportunity.


title:
Millimeter-Wave Aperture Synthesis Imaging of Vega: Evidence for a Ring
  Arc at 95 AU

abstract:
  We present the first millimeter-wave aperture synthesis map of dust around a
main sequence star. A 3'' resolution image of 1.3 mm continuum emission from
Vega reveals a clump of emission 12'' from the star at PA 45 deg, consistent
with the location of maximum 850 micron emission in a lower resolution
JCMT/SCUBA map. The flux density is 4.0+/-0.9 mJy. Adjacent 1.3 mm peaks with
flux densities 3.4+/-1.0 mJy and 2.8+/-0.9 mJy are located 14'' and 13'' from
the star at PA 67 deg and 18 deg, respectively. An arc-like bridge connects the
two strongest peaks. There is an additional 2.4 +/-0.8 mJy peak to the SW 11''
from the star at PA 215 deg and a marginal detection, 1.4+/-0.5 mJy, at the
stellar position, consistent with photospheric emission. An extrapolation from
the 850 micron flux, assuming F_{1.3mm-0.85mm} proportional to lambda^{-2.8},
agrees well with the total detected flux for Vega at 1.3 mm, and implies a dust
emissivity index, beta, of 0.8. We conclude that we have detected all but a
very small fraction of the dust imaged by SCUBA in our aperture synthesis map
and that these grains are largely confined to segments of a ring of radius 95
AU.


title:
Infrared Mass-to-Light Profile Throughout the Infall Region of the Coma
  Cluster

abstract:
  Using a redshift survey of 1779 galaxies and photometry from the 2-Micron
All-Sky Survey (2MASS) covering 200 square degrees, we calculate independent
mass and light profiles for the infall region of the Coma cluster of galaxies.
The redshift survey is complete to $K_s=12.2$ (622 galaxies), 1.2 magnitudes
fainter than $M^*_{K_s}$ at the distance of Coma. We confirm the mass profile
obtained by Geller, Diaferio, & Kurtz. The enclosed mass-to-light ratio
measured in the $K_s$ band is approximately constant to a radius of $10 \Mpc$,
where $M/L_{K_s}= 75\pm 23\mlsun$, in agreement with weak lensing results on
similar scales. Within $2.5\Mpc$, X-ray estimates yield similar mass-to-light
ratios (67$\pm32h$). The constant enclosed mass-to-light ratio with radius
suggests that K-band light from bright galaxies in clusters traces the total
mass on scales $\lesssim10 \Mpc$. Uncertainties in the mass profile imply that
the mass-to-light ratio inside $r_{200}$ may be as much as a factor of 2.5
larger than that outside $r_{200}$. These data demonstrate that K-band light is
not positively biased with respect to the mass; we cannot rule out antibias.
These results imply $\Omega_m = 0.17 \pm 0.05$. Estimates of possible
variations in $M/L_{K_s}$ with radius suggest that the density parameter is no
smaller than $\Omega_m \approx 0.08$.


title: Kinematic and morphological modeling of the bipolar nebula Sa2-237

abstract:
  We present [OIII]500.7nm and Halpha+[NII] images and long-slit, high
resolution echelle spectra in the same spectral regions of Sa2--237, a possible
bipolar planetary nebula. The image shows a bipolar nebula of about 34" extent,
with a narrow waist, and showing strong point symmetry about the central
object, indicating it's likely binary nature. The long slit spectra were taken
over the long axis of the nebula, and show a distinct ``eight'' shaped pattern
in the velocity--space plot, and a maximum projected outflow velocity of
V=106km/s, both typical of expanding bipolar planetary nebulae. By model
fitting the shape and spectrum of the nebula simultaneously, we derive the
inclination of the long axis to be 70 degrees, and the maximum space velocity
of expansion to be 308 km/s. Due to asymmetries in the velocities we adopt a
new value for the system's heliocentric radial velocity of -30km/s. We use the
IRAS and 21cm radio fluxes, the energy distribution, and the projected size of
Sa2-237 to estimate it's distance to be 2.1+-0.37kpc. At this distance Sa2-237
has a luminosity of 340 Lsun, a size of 0.37pc, and -- assuming constant
expansion velocity -- a nebular age of 624 years. The above radial velocity and
distance place Sa2--237 in the disk of the Galaxy at z=255pc, albeit with
somewhat peculiar kinematics.


title:
Low mass T Tauri and young brown dwarf candidates in the Chamaeleon II
  dark cloud found by DENIS

abstract:
  We define a sample designed to select low-mass T Tauri stars and young brown
dwarfs using DENIS data in the Chamaeleon II molecular cloud. We use a star
count method to construct an extinction map of the Chamaeleon II cloud. We
select our low-mass T Tauri star and young brown dwarf candidates by their
strong infrared colour excess in the I-J/J-K_s colour-colour dereddened
diagram. We retain only objects with colours I-J>2, and spatially distributed
in groups around the cloud cores. This provides a sample of 70 stars of which 4
are previously known T Tauri stars. We have carefully checked the reliability
of all these objects by visual inspection on the DENIS images. Thanks to the
association of the optical I-band to the infra-red J and K_s bands in DENIS, we
can apply this selection method to all star formation regions observed in the
southern hemisphere. We also identify six DENIS sources with X-ray sources
detected by ROSAT. Assuming that they are reliable low-mass candidates and
using the evolutionary models for low-mass stars, we estimate the age of these
sources between 1 Myr and < 10 Myr.


title:
Dynamically Close Galaxy Pairs and Merger Rate Evolution in the CNOC2
  Redshift Survey

abstract:
  We investigate redshift evolution in the galaxy merger and accretion rates,
using a well-defined sample of 4184 galaxies with 0.12 < z < 0.55 and R_C <
21.5. We identify 88 galaxies in close (5 < r_p < 20 h^{-1} kpc) dynamical
(delta v < 500 km/s) pairs. These galaxies are used to compute global pair
statistics, after accounting for selection effects resulting from the flux
limit, k-corrections, luminosity evolution, and spectroscopic incompleteness.
We find that the number of companions per galaxy (for -21 < M_B^{k,e} < -18) is
Nc = 0.0321 +/- 0.0077 at z=0.3. The luminosity in companions, per galaxy, is
Lc = 0.0294 +/- 0.0084 x 10^10 h^2 L_sun. We assume that Nc is proportional to
the galaxy merger rate, while Lc is directly related to the mass accretion
rate. After increasing the maximum pair separation to 50 h^{-1} kpc, and
comparing with the low redshift SSRS2 pairs sample, we infer evolution in the
galaxy merger and accretion rates of (1+z)^{2.3 +/- 0.7} and (1+z)^{2.3 +/-
0.9} respectively. These are the first such estimates to be made using only
confirmed dynamical pairs. When combined with several additional assumptions,
this implies that approximately 15% of present epoch galaxies with -21 < M_B <
-18 have undergone a major merger since z=1.


title:
Gamma-ray bursts and gravitational radiation from black hole-torus
  systems

abstract:
  Cosmological gamma-ray bursts (GRBs) are probably powered by systems
harboring a rotating black hole. These may result from hypernovae or black
hole-neutron star coalescence. We identify short/long bursts with hyper- and
suspended-accretion states around slowly/rapidly spinning black holes. Baryon
poor jets, as input to the observed GRB/afterglow emissions, may result from
dissipation in a gap along an open flux-tube on the axis of rotation of the
black hole. The torus is expected to radiate a major fraction of the black hole
luminosity into gravitational waves, which suggests that long GRBs may be the
most powerful LIGO/VIRGO burst sources in the Universe. (Abbreviated)


title: Modeling the corona of AB Doradus

abstract:
  We present a technique that combines Zeeman Doppler imaging (ZDI) principles
with a potential field mapping prescription in order to gain more information
about the surface field topology of rapid rotators. This technique is an
improvement on standard ZDI, which can sometimes suffer from the suppression of
one vector component due to the effects of stellar inclination, poor phase
coverage or lack of flux from dark areas on the surface. Defining a
relationship beween the different vector components allows information from one
component to compensate for reduced information in another. We present
simulations demonstrating the capability of this technique and discuss its
prospects.


title: Gas Inflow in Barred Galaxies - Effects of Secondary Bars

abstract:
  We report here results of high-resolution hydrodynamical simulations of gas
flows in barred galaxies, with a focus on gas dynamics in the central
kiloparsec. In a single bar with an Inner Lindblad Resonance, we find either
near-circular motion of gas in the nuclear ring, or a spiral shock extending
towards the galaxy center, depending on the sound speed in the gas. From a
simple model of a dynamically-possible doubly barred galaxy with resonant
coupling, we infer that the secondary bar is likely to end well inside its
corotation. Such a bar cannot create shocks in the gas flow, and therefore will
not reveal itself in color maps through straight dust lanes: the gas flows
induced by it are different from those caused by the rapidly rotating main
bars. In particular, we find that secondary stellar bars are unlikely to
increase the mass inflow rate into the galactic nucleus.


title: Angular Momentum Profiles of Warm Dark Matter Halos

abstract:
  We compare the specific angular momentum profiles of virialized dark halos in
cold dark matter (CDM) and warm dark matter (WDM) models using high-resolution
dissipationless simulations. The simulations were initialized using the same
set of modes, except on small scales, where the power was suppressed in WDM
below the filtering length. Remarkably, WDM as well as CDM halos are
well-described by the two-parameter angular momentum profile of Bullock et al.
(2001), even though the halo masses are below the filtering scale of the WDM.
Although the best-fit shape parameters change quantitatively for individual
halos in the two simulations, we find no systematic variation in profile shapes
as a function of the dark matter type. The scatter in shape parameters is
significantly smaller for the WDM halos, suggesting that substructure and/or
merging history plays a role producing scatter about the mean angular momentum
distribution, but that the average angular momentum profiles of halos originate
from larger-scale phenomena or a mechanism associated with the virialization
process. The known mismatch between the angular momentum distributions of dark
halos and disk galaxies is therefore present in WDM as well as CDM models. Our
WDM halos tend to have a less coherent (more misaligned) angular momentum
structure and smaller spin parameters than do their CDM counterparts, although
we caution that this result is based on a small number of halos.


title: Variable Stars in the Field of the Globular Cluster NGC 3201

abstract:
  We report on the discovery and analysis of 14 short-period variable stars in
the field of the southern globular cluster NGC 3201, located within roughly two
magnitudes on either side of the main-sequence turnoff. 11 of these variable
stars are eclipsing binaries, one is an RR Lyrae, and two are thus far
unclassified systems. Among the eclipsing binary stars, nine are of the W Ursa
Majoris (W UMa) type, one an Algol (EA) system, and one a detached system.
Using spectroscopic follow-up observations as well as analysis of the
variables' locations in the color-magnitude diagram of the cluster, we find
that only one variable star (a W UMa type blue straggler) is actually a member
of NGC 3201. We present the phased photometry lightcurves for all the variable
star systems as well as their locations in the field-of-view and in the
color-magnitude diagram.


title: Supernovae in isolated galaxies, in pairs and in groups of galaxies

abstract:
  In order to investigate the influence of the environment on the supernova
(SN) production we have performed a statistical investigation of the SNe
discovered in isolated galaxies, in pairs and in groups of galaxies. 22 SNe in
18 isolated galaxies, 48 SNe in 40 galaxies members of 37 pairs and 211 SNe in
170 galaxies members of 116 groups have been selected and studied. We found
that the radial distributions of core-collapse SNe in galaxies located in
different environments are similar, and consistent with that reported by
Bartunov, Makarova & Tsvetkov (1992). SNe discovered in pairs do not privilege
a particular direction with respect to the companion galaxy. Also the azimuthal
distributions inside the hosts members of galaxy groups are consistent with
being isotropics. The fact that SNe are more frequent in the brighter
components of the pairs and groups is expected from the dependence of the SN
rates on the galaxy luminosity. There is an indication that the SN rate is
higher in galaxy pairs compared with that in groups. This can be related to the
enhanced star formation rate in strongly interacting systems. It is concluded
that, with the possible exception of strongly interacting system, the parent
galaxy environment has no direct influence on the SN production


title:
Confidence levels of evolutionary synthesis models III: On sampling and
  Poissonian fluctuations

abstract:
  In terms of statistical fluctuations, stellar population synthesis models are
only asymptotically correct in the limit of a large number of stars, where
sampling errors become asymptotically small. When dealing with stellar
clusters, starbursts, dwarf galaxies or stellar populations within pixels,
sampling errors introduce a large dispersion in the predicted integrated
properties of these populations. We present here an approximate but generic
statistical formalism which allows a very good estimation of the uncertainties
and confidence levels in any integrated property, bypassing extensive Monte
Carlo simulations, and including the effects of partial correlations between
different observables. Tests of the formalism are presented and compared with
proper estimates. We derive the minimum mass of stellar populations which is
required to reach a given confidence limit for a given integrated property. As
an example of this general formalism, which can be included in any synthesis
code, we apply it to the case of young (t < 20 Myr) starburst populations. We
show that, in general, the UV continuum is more reliable than other continuum
bands for the comparison of models with observed data. We also show that
clusters where more than 10^5 Mo have been transformed into stars have a
relative dispersion of about 10% in Q(He+) for ages smaller than 3 Myr. During
the WR phase the dispersion increases to about 25% for such massive clusters.
We further find that the most reliable observable for the determination of the
WR population is the ratio of the luminosity of the WR bump over the Hbeta
luminosity. A fraction of the observed scatter in the integrated properties of
clusters and starbursts can be accounted for by sampling fluctuations.


title: New candidate planetary nebulae in M81

abstract:
  A 34 x 34 arcmin field centred on the spiral galaxy M81 has been searched for
emission-line objects using the prime focus wide field camera (WFC) of the 2.54
m Isaac Newton Telescope (La Palma, Spain). A total of 171 candidate planetary
nebulae (PNe) are found, 54 of which are in common with the ones detected by
Jacoby et al. (1989). The behaviour of PNe excitation as a function of
galactocentric distance is examined, and no significant variations are found.
The PNe luminosity function is built for the disk and bulge of M81, separately.
A distance modulus of 27.92+-0.23 mag is found for disk PNe, in good agreement
with previous distance measurements for M81 (Jacoby et al. 1989; Huterer et al.
1995).


title:
Evidence for binarity in the bipolar planetary nebulae A79, He2-428 and
  M1-91

abstract:
  We present low and high resolution long-slit spectra of three bipolar
planetary nebulae (PNe) with bright central cores: A79, He2-428 and M1-91.
He2-428 and M1-91 have high density (from 10^3.3 to 10^6.5 cm^-3) unresolved
nebular cores that indicate that strong mass loss/exchange phenomena are
occurring close to their central stars. An F0 star is found at the centre of
symmetry of A79; its reddening and distance are consistent with the association
of the star with the nebula. The spectrum of the core of He2-428 shows
indications of the presence of a hot star with red excess emission, probably
arising in a late-type companion. A79 is one of the richest PNe in N and He,
the abundances of M1-91 are at the lower end of the range spanned by bipolar
PNe, and He2-428 shows very low abundances, similar to those measured for halo
PNe. The extended nebulae of A79 and He2-428 have inclined equatorial rings
expanding at a velocity of approx. 15 km/s, with kinematical ages 10^4 yr. The
association of these aged, extended nebulae with a dense nebular core (He2-428)
or a relatively late type star (A79) is interpreted as evidence for the
binarity of their nuclei.


title:
The SCUBA Bright Quasar Survey (SBQS): 850micron observations of the z>4
  sample

abstract:
  We present initial results of a new, systematic search for massive
star-formation in the host galaxies of the most luminous and probably most
massive z>=4 radio-quiet quasars (M(B) <= -27.5; nuL(nu)(1450Ang)>10^13Lsun).
  A total of 38 z>=4 radio-quiet quasars have been observed at the JCMT using
SCUBA at 850microns: 8 were detected (>3sigma) with S(850microns)>~ 10mJy
(submillimetre-loud). The new detections almost triple the number of optically
selected, submillimetre-loud z>~4 radio-quiet quasars known to date. We include
a detailed description of how our quasar sample is defined in terms of radio
and optical properties.
  There is no strong evidence for trends in either detectability or 850microns
flux with absolute magnitude, M(B). We find that the weighted mean flux of the
undetected sources is 2.0 +/- 0.6mJy, consistent with an earlier estimate of
\~3mJy based on more sensitive observations of a sample z>~4 radio-quiet
quasars (McMahon et al., 1999). This corresponds to an inferred starformation
rate of \~1000Msun/yr, similar to Arp220. The typical starformation timescale
for the submillimetre-bright sources is ~1Gyr, 10 times longer than the typical
accretion-driven e-folding timescale of ~5x10^7 years. Our 850micron detection
of the z=4.4 quasar PSS J1048+4407 when analysed in conjunction with 1.2mm
single-dish and interferometric observations suggests that this source is
resolved on angular scales of 1-2" (6-12 kpc). In addition, we present a new
optical spectrum of this source, identifying it as a broad absorption line
(BAL) quasar. The new redshift is outside that covered in a recent CO line
search by Guilloteau et al., (1999), highlighting the need for accurate
redshifts for the obervation and interpretation of high-redshift line studies.


title: Inflationary Cosmology: Theory and Phenomenology

abstract:
  This article gives a brief overview of some of the theory behind the
inflationary cosmology, and discusses prospects for constraining inflation
using observations. Particular care is given to the question of falsifiability
of inflation or of subsets of inflationary models.


title: On the Masses of the Secondary Stars in CVs

abstract:
  Recent theoretical efforts have made predictions for the masses of the
secondary stars in cataclysmic variables. Accurate observational determinations
for M$_2$ are sparse and typically have uncertainties near $\pm$0.1M$_{\odot}$.
How well do theory and observation agree?


title:
X-ray Evidence for Supermassive Black Holes in Non-Active Galaxies.
  Subtitle: Detection of X-ray Flare Events, Interpreted as Tidal Disruptions
  of Stars by SMBHs

abstract:
  It has long been suggested that supermassive black holes in non-active
galaxies might be tracked down by occasional tidal disruptions of stars on
nearly radial orbits. A tidal disruption event would reveal itself by a
luminous flare of electromagnetic radiation. Theorists argued that the
convincing detection of such a tidal disruption event would be the observation
of an event which fulfills the following three criteria: (1) the event should
be of finite duration (a `flare'), (2) it should be very luminous (up to
L_{max} ~ 10^{45} erg/s in maximum), and (3) it should reside in a galaxy that
is otherwise perfectly {\em non-active} (to be sure to exclude an upward
fluctuation in gaseous accretion rate of an {\em active} galaxy). During the
last few years, several X-ray flare events were detected which match exactly
the above criteria. We therefore consider these events to be excellent
candidates for the occurrences of the theoretically predicted tidal disruption
flares.
  In this contribution, we review the previous observations of giant X-ray
flares from normal galaxies, present new results on these objects, critically
discuss alternatives to the favored outburst scenario, and report results from
our ongoing search for further tidal disruption flares based on the ROSAT
all-sky survey database.


title: Detection of Infall Signatures Towards Serpens SMM4

abstract:
  We present the detection of kinematic infall signatures towards the Class 0
protostellar system SMM4 in the Serpens cloud core. We have observed the dense
molecular gas towards the embedded source using millimeter and submillimeter
line transitions of density sensitive molecular tracers. High signal-to-noise
ratio maps obtained in HCO+ J=1-0, J=3-2, and J=4-3, and CS J=2-1 show the
blue-bulge infall signature. The blue-bulge infall signature can be observed in
the centroid velocity maps of protostellar objects when infall dominates over
rotation. The line profiles of HCO+ and CS exhibit the characteristic blue
asymmetric line profile signature consistent with infall. In addition, HCO+ and
CS optical depth profiles obtained using isotopic observations show a red
asymmetry also consistent with an infall interpretation. Using
three-dimensional radiative transfer models based on the rotating, collapse
model of Terebey, Shu and Cassen, we derive infall parameters of the source. To
determine the direction and orientation of molecular outflows in the larger
Serpens cluster, wide-field mapping of CO J=1-0 emission was also performed.


title: Lick Spectral Indices for Super Metal-rich Stars

abstract:
  The Lick Fe5015, Fe5270, Fe5335, Mgb and Mg2 indices are presented for 139
candidate SMR stars of different luminosity class studied in Malagnini et al.
(2000). Evidence is found for a standard (i.e. [Mg/Fe]~0) Mg vs. Fe relative
abundance. Both the Worthey et al. (1994) and Buzzoni et al. (1992, 1994)
fitting functions are found to suitably match the data at super-solar
metallicity regimes. See http://www.merate.mi.astro.it/~eps/home.html for
further details.


title: Stellar Seismology, Stellar Ages and the Cosmological Constant

abstract:
  Solar seismology has allowed precision measurements of both the static and
dynamic structure of our local star, the Sun. In the near future, seismology of
solar-like stars of different ages and masses, necessarily restricted by
angular resolution to low l-modes, will allow studies of the internal structure
of stars at various stages of evolution. Such studies will test not only the
theory of stellar evolution, but also allow the determination of ages of stars
from the helium content in their cores. Such observations can be made
photometrically from space, but also spectroscopically from the ground. We
outline ground-based schemes. By correlating the external properties of nearby
stars with their internal properties, it will be possible to extend local
studies to distant open and globular clusters, and thereby to obtain an age of
the Universe, based on many stars. The combination of the age, the density
parameter Omega and Hubble's constant will allow strong limits to be placed on
the cosmological constant.


title:
HST large field weak lensing analysis of MS 2053-04: study of the mass
  distribution and mass-to-light ratio of X-ray selected clusters at
  0.22<z<0.83

abstract:
  We have detected the weak lensing signal induced by the cluster of galaxies
MS 2053-04 (z=0.58) from a two-colour mosaic of 6 HST WFPC2 images. The best
fit singular isothermal sphere model to the observed tangential distortion
yields an Einstein radius r_E=6.2"+-1.8", which corresponds to a velocity
dispersion of 886^{+121}_{-139} km/s. This result is in good agreement with the
observed velocity dispersion of 817+-80 km/s from cluster members.
  MS 2053 is the third cluster we studied using mosaics of deep WFPC2 images.
For all three clusters we find good agreement between dynamical and weak
lensing velocity dispersions, in contrast to weak lensing studies based on
single WFPC2 pointings on cluster cores. This result demonstrates the
importance of wide field data. We have compared the ensemble averaged cluster
profile to the predicted NFW profile, and find that a NFW profile can fit the
observed lensing signal well. The best fit concentration parameter is found to
be 0.79^{+0.44}_{-0.15} (68% confidence) times the predicted value from an open
CDM model. The observed mass-to-light ratios of the clusters in our sample
evolve with redshift, and are inconsistent with a constant, non-evolving,
mass-to-light ratio at the 99% confidence level. The evolution is consistent
with the results derived from the evolution of the fundamental plane of early
type galaxies. The resulting average mass-to-light ratio for massive clusters
at z=0 is found to be 239+-18+-9 M/L_B. (abridged)


title:
The Optical Gravitational Lensing Experiment. Cepheids in the Galaxy
  IC1613: No Dependence of the Period--Luminosity Relation on Metallicity

abstract:
  We present results of the search for Cepheids in the galaxy IC1613 carried
out as a sub-project of the OGLE-II microlensing survey. 138 Cepheids were
found in the 14.2x14.2 arcmin region in the center of the galaxy. We present
light curves, VI photometry and basic data for all these objects, as well as
color-magnitude diagram of the observed field.
  The Period--Luminosity (PL) diagrams for IC1613 fundamental mode Cepheids for
VI and interstellar extinction insensitive index W_I are constructed.
Comparison of PL relations in metal poor galaxy IC1613 ([Fe/H]~-1.0 dex) with
relations in metal richer Magellanic Clouds allows us to study dependence of
Cepheid PL relations on metallicity in the wide range of metallicities covered
by these three galaxies. The slopes of PL relations in IC1613 are identical as
in the Magellanic Clouds. The comparison of brightness of Cepheids with the
magnitudes of the tip of the red giant branch stars and RR Lyr stars in all
three objects provides information on the stability of zero points of PL
relations in the I and V-band, respectively. We find that the zero points of PL
relations are constant to better than $\pm0.03$ mag over the entire range of
covered metallicities. Thus, the most important conclusion of the paper is that
the Cepheid PL relations do not depend on metallicity. Additionally we
determine the mean distance to IC1613, based on the common distance scale
resulting from four major stellar distance indicators: Cepheids, RR Lyr, TRGB
and red clump stars. The distance modulus to IC1613 is equal to
(m-M)_IC1613=24.20 mag with the standard deviation of +/-0.02 mag from six
measurements and systematic uncertainty of calibrations of +/-0.07 mag.


title:
Column Density Probability Distribution Functions in Turbulent Molecular
  Clouds: A Comparison between Theory and Observations

abstract:
  The one-point statistics of column density distributions of turbulent
molecular cloud models are investigated and compared with observations. In
agreement with the observations, the number N of pixels with surface density S
is distributed exponentially N(S)=exp(-S/S0) in models of driven compressible
supersonic turbulence. However, in contrast to the observations, the
exponential slope defined by S0 is not universal but instead depends strongly
on the adopted rms Mach number and on the smoothing of the data cube. We
demonstrate that this problem can be solved if one restricts the analysis of
the surface density distribution to subregions with sizes equal to the
correlation length of the flow which turns out to be given by the driving
scale. In this case, the column density distributions are universal with a
slope that is in excellent agreement with the observations and independent of
the Mach number or smoothing. The observed molecular clouds therefore are
coherent structures with sizes of order their correlation lengths. Turbulence
inside these clouds must be driven on the largest scales, if at all. Numerical
models of turbulent molecular clouds have to be restricted to cubes with sizes
similar to the correlation lengthscale in order to be compared with
observations. Our results imply that turbulence is generated on scales that are
much larger that the Jeans length. In this case, gravitational collapse cannot
be suppressed and star formation should start in molecular clouds within a
dynamical timescale after their formation.


title:
Mid-IR and CO Observations of the IR/X-Ray Luminous Seyfert I Galaxy
  NGC985: The Making or Breaking of a ULIRG?

abstract:
  We describe ISO and BIMA observations of the z=0.04 Seyfert 1 ring galaxy
NGC985 which suggest close parallels with some quasar host galaxies. NGC985
contains two closely spaced nuclei embedded in an R$^{1/4}$--law stellar bulge
and an outer ring, evidence of an ongoing merger. The system contains
\~1.8x10^{10}Msolar of highly disturbed molecular gas which lies in an
asymmetric bar-like structure with the peak in observed CO column densities
significantly offset from the compact double nucleus. In contrast to this, the
ISO observations show strong dust emission centered on the AGN, located in one
of the two nuclei. Fainter CO, MIR, and radio continuum emission provide a
glimpse of the complexities of star formation in the outer ring. An analysis of
the kinematics of the main CO emission reveal evidence for two dynamically
distinct molecular components within NGC985. The first is a set of isolated
super-giant molecular clouds (SGMCs) which are concentrated within 9-10kpc of
the active nucleus. Although randomly distributed about the center, the clouds
may form part of a clumpy highly-disturbed disk which may be either just
forming around double-nucleus (the making of a ULIRG), or alternatively may be
in the process of being disrupted-perhaps as a result of a powerful nuclear
outflow (the breaking of a ULIRG). A second major concentration of CO lies
offset from the double-nucleus in a dynamically coherent ridge of emission in
which powerful star formation is occurring. We tentatively associate CO
emission with two out of six UV absorption-lines seen in the blue wing of the
very broad Lyman alpha emission. Such an association would imply a complex
inter-relationship between the nuclear CO cloud population in colliding
systems, and AGN-driven winds.


title:
Determination of limits on disc masses around six pulsars at 15 and 90
  microns

abstract:
  We have searched for evidence of emission at 15 microns with ISOCAM and at 90
microns with ISOPHOT from dust orbiting six nearby pulsars, both in binaries
and in isolation, located at distances between about 100 to 1000 pc. No
emission was detected at any of the pulsar positions, and for the nearest
pulsar J0108-1431 the 3 sigma upper limits on the flux density is about 66 mJy
at 15 microns and 22.5 mJy at 90 microns. Upper limits on the masses of
circumpulsar dust are inferred at a given temperature using a simple modelling
of the radiated flux; they are compared to upper limits of orbiting mass
obtained with the dust heating model of Foster & Fisher (1996). These results
suggest that it is unlikely that any of them have sufficiently massive,
circumpulsar discs out of which planets may form in the future.


title: Dark Matter in Dwarf Spheroidals II: Observations and Modelling of Draco

abstract:
  We present stellar radial velocity data for the Draco dwarf spheroidal galaxy
obtained using the AF2/WYFFOS instrument combination on the William Herschel
Telescope. Our dataset consists of 186 member stars, 159 of which have good
quality velocities, extending to a magnitude V=19.5 with a mean velocity
precision of 2 km/s. We find statistically strong evidence of a rising velocity
dispersion consistent with a dark matter halo with gently rising rotation
curve. There is a <2 sigma signature of rotation about the long axis,
inconsistent with tidal disruption being the source of the rising dispersion.
By comparing our dataset with earlier velocities, we find that Draco probably
has a binary distribution and fraction comparable to those in the solar
neighbourhood. We apply a novel maximum likelihood algorithm and fit the
velocity data to a two parameter spherical model with an adjustable dark matter
content and velocity anisotropy. Draco is best fit by a weakly tangentially
anisotropic distribution of stellar orbits in a dark matter halo with a very
slowly rising rotation law. We are able to rule out both a mass-follows-light
distribution and an extended halo with a harmonic core at the 2.5 to 3 sigma
significance level, depending on the details of our assumptions about Draco's
stellar binary population. Our modelling lends support to the idea that the
dark matter in dwarf spheroidals is distributed in the form of massive, nearly
isothermal haloes.


title: Dark Matter in Dwarf Spheroidals I: Models

abstract:
  This paper introduces a new two-parameter family of dwarf spheroidal (dSph)
galaxy models. The density distribution has a Plummer profile and falls like
the inverse fourth power of distance in projection, in agreement with the
star-count data. The first free parameter controls the velocity anisotropy, the
second controls the dark matter content. The dark matter distribution can be
varied from one extreme of mass-follows-light through a near-isothermal halo
with flat rotation curve to the other extreme of an extended dark halo with
harmonic core. This family of models is explored analytically in some detail --
the distribution functions, the intrinsic moments and the projected moments are
all calculated. For the nearby Galactic dSphs, samples of hundreds of discrete
radial velocities are becoming available. A technique is developed to extract
the anisotropy and dark matter content from such data sets by maximising the
likelihood function of the sample of radial velocities. This is constructed
from the distribution function and corrected for observational errors and the
effects of binaries. Tests on simulated data sets show that samples of 1000
discrete radial velocities are ample to break the degeneracy between mass and
anisotropy in the nearby dSphs. Interesting constraints can already be placed
on the distribution of the dark matter with samples of 160 radial velocities
(the size of the present-day data set for Draco).


title:
Re-examining the X-Ray versus Spin-Down Luminosity Correlation of
  Rotation Powered Pulsars

abstract:
  The empirical relation between the X-ray luminosity (in the 2-10 keV band)
and the rate of spin-down energy loss of a sample of 37 pulsars is re-examined
considering recent data from ASCA, RXTE, BeppoSAX, Chandra, and XMM-Newton. The
data show a significant scatter around an average correlation computed
including statistical and systematic errors. All the X-ray luminosities are
found to lie below a critical line corresponding to a maximum efficiency of
conversion of rotational energy into X-rays varying between 0.1 and 80%. The
large dispersion of the X-ray luminosity below the critical line indicates that
other physical parameters uncorrelated with the period and period derivative
need to be included to account for the observed emission at X-ray energies. We
indicate a few possibilities that all conspire to lower the luminosity.


title:
Measuring the Redshift Evolution of Clustering: the Hubble Deep Field
  South

abstract:
  We present an analysis of the evolution of galaxy clustering in the redshift
interval 0<z<4.5 in the HDF-S. The HST optical data are combined with infrared
ISAAC/VLT observations, and photometric redshifts are used for all the galaxies
brighter than I_AB<27.5. The clustering signal is obtained in different
redshift bins using two different approaches: a standard one, which uses the
best redshift estimate of each object, and a second one, which takes into
account the redshift probability function of each object. This second method
makes it possible to improve the information in the redshift intervals where
contamination from objects with insecure redshifts is important. With both
methods, we find that the clustering strength up to z~3.5 in the HDF-S is
consistent with the previous results in the HDF-N. While at redshift lower than
z~1 the HDF galaxy population is un/anti-biased (b<1) with respect to the
underlying dark matter, at high redshift the bias increases up to b~2-3,
depending on the cosmological model. These results support previous claims
that, at high redshift, galaxies are preferentially located in massive haloes,
as predicted by the biased galaxy formation scenario. The impact of cosmic
errors on our analyses has been quantified, showing that errors in the
clustering measurements in the HDF surveys are indeed dominated by shot-noise
in most regimes. Future observations with instruments like the ACS on HST will
improve the S/N by at least a factor of two and more detailed analyses of the
errors will be required. In fact, pure shot-noise will give a smaller
contribution with respect to other sources of errors, such as finite volume
effects or non-Poissonian discreteness effects.


title: A New Measurement of the Average FUV Extinction Curve

abstract:
  We have measured the extinction curve in the far-ultraviolet wavelength
region of (900 -- 1200 A) using spectra obtained with the Berkeley EUV/FUV
spectrometer during the ORFEUS-I and the ORFEUS-II missions in 1993 and 1996.
  From the complete sample of early-type stars observed during these missions,
we have selected pairs of stars with the same spectral type but different
reddenings to measure the differential FUV extinction. We model the effects of
molecular hydrogen absorption and exclude affected regions of the spectrum to
determine the extinction from dust alone. We minimize errors from inaccuracies
in the cataloged spectral types of the stars by making our own determinations
of spectral types based on their IUE spectra. We find substantial scatter in
the curves of individual star pairs and present a detailed examination of the
uncertainties and their effects on each extinction curve. We find that, given
the potentially large uncertainties inherent in using the pair method at FUV
wavelengths, a careful analysis of measurement uncertainties is critical to
assessing the true dust extinction. We present a new measurement of the average
far-ultraviolet extinction curve to the Lyman limit; our new measurement is
consistent with an extrapolation of the standard extinction curve of Savage &
Mathis (1979).


title:
On the relation between the coronal line emission and the IR/X-ray
  emission in Seyfert galaxies

abstract:
  The relation between the X-ray, the coronal line and the infrared (IR)
emissions in a sample of the brightest known Seyfert galaxies is analysed. A
close relationship between the absorption-corrected soft X-ray emission and
both the mid-IR and the coronal line emission is found for the Seyfert type 2
objects in the sample. The coronal line and the X-ray emissions are both main
tracers of the central activity, hence their relationship with the mid-IR
emission points to nuclear energetic process as the main responsibles of the
heating of the circumnuclear dust. On the other hand, the above relations do
not seem to hold for the Seyfert type 1 discussed in the sample, at least when
the comparisons are done in a flux diagram. This is partially because of the
reduced number of objects of this type analysed in this work and the fact that
the measured soft X-ray emission in Seyfert 1s is systematically larger, by at
least an order of magnitude, than that in the Seyfert 2 counterparts. Finally,
the hard X-ray emission in the studied sample appears unrelated to either the
mid-IR or the coronal line emission.


title:
The mass ratio distribution of B-type visual binaries in the Sco OB2
  association

abstract:
  The sample of 115 B-type stars in Sco OB2 association is examined for
existence of visual companions with ADONIS near-infrared adaptive optics system
and coronograph in J and K bands. Practically all components in the separation
range 0.3"-6" (45-900 A.U.) were detected, with magnitudes down to K=16. The K
and J-K photometry of primaries and differential photometry and astrometry of
96 secondaries are presented. Ten secondaries are new physical components, as
inferred from photometric and statistical criteria, while remaining are faint
background stars. After small correction for detection incompleteness and
conversion of fluxes into masses, an unbiased distribution of the components
mass ratio q is derived. The power law f(q)\propto q^{-0.5} fits well the
observations, whereas a q^{-1.8} distribution which corresponds to random
pairing of stars is rejected. The companion star fraction is 0.20 +- 0.04 per
decade of separation, comparable to the highest measured binary fraction among
low-mass PMS stars and ~1.6 times higher than the binary fraction of low-mass
dwarfs in solar neighborhood and open clusters in the same separation range.


title: Simultaneous EUV and IR Observations of the Eclipsing Polar HU Aqr

abstract:
  We present simultaneous EUV and infrared (J,K) observations of the polar HU
Aqr obtained during August 1998 when the star was in a high mass accretion
state. EUV and IR light curves and EUV spectra are presented and compared with
previous observations. The accretion region on the white dwarf has increased in
temperature (124,000K to 240,000K) and radius (0.04 R$_{WD}$ to 0.06 R$_{WD} $)
compared with previous EUV observations made during low mass accretion states.
The EUV and IR photometric observations are shown to have a similar appearance
as a function o f orbital phase. The EUV photometry shows rapid changes and
provides evidence for mass accretion via blobs. The high state IR light curves
present an asymmetric double-humped shape with J=14.8 and K=14.1. We applied an
ellipsoidal model fit to the observations and the result indicates that the
cause of the modulated shape is both due to ellipsoidal variations from the
Roche Lobe filling secondary star and a complex flux combination probably
dominated at all orbital phases by cyclotron emission. The source of maximum
cyclotron emission appears to be in the accretion column high above the white
dwarf surface.


title: The Star Formation History of the Large Magellanic Cloud

abstract:
  Using WFPC2 aboard the Hubble Space Telescope, we have created deep
color-magnitude diagrams in the V and I passbands for approximately 100,000
stars in a field at the center of the LMC bar and another in the disk. The
main--sequence luminosity functions (LFs) from 19 mag < V < 23.5 mag, the red
clump and horizontal branch morphologies, and the differential Hess diagram of
the two fields all strongly imply that the disk and bar have significantly
different star-formation histories (SFHs). The disk's SFH has been relatively
smooth and continuous over the last 15 Gyr while the bar's SFH was dominated by
star formation episodes at intermediate ages. Comparison of the LF against
predictions based on Padova theoretical stellar evolution models and an assumed
age-metallicity relationship allows us to identify the dominant stellar
populations in the bar with episodes of star formation that occurred from 4 to
6 and 1 to 2 Gyr ago. These events accounted, respectively, for approximately
25% and 15% of its stellar mass. The disk field may share a mild enhancement in
SF for the younger episode, and thus we identify the 4 to 6 Gyr episode with
the formation of the LMC bar.


title: The morphological and dynamical evolution of simulated galaxy clusters

abstract:
  We explore the morphological and dynamical evolution of galaxy clusters in
simulations using scalar and vector-valued Minkowski valuations and the concept
of fundamental plane relations. In this context, three questions are of
fundamental interest: 1. How does the average cluster morphology depend on the
cosmological background model? 2. Is it possible to discriminate between
different cosmological models using cluster substructure in a statistically
significant way? 3. How is the dynamical state of a cluster, especially its
distance from a virial equilibrium, correlated to its visual substructure? To
answer these questions, we quantify cluster substructure using a set of
morphological order parameters constructed on the basis of the Minkowski
valuations (MVs). The dynamical state of a cluster is described using global
cluster parameters: in certain spaces of such parameters fundamental band-like
structures are forming indicating the emergence of a virial equilibrium. We
find that the average distances from these fundamental structures are
correlated to the average amount of cluster substructure for our cluster
samples during the time evolution. Furthermore, significant differences show up
between the high- and the low-Omega models. We pay special attention to the
redshift evolution of morphological characteristics and find large differences
between the cosmological models even for higher redshifts.


title: Measuring Sizes of Marginally Resolved Young Globular Clusters with HST

abstract:
  We present a method to derive sizes of marginally resolved star clusters from
HST/WFPC2 observations by fitting King models to observations. We describe
results on both simulated images and on observations of young compact clusters
in NGC 3597 and NGC 1275. From the simulations, we find that we can measure
King model concentrations (c) to an accuracy of about a factor of two for all
combinations of c and King radius (r_0) of interest if the data have high S/N
(>~ 500 for the integrated brightness). If the concentration is accurately
measured, we can measure the King radius accurately. For lower S/N, marginally
resolved King profiles suffer from a degeneracy; different values of the
concentration give different r_0 but have comparable reduced chi-squared
values. In this case, neither the core radius nor the concentration can be
constrained individually, but the half-light radius can be recovered
accurately.
  In NGC 3597, we can only differentiate between concentrations for the very
brightest clusters; these suggest a concentration of ~ 2. Assuming a
concentration of 2 for the rest of the objects, we find an average King radius
for the clusters in NGC 3597 of 0.7 pc, while the clusters in NGC 1275 have an
average radius of 1.1 pc. These are similar to the average core radii for
Galactic globular clusters, 0.92 pc. We find average half-light radii of 5.4 pc
and 6.2 pc for the young clusters in NGC 3597 and NGC 1275, respectively, while
the average half-light radii of Galactic globulars is 3.4 pc. The spread in the
derived radial parameters in each cluster system is comparable to that observed
in the Galactic globular cluster system.


title: The Spectroscopic Orbital Period of HD 45166

abstract:
  HD 45166 was selected as a candidate to the V Sagittae Class. It's spectrum
shows quite narrow emission lines of He, C, N, and O, possibly indicating a low
inclination for the binary system. We performed high resolution and high
stability Coude spectroscopy in order to search for low amplitude radial
velocity variations. The orbital period determined from the radial velocity
curve is 0.357 days, and the radial velocity semi amplitude is K=3.8 km/s. The
system inclination (in degrees), determined from the mass function of the
secondary star, is 0.7 < i < 1.0.


title: Secondary Muon Asymmetries at Sea Levell with Low Systematics

abstract:
  Project GRAND has the capability of measuring the angle and identity of
single tracks of secondary muons at ground level. The array is comprised of 64
stations each containing eight proportional wire planes with a 50 mm steel
absorber plate placed above the bottom two planes in each station. The added
steel absorber plate allows muon tracks to be separated from the less massive
electrons. Over 100 billion identified muon angles have been measured. With the
high statistics available, it is possible to obtain muon angular asymmetries
with low systematics by subtracting west from east (and separately, south from
north) angles; the subtraction eliminates most of the systematic errors while
still retaining adequately small statistical errors on the differences. A
preliminary analysis is performed as a function of solar time to obtain the
effects on the muon rate due to effects of the sun.


title: A novel antimatter detector based on X-ray deexcitation of exotic atoms

abstract:
  We propose a novel antiparticle detector. The gaseous antiparticle
spectrometer (GAPS) effects particle identification through the characteristic
X-rays emitted by antiparticles when they form exotic atoms in gases. GAPS
obtains particularly high grasp (effective area--solid angle product) at lower
particle energies, where conventional schemes are most limited in their
utility. The concept is simple and lightweight, so it can be readily employed
on balloon and space-based missions. An extremely powerful potential
application of GAPS is a space-based search for the neutralino through the
detection of a neutralino annihilation by-product -- the antideuteron.
Paradoxically, this space-based search for the neutralino is capable of
achieving comparable sensitivity to as yet unrealized third generation,
underground dark matter experiments. And GAPS can obtain this performance in a
very modest satellite experiment. GAPS can also provide superior performance in
searches for primary antiprotons produced via neutralino annihilation, black
hole evaporation and in probing subdominant contributions to the antiproton
flux at low energies. In a deep space mission GAPS will obtain higher
sensitivity for a given weight and power than BGO calorimeters.


title: J-Band Spectroscopy of the z = 5.74 BAL QSO SDSSp J104433.04-012502.2

abstract:
  We use the NIRSPEC near-IR spectrometer on Keck II to obtain moderate
resolution (R = 1540) spectroscopy that shows conclusively that the C IV
emission line in the z = 5.74 quasar SDSSp J104433.04-012502.2 is accompanied
by broad, blueshifted C IV absorption. The line has a "balnicity index" of 900
km/s and a rest-frame equivalent width of 13.1 +/- 1.3 relative to the
continuum. This confirms its membership in the class of objects called
"broad-absorption line" (BAL) QSOs. SDSSP J1044-0125 was previously suggested
to be a BAL QSO based on its larger UV-to-X-ray flux ratio than most non-BAL
QSOs. The C IV emission is of normal strength, implying a metallicity similar
to that found in other, lower-redshift QSOs.


title:
A Hubble Space Telescope Lensing Survey of X-ray Luminous Galaxy
  Clusters: II. A Search for Gravitationally Lensed EROs

abstract:
  We present the results of a survey for Extremely Red Objects (EROs) in the
fields of ten galaxy cluster lenses at z~0.2, combining high-resolution Hubble
Space Telescope imaging with deep K-band imaging from UKIRT. We detect 60 EROs
with R-K>=5.3, of which 26 have R-K>=6.0 in a total image plane survey area of
49arcmin^2 down to K=20.6. We use detailed models of the cluster lenses to
quantify the lens amplification and thus correct the observed number counts and
survey area for the effects of gravitational lensing. After making these
corrections, we estimate surface densities at K<=21.6 of 2.5+/-0.4 and
1.2+/-0.3 arcmin^-2 for EROs with R-K>=5.3 and 6.0 respectively. These ERO
number counts agree with previous shallower surveys at K<~19 and flatten
significantly at magnitudes fainter than K~19-20. This flattening may be due to
a transition from an ERO population dominated by evolved galaxies at z~1-2
(K<~19.5) to one dominated by dusty starburst galaxies at z>1 (K>~19.5). We
also compare our results with various model predictions, including a model that
attempts to explain EROs in terms of a single population of elliptical galaxies
formed at high redshift. We find that a formation epoch of z_f~2.5 for this
population matches the observed surface density of R-K>=5.3 EROs quite well,
and the R-K>=6.0 sample less well. More sophisticated models, including
semi-analytic prescriptions, under-predict the ERO surface density by
approximately an order of magnitude, suggesting that these models produce
insufficient stars and/or dust at high redshift.


title:
A Numerical Study of the Chemo-Dynamical Evolution of Elliptical
  Galaxies

abstract:
  We investigate the chemo-dynamical evolution of elliptical galaxies, to
understand the origin of the mass-dependence of photometric properties such as
the colour-magnitude relation (CMR). Our three-dimensional TREE N-body/SPH
numerical simulation takes into account both Type II and Type Ia supernovae and
follows the evolution of the abundances of several chemical elements. We derive
the photometric properties of the simulation end-products and compare them with
the observed CMR.


title: Gravitational Microlensing Events Due to Stellar Mass Black Holes

abstract:
  We present an analysis of the longest timescale microlensing events
discovered by the MACHO Collaboration during a 7 year survey of the Galactic
bulge. We find 6 events that exhibit very strong microlensing parallax signals
due, in part, to accurate photometric data from the GMAN and MPS
collaborations. The microlensing parallax fit parameters are used in a
likelihood analysis, which is able to estimate the distance and masses of the
lens objects based upon a standard model of the Galactic velocity distribution.
This analysis indicates that the most likely masses of 5 of the 6 lenses are >
1 Msun, which suggests that a substantial fraction of the Galactic lenses may
be massive stellar remnants. This could explain the observed excess of long
timescale microlensing events. The lenses for events MACHO-96-BLG-5 and
MACHO-98-BLG-6 are the most massive, with mass estimates of M/Msun = 6 +10/-3
and M/Msun = 6 +7/-3, respectively. The observed upper limits on the absolute
brightness of main sequence stars for these lenses are < 1 Lsun, so both lenses
are black hole candidates. The black hole interpretation is also favored by a
likelihood analysis with a Bayesian prior using a conventional model for the
lens mass function. We consider the possibility that the source stars for some
of these 6 events may lie in the foreground or background of the Galactic
bulge, but we find that this is unlikely. Future HST observations of these
events can either confirm the black hole lens hypothesis or detect the lens
stars and provide a direct measurement of their masses. Future observations of
similar events by SIM or the Keck or VLTI interferometers will allow direct
measurements of the lens masses for stellar remnant lenses as well.


title: Timing in the Time Domain: Cygnus X-1

abstract:
  Quantities characterizing temporal property, e.g. power density, coherence,
and time lag, can be defined and calculated directly in the time domain without
using the Fourier transformation. Spectral hardness, variability duration, and
correlation between different characteristic quantities on different time scale
can be studied in the time domain as well. The temporal analysis technique in
the time domain is a powerful tool, particularly in studying rapid variability
on short time scales (or in high frequencies). Results of studying
variabilities of X-rays from Cyg X-1 with the analysis technique in the time
domain and RXTE data reveal valuable clues to understanding production and
propagation processes of X-rays and structure of accretion disk in the black
hole system.


title: Radio monitoring of a sample of X- and gamma-ray loud blazars

abstract:
  In this paper we present the results of a 4-year (1996 - 1999) radio flux
density monitoring program for a sample of X- and $\gamma$-ray loud blazars.
Our program started in January 1996 and was carried out on monthly basis at the
frequencies of 5 GHz and 8.4 GHz with the 32-m antennas located in Medicina
(Bologna, Italy) and Noto (Siracusa, Italy). 22 GHz data collected in Medicina
from January 1996 to June 1997 will also be presented. The sample of selected
sources comprises most radio loud blazars with $\delta \ge -10^{\circ}$
characterised by emission in the X- and $\gamma$-ray regimes, and target
sources for the BeppoSAX X-ray mission. All sources in the sample, except
J1653+397 (MKN 501), are variable during the four years of our monitoring
program. We classified the type of variability in each source by means of a
structure function analysis. We also computed th$\alpha_{5}^{8.4}$ for all
epochs with nearly simultaneous observations ate spectral index and found that
$\alpha_{5}^{8.4}$ starts flattening at the very beginning o f a radio flare,
or flux density increase.