title:
Planetary nebulae as mass tracers of their parent galaxies: biases in
  the estimate of the kinematical quantities

abstract:
  Multi-object and multi-fiber spectrographs on 4 and 8 meter telescopes make
it possible to use extragalactic planetary nebulae (PNe) in the outer halos of
early-type galaxies as kinematical tracers, where classical techniques based on
integrated stellar light fail. Until now, published PNe radial velocity samples
are small, with only a few tens of radial velocity measurements (except for a
few cases like NGC 5128 or M31), causing uncertainties in the mass and angular
momentum estimates based on these data. To quantify these uncertainties, we
have made equilibrium models for spherical galaxies, with and without dark
matter, and via Montecarlo simulations we produce radial velocity samples with
different sizes. We then apply, to these discrete radial velocity fields, the
same standard kinematical analysis as it is commonly done with small samples of
observed PNe radial velocities. By comparison of the inferred quantities with
those computed from the analytical model, we test for systematic biases and
establish a robust procedure to infer the angular momentum distribution and
radial velocity dispersion profiles from such samples.


title: Photoionization Models of NGC 346

abstract:
  We present spherically symmetric and plane parallel photoionization models of
NGC 346, an HII region in the Small Magellanic Cloud. The models are based on
CLOUDY and on the observations of Peimbert, Peimbert, & Ruiz (2000). We find
that approximately 45% of the H ionization photons escape from the HII region
providing an important ionizing source for the low density interstellar medium
of the SMC. The predicted I(4363)/I(5007) value is smaller than that observed,
probably implying that there is an additional source of energy not taken into
account by the models. From the ionization structure of the best model and the
observed line intensities we determine the abundances of N, Ne, S, Ar, and Fe
relative to O.


title: Cosmological Implications of the PSCz PDF and its Moments

abstract:
  We compare the {\em pdf} and its low-order moments (variance and skewness) of
the smoothed PSCz galaxy density field and of the corresponding simulated PSCz
look-alikes, generated from N-body simulations of 6 different DM models; four
structure normalized with $\Gamma=0.25$ and $\sigma_{8}=0.55
\Omega_{\circ}^{-0.6}$, one COBE normalized and the old SCDM. The galaxy
distributions are smoothed with a Gaussian window at three different smoothing
scales $R_{sm}=5$, 10 and $15 \hm$. We find that the simulation PSCz look-alike
{\em pdf}'s are sensitive only on the normalization of the power spectrum,
probably due to shape similarity of the simulated galaxy power spectrum on the
relevant scales. We find that the only models that are consistent, at a high
significance level, with the observed PSCz {\em pdf} are models with a
relatively low power spectrum normalization $(\sigma_{8}=0.83)$.
  From the phenomenologically derived $\sigma_{8}-moments$ relation, fitted
from the simulation data, we find that the PSCz moments suggest $\sigma_{8}
\simeq 0.7$.


title:
A comprehensive study of reported high metallicity giant HII regions. I.
  Detailed abundance analysis

abstract:
  We present long-slit observations in the optical and near infrared of
fourteen HII regions in the spiral galaxies: NGC 628, NGC 925, NGC 1232 and NGC
1637, all of them reported to have solar or oversolar abundances according to
empirical calibrations. For seven of the observed regions, ion-weighted
temperatures from optical forbidden auroral to nebular line ratios have been
obtained and for six of them, the oxygen abundances derived by standard methods
turn out to be significantly lower than solar. The other one, named CDT1 in NGC
1232, shows an oxygen abundance of 12+log(O/H) = 8.95+-0.20 and constitutes, to
the best of our knowledge, the first high metallicity HII region for which
accurate line temperatures, and hence elemental abundances, have been derived.
  For the rest of the regions no line temperature measurements could be made
and the metallicity has been determined by means of both detailed
photoionisation modelling and the sulphur abundance parameter S_23. Only one of
these regions shows values of O_23 and S_23 implying a solar or oversolar
metallicity.
  According to our analysis, only two of the observed regions can therefore be
considered as of high metallicity. The two of them fit the trends previously
found in other high metallicity HII regions, i.e. N/O and S/O abundance ratios
seem to be higher and lower than solar respectively.


title: Optical identification of sources from the HELLAS2XMM survey

abstract:
  We present preliminary results on the optical identifications of sources from
the High Energy Large Area Survey performed with XMM-Newton (HELLAS2XMM). This
survey covers about 3 square degrees of sky down to a 2-10 keV flux of 7 x
10^-15 erg cm-2 s-1 (Baldi & Molendi these proceedings, Baldi et al. 2001). The
survey good sensitivity over a large area allows us to confirm and extend
previous Chandra results about a population of X-ray luminous but optically
dull galaxies emerging at 2-10 keV fluxes of about 10-14 erg cm-2 s-1. Although
the statistics are still rather poor, it appears that at these X-ray fluxes the
fraction of these galaxies is similar or even higher than that of narrow line
AGN.


title: X-ray bright optically quiet galaxies: the case of P3

abstract:
  Recent X-ray surveys have clearly demonstrated that a population of optically
dull, X-ray bright galaxies is emerging at X-ray fluxes of the order of 10-14
erg cm-2 s-1. The nature of these objects is still unknown. We present the
results of multiwavelength observations of what can be considered the best
studied example: the Chandra source CXOUJ031238.9-765134 optically identified
by Fiore et al. (2000) with an apparently normal galaxy at z=0.159 and called
``Fiore P3''.


title: Components of the Milky Way and GAIA

abstract:
  The GAIA mission will produce an extraordinary database from which we should
be able to deduce not only the Galaxy's current structure, but also much of its
history, and thus cast a powerful light on the way in which galaxies in general
are made up of components, and of how these formed. The database can be fully
exploited only by fitting to it a sophisticated model of the entire Galaxy.
Steady-state models are of fundamental importance even though the Galaxy cannot
be in a steady state. A very elaborate model of the Galaxy will be required to
reproduce the great wealth of detail that GAIA will reveal. A systematic
approach to model-building will be required if such a model is to be
successfully constructed, however. The natural strategy is to proceed through a
series of models of ever increasing elaborateness, and to be guided in the
specification of the next model by mismatches between the data and the current
model.
  An approach to the dynamics of systems with steady gravitational potentials
that we call the `torus programme' promises to provide an appropriate framework
within which to carry out the proposed modelling programme. The basic
principles of this approach have been worked out in some detail and are
summarized here. Some extensions will be required before the GAIA database can
be successfully confronted. Other modelling techniques that might be employed
are briefly examined.


title:
A GRB Detection System using the BGO-Shield of the INTEGRAL-Spectrometer
  SPI

abstract:
  The anticoincidence shield (ACS) of the INTEGRAL-spectrometer SPI consists of
512 kg of BGO crystals. This massive scintillator allows the measurement of
gamma-ray bursts (GRBs) with a very high sensitivity. Estimations have shown
that with the ACS some hundred gamma-ray bursts per year on the 5 sigma level
can be detected, having an equivalent sensitivity to BATSE. The GRB detection
will be part of the real-time INTEGRAL burst-alert system (IBAS). The ACS
branch of IBAS will produce burst alerts and light curves with 50 ms
resolution. It is planned to use ACS burst alerts in the 4th interplanetary
network (IPN).


title:
X-ray Spectra and Light Curves of AR Lac: Temperature Structure,
  Abundances, and Variability

abstract:
  We observed AR Lac, an eclipsing RS CVn binary star, with the Chandra High
Energy Grating Spectrometer for a total of 100 ks divided into six intervals
covering both quadratures and eclipses. We repeated observations at each phase.
At least two flares were seen, in which the flux increased by factors of two
and four. The flares occurred near eclipse phases and compromised detection of
eclipse modulation. The quadrature fluxes were the most stable, but they also
show non-repeating trends. Quadrature line profiles are broadened relative to
eclipse profiles, presumably due to orbital velocity Doppler shifted emission
from each binary component. The spectrum appears to be iron poor and neon rich,
similar to HR 1099, but not as extreme as II Pegasi. We will examine line
strengths, widths, and positions vs. phase, and present preliminary
differential emission measure models and abundance determinations using the
APED emissivity database.
  This work is supported by NASA contract NAS8-38249 (HETG) and SAO SV1-61010
(CXC) to MIT.


title: Population Gradients in Local Group Dwarf Spheroidals

abstract:
  We present a systematic and homogeneous analysis of population gradients for
the Local Group dwarf spheroidals (dSphs) Carina, Sculptor, Sextans, Tucana,
Andromeda I-III, V, and VI. For all of the Milky Way companions studied here we
find significant population gradients. The same is true for the remote dSph
Tucana located at the outskirts of the LG. Among the M 31 dSph companions only
Andromeda I and VI show obvious gradients. In all cases where a HB morphology
gradient is visible, the red HB stars are more centrally concentrated. The
occurence of a HB morphological gradient shows a correlation with a morphology
gradient in the red giant branch. It seems likely that metallicity is the
driver of the gradients in Sextans, Sculptor, Tucana, and Andromeda VI, while
age is an important factor in Carina. We find no evidence that the vicinity of
a nearby massive spiral galaxy influences the formation of the population
gradients.


title:
Development of an XSPEC-Based Spectral Analysis System for the
  Coded-Aperture Hard X-ray Balloon Payload EXITE2

abstract:
  We present the spectral analysis system for the second-generation Energetic
X-ray Imaging Telescope Experiment (EXITE2) balloon payload. EXITE2 is an
imaging hard X-ray telescope using a coded-aperture mask and a NaI/CsI phoswich
detector operating in the energy range 20--600 keV. The instrument was flown on
a high-altitude scientific balloon from Ft. Sumner, NM on 1997 May 7-8. We
describe the details of the EXITE2 spectral analysis system, with emphasis on
those aspects peculiar to coded-aperture instruments. In particular, we have
made our analysis compatible with the standard X-ray spectral fitting package
XSPEC by generating a response matrix in the appropriate format including all
the effects of a coded-aperture system. The use of XSPEC, which may be a first
for coded-aperture data, permits great flexibility in the fitting of spectral
models. The additional effects of our phoswich system, or any other
detector-specific considerations, may be easily included as well. We test our
spectral analysis using observations of the Crab Nebula, and find that the
EXITE2 Crab spectrum is consistent with those recorded by previous instruments
operating in this energy range.


title:
Bayesian blind component separation for Cosmic Microwave Background
  observations

abstract:
  We present a technique for the blind separation of components in CMB data.
The method uses a spectral EM algorithm which recovers simultaneously component
templates, their emission law as a function of wavelength, and noise levels. We
test the method on Planck HFI simulated observations featuring 3 astrophysical
components.


title: Properties of Relativistic Jets in Gamma-Ray Burst Afterglows

abstract:
  We extend our calculation of physical parameters of GRB jets by modeling the
broadband emission of the afterglows 970508, 980519, 991208, 000926, 000418,
and 010222. Together with 990123, 990510, 991216, and 000301c, there are ten
well-observed afterglows for which the initial opening angle of the GRB jet can
be constrained. The jet energies (after the GRB phase) obtained for this set of
afterglows are within one decade around 5E50erg. With the exception of 000418,
which requires a jet wider than 1/2 radians, the jet initial half-angle in the
other cases ranges from 2 deg to 20 deg. We find that, in half of the cases, a
homogeneous ambient medium accommodates the afterglow emission better than the
wind-like 1/r^2 profile medium expected around massive stars. The two types of
media give fits of comparable quality in four cases, a wind medium providing a
better description only for 970508. The circumburst densities we obtain are in
the 0.1-100 per cc range, with the exception of 990123, for which it is below
0.01 per cc. If in all ten cases the observed GRB durations are a good measure
of the ejecta deceleration timescale, then the parameters obtained here lead to
jet initial bulk Lorentz factors between 70 and 300, anticorrelated with the
jet initial aperture, and jet masses around 1E-6 M_sun. Our results on the jet
energy, opening Lorentz factor, and evacuation of material until break-out
provide constraints on theoretical models of GRB jets.


title: Formation of internal shock waves in bent jets

abstract:
  We discuss the circumstances under which the bending of a jet can generate an
internal shock wave. The analysis is carried out for relativistic and
non-relativistic astrophysical jets. The calculations are done by the method of
characteristics for the case of steady simple waves. This generalises the
non-relativistic treatment first used by Icke (1991). We show that it is
possible to obtain an upper limit to the bending angle of a jet in order not to
create a shock wave at the end of the curvature. This limiting angle has a
value of 75 degrees for non-relativistic jets with a polytropic index k = 4/3,
135 degrees for non-relativistic jets with k = 5/3) and 50 degrees for
relativistic jets with k = 5/3. We also discuss under which circumstances jets
will form internal shock waves for smaller deflection angles.


title:
REM Optical Slitless Spectrograph (ROSS): an instrument for prompt low
  resolution spectroscopy of Gamma Ray Bursts

abstract:
  Since the discovery of Gamma-Ray Bursts (GRBs), attempts have been made to
detect correlated optical transient emission from these objects. In January
1999, the ROTSE I robotic telescope detected a bright optical flash
simultaneous with a GRB, thanks to the prompt dissemination to the ground of
the high energy event coordinates. To date, that single observation remains
unique as no other prompt flashes have been seen for other bursts observed with
comparably short response times. This suggests that in general GRB prompt
optical emission may be considerably dimmer than observed for the GRB990123
event. To exploit the better angular localization accuracy of the flying
(HETE-2) or soon to fly (INTEGRAL, AGILE, SWIFT, GLAST) missions for high
energy astrophysics, a new generation of robotic telescopes is being developed.
These will have response times as short as a few seconds and will be sensitive
to signals as faint as m_v ~ 20, thus increasing the chance of detecting even
weak prompt emission. Results from these experiments should provide important
new data about the dynamics and local medium composition of GRBs. In this paper
we describe one of the new instruments, ROSS, to be mounted on the robotic
facility REM, designed to perform low resolution spectroscopy on the prompt
optical flares associated with GRBs.


title: On a matrix method for the study of small perturbations in galaxies

abstract:
  A matrix method is formulated in a Lagrangian representation for the solution
of the characteristic value problem governing modes of oscillation and
instability in a collisionless stellar system. The underlying perturbation
equations govern the Lagrangian displacement of a star in the six-dimensional
phase space. This matrix method has a basis in a variational principle. The
method is developed in detail for radial oscillations of a spherical system.
The basis vectors required for the representation of the Lagrangian
displacement in this case are derived from solutions of the Lagrangian
perturbation equations for radial perturbations in a homogeneous sphere. The
basis vectors are made divergence free in the six-dimensional phase space in
accordance with the requirement of Liouville's theorem that the flow of the
system in the phase space must be incompressible. The basis vectors are made
orthogonal with respect to a properly chosen set of adjoint vectors with the
aid of a Gram-Schmidt procedure. Some basis vectors are null vectors in the
sense that their inner products with their own adjoint vectors vanish. The
characteristic frequencies of the lowest radial modes are calculated in several
approximations for members of a family of spherical models which span a wide
range of central concentrations. The present formulation of the matrix method
can be generalized for nonradial modes in spherical systems and for modes in
axisymmetric systems.


title: Photon Bunching at TeV Energies

abstract:
  Harwit, Protheroe, and Biermann (1999) recently proposed that Bose-Einstein
photon bunching might significantly affect the interpretation of Cerenkov
counts of TeV gamma photons. Here, we show that a combination of two recent
results of Aharonian et al. (2000) and Aharonian et al. (2001) permits us to
set new, more stringent upper limits of $\lesssim 10%$ on the fractional amount
of photon bunching in the 7-10 TeV radiation from Markarian 501. Potential
bunching at even higher energies should nevertheless continue to be
investigated for this and other TeV sources, since a clear understanding of TeV
energy spectra is required to unambiguously determine the spectral energy
density of the mid-infrared extragalactic background.


title:
Mutual Constraints Between Reionization Models and Parameter Extraction
  From Cosmic Microwave Background Data

abstract:
  Spectroscopic studies of high-redshift objects and increasingly precise data
on the cosmic microwave background (CMB) are beginning to independently place
strong complementary bounds on the epoch of hydrogen reionization. Parameter
estimation from current CMB data continues, however, to be subject to several
degeneracies. Here, we focus on those degeneracies in CMB parameter forecasts
related to the optical depth to reionization. We extend earlier work on the
mutual constraints that such analyses of CMB data and a reionization model may
place on each other to a more general parameter set, and to the case of data
anticipated from the $MAP$ satellite. We focus in particular on a semi-analytic
model of reionization by the first stars, although the methods here are easily
extended to other reionization scenarios. A reionization model can provide
useful complementary information for cosmological parameter (CP) extraction
from the CMB, particularly for the degeneracies between the optical depth and
either of the amplitude and index of the primordial scalar power spectrum,
which are still present in the most recent data. Alternatively, by using a
reionization model, known limits on astrophysical quantities can reduce the
forecasted errors on CPs. Forthcoming CMB data also have the potential to
constrain the sites of early star formation, as well as the fraction of baryons
that participate in it. Finally, we examine the implications of an independent,
e.g., spectroscopic, determination of the epoch of reionization for the
determination of CPs from the CMB. This has the potential to significantly
strengthen limits from the CMB on parameters such as the index of the power
spectrum, while having the considerable advantage of being free of the choice
of the reionization model (abridged).


title:
Measuring the Cosmic Equation of State with Counts of Galaxies II: Error
  Budget for the DEEP2 Redshift Survey

abstract:
  In a previous paper, we described a new variant on the classical dN/dz test
which could be performed using upcoming redshift surveys. By observing the
velocity function of galaxies rather than their luminosity function, it is
possible to avoid many of the uncertainties of galaxy evolution while employing
a directly measurable quantity. We previously assumed that counting statistics
would dominate the errors in this method. Here, we present the results of
including cosmic variance and determine the impact of systematic effects on
application of this test to the upcoming DEEP2 Redshift Survey. For DEEP2,
cosmic variance should yield errors roughly twice those predicted from Poisson
statistics. Through Monte Carlo simulations we find that if the functional
form, but not the strength, of any of the major systematic effects (baryonic
infall, velocity errors, and incompleteness) is known, the systematic may
successfully be corrected for using the observed velocity function, leaving a
much smaller residual error. The total uncertainty from systematics is
comparable to that from cosmic variance, but correlated amongst redshift bins.
We find that DEEP2 can provide a much more precise measurement of the cosmic
equation of state parameter w than any available today, albeit weaker than some
other proposed tests.


title:
Measuring the Cosmic Equation of State with Galaxy Clusters in the DEEP2
  Redshift Survey

abstract:
  The abundances of groups and clusters of galaxies are expected to have
changed substantially since high redshift, with the strength of this evolution
dependent upon fundamental cosmological parameters. Upcoming large redshift
surveys of distant galaxies will make it possible to measure these quantities
at z~1; when combined with the results of local redshift surveys currently
underway, the evolution of cluster abundances may be determined. The DEEP2
Redshift Survey, planned to begin in Spring 2002, is particularly well-suited
for this work because of the high spectroscopic resolution to be used; velocity
dispersions of groups will be readily measurable. In this paper, we determine
the constraints on dark energy models that counts of DEEP2 clusters should
provide. We find that comparing cosmological models using the simultaneous
distribution of clusters in both velocity dispersion and redshift yields
significantly stronger constraints than the redshift distribution alone. The
method can be made more powerful by employing a value of the fluctuation
amplitude sigma_8 determined with upcoming techniques (external to DEEP2) that
have no Omega_m degeneracy. The equation-of-state parameter for dark energy
models, w=P/rho, can then be measured to ~0.1 from observations of clusters
alone.


title: The Optical Luminosity Function of Virialized Systems

abstract:
  We determine the optical luminosity function of virialized systems over the
full range of density enhancements, from single galaxies to clusters of
galaxies. The analysis is based on galaxy systems identified from the Nearby
Optical Galaxy (NOG) sample, which is the largest, all-sky catalog of
objectively- identified bound objects presently available. We find that the
B-band luminosity function of systems is insensitive to the choice of the
group-finding algorithms and is well described, over the absolute-magnitude
range -24.5 < M < -18.5, by a Schechter function with alpha=-1.4, Mstar=-23.1
and phistar=4.8 10^{-4} Mpc^-3 The characteristic luminosity of virialized
systems is ~3 times brighter than that of the luminosity function of galaxies.
Our results show that half of the luminosity of the universe is generated in
systems with L<2.9 Lstar and that 10% of the overall luminosity density is
supplied by systems with L>30 Lstar. We find a significant environmental
dependence in the luminosity function of systems, in the sense that overdense
regions, as measured on scales of 5 Mpc, preferentially host brighter, and
presumably more massive, virialized systems.


title: EUVE Observations of Nonmagnetic Cataclysmic Variables

abstract:
  We summarize EUVE's contribution to the study of the boundary layer emission
of high accretion-rate nonmagnetic cataclysmic variables, especially the dwarf
novae SS Cyg, U Gem, VW Hyi, and OY Car in outburst. We discuss the optical and
EUV light curves of dwarf nova outbursts, the quasi-coherent oscillations of
the EUV flux of SS Cyg, the EUV spectra of dwarf novae, and the future of EUV
observations of cataclysmic variables.


title:
The Mass-To-Light Function of Virialized Systems and the Relationship
  Between Their Optical and X-ray Properties

abstract:
  We compare the B-band luminosity function of virialized halos with the mass
function predicted by the Press-Schechter theory in cold dark matter
cosmogonies. We find that all cosmological models fail to match our results if
a constant mass-to-light ratio is assumed. In order for these models to match
the faint end of the luminosity function, a mass-to-light ratio decreasing with
luminosity as $L^{-0.5\pm 0.06}$ is required. For a $\Lambda$CDM model, the
mass-to-light function has a minimum of $\sim 100 h^{-1}_{75}$ in solar units
in the $B$-band, corresponding to $\sim 25%$ of the baryons in the form of
stars, and this minimum occurs close to the luminosity of an $L^*$ galaxy. At
the high-mass end, the $\Lambda$CDM model requires a mass-to-light ratio
increasing with luminosity as $L^{+0.5 \pm 0.26}$. We also derive the halo
occupation number, i.e. the number of galaxies brighter than $\lgal^*$ hosted
in a virialized system. We find that the halo occupation number scales
non-linearly with the total mass of the system, $N\sbr{gal}(>\lgal^*) \propto
m^{0.55\pm0.026}$ or the $\Lambda$CDM model. We find a break in the power-law
slope of the X-ray-to-optical luminosity relation, independent of the
cosmological model. This break occurs at a scale corresponding to poor groups.
In the $\Lambda$CDM model, the poor-group mass is also the scale at which the
mass-to-light ratio of virialized systems begins to increase. This
correspondence suggests a physical link between star formation and the X-ray
properties of halos, possibly due to preheating by supernovae or to efficient
cooling of low-entropy gas into galaxies.


title:
Mapping the interstellar dust with near-infrared observations: An
  optimized multi-band technique

abstract:
  We generalize the technique of Lada et al. (1994) to map dust column density
through a molecular cloud (NICE) to an optimized multi-band technique (NICER)
that can be applied to any multi-band survey of molecular clouds. We present a
first application to a ~625 deg^2 subset of the Two Micron All Sky Survey
(2MASS) data and show that when compared to NICE, the optimized NICER technique
(i) achieves the same extinction peak values, (ii) improves the noise variance
of the map by a factor of 2 and (iii) is able to reach 3 \sigma dust extinction
measurements as low as A_V = 0.5 magnitudes, better than or equivalent to
classical optical star count techniques and below the threshold column density
for the formation of CO, the brightest H2 tracer in radio-spectroscopy
techniques. The application of the NICER techniques to near-infrared data
obtained with a 8 meter-class telescope with a state-of-the-art NIR camera,
such as the VLT-ISAAC combination, will be able to achieve dynamic ranges from
below 10^21 protons cm^-2 to over 10^23 protons cm^-2 (A_V in the range [0.3,
60]) and spatial resolutions < 10'', making use of a single and straightforward
column density tracer, extinction by interstellar dust.


title: The quiescent light curve and evolutionary state of GRO J1655-40

abstract:
  We present ellipsoidal light-curve fits to the quiescent B, V, R and I light
curves of GRO J1655-40 (Nova Scorpii 1994). The fits are based on a simple
model consisting of a Roche-lobe filling secondary and an accretion disc around
the black-hole primary. Unlike previous studies, no assumptions are made about
the interstellar extinction or the distance to the source; instead these are
determined self-consistently from the observed light curves. In order to obtain
tighter limits on the model parameters, we used the distance determination from
the kinematics of the radio jet as an additional constraint. We obtain a value
for the extinction that is lower than was assumed previously; this leads to
lower masses for both the black hole and the secondary star of 5.4 +/- 0.3 Msun
and 1.45 +/- 0.35 Msun, respectively. The errors in the determination of the
model parameters are dominated by systematic errors, in particular due to
uncertainties in the modeling of the disk structure and uncertainties in the
atmosphere model for the chemically anomalous secondary in the system. A lower
mass of the secondary naturally explains the transient nature of the system if
it is either in a late case A or early case B mass-transfer phase.


title: V348 Puppis: a new SW Sex star in the period gap

abstract:
  We present time-resolved optical spectroscopy and photometry of the nova-like
cataclysmic variable V348 Puppis. The system displays the same spectroscopic
behaviour as SW Sex stars, so we classify V348 Pup as a new member of the
class. V348 Pup is the second SW Sex system (the first is V795 Herculis) which
lies in the period gap. The spectra exhibit enhanced HeII 4686 emission,
reminiscent of magnetic cataclysmic variables. The study of this emission line
gives a primary velocity semi-amplitude of K1 ~= 100 km/s. We have also derived
the system parameters, obtaining: M1 ~= 0.65 Msun, M2 ~= 0.20 Msun (q ~= 0.31),
i ~= 80 deg and K2 ~= 323 km/s. The spectroscopic behaviour of V348 Pup is very
similar to that of V795 Her, with the exception that V348 Pup shows deep
eclipses. We have computed the ``0.5-absorption'' spectrum of both systems,
obtaining spectra which resemble the absorption spectrum of a B0 V star. We
propose that absorption in SW Sex systems can be produced by a vertically
extended atmosphere which forms where the gas stream re-impacts the system,
either at the accretion disc or at the white dwarf's magnetosphere (assuming a
magnetic scenario).


title: Ultraluminous Infrared Galaxies and the Origin of QSOs

abstract:
  We review the evidence which suggests that ultraluminous infrared galaxies
(ULIGs) are the precursors of optically selected quasi-stellar objects (QSOs)
and discuss additional data that suggests that the majority, if not all QSOs,
may begin their lives in an intense infrared phase. Implications for the host
galaxies of QSOs are discussed.


title: Mg_2-sigma in Early-Type Galaxies and Spiral Bulges

abstract:
  We analyze new measurements of the Mg_2 central line strength index and
velocity dispersion (sigma) for the galaxies of the ENEAR survey. The
observations are now complete (da Costa et al. 2000) and the sample contains
1223 early-type galaxies. We also analyze the line strength indices for a
sample of 95 spiral bulges (from Sa to Sbc). For the early-type galaxies we
find: i) that the Mg_2-sigma relation for Es and S0s are nearly the same, with
both populations showing comparable scatter, and ii) a marginal difference in
the slope of the Mg_2-sigma relation for cluster and field early-type galaxies.
However, we suggest that before interpreting such a difference in the framework
of a mass-metallicity relation, it is important to take into account the
effects of rotation in the Mg_2-sigma relation. Our preliminary results
indicate that once the rotation effects are minimized by choosing a sample
containing only slow rotators, the Mg_2-sigma relation is similar both for
isolated and clustered galaxies. More data on rotational velocities of
early-type galaxies are needed to confirm this result. For spiral bulges, we
find that their locus in the Mg_2-sigma plane lies always below the one
occupied by early-type galaxies.


title:
A multivariate study of mass composition for simulated showers at the
  Auger South Observatory

abstract:
  The output parameters from the ground array of the Auger South observatory,
were simulated for the typical instrumental and environmental conditions at its
Malarg\"ue site using the code sample-sim. Extensive air showers started by
photons, protons and iron nuclei at the top of the atmosphere were used as
triggers. The study utilized the air shower simulation code Aires with both
QGSJet and Sibyll hadronic interaction models. A total of 1850 showers were
used to produce more than 35,000 different ground events. We report here on the
results of a multivariate analysis approach, including principal component
analysis and neural networks, to the development of new primary composition
diagnostics.


title:
Chandra Observations of the Lensing Cluster EMSS 1358+6245: Implications
  for Self-Interacting Dark Matter

abstract:
  We present Chandra observations of EMSS 1358+6245, a relaxed cooling flow
cluster of galaxies at z = 0.328. We employ a new deprojection technique to
construct temperature, gas, and dark matter profiles. We confirm the presence
of cool gas in the cluster core, and our deprojected temperature profile for
the hot component is isothermal over 30 kpc < r < 0.8 Mpc. Fitting the mass
profile to an NFW model yields r_s = 153 [+161,-83] kpc and c = 8.4
[+3.4,-2.3]. We find good agreement between our dark matter profile and weak
gravitational lensing measurements. We place an upper limit of 42 kpc (90%
confidence limit) on the size of any constant density core. We compare this
result to recent simulations and place a conservative upper limit on the dark
matter particle scattering cross section of 0.1 cm^2/g. This limit implies that
the cross-section must be velocity dependent if the relatively shallow core
mass profiles of dwarf galaxies are a direct result of dark matter
self-interaction.


title: Secular evolution in the central regions of galaxies

abstract:
  In this paper, I mention a few processes which may play a role in the
evolution of the central regions of galaxies. In this context, I briefly
discuss some issues regarding the formation of bulges in spirals, the role of
supermassive black holes, and the importance of nuclear density waves.


title: The Nature of the Faint Radio Population

abstract:
  We present the results obtained so far from the optical follow-up of the
ATESP sub-mJy radio survey. The ATESP results are then compared with the ones
obtained from other deep radio samples and we show how the existing
discrepancies about the nature of the faint radio population can be explained
in terms of selection effects.


title: The GLAST Burst Monitor (GBM)

abstract:
  The selection of the GLAST burst monitor (GBM) by NASA will allow the
investigation of the relation between the keV and the MeV-GeV emission from
gamma-ray bursts. The GBM consists of 12 NaI and 2 BGO crystals allowing a
continuous measurement of the energy spectra of gamma-ray bursts from ~5 keV to
\~30 MeV. One feature of the GBM is its high time resolution for time-resolved
gamma-ray spectroscopy. Moreover the arrangement of the NaI crystals allows a
rapid on-board location (<15 degrees) of a gamma-ray burst within a FoV of ~8.6
sr. This position will be communicated to the main instrument of GLAST making
follow-up observations at high energies possible.


title:
Limits on the TeV flux of diffuse gamma rays as measured with the HEGRA
  air shower array

abstract:
  Using data from the HEGRA air shower array, taken in the period from April
1998 to March 2000, upper limits on the ratio I_gamma /I_CR of the diffuse
photon flux I_gamma to the hadronic cosmic ray flux I_CR are determined for the
energy region 20 TeV to 100 TeV. The analysis uses a gamma-hadron
discrimination which is based on differences in the development of photon- and
hadron-induced air showers after the shower maximum. A method which is
sensitive only to the non-isotropic component of the diffuse photon flux yields
an upper limit of I_gamma /I_CR (at 54 TeV) < 2.0*10^-3 (at the 90% confidence
level) for a sky region near the inner galaxy (20 degrees < galactic longitude
<60 degrees and |galactic latitude|<5 degrees). A method which is sensitive to
both the isotropic and the non-isotropic component yields global upper limits
of I_gamma /I_CR (at 31 TeV) <1.2*10^-2 and I_gamma /I_CR (at 53 TeV) <
1.4*10^-2 (at the 90% confidence level).


title:
The discovery of the "21" micron and "30" micron emission features in
  Planetary Nebulae with Wolf-Rayet central stars

abstract:
  We report the discovery of the "21" micron and "30" micron features in the
planetary nebulae around the hydrogen-deficient stars HD 826 and HD 158269. The
carriers of these features are known to be produced in outflows around
carbon-rich stars. This discovery demonstrates that the bulk of the dust in
these nebulae has been produced during a carbon-rich phase before the
atmospheres of these stars became hydrogen poor. This is the first time that
the "21" micron feature has been detected in any planetary nebula. It shows
that once formed its carrier can survive the formation of the nebula and the
exposure to the UV radiation of the hot central star. This means that the
carrier of "21" micron feature is not transient: the absence of the feature
sets limits on the production of its carrier.


title: The Distance of the Large Magellanic Cloud Cluster NGC 1866

abstract:
  Hubble Space Telescope V,I photometry of stars in the Large Magellanic Cloud
Cluster NGC 1866 shows a well defined cluster main sequence down to V=25 mag,
with little contamination from field or foreground stars. We use the main
sequence fitting procedure to link the distance of NGC 1866 to the Hipparcos
determination of the distance for the Hyades MS stars, making use of
evolutionary prescriptions to allow for differences in the chemical
composition. On this basis we find a true distance modulus for NGC 1866 of
18.35 +/- 0.05 mag. If the cluster is assumed to lie in the LMC plane then the
LMC modulus is 0.02 mag less.


title: The Infrared Continuum Spectrum of VY CMa

abstract:
  We combine spectra of VY CMa obtained with the short- and long-wavelength
spectrometers, SWS and LWS, on the Infrared Space Observatory to provide a
first detailed continuum spectrum of this highly luminous star. The
circumstellar dust cloud through which the star is observed is partially
self-absorbing, which makes for complex computational modeling. We review
previous work and comment on the range of uncertainties about the physical
traits and mineralogical composition of the modeled disk. We show that these
uncertainties significantly affect the modeling of the outflow and the
estimated mass loss. In particular, we demonstrate that a variety of quite
diverse models can produce good fits to the observed spectrum. If the outflow
is steady, and the radiative repulsion on the dust cloud dominates the star's
gravitational attraction, we show that the total dust mass-loss rate is $\sim
4\times 10^{-6}M_{\odot}$ yr$^{-1}$, assuming that the star is at a distance of
1.5 kpc. Several indications, however, suggest that the outflow from the star
may be spasmodic. We discuss this and other problems facing the construction of
a physically coherent model of the dust cloud and a realistic mass-loss
analysis.


title:
Nova Sagittarii 1998 (V4633 Sgr) - a permanent superhump system or an
  asynchronous polar?

abstract:
  We report the results of observations of V4633 Sgr (Nova Sagittarii 1998)
during 1998-2000. Two photometric periodicities were present in the light curve
during the three years of observations: a stable one at P=3.014 h, which is
probably the orbital period of the underlying binary system, and a second one
of lower coherence, approximately 2.5 per cent longer than the former. The
latter periodicity may be a permanent superhump, or alternatively, the spin
period of the white dwarf in a nearly synchronous magnetic system. A third
period, at P=5.06 d, corresponding to the beat between the two periods was
probably present in 1999. Our results suggest that a process of mass transfer
took place in the binary system since no later than two and a half months after
the nova eruption. We derive an interstellar reddening of E(B-V)~0.21 from our
spectroscopic measurements and published photometric data, and estimate a
distance of d~9 kpc to this nova.


title:
On the kinematic deconvolution of the local neighbourhood luminosity
  function

abstract:
  A method for inverting the statistical star counts equation, including proper
motions, is presented; in order to break the degeneracy in that equation it
uses the supplementary constraints required by dynamical consistency. The
inversion gives access to both the kinematics and the luminosity function of
each population in three r\'egimes: the singular ellipsoid, the constant ratio
Schwarzschild ellipsoid plane parallel models and the epicyclic model. This
more realistic model is taylored to account for local neighbourhood density and
velocity distribution.
  The first model is fully investigated both analytically and via means of a
non-parametric inversion technique, while the second model is shown to be
formally its equivalent. The effect of noise and incompleteness in apparent
magnitude is investigated. The third model is investigated via a 5D+2D
non-parametric inversion technique where positivity of the underlying
luminosity function is explicitely accounted for.
  It is argued that its future application to data such as the Tycho catalogue
(and in the upcoming satellite GAIA) could lead -- provided the vertical
potential, and/or the asymmetric drift or w_0 are known -- to a non-parametric
determination of the local neighbourhood luminosity function without any
reference to stellar evolution tracks. It should also yield the proportion of
stars for each kinematic component and a kinematic diagnostic to split the thin
disk from the thick disk or the halo.


title:
Principal Component Analysis of the Cosmic Microwave Background
  Anisotropies: Revealing The Tensor Degeneracy

abstract:
  A principal component analysis of cosmic microwave background (CMB)
anisotropy measurements is used to investigate degeneracies among cosmological
parameters. The results show that a degeneracy with tensor modes -- the `tensor
degeneracy' -- dominates uncertainties in estimates of the baryon and cold dark
matter densities, omega_b = Omega_b h2, omega_c = \Omega_c h^2, from an
analysis of CMB anisotropies alone. The principal component analysis agrees
well with a maximum likelihood analysis of the observations, identifying the
main degeneracy directions and providing an impression of the effective
dimensionality of the parameter space.


title:
Evidence for a non-zero Lambda and a low matter density from a combined
  analysis of the 2dF Galaxy Redshift Survey and Cosmic Microwave Background
  Anisotropies

abstract:
  We perform a joint likelihood analysis of the power spectra of the 2dF Galaxy
Redshift Survey (2dFGRS) and the cosmic microwave background (CMB) anisotropies
under the assumptions that the initial fluctuations were adiabatic, Gaussian
and well described by power laws with scalar and tensor indices of n_s and n_t.
On its own, the 2dFGRS sets tight limits on the parameter combination Omega_m
h, but relatively weak limits on the fraction of the cosmic matter density in
baryons Omega_b/Omega_m. The CMB anisotropy data alone set poor constraints on
the cosmological constant and Hubble constant because of a `geometrical
degeneracy' among parameters. Furthermore, if tensor modes are allowed, the CMB
data allow a wide range of values for the physical densities in baryons and
cold dark matter. Combining the CMB and 2dFGRS data sets helps to break both
the geometrical and tensor mode degeneracies. The values of the parameters
derived here are consistent with the predictions of the simplest models of
inflation, with the baryon density derived from primordial nucleosynthesis and
with direct measurements of the Hubble parameter. In particular, we find strong
evidence for a positive cosmological constant with a pm 2sigma range of 0.65 <
Omega_Lambda < 0.85, completely independently of constraints on Omega_\Lambda
derived from Type Ia supernovae.


title: Using supercluster geometry as a cosmological probe

abstract:
  We study the properties of superclusters detected in the Abell/ACO cluster
catalogue. We identify the superclusters utilizing the `friend-of-friend'
procedure, and then determine supercluster shapes by using the differential
geometry approach. We find that the dominant supercluster morphological feature
is filamentariness. We compare our Abell/ACO supercluster results with the
corresponding ones generated from two different CDM cosmological models in
order to investigate statistically which of the latter models best reproduces
the observational results.


title: Water Maser Emission from the Active Nucleus in M51

abstract:
  22 GHz water vapor `kilomaser' emission is reported from the central region
of the Whirlpool galaxy M 51 (NGC 5194). The red-shifted spectral features
(Vlsr ~ 560 km/s), flaring during most of the year 2000, originate from a
spatially unresolved maser spot of size < 30 mas (< 1.5 pc), displaced by < 250
mas from the nucleus. The data provide the first direct evidence for the
association of an H2O kilomaser with an active galactic nucleus (AGN). In early
2001, blue-shifted maser emission (Vlsr ~ 435 km/s) was also detected. Red- and
blue-shifted features bracket the systemic velocity asymmetrically. Within the
standard model of a rotating Keplerian torus, this may either suggest the
presence of a highly eccentric circumnuclear cloud or red- and blue-shifted
`high velocity' emission from a radially extended torus. Most consistent with
the measured H2O position is, however, an association of the red-shifted H2O
emission with the northern part of the bipolar radio jet. In this scenario, the
(weaker) northern jet is receding while the blue-shifted H2O emission is
associated with the approaching southern jet.


title: H_2 molecules in damped systems

abstract:
  Damped Lyman alpha systems seen in the spectra of high-z QSOs arise in
high-density neutral gas in which molecular hydrogen (H_2) should be
conspicuous. Systematic searches to detect the H_2 lines redshifted into the
Lyman alpha forest at <3400\AA are now possible thanks to the unique
capabilities of UVES on the VLT. Here we summarise the present status of our on
going programme to search for H_2 in DLAs, discuss the physical conditions in
the systems where H_2 is detected and the implications of non-detections.


title: Obscured Accretion and Black Holes

abstract:
  The evidence for obscured AGN and in particular for obscured quasars is
discussed. The spectrum and source modelling of the X-ray Background suggests
that most massive black holes grow by obscured accretion. A possible major
growth phase which is Compton thick is explored and shown to be difficult to
detect directly with current instruments.


title:
Empirical calibration of the near-IR Ca II triplet - I. The stellar
  library and index definition

abstract:
  A new stellar library at the near-IR spectral region developed for the
empirical calibration of the Ca II triplet and stellar population synthesis
modeling is presented. The library covers the range 8348-9020 Angstrom at 1.5
Angstrom (FWHM) spectral resolution, and consists of 706 stars spanning a wide
range in atmospheric parameters. We have defined a new set of near-IR indices,
CaT*, CaT and PaT, which mostly overcome the limitations of previous
definitions, the former being specially suited for the measurement of the Ca II
triplet strength corrected for the contamination from Paschen lines. We also
present a comparative study of the new and the previous calcium indices, as
well as the corresponding transformations between the different systems. A
thorough analysis of the sources of index errors and the procedure to calculate
them is given. Finally, index and error measurements for the whole stellar
library are provided together with the final spectra.


title:
Empirical calibration of the near-IR Ca II triplet - II. The stellar
  atmospheric parameters

abstract:
  We present an homogeneous set of stellar atmospheric parameters (Teff, log g,
[Fe/H]) for a sample of about 700 field and cluster stars which constitute a
new stellar library in the near-infrared developed for stellar population
synthesis in this spectral region (8350-9020 Angstrom). Having compiled the
available atmospheric data in the literature for field stars, we have found
systematic deviations between the atmospheric parameters from different
bibliographic references. The Soubiran, Katz & Cayrel (1998) sample of stars
with very well determined fundamental parameters has been taken as our standard
reference system, and other papers have been calibrated and bootstrapped
against it. The obtained transformations are provided in this paper. Once most
of the datasets were on the same system, final parameters were derived by
performing error weighted means. Atmospheric parameters for cluster stars have
also been revised and updated according to recent metallicity scales and
colour-temperature relations.


title:
Rotational Studies of Late-Type Stars. VII. M34 (NGC 1039) and the
  Evolution of Angular Momentum and Activity in Young Solar-Type Stars

abstract:
  We analyze Keck Hires observations of rotation in F, G, and K dwarf members
of the open cluster M34 (NGC 1039), which is 250 Myr old, and we compare them
to the Pleiades, Hyades, and NGC 6475. The upper bound to rotation seen in M34
is about a factor of two lower than for the 100 Myr-old Pleiades, but most M34
stars are well below this upper bound, and it is the overall convergence in
rotation rates that is most striking. A few K dwarfs in M34 are still rapid
rotators, suggesting that they have undergone core-envelope decoupling,
followed by replenishment of surface angular momentum from an internal
reservoir. Our comparison of rotation in these clusters indicates that the time
scale for the coupling of the envelope to the core must be close to 100 Myr if
decoupling does, in fact, occur.


title: A High Resolution X-ray Image of the Jet in M 87

abstract:
  We present the first high resolution X-ray image of the jet in M 87 using the
Chandra X-ray Observatory. There is clear structure in the jet and almost all
of the optically bright knots are detected individually. The unresolved core is
the brightest X-ray feature but is only 2-3 times brighter than knot A (12.3"
from the core) and the inner knot HST-1 (1.0" from the core). The X-ray and
optical positions of the knots are consistent at the 0.1" level but the X-ray
emission from the brightest knot (A) is marginally upstream of the optical
emission peak. Detailed Gaussian fits to the X-ray jet one-dimensional profile
show distinct X-ray emission that is not associated with specific optical
features. The X-ray/optical flux ratio decreases systematically from the core
and X-ray emission is not clearly detected beyond 20" from the core. The X-ray
spectra of the core and the two brightest knots, HST-1 and A1, are consistent
with a simple power law with alpha = 1.46 +/- 0.05, practically ruling out
inverse Compton models as the dominant X-ray emission mechanism. The core flux
is significantly larger than expected from an advective accretion flow and the
spectrum is much steeper, indicating that the core emission may be due to
synchrotron emission from a small scale jet. The spectral energy distributions
(SEDs) of the knots are well fit by synchrotron models. The spectral indices in
the X-ray band, however are comparable to that expected in the
Kardashev-Pacholczyk synchrotron model but are much flatter than expected in
the pitch angle isotropization model of Jaffe and Perola. The break frequencies
derived from both models drop by factors of 10-100 with distance from the core.


title:
Sulfur, Chlorine, & Argon Abundances in Planetary Nebulae. IIB:
  Abundances in a Southern Sample

abstract:
  We have undertaken a large spectroscopic survey of over 80 planetary nebulae
with the goal of providing a homogeneous spectroscopic database between
3600-9600 Angstroms, as well as a set of consistently determined abundances,
especially for oxygen, sulfur, chlorine, and argon. In the current paper we
calculate and report the S/O, Cl/O, and Ar/O abundance ratios for 45 southern
planetary nebulae (predominantly Type II), using our own recently observed line
strengths published in an earlier paper. One of the salient features of our
work is the use of the NIR lines of [S III] 9069,9532 coupled with the [S III]
temperature, to determine the S++ ionic abundance. We find the following
average abundances for these objects: S/O=0.011(+/-0.0064),
Cl/O=0.00031(+/-0.00012), and Ar/O=0.0051(+/-0.0020).


title: Non-linear Integrated Sachs-Wolfe Effect

abstract:
  We discuss the non-linear extension to the integrated Sachs-Wolfe effect
(ISW) resulting from the divergence of the large scale structure momentum
density field. The non-linear ISW effect leads to an increase in the total ISW
contribution by roughly two orders of magnitude at l ~ 1000. This increase,
however, is still below the cosmic variance limit of the primary anisotropies;
at further small angular scales, secondary effects such as gravitational
lensing and the kinetic Sunyaev-Zel'dovich (SZ) effect dominates the non-linear
ISW power spectrum. We show this second-order non-linear ISW contribution is
effectively same as the contribution previously described as a lensing effect
due to the transverse motion of gravitational lenses and well known as the
Kaiser-Stebbins effect under the context of cosmic strings. Due to geometrical
considerations, there is no significant three point correlation function, or a
bispectrum, between the linear ISW effects and its non-linear extension. The
non-linear ISW contribution can be potentially used as a probe of the
transverse velocity of dark matter halos such as galaxy clusters. Due to the
small contribution to temperature fluctuations, of order few tenths of micro
Kelvin, however, extrating useful measurements on velocities will be
challenging.


title:
3D Identification and Reconstruction of z~1 Clusters: Prospects for the
  DEEP2 Redshift Survey

abstract:
  We have developed a geometrical method based on 3D Voronoi polyhedra and
Delaunay tessellation for identifying and reconstructing clusters of galaxies
in the next generation of deep, flux-limited redshift surveys. We here describe
this algorithm and tests of it using mock catalogs that simulate the
DEEP2/DEIMOS redshift survey, which will begin observations in the Spring of
2002 and will provide a detailed three dimensional map of the large scale
structure up to redshift 1.5.


title: Spectral Reduction Software for the DEEP2 Redshift Survey

abstract:
  The DEEP2/DEIMOS redshift survey, which will begin observing in the Spring of
2002, will gather high quality spectra on ~60000 galaxies in order to study the
evolution of the properties and large scale clustering of galaxies at z~1. The
data rate from DEIMOS will be in excess of 1 Gbyte/hour, and it is therefore
imperative to employ completely automated data reduction techniques to manage
the analysis. We here describe aspects of our data pipeline, which will make
extensive use of B-splines for the sky-subtraction stage and for the
combination of multiple frames.


title:
Synchrotron and Synchrotron Self-Compton Spectral Signatures and Blazar
  Emission Models

abstract:
  We find that energy losses due to synchrotron self-Compton (SSC) emission in
blazar jets can produce distinctive signatures in the time-averaged synchrotron
and SSC spectra of these objects. For a fairly broad range of particle
injection distributions, SSC-loss dominated synchrotron emission exhibits a
spectral dependence $F_\nu \sim \nu^{-3/2}$. The presence or absence of this
dependence in the optical and ultraviolet spectra of flat spectrum radio
quasars such as 3C~279 and in the soft X-ray spectra of high frequency BL Lac
objects such as Mrk 501 gives a robust measure of the importance of SSC losses.
Furthermore, for partially cooled particle distributions, spectral breaks of
varying sizes can appear in the synchrotron and SSC spectra and will be related
to the spectral indices of the emission below the break. These spectral
signatures place constraints on the size scale and the non-thermal particle
content of the emitting plasma as well as the observer orientation relative to
the jet axis.


title: Detection of H3+ in the interstellar medium of IRAS 08572+3915

abstract:
  The first detection of the molecular ion H3+ in an extragalactic object has
been made toward the highly obscured ultraluminous galaxy, IRAS 08572+3915. Two
absorption features near 3.9 microns in its spectrum are identified as the
redshifted 3.668 microns doublet and 3.716 microns singlet lines of H3+, both
previously detected in a number of galactic molecular and diffuse clouds. We
discuss the probable location of the H3+ in this galaxy.


title:
The 2dF Galaxy Redshift Survey: A targeted study of catalogued clusters
  of galaxies

abstract:
  We have carried out a study of known clusters within the 2dF Galaxy Redshift
Survey (2dFGRS) observed areas and have identified 431 Abell, 173 APM and 343
EDCC clusters. Precise redshifts, velocity dispersions and new centroids have
been measured for the majority of these objects, and this information has been
used to study the completeness of these catalogues, the level of contamination
from foreground and background structures along the cluster's line of sight,
the space density of the clusters as a function of redshift, and their velocity
dispersion distributions. We find that the Abell and EDCC catalogues are
contaminated at the level of about 10%, whereas the APM catalogue suffers only
5% contamination. If we use the original catalog centroids, the level of
contamination rises to approximately 15% for the Abell and EDCC catalogues,
showing that the presence of foreground and background groups may alter the
richness of clusters in these catalogues. There is a deficiency of clusters at
$z \sim 0.05$ that may correspond to a large underdensity in the Southern
hemisphere. From the cumulative distribution of velocity dispersions for these
clusters, we derive an upper limit to the space density of $\sigma > 1000 \kms$
clusters of $3.6 \times 10^{-6} \hdens$. This result is used to constrain
models for structure formation; our data favour low-density cosmologies,
subject to the usual assumptions concerning the shape and normalization of the
power spectrum.


title: Evolution of Planetary Nebulae I. An improved synthetic model

abstract:
  We present a new synthetic model to follow the evolution of a planetary
nebula (PN) and its central star, starting from the onset of AGB phase up to
the white dwarf cooling sequence. The model suitably combines various
analytical prescriptions to account for different (but inter-related) aspects
of planetary nebulae, such as: the dynamical evolution of the primary shell and
surrounding ejecta, the photoionisation of H and He by the central star, the
nebular emission of a few relevant optical lines (e.g. Hbeta; HeII4686;
[OIII]5007). Predictions of the synthetic model are tested by comparison with
both findings of hydrodynamical calculations, and observations of Galactic PNe.
The sensitiveness of the results to the models parameters (e.g. transition
time, mass of the central star, H-/He-burning tracks, etc.) is also discussed.
We briefly illustrate the systematic differences that are expected in the
luminosities and lifetimes of PNe with either H- or He-burning central stars,
which result in different ``detection probabilities'' across the H-R diagram,
in both Hbeta and [OIII]5007 lines. Adopting reasonable values of the model
parameters, we are able to reproduce, in a satisfactory way, many general
properties of PNe, like the ionised mass--nebular radius relationship, the
trends of a few main nebular line ratios, and the observed ranges of nebular
shell thicknesses, electron densities, and expansion velocities. The models
naturally predict also the possible transitions from optically-thick to
optically-thin configurations (and vice versa). In this context, the origin of
the Zanstra discrepancy is also analysed. (abridged)


title: On some Uncertainties in Evolutionary Synthesis Models

abstract:
  Ranging from track interpolation techniques through model atmospheres to the
stochastic nature of the IMF, there are many uncertainties which need to be
taken into account when modelling HR diagrams or performing population
synthesis, particularly if comparison with actual data is sought. In this
paper, we highlight (1) the problem of discontinuities along evolutionary
tracks of massive stars (M> 8 Mo), showing that inconsistencies appear in the
computation of the corresponding isochrones, and (2) the sampling fluctuations
produced by the stochastic nature of the IMF, presenting a statistical
formalism to estimate the dispersion in any given observable of a stellar
population due to sampling effects which bypasses the need of performing Monte
Carlo simulations.


title: Detection of Circular Polarization in M81*

abstract:
  We report the detection of circular polarization in the compact radio jet of
the nearby spiral galaxy M81 (M81*). The observations were made with the Very
Large Array at 4.8 and 8.4 GHz and circular polarization was detected at both
frequencies. We estimate a value of $m_{c}=0.54\pm0.06\pm0.07%$ at 8.4 GHz and
$m_{c}=0.27\pm0.06\pm0.07%$ at 4.8 GHz for the fractional circular
polarization. The errors are separated into statistical and systematic terms.
The spectrum of the circular polarization is possibly inverted which would be
unusual for AGN. We also detected no linear polarization in M81* at a level of
0.1% implying that the source has a very high circular-to-linear polarization
ratio as found so far only in Sgr A*, the central radio source in our Galaxy.
This further supports the idea that M81* is a scaled-up version of Sgr A* and
suggests that the polarization properties are intrinsic to the two sources and
are not caused by a foreground screen in the Galaxy.


title:
Cataclysmic Variables with Evolved Secondaries and the Progenitors of AM
  CVn Stars

abstract:
  We present the results of a systematic study of cataclysmic variables (CVs)
and related systems, combining detailed binary-population synthesis (BPS)
models with a grid of 120 binary evolution sequences calculated with a
Henyey-type stellar evolution code. In these sequences, we used 3 masses for
the white dwarf (0.6, 0.8, 1.0 Msun) and seven masses for the donor star in the
range of 0.6-1.4 Msun. The shortest orbital periods were chosen to have
initially unevolved secondaries, and the longest orbital period for each
secondary mass was taken to be just longer than the bifurcation period (16 - 22
hr), beyond which systems evolve towards long orbital periods. These
calculations show that systems which start with evolved secondaries near the
end or just after their main-sequence phase become ultra-compact systems with
periods as short as 7 min. These systems are excellent candidates for AM CVn
stars. Using a standard BPS code, we show how the properties of CVs at the
beginning of mass transfer depend on the efficiency for common-envelope (CE)
ejection and the efficiency of magnetic braking. In our standard model, where
CE ejection is efficient, some 10 per cent of all CVs have initially evolved
secondaries (with a central hydrogen abundance X_c < 0.4) and ultimately become
ultra-compact systems (implying a Galactic birthrate for AM CVn-like stars of
10^{-3} yr^{-1}). Almost all CVs with orbital periods longer than 5 hr are
found to have initially evolved or relatively massive secondaries. We show that
their distribution of effective temperatures is in good agreement with the
distribution of spectral types obtained by Beuermann et al. (1998).


title: Exploring the Early Universe with XMM-Newton

abstract:
  The question of the X-ray background has been largely settled over the last
10 years using the ROSAT satellite. About 70-80 % of the soft X-ray background
was resolved into discrete sources, which are mainly X-ray and optically
unobscured AGNs (Quasars, Sy1). Furthermore we found already several obscured
AGNs in deep ROSAT surveys, which are predicted by the population synthesis
models for the X-ray background, based on the unified AGN schemes. However,
deep X-ray surveys using Chandra} and XMM-Newton allow to test the reliability
of these models, which seem to be still far from unique. Recent observations
with Chandra and XMM-Newton have resolved most of the hard X-ray background
into discrete sources. The first deep XMM-Newton survey was performed in the
Lockman Hole region, one of the sky areas best studied over a wide wavelength
range. About 100 ksec good exposure time have been accumulated with the EPIC
camera during the performance verification phase. We reach a limiting flux of
0.31, 1.4 and 2.4 x 10E-15 erg/cm2/s in the 0.5-2, 2-10 and 5-10 keV energy
bands. A significant number of X-ray sources show hard, probably intrinsically
absorbed X-ray spectra. We discuss the X-ray, optical and infrared properties
of these sources in comparison with the predictions of the recent X-ray
background models.


title:
The initial conditions of isolated star formation. V: ISOPHOT imaging
  and the temperature and energy balance of pre-stellar cores

abstract:
  ISO data taken with the long-wavelength imaging photo-polarimeter ISOPHOT are
presented of 18 pre-stellar cores at three far-infrared wavelengths - 90, 170
and 200 microns. Most of the cores are detected clearly at 170 and 200 but only
one is detected strongly at 90 microns, indicating that mostly they are very
cold, with typical temperatures of only 10-20K. Colour temperature images are
constructed for each of the cores. Most of the cores are seen to be either
isothermal, or to have associated temperature gradients from the core centres
to their edges, with all except one being cooler at the centre. We compare the
data with previous ISOCAM absorption data and calculate the energy balance for
those cores in common between the two samples. We find that the energy radiated
by each core in the far-IR is similar to that absorbed at shorter wavelengths.
Hence there is no evidence for a central heating source in any of the cores -
even those for which previous evidence for core contraction exists. This is all
consistent with external heating of the cores by the local interstellar
radiation field, confirming their pre-stellar nature.


title:
Oscillation power across the HR diagram : sensitivity to the convection
  treatment

abstract:
  Solar-like oscillations are stochastically excited by turbulent convection.
In this work we investigate changes in the acoustic oscillation power spectrum
of solar-type stars by varying the treatment of convection in the equilibrium
structure and the properties of the stochastic excitation model. We consider
different stellar models computed with the standard mixing-length description
by Bohm-Vitense (1958) and with a generalized formulation of the mixing-length
approach by Gough (1976, 1977). We calculate the acoustic power generated by
the turbulent convection which is injected stochastically into the acoustic
pulsation modes.
  Large differences in the oscillation powers are obtained depending on the
choice of the assumed convection formulation. We show that the high-quality
data Eddington will provide, will allow us to distinguish between theoretical
predictions of acoustic power spectra obtained with different convection
models.


title:
Atomic T Tauri disk winds heated by ambipolar diffusion I- Thermal
  structure

abstract:
  Motivated by recent subarcsecond resolution observations of jets from T Tauri
stars, we extend the work of \citep{Safier93a, Safier93b} by computing the
thermal and ionization structure of self-similar, magnetically-driven, atomic
disk winds heated by ambipolar diffusion. Improvements over his work include:
(1) new magnetized cold jet solutions consistent with the underlying accretion
disk \citep{Ferreira97}; (2) a more accurate treatment of ionization and
ion-neutral momentum exchange rates; and (3) predictions for spatially resolved
forbidden line emission (maps, long-slit spectra, and line ratios), presented
in a companion paper, \cite{Garcia2001b}.
  As in \citep{Safier93a}, we obtain jets with a temperature plateau around
$10^4$ K, but ionization fractions are revised downward by a factor of 10-100.
This is due to previous omission of thermal speeds in ion-neutral
momentum-exchange rates and to different jet solutions. The physical origin of
the hot temperature plateau is outlined. In particular we present three
analytical criteria for the presence of a hot plateau, applicable to any given
MHD wind solution where ambipolar diffusion and adiabatic expansion are the
dominant heating and cooling terms. We finally show that, for solutions favored
by observations, the jet thermal structure remains consistent with the usual
approximations used for MHD jet calculations (thermalized, perfectly
conducting, single hydromagnetic cold fluid calculations).


title:
Atomic T Tauri disk winds heated by ambipolar diffusion II-
  Observational tests

abstract:
  Thermal and ionization structures of self-similar, magnetically-driven disk
winds obtained in a companion paper \cite{Garcia2001a} are used to compute a
series of jet synthetic observations. These include spatially resolved
forbidden line emission maps, long-slit spectra, as well as line ratios. Line
profiles and jet widths appear to be good tracers of the wind dynamics and
collimation, whereas line ratios essentially trace gas excitation conditions.
  All the above diagnostics are confronted to observations of T Tauri star
microjets. Convolution by the observing beam is shown to be essential for a
meaningful test of the models. We find that jet widths and qualitative
variations in line profiles with both distance and line tracers are well
reproduced. A low-velocity [\ion{O}{i}] component is also obtained, originating
from the disk wind base. However, this component is too weak, predicted maximum
velocities are too high and electronic and total densities are too low. Denser
and slower magnetized winds, launched from disks with warm chromospheres, might
resolve these discrepancies.


title: Magnetic fields in cluster cores: Faraday rotation in A400 and A2634

abstract:
  We present Faraday rotation data for radio sources in the centers of the
Abell clusters A400 and A2634. These clusters contain large (> 100 kpc), tailed
radio sources, each attached to the central cD galaxy. These clusters do not
have strong cooling cores. Our data extend previous work on rotation measure in
cluster centers to larger scales and non-cooling clusters. The rotation
measure, and thus the magnetic field, is ordered on scales 10-20 kpc in both
clusters. The geometry of the rotation measure appears to be determined by the
distribution of the X-ray emitting gas, rather than by the radio tails
themselves. We combine our data with previously published X-ray and radio data
in order to analyze the magnetic fields in all 12 clusters whose central radio
sources have been imaged in rotation measure. We find that the fields are
dynamically significant in most clusters. We argue that the Faraday data
measure fields in the intracluster medium, rather than in a skin of the radio
source. Finally, we consider the nature and maintenance of the magnetic fields
in these clusters, and conclude that either the cluster-wide field exists at
similar levels, or that a weaker cluster-wide field is amplified by effects in
the core.


title:
ECLAIRs: A microsatellite for the prompt optical and X-ray emission of
  Gamma-Ray Bursts

abstract:
  The prompt gamma-ray emission of Gamma-Ray Bursts (GRBs) is currently
interpreted in terms of radiation from electrons accelerated in internal shocks
in a relativistic fireball. On the other hand, the origin of the prompt (and
early afterglow) optical and X-ray emission is still debated, mostly because
very few data exist for comparison with theoretical predictions. It is however
commonly agreed that this emission hides important clues on the GRB physics and
can be used to constrain the fireball parameters, the acceleration and emission
processes and to probe the surroundings of the GRBs. ECLAIRs is a
microsatellite devoted to the observation of the prompt optical and X-ray
emission of GRBs. For about 150 GRBs/yr, independent of their duration, ECLAIRs
will provide high time resolution high sensitivity spectral coverage from a few
eV up to ~50 keV and localization to ~ 5'' in near real time. This capability
is achieved by combining wide field optical and X-ray cameras sharing a common
field of view (>~ 2.2 steradians) with the coded-mask imaging telescopes
providing the triggers and the coarse localizations of the bursts. Given the
delays to start ground-based observations in response to a GRB trigger, ECLAIRs
is unique in its ability to observe the early phases (the first ~20 sec) of all
GRBs at optical wavelengths. Furthermore, with its mode of operation, ECLAIRs
will enable to search for optical and X-ray precursors expected from
theoretical grounds. Finally ECLAIRsis proposed to operate simultaneously with
GLAST on a similar orbit. This combination will both provide unprecedented
spectral coverage from a few eV up to ~200 GeV for ~100 GRBs/yr, as well as
accurate localization of the GLAST GRBs to enable follow-up studies.


title: Changes in the trajectory of the radio jet in 0735+178?

abstract:
  We present multi-epoch 8.4 and 43 GHz Very Long Baseline Array images of the
BL Lac object 0735+178. The images confirm the presence of a twisted jet with
two sharp apparent bends of 90$^{\circ}$ within two milliarcseconds of the
core, resembling a helix in projection. The observed twisted geometry could be
the result of precession of the jet inlet, but is more likely produced by
pressure gradients in the external medium through which the jet propagates.
Quasi-stationary components are observed at the locations of the 90$^{\circ}$
bends, possibly produced by differential Doppler boosting. Identification of
components across epochs, since the earliest VLBI observations of this source
in 1979.2, proves difficult due to the sometimes large time gaps between
observations. One possible identification suggests the existence of
superluminal components following non--ballistic trajectories with velocities
up to $11.6\pm 0.6 h_{65}^{-1} c$. However, in images obtained after mid-1995,
components show a remarkable tendency to cluster near several jet positions,
suggesting a different scenario in which components have remained nearly
stationary in time at least since mid-1995. Comparison with the earlier
published data, covering more than 19 years of observations, suggests a
striking qualitative change in the jet trajectory sometime between mid-1992 and
mid-1995, with the twisted jet structure with stationary components becoming
apparent only at the later epochs. This would require a re-evaluation of the
physical parameters estimated for 0735+178, such as the observing viewing
angle, the plasma bulk Lorentz factor, and those deduced from these.


title: Secular and orbital variability of Cir X-1 observed in optical spectra

abstract:
  We have observed variations in the optical emission lines from the X-ray
binary Circinus X-1. These variations may be attributed both to orbital
variations and to long term secular changes in line strength. We have detected
double-peaked H-alpha emission lines on two occasions, providing the first
direct evidence for an accretion disk in the system. The separation of the
peaks was different on the two occasions, suggesting that the disk might have a
different size. The equivalent width of the emission lines dropped by more than
a factor of three between 1999 and 2000; this continues the trend seen in
earlier data, so that the H-alpha equivalent width has now declined by a factor
of twenty since 1976. The emission lines do not appear to show signature of
orbital motion, except for the data taken near phase 0, which show a
significant velocity shift.
  We have observed an absorption component to the He I lines on one occasion.
We suggest that, unlike the P Cygni profiles seen in X-ray spectra, this
absorption does not arise in the accelerating zone of a radiatively driven
wind. Instead, the absorption arises in material previously ejected from the
system. It was only seen on this one occasion because the strength of the
emission line had dropped dramatically.


title: OPTIMA: A Photon Counting High-Speed Photometer

abstract:
  OPTIMA is a small, versatile high-speed photometer which is primarily
intended for time resolved observations of young high energy pulsars at optical
wavelengths. The detector system consists of eight fiber fed photon counters
based on avalanche photodiodes, a GPS timing receiver, an integrating CCD
camera to ensure the correct pointing of the telescope and a computerized
control unit. Since January 1999 OPTIMA proves its scientific potential by
measuring a very detailed lightcurve of the Crab Pulsar as well as by observing
cataclysmic variable stars on very short timescales. In this article we
describe the design of the detector system focussing on the photon counting
units and the software control which correlates the detected photons with the
GPS timing signal.


title: Gravity and Non-gravity Modes in the VIRMOS-DESCART Weak Lensing Survey

abstract:
  We analyze the weak lensing data of the VIRMOS imaging survey using
projections (called E and B-modes) of the two independents observed correlation
functions. The E-mode contains all the lensing signal, while noise and
systematics contribute equally to the E and B modes provided that intrinsic
alignment is negligible. The mode separation allows a measurement of the signal
with a \sqrt{2} smaller error bars, and a separate channel to test for
systematic errors. We apply various transformations, including a spherical
harmonic space power spectrum C^E_l and C^B_l, which provides a direct
measurement of the projected dark matter distribution for 500<l<10^4.


title: Drifting sub-pulses in two newly discovered pulsars

abstract:
  We have detected the rare phenomenon of stable, drifting sub-pulse behaviour
in two pulsars discovered in the recent Swinburne intermediate latitude pulsar
survey. The pulsars; PSR J1231-47 and PSR J1919+0134, have approximate periods
(P) of 1.873 and 1.6039 seconds respectively.
  Both pulsars have multi-component profiles, and distinct drifting is observed
across them. We have identified a single drift mode in both pulsars: the drift
rate for PSR J1231-47 being 5.4(1) ms P^{-1} and 5.8(2) ms P^{-1} for PSR
1919+0134. The drifting is linear across the profile with no departure from
linearity at the edges within the sensitivity of our observations.


title: Primordial Magnetic Fields from Dark Energy

abstract:
  Evidences indicate that the dark energy constitutes about two thirds of the
critical density of the universe. If the dark energy is an evolving pseudo
scalar field that couples to electromagnetism, a cosmic magnetic seed field can
be produced via spinoidal instability during the formation of large-scale
structures.


title:
Neutron capture and 2.2 MeV emission in the atmosphere of the secondary
  of an X-ray binary

abstract:
  We consider the production of 2.22 MeV radiation resulting from the capture
of neutrons in the atmosphere of the secondary in an X-ray binary system, where
the neutrons are produced in the accretion disk around the compact primary star
and radiated in all directions. We have considered several accretion disk
models (ADAF, ADIOS, SLE, Uniform-Temperature) and a varity of parameters
(accretion rate, mass of the compact object, mass, temperature and composition
of the secondary star, distance between the two objects, etc.). The neutron
rates are calculated by a network of nuclear reactions in the accretion disk,
and this is handled by a reaction-rate formulation taking into account the
structure equations given by each accretion model. The processes undergone by
the neutrons in the atmosphere of the companion star are studied in great
detail, including thermalization, elastic and inelastic scatterings,
absorption, escape from the surface, decay, and capture by protons. The
radiative transfer of the 2.22 MeV photons is treated separately, taking into
consideration the composition and density of the star's atmosphere. The final
flux of the 2.22 MeV radiation that can be detected from earth is calculated
taking into account the distance to the source, the direction of observation
with respect to the binary system frame, and the rotation of the source, as
this can lead to an observable periodicity in the flux. We produce phasograms
of the 2.22 MeV intensity as well as spectra of the line, where rotational
Doppler shift effects can lead to changes in the spectra that are measurable by
INTEGRAL's spectrometer (SPI).


title: Simulations of Sunyaev-Zel'dovich maps and their applications

abstract:
  We describe a fast method to simulate in a semi-analytical way consistent
maps of the thermal, kinetic and polarised Sunyaev-Zel'dovich effect, featuring
both cluster spatial correlations and large scale velocity flows.


title:
Separation of instrumental and astrophysical foregrounds for mapping CMB
  anisotropies

abstract:
  We address the extended problem of component separation for CMB applications
when a mixture of both astrophysical and instrumental components are present in
the observations, and show how standard methods can be adapted to handle this
more complex inversion problem.


title: A new sample of large angular size radio galaxies. II. The optical data

abstract:
  We constructed and presented in the first paper of this series a new sample
of 84 large angular size radio galaxies by selecting from the NRAO VLA Sky
Survey objects with angular size > 4', declination above +60 degrees and total
flux density at 1.4 GHz > 100 mJy. In this paper we present optical spectra and
images of those galaxies associated with the radio emission for which no
redshift was known prior to our observations. Optical counterparts have been
identified for all (but one) members of the sample. After our observations, a
reliable spectroscopic redshift is available for 67 objects (80%) from the
sample. This paper, second of a series of three, contributes to increase the
number of well defined samples of radio galaxies with ample spectroscopic
information.


title:
HST Ultraviolet and Ground-based Optical Spectropolarimetry of IRAS
  QSOs: Dusty Scattering in Luminous AGN

abstract:
  We present UV and optical spectropolarimetry of two highly polarized
IRAS-selected QSOs, IRAS 13349+2438 and the BALQSO IRAS 14026+4341. The
polarization in both objects rises rapidly toward the blue, peaks near 3000 A
in the rest frame and remains nearly constant for shorter wavelengths. The rest
frame optical polarized flux density spectra also increase rapidly towards the
blue, but then decrease dramatically below 3000 A. This distinctive wavelength
dependence of polarized flux shows that the polarization is produced by dust
scattering. As for many Seyfert, radio and Hyperluminous Infrared Galaxies
(HIGs), the lower polarization of the weak [O III] 4959,5007 lines in IRAS
13349+2438 suggests that the scattering grains lie interior to, or mixed with
the narrow line gas. We construct full radiative transfer models of these
systems consisting of a dusty sphere of modest optical depth illuminated
axisymmetrically from within by a powerlaw QSO spectrum. We show that this
simple model successfully reproduces the qualitative polarization properties of
the objects. Despite similarities to other IRAS-selected BALQSOs, our FOS
spectropolarimetry of IRAS 13349+2438 does not reveal broad absorption lines.
IRAS 14026+4341 has an Al III BAL in both scattered and total flux density. We
discuss these two objects in terms of both orientation and evolutionary unified
schemes for QSOs, BALQSOs and HIGs.


title: Atomic and Molecular Gas in the Starburst Galaxy NGC4945

abstract:
  Spatial and kinematical correlations between HI and CO (2-1) emission of the
southern spiral galaxy NGC4945 are studied with a common angular (23 arcsec)
and velocity resolution (7 km/s). The 21cm continuum emission is also observed.
The HI kinematics yield a galaxy mass of 1.4x10^{11} Mo within a radius of 380
arcsec, with molecular and neutral atomic gas each contributing 2%. Nuclear HI
absorption at velocities 80 km/s higher than systemic indicates gas flowing
towards the centre. HI features at each end of the major axis (R ~ 600 arcsec)
are interpreted as spiral arms that are viewed tangentially and that also cause
prominent emission features in the radio continuum, HI, and CO further inside
the galaxy. A central elongated region showing non-circular motions is
interpreted as a bar which fuels the nuclear starburst. HI and CO
position-velocity data have been analysed using linear resonance theory and
possible locations of resonances are identified.


title: Molecular Gas in the Galactic Halo and Beyond

abstract:
  I review recent observations of molecular gas in the halo of the Milky Way
and in the Magellanic Clouds. Far-ultraviolet absorption line studies of
molecular hydrogen (H_2) with ORFEUS and FUSE have unveiled the presence of a
diffuse molecular hydrogen component in intermediate- and high-velocity clouds
in the Galactic halo. Although the number of measurements is still quite small,
the data suggests that diffuse H_2 in the halo exists only in clouds that
contain a sufficient amount of heavy elements and dust, on whose surface the
H_2 formation proceeds most efficiently. The implications of these observations
for our understanding of the Milky Way halo are discussed.


title: The Outer Halo Cluster System of NGC 1399

abstract:
  We investigate the outer halo globular cluster population of NGC 1399. This
study uses wide-field imaging of this cluster system, which covers the largest
area studied with CCD photometry until now. The cluster system of NGC 1399 is
found to extend further than 100 kpc from the galaxy. A population of
metal-rich, as well as metal-poor clusters has been identified at these large
radii. At radii smaller than 55 kpc the specific frequency of the red cluster
system remains constant, while that of the blue clusters increases proportional
to $r^{0.8\pm0.2}$. For larger radii, the uncertainty of the galaxy light
profile does not permit any reliable statement.


title: The burst behavior of the eclipsing low-mass X-ray binary MXB 1659-298

abstract:
  We present a detailed study of the correlations between the burst properties
and the inferred mass accretion rate for the X-ray transient MXB 1659-298. The
bursts which exhibited oscillations were observed when the source was at
relatively high mass accretion rate, similar to what has been seen for other
sources. However, due to the limited number of observations at lower mass
accretion rates, no bursts were observed at such accretion rates and it is
still possible that when MXB 1659-298 accretes at such low mass accretion
rates, bursts can occur which might still exhibit burst oscillations. No clear
correlations were found between the different burst properties and accretion
rate, in contrast to what has been found for KS 1731-260 and 4U 1728-34, but
similar to what has been reported for Aql X-1. However, this lack of
correlation for MXB 1659-298 and Aql X-1 might be due to the limited range of
mass accretion rate observed for those sources compared to KS 1731-260 and 4U
1728-34.


title:
Galactic Cosmochronometry from Radioactive Elements in the Spectra of
  Very Old Metal-Poor Stars

abstract:
  In a short review of neutron-capture elemental abundances in Galactic halo
stars, emphasis is placed on the use of these elements to estimate the age of
the Galactic halo. Two prominent characteristics of neutron-capture elements in
halo stars are their large star-to-star scatter in the overall abundance level
with respect to lighter elements, and the dominance of r-process abundance
patterns at lowest stellar metallicities. The r-process abundance signature
potentially allows the direct determination of the age of the earliest Galactic
halo nucleosynthesis events, but further developments in r-process theory, high
resolution spectroscopy of very metal-poor stars, and in basic atomic data are
needed to narrow the uncertainties in age estimates. Attention is brought to
the importance of accurate transition probabilities in neutron-capture element
cosmochronometry. Recent progress in the transition probabilities of rare earth
elements is discussed, along with suggestions for future work on other species.


title:
Chemical Abundance Variations in Globular Clusters: Recent Results from
  Mildly Metal-Poor M5

abstract:
  We present a chemical composition analysis of 36 giant stars in mildly
metal-poor globular cluster M5. In comparing the M5 results to those obtained
in M4, a cluster previously considered to be a ``twin'' in age, metallicity and
chemical composition, we find large star-to-star variations in the abundances
of elements sensitive to proton-capture nucleosynthesis, similar [Fe/H] values,
but factor of two differences in some alpha-capture, odd-Z and slow
neutron-capture process elements. Among stars in globular clusters, apparently
there are no definitive ``single'' values of [el/Fe] at a given [Fe/H] for many
important elements.


title: Vortex Configurations, Oscillations and Pinning in Neutron Star Crust

abstract:
  The rotating neutron superfluid in the inner crust of a neutron star is
threaded by quantized vortex lines. The pinning force from lattice nuclei and
the Magnus force from neutron superfluid act onto a vortex line that has a
finite tension. The configuration of a vortex line in equilibrium comprises a
number of pinned straight lengths separated by unpinned kinks when the rotation
axis is slightly inclined to the major axis of a crystal lattice and the Magnus
force is not so strong. Energy of $\sim 4 {MeV}$ is required to form a kink at
densities of $\sim 3.4 \times 10^{13}{g cm}^{-3}$. Magnus force makes the
vortex line parabolic on global scale. There exist two modes, rotational and
helical (Kelvin), for oscillations allowed on a vortex line. The vortex
oscillations in the pinned straight segments are possible only above a minimum
frequency. We find no unstable mode that grows with time. Hence, the vortex
configurations with kinks may be stable and yield the strongly pinned state.
The essence of our results may not be altered even when we consider the vortex
behaviors in a polycrystalline structure. Our studies suggest that pinning of a
vortex line in a polycrystalline structure would be still strong enough to
explain the large glitches.


title: The Dyer-Roeder distance-redshift relation in inhomogeneous universes

abstract:
  Using Monte-Carlo methods, we determine the best-fit value of the homogeneity
parameter alpha in the Dyer-Roeder distance-redshift relation for a variety of
redshifts, inhomogeneity models and cosmological parameter values. The relation
between alpha and the fraction of compact objects, f_p, is found to be
approximately linear. This relation can be parametrized with reasonable
accuracy for all cases treated in this paper by alpha = a*f_p, where a = 0.6.


title: Chandra Observations of the Luminous IR Galaxy NGC3256

abstract:
  We present a detailed analysis of high-resolution Chandra observations of the
merger system NGC3256, the most IR luminous galaxy in the nearby universe. The
X-ray data show that several discrete sources embedded in complex diffuse
emission contribute ~>20 of the total emission (L_x^tot ~8E41 ergs/s in the
0.5-10 keV energy range). The compact sources are hard and extremely bright and
their emission is probably dominated by accretion driven processes. Both galaxy
nuclei are detected with L_x ~3-10E40 ergs/s. No evidence is found for the
presence of an active nucleus in the southern nucleus, contrary to previous
speculation. Once the discrete sources are removed, the diffuse component has a
soft spectrum which can be modelled by the superposition of 3 thermal plasma
components with temperatures kT = 0.6, 0.9 and 3.9 keV. Alternatively, the
latter component can be described as a power-law with index Gamma ~3. Some
evidence is found for a radial gradient of the amount of absorption and
temperature of the diffuse component. We compare the X-ray emission with
optical, Halpha and NICMOS images of NGC3256 and find a good correlation
between the inferred optical/near-IR and X-ray extinctions. Although Inverse
Compton scattering could be important in explaining the hard X-rays seen in the
compact sources associated with the nuclei, the observed diffuse emission is
probably of thermal origin. The observed X-ray characteristics support a
scenario in which the powerful X-ray emission is driven solely by the current
episode of star formation.


title: On the problem of initial conditions in cosmological N-body simulations

abstract:
  Cosmological N-body simulations aim to calculate the non-linear gravitational
growth of structures via particle dynamics.
  A crucial problem concerns the setting-up of the initial particle
distribution, as standard theories of galaxy formation predict the properties
of the initial continuous density field with small amplitude correlated
Gaussian fluctuations. The discretisation of such a field is a complex issue
and particle fluctuations are especially relevant at small scales where
non-linear dynamics firstly takes place. In general, most of the procedures
which may discretise a continuous field, gives rise to Poisson noise, which
would then dominate the non-linear small-scales dynamics due to
nearest-neighbours interactions. In order to avoid such a noise, and to
consider the dynamics as due only to large scale (smooth) fluctuations, an
ad-hoc method (lattice or glassy system plus correlated displacements) has been
introduced and used in cosmological simulations. We show that such a method
gives rise to a particle distribution which does not have any of the
correlation properties of the theoretical continuous density field. This is
because discreteness effects, different from Poisson noise but nevertheless
very important, determine particle fluctuations at any scale, making it
completely different from the original continuous field. We conclude that
discreteness effects play a central role in the non-linear evolution of N-body
simulations.


title: The Crab pulsar in the 0.75-30 MeV range as seen by CGRO COMPTEL

abstract:
  We present the time-averaged characteristics of the Crab pulsar in the
0.75-30 MeV energy window using data from the imaging Compton Telescope COMPTEL
aboard the Compton Gamma-Ray Observatory (CGRO) collected over its 9 year
mission. Exploiting the exceptionally long COMPTEL exposure on the Crab allowed
us to derive significantly improved COMPTEL spectra for the Crab nebula and
pulsar emissions, and for the first time to accurately determine at low-energy
gamma-rays the pulse profile as a function of energy. These timing data,
showing the well-known main pulse and second pulse at a phase separation of 0.4
with strong bridge emission, are studied together with data obtained at
soft/hard X-ray energies from the ROSAT HRI, BeppoSAX LECS, MECS and PDS, at
soft gamma-rays from CGRO BATSE and at high-energy gamma-rays from CGRO EGRET
in order to obtain a coherent high-energy picture of the Crab pulsar from 0.1
keV up to 10 GeV.


title: The TNG Near Infrared Camera Spectrometer

abstract:
  NICS (acronym for Near Infrared Camera Spectrometer) is the near-infrared
cooled camera-spectrometer that has been developed by the Arcetri Infrared
Group at the Arcetri Astrophysical Observatory, in collaboration with the
CAISMI-CNR for the TNG (the Italian National Telescope Galileo at La Palma,
Canary Islands, Spain).
  As NICS is in its scientific commissioning phase, we report its observing
capabilities in the near-infrared bands at the TNG, along with the measured
performance and the limiting magnitudes. We also describe some technical
details of the project, such as cryogenics, mechanics, and the system which
executes data acquisition and control, along with the related software.


title: The evolution of galaxy clustering since z=1

abstract:
  We present results of an investigation of clustering evolution of field
galaxies between a redshift of z~1 and the present epoch. The current analysis
relies on a sample of ~3600 galaxies from the Calar Alto Deep Imaging Survey
(CADIS). The multicolor classification and redshift determination is reliable
up to I=23. The redshift distribution extends to z~1.1, the resolution is Delta
cz=12000 km s^-1. Thus the amplitude of the three-dimensional correlation
function has to be estimated by means of the projected correlation function
w(r_p). The validity of the deprojection was tested on the Las Campanas
Redshift Survey (LCRS). The LCRS also serves as ''local'' measurement. We
invented a new method to overcome the influence of redshift errors on w(r_p).
For evolution of the clustering strength the ansatz xi(r_com,z)proportional to
(1+z)^q is used. For the galaxies as a whole the evolution parameter turns out
to be q~-1.9, according to the prediction of linear theory. A formal dependency
on the cosmology is presumably due to the small number of fields observed.
However, the measured clustering growth clearly depends on Hubble type. At z~1
early type galaxies are already much stronger clustered, an increase with q~-1
is sufficient to explain the present day amplitude of the correlation function.


title:
CCD Photometry of the Classic Second Parameter Globular Clusters M3 and
  M13

abstract:
  We present high-precision V, B-V color-magnitude diagrams (CMDs) for the
classic second parameter globular clusters M3 and M13 from wide-field deep CCD
photometry. The data for the two clusters were obtained during the same
photometric nights with the same instrument, allowing us to determine accurate
relative ages. Based on a differential comparison of the CMDs using the Delta
(B-V) method, an age difference of 1.7 +/- 0.7 Gyr is obtained between these
two clusters. We compare this result with our updated horizontal-branch (HB)
population models, which confirm that the observed age difference can produce
the difference in HB morphology between the clusters. This provides further
evidence that age is the dominant second parameter that influences HB
morphology.