title:
Virial theorem analysis of 3D numerical simulations of MHD
  self-gravitating turbulence

abstract:
  We discuss the virial balance of all members of a cloud ensemble in numerical
simulations of self-gravitating MHD turbulence. We first discuss the choice of
reference frame for evaluating the terms entering the virial theorem (VT),
concluding that the balance of each cloud should be measured in its own
reference frame. We then report preliminary results suggesting that a) the
clouds are far from virial equilibrium, with the ``geometric'' (time
derivative) terms dominating the VT. b) The surface terms in the VT are as
important as the volume ones, and tend to decrease the action of the latter. c)
This implies that gravitational binding should be considered including the
surface terms in the overall balance.


title: The power spectrum of galaxies in the 2dF 100k redshift survey

abstract:
  We compute the real-space power spectrum and the redshift-space distortions
of galaxies in the 2dF 100k galaxy redshift survey using pseudo-Karhunen-Loeve
eigenmodes and the stochastic bias formalism. Our results agree well with those
published by the 2dFGRS team, and have the added advantage of producing
easy-to-interpret uncorrelated minimum-variance measurements of the
galaxy-galaxy, galaxy-velocity and velocity-velocity power spectra in 27
k-bands, with narrow and well-behaved window functions in the range 0.01h/Mpc <
k < 0.8h/Mpc. We find no significant detection of baryonic wiggles, although
our results are consistent with a standard flat Omega_Lambda=0.7
``concordance'' model and previous tantalizing hints of baryonic oscillations.
We measure the galaxy-matter correlation coefficient r > 0.4 and the
redshift-distortion parameter beta=0.49+/-0.16 for r=1 (beta=0.47+/- 0.16
without finger-of-god compression). Since this is an apparent-magnitude limited
sample, luminosity-dependent bias may cause a slight red-tilt in the power
spectum. A battery of systematic error tests indicate that the survey is not
only impressive in size, but also unusually clean, free of systematic errors at
the level to which our tests are sensitive. Our measurements and window
functions are available at http://www.hep.upenn.edu/~max/2df.html together with
the survey mask, radial selection function and uniform subsample of the survey
that we have constructed.


title: Experimental CMB Status and Prospects: A Report from Snowmass 2001

abstract:
  In recent years the promise of experimental study of the cosmic microwave
background (CMB) has been demonstrated. Herein a brief summary of the field is
followed by an indication of future directions. The prospects for further
revelations from the details of the CMB are excellent. The future work is
well-suited to the interests of high energy physics experimentalists: the
projects seek to understand the fundamental nature of the universe, require
subtle experimental techniques to keep systematics in control, produce large,
rich data sets, and must be implemented by multi-institutional collaborations.


title:
The New Gamma-ray Pulsar PSR J2229+6114, its Pulsar Wind Nebula, and
  Comparison with the Vela Pulsar

abstract:
  With a period of 51.6 ms and spin-down power 2.2x10^{37} erg s^{-1}, PSR
J2229+6114 is a compelling identification for the EGRET source 3EG J2227+6122
in which error circle it resides. Striking features of the Chandra X-ray image
are an incomplete elliptical arc and a possible jet, similar to the structures
that dominate the appearance of the Vela PWN. Approximately 70% of the 2-10 keV
X-ray emission comes from a centrally peaked, diffuse nebula of radius 100"
with a power-law spectrum of photon index 1.45 +/- 0.19. The pulsar itself has
a marginally harder spectrum with photon index 0.99 +/- 0.27. For an assumed
distance of 3 kpc the ratio of X-ray luminosity to spin-down power of PSR
J2229+6114 is only 8 x 10^{-5}. We discuss a model in which such inefficient
X-ray emission is the signature of a highly magnetized pulsar wind that
prevents an internal MHD shock, at the location of the X-ray arc, from strongly
compressing the flow. The incomplete X-ray arc is consistent with beaming from
a relativistic equatorial outflow, while a surrounding radio shell is probably
the forward shock in the surrounding ISM. An MeV source at this location was
previously detected by the COMPTEL experiment on CGRO. This, plus the flat
X-ray spectrum in the 2-10 keV band, suggests that PSR J2229+6114 is one of the
brightest pulsars at 1 MeV, even while it is inconspicuous at radio through
X-ray wavelengths, and as steep as the Crab above 100 MeV. The apparent variety
of broad-band spectra displayed by high-energy pulsars bolsters the theory that
rotation-powered pulsars dominate the unidentified Galactic EGRET source
population.


title: The Intriguing Plerionic Supernova Remnant: G21.5-0.9

abstract:
  G21.5-0.9 is a plerionic supernova remnant (SNR) whose properties hint at the
presence of a pulsar -- yet no pulsations have been found at any wavelength.
Early observations with Chandra led to the discovery of an extended component,
making the SNR at least twice as big as originally thought. Our analysis
indicates that this low-surface brightness extended component is non-thermal.
We perform a spatially resolved spectroscopy using a 72 ksec exposure with
ACIS-S, and find no evidence of line emission. The 5-arcminute diameter remnant
is well fitted with a power law with a photon index steepening from 1.5
(central core) to 2.7 (extended component) and a column density N_H=2.2 10^22
cm^-2. Using a 76 ksec exposure with the HRC, we derive an upper limit of 16%
on the pulsed fraction from a putative pulsar. We also infer the parameters of
the `hidden pulsar' in G21.5-0.9 in comparison with the Crab and 3C 58 pulsars.
This remnant remains unique and intriguing since it is, to date, the only
candidate whose size is bigger in X-rays than in the radio.


title:
Physical parameters in the hot spots and jets of Compact Symmetric
  Objects

abstract:
  We present a model to determine the physical parameters of jets and hot spots
of a sample of CSOs under very basic assumptions like synchrotron emission and
minimum energy conditions. Based on this model we propose a simple evolutionary
scenario for these sources assuming that they evolve in ram pressure
equilibrium with the external medium and constant jet power. The parameters of
our model are constrained from fits of observational data (radio luminosity,
hot spot radius and hot spot advance speed) versus projected linear size. From
these plots we conclude that CSOs evolve self-similarly and that their radio
luminosity increases with linear size along the first kiloparsec. Assuming that
the jets feeding CSOs are relativistic from both kinematical and
thermodynamical points of view, we use the values of the pressure and particle
number density within the hot spots to estimate the fluxes of momentum
(thrust), energy, and particles of these relativistic jets. The mean jet power
obtained in this way is within an order of magnitude that inferred for FRII
sources, which is consistent with CSOs being the possible precursors of large
doubles. The inferred flux of particles corresponds to, for a barionic jet,
about a 10% of the mass accreted by a black hole of $10^8 {\rm M_{\odot}}$ at
the Eddington limit, pointing towards a very efficient conversion of accretion
flow into ejection, or to a leptonic composition of jets.


title:
Implications of the synchrotron emission in plerionic nebulae: a second
  component in the Crab Nebula

abstract:
  High-quality spatially resolved spectra of synchrotron emission from plerions
represent a powerful diagnostic tool for the physical conditions in these
objects. A fundamental question is to what extent spatial variations of the
synchrotron spectrum originate from the evolution of a single population of
injected electrons, and when instead they imply the coexistence of different
populations of electrons. Here I shall discuss observations of the Crab Nebula
at millimetric wavelengths which, compared with a radio map, show evidence for
the emergence of a second synchrotron component, characterized by a flatter
spectrum and undetected in the radio range. This component is confined to the
inner part of the nebula, and cannot originate from synchrotron-dominated
evolution, also because in the Crab Nebula the electrons emitting at millimeter
wavelengths evolve almost adiabatically. Then its discovery indicates that
there are more populations of injected particles. Finally, the detection of a
low-frequency break in the spectra of synchrotron filaments can be interpreted
as an effect of higher magnetic fields in filaments.


title: Void Scaling and Void Profiles in CDM Models

abstract:
  An analysis of voids using cosmological N-body simulations of cold dark
matter models is presented. It employs a robust statistics of voids, that was
recently applied to discriminate between data from the Las Campanas Redshift
Survey and different cosmological models. Here we extend the analysis to 3D and
show that typical void sizes D in the simulated galaxy samples obey a linear
scaling relation with the mean galaxy separation lambda: D=D_0+nu*lambda. It
has the same slope nu as in 2D, but with lower absolute void sizes. The scaling
relation is able to discriminate between different cosmologies. For the best
standard LCDM model, the slope of the scaling relation for voids in the dark
matter halos is too steep as compared to the LCRS, with too small void sizes
for well sampled data sets. The scaling relation of voids for dark matter halos
with increasing mass thresholds is even steeper than that for samples of
galaxy-mass halos where we sparse sample the data. This shows the stronger
clustering of more massive halos. Further, we find a correlation of the void
size to its central and environmental average density. While there is little
sign of an evolution in samples of small DM halos with v_{circ} ~ 90 km/s,
voids in halos with circular velocity over 200 km/s are larger at redshift z =
3 due to the smaller halo number density. The flow of dark matter from the
underdense to overdense regions in an early established network of large scale
structure is also imprinted in the evolution of the density profiles with a
relative density decrease in void centers by 0.18 per redshift unit between z=3
and z=0.


title: Strange stars as persistent sources of gravitational waves

abstract:
  We investigate the relevance of the gravitational-wave driven r-mode
instability for strange stars. We find that the unstable r-modes affect strange
stars in a way that is quite distinct from the neutron star case. For accreting
strange stars we show that the onset of r-mode instability does not lead to the
thermo-gravitational runaway that is likely to occur in neutron stars. Instead,
the strange star evolves towards a quasi-equilibrium state on a timescale of
about a year. This mechanism could thus explain the clustering of
spin-frequencies inferred from kHz QPO data in Low-mass X-ray binaries. For
young strange stars we show that the r-mode driven spin-evolution is also
distinct from the neutron star case. In a young strange star the r-mode
undergoes short cycles of instability during the first few months. This is
followed by a quasi-adiabatic phase where the r-mode remains at a small,
roughly constant, amplitude for thousands of years. Another distinguishing
feature from the neutron star case is that the r-modes in a strange star never
grow to large amplitudes. Our results suggest that the r-modes in strange star
emit a persistent gravitational-wave signal that should be detectable with
large-scale interferometers given an observation time of a few months. If
detected, these signals would provide unique evidence for the existence of
strange stars, which would put useful constraints on the parameters of QCD.


title: A 2.09-h Photometric Periodicity in GW Librae

abstract:
  We have found a 2.09 h modulation in brightness of the dwarf nova GW Lib.
This bears no special relationship to the 1.28 h spectroscopic period that is
believed to be the orbital period. It was present in May 2001, but not in
observations made in 1997 and 1998 and is of unknown origin. Similar
unexplained periodicities are present in FS Aur and V2051 Oph.


title: Gamma ray bursts: some facts and ideas

abstract:
  Gamma Ray Bursts (GRBs) are the most explosive events after the big bang:
their energy output corresponds to a sizeable fraction of a solar mass entirely
converted into energy in a few seconds. Although many questions about their
progenitors remain to be answered, it is likely that they are generated by a
newly formed and fast spinning black hole. The colossal power characterizing
GRBs is carried by a surprisingly small amount of matter, which is accelerated
to speeds differing from c by one part in ten thousands. GRBs are then the most
(special and general) relativistic objects we know of. Since GRBs are the
brightest sources at high redshift, albeit for a limited amount of time, they
are also the best torchlights we have to shine the far universe.


title:
Structure of Proton Component of Neutron Star Matter for Realistic
  Nuclear Models

abstract:
  We study properties of the proton component of neutron star matter for a
number of realistic nuclear models. Protons which form a few percent admixture
tend to be localized in potential wells corresponding to neutron matter
inhomogeneities created by the protons in the neutron medium. We calculate the
energy of the Wigner-Seitz cell enclosing a single localized proton. The
neutron background is treated in the Thomas-Fermi approximation and the
localized proton is described by the Gaussian wave function. The neutron
density profile is obtained by solving the appropriate variational equation.
This approach gives lower energies of localized protons than obtained
previously with less sophisticated methods.


title: Deep inside the core of Abell 1795: the Chandra view

abstract:
  We present X-ray spatial and spectral analysis of the Chandra data from the
central 400 kpc (H0 = 50 km/s/Mpc) of the cluster of galaxies Abell 1795. The
plasma temperature rises outwards by a factor of 3, whereas the iron abundance
decreases by a factor of 4. The spatial distribution of Oxygen, Neon, Sulphur,
Silicon and Iron shows that supernovae Type Ia dominate the metal enrichment
process of the cluster plasma within the inner 150 kpc. Resolving both the gas
density and temperature in 9 radial bins, we recover the gravitational mass
density profile and show that it flattens within 100 kpc as rho_DM \propto
r^{-0.6} with a power law index flatter than -1 at >3 sigma level. The observed
motion of the central galaxy and the presence of excesses and deficits along
the North-South direction in the brightness distribution indicate that the
central cluster region is not relaxed. In the absence of any non-gravitational
heating source, the data from the inner ~200 kpc indicate the presence of a
cooling flow with an integrated mass deposition rate of about 100 Msun/yr. Over
the same cluster region, the observed rate of 74 Msun/yr is consistent with the
recent XMM Reflection Grating Spectrometer limit of 150 Msun/yr.


title: Diquark Properties and the TOV Equations

abstract:
  We present various results from including diquark properties and the gap
equations into the TOV equations for compact quark objects. One such property
is the diquark form factor, which has a strong influence on various quantities.
We discuss the consequences for quark stars.


title: Mass loss from galaxies: feeding the IGM, recycling in the IGM

abstract:
  As a result of internal processes or environmental effects like ram-pressure
stripping or collisions, galaxies lose a significant part of their stellar and
gaseous content. Whereas the impact of such stripping on galaxy evolution has
been well studied, much less attention has been given to the fate of the
expelled material in the intergalactic or intracluster medium (IGM/ICM).
Observational evidence exists showing that a fraction of the injected matter is
actually recycled to form a new generation of galaxies, such as the Tidal Dwarf
Galaxies discovered near numerous interacting systems. Using a set of
multiwavelength data, we are now able to roughly analyze the processes
pertaining to their formation: from an instability in the HI clouds, through
the formation of molecular gas, and to the onset of star formation.


title:
The cosmic microwave background radiation temperature at z = 3.025
  toward QSO 0347--3819

abstract:
  From the analysis of the CII fine-structure population ratio in the damped
Ly_alpha system at z = 3.025 toward the quasar Q0347--3819 we derive an upper
bound of 14.6 (+/- 0.2) K on the cosmic microwave background temperature
regardless the presence of other different excitation mechanisms. The analysis
of the ground state rotational level populations of H_2 detected in the system
reveals a Galactic-type UV radiation field ruling out UV pumping as an
important excitation mechanism for CII. The low dust content estimated from the
Cr/Zn ratio indicates that the IR dust emission can also be neglected. When the
collisional excitation is considered, we measure a temperature for the cosmic
background radiation of T = 12.1 (+1.7, -3.2) K. The results are in agreement
with the T = 10.968 (+/-) 0.004 K predicted by the hot Big Bang cosmology at z
= 3.025.


title: The evolution of disk galaxies in clusters

abstract:
  We are carrying out a programme to measure the evolution of the stellar and
dynamical masses and M/L ratios for a sizeable sample of
morphologically-classified disk galaxies in rich galaxy clusters at 0.2<z<0.9.
Using FORS2 at the VLT we are obtaining rotation curves for the cluster spirals
so that their Tully-Fisher relation can be studied as a function of redshift
and compared with that of field spirals. We already have rotation curves for 10
cluster spirals at z=0.83, and 25 field spirals at lower redshifts and we plan
to increase this sample by one order of magnitude. We present here the first
results of our study, and discuss the implications of our data in the context
of current ideas and models of galaxy formation and evolution.


title:
Precursor Plerionic Activity and High Energy Gamma-Ray Emission in the
  Supranova Model of Gamma-Ray Bursts

abstract:
  The supranova model of gamma-ray bursts (GRBs), in which the GRB event is
preceded by a supernova (SN) explosion by a few months to years, has recently
gained support from Fe line detections in X-ray afterglows. A crucial
ingredient of this model yet to be studied is the fast-rotating pulsar that
should be active during the time interval between the SN and the GRB, driving a
powerful wind and a luminous plerionic nebula. We discuss some observational
consequences of this precursor plerion, which should provide important tests
for the supranova model: 1) the fragmentation of the outlying SN ejecta
material by the plerion and its implications for Fe line emission; and 2) the
effect of inverse Compton cooling and emission in the GRB external shock due to
the plerion radiation field. The plerion-induced inverse Compton emission can
dominate in the GeV-TeV energy range during the afterglow, being detectable by
GLAST from redshifts $z \lesssim 1.5$ and distinguishable from self-Compton
emission by its spectrum and light curve. The prospects for direct detection
and identification of the precursor plerion emission are also briefly
considered.


title: Chemical Abundances in High-Redshift Neutral Clouds

abstract:
  Neutral hydrogen clouds with high column density detected towards distant
quasars are unique probes of elemental nucleosynthesis and chemical evolution
in the low metallicity regime. They provide measurements for several elements
at very early times which are unfeasible in other astrophysical environments.
Comparison between refractory and non-refractory elements provides evidence for
the presence of dust, and the recently measured Ar probes photoionization. A
prominent characteristic is the dominance of a solar abundance pattern, which
is somewhat unexpected at low metallicities. It is argued that this property
and Nitrogen observations can be used to constrain the age of the Damped
Ly_alpha systems and the epoch of star formation.


title: Optical observations of the supernova remnant AX J2001+3235

abstract:
  We present results from a first analysis of optical data on G 69.4+2.4
obtained with the 0.3 m and 1.3 m telescopes at Skinakas Observatory.
Filamentary emission is detected in the [OIII] 5007 A and Halpha+[NII] images
oriented in the south-west, north-east direction. The Halpha+[NII] images
reveal a complex network of filaments, while the [OIII] images show a single
filament. Low resolution spectra were also obtained which identify the observed
emission as emission from shock heated gas.


title:
Acoustic peaks and dips in the CMB power spectrum: observational data
  and cosmological constraints

abstract:
  The locations and amplitudes of three acoustic peaks and two dips in the last
releases of the Boomerang, MAXIMA and DASI measurements of the cosmic microwave
background (CMB) anisotropy power spectra as well as their statistical
confidence levels are determined in a model-independent way. It is shown that
the Boomerang-2001 data (Netterfield et al. 2001) fixes the location and
amplitude of the first acoustic peak at more than 3\sigma confidence level. The
next two peaks and dips are determined at a confidence level above 1\sigma but
below 2\sigma. The locations and amplitudes of the first three peaks and two
dips are 212+/-17, 5426+/-1218\mu K^2, 544+/-56, 2266+/-607\mu K^2, 843+/-35,
2077+/-876\mu K^2, 413+/-50, 1960+/-503\mu K^2, 746+/-89, 1605+/-650\mu K^2
respectively (1\sigma errors include statistical and systematic errors). The
MAXIMA and DASI experiments give similar values for the extrema which they
determine. The determined cosmological parameters from the CMB acoustic extrema
data show good agreement with other determinations, especially with the baryon
content as deduced from standard nucleosynthesis constraints. These data
supplemented by the constraints from direct measurements of some cosmological
parameters and data on large scale structure lead to a best-fit model which
agrees with practically all the used experimental data within 1\sigma. The
best-fit parameters are: \Omega_{\Lambda}=0.64^{+0.14}_{-0.27}, \Omega_{m}=
0.36^{+0.21}_{-0.11}, \Omega_b=0.047^{+0.093}_{-0.024},
n_s=1.0^{+0.59}_{-0.17}, h=0.65^{+0.35}_{-0.27} and \tau_c=0.15^{+0.95}_{-0.15}
(plus/minus values show 1\sigma upper/lower limits obtained by marginalization
over all other model parameters). The best-fit values of \Omega_{\nu} and T/S
are close to zero, their 1\sigma upper limits are 0.17 and 1.7 respectively.


title:
Discovering Mass Clumps in Distant Galaxies with Lensing: The Case of
  B1422+231

abstract:
  Substructure in distant gravitational lens galaxies can be detected because
it alters the brightnesses and shapes of the lensed images. The optical and
radio flux ratios in the four-image lens B1422+231 imply that there is a \sim
10^4-10^7 Msun/h mass clump in the lens galaxy in front of image A; this is the
first constraint on the mass of a particular clump lying in a distant galaxy
and detected by its mass. The data also indicate that a small clump, perhaps a
star, is passing in front of image B and making the optical flux ratios
variable. Both of these hypotheses can be tested with new observations.
B1422+231 demonstrates how data at different wavelengths can be used in
individual lenses to probe individual mass clumps in distant galaxies.


title: A CCD mosaic of an extended remnant in Cygnus

abstract:
  We present the first CCD mosaic ever produced for the supernova remnant G
65.3+5.7 in [OII] 3727 at a moderate angular resolution. The remnant was
observed with the 0.3 m wide-field telescope at Skinakas Observatory, Crete,
Greece. Low resolution spectroscopy was performed at selected areas around this
extended remnant. The spectral data are under analysis, while a first
processing of the imaging observations produced impressive results.


title:
New Globular Cluster Age Estimates and Constraints on the Cosmic
  Equation of State and The Matter Density of the Universe

abstract:
  New estimates of globular cluster distances, combined with revised ranges for
input parameters in stellar evolution codes and recent estimates of the
earliest redshift of cluster formation allow us to derive a new 95% confidence
level lower limit on the age of the Universe of 11 Gyr. This is now
definitively inconsistent with the expansion age for a flat Universe for the
currently allowed range of the Hubble constant unless the cosmic equation of
state is dominated by a component that violates the strong energy condition.
This solidifies the case for a dark energy-dominated universe, complementing
supernova data and direct measurements of the geometry and matter density in
the Universe. The best-fit age is consistent with a cosmological
constant-dominated (w=pressure/energy density = -1) universe. For the Hubble
Key project best fit value of the Hubble Constant our age limits yields the
constraints w < -0.4 and Omega_matter < 0.38 at the 68 % confidence level, and
w < -0.26 and Omega_matter < 0.58 at the 95 % confidence level.


title: Mid-Infrared Detection of a Hot Molecular Core in G29.96-0.02

abstract:
  We present high angular resolution (~0.5") 10 and 18 micron images of the
region around G29.96-0.02 taken from the Gemini North 8-m telescope using the
mid-infrared imager and spectrometer OSCIR. These observations were centered on
the location of a group of water masers, which delineate the site of a hot
molecular core believed to contain an extremely young, massive star. We report
here the direct detection of a hot molecular core at mid-infrared wavelengths
at this location. The size and extent of the core at 18 microns appears to be
very similar to the morphology as seen in integrated NH3 maps. However, our
observations indicate that the mid-infrared emission may not be exactly
coincident with the NH3 emission.


title:
NGC 4314. IV. Photometry of Star Clusters with Hubble Space Telescope -
  History of Star Formation in the Vicinity of a Nuclear Ring

abstract:
  Using HST WFPC2 images, we have obtained U, B, V, I, and H-alpha photometry
for 76 star clusters in the nuclear star-forming ring of the barred spiral
galaxy NGC 4314. These clusters are likely associated with an inner Inner
Lindblad Resonance, or IILR. The blue colors and H-alpha emission for most of
these clusters imply very young ages of 1-15 Myr. Age estimates based on
several reddening-free parameters indicate that the present epoch of star
formation has lasted at least 30 Myr. By estimating the masses of stars in the
clusters and comparing with the H-alpha luminosity, we conclude that a
significant fraction of ongoing star formation in the nuclear ring of NGC 4314
occurs in clusters. The cluster masses identify these as young open clusters,
not young globular clusters. Further out in the galaxy, just exterior to the
ring of young stars, previous ground-based observations revealed two symmetric
stellar spiral arms which may be associated with an outer Inner Lindblad
Resonance, or OILR. With our HST data, we have revealed part of this structure
and its colors in more detail. The spiral arm colors are consistent with
stellar ages between 40 and 200 Myr. The age difference between the inner ring
of young stars (IILR) and the larger oval-like feature containing the blue arms
(OILR) supports an interpretation of the morphology of the nuclear region of
NGC 4314 that requires a reservoir of gas that becomes more compact over time.
We speculate that as the gas distribution becomes more centrally concentrated,
it interacts with these two resonances. Each resonance triggers star formation,
resulting in two distinct epochs of star formation.


title: Chaos in the Solar System

abstract:
  The physical basis of chaos in the solar system is now better understood: in
all cases investigated so far, chaotic orbits result from overlapping
resonances. Perhaps the clearest examples are found in the asteroid belt.
Overlapping resonances account for its Kirkwood gaps and were used to predict
and find evidence for very narrow gaps in the outer belt. Further afield, about
one new ``short-period'' comet is discovered each year. They are believed to
come from the ``Kuiper Belt'' (at 40 AU or more) via chaotic orbits produced by
mean-motion and secular resonances with Neptune. Finally, the planetary system
itself is not immune from chaos. In the inner solar system, overlapping secular
resonances have been identified as the possible source of chaos. For example,
Mercury, in 10^{12} years, may suffer a close encounter with Venus or plunge
into the Sun. In the outer solar system, three-body resonances have been
identified as a source of chaos, but on an even longer time scale of 10^9 times
the age of the solar system. On the human time scale, the planets do follow
their orbits in a stately procession, and we can predict their trajectories for
hundreds of thousands of years. That is because the mavericks, with shorter
instability times, have long since been ejected. The solar system is not
stable; it is just old!


title: NGC 6994 - clearly not a physical stellar ensemble

abstract:
  The sparse stellar ensemble NGC 6994 = M73 has recently been discussed as a
possible remnant of an old open cluster. In order to solve the controversy on
the nature of this object we have taken high-resolution spectra of the six
brightest stars within 6' angular distance of its nominal position. These stars
are the only obvious member candidates for an eventual cluster or cluster
remnant since fainter stars do not show any significant concentration in the
plane of the sky. The radial velocities, atmospheric parameters, and absolute
magnitudes derived from the spectra reveal that the six candidates do not share
the same kinematics and lie at different distances from the Sun. The proper
motions provided by the Tycho-2 catalogue show that there is also a large
spread in the tangential motions of these stars, in agreement with the
spectroscopic results. This leads to the conclusion that the few bright stars
that constitute NGC 6994 are not a physical system (cluster, cluster remnant,
or group). They must instead be understood as a projective chance alignment of
physically unrelated field stars.


title: The role of chaotic resonances in the solar system

abstract:
  Our understanding of the Solar System has been revolutionized over the past
decade by the finding that the orbits of the planets are inherently chaotic. In
extreme cases, chaotic motions can change the relative positions of the planets
around stars, and even eject a planet from a system. Moreover, the spin axis of
a planet-Earth's spin axis regulates our seasons-may evolve chaotically, with
adverse effects on the climates of otherwise biologically interesting planets.
Some of the recently discovered extrasolar planetary systems contain multiple
planets, and it is likely that some of these are chaotic as well.


title:
Viscoelastic Analogy for the Acceleration and Collimation of
  Astrophysical Jets

abstract:
  Jets are ubiquitous in astronomy. It has been conjectured that the existence
of jets is intimately connected with the spin of the central object and the
viscous angular momentum transport of the inner disk. Bipolar jet-like
structures propelled by the viscous torque on a spinning central object are
also known in a completely different context, namely the flow in the laboratory
of a viscoelastic fluid. On the basis of an analogy of the tangled magnetic
field lines of magnetohydrodynamic (MHD) turbulence to the tangled polymers of
viscoelastic polymer solutions, we propose a viscoelastic description of the
dynamics of highly turbulent conductive fluid. We argue that the same mechanism
that forms jets in viscoelastic fluids in the laboratory may be responsible for
collimating and powering astrophysical jets by the angular momentum of the
central object.


title:
Structure of rapidly rotating strange stars: salient differences from
  neutron stars

abstract:
  Structure parameters of rapidly rotating strange stars are compared with
those for neutron stars. The salient differences are pointed out.


title:
Imaging the 3-D cosmological mass distribution with weak gravitational
  lensing

abstract:
  I show how weak gravitational lensing can be used to image the 3-D mass
distribution in the Universe. An inverse relation to the lensing equation,
relating the lensing potential evaluated at each source to the full 3-D
Newtonian potential, is derived. I consider the normal modes of the lensing
problem and clarify the equations using a small-angle approximation. Finally I
consider the prospects of using this method to estimate the 3-D matter
distribution from a realistic galaxy lensing survey.


title: Mass Reconstruction with CMB Polarization

abstract:
  Weak gravitational lensing by the intervening large-scale structure of the
Universe induces high-order correlations in the cosmic microwave background
(CMB) temperature and polarization fields. We construct minimum variance
estimators of the intervening mass distribution out of the six quadratic
combinations of the temperature and polarization fields. Polarization begins to
assist in the reconstruction when E-mode mapping becomes possible on
degree-scale fields, i.e. for an experiment with a noise level of ~40 uK-arcmin
and beam of ~7', similar to the Planck experiment; surpasses the temperature
reconstruction at ~26 uK-arcmin and 4'; yet continues to improve the
reconstruction until the lensing B-modes are mapped to l ~ 2000 at ~0.3
uK-arcmin and 3'. Ultimately, the correlation between the E and B modes can
provide a high signal-to-noise mass map out to multipoles of L ~ 1000,
extending the range of temperature-based estimators by nearly an order of
magnitude. We outline four applications of mass reconstruction: measurement of
the linear power spectrum in projection to the cosmic variance limit out to L ~
1000 (or wavenumbers 0.002 < k < 0.2 in h/Mpc), cross-correlation with cosmic
shear surveys to probe the evolution of structure tomographically,
cross-correlation of the mass and temperature maps to probe the dark energy,
and the separation of lensing and gravitational wave B-modes.


title:
Probing the pc- and kpc-scale environment of the powerful radio galaxy
  Hercules A

abstract:
  We present the kpc-scale behaviour of the powerful extragalactic radio source
Hercules A and the behaviour of the intracluster gas in which the radio source
is situated. We have found that Hercules A exhibits a strong Laing-Garrington
effect. The X-ray observations have revealed an extended X-ray emission
elongated along the radio galaxy axis. The estimated temperature of the cluster
is kT = 2.45 keV and the central electron density is no~7.8 x 10^(-3) cm^(-3)
which reveals a hot, dense environment in which Hercules A is situated. From
the combined study of the radio and X-ray data we have estimated a central
value of 3<Bo (muG)<9. We also present the most recent results from the
analysis of the radio data on the pc-scale structure of the radio galaxy,
observed at 18 cm by the EVN-MERLIN array. A faint but compact radio source,
coincident with the optical centre of Hercules A was detected by the EVN at 18
mas resolution. The total flux density of the EVN core is 14.6 mJy. Its angular
size is 18 x 7 mas with a position angle of ~139 degrees. There is also
evidence for extended emission in the NW-SE direction, most probably from the
eastern pc-scale jet. If this is true then there is a misalignment between the
direction of the pc-eastern and the aligned kpc-scale jets of ~35 degrees.


title: The brown dwarf desert as a consequence of orbital migration

abstract:
  We show that the dearth of brown dwarfs in short-period orbits around
Solar-mass stars - the brown dwarf desert - can be understood as a consequence
of inward migration within an evolving protoplanetary disc. Brown dwarf
secondaries forming at the same time as the primary star have masses which are
comparable to the initial mass of the protoplanetary disc. Subsequent disc
evolution leads to inward migration, and destruction of the brown dwarf, via
merger with the star. This is in contrast with massive planets, which avoid
this fate by forming at a later epoch when the disc is close to being
dispersed. Within this model, a brown dwarf desert arises because the mass at
the hydrogen burning limit is coincidentally comparable to the initial disc
mass for a Solar mass star. Brown dwarfs should be found in close binaries
around very low mass stars, around other brown dwarfs, and around Solar-type
stars during the earliest phases of star formation.


title: The Chandra Deep Field North Survey. IX. Extended X-ray Sources

abstract:
  The ~1 Ms Chandra Deep Field North observation is used to study the extended
X-ray sources in the region surrounding the Hubble Deep Field North (HDF-N),
yielding the most sensitive probe of extended X-ray emission at cosmological
distances to date. A total of six such sources are detected, the majority of
which align with small numbers of optically bright galaxies. Their angular
sizes, band ratios, and X-ray luminosities -- assuming they lie at the same
distances as the galaxies coincident with the X-ray emission -- are generally
consistent with the properties found for nearby groups of galaxies. One source
is notably different and is likely to be a poor-to-moderate X-ray cluster at
high redshift (i.e., z > 0.7). We are also able to place strong constraints on
the optically detected cluster of galaxies ClG 1236+6215 at z=0.85 and the
wide-angle-tail radio galaxy VLA J123725.7+621128 at z~1-2. With rest-frame
0.5--2.0 keV X-ray luminosities of <(3-15)e42 ergs s^{-1}, the environments of
both sources are either likely to have a significant deficit of hot
intra-cluster gas compared to local clusters of galaxies, or they are X-ray
groups. We find the surface density of extended X-ray sources in this
observation to be 167 (+97,-67) deg^{-2} at a limiting soft-band flux of
approximately 3e-16 ergs s^{-1} cm^{-2}. No evolution in the X-ray luminosity
function of clusters is needed to explain this value. (Abridged)


title: Chandra observations of PSR B1509-58 and Supernova Remnant G320.4-1.2

abstract:
  The young and energetic pulsar B1509-58 powers a bright X-ray synchrotron
nebula, embedded in the unusual supernova remnant G320.4-1.2. We present
observations of this system with the Chandra X-ray Observatory, which show a
spectacularly complicated source. The nebula is dominated by a bright
collimated feature which we interpret as a relativistic jet directed along the
pulsar spin axis. Several compact knots can be seen in the immediate vicinity
of the pulsar. While many of these features are similar to those seen around
the Crab pulsar, the nebula surrounding PSR B1509-58 shows important
differences which are possibly a result of the the latter's low nebular
magnetic field and low density environment.


title:
Observations of the Non-Thermal X-ray Emission from the Galactic
  Supernova Remnant G347.3-0.5

abstract:
  G347.3-0.5 (RX J1713.7-3946) is a member of the new class of shell-type
Galactic supernova remnants (SNRs) that feature non-thermal components to their
X-ray emission. We have analyzed the X-ray spectrum of this SNR over a broad
energy range (0.5 to 30 keV) using archived data from observations made with
two satellites, the Roentgenstaellit (ROSAT) and the Advanced Satellite for
Cosmology and Astrophysics (ASCA), along with data from our own observations
made with the Rossi X-ray Timing Explorer (RXTE). Using a combination of the
models EQUIL and SRCUT to fit thermal and non-thermal emission, respectively,
from this SNR, we find evidence for a modest thermal component to G347.3-0.5's
diffuse emission with a corresponding energy of kT = 1.4 keV. We also obtain an
estimate of 70 TeV for the maximum energy of the cosmic-ray electrons that have
been accelerated by this SNR.


title: Pulsar Wind Nebulae as High Energy Gamma-Ray Emitters

abstract:
  There is growing evidence that some variable high-energy gamma-ray sources
are associated with pulsar wind nebulae. We review the current status of X-ray
and radio studies of the sources most likely to be significant emitters above
100 MeV. The assumption of the gamma-radiation arising from synchrotron
processes puts a lower limit on the magnetic field and suggests there may be
significant doppler boosting causing the asymmetries seen in the morphology of
these nebulae. However, these sources are also in close proximity to molecular
clouds, suggesting that variable gamma-ray emission may arise from a ram
pressure confined pulsar wind nebula in a dense medium.


title: Fast Search Techniques for High Energy Pulsars

abstract:
  Modified versions of two "standard" pulsar search techniques are presented
that allow large-scale searches for pulsations in long duration high-energy
data sets using relatively modest amounts of computer time. For small numbers
of photons (N_phot <~ 10^4), optimized brute-force epoch folding searches are
preferred. For larger numbers of photons, advanced Fourier domain acceleration
searches are used. Using these techniques, my collaborators and I have searched
Chandra observations of the CasA supernova remnant (SNR) point source and the
isolated neutron star RX J1856.5-3754 for pulsations, and confirmed the 65.6 ms
pulsar in the 3C 58 SNR during a blind search of archival RXTE data.


title: Neutrino production in a time-dependent matter background

abstract:
  We show that neutrinos can be produced through standard electroweak
interactions in matter with time-dependent density.


title:
Production of neutrons, neutrinos and gamma-rays by a very fast pulsar
  in the Galactic Center region

abstract:
  We consider the possibility that the excess of cosmic rays near $\sim
10^{18}$ eV, reported by the AGASA and SUGAR groups from the direction of the
Galactic Center, is caused by a young, very fast pulsar in the high density
medium. The pulsar accelerates iron nuclei to energies $\sim 10^{20}$ eV, as
postulated by the Galactic models for the origin of the highest energy cosmic
rays. The iron nuclei, after about 1 yr since pulsar formation, leave the
supernova envelope without energy losses and diffuse through the dense central
region of the Galaxy. Some of them collide with the background matter creating
neutrons (from desintegration of Fe), neutrinos and gamma-rays (in inelastic
collisions). Wse suggest that neutrons produced at a specific time after the
pulsar formation are responsible for the observed excess of cosmic rays at
$\sim 10^{18}$ eV. From normalization of the calculated neutron flux to the one
observed in the cosmic ray excess, we predict the neutrino and gamma-ray
fluxes. It has been found that the 1 km$^2$ neutrino detector of the IceCube
type should detect from a few up to several events per year from the Galactic
Center, depending on the parameters of the considered model. Also future
systems of Cherenkov telescopes (CANGAROO III, HESS, VERITAS) should be able to
observe 1 - 10 TeV $\gamma$-rays from the Galactic Center if the pulsar was
created inside a huge molecular cloud about $3-10\times 10^3$ yrs ago.


title: Archeops, mapping the CMB sky from large to small angular scales

abstract:
  Archeops is a balloon-borne experiment designed to measure the temperature
fluctuations of the CMB on a large region of the sky ($\simeq 30%$) with a high
angular resolution (10 arcminutes) and a high sensitivity ($60\mu K$ per
pixel). Archeops will perform a measurement of the CMB anisotropies power
spectrum from large angular scales ($\ell\simeq 30$) to small angular scales
($\ell \simeq 800$). Archeops flew for the first time for a test flight in July
1999 from Sicily to Spain and the first scientific flight took place from
Sweden to Russia in January 2001. The data analysis is on its way and I present
here preliminary results, realistic simulations showing the expected accuracy
on the measurement of the power spectrum and perspectives for the incoming
flights (Winter 2001/2003).


title:
Archeops: A CMB anisotropy balloon experiment measuring a broad range of
  angular scales

abstract:
  The Cosmic Microwave Background Radiation is the oldest photon radiation that
can be observed, having been emitted when the Universe was about 300,000 year
old. It is a blackbody at 2.73 K, and is almost perfectly isotropic, the
anisotropies being about one part to 100,000. However, these anisotropies,
detected by the COBE satellite in 1992, constrain the cosmological parameters
such as the curvature of the Universe. Archeops is a balloon-borne experiment
designed to map these anisotropies. The instrument is composed of a 1.5 m
telescope and bolometers cooled at 85 mK to detect radiation between 150 and
550 GHz. To lower parasitic signals, the instrument is borne by a stratospheric
balloon during the arctic night. This instrument is also a preparation for the
Planck satellite mission, as its design is similar to HFI. We discuss here the
results of the first scientific flight from Esrange (near Kiruna, Sweden) to
Russia on January 29th 2001, which led to a 22 % (sub)millimetre sky coverage
unprecedented at this resolution. Here, we put some emphasis on interstellar
dust foreground emission observations.


title: The central kiloparsec of starbursts and AGN: The La Palma connection

abstract:
  We describe selected highlights of the international conference ``The Central
Kiloparsec of Starbursts and AGN: The La Palma Connection'', held in May 2001
in Los Cancajos on the Spanish island of La Palma.


title:
Archeops: A balloon experiment to measure CMB anisotropies with a broad
  range of angular sizes

abstract:
  The Cosmic Microwave Background Radiation is the oldest photon radiation that
can be observed, having been emitted when the Universe was about 300,000 year
old. It is a blackbody at 2.73 K, and is almost perfectly isotropic, the
anisotropies being about one part to 100,000. However, these anisotropies,
detected by the COBE satellite in 1992, constrain the cosmological parameters
such as the curvature of the Universe.
  Archeops is a balloon-borne experiment designed to map these anisotropies.
The instrument is composed of a 1.5 m telescope and bolometers cooled at 85 mK
to detect radiation between 150 and 550 GHz. To lower atmosphere parasitic
signal, the instrument is lifted at 32 km altitude with a stratospheric balloon
during the arctic night. This instrument is also a preparation for the Planck
satellite mission, as its design is similar.
  We discuss here the results of the first scientific flight from Esrange (near
Kiruna, Sweden) to Russia on January 29th 2001, which led to a 22 %
(sub)millimetre sky coverage unprecedented at this resolution.


title:
The Diabolo photometer and the future of ground-based millimetric
  bolometer devices

abstract:
  The millimetric atmospheric windows at 1 and 2 mm are interesting targets for
cosmological studies. Two broad areas appear leading this field: 1) the search
for high redshift star-forming galaxies and 2) the measurement of
Sunyaev-Zel'dovich (SZ) effect in clusters of galaxies at all redshifts. The
Diabolo photometer is a dual-channel photometer working at 1.2 and 2.1 mm and
dedicated to high angular resolution measurements of the Sunyaev--Zel'dovich
effect towards distant clusters. It uses 2 by 3 bolometers cooled down to 0.1 K
with a compact open dilution cryostat. The high resolution is provided by the
IRAM 30 m telescope. The result of several Winter campaigns are reported here,
including the first millimetric map of the SZ effect that was obtained by
Pointecouteau et al. (2001) on RXJ1347-1145, the non-detection of a millimetric
counterpart to the radio decrement towards PC1643+4631 and 2 mm number count
upper limits. We discuss limitations in ground-based single-dish millimetre
observations, namely sky noise and the number of detectors. We advocate the use
of fully sampled arrays of (100 to 1000) bolometers as a big step forward in
the millimetre continuum science. Efforts in France are briefly mentionned.


title: 1RXS J232953.9+062814: a New SU UMa Dwarf Nova below the Period Minimum

abstract:
  1RXS J232953.9+062814 was identified as a cataclysmic variable by Wei et al.
(1999). Four low-resolution spectra of 1RXS J232953.9+062814 were obtained by
using the 2.16-m telescope of the National Astronomical Observatories, in which
two of them were at outburst, and the other two were at quiescence. The system
is about 16.8 B and 16.5 V at quiescence, and 12.6 B and 12.6 V at outburst.
The quiescent spectra were dominated by double-peaked Balmer emissions, which
indicates a hydrogen-rich system with a high-inclination accretion disc. MgH
and TiO absorption bands appeared in the quiescent spectrum imply a companion
with a spectral type of early M dwarf. If we take it as a M0 dwarf, the system
is located at a distance of 350 pc with a proper motion velocity 150 km
s$^{-1}$. The superhump period of 0.046311 days (Uemura et al. 2001) was
confirmed by our V photometry. The short period and the hydrogen-rich nature
reveal that this system is another SU Ursae Majoris-type dwarf nova below the
period minimum after V485 Centauri. 1RXS J232953.9+062814 is one of the most
important systems for studying the evolutionary scenario of cataclysmic
variables since it is much brighter than V485 Cen.


title: The Multiple Stellar Populations in Omega Centauri

abstract:
  In this contribution I am going to present some preliminary results of a
high-resolution spectroscopic campaign focussed on the most metal rich red
giant stars in Omega Cen. This study is part of a long term project we started
a few years ago, which is aimed at studying the properties of the different
stellar populations in Omega Cen. The final goal of the whole project is the
global understanding of both the star formation and the chemical evolution
history of this complex stellar system.


title: The Bologna Key Project on Omega Cen

abstract:
  In this contribution we schematically summarize a number of ongoing,
coordinated spectro-photometric projects devoted to the study of the stellar
population properties in Omega Cen. All of these investigations are part of a
global comprehensive project led by our team to address the complex formation
history of stars in this cluster.


title: Chandra Spectroscopy of Pulsars and their Wind Nebulae

abstract:
  We present preliminary results from a systematic spectral study of pulsars
and their wind nebulae using the Chandra X-Ray Observatory. The superb spatial
resolution of Chandra allows us to differentiate the compact object's spectrum
from that of its surrounding nebulae. Specifically, for six Crab-like pulsars,
we compare spectral fits of the averaged pulsar wind nebulae (PWN) emission to
that of the central core using an absorbed power-law model. These results
suggest an empirical relationship between the bulk averaged photon indicies
(Gamma) for the PWNe and the pulsar cores; Gamma_PWN = 0.8 X Gamma_core + 0.8.
The photon indices of PWNe are found to fall in the range of 1.3 < Gamma_PWN <
2.3. We propose that the morphological and spectral characteristics of the
pulsars observed herein seem to indicate consistent emission mechanisms common
to all young pulsars. We point out that the previous spectral results obtained
for most X-ray pulsars are likely contaminated by PWN emission.


abstract:
  The summary of 1996-1998 visual observations collected by the Polish Comets
and Meteors Workshop is presented. In total, during 2328.12 effective observing
hours 14085 meteors were seen and plotted onto gnomonic starmaps by 41
observers. The date, time, magnitude, angular velocity and equatorial
coordinates for each observed event are given. The full 1996--1998 Polish
Visual Meteor Database (PVMDB) is accessible via INTERNET


title: 15 Years Going Steady - Timing the Magnetar 1E 1841-045

abstract:
  We report on a long-term monitoring campaign of 1E 1841-045, the 12-s
anomalous X-ray pulsar and magnetar candidate at the center of the supernova
remnant Kes 73. We have obtained approximately monthly observations of the
pulsar with the Rossi X-ray Timing Explorer spanning over two years, during
which time 1E 1841-045 is found to be rotating with sufficient stability to
derive a phase-connected timing solution. A linear ephemeris is consistent with
observations of the pulse period made over the last 15 yrs with the Ginga,
ASCA, XTE, & SAX observatories. Phase residuals suggest the presence of "timing
noise", as is typically observed from young radio pulsars. These results
confirm a rapid, constant spin-down for the pulsar, which continues to maintain
a steady flux; this is inconsistent with most accretion scenarios.


title: Asymmetric Supernovae from Magneto-Centrifugal Jets

abstract:
  Strong toroidal magnetic fields generated in stellar collapse can generate
magneto-centrifugal jets in analogy to those found in simulations of black hole
accretion and explain why all core collapse supernovae are found to be
substantially asymmetric and predominantly bi-polar. We describe two phases:
the initial LeBlanc-Wilson jet and a subsequent protopulsar or toroidal jet
that propagates at about the core escape velocity. The jets will produce bow
shocks that tend to expel matter, including iron and silicon, into equatorial
tori, accounting for observations of the element distribution in Cas A. A
magnetic ``switch'' mechanism may apply in instances of low density and large
magnetic field with subsequent increase in the speed and collimation of the
toroidal jet, depositing relatively little momentum. The result could be enough
infall to form a black hole with a third, highly relativistic jet that could
catch up to the protopulsar jet after it has emerged from the star. The
interaction of these two jets could generate internal shocks and explain the
presence of iron lines in the afterglow. Recent estimates that typical
gamma-ray burst energy is about 3x10^50 erg imply either a very low efficiency
for conversion of rotation into jets, or a rather rapid turnoff of the jet
process even though the black hole still rotates rapidly. Magnetars and
``hypernovae'' might arise in an intermediate parameter regime of energetic
jets that yield larger magnetic fields and provide more energy than the routine
case, but that are not so tightly collimated that they yield failed supernova.
(slightly abridged)


title: Hiccups in the night: X-ray monitoring of the two Crab-like LMC pulsars

abstract:
  We are undertaking an extensive X-ray monitoring campaign of the two
Crab-like pulsars in the Large Magellanic Clouds, PSR B0540-69 and PSR
J0537-6910. We present our current phase-connected timing analysis derived from
a set of 50 pointed X-ray observations spanning several years. From our initial
1.2 yr monitoring program of the young 50 ms pulsar PSR B0540-69, we find the
first compelling evidence for a glitch in its rotation. This glitch is
characterized by dv / v = 1.90 +/- 0.05 X 10E-9 and $dvdot/ vdot = (8.5 +/- 0.5
X 10E-5. Taking into account the glitch event, we derive a braking index of n =
1.81 +/- 0.07, significantly lower than previous reported. For the 16 ms
pulsar, PSR J0537-6910, we recorded 6 large glitch events during a period of
nearly 3 years, the highest rate of all known Crab-like systems. Despite the
extreme timing activity, the long term spin-down of this pulsar continues to
average -1.9743 X 10E-10 Hz/s.


title: Explaining the Lyman-alpha forest

abstract:
  It is shown that many properties of Ly-alpha forest absorbers can be derived
using simple physical arguments. Analytical expressions are derived for the
density and the size of an absorber as a function of its neutral hydrogen
column density, which agree well with both observations and hydrodynamical
simulations. An expression is presented to compute Omega_IGM from the observed
column density distribution, independent of the overall shape of the absorbers.
Application to the observed column density distribution shows that at high
redshift most of the baryons are in the forest and suggests a simple
interpretation for its shape and evolution.


title: Dark matter distribution in dwarf spheroidal galaxies

abstract:
  We study the distribution of dark matter in dwarf spheroidal galaxies by
modelling the moments of their line-of-sight velocity distributions. We discuss
different dark matter density profiles, both cuspy and possessing flat density
cores. The predictions are made in the framework of standard dynamical theory
of two-component (stars and dark matter) spherical systems with different
velocity distributions. We compare the predicted velocity dispersion profiles
to observations in the case of Fornax and Draco dwarfs. For isotropic models
the dark haloes with cores are found to fit the data better than those with
cusps. Anisotropic models are studied by fitting two parameters, dark mass and
velocity anisotropy, to the data. In this case all profiles yield good fits but
the steeper the cusp of the profile, the more tangential is the velocity
distribution required to fit the data. To resolve this well-known degeneracy of
density profile versus velocity anisotropy we obtain predictions for the
kurtosis of the line-of-sight velocity distribution for models found to provide
best fits to the velocity dispersion profiles. It turns out that profiles with
cores typically yield higher values of kurtosis which decrease more steeply
with distance than the cuspy profiles, which will allow to discriminate between
the profiles once the kurtosis measurements become available. We also show that
with present quality of the data the alternative explanation of velocity
dispersions in terms of Modified Newtonian Dynamics cannot yet be ruled out.


title: Hydrodynamical Models of Pulsar wind Bow-Shock Nebulae

abstract:
  We present hydrodynamical simulations, using a 2-D two fluid model, of bow
shocks in a representative regime for pulsar wind driven bow-shock nebulae. We
also investigate the behaviour of a passive toroidal magnetic field wounded
around the pulsar velocity direction. Moreover we estimate the opacity of the
bow-shock to penetration of ISM neutral hydrogen. Finally we compare these
numerical results with those from an analytical model.


title:
A new method for the estimate of H_0 from quadruply imaged gravitational
  lens systems

abstract:
  We present a new method to estimate the Hubble constant H_0 from the measured
time delays in quadruply imaged gravitational lens systems. We show how it is
possible to get an estimate of H_0 without the need to completely reconstruct
the lensing potential thus avoiding any a priori hypotheses on the expression
of the galaxy lens model. Our method only needs to assume that the lens
potential may be expressed as r^{\alpha} F(\theta), whatever the shape function
F(\theta) is, and it is thus able to fully explore the degeneracy in the mass
models taking also into account the presence of an external shear. We test the
method on simulated cases and show that it does work well in recovering the
correct value of the slope \alpha of the radial profile and of the Hubble
constant H_0. Then, we apply the same method to the real quadruple lenses
PG1115+080 and B1422+231 obtaining H_0 = 58_{-15}^{+17} km/s/Mpc (68% CL).


title: Software and Sociology in UK Astronomy

abstract:
  I discuss the remit of Starlink's software strategy groups and a particular
item on the agenda of a meeting of the image processing software strategy group
held on 26th January 2001: `Why don't people use Starlink software?'. The
answer to this question was speculated to be primarily a sociological effect:
those people supervising UK astronomy Ph.D. students are largely people who had
learnt their trade at a time when Starlink had a less than perfect reputation.
I report on the recommendations made to Starlink to counter this effect.


title: The Density and Location of the X-ray Absorbing Gas in NGC 3516

abstract:
  A new Chandra observation and archival observations by ASCA are used to
investigate spectral variations in the Sy1 galaxy NGC 3516 over a period of 7
years. A large change in flux (factor ~50 at 1keV) is observed between an ASCA
observation in '94 and the Chandra observation in 2000, with the source close
to the all-time maximum and minimum X-ray flux states, respectively. We find
the variations in the observed flux and spectra at these epochs to be
consistent with a constant column density of line-of-sight material reacting to
changes in the ionizing continuum. The data from the two epochs are consistent
with a simple decrease (by a factor 8-10) in the luminosity of a constant
0.5-50 keV slope source and a line-of-sight absorber with an equivalent
hydrogen column density of 10^21.9 cm^-2. Intermediate luminosities, sampled
during other ASCA observations, are all fitted by the same model with a very
small change in spectral index (well below \Delta\Gamma=0.2). In addition,
analysis of the long (360 ks) ASCA observation in 1998 shows clear "color"
variations that are entirely consistent with this model and are interpreted as
due to changes in the opacity of the absorbing gas. The data allow us to put a
conservative upper limit of 60 ks on the recombination time which translates to
a lower limit of about 2.4 times 10^6 cm^-3 on the density of the recombining
gas and an upper limit of about 6 times 10^17 h_{75}^-2 cm on its distance from
the central source. These are the best limits obtained so far on the density
and location of the X-ray absorbing gas in a type-1 AGN. They indicate that the
absorbing gas is different, in terms of its density and location, from the
ionized gas commonly observed in type-II AGN. [Abridged]


title: Oxygen and nitrogen abundances in Virgo and field spirals

abstract:
  The oxygen and nitrogen abundances in the HII regions of the nine Virgo
spirals of the sample from Skillman et al (1996) and in nine field spiral
galaxies are re-determined with the recently suggested P - method. We confirm
that there is an abundance segregation in the sample of Virgo spirals in the
sense that the HI deficient Virgo spirals near the core of the cluster have
higher oxygen abundances in comparison to the spirals at the periphery of the
Virgo cluster. At the same time both the Virgo periphery and core spirals have
counterparts among field spirals. We conclude that if there is a difference in
the abundance properties of the Virgo and field spirals, this difference
appears to be small and masked by the observational errors.


title:
The Galactic Centre Source IRS 13E: a Post-LBV Wolf-Rayet Colliding Wind
  Binary?

abstract:
  IRS 13E is an infrared, mm and X-ray source in the Galactic Centre. We
present the first Chandra X-ray spectrum for IRS 13E and show that it is
consistent with a luminous and highly absorbed X-ray binary system. Since the
X-ray luminosity is too large for a solitary star, our interpretation is that
of an early-type long-period binary with strong colliding winds emission. This
naturally explains the observed X-ray spectrum and count rate as well as its
lack of significant short term variability. Due to the short lifetime of any
nebula 0.2 pc from the putative central super-massive black-hole, we argue that
the primary of IRS 13E has exited the LBV phase in the last few thousand years.


title: X-Ray Spectral Components of Starburst Galaxies

abstract:
  X-ray emission processes in starburst galaxies (SBGs) are assessed, with the
aim of identifying and characterizing the main spectral components. Our survey
of spectral properties, complemented with a model for the evolution of galactic
stellar populations, leads to the prediction of a complex spectrum. Comparing
the predicted spectral properties with current X-ray measurements of the nearby
SBGs M82 and N253, we draw the following tentative conclusions: 1) X-ray
binaries with accreting NS are the main contributors in the 2-15 keV band, and
could be responsible for the yet uninterpreted hard component required to fit
the observed 0.5-10 keV spectra of SBGs; 2) diffuse thermal plasma contributes
at energies less than about 1 keV; 3) nonthermal emission, from Compton
scattering of FIR and CMB radiation field photons off supernova-accelerated
relativistic electrons, and AGN-like emission, are likely be the dominant
emission at energies >30 keV; 4) supernova remnants make a relatively minor
contribution to the X-ray continuum but may contribute appreciably to the Fe-K
emission at 6.7 keV.


title: Structure formation in the quintessential Universe

abstract:
  I review the main characteristics of structure formation in the
quintessential Universe. Assuming equation of state w=p/\varrho=$const I
provide a brief description of the background cosmology and discuss the linear
growth of density perturbations, the strongly nonlinear evolution, the power
spectra and rms fluctuations as well as mass functions focusing on the three
values w=-1, -2/3 and -1/3. Finally I describe the presently available and
future constraints on w.


title:
General Relativistic Electromagnetic Fields of a Slowly Rotating
  Magnetized Neutron Star. II. Solution of the Induction Equations

abstract:
  We have solved numerically the general relativistic induction equations in
the interior background spacetime of a slowly rotating magnetized neutron star.
The analytic form of these equations was discussed in a recent paper (Rezzolla
et al 2001a), where corrections due both to the spacetime curvature and to the
dragging of reference frames were shown to be present. Through a number of
calculations we have investigated the evolution of the magnetic field with
different rates of stellar rotation, different inclination angles between the
magnetic moment and the rotation axis, as well as different values of the
electrical conductivity. All of these calculations have been performed for a
constant temperature relativistic polytropic star and make use of a consistent
solution of the initial value problem which avoids the use of artificial
analytic functions. Our results show that there exist general relativistic
effects introduced by the rotation of the spacetime which tend to decrease the
decay rate of the magnetic field. The rotation-induced corrections are however
generally hidden by the high electrical conductivity of the neutron star matter
and when realistic values for the electrical conductivity are considered, these
corrections become negligible even for the fastest known pulsar.


title:
The Structure of the Oxygen-rich Supernova Remnant G292.0+1.8 from
  Chandra X-ray Images: Shocked Ejecta and Circumstellar Medium

abstract:
  We present results from the observation of the young Galactic supernova
remnant (SNR) G292.0+1.8 with the Advanced CCD Imaging Spectrometer (ACIS) on
board the {\it Chandra X-ray Observatory}. In the 0.3 $-$ 8 keV band, the high
resolution ACIS images reveal a complex morphology consisting of knots and
filaments, as well as the blast wave around the periphery of the SNR. We
present equivalent width (EW) maps for the elemental species O, Ne, Mg, and Si,
which allow us to identify regions of enhanced metallicity in the SNR.
G292.0+1.8 is bright in O, Ne, and Si; weaker in S and Ar; with little Fe. The
EW and broad-band images indicate that the metal-rich ejecta are distributed
primarily around the periphery of the SNR. The central belt-like structure has
normal solar-type composition, strongly suggesting that it is primarily
emission from shocked circumstellar medium rather than metal-rich ejecta. We
propose that the belt traces its origin to enhanced mass loss in the star's
equatorial plane during the slow, red supergiant phase. We also identify thin
filaments with normal composition, centered on and extending nearly
continuously around the outer boundary of the SNR. These may originate in a
shell caused by the stellar winds from the massive progenitor in the red/blue
supergiant phases, over-run by the blast wave.


title: Ongoing massive star formation in the bulge of M51

abstract:
  We studied the HST-WFPC2 observations of the inner kpc of the interacting
galaxy M51 in six bands from 2550 to 8140 Angstrom. The images show an oval
shaped area ("bulge") of 11x16 arcsec or 450x650 pc around the nucleus,
dominated by a smooth population of old stars with overimposed dust lanes. We
found 30 bright point-like sources in the bulge of M51; many of these are
bright in the UV. They are located in elongated "strings" which follow the
general pattern of the dust lanes. The spectral energy distributions of the
pointsources are compared with those of clusters or single stars. We present
arguments that the pointsources are isolated massive stars or small groups of a
few massive stars. The energy distributions are best fitted with those of
single stars with 4000<Teff<50000 K, 4.2<log L/Lsun<7.2, and 12<Mstar<200 Msun.
We have derived upper limits to the total mass of low mass stars that could be
"hiding" within the point sources. For the bluest sources the upper limit is
only a few hundred Msun. We conclude that massive stars are formed outside
clusters (or in very low mass clusters) in the bulge of M51. The estimated star
formation rate in the bulge is 1 to 2x10^(-3) Msun/yr. This star formation rate
could be sustained for about 200 to 400 Myrs, suggesting that the ongoing
massive star formation in the bulge of M51 is fed/triggered by the interaction
with its companion about 400 Mrs ago. Theoretical cloud-models show that CO is
destroyed in low extinction clouds near the bright nucleus of M51, so that H_2,
[OI] and [CII] are the dominants coolants. This condition favors the formation
of massive stars, in agreement with the observations. This mode of massive-star
formation in the bulge of M51 may resemble the star formation in the early
Universe, when the CO and dust contents were low due to the low metallicity.


title: Non-circular rotating beams and CMB experiments

abstract:
  This paper is concerned with small angular scale experiments for the
observation of cosmic microwave background anisotropies. In the absence of
beam, the effects of partial coverage and pixelisation are disentangled and
analyzed (using simulations). Then, appropriate maps involving the CMB signal
plus the synchrotron and dust emissions from the Milky Way are simulated, and
an asymmetric beam --which turns following different strategies-- is used to
smooth the simulated maps. An associated circular beam is defined to estimate
the deviations in the angular power spectrum produced by beam asymmetry without
rotation and, afterwards, the deviations due to beam rotation are calculated.
For a certain large coverage, the deviations due to pure asymmetry and
asymmetry plus rotation appear to be very systematic (very similar in each
simulation). Possible applications of the main results of this paper to data
analysis in large coverage experiments --as PLANCK-- are outlined.


title: An Upper Limit to the Mass of rho1 Cnc's Radial Velocity Companion

abstract:
  Doppler spectroscopy of rho1 Cnc has detected evidence of a companion with an
orbital period of 14.65 days and a minimum mass of 0.88 Jupiter masses.
Astrometric observations performed with the Hubble Space Telescope Fine
Guidance Sensor 1r using a novel new observing technique have placed an upper
limit on the astrometric reflex motion of rho1 Cnc in a time period of only one
month. These observations detected no reflex motion induced by the 14.65 day
period radial velocity companion, allowing us to place a 3-sigma upper limit of
\~0.3 milliarcseconds on the semi-major axis of this motion, ruling out the
preliminary Hipparcos value of 1.15 milliarcseconds. The corresponding upper
limit on the true mass of the companion is ~30 Mj, confirming that it is a
sub-stellar object.


title:
Chandra X-ray Spectroscopy of Kes75, its Young Pulsar, and its
  Synchrotron Nebula

abstract:
  We have observed the young Galactic supernova remnant Kes 75 with the Chandra
X-ray Observatory. This object is one of an increasing number of examples of a
shell-type remnant with a central extended radio core harboring a pulsar. Here
we present a preliminary spatially resolved spectroscopic analysis of the
Kes~75 system. We find that the spectrum of the pulsar is significantly harder
than that of the wind nebula, and both of these components can be isolated from
the diffuse thermal emission that seems to follow the same distribution as the
extended radio shell. When we characterize the thermal emission with a model of
an under-ionized plasma and non-solar elemental abundances, we require a
significant diffuse high energy component, which we model as a power-law with a
photon index similar to that of the synchrotron nebula.


title: B1422+231: The influence of mass substructure on strong lensing

abstract:
  In this work we investigate the gravitationally lensed system B1422+231.
High--quality VLBI image positions, fluxes and shapes as well as an optical HST
lens galaxy position are used. First, two simple and smooth models for the lens
galaxy are applied to fit observed image positions and fluxes; no even remotely
acceptable model was found. Such models also do not accurately reproduce the
image shapes. In order to fit the data successfully, mass substructure has to
be added to the lens, and its level is estimated. To explore expectations about
the level of substructure in galaxies and its influence on strong lensing,
N-body simulation results of a model galaxy are employed. By using the mass
distribution of this model galaxy as a lens, synthetic data sets of different
four image system configurations are generated and simple lens models are again
applied to fit them. The difficulties in fitting these lens systems turn out to
be similar to the case of some real gravitationally lensed systems, thus
possibly providing evidence for the presence and strong influence of
substructure in the primary lens galaxy.


title: Massive Star Mergers: Induced Mixing and Nucleosynthesis

abstract:
  We study the nucleosynthesis and the induced mixing during the merging of
massive stars inside a common envelope. The systems of interest are close
binaries, initially consisting of a massive red supergiant and a main-sequence
companion of a few solar masses. We apply parameterized results based on
hydrodynamical simulations to model the stream-core interaction and the
response of the star in a standard stellar-evolution code. Preliminary results
are presented illustrating the possibility of unusual nucleosynthesis and
post-merging dredge-up which can cause composition anomalies in the
supergiant's envelope.


title:
Optical and Near-Infrared Structural Properties of Cluster Galaxies at
  $z \sim 0.3$

abstract:
  Structural parameters (half-light radius $r_e$, mean effective surface
brightness $<\mu>_e$, and Sersic index n) are derived for a sample of galaxies
in the rich cluster AC 118 at z=0.31: so far the largest (N=93) sample of
galaxies at intermediate-redshift with structural parameters measured in the
near-infrared. The parameters are obtained in two optical wavebands (V and R)
and in the K-band. The distributions of $r_e$ at z=0.31 match those for the
Coma cluster both in the optical and in the NIR. The similarity of the two
distributions proves that the galaxies at the bright end of the luminosity
function did not significantly change their sizes since $z\sim0.3$ to the
present epoch. The ratio of the optical to the NIR half-light radius shows a
marked trend with the Sersic index n. In galaxies with $n\gtrsim4$ (typical
bright ellipticals) $r_{e,NIR}\sim 0.6 r_{e,opt}$, while the average ratio is
0.8 for galaxies with lower n (typical disk systems). Moreover, the NIR Sersic
index is systematically larger than in the optical for $n\lesssim4$. These
results, translated into optical and optical-NIR color gradients, imply that
the optical color gradients at $z\sim$0.3 are similar to those of nearby
galaxies. The optical-NIR color gradients are larger, ranging from -0.73
mag/dex for $n\lesssim4$ to -0.35 mag/dex for $n\gtrsim4$. We discuss these
results in terms of 'pure age' and 'pure metallicity' gradient models. The lack
of any major change in $r_{e,NIR}$ since $z\sim0.3$ suggests that merging
involving bright galaxies did not play a significant role in the last $\sim$4.4
Gyr.


title: Analysis of On-Orbit ACIS Squeegee Mode Data on Chip I0

abstract:
  The MIT and CXC ACIS teams have explored a number of measures to ameliorate
the effects of radiation damage suffered by the ACIS FI CCDs. One of these
measures is a novel CCD read-out method called ``squeegee mode''. A variety of
different implementations of the squeegee mode have now been tested on the I0
CCD.
  Our results for the fitted FWHM at Al-K$\alpha$ and Mn-K$\alpha$ clearly
demonstrate that all the squeegee modes provide improved performance in terms
of reducing CTI and improving spectral resolution. Our analysis of the
detection efficiency shows that the so-called squeegee modes ``Vanilla'' and
``Maximum Observing Efficiency'' provide the same detection efficiency as the
standard clocking, once the decay in the intensity of the radioactive source
has been taken into account. The squeegee modes which utilize the slow parallel
transfer (``Maximum Spectral Resolution'', ``Maximum Angular Resolution'', and
``Sub-Array'') show a significantly lower detection efficiency than the
standard clocking. The slow parallel transfer squeegee modes exhibit severe
grade migration from flight grade 0 to flight grade 64 and a smaller migration
into ASCA g7. The latter effect can explain some of the drop in detection
efficiency. (ABRIDGED ABSTRACT)


title: Spatially resolved imaging spectroscopy of T Tauri

abstract:
  The small separation of the individual stellar components in the TTau system
has prevented spectroscopy of the individual components in the near-infrared
(NIR) in the past. We present NIR data (H- and K-band) on this object taken
using the ALFA adaptive optics (AO) system in combination with the 3D integral
field spectrograph. Except for the Brackett series seen in emission, the NIR
spectra of \tts{} appear featureless, suggesting that warm dust dominates the
radiation. No ro-vibrational lines of molecular hydrogen were found in close
vicinity to the stars. The Brackett line emission from \ttn{} and S could not
be resolved with the 3.5-m-telescope, implying that it arises within 6 AU from
the stars. The line ratios between Br$\gamma$ (2.166 \mum{}) and Br10 (1.736
\mum{}) toward \ttn{} and \tts{} are similar, suggesting similar selective
extinctions towards the respective emitting regions. Our results are consistent
with a model that describes \tts{} as a pre-main sequence star surrounded by a
small edge-on disk, leaving the polar regions relatively unobscured. We present
numerical simulations which support this model.


title:
The 2dF Galaxy Redshift Survey: The dependence of galaxy clustering on
  luminosity and spectral type

abstract:
  We investigate the dependence of galaxy clustering on luminosity and spectral
type using the 2dF Galaxy Redshift Survey (2dFGRS). Spectral types are assigned
using the principal component analysis of Madgwick et al. We divide the sample
into two broad spectral classes: galaxies with strong emission lines
(`late-types'), and more quiescent galaxies (`early-types'). We measure the
clustering in real space, free from any distortion of the clustering pattern
due to peculiar velocities, for a series of volume-limited samples. The
projected correlation functions of both spectral types are well described by a
power law for transverse separations in the range 2 < (sigma/Mpc/h) < 15, with
a marginally steeper slope for early-types than late-types. Both early and late
types have approximately the same dependence of clustering strength on
luminosity, with the clustering amplitude increasing by a factor of ~2.5
between L* and 4 L*. At all luminosities, however, the correlation function
amplitude for the early-types is ~50% higher than that of the late-types. These
results support the view that luminosity, and not type, is the dominant factor
in determining how the clustering strength of the whole galaxy population
varies with luminosity.


title: Hard X-ray states and radio emission in GRS 1915+105

abstract:
  We have compared simultaneous Ryle Telescope radio and Rossi X-Ray Timing
Explorer X-ray observations of the galactic microquasar GRS 1915+105, using the
classification of the X-ray behaviour in terms of three states as previously
established. We find a strong (one-to-one) relation between radio oscillation
events and series of spectrally hard states in the X-ray light curves, if the
hard states are longer than ~100s and are "well separated" from each other. In
all other cases the source either shows a low-level or a high level radio
emission, but no radio oscillation events. During intervals when the source
stays in the hard spectral state for periods of days to months, the radio
behaviour is quite different; during some of these intervals a quasi-continuous
jet is formed with an almost flat synchrotron spectrum extending to at least
the near-infrared. Based on the similarities between the oscillation profiles
at different wavelengths, we suggest a scenario which can explain most of the
complex X-ray : radio behaviour of GRS 1915+105. We compare this behaviour with
that of other black hole sources and challenge previous reports of a relation
between spectrally soft X-ray states and the radio emission.


title: On QSO Distances and Lifetimes in a Local Model

abstract:
  It was previously shown from the redshifts and positions of the compact,
high-redshift objects near the Seyfert galaxy NGC 1068 that they appear to have
been ejected from the center of the galaxy in at least four similarly
structured triplets. Here some of the consequences of assuming such a local
model for QSOs are examined. From the ages of the ejection events it is found
that in a relatively short time (10 - 100 million years) the intrinsic redshift
component in these objects disappears and their luminosity increases to a value
close to that of a normal galaxy. This period may then determine the
approximate lifetime of a QSO and, in this scenario, QSOs may represent the
first, short-lived stage in the life of a galaxy. It is shown that when QSOs
are assumed to be "local", their generation rate is found to be constant
throughout the age of the Universe. There is no need to invoke an epoch of
enhanced, high-luminosity QSO production as is required if their redshifts are
assumed to be purely cosmological. Because QSO lifetimes are relatively short
(less than 100 million yrs), an initial event (Big Bang) may still be required
to explain the high-redshift galaxies whose intrinsic redshift component will
have long since disappeared. The Hubble expansion is therefore still expected
to apply for normal galaxies.


title: On the possible reason for non-detection of TeV-protons in SNRs

abstract:
  The theory of shock acceleration predicts the maximum particle energy to be
limited only by the acceleration time and the size (geometry) of the shock.
This led to optimistic estimates for the galactic cosmic ray energy achievable
in the SNR shocks. The estimates imply that the accelerated particles, while
making no strong impact on the shock structure (test particle approach) are
nevertheless scattered by strong self-generated Alfven waves (turbulent boost)
needed to accelerate them quickly. We demonstrate that these two assumptions
are in conflict when applied to SNRs of the age required for cosmic ray
acceleration to the ``knee'' energy.
  We study the combined effect of acceleration nonlinearity (shock modification
by accelerated particles) and wave generation on the acceleration process. We
show that the refraction of self-generated waves resulting from the
deceleration of the plasma flow by the pressure of energetic particles causes
enhanced losses of these particles. This effect slows down the acceleration and
changes the shape of particle spectrum near the cut-off. The implications for
observations of TeV emission from SNR remnants are also discussed.


title: Low-Mass Neutron Stars as Anomalous Pulsars

abstract:
  A neutron star with mass close to the lower limit might be a reasonable model
for some anomalous pulsars. Emission is thermal. X-ray luminosity is high.
Spatial velocity can be high. Since the radius is predicted to be large, the
magnetic field calculated for spin-down is lower than that required by the
magnetar model.


title: X-ray Spectroscopy of Cataclysmic Variables

abstract:
  In cataclysmic variables (CVs), accretion onto white dwarfs produces high
temperature, high density plasmas. They cool down from kT~10 keV via
bremsstrahlung continuum and K and L shell line emissions. The small volume
around white dwarfs means that the plasma densities are much higher than in,
e.g., stellar coronae, probably beyond the range well-described by existing
models. I will describe potential diagnostics of the temperatures, the
densities, and the optical depths of X-ray emitting plasmas in CVs, and present
the recent Chandra grating spectra of the magnetic CV V1223 Sgr as an example.


title: A Non-parametric Analysis of the CMB Power Spectrum

abstract:
  We examine Cosmic Microwave Background (CMB) temperature power spectra from
the BOOMERANG, MAXIMA, and DASI experiments. We non-parametrically estimate the
true power spectrum with no model assumptions. This is a significant departure
from previous research which used either cosmological models or some other
parameterized form (e.g. parabolic fits). Our non-parametric estimate is
practically indistinguishable from the best fit cosmological model, thus
lending independent support to the underlying physics that governs these
models. We also generate a confidence set for the non-parametric fit and
extract confidence intervals for the numbers, locations, and heights of peaks
and the successive peak-to-peak height ratios. At the 95%, 68%, and 40%
confidence levels, we find functions that fit the data with one, two, and three
peaks respectively (0 <= l <= 1100). Therefore, the current data prefer two
peaks at the 1 sigma level. However, we also rule out a constant temperature
function at the >8 sigma level. If we assume that there are three peaks in the
data, we find their locations to be within l_1 = (118,300), l_2 = (377,650),
and l_3 = (597,900). We find the ratio of the first peak-height to the second
(Delta T_1)/(Delta T_2)^2= (1.06, 4.27) and the second to the third (Delta
T_2)/(Delta T_3)^2= (0.41, 2.5). All measurements are for 95% confidence. If
the standard errors on the temperature measurements were reduced to a third of
what they are currently, as we expect to be achieved by the MAP and Planck CMB
experiments, we could eliminate two-peak models at the 95% confidence limit.
The non-parametric methodology discussed in this paper has many astrophysical
applications.


title: Non-Parametric Inference in Astrophysics

abstract:
  We discuss non-parametric density estimation and regression for astrophysics
problems. In particular, we show how to compute non-parametric confidence
intervals for the location and size of peaks of a function. We illustrate these
ideas with recent data on the Cosmic Microwave Background. We also briefly
discuss non-parametric Bayesian inference.


title:
A Comparative Study of the Absolute-Magnitude Distributions of
  Supernovae

abstract:
  The Asiago Supernova Catalog is used to carry out a comparative study of
supernova absolute-magnitude distributions. An overview of the absolute
magnitudes of the supernovae in the current observational sample is presented,
and the evidence for subluminous and overluminous events is examined. The
fraction of supernovae that are underluminous (M_B > -15) appears to be higher
(perhaps much higher) than one fifth but it remains very uncertain. The
fraction that are overluminous (M_B < -20) is lower (probably much lower) than
0.01. The absolute-magnitude distributions for each supernova type, restricted
to events within 1 Gpc, are compared. Although these distributions are affected
by observational bias in favor of the more luminous events, they are useful for
comparative studies. We find mean absolute blue magnitudes (for H_0=60) of
-19.46 for normal Type Ia supernovae (SNe Ia), -18.04 for SNe Ibc, -17.61 and
-20.26 for normal and bright SNe Ibc considered separately, -18.03 for SNe
II-L, -17.56 and -19.27 for normal and bright SNe II-L considered separately,
-17.00 for SNe II-P, and -19.15 for SNe IIn.


title: The CMB - Contemporary Measurements and Cosmology

abstract:
  Since the discovery of the Cosmic Microwave Background (CMB) in 1965,
characterization of the CMB anisotropy angular power spectrum has become
somewhat of a holy grail for experimental cosmology. Because CMB anisotropy
measurements are difficult, the full potential of the CMB is only now being
realized. Improvements in experimental techniques and detector technology have
yielded an explosion of progress in the past couple of years resulting in the
ability to use measurements of the CMB to place meaningful constraints on
cosmological parameters. In this review, I discuss the theory behind the CMB
but focus primarily on the experiments, reviewing briefly the history of CMB
anisotropy measurements and focusing on the recent experiments that have
revolutionized this field. Results from these modern experiments are reviewed
and the cosmological implications discussed. I conclude with brief comments
about the future of CMB physics.


title: The Pulsar Wind Nebula of G11.2-0.3

abstract:
  We present high-resolution radio and X-ray studies of the composite supernova
remnant G11.2-0.3. Using archival VLA data, we perform radio spectral
tomography to measure for the first time the spectrum of the shell and plerion
separately. We compare the radio morphology of each component to that observed
in the hard and soft Chandra X-ray images. We measure the X-ray spectra of the
shell and the emission in the interior and discuss the hypothesis that soft
X-ray emission interior to the shell is the result of the expanding pulsar wind
shocking with the supernova ejecta. We also see evidence for spatial
variability in the hard X-ray emission near the pulsar, which we discuss in
terms of ion mediated relativistic shocks.


title: Euler, Jacobi, and Missions to Comets and Asteroids

abstract:
  Whenever a freely spinning body is found in a complex rotational state, this
means that either the body is a recent victim of an impact or a tidal
interaction, or is a fragment of a recently disrupted progenitor. Another
factor (relevant for comets) is outgassing. Due to impacts, tidal forces and
outgassing, the asteroidal and cometary precession must be a generic
phenomenon: while some rotators are in the state of visible tumbling, a much
larger amount of objects must be performing narrow-cone precession not so
easily observable from the Earth. The internal dissipation in a freely
precessing top leads to relaxation (gradual damping of the precession) and
sometimes to spontaneous changes in the rotation axis. Recently developed
theory of dissipative precession of a rigid body reveals that this is a highly
nonlinear process: while the body is precessing at an angular rate $ \omega$,
the precession-caused stresses and strains in the body contain components
oscillating at other frequencies. Dependent upon the spin state, those
frequencies may be higher or, most remarkably, lower than the precession rate.
In many states dissipation at the harmonics is comparable to or even exceeds
that at the principal frequency. For this and other reasons, in many spin
states the damping of asteroidal and cometary wobble happens faster, by several
orders, than believed previously. This makes it possible to measure the
precession-damping rate. The narrowing of the precession cone through the
period of about a year can be registered by the currently available
spacecraft-based observational means. However, in the near-separatrix spin
states a precessing rotator can considerably slow down its relaxation.


title: Filaments in the Galactic Center -- with special reference to the Snake

abstract:
  The nonthermal filaments in the Galactic Center constitute one of the great
mysteries of this region of the Galaxy. We summarise the observational data on
these filaments and critically review the various theories which currently
outnumber the observed filaments. We summarise out theory for the longest of
these filaments, the Snake, and discuss the relevance of this model for the
other filaments in the Galactic Center region. The physics involved in our
model for the Snake involves much of the physics that has dominated the career
of Professor Don Melrose. In particular, the diffusion of relativistic
electrons in the Snake is determined from the theory of resonant scattering by
Alfv\'en waves.


title:
Stellar Nuclear Rings in Barred Galaxies: Fossils of Past Circumnuclear
  Starbursts?

abstract:
  We have found four barred S0 galaxies -- NGC 936, NGC 3945, NGC 4340, and NGC
4371 -- which contain smooth, luminous, purely stellar nuclear rings within
their bars. These rings have little or no dust, no evidence for recent star
formation, and are approximately the same color as surrounding bar and bulge.
Thus, they are probably the aged remnants of bar-driven circumnuclear starburst
episodes similar to those seen in barred galaxies today.
  Using kinematic data from long-slit spectroscopy, we construct rotation and
resonance curves for two of the galaxies. In both cases, the nuclear rings
appear to be located near or at the inner inner Lindblad resonances of the
large-scale bars.
  We also discuss the difficulties inherent in detecting and identifying such
rings, and show some of the surprising ways in which stellar rings can distort
galaxy isophotes and ellipse fits.


title: The HI Environment of Three Superbubbles in the Large Magellanic Cloud

abstract:
  The ambient interstellar environment of wind- and supernova-driven
superbubbles strongly affects their evolution, but its properties are rarely
well-determined. We have therefore obtained HI aperture synthesis imaging of
the environment around three similar, optically-selected superbubble nebulae in
the Large Magellanic Cloud. The resulting HI maps show that the ambient gas
distribution around these superbubbles differ to an extreme: DEM L25 shows no
neutral shell component, but is nestled within an HI hole; DEM L50 shows a
massive neutral shell component, but is otherwise within an HI void; and DEM
L301 shows no correspondence at all between the optical nebula and HI
distribution. There is also poor correspondence between the HI and optical
kinematics. These results strongly caution against inferring properties of the
ambient neutral environment of individual superbubbles without direct
observations. Finally, all three objects show some evidence of shock activity.


title: From Neutron Stars to Strange Stars

abstract:
  This paper discusses several most intruigung astrophysical implications
connected with the possible absolute stability of strange quark matter.This is
followed by a discussion of two astrophysical signals that may point at the
existence of quark matter in both isolated neutron stars as well as in neutron
stars in low-mass x-ray binaries (LMXBs).


title: Evolution and Explosion of Very Massive Primordial Stars

abstract:
  While the modern stellar IMF shows a rapid decline with increasing mass,
theoretical investigations suggest that very massive stars (>100 solar masses)
may have been abundant in the early universe. Other calculations also indicate
that, lacking metals, these same stars reach their late evolutionary stages
without appreciable mass loss. After central helium burning, they encounter the
electron-positron pair instability, collapse, and burn oxygen and silicon
explosively. If sufficient energy is released by the burning, these stars
explode as brilliant supernovae with energies up to 100 times that of an
ordinary core collapse supernova. They also eject up to 50 solar masses of
radioactive Ni56. Stars less massive than 140 solar masses or more massive than
260 solar masses should collapse into black holes instead of exploding, thus
bounding the pair-creation supernovae with regions of stellar mass that are
nucleosynthetically sterile. Pair-instability supernovae might be detectable in
the near infrared out to redshifts of 20 or more and their ashes should leave a
distinctive nucleosynthetic pattern.


title:
Contribution of starburst mergers at z~1 to the strong evolution of
  infrared and submillimeter deep surveys

abstract:
  Recent FIR/submm deep surveys revealed large number of ULIGs, which are
proposed to lie at z>1, and in normally interacting systems with very dusty
environments. We discussed in a previous paper that a population with a fast
evolving infrared burst phase triggered by gas rich mergers at z~1 interpreted
successfully the steep slope of IRAS 60um counts, leaving still a reasonable
CIRB level at this wavelength. To extend the model to mid- and far-IR, we adopt
a template SED as typical for nearby IR bright galaxies, such as Arp220. We
construct the SED for the starburst mergers at z~1 by a simple dust extinction
law and a thermal continuum assumption for the FIR emission. Since the
radiation process at MIR for the merging systems is still uncertain, we assume
it is similar to that of Arp220, but modify it by the observed flux correlation
of ULIGs from IRAS, ISOCAM deep surveys. We show in this paper that the strong
evolution of the ELAIS 90um, ISO 170um and the SCUBA 850um could be
sufficiently accounted for by such an evolutionary scenario, especially for the
hump of the ISOCAM 15um source count around 0.4mJy. From current best fit
results, we find that the dust temperature of those merging system at z~1 would
be higher than that of Arp220 for a reconciliation of the multi-wavelength deep
surveys. The major difference of our current model prediction is that we see a
fast convergence of the differential number counts at 60um below 50mJy, which
is about a factor of two brighter than other model predictions. Future IR
satellite like Astro-F,SIRTF would give strong constraints to the models.