title:
Observation and Modelling of Starburst Driven Galactic Winds: A Review
  in honour of John Dyson

abstract:
  Starburst galaxies are generally associated with extended X-ray and radio
halos, giving a clear hint of an outflow of gas and relativistic particles from
the disk into the halo. The driving agents are, not surprisingly, active star
forming regions, injecting hot gas and cosmic rays generated by supernova
remnant and superbubble shock waves. The dynamics of the outflow and the
thermal evolution of the plasma are strongly coupled, and therefore a
self-consistent model is necessary for a satisfactory description. Since the
plasma temperature is between one and a few million Kelvin, the halo is most
conspicuous in soft X-rays. It will be shown that X-ray data obtained recently
with XMM-Newton EPIC pn bear clear spectral signatures that are in strong
disagreement with an isothermal halo in collisional ionization equilibrium
(CIE). Instead a temperature structure in X-ray halos is observed. It will be
demonstrated that a galactic wind outflow model in which the non-equilibrium
ionization structure is calculated self-consistently can give a satisfactory
and physical explanation for the X-ray spectral characteristics, e.g. in case
of the local starburst galaxy NGC 3079. In particular, high subsolar
abundances, that have been reported from X-ray observations in some cases, are
shown to be artefacts of CIE spectral fit models. It is found that spectral
models are strongly constrained by the presence of diagnostic lines such as
OVII and OVIII as well as Fe-L line complexes. Thus a detailed spectral X-ray
model will help to provide important galactic wind parameters, such as mass
loss rate and velocity profile, which may also serve as valuable input for
galactic outflows in the early universe.


title: Multi-epoch spectroscopy and XMM-Newton observations of RX J2115-58

abstract:
  We present phase resolved optical spectroscopy and X-ray light curves of the
asynchronous polar RX J2115-58 as they change on the beat period.


title: Evidence and Implications of Pressure Fluctuations in the ISM

abstract:
  A recent survey of the fine-structure excitation of neutral carbon reveals
that the interstellar medium in the Galactic plane exhibits a thermal pressure,
nT/k, that ranges from about 10^3 to 10^4 cm{-3}K from one location to the
next, with occasional excursions in excess of about 10^5 cm^{-3}K. The large
excitations for small amounts of gas indicate that some regions are either
subjected to shocks or must be pressurized within time scales much shorter than
the time needed to reach thermal equilibrium. These rapid fluctuations probably
arise from the cascade of macroscopic mechanical energy to small scales through
a turbulent cascade. One consequence of this effect is that changes in gas
temperature can arise from near adiabatic compressions and expansions, and this
may explain why investigations of 21-cm emission and absorption reveal the
presence of hydrogen at temperatures well below the expected values derived
from the balance of various known heating and cooling processes.


title:
A wide field Hubble Space Telescope study of the cluster CL0024+16 at
  z=0.4. I: morphological distributions to 5 Mpc radius

abstract:
  We describe a new wide field Hubble Space Telescope survey of the galaxy
cluster Cl0024+16 (z~0.4) consisting of a sparse-sampled mosaic of 39 Wide
Field and Planetary Camera 2 images which extends to a cluster radius of 5 Mpc.
[Abridged] We examine both the morphology-radius (T-R) and morphology-density
(T-Sigma) relations and demonstrate sensitivities adequate for measures from
the core to a radius of 5 Mpc, spanning over 3 decades in local projected
density. The fraction of early-type galaxies declines steeply from the cluster
center to 1 Mpc radius and more gradually thereafter, asymptoting towards the
field value at the periphery. We discuss our results in the context of three
distinct cluster zones, defined according to different physical processes that
may be effective in transforming galaxy morphology in each. By treating
infalling galaxies as isolated test particles, we deduce that the most likely
processes responsible for the mild gradient in the morphological mix outside
the virial radius are harassment and starvation. Although more data are needed
to pin down the exact mechanisms, starvation seems more promising in that it
would naturally explain the stellar and dynamical homogeneity of cluster E/S0s.
However, we find significant scatter in the local density at any given radius
outside 0.5 Mpc, and that the same T-Sigma relation holds in subregions of the
cluster, independent of location. In this hitherto unprobed region, where the
potential of the cluster is weak, galaxies apparently retain their identities
as members of infalling sub-groups whose characteristic morphological
properties remain intact. Only upon arrival in the central regions is the
substructure erased, as indicated by the tight correlation between cluster
radius and Sigma.


title: A post-WMAP perspective on inflation

abstract:
  Recent results from the Wilkinson Microwave Anisotropy Probe have been called
a corroboration, or even a confirmation, of inflation. Yet, the results include
features that require, at least, a significant distortion of what is usually
meant by inflation. At the same time, critics have leveled the charge that
inflation is an arbitrarily pliable theory and is therefore beyond proof or
disproof. This startling dissonance in attitudes toward inflation seems to have
grown out of the lack of a clear framework with which to evaluate the
inflationary paradigm. In this rhetorical pamphlet we reexamine the
inflationary paradigm, attempt to articulate explicitly how the paradigm and
its descendant models are falsifiable, and make a sober assessment of the
successes and failures of inflation.


title: Oligarchic growth of giant planets

abstract:
  Runaway growth ends when the largest protoplanets dominate the dynamics of
the planetesimal disk; the subsequent self-limiting accretion mode is referred
to as ``oligarchic growth.'' Here, we begin by expanding on the existing
analytic model of the oligarchic growth regime. From this, we derive global
estimates of the planet formation rate throughout a protoplanetary disk. We
find that a relatively high-mass protoplanetary disk ($\sim$ 10$\times$
minimum-mass) is required to produce giant planet core-sized bodies ($\sim$ 10
M$_{\oplus}$) within the lifetime of the nebular gas ($\la$ 10 million years).
However, an implausibly massive disk is needed to produce even an Earth mass at
the orbit of Uranus by 10 Myrs. Subsequent accretion without the dissipational
effect of gas is even slower and less efficient. In the limit of
non-interacting planetesimals, a reasonable-mass disk is unable to produce
bodies the size of the Solar System's two outer giant planets at their current
locations on {\it any} timescale; if collisional damping of planetesimal random
velocities is sufficiently effective, though, it may be possible for a
Uranus/Neptune to form in situ in less than the age of the Solar System. We
perform numerical simulations of oligarchic growth with gas, and find that
protoplanet growth rates agree reasonably well with the analytic model as long
as protoplanet masses are well below their estimated final masses. However,
accretion stalls earlier than predicted, so that the largest final protoplanet
masses are smaller than those given by the model. Thus the oligarchic growth
model, in the form developed here, appears to provide an upper limit for the
efficiency of giant planet formation.


title: On the Relationship between Cooling Flows and Bubbles

abstract:
  A common feature of the X-ray bubbles observed in Chandra images of some
"cooling flow" clusters is that they appear to be surrounded by bright, cool
shells. Temperature maps of a few nearby luminous clusters reveal that the
shells consist of the coolest gas in the clusters -- much cooler than the
surrounding medium. Using simple models, we study the effects of this cool
emission on the inferred cooling flow properties of clusters. We find that the
introduction of bubbles into model clusters that do NOT have cooling flows
results in temperature and surface brightness profiles that resemble those seen
in nearby "cooling flow" clusters. They also approximately reproduce the recent
XMM-Newton and Chandra observations of a high minimum temperature of 1-3 keV.
Hence, bubbles, if present, must be taken into account when inferring the
physical properties of the ICM. In the case of some clusters, bubbles may
account entirely for these observed features, calling into question their
designation as clusters with cooling flows. However, since not all nearby
"cooling flow" clusters show bubble-like features, we suggest that there may be
a diverse range of physical phenomena that give rise to the same observed
features.


title:
A Constraint on Electromagnetic Acceleration of Highest Energy Cosmic
  Rays

abstract:
  The energetics of electromagnetic acceleration of ultra-high-energy cosmic
rays (UHECRs) is constrained both by confinement of a particle within an
acceleration site and by radiative energy losses of the particle in the
confining magnetic fields. We demonstrate that the detection of ~ 3 x 10^{20}
eV events is inconsistent with the hypothesis that compact cosmic accelerators
with high magnetic fields can be the sources of UHECRs. This rules out the most
popular candidates, namely spinning neutron stars, active galactic nuclei
(AGNs), and gamma-ray burst blast waves. Galaxy clusters and, perhaps, AGN
radio lobes remain the only possible (although not very strong) candidates for
UHECR acceleration sites. Our analysis places no limit on linear accelerators.
With the data from the future Auger experiment one should be able to answer
whether a conventional theory works or some new physics is required to explain
the origin of UHECRs.


title: Element Abundances through the Cosmic Ages

abstract:
  The horizon for studies of element abundances has expanded dramatically in
the last ten years. Once the domain of astronomers concerned chiefly with stars
and nearby galaxies, this field has now become a key component of observational
cosmology, as technological advances have made it possible to measure the
abundances of several chemical elements in a variety of environments at
redshifts up to z = 4, when the universe was in its infancy. In this series of
lectures I summarise current knowledge on the chemical make-up of distant
galaxies observed directly in their starlight, and of interstellar and
intergalactic gas seen in absorption against the spectra of bright background
sources. The picture which is emerging is one where the universe at z = 3
already included many of the constituents of today's galaxies-even at these
early times we see evidence for Population I and II stars, while the `smoking
gun' for Population III objects may be hidden in the chemical composition of
the lowest density regions of the intergalactic medium, yet to be deciphered.


title: X-ray Fluctuation Power Spectral Densities of Seyfert 1 Galaxies

abstract:
  By combining complementary monitoring observations spanning long, medium and
short time scales, we have constructed power spectral densities (PSDs) of six
Seyfert~1 galaxies. These PSDs span $\gtrsim$4 orders of magnitude in temporal
frequency, sampling variations on time scales ranging from tens of minutes to
over a year. In at least four cases, the PSD shows a "break," a significant
departure from a power law, typically on time scales of order a few days. This
is similar to the behavior of Galactic X-ray binaries (XRBs), lower mass
compact systems with breaks on time scales of seconds. NGC 3783 shows tentative
evidence for a doubly-broken power law, a feature that until now has only been
seen in the (much better-defined) PSDs of low-state XRBs. It is also
interesting that (when one previously-observed object is added to make a small
sample of seven), an apparently significant correlation is seen between the
break time scale $T$ and the putative black hole mass $M_{\rm BH}$, while none
is seen between break time scale and luminosity. The data are consistent with
the linear relation $ T = M_{\rm BH}/10^{6.5} \Msun$; extrapolation over 6--7
orders of magnitude is in reasonable agreement with XRBs. All of this
strengthens the case for a physical similarity between Seyfert~1s and XRBs.


title: IGR J16318-4848: an X-ray source in a dense envelope?

abstract:
  The hard X-ray source IGR J16318-4848 was recently discovered by the INTEGRAL
observatory (Courvoisier et al.) and subsequently uncovered in archival data of
ASCA observations in 1994 (Murakami et al.). We present results of a detailed
analysis of the ASCA data. The spectrum of the source in the 0.5--10 keV band
is extraordinarily hard and is virtually unobservable below 4 keV because of
strong photoabsorption NHL L>4e23 cm^-2. The 4--10 keV emission is dominated by
a Kalpha line of neutral or weakly ionized iron with an equivalent width of
\~2.5 keV. There is also an indication for a second line at ~7 keV. Our
analysis of archival observations of the IGR J16318-4848 infrared counterpart,
discovered by Foschini et al., shows that the point source is detected at
different wavelengths in the 1--15 micron range. The available data suggest
that IGR J16318-4848 is an X-ray binary system enshrouded by a dense envelope.
It is possible that the source is a wind-fed high-mass X-ray binary similar to
GX 301-2. We argue that IGR J16318-4848 might be the first representative of a
previously unknown population of highly absorbed galactic X-ray sources, which
remained undetected with X-ray missions before INTEGRAL.


title: HI Imaging Observations of Superthin Galaxies. I. UGC7321

abstract:
  We have used the Very Large Array to image the isolated ``superthin'' galaxy
UGC7321 in the HI line with a spatial resolution of 16'' and a spectral
resolution of 24 kHz (5.2 km/s). We have reached a sensitivity of ~0.38 mJy/bm
per channel, which corresponds to a column density of 8 x 10**{18} cm**{-2} (1
sigma). UGC7321 has a gas-rich disk with M_HI = (1.06 +/- 0.01) 10**9 Msun and
MHI/LB = 1.0 (solar units), and no detectable radio continuum emission (F_CONT
= 0.41 +/- 0.25 mJy). The global \HI distribution of UGC 7321 is rather
symmetric and extends to ~1.5 times the optical radius (D_HI = 8.65' +/- 0.15')
at n_HI = 3 x 10**{19} atoms cm**{-2}). An ``integral sign'' warp is observed
in the HI disk, commencing near the edge of the stellar distribution, and
twisting back toward the equatorial plane in the outermost regions. In
addition, the position-velocity diagram suggests the presence of a bar or inner
arm within ~40'' from the center. The rotation curve of UGC7321 is slowly
rising; it reaches its asymptotic velocity of ~110 km/s ~2.5' from the center
(about 0.9 optical radii) and declines near the edge of the HI disk. The ratio
of the inferred dynamical mass to the mass in gas and stars is ~12, implying
that UGC7321 is a highly dark-matter dominated galaxy.


title: The intrinsic high metallicity of cSNRs

abstract:
  Here we present semi-analytical solutions of the hydrodynamics of compact
supernova remnants (cSNRs) and their chemical evolution. Two models of $15
M_{\odot}$ and $25 M_{\odot}$ supernova explosions evolving in a high density
medium ($n_0 \sim 10^7 cm^{-3}$) are throughly discussed.


title:
Chandra Grating Spectroscopy of the X-ray Binary 4U 1700-37 in a Flaring
  State

abstract:
  Chandra X-ray Observatory grating spectra of the supergiant X-ray Binary 4U
1700-37 reveal emission lines from hydrogen and helium-like S, Si, Mg, and Ne
in the 4-13 A range. The spectrum also shows fluorescent lines from S, Si, and
a prominent Fe K alpha line at 1.94 A. The lines contribute to the previously
unaccounted "soft excess" in the flux in this range at orbital phi~0.7. The
X-ray source was observed during intermittent flaring, and the strengths of the
lines vary with the source state. The widths of the lines (FWHM approximately
1000-2000 km/s) can result from either Compton scattering or Doppler shifts.
Power spectra of the hard X-rays show red noise and the soft X-rays and lines
show in addition quasiperiodic oscillations (QPOs) and a power-spectral break.
Helium-like triplets of Si and Mg suggest that the gas is not in a pure
photoionization equilibrium. We discuss whether resonant scattering could
affect the line ratios or whether a portion of the wind may be heated to
temperatures T~10^6 K.


title: Phase Correlations in Non-Gaussian Fields

abstract:
  We present the general relationship between phase correlations and the
hierarchy of polyspectra in the Fourier space, and the new theoretical
understanding of the phase information is provided. Phase correlations are
related to the polyspectra only through the non-uniform distributions of the
phase sum $\theta_{\sbfm{k}_1} + ... + \theta_{\sbfm{k}_N}$ with closed wave
vectors, $\bfm{k}_1 + ... + \bfm{k}_N = 0$. The exact relationship is given by
the infinite series, which one can truncate in a consistent manner. The method
to calculate the series to arbitrary order is explained, and the explicit
expression of the first-order approximation is given. A numerical demonstration
proves that the distribution of the phase sum is a robust estimator and
provides an alternative statistic to search for the non-Gaussianity.


title: Double-Peaked Broad Emission Lines and the Geometry of Accretion in AGNs

abstract:
  Although accretion disks are a theoretically appealing model for the geometry
and dynamics of the gas in the vicinity of black holes in Active Galactic
Nuclei (AGN), there is little direct observational evidence for their
existence. The telltale signature of disk emission in AGN -- double peaked
emission lines -- have so far been found in only two dozen cases in the
optical. We have selected about 100 double-peaked broad emission line AGN from
the Sloan Digital Sky Survey (SDSS) from a large sample of over 4000 AGN with
z<0.4. By comparing the properties of these AGN with those of the full sample,
we hope to isolate the defining characteristics of disk-emitters and ultimately
answer the question: "If all AGN have accretion disks, why don't they all show
double-peaked disk emission lines?" Here we present Gaussian parameterized
Halpha line-profile measurements for the sample of double-peaked AGN in
comparison with circular and elliptical accretion disk models.


title: A Turbulent Interstellar Medium Origin of the Binary Period Distribution

abstract:
  In this paper, we present a semi-empirical model of isolated binary star
formation. This model includes the effects of turbulence in the initial state
of the gas, and has binary orbital parameters consistent with observation. Our
fundamental assumption is that the angular momenta of binary star systems is
directly related to the net angular momentum induced by turbulence in parent
molecular cloud cores. The primary results of this model are as follows. (i) A
quantitative prediction of the initial width of the binary period distribution
($\sigma_{\log {P}_d} = 1.6 - 2.1$ for a star formation efficiency in the range
$\epsilon_* = 0.1 - 0.9$). (ii) A robust, negative anticorrelation of binary
period and mass ratio. (iii) A robust, positive correlation of binary period
and eccentricity. (iv) A robust prediction that the binary separation of
low-mass systems should be more closely separated than those of solar-mass or
larger. These predictions are in good agreement with observations of PMS binary
systems with periods $P > 10^3$ d, which account for the majority of all
binaries.
  We conclude with a brief discussion of the implications of our results for
observational and theoretical studies of multiple star formation.


title:
Detectability of the Warm/Hot Intergalactic Medium Through Emission
  Lines of OVII and OVIII

abstract:
  Most of cosmic baryons predicted by the big-bang nucleosynthesis has evaded
the direct detection. Recent numerical simulations indicate that approximately
30 to 50 percent of the total baryons in the present universe is supposed to
take a form of warm/hot intergalactic medium (WHIM) whose X-ray continuum
emission is very weak. To identify those missing baryons, we consider in detail
the detectability of WHIM directly through emission lines of OVII (561, 568,
574, 665eV) and OVIII (653eV). For this purpose, we create mock spectra of the
emission lines of WHIM using a light-cone output of the cosmological
hydrodynamic simulations. Since the predicted fluxes are generally below the
current detection limit, the unambiguous detection requires a dedicated X-ray
satellite mission that we also discuss in detail. We find that our proposed
mission is sensitive to the WHIM with gas temperature $T=10^{6-7}$K and
overdensity $\delta=10-100$ up to a redshift of 0.3 without being significantly
contaminated by the cosmic X-ray background and the Galactic emissions. Thus
such a mission provides a unique and important tool to identify a large
fraction of otherwise elusive baryons in the universe.


title:
Deep Keck adaptive optics searches for extrasolar planets in the dust of
  Epsilon Eridani and Vega

abstract:
  A significant population of nearby stars have strong far-infrared excesses,
now known to be due to circumstellar dust in regions analogous to the Kuiper
Belt of our solar system, though orders of magnitude more dense. Recent sub-mm
and mm imaging of these systems resolves the circumstellar dust and reveals
complex structures, often in the form of rings with azimuthal non-axisymmetric
variations. This structure might well be due to the presence of embedded brown
dwarfs or planets. We have carried out deep adaptive optics imaging of two
nearby stars with such asymmetric dust: Epsilon Eridani and Vega. Ten and seven
candidate companions were seen in and near the dust rings of Epsilon Eridani
and Vega respectively, but second-epoch proper motion measurements indicate
that all are background objects. Around these two stars we can thus exclude
planetary companions at spatial scales comparable to the radius of the dust
structures to a level of MK=24, corresponding to 5 Jupiter masses, for Epsilon
Eridani, and MK=19-21, corresponding to 6-8 Jupiter masses, for Vega.


title: Stochastic evolution of cosmological parameters in the early universe

abstract:
  We develop a stochastic formulation of cosmology in the early universe, after
considering the scatter in the redshift-apparent magnitude diagram in the early
epochs as an observational evidence for the non-deterministic evolution of
early universe. We consider the stochastic evolution of density parameter in
the early universe after the inflationary phase qualitatively, under the
assumption of fluctuating $w$ factor in the equation of state, in the
Fokker-Planck formalism. Since the scale factor for the universe depends on the
energy density, from the coupled Friedmann equations we calculated the two
variable probability distribution function assuming a flat space geometry.


title: Classical stochastic approach to cosmology revisited

abstract:
  The classical stochastic model of cosmology recently developed by us is
reconsidered. In that approach the parameter $w$ defined by the equation of
state $p=w{\rho}$ was taken to be fluctuating with mean zero and we compared
the theoretical probability distribution function(PDF) for the Hubble parameter
with observational data corresponding to a universe with matter and vacuum
energy. Eventhough qualitative agreement between the two was obtained, an
attempt is herein made to introduce a more realistic assumption for the mean of
$w$ and use it for the calculations. In the present theory the mean values of
both $p$ and $w$ are taken to be nonzero. The theoretical and observational
PDFs are compared for different epochs and values of the Hubble parameter. The
corresponding values of the diffusion constant $D$ obtained are approximately
constant. We use the scatter in the observed redshift-magnitude data of Type Ia
supernova to place limits on the stochastic variation in expansion rate and
consequently, on the stochastic variation of the equation of state.


title: The 21Na(p,gamma)22Mg Reaction and Oxygen-Neon Novae

abstract:
  The 21Na(p,gamma)22Mg reaction is expected to play an important role in the
nucleosynthesis of 22Na in Oxygen-Neon novae. The decay of 22Na leads to the
emission of a characteristic 1.275 MeV gamma-ray line. This report provides the
first direct measurement of the rate of this reaction using a radioactive 21Na
beam, and discusses its astrophysical implications. The energy of the important
state was measured to be E$_{c.m.}$= 205.7 $\pm$ 0.5 keV with a resonance
strength $\omega\gamma = 1.03\pm0.16_{stat}\pm0.14_{sys}$ meV.


title: Mission: Impossible (Escape from the Lyman Limit)

abstract:
  We investigate the intrinsic opacity of high-redshift galaxies to outgoing
ionising photons using high-quality photometry of a sample of 27
spectroscopically-identified galaxies of redshift 1.9<z<3.5 in the Hubble Deep
Field. Our measurement is based on maximum-likelihood fitting of model galaxy
spectral energy distributions-including the effects of intrinsic Lyman-limit
absorption and random realizations of intervening Lyman-series and Lyman-limit
absorption-to photometry of galaxies from space- and ground-based broad-band
images. Our method provides several important advantages over the methods used
by previous groups, including most importantly that two-dimensional sky
subtraction of faint-galaxy images is more robust than one-dimensional sky
subtraction of faint-galaxy spectra. We find at the 3sigma statistical
confidence level that on average no more than 4% of the ionising photons escape
galaxies of redshift 1.9<z<3.5. This result is consistent with observations of
low- and moderate-redshift galaxies but is in direct contradiction to a recent
result based on medium-resolution spectroscopy of high-redshift (z~3) galaxies.
Dividing our sample in subsamples according to luminosity, intrinsic
ultraviolet colour, and redshift, we find no evidence for selection effects
that could explain such discrepancy. Even when all systematic effects are
included, the data could not realistically accomodate any escape fraction value
larger than ~15%.


title:
The physics of pulses in gamma-ray bursts: emission processes, temporal
  profiles and time lags

abstract:
  We present a simple, semi-analytical model to explain GRB temporal and
spectral properties in the context of the internal shock model. Each individual
pulse in the temporal profiles is produced by the deceleration of fast moving
material by a comparatively slower layer within a relativistic wind. The
spectral evolution of synthetic pulses is first obtained with standard
equipartition assumptions to estimate the post-shock magnetic field and
electron Lorentz factor. We get Ep propto t^-delta with delta=7/2 which is much
steeper than the observed slopes delta(obs) <= 1.5. We therefore consider the
possibility that the equipartition parameters depend on the shock strength and
post-shock density. We then get a much better agreement with the observations
and our synthetic pulses satisfy both the hardness-intensity and
hardness-fluence correlations. We also compute time lags between profiles in
different energy channels and we find that they decrease with increasing
hardness. We finally compare our predicted time lag - luminosity relation to
the Norris et al. (2000) result obtained from 6 bursts with known redshift.


title: The expected photospheric emission of GRBs in the internal shock model

abstract:
  The prompt emission of gamma-ray bursts (hereafter GRBs) probably comes from
a highly relativistic wind which converts its kinetic energy into radiation via
the formation of shocks within the wind itself. Such "internal shocks" can
occur if the wind is generated with a highly non uniform distribution of the
Lorentz factor Gamma. Taking into account such a variable distribution of
Gamma, we estimate the expected thermal emission of the relativistic wind when
it becomes transparent. We compare this emission (temporal profile + spectrum)
to the emission produced by the internal shocks. In most cases we predict a
rather bright thermal emission that could easily be detected. This favors
acceleration mechanisms for the wind where the main energy reservoir is under
magnetic rather than thermal form. Such scenarios can produce thermal X-ray
precursors comparable to those observed by GINGA and WATCH/GRANAT.


title: On the nature of X-ray Flashes

abstract:
  We have developed a toy model for internal shocks which has been used to
generate a large number of synthetic GRBs in order to find in the parameter
space the conditions which can lead to the formation of X-ray flashes. The key
condition appears to be a small contrast of the Lorentz factor in the
relativistic wind emitted by the central engine.


title:
Illuminating Protogalaxies? The Discovery of Extended Lyman-alpha
  Emission around a QSO at z=4.5

abstract:
  We have discovered extended Lyman-$\alpha$ emission around a $z=4.5$ QSO in a
deep long-slit spectrum with Keck/LRIS at moderate spectral resolution
($R\approx 1000$). The line emission extends 5\,arcsec beyond the continuum of
the QSO and is spatially asymmetric. This extended line emission has a spectral
extent of 1000km/s, much narrower in velocity spread than the broad
Lyman-$\alpha$ from the QSO itself and slightly offset in redshift. No evidence
of continuum is seen for the extended emission line region, suggesting that
this recombination line is powered by reprocessed QSO Lyman continuum flux
rather than by local star formation. This phenomenon is rare in QSOs which are
not radio loud, and this is the first time it has been observed at $z>4$. It
seems likely that the QSO is illuminating the surrounding cold gas of the host
galaxy, with the ionizing photons producing Lyman-$\alpha$ fluorescence. As
suggested by Haiman \& Rees (2001), this ``fuzz'' around a distant quasar may
place strong constraints on galaxy formation and the extended distribution of
cold, neutral gas.


title: Accurate Internal Proper Motions of Globular Clusters

abstract:
  We have undertaken a long term program to measure high precision proper
motions of nearby Galactic globular cluster (GC) stars using multi-epoch
observations with the WFPC2 and the ACS cameras on-board the Hubble Space
Telescope. The proper motions are used to study the internal cluster
kinematics, and to obtain accurate cluster distances. In this paper, we also
show how the proper motions of the field stars projected in the direction of
the studied clusters can be used to set constraints on the Galaxy kinematics.


title:
Statistical Study of the Blue Straggler Properties in Galactic Globular
  Clusters

abstract:
  In this paper we report on the most significant results from a statistical
analysis of the main properties of globular cluster blue straggler stars (BSS)
extracted from the HST snapshot database of photometrically homogeneous CMDs
(Piotto et al. 2002). The BSS relative frequency presents a significant
anticorrelation with the collisional rate and with the cluster total absolute
luminosity.


title: Hot Stellar Populations in Globular Clusters: a Photometrist's View

abstract:
  We briefly review the recent results on hot horizontal-branch stars in
globular clusters. Since the first Ivanfest, in 1992, there have been a number
of new observational lines of evidence which have allowed significant progress
in our understanding of blue-tail stars, though new, even more intriguing
questions arise. Despite this progress, we still do not know the answer to the
main question: why are there blue-HB-tail stars? The new photometric data bases
collected in the last few years, and the forthcoming multi-fiber observational
campaigns on 10m-class telescopes, might be the key to solve this puzzle. We
will show an example of how these data bases can disclose important properties
of blue HB stars.


title: Rotation of Hot Horizontal Branch Stars in Galactic Globular Clusters

abstract:
  We present high resolution UVES+VLT spectroscopic observations of 61 stars in
the extended blue horizontal branches of the Galactic globular clusters NGC
1904 (M79), NGC 2808, NGC 6093 (M80), and NGC 7078 M15). Our data reveal for
the first time the presence in NGC 1904 of a sizable population of fast (v
sin(i) >= 20 km/s) horizontal branch (HB) rotators, confined to the cool end of
the EHB, similar to that found in M13. We also confirm the fast rotators
already observed in NGC 7078. The cooler stars (T_eff < 11,500 K) in these
three clusters show a range of rotation rates, with a group of stars rotating
at ~ 15 km/s or less, and a fast rotating group at ~ 30 km/s. Apparently, the
fast rotators are relatively more abundant in NGC 1904 and M13, than in NGC
7078. No fast rotators have been identified in NGC 2808 and NGC 6093. All the
stars hotter than T_eff ~ 11,500 K have projected rotational velocities vsini<
12 km/s. The connection between photometric gaps in the HB and the change in
the projected rotational velocities is not confirmed by the new data. However,
our data are consistent with a relation between this discontinuity and the HB
jump.


title: The Red Giant Branch Bump

abstract:
  We present a comparison between theoretical models and the observed magnitude
difference between the horizontal branch and the red giant branch bump for a
sample of 53 clusters. We find a general agreement, though some discrepancy is
still present at the two extremes of the metallicity range of globular
clusters.


title: Magnetars in the afterglow era

abstract:
  The X-ray afterglow that is observed following large flares on magnetars can
be accurately fit by simple and quantitative theoretical models: The long term
afterglow, lasting of order weeks, can be understood as thermal radiation of a
heated neutron star crust that is re-scattered in the magnetosphere. Short term
afterglow is well fit by the cooling of a non-degenerate, pair-rich layer,
which gradually shrinks and releases heat to a pair-free zone above it.
Measurements of persistent optical and infrared emission directly probe long
lived currents in the magnetosphere which are a likely source of collective
plasma emission. The superstrong magnetic field plays an important role in
generating these various emissions, and previous inference of its strength in
magnetars is supported by the good fits with observation.


title:
Empirical calibration of the near-IR CaII triplet - IV. The stellar
  population synthesis models

abstract:
  We present a new stellar population synthesis model, which predicts SEDs for
single-age single-metallicity stellar populations, SSPs, at resolution 1.5A
(FWHM) in the spectral region of the near-IR CaII triplet feature. The main
ingredient of the model is a new extensive empirical stellar spectral library
presented in Cenarro et al., which is composed of more than 600 stars. Two main
products of interest for stellar population analysis are presented. The first
is a library of SEDs for SSPs covering a large range of ages, metallicities and
different IMF types. They are well suited to model galaxy data, since the SSP
spectra, with flux-calibrated response curves, can be smoothed to match the
resolution of galaxy data, taking into account the internal velocity dispersion
of the galaxy, allowing the user to analyze the observed spectrum in its own
system. We also produce integrated absorption line indices for the same SSPs in
the form of equivalent widths. We find the following behaviour for the CaII
feature in old-aged SSPs: i) the CaII triplet feature does not change much with
time for all metallicities for ages larger than ~3 Gyr, ii) this index shows a
strong dependence with metallicity for values below [M/H] ~-0.5 and iii) for
larger metallicities this feature does not show a significant dependence either
on age or on the metallicity, being more sensitive to changes in the slope of
power-like IMF shapes. The SSP spectra have been calibrated with measurements
for globular clusters. Fitting the models to two early-type galaxies of
different luminosities, we find that the CaII measurements cannot be fitted
unless a very dwarf-dominated IMF is imposed, or if the Ca abundance is even
lower than the Fe abundance.


title: WMAP Constraints on Quintessence

abstract:
  We use recent results from the Wilkinson Microwave Anisotropy Probe (WMAP)
for the locations of peaks and troughs of the Cosmic Microwave Background (CMB)
power spectrum, together with constraints from large-scale structure, to study
a quintessence model in which the pure exponential potential is modified by a
polynomial factor. We find that the model is compatible with all the recent
data for a wide range of cosmological and potential parameters. Moreover,
quintessence is favoured compared to $\Lambda$CDM for $n_s\approx 1$ and
relatively high values of the average fraction of dark energy before last
scattering (``early quintessence''); for $n_s<1$, quintessence and $\Lambda$CDM
give similar results, except for high values of early quintessence, in which
case $\Lambda$CDM is favoured.


title:
Measuring the Absolute Height and Profile of the Mesospheric Sodium
  Layer using a Continuous Wave Laser

abstract:
  We have developed and tested a novel method, based on LIDAR, of measuring the
height and profile of the mesospheric sodium layer using a continuous wave
laser. It is more efficient than classical LIDAR as the laser is on for 50% of
the time, and so can in principle be used during laser guide star adaptive
optics observations. It also has significant advantages over direct imaging
techniques because it does not require a second telescope, is almost
independent of the atmospheric conditions, and avoids triangulation problems in
determining the height. In the long term, regular monitoring using this method
would allow a valuable database of sodium layer profiles, heights, and return
flux measurements to be built up which would enable observatory staff
astronomers to schedule observations optimally. In this paper we describe the
original experiment carried out using the ALFA laser guide star system at Calar
Alto Observatory in Spain. We validate the method by comparing the LIDAR
results with those obtained from simultaneous imaging from an auxiliary
telescope. Models are presented of a similar system to be implemented in the
Very Large Telescope Laser Guide Star Facility, which will enable the initial
focus setting for the adaptive optics systems to be determined with an accuracy
of less than 200 m on a timescale of 1 minute.


title: The Galactic Population of Low- and Intermediate-Mass X-ray Binaries

abstract:
  (abridged) We present the first study that combines binary population
synthesis in the Galactic disk and detailed evolutionary calculations of low-
and intermediate-mass X-ray binaries (L/IMXBs). We show that the formation
probability of IMXBs with initial donor masses of 1.5--4 Msun is typically >~5
times higher than that of standard LMXBs, and suggest that the majority of the
observed systems may have descended from IMXBs. Distributions at the current
epoch of the orbital periods, donor masses, and mass accretion rates have been
computed, as have orbital-period distributions of BMPs. Several significant
discrepancies between the theoretical and observed distributions are discussed.
The orbital-period distribution of observed BMPs strongly favors cases where
the envelope of the neutron-star progenitor is more easily ejected during the
common-envelope phase. However, this leads to a >~100-fold overproduction of
the theoretical number of luminous X-ray sources relative to the total observed
number of LMXBs. X-ray irradiation of the donor star may result in a dramatic
reduction in the X-ray active lifetime of L/IMXBs, thus possibly resolving the
overproduction problem, as well as the long-standing BMP/LMXB birthrate
problem.


title: On the thermodynamical limit of self-gravitating systems

abstract:
  It is shown that the diluted thermodynamical limit of a self-gravitating
system proposed by de Vega and Sanchez suffers from the same problems as the
usual thermodynamical limit and leads to divergent thermodynamical functions.
This question is also discussed from the point of view of mean field theory.


title: Constraints on the UV metagalactic emissivity using the LyA forest

abstract:
  Numerical hydrodynamical simulations have proven a successful means of
reproducing many of the statistical properties of the LyA forest as measured in
high redshift (z > 4) quasar spectra. The source of ionization of the
Intergalactic Medium (IGM), however, remains unknown. We investigate how the
LyA forest may be used to probe the nature of the sources. We show that the
attenuation of Lyman continuum photons by the IGM depends sensitively on the
emissivity of the sources, permitting a strong constraint to be set on the
required emissivity to match the measured values of the mean IGM LyA optical
depth. We also investigate the effect of fluctuations in the UV background. We
derive the distribution function of the background radiation field produced by
discrete sources in an infinite universe, including the effects of attenuation
by an intervening absorbing medium. We show that for z > 5, the fluctuations
boost the mean LyA optical depth in a scenario in which QSO sources dominate
the UV background. The fluctuations will also result in large spatial
correlations in the ionization level of the IGM at high redshifts, providing a
means of discriminating between scenarios in which stars and galaxies dominate
the UV background vs a QSO-dominated background.


title: Modeling Dynamical Dark Energy

abstract:
  Cosmological models with different types of Dark Energy are becoming viable
alternatives for standard models with the cosmological constant. Yet, such
models are more difficult to analyze and to simulate. We present analytical
approximations and discuss ways of making simulations for two families of
models, which cover a wide range of possibilities and include models with both
slow and fast changing ratio w=p\rho. More specifically, we give analytical
expressions for the evolution of the matter density parameter Omega_m(z) and
the virial density contrast Delta_c at any redshift z. The latter is used to
identify halos and to find their virial masses. We also provide an
approximation for the linear growth factor of linear fluctuations between
redshift z=40 and z=0. This is needed to set the normalization of the spectrum
of fluctuations. Finally, we discuss the expected behavior of the halo mass
function and its time evolution.


title: Halo properties in models with dynamical Dark Energy

abstract:
  We study properties of dark matter halos in a variety of models which include
Dark Energy (DE). We consider both DE due to a scalar field self--interacting
through Ratra-Peebles or SUGRA potentials, and DE with constant negative
w=p\rho >-1. We find that at redshift zero the nonlinear power spectrum of the
dark matter, and the mass function of halos, practically do not depend on DE
state equation and are almost indistinguishable from predictions of the LCDM
model. This is consistent with the nonlinear analysis presented in the
accompanying paper. It is also a welcome feature because LCDM models fit a
large variety of data. On the other hand, at high redshifts DE models show
substantial differences from LCDM and substantial differences among themselves.
Halo profiles differ even at z=0. DE halos are denser than LCDM in their
central parts because the DE halos collapse earlier. Nevertheless, differences
between the models are not so large. For example, the density at 10 kpc of a DE
\~10^{13}Msun halo deviates from LCDM by not more than 50%. This, however,
means that DE is not a way to ease the problem with cuspy dark matter profiles.
Addressing another cosmological problem - abundance of subhalos -- we find that
the number of satellites of halos in various DE models does not change relative
to the LCDM, when normalized to the same circular velocity of the parent halo.
To summarize, the best way to find which DE model fits the observed Universe is
to look for evolution of halo properties. For example, the abundance of galaxy
groups with mass larger than 10^{13}\Msun at z> 2 can be used to discriminate
between the models, and, thus, to constrain the nature of DE.


title: On the nature of the ring-like structure in the outer Galactic disk

abstract:
  We examine the tidal disruption of satellite galaxies in a cosmological
simulation of the formation of a disk galaxy in the $\Lambda$CDM scenario. We
find that the disruption of satellite galaxies in orbits roughly coplanar with
the disk leads naturally to the formation of ring-like stellar structures
similar to that recently discovered in the outer disk of the Milky Way. Two
interpretations appear plausible in this context. One is that the ring is a
transitory, localized radial density enhancement reflecting the apocenter of
particles stripped from a satellite during a recent pericentric passage (a
``tidal arc'' reminiscent of the tidal arms seen in disk galaxy mergers). In
the second scenario, the ring is analogous to the ``shells'' found around some
elliptical galaxies, and would result from a minor merger that took place
several Gyr ago. The two interpretations differ in several ways. Tidal arcs are
expected to span a limited longitude range; may carry a substantial fraction of
the original mass of the satellite; should exhibit a significant velocity
gradient with Galactic longitude; and are in all likelihood asymmetric above
and below the plane of the disk. Shells, on the other hand, may comprise at
most a small fraction of the original mass of the satellite and, due to their
more relaxed state, ought to be symmetric above and below the plane, with no
discernible velocity gradients across the structure. If confirmed as a tidal
feature, the ring discovered by SDSS in the outer Galactic disk would
strengthen the view--supported by numerical simulations--that minor mergers
have played a significant role building up not only the stellar halo, but also
the disk components of the Galaxy.


title: Variable Cosmological Constant as a Planck Scale Effect

abstract:
  We construct a semiclassical FLRW cosmological model assuming a running
cosmological constant (CC). It turns out that the CC becomes variable at
arbitrarily low energies due to the remnant quantum effects of the heaviest
particles, e.g. the Planck scale physics. These effects are universal in the
sense that they lead to a low-energy structure common to a large class of
high-energy theories. Remarkably, the uncertainty concerning the unknown
high-energy dynamics is accumulated into a single parameter \nu, such that the
model has an essential predictive power. Future Type Ia supernovae experiments
(like SNAP) can verify whether this framework is correct. For the flat FLRW
case and a moderate value \nu ~0.01, we predict an increase of 10-20% in the
value of Omega_{Lambda} at redshifts z=1-1.5 perfectly reachable by SNAP.


title:
DIRECT Distances to Nearby Galaxies Using Detached Eclipsing Binaries
  and Cepheids. IX. Variables in the Field M31Y Discovered with Image
  Subtraction

abstract:
  The DIRECT Project aims to obtain direct distances to two Local Group
galaxies, M31 and M33, which occupy a crucial position near the bottom of the
cosmological distance ladder. The first step is to search for detached
eclipsing binaries (DEBs) and Cepheids using 1 m class telescopes to select
good candidates, which will be followed up spectroscopically on 6.5-10 m class
telescopes. In this ninth paper we present a catalog of variable stars
discovered with image subtraction in field M31Y [RA=10.97 deg, Dec=41.69 deg,
J2000.0]. The data were obtained with the FLWO 1.2 m telescope on 25 nights,
over a period of 6 months. In our search covering 22x22 arcmin we discovered 41
eclipsing binaries, 126 Cepheids, and 97 other periodic or nonperiodic
variables, including a LBV candidate, a nova and a galactic CV. The catalog of
variables, as well as their photometry and finding charts, is available
electronically via anonymous ftp and the World Wide Web. The complete set of
the CCD frames is available upon request.


title: Probing the Size of Low-Redshift Lyman-alpha Absorbers

abstract:
  The 3C 273 and RX J1230.8+0115 sightlines probe the outskirts of the Virgo
Cluster at physical separations between the sightlines of 200-500 h_70 kpc. We
present an analysis of HST STIS echelle and FUSE UV spectroscopy of RX
J1230.8+0115 in which we detect five Lyman-alpha absorbers at Virgo distances.
One of these absorbers is a blend of two strong metal line absorbers coincident
in velocity with the highest neutral hydrogen column density absorber in the 3C
273 sightline ~350 h_70 kpc away. The consistency of the metal line column
density ratios in the RX J1230.8+0115 sightline allows us to determine the
ionization mechanism (photoionization) for these absorbers. While the low
signal-to-noise ratio of the FUSE spectrum limits our ability to model the
neutral hydrogen column density of these absorbers, we are able to constrain
them to be in the range 10^{16-17} cm^-2. The properties of these absorbers are
similar to those of the 3C 273 absorber studied by Tripp et al. However, the
inferred line-of-sight size for the 3C 273 absorber is only 70 pc, much smaller
than those inferred in RX J1230.8+0115, which are 10-30 h_70 kpc. The small
sizes of all three absorbers are at odds with the >~350 h_70 kpc minimum
transverse size implied by an application of the standard QSO line pairs
analysis. On the basis of absorber associations between these two sight lines
we conclude that a large-scale structure filament produces a correlated, not
contiguous, gaseous structure in this region of the Virgo Supercluster. These
data may indicate that we are detecting overdensities in the large scale
structure filaments in this region. Alternatively, the presence of a galaxy 71
h_70 kpc from a 3C 273 absorber may indicate that we have probed outflowing,
starburst driven shells of gas associated with nearby galaxies.


title: Stellar Contribution to the Galactic Bulge Microlensing Optical Depth

abstract:
  We estimate the optical depth to self-lensing by stars in the Galactic bulge
using the HST star counts of Holtzman et al and Zoccali et al as extrapolated
by Gould into the brown-dwarf and remnant regimes and deprojected along the
line of sight using the model of Dwek et al. We find a self-lensing optical
depth tau(bulge-bulge)=0.98 x 10^{-6}. When combined with the lensing of bulge
stars by foreground stars in the disk, this yields tau(bulge-total)=1.63 x
10^{-6}, in reasonable agreement with the estimates of tau=2.13 +/- 0.40 x
10^{-6} and tau=1.08 +/- 0.30 x 10^{-6} based on observations of clump giants
by the MACHO and EROS collaborations.


title: Limits on thermal conduction in galaxy clusters

abstract:
  We have calculated lower limits for the global effective thermal conductivity
in a sample of 165 Abell clusters. We assumed that cluster X-ray luminosity is
compensated by a conductive heat flux which we then compare with an upper limit
to the temperature gradient inferred from the cluster temperature and radius.
This gives a lower limit to the thermal conductivity and therefore to the
relative suppression from the Spitzer conductivity, kappa_{Sp}. Not a single
cluster requires super-Spitzer values of thermal conduction to balance the
observed X-ray luminosity. The suppression coefficient f=kappa/kappa_{Sp} is
clustered in a range 10^{-2} < f < 0.4. A weak dependence of $f$ versus $z$ is
observed over $ 0 < z <0.41$. Possible biases and/or selection effects are
discussed.


title: Adiabatic Growth of Massive Black Holes

abstract:
  We discuss the process of adiabatic growth of central black holes in the
presence of a stationary, pre-existing distribution of collisionless stars.
Within the limitations of the assumptions, the resulting models make robust
physical predictions for the presence of a central cusp in the stellar and dark
matter density, a Keplerian rise in the velocity dispersion, and a significant
tangential polarization of the velocity tensor. New generations of numerical
models have confirmed and extended previous results, permit the study of
axisymmetric and triaxial systems, and promise new insight into the dynamics of
the central regions of galaxies. These studies enable detailed comparisons with
observations, further our understanding on the fueling processes for AGNs and
quiescent black holes, and help elucidate the secular evolution of the inner
regions and spheroids of galaxies.


title: Black Holes and Pulsar Binaries

abstract:
  Stellar mass black holes are formed in the field, and are observed in
binaries. Population synthesis estimates for the formation of BH-PSR binaries
suggest these may be observed, but with very large formal uncertainties in the
formation rate. In globular clusters, exchanges and binary interactions present
more channels for BH-PSR formation, while ejection through recoil can remove a
large fraction of the initial black hole population. A BH-PSR system ought to
be observed in the near future, most likely in a globular cluster.


title: The Dark Matter Distribution in Galaxy Cluster Cores

abstract:
  Galaxy cluster mass distributions offer an important test of the cold dark
matter picture of structure formation, and may even contain clues about the
nature of dark matter. X-ray imaging spectroscopy of relaxed systems can map
cluster dark matter distributions, but are usually complicated by the presence
of central cool components in the intracluster medium. Here we describe a
statistically correct approach to distinguishing amongst simple alternative
models of the cool component, and apply it to one cluster. We also present mass
profiles and central density slopes for five clusters derived from Chandra
data, and illustrate how assumptions about the cool component affect the
resulting mass profiles. For four of these objects, we find that the central
density profile (r < 200 h_50^-1 kpc) rho(r) = r^a with -2 < a < -1, for either
of two models of the central cool component. These results are consistent with
standard CDM predictions.


title: A Chandra Study of the Complex Structure in the Core of 2A 0335+096

abstract:
  We present a Chandra observation of the central (r< 200kpc) region of the
cluster of galaxies 2A 0335+096, rich in interesting phenomena. On large scales
(r> 40kpc), the X-ray surface brightness is symmetric and slightly elliptical.
The cluster has a cool dense core; the radial temperature gradient varies with
position angle. The radial metallicity profile shows a pronounced central drop
and an off-center peak. Similarly to many clusters with dense cores, 2A
0335+096 hosts a cold front at r\approx 40kpc south of the center. The gas
pressure across the front is discontinuous by a factor A_P=1.6\pm 0.3,
indicating that the cool core is moving with respect to the ambient gas with a
Mach number M\approx 0.75\pm 0.2. The central dense region inside the cold
front shows an unusual X-ray morphology, which consists of a number of X-ray
blobs and/or filaments on scales \gtrsim 3kpc, along with two prominent X-ray
cavities. The X-ray blobs are not correlated with either the optical line
emission (H\alpha+[NII]), member galaxies or radio emission. Deprojected
temperature of the dense blobs is consistent with that of the less dense
ambient gas, so these gas phases do not appear to be in thermal pressure
equilibrium. An interesting possibility is a significant, unseen non-thermal
pressure component in the inter-blob gas, possibly arising from the activity of
the central AGN. We discuss two models for the origin of the gas blobs --
hydrodynamic instabilities caused by the observed motion of the gas core, or
``bubbling'' of the core caused by multiple outbursts of the central AGN.


title: Ejection of a Low Mass Star in a Young Stellar System in Taurus

abstract:
  We present the analysis of high angular resolution VLA radio observations,
made at eleven epochs over the last 20 years, of the multiple system T Tauri.
One of the sources (Sb) in the system has moved at moderate speed (5-10 km/s),
on an apparently elliptical orbit during the first 15 years of observations,
but after a close (< 2 AU) encounter with the source Sa, it appears to have
accelerated westward to about 20 km/s in the last few years. Such a dramatic
orbital change most probably indicates that Sb has just suffered an ejection -
which would be the first such event ever detected. Whether Sb will ultimately
stay on a highly elliptical bound orbit, or whether it will leave the system
altogether will be known with about five more years of observations.


title: Chandra Observations of Extended X-ray Emission in Arp 220

abstract:
  We resolve the extended X-ray emission from the prototypical ultraluminous
infrared galaxy Arp 220. Extended, faint edge-brightened, soft X-ray lobes
outside the optical galaxy are observed to a distance of 10 to 15 kpc on each
side of the nuclear region. Bright plumes inside the optical isophotes coincide
with the optical line emission and extend 11 kpc from end to end across the
nucleus. The data for the plumes cannot be fit by a single temperature plasma,
and display a range of temperatures from 0.2 to 1 keV. The plumes emerge from
bright, diffuse circumnuclear emission in the inner 3 kpc centered on the
Halpha peak, which is displaced from the radio nuclei. There is a close
morphological correspondence between the Halpha and soft X-ray emission on all
spatial scales. We interpret the plumes as a starburst-driven superwind, and
discuss two interpretations of the emission from the lobes in the context of
simulations of the merger dynamics of Arp 220.


title:
Probing the Spatial Distribution of Extrasolar Planets with
  Gravitational Microlensing

abstract:
  Under the current microlensing planet search strategy of monitoring events
caused by stellar-mass lenses, only planets located within a narrow region of
separations from central stars can be effectively detected. However, with the
dramatic increase of the monitoring frequency, two additional populations of
free-floating and wide-orbit planets can be detected. In this paper, we
investigate the lensing properties of events caused by wide-orbit planets and
find that the light curves of a significant fraction of these events will
exhibit signatures of central stars, enabling one to distinguish them from
those caused by free-floating planets. Due to the large primary/planet mass
ratio, the effect of the central star endures to considerable separations. We
find that for a Jupiter-mass planet the signatures of the central star can be
detected with fractional deviations of > 5% from the best-fitting single-lens
light curves for > 80% of events caused by bound planets with separations < 10
AU and the probability is still substantial for planets with separations up to
20 AU. Therefore, detecting a large sample of these events will provide useful
information about the distribution of extrasolar planets around their central
stars. Proper estimation of the probability of distinguishing events caused by
wide-orbit planets from those caused by free-floating planets will be important
for the correct determination of the frequency of free-floating planets, whose
microlensing sample will be contaminated by wide-orbits planets.


title:
Effects of dark-matter density profiles on bulge formation in very
  late-type galaxies

abstract:
  The dynamical evolution of super star clusters has been investigated in dark
matter halos depicted with a cuspy- or soft-core density profile. The
simulations show that (1) exponential bulges with central cusps form in both
cases;(2) distinctive bulge formation rates are derived for cuspy- and
soft-core profile; (3) masses of bulges and nuclear clusters are more heavier
in case of cuspy-core profile; (4) massive, nuclear star clusters possibly form
with no discernible bulges at different ages in cuspy- or soft-core cases.


title: NGC 1245 - an intermediate age open cluster

abstract:
  The B,V CCD photometry of 916 stars in the field of the high galactic
latitude intermediate age open cluster NGC 1245 is presented. The cluster
parameters were estimated with the help of V vs (B-V) colour-magnitude diagram
(CMD). After correcting for intra-cluster reddening, the mean reddening towards
the cluster was found to be 0.29$\pm$0.05 mag, with a distance modulus of
12.4$\pm$0.3 mag. The cluster is found to be located at a distance of 3 Kpc.
The isochrone fits using Girardi et al. (2000) isochrones to the cluster CMD
estimated an age of 890$\pm$100 Myr. The synthetic CMDs obtained using Girardi
et al. (2000) models incorporating photometric errors and 10% binary stars
estimated an age of 1 Gyr for the cluster. The luminosity function (LF) of the
main-sequence shows dips, which might arise due to some known gaps in the
main-sequence, including the Bohm-Vitense gap. The LF and the integrated LF
computed from the observed CMD is compared with those computed from the
sythetic CMDs for five values of mass function slope. The estimation of the
slope of the present day mass function indicates a flatter value compared to
the Salpeter value, though an accurate estimation is not possible due to the
large dips found in the LF. The apparent paucity of stars seen near the cluster
center is estimated to have a statistical significance of 2 sigma.


title: Photometry and low resolution spectroscopy of hot post-AGB candidates

abstract:
  We have obtained Johnson U, B, V and Cousins R, I photometry and low
resolution spectra of a small sample of hot post-AGB candidates. Using the
present data in combination with JHK data from 2MASS, infrared data from the
MSX catalog and the IRAS fluxes, we have studied the spectral energy
distribution (SED) of these stars. Using the DUSTY code we have estimated the
dust temperatures, the distances to the stars, the mass-loss rates, angular
radii of the inner boundary of the dust envelopes and dynamical ages from the
tip of the AGB. These candidates have also been imaged through a narrow band
H-alpha filter, to search for nebulosity around the central stars. Our H-alpha
images revealed the bipolar morphology of the low excitation PN IRAS 17395-0841
with an angular extent of 2.8arcsec. The bipolar lobes of IRAS 17423-1755 in
H-alpha were found to have an angular extent of 3.5arcsec (south-east lobe) and
2.2arcsec (north-west lobe). The dust envelope characteristics, low resolution
spectrum and IRAS colors suggest that IRAS 18313-1738 is similar to the
proto-planetary nebula (PPN) HD 51585. The SED of IRAS 17423-1755, IRAS
18313-1738 and IRAS 19127+1717 show a warm dust component (in addition to the
cold dust) which may be due to recent and ongoing mass-loss.


title: SCUBA Observations of High Redshift Radio Galaxies

abstract:
  High redshift radio galaxies (HzRGs) are key targets for studies of the
formation and evolution of massive galaxies. The role of dust in these
processes is uncertain. We have therefore observed the dust continuum emission
from a sample of z > 3 radio galaxies with the SCUBA bolometer array. We
confirm and strengthen earlier results, that HzRGs are massive starforming
systems and that submillimeter detection rate appears to be primarily a strong
function of redshift. We also observed HzRG-candidates which have sofar eluded
spectroscopic redshift determination. Four of these have been detected, and
provide evidence that they may be extremely obscured radio galaxies, possibly
in an early stage of their evolution.


title: High Resolution Simulations of the Global and Local ISM

abstract:
  We present the first to date high resolution calculations of the ISM down to
scales of 0.625 pc of the global and local ISM. The simulations show the
morphology and structure of the different ISM phases and reproduce many of the
features that have been observed in the Milky Way and other galaxies. In
particular, they show that the hot gas has a moderately low volume filling
factor (~20%) even in the absence of magnetic fields. Also, cold gas is mainly
concentrated in filamentary structures running perpendicular to the midplane
forming and dissipating within 10-12 Myr. Compression is the dominant process
for their formation, but thermal instability also plays a role. Also the
evolution of the Local Bubble is simulated by multi-supernova explosions;
calculated extensions after ~13 Myr match observations.


title:
Spatial analysis of the Halpha emission in the local star-forming UCM
  galaxies

abstract:
  We present a photometric study of the Halpha emission in the Universidad
Complutense de Madrid (UCM) Survey galaxies. This work complements our
previously-published spectroscopic data. We study the location of the
star-forming knots, their intensity, concentration, and the relationship of
these properties with those of the host galaxy. We also estimate that the
amount of Halpha emission that arises from the diffuse ionized gas is about
15-30% of the total Halpha flux for a typical UCM galaxy. This percentage seems
to be independent of the Hubble type. Conversely, we found that an `average'
UCM galaxy harbours a star formation event with 30% of its Halpha luminosity
arising from a nuclear component. The implications of these results for
higher-redshift studies are discussed, including the effects of galaxy size and
the depth of the observations. A correlation between the SFR and the Balmer
decrement is observed, but such correlation breaks down for large values of the
extinction. Finally, we recalculate the Halpha luminosity function and star
formation rate density of the local Universe using the new imaging data. Our
results point out that, on average, spectroscopic observations detected about
one third of the total emission-line flux of a typical UCM galaxy. The new
values obtained for the Halpha luminosity density and the star formation rate
density of the local Universe are 10^(39.3+/-0.2) erg s-1 Mpc-3, and
rho_SFR=0.016^(+0.007)_(-0.004) Mass_sun yr-1 Mpc-3 (H_0=50 km s-1 Mpc-1,
Omega_M=1.0, Lambda=0). The corresponding values for the `concordance
cosmology' (H_0=70 km s-1 Mpc-1, Omega_M=0.3, Lambda=0.7) are 10^(39.5+/-0.2)
erg s-1 Mpc-3 rho_SFR=0.029^(+0.008)_(-0.005) Mass_sun yr-1 Mpc-3.


title: Bottleneck effect in three-dimensional turbulence simulations

abstract:
  At numerical resolutions around $512^3$ and above, three-dimensional energy
spectra from turbulence simulations begin to show noticeably shallower spectra
than $k^{-5/3}$ near the dissipation wavenumber (`bottleneck effect'). This
effect is shown to be significantly weaker in one-dimensional spectra such as
those obtained in wind tunnel turbulence. The difference can be understood in
terms of the transformation between one-dimensional and three-dimensional
energy spectra under the assumption that the turbulent velocity field is
isotropic. Transversal and longitudinal energy spectra are similar and can both
accurately be computed from the full three-dimensional spectra. Second-order
structure functions are less susceptible to the bottleneck effect and may be
better suited for inferring the scaling exponent from numerical simulation
data.


title:
New optical and near-infrared Surface Brightness Fluctuations models. A
  primary distance indicator ranging from Globular Clusters to distant
  galaxies?

abstract:
  We present new theoretical models for Surface Brightness Fluctuations (SBF)
both for optical and near-infrared bands in standard ground-based and Hubble
Space Telescope filter systems. Simple Stellar Population simulations are
adopted. Models cover the age and metallicity ranges from $t=5$ to $15~Gyr$ and
from $Z=0.0001$ to 0.04 respectively. Effects due to the variation of the
Initial Mass Function and the stellar color-temperature relations are explored.
Particular attention is devoted to very bright stars in the color-magnitude
diagram and to investigate the effects of mass loss along the Red Giant Branch
(RGB) and the Asymptotic Giant Branch (AGB). It is found that $U$ and $B$ bands
SBF amplitudes are powerful diagnostics for the morphology of the Horizontal
Branch and the Post-AGB stars population. We point out that a careful treatment
of mass loss process along the RGB and AGB is fundamental in determining
reliable SBF evaluations. The SBF measurements are used to give robust
constraints on the evolution of AGB stars, suggesting that mass loss activity
on AGB stars should be twice more efficient than on the RGB stars. Our models
are able to reproduce the absolute SBF magnitudes of the Galactic Globular
Clusters and of galaxies, and their integrated colors. New calibrations of
absolute SBF magnitude in $V$, $R$, $I$, and $K$ photometric filters are
provided, which appear reliable enough to directly gauge distances bypassing
other distance indicators. The SBF technique is also used as stellar population
tracer to derive age and metallicity of a selected sample of galaxies of known
distances. Finally, {\it SBF color} versus {\it integrated color} diagrams are
proposed as particularly useful in removing the well known {\it age-metallicity
degeneracy} affecting our knowledge of remote stellar systems.


title: Field ZAMS stars in the solar neighborhood: Where have they come from ?

abstract:
  In the course of an all-sky survey for young stars in the solar neighborhood
we have found a tight kinematic group of ten F-G type zero-age main sequence
stars in the field. Here we discuss the origin of these stars. Backtracking the
space motions of these stars we argue that likely candidates for the parent
association are the Perseus OB3 (Per OB3), Upper Centaurus-Lupus (UCL), and
Lower Centaurus-Crux (LCC) associations, and that we are witnessing the ongoing
diffusion of (at least one of) these associations into the field.


title: The Twin-Jet of NGC1052 at Radio, Optical, and X-ray Frequencies

abstract:
  We present results from a combined radio, optical, and X-ray study of the
jet-associated emission features in NGC1052. We analyse the radio-optical
morphology and find a good positional correlation between the radio jet and the
optical emission cone. Two optical emission knots are directly associated with
radio counterparts exhibiting a radio to X-ray broadband spectrum not
compatible with synchrotron emission. We discuss the possibility that the
thermal soft spectrum of the extended X-ray emission originates from jet driven
shocks produced in the interaction between the jet-plasma and its surrounding
medium.


title: Galactic Center Shells and a Recurrent Starburst Model

abstract:
  By applying filtering techniques to remove straight filaments in the 20-cm
VLA radio image of the Galactic Center Arc region, we have shown that numerous
concentric radio shells of radii 5 to 20 pc are surrounding the Pistol and
Sickle region, which we call Galactic Center Shells (GCS). Each shell has
thermal energy of the order of $10^{49-50}$ erg. Several CO-line shells are
associated, whose kinetic energies are of the order of $10^{49-50}$ erg.
Summing up the energies of recognized GCSs, the total energy amounts to $\sim
10^{51}$ erg. The GCSs show an excellent correlation with the FIR shells
observed at 16--26 microns with the MSX. We propose a model in which GCSs were
produced by recurrent and/or intermittent starbursts in the Pistol area during
the last million yr. The most recent burst occurred some $10^5$ years ago,
producing an inner round-shaped shell (GCS I); earlier ones a million years ago
produced outer shells (GCS II and III), which are more deformed by interactions
with the surrounding ISM and Sgr A halo. We argue that recurrent starbursts had
also occurred in the past, which produced larger scale hyper shell structures
as well. A burst some million years ago produced the Galactic Center Lobe, and
a much stronger one 15 million years ago produced the North Polar Spur.


title:
The mass-velocity and intensity-velocity relations in jet-driven
  molecular outflows

abstract:
  We use numerical simulations to examine the mass-velocity and
intensity-velocity relations in the CO J=2-1 and H$_2$ S(1)1-0 lines for
jet-driven molecular outflows. Contrary to previous expectations, we find that
the mass-velocity relation for the swept-up gas is a single power-law, with a
shallow slope $\simeq -1.5$ and no break to a steeper slope at high velocities.
An analytic bowshock model with no post-shock mixing is shown to reproduce this
behaviour very well.
  We show that molecular dissociation and the temperature dependence of the
line emissivity are both critical in defining the shape of the line profiles at
velocities above $\sim$ 20 km s$^{-1}$. In particular, the simulated CO J=2-1
intensity-velocity relation does show a break in slope, even though the
underlying mass distribution does not. These predicted CO profiles are found to
compare remarkably well with observations of molecular outflows, both in terms
of the slopes at low and high velocities and in terms of the range of break
velocities at which the change in slope occurs. Shallower slopes are predicted
at high velocity in higher excitation lines, such as H$_2$ S(1)1-0.
  This work indicates that, in jet-driven outflows, the CO J=2-1 intensity
profile reflects the slope of the underlying mass-velocity distribution only at
velocities $\le $ 20 km/s, and that higher temperature tracers are required to
probe the mass distribution at higher speed.


title: Peculiar Relics from Primordial Black Holes in the Inflationary Paradigm

abstract:
  Depending on various assumptions on the energy scale of inflation and
assuming a primordial power spectrum of a Broken Scale Invariance (BSI) type,
we explore the possibility for Primordial Black Holes (PBH) and Planck relics
to contribute substantially to cold dark matter in the Universe. A recently
proposed possibility to produce planck relics in 4-dimensional string gravity
is considered. Possible experimental detection through gravitational waves is
further explored. We stress that inflation with a low energy scale, and also
possibly when Planck relics are produced, leads unavoidably to relics
originating from PBHs that are not effectively classical during their
formation, rendering the usual formalism inadequate for them.


title: The RGB Bump in dwarf Spheroidal galaxies: discovery and perspectives

abstract:
  I report on the recent discoveries of the Red Giant Branch Bump(s) in many
dwarf Spheroidal galaxies of the Local Group. The perspectives for the use of
this new observational feature to obtain constraints on the Star Formation
History and Age-Metallicity Relation of nearby galaxies are shortly explored
and reviewed.


title: Quasar Evolution Driven by Galaxy Encounters in Hierarchical Structures

abstract:
  We link the evolution of the galaxies in the hierarchical clustering scenario
with the changing accretion rates of cold gas onto the central massive black
holes that power the quasars. We base on galaxy interactions as main triggers
of accretion; the related scaling laws are taken up from Cavaliere & Vittorini
(2000), and grafted to a semi-analytic code for galaxy formation. As a result,
at high $z$ the protogalaxies grow rapidly by hierarchical merging; meanwhile,
much fresh gas is imported and also destabilized, so the holes are fueled at
their full Eddington rates. At lower $z$ the galactic dynamical events are
mostly encounters in hierarchically growing groups; now the refueling peters
out, as the residual gas is exhausted while the destabilizing encounters
dwindle. So, with no parameter tuning other than needed for stellar
observables, our model uniquely produces at $z>3$ a rise, and at $z\lesssim 2.5
$ a decline of the bright quasar population as steep as observed. In addition,
our results closely fit the observed luminosity functions of quasars, their
space density at different magnitudes from $z\approx 5$ to $z\approx 0$, and
the local $m_{BH}-\sigma$ relation.


title: Decline of the space density of quasars between z=2 and z=4

abstract:
  We define a new complete sample of 13 optically-luminous radio quasars
M_AB(1450 Angstrom) < -26.9 mag and log P_1.4 GHz(W/Hz) > 25.7 with redshift
3.8 < z < 4.5, obtained by cross-correlating the FIRST radio survey and the APM
catalogue of POSS-I. We measure the space density to be 1.0 +/- 0.3 /Gpc^3, a
factor 1.9 +/- 0.7 smaller than the space density of similar quasars at z=2.
Using a new measurement of the radio-loud fraction of quasars we find that at
z=4 the total space density of quasars with M_AB(1450 Angstrom) < -26.9 is 7.4
+/- 2.6/Gpc^3. This is a factor 1.8 +/- 0.8 less than the space density at z=2,
found by the 2dF quasar survey. This (z=2)/(z=4) ratio, consistent with that of
the radio-loud quasars, is significantly different from the ratio of about 10
found for samples including lower-luminosity quasars. This suggests that the
decline of the space density beyond z=2 is slower for optically-luminous
quasars than for less-luminous ones.


title: Neutrino-Driven Explosions in GRBs and Hypernovae

abstract:
  We study the physics behind the neutrino-driven mechanism for gamma-ray
bursts and hypernovae, deriving the critical density at which these outbursts
occur in the collapsar model. The agreement between this derivation and results
from past collapsar simulations (MacFadyen & Woosley 2000) is excellent,
implying that we have captured the essential physics. We then use this
derivation to study a range of progenitors for collapsar gamma-ray bursts. We
derive how much of the star will accrete onto the black hole core before the
infall density drops below this critical density, leading to an estimate of the
remnant black hole mass for GRBs and hypernovae. We also estimate the time
delays between gravity wave or neutrino signals and the onset of the explosion
or burst event. This derivation, combined with future observational
constraints, provides a physical insight into the structure of the GRB
progenitor.


title: The large-scale anomalous microwave emission revisited by WMAP

abstract:
  We present a new study of the high latitude galactic contributions to the
millimeter sky, based on an analysis of the WMAP data combined with several
templates of dust emission (DIRBE/COBE and FIRAS/COBE) and gas tracers (HI and
Halpha). To study the IR to millimeter properties of the diffuse sky at high
galactic latitude, we concentrate on the emission correlated with the HI gas.
We compute the emission spectrum of the dust/free-free/synchrotron components
associated with HI gas from low to large column densities. A significant
residual WMAP emission over the free-free, synchrotron and the dust
contribution is found from 3.2 to 9.1 mm. We show that this residual WMAP
emission (normalised to 10$^{20}$ atoms/cm$^2$) (1) exhibits a constant
spectrum from 3.2 to 9.1 mm and (2) significantly decreases in amplitude when
N$_{HI}$ increases, contrary to the HI-normalised far-infrared emission which
stays rather constant. It is thus very likely that the residual WMAP emission
is not associated with the Large Grain dust component. The decrease in
amplitude with increasing opacity ressembles in fact to the decrease of the
transiently heated dust grain emission observed in dense interstellar clouds.
This is supported by an observed decrease of the HI-normalised 60 microns
emission with HI column densities. Although this result should be interpreted
with care due to zodiacal residual contamination at 60 microns, it suggests
that the WMAP excess emission is associated with the small transiently heated
dust particles. On the possible models of this so-called ``anomalous microwave
emission'' linked to the small dust particles are the spinning dust and the
excess millimeter emission of the small grains, due to the cold temperatures
they can reach between two successive impacts with photons.


title:
Zeeman tomography of magnetic white dwarfs: General method and
  application to EF Eridani

abstract:
  We have developed a new method to derive the magnetic field distribution on
the surfaces of rotating magnetic white dwarfs from phase-resolved flux and
circular polarization spectra. An optimization code based on an evolutionary
strategy is used to fit synthetic Zeeman spectra for a variety of model
geometries described in the framework of a truncated multipole expansion. We
demonstrate that the code allows the reconstruction of relatively complex
fields using noise-added synthetic input spectra. As a first application, we
analyze flux and circular polarization spectra of the polar EF Eri in a low
state of accretion taken with FORS1 at the ESO VLT.


title:
Does a Good Conservation of Jacobi's Constant Imply a Good Orbital
  Numerical Integration?: I. Resonant Orbits

abstract:
  In this paper we show two examples of numerical orbital integrations (Planar
Circular Restricted Three Body Problem) in which even though the conservation
of Jacobi's constant is near to 1 part in 10e8, the integration proves to be
wrong. That is, for some particular cases the Jacobi's constant is insensitive
to very important qualitative (not quantitative) changes in the integrated
orbit which are produced by numerical errors. We provide specific
recomendations to test and ensure that a numerical code is working properly,
regardless the numerical method employed.


title:
Bayesian Analysis of the Chaplygin Gas and Cosmological Constant Models
  using the SNe Ia Data

abstract:
  The type Ia supernovae observational data are used to estimate the parameters
of a cosmological model with cold dark matter and the Chaplygin gas. The
Chaplygin gas model depends essentially on four parameters: the Hubble
constant, the velocity of the sound of the Chaplygin gas, the curvature of the
Universe and the fraction density of the Chaplygin gas and the cold dark
matter. The Bayesian parameter estimation yields $H_0 = 62.1^{+3.3}_{-3.4}
km/Mpc.s$, $\Omega_{k0} = -0.84^{+1.51}_{-1.23}$, $\Omega_{m0} =
0.0^{+0.82}_{-0.0}$, $% \Omega_{c0} = 1.40^{1.15}_{-1.16}$, $\bar{A} = c_s^2 =
0.93^{+0.07}_{-0.21} c $, $t_0 = 14.2^{+2.8}_{-1.3} Gy$ and $q_0 = -
0.98^{+1.02}_{-0.62}$. These and other results indicate that a Universe
completely dominated by the Chaplygin gas is favoured, at least as the type Ia
supernovae data are concerned. A closed and accelerating Universe is also
favoured. The Bayesian statistics indicates that the Chaplygin gas model is
more likely than the standard cosmological constant ($\Lambda CDM$) model at
55.3% confidence level when an integration on all free parameters is performed.
Assuming the spatially flat curvature, this percentage mounts to 65.3%. On the
other hand, if the density of dark matter is fixed at zero value, the Chaplygin
gas model becomes more preferred than the $\Lambda CDM$ model at 91.8%
confidence level. Finally, the hypothesis of flat Universe and baryonic matter
($\Omega_{b0}=0.04$) implies a Chaplygin gas model preferred over the $\Lambda
CDM$ at a confidence level of 99.4%.


title: Jets from X-ray binaries

abstract:
  Relativistic outflows, or `Jets', represent one of the most obvious,
important and yet poorly-explained phenomena associated with accreting
relativistic objects, including X-ray binaries. In the past decade we have
observed highly relativistic flows, the resultant in-situ particle acceleration
in the ISM, and begun to unearth the subtleties of the accretion -- outflow
coupling on timescales from seconds to years. In this chapter I shall attempt,
subjectively, to describe the state of research into jets from X-ray binaries
as it stands at the beginning of 2003.


title: Using Intracluster Light to Study Cluster Evolution

abstract:
  We present some early results from our deep imaging survey of galaxy clusters
intended to detect and study intracluster light (ICL). From our observations to
date, we find that ICL is common in galaxy clusters, and that substructure in
the ICL also appears to be common as well. We also discuss some initial
comparisons of our imaging results to high-resolution numerical simulations of
galaxy clusters, and give avenues for future research.


title:
The Incidence of Strong-Lensing Clusters in the Red-Sequence Cluster
  Survey

abstract:
  The incidence of giant arcs due to strong-lensing clusters of galaxies is
known to be discrepant with current theoretical expectations. This result
derives from a comparison of several cluster samples to predictions in the
framework of the currently favored $\Lambda$CDM cosmology, and one possible
explanation for the discrepancy is that this cosmological model is not correct.
In this paper we discuss the incidence of giant arcs in the Red-Sequence
Cluster Survey (RCS), which again shows significant disagreement with
theoretical predictions. We briefly describe a total of eight strong lens
systems, seven of which are discussed here for the first time. Based on the
details of these systems, in particular on the ratio of single to multiple arc
systems, we argue that it may be possible to explain this discrepancy in the
currently favored cosmology, by modifying the details of the lenses themselves.
Specifically, the high incidence of multiple arc systems and their overall high
redshift suggests that a sub-population of the global cluster population is
responsible for much of the observed lensing. The lack of lensing clusters at
$z<0.64$ in the RCS indicates that a property associated with clusters at early
times results in the boosted lensing cross sections; likely a combination of
ellipticity and elongation along the line of sight, substructure, and changes
in the cluster mass profiles is responsible. Cluster mass, which should evolve
to globally higher values toward lower redshifts, is clearly not the most
significant consideration for the formation of giant arcs.


title: VLBI Astrometry

abstract:
  VLBI astrometry allows coordinates of celestial radio sources to be
determined with submilliarcsecond accuracy. In particular, with differential
VLBI astrometry, the standard errors of relative positions and proper motions
can be as small as 10 microarcseconds and 10 microarcseconds per year,
respectively. I will review astrometric observations of AGN, M81*, a supernova,
pulsars, and radio stars, including the guide star, HR 8703, for the
NASA/Stanford gyroscope relativity mission, Gravity Probe B.


title: Dispersion in the lifetime and accretion rate of T Tauri discs

abstract:
  We compare evolutionary models for protoplanetary discs that include disc
winds with observational determinations of the disc lifetime and accretion rate
in Taurus. Using updated estimates for stellar ages in Taurus, together with
published classifications, we show that the evolution of the disc fraction with
stellar age is similar to that derived for ensembles of stars within young
clusters. Around 30 percent of stars lose their discs within 1 Myr, while the
remainder have disc lifetimes that are typically in the 1-10 Myr range. We show
that the latter range of ages is consistent with theoretical models for disc
evolution, provided that there is a dispersion of around 0.5 in the log of the
initial disc mass. The same range of initial conditions brackets the observed
variation in the accretion rate of Classical T Tauri stars at a given age. We
discuss the expected lifetime of discs in close binary systems, and show that
our models predict that the disc lifetime is almost constant for separations
exceeding 10 au. This implies a low predicted fraction of binaries that pair a
Classical T Tauri star with a Weak-lined T Tauri star, and is in better
agreement with observations of the disc lifetime in binaries than disc models
that do not include disc mass loss in a wind.


title: Determining Neutrino Mass from the CMB Alone

abstract:
  Distortions of Cosmic Microwave Background (CMB) temperature and polarization
maps caused by gravitational lensing, observable with high angular resolution
and high sensitivity, can be used to measure the neutrino mass. Assuming two
massless species and one with mass m_nu we forecast sigma(m_nu) = 0.15 eV from
the Planck satellite and sigma(m_nu)=0.04 eV from observations with twice the
angular resolution and about 20 times the sensitivity. A detection is likely at
this higher sensitivity since the observation of atmospheric neutrino
oscillations require mass-squared differences greater than about (0.04 eV)^2.


title:
Star formation histories of early-type galaxies. I: Higher order Balmer
  lines as age indicators

abstract:
  (shortened) We have obtained blue integrated spectra of 175 nearby early-type
galaxies, covering a wide range in galaxy velocity dispersion, and emphasizing
those with sigma < 100 km/s. Galaxies have been observed both in the Virgo
cluster and in lower-density environments. The main goals are the evaluation of
higher order Balmer lines as age indicators, and differences in stellar
populations as a function of mass, environment and morphology. In this first
paper our emphasis is on presenting the evolutionary population synthesis
models. Lower-sigma galaxies exhibit a substantially greater intrinsic scatter,
in a variety of line strength indicators, than do higher-sigma galaxies, with
the large intrinsic scatter setting in below a sigma of 100 km/s. Modeling of
the observed spectral indices indicates that the strong Balmer lines found
primarily among the low-sigma galaxies are caused by young age, rather than by
low metallicity. Thus we find a trend between the population age and the
velocity dispersion, such that low sigma galaxies have younger
luminosity-weighted mean ages. We have repeated this analysis using several
different Balmer lines, and find consistent results from one spectral indicator
to another.


title: The speed of gravity has not been measured from time delays

abstract:
  The recent passage of Jupiter by the quasar QSO J0842+1835 at a separation of
3.7 arcminutes on September 8, 2002, combined with recent advances in
interferometric radio timing, has allowed for the first measurement of
higher-order post-Newtonian terms in the Shapiro time delay which depend
linearly on the velocity of the gravitating body. Claims have been made that
these measurements also allow for the measurement of the propagation speed of
the gravitational force. This conclusion disagrees with recent calculations
done in the parameterized post-Newtonian (PPN) model, which find no dependence
of the velocity-dependent terms in the time delay on the speed of gravity to
the stated order. Here, to test out these claims and counterclaims, we
calculate the time delay in the limit of an instantaneous gravitational force,
and find that the velocity-dependent terms are in complete agreement with
previous PPN calculations, with no dependence on the speed of gravity. We
conclude that the speed of gravity cannot be determined by measuring these
terms in the Shapiro time delay, and suggest a reason why other groups
mistakenly came to the opposite conclusion.


title:
Nearby Seyfert galaxies are possible sources of cosmic rays above
  4*10^19 eV: Updated Results

abstract:
  Arrival directions of 63 extensive air showers with energies
4*10^19<E<=3*10^20 eV detected by the AGASA, Yakutsk, Haverah Park arrays are
analyzed in order to identify possible sources of cosmic rays with these
energies. We searched for active galactic nuclei within error boxes around the
shower-arrival directions and calculated the probabilities of objects being in
the error boxes by chance. Our previous result obtained in 1996-2001 (see
references in the text) is confirmed: the probabilities are small, P>3 sigma
(sigma is the parameter of Gaussian distribution) for Seyfert galaxies with
redshifts z<0.01 (along with BL Lacertae objects). The Seyfert galaxies are
characterized by moderate luminosities (L<10^46 erg/s) and weak radio and X-ray
emission.


title: Massive Black Holes at High Redshifts

abstract:
  Black holes with masses M_BH~10^{8.5} M_Sun dominate the accretion history of
the Universe. These black hole masses are typical of those found in
radio-selected galaxies today, suggesting that the giant elliptical hosts of
low redshift radio galaxies were the hosts of powerful, mostly radio-quiet,
quasars in the high redshift Universe. The reason that all radio galaxies are
found in such hosts may be the correlation of black hole mass with radio
luminosity, but it is emphasized that accretion rate too plays an important
role in the production of powerful radio jets. The tight K-z relation of
luminous, high redshift, radio galaxies is probably a selection effect due to
the selection on high black hole masses and high accretion rates. Luminous
radio galaxies are the radio-loud part of the ``quasar-2'' population, and the
ratio of radio-loud quasars to luminous radio galaxies, about 1:1, is so far
our only good estimate of the relative numbers of quasar-1s and quasar-2s. The
numbers of radio-quiet and radio-intermediate quasar-2s are still uncertain,
but a much larger population than the quasar-1s would conflict with constraints
from the present-day black hole mass density. A comparison of the number
densities of dark matter haloes and the high redshift quasars, however,
suggests that there are plenty of dark haloes capable of hosting the known high
redshift AGN and thus room for a significant, but not huge, quasar-2
population.


title: Might Dark Matter be Actually Black?

abstract:
  There have been proposals that primordial black hole remnants (BHRs) are the
dark matter, but the idea is somewhat vague. We argue here first that the
generalized uncertainty principle (GUP) may prevent black holes from
evaporating completely, in a similar way that the standard uncertainty
principle prevents the hydrogen atom from collapsing. Secondly we note that the
hybrid inflation model provides a plausible mechanism for production of large
numbers of small black holes. Combining these we suggest that the dark matter
might be composed of Planck-size BHRs and discuss the possible constraints and
signatures associated with this notion.


title: Laboratory Investigations into the Extreme Universe

abstract:
  Recent years have seen tremendous progress in our understanding of the
extreme universe, which in turn points to even deeper questions to be further
addressed. History has shown that the symbiosis between direct observations and
laboratory investigations is instrumental in the progress of astrophysics.
Current frontier astrophysical phenomena related to particle astrophysics and
cosmology typically involve one or more of the following conditions: (1)
extremely high energy events;(2) very high density, high temperature processes;
(3) super strong field environments. Laboratory experiments using high
intensity lasers and particle beams can calibrate astrophysical observation or
detection processes, investigate the underlying dynamics of astrophysical
phenomena, and probe fundamental physics in extreme limits. We give examples of
possible laboratory experiments that investigate into the extreme universe.


title: New SX Phoenicis Stars in the Globular Cluster M53

abstract:
  Through time-series CCD photometry of the metal-poor globular cluster M53, we
have discovered eight new SX Phoenicis type stars (labeled from SXP1 to SXP8).
All the new SX Phoenicis stars are located in the blue straggler star region of
a color-magnitude diagram of M53. One of these stars (SXP2) is found to have
very closely separated pulsation frequencies: $f_1/f_2 = 0.9595$ where $f_1$
and $f_2$ are primary and secondary frequencies. This may be due to excitation
of non-radial modes. Six of these SX Phoenicis stars are considered to be
pulsating in the fundamental mode. They show a tight linear correlation between
the period and luminosity. We derive a period - luminosity relation for the
fundamental mode for the period range of $-1.36 < Log P[d]< -1.15$ :
$<V>=-3.010(\pm0.262)Log P + 15.310(\pm0.048)$ with an rms scatter of 0.038,
corresponding to $<M_V>=-3.010 Log P - 1.070$ for an adopted distance modulus
of $(m-M)_V=16.38$ (Harris 1996).


title:
On the Evolution of Nonlinear N-body systems: Substructure of a Distant
  Galaxy Cluster

abstract:
  The graph-theoretical S-tree technique developed for the study of the
nonlinear N-body systems, is used for the study for the first time of the
substructure of a high redshift cluster of galaxies, namely of MS 1054-03,
z\simeq 0.8. Nearby galaxy clusters studied via the same S-tree code reveal
several clearly distinguished subgroups with significant bulk velocities.
Therefore the study of distant clusters can enable to trace the evolution of
their dynamics over cosmological time scales. The study of the MS 1054-03
showed a different structure, i.e. no evidence of merging subgroups but only of
a core of galaxies with velocity dispersion about 700 km s^{-1} while the
velocity dispersion of the main cluster 1870 km s^{-1}. Further study of
samples of high redshift clusters will enable to conclude whether this
discrepancy in the structure and dynamics between nearby and distant galaxy
clusters is a genuine evolutionary effect.


title:
Expected constraints on the generalized Chaplygin equation of state from
  future supernova experiments and gravitational lensing statistics

abstract:
  This paper aims to study the use of future SNAP data together with the result
of searches for strong gravitational lenses in future large quasar surveys to
constrain the Generalized Chaplygin Gas (GCG) model. The GCG is considered as a
possible unification scheme for dark matter-dark energy. It is found that both
experiments should be able to place important constraints on the model,
especially when both tests are used together.


title: Dynamical magnetic relaxation: A nonlinear magnetically driven dynamo

abstract:
  A non-linear, time-dependent, magnetically driven dynamo theory which shows
how magnetically dominated configurations can relax to become helical on the
largest scale available is presented. Coupled time-dependent differential
equations for large scale magnetic helicity, small scale magnetic helicity,
velocity, and the electromotive force are solved. The magnetic helicity on
small scales relaxes to drive significant large scale helical field growth on
dynamical (Alfv\'en crossing) time scales, independent of the magnitude of
finite microphysical transport coefficients, after which the growing kinetic
helicity slows the growth to a viscously limited pace. This magnetically driven
dynamo complements the nonlinear kinetic helicity driven dynamo; for the
latter, the growing magnetic helicity fluctuations suppress, rather than drive,
large scale magnetic helicity growth. A unified set of equations accommodates
both types of dynamos.