title:
Dense molecular gas in quasar host galaxies: a search for HCN emission
  from BR B1202-0725 at z=4.695

abstract:
  We report on the results of a search using the VLA for redshifted HCN(1-0)
emission from the host galaxy of BR B1202-0725, an optically luminous quasar at
z=4.695. The host galaxy emits strongly in the rest-frame far-infrared, and
shows characteristics very similar to that of more local, ultraluminous
infrared galaxies, in which a significant fraction of the far-infrared emission
is powered by star formation. We find a 3-sigma upper limit to the HCN(1-0)
emission of 4.9 x 10^10 K kms^-1 pc^2, assuming a lambda-cosmology. This limit
is consistent with correlations derived from measurements of the HCN, CO, and
far-infrared emission for a sample of more local galaxies, including starbursts
(Solomon et al, 1992a).


title: X-Ray Emission from the Pre-Planetary Nebula Henize 3-1475

abstract:
  We report the first detection of X-ray emission in a pre-planetary nebula,
Hen 3-1475. Pre-planetary nebulae are rare objects in the short transition
stage between the Asymptotic Giant Branch and planetary nebula evolutionary
phases, and Hen 3-1475, characterised by a remarkable S-shaped chain of optical
knots, is one of the most noteworthy members of this class. Observations with
the Advanced CCD Imaging Spectrometer (ACIS) onboard the Chandra X-Ray
observatory show the presence of compact emission coincident with the brightest
optical knot in this bipolar object, which is displaced from the central star
by 2.7 arcsec along the polar axis. Model fits to the X-ray spectrum indicate
an X-ray temperature and luminosity, respectively, of (4.3-5.7) 10^6 K and
(4+/-1.4) 10^{31} (D/5 kpc)^2 erg s^{-1}, respectively. Our 3-sigma upper limit
on the luminosity of compact X-ray emission from the central star in Hen 3-1475
is ~5 10^{31} (D/5 kpc)^2 erg s^{-1}. The detection of X-rays in Hen 3-1475 is
consistent with models in which fast collimated post-AGB outflows are crucial
to the shaping of planetary nebulae; we discuss such models in the context of
our observations.


title:
Radiative Transfer Modeling of Passive Circumstellar Disks: Application
  to HR4796A

abstract:
  We present a radiative transfer model which computes the spectral energy
distribution of a passive, irradiated, circumstellar disk, assuming the grains
are in radiative equilibrium. Dependence on radial density profile, grain
temperature estimation, and optical depth profiles on the output SED are
discussed. The bist fit model for HR4796A has a minimum and maximum spherical
grain size of 2.2 and 1000 \mu$m respectively, a size distribution slightly
steeper than the "classical" -3.5 MRN power law, grains composed of silicates,
trolite, ice, and organics and a peak radial density of 1.0 x 10^-17 g cm^-2 at
70 AU, yielding a disk mass of roughly 2 M_{oplus}$.


title:
Discrete Components in the Radial Velocities of 83 ScI Galaxies:
  Examining the Accuracy of Tully-Fisher Distances

abstract:
  Our previous analyses of the redshifts and distances of galaxies included 55
spiral galaxies and 36 Type Ia Supernovae galaxies in three separate groups.
All groups showed evidence that their radial velocities contain the same
discrete velocity components that are predicted from the early work of Tifft.
Here we examine another new source sample containing 83 ScI galaxies. When
B-band distances are used, we find clear evidence that the discrete velocities
defined by Tifft's most common velocity period are present in the radial
velocities of these galaxies. Assuming this is true, we are then able to use
the visibility, or ease of detection, of the discrete components as an
indication of the distance accuracy of the galaxies, comparing B- and I-band
distances, galaxy inclination ranges, and galaxy rotation velocity ranges. We
find (a), that, contrary to expectation, B-band distances for these sources are
considerably more accurate than I-band, (b), that the distance accuracy varies
with galaxy inclination, as expected, with the most consistent distances
obtained for inclinations between 48 and 65 degrees, and (c), that distances
are probably more accurate for small rotation velocities. With these results
for the 83 ScI galaxies, discrete velocity components have now been detected in
all 174 galaxies examined.


title: Simulations of weak gravitational lensing

abstract:
  We describe the simulation data produced by a pilot programme to compute mock
weak gravitational lensing maps for a range of currently popular cosmological
models by ray tracing through high-resolution N-body simulations. The programme
required only a modest investment in computer time to produce maps accurate to
arcminute scales covering hundreds of square degrees of sky for 4 cosmological
models.


title:
Measuring the Small-Scale Power Spectrum of Cosmic Density Fluctuations
  Through 21 cm Tomography Prior to the Epoch of Structure Formation

abstract:
  The thermal evolution of the cosmic gas decoupled from that of the cosmic
microwave background (CMB) at a redshift z~200. Afterwards and before the first
stars had formed, the cosmic neutral hydrogen absorbed the CMB flux at its
resonant 21cm spin-flip transition. We calculate the evolution of the spin
temperature for this transition and the resulting anisotropies that are
imprinted on the CMB sky due to linear density fluctuations during this epoch.
These anisotropies at an observed wavelength of 10.56[(1+z)/50] meters, contain
an amount of information that is orders of magnitude larger than any other
cosmological probe. Their detection, although challenging, could tightly
constrain any possible running of the spectral index from inflation (as
suggested by WMAP), small deviations from Gaussianity, or any significant
contribution from neutrinos or warm dark matter to the cosmic mass budget.


title: The Linear Instability of Astrophysical Flames in Magnetic Fields

abstract:
  Supernovae of Type Ia are used as standard candles for cosmological
observations despite the as yet incomplete understanding of their explosion
mechanism. In one model, these events are thought to result from subsonic
burning in the core of an accreting Carbon/Oxygen white dwarf that is
accelerated through flame wrinkling and flame instabilities. Many such white
dwarfs have significant magnetic fields. Here we derive the linear effects of
such magnetic fields on one flame instability, the well-known Landau-Darrieus
instability. When the magnetic field is strong enough that the flame is
everywhere sub-Alfvenic, the instability can be greatly suppressed.
Super-Alfvenic flames are much less affected by the field, with flames
propagating parallel to the field somewh at destabilized, and flames
propagating perpendicular to the field somewhat stabili zed. Trans-Alfvenic
parallel flames, however, like trans-Alfvenic parallel shocks, are seen to be
non-evolutionary; understanding the behavior of these flames will require
careful numerical simulation.


title: The central image of a gravitationally lensed quasar

abstract:
  A galaxy can act as a gravitational lens, producing multiple images of a
background object. Theory predicts there should be an odd number of images but,
paradoxically, almost all observed lenses have 2 or 4 images. The missing image
should be faint and appear near the galaxy's center. These ``central images''
have long been sought as probes of galactic cores too distant to resolve with
ordinary observations. There are five candidates, but in one case the third
image is not necessarily a central image, and in the others, the central
component might be a foreground source rather than a lensed image. Here we
report the most secure identification of a central image, based on radio
observations of PMN J1632-0033, one of the latter candidates. Lens models
incorporating the central image show that the mass of the lens galaxy's central
black hole is less than 2 x 10^8 M_sun, and the galaxy's surface density at the
location of the central image is more than 20,000 M_sun per square parsec, in
agreement with expectations based on observations of galaxies hundreds of times
closer to the Earth.


title:
Constraints on Quasar Continuum, BELR, and BALR Physics from SDSS
  Composite Spectra

abstract:
  We review recent results on quasars from the SDSS as they relate to our
understanding of the UV/optical continuum, the broad emission line region, and
the broad absorption line region. The ensemble average colors of large numbers
of quasars promise to provide constraints on the optical/UV continuum emission
mechanism. High-ionization emission-line blueshifts and emission line
properties as a function of optical/UV spectral index trace the structure of
the broad emission line region. Statistical analysis of the broad absorption
line quasar population suggests that they are more ubiquitous than one might
otherwise think and are not likely to represent a completely distinct
population of quasars, but that the BAL trough properties are a function of the
underlying optical continuum and emission properties of the quasar.


title: Some Recent Peculiarities of the Early Afterglow

abstract:
  We consider some recent developments in GRB/afterglow observations: (i) the
appearance of a very hard prompt component in GRB 941017, and (ii) variability
in the early afterglow light curves of GRB 021004 and GRB 030329. We show that
these observations fit nicely within the internal-external shocks model. The
observed variability indicates that the activity of the inner engine is more
complicated than was thought earlier and that it involves patchy shells and
refreshed shocks. We refute the claims of Berger et al. and of Sheth et al.
that the radio and mm observations of GRB 030329 are inconsistent with
refreshed shocks.


title: Gas Physics, Disk Fragmentation, and Bulge Formation in Young Galaxies

abstract:
  We investigate the evolution of star-forming gas-rich disks, using a 3D
chemodynamical model including a dark halo, stars, and a two-phase interstellar
medium with feedback processes from the stars. We show that galaxy evolution
proceeds along very different routes depending on whether it is the gas disk or
the stellar disk which first becomes unstable, as measured by the respective
Q-parameters. This in turn depends on the uncertain efficiency of energy
dissipation of the cold cloud component from which stars form. When the cold
gas cools efficiently and drives the instability, the galactic disk fragments
and forms a number of massive clumps of stars and gas. The clumps spiral to the
center of the galaxy in a few dynamical times and merge there to form a central
bulge component in a strong starburst. When the kinetic energy of the cold
clouds is dissipated at a lower rate, stars form from the gas in a more
quiescent mode, and an instability only sets in at later times, when the
surface density of the stellar disk has grown sufficiently high. The system
then forms a stellar bar, which channels gas into the center, evolves, and
forms a bulge whose stars are the result of a more extended star formation
history. We investigate the stability of the gas-stellar disks in both regimes,
as well as the star formation rates and element enrichment. We study the
morphology of the evolving disks, calculating spatially resolved colours from
the distribution of stars in age and metallicity, including dust absorption. We
then discuss morphological observations such as clumpy structures and chain
galaxies at high redshift as possible signatures of fragmenting, gas-rich
disks. Finally, we investigate abundance ratio distributions as a means to
distinguish the different scenarios for bulge formation.


title: On expansion parallax distances for planetary nebulae

abstract:
  The distances to individual wind-driven bubbles such as Planetary Nebulae
(PNe) can be determined using expansion parallaxes: the angular expansion
velocity in the sky is compared to the radial velocity of gas measured
spectroscopically. Since the one is a pattern velocity, and the other a matter
velocity, these are not necessarily the same. Using the jump conditions for
both shocks and ionization fronts, I show that for typical PNe the pattern
velocity is 20 to 30% larger than the material velocity, and the derived
distances are therefore typically 20 to 30% too low. I present some corrected
distances and suggest approaches to be used when deriving distances using
expansion parallaxes


title: Pulsars With Jets May Harbor Dynamically Important Accretion Disks

abstract:
  For many astrophysical sources with jets, there is evidence for the
contemporaneous presence of disks. In contrast, pulsars such as the Crab and
Vela show jets but have not yet revealed direct evidence for accretion disks.
Here we show that for such pulsars, an accretion disk radiating below
detectable thresholds may simultaneously account for (1) observed deviations in
the braking indices from that of the simple dipole, (2) observed pulsar timing
ages, and (3) possibly even the jet morphology via a disk outflow that
interacts with the pulsar wind within, collimating and/or redirecting it.


title: Optical Spectroscopy of K-selected Extremely Red Galaxies

abstract:
  We have obtained spectroscopic redshifts for 24 red galaxies from a sample
with median Ks=18.7 and F814W - Ks > 4, using the Keck telescope. These
EROshave high resolution morphologies from HST (Yan & Thompson 2003). Among the
24 redshifts, the majority (92%) are at $ 0.9 < z < 1.5$. We derived the
rest-frame J-band luminosity function at $z_{median} =1.14$. Our result
suggests that the luminosity evolution between bright EROs at $z\sim 1$ and the
present-day $>$L$^*$ massive galaxies is at most about 0.7 magnitude. Combining
the morphologies and deep spectroscopy revealed the following properties: (1)
86% of the spectra have absorption features from old stars, suggesting that the
dominant stellar populations seen in the rest-frame UV are old stars. 50% of
the sources have pure absorption lines, while the remaining 50% have emission
lines, indicating recent star formation. We conclude that the color criterion
for EROs is very effective in selecting old stellar populations at $z \sim 1$,
and a large fraction of these systems with prominent old stellar populations
also have recent star formation. (2) The 12 emission line systems have the same
number of disk and bulge galaxies as in the remaining 12 pure absorption line
systems. We conclude that spectral classes do not have a simple, direct
correspondence with morphological types. (3) Three EROs could be isolated, pure
passively evolving early-type galaxies at $z\sim 1$. This implies that only a
small fraction (10%--15%) of early-type galaxies are formed in a rapid burst of
star formation at high redshifts and evolved passively since then. (Abridged).


title:
The Effects of Rotation on Thermal X-Ray Afterglows Resulting from
  Pulsar Glitches

abstract:
  We derive the anisotropic heat transport equation for rotating neutron stars
and the thermal equilibrium condition in a relativistic rotating axisymmetric
star is also derived through a simple variational argument. With a simple model
of neutron star, we model the propagation of heat pulses resulting from
transient energy releases inside the star. {\bf Such sudden energy release can
occur in pulsars during glitches.} Even in slow rotation limit ($\Omega\leq
1\times 10^{3}{s}^{-1}$), the results with rotational effects involved could be
noticeably different from those obtained with a spherically symmetric metric in
terms of the time scales and magnitudes of thermal afterglow. The effects of
gravitational lensing and frame dragging on the X-ray light curve pulsations
are also studied. The results we obtain indicate that the effect of rotation on
the light curve modulation is small, and the spacetime curvature effect
predominates. The metric components and rotational deformation on the stellar
structure are calculated by using Hartle-Thorne formalism. {\bf We have applied
our model to study the thermal response time scales of pulsars after glitches
and find that the centrifugal force produced by rotation can substantially
reduce the response time by a factor of three between non-rotating star and
rotating star with $\Omega \sim 900 s^{-1}$. The equation of state can also
affect the duration of response.


title:
Towards a Deterministic Model of Planetary Formation I: a Desert in the
  Mass and Semi Major Axis Distributions of Extra Solar Planets

abstract:
  We examine the accretion of cores of giant planets from planetesimals, gas
accretion onto the cores, and their orbital migration. We adopt a working model
for nascent protostellar disks with a wide variety of surface density
distributions in order to explore the range of diversity among extra solar
planetary systems. If some cores can acquire more mass than a critical value of
several Earth masses during the persistence of the disk gas, they would be able
to rapidly accrete gas and evolve into gas giant planets. The gas accretion
process is initially regulated by the Kelvin-Helmholtz contraction of the
planets' gas envelope. Based on the assumption that the exponential decay of
the disk-gas mass occurs on the time scales $\sim 10^{6}-10^{7}$ years and that
the disk mass distribution is comparable to those inferred from the
observations of circumstellar disks of T Tauri stars, we carry out simulations
to predict the distributions of masses and semi major axes of extra solar
planets. Since planets' masses grow rapidly from $10 M_{\oplus}$ to $100
M_{\oplus}$, the gas giant planets rarely form with asymptotic masses in this
intermediate range. Our model predicts a paucity of extra solar planets with
mass in the range 10-$100 M_{\oplus}$ and semi major axis less than 3AU. We
refer to this deficit as a ``planet desert''. The effect of migration is to
sharpen the boundaries and to enhance the contrast of the planet desert. The
mass and semi major axis distributions generated in our simulations for the gas
giants are consistent with those of the known extra solar planets.


title:
Early ($<$0.3 day) R-band light curve of the optical afterglow of
  GRB030329

abstract:
  We observed the optical afterglow of the bright gamma-ray burst GRB030329 on
the nights of 2003 March 29, using the Kiso observatory (the University of
Tokyo) 1.05 m Schmidt telescope. Data were taken from March 29 13:21:26 UT to
17:43:16 (0.072 to 0.253 days after the burst), using an $Rc$-band filter. The
obtained $Rc$-band light curve has been fitted successfully by a single power
law function with decay index of $0.891\pm0.004$. These results remain
unchanged when incorporating two early photometric data points at 0.065 and
0.073 days, reported by Price et al.(2003) using the SSO 40 inch telescope, and
further including RTT150 data (Burenin et al. 2003) covering at about 0.3 days.
Over the period of 0.065-0.285 days after the burst, any deviation from the
power-law decay is smaller than $\pm$0.007 mag. The temporal structure reported
by Uemura et al. (2003) does not show up in our $R$-band light curve.


title: The Carbon content in the Galactic CygnusX/DR21 star forming region

abstract:
  Observations of Carbon bearing species are among the most important
diagnostic probes of ongoing star formation. CO is a surrogate for H$_2$ and is
found in the vicinity of star formation sites. There, [CI] emission is thought
to outline the dense molecular cores and extend into the lower density regions,
where the impinging interstellar UV radiation field plays a critical role for
the dissociation and ionization processes. Emission of ionized carbon ([CII])
is found to be even more extended than [CI] and is linking up with the ionized
medium. These different tracers emphasize the importance of multi-wavelength
studies to draw a coherent picture of the processes driving and driven by high
mass star formation. Until now, large scale surveys were only done with low
resolution, such as the COBE full sky survey, or were biased to a few selected
bright sources (e.g. Yamamoto et al. 2001, Schneider et al. 2003). A broader
basis of unbiased, high-resolution observations of [CI], CO, and [CII] may play
a key role to probe the material processed by UV radiation.


title: Combining Astrometry and Spectroscopy

abstract:
  Orbital solutions for binary or multiple stellar systems that combine
astrometry (e.g., position angles and angular separations) with spectroscopy
(radial velocities) have important advantages over astrometric-only or
spectroscopic-only solutions. In many cases they allow the determination of the
absolute masses of the components, as well as the distance. Yet, these kinds of
combined solutions that use different types of observations in a global
least-squares fit are still not very common in the literature. An outline of
the procedure is presented, along with examples to illustrate the sort of
results that can be obtained. The same method can easily be extended to include
other types of measurements (times of eclipse, Hipparcos observations,
interferometric visibilities and closure phases, parallaxes, lunar
occultations, etc.), which often complement each other and strengthen the
solution.


title: XMM-Newton observations of 3C 273

abstract:
  A series of nine XMM-Newton observations of the radio-loud quasar 3C 273 are
presented, concentrating mainly on the soft excess. Although most of the
individual observations do not show evidence for iron emission, co-adding them
reveals a weak, broad line (EW ~ 56 eV). The soft excess component is found to
vary, confirming previous work, and can be well fitted with multiple blackbody
components, with temperatures ranging between ~40 and ~330 eV, together with a
power-law. Alternatively, a Comptonisation model also provides a good fit, with
a mean electron temperature of ~350 eV, although this value is higher when the
soft excess is more luminous over the 0.5-10 keV energy band. In the RGS
spectrum of 3C 273, a strong detection of the OVII He-alpha absorption line at
zero redshift is made; this may originate in warm gas in the local
intergalactic medium, consistent with the findings of both Fang et al. (2003)
and Rasmussen et al. (2003).


title: DW Cancri: a magnetic VY Scl star with an orbital period of 86 minutes

abstract:
  We present the first time-resolved spectroscopic study of the cataclysmic
variable DW Cancri. We have determined an orbital period of 86.10 +- 0.05 min,
which places the system very close to the observed minimum period of
hydrogen-rich cataclysmic variables. This invalidates previous speculations of
DW Cnc being either a permanent superhumper below the period minimum or a
nova-like variable with an orbital period longer than 3 hours showing
quasi-periodic oscillations. The Balmer and HeI lines have double-peaked
profiles and exhibit an intense S-wave component moving with the orbital
period. Remarkably, the Balmer and HeI radial velocity curves are modulated at
two periods: 86.10 +- 0.05 min (orbital) and 38.58 +- 0.02 min. The same short
period is found in the equivalent width variations of the single-peaked HeII
4686 line. We also present time-resolved photometry of the system which shows a
highly-coherent variation at 38.51 min, consistent with the short spectroscopic
period. The large number of similarities with the short-period intermediate
polar V1025 Cen lead us to suggest that DW Cnc is another intermediate polar
below the period gap, and we tentatively identify the photometric and
spectroscopic 38-min signals with the white dwarf spin period. DW Cnc has never
been observed to undergo an outburst, but it occasionally exhibits low states
\~2 mag fainter than its typical brightness level of V~14.5, resembling the
behaviour of the high mass-transfer VY Scl stars.


title:
Modelling galactic spectra: II - Simultaneous study of stellar dynamics
  and stellar mix in NGC3258

abstract:
  In this paper we adopt a method to analyse absorption line spectra from
elliptical galaxies that determines the dynamics of the galaxy and at the same
time offers a way to study the stellar populations in that galaxy by a direct
fit to the spectra. The result of the modelling is a distribution function for
each stellar population that is considered in the fit. The method is described
in detail in an accompanying paper.
  This paper reports on a dynamical stellar population study in NGC3258, based
on spectra in two different wavelength regions, the near-IR Ca II triplet
around 8600A and the Ca H and K lines around 3900A. These absorption lines have
discriminating power toward various stellar types.
  The dynamical model shows an increase in dwarfs (represented by G2V stars)
toward the centre. Most of the rotation in the model is delivered by the giants
(represented by M1III stars). Moreover, the different models that were
considered indicate that establishing a potential for a galaxy is dependent on
the wavelength range used for the modelling.


title: Impulsive electron acceleration by Gravitational Waves

abstract:
  We investigate the non-linear interaction of a strong Gravitational Wave with
the plasma during the collapse of a massive magnetized star to form a black
hole, or during the merging of neutron star binaries (central engine). We found
that under certain conditions this coupling may result in an efficient energy
space diffusion of particles. We suggest that the atmosphere created around the
central engine is filled with 3-D magnetic neutral sheets (magnetic nulls). We
demonstrate that the passage of strong pulses of Gravitational Waves through
the magnetic neutral sheets accelerates electrons to very high energies.
Superposition of many such short lived accelerators, embedded inside a
turbulent plasma, may be the source for the observed impulsive short lived
bursts. We conclude that in several astrophysical events, gravitational pulses
may accelerate the tail of the ambient plasma to very high energies and become
the driver for many types of astrophysical bursts.


title: The formation of the double neutron star pulsar J0737--3039

abstract:
  We find that the orbital period (2.4 hours), eccentricity (0.09), dipole
magnetic field strength (6.9 x 10^9 Gauss) and spin period (22 ms) of the new
highly relativistic double neutron star system PSR J0737-3039 can all be
consistently explained if this system originated from a close helium star plus
neutron star binary (HeS-NS) in which at the onset of the evolution the helium
star had a mass in the range 4.0 to 6.5 M_sun and an orbital period in the
range 0.1 to 0.2 days. Such systems are the post-Common-Envelope remnants of
wide Be/X-ray binaries (orbital period ~ 100 to 1000 days) which consist of a
normal hydrogen-rich star with a mass in the range 10 - 20 M_sun and a neutron
star. The close HeS-NS progenitor system went through a phase of mass transfer
by Roche-lobe overflow at a high rate lasting a few times 10^4 years; assuming
Eddington-limited disk accretion onto the neutron star this star was spun up to
its present rapid spin rate. At the moment of the second supernova explosion
the He star had a mass in the range 2.3 to 3.3 M_sun and in order to obtain the
present orbital parameters of PSR J0737-3039 a kick velocity in the range 70 -
230 km/s must have been imparted to the second neutron star at its birth.


title: Roche tomography of the secondary stars in CVs

abstract:
  The secondary stars in cataclysmic variables (CVs) are key to our
understanding of the origin, evolution and behaviour of this class of
interacting binary. In seeking a fuller understanding of these objects, the
challenge for observers is to obtain images of the secondary star. This goal
can be achieved through Roche tomography, an indirect imaging technique that
can be used to map the Roche-lobe-filling secondary. The review begins with a
description of the basic principles that underpin Roche tomography, including
methods for determining the system parameters. Finally, we conclude with a look
at the main scientific highlights to date, including the first unambiguous
detection of starspots on AE Aqr B, and consider the future prospects of this
technique.


title: Dark Matter in Galaxies: Observational overview

abstract:
  I review the observational side of the present state of the debate about the
dark matter in galaxies, with emphasis on the core/cusp problem in low surface
brightness galaxies, and the question of maximum / sub-maximum disks in spiral
galaxies. Some remarks are made about the dwarf spheroidals around the Milky
Way, and about elliptical galaxies.


title: Bars and the connection between dark and visible matter

abstract:
  Isolated barred galaxies evolve by redistributing their internal angular
momentum, which is emitted mainly at the inner disc resonances and absorbed
mainly at the resonances in the outer disc and the halo. This causes the bar to
grow stronger and its pattern speed to decrease with time. A massive,
responsive halo enhances this process. I show correlations and trends between
the angular momentum absorbed by the halo and the bar strength, pattern speed
and morphology. It is thus possible to explain why some disc galaxies are
strongly barred, while others have no bar, or only a short bar or an oval. In
some cases, a bar is found also in the halo component. This ``halo bar'' is
triaxial, but more prolate-like, is shorter than the disc bar and rotates with
roughly the same pattern speed. I finally discuss whether bars can modify the
density cusps found in cosmological CDM simulations of dark matter haloes.


title: Modelling galactic spectra: I - A dynamical model for NGC3258

abstract:
  In this paper we present a method to analyse absorption line spectra of a
galaxy designed to determine the stellar dynamics and the stellar populations
by a direct fit to the spectra. This paper is the first one to report on the
application of the method to data. The modelling results in the knowledge of
distribution functions that are sums of basis functions. The practical
implementation of the method is discussed and a new type of basis functions is
introduced.
  With this method, a dynamical model for NGC 3258 is constructed. This galaxy
can be successfully modelled with a potential containing 30% dark matter within
1r_e with a mass of 1.6x10^11 M_o. The total mass within 2r_e is estimated as
5x10^11 M_o, containing 63% dark matter. The model is isotropic in the centre,
is radially anisotropic between 0.2 and 2 kpc (0.88 r_e) and becomes
tangentially anisotropic further on. The photometry reveals the presence of a
dust disk near the centre.


title: Stationary accretion disks launching super fast-magnetosonic MHD jets

abstract:
  We present self-similar models of resistive viscous Keplerian disks driving
non-relativistic magnetohydrodynamics (MHD) jets becoming super
fast-magnetosonic. We show that in order to obtain such solutions, the thermal
pressure must be a sizeable fraction of the poloidal magnetic pressure at the
Alfven surface. These steady solutions which undergo a recollimation shock
causally disconnected from the driving engine, account for structures with a
high temperature plasma in the sub-Alfvenic region. We suggest that only
unsteady outflows with typical time-scales of several disk dynamical
time-scales can be produced if the suitable pressure conditions are not
fulfilled.


title:
Resolving the Stellar Population of the Standard Elliptical Galaxy
  NGC3379

abstract:
  Using the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) on
board the Hubble Space Telescope, we have obtained F110W (J-band) and F160W
(H-band) images of three fields in NGC3379, a nearby normal giant elliptical
galaxy. These images resolve individual red giant stars, yielding the first
accurate color-magnitude diagrams for a normal luminous elliptical. The
photometry reaches 1 magnitude below the red giant branch tip with errors of <
0.2 mags in F110W-F160W. A strong break in the luminosity function at F160W =
23.68 +/- 0.06 is identified as the tip of the red giant branch (RGB);
comparison with theoretical isochrones implies a distance of 10.8 +/- 0.6 Mpc,
in good agreement with a number of previous estimates using various techniques.
The mean metallicity is close to solar, but there is an appreciable spread in
abundance, from at least as metal poor as [Fe/H] = -1.5 to as high as +0.8.
There is a significant population of stars brighter than the RGB tip by up to
about 1 magnitude. The observations of each field were split over two epochs,
separated by 2-3 months, allowing the identification of candidate long period
variables; at least 40% of the stars brighter than the RGB tip are variable.
Lacking period determinations, the exact nature of these variables remains
uncertain, but the bright AGB stars and variables are similar to those found in
metal rich globular clusters and are not luminous enough to imply an
intermediate age population. All of the evidence points to a stellar population
in NGC3379 which is very similar to the bulge of the Milky Way, or an
assortment of Galactic globular clusters covering a large metallicity spread.


title: Simultaneous INTEGRAL/RXTE Observations of GRS 1915+105

abstract:
  We present the first results of simultaneous INTEGRAL and RXTE observations
of the microquasar GRS 1915+105. We focus on the analysis of the unique highly
variable observation and show that we might have observed a new class of
variability. We then study the energetic dependence of a low frequency QPO from
our steady observations.


title: The 2dF Galaxy Redshift Survey: Clustering properties of radio galaxies

abstract:
  The clustering properties of local, S_{1.4 GHz} > 1 mJy, radio sources are
investigated for a sample of 820 objects drawn from the joint use of the FIRST
and 2dF Galaxy Redshift surveys. To this aim, we present 271 new bj < 19.45
spectroscopic counterparts of FIRST radio sources to be added to those already
introduced in Magliocchetti et al. (2002). The two-point correlation function
for the local radio population is found to be entirely consistent with
estimates obtained for the whole sample of 2dFGRS galaxies. We estimate the
parameters of the real-space correlation function xi(r)=(r/r_0)^{-\gamma},
r_0=6.7^{+0.9}_{-1.1} Mpc and \gamma=1.6\pm 0.1, where h=0.7 is assumed.
Different results are instead obtained if we only consider sources that present
signatures of AGN activity in their spectra. These objects are shown to be very
strongly correlated, with r_0=10.9^{+1.0}_{-1.2} Mpc and \gamma=2\pm 0.1, a
steeper slope than has been claimed in other recent works. No difference is
found in the clustering properties of radio-AGNs of different radio luminosity.
These results show that AGN-fuelled sources reside in dark matter halos more
massive than \sim 10^{13.4} M_{\sun}},higher the corresponding figure for
radio-quiet QSOs. This value can be converted into a minimum black hole mass
associated with radio-loud, AGN-fuelled objects of M_{BH}^{min}\sim 10^9
M_{\sun}. The above results then suggest -at least for relatively faint radio
objects -the existence of a threshold black hole mass associated with the onset
of significant radio activity such as that of radio-loud AGNs; however, once
the activity is triggered, there appears to be no evidence for a connection
between black hole mass and level of radio output. (abridged)


title: Observing the high redshift universe using the VIMOS-IFU

abstract:
  We describe the advantages of using Integral Field Spectroscopy to observe
deep fields of galaxy. The VIMOS Integral Field Unit is particularly suitable
for this kind of studies thanks to its large field-of-view (~ 1 arcmin^2).
After a short description of the VIMOS-IFU data reduction, we detail the main
scientific issues which can be addressed using observations of the Hubble Deep
Field South with a combination of Integral Field Spectroscopy and broad band
optical and Near-Infrared imaging.


title: Constraints on braneworld inflation from CMB anisotropies

abstract:
  We obtain observational constraints on Randall--Sundrum type II braneworld
inflation using a compilation of data including WMAP, the 2dF and latest SDSS
galaxy redshift surveys. We place constraints on three classes of inflation
models (large-field, small-field and hybrid models) in the high-energy regime,
which exhibit different behaviour compared to the low-energy case. The quartic
potential is outside the $2\sigma$ observational contour bound for a number of
$e$-folds less than 60, and steep inflation driven by an exponential potential
is excluded because of its high tensor-to-scalar ratio. It is more difficult to
strongly constrain small-field and hybrid models due to additional freedoms
associated with the potentials, but we obtain upper bounds for the energy scale
of inflation and the model parameters in certain cases. We also discuss
possible ways to break the degeneracy of consistency relations and inflationary
observables.


title: High-frequency polarization properties of southern Kuhr sources

abstract:
  We have carried out observations at 18.5 GHz with the Australia Telescope
Compact Array (ATCA) of 250 out of the 258 Southern extragalactic sources in
the complete 5 GHz 1 Jy sample by K\"uhr et al. (1981). In this paper we focus
on the polarization properties of this sample, while other properties will be
addressed in a future paper. In our analysis we subdivide the sample into flat
and steep spectrum sources following Stickel et al. (1994) classification,
where spectral indices were measured between 2.7 and 5 GHz. The polarized flux
has been measured with a S/N > 5 for 170 sources (114 flat-spectrum and 56
steep-spectrum) and upper limits have been set for additional 27 sources (12
flat-spectrum and 15 steep-spectrum). The median polarization degree at 18.5
GHz for the flat-spectrum sub-sample is \Pi_{18.5}\simeq 2.7%, about a factor
of 2 higher than at 1.4 GHz (\Pi_{1.4}\simeq 1.4%, based on NVSS data). For
flat-spectrum sources we find a weak correlation between \Pi_{18.5} and the
high frequency (5--18.5 GHz) spectral index. No evidences of significant
correlations of the polarization degree with other source properties are found.
The median value of \Pi_{18.5} for the steep spectrum sources is \simeq 4.8%,
but our sample might be biased against extended sources. We find indications of
a correlation between \Pi_{18.5} and both the low frequency (1.4--5 GHz) and
the high frequency (5--18.5 GHz) spectral indices. An important application of
this work is the possibility to estimate the contamination of CMB polarization
maps by extragalactic radio sources. Our results indicate that such
contamination is within the range of estimates given by Mesa et al. (2002).


title:
Population Synthesis in the Blue III. The Integrated Spectrum of M67 and
  the Spectroscopic Age of M32

abstract:
  We construct an integrated spectrum of the intermediate age, solar
metallicity Galactic cluster M67, from individual spectra of cluster members.
The integrated spectrum is used as a template to test our stellar population
synthesis (SPS) models, in an age and [Fe/H] regime where such models remain
largely untested. We show that our models predict a spectroscopic age of 3.5
+/- 0.5 Gyr for M67, in excellent agreement with the age we derive from the
color-magnitude diagram of the cluster. The same age is obtained when using
Hbeta, Hgamma or Hdelta as the age indicator. Our models predict the abundances
of Fe, Mg, C and N in agreement with detailed abundance analyses of cluster
stars, to within 0.1 dex. Encouraged by the high degree of consistency of our
models, we apply them to the study of the integrated spectrum of the central 3
arcsec of the compact elliptical galaxy M32. The resulting luminosity-weighted
age of the galaxy ranges between 2 and 3.5 Gyr, depending on the Balmer line
used. According to our models, the center of M32 seems to have a super-solar
light-weighted Fe abundance, ranging between [Fe/H] ~ +0.1 and +0.3, depending
on the Fe line adopted. Light-weighted abundance ratios found for the center of
M32 are as follows: [Mg/Fe] ~ -0.1 -- -0.2, [C/Fe] and [N/Fe] ~ 0. We find that
single SPS models with a solar-scaled abundance pattern cannot fit all the
Balmer and metal lines in the integrated spectrum of M32. There is a systematic
trend in the sense that bluer absorption lines indicate a younger age and a
higher [Fe/H]. This slight inconsistency can be due either to (unaccounted for)
abundance ratio effects on blue iron and Balmer line indices, or to a spread of
the ages of the stellar populations in M32. Current stellar population models
cannot break this degeneracy at the level of accuracy required to address this
problem.


title:
Can satellites deliver substructures and black holes to inner halo by
  dynamical friction?

abstract:
  A fully analytical formulation is developed to make dynamical friction
modeling more realistic. The rate for a satellite to decay its orbit in a host
galaxy halo is often severely overestimated when applying ChandraSekhar's
formula without correcting for the tidal loss of the satellite and the
adiabactic growth of the host galaxy potential over the Hubble time. As a
satellite decays to the inner and denser region of the host galaxy, the high
ambient density speeds up their exchange of energy and angular momentum, but
shrinks the Roche lobe of the satellite by tides. Eventually both processes of
orbital decay and tidal stripping hang up altogether once the satellite is
light enough. These competing processes can be modeled analytically for a
satellite if we parametrize the massloss history by an empirical formula. We
also incorporate the adiabatic contraction of orbits due to growth of the host
potential well. Observed dwarf galaxies often show a finite density core, which
determines how much inwards its remnants could be delivered to the host galaxy.
Ghost streams or remnant cores or globular clusters of satellites should
populate preferentially the outer halo (e.g., the Magellanic stream and the
Ursa Minor dwarf), rather than the inner halo (e.g., the Sgr stream and the
Omega-cen cluster). Massloss due to strong tides in the inner galaxy also makes
it problematic for any small central black holes in nuclei of satellite
galaxies to decay in orbit and merge into the center of the host galaxy.


title: Variable stars in M31 from the MEGA survey

abstract: This paper has been withdrawn.


title: MEGA: Microlensing Exploration of the Galaxy and Andromeda

abstract: This paper has been withdrawn.


title:
Antimatter from the cosmological baryogenesis and the anisotropies and
  polarization of the CMB radiation

abstract:
  We discuss the hypotheses that cosmological baryon asymmetry and entropy were
produced in the early Universe by phase transition of the scalar fields in the
framework of spontaneous baryogenesis scenario. We show that annihilation of
the matter-antimatter clouds during the cosmological hydrogen recombination
could distort of the CMB anisotropies and polarization by delay of the
recombination. After recombination the annihilation of the antibaryonic clouds
(ABC) and baryonic matter can produce peak-like reionization at the high
redshifts before formation of quasars and early galaxy formation. We discuss
the constraints on the parameters of spontaneous baryogenesis scenario by the
recent WMAP CMB anisotropy and polarization data and on possible manifestation
of the antimatter clouds in the upcoming PLANCK data.


title: Using Narrow Band Photometry to Classify Stars and Brown Dwarfs

abstract:
  We present a new system of narrow band filters in the near infrared that can
be used to classify stars and brown dwarfs. This set of four filters, spanning
the H band, can be used to identify molecular features unique to brown dwarfs,
such as H2O and CH4. The four filters are centered at 1.495 um (H2O), 1.595 um
(continuum), 1.66 um (CH4), and 1.75 um (H2O). Using two H2O filters allows us
to solve for individual objects' reddenings. This can be accomplished by
constructing a color-color-color cube and rotating it until the reddening
vector disappears. We created a model of predicted color-color-color values for
different spectral types by integrating filter bandpass data with spectra of
known stars and brown dwarfs. We validated this model by making photometric
measurements of seven known L and T dwarfs, ranging from L1 - T7.5. The
photometric measurements agree with the model to within +/-0.1 mag, allowing us
to create spectral indices for different spectral types. We can classify A
through early M stars to within +/-2 spectral types, late-type M and L dwarfs
to within +/-0.3 spectral types and T dwarfs to within +/-0.1 spectral types
1-sigma. Thus, we can distinguish between a T1 and a T3 dwarf. The four
physical bands can be converted into two reddening-free indices, mu1 and mu2,
and an extinction, AV, for the individual object. This technique, which is
equivalent to extremely low resolution spectroscopy, can be used to survey
large areas to provide rough spectral classifications for all the stars in the
area, ranging down to the coolest brown dwarfs. It should prove particularly
useful in young clusters where reddening can be high.


title: Doppler tomography of accretion in binaries

abstract:
  Since its conception, Doppler tomography has matured into a versatile and
widely used tool. It exploits the information contained in the
highly-structured spectral line-profiles typically observed in
mass-transferring binaries. Using inversion techniques akin to medical imaging,
it permits the reconstruction of Doppler maps that image the accretion flow on
micro-arcsecond scales. I summarise the basic concepts behind the technique and
highlight two recent results; the use of donor star emission as a means to
system parameter determination, and the real-time movies of the evolving
accretion flow in the cataclysmic variable WZ Sge during its 2001 outburst. I
conclude with future opportunities in Doppler tomography by exploiting the
combination of superior data sets, second generation reconstruction codes and
simulated theoretical tomograms to delve deeper into the physics of accretion
flows.


title: A new design for a very low frequency space borne radio interferometer

abstract:
  The non transparency and severe propagation effects of the terrestrial
ionosphere make it impossible for Earth based instruments to study the universe
at low radio frequencies. An exploration of the low frequency radio window with
the resolution and sensitivity essential to meet the scientific objectives will
necessarily require a dedicated satellite based interferometer operating at
these frequencies. Such missions have been proposed in the literature for about
past fifteen years. Today, the steady and impressive advances in technology and
computing resources have brought us on the brink of a quantum jump in the
performance and capabilities of such missions, increasing their scientific
desirability many-fold. This paper presents the concept design which emerged
from a study to investigate the feasibility of a low frequency satellite based
interferometer operating in the frequency range 0.1 -- $40 MHz$ titled {\em
PrepAration for Radio Interferometry in Space (PARIS)}. The salient features of
the design are: an on-board correlator to reduce the data volumes to be
transmitted to the Earth by about two orders of magnitude; use of three
orthogonal dipoles in place of two to achieve better polarisation
characteristics; direct digitisation of the entire radio frequency band of
interest which eliminates the need for a local oscillator system; an overlap in
the observing frequency range with upcoming ground based instruments for aid in
imaging and calibration and an all-sky imaging capability. The most
constraining bottle neck for the present design is the large
intra-constellation telemetry requirement. It is expected that technological
solutions to meet this requirement will be found in near future as other
formation flying missions which share this requirement emerge.


title: From gas to starburst and AGN

abstract:
  Although it is clear that the circumnuclear regions of galaxies are
intimately related to their host galaxies, most directly through their bars, it
remains unclear what exactly initiates and fuels nuclear stellar (starburst)
and non-stellar (AGN) activity. Deviations from axisymmetry in the
gravitational potential of a galaxy, set up by a bar or an interaction, are
known to cause gas inflow, and must at some scale and level be related to the
fueling of AGN and starbursts. We review the observed relations between bars
and interactions on the one, and nuclear activity of the Seyfert and starburst
variety on the other hand, and conclude that none of these relations is
particularly significant in a statistical sense, except in extreme and rare
cases, such as ultra-luminous infrared galaxies. Nuclear rings of star
formation, however, are not only related directly to non-axisymmetries in the
potential, but also, it seems, to the occurrence of nuclear activity. Their
role as potential tracers of the fueling process must be further explored.


title:
Rapid Growth of Massive Galaxies: A Paradox for Hierarchical Formation
  Models

abstract:
  On behalf of the survey teams I summarize the designs and results of the Las
Campanas Infrared Survey and Gemini Deep Deep Survey, both of which were
initiated to understand the nature of red galaxies and to study the history of
stellar mass assembly. Our results from luminosity function analysis, ISM
absorption line measurements, and spectral synthesis modeling show that
near-infrared selected galaxies at 1<z<2 are not only massive and abundant but
also old and metal enriched, indicating rapid formation of massive systems at
higher redshifts.


title: Primordial power spectrum from WMAP

abstract:
  The observed angular power spectrum of the cosmic microwave background
temperature anisotropy, $C_l$, is a convolution of a cosmological radiative
transport kernel with an assumed primordial power spectrum of inhomogeneities.
Exquisite measurements of $C_l$ over a wide range of multipoles from the
Wilkinson Microwave Anisotropy Probe (WMAP) has opened up the possibility to
deconvolve the primordial power spectrum for a given set of cosmological
parameters (base model). We implement an improved (error sensitive)
Richardson-Lucy deconvolution algorithm on the measured angular power spectrum
from WMAP assuming a concordance cosmological model. The most prominent feature
of the recovered $P(k)$ is a sharp, infra-red cut off on the horizon scale. The
resultant $C_l$ spectrum using the recovered spectrum has a likelihood far
better than a scale invariant, or, `best fit' scale free spectra
($\Delta\ln{\cal L}=25$ {\it w.r.t.} Harrison Zeldovich, and, $\Delta\ln{\cal
L}=11$ {\it w.r.t.} power law with $n_s=0.95$). The recovered $P(k)$ has a
localized excess just below the cut-off which leads to great improvement of
likelihood over the simple monotonic forms of model infra-red cut-off spectra
considered in the post WMAP literature. The recovered $P(k)$, in particular,
the form of infra-red cut-off is robust to small changes in the cosmological
parameters. We show that remarkably similar form of infra-red cutoff is known
to arise in very reasonable extensions and refinements of the predictions from
simple inflationary scenarios. Our method can be extended to other cosmological
observations such as the measured matter power spectrum and, in particular, the
much awaited polarization spectrum from WMAP.


title: Dark Energy Tomography

abstract:
  We study how parameter error forecasts for tomographic cosmic shear
observations are affected by sky coverage, density of source galaxies,
inclusion of CMB experiments, simultaneou fitting of non--dark energy
parameters, and the parametrization of the history of the dark energy
equation-of-state parameter w(z). We find tomographic shear-shear power spectra
on large angular scales (l<1000) inferred from all-sky observations, in
combination with Planck, can achieve sigma(w0)=0.06 and sigma(wa)=0.09 assuming
the equation-of-state parameter is given by w(z)=w0+wa(1-a(z)) and that nine
other matter content and primordial power spectrum parameters are
simultaneously fit. Taking parameters other than w0, wa and Omegam to be
completely fixed by the CMB we find errors on w0 and wa that are only 10% and
30% better respectively, justifying this common simplifying assumption. We also
study `dark energy tomography': reconstuction of w(z) assumed to be constant
within each of five independent redshift bins. With smaller-scale information
included by use of the Jain & Taylor ratio statistic we find sigma(wi)<0.1 for
all five redshift bins and sigma(wi)<0.02 for both bins at z<0.8. Finally,
addition of cosmic shear can also reduce errors on quantities already
determined well by the CMB. We find the sum of neutrino masses can be
determined to +-0.013eV and that the primordial power specrum power-law index,
ns, as well as dns/dlnk, can be determined more than a factor of two better
than by Planck alone. These improvements may be highly valuable since the lower
bound on the sum of neutrino masses is 0.06eV as inferred from atmospheric
neutrino oscillations, and slow-roll models of inflation predict non-zero
dns/dlnk at the forecasted error levels when |n_S-1|>0.04.


title:
SDSS J115517.35+634622.0: A Newly Discovered Gravitationally Lensed
  Quasar

abstract:
  We report the discovery of SDSSJ115517.35+634622.0, a previously unknown
gravitationally lensed quasar. The lens system exhibits two images of a $z =
2.89$ quasar, with an image separation of $1{\farcs}832 \pm 0.007$ . Near-IR
imaging of the system reveals the presence of the lensing galaxy between the
two quasar images. Based on absorption features seen in the Sloan Digital Sky
Survey (SDSS) spectrum, we determine a lens galaxy redshift of $z = 0.1756$.
The lens is rather unusual in that one of the quasar images is only
$0{\farcs}22\pm0{\farcs}07$ ($\sim 0.1 R_{\rm eff}$) from the center of the
lens galaxy and photometric modeling indicates that this image is significantly
brighter than predicted by a SIS model. This system was discovered in the
course of an ongoing search for strongly lensed quasars in the dataset from the
SDSS.


title: Was the X-ray Afterglow of GRB 970815 Detected?

abstract:
  GRB 970815 was a well-localized gamma-ray burst (GRB) detected by the All-Sky
Monitor (ASM) on the Rossi X-Ray Timing Explorer (RXTE) for which no afterglow
was identified despite follow-up ASCA and ROSAT pointings and optical imaging
to limiting magnitude R > 23. While an X-ray source, AX/RX J1606.8+8130,was
detected just outside the ASM error box, it was never associated with the GRB
because it was not clearly fading and because no optical afterglow was ever
discovered. We recently made deep optical observations of the AX/RX
J1606.8+8130 position, which is blank to a limit of V > 24.3 and I > 24.0,
implying an X-ray-to-optical flux ratio f{X}/f{V} > 500. In view of this
extreme limit, we analyze and reevaluate the ASCA and ROSAT data and conclude
that the X-ray source AX/RX J1606.8+8130 was indeed the afterglow of GRB
970815, which corresponds to an optically ``dark'' GRB. Alternatively, if AX/RX
J1608+8130 is discovered to be a persistent source, then it could be associated
with EGRET source 3EG J1621+8203, whose error box includes this position.


title:
GRB 021004: A Possible Shell Nebula around a Wolf-Rayet Star Gamma-Ray
  Burst Progenitor

abstract:
  The rapid localization of GRB 021004 by the HETE-2 satellite allowed nearly
continuous monitoring of its early optical afterglow decay, as well as
high-quality optical spectra that determined a redshift of z=2.328 for its
host, an active starburst galaxy with strong Lyman-alpha emission and several
absorption lines. Spectral observations show multiple absorbers blueshifted by
up to 3,155 km/s relative to the host galaxy Lyman-alpha emission.We argue that
these correspond to a fragmented shell nebula, gradually enriched by a
Wolf-Rayet wind over the lifetime of a massive progenitor bubble. In this
scenario, the absorbers can be explained by circumstellar material that have
been radiatively accelerated by the GRB emission. Dynamical and photoionization
models are used to provide constraints on the radiative acceleration from the
early afterglow.


title: TeV Gamma-ray Observations and the Origin of Cosmic Rays: I

abstract:
  This is the first of three plenary talks with the same title given at the
28th ICRC in Tsukuba, Japan in August, 2003. A brief description of the
techniques for detecting gamma rays at TeV energies is followed by a summary of
the observational status of the field. The expectations of the field from a
cosmic ray perspective are compared with these early results. The majority of
sources detected with some certainty are extragalactic; the observational
status of these sources is summarized. The most complete set of observations
are those dealing with the detection of blazars for which a catalog is
presented. This discipline is now established as a new branch of observational
astronomy.


title:
A Search for Short Time-Scale Optical Variability in the GRB 030329
  Afterglow

abstract:
  We present a densely sampled R-band light curve of the optical afterglow of
GRB 030329 obtained during the period 15.5-23 hours after the burst. This
dataset allows us to search for short time-scale fluctuations that must be
present at some level due to inhomogeneities in the circumburst medium and/or
if the afterglow is intrinsically variable.


title: A possible hydrodynamical equivalence for astrophysical jets

abstract:
  The idea of a unified model for quasars and micro-quasars has been considered
for a long time, despite the different environments and physical conditions
where both classes of objects reside. Here we show the existence of a simple
scaling law, relating the maximum size of a jet to the properties of the gas
medium into which it expands. This appears to be valid for all types of
hydrodynamical jets, and can be thought of as a broad unified model. The
expansion velocity of the jet and the physical properties of the surrounding
gas combine in such a way that a limit to the maximum extent of jets at
different scales can be obtained.


title: Rapid Oscillations in Cataclysmic Variables

abstract:
  I give an overview of the rich phenomenology of dwarf nova oscillations
(DNOs) and Quasi-periodic Oscillations (QPOs) observed in cataclysmic variable
stars (CVs). The favoured interpretation of these rapid brightness modulations
(3 - >1000 s time scales) is that they are magnetic in nature - magnetically
channelled accretion from the inner accretion disc for DNOs and possible
magnetically excited travelling waves in the disc for QPOs. There is increasing
evidence for the magnetic aspects, which extend to lower field the well known
properties of strong field (polars) and intermediate strength field
(intermediate polars) CVs. The result is that almost all CVs show the presence
of magnetic fields on their white dwarf primaries - though for many the
intrinsic field may be locally enhanced by the accretion process itself. There
are many parallel behaviours with the QPOs seen in X-Ray binaries, with high
and low frequency X-Ray QPOs resembling respectively the DNOs and QPOs in CVs.


title: Testing the Cosmological Constant as a Candidate for Dark Energy

abstract:
  It may be difficult to single out the best model of dark energy on the basis
of the existing and planned cosmological observations, because many different
models can lead to similar observational consequences. However, each particular
model can be studied and either found consistent with observations or ruled
out. In this paper, we concentrate on the possibility to test and rule out the
simplest and by far the most popular of the models of dark energy, the theory
described by general relativity with positive vacuum energy (the cosmological
constant). We evaluate the conditions under which this model could be ruled out
by the future observations made by the Supernova/Acceleration Probe SNAP (both
for supernovae and weak lensing) and by the Planck Surveyor cosmic microwave
background satellite.


title: The Unidentified InfraRed Features after ISO

abstract:
  The Infrared Space Observatory (ISO) has provided the first complete mid-IR
spectra for a wide range of objects. Almost all of these spectra are dominated
by the well-known infrared emission features at 3.3, 6.2, 7.7, and 11.2 $\mu$m,
the so-called Unidentified Infra-Red (UIR) features. Besides the major
features, there is an array of minor features and broad plateaux stretching
from 3 to 20 $\mu$m which reveal subtle details of conditions in the emission
zones and properties of the carriers. Generally attributed to the vibrational
relaxation of UV-pumped Polycyclic Aromatic Hydrocarbon molecules (PAHs)
containing some 50--100 C-atoms, these UIR spectra are a treasure trove of
information. The ISO spectra have, for the first time, allowed a systematic
analysis of the spectral characteristics of the UIR features in a wide variety
of environments. The peak positions, profiles, and relative strengths of the
major features vary from source to source and spatially within sources. These
specific profiles are not unique to certain object types but can occur within
each individual source. Here, we review ISO and recent ground-based
observations and assess some of their implications.


title:
Chandra Observations of ULIRGs: Extended Hot Gas Halos in Merging
  Galaxies

abstract:
  We study the properties of hot gaseous halos in 10 nearby ultraluminous IRAS
galaxies observed with the ACIS instrument on board Chandra. For all sample
galaxies, diffuse soft X-ray emissions are found within ~10 kpc of the central
region; their spectra are well fitted by a MEKAL model plus emission lines from
alpha-elements and other ions. The temperature of the hot gas is about 0.7 keV
and metallicity is about 1 solar. Outside the central region, extended hot
gaseous halos are found for nine out of the ten ULIRGs. Most spectra of these
extended halos can be fitted with a MEKAL model with a temperature of about 0.6
keV and a low metallicity (~ 0.1 solar). We discuss the implications of our
results on the origin of X-ray halos in elliptical galaxies and the feedback
processes associated with starbursts.


title:
Joint X-Ray and Optical Measurements of the Mass Distribution of the
  Distant Galaxy Cluster CLJ 0152.7-1357

abstract:
  We present joint X-ray and optical observations of the high redshift (z~0.83)
lensing cluster CLJ0152.7-1357 made with the Chandra X-ray Observatory and the
Keck telescope. We confirm the existence of significant substructure at both
X-ray and optical wavelengths in the form of two distinct clumps, whose
temperatures are 6.6(-1.5,+2.4) keV and 5.7(-1.6,+2.9) keV, respectively. The
X-ray surface brightness profiles of the two clumps can be fitted by either a
single beta-model or an NFW-like profile; the latter giving better fits to the
central regions. We find that the X-ray derived mass of this cluster is in good
agreement with independent lensing measurements. While its appearance indicates
that the cluster has not reached a dynamical equilibrium state, its X-ray
luminosity L_x, temperature T and dynamical mass M are consistent with the
well-defined L_x-T and M-T relations for low-redshift galaxy clusters, which
suggests that the dynamical properties of the clusters have remained almost
unchanged since z~0.8.


title: The Mass Function of Newly Formed Stars (Review)

abstract:
  The topic of the stellar "original mass function" has a nearly 50 year
history,dating to the publication in 1955 of Salpeter's seminal paper. In this
review I discuss the many more recent results that have emerged on the initial
mass function (IMF), as it is now called, from studies over the last decade of
resolved populations in star forming regions and young open clusters.


title:
The Future of High Angular Resolution Star and Planet Formation Science
  in the Optical/Infrared

abstract:
  This presentation summarizes how some of the most pressing questions in the
field of star and planet formation can be addressed by high angular resolution
optical/infrared capabilities, and how many of these capabilities will in fact
be available with realization of the space and ground facilities currently
being planned for the 2005-2020 time frame.


title:
An Assessment of Dynamical Mass Constraints on Pre-Main Sequence
  Evolutionary Tracks

abstract:
  [abridged] We have assembled a database of stars having both masses
determined from measured orbital dynamics and sufficient spectral and
photometric information for their placement on a theoretical HR diagram. Our
sample consists of 115 low mass (M < 2.0 Msun) stars, 27 pre-main sequence and
88 main sequence. We use a variety of available pre-main sequence evolutionary
calculations to test the consistency of predicted stellar masses with
dynamically determined masses. Despite substantial improvements in model
physics over the past decade, large systematic discrepancies still exist
between empirical and theoretically derived masses. For main-sequence stars,
all models considered predict masses consistent with dynamical values above 1.2
Msun, some models predict consistent masses at solar or slightly lower masses,
and no models predict consistent masses below 0.5 Msun but rather all models
systematically under-predict such low masses by 5-20%. The failure at low
masses stems from the poor match of most models to the empirical main-sequence
below temperatures of 3800 K where molecules become the dominant source of
opacity and convection is the dominant mode of energy transport. For the
pre-main sequence sample we find similar trends. There is generally good
agreement between predicted and dynamical masses above 1.2 Msun for all models.
Below 1.2 Msun and down to 0.3 Msun (the lowest mass testable) most
evolutionary models systematically under-predict the dynamically determined
masses by 10-30% on average with the Lyon group models (e.g. Baraffe et al.
1998) predicting marginally consistent masses *in the mean* though with large
scatter.


title:
Searching for sources of the highest energy cosmic rays: low statistics,
  pitfalls, and possible clues

abstract:
  The clustering properties of the highest energy cosmic rays and their
correlations with candidate sources are re-examined using the most recently
available AGASA data and a rigorous correlation analysis. The statistical
methodology incorporates some important points not considered in previous
studies. Results include small angle clustering significances consistent with,
but somewhat less than, earlier findings, a possible large scale anisotropy for
events with energies $E \approx 5 - 8 \times 10^{19} \mathrm{eV}$, and no
statistically significant cross correlations with BL Lacertae or blazars. A
marginally significant cross correlation exists for events with energies $E > 8
\times 10^{19} \mathrm{eV}$ with a set of Abell clusters, but no definitive
conclusion can yet be drawn from this result.


title: Dynamos, Super-pulsars and Gamma-ray bursts

abstract:
  The remnant of a neutron star binary coalescence is expected to be
temporarily stabilised against gravitational collapse by its differential
rotation. We explore the possibility of dynamo activity in this remnant and
assess the potential for powering a short-duration gamma-ray burst (GRB). We
analyse our three-dimensional hydrodynamic simulations of neutron star mergers
with respect to the flow pattern inside the remnant. If the central, newly
formed super-massive neutron star remains stable for a good fraction of a
second an efficient low-Rossby number $\alpha-\Omega$-dynamo will amplify the
initial seed magnetic fields exponentially. We expect that values close to
equipartition field strength will be reached within several tens of
milliseconds. Such a super-pulsar could power a GRB via a relativistic wind,
with an associated spin-down time scale close to the typical duration of a
short GRB. Similar mechanisms are expected to be operational in the surrounding
torus formed from neutron star debris.


title:
Model-Independent Constraints on Dark Energy Density from Flux-averaging
  Analysis of Type Ia Supernova Data

abstract:
  We reconstruct the dark energy density $\rho_X(z)$ as a free function from
current type Ia supernova (SN Ia) data (Tonry et al. 2003; Barris et al. 2003;
Knop et al. 2003), together with the Cosmic Microwave Background (CMB) shift
parameter from CMB data (WMAP, CBI, and ACBAR), and the large scale structure
(LSS) growth factor from 2dF galaxy survey data. We parametrize $\rho_X(z)$ as
a continuous function, given by interpolating its amplitudes at equally spaced
$z$ values in the redshift range covered by SN Ia data, and a constant at
larger $z$ (where $\rho_X(z)$ is only weakly constrained by CMB data). We
assume a flat universe, and use the Markov Chain Monte Carlo (MCMC) technique
in our analysis. We find that the dark energy density $\rho_X(z)$ is constant
for $0 \la z \la 0.5$ and increases with redshift $z$ for $0.5 \la z \la 1$ at
68.3% confidence level, but is consistent with a constant at 95% confidence
level. For comparison, we also give constraints on a constant equation of state
for the dark energy.
  Flux-averaging of SN Ia data is required to yield cosmological parameter
constraints that are free of the bias induced by weak gravitational lensing
\citep{Wang00b}. We set up a consistent framework for flux-averaging analysis
of SN Ia data, based on \cite{Wang00b}. We find that flux-averaging of SN Ia
data leads to slightly lower $\Omega_m$ and smaller time-variation in
$\rho_X(z)$. This suggests that a significant increase in the number of SNe Ia
from deep SN surveys on a dedicated telescope \citep{Wang00a} is needed to
place a robust constraint on the time-dependence of the dark energy density.


title:
Short-period AM CVn systems as optical, X-ray and gravitational wave
  sources

abstract:
  We model the population of AM CVn systems in the Galaxy and discuss the
detectability of these systems with optical, X-ray and gravitational wave
detectors. We concentrate on the short period (P < 1500 s) systems, some of
which are expected to be in a phase of direct impact accretion. Using a
self-consistent model for the star formation history and radial distribution of
stars in the Galaxy plus simple models for the emission of optical and X-ray
radiation from the AM CVn systems and interstellar absorption, we derive the
sample of short-period AM CVn systems that can be detected in the optical
and/or X-ray bands. At the shortest periods the detectable systems are all
X-ray sources, some with periods as short as three minutes. At periods above 10
minutes most detectable systems are optical sources. About one third of the
X-ray sources are also detectable in the optical band. We also calculate the
gravitational wave signal of the short-period AM CVn systems. We find that
potentially several thousand AM CVn systems can be resolved by the
gravitational wave detector LISA, comparable to the expected number of detached
double white dwarfs that can be resolved. We estimate that several hundreds of
the AM CVn systems resolvable by LISA, are also detectable in the optical
and/or X-ray bands.


title:
Density Profiles of Cold Dark Matter Substructure: Implications for the
  Missing Satellites Problem

abstract:
  The structural evolution of substructure in cold dark matter (CDM) models is
investigated combining ``low-resolution'' satellites from cosmological N-body
simulations of parent halos with N=10^7 particles with high-resolution
individual subhalos orbiting within a static host potential. We show that, as a
result of mass loss, convergence in the central density profiles requires the
initial satellites to be resolved with N=10^7 particles and parsec-scale force
resolution. We find that the density profiles of substructure halos can be well
fitted with a power-law central slope that is unmodified by tidal forces even
after the tidal stripping of over 99% of the initial mass and an exponential
cutoff in the outer parts. The solution to the missing-satellites problem
advocated by Stoehr et al. in 2002 relied on the flattening of the dark matter
(DM) halo central density cusps by gravitational tides, enabling the observed
satellites to be embedded within DM halos with maximum circular velocities as
large as 60 km/s. In contrast, our results suggest that tidal interactions do
not provide the mechanism for associating the dwarf spheroidal satellites
(dSphs) of the Milky Way with the most massive substructure halos expected in a
CDM universe. We compare the predicted velocity dispersion profiles of Fornax
and Draco to observations, assuming that they are embedded in CDM halos. Models
with isotropic and tangentially anisotropic velocity distributions for the
stellar component fit the data only if the surrounding DM halos have maximum
circular velocities in the range 20-35 km/s. If the dSphs are embedded within
halos this large then the overabundance of satellites within the concordance
LCDM cosmological model is significantly alleviated, but this still does not
provide the entire solution.


title: Hyperatlas: A New Framework for Image Federation

abstract:
  Hyperatlas is an open standard intended to facilitate the large-scale
federation of image-based data. The subject of hyperatlas is the space of
sphere-to-plane projection mappings (the FITS-WCS information), and the
standard consists of coherent collections of these on which data can be
resampled and thereby federated with other image data. We hope for a
distributed effort that will produce a multi-faceted image atlas of the sky,
made by federating many different surveys at different wavelengths and
different times. We expect that hyperatlas-compliant imagery will be published
and discovered through an International Virtual Observatory Alliance (IVOA)
registry, and that grid-based services will emerge for the required resampling
and mosaicking.


title: Atlasmaker: A Grid-based Implementation of the Hyperatlas

abstract:
  The Atlasmaker project is using Grid technology, in combination with NVO
interoperability, to create new knowledge resources in astronomy. The product
is a multi-faceted, multi-dimensional, scientifically trusted image atlas of
the sky, made by federating many different surveys at different wavelengths,
times, resolutions, polarizations, etc. The Atlasmaker software does resampling
and mosaicking of image collections, and is well-suited to operate with the
Hyperatlas standard. Requests can be satisfied via on-demand computations or by
accessing a data cache. Computed data is stored in a distributed virtual file
system, such as the Storage Resource Broker (SRB). We expect these atlases to
be a new and powerful paradigm for knowledge extraction in astronomy, as well
as a magnificent way to build educational resources. The system is being
incorporated into the data analysis pipeline of the Palomar-Quest synoptic
survey, and is being used to generate all-sky atlases from the 2MASS, SDSS, and
DPOSS surveys for joint object detection.


title: The binary black hole scenario for the BL Lacertae object AO 0235+16

abstract:
  Recent analysis of the long term radio lightcurve of the extremely variable
BL Lacertae object AO 0235+16 by Raiteri et al. (2001) have revealed the
presence of recurrent outbursts in this source with a period of ~ 5.7 +/- 0.5
yr. Periodicity analysis of the optical lightcurve also show evidence for a
shorter period. Here we discuss whether such a behavior can be explained by a
binary black hole model where the accretion disk of one of the supermassive
black holes is precessing due to the tidal effects of the companion. We
estimate the mass of the accreting hole and analyze under what constraints onto
the secondary mass and the orbital parameters of the system it is possible to
provide a viable interpretation of the available multiwavelength data.


title:
Alignment of radio emission and quasars across NGC 613 and NGC 936 and
  radio ejection from NGC 941

abstract:
  NGC 613 (AM 0132-294) is a multi armed spiral with an active nucleus. Radio
emission is aligned along the narrow inner bar of the spiral and appears to
include inner and outer pairs of radio sources which define a line of ejection
from this nucleus. Four high redshift quasars from the 2dF survey fall further
out along this same line. The redshifts of these four, plus two others in this
general direction, are close to the peak values in the periodic redshift
distribution of quasars. In separation, redshifts and other properties there is
an almost exact duplicate of NGC 613 in the pair of z ~ 2 quasars paired across
the radio ejecting, barred galaxy NGC 936.NGC 941, a companion to NGC 936, has
a quasar apparently connected to it by a radio bridge which shows structure at
high resolution.One of the pair across NGC 936, a strong Parks quasar, is also
accurately aligned with another strong Parks quasar further away. Possible
relationships between other quasars and low redshift galaxies in a broader
region around NGC 936 are discussed.


title:
Uncovering galactic and extragalactic planets by gravitational
  microlensing

abstract:
  With its planet detection efficiency reaching a maximum for orbital radii
between 1 and 10 AU, microlensing provides a unique sensitivity to planetary
systems similar to our own around galactic and even extragalactic stars acting
as lenses on observed background stars, and in particular can detect
terrestrial planets in the habitable zone. The absence of planetary signals in
the 1995-1999 PLANET data implies that less than 1/3 of galactic M-dwarfs
harbour jupiters at orbital radii between 1.5 and 4 AU. If a fraction f_p of
stars is surrounded by a planet, annual detections of 15--25 f_p jupiters and
2-3 f_p earths around galactic stars would result from PLANET, a space-based
campaign would yield 1200 f_p jupiters and 30 f_p earths, and a northern
microlensing network could detect 15-35 f_p jupiters and 4-10 f_p saturns
around M31 stars.


title:
Uncovering stellar atmospheres with gravitational microlensing
  telescopes

abstract:
  A strong differential magnification over the face of the source star passing
the caustic created by a binary lens star allows to measure its radial
intensity profile with an angular resolution of 20-60 nas from broad-band
photometric observations for ~15 stars per year and to study its chemical
composition from time-resolved high-resolution spectroscopy for ~2 stars per
year.


title:
Parametric Recovery of Line-of-Sight Velocity Distributions from
  Absorption-Line Spectra of Galaxies via Penalized Likelihood

abstract:
  We investigate the accuracy of the parametric recovery of the line-of-sight
velocity distribution (LOSVD) of the stars in a galaxy, while working in pixel
space. Problems appear when the data have a low signal-to-noise ratio, or the
observed LOSVD is not well sampled by the data. We propose a simple solution
based on maximum penalized likelihood and we apply it to the common situation
in which the LOSVD is described by a Gauss-Hermite series. We compare different
techniques by extracting the stellar kinematics from observations of the barred
lenticular galaxy NGC 3384 obtained with the SAURON integral-field
spectrograph.


title: High Energy Neutrino Generator for Neutrino Telescopes

abstract:
  We present the high energy neutrino Monte Carlo event generator ANIS (All
Neutrino Interaction Simulation). The aim of the program is to provide a
detailed and flexible neutrino event simulation for high energy neutrino
detectors, such as AMANDA and ICECUBE. It generates neutrinos of any flavor
according to a specific flux, propagates them through the Earth and in a final
step simulates neutrino interactions within a specified volume. All relevant
standard model processes are implemented. We discuss strength and limitations
of the program, and provide as an example event rates for atmospheric and E^-2
neutrino spectra.


title:
The Cellular Burning Regime in Type Ia Supernova Explosions - II. Flame
  Propagation into Vortical Fuel

abstract:
  We investigate the interaction of thermonuclear flames in Type Ia supernova
explosions with vortical flows by means of numerical simulations. In our study,
we focus on small scales, where the flame propagation is no longer dominated by
the turbulent cascade originating from large-scale effects. Here, the flame
propagation proceeds in the cellular burning regime, resulting from a balance
between the Landau-Darrieus instability and its nonlinear stabilization. The
interaction of a cellularly stabilized flame front with a vortical fuel flow is
explored applying a variety of fuel densities and strengths of the velocity
fluctuations. We find that the vortical flow can break up the cellular flame
structure if it is sufficiently strong. In this case the flame structure adapts
to the imprinted flow field. The transition from the cellularly stabilized
front to the flame structure dominated by vortices of the flow proceeds in a
smooth way. The implications of the results of our simulations for Type Ia
Supernova explosion models are discussed.


title: X-ray and gamma-ray observations of millisecond pulsars

abstract:
  The launch of several sensitive X-ray and gamma-ray instruments during the
last decade heralded a new era in the research of millisecond pulsars. The
current number of millisecond pulsars detected in the X-ray spectral window is
about 30, including those located in globular clusters, which represents a
significant fraction of the total number of spin-down powered pulsars emitting
high-energy radiation.In this paper the observational X/gamma-ray status is
reported for a subset of X-ray emitting millisecond pulsars which show
high-energy tails: PSR B1821-24, PSR J0218+4232 and PSR B1937+21. The prospects
for future detection of these 3 millisecond pulsars at soft (INTEGRAL) and hard
(AGILE/GLAST) gamma-rays are discussed.


title:
High-Resolution X-ray Spectroscopy of the Interstellar Medium: Structure
  at the Oxygen Absorption Edge

abstract:
  (Abbrev.) We present high-resolution spectroscopy of the oxygen K-shell
interstellar absorption edge in 7 X-ray binaries using the HETGS onboard
Chandra. Using the brightest sources as templates, we found a best-fit model of
2 absorption edges and 5 Gaussian absorption lines. All of these features can
be explained by the recent predictions of K-shell absorption from neutral and
ionized atomic oxygen. We identify the K alpha and K beta absorption lines from
neutral oxygen, as well as the S=3/2 absorption edge. The expected S=1/2 edge
is not detected in these data due to overlap with instrumental features. We
also identify the K alpha absorption lines from singly and doubly ionized
oxygen. The OI K alpha absorption line is used as a benchmark with which to
adjust the absolute wavelength scale for theoretical predictions of the
absorption cross-sections. We find that shifts of 30-50 mA are required,
consistent with differences previously noticed from comparisons of the theory
with laboratory measurements. Significant oxygen features from dust or
molecular components, as suggested in previous studies, are not required by our
HETGS spectra. With these spectra, we can begin to measure the large-scale
properties of the ISM. We place a limit on the velocity dispersion of the
neutral lines of <200 km s^{-1}, consistent with measurements at other
wavelengths. We also make the first measurement of the oxygen ionization
fractions in the ISM. We constrain the interstellar ratio of OII/OI to ~0.1 and
the ratio of OIII/OI to <0.1.


title: A rolling tachyon field for both dark energy and dark halos of galaxies

abstract:
  Distance measurements to type Ia supernovae (SNe Ia) indicate that the
universe is accelerating and it is spatially flat. Otherwise, the rotation
curves for galaxies or galaxy clusters reveal the existence of a dark matter
component. Then, approximately 0.35 of the total energy density of the universe
consists of dark matter, and 0.65 of the energy density corresponds to dark
energy. These two dark components of the universe have different properties
such that: dark matter clusters gravitationally at galactic scales while dark
energy, dominating at large scale, does not cluster gravitationally. It seems
difficult to find a candidate which explains the observations at both large and
small scales. In this paper we take into account a scalar field, more precisely
a rolling tachyon arising from string theory, which seems be capable to explain
the observations at different scales. We examine this scalar field behavior at
galactic scales and we fit the rotational curve data of spiral galaxies. Our
results are comparable with the curves obtained on one hand from a complex
scalar field, which only plays the role of the dark matter at galactic scales,
and on the other hand from the MOND model.


title: Why Massive Black Holes are Small in Disk Galxies?

abstract:
  A potential mechanism is proposed to account for the fact that supermassive
black holes (SMBHs) in disk galaxies appear to be smaller than those in
elliptical galaxies in the same luminosity range. We consider the formation of
SMBHs by radiation drag (Poynting-Robertson effect), which extracts angular
momentum from interstellar matter and thereby drives the mass accretion onto a
galactic center. In particular, we quantitatively scrutinize the efficiency of
radiation drag in a galaxy composed of bulge and disk, and elucidate the
relation between the final mass of SMBH and the bulge-to-disk ratio of the
galaxy. As a result, it is found that the BH-to-galaxy mass ratio, $M_{\rm
BH}/M_{\rm galaxy}$, decreases with a smaller bulge-to-disk ratio, due to the
effects of geometrical dilution and opacity, and is reduced maximally by two
orders of magnitude, resulting in $M_{\rm BH}/M_{\rm galaxy}\approx 10^{-5}$.
In contrast, if only the bulge components in galaxies are focused, the
BH-to-bulge mass ratio becomes $M_{\rm BH}/M_{\rm bulge}\approx 10^{-3}$, which
is similar to that found in elliptical galaxies. Thus, it turns out that the
mass of SMBH primarily correlates with a bulge, not with a disk, consistently
with observational data.


title: Magnetic field generation in relativistic shocks

abstract:
  We present an analytical estimate for the magnetic field strength generated
by the Weibel instability in ultra-relativistic shocks in a hydrogen plasma. We
find that the Weibel instability is, by itself, not capable of converting the
kinetic energy of protons penetrating the shock front into magnetic field
energy. Other (nonlinear) processes must determine the magnetic field strength
in the wake of the shock.


title:
Starbursts in barred spiral galaxies. VI. HI observations and the K-band
  Tully-Fisher relation

abstract:
  This paper is primarily a study of the effect of a bar on the neutral
hydrogen (HI) content of starburst and Seyfert galaxies. We also make
comparisons with a sample of ``normal'' galaxies and investigate how well
starburst and Seyfert galaxies follow the fundamental scaling Tully-Fisher (TF)
relation defined for normal galaxies. 111 Markarian (Mrk) IRAS galaxies were
observed at the Nancay radiotelescope. These measurements are complemented by
data from the literature to form a sample of 105 unbarred and 113 barred Mrk
IRAS galaxies. Barred galaxies have lower total and bias-corrected HI masses
than unbarred galaxies, and this is true for both Mrk IRAS and normal galaxies.
This robust result suggests that bars funnel the HI gas toward the center of
the galaxy where it becomes molecular before forming new stars. The Mrk IRAS
galaxies have higher bias-corrected HI masses than normal galaxies. They also
show significant departures from the TF relation, both in the B and K bands.
The most deviant points from the TF relation tend to have a strong far-infrared
luminosity and a low oxygen abundance. These results suggest that a fraction of
our Mrk IRAS galaxies are still in the process of formation, and that their
neutral HI gas, partly of external origin, has not yet reached a stationary
state.


title:
A comprehensive set of elemental abundances in damped Ly-alpha systems:
  revealing the nature of these high-redshift galaxies

abstract:
  By combining our UVES-VLT spectra of a sample of four damped Ly-alpha systems
(DLAs) toward the quasars Q0100+13, Q1331+17, Q2231-00 and Q2343+12 with the
existing HIRES-Keck spectra, we covered the total spectral range from 3150 to
10000 A for the four quasars. This large wavelength coverage and the high
quality of the spectra allowed us to measure the column densities of up to 21
ions, namely of 15 elements - N, O, Mg, Al, Si, P, S, Cl, Ar, Ti, Cr, Mn, Fe,
Ni, Zn. Such a large amount of information is necessary to constrain the
photoionization and dust depletion effects, two important steps in order to
derive the intrinsic chemical abundance patterns of DLAs. We evaluated the
photoionization effects with the help of the Al+/Al++, Fe+/Fe++, N0/N+ and
Ar/Si,S ratios, and computed dust corrections. Our analysis revealed that the
DLA toward Q2343+12 requires important ionization corrections. The access to
the complete series of relatively robust intrinsic elemental abundances in the
other three DLAs allowed us to constrain their star formation history, their
age and their star formation rate by a detailed comparison with a grid of
chemical evolution models for spiral and dwarf irregular galaxies. Our results
show that the galaxies associated with these three DLAs in the redshift
interval z_abs = 1.7-2.5 are either outer regions of spiral disks (radius >= 8
kpc) or dwarf irregular galaxies (with a bursting or continuous star formation
history) with ages varying from some 50 Myr only to >~ 3.5 Gyr and with
moderate star formation rates per unit area of -2.1 < log \psi < -1.5 M_{sol}
yr^{-1} kpc^{-2}.


title: XMM Observations of an IXO in NGC 2276

abstract:
  We present the results from a ~53 ksec XMM observation of NGC 2276. This
galaxy has an unusual optical morphology with the disk of this spiral appearing
to be truncated along the western edge. This XMM observation shows that the
X-ray source at the western edge is a bright Intermediate X-ray Object (IXO).
Its spectrum is well fit by a multi-color disk blackbody model used to fit
optically thick standard accretion disks around black holes. The luminosity
derived for this IXO is 1.1x10^41 erg/s in the 0.5 - 10 keV band making it one
of the most luminous discovered to date. The large source luminosity implies a
large mass black hole if the source is radiating at the Eddington rate. On the
other hand, the inner disk temperature determined here is too high for such a
massive object given the standard accretion disk model. In addition to the IXO
we find that the nuclear source in this galaxy has dimmed by at least a factor
of several thousand in the eight years since the ROSAT HRI observations.


title: The Sun's Preferred Longitudes and the Coupling of Magnetic Dynamo Modes

abstract:
  Observations show that solar activity is distributed non-axisymmetrically,
concentrating at "preferred longitudes". This indicates the important role of
non-axisymmetric magnetic fields in the origin of solar activity. We
investigate the generation of the non-axisymmetric fields and their coupling
with axisymmetric solar magnetic field. Our kinematic generation (dynamo) model
operating in a sphere includes solar differential rotation, which approximates
the differential rotation obtained by inversion of helioseismic data, modelled
distributions of the turbulent resistivity, non-axisymmetric mean helicity, and
meridional circulation in the convection zone. We find that (1) the
non-axisymmetric modes are localised near the base of the convection zone,
where the formation of active regions starts, and at latitudes around
$30^{\circ}$; (2) the coupling of non-axisymmetric and axisymmetric modes
causes the non-axisymmetric mode to follow the solar cycle; the phase relations
between the modes are found. (3) The rate of rotation of the first
non-axisymmetric mode is close to that determined in the interplanetary space.


title: High-Energy Cosmic Rays from Galactic and Extragalactic Gamma-Ray Bursts

abstract:
  A model for high-energy (>10^14 eV) cosmic rays (HECRs) from galactic and
extragalactic gamma-ray bursts (GRBs) is summarized. Relativistic outflows in
GRBs are assumed to inject power-law distributions of CR protons and ions to
the highest (>10^20 eV) energies. A diffusive propagation model for HECRs from
a single recent GRB within 1 kpc from Earth explains the CR spectrum near and
above the knee. The CR spectrum at energies above 10^18 eV is fit with a
component from extragalactic GRBs. By normalizing the energy injection rate to
that required to produce the CR flux from extragalactic sources observed
locally, we determine the amount of energy a typical GRB must release in the
form of nonthermal hadrons. Our interpretation of the HECR spectrum requires
that GRBs are hadronically dominated, which would be confirmed by the detection
of HE neutrinos from GRBs.


title: Merging Galaxies in the SDSS EDR

abstract:
  We present a new catalog of merging galaxies obtained through an automated
systematic search routine. The 1479 new pairs of merging galaxies were found in
approximately 462 sq deg of the Sloan Digital Sky Survey Early Data Release
(SDSS EDR; Stoughton et al. 2002) photometric data, and the pair catalog is
complete for galaxies in the magnitude range 16.0 <= g* <= 20.
  The selection algorithm, implementing a variation on the original
Karachentsev (1972) criteria, proved to be very efficient and fast. Merging
galaxies were selected such that the inter-galaxy separations were less than
the sum of the component galaxies' radii.
  We discuss the characteristics of the sample in terms of completeness, pair
separation, and the Holmberg effect. We also present an online atlas of images
for the SDSS EDR pairs obtained using the corrected frames from the SDSS EDR
database. The atlas images also include the relevant data for each pair member.
  This catalog will be useful for conducting studies of the general
characteristics of merging galaxies, their environments, and their component
galaxies. The redshifts for a subset of the interacting and merging galaxies
and the distribution of angular sizes for these systems indicate the SDSS
provides a much deeper sample than almost any other wide-area catalog to date.


title: The environments of hyperluminous infrared galaxies at 0.44<z<1.55

abstract:
  We present deep wide-field K-band observations of six Hyperluminous Infrared
Galaxies (HLIRGs) spanning a redshift range 0.44<z<1.55. The sample resides in
a wide variety of environments, from the field to Abell 2 clusters, with a mean
galaxy-HLIRG clustering amplitude of B_gh=190+/-45. The range in environments,
and the mean clustering level, are both greater than those seen in local
IR-luminous galaxies, from which we infer that the range of galaxy evolution
processes driving IR-luminous galaxy evolution at z>0.5 is greater than
locally, and includes mergers between gas-rich spiral galaxies in the field,
but also includes encounters in clusters and hierarchical buildup. The
similarity in the range of environments and mean clustering amplitude between
our sample and QSOs over a similar redshift range is consistent with the
interpretation where evolutionary connections between IR-luminous galaxies and
QSOs are stronger at z>0.5 than locally, and that, at these redshifts, the
processes that drive QSO evolution are similar to those that drive IR-luminous
galaxy evolution. From comparison of the HLIRG and QSO host galaxies we further
postulate that a larger fraction of IR-luminous galaxies pass through an
optical QSO stage at z>0.5 than locally.


title: Star Formation and Feedback in Dwarf Galaxies

abstract:
  We examine the star formation history and stellar feedback effects of dwarf
galaxies under the influence of extragalactic ultraviolet radiation. We
consider the dynamical evolution of gas in dwarf galaxies using a
one-dimensional, spherically symmetric, Lagrangian numerical scheme to compute
the effects of radiative transfer and photoionization. We include a
physically-motivated star formation recipe and consider the effects of
feedback. Our results indicate that star formation in the severe environment of
dwarf galaxies is a difficult and inefficient process. For intermediate mass
systems, such as the dSphs around the Galaxy, star formation can proceed with
in early cosmic epochs despite the intense background UV flux. Triggering
processes such as merger events, collisions, and tidal disturbance can lead to
density enhancements, reducing the recombination timescale, allowing gas to
cool and star formation to proceed. However, the star formation and gas
retention efficiency may vary widely in galaxies with similar dark matter
potentials, because they depend on many factors, such as the baryonic fraction,
external perturbation, IMF, and background UV intensity. We suggest that the
presence of very old stars in these dwarf galaxies indicates that their initial
baryonic to dark matter content was comparable to the cosmic value. This
constraint suggests that the initial density fluctuation of baryonic matter may
be correlated with that of the dark matter. For the more massive dwarf
elliptical galaxies, the star formation efficiency and gas retention rate is
much higher. Their mass to light ratio is regulated by star formation feedback,
and is expected to be nearly independent of their absolute luminosity. The
results of our theoretical models reproduce the observed $M/L-M_v$ correlation.


title: EXPLORE/OC: A Search for Planetary Transits in the Field of NGC 2660

abstract:
  We present preliminary photometric results of a monitoring study of the open
cluster NGC 2660 as part of the EXPLORE/OC project to find planetary transits
in Galactic open clusters. Analyzing a total of 21000 stars (3000 stars with
photometry to 1% or better) yielded three light curves with low-amplitude
signals like those typically expected for transiting hot Jupiters. Although
their eclipses are most likely caused by non-planetary companions, our methods
and photometric precision illustrate the potential to detect planetary transits
around stars in nearby open clusters.