title:
Current constraints on Cosmological Parameters from Microwave Background
  Anisotropies

abstract:
  We compare the latest observations of Cosmic Microwave Background (CMB)
Anisotropies with the theoretical predictions of the standard scenario of
structure formation. Assuming a primordial power spectrum of adiabatic
perturbations we found that the total energy density is constrained to be
$\Omega_{tot}=1.03\pm0.06$ while the energy density in baryon and Cold Dark
Matter (CDM) are $\Omega_bh^2=0.021\pm0.003$ and $\Omega_{cdm}h^2=0.12\pm0.02$,
(all at 68% C.L.) respectively. The primordial spectrum is consistent with
scale invariance, ($n_s=0.97\pm0.04$) and the age of the universe is
$t_0=14.6\pm0.9$ Gyrs. Adding informations from Large Scale Structure and
Supernovae, we found a strong evidence for a cosmological constant
$\Omega_{\Lambda}=0.70_{-0.05}^{+0.07}$ and a value of the Hubble parameter
$h=0.69\pm0.07$. Restricting this combined analysis to flat universes, we put
constraints on possible 'extensions' of the standard scenario. A gravity waves
contribution to the quadrupole anisotropy is limited to be $r \le 0.42$ (95%
c.l.). A constant equation of state for the dark energy component is bound to
be $w_Q \le -0.74$ (95% c.l.). We constrain the effective relativistic degrees
of freedom $N_\nu \leq 6.2$ and the neutrino chemical potential $-0.01 \leq
\xi_e \leq 0.18$ and $|\xi_{\mu,\tau}|\leq 2.3$ (massless neutrinos).


title: Options for cosmology at redshifts above one

abstract:
  We show that detailed exploration of the $1<z<2$ redshift region can provide
for definitive testing not only of the standard inflationary cosmological
paradigm with its fine-tuned cosmological constant and its mysteriously late
($z<1$) onset of cosmic acceleration, but also for the non fine-tuned,
alternate conformal cosmological model, a cosmology which accelerates both
above and below $z=1$. In particular we confront both of these models with the
currently available type Ia supernovae standard candle and extended FRII radio
source standard yardstick data, with these latter data being particularly
pertinent as they already include a sizeable number of points in the $1<z<2$
region. We find that both models are able to account for all available $0<z<2$
data equally well; and with the conformal model explicitly being able to fit
the data while being an accelerating one in the $z>1$ region, one is thus
currently unable to ascertain whether the universe is accelerating or
decelerating between $z=1$ and $z=2$. To be able to visualize the supernovae
and radio galaxy data simultaneously, we present a representation of the radio
galaxy data in terms of an equivalent apparent magnitude Hubble diagram. We
discuss briefly some implications of the anisotropies in the cosmic microwave
background for the conformal theory, and show that in that theory fluctuations
which set in at around nucleosynthesis can readily generate the first peak in
the anisotropy data.


title:
Luminosity functions of X-ray binaries and the dynamical history of
  their host galaxies

abstract:
  The X-ray sources observed in nearby galaxies show brightness distributions
(log(N(>S))--log(S) curves) which can be described as single or broken power
laws. Single power-law distributions are often found for sources in galaxies
with vigorous ongoing star-formation activity, while broken power laws are
found in elliptical galaxies and in bulges of spiral galaxies. The luminosity
break can be caused by a population of X-ray binaries which contain a neutron
star accreting at the Eddington limit or by aging of the X-ray binary
population. We show that a simple birth-death model can reproduce single and
broken power-law log(N(>S))--log(S) curves. We have found that power-law
log(N(>S))--log(S) curves are a consequence of smooth continuous formation of
X-ray binaries and a luminosity break is the signature of a starburst episode
in the recent past. The luminosity break is robust and is determined by the
lifespans of the X-ray binaries relative to the look-back time to the starburst
epoch. The model successfully explains the different forms of
log(N(>S))--log(S) curves for the disk and bulge sources in the spiral galaxy
M81.


title: The Quintuple Quasar: Radio and Optical Observations

abstract:
  We present results from high-resolution radio and optical observations of PMN
J0134-0931, a gravitational lens with a unique radio morphology and an
extremely red optical counterpart. Our data support the theory of Keeton & Winn
(2003): five of the six observed radio components are multiple images of a
single quasar, produced by a pair of lens galaxies. Multi-frequency VLBA maps
show that the sixth and faintest component has a different radio spectrum than
the others, confirming that it represents a second component of the background
source rather than a sixth image. The lens models predict that there should be
additional faint images of this second source component, and we find evidence
for one of the predicted images. The previously-observed large angular sizes of
two of the five bright components are not intrinsic (which would have excluded
the possibility that they are lensed images), but are instead due to scatter
broadening. Both the extended radio emission observed at low frequencies, and
the intrinsic image shapes observed at high frequencies, can be explained by
the lens models. The pair of lens galaxies is marginally detected in HST
images. The differential extinction of the quasar images suggests that the
extreme red color of the quasar is at least partly due to dust in the lens
galaxies.


title:
Photoelectric heating and [CII] cooling in translucent clouds: results
  for cloud models based on simulations of compressible MHD turbulence

abstract:
  The photoelectric heating is believed to be the main heating mechanism in
cool HI clouds. The heating rate can be estimated through observations of the
[CII] line emission, since this is the main coolant in regions where the
photoelectric effect dominates the heating. Comparison of the [CII] emission
with the far-infrared (FIR) emission allows to constrain the efficiency of the
photoelectric heating, using model calculations that take into account the
strength of the radiation field. Recent [CII] observations carried out with the
ISO satellite have made this study possible. In this work we study the
correlation between FUV absorption and FIR emission using three-dimensional
models. The density distributions are obtained with numerical simulations of
compressible magneto-hydrodynamic turbulence, with rms sonic Mach numbers
0.6<M<10. The FIR intensities are solved with detailed radiative transfer
calculations. The [CII] line radiation is estimated assuming the [CII] line
cooling equals the FUV absorption multiplied by the efficiency of the
photoelectric heating, epsilon. The average ratio between the predicted [CII]
and FIR emissions is found to be remarkably constant between different models,
implying that the derived values of epsilon should not depend on the rms Mach
number. The comparison with empirical data from translucent, high latitude
clouds yields an estimate of the photoelectric heating efficiency of 2.9 10^-2.
This value confirms previous theoretical predictions. Our models show that most
of the scatter in the observed [CII] and FIR intensities can be understood as a
result of the highly fragmented density field in turbulent HI clouds. The
scatter can be reproduced with models with supersonic turbulence, while
subsonic turbulence fails to generate the observed scatter.


title: The Quintuple Quasar: Mass Models and Interpretation

abstract:
  The strange morphology of the six-component gravitational lens PMN J0134-0931
has resisted explanation. We present the first successful quantitative models
for the system, based on the idea that there are two lens galaxies and two
components of the background source. One source is quintuply imaged and
corresponds to the five brightest observed radio components. The other source
is triply imaged and corresponds to the sixth component, along with two others
too faint to have been detected. The models reproduce the observed image
positions and fluxes, and make falsifiable predictions about other properties
of the system. Some of these predictions have been confirmed by high-resolution
radio and optical observations, as described in the companion paper by Winn et
al. (2003). Although we cannot determine the lens model uniquely with current
data, we predict that the lens galaxies are spiral galaxies with roughly equal
velocity dispersions sigma~120km/s and a projected separation of only 0.4" (2/h
kpc at z_l=0.76). This system is the first known lens with five images of a
single quasar, and the second with more than four images.


title: A View through Faraday's fog: Parsec scale rotation measures in AGN

abstract:
  Rotation measure observations of 9 quasars, 4 BL Lacertae objects, and 3
radio galaxies are presented. The rest frame rotation measures in the cores of
the quasars and the jets of the radio galaxy M87 are several thousand radians
per meter squared. The BL Lacertae objects and the jets of the quasars have
rest frame rotation measures of a few hundred radians per meter squared. A
nuclear rotation measure of 500 radians per meter squared in the rest frame is
suggested as the dividing line between quasar and BL Lacertae objects. The
substantial rotation measures of the BL Lacertae objects and quasars cast doubt
on the previous polarization position angle investigations of these objects at
frequencies of 15 GHz or less. BL Lacertae itself has a rotation measure that
varies in time, similar to the behavior observed for the quasars 3C273 and
3C279. A simple model with magnetic fields of 40 microgauss or less can account
for the observed rotation measures.


title: The Secondary Stars in Short Period (Magnetic) Cataclysmic Variables

abstract:
  We review the recent knowledge base pertaining to causes for mass accretion
variations (high/low states) in highly magnetic cataclysmic variables (i.e.
polars). We then examine what theory has to say about the properties of the
secondary stars (the mass donors) with respect to those CVs with very short
orbital periods. Finally, we use recent observations of EF Eri in an extended
low state to provide direct observational evidence which shows that this CV, as
well as a few others, likely contain very low mass, sub-stellar secondary
stars.


title: Ultraviolet and optical properties of Narrow-Line Seyfert 1 galaxies

abstract:
  Narrow Line Seyfert 1 (NLS1) galaxies are remarkable for their extreme
continuum and emission line properties which are not well understood. New
results bearing on the spectroscopic characteristics of these objects are
presented here, with the aim of establishing their typical ultraviolet and
optical spectral behavior. We employ HST observations of 22 NLS1s, which
represent a substantial improvement over previous work in terms of data quality
and sample size. High signal-to-noise NLS1 composite spectra are constructed,
allowing accurate measurements of the continuum shape and the strengths,
ratios, and widths for lines, including weak features which are barely
identifiable in other Active Galactic Nuclei (AGN) composites. We find that the
NLS1 sources have redder UV-blue continua than those typically measured in
other quasars and Seyferts. Objects with UV line absorption show redder
spectra, suggesting that dust is important in modifying the continuum shapes.
The data also permit a detailed investigation of the previously proposed link
between NLS1s and z >~ 4 quasars. Direct comparison of their composite spectra,
as well as a Principal Component Analysis, suggest that high-z QSOs do not show
a strong preference toward NLS1 behavior.


title: The Optical Counterpart of the Isolated Neutron Star RX J1605.3+3249

abstract:
  We have detected the optical counterpart to the nearby isolated neutron star
RX J1605.3+3249 using observations from the Space Telescope Imaging
Spectrometer aboard the Hubble Space Telescope. The counterpart, with
m_{50CCD}=26.84+/-0.07 mag and very blue colors, lies close to the ROSAT HRI
error circle and within the Chandra error circle. The spectrum is consistent
with a Rayleigh-Jeans tail whose emission is a factor of ~14 above the
extrapolation of the X-ray blackbody, and the source has an unabsorbed
X-ray-to-optical flux ratio of log(fX/fopt)=4.4, similar to that of other
isolated neutron stars. This confirms the classification of RX J1605.3+3249 as
a neutron star.


title: Studying clusters with Planck

abstract:
  We use mock Sunyaev-Zel'dovich effect (SZE) maps to investigate how well the
Planck mission might find and characterize clusters of galaxies. We discuss
different combinations of frequency maps and different methods for identifying
cluster candidates. The resulting catalogues are not complete even for
relatively high mass thresholds, but the full sky nature of the mission ensures
a large sample of massive, high-z clusters which will be ideal for many
studies. We make a preliminary attempt to identify the X-ray, optical and weak
lensing properties of the Planck sample.


title: Probing Planck-scale Physics with Extragalactic Sources?

abstract:
  At Planck-scale, spacetime is "foamy" due to quantum fluctuations predicted
by quantum gravity. Here we consider the possibility of using spacetime
foam-induced phase incoherence of light from distant galaxies and gamma-ray
bursters to probe Planck-scale physics. In particular, we examine the
cumulative effects of spacetime fluctuations over a huge distance. Our analysis
shows that they are far below what is required in this approach to shed light
on the foaminess of spacetime.


title: The Vela Pulsar's Radio Nebula

abstract:
  We have discovered that the radio nebula surrounding the Vela pulsar covers a
much wider extent than previously reported, with two lobes to the North and
South of the pulsar. Indications of this object have been reported previously,
but its symmetric morphology around the pulsar and other details had not been
identified as they were hidden due to poor sensitivity to low spatial
frequencies.
  The structure is highly polarised and the polarisation vectors, once
corrected for Faraday rotation, reveal symmetry with respect to the spin axis
of the pulsar. The X-ray emission found by Chandra lies at the centre of this
structure, in a region which has no detectable excess of radio emission. We
estimate total fluxes and regional fluxes from the Northern and Southern lobes,
plus the X-ray region at four radio frequencies; 1.4, 2.4, 5 and 8.5 GHz. We
present the corresponding images in both the total and polarised intensities,
as well as those showing the derotated linear polarisation vectors.


title:
The Vela Pulsar's proper motion and parallax derived from VLBI
  observations

abstract:
  The Vela pulsar is the brightest pulsar at radio wavelengths. It was the
object that told us (via its glitching) that pulsars were solid rotating bodies
not oscillating ones. Along with the Crab pulsar is it the source of many of
the models of pulsar behavior. Therefore it is of vital importance to know how
far away it is, and its origin.
  The proper motion and parallax for the Vela pulsar have been derived from 2.3
and 8.4 GHz Very Long Baseline Interferometry (VLBI) observations. The data
spans 6.8 years and consists of eleven epochs. We find a proper motion of
$\mu_{\alpha {\rm cos}\delta}= -49.61 \pm 0.06, \mu_\delta= 29.8 \pm 0.1$ \myr
and a parallax of $3.4 \pm 0.2$ mas, which is equivalent to a distance of
$293_{-17}^{+19}$ pc. When we subtract out the galactic rotation and solar
peculiar velocity we find $\mu_* = 45 \pm 1.3$ \myr with a position angle (PA)
of $301^\circ\pm1.8$ which implies that the proper motion has a small but
significant offset from the X-ray nebula's symmetry axis.


title: XMM-Newton observations of an absorbed z=0.67 QSO: no dusty torus?

abstract:
  We present XMM-Newton observations of AXJ0341.4-4453, a mildly reddened A_V<7
QSO at a redshift of z=0.672. The XMM-Newton spectrum shows a large obscuring
column N_H~10^23 cm^{-2} corresponding to A_V~70, in agreement with previous
results based on the lower limit of the ASCA hardness ratio. The X-ray spectrum
is represented by a 'scattering' model with Gamma~2.0 with the scattered
power-law normalization being a few per cent of the hard component. No FeK line
is detected with a 90 per cent upper limit on its equivalent width of ~360eV.
The large discrepancy between the column density observed in X-rays and that
inferred from the Balmer decrement can be explained by dust sublimation near
the nucleus. Then, the X-ray and the optical obscuration come from two
different regions: the X-ray close to the accretion disk while the optical at
much larger >0.25pc scales.


title: Spectral Ages of CSOs and CSS Sources

abstract:
  This paper deals with the spectral ageing study of a representative sample of
compact symmetric objects (CSOs) and compact steep spectrum (CSS) sources.
Observations reveal a distinctive high-frequency steepening of the radio
spectra of many of these sources. The existence of such a spectral feature is
expected or may be naturally interpreted in terms of radiative ageing of
synchrotron emitting electrons. The small angular size of CSS sources makes it
relatively easy to measure their integrated spectra over a wide frequency range
for a conspicuous number of objects. For those sources whose emission is
dominated by the mini-lobes, the integrated spectra can be used to constrain
the source age. Assuming equipartition magnetic fields, the spectral ages we
found are in the range from 10^2 to 10^5 yr. Multifrequency VLBA observations
allow us to study the spectral properties of two CSOs: B1323+321 and B1943+546.
The case of B1943+546 is particularly interesting since for this source a
kinematic age has been derived from the proper motion of the hot spots. We
found that spectral and kinematic ages agree within a factor of 2. The overall
results presented here confirm that the CSOs and CSS sources are indeed young
objects. Finally, we show some examples of compact sources characterised by an
extraordinary steep and curved spectrum. It is plausible that these are relic
sources in which the injection of fresh electrons has ceased for a significant
fraction of their lifetime. These observations may indicate either the presence
of intermittent activity or a class of short-living objects.


title:
Dust-to-gas ratios in the starburst regions of luminous infrared
  galaxies

abstract:
  We investigate the properties of dust and dust-to-gas ratios in different
starburst regions of luminous infrared galaxies (LIGs). We refer to the sample
of seven LIGs recently observed in the mid-infrared by Soifer et al. (2001)
using the Keck telescopes with spatial resolution approaching the diffraction
limit. These seven objects are among the closest LIGs and have been classified
as starburst galaxies from optical spectroscopy. Our goal consists in modelling
the continuum spectral energy distribution (SED) of each galaxy, particularly
in the infrared range. Models are further constrained by observed emission-line
ratios in the optical range. The multi-cloud models consistently account for
the coupled effect of shock, photoionization by hot stars, and diffuse
secondary radiation from the shock-heated gas. Emission from clouds in the
neighbourhood of evolved starbursts and with high shock velocities (~ 500 km/s)
explains both the bremsstrahlung and reradiation from dust in the mid-infrared.
Clouds with lower velocity (~ 100 km/s) and corresponding to younger starbursts
also contribute to both line and continuum spectra. Both low- and high-velocity
clouds are thus present in nearly all the sample galaxies. For all the
galaxies, an old stellar population is revealed by black body emission in the
optical-NIR range. Dust-to-gas ratios vary in different regions of individual
galaxies.


title:
High efficiency of soft X-ray radiation reprocessing in supersoft X-ray
  sources due to multiple scattering

abstract:
  Detailed analysis of the lightcurve of CAL 87 clearly has shown that the high
optical luminosity comes from the accretion disc rim and can only be explained
by a severe thickening of the disc rim near the location where the accretion
stream impinges. This area is irradiated by the X-rays where it faces the white
dwarf. Only if the reprocessing rate of X-rays to optical light is high a
luminosity as high as observed can be understood. But a recent detailed study
of the soft X-ray radiation reprocessing in supersoft X-ray sources has shown
that the efficiency is not high enough. We here propose a solution for this
problem. As already discussed in the earlier lightcurve analysis the impact of
the accretion stream at the outer disc rim produces a ``spray'', consisting of
a large number of individual gas blobs imbedded in a surrounding corona. For
the high mass flow rate this constitutes an optically thick vertically extended
screen at the rim of the accretion disc. We analyse the optical properties of
this irradiated spray and find that the multiple scattering between these gas
blobs leads to an effective reprocessing of soft X-rays to optical light as
required by the observations.


title: Superhumps in V1141 Aquilae

abstract:
  The results of the CCD observations of the 2002 superoutburst of V1141 Aql
are described. We have detected clear superhumps characterized by the period of
0.05930(5) days. There was another, much weaker, modulation in the light curve
of V1141 Aql. Its amplitude is equal to $0.012\pm0.002$ mag and its period to
0.03923(8) days. We have also discovered quasi periodic oscillations (QPOs)
with a mean period equal to 130 s and amplitude of $0.025\pm0.004$ mag.


title: High-energy cosmic gamma rays from the `Single Source'

abstract:
  Some six years ago, we (Erlykin and Wolfendale, 1997) proposed the `single
source model' in which a local, recent supernova remnant (SNR) was responsible
for the `knee' in the cosmic ray (CR) energy spectrum at ~3PeV. Stimulated by
the paper by Bhadra (2002), which drew attention to a possible gamma ray
signature of this local remnant, we now study the situation for the local
source and we conclude that, in contrast to Bhadra's conclusion, the
non-observation of this remnant is understandable - at least using our SNR
model. It is due to the fact that this SNR, being local, develops in the local
hot interstellar medium (HISM) with its low density of gas and also being
nearby it will be an extended source occupying up to 40$^\circ$ of the sky and
thus indistinguishable from the background.


title:
Problems in suppressing cooling flows in clusters of galaxies by global
  heat conduction

abstract:
  I use a simple analytical model to show that simple heat conduction models
cannot significantly suppress cluster cooling flows. I build a static medium
where heat conduction globally balances radiative cooling, and then perturb it.
I show that a perturbation extending over a large fraction of the cooling flow
region will grow to the non-linear regime within a Hubble time. Such
perturbations are reasonable in clusters which frequently experience mergers
and/or AGN activity. This result strengthens previous findings which show that
a steady solution does not exist for a constant heat conduction coefficient.


title: A New Sample of Distant Compact Groups From DPOSS

abstract:
  We have identified eighty-four small, high density groups of galaxies out to
z ~ 0.2 in a region of ~ 2000 square degrees around the north galactic pole
using DPOSS (the Digitized Second Palomar Observatory Sky Survey). The groups
have at least four galaxies satisfying more stringent criteria than those used
by Hickson in his pioneering work in 1982: the adopted limiting surface
brightness for each group is brighter (24 mag/arcsec^2 instead of 26
mag/arcsec^2), and the spread in magnitude among the member galaxies is
narrower (two magnitudes instead of three). We also adopt a slightly modified
version of the isolation criterion used by Hickson, in order to avoid rejecting
groups with projected nearby faint background galaxies. A 10% contamination
rate due to projection effects is expected for this sample based on extensive
simulations.


title:
Chemodynamical gas flow cycles and their influence on the chemical
  evolution of dwarf irregular galaxies

abstract:
  Here we investigate an exemplary chemodynamical evolutionary simulation of a
dwarf irregular galaxy. By means of this model we demonstrate the existence of
three gas mixing cycles: 1) An inner "local cycle" mixing the metals produced
in stars locally, and 2) an outer "galactic cycle" on which hot gas is driven
out of the galaxy by multiple supernovae type II and mixes on a short timescale
with the available cold gas. 3) Only a small fraction of the metals leaves the
galactic gravitational field and follows the "global cycle" with the
intergalactic matter. The large-scale mixing results in a temporary depletion
of supernova ejected metals. We will discuss this "delayed recycling" and its
influence on the chemical evolution, especially on the nitrogen over oxygen
ratio which is increased temporarily. These results presented her are also
relevant for less sophisticated analytical approaches and chemical evolutionary
models of galaxies which have to parameterize the metal loss through outflow.


title:
Observed Non-Steady State Cooling and the Moderate Cluster Cooling Flow
  Model

abstract:
  We examine recent developments in the cluster cooling flow scenario following
recent observations by Chandra and XMM-Newton. We show that the distribution of
gas emissivity verses temperature determined by XMM-Newton gratings
observations demonstrates that the central gas in cooling flow clusters cannot
be in simple steady-state. Combining this result with the lack of spectroscopic
evidence for gas below one-third of the ambient cluster temperature is strong
evidence that the gas is heated intermittently. While the old steady-state
isobaric cooling flow model is incompatible with recent observations, a
"moderate cooling flow model", in which the gas undergoes intermittent heating
that effectively reduces the age of a cooling flow is consistent with
observations. Most of the gas within cooling flows resides in the hottest gas,
which is prevented from cooling continuously and attaining a steady-state
configuration. This results in a mass cooling rate that decreases with
decreasing temperature, with a much lower mass cooling rate at the lowest
temperatures. The present paper strengthens the moderate cooling flow model,
which can accommodate the unique activities observed in cooling flow clusters.


title:
On the usefulness of finding charts Or the runaway carbon stars of the
  Blanco & McCarthy field 37

abstract:
  We have been recently faced with the problem of cross--identifying stars
recorded in historical catalogues with those extracted from recent fully
digitized surveys (such as DENIS and 2MASS). Positions mentioned in the old
catalogues are frequently of poor precision, but are generally accompanied by
finding charts where the interesting objects are flagged. Those finding charts
are sometimes our only link with the accumulated knowledge of past literature.
While checking the identification of some of these objects in several
catalogues, we had the surprise to discover a number of discrepancies in recent
works.The main reason for these discrepancies was generally the blind
application of the smallest difference in position as the criterion to identify
sources from one historical catalogue to those in more recent surveys. In this
paper we give examples of such misidentifications, and show how we were able to
find and correct them.We present modern procedures to discover and solve
cross--identification problems, such as loading digitized images of the sky
through the Aladin service at CDS, and overlaying entries from historical
catalogues and modern surveys. We conclude that the use of good finding charts
still remains the ultimate (though time--consuming) tool to ascertain
cross--identifications in difficult cases.


title: Central Proper-Motion Kinematics of NGC 6752

abstract:
  We present proper motions derived from WFPC2 imaging for stars in the core of
the peculiar globular cluster NGC 6752. The central velocity dispersion in both
components of the proper motion is 12 km/s. We discuss the implications of this
result as well as the intrinsic difficulties in making such measurements. We
also give an alternative correction for the 34-row problem in the WFPC2 CCDs.


title:
Automated Determination of Stellar Parameters from Simulated Dispersed
  Images for DIVA

abstract:
  We have assessed how well stellar parameters (T_eff, logg and [Fe/H]) can be
retrieved from low-resolution dispersed images to be obtained by the DIVA
satellite. Although DIVA is primarily an all-sky astrometric mission, it will
also obtain spectrophotometric information for about 13 million stars
(operational limiting magnitude V ~ 13.5 mag). Constructional studies foresee a
grating system yielding a dispersion of ~200nm/mm on the focal plane (first
spectral order). For astrometric reasons there will be no cross dispersion
which results in the overlapping of the first to third diffraction orders. The
one-dimensional, position related intensity function is called a DISPI
(DISPersed Intensity). We simulated DISPIS from synthetic spectra (...) for a
limited range of metallicites i.e. our results are for [Fe/H] in the range -0.3
to 1 dex. We show that there is no need to deconvolve these low resolution
signals in order to obtain basic stellar parameters. Using neural network
methods and by including simulated data of DIVA's UV telescope, we can
determine T_eff to an average accuracy of about 2% for DISPIS from stars with
2000 K < T_eff < 20000 K and visual magnitudes of V=13 mag (end of mission
data). logg can be determined for all temperatures with an accuracy better than
0.25 dex for magnitudes brighter than V=12 mag. For low temperature stars with
2000 K < T_eff < 5000 K and for metallicities in the range -0.3 to +1 dex a
determination of [Fe/H] is possible (to better than 0.2 dex) for these
magnitudes. Additionally we examined the effects of extinction E(B-V) on DISPIS
and found that it can be determined to better than 0.07 mag for magnitudes
brighter than V=14 mag if the UV information is included.


title: Ultra-High Energy Cosmic Rays in a Structured and Magnetized Universe

abstract:
  We simulate propagation of cosmic ray nucleons above 10^{19} eV in scenarios
where both the source distribution and magnetic fields within about 50 Mpc from
us are obtained from an unconstrained large scale structure simulation. We find
that consistency of predicted sky distributions with current data above 4 x
10^{19} eV requires magnetic fields of ~0.1 microGauss in our immediate
environment, and a nearby source density of ~10^{-4}-10^{-3} Mpc^{-3}. Radio
galaxies could provide the required sources, but only if both high and
low-luminosity radio galaxies are very efficient cosmic ray accelerators.
Moreover, at ~10^{19} eV an additional isotropic flux component, presumably of
cosmological origin, should dominate over the local flux component by about a
factor three in order to explain the observed isotropy. This argues against the
scenario in which local astrophysical sources of cosmic rays above ~10^{19} eV
reside in strongly magnetized (B~0.1 microGauss) and structured intergalactic
medium. Finally we discuss how future large scale full-sky detectors such as
the Pierre Auger project will allow to put much more stringent constraints on
source and magnetic field distributions.


title:
The 3-D kinematics of water masers around the semiregular variable RT
  Virginis

abstract:
  We report observations of water masers around the semiregular variable RT
Virginis (RT Vir), which have been made with the Very Long Baseline Array
(VLBA) of the National Radio Astronomy Observatory (NRAO) at five epochs, each
separated by three weeks of time. We detected about 60 maser features at each
epoch. Overall, 61 features, detected at least twice, were tracked by their
radial velocities and proper motions. The 3-D maser kinematics exhibited a
circumstellar envelope that is expanding roughly spherically with a velocity of
about 8 km/s. Asymmetries in both the spatial and velocity distributions of the
maser features were found in the envelope, but less significant than that found
in other semiregular variables. Systematic radial-velocity drifts of individual
maser features were found with amplitudes of <= 2 km/s/yr. For one maser
feature, we found a quadratic position shift with time along a straight line on
the sky. This apparent motion indicates an acceleration with an amplitude of 33
km/s/yr, implying the passage of a shock wave driven by the stellar pulsation
of RT Vir. The acceleration motion is likely seen only on the sky plane because
of a large velocity gradient formed in the accelerating maser region. We
estimated the distance to RT Vir to be about 220 pc on the basis of both the
statistical parallax and model-fitting methods for the maser kinematics.


title: Searching for Clusters with SUMSS

abstract:
  Statistical overdensities of radiosources in the Sydney University Molonglo
Sky Survey (SUMSS) are used as signposts to identify high-redshift clusters of
galaxies. These potential clusters have been observed at 20 and 13 cm at the
Australia Telescope Compact Array (ATCA) to obtain better positional accuracy
for the sources. A subsample have been imaged in V, R and I at the 2.3-m
telescope at Siding Spring and in J and K at the Anglo Australian Telescope
(AAT) and the New Technology Telescope (NTT) at La Silla, Chile. The colours
obtained from these observations will be used to estimate redshifts for the
potential cluster members.


title:
Discrete X-ray Signatures of a Photoionized Plasma Above the Accretion
  Disk of the Neutron Star EXO 0748-676

abstract:
  During the disk-mediated accretion phase, the high-resolution X-ray spectrum
of the low-mass X-ray binary system EXO 0748-676 reveals a photoionized plasma
which is orbiting the neutron star. Our observations with the Chandra High
Energy Transmission Grating Spectrometer (HETGS) constrain the structure of the
upper layers of the accretion disk, by means of the recombination emission
lines from the H-like and He-like ions of O, Ne, and Mg, which have a mean
velocity broadening of 750 +- 120 km/s. The Mg XI emission region has density
n_e > 10^12 cm^-3 and is located within 7 x 10^9 and 6 x 10^10 cm of the
neutron star, while the temperature of the Ne X region is kT < 20 eV. These
lines favor a vertically stratified distribution of ions in the disk. The
spectra show that the line region is spatially extended and unabsorbed, while
the continuum region is compact and heavily absorbed. The absorber has variable
column density and is composed of both neutral and ionized gas, which can
explain the stochastic and periodic X-ray intensity dips, the X-ray continuum
evolution, and the O VII and Mg XI K-shell absorption edges. The absorber is
located 8 to 15 deg above the disk midplane, inclusive of two bulges near the
disk edge. This outer disk gas may participate in the outflow of ionized plasma
which was previously identified in XMM-Newton grating spectra obtained during
type I bursts. The thickened photoionized region above the disk can be produced
by heating from the neutron star X-rays and by the impact of the accretion
stream.


title:
Ha Rotation Curves of z~1 Galaxies: Unraveling the Evolution of the
  Tully-Fisher Relation

abstract:
  We describe the first results of a programme to obtain rotation curves of z~1
disc galaxies in the near-infrared using the Ha emission line in order to study
the Tully-Fisher relation. To put any observed evolution into perspective and
to investigate any possible selection biases, we constructed a control sample
of low redshift galaxies that had rotation velocities and images available for
measuring their dynamical, photometric, and morphological properties. Compared
to local objects with isophotal sizes similar to the high redshift targets, we
find that our sample of galaxies with spatially resolved rotation curves, the
most distant sample so far (<z>~0.9), clearly reveals a brightening of ~1.1 mag
in the rest-frame B-band. The observed offset can be explained by a combination
of increasing surface brightness, decreasing rotation speeds, and slightly
smaller disc scale lengths of the high redshift galaxies.


title: An X-ray Atlas of Groups of Galaxies

abstract:
  A search was conducted for a hot intragroup medium in 109 low-redshift galaxy
groups observed with the ROSAT PSPC. Evidence for diffuse, extended X-ray
emission is found in at least 61 groups. Approximately one-third of these
detections have not been previously reported in the literature.
  Most of the groups are detected out to less than half of the virial radius
with ROSAT. Although some spiral-rich groups do contain an intragroup medium,
diffuse emission is restricted to groups that contain at least one early-type
galaxy.


title:
High Resolution STIS/HST and HIRES/Keck Spectra of Three Weak MgII
  Absorbers Toward PG 1634+706

abstract:
  High resolution optical (HIRES/Keck) and UV (STIS/HST) spectra, covering a
large range of chemical transitions, are analyzed for three single-cloud weak
MgII absorption systems along the line of sight toward the quasar PG 1634+706.
Weak MgII absorption lines in quasar spectra trace metal-enriched environments
that are rarely closely associated with the most luminous galaxies (>0.05L^*).
The two weak MgII systems at z=0.81 and z=0.90 are constrained to have >=solar
metallicity, while the metallicity of the z=0.65 system is not as
well-constrained, but is consistent with >1/10th solar. These weak MgII clouds
are likely to be local pockets of high metallicity in a lower metallicity
environment. All three systems have two phases of gas, a higher density region
that produces narrower absorption lines for low ionization transitions, such as
MgII, and a lower density region that produces broader absorption lines for
high ionization transitions, such as CIV. The CIV profile for one system (at
z=0.81) can be fit with a single broad component (b~10 km/s), but those for the
other two systems require one or two additional offset high ionization clouds.
Two possible physical pictures for the phase structure are discussed: one with
a low-ionization, denser phase embedded in a lower density surrounding medium,
and the other with the denser clumps surrounding more highly ionized gas.


title:
Investigation of the obscuring circumnuclear torus in the active galaxy
  Mrk231

abstract:
  Here we report on observations of powerful hydroxyl (OH) line emissions that
trace the obscuring material within the circumnuclear environment of the galaxy
Markarian 231. The hydroxyl (mega)-maser emission shows the characteristics of
a rotating, dusty, molecular torus (or thick disk) located between 30 and 100
pc from the central engine. We now have a clear view of the physical
conditions, the kinematics and the spatial structure of this material on
intermediate size scales, confirming the main tenets of unification models.


title: Early Universe Sources for Cosmic Microwave Background Non-Gaussianity

abstract:
  In the framework of inflationary models with non-vacuum initial states for
cosmological perturbations, we study non-Gaussian signatures on the cosmic
microwave background radiation produced by a broken-scale-invariant model which
incorporates a feature at a privileged scale in the primordial power spectrum.


title: The Radio Structure of High-Energy Peaked BL Lacertae Objects

abstract:
  We present VLA and first-epoch VLBA observations that are part of a program
to study the parsec-scale radio structure of a sample of fifteen
high-energy-peaked BL Lacs (HBLs). The sample was chosen to span the range of
logarithmic X-ray to radio flux ratios observed in HBLs. As this is only the
first epoch of observations, proper motions of jet components are not yet
available; thus we consider only the structure and alignment of the parsec- and
kiloparsec-scale jets. Like most low-energy-peaked BL Lacs (LBLs), our HBL
sample shows parsec-scale, core-jet morphologies and compact, complex
kiloparsec-scale morphologies. Some objects also show evidence for bending of
the jet 10-20pc from the core, suggesting interaction of the jet with the
surrounding medium. Whereas LBLs show a wide distribution of parsec- to
kpc-scale jet misalignment angles, there is weak evidence that the jets in HBLs
are more well-aligned, suggesting that HBL jets are either intrinsically
straighter or are seen further off-axis than LBL jets.


title:
Broad Halpha wings in Nebulae around Evolved Stars and in Young
  Planetary Nebulae

abstract:
  Eleven objects that have been reported as proto-planetary nebula or as young
planetary nebulae that show very extended Halpha wings are presented. The
extension of these wings is larger than 800 km/s. Data for two symbiotic stars
that show this same characteristic is also presented. Raman scattering is the
mechanism that best explains the wings in 10 of the PNe and in the 2 symbiotic
stars. In the PN IRAS 20462+3416 the wing profile can be explained by very
intense stellar wind.


title: Radial Velocity Studies of Close Binary Stars.VIII

abstract:
  Radial-velocity measurements and sine-curve fits to the orbital velocity
variations are presented for the seventh set of ten close binary systems: V410
Aur, V523 Cas, QW Gem, V921 Her, V2357 Oph, V1130 Tau, HN UMa, HX UMa, HD
93917, NSV 223. All systems, but three (V523 Cas, HD 93917, NSV 223), were
discovered photometrically by the Hipparcos mission. All systems are
double-lined (SB2) binaries and all, but the detached, very close system V1130
Tau, are contact binaries. The broadening-function permitted improvement of the
orbital elements for V523 Cas, which was the only system observed before for
radial velocity variations. Spectroscopic/visual companions were detected for
V410 Aur and HX UMa.


title:
High-Resolution Radio Imaging of Gravitational Lensing Candidates in the
  1 Jansky BL Lac Sample

abstract:
  While BL Lacertae objects are widely believed to be highly beamed,
low-luminosity radio galaxies, many radio-selected BL Lacs have extended radio
power levels and optical emission lines that are too luminous to be
low-luminosity radio galaxies. Also, Stocke & Rector discovered an excess of
MgII absorption systems along BL Lac sightlines compared to quasars, suggesting
that gravitational lensing may be another means of creating the BL Lac
phenomenon in some cases. We present a search for gravitationally-lensed BL
Lacs with deep, high-resolution, two-frequency VLA radio maps of seven lensing
candidates from the 1 Jansky BL Lac sample. We find that none of these objects
are resolved into an Einstein ring like B 0218+357, nor do any show multiple
images of the core. All of the lensing candidates that were resolved show a
flat-spectrum core and very unusual, steep-spectrum extended morphology that is
incompatible with a multiply lensed system. Thus, while these observations do
not rule out microlensing, no macrolensing is observed.


title: A star-forming galaxy at z=5.78 in the Chandra Deep Field South

abstract:
  We report the discovery of a luminous z=5.78 star-forming galaxy in the
Chandra Deep Field South. This galaxy was selected as an `i-drop' from the
GOODS public survey imaging with HST/ACS (object 3 in Stanway, Bunker & McMahon
2003, astro-ph/0302212). The large colour of (i'-z')_AB=1.6 indicated a
spectral break consistent with the Lyman-alpha forest absorption short-ward of
Lyman-alpha at z~6. The galaxy is very compact (marginally resolved with ACS
with a half-light radius of 0.08arcsec, so r_hl<0.5kpc/h_70). We have obtained
a deep (5.5-hour) spectrum of this z'(AB)=24.7 galaxy with the DEIMOS optical
spectrograph on Keck, and here we report the discovery of a single emission
line centred on 8245Ang detected at 20sigma with a flux of f~2E-17 ergs/s/cm^2.
The line is clearly resolved with detectable structure at our resolution of
better than 55km/s, and the only plausible interpretation consistent with the
ACS photometry is that we are seeing Lyman-alpha emission from a z=5.78 galaxy.
This is the highest redshift galaxy to be discovered and studied using HST
data. The velocity width Delta(v)_FWHM=260km/s and rest-frame equivalent width
(W=20Ang) indicate that this line is most probably powered by star formation,
as an AGN would typically have larger values. The starburst interpretation is
supported by our non-detection of the high-ionization NV1240Ang emission line,
and the absence of this source from the deep Chandra X-ray images. The star
formation rate inferred from the rest-frame UV continuum is 34M_sun/yr/h^2_70
(Omega_M=0.3, Omega_Lambda=0.7). This is the most luminous starburst known at
z>5. Our spectroscopic redshift for this object confirms the validity of the
i'-drop technique of Stanway, Bunker & McMahon (2003) to select star-forming
galaxies at z~6.


title:
Discovery of Two Distant Type Ia Supernovae in the Hubble Deep Field
  North with the Advanced Camera for Surveys

abstract:
  We present observations of the first two supernovae discovered with the
recently installed Advanced Camera for Surveys (ACS) on the Hubble Space
Telescope. The supernovae were found in Wide Field Camera images of the Hubble
Deep Field North taken with the F775W, F850LP, and G800L optical elements as
part of the ACS guaranteed time observation program. Spectra extracted from the
ACS G800L grism exposures confirm that the objects are Type Ia supernovae (SNe
Ia) at redshifts z=0.47 and z=0.95. Follow-up HST observations have been
conducted with ACS in F775W and F850LP and with NICMOS in the near-infrared
F110W bandpass, yielding a total of 9 flux measurements in the 3 bandpasses
over a period of 50 days in the observed frame. We discuss many of the
important issues in doing accurate photometry with the ACS. We analyze the
multi-band light curves using two different fitting methods to calibrate the
supernovae luminosities and place them on the SNe Ia Hubble diagram. The
resulting distances are consistent with the redshift-distance relation of the
accelerating universe model, although evolving intergalactic grey dust remains
as a less likely possibility. The relative ease with which these SNe Ia were
found, confirmed, and monitored demonstrates the potential ACS holds for
revolutionizing the field of high-redshift SNe Ia, and therefore of testing the
accelerating universe cosmology and constraining the "epoch of deceleration".


title:
The Reionization History at High Redshifts I: Physical Models and New
  Constraints from CMB Polarization

abstract:
  The recent discovery of a high optical depth tau to Thomson scattering from
the WMAP data implies that significant reionization took place at redshifts
z~15. This discovery has important implications for the sources of
reionization, and allows, for the first time, constraints to be placed on
physical reionization scenarios out to redshift z~20. Using a new suite of
semi-analytic reionization models, we show that the high value of tau requires
a surprisingly high efficiency epsilon of the first generation of UV sources
for injecting ionizing photons into the intergalactic medium. We find that no
simple reionization model can be consistent with the combination of the WMAP
result with data from the z<6.5 universe. Satisfying both constraints requires
either of the following: (i) H_2 molecules form efficiently at z~20, survive
feedback processes, and allow UV sources in halos with virial temperatures
below Tvir=10^4 K to contribute substantially to reionization, or (ii) the
efficiency epsilon in halos with Tvir>10^4K decreased by a factor of ~ 30
between (z~20) and (z~6). We discuss the relevant physical issues to produce
either scenario, and argue that both options are viable, and allowed by current
data. In detailed models of the reionization history, we find that the
evolution of the ionized fractions in the two scenarios have distinctive
features that Planck can distinguish at 3 sigma significance. At the high WMAP
value for tau, Planck will also be able to provide tight statistical
constraints on reionization model parameters, and elucidate much of the physics
at the end of the Dark Ages. The sources responsible for the high optical depth
discovered by WMAP should be directly detectable out to z~15 by the James Webb
Space Telescope.


title:
The Reionization History at High Redshifts II: Estimating the Optical
  Depth to Thomson Scattering from CMB Polarization

abstract:
  In light of the recent inference of a high optical depth to Thomson
scattering, tau, from the WMAP data we investigate the effects of extended
periods of partial ionization and ask if the value of tau inferred by assuming
a single sharp transition is an unbiased estimate. We construct and consider
several representative ionization models and evaluate their signatures in the
CMB. If tau is estimated with a single sharp transition we show that there can
be a significant bias in the derived value (and therefore a bias in sigma8 as
well). For WMAP noise levels the bias in tau is smaller than the statistical
uncertainty, but for Planck or a cosmic variance limited experiment the tau
bias could be much larger than the statistical uncertainties. This bias can be
reduced in the ionization models we consider by fitting a slightly more
complicated ionization history, such as a two-step ionization process. Assuming
this two-step process we find the Planck satellite can simultaneously determine
the initial redshift of reionization to +-2 and tau to +-0.01 Uncertainty about
the ionization history appears to provide a limit of about 0.005 on how well
tau can be estimated from CMB polarization data, much better than expected from
WMAP but significantly worse than expected from cosmic-variance limits.


title:
A First Look at White Dwarf - M Dwarf Pairs in the Sloan Digital Sky
  Survey (SDSS)

abstract:
  We have identified 109 White Dwarf (WD) - M dwarf pairs in the Sloan Digital
Sky Survey (SDSS) with g < 20th magnitude. For each system we determined the
temperature of the WD primary and the spectral type of the M dwarf secondary.
Using H-alpha emission as a proxy for the chromospheric activity level of the M
dwarf, we investigated correlations between the activity level and properties
of the system. Compared with field M dwarfs (Hawley et al. 1996), we see a
slightly higher active fraction of early-type stars, with activity levels
similar to the field.
  We have conducted followup observations at the ARC 3.5m telescope to obtain
radial velocity information and to search for short period binaries, which may
be on the verge of interacting. We report on one system with a 4.1 hour period,
and several additional systems with significant velocity variations.


title:
Multi-level 3D non-LTE computations of lithium lines in the metal-poor
  halo stars HD140283 and HD84937

abstract:
  The lithium abundances in metal-poor halo stars are of importance for
cosmology, galaxy evolution and stellar structure. In an attempt to study
possible systematic errors in the derived Li abundances, the line formation of
LiI lines has been investigated by means of realistic 3D hydrodynamical model
atmospheres of halo stars and 3D non-LTE radiative transfer calculations. These
are the first detailed 3D non-LTE computations reported employing a multi-level
atomic model showing that such problems are now computationally tractable. The
detailed computations reveal that the LiI population has a strong influence
from the radiation field rather than the local gas temperature, indicating that
the low derived Li abundances found by Asplund et al. (1999) are an artifact of
their assumption of LTE. Relative to 3D LTE, the detailed calculations show
pronounced over-ionization. In terms of abundances the 3D non-LTE values are
within 0.05 dex of the 1D non-LTE results for the particular cases of HD140283
and HD84937, which is a consequence of the dominance of the radiation in
determining the population density of LiI. Although 3D non-LTE can be expected
to give results rather close (+/-0.1 dex) to 1D non-LTE for this reason, there
may be systematic trends with metallicity and effective temperature.


title:
Stellar abundance analyses in the light of 3D hydrodynamical model
  atmospheres

abstract:
  I describe recent progress in terms of 3D hydrodynamical model atmospheres
and 3D line formation and their applications to stellar abundance analyses of
late-type stars. Such 3D studies remove the free parameters inherent in
classical 1D investigations (mixing length parameters, macro- and
microturbulence) yet are highly successful in reproducing a large arsenal of
observational constraints such as detailed line shapes and asymmetries. Their
potential for abundance analyses is illustrated by discussing the derived
oxygen abundances in the Sun and in metal-poor stars, where they seem to
resolve long-standing problems as well as significantly alter the inferred
conclusions.


title: Radiative transfer in 3D model stellar atmospheres

abstract:
  Recently 3D hydrodynamical simulations of stellar surface convection have
become feasible thanks to advances in computer technology and efficient
numerical algorithms. Available observational diagnostics indicate that these
models are highly realistic in describing the topology of stellar granulation
and for spectral line formation purposes. The traditional free parameters
(mixing length parameters, micro- and macroturbulence) always inherent in
standard 1D analyses have thus finally become obsolete. These 3D models can
therefore both shed light on the elusive nature of stellar convection as well
as be employed in element abundance analyses. In the present contribution we
will describe some aspects of the models and possible applications of them in
terms of radiative transfer.


title: New generations of stellar model atmospheres

abstract:
  Stellar model atmospheres form the basis for any element abundance
determination and hence are crucial ingredients for studies of stellar,
galactic and cosmic evolution. With recent observational progress with the
advent of 8m-class telescopes and efficient spectrographs, the dominant source
of uncertainty today originates with the assumptions and approximations in the
analyses, emphasizing the great need for continuing efforts in improving the
realism of stellar atmosphere modelling. In the present contribution I will
describe recent progress in this regard by focussing on three complementary
types of model atmospheres: line-blanketed non-LTE models of hot stars, 3D
hydrodynamical models of cool stars and semi-empirical models for large-scale
stellar abundance analyses.


title:
A Limit Relation between Black Hole Mass and H$\beta$ Width: Testing
  Super-Eddington Accretion in Active Galactic Nuclei

abstract:
  (abbreviated) We show that there is a limit relation between the black hole
mass and the width at the half maximum of H$\beta$ for active galactic nuclei
(AGNs) with super-Eddington accretion rates. When a black hole has a
super-Eddington accretion rate, the empirical relation of reverberation mapping
has two possible ways. First, it reduces to a relation between the black hole
mass and the size of the broad line region due to the photon trapping effects
inside the accretion disk. For the Kaspi et al.'s empirical reverberation
relation, we get the limit relation as $M_{\rm BH}=(2.9 - 12.6)\times
10^6M_{\odot} (\upsilon_{\rm FWHM}/10^3{\rm km s^{-1}})^{6.67}$, called as the
Eddington limit. Second, the Eddington limit luminosity will be relaxed if the
trapped photons can escape from the magnetized super-Eddington accretion disk
via the photon bubble instability, and the size of the broad line region will
be enlarged according to the empirical reverberation relation, leading to a
relatively narrow width of H$\beta$. We call this the Begelman limit.
  Super-Eddington accretions in a sample composed of 164 AGNs have been
searched by this limit relation. We find there are a handful of objects locate
between the Eddington and Begelman limit lines, they may be candidates of
super-Eddington accretors in a hybrid structure of photon trapping and photon
bubble instability. The maximum width of H$\beta$ is in the reange of $(3.0 -
3.8)\times 10^3$ km s$^{-1}$ for the maximum mass black holes with
super-Eddington accretion rates among AGNs. We suggest that this limit relation
is more reliable and convenient to test whether a source is super-Eddington and
useful to probe the structure of the super-Eddington accretion process.


title:
The ISOGAL field FC--01863+00035: Mid-IR interstellar extinction and
  stellar populations

abstract:
  A 0.35\degr $\times$ 0.29\degr field centered at $l$=--18.63\degr,
$b$=0.35\degr was observed during the ISOGAL survey by ISOCAM imaging at
7$\mu$m and 15{\rm $\mu$m}. 648 objects were detected and their brightness are
measured. By combining with the DENIS data in the near-infrared J and K$_{\rm
S}$ bands, one derives the extinction at 7{\rm $\mu$m} through ${\rm A_{K_{\rm
S}}-A_7= 0.35 (A_J-A_{K_{\rm S}})}$ which yields A$_{7}$/A$_{\it V}$ $\sim$0.03
from the near-IR extinction values of van de Hulst--Glass (Glass 1999). The
extinction structure along the line of sight is then determined from the values
of J--K$_{\rm S}$ or K$_{\rm S}$--[7] of the ISOGAL sources identified as RGB
or early AGB stars with mild mass-loss. The distribution of A$_{\it V}$ ranges
from 0 to $\sim$45 and it reflects the concentration of the extinction in the
spiral arms. Based on their locations in color-magnitude diagrams and a few
cross-identifications with IRAS and MSX sources, the nature of objects is
discussed in comparison with the case of a low extinction field in Baade's
Window. Most of the objects are either AGB stars with moderate mass loss rate
or luminous RGB stars. Some of them may be AGB stars with high mass loss rate.
In addition, a few young stellar objects (YSOs) are present.


title: Graviton mass and total relative density of mass Omega_tot in Universe

abstract:
  It is noticed that the total relative density of mass in the Universe
Omega_tot should exceed 1, i.e. Omega_tot=1+f^2/6 according to the field
relativistic theory of gravity (RTG), which is free of the cosmological
singularity and which provides the Euclidean character for the 3-dimensional
space. Here f is the ratio of the graviton mass m_g to the contemporary value
of the ``Hubble mass'' m^0_H=\hbar H_0/c^2\simeq 3,8\cdot 10^{-66}h(g)
(h=0,71\pm0,07). Applying results of the experimental data processing presented
in [1] an upper limit for the graviton mass is established as m_g\leq 3,2\cdot
10^{-66}g at the 95% confidence level.


title: XMM-Newton observation of the Seyfert 1 ESO 198-G24

abstract:
  We present the results from an XMM-Newton observation (January 24, 2001) of
the bright Seyfert 1 galaxy ESO 198-G24 (z=0.045). We found that this Seyfert
has an intrinsic 2-10 keV luminosity of about 10^44 erg s-1. This source shows
no intrinsic absorption in addition to the Galactic absorption (N_{H}~3 x 10^20
cm-2). We found both with EPIC and RGS that this source possesses significantly
steeper spectra below ~ 1.5-2 keV than observed at higher X-ray energies, the
so-called soft X-ray excess. The RGS spectra reveal no significant narrow
absorption lines suggesting that if there is a warm absorber, it either has a
relatively low column density, or a very high ionization parameter. The RGS
data are well described by the combination of a power-law, a modified black
body continuum, and weak relativistic lines of O VIII, and C VI Lyalpha.
However other interpretations are not definitely excluded. The 2-10 keV energy
band is well fitted by an absorbed power-law with a photon spectral index of
Gamma=1.77 +/- 0.04 (consistent with the typical Gamma~1.7 found in Seyfert 1
galaxies). We found the presence of a narrow Gaussian emission line at 6.41 keV
(i.e < Fe XVII) with a moderate equivalent width of about 60-70 eV, and we
found an upper limit for a broad component, if any, of 75 eV. We also found a
weak absorption edge associated with cold iron with an optical depth of about
0.2.


title: The role of inner density waves in fueling galactic nuclei

abstract:
  I present here an heterogeneous selection of nearby galaxies in which inner
density waves (bars, spirals, m=1 modes) have been observed, and which are
presumed to host a supermassive black hole, to illustrate the importance of
such inner waves in the fueling of the central 10s of parsecs.


title:
Centimetre continuum emission from young stellar objects in Cederblad
  110

abstract:
  The low-mass star formation region associated with the reflection nebula
Cederblad 110 in the Chamaeleon I cloud was mapped with the Australian
Telescope Compact Array (ATCA) at 6 and 3.5cm. Altogether 11 sources were
detected, three of which are previously known low mass young stellar objects
associated with the nebula: the illuminating star IRS2 (Class III, Einstein
X-ray source CHX7), the brightest far-infrared source IRS4 (Class I), and the
weak X-ray source CHX10a (Class III). The other young stellar objects in the
region, including the Class 0 protostar candidate Cha-MMS1, were not detected.
The radio spectral index of IRS4 (alpha = 1.7 +/- 0.3) is consistent with
optically thick free-free emission arising from a dense ionized region,
probably a jet-induced shock occurring in the circumstellar material. As the
only Class I protostar with a 'thermal jet' IRS4 is the strongest candidate for
the central source of the molecular outflow found previously in the region. The
emission from IRS2 has a flat spectrum (alpha = 0.05 +/- 0.05) but shows no
sign of polarization, and therefore its origin is likely to be optically thin
free-free emission either from ionized wind or a collimated jet. The strongest
source detected in this survey is a new compact object with a steep negative
spectral index (-1.1) and a weak linear polarization (about 2 %), which
probably represents a background radio galaxy.


title:
Continuum and spectral line observations of the OH Megamaser galaxy Arp
  220

abstract:
  We present MERLIN observations of the continuum (both 1.6 and 5 GHz) and OH
maser emission towards Arp220. the correct spatial configuration of the various
componnents of the galaxy is revealed. In the eastern component the masers are
shown to be generally coincident with the larger scale continuum emission; in
the west, the masers and continuum do not generally arise from the same
location. A velocity gradient (0.32+/-0.03km/s/pc) is found in the eastern
nuclear region in MERLIN scales; this gradient is three times smaller than seen
in OH and implies that the OH gas lies inside the HI. A re-analysis of
previously presented global VLBI data (Lonsdale et al. 1998) reveals a very
high velocity gradient (18.67+/-0.12km/s/pc) in one component, possibly the
site of a heavily obscured AGN.


title:
Bursts, eclipses, dips and a refined position for the luminous low-mass
  X-ray binary in the globular cluster Terzan 6

abstract:
  GRS 1747-312 is a bright transient X-ray source in the globular cluster
Terzan 6 with quasi-periodic outbursts approximately every 4.5 months. We
carried out 2-60 keV target-of-opportunity observations during eight outbursts
with the Proportional Counter Array on the RXTE satellite, for a total exposure
time of 301 ks, and detect the first unambiguous thermonuclear X-ray bursts
from this source. This identifies the compact accretor in this binary as a
neutron star. The neutron star identification implies that twelve out of
thirteen luminous (above 10^36 erg/s X-ray sources in Galactic globular
clusters harbor neutron stars, with AC211's nature (in M15) remaining elusive.
We observed 24 transitions of eclipses of the X-ray emitting region by the
companion star and are able to improve the accuracy of the orbital period by a
factor of 10^4. The period is P=0.514980303(7) d. We do not detect a period
derivative with an upper limit of |\dot{P}/P|=3X10^-8 yr^{-1}. Archival Chandra
data were analyzed to further refine the X-ray position, and the cluster's
center of gravity was re-determined from optical data resulting in a correction
amounting to 2 core radii. We find that GRS 1747-312 is 0.2+/-0.2 core radii
from the cluster center.


title: The Carina Project: I. Bright Variable Stars

abstract:
  We present new BV time series data of the Carina dwarf spheroidal galaxy.
Current data cover an area of about 0.3 square degrees around the center of the
galaxy and allowed us to identify 92 variables. Among them 75 are RR Lyrae
stars, 15 are "bona fide" Anomalous Cepheids, one might be a Galactic field RR
Lyrae, and one is located along the Carina Red Giant Branch. Expanding upon the
seminal photographic investigation by Saha, Monet & Seitzer (1986) we supply
for the first time accurate estimates of their pulsation parameters (periods,
amplitudes, mean magnitude and colors) on the basis of CCD photometry.
Approximately 50% of both RR Lyrae and Anomalous Cepheids are new
identifications. Among the RR Lyrae sample 6 objects are new candidate
double-mode variables. On the basis of their pulsation properties we estimated
that two variables (V152, V182) are about 50% more massive than typical RR
Lyrae stars, while the bulk of the Anomalous Cepheids are roughly a factor of
two more massive than fundamental mode RR Lyrae stars. This finding supports
the evidence that these objects are intermediate-mass stars during central He
burning phases. The data for Carina, together with data available in the
literature, strongly support the conclusion that dSph galaxies can barely be
classified into the classical Oosterhoff dichotomy. The mean period of
fundamental mode RR Lyrae in Carina resembles that found for Oosterhoff type II
clusters, whereas the ratio between first overtones and total number of RR
Lyrae is quite similar to that found in Oosterhoff type I clusters.


title: X-Ray and Gamma-Ray Emission from the PSR 1259-63 / Be Star System

abstract:
  PSR 1259-63 is a radio pulsar orbiting a Be star in a highly eccentric orbit.
Soft and hard X-rays are observed from this binary system. We apply the shock
powered emission model to this system. The collision of the pulsar and Be star
winds forms a shock, which accelerates electrons and positrons to the
relativistic energies. We derive the energy distribution of relativistic
electrons and positrons as a function of the distance from the shock in the
pulsar nebula. We calculate the X-rays and $\gamma$-rays emitted from the
relativistic electrons and positrons in the nebula at various orbital phases,
taking into account the Klein-Nishina effect fully. The shock powered emission
model can explain the observed X-ray properties approximately. We obtain from
the comparison with observations that a fraction of $\sim 0.1$ of the pulsar
spin-down luminosity should be transformed into the relativistic electrons and
positrons. We find that the magnetization parameter of the pulsar wind, the
ratio of the Poynting flux to the kinetic energy flux, is $\sim 0.1$
immediately upstream of the termination shock of the pulsar wind, and may
decrease with distance from the pulsar. We predict the flux of 10 MeV - 100 GeV
$\gamma$-rays which may be nearly equal to the detection threshold in the
future projects.


title:
The frozen (inactive) disk in Sgr A: freezing the accretion of the hot
  gas too?

abstract:
  The black hole in our Galactic Center is extremely underluminous for the
amount of hot gas available for accretion. Theoretical understanding of this
fact rests on a likely but not entirely certain assumption that the electrons
in the accreting gas are much cooler than the protons. In this case the hot gas
as a whole is too hot to accrete, and is too tenous to radiate away its
gravitational energy. Here we propose a drastically different picture of the
accretion process in Sgr A* not based on the unchecked two-temperature
assumption. Namely, we argue that there should exist a very cold inactive disk
-- a remnant of a past stronger accretion activity in Sgr A*. Such a disk would
be a very efficient cooling surface for the hot flow. We show that under
certain conditions the cooling due to thermal conduction cannot be balanced by
the viscous heating in the hot flow. Along with the heat, the hot flow loses
its viscosity and thus ability to accrete. It settles (condences) onto the cold
disk slighlty inside of the circularization radius. If the latter is very
large, then the liberated energy, and the luminosity emitted, is orders of
magnitude less than naively expected. We build a simple analytical model for
this flow and calculate the expected spectra that appear to be in a very
reasonble agreement with observations. Strong additional support for the
presence of the inactive disk comes from the recent observations of X-ray
flares in Sgr A*. The properties of these flares are very similar to those
produced by stars passing through a cold disk.


abstract:
  We present the results of XMM-Newton observations of four high-z quasars, two
radio-loud and two radio-quiet. One of the radio-loud objects, PKS 2126-158,
clearly shows absorption in excess of the galactic value as claimed before from
ASCA and ROSAT observations. For PKS 2149-306 the evidence for excess
absorption is only marginal in contrast to previous results. The location of
the absorber in PKS 2126-158 is compatible with the redshift of the source.
Both, a warm and a cold absorber are allowed by the X-ray data. Both quasars
have very flat photon spectra (\Gamma \la 1.5) and the high photon statistics
reveal small deviations from a simple power law form. For the two radio-quiet
objects, Q 0000-263 and Q 1442+2931, we determine, for the first time, reliable
spectral parameters. Both quasars have steeper power laws (\Gamma \sim 2) and
show absorption consistent with the galactic value, similar to radio-quiet
quasars at low redshifts.
  In the case of Q 0000-263 the presence of the damped Ly$\alpha $ system
(N(HI)\sim 2.6\times 10^{21} cm^{-2} at z = 3.39) cannot be examined further
due to the limited photon statistics in all instruments.


title:
Hyades dynamics from N-body simulations: Accuracy of astrometric radial
  velocities from Hipparcos

abstract:
  The internal velocity structure in the Hyades cluster as seen by Hipparcos is
compared with realistic N-body simulations using the NBODY6 code, which
includes binary interaction, stellar evolution and the Galactic tidal field.
The model allows to estimate reliably the accuracy of astrometric radial
velocities in the Hyades as derived by Lindegren et al. (2000) and Madsen et
al. (2002) from Hipparcos data, by applying the same estimation procedure on
the simulated data. The simulations indicate that the current cluster velocity
dispersion decreases from 0.35 km/s at the cluster centre to a minimum of 0.20
km/s at 8 pc radius (2-3 core radii), from where it slightly increases
outwards. A clear negative correlation between dispersion and stellar mass is
seen in the central part of the cluster but is almost absent beyond a radius of
3 pc. It follows that the (internal) standard error of the astrometric radial
velocities relative to the cluster centroid may be as small as 0.2 km/s for a
suitable selection of stars, while a total (external) standard error of 0.6
km/s is found when the uncertainty of the bulk motion of the cluster is
included. Attempts to see structure in the velocity dispersion using
observational data from Hipparcos and Tycho-2 are inconclusive.


title:
Galaxy merging, the Fundamental Plane of elliptical galaxies, and the
  Mbh-sigma relation

abstract:
  We explore the effects of dissipationless merging on the Fundamental Plane of
elliptical galaxies by using a N-body code based on a new, high performance
numerical scheme (Dehnen 2002). We investigate the extreme cases of galaxy
growth by equal mass merging and accretion of small stellar systems; in a
subset of simulations we also consider the presence of dark matter halos around
the merging galaxies. Curiously, we found that the Fundamental Plane is
preserved by major merging, while in the accretion scenario its edge--on
thickness is only marginally reproduced, with substantial thickening in the
case of merging with low angular momentum. We also found that both the
Faber-Jackson and Kormendy relations are not reproduced by the simulations.
Finally, we discuss the implications of our results for the origin of the
Mbh-sigma and Magorrian relations. We found that dissipationless merging is
unable to reproduce the Mbh-sigma relation, if Mbhs add linearly (while the
Magorrian relation is nicely reproduced); on the contrary a black hole merging
with substantial emission of gravitational waves reproduces the Mbh-sigma
relation but fails at reproducing the Magorrian relation. [Abridged]


title: Stochastic appearance in stars and high energy sources

abstract:
  Many phenomena such as stellar variability, stellar explosions, behavior of
different kind of X-ray and gamma-ray sources, processes in active galactic
nuclei and other astrophysical objects show stochastic features. Brief
description of these phenomena is given in this review.


title:
Turbulent magnetic Prandtl number and magnetic diffusivity quenching
  from simulations

abstract:
  Forced turbulence simulations are used to determine the turbulent kinematic
viscosity, nu_t, from the decay rate of a large scale velocity field. Likewise,
the turbulent magnetic diffusivity, eta_t, is determined from the decay of a
large scale magnetic field. In the kinematic regime, when the field is weak,
the turbulent magnetic Prandtl number, nu_t/eta_t, is about unity. When the
field is nonhelical, eta_t is quenched when magnetic and kinetic energies
become comparable. For helical fields the quenching is stronger and can be
described by a dynamical quenching formula.


title: The Magnetic Power Spectrum in Faraday Rotation Screens

abstract:
  The autocorrelation function and similarly the Fourier-power spectrum of a
rotation measure (RM) map of an extended background radio source can be used to
measure components of the magnetic autocorrelation and power-spectrum tensor
within a foreground Faraday screen. It is possible to reconstruct the full
non-helical part of this tensor in the case of an isotropic magnetic field
distribution statistics. The helical part is only accessible with additional
information; e.g. the knowledge that the fields are force-free. The magnetic
field strength, energy spectrum and autocorrelation length l_B can be obtained
from the non-helical part alone. We demonstrate that l_B can differ
substantially from l_RM, the observationally easily accessible autocorrelation
length of an RM map. In typical astrophysical situation l_RM > l_B. Any RM
study, which does not take this distinction into account, likely underestimates
the magnetic field strength. For power-law magnetic power spectra, and for
patchy magnetic field configurations the central RM autocorrelation function is
shown to have characteristic asymptotic shapes. Ways to constrain the volume
filling factor of a patchy field distribution are discussed. We discuss
strategies to analyse observational data, taking into account - with the help
of a window function - the limited extent of the polarised radio source, the
spatial distribution of the electron density and average magnetic energy
density in the screen, and allowing for noise reducing data weighting. We
briefly discuss the effects of possible observational artefacts, and strategies
to avoid them.


title: Formation of Cool Cores in Galaxy Clusters via Hierarchical Mergers

abstract:
  We present a new scenario for the formation of cool cores in rich galaxy
clusters based on results from recent high spatial dynamic range, adaptive mesh
Eulerian hydrodynamic simulations of large-scale structure formation. We find
that cores of cool gas, material that would be identified as a classical
cooling flow based on its X-ray luminosity excess and temperature profile, are
built from the accretion of discrete, stable subclusters. Any ``cooling flow''
present is overwhelmed by the velocity field within the cluster - the bulk flow
of gas through the cluster typically has speeds up to about 2,000 km s^-1 and
significant rotation is frequently present in the cluster core. The inclusion
of consistent initial cosmological conditions for the cluster within its
surrounding supercluster environment is crucial when simulating the evolution
of cool cores in rich galaxy clusters. This new model for the hierarchical
assembly of cool gas naturally explains the high frequency of cool cores in
rich galaxy clusters despite the fact that a majority of these clusters show
evidence of substructure which is believed to arise from recent merger
activity. Furthermore, our simulations generate complex cluster cores in
concordance with recent X-ray observations of cool fronts, cool ``bullets'',
and filaments in a number of galaxy clusters. Our simulations were computed
with a coupled N-body, Eulerian, adaptive mesh refinement, hydrodynamics
cosmology code that properly treats the effects of shocks and radiative cooling
by the gas. We employ up to seven levels of refinement to attain a peak
resolution of 15.6 h^-1 kpc within a volume 256 h-1 Mpc on a side and assume a
standard LambdaCDM cosmology.


title: Radial velocities of early-type stars in the Perseus OB2 association

abstract:
  We present radial velocities for 29 B- and A-type stars in the field of the
nearby association Perseus OB2. The velocities are derived from spectra
obtained with AURELIE, via cross correlation with radial velocity standards
matched as closely as possible in spectral type. The resulting accuracy is ~2 -
3 km s$^{-1}$. We use these measurements, together with published values for a
few other early-type stars, to study membership of the association. The mean
radial velocity (and measured velocity dispersion) of Per OB2 is 23.5 \pm 3.9
km s$^{-1}$, and lies ~15 km s$^{-1}$ away from the mean velocity of the local
disk field stars. We identify a number of interlopers in the list of possible
late-B- and A-type members which was based on Hipparcos parallaxes and proper
motions, and discuss the colour-magnitude diagram of the association.


title: What we learn from the afterglow of GRB 021211

abstract:
  The behaviour of the afterglow (AG) of gamma-ray bursts (GRBs) directly
provides, in the cannonball (CB) model, information about the environment of
their progenitor stars. The well observed early temporal decline of the AG of
GRB 021211 is precisely the one predicted in the presence of a progenitor's
``wind'' which resulted in a density profile $\propto 1/r^2$ around the star.
The subsequent fast fading --which makes this GRB ``quasi-dark''-- is the one
anticipated if, further away, the interstellar density is roughly constant and
relatively high. The CB-model fit to the AG clearly shows the presence of an
associated supernova akin to SN1998bw, and allows even for the determination of
the broad-band spectrum of the host galaxy. GRB 990123 and GRB 021004, whose
AGs were also measured very early, are also discussed.


title: ASCA observation of Unusually X-ray Hard Radio Quiet QSO Kaz 102

abstract:
  We have observed a radio-quiet QSO Kaz 102 (z=0.136) with ASCA as a part of
our program of complete spectral characterization of hard X-ray selected AGNs.
We found that Kaz 102 shows unusual spectral properties. A simple power-law
with absorption in our galaxy gave a satisfactory description of the spectrum.
However, it showed a very hard photon index of Gamma=1.0 with no sign of deep
absorption or a prominent spectral feature. We further explored the Compton
reflection with Fe K-alpha line and warm absorber models for hardening the
spectrum. Both gave statistically satisfactory fits. However, the Compton
reflection model requires a very low metal abundance (0.03-0.07 in solar
units).The warm absorber model with no direct component is preferred and gave a
very high ionization parameter xi=200. If this is the case, the values of xi,
warm absorber column density, and variability over about 10 years may suggest
that the warm absorber resides in the broad-line region and crosses the line of
sight to the central X-ray source.


title: Primordial Nucleosynthesis in Light of WMAP

abstract:
  Big bang nucleosynthesis has long provided the primary determination of the
cosmic baryon density $\omb h^2$, or equivalently the baryon-to-photon ratio,
\eta. Recently, data on CMB anisotropies have become increasingly sensitive to
\eta. The comparison of these two independent measures provides a key test for
big bang cosmology. The first release of results from the Wilkinson Microwave
Anisotropy Probe (WMAP) marks a milestone in this test. With the precision of
WMAP, the CMB now offers a significantly stronger constraint on \eta. We
discuss the current state of BBN theory and light element observations
(including their possible lingering systematic errors). The resulting BBN
baryon density prediction is in overall agreement with the WMAP prediction, an
important and non-trivial confirmation of hot big bang cosmology. Going beyond
this, the powerful CMB baryometer can be used as an input to BBN and one can
accurately predict the primordial light element abundances. By comparing these
with observations one can obtain new insight into post-BBN nucleosynthesis
processes and associated astrophysics. Finally, one can test the possibility of
nonstandard physics at the time of BBN, now with all light elements available
as probes. Indeed, with the WMAP precision \eta, deuterium is already beginning
to rival \he4's sensitivity to nonstandard physics, and additional D/H
measurements can improve this further.


title: An Obscured Radio Galaxy at High Redshift

abstract:
  Perhaps as many as 10% of high redshift radio galaxy (HzRG; z > 2) candidates
that are selected using an Ultra Steep radio Spectrum (USS) criterion fail to
show optical emission (continuum, lines) in deep Keck exposures. Their parent
objects are only detected in the near-IR and are probably heavily obscured
and/or at very high redshift. To search for signatures of dust and help
constrain the nature and redshifts of these ``no-z'' radio galaxies, we have
conducted a program of submillimeter and millimeter observations. Here we
report the first results of a detailed study of one of these objects, WN
J0305+3525.
  WN J0305+3525 appears associated with a small group of K ~ 21 - 22 objects
and is strongly detected at both 850 micron and 1.25 mm. On the basis of its
faint K-band magnitude, spectral energy distribution (SED) and other evidence
we estimate that the radio galaxy is probably at a redshift z = 3 +/- 1. This
would make WN J0305+3525 a radio-loud Hyper Luminous Infrared Galaxy (LFIR ~
10^13 Lsun) similar to, but more obscured than, other dusty radio galaxies in
this redshift range. This, together with the absence of Lya emission and
compact (theta < 1.9") radio structure, suggests that WN J0305+3525 is embedded
in a very dense, dusty medium and is probably at an early stage of its
formation.


title: Addendum to: Update on neutrino mixing in the early Universe

abstract:
  In the light of the recent WMAP results we update the constraints on a class
of non standard BBN models with a simultaneous combination of non standard
neutrino distributions and extra effective number of neutrinos in the expansion
rate. These models can be described in terms of the two parameters Delta
N_nu^tot, constrained by the primordial Helium abundance Y_p measurement, and
Delta N_nu^rho, constrained by a combination of CMB and primordial Deuterium
data. Small deviations from standard BBN are suggested. Different non standard
scenarios can be distinguished by a measurement of the difference Delta
N_nu^f_nu=Delta N_nu^tot-Delta N_nu^rho. From the current data we estimate
Delta N_nu^f_nu simeq -1.4^{+0.9}_{-1.4}, mildly disfavouring solutions with a
low expansion rate, characterized by Delta N_nu^f_nu=0 and negative Delta
N_nu^rho. Active-sterile neutrino mixing could be a viable explanation only for
high values of Y_p gtrsim 0.24. The existence of large positive neutrino
chemical potentials xi_i sim 0.05, implying Delta N_nu^rho simeq 0, would be a
possible explanation of the data within the analyzed class of non standard BBN
models. Interestingly it would also provide a way to evade the cosmological
bounds for `class A 3+1' four neutrino mixing models. A scenario with a
decaying sterile neutrino is also considered.


title:
Physical conditions in the O++ zone from ISO and HST data. NGC 6543
  revisited

abstract:
  We revise the physical conditions in the O++ zone of the planetary nebula NGC
6543, obtaining two different estimates of the electron temperature (Te) and
one estimate of the electron density (Ne). The electron temperature is computed
by means of two independent methods, the nebular-to-auroral ratio [O III]
5007/4363, and the diagnostic diagram that combines 5007 to the [O III]
infrared lines 52m and 88m. The optical and infrared fluxes have been obtained
from archive HST/WFPC2 images and ISO LWS spectra respectively, and the
continuum intensity in the optical has been measured from narrow-slit spectra
obtained with the Isaac Newton Telescope at La Palma. The measured continuum
intensity is higher than predicted by recombination theory under the hypothesis
that all the Ly-alpha photons either escape or are destroyed. This fact can be
explained in terms of an enhancement of the 2-photon continuum due to Ly-alpha
conversion, a process that depends strongly on the local structure of the
nebula. Alternative possibilities, outside the framework of recombination
theory, have also been considered: e.g., the optical tail in the X-ray emission
of a very hot plasma, and dust scattering of stellar radiation, but these
hypotheses are not supported by quantitative estimates. While the electron
temperature and density derived from the diagnostic diagram agree with the most
recent determination, the temperature derived from 5007/4363,, Te(O++)_opt, is
somewhat smaller than previously published values. We discuss several technical
issues that contribute to the overall uncertainty in our results, focusing on
the instrumental effects that might bias the [O III] 4363 intensity. We also
discuss the effects of the collisional de-excitation of the O++ ground terms on
the relation between Te(O++)_opt and Te(O++)_IR.


title:
Joint CMB and Weak Lensing Analysis; Physically Motivated Constraints on
  Cosmological Parameters

abstract:
  We use Cosmic Microwave Background (CMB) observations together with the
Red-sequence Cluster Survey (RCS) weak lensing results to derive constraints on
a range of cosmological parameters. This particular choice of observations is
motivated by their robust physical interpretation and complementarity. Our
combined analysis, including a weak nucleosynthesis constraint, yields accurate
determinations of a number of parameters including the amplitude of
fluctuations sigma_8 = 0.89+/-0.05 and matter density Omega_m =0.30+/-0.03. We
also find a value for the Hubble parameter of H_0 =70+/-3km/s/Mpc, in good
agreement with the Hubble Space Telescope (HST) key--project result. We
conclude that the combination of CMB and weak lensing data provides some of the
most powerful constraints available in cosmology today.


title: One-Armed Spiral Instability in Differentially Rotating Stars

abstract:
  We investigate the dynamical instability of the one-armed spiral m=1 mode in
differentially rotating stars by means of 3+1 hydrodynamical simulations in
Newtonian gravitation. We find that both a soft equation of state and a high
degree of differential rotation in the equilibrium star are necessary to excite
a dynamical m=1 mode as the dominant instability at small values of the ratio
of rotational kinetic to potential energy, T/|W|. We find that this spiral mode
propagates outward from its point of origin near the maximum density at the
center to the surface over several central orbital periods. An unstable m=1
mode triggers a secondary m=2 bar mode of smaller amplitude, and the bar mode
can excite gravitational waves. As the spiral mode propagates to the surface it
weakens, simultaneously damping the emitted gravitational wave signal. This
behavior is in contrast to waves triggered by a dynamical m=2 bar instability,
which persist for many rotation periods and decay only after a
radiation-reaction damping timescale.


title: Sgr A* Companion S0-2: A Probe of Very High-Mass Star Formation

abstract:
  The star S0-2, which is orbiting Sgr A* with a 15-yr period, almost certainly
did not form in situ. We propose that it was injected into this close orbit by
the tidal disruption of a massive-star binary, whose primary was more massive
than S0-2 and at least 60 Msun. From numerical integrations we find that 1-2%
of incoming binaries with closest approach equal to 130 AU leave the secondary
in an orbit with eccentricity within 0.01 of that of SO-2. If additional stars
are found orbiting Sgr A* with relatively short periods, they could be used to
probe the formation of massive stars in the Galactocentric region, even though
the massive stars themselves have long since perished.


title: GZ Cancri: a cataclysmic variable at the lower edge of the period gap

abstract:
  We present calibrated photometry and time-resolved spectroscopy of the
cataclysmic variable GZ Cnc. Radial velocities of the H-alpha emission line
reveal an orbital period of 0.08825(28) d, or 2.118(07) h, placing the system
at the lower edge of the period gap. One of our observations catches the system
on the rise to an overlooked, possibly small-amplitude, outburst. At certain
phases during this stage the profiles of the emission lines are distorted by a
high velocity absorption component. We discuss this phenomenon in the context
of the recent suggestion that the long-term lightcurve of GZ Cnc resembles
those of intermediate polars.


title: The Thermal Memory of Reionization History

abstract:
  The recent measurement by WMAP of a large electron scattering optical depth
tau_e = 0.17 +- 0.04 is consistent with a simple model of reionization in which
the intergalactic medium (IGM) is ionized at redshift z ~ 15, and remains
highly ionized thereafter. Here, we show that existing measurements of the IGM
temperature from the Lyman-alpha forest at z ~ 2 - 4 rule out this ``vanilla''
model. Under reasonable assumptions about the ionizing spectrum, as long as the
universe is reionized before z = 10, and remains highly ionized thereafter, the
IGM reaches an asymptotic thermal state which is too cold compared to
observations. To simultaneously satisfy the CMB and forest constraints, the
reionization history must be complex: reionization begins early at z >~ 15, but
there must have been significant (order unity) changes in fractions of neutral
hydrogen and/or helium at 6 < z < 10, and/or singly ionized helium at 4 < z <
10. We describe a physically motivated reionization model that satisfies all
current observations. We also explore the impact of a stochastic reionization
history and show that a late epoch of (HeII --> HeIII) reionization induces a
significant scatter in the IGM temperature, but the scatter diminishes with
time quickly. Finally, we provide an analytic formula for the thermal
asymptote, and discuss possible additional heating mechanisms that might evade
our constraints.


title: The 1000 Brightest HIPASS Galaxies: HI Mass Function and Omega_HI

abstract:
  We present a new accurate measurement of the HI mass function of galaxies
from the HIPASS Bright Galaxy Catalog, a sample of 1000 galaxies with the
highest HI peak flux densities in the southern hemisphere (Koribalski et al.
2003). This sample spans nearly four orders of magnitude in HI mass (from log
M_HI/M_sun=6.8 to 10.6, H0=75) and is the largest sample of HI selected
galaxies to date. We develop a bivariate maximum likelihood technique to
measure the space density of galaxies, and show that this is a robust method,
insensitive to the effects of large scale structure. The resulting HI mass
function can be fitted satisfactorily with a Schechter function with faint-end
slope alpha=-1.30. This slope is found to be dependent on morphological type,
with later type galaxies giving steeper slopes. We extensively test various
effects that potentially bias the determination of the HI mass function,
including peculiar motions of galaxies, large scale structure, selection bias,
and inclination effects, and quantify these biases. The large sample of
galaxies enables an accurate measurement of the cosmological mass density of
neutral gas: Omega_HI=(3.8 +/- 0.6) x 10^{-4}. Low surface brightness galaxies
contribute only 15% to this value, consistent with previous findings.


title: Constraining Hadronic Superfluidity with Neutron Star Precession

abstract:
  I show that the standard picture of the neutron star core containing
coexisting neutron and proton superfluids, with the proton component forming a
type II superconductor threaded by flux tubes, is inconsistent with
observations of long-period (~1 yr) precession in isolated pulsars. I conclude
that either the two superfluids coexist nowhere in the stellar core, or the
core is a type I superconductor rather than type II. Either possibility would
have interesting implications for neutron star cooling and theories of spin
jumps (glitches).


title: Line Formation in the Inner Starburst Regions of AGN

abstract:
  We review the evidence for young stellar populations in the inner (< 200 pc)
regions of Active Galactic Nuclei (AGN), and the physical mechanisms through
which the stars can potentially create the emission lines that characterize
AGN.


title: Top-Down Fragmentation of a Warm Dark Matter Filament

abstract:
  We present the first high-resolution n-body simulations of the fragmentation
of dark matter filaments. Such fragmentation occurs in top-down scenarios of
structure formation, when the dark matter is warm instead of cold. In a
previous paper (Knebe et al. 2002, hereafter Paper I), we showed that WDM
differs from the standard Cold Dark Matter (CDM) mainly in the formation
history and large-scale distribution of low-mass haloes, which form later and
tend to be more clustered in WDM than in CDM universes, tracing more closely
the filamentary structures of the cosmic web. Therefore, we focus our
computational effort in this paper on one particular filament extracted from a
WDM cosmological simulation and compare in detail its evolution to that of the
same CDM filament. We find that the mass distribution of the halos forming via
fragmentation within the filament is broadly peaked around a Jeans mass of a
few 10^9 Msun, corresponding to a gravitational instability of smooth regions
with an overdensity contrast around 10 at these redshifts. Our results confirm
that WDM filaments fragment and form gravitationally bound haloes in a top-down
fashion, whereas CDM filaments are built bottom-up, thus demonstrating the
impact of the nature of the dark matter on dwarf galaxy properties.


title:
Biasing and Genus Statistics of Dark Matter Halos in the Hubble Volume
  Simulation

abstract:
  We present a numerical analysis of genus statistics for dark matter halo
catalogs from the Hubble volume simulation. The huge box-size of the Hubble
volume simulation enables us to carry out a reliable statistical analysis of
the biasing properties of halos at a Gaussian smoothing scale of R_G>30Mpc/h
with a cluster-mass scale of between 7*10^{13}Msolar/h and 6*10^{15}Msolar/h. A
detailed comparison of the genus for dark matter halos with that for the mass
distribution shows that the non-Gaussianity induced by the halo biasing is
comparable to that by nonlinear gravitational evolution, and both the shape and
the amplitude of the genus are almost insensitive to the halo mass at
R_G>30Mpc/h. In order to characterize the biasing effect on the genus, we apply
a perturbative formula developed by Matsubara (1994). We find that the
perturbative formula well describes the simulated halo genus at R_G>50Mpc/h.
The result indicates that the biasing effect on the halo genus is well
approximated by nonlinear deterministic biasing up to the second-order term in
the mass density fluctuation. The two parameters describing the linear and
quadratic terms in the nonlinear biasing accurately specify the genus for
galaxy clusters.


title: MOND and the fundamental plane of elliptical galaxies

abstract:
  It is shown that the MOdified Newtonian Dynamics (MOND) explains the tilt of
the fundamental plane of elliptical galaxies without the need of non-baryonic
dark matter. Results found for elliptical galaxies extends to globular clusters
and galaxy clusters, showing that MOND agrees with observations over 7 order of
magnitude in acceleration.


title:
Autocorrelation function of the soft X-ray background produced by
  warm-hot gas in dark halos

abstract:
  We calculate the angular two-point autocorrelation function (ACF) of the soft
X-ray background (SXRB) produced by the warm-hot intergalactic medium (WHIM)
associated with dark halos, motivated primarily by searching for missing
baryons and distinguishing different physical processes of the WHIM in dark
halos. We employ a purely analytic model for the halo population which is
completely determined by the universal density profile and the Press-Schechter
mass function. We then adopt a phenomenological approach to nongravitational
processes of the WHIM such as preheating and radiative cooling. It shows that
the power spectra of the SXRB predicted by three WHIM models, namely, the
self-similar model, preheating model and cooling model demonstrate remarkably
different signatures in both amplitude and shape, with the peak locations
moving from 4X10^4 for the self-similar model to a smaller value of (3-5)X10^3
when nongravitational processes are taken into account. The corresponding ACFs
for preheating and cooling models become shallower too as compared with the
prediction of the self-similar model. This may permit an effective probe of the
physical processes of the WHIM in massive halos in conjunction with the
observationally determined power spectrum or ACF of the SXRB from diffuse WHIM.
However, a direct comparison of our theoretical predictions with existing data
(e.g. the ACF determined from ROSAT observations) is still difficult because of
the dominant contribution of AGNs in the soft X-ray sky. We discuss briefly the
implication of our results for resolving the missing baryon problem in the
local universe.