title: Does the mixing length parameter depend on metallicity?

abstract:
  This paper is a further step in the investigation of the morphology of the
color-magnitude diagram of Galactic globular clusters, and the fine-tuning of
theoretical models, made possible by the recent observational efforts to build
homogeneous photometric databases. In particular, we examine here the
calibration of the morphological parameter W(HB) vs. metallicity, originally
proposed by Brocato et al. (1998), which essentially measures the color
position of the red-giant branch. We show that the parameter can be used to
have a first-order estimate of the cluster metallicity, since the dispersion
around the mean trend with [Fe/H] is compatible with the measurement errors.
The tight W(HB)-[Fe/H] relation is then used to show that variations in helium
content or age do not affect the parameter, whereas it is strongly influenced
by the mixing-length parameter alpha (as expected). This fact allows us, for
the first time, to state that there is no trend of alpha with the metal content
of a cluster. A thorough examination of the interrelated questions of the
alpha-elements enhancement and the color-T(eff) transformations, highlights
that there is an urgent need for an independent assessment of which of the two
presently accepted metallicity scales is the true indicator of a cluster's iron
content. Whatever scenario is adopted, it also appears that a deep revision of
the (V-I)-temperature relations is needed.


title:
The Upper Asymptotic Giant Branch of the Elliptical Galaxy Maffei 1, and
  Comparisons with M32 and NGC 5128

abstract:
  Deep near-infrared images obtained with adaptive optics systems on the Gemini
North and Canada-France-Hawaii telescopes are used to investigate the bright
stellar content and central regions of the nearby elliptical galaxy Maffei 1.
Stars evolving on the upper asymptotic giant branch (AGB) are resolved in a
field 3 arcmin from the center of the galaxy. The locus of bright giants on the
(K, H-K) color-magnitude diagram is consistent with a population of stars like
those in Baade's Window reddened by E(H-K) = 0.28 +/- 0.05 mag. This
corresponds to A_V = 4.5 +/- 0.8 mag, and is consistent with previous estimates
of the line of sight extinction computed from the integrated properties of
Maffei 1. The AGB-tip occurs at K = 20.0, which correponds to M_K = -8.7;
hence, the AGB-tip brightness in Maffei 1 is comparable to that in M32, NGC
5128, and the bulges of M31 and the Milky-Way. The near-infrared luminosity
functions (LFs) of bright AGB stars in Maffei 1, M32, and NGC 5128 are also in
excellent agreement, both in terms of overall shape and the relative density of
infrared-bright stars with respect to the fainter stars that dominate the light
at visible and red wavelengths. It is concluded that the brightest AGB stars in
Maffei 1, NGC 5128, M32, and the bulge of M31 trace an old, metal-rich
population, rather than an intermediate age population. It is also demonstrated
that Maffei 1 contains a distinct red nucleus, and this is likely the optical
signature of low-level nuclear activity and/or a distinct central stellar
population. Finally, there is an absence of globular clusters brighter than the
peak of the globular cluster LF in the central 700 x 700 parsecs of Maffei 1.


title: $^{180}$Ta production in the classical s-process

abstract:
  The production and survival of the quasistable isomer $^{180}$Ta during the
stellar nucleosynthesis has remained a matter of discussion for years. A
careful analysis of the available experimental data and theoretical
calculations enabled us to reproduce the observed solar abundance of $^{180}$Ta
in the classical s-process ($kT=28$ keV -- 33 keV).


title:
HST color-magnitude diagrams of 74 galactic globular clusters in the HST
  F439W and F555W bands

abstract:
  We present the complete photometric database and the color-magnitude diagrams
for 74 Galactic globular clusters observed with the HST/WFPC2 camera in the
F439W and F555W bands. A detailed discussion of the various reduction steps is
also presented, and of the procedures to transform instrumental magnitudes into
both the HST F439W and F555W flight system and the standard Johnson B and V
systems. We also describe the artificial star experiments which have been
performed to derive the star count completeness in all the relevant branches of
the color magnitude diagram. The entire photometric database and the
completeness function will be made available on the Web immediately after the
publication of the present paper.


title: Cosmological dark matter annihilations into gamma-rays - a closer look

abstract:
  We investigate the prospects of detecting weakly interacting massive particle
(WIMP) dark matter by measuring the contribution to the extragalactic gamma-ray
radiation induced, in any dark matter halo and at all redshifts, by WIMP pair
annihilations into high-energy photons. We perform a detailed analysis of the
distinctive spectral features of this signal, recently proposed in a short
letter by three of the authors, with emphasis on the signature due to
monochromatic gamma-ray yields: the combined effect of cosmological redshift
and absorption along the line of sight produces sharp bumps, peaked at the rest
frame energy of the lines and asymmetrically smeared to lower energies. The
level of the flux depends both on the particle physics scenario for WIMP dark
matter and on the question of how dark matter clusters. Uncertainties
introduced by the latter are thoroughly discussed implementing a realistic
model inspired by results of the state-of-the-art N-body simulations and
semi-analytic modeling in the cold dark matter structure formation theory. We
also address the question of the potential gamma-ray background originating
from blazars, presenting a novel calculation. Comparing the signal with the
background, we find that there are viable configurations, in the combined
parameter space defined by the particle physics setup and the structure
formation scenario, for which the WIMP induced extragalactic gamma-ray signal
will be detectable in the new generation of gamma-ray telescopes such as GLAST.


title: A dynamical mechanism for establishing apsidal resonance

abstract:
  We show that in a system of two planets initially in nearly circular orbits,
an impulse perturbation that imparts a finite eccentricity to one planet's
orbit causes the other planet's orbit to become eccentric as well, and also
naturally results in a libration of their relative apsidal longitudes for a
wide range of initial conditions. We suggest that such a mechanism may explain
orbital eccentricities and apsidal resonance in some exo-planetary systems. The
eccentricity impulse could be caused by the ejection of a planet from these
systems, or by torques from a primordial gas disk. The amplitude of secular
variations provides an observational constraint on the dynamical history of
such systems.


title: Models of Galaxy Clusters with Thermal Conduction

abstract:
  We present a simple model of hot gas in galaxy clusters, assuming hydrostatic
equilibrium and energy balance between radiative cooling and thermal
conduction. For five clusters, A1795, A1835, A2199, A2390 and RXJ1347.5-1145,
the model gives a good description of the observed radial profiles of electron
density and temperature, provided we take the thermal conductivity $\kappa$ to
be about 30% of the Spitzer conductivity. Since the required $\kappa$ is
consistent with the recent theoretical estimate of Narayan & Medvedev (2001)
for a turbulent magnetized plasma, we consider a conduction-based equilibrium
model to be viable for these clusters. We further show that the hot gas is
thermally stable because of the presence of conduction. For five other
clusters, A2052, A2597, Hydra A, Ser 159-03 and 3C295, the model requires
unphysically large values of $\kappa$ to fit the data. These clusters must have
some additional source of heat, most likely an active galactic nucleus since
all the clusters have strong radio galaxies at their centers. We suggest that
thermal conduction, though not dominant in these clusters, may nevertheless
play a significant role by preventing the gas from becoming thermally unstable.


title: Four new planets orbiting somewhat metal-enriched stars

abstract:
  We report the detection of four new extra-solar planets from the
Anglo-Australian Planet Search orbiting the somewhat metal-enriched stars
HD73526, HD76700, HD30177 and HD2039. The planetary companion of HD 76700 has a
circular orbit with a period of 3.98d. With M sin i=0.197+-0.017 Mjup, or 0.69
times the mass of Saturn, is one of the lowest minimum mass extra-solar planets
yet detected. The remaining planets all have elliptical orbits with periods
ranging from 190.5d to 4.4yr. All four planets have been found orbiting stars
from a sub-sample of twenty metal-enriched and faint (V<9) stars, which was
added to the Anglo-Australian Planet Search's magnitude-limited V$<$7.5 main
sample in October 1998. These stars were selected to be metal-enriched on the
basis of their Stromgren photometry, and their enrichment has been subsequently
confirmed by detailed spectroscopic analysis.


title: Differential rotation decay in the radiative envelopes of CP stars

abstract:
  Stars of spectral classes A and late B are almost entirely radiative. CP
stars are a slowly rotating subgroup of these stars. It is possible that they
possessed long-lived accretion disks in their T Tauri phase. Magnetic coupling
of disk and star leads to rotational braking at the surface of the star.
Microscopic viscosities are extremely small and will not be able to reduce the
rotation rate of the core of the star. We investigate the question whether
magneto-rotational instability can provide turbulent angular momentum
transport. We illuminate the question whether or not differential rotation is
present in CP stars. Numerical MHD simulations of thick stellar shells are
performed. An initial differential rotation law is subject to the influence of
a magnetic field. The configuration gives indeed rise to magneto-rotational
instability. The emerging flows and magnetic fields transport efficiently
angular momentum outwards. Weak dependence on the magnetic Prandtl number
(~0.01 in stars) is found from the simulations. Since the estimated time-scale
of decay of differential rotation is 10^7-10^8 yr and comparable to the
life-time of A stars, we find the braking of the core to be an ongoing process
in many CP stars. The evolution of the surface rotation of CP stars with age
will be an observational challenge and of much value for verifying the
simulations.


title: Modelling flux tube dynamics

abstract:
  Over the last few years, numerical models of the behavior of solar magnetic
flux tubes have gone from using methods that were essentially one-dimensional
(i.e. the thin flux tube approximation), over more or less idealized
two-dimensional simulations, to becoming ever more realistic three-dimensional
case studies. Along the way a lot of new knowledge has been picked up as to the
e.g. the likely topology of the flux tubes, and the instabilities that they are
subjected to etc. Within the context of what one could call the ``flux tube
solar dynamo paradigm,'' I will discuss recent results of efforts to study
buoyant magnetic flux tubes ascending from deep below the photosphere, before
they emerge in active regions and interact with the field in the overlying
atmosphere: i.e. I am not addressing the flux tubes associated with magnetic
bright points, which possibly are generated by a small-scale dynamo operating
in the solar photosphere. The presented efforts are numerical MHD simulations
of twisted flux ropes and loops, interacting with rotation and convection.
Ultimately the magnetic surface signatures of these simulations, when compared
to observations, constraints the dynamo processes that are responsible for the
generation of the flux ropes in the first place. Along with these new results
several questions pop up (both old and new ones), regarding the nature of flux
tubes and consequently of the solar dynamo.


title: Constraining the Galactic Bar Parameters with Red Clump Giants

abstract:
  We show that the small intrinsic spread in luminosities of red clump giants
can be used to constrain the differences in the streaming motions of Galatic
bulge stars on the near side and those on the far side. We propose two methods
to select two samples with one preferentially on the near side and the other on
the far side. In the first method, we divide red clump giants into a bright
sample and a faint one; stars in the bright sample will be on average more on
the near side and vice versa. The second method relies on the fact that lensed
bulge stars lie preferentially on the far side due to the enhanced lensing
probability by the stars on the near side and in the disk. If the radial
streaming motion is ~50km/s, we find the difference in the average radial
velocity between the bright and faint samples can reach ~33km/s while the
corresponding difference is about ~10km/s between the lensed stars and all
observed stars. The difference in the average proper motion between the bright
and faint samples is about ~1.6mas/yr if there is a tangential streaming motion
of 100km/s; the corresponding shift between the lensed stars and all observed
stars is ~1mas/yr. To observe the shifts in the radial velocity and proper
motion, roughly one hundred microlensing events, and/or bright/faint red clump
giants, need to be observed either spectroscopically or astrometrically. The
spectroscopic observations can be performed efficiently using multi-object
spectrographs already available. The proper motion signature of microlensed
objects can be studied using ground-based telescopes and HST. These
observations will provide strong constraints on the Galactic bar parameters
(abridged).


title:
Screening Corrections to the Electron Capture Rates in Dense Stars by
  the Relativistically Degenerate Electron Liquid

abstract:
  We calculate the screening corrections to the electron capture rates in dense
stars by the relativistically degenerate electron liquid. In order to calculate
the screening corrections we adopt the linear response theory which is widely
used in the field of solid state physics and liquid metal physics. In
particular, we use the longitudinal dielectric function for the
relativistically degenerate electron liquid derived by Jancovici. We calculate
the screening potential at the position of the nucleus. By using this screening
potential one can calculate the screening corrections to the electron capture
rates. We will present accurate analytic fitting formulae which summarize our
numerical results. These fitting formulae will facilitate the application of
the present results. The screening corrections to the electron capture rates
are typically a few percent.


title:
The Optical Gravitational Lensing Experiment. Search for Planetary and
  Low-Luminosity Object Transits in the Galactic Disk. Results of 2001 Campaign
  - Supplement

abstract:
  The photometric data collected during 2001 season OGLE-III planetary/low
luminosity object transit campaign were reanalyzed with the new transit search
technique -- the BLS method by Kovacs, Zucker and Mazeh. In addition to all
presented in our original paper transits, additional 13 objects with transiting
low-luminosity companions were discovered. We present here a supplement to our
original catalog -- the photometric data, light curves and finding charts of
all 13 new objects.
  The model fits to the transit light curves indicate that a few new objects
may be Jupiter-sized (R<1.6 R_Jup). OGLE-TR-56 is a particularly interesting
case. Its transit has only 13 mmag depth, short duration and a period of
1.21190 days. Model fit indicates that the companion may be Saturn-sized if the
passage were central. Spectroscopic follow-up observations are encouraged for
final classification of the transiting objects as planets, brown dwarfs or late
M-type dwarf stars.
  We also provide the most recent ephemerides of other most promising planetary
transits: OGLE-TR-10 and OGLE-TR-40 based on observations collected in June
2002.
  All photometric data are available to the astronomical community from the
OGLE Internet archive.


title:
Effect of Muons on the Phase Transition in Magnetised Proto-Neutron Star
  Matter

abstract:
  We study the effect of inclusion of muons and the muon neutrinos on the phase
transition from nuclear to quark matter in a magnetised proto-neutron star and
compare our results with those obtained by us without the muons. We find that
the inclusion of muons changes slightly the nuclear density at which transition
occurs.However the dependence of this transition density on various chemical
potentials, temperature and the magnetic field remains quantitatively the same.


title: BeppoSAX Wide Field Cameras observations of six type I X-ray bursters

abstract:
  We have discovered three certain (SAX J1324.5-6313, 2S 1711-339 and SAX
J1828.5-1037) and two likely (SAX J1818.7+1424 and SAX J2224.9+5421) new
thermonuclear X-ray burst sources with the BeppoSAX Wide Field Cameras, and
observed a second burst ever from a sixth one (2S 0918-549). Four of them
(excluding 2S 1711-339 and 2S 0918-549) are newly detected X-ray sources from
which we observed single bursts, but no persistent emission. We observe the
first 11 bursts ever from 2S 1711-339; persistent flux was detected during the
first ten bursts, but not around the last burst. A single burst was recently
detected from 2S 0918-549 by Jonker et al.(2001); we observe a second burst
showing radius expansion, from which a distance of 4.2 kpc is derived.
According to theory, bursts from very low flux levels should last ~100 s. Such
is indeed the case for the last burst from 2S 1711-339, the single burst from
SAX J1828.5-1037 and the two bursts from 2S 0918-549, but not for the bursts
from SAX J1324.5-6313, SAX J1818.7+1424 and SAX J2224.9+5421. The bursts from
the latter sources all last ~20 s. We suggest that SAX J1324.5-6313, SAX
J1818.7+1424, SAX J1828.$-1037 and SAX J2224.9+5421 are members of the recently
proposed class of bursters with distinctively low persistent flux levels, and
show that the galactic distribution of this class is compatible with that of
the standard low-mass X-ray binaries.


title:
Statistical characteristics of observed Ly-$\alpha$ forest and the shape
  of initial power spectrum

abstract:
  Properties of $\sim$ 5000 observed Ly-$\alpha$ absorbers are investigated
using the model of formation and evolution of DM structure elements based on
the Zel'dovich theory. This model is generally consistent with simulations of
absorbers formation, accurately describes the Large Scale Structure observed in
the galaxy distribution at small redshifts and emphasizes the generic
similarity of the LSS and absorbers.
  The simple physical model of absorbers asserts that they are composed of DM
and gaseous matter and it allows us to estimate the column density and
overdensity of DM and gaseous components and the entropy of the gas trapped
within the DM potential wells. The parameters of DM component are found to be
consistent with theoretical expectations for the Gaussian initial perturbations
with the WDM--like power spectrum. We demonstrate the influence of the main
physical factors responsible for the absorbers evolution.
  The analysis of redshift distribution of absorbers confirms the self
consistence of the assumed physical model and allows to estimate the shape of
the initial power spectrum at small scales what in turn restricts the mass of
dominant fraction of DM particles to $M_{DM}\approx 0.6 - 2$ keV. Our results
verify the redshift variations of intensity of the UV background by about $4 -
6$ times and indicate that, perhaps, the available observations underestimate
the intensity of this background.


title: The nature of the prompt X-ray and radio emission from SN2002ap

abstract:
  We report on the combined X-ray and radio observations of the type Ic SN
2002ap, using XMM-Newton ToO observation of M74 and the Giant Metrewave Radio
Telescope (GMRT). We account for the presence of a nearby source in the
pre-supernova Chandra field of view in our measurements of the X-ray flux (0.3
- 10 KeV) 5.2 days after the explosion. The X-ray spectrum is well fitted by a
power law spectrum with photon index $\alpha= 2.6$. Our results suggest that
the prompt X-ray emission originates from inverse Compton scattering of
photospheric thermal emission by energetic electrons. Radio observations with
the GMRT at 610 MHz (8 days after the explosion) and 1420 MHz (70 days after
the explosion) are combined with the high frequency VLA observations of SN
2002ap reported earlier, and the early radiospheric properties of SN 2002ap are
compared with similar data from two other supernovae. Finally, the GMRT radio
map reveals four other X-ray sources in the field of view of M74 with radio
counterparts.


title: Chandra follow-up of bursters with low persistent emission

abstract:
  We report on Chandra ACIS-S observations of five type I X-ray bursters with
low persistent emission: SAX J1324.5-6313, SAX J1752.3-3128, SAX J1753.5-2349,
SAX J1806.5-2215 and SAX J1818.7+1424. We designate candidate persistent
sources for four X-ray bursters. All candidates are detected at a persistent
luminosity level of 10^(32-33) erg/s, comparable to soft X-ray transients in
quiescence. From the number of bursters with low persistent emission detected
so far with the Wide Field Cameras, we estimate a total of such sources in our
Galaxy between 30 and 4000.


title: Cosmological parameters from lensed supernovae

abstract:
  We investigate the possibility of measuring the Hubble constant, the
fractional energy density components and the equation of state parameter of the
``dark energy'' using lensed multiple images of high-redshift supernovae. With
future instruments, such as the SNAP and NGST satellites, it will become
possible to observe several hundred lensed core-collapse supernovae with
multiple images. Accurate measurements of the image separation, flux-ratio,
time-delay and lensing foreground galaxy will provide complementary information
to the cosmological tests based on, e.g., the magnitude-redshift relation of
Type Ia supernovae, especially with regards to the Hubble parameter that could
be measured with a statistical uncertainty at the one percent level. Assuming a
flat universe, the statistical uncertainty on the mass density is found to be
sigma^stat_m <0.05. However, systematic effects from the uncertainty of the
lens modeling are likely to dominate. E.g., if the lensing galaxies are
extremely compact but are (erroneously) modeled as singular isothermal spheres,
the mass density is biased by sigma^syst_m =0.1.
  We argue that wide-field near-IR instruments such as the one proposed for the
SNAP mission are critical for collecting large statistics of lensed supernovae.


title:
Analysing Large Scale Structure: I. Weighted Scaling Indices and
  Constrained Randomisation

abstract:
  The method of constrained randomisation is applied to three-dimensional
simulated galaxy distributions. With this technique we generate for a given
data set surrogate data sets which have the same linear properties as the
original data whereas higher order or nonlinear correlations are not preserved.
The analysis of the original and surrogate data sets with measures, which are
sensitive to nonlinearities, yields information about the existence of
nonlinear correlations in the data. We demonstrate how to generate surrogate
data sets from a given point distribution, which have the same linear
properties (power spectrum) as well as the same density amplitude distribution.
We propose weighted scaling indices as a nonlinear statistical measure to
quantify local morphological elements in large scale structure. Using
surrogates is is shown that the data sets with the same 2-point correlation
functions have slightly different void probability functions and especially a
different set of weighted scaling indices. Thus a refined analysis of the large
scale structure becomes possible by calculating local scaling properties
whereby the method of constrained randomisation yields a vital tool for testing
the performance of statistical measures in terms of sensitivity to different
topological features and discriminative power.


title: Physical Properties of Low-Luminosity Galaxies at z ~ 2

abstract:
  We report the results obtained from ISAAC/VLT near-IR spectroscopy of two
low-luminosity z ~ 1.9 galaxies located in the core of the lensing cluster
AC114. The amplification factor allowed to obtain, for the first time, physical
properties (SFR, abundance ratios, mass, etc) of star-forming galaxies, 1 to 2
magnitudes fainter than in previous studies of Lyman-break galaxies at z ~ 3.


title:
Hydrogen wall and heliosheath Lyman-alpha absorption toward nearby
  stars: possible constraints on the heliospheric interface plasma flow

abstract:
  In this paper, we study heliospheric Ly-$\alpha$ absorption toward nearby
stars in different lines of sight. We use the Baranov-Malama model of the solar
wind interaction with a two-component (charged component and H atoms)
interstellar medium. Interstellar atoms are described kinetically in the model.
The code allows us to separate the heliospheric absorption into two components,
produced by H atoms originating in the hydrogen wall and heliosheath regions,
respectively. We study the sensitivity of the heliospheric absorption to the
assumed interstellar proton and H atom number densities. These theoretical
results are compared with interstellar absorption toward six nearby stars
observed by the Hubble Space Telescope.


title: Cosmic ray drift, the second knee and galactic anisotropies

abstract:
  We show that the second knee in the cosmic ray spectrum (i.e. the steepening
occurring at $E\simeq 4\times 10^{17}$ eV) could be related to drift effects
affecting the heaviest nuclear component, the iron group nuclei, in a scenario
in which the knee at $3\times 10^{15}$ eV indicates the onset of drift effects
in the lighter proton component. We also study the anisotropies resulting from
diffusion and drift currents in the Galaxy, showing their potential relevance
to account for the AGASA observations at $E\sim 10^{18}$ eV, before the
extragalactic component becomes dominant.


title:
The 7.5 Magnitude Limit Sample of Bright Short-Period Binary Stars. I.
  How Many Contact Binaries Are There?

abstract:
  A sample of bright contact binary stars (W UMa-type or EW, and related: with
beta Lyr light curves, EB, and ellipsoidal, ELL - in effect, all but the
detached, EA), to the limit of Vmax = 7.5 magnitude is deemed to include all
discoverable short-period (P<1 days) binaries with photometric variation larger
than about 0.05 magnitude. Of the 32 systems in the final sample, 11 systems
have been discovered by the Hipparcos satellite. The combined spatial density
is evaluated at (1.02+/-0.24)x10^-5 pc^-3. The Relative Frequency of Occurrence
(RFO), defined in relation to the Main Sequence stars, depends on the
luminosity. An assumption of RFO~1/500 for MV>+1.5 is consistent with the data,
although the number statistics is poor with the resulting uncertainty in the
spatial density and the RFO by a factor of about two. The RFO rapidly decreases
for brighter binaries to a level of 1/5,000 for MV<+1.5 and to 1/30,000 for
MV<+0.5. The high RFO of 1/130, previously determined from the deep OGLE-I
sample of Disk Population W UMa-type systems towards Baade's Window, is
inconsistent with and unconfirmed by the new results. Possible reasons for the
large discrepancy are discussed. They include several observational effects,
but also a possibility of a genuine increase in the contact-binary density in
the central parts of the Galaxy.


title: Modeling radio mini-halos in cooling flow clusters

abstract:
  We have developed a model in which the diffuse synchrotron emission from
radio mini-halos, observed in some cooling flow clusters, is due to a relic
population of relativistic electrons reaccelerated by MHD turbulence via
Fermi-like processes. In this model the energetics is supplied by the cooling
flow itself. Here, the model (successfully applied to the Perseus cluster,
A426) is preliminarily applied to the possible mini-halo candidate A2626, for
which we present VLA data.


title:
Causal perturbation theory in general FRW cosmologies I: energy momentum
  conservation and matching conditions

abstract:
  We describe energy--momentum conservation in relativistic perturbation theory
in general FRW backgrounds with causal source terms, such as the presence of
cosmic defect networks. We provide a prescription for a linear energy--momentum
pseudo-tensor in a curved FRW universe, decomposing it using eigenfunctions of
the Helmholtz equation. We also construct conserved vector densities for the
conformal geometry of these spacetimes and relate these to our pseudo-tensor,
demonstrating the equivalence of these two approaches. We also relate these
techniques to the role played by residual gauge freedom in establishing
matching conditions at early phase transitions, which we can express in terms
of components of our pseudo-tensor. This formalism is concise and geometrically
sound on both sub- and superhorizon scales, thus extending existing work to a
physically (and numerically) useful context.


title: New Tests of the Cluster Entropy Floor Hypothesis

abstract:
  Recent efforts to account for the observed X-ray luminosity - temperature
relation of galaxy clusters has led to suggestions that the ICM has an apparent
``entropy floor'' at or above the level of 300 keV cm^2. Here, we propose new
tests based on the thermal Sunyaev-Zeldovich effect and on the cluster gas mass
- temperature trend (from X-ray data) to probe the level of excess entropy in
the ICM. We show that these new tests lend further support to the case for a
high entropy floor in massive clusters.


title: Evolution of the X-ray Properties of Clusters of Galaxies

abstract:
  The amount and nature of the evolution of the X-ray properties of clusters of
galaxies provides information on the formation of structure in the universe and
on the properties of the universe itself. The cluster luminosity - temperature
relation does not evolve strongly, suggesting that the hot X-ray gas had a more
complicated thermodynamic history than simply collapsing into the cluster
potential well. Cluster X-ray luminosities do evolve. The dependence of this
evolution on redshift and luminosity is characterized using two large high
redshift samples. Cluster X-ray temperatures also evolve. This evolution
constrains the dark matter and dark energy content of the universe as well as
other parameters of cosmological interest.


title:
The high-energy gamma-ray fluence and energy spectrum of GRB 970417a
  from observations with Milagrito

abstract:
  Evidence of TeV emission from GRB970417a has been previously reported using
data from the Milagrito detector. Constraints on the TeV fluence and the energy
spectrum are now derived using additional data from a scaler system that
recorded the rate of signals from the Milagrito photomultipliers. This analysis
shows that if emission from GRB970417a has been observed, it must contain
photons with energies above 650 GeV. Some consequences of this observation are
discussed.


title: Quantum instability of magnetized stellar objects

abstract:
  The equations of state for degenerate electron and neutron gases are studied
in the presence of magnetic fields. After including quantum effects to study
the structural properties of these systems, it is found that some
hypermagnetized stars can be unstable based on the criterium of stability of
pressures. Highly magnetized white dwarfs should collapse producing a supernova
type Ia, whilst superstrongly magnetized neutron stars cannot stand their own
magnetic field and must implode, too. A comparison of our results with a set of
the available observational data of some compact stars is also presented, and
the agreement between this theory and observations is verified.


title: The nonlinear small-scale dynamo and isotropic MHD turbulence

abstract:
  This is a brief review of the main results of our recent studies of the
nonlinear evolution of the small-scale MHD dynamo in the high-Prandtl-number
regime and of the structure of the resulting saturated state of the isotropic
homogeneous MHD turbulence. It is emphasized that the MHD regime without a
uniform mean field (as is the case in our studies) is fundamentally different
from the one in which such a field is externally imposed. The ability of the
turbulence to bend and fold the magnetic-field lines leads to the emergence of
a distinctive small-scale structure. The fields are organized in folds of
characteristic length comparable to the size of the largest turbulent eddies
with spatial-direction reversals at the resistive scale. These folds are very
hard to destroy. In the nonlinear regime, the folding structure coexists with
Alfven waves propagating along the folds. The turbulent energy injected by the
forcing is dissipated in part resistively via the small-scale magnetic fields,
and in part viscously via the Alfven waves.


title: Millimetre Science with the Upgraded Australia Telescope

abstract:
  A new astronomical window into the southern skies has been opened with the
high-frequency upgrade to the Australia Telescope Compact Array (ATCA), which
allows radio-interferometric mapping of sources at wavelengths as short as 3mm.
In anticipation of the upgrade's completion, a two-day workshop was held at the
University of Melbourne in November 2001. The workshop covered a diverse range
of fields, tied together by a common theme of identifying key areas where ATCA
observations can have an impact. More than half of the talks were concerned
with molecular clouds and star formation, with the remainder covering topics
such as molecular gas in the Galactic Centre, Seyfert nuclei, and high-redshift
objects. Some early results from the 3mm and 12mm prototype systems were also
presented. In consultation with the speakers, we are presenting in this article
a summary of the talks. The original slides are available at
http://www.atnf.csiro.au/whats_on/workshops/mm_science2001/ .


title: On the formation and evolution of black-hole binaries

abstract:
  We present the results of a systematic study of the formation and evolution
of binaries containing black holes and normal-star companions with a wide range
of masses. We first reexamine the standard formation scenario for close
black-hole binaries, where the spiral-in of the companion in the envelope of a
massive star causes the ejection of the envelope. We estimate the formation
rates for different companion masses and different assumptions about the
common-envelope structure and other model parameters. We find that black-hole
binaries with intermediate- and high-mass secondaries can form for a wide range
of assumptions, while black-hole binaries with low-mass secondaries can only
form with apparently unrealistic assumptions (in agreement with previous
studies). We then present detailed binary evolution sequences for black-hole
binaries with secondaries of 2 to 17 Msun and demonstrate that in these systems
the black hole can accrete appreciably even if accretion is Eddington limited
(up to 7 Msun for an initial black-hole mass of 10 Msun) and that the black
holes can be spun up significantly in the process. We discuss the implications
of these calculations for well-studied black-hole binaries (in particular GRS
1915+105), ultra-luminous X-ray sources and Cygnus X-1. Finally, we discuss how
some of the assumptions in the standard model could be relaxed to allow the
formation of low-mass, short-period black-hole binaries which appear to be very
abundant in Nature. (Abstract abridged)


title:
Radio/X-Ray Luminosity Relation for X-Ray Bright Galactic Nuclei:
  Implications on Weighing Supermassive Black Hole

abstract:
  Optically thin and geometrically thick accretion flows are known to be
responsible for the observed radio/X-ray luminosity relation of the X-ray
bright galactic nuclei. It has also been suggested that supermassive black hole
masses can be estimated from measurements of the core radio luminosity and the
X-ray luminosity by using the advection-dominated accretion flow (ADAF) model.
In this study we increase the number of data available by compiling the
radio/X-ray fluxes and the mass in published literatures, and compare the
observed ratio of the luminosities with predictions from various models of
optically thin accretion flows. Semi-analytically derived relations of the
luminosities are presented in cases of the standard ADAF model and modified
ADAF models, in which a truncation of inner parts of the flows and winds
causing a reduction of the infalling matter are included. We show that the
observed relation can be used indeed to estimate the supermassive black hole
mass, provided that properties of such accretion flows are known. Having
investigated sensitivities of the method on modifications of the 'standard'
ADAF model, we find that a general trend of model predictions from the
'standard' ADAF, the truncated ADAF and the 'windy' ADAF are somewhat
indistinguishable. We also find, however, that the extreme case of the windy
model is inconsistent with currently available observational data, unless
microphysics parameters are to be substantially changed. High resolution radio
observations, however, are required to avoid the contamination of non-disk
components, such as, a jet component, which, otherwise, results in the
over-estimated SMBH mass.


title: Forming Globular Cluster Systems Semi-analytically

abstract:
  We describe a scheme for the formation of globular cluster systems in
early-type galaxies using a semi-analytic model of galaxy formation. Operating
within a Lambda CDM cosmology, we assume that metal-poor globular clusters are
formed at high-redshift in pre-galactic fragments, and that the subsequent
gas-rich merging of these fragments leads to the formation of metal-rich
clusters. We compare our results with contemporary data, and look at the
particular case of the globular cluster and stellar metallicity distribution
function of the nearby elliptical galaxy Centaurus A.


title:
NE2001.I. A New Model for the Galactic Distribution of Free Electrons
  and its Fluctuations

abstract:
  We present a new model for the Galactic distribution of free electrons. It
(a) describes the distribution of the free electrons responsible for pulsar
dispersion measures and thus can be used for estimating the distances to
pulsars; (b) describes large-scale variations in the strength of fluctuations
in electron density that underly interstellar scattering; (c) can be used to
interpret interstellar scattering and scintillation observations of Galactic
objects and of extragalactic objects, such as intrinsically compact AGNs and
Gamma-ray burst afterglows; and (d) serves as a preliminary, smooth spatial
model of the warm ionized component of the interstellar gas. This work builds
upon and supercedes the Taylor & Cordes (1993) model by exploiting new
observations and analysis methods. For lines of sight directed out of the
Galactic plane, the new model yields substantially larger values for pulsar
dispersion measures, except for directions dominated by the local hot bubble.
Unlike the TC93 model, the new model provides sufficient electrons to account
for the dispersion measures of the vast majority of known, Galactic pulsars.
The new model is described and exemplified using plots of astronomically useful
quantities on Galactic-coordinate grids. Software available on the Internet is
also described. Future observations and analysis techniques that will improve
the Galactic model are outlined.


title:
Spectral Energy Distributions of Flat Spectrum Radio Quasars observed
  with BeppoSAX

abstract:
  We report the BeppoSAX observations of 6 Flat Spectrum Radio Quasars. Three
of them have a clear detection up to 100 keV with the PDS instrument. For 4
objects the X-ray spectrum is satisfactorily fitted by a power-law continuum
with Galactic absorption. 2251+158 show the presence of absorption higher than
the galactic value, while the spectrum of the source 0208-512 shows a complex
structure, with evidence of absorption at low energy. We construct the Spectral
Energy Distributions adding historical data to the broad band X-ray spectra
obtained with $Beppo$SAX and reproduce them with a one-zone Synchrotron-Inverse
Compton model (including both SSC and External Compton). The implications are
briefly discussed.


title:
A Parsec-Scale Study of the 5/15 GHz Spectral Indices of the Compact
  Radio Sources in M82

abstract:
  Observations of the starburst galaxy, M82, have been made with the VLA in its
A-configuration at 15 GHz and MERLIN at 5 GHz enabling a spectral analysis of
the compact radio structure on a scale of < 0.1'' (1.6 pc). Crucial to these
observations was the inclusion of the Pie Town VLBA antenna, which increased
the resolution of the VLA observations by a factor of ~2. A number of the
weaker sources are shown to have thermal spectra and are identified as HII
regions with emission measures ~10^7 cm^-6 pc. Some of the sources appear to be
optically thick at 5 GHz implying even higher emission measures of ~10^8 cm^-6
pc. The number of compact radio sources in M82 whose origin has been determined
is now 46, of which 30 are supernova related and the remaining 16 are HII
regions. An additional 15 sources are noted, but have yet to be identified,
meaning that the total number of compact sources in M82 is at least 61. Also,
it is shown that the distribution of HII regions is correlated with the
large-scale ionised gas distribution, but is different from the distribution of
supernova remnants. In addition, the brightest HII region at (B1950) 09h 51m
42.21s +69 54' 59.2'' shows a spectral index gradient across its resolved
structure which we attribute to the source becoming optically thick towards its
centre.


title:
On particle acceleration in turbulent shear boundary layers of
  relativistic jets

abstract:
  We discuss processes accelerating cosmic ray electrons at boundaries of
relativistic jets. The resulting spectrum is expected to posses two
characteristic components: a power-law distribution at lower energies and a
harder high energy component preceding the high energy cut-off. An example of
high energy spectrum from such electron distribution is presented, including
the synchrotron and the inverse-Compton components. A characteristic feature of
the synchrotron spectrum of such electrons is its highest frequency part which
occurs above the power-law fitted to the low frequency spectral range.


title:
On relativistic jet/counterjet asymmetry in the presence of radiating
  jet boundary layer

abstract:
  We consider radiation of relativistic electrons accelerated within the jet
extended boundary layer. Due to velocity shear across the boundary the observed
jet/counterjet brightness ratio is diminished as compared to the one derived
for the jet spine. Thus the jet Lorentz factor evaluated from the observed jet
asymmetry can be an underestimated value influenced by observation of the
slower boundary layer. We briefly discuss several consequences of the radiating
boundary layer model in the context of recent Chandra and XMM observations of
the large scale jets.


title: H- and He-burning central stars and the evolution to white dwarfs

abstract:
  The structure and evolution of central stars of planetary nebulae (CSPNe) is
reviewed. CSPNe represent the rapid transitional stage between the Asymptotic
Giant Branch (AGB) and the white-dwarf domain. It is shown that the whole
evolution off the AGB through the central-star regime depends on the
evolutionary history. The detailed evolution into a white dwarf is controlled
by the internal stellar structure which, in turn, is determined by the duration
of the preceding AGB evolution and therefore by the AGB mass-loss history.
  The evolution of hydrogen-deficient central stars has been a matter of debate
since many years. Convective overshoot appears to be a key ingredient to model
these objects. Various thermal-pulse scenarios with inclusion of overshoot are
discussed, leading to surface abundances in general agreement with those
observed for Wolf-Rayet central stars.


title: STJ Observations of the Eclipsing Polar HU Aqr

abstract:
  We apply an eclipse mapping technique to observations of the eclipsing
magnetic cataclysmic variable HU Aqr. The observations were made with the
S-Cam2 Superconducting Tunnel Junction detector at the WHT in October 2000,
providing high signal-to-noise observations with simultaneous spectral and
temporal resolution. HU Aqr was in a bright (high accretion) state (V=14.7) and
the stream contributes as much to the overall system brightness as the
accretion region on the white dwarf. The stream is modelled assuming accretion
is occuring onto only one pole of the white dwarf. We find enhanced brightness
towards the accretion region from irradiation and interpret enhanced brightness
in the threading region, where the ballistic stream is redirected to follow the
magnetic field lines of the white dwarf, as magnetic heating from the
stream-field interaction, which is consistent with recent theoretical results.
Changes in the stream eclipse profile over one orbital period indicate that the
magnetic heating process is unstable.


title: Sulphur and iron abundances in halo stars

abstract:
  From equivalent widths of the SI lines at 8694 A, Israelian & Rebolo (2001)
and Takada-Hidai et al. (2002) have derived a surprisingly high sulphur-to-iron
ratio ([S/Fe] = 0.5 to 0.7) in six halo stars with [Fe/H] ~ -2.0 suggesting
perhaps that hypernovae made a significant contribution to the formation of
elements in the early Galaxy. To investigate this problem we have used
high-resolution spectra obtained with the ESO VLT/UVES spectrograph to
determine the S/Fe ratio in 19 main-sequence and subgiant stars ranging in
[Fe/H] from -3.2 to -0.7. The sulphur abundances are determined from SI lines
at 8694 A and 9212 - 9237 A, and the iron abundances from about 20 FeII lines.
S/Fe ratios as derived from 1D model atmospheres are presented and possible 3D
effects are discussed. The initial results from our survey do not confirm the
high values of [S/Fe] quoted above; instead we find that the ratio [S/Fe]
remains constant at about 0.35 dex for metallicities -3 < [Fe/H] -1.


title:
Complex dynamics in a simple model of pulsations for Super-Asymptotic
  Giant Branch Stars

abstract:
  When intermediate mass stars reach their last stages of evolution they show
pronounced oscillations. This phenomenon happens when these stars reach the
so-called Asymptotic Giant Branch (AGB), which is a region of the
Hertzsprung-Russell diagram located at about the same region of effective
temperatures but at larger luminosities than those of regular giant stars. The
period of these oscillations depends on the mass of the star. There is growing
evidence that these oscillations are highly correlated with mass loss and that,
as the mass loss increases, the pulsations become more chaotic. In this paper
we study a simple oscillator which accounts for the observed properties of this
kind of stars. This oscillator was first proposed and studied by Icke et al.
[Astron.Astrophys. 258, 341 (1992)] and we extend their study to the region of
more massive and luminous stars - the region of Super-AGB stars. The oscillator
consists of a periodic nonlinear perturbation of a linear Hamiltonian system.
The formalism of dynamical systems theory has been used to explore the
associated Poincare map for the range of parameters typical of those stars. We
have studied and characterized the dynamical behaviour of the oscillator as the
parameters of the model are varied, leading us to explore a sequence of local
and global bifurcations. Among these, a tripling bifurcation is remarkable,
which allows us to show that the Poincare map is a nontwist area preserving
map. Meandering curves, hierarchical-islands traps and sticky orbits also show
up. We discuss the implications of the stickiness phenomenon in the evolution
and stability of the Super-AGB stars.


title: Galaxy Clusters with Chandra

abstract:
  We discuss Chandra results related to 1) cluster mergers and cold fronts and
2) interactions between relativistic plasma and hot cluster atmospheres. We
describe the properties of cold fronts using NGC1404 in the Fornax cluster and
A3667 as examples. We discuss multiple surface brightness discontinuities in
the cooling flow cluster ZW3146. We review the supersonic merger underway in
CL0657. Finally, we summarize the interaction between plasma bubbles produced
by AGN and hot gas using M87 and NGC507 as examples.


title: XMM-Newton observation of the Lockman Hole II. Spectral analysis

abstract:
  We present the results of the X-ray spectral analysis of the first deep X-ray
survey with the XMM-Newton observatory during Performance Verification. We
restrict the analysis to the sample of 98 sources with more than 70 net counts
(flux limit in the [0.5-7] keV band of 1.6 10^{-15} erg cm^{-2} s^{-1}) of
which 61 have redshift identification. We find no correlation between the
spectral index Gamma and the intrinsic absorption column density N_H and, for
both the Type-1 and Type-2 AGN populations, we obtain <Gamma>~2. The
progressive hardening of the mean X-ray source spectrum with decreasing flux is
essentially due to an increase in intrinsic absorption. The marked separation
between the two AGN populations in several diagnostics diagrams, involving
X-ray colour, X-ray flux, optical/near IR colour and optical brightness, is
also a consequence of different absorption column densities and enables the
classification of optically faint obscured AGN. About 27% of the subsample with
R-K' colour are EROs (R-K>5) and most of these 18 X-ray selected EROs contain
anobscured AGN as revealed by their high X-ray-to-optical/near IR flux ratios.
There are six sources in our sample with L_X[0.5-10]>10^44 erg s^{-1} and
log(N_H)>10^22 cm^{-2}: which are likely Type-2 QSOs and we thus derive a
density of ~69 objects of this class per square degree.


title:
Line-of-sight Effects on Observability of Kink and Sausage Modes in
  Coronal Structures with Imaging Telescopes

abstract:
  Kink modes of solar coronal structures, perturbing the loop in the direction
along the line-of-sight (LOS), can be observed as emission intensity
disturbances propagating along the loop provided the angle between the LOS and
the structure is not ninety degrees. The effect is based upon the change of the
column depth of the loop (along the LOS) by the wave. The observed amplitude of
the emission intensity variations can be larger than the actual amplitude of
the wave by a factor of two and there is an optimal angle maximizing the
observed amplitude. For other angles this effect can also attenuate the
observed wave amplitude. The observed amplitude depends upon the ratio of the
wave length of kink perturbations to the width of the structure and on the
angle between the LOS and the axis of the structure. Sausage modes are always
affected negatively from the observational point of view, as the observed
amplitude is always less than the actual one. This effect should be taken into
account in the interpretation of wave phenomena observed in the corona with
space-borne and ground-based imaging telescopes.


title: Luminosities of AGB Variables

abstract:
  The prevailing evidence suggests that most large-amplitude AGB variables
follow the period luminosity (PL) relation that has been established for Miras
in the LMC and galactic globular clusters. Hipparcos observations indicate that
most Miras in the solar neighbourhood are consistent with such a relation.
There are two groups of stars with luminosities that are apparently greater
than the PL relation would predict: (1) in the LMC and SMC there are large
amplitude variables, with long periods, P> 420 days, which are probably
undergoing hot bottom burning, but which are very clearly more luminous than
the PL relation (these are visually bright and are likely to be among the first
stars discovered in more distant intermediate age populations); (2) in the
solar neighbourhood there are short period, P<235 days, red stars which are
probably more luminous than the PL relation. Similar short-period red stars,
with high luminosities, have not been identified in the Magellanic Clouds.


title:
1.65 micron H-band Surface Photometry of Galaxies. X: Structural and
  Dynamical Properties of Elliptical Galaxies

abstract:
  We analyse the structural and dynamical properties of a sample of 324 nearby
elliptical and dwarf elliptical galaxies observed during an extensive NIR
survey in H-band (1.65 micron). The Fundamental Plane (FP) is determined and a
significant tilt is assessed. The origins of such a tilt are investigated by
means of a spherically symmetric, isotropic pressure supported dynamical model
relying on the observed surface brightness profiles. The systematic variation
of the shape coefficient converting the measured central velocity dispersion $
sigma_0$ into the virial rms velocity $ sigma_{rms}$ is found to be the main
cause of the tilt, due to aperture effects. Moreover the ratio between the
dynamical mass $M_{dyn}$ and the total H-band luminosity $L_H$ turns out to be
roughly constant along the luminosity sequence of ellipticals: H-band
luminosity is therefore a reliable and cheap estimator of the dynamical mass of
the Es.


title: Predictions of variable mass loss for Luminous Blue Variables

abstract:
  We present radiation-driven wind models for Luminous Blue Variables (LBVs)
and predict their mass-loss rates. We study the effects of lower masses and
modified abundances in comparison to the normal OB supergiants, and we find
that the main difference in mass loss is due to the lower masses of LBVs. In
addition, we find that the increase in helium abundance changes the mass-loss
properties by small amounts (up to about 0.2 dex in log Mdot), while CNO
processing is relatively unimportant for the mass-loss rate. A comparison
between our mass loss predictions and the observations is performed for four
relatively well-studied LBVs. The comparison shows that (i) the winds of LBVs
are driven by radiation pressure on spectral lines, (ii) the variable mass loss
behaviour of LBVs during their S Doradus-type variation cycles is explained by
changes in the line driving efficiency, notably due to the
recombination/ionisation of Fe IV/III and Fe III/II, and finally, (iii) the
winds of LBVs can be used to derive their masses, as exemplified by the case of
AG Car, for which we derive a present-day mass of 35 Msun.


title:
XMM-Newton and VLA Observations of the Variable Wolf-Rayet Star EZ CMa:
  Evidence for a Close Companion?

abstract:
  We present new X-ray and radio observations of the WR star EZ CMa (HD 50896)
obtained with XMM-Newton and the VLA. This WN4 star shows optical/UV
variability at a period of 3.76 d whose cause is unknown. VLA flux measurements
at five frequencies show the radio spectral energy distribution is
well-described by a power law with spectral index +0.69 (+-0.05), as expected
for free-free wind emission. The derived ionized mass loss rate allowing for
distance uncertainties is M(dot) = 3.8 (+-2.6)e-5 M_sun/yr. The CCD X-ray
spectra show prominent Si XIII and S XV emission lines and can be acceptably
modeled as an absorbed multi-temperature optically thin plasma. Nonsolar
abundances are inferred with Fe notably deficient. The X-ray emission is
dominated by cool plasma at kT_cool = 0.6 keV, but a harder component is also
detected with a derived temperature kT_hot = 3.0 - 4.2 keV if the emission is
thermal. This is too high to be explained by radiative wind shock models and
the luminosity of the hard component is 3 orders of magnitude lower than
expected for accretion onto a neutron star companion. We argue that the hard
emission could be produced by the WR wind shocking onto a normal
(nondegenerate) stellar companion at close separation. Using comparable data
sets, we show that the X-ray and radio properties of EZ CMa are strikingly
similar to those of the WN5-6 star WR110. This similarity points to common
X-ray and radio emission processes in WN stars and discredits the idea that EZ
CMa is anomalous within its class.


title:
On the nature of a secondary main sequence turn-off in the rich LMC
  cluster NGC 1868

abstract:
  Evidence for a second main-sequence turn-off in a deep colour-magnitude
diagram of NGC 1868 is presented. The data were obtained with HST/WFPC2 and
reach down to m_{555} ~ 25. Besides the usual t ~ 0.8 Gyr turn-off found in
previous analyses, another possible turn-off is seen at m_{555} ~ 21 (M_V ~
2.5), which is consistent with an age of t ~ 3 Gyrs. This CMD feature stands
out clearly especially when contaminating field LMC stars are statistically
removed. The background subtracted CMD also visibly displays a red subgiant
branch extending about 1.5 mag below the younger turn-off and the clump of red
giants. The significance of the secondary turn-off in NGC 1868 was confirmed
with Monte-Carlo simulations and bootstrapping techniques. Star-counts in
selected regions in the cluster CMD indicate a mass ratio of old
population/young population in the range 5% <= M_{old} / M_{young} <= 12%,
depending on the mass function slope. The existence of such a subpopulation in
NGC 1868 is significant even in the presence of uncertainties in background
subtraction. The possibility that the secondary turn-off is associated with the
field star population was examined by searching for similar features in CMDs of
field stars. Statistically significant excesses of stars redwards of the
main-sequence were found in all such fields in the range 20 <= m_{555} <= 22.
These however are much broader features that do not resemble the main-sequence
termination of a single population. We also discuss other alternative
explanations for the feature at m_{555} ~ 21, such as unresolved binarism,
peculiar stars or CMD discontinuities associated with the Bohm-Vitense gap.


title: The orientation of the Seyfert nucleus in Markarian 348

abstract:
  Multi-frequency observations of Mrk 348 are presented consisting of 2 epochs
of MERLIN data at 5 GHz, ISOPHOT data at 170, 90, 60 and 25 micron, NOT images
at U, B, R and I bands and data at 1350 micron from the archive for SCUBA. The
new optical images reveal a disrupted arm that ends towards the eastern
companion of Mrk 348, consistent with the hypothesis that Mrk 348 and its
companion form an interacting system. 5 GHz MERLIN imaging shows that only one
of the radio components of Mrk 348 is polarized (%P=5). The broadband spectrum
of Mrk 348 is flat between the radio and millimetre bands, suggesting that
synchrotron emission extends to high frequencies. Mrk 348 has many of the
characteristics of a radio-loud object. We discuss the orientation of the radio
axis of Mrk 348 with respect to the line of sight. We conclude that the
evidence is conflicting, and the geometry in Mrk 348 is not well-described by a
simple edge-on or face-on model.


title: Natural Quintessence and the Brane World

abstract:
  Although quintessence models have attractive cosmological features, they face
two major difficulties. First, it has not yet been possible to find one which
convincingly realizes the goal of explaining present-day cosmic acceleration
generically using only attractor solutions. Second, quintessence has proven
difficult to obtain within realistic microscopic theories, largely due to two
major obstructions. Both of these difficulties are summarized in this article,
together with a recent proposal for circumventing the second of them within a
brane-world context. It is shown that this proposal leads to a broader class of
dynamics for the quintessence field, in which its couplings slowly run (or:
walk) over cosmological time scales. The walking of the quintessence couplings
opens up new possibilities for solving the first problem: that of obtaining
acceptable transitions between attractor solutions.


title: The Diverse Properties of GPS Sources

abstract:
  We discuss the morphology and kinematics of five gigahertz-peaked spectrum
(GPS) sources that have been observed with the VLBA. We find a wide range of
observed properties including core-jet structure, superluminal motion,
variability, extended structure, and polarization, all of which appear to
deviate from commonly-accepted GPS paradigms (e.g., O'Dea 1998). We suggest
that the observed low frequency cutoff in GPS sources may be primarily due to
free-free absorption rather than synchrotron self-absorption.


title:
Radio Sources in Low-Luminosity Active Galactic Nuclei. III. "AGNs" in a
  Distance-Limited Sample of "LLAGNs"

abstract:
  (abbreviated): This paper presents the results of a high resolution radio
imaging survey of all known (96) low-luminosity active galactic nuclei (LLAGNs)
at D<19Mpc. We find that almost half of all LINERs and low-luminosity Seyferts
have flat-spectrum radio cores when observed at 150mas resolution. Higher
(2mas) resolution observations of a flux-limited subsample have provided a 100%
(16 of 16) detection rate of pc-scale radio cores, with implied brightness
temperatures > 10^8 K. The five LLAGNs with the highest core radio fluxes also
have pc-scale `jets.' Compact radio cores are almost exclusively found in
massive ellipticals and in type1 nuclei. The core radio power is correlated
with the nuclear optical `broad' Halpha luminosity, the nuclear optical
`narrow' emission line luminosity and width, and with the galaxy luminosity. In
these correlations LLAGNs fall close to the low-luminosity extrapolations of
more powerful AGNs. About half of all LLAGNs with multiple epoch data show
significant inter-year radio variability.
  Investigation of a sample of ~150 nearby bright galaxies, most of them
LLAGNs, shows that the nuclear (<150mas size) radio power is strongly
correlated with both the black hole mass and the galaxy bulge luminosity;
linear regression fits to all ~150 galaxies give: log P(2cm) = 1.31 log
M_blackhole + 8.77 and log P(2cm) = 1.89 log L_B(bulge) - 0.17. Low accretion
rates are implied in both advection- and jet-type models. In brief, all
evidence points towards the presence of accreting massive black holes in a
large fraction, perhaps all, of LLAGNs.


title:
Recent progress in understanding the hot and warm gas phases in the
  halos of star-forming galaxies

abstract:
  In this contribution we present a few selected examples of how the latest
generation of space-based instrumentation -- NASA's Chandra X-ray Observatory
and the Far-Ultraviolet Spectroscopic Explorer (FUSE) -- are finally answering
old questions about the influence of massive star feedback on the warm and hot
phases of the ISM and IGM. In particular, we discuss the physical origin of the
soft thermal X-ray emission in the halos of star-forming and starburst
galaxies, its relationship to extra-planar H-alpha emission, and plasma
diagnostics using FUSE observations of O VI absorption and emission.


title:
The impact of relativistic corrections and component separation in the
  measurement of the SZ effect and on the small angular scale non-Gaussianity
  of the CMB

abstract:
  We study the effect of imperfect subtraction of the Sunyaev-Zel'dovich effect
(SZE) using a robust and non-parametric method to estimate the SZE residual in
the Planck channels. We include relativistic corrections to the SZE, and
present a simple fitting formula for the SZE temperature dependence for the
Planck channels. We show how the relativistic corrections constitute a serious
problem for the estimation of the kinematic SZE component from Planck data,
since the key channel to estimate the kinematic component of the SZE, at 217
GHz, will be contaminated by a non-negligible thermal SZE component. The
imperfect subtraction of the SZE will have an effect on both the Planck cluster
catalogue and the recovered CMB map. In the cluster catalogue, the relativistic
corrections are not a major worry for the estimation of the total cluster flux
of the thermal SZE component, however, they must be included in the SZE
simulation when calculating the selection function and completeness level. The
power spectrum of the residual at 353 GHz, where the intensity of the thermal
SZE is maximum, does not contribute significantly to the power spectrum of the
CMB. We calculate the non-Gaussian signal due to the SZE residual in the 353
GHz CMB map using a simple Gaussianity estimator, and this estimator detects a
4.25-sigma non-Gaussian signal at small scales, which could be mistaken for a
primordial non-Gaussian signature. The other channels do not show any
significant departure from Gaussianity with our estimator.


title: Intermediate Element Abundances in Galaxy Clusters

abstract:
  We present the abundances of the intermediate elements obtained by performing
a stacked analysis of all the galaxy clusters in the archive of the X-ray
telescope ASCA. We give the abundances of Fe, Si, S, and Ni as a function of
cluster temperature from 1--10 keV, and place strong upper limits on the
abundances of Ca and Ar. We show that the abundances of the most
well-determined elements Fe, Si, and S in conjunction with recent theoretical
supernovae yields do not give a consistent solution for the fraction of
material produced by Type Ia and Type II supernovae at any single temperature.
However, the general trend is for higher temperature clusters to have more of
their metals produced in Type II supernovae than in Type Ias.


title: Detecting the Baryons in Matter Power Spectra

abstract:
  We examine power spectra from the Abell/ACO rich cluster survey and the 2dF
Galaxy Redshift Survey (2dfGRS) for observational evidence of features produced
by the baryons. A non-negligible baryon fraction produces relatively sharp
oscillatory features at specific wavenumbers in the matter power spectrum.
However, the mere existence of baryons will also produce a global suppression
of the power spectrum. We look for both of these features using the false
discovery rate (FDR) statistic. We show that the window effects on the
Abell/ACO power spectrum are minimal, which has allowed for the discovery of
discrete oscillatory features in the power spectrum. On the other hand, there
are no statistically significant oscillatory features in the 2dFGRS power
spectrum, which is expected from the survey's broad window function. After
accounting for window effects, we apply a scale-independent bias to the 2dFGRS
power spectrum, P_{Abell}(k) = b^2P_{2dF}(k) and b = 3.2. We find that the
overall shapes of the Abell/ACO and the biased 2dFGRS power spectra are
entirely consistent over the range 0.02 <= k <= 0.15hMpc^-1. We examine the
range of Omega_{matter} and baryon fraction for which these surveys could
detect significant suppression in power. The reported baryon fractions for both
the Abell/ACO and 2dFGRS surveys are high enough to cause a detectable
suppression in power (after accounting for errors, windows and k-space
sampling). Using the same technique, we also examine, given the best fit baryon
density obtained from BBN, whether it is possible to detect additional
suppression due to dark matter-baryon interaction. We find that the limit on
dark matter cross section/mass derived from these surveys are the same as those
ruled out in a recent study by Chen, Hannestad and Scherrer.


title:
The Orbit and Position of the X-ray Pulsar XTE J1855-026 - an Eclipsing
  Supergiant System

abstract:
  A pulse timing orbit has been obtained for the X-ray binary XTE J1855-026
using observations made with the Proportional Counter Array on board the Rossi
X-ray Timing Explorer. The mass function obtained of ~16Mo together with the
detection of an extended near-total eclipse confirm that the primary star is a
supergiant as predicted. The orbital eccentricity is found to be very low with
a best fit value of 0.04 +/- 0.02. The orbital period is also refined to be
6.0724 +/- 0.0009 days using an improved and extended light curve obtained with
RXTE's All Sky Monitor. Observations with the ASCA satellite provide an
improved source location of R.A. = 18h 55m 31.3s}, decl. = -02o 36' 24.0"
(2000) with an estimated systematic uncertainty of less than 12". A
serendipitous new source, AX J1855.4-0232, was also discovered during the ASCA
observations.


title: Analysis of colour-magnitude diagrams of rich LMC clusters: NGC 1831

abstract:
  We present the analysis of a deep colour-magnitude diagram (CMD) of NGC 1831,
a rich star cluster in the LMC. The data were obtained with HST/WFPC2 in the
F555W (~V) and F814W (~I) filters, reaching m_555 ~ 25. We discuss and apply a
method of correcting the CMD for sampling incompleteness and field star
contamination. Efficient use of the CMD data was made by means of direct
comparisons of the observed to model CMDs. The model CMDs are built by an
algorithm that generates artificial stars from a single stellar population,
characterized by an age, a metallicity, a distance, a reddening value, a
present day mass function and a fraction of unresolved binaries. Photometric
uncertainties are empirically determined from the data and incorporated into
the models as well. Statistical techniques are presented and applied as an
objective method to assess the compatibility between the model and data CMDs.
By modelling the CMD of the central region in NGC 1831 we infer a metallicity Z
= 0.012, 8.75 < log(tau) < 8.80, 18.54 < (m-M)_0 < 18.68 and 0.00 < E(B-V) <
0.03. For the position dependent PDMF slope (alpha = -dlog(Phi(M))/dlog(M)), we
clearly observe the effect of mass segregation in the system: for projected
distances R < 30 arcsec, alpha ~ 1.7, whereas 2.2 < alpha < 2.5 in the outer
regions of NGC 1831.


title: A Cold Front in a Preheated Galaxy Cluster

abstract:
  We present a simulated cluster of galaxies, modeled with a pre-heated
intracluster medium, that exhibits X-ray features similar to the `cold fronts'
seen in Chandra observations. Mock observations at a particular epoch show
factor two discontinuities in X-ray temperature and factor four in surface
brightness on a spatial scale <= 100 kpc. Analysis of the cluster's dynamical
history reveals that the front is a transient contact discontinuity created by
an ongoing merger of two roughly equal mass subgroups. The cold front feature
in this realization is amplified by the adiabatic expansion of one of the
subgroups following its ablation from the center of its local dark matter
potential. The presence of cold front features in a cluster modeled without
radiative cooling or magnetic fields implies that such relatively complex
physics is not a necessary element of the phenomenon and suggests that the
prevalence of such features in high resolution X-ray images of clusters may
simply reflect the high frequency of ongoing mergers driven by gravity and
comparatively simple hydrodynamics.


title: Discovery of Spectral Variability of Markarian 421 at TeV Energies

abstract:
  The detection of spectral variability of the gamma-ray blazar Mrk 421 at TeV
energies is reported. Observations with the Whipple Observatory 10m gamma-ray
telescope taken in 2000/2001 revealed exceptionally strong and long-lasting
flaring activity.
  Flaring levels of 0.4 to 13 times that of the Crab Nebula flux provided
sufficient statistics for a detailed study of the energy spectrum between 380
GeV and 8.2 TeV as a function of flux level. These spectra are well described
by a power law with an exponential cutoff. There is no evidence for variation
in the cutoff energy with flux, and all spectra are consistent with an average
value for the cutoff energy of 4.3 TeV. The spectral index varies between 1.89
in a high flux state and 2.72 in a low state.
  The correlation between spectral index and flux is tight when averaging over
the total 2000/2001 data set. Spectral measurements of Mrk~421 from previous
years (1995/96 and 1999) by the Whipple collaboration are consistent with this
flux-spectral index correlation, which suggest that this may be a constant or a
long-term property of the source.
  If a similar flux-spectral index correlation were found for other gamma-ray
blazars, this universal property could help disentangle the intrinsic emission
mechanism from external absorption effects.


title: The mass function

abstract:
  We present the mass functions for different mass estimators for a range of
cosmological models. We pay particular attention to how universal the mass
function is, and how it depends on the cosmology, halo identification and mass
estimator chosen. We investigate quantitatively how well we can relate observed
masses to theoretical mass functions.


title: Chemical Abundances of Extragalactic H II regions

abstract:
  The determination of the heavy element abundances from giant extragalactic H
II regions is based on collisionally excited lines. We argue that in the
presence of temperature variations the abundances determined are lower limits
to the real heavy element abundances. To determine the real abundances it is
necessary to take into account the temperature variations present in these
nebulae. We discuss the relevance of obtaining accurate line intensities of
recombination lines of H, He, C, and O to determine the chemical composition of
extragalactic H II regions. We suggest that Pagel's method to derive the O/H
ratio should be calibrated by using recombination lines instead of
photoionization models or abundances derived from collisionally excited lines.


title: GRB 010921: Strong Limits on an Underlying Supernova from HST

abstract:
  GRB 010921 was the first HETE-2 GRB to be localized via its afterglow
emission. The low-redshift of the host galaxy, z=0.451, prompted us to
undertake intensive multi-color observations with the Hubble Space Telescope
with the goal of searching for an underlying supernova component. We do not
detect any coincident supernova to a limit 1.34 mag fainter than SN 1998bw at
99.7% confidence, making this one of the most sensitive searches for an
underlying SN. Analysis of the afterglow data allow us to infer that the GRB
was situated behind a net extinction (Milky Way and the host galaxy) of A_V ~
1.8 mag in the observer frame. Thus, had it not been for such heavy extinction
our data would have allowed us to probe for an underlying SN with brightness
approaching those of more typical Type Ib/c supernovae.


title: EVN and MERLIN confirmation of the LS5039 jets

abstract:
  The microquasar nature of LS5039 was revealed by May 1999 VLBA+VLA
observations showing a two-sided jet at milliarcsecond scales. Here we present
follow-up interferometric observations carried out with the EVN and MERLIN at 5
GHz in March 2000. The obtained maps with both the EVN and MERLIN show a
two-sided jet with a similar position angle to the previous VLBA+VLA map. The
total length of the jet arms is ~60 mas in the EVN map and ~300 mas in the
MERLIN map. A brightness and length asymmetry of the jets, compatible with the
earlier observations, is also present in the maps. Overall, these observations
confirm the existence of a two-sided jet structure in LS 5039 and seem to
indicate their persistent nature.


title: The Sloan Digital Sky Survey

abstract:
  The Sloan Digital Sky Survey (SDSS) is making a multi-colour, three
dimensional map of the nearby Universe. The survey is in two parts. The first
part is imaging one quarter of the sky in five colours from the near
ultraviolet to the near infrared. In this imaging survey we expect to detect
around 50 million galaxies to a magnitude limit g ~ 23. The second part of the
survey, taking place concurrently with the imaging, is obtaining spectra for up
to 1 million galaxies and 100,000 quasars. From these spectra we obtain
redshifts and hence distances, in order to map out the three-dimensional
distribution of galaxies and quasars in the Universe. These observations will
be used to constrain models of cosmology and of galaxy formation and evolution.
  This article describes the goals and methods used by the SDSS, the current
status of the survey, and highlights some exciting discoveries made from data
obtained in the first two years of survey operations.


title: Bursts of extensive air showers: chaos vs. stochasticity

abstract:
  Bursts of the count rate of extensive air showers (EAS) lead to the
appearance of clusters in time series that represent EAS arrival times. We
apply methods of nonlinear time series analysis to twenty EAS cluster events
found in the data set obtained with the EAS-1000 prototype array. In
particular, we use the Grassberger-Procaccia algorithm to compute the
correlation dimension of the time series in the vicinity of the clusters. We
find that four cluster events produce signs of chaos in the corresponding time
series. By applying a number of supplementary methods we assess that the nature
of the observed behaviour of the correlation dimension is likely to be
deterministic. We suggest a simple qualitative model that might explain an
origin of clusters in general and "possibly chaotic" clusters in particular.
Finally, we compare our conclusions with the results of similar investigations
performed by the EAS-TOP and LAAS groups.


title:
The K20 survey. IV. The redshift distribution of Ks<20 galaxies: a test
  of galaxy formation models

abstract:
  We present the redshift distribution of a complete sample of 480 galaxies
with Ks<20 distributed over two independent fields covering a total area of 52
arcmin^2. The redshift completeness is 87% and 98% respectively with
spectroscopic and high-quality and tested photometric redshifts. The redshift
distribution of field galaxies has a median redshift z_{med}\sim 0.80, with
\sim 32% and \sim 9% of galaxies at z>1 and z>1.5 respectively. A ``blind''
comparison is made with the predictions of a set of the most recent LambdaCDM
hierarchical merging and pure luminosity evolution (PLE) models. The
hierarchical merging models overpredict and underpredict the number of galaxies
at low-z and high-z respectively, whereas the PLE models match the median
redshift and the low-z distribution, still being able to follow the high-z tail
of N(z). We briefly discuss the implications of this comparison and the
possible origins of the observed discrepancies. We make the redshift
distribution publicly available.


title:
Spectral Types of Planetary Host Star Candidates: Two New Transiting
  Planets?

abstract:
  Recently, 46 low-luminosity object transits were reported from the Optical
Gravitational Lensing Experiment. Our follow-up spectroscopy of the 16 most
promising candidates provides a spectral classification of the primary.
Together with the radius ratio from the transit measurements, we derived the
radii of the low-luminosity companions. This allows to examine the possible
sub-stellar nature of these objects. Fourteen of them can be clearly identified
as low-mass stars. Two objects, OGLE-TR-03 and OGLE-TR-10 have companions with
radii of 0.15 R_sun which is very similar to the radius of the transiting
planet HD209458B. The planetary nature of these two objects should therefore be
confirmed by dynamical mass determinations.


title: The turn-over scenario for white dwarfs and neutron stars

abstract:
  We study numerically the so-called ``turn-over scenario'' for rotating
magnetic white dwarfs and neutron stars. According to this scenario, the
magnetic symmetry axis of the model inclines at a gradually increasing angle
(the so-called ``turn-over angle'') relative to the invariant angular momentum
axis. Consequently, the model becomes ``perpendicular rotator'' (i.e., its
turn-over angle becomes almost 90 degrees) on a ``turn-over timescale''
calculated to be ~ (a few)x10^6 - (a few)x10^7 yr for the examined white dwarf
models and ~ 10^1 - 10^3 yr for the examined neutron star models. Furthermore,
the initial differential rotation of the model turns to uniform rotation due to
angular momentum mixing caused by hydrodynamic Alfven waves propagating along
the poloidal magnetic field lines. Our numerical results show that, during the
turn-over phase, the spin-down time rate is large, while the spin-down power
remains small; so, the turn-over phase is a characteristic case for which an
eventually observed large spin-down time rate should not be interpreted as
implying a large spin-down power.


title: The Galactic Kinematics of Mira Variables

abstract:
  The galactic kinematics of Mira variables derived from radial velocities,
Hipparcos proper motions and an infrared period-luminosity relation are
reviewed. Local Miras in the 145-200day period range show a large asymmetric
drift and a high net outward motion in the Galaxy. Interpretations of this
phenomenon are considered and (following Feast and Whitelock 2000) it is
suggested that they are outlying members of the bulge-bar population and
indicate that this bar extends beyond the solar circle.


title: The galaxy luminosity function in the cluster of galaxies Abell 496

abstract:
  We have derived the galaxy luminosity function (GLF) in the cluster of
galaxies Abell 496 from a wide field image in the I band. A single Schechter
function reproduces quite well the GLF in the 17 <= I_{AB} <= 22 (-19.5 <= M_I
<= -14.5) magnitude interval, and the power law index of this function is found
to be somewhat steeper in the outer regions than in the inner regions. This
result agrees with the idea that faint galaxies are more abundant in the outer
regions of clusters, while in the denser inner regions they have partly been
accreted by larger galaxies or have been dimmed or even disrupted by tidal
interactions.


title: Chandra Detects Relativistic Broad Absorption Lines from APM 08279+5255

abstract:
  We report the discovery of X-ray broad absorption lines (BALs) from the
BALQSO APM 08279+5255 originating from material moving at relativistic
velocities with respect to the central source. The large flux magnification by
a factor of ~ 100 provided by the gravitational lens effect combined with the
large redshift (z = 3.91) of the quasar have facilitated the acquisition of the
first high signal-to-noise X-ray spectrum of a quasar containing X-ray BALs.
Our analysis of the X-ray spectrum of APM 08279+5255 places the rest-frame
energies of the two observed absorption lines at 8.1 and 9.8 keV. The detection
of each of these lines is significant at the > 99.9% confidence level based on
the F-test. Assuming that the absorption lines are from Fe xxv Kalpha, the
implied bulk velocities of the X-ray BALs are ~ 0.2c and ~ 0.4c, respectively.
The observed high bulk velocities of the X-ray BALs combined with the
relatively short recombination time-scales of the X-ray absorbing gas imply
that the absorbers responsible for the X-ray BALs are located at radii of < 2 x
10^(17) cm, within the expected location of the UV absorber. With this implied
geometry the X-ray gas could provide the necessary shielding to prevent the UV
absorber from being completely ionized by the central X-ray source, consistent
with hydrodynamical simulations of line-driven disk winds. Estimated
mass-outflow rates for the gas creating the X-ray BALs are typically less than
a solar mass per year. Our spectral analysis also indicates that the continuum
X-ray emission of APM 08279+5255 is consistent with that of a typical
radio-quiet quasar with a spectral slope of Gamma = 1.72(-0.05,+0.06).


title:
Searching for Hydrogen in Type Ib Supernovae, and for Helium and
  Hydrogen in Type Ic

abstract:
  Identifying the progenitors of Type Ib and Type Ic supernovae requires
knowing, among other things, whether SNe Ib eject hydrogen, and whether SNe Ic
eject helium, and perhaps even hydrogen. Recently it has become clear that some
SNe Ib do eject hydrogen, and it may be that all SNe Ib do. Two arguments that
have been made in the past that SNe Ic eject helium are difficult to confirm,
but I discuss other possible evidence that SNe Ic eject helium, as well as
hydrogen. If so, these elements extend to lower ejection velocities than in SNe
Ib. The spectroscopic differences between SNe Ib and SNe Ic may depend on the
radial distributions of the helium and hydrogen as well as on the ejected
masses of helium and hydrogen. We should consider the possibility that SNe Ic
are more mixed up.


title:
Chemical composition of B-type supergiants in the OB8, OB10, OB48, OB78
  associations of M31

abstract:
  Absolute and differential chemical abundances are presented for the largest
group of massive stars in M31 studied to date. These results were derived from
intermediate resolution spectra of seven B-type supergiants, lying within four
OB associations covering a galactocentric distance of 5 - 12 kpc. The results
are mainly based on an LTE analysis, and we additionally present a full
non-LTE, unified model atmosphere analysis of one star (OB78-277) to
demonstrate the reliability of the differential LTE technique. A comparison of
the stellar oxygen abundance with that of previous nebular results shows that
there is an offset of between ~0.15 - 0.4 dex between the two methods which is
critically dependent on the empirical calibration adopted for the R23 parameter
with [O/H]. However within the typical errors of the stellar and nebular
analyses (and given the strength of dependence of the nebular results on the
calibration used) the oxygen abundances determined in each method are fairly
consistent. We determine the radial oxygen abundance gradient from these stars,
and do not detect any systematic gradient across this galactocentric range. We
find that the inner regions of M31 are not, as previously thought, very 'metal
rich'. Our abundances of C, N, O, Mg, Si, Al, S and Fe in the M31 supergiants
are very similar to those of massive stars in the solar neighbourhood.


title: Measuring spacetime: from big bang to black holes

abstract:
  Nerd abstract: Observational constraints on spacetime are reviewed, focusing
on how the underlying physics (dark matter, dark energy, gravity) can be tested
rather than assumed.
  Popular abstract: Space is not a boring static stage on which events unfold
over time, but a dynamic entity with curvature, fluctuations and a rich life of
its own which is a booming area of study. Spectacular new measurements of the
cosmic microwave background, gravitational lensing, type Ia supernovae,
large-scale structure, spectra of the Lyman alpha forest, stellar dynamics and
x-ray binaries are probing the properties of spacetime over 22 orders of
magnitude in scale. Current measurements are consistent with an infinite flat
everlasting Universe containing about 30% cold dark matter, 65% dark energy and
at least two distinct populations of black holes.


title: Faint AGN and the Ionizing Background

abstract:
  We determine the evolution of the faint, high-redshift, optical luminosity
function (LF) of AGN implied by several observationally-motivated models of the
ionizing background. Our results depend crucially on whether we use the total
ionizing rate measured by the proximity effect technique or the lower
determination from the flux decrement distribution of Ly alpha forest lines.
Assuming a faint-end LF slope of 1.58 and the SDSS estimates of the bright-end
slope and normalization, we find that the LF must break at M_B*=-24.2,-22.3,
-20.8 at z=3,4, 5 if we adopt the lower ionization rate and assume no stellar
contribution to the background. The break must occur at M_B*=-20.6,-18.7, -18.7
for the proximity effect background estimate. These values brighten by as much
as ~2 mag if high-z galaxies contribute to the background with an escape
fraction of ionizing photons consistent with recent estimates: f_e=0.16. By
comparing to faint AGN searches, we find that the typically-quoted proximity
effect estimates of the background imply an over-abundance of faint AGN (even
with f_e=1). Even adopting the lower bound on proximity effect measurements,
the stellar escape fraction must be high: f_e>0.2. Conversely, the lower flux-
decrement-derived background requires a limited stellar contribution: f_e<0.05.
Our derived LFs together with the locally-estimated black hole density suggest
that the efficiency of converting mass to light in optically-unobscured AGN is
somewhat lower than expected, <0.05. Comparison with similar estimates based on
X-ray counts suggests that more than half of all AGN are obscured in the
UV/optical. We also derive lower limits on typical AGN lifetimes and obtain
>10^7 yrs for favored cases.


title: Magnetic fields in barred galaxies I. The atlas

abstract:
  The total and polarized radio continuum emission of 20 barred galaxies was
observed with the Very Large Array (VLA) at 3, 6, 18 and 22 cm and with the
Australia Telescope Compact Array (ATCA) at 6 cm and 13 cm. Maps at 30 arcsec
angular resolution are presented here. Polarized emission (and therefore a
large-scale regular magnetic field) was detected in 17 galaxies. Most galaxies
of our sample are similar to non-barred galaxies with respect to the
radio/far-infrared flux correlation and equipartition strength of the total
magnetic field. Galaxies with highly elongated bars are not always
radio-bright. We discuss the correlation of radio properties with the aspect
ratio of the bar and other measures of the bar strength. We introduce a new
measure of the bar strength, \Lambda, related to the quadrupole moment of the
bar's gravitational potential. The radio surface brightness I of the barred
galaxies in our sample is correlated with \Lambda, I \propto \Lambda^0.4+/-0.1,
and thus is highest in galaxies with a long bar where the velocity field is
distorted by the bar over a large fraction of the disc. In these galaxies, the
pattern of the regular field is significantly different from that in non-barred
galaxies. In particular, field enhancements occur upstream of the dust lanes
where the field lines are oriented at large angles to the bar's major axis.
Polarized radio emission seems to be a good indicator of large-scale
non-axisymmetric motions.


title: Density profiles and clustering of dark halos and clusters of galaxies

abstract:
  Density profiles of cosmological virialized systems, or dark halos, have
recently attracted much attention. I first present a brief historical review of
numerical simulations to quantify the halo density profiles. Then I describe
the latest results on the universal density profile and their observational
confrontation. Finally I discuss a clustering model of those halos with
particular emphasis on the cosmological light-cone effect.


title:
A neutral hydrogen distance limit to the relativistic binary PSR
  J1141-6545

abstract:
  We have obtained an HI absorption spectrum of the relativistic binary PSR
J1141-6545 and used it to constrain the distance to the system. The spectrum
suggests that the pulsar is at, or beyond, the tangent point, estimated to be
at 3.7 kpc. PSR J1141-6545 offers the promise of stringent tests of General
Relativity (GR) by comparing its observed orbital period derivative with that
derived from other relativistic observables. At the distance of PSR J1141-6545
it should be possible to verify GR to an accuracy of just a few percent, as
contributions to the observed orbital period derivative from kinematic terms
will be a small fraction of that induced by the emission of gravitational
radiation. PSR J1141-6545 will thus make an exceptional gravitational
laboratory.


title:
Rayleigh Laser Guide Star Systems: UnISIS Bow Tie Shutter and CCD39
  Wavefront Camera

abstract:
  Laser guide star systems based on Rayleigh scattering require some means to
deal with the flash of low altitude laser light that follows immediately after
each laser pulse. These systems also need a fast shutter to isolate the high
altitude portion of the focused laser beam to make it appear star-like to the
wavefront sensor. We describe how these tasks are accomplished with UnISIS, the
Rayleigh laser guided adaptive optics system at the Mt. Wilson Observatory
2.5-m telescope. We use several methods: a 10,000 RPM rotating disk, dichroics,
a fast sweep and clear mode of the CCD readout electronics on a 10 $\mu$s
timescale, and a Pockel's cell shutter system. The Pockel's cell shutter would
be conventional in design if the laser light were naturally polarized, but the
UnISIS 351 nm laser is unpolarized. So we have designed and put into operation
a dual Pockel's cell shutter in a unique bow tie arrangement.


title: Magnetic dissipation: Spatial and temporal structure

abstract:
  A magnetically dominated plasma driven by motions on boundaries at which
magnetic field lines are anchored is forced to dissipate the work being done
upon it, no matter how small the electrical resistivity. Numerical experiments
have clarified that dissipation is achieved through the formation of a
hierarchy of electrical current sheets. The probability distribution function
of the local winding of magnetic field lines is nearly Gaussian, with a width
of the order unity. The dissipation is highly irregular in space and time, but
the average level of dissipation is well described by a scaling law that is
independent of the electrical resistivity. If the boundary driving is suspended
for a period of time the magnetic dissipation rapidly drops to insignificant
levels, leaving the magnetic field in a nearly force-free state. Renewed
boundary driving leads to a quick return to dissipation levels compatible with
the rate of boundary work, with dissipation starting much more rapidly than
when starting from idealized initial conditions with a uniform magnetic field.
Application of these concepts to the solar corona lends credibility to
realistic, three-dimensional numerical models that predict emission measures,
coronal structures, and heating rates compatible with observations.


title:
Constraints on star formation theories from the Serpens molecular cloud
  and protocluster

abstract:
  We have mapped the large-scale structure of the Serpens cloud core using
moderately optically thick (13CO(1--0) and CS(2--1)) and optically thin tracers
(C18O(1--0), C34S(2--1), and N2H+(1--0)), using the 16-element focal plane
array operating at a wavelength of 3mm at the Five College Radio Astronomy
Observatory. Our main goal was to study the large-scale distribution of the
molecular gas in the Serpens region and to understand its relation with the
denser gas in the cloud cores, previously studied at high angular resolution.
All our molecular tracers show two main gas condensations, or sub-clumps,
roughly corresponding to the North-West and South-East clusters of
submillimeter continuum sources. We also carried out a kinematical study of the
Serpens cloud. The 13CO and C18O(1--0) maps of the centroid velocity show an
increasing, smooth gradient in velocity from East to West, which we think may
be caused by a global rotation of the Serpens molecular cloud whose rotation
axis is roughly aligned in the SN direction. Although it appears that the cloud
angular momentum is not sufficient for being dynamically important in the
global evolution of the cluster, the fact that the observed molecular outflows
are roughly aligned with it may suggest a link between the large-scale angular
momentum and the circumstellar disks around individual protostars in the
cluster. We also used the normalized centroid velocity difference as an infall
indicator. We find two large regions of the map, approximately coincident with
the SE and NW sub-clumps, which are undergoing an infalling motion. Although
our evidence is not conclusive, our data appear to be in qualitative agreement
with the expectation of a slow contraction followed by a rapid and highly
efficient star formation phase in localized high density regions.


title: Seyfert 2 Galaxies with Spectropolarimetric Observations

abstract:
  We present a compilation of radio, infrared, optical and hard X-ray (2-10kev)
data for a sample of 90 Seyfert 2 galaxies(Sy2s) with spectropolarimetric
observations (41 Sy2s with detection of polarized broad lines (PBL) and 49
without PBL). Compared to Sy2s without PBL, Sy2s with PBL tend to be
earlier-type spirals, and show warmer mid-infrared color and significant excess
of emissions (including the hard X-ray(2-10kev), [O {\sc iii}]$\lambda$5007,
infrared (25 $\mu$m) and radio). Our analyses indicate that the majority of
Sy2s without PBL are those sources having less powerful AGN activities, most
likely caused by low accretion rate. It implies that the detectability of the
polarized broad emission lines in Sy2s may depend on their central AGN
activities in most cases. Based on the available data, we find no compelling
evidence for the presence of two types of Sy2s, one type of them has been
proposed to be intrinsically different from Sy2s claimed in Unification Model.


title:
Iteration Method to Derive Exact Rotation Curves from Position-Velocity
  Diagrams of Spiral Galaxies

abstract:
  We present an iteration method to derive exact rotation curves (RC) of spiral
galaxies from observed position-velocity diagrams (PVD), which comprises the
following procedure. An initial rotation curve, RC0, is adopted from an
observed PV diagram (PV0), obtained by any simple method such as the
peak-intensity method. Using this rotation curve and an observed radial
distribution of intensity (emissivity), we construct a simulated PV diagram
(PV1). The difference between a rotation curve obtained from this PV1 and the
original RC (e.g., difference between peak-intensity velocities) is used to
correct the initial RC to obtain a corrected rotation curve, RC1. This RC1 is
used to calculated another PVD (PV2) using the observed intensity distribution,
and to obtain the second iterated RC (RC2). This iteration is repeated until
PV$i$ converges to PV0, so that the differences between PV$i$ and PV0 becomes
minimum. Finally RC$i$ is adopted as the most reliable rotation curve. We apply
this method to some observed PVDs of nearby galaxies, and show that the
iteration successfully converges to give reliable rotation curves. We show that
the method is powerful to detect central massive objects.


title: Weakly mass-loaded accretion disks

abstract:
  Accretion disks with an additional mass input on the disk surface from
environment are considered in the limit of low mass input rate, i.e. when the
accretion flow remains keplerian. Due to dissipation of kinetic energy of the
infalling gas disk temperature increases, and can deviate significantly from
standard temperature of reprocessing accretion disks in their outer regions.
This increase in temperature produces an excess of emission in a
long-wavelength range of the disk spectrum. An illustrative example of the
spectrum of a weakly mass-loaded disk (the surface mass input rate Mdot_{load}
~= 1.5 times 10^{-8} Msun yr^{-1}) reasonably reproducing FIR excess observed
in CS Chameleon is given.