title: Primordial magnetic fields from cosmological phase transitions

abstract:
  We study the generation of large scale primordial magnetic fields by a
cosmological phase transition during the radiation dominated era. The setting
is a theory of N charged scalar fields coupled to an abelian gauge field, that
undergoes a phase transition at a critical temperature much larger than the
electroweak scale. The dynamics after the transition features two distinct
stages: a spinodal regime dominated by linear long-wavelength instabilities,
and a scaling stage in which the non-linearities and backreaction of the scalar
fields are dominant.This second stage describes the growth of horizon sized
domains.We implement a formulation based on the non-equilibrium Schwinger-Dyson
equations to obtain the spectrum of magnetic fields that includes the
dissipative effects of the plasma. We find that large scale magnetogenesis is
efficient during the scaling regime.Charged scalar field fluctuations with
wavelengths of the order of the Hubble radius induce large scale magnetogenesis
via loop effects. The leading processes are: pair production, pair annihilation
and low energy bremsstrahlung, these processes while forbidden in equilibrium
are allowed strongly out of equilibrium.The ratio between the energy density on
scales larger than L and that in the background radiation r(L,T)= rho_B(L,T)/
rho_{cmb}(T) is r(L,T) sim 10^{-34} at the Electroweak scale and r(L,T) sim
10^{-14} at the QCD scale for L sim 1 Mpc.The resulting spectrum is insensitive
to the magnetic diffusion length and equipartition between electric and
magnetic fields does not hold. We conjecture that a similar mechanism could be
operative after the QCD chiral phase transition.


title: The Origin of Soft X-rays in DQ Herculis

abstract:
  DQ Herculis (Nova Herculis 1934) is a deeply eclipsing cataclysmic variable
containing a magnetic white dwarf primary. The accretion disk is thought to
block our line of sight to the white dwarf at all orbital phases due to its
extreme inclination angle. Nevertheless, soft X-rays were detected from DQ Her
with ROSAT PSPC. To probe the origin of these soft X-rays, we have performed
Chandra ACIS observations. We confirm that DQ Her is an X-ray source. The bulk
of the X-rays are from a point-like source and exhibit a shallow partial
eclipse. We interpret this as due to scattering of the unseen central X-ray
source, probably in an accretion disk wind. At the same time, we observe what
appear to be weak extended X-ray features around DQ Her, which we interpret as
an X-ray emitting knot in the nova shell.


title:
Ten Million Degree Gas in M 17 and the Rosette Nebula: X-ray Flows in
  Galactic H II Regions

abstract:
  We present the first high-spatial-resolution X-ray images of two high-mass
star forming regions, the Omega Nebula (M 17) and the Rosette Nebula (NGC
2237--2246), obtained with the Chandra X-ray Observatory Advanced CCD Imaging
Spectrometer (ACIS) instrument. The massive clusters powering these H II
regions are resolved at the arcsecond level into >900 (M 17) and >300 (Rosette)
stellar sources similar to those seen in closer young stellar clusters.
However, we also detect soft diffuse X-ray emission on parsec scales that is
spatially and spectrally distinct from the point source population. The diffuse
emission has luminosity L_x ~ 3.4e33 ergs/s in M~17 with plasma energy
components at kT ~0.13 and ~0.6 keV (1.5 and 7 MK), while in Rosette it has L_x
\~6e32 ergs/s with plasma energy components at kT ~0.06 and ~0.8 keV (0.7 and 9
MK). This extended emission most likely arises from the fast O-star winds
thermalized either by wind-wind collisions or by a termination shock against
the surrounding media. We establish that only a small portion of the wind
energy and mass appears in the observed diffuse X-ray plasma; in these blister
H II regions, we suspect that most of it flows without cooling into the
low-density interstellar medium. These data provide compelling observational
evidence that strong wind shocks are present in H II regions.


title:
Alfvenic Turbulence in the Extended Solar Corona: Kinetic Effects and
  Proton Heating

abstract:
  We present a model of magnetohydrodynamic (MHD) turbulence in the extended
solar corona that contains the effects of collisionless dissipation and
anisotropic particle heating. Measurements made by UVCS/SOHO have revived
interest in the idea that ions are energized by the dissipation of ion
cyclotron resonant waves, but such high-frequency (i.e., small wavelength)
fluctuations have not been observed. A turbulent cascade is one possible way of
generating small-scale fluctuations from a pre-existing population of
low-frequency MHD waves. We model this cascade as a combination of advection
and diffusion in wavenumber space. The dominant spectral transfer occurs in the
direction perpendicular to the background magnetic field. As expected from
earlier models, this leads to a highly anisotropic fluctuation spectrum with a
rapidly decaying tail in parallel wavenumber. The wave power that decays to
high enough frequencies to become ion cyclotron resonant depends on the
relative strengths of advection and diffusion in the cascade. For the most
realistic values of these parameters, though, there is insufficient power to
heat protons and heavy ions. The dominant oblique fluctuations (with dispersion
properties of kinetic Alfven waves) undergo Landau damping, which implies
strong parallel electron heating. We discuss the probable nonlinear evolution
of the electron velocity distributions into parallel beams and discrete
phase-space holes (similar to those seen in the terrestrial magnetosphere)
which can possibly heat protons via stochastic interactions.


title: NGC7538S - a High-Mass Protostar with a Massive Rotating Disk

abstract:
  We report the detection of a massive rotating disk around the high-mass Class
0 candidate NGC 7538S. The disk is well-resolved with BIMA (HPBW =3.7") in 3.4
mm continuum and in H13CN J = 1 - 0. It is seen nearly edge on and has a size
of ~ 30,000 AU. A young, powerful outflow perpendicular to the rotating disk is
mapped in SiO J = 2 - 1 and HCO+ J = 1 - 0. The dynamical age of the outflow is
< 10,000 yr. The velocity gradient seen in H13CN is consistent with Keplerian
rotation. Assuming that the gas is gravitationally bound, the mass of the
central object is ~ 40 Msun. The mass of the continuum ``disk'' is <= 100 Msun
and has a luminosity of 10^4 Lsun. H13CN gives a mass ~ 400 Msun for the
rotating disk, and ~ 1000 Msun for the extended (20") envelope. Our
observations confirm that this is an extremely massive protostar in its
earliest stages.


title:
Theoretical Models for Producing Circularly Polarized Radiation in
  Extragalactic Radio Sources

abstract:
  We discuss the production of circular polarization in compact radio sources
both by the intrinsic mechanism and by Faraday conversion. We pay particular
attention to the magnetic field structure, considering partially ordered fiel
ds and Laing sheets, and distinguishing between uniform and unidirectional
fields. (The latter can be constrained b y flux conservation arguments.) In
most cases, Faraday conversion is the more important mechanism. Conversion
opera tes on Stokes U, which can be generated by internal Faraday rotation, or
by magnetic field fluctuations, which can therefore produce circular
polarization even in a pure pair plasma. We also show that the spectrum of
circular pola rization in an inhomogeneous jet can be quite different from that
in a uniform source, being flat or even inverted.


title:
Detection of x-rays from galaxy groups associated with the
  gravitationally lensed systems PG 1115+080 and B1422+231

abstract:
  Gravitational lenses that produce multiple images of background quasars can
be an invaluable cosmological tool. Deriving cosmological parameters, however,
requires modeling the potential of the lens itself. It has been estimated that
up to a quarter of lensing galaxies are associated with a group or cluster
which perturbs the gravitational potential. Detection of X-ray emission from
the group or cluster can be used to better model the lens. We report on the
first detection in X-rays of the group associated with the lensing system PG
1115+080 and the first X-ray image of the group associated with the system
B1422+231. We find a temperature and rest-frame luminosity of 0.8 +/- 0.1 keV
and 7 +/- 2 x 10^{42} ergs/s for PG 1115+080 and 1.0 +infty/-0.3 keV and 8 +/-
3 x 10^{42} ergs/s for B1422+231. We compare the spatial and spectral
characteristics of the X-ray emission to the properties of the group galaxies,
to lens models, and to the general properties of groups at lower redshift.


title:
Realistic Neutrino Opacities for Supernova Simulations With Correlations
  and Weak Magnetism

abstract:
  Advances in neutrino transport allow realistic neutrino interactions to be
incorporated into supernova simulations. We add tensor couplings to
relativistic RPA calculations of neutrino opacities. Our results reproduce
free-space neutrino-nucleon cross sections at low density, including weak
magnetism and recoil corrections. In addition, our opacities are
thermodynamically consistent with relativistic mean field equations of state.
We find antineutrino mean free paths that are considerably larger then those
for neutrinos. This difference depends little on density. In a supernova, this
difference could lead to an average energy of $\bar\nu_\mu$ that is larger than
that for $\nu_\mu$ by an amount that is comparable to the energy difference
between $\nu_\mu$ and $\bar\nu_e$


title: The Spectra of T Dwarfs. II. Red Optical Data

abstract:
  We present 6300--10100 {\AA} spectra for a sample of 13 T dwarfs observed
using LRIS mounted on the Keck I 10m Telescope. A variety of features are
identified and analyzed, including pressure-broadened K I and Na I doublets;
narrow Cs I and Rb I lines; weak CaH, CrH, and FeH bands; strong H$_2$O
absorption; and a possible weak CH$_4$ band. H$\alpha$ emission is detected in
three of the T dwarfs, strong in the previously reported active T dwarf 2MASS
1237+6526 and weak in SDSS 1254$-$0122 and 2MASS 1047+2124. None of the T
dwarfs exhibit Li I absorption. Guided by the evolution of optical spectral
features with near-infrared spectral type, we derive a parallel optical
classification scheme, focusing on spectral types T5 to T8, anchored to select
spectral standards. We find general agreement between optical and near-infrared
types for nearly all of the T dwarfs so far observed, including two
earlier-type T dwarfs, within our classification uncertainties ($\sim$1
subtype). These results suggest that competing gravity and temperature effects
compensate for each other over the 0.6--2.5 $\micron$ spectral region. We
identify one possible means of disentangling these effects by comparing the
strength of the K I red wing to the 9250 {\AA} H$_2$O band. One of our objects,
2MASS 0937+2931, exhibits a peculiar spectrum, with a substantial red slope and
relatively strong FeH absorption, both consequences of a metal-deficient
atmosphere. Based on its near-infrared properties and substantial space motion,
this object may be a thick disk or halo brown dwarf.


title: Fundamental Parameters of Massive Stars

abstract:
  We discuss the determination of fundamental parameters of `normal' hot,
massive OB-type stars, namely temperatures, luminosities, masses, gravities and
surface abundances. We also present methods used to derive properties of
stellar winds -- mass-loss rates and wind velocities from early-type stars.


title: Massive Stars in Transition

abstract:
  We discuss the various post-main sequence phases of massive stars, focusing
on Wolf-Rayet stars, Luminous Blue Variables, plus connections with other
early-type and late-type supergiants. End states for massive stars are also
investigated, emphasising connections between Supernovae originating from
core-collapse massive stars and Gamma Ray Bursts.


title:
Photospheric Opacity and Over-Expanded Envelopes of Asymptotic Giant
  Branch Stars

abstract:
  I suggest that the behavior of the photospheric opacity in oxygen-rich
(similar to solar abundance) upper asymptotic giant branch stars may cause
these stars to substantially expand for a few thousand years. I term this
process over-expansion. This may occur when the photospheric (effective)
temperature drops to Tp~3000K, and because the opacity sharply increases as
temperature further decreases down to Tp~2000K$. The much higher opacity
implies a much lower photospheric density, which stabilizes the envelope
structure. As mass loss proceeds, the star eventually contracts to become a
post-asymptotic giant branch star. Some possible outcomes of the over-expanded
phase are discussed: (1) The over-expanded phase may be connected to the
formation of semi-periodic concentric arcs (rings; shells); (2) The
over-expanded phase may be related to the positive correlation between the mass
loss rate and the transition to axisymmetric mass loss geometry; and (3) An
over-expanded asymptotic giant branch star, which doubles its radius, is
somewhat more likely to swallow a low mass companion.


title: Possible Post-AGB Stars

abstract:
  Radial velocities were measured for 5 potential post-AGB stars, two in the
globular cluster NGC 1851 and three in the dSph galaxy Ursa Minor. All five
potential PAGB stars were found to be radial velocity non-members.


title: Note on the Sunyaev-Zel'dovich thermal effect

abstract:
  In a previous publication we have derived an expression for the full
distorted spectrum arising when the photons of the cosmic background radiation
are absorbed and emitted by an optically thin gas. The expression simply adds
up the effects of the joint probability that an electron absorbs an incoming
photon of frequency}$\bar{\nu}${\small and emits it with a frequency}$\nu
${\small . We here show that such an expression is identical to the Kompaneets
equation describing the thermal Sunyaev-Zel'dovich effect. This clearly shows
that the two pictures, diffusion and absorption-emission are mathematically
equivalent to first order in the Compton parameter. Other consequences of this
result are also discussed.


title: Jets in GRBs: Tests and Predictions for the Structured Jet Model

abstract:
  The two leading interpretations of achromatic breaks that are observed in the
light curves of GRBs afterglow are (i) the manifestation of the edge of a jet,
which has a roughly uniform energy profile and a sharp edge and (ii) a line of
sight effect in jets with a variable energy profile. The first scenario
requires the inner engine to produce a jet with a different opening angle each
explosion, while the latter requires a standard engine. The physical structure
of the jet is a crucial factor in understanding GRB progenitors, and therefore
discriminating the two jet scenarios is particularly relevant. In the
structured jet case, specific predictions can be made for the distribution of
observed break angles $\theta_{\rm break}$, while that distribution is
arbitrary in the first scenario. We derive the theoretical distribution for the
structured jet model. Specifically, we predict the most common angle to be
about 0.12 rad, in rough agreement with the sample. If this agreement would
hold as the sample size increases, it would strengthen the case for the
standard jet hypothesis. We show that a prediction of this model is that the
average viewing angle is an increasing function of the survey sensitivity, and
in particular that a mission like {\em Swift} will find the typical viewing
angle to be about 0.3 rad. The local event rate predicted by this model is
$R_{\rm GRB}(z=0)\sim 0.5 $ Gpc$^{-3}$ yr$^{-1}$.


title:
A Laboratory Investigation of Supersonic Clumpy Flows: Experimental
  Design and Theoretical Analysis

abstract:
  We present a design for high energy density laboratory experiments studying
the interaction of hypersonic shocks with a large number of inhomogeneities.
These ``clumpy'' flows are relevant to a wide variety of astrophysical
environments including the evolution of molecular clouds, outflows from young
stars, Planetary Nebulae and Active Galactic Nuclei. The experiment consists of
a strong shock (driven by a pulsed power machine or a high intensity laser)
impinging on a region of randomly placed plastic rods. We discuss the goals of
the specific design and how they are met by specific choices of target
components. An adaptive mesh refinement hydrodynamic code is used to analyze
the design and establish a predictive baseline for the experiments. The
simulations confirm the effectiveness of the design in terms of articulating
the differences between shocks propagating through smooth and clumpy
environments. In particular, we find significant differences between the shock
propagation speeds in a clumpy medium compared to a smooth one with the same
average density. The simulation results are of general interest for foams in
both inertial confinement fusion and laboratory astrophysics studies. Our
results highlight the danger of using average properties of inhomogeneous
astrophysical environments when comparing timescales for critical processes
such as shock crossing and gravitational collapse times.


title: Gravity Indicators in the Near-Infrared Spectra of Brown Dwarfs

abstract:
  We investigate the sensitivity to temperature and gravity of the strong
absorption features in the J- and K-band spectra of substellar objects. We
compare the spectra of giants and young M dwarfs (of low gravity) to field M
and L dwarfs (of high gravity) and to model spectra from the Lyon group. We
find that low-resolution spectra of M4 - M9 stars and young brown dwarfs at R ~
350 and S/N > 70 can determine the spectral type to a precision of pm 1
subtype, using the H2O and CO bands, and can measure the surface gravity to pm
0.5 dex, using the atomic lines of KI and NaI. This result points toward the
development of photometric spectral indices to separate low-mass members from
foreground and background objects in young clusters and associations. We also
emphasize the complexity of the interpretation of the empirical quantities
(e.g., spectral types) in terms of the physical variables (e.g., temperature,
opacities) in the cool atmospheres of young brown dwarfs.


title:
Chandra Observations of Expanding Shells in the Dwarf Starburst Galaxy
  NGC 3077

abstract:
  Deep Chandra observations (53 ks, ACIS-S3) of NGC 3077, a starburst dwarf
galaxy in the M 81 triplet, resolve the X-ray emission from several
supershells. The emission is brightest in the cavities defined by expanding
shells detected previously in H alpha emission (Martin 1998). Thermal emission
models fitted to the data imply temperatures ranging from ~1.3 to 4.9 x 10^(6)
K and indicate that the strongest absorption is coincident with the densest
clouds traced by CO emission. The fitted emission measures give pressures of
P/k~10^(5-6) xi^(-0.5) f_(v)^(-0.5) K cm^(-3) (xi: metallicity of the hot gas
in solar units, f_(v): volume filling factor). Despite these high pressures,
the radial density profile of the hot gas is not as steep as that expected in a
freely expanding wind (e.g., as seen in the neighboring starburst galaxy M 82)
implying that the hot gas is still confined by the H alpha shells. The chaotic
dynamical state of NGC 3077 undermines reliable estimates of the escape
velocity. The more relevant quantity for the ultimate fate of the outflow is
probably the gas density in the rich intragroup medium. Based on the HI
distribution of NGC 3077 and a connected tidal tail we argue that the wind has
the potential to leave the gravitational well of NGC 3077 to the north but not
to the south. The total 0.3-6.0 keV X-ray luminosity is ~2-5 x 10^(39) erg
s^(-1) (depending on the selected thermal plasma model). Most (~85%) of the
X-ray luminosity in NGC 3077 comes from the hot interstellar gas; the remainder
comes from six X-ray point sources. In spite of previous claims to the
contrary, we do not find X-ray emission originating from the prominent tidal
tail near NGC 3077.


title: On the non-thermal high energy radiation of galaxy clusters

abstract:
  The origin of the nonthermal EUV and hard X-ray emission "excess" reported
from some galaxy clusters has been intensively debated over last several years.
The most favored models which refer this excess to relativistic electrons
upscattering the 2.7 K CMBR generally requires very low magnetic field,
significantly below the estimates derived from the Faraday Rotation
Measurements, unless one invokes rather nonstandard assumptions concerning the
energy and pitch angle distributions of nonthermal electrons. In this paper we
suggest a new model assuming that the "nonthermal" excess is due to synchrotron
radiation of ultrarelativistic (multi-TeV) electrons of "photonic" origin.
These electrons are continuously introduced throughout the entire intracluster
medium by very high energy (hypothetical) gamma-rays through interactions with
the diffuse extragalactic radiation fields. We present numerical calculations
for the Coma cluster, and briefly discuss implications of the model for other
galaxy clusters both in the X- and gamma-ray energy domains.


title:
An X-Ray Detection Possibility of Star-Formation-Bursting
  Proto-Elliptical Galaxies

abstract:
  A possibility to detect X-rays from star-formation burst activities in
proto-elliptical galaxies is considered. The X-ray flux of an emission due to
inverse Compton scattering of the cosmic microwave background (CMB) by high
energy electrons accelerated in SNRs is shown to increase as z increases far
beyond unity, since the local CMB flux largely increases in association with a
z-increase. The flux is estimated for the case of a very high rate of type II
supernovae at an initial star formation burst of a proto-elliptical galaxy and
is found to be detectable with a future large X-ray telescope such as intended
in the XEUS mission.


title:
Angular Momentum Transport by Internal Gravity Waves. I - Pop I Main
  Sequence Stars

abstract:
  We examine the generation of gravity waves by the surface convection zone of
low-mass main sequence stars with solar metallicity. It is found that the total
momentum luminosity in waves rises with stellar mass, up to the
quasi-disappearance of the convection zone around 6500K (corresponding to a
mass of about 1.4 Msun for solar metallicity) where the luminosity drastically
drops. We calculate the net momentum extraction associated with these waves and
explain how the calculated mass dependence helps resolve the enigma of the Li
dip in terms of rotational mixing, forming a coherent picture of mixing in all
main sequence stars.


title:
Trade-off between angular resolution and straylight contamination in CMB
  anisotropy experiments. I. Pattern simulations

abstract:
  The study of Cosmic Microwave Background (CMB) anisotropies represents one of
the most powerful Cosmological tools. After the great success of the two NASA's
satellite missions COBE and WMAP, Planck represents the third generation of
mm-wave instruments designed for space observations of CMB anisotropies within
the new Cosmic Vision 2020 ESA Science Programme. The Planck survey will cover
the whole sky with unprecedented sensitivity, angular resolution and frequency
coverage, using two instruments that share the focal region of a 1.5 m off-axis
dual reflector telescope: the Low Frequency Instrument (LFI) and the High
Frequency Instrument (HFI). Within the LFI optical interfaces optimisation
activity, two concurrent demands have to be satisfied: the best angular
resolution (which impacts the ability to reconstruct the anisotropy power
spectrum of the CMB anisotropies at high multipoles) and the lowest level of
straylight contamination (that may be one of the most critical sources of
systematic effects). We present the results of the optical simulations aimed to
establish the trade-off between angular resolution and straylight rejection,
carried out for the 100 GHz channel of Planck Low Frequency Instrument. Antenna
pattern of different models of dual profiled corrugated conical feed horns have
been simulated using advanced simulation techniques, considering the whole
spacecraft geometry in order to obtain truthful sidelobe predictions. Optical
computation accuracy necessary to provide strong straylight evaluation in
reasonable computational time is shown and the inadequacy of a Gaussian feed
model in realistic far pattern predictions is demonstrated. This paper is based
on LFI activities.


title:
Is the Long-Term Persistency of Circular Polarisation due to the
  Constant Helicity of the Magnetic Fields in Rotating Quasar Engines?

abstract:
  Many compact radio sources like quasars, blazars, radio galaxies, and
micro-quasars emit circular polarisation (CP) with surprising temporal
persistent handedness. We propose that the CP is caused by Faraday conversion
of linear polarisation synchrotron light which propagates along a line-of-sight
through helical magnetic fields. Jet outflows from radio galaxies should have
the required magnetic helicity in the emission region due to the magnetic
torque of the accretion disc. Also advection dominated accretion flow (ADAF)
should contain magnetic fields with the same helicity. However, a jet region
seems to be the more plausible origin of CP. The proposed scenario requires
Faraday rotation (FR) to be insignificant in the emission region. The proposed
mechanism works in electron-positron e+/e- as well as electron-proton e/p
plasma. In the latter case, the emission region should consist of individual
flux tubes with independent polarities in order to suppress too strong FR - as
it was already proposed for FR based CP generation models. The predominant CP
is expected to mostly counter-rotate (rotation is measured here in
sky-projection) with respect to the central engine in all cases (jet or ADAF,
e+/e- or e/p plasma) and therefore allows to measure the sense of rotation of
quasar engines. The engine of SgrA* is expected - in this scenario - to rotate
clockwise and therefore counter-Galactic, as do the young hot stars in its
vicinity, which are thought to feed SgrA* by their winds. Generally, sources
with Stokes-V<0 (V>0) are expected to rotate clockwise


title:
Simultaneous UV and X-ray Spectroscopy of the Seyfert 1 Galaxy NGC 5548.
  I. Physical Conditions in the UV Absorbers

abstract:
  We present new UV spectra of the nucleus of the Seyfert 1 galaxy NGC 5548,
which we obtained with the Space Telescope Imaging Spectrograph at high
spectral resolution, in conjunction with simultaneous Chandra X-ray Observatory
spectra. Taking advantage of the low UV continuum and broad emission-line
fluxes, we have determined that the deepest UV absorption component covers at
least a portion of the inner, high-ionization narrow-line region (NLR). We find
nonunity covering factors in the cores of several kinematic components, which
increase the column density measurements of N V and C IV by factors of 1.2 to
1.9 over the full-covering case; however, the revised columns have only a minor
effect on the parameters derived from our photoionization models. For the first
time, we have simultaneous N V and C IV columns for component 1 (at -1040
km/s), and find that this component cannot be an X-ray warm absorber, contrary
to our previous claim based on nonsimultaneous observations. We find that
models of the absorbers based on solar abundances severely overpredict the O VI
columns previously obtained with the Far Ultraviolet Spectrograph, and present
arguments that this is not likely due to variability. However, models that
include either enhanced nitrogen (twice solar) or dust, with strong depletion
of carbon in either case, are successful in matching all of the observed ionic
columns. These models result in substantially lower ionization parameters and
total column densities compared to dust-free solar-abundance models, and
produce little O VII or O VIII, indicating that none of the UV absorbers are
X-ray warm absorbers.


title: John Clifford Barton: Obituary and Bibliography

abstract:
  John Barton was one of the experimental founders of particle astrophysics,
working in deep underground locations all over the world. This note combines
the obituary published in The Independent with a complete list of his
publications.


title: KBO binaries: are they really primordial ?

abstract:
  Given the large orbital separation and high satellite-to-primary mass ratio
of all known Kuiper Belt Object (KBO) binaries, it is important to reassess
their stability as bound pairs with respect to several disruptive mechanisms.
Besides the classical shattering and dispersing of the secondary due to a
high-velocity impact, we considered the possibility that the secondary is
kicked off its orbit by a direct collision of a small impactor, or that it is
gravitationally perturbed due to the close approach of a somewhat larger TNO.
  Depending on the values for the size/mass/separation of the binaries that we
used, 2 or 3 of the 8 pairs can be dispersed in a timescale shorter than the
age of the solar system in the current rarefied environment. A contemporary
formation scenario could explain why we still observe these binaries, but no
convincing mechanism has been proposed to date. The primordial formation
scenarios, which seem to be the only viable ones, must be revised to increase
the formation efficiency in order to account for this high dispersal rate.
Objects like the large-separatioKBO binary n2001 QW$_{322}$ must have been
initially an order of magnitude more numerous.
  If the KBO binaries are indeed primordial, then we show that the mass
depletion of the Kuiper belt cannot result from collisional grinding, but must
rather be due to dynamical ejection.


title:
The Optical Counterpart to SAX J1808.4-3658 in Quiescence: Evidence of
  an Active Radio Pulsar?

abstract:
  The optical counterpart of the binary millisecond X-ray pulsar SAX
J1808.4-3658 during quiescence was detected at V = 21.5 mag by Homer et al.
(2001). This star shows a 6% semi-amplitude sinusoidal modulation of its flux
at the orbital period of the system. It was proposed that the modulation arises
from X-ray irradiation of the intrinsically faint companion by a remnant
accretion disk, and that the bulk of the optical emission arises from viscous
dissipation in the disk. The serious difficulty in this scenario lies in the
estimate of the irradiating luminosity required to match the observational
data, that is a factor 10-50 higher than the quiescent X-ray luminosity of this
source. To overcome this problem, we propose an alternative scenario, in which
the irradiation is due to the release of rotational energy by the fast spinning
neutron star, switched on, as magneto-dipole rotator (radio pulsar), during
quiescence. Our computations indicate that the optical magnitudes are fully
consistent with this hypothesis. In this case the observed optical luminosity
may be the first evidence that a radio pulsar is active in this system in
quiescence, a key phase for understanding the evolution of this class of
objects.


title: Full-Sky Search for Ultra High Energy Cosmic Ray Anisotropies

abstract:
  Using data from the SUGAR and the AGASA experiments taken during a 10 yr
period with nearly uniform exposure to the entire sky, we search for
large-scale anisotropy patterns in the arrival directions of cosmic rays with
energies > 10^{19.6} eV. We determine the angular power spectrum from an
expansion in spherical harmonics for modes out to \ell=5. Based on available
statistics, we find no significant deviation from isotropy. We compare the
rather modest results which can be extracted from existing data samples with
the results that should be forthcoming as new full-sky observatories begin
operation.


title: Exoplanet detection capability of the COROT space mission

abstract:
  COROT will be the first high precision photometric satellite to be launched
with the aim of detecting exoplanets by the transit method. In this paper, we
present the simulations we have carried out in order to assess the detection
capability of COROT. Using the model of stellar population synthesis of the
Galaxy developed at Besancon Observatory (Robin & Creze 1986) and a simple
cross-correlation technique (Borde et al. 2001), we find that COROT has the
capacity to detect numerous exoplanets, not only Jupiter and Uranus-class ones,
but also hot terrestrial planets, if they exist. We show that small exoplanets
should be mainly gathered around 14-15th magnitude K2-M2 dwarfs and giant
exoplanets around 15-16th magnitude F7-G2 dwarfs. We study the effect of
crowding and the impact of a high stellar variability noise that both reduce
the detection capability of the instrument.


title: The three dimensional structure of the giant stellar stream in Andromeda

abstract:
  The wide-field CCD camera at the CFH telescope was used to survey the giant
stellar stream in the Andromeda galaxy, resolving stars down the red giant
branch in M31 to I ~ 25, a magnitude deeper than our previous INT survey of
this galaxy and extending 1 degree further out. The stream is seen to extend
out to the south-east of M31 as far as we have surveyed (some 4.5 degrees,
corresponding to a projected distance ~60 kpc). It is a linear structure in
projection, and the eastern edge of the stream presents a sharp boundary in
star counts suggesting that it remains a coherent structure. By analysing the
luminosity function of the metal rich component of the stream we find that, at
the furthest extent of our survey, the stream is 100 kpc further away along the
line of sight than M31. It can then be traced to a point on the north-western
side of the galaxy where it is some 30 kpc in front of M31, at which point the
stream turns away from our survey area.


title: Peculiar spectral and power spectral behaviour of the LMXB GX 13+1

abstract:
  We present results of an analysis of all 480 ks of Rossi X-ray Timing
Explorer Proportional Counter Array data obtained from 17 May 1998 to 11
October 1998 on the luminous low mass X-ray binary GX 13+1. We analysed the
spectral properties in colour-colour diagrams (CDs) and hardness-intensity
diagrams (HIDs) and fitted the power spectra with a multi-Lorentzian model. GX
13+1 traces out a curved track in the CDs on a time scale of hours, which is
very reminiscent of a standard atoll track containing an island, and lower and
upper banana branch. However, both count rate and power spectral properties
vary along this track in a very unusual way, not seen in any other atoll or Z
source. The count rate, which varied by a factor of ~1.6, along a given track
first decreases and then increases, causing the motion through the HIDs to be
in the opposite sense to that in the CD, contrary to all other Z and atoll
sources. Along a CD track, the very low frequency noise uniquely decreases in
amplitude from ~5 to ~2% (rms). The high frequency noise amplitude decreases
from ~4% to less than 1% and its characteristic frequency decreases from ~10 to
\~5 Hz. The 57-69 Hz quasi-periodic oscillation (QPO) found earlier is also
detected, and no kHz QPOs are found. In addition the entire track shows secular
motion on a time scale of about a week. The average count rate as well as the
amplitude of the very low frequency noise correlate with this secular motion.
We discuss a possible explanation for the peculiar properties of GX 13+1 in
terms of an unusual orientation or strength of a relativistic jet.


title:
Line Intensities and Molecular Opacities of the FeH
  $F^4\Delta_i-X^4\Delta_i$ Transition

abstract:
  We calculate new line lists and opacities for the $F^4\Delta_i-X^4\Delta_i$
transition of FeH. The 0-0 band of this transition is responsible for the
Wing-Ford band seen in M-type stars, sunspots and brown dwarfs. The new
Einstein A values for each line are based on a high level ab initio calculation
of the electronic transition dipole moment. The necessary rotational line
strength factors (H\"onl-London factors) are derived for both the Hund's case
(a) and (b) coupling limits. A new set of spectroscopic constants were derived
from the existing FeH term values for v=0, 1 and 2 levels of the $X$ and $F$
states. Using these constants extrapolated term values were generated for v=3
and 4 and for $J$ values up to 50.5. The line lists (including Einstein A
values) for the 25 vibrational bands with v$\leq$4 were generated using a
merged list of experimental and extrapolated term values. The FeH line lists
were use to compute the molecular opacities for a range of temperatures and
pressures encountered in L and M dwarf atmospheres. Good agreement was found
between the computed and observed spectral energy distribution of the L5 dwarf
2MASS-1507.


title: The Massive Triple Star System HD 16429 A

abstract:
  HD 16429 A is a triple star system consisting of a single-lined spectroscopic
binary and a widely separated third component, previously identified via
speckle interferometry. Here I present the first orbital elements for the
unblended spectroscopic binary as well as estimates of the spectral types and
relative flux contributions for each visible component based upon a Doppler
tomographic reconstruction of their spectra. There are several stars around HD
16429 A, including the nearby Be X-ray binary and microquasar LS I +61 303,
which all probably belong to a sub-cluster within the Cas OB6 association.


title:
Cosmological Shock Waves and Their Role in the Large Scale Structure of
  the Universe

abstract:
  We study the properties of cosmological shock waves identified in
high-resolution, N-body/hydrodynamic simulations of a $\Lambda$CDM universe and
their role on thermalization of gas and acceleration of nonthermal, cosmic ray
(CR) particles. External shocks form around sheets, filaments and knots of mass
distribution when the gas in void regions accretes onto them. Within those
nonlinear structures, internal shocks are produced by infall of previously
shocked gas to filaments and knots, and during subclump mergers, as well as by
chaotic flow motions. Due to the low temperature of the accreting gas, the Mach
number of external shocks is high, extending up to $M\sim 100$ or higher. In
contrast, internal shocks have mostly low Mach numbers. For all shocks of
$M\ge1.5$ the mean distance between shock surfaces over the entire computed
volume is $\sim4 h^{-1}$ Mpc at present, or $\sim 1 h^{-1}$ Mpc for internal
shocks within nonlinear structures. Identified external shocks are more
extensive, with their surface area $\sim2$ times larger than that of identified
internal shocks at present. However, especially because of higher preshock
densities, but also due to higher shock speeds, internal shocks dissipate more
energy. Hence, the internal shocks are mainly responsible for gas
thermalization as well as CR acceleration. In fact, internal shocks with $2 \la
M \la 4$ contribute $\sim 1/2$ of the total dissipation. Using a nonlinear
diffusive shock acceleration model for CR protons, we estimate the ratio of CR
energy to gas thermal energy dissipated at cosmological shock waves to be
$\sim1/2$ through the history of the universe. Our result supports scenarios in
which the intracluster medium contains energetically significant populations of
CRs.


title:
Numerical Study of Compressible Magnetohydrodynamic Turbulence in Two
  Dimensions

abstract:
  We have studied forced turbulence of compressible magnetohydrodynamic (MHD)
flows through two-dimensional simulations with different numerical resolutions.
First, hydrodynamic turbulence with Mach number $<M_s >_{\rm init} \equiv < v
>_{\rm rms}/ c_s = 1$ and density compression ${< \delta\rho / \rho >}_{\rm
rms} \simeq 0.45$ was generated by enforcing a random force. Then, initial,
uniform magnetic fields of various strengths were added with Alfv\'enic Mach
number $<M_A >_{\rm init} \equiv < v >_{\rm rms} / c_{A, {\rm init}} \gg 1$. An
isothermal equation of state was employed, and no explicit dissipation was
included. After the MHD turbulence is saturated, the resulting flows are
categorized as very weak field (VWF), weak field (WF), and strong field (SF)
classes, which have $<M_A > \equiv < v >_{\rm rms} / < c_A >_{\rm rms} \gg 1$,
$<M_A > > 1$, and $<M_A > \sim 1$, respectively. Not only in the SF regime but
also in the WF regime, turbulent transport is suppressed by the magnetic field.
In the SF cases, the energy power spectra in the inertial range, although no
longer power-law, exhibit a range with slopes close to $\sim1.5$, hinting the
Iroshnikov-Kraichnan spectrum. Our simulations were able to produce the SF
class behaviors only with high resolution of at least $1024^2$ grid cells. The
specific requirements for the simulation of the SF class should depend on the
code (and the numerical scheme) as well as the initial setup, but our results
do indicate that very high resolution would be required for converged results
in simulation studies of MHD turbulence.


title: n-point Gravitational Lenses with 5(n-1) Images

abstract:
  It has been conjectured (astro-ph/0103463) that a gravitational lens
consisting of n point masses can not produce more than 5(n-1) images as is
known to be the case for n = 2 and 3. The reasoning is based on the number of
finite limit points 2(n-1) which we believe to set the maximum number of
positive images and the fact that the number of negative images exceeds the
number of positive images by (n-1). It has been known that an n-point lens
system (n\ge 3) can produce (3n+1) images and so has been an explicit lens
configuration with (3n+1) images. We start with the well-known n-point lens
configuration that produces (3n+1) images and produce (2n-1) extra images by
adding a small (n+1)-th mass so that the resulting (n+1)-point lens
configuration has (2n) discrete limit points and produces 5n images of a
source. It still remains to confirm in abstraction that the maximum number of
positive image domains of a caustic domain is bounded by the number of the
limit points.


title: Relic Radio Bubbles and Cluster Cooling Flows

abstract:
  Recent suggestions that buoyant radio emitting cavities in the intracluster
medium can cause significant reheating of cooling flows are re-examined when
the effects of the intracluster magnetic field are included. Expansion of the
cavity creates a tangential magnetic field in the ICM around the radio source,
and this field can suppress instabilities that mix the ICM and the radio
source. The onset of instability can be delayed for ~100 million years, and
calculation of the actual reheating time shows that this may not occur until
about 1Gy after creation of the cavity. These results may explain why the relic
radio bubbles are still intact at such late times, and it may imply that the
role of radio sources in reheating the ICM should be re-examined. In addition,
the existence of relic radio cavities may also imply that the particle content
of radio source lobes is primarily electrons and protons rather than electrons
and positrons.


title:
A Multi-Frequency Radio Study of Supernova Remnant G292.0+1.8 and its
  Pulsar Wind Nebula

abstract:
  (Abridged) We present a detailed radio study of the young supernova remnant
(SNR) G292.0+1.8 and its associated pulsar PSR J1124-5916, using the Australia
Telescope Compact Array at observing wavelengths of 20, 13 and 6 cm. We find
that the radio morphology of the source consists of three main components: a
polarized flat-spectrum central core coincident with the pulsar J1124-5916, a
surrounding circular steep-spectrum plateau with sharp outer edges and,
superimposed on the plateau, a series of radial filaments with spectra
significantly flatter than their surroundings. HI absorption argues for a lower
limit on the distance to the system of 6 kpc.
  The core clearly corresponds to radio emission from a pulsar wind nebula
powered by PSR J1124-5916, while the plateau represents the surrounding SNR
shell. The plateau's sharp outer rim delineates the SNR's forward shock, while
the thickness of the plateau region demonstrates that the forward and reverse
shocks are well-separated. Assuming a distance of 6 kpc and an age for the
source of 2500 yr, we infer an expansion velocity for the SNR of ~1200 km/s and
an ambient density ~0.9 cm^-3. We interpret the flat-spectrum radial filaments
superimposed on the steeper-spectrum plateau as Rayleigh-Taylor unstable
regions between the forward and reverse shocks of the SNR. The flat radio
spectrum seen for these features results from efficient second-order Fermi
acceleration in strongly amplified magnetic fields.


title:
Detailed comparison of the structures and kinematics of simulated and
  observed barred galaxies

abstract:
  We examine the observable properties of simulated barred galaxies including
radial mass profiles, edge-on structure and kinematics, bar lengths and pattern
speed evolution for detailed comparison to real systems. We have run several
simulations in which bars are created through inherent instabilities in
self-consistent simulations of a realistic disc+halo galaxy model with a
disc-dominated, flat rotation curve. These simulations were run at high (N=20M
particles) and low (N=500K) resolution to test numerical convergence. We
determine the pattern speeds in simulations directly from the phase angle of
the bar versus time and the Tremaine-Weinberg method. Fundamental dynamics do
not change between the high and low resolution, suggesting that convergence has
been reached in this case. We find the higher resolution is needed to simulate
structural and kinematic properties accurately. The edge-on view of the
higher-resolution system clearly shows the bending instability and formation of
a peanut-shaped bulge. We determined bar lengths by different means to
determine the simulated bar is fast, with a corotation to bar length ratio
under 1.5. Simulated bars in these models form with pattern speeds slower than
those observed and slow down during their evolution. Dynamical friction between
the bar and dark halo is responsible for this deceleration, as revealed by the
transfer of angular momentum between the disc and the halo. However, even
though the pattern speed is reduced at later times, the instantaneous scale
length of the disc has grown sufficiently for the bar motion to agree with many
observations. By using a different model and simulation technique than other
authors, we are able to compare the robustness of these methods.


title:
A Systematic Study of X-Ray Flares from Low-Mass Young Stellar Objects
  in the Rho Ophiuchi Star-Forming Region with Chandra

abstract:
  We report on the results of a systematic study of X-ray flares from low-mass
young stellar objects, using Chandra observations of the main region of the Rho
Oph. From 195 X-ray sources, including class I-III sources and some young brown
dwarfs, we detected a total of 71 X-ray flares. Most of the flares have the
typical profile of solar and stellar flares, fast rise and slow decay. We
derived the time-averaged temperature (kT), luminosity (L_X), rise and decay
timescales (tau_r and tau_d) of the flares, finding that (1) class I-II sources
tend to have a high kT, (2) the distribution of L_X during flares is nearly the
same for all classes, and (3) positive and negative log-linear correlations are
found between tau_r and tau_d, and kT and tau_r. In order to explain these
relations, we used the framework of magnetic reconnection model to formulate
the observational parameters as a function of the half-length of the
reconnected magnetic loop (L) and magnetic field strength (B). The estimated L
is comparable to the typical stellar radius of these objects (10^{10-11} cm),
which indicates that the observed flares are triggered by solar-type loops,
rather than larger ones (10^{12} cm) connecting the star with its inner
accretion disk. The higher kT observed for class I sources may be explained by
a higher magnetic field strength (about 500 G) than for class II-III sources
(200-300 G).


title: Unidentified Infrared Bands in the Interstellar Medium across the Galaxy

abstract:
  We present a set of 6-12 micron ISOPHOT-S spectra of the general interstellar
medium of the Milky Way. This part of the spectrum is dominated by a series of
strong, wide emission features commonly called the Unidentified Infrared Bands.
The sampled area covers the inner Milky Way from l = -60 degr to +60 degr with
a ten-degree step in galactic longitude and nominal latitudes 0,+-1 degr. For
each grid position the actual observed direction was selected from IRAS 100
micron maps to minimize contamination by point sources and molecular clouds.
All spectra were found to display the same spectral features. Band ratios are
independent of band strength and Galactic coordinates. A comparison of total
observed flux in band features and IRAS 100 micron emission, a tracer for large
interstellar dust grains, shows high correlation at large as well as small
1-arcmin scales. This implies a strong connection between large dust grains and
the elusive band carriers; the evolutionary history and heating energy source
of these populations must be strongly linked. The average mid-infrared spectrum
of the Milky Way is found to be similar to the average spectrum of spiral
galaxy NGC 891 and the spectra of other spirals. The common spectrum can
therefore be used as a template for the 6-12 micron emission of late-type
spiral galaxies. Finally, we show that interstellar extinction only weakly
influences the observed features even at lambda = 10 microns, where the
silicate absorption feature is strongest.


title:
GaBoDS: The Garching-Bonn Deep Survey -- I. Anatomy of galaxy clusters
  in the background of NGC 300

abstract:
  The Garching-Bonn Deep Survey (GaBoDS) is a virtual 12 square degree cosmic
shear and cluster lensing survey, conducted with the WFI@2.2m MPG/ESO telescope
at La Silla. It consists of shallow, medium and deep random fields taken in
R-band in subarcsecond seeing conditions at high galactic latitude. A
substantial amount of the data was taken from the ESO archive, by means of a
dedicated ASTROVIRTEL program.
  In the present work we describe the main characteristics and scientific goals
of GaBoDS. Our strategy for mining the ESO data archive is introduced, and we
comment on the Wide Field Imager data reduction as well. In the second half of
the paper we report on clusters of galaxies found in the background of NGC 300,
a random archival field. We use weak gravitational lensing and the red cluster
sequence method for the selection of these objects. Two of the clusters found
were previously known and already confirmed by spectroscopy. Based on the
available data we show that there is significant evidence for substructure in
one of the clusters, and an increasing fraction of blue galaxies towards larger
cluster radii. Two other mass peaks detected by our weak lensing technique
coincide with red clumps of galaxies. We estimate their redshifts and masses.


title:
An Optical and Near Infrared Search for Brown Dwarfs in the Pleiades
  Cluster

abstract:
  We have carried out a brown dwarf search over an area of 14' x 23' near the
central portion of the Pleiades open cluster in five optical and near infrared
bands (i', Z, J, H, Ks) with 10 sigma detection limits of i' = 22.0, J = 20.0
and Ks = 18.5 mag. The surveyed area has large extinction in excess of Av = 3
in the Pleiades region. We detected four new brown dwarf candidates from the
colour-colour (J-K, i'-J) and the colour-magnitude (J, i'-K) diagrams. We
estimated their masses as 0.046 Msun down to 0.028 Msun. The least massive one
is estimated to have a mass smaller than Roque 25 or int-pl-IZ-69, and maybe
the lowest mass object found so far in the Pleiades cluster.


title: Gravitational Lensing by CDM Halos: Singular versus Nonsingular Profiles

abstract:
  The gravitational lensing properties of cosmological halos depend upon the
mass distribution within each halo. The description of halos as nonsingular,
truncated isothermal spheres, a particular solution of the isothermal
Lane-Emden equation (suitably modified for Lambda nonzero), has proved to be a
useful approximation for the halos which form from realistic initial conditions
in a CDM universe. The nonsingular TIS model reproduces many of the
quantitative features of the N-body results for CDM halos, except in the very
center, where CDM N-body halos show density profiles which vary as rho ~
r^(-alpha), alpha>1, instead of a small flat core. Possible discrepancies
between these cuspy halo predictions of the CDM N-body simulations and
observations of the inner mass profiles of dwarf and LSB disk galaxies based
upon their rotation curves and of clusters based upon strong lensing
measurements have led to a search for other diagnostics. A description of the
lensing by TIS halos would be useful in this regard, as a self-consistent model
for CDM halos in a proper cosmological context, nonsingular but otherwise
consistent with the CDM N-body results. We derive here the basic lensing
properties of individual TIS halos. For comparison, we also consider three
singular profiles: the Navarro-Frenk-White density profile, the singular
isothermal sphere, and the Schwarzschild lens. For all profiles, we compute the
critical curves and caustics, the image separation, the magnification and
brightness ratio, the shear, the time delay, and the average shear inside the
tidal radius. This provides tools for studying the statistical properties of
lensing by TIS and other lenses in the context of a theory of cosmological
structure formation.


title: New R CrB-Type Star HadV98

abstract:
  HadV98 = CoD-22 12017 = GSC 6825.253 is a variable star discovered by Katsumi
Haseda. This object has been recently confirmed to be a new R CrB star
(Hasselbach et al. 2002), as had been originally proposed by us at the time of
the discovery alert in VSNET. We studied the light curve based on Haseda's
photographic material and ASAS-3 V-band data. There was only major fading
episode in the past decade. The fading started in 2001 May was composed of at
least two minima, and followed by a slow recovery.


title: 3C459: A highly asymmetric radio galaxy with a starburst

abstract:
  Multifrequency radio observations of the radio galaxy 3C459 using MERLIN, VLA
and the EVN, and an optical HST image using the F702W filter are presented. The
galaxy has a very asymmetric radio structure, a high infrared luminosity and a
young stellar population. The eastern component of the double-lobed structure
is brighter, much closer to the nucleus and is significantly less polarized
than the western one. This is consistent with the jet on the eastern side
interacting with dense gas, which could be due to a merged companion or dense
cloud of gas. The HST image of the galaxy presented here exhibits filamentary
structures, and is compared with the MERLIN 5-GHz radio map. EVN observations
of the prominent central component, which has a steep radio spectrum, show a
strongly curved structure suggesing a bent or helical radio jet. The radio
structure of 3C459 is compared with other highly asymmetric, Fanaroff-Riley II
radio sources, which are also good candidates for studying jet-cloud
interactions. Such sources are usually of small linear size and it is possible
that the jets are interacting with clouds of infalling gas that fuel the radio
source.


title: Messengers of the Extreme Universe

abstract:
  We give a brief overview of the highest energy messengers: very high energy
photons, neutrinos, and ultra-high energy cosmic rays. The mysterious workings
of the extreme universe should soon be unveil with new observatories now under
construction.


title: The characteristic stellar mass as a function of redshift

abstract:
  We present a model for the star formation process during the initial collapse
of dark matter haloes at redshifts z=0-30. We derive a simple expression for
the characteristic stellar mass scale during this initial burst of star
formation. In our picture, this characteristic scale reflects both the minimum
temperature to which the gas can cool (determined by the metallicity and the
temperature of the cosmic microwave background) and the pressure of overlying
baryons in the collapsing halo. This prescription reproduces both the large
mass scales found in simulations of Population III star formation and the near
solar values observed for star formation at low redshift.


title: Inflation and the Cosmic Microwave Background

abstract:
  I present a pedagogical review of inflation and the cosmic microwave
background. I describe how a short period of accelerated expansion can replace
the special initial conditions of the standard big bang model. I also describe
the development of CMBology: the study of the cosmic microwave background. This
cool (3 K) new cosmological tool is an increasingly precise rival and
complement to many other methods in the race to determine the parameters of the
Universe: its age, size, composition and detailed evolution.


title:
Propagation of light in low pressure ionised and atomic hydrogen.
  Application to astrophysics

abstract:
  The "Impulsive Stimulated Raman Scattering" (ISRS) performed using ultrashort
laser pulses shifts the light frequencies. Tried using ordinary incoherent
light, it keeps its qualitative properties except the nonlinearity due to the
power of the laser pulses. The relative frequency shifts of the "Coherent Raman
Effect on Incoherent Light" (CREIL) which is obtained do not depend on the
intensity and, in a first approximation, on the frequency of the light. As
CREIL does not blur the images and the spectra, its shifts may be confused with
Doppler shifts. ISRS and CREIL are parametric effects which do not excite the
matter, transferring energy from hot beams to cold beams; for CREIL, the cold
light is thermal radiation which is heated.
  CREIL requires low pressure gases acting as catalysts. These gases must have
Raman transitions in the radiofrequencies range: for instance H2+ or excited
atomic hydrogen in a magnetic field.
  The spectral lines resulting from a simultaneous absorption (or emission) and
CREIL have a width at least equal to the frequency shift, so that the lines of
a complex spectrum may be weakened and mixed, becoming nearly invisible. In
astrophysics, molecular hydrogen is ionised, but so quickly destroyed by
collisions that it persists only at pressures low enough to provide CREIL: Thus
it is invisible. It contributes to the "cosmological redshift" and to an
amplification of the 2.7K radiation.
  Using CREIL, the interpretation of the spectra of the quasars requires only
usual laws of physics, usual matter and usual astronomical objects: a star, an
accretion disk, satellites in a plasma of atomic hydrogen.


title:
Compact calculation of the Perihelion Precession of Mercury in General
  Relativity, the Cosmological Constant and Jacobi's Inversion problem

abstract:
  The geodesic equations resulting from the Schwarzschild gravitational metric
element are solved exactly including the contribution from the Cosmological
constant. The exact solution is given by genus 2 Siegelsche modular forms. For
zero cosmological constant the hyperelliptic curve degenerates into an elliptic
curve and the resulting geodesic is solved by the Weierstra$\ss$ Jacobi modular
form. The solution is applied to the precise calculation of the perihelion
precession of the orbit of planet Mercury around the Sun.


title: A Two-Component Model for the Light Curves of Hypernovae

abstract:
  The light curves of 'hypernovae', i.e. very energetic supernovae with $E_{51}
\equiv E/10^{51}$ergs $\gsim 5-10$ are characterized at epochs of a few months
by a phase of linear decline. Classical, one-dimensional explosion models fail
to simultaneously reproduce the light curve near peak and at the linear decline
phase. The evolution of these light curves may however be explained by a simple
model consisting of two concentric components. The outer component is
responsible for the early part of the light curve and for the broad absorption
features observed in the early spectra of hypernovae, similar to the
one-dimensional models. In addition, a very dense inner component is added,
which reproduces the linear decline phase in the observed magnitude-versus-time
relation for SNe 1998bw, 1997ef, and 2002ap. This simple approach does contain
one of the main features of jet-driven, asymmetric explosion models, namely the
presence of a dense core. Although the total masses and energies derived with
the two-component model are similar to those obtained in previous studies which
also adopted spherical symmetry, this study suggests that the ejecta are
aspherical, and thus the real energies and masses may deviate from those
derived assuming spherical symmetry. The supernovae which were modeled are
divided into two groups, according to the prominence of the inner component:
the inner component of SN 1997ef is denser and more $^{56}$Ni-rich, relative to
the outer component, than the corresponding inner components of SNe 1998bw and
2002ap. These latter objects have a similar inner-to-outer component ratio,
although they have very different global values of mass and energy.


title: Jets and Black Holes in Hypernova Explosions

abstract:
  Bipolar explosion models for hypernovae (very energetic supernovae),
associated with the black hole formation, are presented. The model features are
as follows: (1) Fe-peak elements are ejected at high velocities to reach the
surface region, while dense O-rich materials occupy the central region at low
velocities. (2) The abundance ratios (Zn, Co)/Fe are enhanced while the ratios
(Mn, Cr)/Fe are suppressed. The overall abundances are consistent with those
observed in extremely metal-poor stars formed at the very early phase of the
Galaxy, suggesting significant contribution of such explosions to the early
Galactic chemical evolution. (3) Certain relations among the optical
luminosity, the chemical composition, and the property of the central remnant
are predicted. Such relations may serve for identifying possible gravitational
wave emitters in the future.


title:
Star Cluster Formation and Evolution in Nearby Starburst Galaxies: II.
  Initial Conditions

abstract:
  We use the ages, masses and metallicities of the rich young star cluster
systems in the nearby starburst galaxies NGC 3310 and NGC 6745 to derive their
cluster formation histories and subsequent evolution. We further expand our
analysis of the systematic uncertainties involved in the use of broad-band
observations to derive these parameters by examining the effects of a priori
assumptions on the individual cluster metallicities. The age (and metallicity)
distributions of both the clusters in the circumnuclear ring in NGC 3310 and of
those outside the ring are statistically indistinguishable, but there is a
clear and significant excess of higher-mass clusters IN the ring compared to
the non-ring cluster sample; it is likely that the physical conditions in the
starburst ring may be conducive for the formation of higher-mass star clusters,
on average, than in the relatively more quiescent environment of the main
galactic disc. For the NGC 6745 cluster system we derive a median age of ~10
Myr. NGC 6745 contains a significant population of high-mass "super star
clusters", with masses in the range 6.5 <= log(M_cl/M_sun) <= 8.0. This
detection supports the scenario that such objects form preferentially in the
extreme environments of interacting galaxies. The age of the cluster
populations in both NGC 3310 and NGC 6745 is significantly lower than their
respective characteristic cluster disruption time-scales. This allows us to
obtain an independent estimate of the INITIAL cluster mass function slope,
alpha = 2.04(+- 0.23)(+0.13)(-0.43) for NGC 3310, and 1.96(+- 0.15)(+- 0.19)
for NGC 6745, respectively, for masses M_cl >= 10^5 M_sun and M_cl >= 4 x 10^5
M_sun. These mass function slopes are consistent with those of other young star
cluster systems in interacting and starburst galaxies.


title:
Ultrahigh Energy Cosmic Rays and Prompt TeV Gamma Rays from Gamma Ray
  Bursts

abstract:
  Gamma Ray Bursts (GRBs) have been proposed as one {\it possible} class of
sources of the Ultrahigh Energy Cosmic Ray (UHECR) events observed up to
energies $\gsim10^{20}\ev$. The synchrotron radiation of the highest energy
protons accelerated within the GRB source should produce gamma rays up to TeV
energies. Here we briefly discuss the implications on the energetics of the GRB
from the point of view of the detectability of the prompt TeV gamma rays of
proton-synchrotron origin in GRBs in the up-coming ICECUBE muon detector in the
south pole.


title:
Covariant analysis of Newtonian multi-fluid models for neutron stars: I
  Milne-Cartan structure and variational formulation

abstract:
  This is the first of a series of articles showing how 4 dimensionally
covariant analytical procedures developed in the context of General Relativity
can be usefully adapted for application in a purely Newtonian framework where
they provide physical insights (e.g. concerning helicity currents) that are not
so easy to obtain by the traditional approach based on a 3+1 space time
decomposition. After an introductory presentation of the relevant Milne
spacetime structure and the associated Cartan connection, the essential
principles are illustrated by application to the variational formulation of
simple barotropic perfect fluid models. This variational treatment is then
extended to conservative multiconstituent self gravitating fluid models of the
more general kind that is needed for treating the effects of superfluidity in
neutron stars.


title: Modeling peculiar velocities of dark matter halos

abstract:
  We present a simple model that accurately describes various statistical
properties of peculiar velocities of dark matter halos. We pay particular
attention to the following two effects; first, the evolution of the halo
peculiar velocity depends on the local matter density, instead of the global
density. Second, dark matter halos are biased tracers of the underlying mass
distribution, thus halos tend to be located preferentially at high density
regions. For the former, we develop an empirical model calibrated with N-body
simulations, while for the latter, we use a conventional halo bias models based
on the extended Press-Schechter model combined with an empirical log-normal
probability distribution function of the mass density distribution. We find
that compared with linear theory, the present model significantly improves the
accuracy of predictions of statistical properties of the halo peculiar velocity
field including the velocity dispersion, the probability distribution function,
and the pairwise velocity dispersion at large separations. Thus our model
predictions may be useful in analyzing future observations of the peculiar
velocities of galaxy clusters.


title: Stellar Abundances in Dwarf Irregular Galaxies

abstract:
  Dwarf irregular galaxies appear to have undergone very slow chemical
evolution since they have low nebular abundances, but have had ongoing star
formation over the past 15 Gyr. They are too distant for red giant abundance
analyses to examine the details of their chemical evolution, however the
isolated, bright blue supergiants do allow us to determine their present-day
iron abundances to compare with both stellar and nebular alpha-element results.
The [alpha/Fe] ratios in four Local Group dwarf irregular galaxies (NGC6822,
WLM, Sextans A, and GR 8) all appear to have solar ratios regardless of the
differences in their metallicities and star formation histories. Surprisingly,
WLM's stellar metallicity is three times higher than the nebular oxygen
abundance. We compare the [alpha/Fe] ratios in the dwarf irregulars to those
from recent analyses of red giant branch stars in dwarf spheroidal galaxies,
and also to damped Ly-alpha systems, and discuss these in the context of model
predictions.


title: Measuring primordial non-Gaussianity in the cosmic microwave background

abstract:
  We derive a fast way for measuring primordial non-Gaussianity in a nearly
full-sky map of the cosmic microwave background. We find a cubic combination of
sky maps combining bispectrum configurations to capture a quadratic term in
primordial fluctuations. Our method takes only N^1.5 operations rather than
N^2.5 of the bispectrum analysis (1000 times faster for l=512), retaining the
same sensitivity. A key component is a map of underlying primordial
fluctuations, which can be more sensitive to the primordial non-Gaussianity
than a temperature map. We also derive a fast and accurate statistic for
measuring non-Gaussian signals from foreground point sources. The statistic is
10^6 times faster than the full bispectrum analysis, and can be used to
estimate contamination from the sources. Our algorithm has been successfully
applied to the Wilkinson Microwave Anisotropy Probe sky maps by Komatsu et al.
(2003).


title:
Role of clusters of galaxies in the evolution of the metal budget in the
  Universe

abstract:
  Using the guidelines on SN element production provided by XMM-Newton, we
summarize the results of ASCA observations on the element abundance in groups
and clusters of galaxies. We show that while the metal production in groups
could be described by a stellar population with a standard local IMF, clusters
of galaxies require a more top-heavy IMF. We attribute an excess heavy element
production to an IMF evolution with redshift. Dating the galaxy formation in
clusters by observations of the star-formation rate, we conclude that the IMF
variations have occurred preferentially at z>~4. We further combine our
metallicity measurements with the mass function of clusters to estimate the
role of clusters in the evolution of the metal content of the Universe. We
argue that at no epoch stars are a major container of metals, unless groups of
galaxies are not representative for the star-formation. This lends further
support for the reduced (0.6 solar) mass-averaged oxygen abundance in the
stellar population.


title: The XMM-LSS survey. Survey design and first results

abstract:
  We have designed a medium deep large area X-ray survey with XMM - the XMM
Large Scale Structure survey, XMM-LSS - with the scope of extending the
cosmological tests attempted using ROSAT cluster samples to two redshift bins
between 0<z<1 while maintaining the precision of earlier studies. Two main
goals have constrained the survey design: the evolutionary study of the
cluster-cluster correlation function and of the cluster number density. The
results are promising and, so far, in accordance with our predictions as to the
survey sensitivity and cluster number density. The feasibility of the programme
is demonstrated and further X-ray coverage is awaited in order to proceed with
a truly significant statistical analysis. (Abridged)


title:
The XMM-LSS Survey. First high redshift galaxy clusters: relaxed and
  collapsing systems

abstract:
  We present five newly found galaxy clusters at z>0.6 from the XMM Large-Scale
Structure Survey (XMM-LSS). All five objects are extended X-ray sources in the
XMM images. For three of them we have sufficient spectroscopically confirmed
member galaxies that an estimate of the velocity dispersion is possible: XLSSC
001 at z=0.613 and \sigma_V=867^{+80}_{-60} km/s, XLSSC 002 at z=0.772 and
\sigma_V=524^{+267}_{-116} km/s and XLSSC 003 at z=0.839 and
\sigma_V=780^{+137}_{-75} km/s. These three clusters have X-ray bolometric
luminosities L_X \sim 1-3 \times 10^{44} erg/s and temperatures 2-4 keV, and
consequently are less massive than previously known clusters at similar
redshifts, but nevertheless they follow the low redshift scaling relations
between L_X, T and \sigma_V, within the limits of the measurement errors. One
of the clusters, XLSSC 004, is detected independently as an overdensity of
galaxies of a colour R-z'=1.4 that matches the redshift of the central galaxy
z=0.87, although it cannot unambiguously be confirmed by the spectroscopic
observations alone. The highest redshift candidate cluster pertaining to this
paper, XLSSC 005, is most likely a double cluster complex at a redshift around
unity, associated with an extended X-ray source with probable substructure.


title: Running of the Scalar Spectral Index from Inflationary Models

abstract:
  The scalar spectral index n is an important parameter describing the nature
of primordial density perturbations. Recent data, including that from the WMAP
satellite, shows some evidence that the index runs (changes as a function of
the scale k at which it is measured) from n>1 (blue) on long scales to n<1
(red) on short scales. We investigate the extent to which inflationary models
can accomodate such significant running of n. We present several methods for
constructing large classes of potentials which yield a running spectral index.
We show that within the slow-roll approximation, the fact that n-1 changes sign
from blue to red forces the slope of the potential to reach a minimum at a
similar field location. We also briefly survey the running of the index in a
wider class of inflationary models, including a subset of those with
non-minimial kinetic terms.


title: Cyclical behaviour and disc truncation in the Be/X-ray binary A0535+26

abstract:
  A0535+26 is shown to display quantised IR excess flux states, which are
interpreted as the first observational verification of the resonant truncation
scheme proposed by Okazaki and Negueruela (2001) for BeXRBs. The simultaneity
of X-ray activity with transitions between these states strongly suggests a
broad mechanism for outbursts, in which material lost from the disc during the
reduction of truncation radius is accreted by the NS. Furthermore changes
between states are shown to be governed by a 1500 day period, probably due to
precession of the Be disc, which profoundly dictates the global behaviour of
the system. Such a framework appears to be applicable to BeXRBs in general.


title: The First Detailed Look at a Brown Dwarf Disk

abstract:
  The combination of mid-infrared and recent submm/mm measurements allows us to
set up the first comprehensive spectral energy distribution (SED) of the
circumstellar material around a young Brown Dwarf. Simple arguments suggest
that the dust is distributed in the form of a disk. We compare basic models to
explore the disk parameters. The modeling shows that a flat disk geometry fits
well the observations. A flared disk explains the SED only if it has a
puffed-up inner rim and an inner gap much larger than the dust sublimation
radius. Similarities and differences with disks around T Tauri stars are
discussed.


title:
Sensitivity of the IceCube Detector to Astrophysical Sources of High
  Energy Muon Neutrinos

abstract:
  We present the results of a Monte-Carlo study of the sensitivity of the
planned IceCube detector to predicted fluxes of muon neutrinos at TeV to PeV
energies. A complete simulation of the detector and data analysis is used to
study the detector's capability to search for muon neutrinos from sources such
as active galaxies and gamma-ray bursts. We study the effective area and the
angular resolution of the detector as a function of muon energy and angle of
incidence. We present detailed calculations of the sensitivity of the detector
to both diffuse and pointlike neutrino emissions, including an assessment of
the sensitivity to neutrinos detected in coincidence with gamma-ray burst
observations. After three years of datataking, IceCube will have been able to
detect a point source flux of E^2*dN/dE = 7*10^-9 cm^-2s^-1GeV at a 5-sigma
significance, or, in the absence of a signal, place a 90% c.l. limit at a level
E^2*dN/dE = 2*10^-9 cm^-2s^-1GeV. A diffuse E-2 flux would be detectable at a
minimum strength of E^2*dN/dE = 1*10^-8 cm^-2s^-1sr^-1GeV. A gamma-ray burst
model following the formulation of Waxman and Bahcall would result in a 5-sigma
effect after the observation of 200 bursts in coincidence with satellite
observations of the gamma-rays.


title:
A Model-Independent Determination of the Expansion and Acceleration
  Rates of the Universe as a Function of Redshift and Constraints on Dark
  Energy

abstract:
  Determination of the expansion and acceleration history of the universe is
one of the fundamental goals of cosmology. Detailed measurements of these rates
as a function of redshift can provide new physical insights into the nature and
evolution of the dark energy, which apparently dominates the global dynamics of
the universe at the present epoch. We present here dimensionless coordinate
distances y(z) to twenty radio galaxies reaching out to z of about 1.8, the
redshift range currently not covered by Supernova standard candle observations.
We develop a simple numerical method for a direct determination of the
expansion and acceleration rates, E(z) and q(z), from the data, which makes no
assumptions about the underlying cosmological model or the equation of state
parameter w. This differential method is in contrast to the traditional
cosmological tests, where particular model equations are integrated and then
compared with the observations. The new model-independent method is applied to
currently available Supernova data and the data on radio galaxies presented
here. We derive the expansion rate of the universe as a function of redshift,
E(z), and for the first time obtain a direct estimate of the acceleration rate
of the universe as a function of redshift, q(z), in a way that is independent
of assumptions regarding the dark energy and its redshift evolution. The
current observations indicate that the universe transitions from acceleration
to deceleration at a redshift greater than 0.3, with a best fit estimate of
about 0.45; this transition redshift and our determinations of E(z) are broadly
in agreement with the currently popular Friedmann-Lemaitre cosmology with Omega
= 0.3, and Lambda = 0.7, even though no model assumptions are made in deriving
the fits for E(z) and q(z).


title: Chaos and chaotic phase mixing in cuspy triaxial potentials

abstract:
  This paper investigates chaos and chaotic phase mixing in triaxial Dehnen
potentials which have been proposed to describe realistic ellipticals. Earlier
work is extended by exploring the effects of (1) variable axis ratios, (2)
`graininess' associated with stars and bound substructures, idealised as
friction and white noise, and (3) large-scale organised motions presumed to
induce near-random forces idealised as coloured noise with finite
autocorrelation time. Three important conclusions are: (1) not all the chaos
can be attributed to the cusp; (2) significant chaos can persist even for
axisymmetric systems; and (3) introducing a supermassive black hole can
increase both the relative number of chaotic orbits and the size of the largest
Lyapunov exponent. Sans perturbations, distribution functions associated with
initially localised chaotic ensembles evolve exponentially towards a nearly
time-independent form at a rate L that correlates with the finite time Lyapunov
exponents associated with the evolving orbits. Perturbations accelerate phase
space transport by increasing the rate of phase mixing in a given phase space
region and by facilitating diffusion along the Arnold web that connects
different phase space regions, thus facilitating an approach towards a true
equilibrium. The details of the perturbation appear unimportant. All that
matters are the amplitude and the autocorrelation time, upon which there is a
weak logarithmic dependence. Even comparatively weak perturbations can increase
L by a factor of three or more, a fact that has potentially significant
implications for violent relaxation.


title: Formation of globular clusters in hierarchical cosmology

abstract:
  We study the formation of globular clusters (GCs) in a Milky Way-size galaxy
using a high-resolution cosmological simulation. The clusters in our model form
in the dense cores of supergiant molecular clouds in the gaseous disks of
high-redshift galaxies. The properties of clusters are estimated using a
physically-motivated subgrid model of the isothermal cloud collapse. The first
clusters in the simulation form at z ~ 12, while we conjecture that the best
conditions for GC formation appear to be at z ~ 3-5. Most clusters form in the
progenitor galaxies of the virial mass >10^9 Msun and the total mass of the
cluster population is strongly correlated with the mass of its host galaxy with
a fraction ~2x10^-4 of the galactic baryons being in the form of GCs. In
addition, the mass of the GC population and the maximum cluster mass in a given
region strongly correlate with the local average star formation rate. We find
that the mass, size, and metallicity distributions of the cluster population
identified in the simulation are remarkably similar to the corresponding
distributions of the Milky Way globulars. We find no clear mass-metallicity or
age-metallicity correlations for the old clusters. The zero-age cluster mass
function can be approximated by a power-law, dN/dM ~ M^-alpha, with alpha ~ 2,
in agreement with the mass function of young stellar clusters in starbursting
galaxies. However, the shape of the zero-age mass function may be better
described by the high-mass tail of a lognormal distribution which peaks at
~10^3 Msun. We discuss in detail the origin, universality, and dynamical
evolution of the globular cluster mass function. Our results indicate that
globular clusters with properties similar to those of observed clusters can
form naturally within young dense gaseous disks at z >~ 3 in the LCDM
cosmology.


title: Time delay measurement of the lensed quasar HE1104-1805

abstract:
  We have measured the time delay between the two images of the gravitationally
lensed quasar HE1104-1805 by combining observations made with the Wise
Observatory 1m telescope and published observations of this system by Schechter
et al., spanning a total of five years, from 1997 to 2002. Based on a variety
of techniques, we find that the best fit time delay is -161 (+/-7)(+34 -11)
days. The 68% and 95% confidence intervals include the systematic errors due to
an observed component of uncorrelated variability between images. The delay is
shorter than predicted by simple models and may indicate a large external shear
or a large value of the Hubble parameter, h>0.75 (95% confidence). The residual
light curve between the two images shows a longterm trend of ~0.04 mag/yr,
presumably the result of microlensing by stars in the lens galaxy, but also
short timescale (~1 month) variability with a mean amplitude of about 0.07 mag.


title:
The redshift distribution of gravitational lenses revisited: Constraints
  on galaxy mass evolution

abstract:
  The redshifts of lens galaxies in known gravitational lens systems probe the
volume distribution of lensing mass. Following earlier work by Kochanek, we
re-derive the lens redshift probability distribution, allowing for mass and
number density evolution of the lensing galaxies, and apply this test to a much
enlarged sample of lens systems. From a literature survey of all known lenses,
we have selected an unbiased sample of 15 lenses with complete redshift
information. For a flat Universe and no lens evolution, we can only put an
upper limit on the cosmological constant of Omega_lambda<0.89 at the 95% CL.
Omega_lambda~0.7 and no evolution is consistent with the data. Allowing for
evolution in an Omega_m=0.3, Omega_lambda=0.7 cosmology, we find that the
best-fit evolution in sigma* (i.e., the characteristic velocity dispersion in a
Schechter-like function) of early-type galaxies, in the redshift range z~0 to
1, is d[log sigma*(z)]/dz=-0.10+/-0.06. This is consistent with no evolution
and implies that, at 95% CL, sigma* of early-type galaxies at z~1 was at least
63% of its current value. Alternatively, if there is no mass evolution, a
present-day value of sigma*>175 km/s for elliptical galaxies is required (95%
CL).


title: A Merged Catalog of Clusters of Galaxies from Early SDSS Data

abstract:
  We present a catalog of 799 clusters of galaxies in the redshift range z_est
= 0.05 - 0.3 selected from ~400 deg^2 of early SDSS commissioning data along
the celestial equator. The catalog is based on merging two independent
selection methods -- a color-magnitude red-sequence maxBCG technique (B), and a
Hybrid Matched-Filter method (H). The BH catalog includes clusters with
richness \Lambda >= 40 (Matched-Filter) and N_gal >= 13 (maxBCG), corresponding
to typical velocity dispersion of \sigma_v >~ 400 km s^{-1} and mass (within
0.6 h^{-1) Mpc radius) >~ 5*10^{13} h^{-1} M_sun. This threshold is below Abell
richness class 0 clusters. The average space density of these clusters is
2*10^{-5} h^3 Mpc^{-3}. All NORAS X-ray clusters and 53 of the 58 Abell
clusters in the survey region are detected in the catalog; the 5 additional
Abell clusters are detected below the BH catalog cuts. The cluster richness
function is determined and found to exhibit a steeply decreasing cluster
abundance with increasing richness. We derive observational scaling relations
between cluster richness and observed cluster luminosity and cluster velocity
dispersion; these scaling relations provide important physical calibrations for
the clusters. The catalog can be used for studies of individual clusters, for
comparisons with other sources such as X-ray clusters and AGNs, and, with
proper correction for the relevant selection functions, also for statistical
analyses of clusters.


title:
The Probability Distribution Function of Light in the Universe: Results
  from Hydrodynamic Simulations

abstract:
  While second and higher order correlations of the light distribution have
received extensive study, the lowest order probability distribution function
(PDF) -- the probability that a unit volume of space will emit a given amount
of light -- has received very little attention. We estimate this function with
the aid of hydrodynamic simulations of the Lambda CDM model, finding it
significantly different from the mass density PDF, and not simply related to it
by linear bias or any of the other prescriptions commonly adopted. If the
optical light PDF is, in reality, similar to what we find in the simulations,
then some measures of Omega_M based on mass-to-light ratio and the cosmic
virial theorem will have significantly underestimated Omega_M. Basically, the
problem is one of selection bias, with galaxy forming regions being
unrepresentative of the dark matter distribution in a way not described by
linear bias. Knowledge of the optical PDF and the plausible assumption of a
log-normal distribution for the matter PDF will allow one to correct for these
selection biases. We find that this correction (which amounts to 20-30%) brings
the values of Omega_M estimated by using the mass-to-light ratio and the cosmic
virial theorem to the range 0.2-0.3, in better agreement with the WMAP result
than the uncorrected estimates. In addition, the relation between mass and
light PDFs gives us insight concerning the nature of the void phenomenon. In
particular our simulation indicates that 20% of mass is distributed in voids,
which occupy 85% of volume in the universe.


title:
Numerical Simulations of the Light Propagation in the Gravitational
  Field of Moving Bodies

abstract:
  One of the most subtle points in the modern relativistic models for
microarcsecond astrometrical observations is the treatment of the influence of
translational motion of gravitating bodies on the light propagation. This paper
describes numerical simulations of the light propagation in the gravitational
field of moving gravitating bodies as well as summarizes the underlying theory.
The simulations include high-precision numerical integrations of both
post-Newtonian and post-Minkowskian differential equations of light propagation
and a detailed comparison of the results of the numerical integrations with
various available approximate analytical formulas. The simulations has been
performed both for hypothetical bodies with various parameters of trajectories
as well as for all the major bodies of the solar system using the JPL ephemeris
DE405/LE405 to calculate their motion.
  It is shown that for the accuracy of $\sim 0.2$ $\mu$as it is sufficient to
use the well-known solution for the light propagation in the field of a
motionless mass monopole and substitute in that solution the position of the
body at the moment of closest approach between the actual trajectory of the
body and the unperturbed light path (as it was first suggested by Hellings
(1986)). For a higher accuracy one should use either the post-Newtonian
solution for uniformly moving bodies (Klioner & Kopeikin, 1992) or the
post-Minkowskian solution for arbitrarily moving bodies (Kopeikin & Schaefer,
1999). For astrometric observations performed from within the solar system
these two solutions guarantee the accuracy of $\sim 0.002$ $\mu$as and are
virtually indistinguishable from each other.


title: Formation of a Black Hole in the Dark

abstract:
  We show that the black hole in the x-ray binary Cygnus X-1 was formed in situ
and did not receive an energetic trigger from a nearby supernova. The
progenitor of the black hole had an initial mass greater than 40 solar masses
and during the collapse to form the ~10 solar mass black hole of Cygnus X-1,
the upper limit for the mass that could have been suddenly ejected is ~1 solar
mass, much less than the mass ejected in a supernova. The observations suggest
that high-mass stellar black holes may form promptly, when massive stars
disappear silently.


title: Numerical Likelihood Analysis of Cosmic Ray Anisotropies

abstract:
  A numerical likelihood approach to the determination of cosmic ray
anisotropies is presented which offers many advantages over other approaches.
It allows a wide range of statistically meaningful hypotheses to be compared
even when full sky coverage is unavailable, can be readily extended in order to
include measurement errors, and makes maximum unbiased use of all available
information.


title: Mass loss and rotational CO emission from Asymptotic Giant Branch stars

abstract:
  We present submillimeter observations of rotational transitions of carbon
monoxide from J = 2 -> 1 up to 7 -> 6 for a sample of Asymptotic Giant Branch
stars and red supergiants. It is the first time that the high transitions J = 6
-> 5 and 7 -> 6 are included in such a study. With line radiative transfer
calculations, we aim to determine the mass-loss history of these stars by
fitting the CO line intensities. We find that the observed line intensities of
the high transitions, including the J = 4 -> 3 transition, are significantly
lower than the predicted values. We conclude that the physical structure of the
outflow of Asymptotic Giant Branch stars is more complex than previously
thought. In order to understand the observed line intensities and profiles, a
physical structure with a variable mass-loss rate and/or a gradient in
stochastic gas velocity is required. A case study of the AGB star WX Psc is
performed. We find that the CO line strengths may be explained by variations in
mass-loss on time scales similar to those observed in the separated arc-like
structures observed around post-AGB stars. In addition, a gradient in the
stochastic velocity may play a role. Until this has been sorted out fully, any
mass loss determinations based upon single CO lines will remain suspect.


title: SCROD: School Cosmic Ray Outreach Detector

abstract:
  We report progress on applying technologies developed for LHC-era experiments
to cosmic ray detection, using scintillating tiles with embedded
wavelength-shifting fibers and avalanche photodiode readouts as parts of a
robust, inexpensive cosmic air shower detector. We are planning to deploy such
detectors in high schools as part of an outreach effort able to search for
long-distance correlations between airshowers.


title: Solar-Type Post-T Tauri Stars in the Nearest OB Subgroups

abstract:
  I discuss results from the recent spectroscopic survey for solar-type pre-MS
stars in the Lower Centaurus-Crux (LCC) and Upper Centaurus-Lupus (UCL) OB
subgroups by Mamajek, Meyer, & Liebert (2002, AJ, 124, 1670). LCC and UCL are
subgroups of the Sco-Cen OB association, and the two nearest OB subgroups to
the Sun. In the entire survey of 110 pre-main sequence stars, there exists only
one Classical T Tauri star (PDS 66), implying that only ~1% of ~1 Msun stars
are still accreting at age 13$\pm$7 (1$\sigma$) Myr. Accounting for
observational errors, the HRD placement of the pre-MS stars is consistent with
the bulk of star-formation taking place within 5-10 Myr. In this contribution,
I estimate conservative upper limits to the intrinsic velocity dispersions of
the post-T Tauri stars in the LCC and UCL subgroups (<1.6 km/s and <2.2 km/s,
respectively; 95% CL) using Monte-Carlo simulations of Tycho-2 proper motions
for candidate subgroup members. I also demonstrate that a new OB subgroup
recently proposed to exist in Chamaeleon probably does not.


title:
The Evolution of Baryon Density Fluctuations in Multi-Component
  Cosmological Simulations

abstract:
  We critically examine how the evolution of the matter density field in
cosmological simulations is affected by details of setting up initial
conditions. We show that it is non-trivial to realise an initial distribution
of matter in N-body/hydrodynamic simulations so that the baryon and dark matter
density fluctuations and their velocities evolve consistently as theoretically
predicted. We perform a set of cosmological simulations and use them to
distinguish and verify an appropriate method for generating initial conditions.
We show that a straightforward way of applying the Zel'dovich approximation to
each component using distinct transfer functions results in an incorrect growth
of density fluctuations and that it is necessary to correct velocities at the
initial epoch. The unperturbed uniform particle distribution must be also
generated appropriately to avoid tight coupling of the baryonic and dark matter
components. We recommend using independent ``glass'' particle distributions,
using distinct transfer functions for baryons and dark matter, and taking into
account the difference in the velocity fields at the initialisation epoch. The
proposed method will be useful for studies of the evolution of the
intergalactic medium and the formation of the first cosmological objects using
numerical simulations.


title: Future Evolution of Structure in an Accelerating Universe

abstract:
  Current cosmological data indicate that our universe contains a substantial
component of dark vacuum energy that is driving the cosmos to accelerate. We
examine the immediate and longer term consequences of this dark energy (assumed
here to have a constant density). Using analytic calculations and supporting
numerical simulations, we present criteria for test bodies to remain bound to
existing structures. We show that collapsed halos become spatially isolated and
dynamically relax to a particular density profile with logarithmic slope
steeper than -3 at radii beyond r_200. The asymptotic form of the space-time
metric is then specified. We develop this scenario further by determining the
effects of the accelerating expansion on the background radiation fields and
individual particles. In an appendix, we generalize these results to include
quintessence.


title: Ordinary and Viscosity-Damped MHD Turbulence

abstract:
  We compare the properties of ordinary strong magnetohydrodynamic (MHD)
turbulence in a strongly magnetized medium with the recently discovered
viscosity-damped regime. We focus on energy spectra, anisotropy, and
intermittency. Our most surprising conclusion is that in ordinary strong MHD
turbulence the velocity and magnetic fields show different high-order structure
function scalings. Moreover this scaling depends on whether the intermittency
is viewed in a global or local system of reference. This reconciles seemingly
contradictory earlier results. On the other hand, the intermittency scaling for
viscosity-damped turbulence is very different, and difficult to understand in
terms of the usual phenomenological models for intermittency in turbulence. Our
remaining results are in reasonable agreement with expectations. First, we find
that our high resolution simulations for ordinary MHD turbulence show that the
energy spectra are {\it compatible} with a Kolmogorov spectrum, while
viscosity-damped turbulence shows a shallow $k^{-1}$ spectrum for the magnetic
fluctuations. Second, a new numerical technique confirms that ordinary MHD
turbulence exhibits Goldreich-Sridhar type anisotropy, while viscosity-damped
MHD turbulence shows extremely anisotropic eddy structures. Finally, we show
that many properties of incompressible turbulence for both the ordinary and
viscosity-damped regimes carry over to the case of compressible turbulence.


title:
Analysis of the Interaction Effects in the Southern Galaxy Pair
  Tol1238-364 and ESO381-G009

abstract:
  In the context of the connection among galaxy-galaxy interaction, starbursts
and nuclear activity, we present and discuss a quantitative morphological
analysis based on BVR images and a detailed spectroscopic investigation of two
interacting galaxies, the Seyfert 2 Tol1238-364 (IC 3639) and its companion
ESO381-G009, forming a triple system with ESO381-G006. Broad-band optical
photometry is complemented by Halpha imaging, which provides information about
the distribution of star forming regions across the galaxies. Long-slit
spectroscopic data obtained at different position angles of the slit are
employed to determine the physical conditions of circumnuclear and extranuclear
regions. A mixture of thermal and non-thermal ionizing radiation is found in
the surroundings of the nucleus of Tol1238-364 and the energy budget supports
the presence of a circumnuclear starburst.Several regions in both the galaxies
show anomalous line ratios: additional ionization by shock-heating and low
ionization of some extranuclear HII regions are suggested as possible
explanations. An analysis of the emission-line profiles reveals the presence of
a broad Halpha component in the nuclear region of Tol1238-364. Independent
estimates of the star formation rates (SFR) were obtained through
flux-calibrated Halpha-images and FIR emission in the four IRAS bands. Overall
SFR densities have been compared with the SFR densities derived from Halpha
emission in the individual regions of the galaxies sampled by long-slit
spectra. In both galaxies an enhancement of the star formation activity with
respect to isolated galaxies is revealed. The prevalence of starburst or
nuclear activity has been examined through FIR color indices. The interaction
scenario is discussed on the basis of the observed galaxy properties.