title: A Calculation of Cosmological Scale from Quantum Coherence

abstract:
  We use general arguments to examine the energy scales for which a quantum
coherent description of gravitating quantum energy units is necessary. The
cosmological dark energy density is expected to decouple from the
Friedman-Lemaitre energy density when the Friedman-Robertson-Walker scale
expansion becomes sub-luminal, at which time the usual microscopic interactions
of relativistic quantum mechanics (QED, QCD, etc) open new degrees of freedom.
The expected gravitational vacuum energy density at that scale would be
expected to freeze out due to the loss of gravitational coherence. We define
the vacuum energy which generates this cosmological constant to be that of a
zero temperature Bose condensate at this gravitational de-coherence scale.
Since the arguments presented involve primarily counting of degrees of freedom,
we expect the statistical equilibrium states of causally disconnected regions
of space to be independently identical. Thus, there is no luminal "horizon"
problem associated with the lack of causal influences between spatially
separated regions in this approach. The scale of the amplitude of fluctuations
produced during de-coherence of cosmological vacuum energy are found to evolve
to values consistent with those observed in cosmic microwave background
radiation and galactic clustering.


title:
Synthetic Spectral Analysis of the Hot Component in the S-Type Symbiotic
  Variable EG Andromeda

abstract:
  We have applied grids of NLTE high gravity model atmospheres and optically
thick accretion disk models for the first time to archival IUE and FUSE spectra
of the S-type symbiotic variable EG And taken at superior spectroscopic
conjunction when Rayleigh scattering should be minimal and the hot component is
viewed in front of the red giant. For EG And's widely accepted, published hot
component mass, orbital inclination and distance from the Hipparcos parallax,
we find that hot, high gravity, NLTE photosphere model fits to the IUE spectra
yield distances from the best-fitting models which agree with the Hipparcos
parallax distance but at temperatures substantially lower than the modified
Zanstra temperatures. NLTE fits to an archival FUSE spectrum taken at the same
orbital phase as the IUE spectra yield the same temperature as the IUE
temperature (50,000K). However, for the same hot component mass, inclination
and parallax-derived distance, accretion disk models at moderately high
inclinations, $\sim 60-75^{\circ}$ with accretion rates $\dot{M} = 1\times
10^{-8}$ to $1\times 10^{-9} M_{\sun}/yr$ for white dwarf masses $M_{wd} = 0.4
M_{\sun}$ yield distances grossly smaller than the distance from the Hipparcos
parallax. Therefore, we rule out an accretion disk as the dominant source of
the FUV flux. Our findings support a hot bare white dwarf as the dominant
source of FUV flux.


title:
The 2dF Galaxy Redshift Survey: luminosity functions by density
  environment and galaxy type

abstract:
  We use the 2dF Galaxy Redshift Survey to measure the dependence of the
bJ-band galaxy luminosity function on large-scale environment, defined by
density contrast in spheres of radius 8h-1Mpc, and on spectral type, determined
from principal component analysis. We find that the galaxy populations at both
extremes of density differ significantly from that at the mean density. The
population in voids is dominated by late types and shows, relative to the mean,
a deficit of galaxies that becomes increasingly pronounced at magnitudes
brighter than M_bJ-5log10h <-18.5. In contrast, cluster regions have a relative
excess of very bright early-type galaxies with M_bJ-5log10h < -21. Differences
in the mid to faint-end population between environments are significant: at
M_bJ-5log10h=-18 early and late-type cluster galaxies show comparable
abundances, whereas in voids the late types dominate by almost an order of
magnitude. We find that the luminosity functions measured in all density
environments, from voids to clusters, can be approximated by Schechter
functions with parameters that vary smoothly with local density, but in a
fashion which differs strikingly for early and late-type galaxies. These
observed variations, combined with our finding that the faint-end slope of the
overall luminosity function depends at most weakly on density environment, may
prove to be a significant challenge for models of galaxy formation.


title: Reverberation Mapping of Active Galactic Nuclei

abstract:
  Reverberation mapping is a proven technique that is used to measure the size
of the broad emission-line region and central black hole mass in active
galactic nuclei. More ambitious reverberation mapping programs that are well
within the capabilities of Hubble Space Telescope could allow us to determine
the nature and flow of line-emitting gas in active nuclei and to assess
accurately the systematic uncertainties in reverberation-based black hole mass
measurements.


title: Theoretical uncertainty in baryon oscillations

abstract:
  We discuss the systematic uncertainties in the recovery of dark energy
properties from the use of baryon acoustic oscillations as a standard ruler. We
demonstrate that while unknown relativistic components in the universe prior to
recombination would alter the sound speed, the inferences for dark energy from
low-redshift surveys are unchanged so long as the microwave background
anisotropies can measure the redshift of matter-radiation equality, which they
can do to sufficient accuracy. The mismeasurement of the radiation and matter
densities themselves (as opposed to their ratio) would manifest as an incorrect
prediction for the Hubble constant at low redshift. In addition, these
anomalies do produce subtle but detectable features in the microwave
anisotropies.


title: PSR 2303+30: A single system of drifting subpulses, moding and nulling

abstract:
  Analyses of multiple pulse sequences of B2303+30 reveal that this pulsar has
two distinct emission modes. One mode (B) follows a steady even-odd pattern and
is more intense. The second mode (Q) is characteristically weak, but has
intermittent driftbands with a periodicity of approximately 3 P/cycles, and
nulls much more frequently than the B mode. Both modes occur with roughly equal
frequency and their profiles have a similar single-humped form with a slight
asymmetry. Our observations and analyses strongly suggest that the subpulse
driftrates in both modes are linked in a series of cycles, which can be
modelled as relaxing oscillations in the underlying circulation rate.


title:
Assessment of a high-resolution central scheme for the solution of the
  relativistic hydrodynamics equations

abstract:
  We assess the suitability of a recent high-resolution central scheme
developed by Kurganov & Tadmor (2000) for the solution of the relativistic
hydrodynamics equations. The novelty of this approach relies on the absence of
Riemann solvers in the solution procedure. The computations we present are
performed in one and two spatial dimensions in Minkowski spacetime. Standard
numerical experiments such as shock tubes and the relativistic flat-faced step
test are performed. As an astrophysical application the article includes
two-dimensional simulations of the propagation of relativistic jets using both
Cartesian and cylindrical coordinates. The simulations reported clearly show
the capabilities of the numerical scheme to yield satisfactory results, with an
accuracy comparable to that obtained by the so-called high-resolution
shock-capturing schemes based upon Riemann solvers (Godunov-type schemes), even
well inside the ultrarelativistic regime. Such central scheme can be
straightforwardly applied to hyperbolic systems of conservation laws for which
the characteristic structure is not explicitly known, or in cases where the
exact solution of the Riemann problem is prohibitively expensive to compute
numerically. Finally, we present comparisons with results obtained using
various Godunov-type schemes as well as with those obtained using other
high-resolution central schemes which have recently been reported in the
literature.


title: The Subaru Deep Field Project: Lyman$\alpha$ Emitters at Redshift of 6.6

abstract:
  We present new results of a deep optical imaging survey using a narrowband
filter ($NB921$) centered at $\lambda =$ 9196 \AA ~ together with $B$, $V$,
$R$, $i^\prime$, and $z^\prime$ broadband filters in the sky area of the Subaru
Deep Field which has been promoted as one of legacy programs of the 8.2m Subaru
Telescope. We obtained a photometric sample of 58 Ly$\alpha$ emitter candidates
at $z \approx$ 6.5 -- 6.6 among $\sim 180$ strong $NB921$-excess ($z^\prime -
NB921 > 1.0$) objects together with a color criterion of $i^\prime - z^\prime >
1.3$. We then obtained optical spectra of 20 objects in our $NB921$-excess
sample and identified at least nine Ly$\alpha$ emitters at $z \sim 6.5$ -- 6.6
including the two emitters reported by Kodaira et al. (2003). Since our
Ly$\alpha$ emitter candidates are free from strong amplification of
gravitational lensing, we are able to discuss their observational properties
from a statistical point of view. Based on these new results, we obtain a lower
limit of the star formation rate density of $\rho_{\rm SFR} \simeq 5.5 \times
10^{-4}$ $h_{0.7}$ $M_\odot$ yr$^{-1}$ Mpc$^{-3}$ at $z \approx 6.6$, being
consistent with our previous estimate. We discuss the nature of star-formation
activity in galaxies beyond $z=6$.


title: Observational constraints on patch inflation in noncommutative spacetime

abstract:
  We study constraints on a number of patch inflationary models in
noncommutative spacetime using a compilation of recent high-precision
observational data. In particular, the four-dimensional General Relativistic
(GR) case, the Randall-Sundrum (RS) and Gauss-Bonnet (GB) braneworld scenarios
are investigated by extending previous commutative analyses to the infrared
limit of a maximally symmetric realization of the stringy uncertainty
principle. The effect of spacetime noncommutativity modifies the standard
consistency relation between the tensor spectral index and the tensor-to-scalar
ratio. We perform likelihood analyses in terms of inflationary observables
using new consistency relations and confront them with large-field inflationary
models with potential V \propto \vp^p in two classes of noncommutative
scenarios. We find a number of interesting results: (i) the quartic potential
(p=4) is rescued from marginal rejection in the class 2 GR case, and (ii) steep
inflation driven by an exponential potential (p \to \infty) is allowed in the
class 1 RS case. Spacetime noncommutativity can lead to blue-tilted scalar and
tensor spectra even for monomial potentials, thus opening up a possibility to
explain the loss of power observed in the cosmic microwave background
anisotropies. We also explore patch inflation with a Dirac-Born-Infeld tachyon
field and explicitly show that the associated likelihood analysis is equivalent
to the one in the ordinary scalar field case by using horizon-flow parameters.
It turns out that tachyon inflation is compatible with observations in all
patch cosmologies even for large p.


title:
Asteroseismology of exoplanets hosts stars : tests of internal
  metallicity

abstract:
  Exoplanets host stars present a clear metallicity excess compared to stars
without detected planets, with an average overabundance of 0.2 dex. This excess
may be primordial, in which case the stars should be overmetallic down to their
center, or it may be due to accretion in the early phases of planetary
formation, in which case the stars would be overmetallic only in their outer
layers. In the present paper, we show the differences in the internal structure
of stars, according to the chosen scenario. Namely two stars with the same
observable parameters (luminosity, effective temperature, outer chemical
composition) are completely different in their interiors according to their
past histories, which we reconstitute through the computations of their
evolutionary tracks. It may happen that stars with an initial overmetallicity
have a convective core while the stars which suffered accretion do not. We
claim that asteroseismic studies of these exoplanets host stars can give clues
about their internal structures and metallicities, which may help in
understanding planetary formation.


title: Horizontal Branch A- and B-type Stars in Globular Clusters

abstract:
  Globular clusters offer ideal laboratories to test the predictions of stellar
evolution. When doing so with spectroscopic analyses during the 1990s, however,
the parameters we derived for hot horizontal branch stars deviated
systematically from theoretical predictions. The parameters of cooler, A-type
horizontal branch stars, on the other hand, were consistent with evolutionary
theories. In 1999, two groups independently suggested that diffusion effects
might cause these deviations, which we verified subsequently. I will discuss
these observations and analyses and their consequences for interpreting
observations of hot horizontal branch stars.


title: A Micro-glitch in the Millisecond Pulsar B1821-24 in M28

abstract:
  We report on the observation of a very small glitch observed for the first
time in a millisecond pulsar, PSR B1821-24 located in the globular cluster M28.
Timing observations were mainly conducted with the Nancay radiotelescope
(France) and confirmation comes from the 140ft radiotelescope at Green Bank and
the new Green Bank Telescope data. This event is characterized by a rotation
frequency step of 3 nHz, or 10^-11 in fractional frequency change along with a
short duration limited to a few days or a week. A marginally significant
frequency derivative step was also found. This glitch follows the main
characteristics of those in the slow period pulsars, but is two orders of
magnitude smaller than the smallest ever recorded. Such an event must be very
rare for millisecond pulsars since no other glitches have been detected when
the cumulated number of years of millisecond pulsar timing observations up to
2001 is around 500 for all these objects. However, pulsar PSR B1821-24 is one
of the youngest among the old recycled ones and there is likely a correlation
between age, or a related parameter, and timing noise. While this event happens
on a much smaller scale, the required adjustment of the star to a new
equilibrium figure as it spins down is a likely common cause for all glitches.


title:
Neutrons and particularities of nucleogenesis at early stage of the
  Universe evolution

abstract:
  At the early stage of the Universe evolution, when photons and neutrinos are
no longer able to prevent nucleosynthesis, the key role is given to neutron
component of matter. Neutron component creates a certain variety of the
lightest chemical elements and disappears leaving a sufficient portion of
Helium isotopes and some tiny portions of Li and Be isotopes. Free neutrons
disappear in energetic flame of these reactions not using even a quarter of
their own lifetime. Further the Universe matter has been evolving smoothly
without free neutrons.
  The following physical principle is taken as a basis: interactions of the
most fast component in speed are considered as main and taken into account
first. Substance component that meets this requirement provides a thermodynamic
equilibrium in the system. It is obvious that fast component of the substance
is the neutrons. Other components cause slow change as compared with actions of
the main one.
  Thermodynamic description of nucleus matter is carried out in the same way as
it is made in the well-known problem of ``ionization equilibrium'' of atomic
plasma.


title:
Stability of hydrodynamical relativistic planar jets. I. Linear
  evolution and saturation of Kelvin-Helmholtz modes

abstract:
  The effects of relativistic dynamics and thermodynamics in the development of
Kelvin-Helmholtz instabilities in planar, relativistic jets along the early
phases (namely linear and saturation phases) of evolution has been studied by a
combination of linear stability analysis and high-resolution numerical
simulations for the most unstable first reflection modes in the temporal
approach. Three different values of the jet Lorentz factor (5, 10 and 20) and a
few different values of specific internal energy of the jet matter (from 0.08
to $60.0 c^2$) have been considered. Figures illustrating the evolution of the
perturbations are also shown.


title:
Physical Properties and Baryonic Content of Low-Redshift Intergalactic
  Ly-alpha and O VI Absorption Systems: The PG1116+215 Sight Line

abstract:
  We present HST and FUSE observations of the intergalactic absorption toward
PG1116+215 in the 900-3000 A spectral region. We detect 25 Ly-alpha absorbers
at rest-frame equivalent widths W_r > 30 mA, yielding (dN/dz)_Ly-alpha =
154+/-18 over an unblocked redshift path of 0.162. Two additional weak Ly-alpha
absorbers with W_r ~ 15-20 mA are also present. Eight of the Ly-alpha absorbers
have large line widths (b > 40 km/sec). The detection of narrow OVI in the
broad Ly-alpha absorber at z=0.06244 supports the idea that the Ly-alpha
profile is thermally broadened in gas with T > 10^5 K. We find dN/dz ~ 50 for
broad Ly-alpha absorbers with W_r > 30 mA and b > 40 km/sec. If the broad
Ly-alpha lines are dominated by thermal broadening in hot gas, the amount of
baryonic material in these absorbers is enormous, perhaps as much as half the
baryonic mass in the low-redshift universe. We detect OVI absorption in several
of the Ly-alpha clouds along the sight line. Two detections at z=0.13847 and
z=0.16548 are confirmed by the presence of other ions at these redshifts, while
the detections at z=0.04125, 0.05895, 0.05928, and 0.06244 are based upon the
Ly-alpha and OVI detections alone. The information available for 13
low-redshift OVI absorbers with W_r > 50 mA along 5 sight lines yields
(dN/dz)_OVI ~ 14 and Omega_b(OVI) > 0.0027/h_75, assuming a metallicity of 0.1
solar and an OVI ionization fraction < 0.2. The properties and prevalence of
low-redshift OVI absorbers suggest that they too may be a substantial baryon
repository, perhaps containing as much mass as stars and gas inside galaxies.
The redshifts of the OVI absorbers are highly correlated with the redshifts of
galaxies along the sight line, though few of the absorbers lie closer than
600/h_75 kpc to any single galaxy. [abbreviated]


title:
Astrocomp: a web service for the use of high performance computers in
  Astrophysics

abstract:
  Astrocomp is a joint project, developed by the INAF-Astrophysical Observatory
of Catania, University of Roma La Sapienza and Enea. The project has the goal
of providing the scientific community of a web-based user-friendly interface
which allows running parallel codes on a set of high-performance computing
(HPC) resources, without any need for specific knowledge about parallel
programming and Operating Systems commands. Astrocomp provides, also, computing
time on a set of parallel computing systems, available to the authorized user.
At present, the portal makes a few codes available, among which: FLY, a
cosmological code for studying three-dimensional collisionless self-gravitating
systems with periodic boundary conditions; ATD, a parallel tree-code for the
simulation of the dynamics of boundary-free collisional and collisionless
self-gravitating systems and MARA, a code for stellar light curves analysis.
Other codes are going to be added to the portal.


title: Reaction Rates Uncertainties and the Production of F19 in AGB Stars

abstract:
  We present nucleosynthesis calculations and the resulting 19F stellar yields
for a large set of models with different masses and metallicity. We find that
the production of fluorine depends on the temperature of the convective pulses,
the amount of primary 12C mixed into the envelope by third dredge up and the
extent of the partial mixing zone. Then we perform a detailed analysis of the
reaction rates involved in the production of 19F and the effects of their
uncertainties. We find that the major uncertainties are associated with the
14C(alpha,gamma)18O and the 19F(alpha,p)22Ne reaction rates. For these two
reactions we present new estimates of the rates and their uncertainties. The
importance of the partial mixing zone is reduced when using our estimate for
the 14C(alpha,gamma)18O rate. Taking into account both the uncertainties
related to the partial mixing zone and those related to nuclear reactions, the
highest values of 19F enhancements observed in AGB stars are not matched by the
models. This is a problem that will have to be revised by providing a better
understanding of the formation and nucleosynthesis in the partial mixing zone,
also in relation to reducing the uncertainties of the 14C(alpha,gamma)18O
reaction rate. At the same time the possible effect of Cool Bottom Processing
at the base of the convective envelope should be included in the computation of
AGB nucleosynthesis. This process could in principle help matching the highest
19F abundances observed by decreasing the C/O ratio at the surface of the star,
while leaving the 19F abundance unchanged.


title: The isolated elliptical NGC 4555 observed with Chandra

abstract:
  We present analysis of a Chandra observation of the elliptical galaxy NGC
4555. The galaxy lies in a very low density environment, either isolated from
all galaxies of similar mass or on the outskirts of a group. Despite this, NGC
4555 has a large gaseous halo, extending to ~60 kpc. We find the mean gas
temperature to be ~0.95 keV and the Iron abundance to be ~0.5 solar. We model
the surface brightness, temperature and abundance distribution of the halo and
use these results to estimate parameters such as the entropy and cooling time
of the gas, and the total gravitational mass of the galaxy. In contrast to
recent results showing that moderate luminosity ellipticals contain relatively
small quantities of dark matter, our results show that NGC 4555 has a massive
dark halo and large mass-to-light ratio (56.8 [+34.2,-35.8] solar at 50 kpc,
42.7 [+14.6,-21.2] solar at 5 effective radii, 1 sigma errors). We discuss this
disparity and consider possible mechanisms by which galaxies might reduce their
dark matter content.


title: The global mass function of M15

abstract:
  Data obtained with the NICMOS instrument on board the Hubble Space Telescope
(HST) have been used to determine the H-band luminosity function (LF) and mass
function (MF) of three stellar fields in the globular cluster M15, located ~7'
from the cluster centre. The data confirm that the cluster MF has a
characteristic mass of ~0.3 Msolar, as obtained by Paresce & De Marchi (2000)
for a stellar field at 4.6' from the centre. By combining the present data with
those published by other authors for various radial distances (near the centre,
at 20" and at 4.6'), we have studied the radial variation of the LF due to the
effects of mass segregation and derived the global mass function (GMF) using
the Michie-King approach. The model that simultaneously best fits the LF at
various locations, the surface brightness profile and the velocity dispersion
profile suggests that the GMF should resemble a segmented power-law with the
following indices: x ~ 0.8 for stars more massive than 0.8 Msolar, x ~ 0.9 for
0.3 - 0.8 Msolar and x ~ -2.2 at smaller masses (Salpeter's IMF would have
x=1.35). The best fitting model also suggests that the cluster mass is ~5.4
10^5 Msolar and that the mass-to-light ratio is on average M/L_V ~ 2.1, with
M/L_V ~ 3.7 in the core. A large amount of mass (~ 44 %) is found in the
cluster core in the form of stellar heavy remnants, which may be sufficient to
explain the mass segregation in M15 without invoking the presence of an
intermediate-mass black hole.


title: The composition of cosmic rays at the knee

abstract:
  The present experimental status concerning the composition of cosmic rays in
the PeV region is reviewed. The results are compared to predictions of
contemporary models for the acceleration and propagation of galactic cosmic
rays.


title: Prospects for obtaining an r-process from Gamma Ray Burst Disk Winds

abstract:
  We discuss the possibility that r-process nucleosynthesis may occur in the
winds from gamma ray burst accretion disks. This can happen if the temperature
of the disk is sufficiently high that electron antineutrinos are trapped as
well as neutrinos. This implies accretion disks with greater than a solar mass
per second accretion rate, although lower accretion rates with higher black
hole spin parameters may provide viable environments as well. Additionally, the
outflow from the disk must either have relatively low entropy, e.g. around s =
10, or the initial acceleration of the wind must be slow enough that it is
neutrino and antineutrino capture as opposed to electron and positron capture
that sets the electron fraction.


title: Unraveling the Helix Nebula: Its Structure and Knots

abstract:
  Through HST imaging of the inner part of the main-ring of the Helix Nebula
together with CTIO 4-m images of the fainter outer parts, we have an
unprecedented-quality view of the nearest bright planetary nebula. These images
have allowed determination that the main-ring of the nebula is composed of an
inner-disk of about 499\arcsec diameter (0.52 pc) surrounded by an outer-ring
(in reality a torus) of 742\arcsec diameter (0.77 pc) whose plane is highly
inclined to the plane of the disk. This outer-ring is surrounded by an
outermost-ring of 1500\arcsec (1.76 pc) diameter which is flattened on the side
colliding with the ambient interstellar medium. The inner-disk has an extended
distribution of low density gas along its rotational axis of symmetry and the
disk is optically thick to ionizing radiation, as is the outer-ring.
  Published radial velocities of the knots provides support for the
two-component structure of the main-ring of the nebula and to the idea that the
knots found there are expanding along with the nebular material from which it
recently originated. There is a change in the morphology of the knots as a
function of the distance from the local ionization front. This supports a
scenario in which the knots are formed in or near the ionization front and are
then sculpted by the stellar radiation from the central star as the ionization
front advances beyond them.


title:
Disk or Halo white dwarfs? Kinematic analysis of high proper motion
  surveys

abstract:
  We present an alternative method for the kinematic analysis of high proper
motion surveys and discuss its application to the survey of Oppenheimer et al.
(2001) for the selection of reliable halo white dwarfs (WDs). The local WD
space density we estimate is (1-2) 10^{-5}MSun/pc^{3}, which is about an order
of magnitude smaller than the value derived in Oppenheimer et al. (2001), and
is consistent with the values obtained from recent reanalyses of the same data
(e.g. Reid et al. 2001, Reyle et al. 2001, Torres et al. 2002, Salim et al.
2004). Our result, which corresponds to a fraction of 0.1%-0.2% of the local
dark matter, does not support the scenario suggested by the microlensing
experiments that ancient cool WDs could contribute significantly to the dark
halo of the Milky Way.


title: Prospects in Classical Nova Modeling and Nucleosynthesis

abstract:
  Classical novae are fascinating stellar events, at the crossroads of
astrophysics, nuclear physics and cosmochemistry. In this review, we outline
the history of nova modeling with special emphasis on recent advances and
perspectives in multidimensional simulations. Among the topics that are
covered, we analyze the interplay between nova outbursts and the Galactic
chemical abundances, the synthesis of radioactive nuclei of interest for
gamma-ray astronomy, such as 7Li, 22Na or 26Al, and the recent discovery of
presolar meteoritic grains, likely condensed in nova shells.


title: Late-type Stars in the Inner Galaxy

abstract:
  Asymptotic Giant Branch (AGB) stars are good tracers of the Galactic
structure. They are bright in the infrared and can therefore be detected even
in the most obscured regions of the Galaxy. Maser emission from their
circumstellar envelopes can be detected throughout the Galaxy, and reveals the
stellar line-of-sight velocities with an accuracy of a few km/s.
  Our SiO maser survey of AGB stars was able to detect 255 new maser sources,
thereby doubling the number of known stellar line-of-sight velocities toward
the inner Galaxy. The longitude-velocity diagram of the SiO maser stars clearly
reveals a stellar Galactic nuclear disk and suggests that they are related to
the bar component. Using DENIS, 2MASS, ISOGAL, MSX and IRAS photometry, we can
study the nature of the masing stars, deriving their luminosities and mass-loss
rates, and establishing them as mostly variable AGB stars. In deriving
extinction corrections from the surrounding field population colors, we were
also able to constrain the near-infrared extinction law toward the inner
Galaxy.


title:
Black Holes: Physics and Astrophysics - Stellar-mass, supermassive and
  primordial black holes

abstract:
  I present an elementary primer of black hole physics, including its general
relativity basis, all peppered with astrophysical illustrations. Following a
brief review of the process stellar collapse to a black hole, I discuss the
gravitational redshift, particle trajectories in gravitational fields, the
Schwarzschild and Kerr solutions to Einstein's equations, orbits in
Schwarzschild and in Kerr geometry, and the dragging of inertial frames. I
follow with a brief review of galactic X-ray binary systems with known black
holes, stressing the QPO phenomenon in particular.
  I then discuss the evidence from AGN for the existence of supermassive black
holes in galaxy nuclei, as well as evidence for such black holes in ordinary
galaxy nuclei. I use the free motion of gas parcels to illustrate aspects of
accretion disks around black holes, showing how to calculate energy efficiency
and surface emissivity of disks, and the rate of black hole spin-up. I recall
the primary methods for black hole mass determination, the correlation of black
hole mass with the stellar velocity dispersion of its neighborhood, and
implications for the origin of supermassive black holes. Finally, I consider
the formation of primordial black holes, and calculation of their mass spectrum
at present in the case of scale invariant primordial inhomogeneities.


title: Accretion flows in early-type galaxies and CMB experiments

abstract:
  We investigate the possible contribution from the emission of accretion flows
around supermassive black holes in early type galaxies to current measurements
of the Cosmic Microwave Background (CMB) at radio frequencies. We consider a
range of luminosities suggested by targeted radio observations and accretion
models and compute the residual contribution of these sources to the spectrum
and bispectrum of the observed CMB maps. As for high-resolution CMB
experiments, we find that the unresolved component of these sources could make
up to ~40-50% of the observed CBI and BIMA power spectrum at l > 2000. As a
consequence, the inferred sigma_8^{SZ} value could be biased high by up to
6-7%. As for all sky experiments, we find that the contribution of
accretion-flow sources to the WMAP bispectrum is at the 2-3 per cent level at
most. At the flux limit that Planck will achieve, however, these sources may
contribute up to 15 per cent of the bispectrum in the 60-100 GHz frequency
range. Moreover, Planck should detect hundreds of these sources in the 30-300
GHz frequency window. These detections, possibly coupled with galaxy type
confirmation from optical surveys, will allow number counts to put tighter
constraints on early-type galaxies radio luminosity and accretion flows
properties. These sources may also contribute up to the 30 per cent level to
the residual radio sources power spectrum in future high-resolution SZ surveys
(like ACT or APEX) reaching mJy flux limits.


title:
A Matched Catalogue i-dropout galaxies at z~6 in the Hubble Ultra Deep
  Field

abstract:
  A recent preprint by Yan & Windhorst (astro-ph/0407493) independently repeats
our selection of candidate z~6 galaxies in the Hubble Ultra Deep Field
(astro-ph/0403223). The agreement of this independent study with our original
work is excellent, and most of the i-band drop-out galaxies are reproduced. To
avoid confusion with various ID numbers for sources, we present the community
with a matched list of i-band drop-outs in the Hubble Ultra Deep Field.


title: Weak Lensing Detection of Cl 1604+4304 at z = 0.90

abstract:
  We present a weak lensing analysis of the high-redshift cluster Cl 1604+4304.
At z=0.90, this is the highest-redshift cluster yet detected with weak lensing.
It is also one of a sample of high-redshift, optically-selected clusters whose
X-ray temperatures are lower than expected based on their velocity dispersions.
Both the gas temperature and galaxy velocity dispersion are proxies for its
mass, which can be determined more directly by a lensing analysis. Modeling the
cluster as a singular isothermal sphere, we find that the mass contained within
projected radius R is 3.69+-1.47 * (R/500 kpc) 10^14 M_odot. This corresponds
to an inferred velocity dispersion of 1004+-199 km/s, which agrees well with
the measured velocity dispersion of 989+98-76 km/s (Gal & Lubin 2004). These
numbers are higher than the 575+110-85 km/s inferred from Cl 1604+4304 X-ray
temperature, however all three velocity dispersion estimates are consistent
within ~ 1.9 sigma.


title: Bar-Driven Evolution and 2D Spectroscopy of Bulges

abstract:
  A multi-faceted approach is described to constrain the importance of
bar-driven evolution in disk galaxies, particularly bulge formation. N-body
simulations are used to construct stellar kinematic bar diagnostics for edge-on
systems and to quantify the expected vertical structure of bars, and they are
compared to observations of 30 edge-on spirals, most with a boxy bulge.
Long-slit spectra of the galaxies show characteristic double-hump rotation
curves, dispersion profiles with secondary peaks and/or flat maxima, and
correlated h3 and V profiles, indicating that most of them harbor edge-on bars.
The presence of cold, quasi-axisymmetric central stellar disks is also
suggested, presumably formed through bar-driven gaseous inflow and star
formation. K-band imaging of the same galaxies spectacularly highlights radial
variations of the bars' scaleheights, as expected from vertical disk
instabilities. The light profiles also vary radially in shape but never
approach a classic de Vaucouleurs law. Filtering of the images further isolates
the specific orbit families at the origin of the boxy structure, which can be
directly related to periodic orbit calculations in 3D barred potentials. Bars
are thus shown to contribute substantially to the formation of both large-scale
triaxial bulges and embedded central disks. Relevant results from the SAURON
survey of the stellar/ionized-gas kinematics and stellar populations of
spheroids are also described. Examples are used to illustrate the potential of
coupling stellar kinematics and linestrengths (age and metallicity), here
specifically to unravel the dynamical evolution and related chemical enrichment
history of bars and bulges. [Abridged]


title:
A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy: III. Constraints
  on the Flattening of the Galactic Halo

abstract:
  M giants selected from the Two Micron All Sky Survey (2MASS) have been used
to trace streams of tidal debris apparently associated with the Sagittarius
dwarf spheroidal galaxy (Sgr) that entirely encircle the Galaxy. While the Sgr
M giants are generally aligned with a single great circle on the sky, we
measure a difference of 10.4 +- 2.6 degrees between the mean orbital poles of
the great circles that best fit debris leading and trailing Sgr, which can be
attributed to the precession of Sgr's orbit over the range of phases explored
by the data set. Simulations of the destruction of Sgr in potentials containing
bulge, disk and halo components best reproduce this level of precession along
the same range of orbital phases if the potential contours of the halo are only
slightly flattened, with the ratio between the axis length perpendicular to and
in the disk in the range q = 0.90-0.95 (corresponding to isodensity contours
with q_\rho ~ 0.83 - 0.92). Oblate halos are strongly preferred over prolate
(q_\rho > 1) halos, and flattenings in the potential of q <= 0.85 (q_\rho <=
0.75) and q >= 1.05 (q_\rho >= 1.1) are ruled out at the 3-sigma level. More
extreme values of q <= 0.80 (q_\rho <= 0.6) and q >= 1.25 (q_\rho >= 1.6) are
ruled out at the 7-sigma and 5-sigma levels respectively. These constraints
will improve as debris with larger separation in orbital phase can be found.


title:
A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy: IV. Modeling the
  Sagittarius Tidal Tails

abstract:
  M giants recovered from the Two Micron All-Sky Survey (2MASS) have recently
been used to map the position and velocity distributions of tidal debris from
the Sagittarius (Sgr) dwarf spheroidal galaxy entirely around the Galaxy. We
compare this data set to both test particle orbits and N-body simulations of
satellite destruction run within a variety of rigid Milky Way potentials and
find that the mass of the Milky Way within 50 kpc of its center should be
3.8-5.6 x 10^11 Msun in order for any Sgr orbit to simultaneously fit the
velocity gradient in the Sgr trailing debris and the apocenter of the Sgr
leading debris. Orbital pole precession of young debris and leading debris
velocities in regions corresponding to older debris provide contradictory
evidence in favor of oblate/prolate Galactic halo potentials respectively,
leading us to conclude that the orbit of Sgr has evolved over the past few Gyr.
  Based upon the velocity dispersion and width along the trailing tidal stream
we estimate the current bound mass of Sgr to be M_Sgr = 2 - 5 x 10^8 Msun
independant of the form of the Galactic potential; this corresponds to a range
of mass to light ratios (M/L)_Sgr = 14 - 36 (M/L)_Sun for the Sgr core. Models
with masses in this range best fit the apocenter of leading Sgr tidal debris
when they orbit with a radial period of roughly 0.85 Gyr and have periGalactica
and apoGalactica of about 15 kpc and 60 kpc respectively. These distances will
scale with the assumed distance to the Sgr dwarf and the assumed depth of the
Galactic potential. The density distribution of debris along the orbit in these
models is consistent with the M giant observations, and debris at all orbital
phases where M giants are obviously present is younger (i.e. was lost more
recently from the satellite) than the typical age of a Sgr M giant star.


title:
On the importance of the few most massive stars: the ionizing cluster of
  NGC 588

abstract:
  We present the results of a double analysis of the ionizing cluster in NGC
588, a giant HII region (GHR) in the outskirts of the nearby galaxy M33. For
this purpose, we obtained ground based long-slit spectroscopy and combined it
with archival ground based and space borne imaging and spectroscopy, in the
wavelength range 1100-9800 A. A first modeling of the cluster was performed
using integrated properties, such as the spectral energy distribution (SED),
broad band colors, nebular emission Hbeta equivalent width, the main
ultraviolet resonance lines, and the presence of Wolf-Rayet star features. By
applying standard assumptions about the initial mass function (IMF), we were
unable to fit satisfactorily these observational data. This contradictory
result led us to carry out a second modeling, based on a resolved photometric
analysis of individual stars in Hubble Space Telescope (HST) images, by means
of finding the best fit isochrone in color-magnitude diagrams (CMD), and
assigning a theoretical SED to each individual star. The overall SED of the
cluster, obtained by integrating the individual stellar SEDs, is found to fit
better the observed SED than the best solution found through the integrated
first analysis, but at a significantly later stage of evolution of the cluster
of 4.2 Myr, as obtained from the best fit to the CMD. A comparative analysis of
both methods traces the different results to the effects of statistical
fluctuations in the upper end of the IMF, which are significant in NGC 588,
with a computed cluster mass of 5600 Msun, as predicted by Cervino et al
(2002). We discuss the results in terms of the strong influence of the few most
massive stars, six in the case of NGC 588, that dominate the overall SED and,
in particular, the ionizing far ultraviolet range beyond the Lyman limit.


title:
Physical Structure of Planetary Nebulae. III. The Large and Evolved NGC
  1360

abstract:
  NGC 1360 is a large planetary nebula (PN) without an obvious shell
morphology. We have analyzed H-alpha images and high-dispersion echelle spectra
of NGC 1360 in order to construct spatio-kinematic models and to determine its
density distribution. The best-fit model indicates that NGC 1360 is a prolate
ellipsoidal shell whose major axis is twice as long as its minor axis and is
tilted by 60 arcdeg with respect to the line of sight. The large kinematic age
of the shell, ~10,000 yr, and the low density of the nebula, <130 H-atom cm^-3,
imply that NGC 1360 is an evolved PN and has begun to merge with the
interstellar medium. The observed morphology and surface brightness profiles of
NGC 1360 can be described well as a thick shell with a Gaussian radial density
profile without a sharp inner edge, indicating a lack of on-going compression
by a fast stellar wind. The FLIERs observed in NGC 1360 near the end of its
major axis expand faster and are younger than the nebular shell.


title: Reviewing: The outer ejecta of eta Carinae

abstract:
  The nebula around eta Carinae consists of two distinct parts: the Homunculus
and the outer ejecta. The outer ejecta are mainly a collection of numerous
filaments, shaped irregularly and distributed over an area of 1arcminx1arcmin.
While the Homunculus is mainly a reflection nebula, the outer ejecta are an
emission nebula. Kinematic analysis of the outer ejecta (as the Homunculus)
show their bi-directional expansion. Radial velocities in the outer ejecta
reach up to >2000km/s and the gas gives rise to X-ray emission. The temperature
of the X-ray gas is of the order of 0.65 keV. These shock temperatures indicate
velocities of the shocking gas of 750km/s, about what was found for the average
expansion velocity of the outer ejecta. HST/STIS data from the strings, long,
highly collimated structures in the outer ejecta, show that the electron
density of the strings is of the order of 10^4cm^-3 Other structures in the
outer ejecta show similar values. String 1 has a mass of about 3 10^-4M_\sun, a
density gradient along the strings or a denser leading head was not found.


title:
Orbit Simulation for the Determination of Relativistic and Solar-System
  Parameters for the ASTROD Space Mission

abstract:
  ASTROD (Astrodynamical Space Test of Relativity using Optical Devices)
mission concept is to conduct high-precision measurement of relativistic
effects,solar-system parameters and gravitational waves. In this paper, we
first extend the stochastic model to simulate the determination of the masses
of three big asteroids (Ceres, Vesta and Pallas). With one range observation
per day for each spacecraft from 25 days to 800 days of the mission and ten
range observations per day for each spacecraft from 800 days to 1050 days of
the mission (when the apparent positions of the two spacecraft are close to the
Sun), the accuracies of determining these parameters are 4.6*10**(-7) for
gamma, 4.0*10**(-7) for beta, 1.2*10**(-8) for J2, and 6.4*10**(-5) M_Ceres,
7.6*10**(-4) M_Pallas, 8.1*10**(-5) M_Vesta for the mass determination of
Ceres, Pallas and Vesta respectively. We then include in the simulation and
determination the rate of change of the gravitational constant (G-dot), and an
anomalous constant acceleration (aa) directed towards the Sun (Pioneer
Anomaly). At the end of 1050 days of simulation, the accuracies of determining
these two parameters are 9.5*10**(-15)/yr for G-dot/G and 2.0*10**(-16) m/s2
for a_a. The mass loss rate of the inner solar system is at the level of
1*10**(-13) M_Sun/yr. The accurate determinat-ion of Ġ/G will mean a need
to simultaneously determine the mass loss rate. In other words, the mission
gives a way to monitor the mass loss rate of the Sun if Ġ/G can be
determined independently.


title: Effects of Destriping Errors on Estimates of the CMB Power Spectrum

abstract:
  Destriping methods for constructing maps of the Cosmic Microwave Background
(CMB) anisotropies have been investigated extensively in the literature.
However, their error properties have been studied in less detail. Here we
present an analysis of the effects of destriping errors on CMB power spectrum
estimates for Planck-like scanning strategies. Analytic formulae are derived
for certain simple scanning geometries that can be rescaled to account for
different detector noise. Assuming {Planck-like low-frequency noise, the noise
power spectrum is accurately white at high multipoles (l<50). D estriping
errors, though dominant at lower multipoles, are small in comparison to the
cosmic variance. These results show that simple destriping map-making methods
should be perfectly adequate for the analysis of Planck data and support the
arguments given in an earlier paper in favour of applying a fast hybrid power
spectrum estimator to CMB data with realistic `1/f' noise.


title: Renormalization-group running cosmologies - a scale-setting procedure

abstract:
  For cosmologies including scale dependence of both the cosmological and the
gravitational constant, an additional consistency condition dictated by the
Bianchi identities emerges, even if the energy-momentum tensor of ordinary
matter stays individually conserved. For renormalization-group (RG) approaches
it is shown that such a consistency relation ineluctably fixes the RG scale
(which may have an explicit as well as an implicit time dependence), provided
that the solutions of the RG equation for both quantities are known. Hence,
contrary to the procedures employed in the recent literature, we argue that
there is no more freedom in identification of the RG scale in terms of the
cosmic time in such cosmologies. We carefully set the RG scale for the RG
evolution phrased in a quantum gravity framework based on the hypothetical
existence of an infrared (IR) fixed point, for the perturbative regime within
the same framework, as well as for an evolution within quantum field theory
(QFT) in a curved background. In the latter case, the implications of the scale
setting for the particle spectrum are also briefly discussed.


title: Fitting Type Ia supernovae with coupled dark energy

abstract:
  We discuss the possible consistency of the recently discovered Type Ia
supernovae at z>1 with models in which dark energy is strongly coupled to a
significant fraction of dark matter, and in which an (asymptotic) accelerated
phase exists where dark matter and dark energy scale in the same way. Such a
coupling has been suggested for a possible solution of the coincidence problem,
and is also motivated by string cosmology models of "late time" dilaton
interactions. Our analysis shows that, for coupled dark energy models, the
recent data are still consistent with acceleration starting as early as at
$z=3$ (to within 90% c.l.), although at the price of a large "non-universality"
of the dark energy coupling to different matter fields. Also, as opposed to
uncoupled models which seem to prefer a ``phantom'' dark energy, we find that a
large amount of coupled dark matter is compatible with present data only if the
dark energy field has a conventional equation of state w>-1.


title:
Stability of hydrodynamical relativistic planar jets. II. Long-term
  nonlinear evolution

abstract:
  In this paper we continue our study of the Kelvin-Helmholtz (KH) instability
in relativistic planar jets following the long-term evolution of the numerical
simulations which were introduced in Paper I. The models have been classified
into four classes (I to IV) with regard to their evolution in the nonlinear
phase, characterized by the process of jet/ambient mixing and momentum
transfer. Models undergoing qualitatively different non-linear evolution are
clearly grouped in well-separated regions in a jet Lorentz
factor/jet-to-ambient enthalpy diagram. Jets with a low Lorentz factor and
small enthalpy ratio are disrupted by a strong shock after saturation. Those
with a large Lorentz factor and enthalpy ratio are unstable although the
process of mixing and momentum exchange proceeds to a longer time scale due to
a steady conversion of kinetic to internal energy in the jet. In these cases,
the high value of the initial Lorentz seems to prevent transversal velocity
from growing far enough to generate the strong shock that breaks the slower
jets. Finally, jets with either high Lorentz factors and small enthalpy ratios
or low Lorentz factors and large enthalpy ratios appear as the most stable.


title: The XENON Dark Matter Search Experiment

abstract:
  The XENON experiment aims at the direct detection of dark matter in the form
of WIMPs (Weakly Interacting Massive Particles) via their elastic scattering
off Xe nuclei. A fiducial mass of 1000 kg, distributed in ten independent
liquid xenon time projection chambers(LXeTPCs) will be used to probe thelowest
interaction cross section predicted by SUSY models. The TPCs are operated in
dual (liquid/gas) phase, to allow a measurement of nuclear recoils down to
16keV energy, via simultaneous detection of the ionization, through secondary
scintillation in the gas, and primary scintillation in the liquid. Thedistinct
ratio of primary to secondary scintillation for nuclear recoils from WIMPs (or
neutrons), and for electron recoils from background, iskey to the
event-by-event discrimination capability of XENON. A dual phase xenon prototype
has been realized and is currently being tested, along with otherprototypes
dedicated to other measurements relevant to the XENON program. As part of the
R&D phase, we will realize and move underground a first XENON module (XENON10)
with at least 10 kg fiducial mass to measure the background rejection
capability and to optimize the conditions for continuous and stable detector
operation underground. We present some of the results from the ongoing R&D and
summarize the expected performance of the 10 kg experiment, from MonteCarlo
simulations. The main design features of the 100 kg detector unit(XENON100),
with which we envisage to make up the 1 tonne sensitive mass ofXENON1T will
also be presented.


title:
A dynamical model for the CSO-MSO-FRII evolution: hints from hot spot
  properties

abstract:
  Compact Symmetric Objects (CSOs) are considered the young counterparts of
large doubles according to advance speeds measured or inferred from spectral
ageing. Here we present a simple power law model for the CSO/FRII evolution
based on the study of sources with well defined hot-spots. The luminosity of
the hot spots is estimated under minimum energy conditions. The advance of the
source is considered to proceed in ram pressure equilibrium with the ambient
medium. Finally, we also assume that the jets feeding the hot spots are
relativistic and have a time dependent power. Comparison with observational
data allows to interpret the CSO-FRII evolution in terms of decreasing jet
power with time.


title:
A Constant Bar Fraction out to Redshift z~1 in the Advanced Camera for
  Surveys Field of the Tadpole Galaxy

abstract:
  Bar-like structures were investigated in a sample of 186 disk galaxies larger
than 0.5 arcsec that are in the I-band image of the Tadpole galaxy taken with
the HST ACS. We found 22 clear cases of barred galaxies, 21 galaxies with small
bars that appear primarily as isophotal twists in a contour plot, and 11 cases
of peculiar bars in clump-cluster galaxies, which are face-on versions of chain
galaxies. The latter bars are probably young, as the galaxies contain only weak
interclump emission. Four of the clearly barred galaxies at z~0.8-1.2 have
grand design spirals. The bar fraction was determined as a function of galaxy
inclination and compared with the analogous distribution in the local Universe.
The bar fraction was also determined as a function of galaxy angular size.
These distributions suggest that inclination and resolution effects obscure
nearly half of the bars in our sample. The bar fraction was also determined as
a function of redshift. We found a nearly constant bar fraction of 0.23+-0.03
from z~0 to z=1.1. When corrected for inclination and size effects, this
fraction is comparable to the bar fraction in the local Universe, ~0.4, as
tabulated for all bar and Hubble types in the Third Reference Catalogue of
Galaxies. The average major axis of a barred galaxy in our sample is ~10 kpc
after correcting for redshift with a LambdaCDM cosmology. Galaxy bars were
present in normal abundance at least ~8 Gy ago (z~1); bar dissolution cannot be
common during a Hubble time unless the bar formation rate is comparable to the
dissolution rate.


title:
Modeling the gas reservoir of circumstellar disks around young G-type
  stars

abstract:
  Interpretation of molecular line observations in tenuous circumstellar disks
around young G-type stars in terms of a disk mass is difficult without a model
that describes the chemical structure of these disks. This paper now discusses
the chemistry in tenuous disks around young solar-type stars based on disk
models that take into account the presence of a stellar chromosphere. The
example of the disk around a 70 Myr old solar-type star shows that the
dissociating radiation from the chromosphere is stronger than the interstellar
ultraviolet radiation field up to a distance of ~400 AU from the star. Similar
to other studies in this research field, it is found that, due to
photodissociation, the CO-to-H_2 ratio is far from the canonical value of 10^-4
for molecular clouds. Moreover, the dust-to-gas mass ratio, as well as the dust
grain size play an important role for the H_2 abundance in these disks.


title:
Space-time variation of the fine structure constant and evolution of
  isotope abundances

abstract:
  At present several groups are analyzing astrophysical data in a search for
time-variation of the fine structure constant $\alpha$. Here we discuss how to
exclude systematic effects caused by the changes in the isotope abundances
during the evolution of the universe. We suggest using particular combinations
of the transition frequencies of O II, Al II, Al III, Si II and Mn II as
anchors, which are insensitive to $\alpha$-variation and to changes in isotope
abundances. These anchors can be used to determine the cosmological redshift.
Then, one can use other combinations of frequencies as probes for the
time-variation of $\alpha$ and another set as probes for the isotopic
abundances. In this way it is possible to eliminate one source of the
systematic errors in the search for $\alpha$-variation and get new information
about evolution of the isotopes. On the level of accuracy that has already been
reached in the search for $\alpha$-variation it is possible to see ~10% changes
in isotope abundances of Si and Ni.


title: INTEGRAL observations of the peculiar BeX System SAX J2103.5+4545

abstract:
  We present an INTEGRAL data analysis of the X-ray transient \object{SAX
J2103.5+4545} during two outbursts detected in December 2002. The INTEGRAL
coordinates and error circle agree with the position of the recently proposed
optical counterpart. A power-law plus cut-off model provided a good fit to the
4-150 keV spectrum yielding a photon index of 1.0+-0.1, a cut-off energy
E_cut=7.6+-2.0 keV and a folding energy E_fold=30.9+-2.5 keV. The X-ray
luminosity in the 4-150 keV energy range was found to be 6.0x10^36 erg/s,
assuming a distance of 6.5 kpc. This luminosity, together with the derived
photon index, indicate that the source is in a bright state. A 354.9$+-0.5
second pulse period is measured. This value is significantly smaller than
previous measurements, indicating a long-term spin-up episode.


title: Gamma-ray burst internal shocks with magnetization

abstract:
  (Please note that the abstract has been significantly shorted) We investigate
Gamma-ray Burst (GRB) internal shocks with moderate magnetization, with the
magnetization parameter $\sigma$ ranging from 0.001 to 10. Possible magnetic
dissipation in the stripped magnetized shells is also taken into account
through introducing a parameter $k$ ($0<k\leq 1$), which is the ratio of the
electric field strength of the downstream and the upstream. By solving the
general MHD jump conditions, we show that the dynamic evolution of the shock
with magnetic dissipation is different from the familiar one obtained in the
ideal MHD limit. In view of the possible high degree of linear polarization of
GRB 021206 and the identification of a possible highly magnetized flow in GRB
990123 and GRB 021211, we suggest that a mildly magnetized internal shock model
($0.01<\sigma<1$) with moderate magnetic dissipation is a good candidate to
explain the GRB prompt emission data.


title: Turbulence and galactic structure

abstract:
  Interstellar turbulence is driven over a wide range of scales by processes
including spiral arm instabilities and supernovae, and it affects the rate and
morphology of star formation, energy dissipation, and angular momentum transfer
in galaxy disks. Star formation is initiated on large scales by gravitational
instabilities which control the overall rate through the long dynamical time
corresponding to the average ISM density. Stars form at much higher densities
than average, however, and at much faster rates locally, so the slow average
rate arises because the fraction of the gas mass that forms stars at any one
time is low, ~10^{-4}. This low fraction is determined by turbulence
compression, and is apparently independent of specific cloud formation
processes which all operate at lower densities. Turbulence compression also
accounts for the formation of most stars in clusters, along with the cluster
mass spectrum, and it gives a hierarchical distribution to the positions of
these clusters and to star-forming regions in general. Turbulent motions appear
to be very fast in irregular galaxies at high redshift, possibly having speeds
equal to several tenths of the rotation speed in view of the morphology of
chain galaxies and their face-on counterparts. The origin of this turbulence is
not evident, but some of it could come from accretion onto the disk. Such high
turbulence could help drive an early epoch of gas inflow through viscous
torques in galaxies where spiral arms and bars are weak. Such evolution may
lead to bulge or bar formation, or to bar re-formation if a previous bar
dissolved. We show evidence that the bar fraction is about constant with
redshift out to z~1, and model the formation and destruction rates of bars
required to achieve this constancy.


title: EROS: a Galactic Microlensing Odyssey

abstract:
  The EROS microlensing survey has monitored nearly 100 million stars for seven
years, to search for halo brown dwarfs and compact objects in the Galactic
disk. In this paper, we review the various EROS observation programs and the
corresponding microlensing search results. In particular, based on LMC and SMC
observations, EROS excludes a major contribution from compact objects with
masses in the range 2. x 10^{-7} - 1 M_{\odot} to the Galactic halo. Less than
25% of the standard halo mass can be made of such objects, while the EROS
measured optical depths toward the Galactic spiral arms (< tau_{SA} > \simeq
0.43 x 10^{-6}) and Galactic bulge (< tau_{GC} > \simeq 0.93 x 10^{-6}) are
compatible with Galactic model predictions if the contribution from an
elongated bar in the centre is taken into account.


title: The fate of Lyman photons in local Starburst: new ACS/HST images

abstract:
  We review the imaging and spectroscopic properties of the Lyman alpha
emission in starburst galaxies. The Lyman alpha photons escape is largely
driven by kinematical and orientation effects related to the presence of large
scale expanding shells of neutral hydrogen. The various Lyman alpha profiles
can be linked to the evolutionary state of the starburst. Our recent Lyman
alpha imaging study using the HST-ACS is presented here: it highlights the
presence of diffuse extended emission of low intensity leaking out the diffuse
HI components. The similarities with the line profiles observed on high
redshift galaxies is an important fact that cautions the use of Lyman alpha to
derive the cosmic star formation rate and constrains the search for high
redshift galaxies.


title: X-ray properties of the "Composite" Seyfert/Star-forming galaxies

abstract:
  An enigmatic, small class of IR and X-ray luminous sources, named
``Composite'' starburst/Seyfert galaxies, has been defined from IRAS and RASS
data. The objects have optical spectra dominated by the features of HII
galaxies (plus, in some cases, weak Seyfert signatures) but X-ray luminosities
higher than expected from starbursts and more typical of Seyfert nuclei. The
true nature of this class of objects is still unknown. We present Chandra data
of four of these galaxies that were obtained to investigate the nature of the
X-ray source. The X-ray spectrum, the lack of any significant extended
component, and the observed variability indicate that the AGN is the dominant
component in the X-ray domain.


title: Anthropic predictions: the case of the cosmological constant

abstract:
  Anthropic models can give testable predictions, which can be confirmed or
falsified at a specified confidence level. This is illustrated using the
successful prediction of the cosmological constant as an example. The history
and the nature of the prediction are reviewed. Inclusion of other variable
parameters and implications for particle physics are briefly discussed.


title:
Temporal evolution of magnetic molecular shocks I. Moving grid
  simulations

abstract:
  We present time-dependent 1D simulations of multifluid magnetic shocks with
chemistry resolved down to the mean free path. They are obtained with an
adaptive moving grid implemented with an implicit scheme. We examine a broad
range of parameters relevant to conditions in dense molecular clouds, with
preshock densities between 10^3 and 10^5 cm-3, velocities between 10 and 40
km/s, and three different scalings for the transverse magnetic field: B=0,0.1,1
\mu G \sqrt{n.cm3}. We first use this study to validate the results of
Chi\`eze, Pineau des For\^ets & Flower (1998), in particular the long delays
necessary to obtain steady C-type shocks, and we provide evolutionary
time-scales for a much greater range of parameters. We also present the first
time-dependent models of dissociative shocks with a magnetic precursor,
including the first models of stationary CJ shocks in molecular conditions. We
find that the maximum speed for steady C-type shocks is reached before the
occurrence of a sonic point in the neutral fluid, unlike previously thought. As
a result, the maximum speed for C-shocks is lower than previously believed.
Finally, we find a large amplitude bouncing instability in J-type fronts near
the H2 dissociation limit (u ~ 25-30 km/s), driven by H2
dissociation/reformation. At higher speeds, we find an oscillatory behaviour of
short period and small amplitude linked to collisional ionisation of H. Both
instabilities are suppressed after some time when a magnetic field is present.
In a companion paper, we use the present simulations to validate a new
semi-analytical construction method for young low-velocity magnetic shocks
based on truncated steady-state models.


title:
Temporal evolution of magnetic molecular shocks II. Analytics of the
  steady state and semi-analytical construction of intermediate ages

abstract:
  In the first paper of this series (Paper I) we computed time dependent
simulations of multifluid shocks with chemistry and a transverse magnetic field
frozen in the ions, using an adaptive moving grid. In this paper, we present
new analytical results on steady-state molecular shocks. Relationships between
density and pressure in the neutral fluid are derived for the cold magnetic
precursor, hot magnetic precursor, adiabatic shock front, and the following
cooling layer. The compression ratio and temperature behind a fully
dissociative adiabatic shock is also derived. To prove that these results may
even hold for intermediate ages, we design a test to locally characterise the
validity of the steady state equations in a time-dependent shock simulation.
Applying this tool to the results of Paper I, we show that most of these shocks
(all the stable ones) are indeed in a quasi-steady state at all times, i.e. : a
given snapshot is composed of one or more truncated steady shock. Finally, we
use this property to produce a construction method of any intermediate time of
low velocity shocks (u < 20 km/s) with only a steady-state code. In particular,
this method allows one to predict the occurrence of steady CJ-type shocks more
accurately than previously proposed criteria.


title: IAC-Star: a Code for Synthetic Color-Magnitude Diagram Computation

abstract:
  The code IAC-star is presented. It generates synthetic HR and color-magnitude
diagrams (CMDs) and is mainly aimed to star formation history studies in nearby
galaxies. Composite stellar populations are calculated on a star by star basis,
by computing the luminosity, effective temperature and gravity of each star by
direct bi-logarithmic interpolation in the metallicity and age grid of a
library of stellar evolution tracks. Visual (broad band and HST) and infrared
magnitudes are also provided for each star after applying bolometric
corrections. The Padua (Bertelli et al. 1994, Girardi et al. 2000) and Teramo
(Pietrinferni et al. 2004) stellar evolution libraries and various bolometric
corrections libraries are used in the current version. A variety of star
formation rate functions, initial mass functions and chemical enrichment laws
are allowed and binary stars can be computed. Although the main motivation of
the code is the computation of synthetic CMDs, it also provides integrated
masses, luminosities and magnitudes as well as surface brightness fluctuation
luminosities and magnitudes for the total synthetic stellar population, and
therefore it can also be used for population synthesis research. The code is
offered for free use and can be executed at the site {\tt
http://iac-star.iac.es}, with the only requirement of referencing this paper
and crediting as indicated in the site.


title: The role of interactions

abstract:
  Interactions between galaxies are suggested to be a mechanism responsible for
feeding Active Galactic Nuclei (AGN). Theoretical models show that interactions
are an efficient way to drive gas from the galaxy to the nucleus, however, the
observational evidence on this subject is controversial. Here we review results
in this field, discuss possible limitations of previous studies and the
importance of dealing with selection effects. We also show that there is no
significant difference in the percentage of low luminosity AGN and normal
galaxies with companions, and discuss possible interpretations of this result.


title: Discrete Components in the Radial Velocities of ScI Galaxies

abstract:
  We examine the V_{CMB} velocities and Tully-Fisher distances of 83 ScI
galaxies and find that their velocities contain the same discrete velocity
components identified previously by Tifft. After removing the discrete velocity
components, the scatter remaining on the Hubble plot is in good agreement with
the Tully-Fisher distance uncertainties. Although there is, as yet, no physical
explanation for these discrete components, the fact that they appear to be
identical to those found previously by Tifft suggests that their reality needs
to be taken seriously.


title: Evolution and Yields of Extremely Metal Poor Intermediate Mass Stars

abstract:
  Intermediate mass stellar evolution tracks from the main sequence to the tip
of the AGB for five initial masses (2 to 6Msun) and metallicity Z=0.0001 have
been computed. The detailed 1D structure and evolution models include
exponential overshooting, mass loss and a detailed nucleosynthesis network with
updated nuclear reaction rates. The network includes a two-particle heavy
neutron sink for approximating neutron density in the He-shell flash. It is
shown how the neutron-capture nucleosynthesis is important in models of very
low metallicity for the formation of light neutron-heavy species, like sodium
or the heavy neon and magnesium isotopes. The models have high resolution, as
required for modeling the third dredge-up. All sequences have been followed
from the pre-main sequence to the end of the AGB when all envelope mass is
lost. Detailed structural and chemical model properties as well as yields are
presented. This set of stellar models is based on standard assumptions and
updated input physics. It can be confronted with observations of
extremely-metal poor stars and may be used to assess the role of AGB stars in
the origin of abundance anomalies of some Globular Cluster members of
correspondingly low metallicity.


title:
Chandra Detection of a Synchrotron Nebula Around the Vela-like Pulsar
  J1016-5857

abstract:
  We report on a 19 ks observation of the pulsar J1016-5857 with the Chandra
X-ray Observatory. This "Vela-like" pulsar has rotation period 107 ms,
characteristic age 21 kyr, and spin-down power 2.6e36 ergs/s. A relatively
bright centrally peaked source of radius ~25" around the radio pulsar position
has a spectrum that is well fitted by an absorbed power law with photon index
1.32+-0.25. We regard this as a newly identified pulsar wind nebula that we
designate PWN G284.0-1.8. We do not detect the pulsar either as a point X-ray
source or as a pulsed source in a 55 ks observation with the Rossi X-ray Timing
Explorer. The isotropic PWN luminosity is 3e32 ergs/s in the 2-10 keV range,
for a distance of 3 kpc that is consistent with the measured neutral hydrogen
column density. The unpulsed flux from the pulsar is less than 30% of the
measured PWN flux. The brightest component of the PWN, near the pulsar, shows
extended emission of size ~2" that may indicate, by analogy with other young
pulsars, the wind termination shock. In the Chandra image we also detect a very
faint extended structure ~1' by 2' in size that is highly asymmetric about the
pulsar position. This structure is a good match in width and position angle to
the tip of a "finger" of radio emission that appears to connect to the nearby
supernova remnant G284.3-1.8, but we cannot characterize it further with the
available data. There is a variable X-ray point source only 1.5 arcmin from the
pulsar, which we identify using optical spectroscopy as an accreting binary.


title: Calibrating Photometric Redshifts of Luminous Red Galaxies

abstract:
  We discuss the construction of a photometric redshift catalogue of Luminous
Red Galaxies (LRGs) from the Sloan Digital Sky Survey (SDSS), emphasizing the
principal steps necessary for constructing such a catalogue -- (i)
photometrically selecting the sample, (ii) measuring photometric redshifts and
their error distributions, (iii) and estimating the true redshift distribution.
We compare two photometric redshift algorithms for these data and find that
they give comparable results. Calibrating against the SDSS and SDSS-2dF
spectroscopic surveys, we find that the photometric redshift accuracy is
$\sigma \sim 0.03$ for redshifts less than 0.55 and worsens at higher redshift
($\sim 0.06$). These errors are caused by photometric scatter, as well as
systematic errors in the templates, filter curves, and photometric zeropoints.
We also parametrize the photometric redshift error distribution with a sum of
Gaussians, and use this model to deconvolve the errors from the measured
photometric redshift distribution to estimate the true redshift distribution.
We pay special attention to the stability of this deconvolution, regularizing
the method with a prior on the smoothness of the true redshift distribution.
The methods we develop are applicable to general photometric redshift surveys.


title:
Computer science approach to the stellar fabric of violent starforming
  regions in AGN

abstract:
  In order to analyse the large numbers of Seyfert galaxy spectra available at
present, we are testing new techniques to derive their physical parameters
fastly and accurately.
  We present an experiment on such a new technique to segregate old and young
stellar populations in galactic spectra using machine learning methods. We used
an ensemble of classifiers, each classifier in the ensemble specializes in
young or old populations and was trained with locally weighted regression and
tested using ten-fold cross-validation. Since the relevant information
concentrates in certain regions of the spectra we used the method of sequential
floating backward selection offline for feature selection.
  Very interestingly, the application to Seyfert galaxies proved that this
technique is very insensitive to the dilution by the Active Galactic Nucleus
(AGN) continuum. Comparing with exhaustive search we concluded that both
methods are similar in terms of accuracy but the machine learning method is
faster by about two orders of magnitude.


title:
XMM-Newton Observations of A133: A Weak Shock Passing through the Cool
  Core

abstract:
  We use XMM-Newton observations of the cluster of galaxies A133 to study the
X-ray spectrum of the intracluster medium (ICM). We find a cold front to the
southeast of the cluster core. From the pressure profile near the cold front,
we derive an upper limit to the velocity of the core relative to the rest of
the cluster of <230 km s^-1. Our previous Chandra image of A133 showed a
complex, bird-like morphology in the cluster core. Based on the XMM-Newton
spectra and hardness ratio maps, we argue that the wings of this structure are
a weak shock front. The shock was probably formed outside the core of the
cluster, and may be heating the cluster core. Our Chandra image also showed a
``tongue'' of relatively cool gas extending from the center of the cD to the
center of the radio relic. The XMM-Newton results are consistent with the idea
that the tongue is the gas which has been uplifted by a buoyant radio bubble
including the radio relic to the northwest of the core. Alternatively, the
tongue might result from a cluster merger. The small velocity of the core
suggests that the bubble including the relic has moved by buoyancy, rather than
by motions of the core or the ICM. We do not find clear evidence for nonthermal
X-ray emission from the radio relic. Based on the upper limit on the inverse
Compton emission, we derive a lower limit on the magnetic field in the relic of
B>~1.5\mu G.


title: Euclidean Algorithm for a Gravitational Lens in a Polynomial Equation

abstract:
  The Euclidean algorithm in algebra is applied to a class of gravitational
lenses for which the lens equation consists of any set of coupled polynomial
equations in the image position. In general, this algorithm allows us to reduce
an apparently coupled system to a single polynomial in one variable (say $x$ in
Cartesian coordinates) without the other component (say $y$), which is
expressed as a function of the first component. This reduction enables us to
investigate the lensing properties in an algebraic manner: For instance, we can
obtain an analytic expression of the caustics by computing the discriminant of
the polynomial equation. To illustrate this Euclidean algorithm, we re-examine
a binary gravitational lens and show that the lens equation is reduced to a
single real fifth-order equation, in agreement with previous works. We apply
this algorithm also to the linearlized Kerr lens and find that the lens
equation is reduced to a single real fifth-order one.


title: Helical coronal ejections and their role in the solar cycle

abstract:
  The standard theory of the solar cycle in terms of an alpha-Omega dynamo
hinges on a proper understanding of the nonlinear alpha effect. Boundary
conditions play a surprisingly important role in determining the magnitude of
alpha. For closed boundaries, the total magnetic helicity is conserved, and
since the alpha effect produces magnetic helicity of one sign in the large
scale field, it must simultaneously produce magnetic helicity of the opposite
sign. It is this secondary magnetic helicity that suppresses the dynamo in a
potentially catastrophic fashion. Open boundaries allow magnetic helicity to be
lost. Simulations are presented that allow an estimate of alpha in the presence
of open or closed boundaries, either with or without solar-like differential
rotation. In all cases the sign of the magnetic helicity agrees with that
observed at the solar surface (negative in the north, positive in the south),
where significant amounts of magnetic helicity can be ejected via coronal mass
ejections. It is shown that open boundaries tend to alleviate catastrophic
alpha quenching. The importance of looking at current helicity instead of
magnetic helicity is emphasized and the conceptual advantages are discussed.


title:
Statistical distribution of gravitational-lensing excursion angles:
  Winding ways to us from the deep universe

abstract:
  We investigate statistical distributions of differences in
gravitational-lensing deflections between two light rays, the so-called lensing
excursion angles. A probability distribution function of the lensing excursion
angles, which plays a key role in estimates of lensing effects on angular
clustering of objects (such as galaxies, QSOs and also the CMB temperature
map), is known to consist of two components; a Gaussian core and an exponential
tail. We use numerical gravitational-lensing experiments in a Lambda-CDM
cosmology for quantifying these two components. We especially focus on the
physical processes responsible for generating those two components. We develop
a simple empirical model for the exponential tail which allows us to explore
its origin. We find that the tail is generated by the coherent lensing scatter
by massive halos with M>10^14h^-1Msun at z<1 and that its exponential shape
arises due to the exponential cut-off of the halo mass function at that mass
range. On scales larger than 1 arc minute, the tail does not have a practical
influence on the lensing effects on the angular clustering. Our model predicts
that the coherent scatter may have non-negligible effects on angular clustering
at sub-arcminute scales.


title:
The non-linear evolution of bispectrum from the scale-free N-body
  simulation

abstract:
  We have accurately measured the bispectrum for four scale-free models of
structure formation with the spectral index $n=1$, 0, -1, and -2. The
measurement is based on a new method that can effectively eliminate the alias
and numerical artifacts, and reliably extend the analysis into the strongly
non-linear regime. The work makes use of a set of state-of-the art N-body
simulations that have significantly increased the resolution range compared
with the previous studies on the subject. With these measured results, we
demonstrated that the measured bispectrum depends on the shape and size of
$k$-triangle even in the strongly nonlinear regime. It increases with
wavenumber and decreases with the spectral index. These results are in contrast
with the hypothesis that the reduced bispectrum is a constant in the strongly
non-linear regime. We also show that the fitting formula of Scoccimarro &
Frieman (1999) does not describe our simulation results well (with a typical
error about 40 percent). In the end, we present a new fitting formula for the
reduced bispectrum that is valid for $-2 \leq n \leq 0$ with a typical error of
10 percent only.


title: New results on clusters of galaxies observed with XMM-Newton

abstract:
  Clusters of galaxies contain a hot gas, which emits in X-rays. X-ray
telescopes such as XMM-Newton allow to study this plasma to obtain information
on physical quantities of these objects. We present here some results on the
total mass density distribution of clusters obtained with XMM-Newton based on
the hydrostatic approach. These results can be compared to models based on cold
dark matter. Generally good agreement is found between observations and models.
Furthermore we present a study on physical properties of a distant merging
cluster of galaxies, which demonstrates the potential of XMM-Newton studies on
this class of objects.


title:
A uniform X-ray analysis of 79 distant galaxy clusters with ROSAT and
  ASCA

abstract:
  We present a uniform analysis of the ROSAT HRI and the ASCA GIS/SIS data for
79 distant clusters of galaxies in the redshift range, 0.1 < z < 0.82 to study
the global structures of the intracluster medium. We have constructed an X-ray
catalog consisting of the largest sample of clusters in the redshift range for
which pointed X-ray observations were carried out with both the observatories.
We determined the emission-weighted X-ray temperatures of the clusters with
ASCA, while we studied surface brightness distribution with the ROSAT HRI
utilizing the isothermal beta model. We investigated the statistical properties
and trends for redshift evolution of the X-ray parameters including the
temperature, the density profile of the intracluster gas and the gas-mass
fraction within r500. We also present correlations of the cluster parameters
with the X-ray temperature and with the core radius and compare them with the
predictions of the self-similar model, from which we discuss the possible
origin of the double structure discovered in the core radius distribution.


title: Superluminal Particles, Cosmology and Cosmic-Ray Physics

abstract:
  Non-tachyonic superluminal sectors of matter (superbradyons), with critical
speeds in vacuum much larger than the speed of light, can quite naturally exist
and play an important role in both cosmic-ray physics (anomalous high-energy
events) and cosmology (big-bang physics, alternatives to inflation, dark
matter...). They can even be the real "elementary" particles. An updated
discussion of the subject is presented, in relation with recent theoretical and
experimental results. Prospects for future searches are also reexamined.
Lorentz symmetry violation (LSV) models based on mixing with superbradyons are
compared with LDRK (linearly deformed relativistic kinematics) and QDRK
(quadratically deformed relativistic kinematics) such as defined in our
previous paper physics/0003080 .


title: Quintessence and the Transition to an Accelerating Universe

abstract:
  The implications of seven popular models of quintessence based on
supergravity or M/string theory for the transition from a decelerating to an
accelerating universe are explored. All seven potentials can mimic the
LambdaCDM model at low redshifts 0 < z < 5. However, for a natural range of
initial values of the quintessence field, the SUGRA and Polonyi potentials
predict a transition redshift z_t = 0.5 for Omega_Lambda0 = 0.70, in agreement
with the observational value z_t = 0.46 and in mild conflict with the LambdaCDM
value z_t = 0.67. Tables are given for the quintessence potentials for the
recent average wbar_0 of the equation of state parameter, and for w_0 and w_1
in the low-z approximation w = w_0 + w_1 z. It is argued that for the
exponential potential e^{lambda phi} to produce a viable present-day cosmology,
lambda <= sqrt{2}. A robust, scaled numerical method is presented for
simulating the cosmological evolution of the scalar field.


title:
NGC 5385, NGC 2664 and Collinder 21: three candidate Open Cluster
  Remnants

abstract:
  We present CCD UBVI photometric and medium/high resolution spectroscopic
observations obtained in the field of the previously unstudied dissolving open
cluster candidates NGC 5385, NGC 2664 and Collinder~21. Our analysis stands on
the discussion of star counts, photometry, radial velocity distribution, and
proper motions available from the Tycho~2 catalogue. All the three aggregates
clearly emerge from the mean Galactic field, but, regrettably, the close
scrutiny of proper motions and radial velocities reveals that we are not facing
any physical group. Instead, what we are looking at are just chance alignments
of a few bright unrelated stars. Our analysis casts some doubt on the Bica et
al. (2001) criterion to look for Possible Open Cluster Remnants. It seems
mandatory to define a better criterion to adopt for further investigations.


title:
Asteroid Perturbations and Mass Determination for the ASTROD Space
  Mission

abstract:
  Due to the high-precision nature of the ASTROD (Astrodynamical Space Test of
Relativity using Optical Devices) mission concept, the asteroid perturbations
on the ASTROD spacecraft is crucial. These perturbations need to be modelled
and determined together with relativistic effects and other solar-system
parameters. In a previous investigation (Su et al., Planetary and Space
Science, 47, 339-43[1999]), we used the mass estimation of Ceres, Pallas and
Vesta in the literature to calculate their perturbations on the ASTROD
spacecraft. Recently, we established an ephemeris framework (CGC 1) including
the 3 big asteroids and used this ephemeris framework to simulate the
determination of their masses together with other solar-system parameters and
relativistic-gravity parameters. In this paper, we extend the CGC 1 to CGC 2
ephemeris framework to include 492 asteroids (with diameter > 65 km) . We then
use CGC 2 to simulate the determination of ten parameters -- the masses of
Ceres, Pallas and Vesta, the six average densities for the other 489 asteroids,
classified into C, S,M,E,G and U types, and the rate of change of the
gravitational constant G. The fractional mass uncertainties for Ceres, Pallas
and Vesta are about 10**(-3)-10**(-4); the fractional density uncertainties for
six types of asteroids are about 10**(-2)-10**(-3); that for G-dot/G is about
10**(-14)-10**(-15)/yr. This mass and density determination will be useful for
the determination and understanding of the structure and origin of asteroids.


title:
X-ray He-like ion diagnostics: New computations for photoionized plasma.
  II: Influence of different parameters

abstract:
  In a previous article, with a new code designed for a photoionized thick hot
medium using a full transfer treatment of both lines and continuum, we have
studied the He-like emission of a medium photoionized by an X-ray source. We
considered the influence of density, ionization parameter and column density.
We stressed that photoionized media are not uniform in temperature and we
showed that photoexcitation and large column densities should be considered to
avoid misinterpretation of the properties of the medium. To complete the
possible situations observed in photoionized plasmas, we consider here the
influence of microturbulence due for instance to a velocity gradient, of
different element abundance, and of different ionizing spectral distributions.
All new situations are computed using the same code, but with an improved
version of our He-like atomic model. We give values of the G and R ratios, the
equivalent width, and the ionic column densities with a greater accuracy than
previously achieved. A large microturbulence results in a decrease of the G
ratios for large column densities, for which the He-triplet resonant lines are
optically thick. On the contrary, the R ratio is almost independent of the
dispersion velocity and the element abundances, as long as the intercombination
lines are optically thin. Through two 'universal diagrams' not depending on any
parameter, we also present a way to determine the ionization parameter and the
total column density of the emitting regions from the temperature of the
observed radiative recombination continuum of a given ion and its column
density.


title: Clumpy filaments of the Chamaeleon I cloud: C18O mapping with the SEST

abstract:
  The Chamaeleon I dark cloud (Cha I} has been mapped in C18O J=1-0 with an
angular resolution of 1 arcmin using the SEST telescope. The large scale
structures previously observed with lower spatial resolution in the cloud turn
into a network of clumpy filaments. The automatic Clumpfind routine developed
by Williams et al. 1994 is used to identify individual clumps in a consistent
way. Altogether 71 clumps were found and the total mass of these clumps is 230
Mo. The dense 'cores' detected with the NANTEN telescope (Mizuno et al. 1999)
and the very cold cores detected in the ISOPHOT serendipity survey (Toth et al.
2000) form parts of these filaments but decompose into numerous 'clumps' The
filaments are preferentially oriented at right angles to the large-scale
magnetic field in the region. We discuss the cloud structure, the physical
characteristics of the clumps and the distribution of young stars. The observed
clump mass spectrum is compared with the predictions of the turbulent
fragmentation model of Padoan & Nordlund 2002. An agreement is found if
fragmentation has been driven by very large-scale hypersonic turbulence, and if
it has had time to dissipate into modestly supersonic turbulence in the
interclump gas by the present time.


title:
Radial Gas Flows in Colliding Galaxies: Connecting Simulations and
  Observations

abstract:
  (abridged) We investigate the detailed response of gas to the formation of
transient and long-lived dynamical structures induced in the early stages of a
disk-disk collision, and identify observational signatures of radial gas inflow
through a detailed examination of the collision simulation of an equal mass
bulge dominated galaxy. Stars respond to the tidal interaction by forming both
transient arms and long lived m=2 bars, but the gas response is more transient,
flowing directly toward the central regions within about 10^8 years after the
initial collision. The rate of inflow declines when more than half of the total
gas supply reaches the inner few kpc, where the gas forms a dense nuclear ring
inside the stellar bar. The average gas inflow rate to the central 1.8 kpc is
\~7 Msun/yr with a peak rate of 17 Msun/yr. The evolution of gas in a bulgeless
progenitor galaxy is also discussed, and a possible link to the ``chain
galaxy'' population observed at high redshifts is inferred. The evolution of
the structural parameters (the asymmetry and concentration) of both stars and
gas are studied in detail. Further, a new structural parameter (the compactness
parameter K) that traces the evolution of the size scale of the gas relative to
the stellar disk is introduced. Non-circular gas kinematics driven by the
perturbation of the non-axisymmetric structure can produce distinct emission
features in the "forbidden velocity quadrants'' of the position-velocity
diagram (PVD). The dynamical mass calculated using the rotation curve derived
from fitting the emission envelope of the PVD can determine the true mass to
within 20% to 40%. The evolution of the molecular fraction $M_H2/M_(H2 + HI)
and the compactness (K) are potential tracers to quantitatively assign the age
of the interaction.


title:
Dynamical Mass Estimates for Two Luminous Young Stellar Clusters in
  Messier 83

abstract:
  Using new data from the UVES spectrograph on the ESO Very Large Telescope and
archive images from the Hubble Space Telescope, we have measured projected
velocity dispersions and structural parameters for two bright young star
clusters in the nearby spiral galaxy NGC 5236. One cluster is located near the
nuclear starburst of NGC 5236, at a projected distance of 440 pc from the
centre, while the other is located in the disk of the galaxy at a projected
galactocentric distance of 2.3 kpc. We estimate virial masses for the two
clusters of (4.2+/-0.7)x10^5 Msun and (5.2+/-0.8)x10^5 Msun and ages (from
broad-band photometry) of 10^(7.1+/-0.2} years and 10^(8.0+/-0.1) years,
respectively. Comparing the observed mass-to-light (M/L) ratios with simple
stellar population models, we find that the data for both clusters are
consistent with a Kroupa-type stellar mass function (MF). In particular, we
rule out any MF with a significantly lower M/L ratio than the Kroupa MF, such
as a Salpeter-like MF truncated at a mass of 1 Msun or higher. These clusters
provide a good illustration of the fact that massive, globular cluster-like
objects ("super star clusters") can form at the present epoch even in the disks
of seemingly normal, undisturbed spiral galaxies.


title:
Unified treatment of cosmological perturbations from super-horizon to
  small scales

abstract:
  We study the evolution of cosmological perturbations, using a hybrid
approximation scheme which upgrades the weak-field limit of Einstein's field
equations to account for post-Newtonian scalar and vector metric perturbations
and for leading-order source terms of gravitational waves, while including also
the first and second-order perturbative approximations. Our equations, which
are derived in the Poisson gauge, provide a unified description of matter
inhomogeneities in a Universe filled with a pressureless and irrotational fluid
and a cosmological constant, ranging from the linear to the highly non-linear
regime. The derived expressions for scalar, vector and tensor modes can have a
wide range of cosmological applications, ranging from secondary CMB anisotropy
and polarization effects, cosmographic relations in a inhomogeneous Universe,
gravitational lensing effects and the stochastic gravitational-wave backgrounds
generated by non-linear cosmic structures.


title:
An Accretion-Jet Model for Black Hole Binaries: Interpreting the
  Spectral and Timing Features of XTE J1118+480

abstract:
  Multi-wavelength observations of the black hole X-ray binary XTE J1118+480
have offered abundant spectral and timing information about the source, and
have thus provided serious challenges to theoretical models. We propose a
coupled accretion-jet model to interpret the observations. We model the
accretion flow as an outer standard thin accretion disk truncated at a
transition radius by an inner hot accretion flow. The accretion flow accounts
for the observed UV and X-ray emission, but it substantially under-predicts the
radio and infrared fluxes, even after we allow for nonthermal electrons in the
hot flow. We attribute the latter components to a jet. We model the jet
emission by means of the internal shock scenario which is widely employed for
gamma-ray bursts. In our accretion-jet model of XTE J1118+480, the jet
dominates the radio and infrared emission, the thin disk dominates the UV
emission, and the hot flow produces most of the X-ray emission. The optical
emission has contributions from all three components: jet, thin disk, and hot
flow. The model qualitatively accounts for timing features, such as the
intriguing positive and negative time lags between the optical and X-ray
emission, and the wavelength-dependent variability amplitude.


title:
The XMM-Newton observation of GRB 040106 : evidence for an afterglow in
  a wind environment

abstract:
  We present the XMM-Newton observation of GRB 040106. From the X-ray spectral
index and temporal decay, we argue that the afterglow is consistent with a
fireball expanding in a wind environment. A constant density environment is
excluded by the data. This is one of the very few cases in which this
conclusion can be drawn.


title: Rapid multiperiodic variability in a high-mass X-ray binary

abstract:
  Positions of High-Mass X-ray Binaries are often known precisely enough to
unambiguously identify the optical component, and a number of those stars are
monitored by the OGLE and MACHO collaborations. The light curves of two such
candidates are examined for evidence of Be star behavior and for periodicity.
One of the stars exhibits two periods of 6.833 and 15.586 hours, much shorter
and more stable than periods of Be/X-Ray Binaries that are attributed to the Be
star's disk, but consistent with short-term Be variability attributed to
pulsations. The multiperiodicity is quantified with Fourier techniques and
examined for phase stability; a combination of radial and non-radial pulsations
is discussed.


title: HIROCS - a galaxy cluster survey at high redshifts

abstract:
  As a step towards our understanding of galaxy evolution and for testing
predictions of cosmological models we started a survey for galaxy clusters
intending to identify candidates out to redshifts of ~1.5: HIROCS (= Heidelberg
InfraRed/Optical Cluster Survey) is a multi-color survey (B, R, i, z and H)
covering 11 square degrees in four fields on the sky. Our survey aims at a
5sigma detection of an L*+1 elliptical galaxy at z = 1.5. Classification of all
objects and determination of photometric redshifts is done by the
multi-color-classification scheme developed for the CADIS and COMBO-17 surveys.
Cluster identification will be done by identifying overdensities in 3D-space
(RA, DEC, zphot). First tests of our cluster finding algorithm on fields
observed within CADIS and COMBO-17 revealed several cluster candidates.


title:
Numerical dissipation and the bottleneck effect in simulations of
  compressible isotropic turbulence

abstract:
  The piece-wise parabolic method (PPM) is applied to simulations of forced
isotropic turbulence with Mach numbers $\sim 0.1... 1$. The equation of state
is dominated by the Fermi pressure of an electron-degenerate fluid. The
dissipation in these simulations is of purely numerical origin. For the
dimensionless mean rate of dissipation, we find values in agreement with known
results from mostly incompressible turbulence simulations. The calculation of a
Smagorinsky length corresponding to the rate of numerical dissipation supports
the notion of the PPM supplying an implicit subgrid scale model. In the
turbulence energy spectra of various flow realisations, we find the so-called
bottleneck phenomenon, i.e., a flattening of the spectrum function near the
wavenumber of maximal dissipation. The shape of the bottleneck peak in the
compensated spectrum functions is comparable to what is found in turbulence
simulations with hyperviscosity. Although the bottleneck effect reduces the
range of nearly inertial length scales considerably, we are able to estimate
the value of the Kolmogorov constant. For steady turbulence with a balance
between energy injection and dissipation, it appears that $C\approx 1.7$.
However, a smaller value is found in the case of transonic turbulence with a
large fraction of compressive components in the driving force. Moreover, we
discuss length scales related to the dissipation, in particular, an effective
numerical length scale $\Delta_{\mathrm{eff}}$, which can be regarded as the
characteristic smoothing length of the implicit filter associated with the PPM.