title: The Kinematics of Thick Disks in External Galaxies

abstract:
  We present kinematic measurements of the thick and thin disks in two edge-on
galaxies. We have derived stellar rotation curves at and above the galaxies'
midplanes using Ca II triplet features measured with the GMOS spectrograph on
Gemini North. In one galaxy, FGC 1415, the kinematics above the plane show
clear rotation that lags that of the midplane by ~20-50%, similar to the
behavior seen in the Milky Way. However, the kinematics of the second galaxy,
FGC 227, are quite different. The rotation above the plane is extremely slow,
showing <25% of the rotation speed of the stars at the midplane. We decompose
the observed rotation curves into a superposition of thick and thin disk
kinematics, using 2-dimensional fits to the galaxy images to determine the
fraction of thick disk stars at each position. We find that the thick disk of
FGC 1415 rotates at 30-40% of the rotation speed of the thin disk. In contrast,
the thick disk of FGC 227 is very likely counter-rotating, if it is rotating at
all. These observations are consistent with the velocity dispersion profiles we
measure for each galaxy. The detection of counter-rotating thick disks
conclusively rules out models where the thick disk forms either during
monolithic collapse or from vertical heating of a previous thin disk. Instead,
the data strongly support models where the thick disk forms from direct
accretion of stars from infalling satellites.


title: A new method optimized to use Gamma Ray Bursts as cosmic rulers

abstract:
  We present a new method aimed to handle long Gamma-Ray Burst (GRBs) as cosmic
rulers. The recent discovery of a tight correlation between the collimation
corrected GRB energy and the peak of the gamma-ray spectrum has opened the
possibility to use GRBs as a new category of standard candles. Unfortunately,
because of the lack of low-z GRBs, up to now this correlation is obtained from
high-z GRBs with the consequence that it depends on the cosmological parameters
we pretend to constrain. Hopefully this circularity problem will be solved
when, in a few years, the low-z GRB sample will be increased enough. In the
meanwhile we present here a new Bayesian method that eases the aforesaid
circularity problem, and allows to introduce new constrains on the cosmological
(Om,OL) diagram as well as to explore the universe kinematics up to z~3. The
method we propose offers the further advantage to make handy the problem of the
(Om,OL) loitering line singularity which inevitably appears when standard
candles with z>2 are used. The combination of GRB with SN Ia data makes the
popular LambdaCDM cosmology more consistent with the Hubble diagram at a 68%
confidence level. For a flat cosmology we find Om=0.28\pm0.03 for the combined
GRB+SN Ia data set. Correspondingly, the transition redshift between cosmic
deceleration and acceleration is z_T=0.73\pm0.09, slightly larger than the
value found by considering SNe Ia alone. We briefly discuss our results also in
terms of non--LambdaCDM dark energy models.


title: Islands in the Lambda-sea: An alternative cosmological model

abstract:
  We propose an alternate cosmological model in which our observable universe
is an island in a cosmological constant sea. Initially the universe is filled
with cosmological constant of the currently observed value but is otherwise
empty. In this eternal or semi-eternal de Sitter spacetime, we show that local
quantum fluctuations (upheavals) can violate the null energy condition and
create islands of matter. The perturbation spectra of quantum fields other than
that responsible for the upheaval, are shown to be scale invariant. With
further cosmic evolution the island disappears and the local universe returns
to its initial cosmological constant dominated state.


title:
X-ray spectral analysis of optically faint sources in the Chandra Deep
  Fields

abstract:
  We present the results of a detailed spectral analysis of optically faint
hard X-ray sources in the Chandra deep fields selected on the basis of their
high X-ray to optical flux ratio (X/O). The stacked spectra of high X/O sources
in both Chandra deep fields, fitted with a single power-law model, are much
harder than the spectrum of the X-ray background (XRB). The average slope is
also insensitive to the 2-8 keV flux, being approximately constant around
Gamma~1 over more than two decades, strongly indicating that high X/O sources
represent the most obscured component of the XRB. For about half of the sample,
a redshift estimate (in most of the cases a photometric redshift) is available
from the literature. Individual fits of a few of the brightest objects and of
stacked spectra in different redshift bins imply column densities in the range
10^{22-23.5} cm^{-2}. A trend of increasing absorption towards higher redshifts
is suggested.


title:
Lambda-Cold Dark Matter, Stellar Feedback, and the Galactic Halo
  Abundance Pattern

abstract:
  (Abridged) The hierarchical formation scenario for the stellar halo requires
the accretion and disruption of dwarf galaxies, yet low-metallicity halo stars
are enriched in alpha-elements compared to similar, low-metallicity stars in
dwarf spheroidal (dSph) galaxies. We address this primary challenge for the
hierarchical formation scenario for the stellar halo by combining chemical
evolution modelling with cosmologically-motivated mass accretion histories for
the Milky Way dark halo and its satellites. We demonstrate that stellar halo
and dwarf galaxy abundance patterns can be explained naturally within the LCDM
framework. Our solution relies fundamentally on the LCDM model prediction that
the majority of the stars in the stellar halo were formed within a few
relatively massive, ~5 x 10^10 Msun, dwarf irregular (dIrr)-size dark matter
halos, which were accreted and destroyed ~10 Gyr in the past. These systems
necessarily have short-lived, rapid star formation histories, are enriched
primarily by Type II supernovae, and host stars with enhanced [a/Fe]
abundances. In contrast, dwarf spheroidal galaxies exist within low-mass dark
matter hosts of ~10^9 Msun, where supernovae winds are important in setting the
intermediate [a/Fe] ratios observed. Our model includes enrichment from Type Ia
and Type II supernovae as well as stellar winds, and includes a
physically-motivated supernovae feedback prescription calibrated to reproduce
the local dwarf galaxy stellar mass - metallicity relation. We use
representative examples of the type of dark matter halos we expect to host a
destroyed ``stellar halo progenitor'' dwarf, a surviving dIrr, and a surviving
dSph galaxy, and show that their derived abundance patterns, stellar masses,
and gas masses are consistent with those observed for each type of system.


title:
Correlated Mixture Between Adiabatic and Isocurvature Fluctuations and
  Recent CMB Observations

abstract:
  This work presents a reduced chi^2_nu test to search for non-gaussian signals
in the CMBR TT power spectrum of recent CMBR data, WMAP, ACBAR and CBI data
sets, assuming a mixed density field including adiabatic and isocurvature
fluctuations. We assume a skew positive mixed model with adiabatic inflation
perturbations plus additional isocurvature perturbations possibly produced by
topological defects. The joint probability distribution used in this context is
a weighted combination of Gaussian and non-Gaussian random fields. Results from
simulations of CMBR temperature for the mixed field show a distinct signature
in CMB power spectrum for very small deviations (~ 0.1%) from a pure Gaussian
field, and can be used as a direct test for the nature of primordial
fluctuations. A reduced chi^2_nu test applied on the most recent CMBR
observations reveals that an isocurvature fluctuations field is not ruled out
and indeed permits a very good description for a flat geometry Lambda-CDM
universe, chi^2_930 ~ 1.5, rather than the simple inflationary standard model
with chi^2_930 ~ 2.3. This result may looks is particular discrepant with the
reduced chi^2 of 1.07 obtained with the same model in Spergel et al. (2003) for
temperature only, however, our work is restricted to a region of the parameter
space that does not include the best fit model for TT only of Spergel et al.
(2003).


title: Global Star Formation from z=5e-8 to z=20

abstract:
  Starting with the assertion that the problem of isolated, single star
formation is essentially solved, this paper examines some of the missing steps
needed to go from there to understanding the star formation history of the
Universe. Along the way, some results on the formation of star clusters in the
Milky Way and the properties of GMCs in nearby galaxies are briefly examined.


title: Nonlinear Evolutions and Non-Gaussianity in Generalized Gravity

abstract:
  We use the Hamilton-Jacobi theory to study the nonlinear evolutions of
inhomogeneous spacetimes during inflation in generalized gravity. We find the
exact solutions to the lowest order Hamilton-Jacobi equation for special scalar
potentials and introduce an approximation method for general potentials. The
conserved quantity invariant under a change of timelike hypersurfaces proves
useful in dealing with gravitational perturbations. In the long-wavelength
approximation, we find a conserved quantity related to the new canonical
variable that makes the Hamiltonian density vanish, and calculate the
non-Gaussianity in generalized gravity. The slow-roll inflation models with a
single scalar field in generalized gravity predict too small non-Gaussianity to
be detected by future CMB experiments.


title: Constraining the thermal history of the Warm-Hot Intergalactic Medium

abstract:
  We have identified a large-scale structure traced by galaxies at z=0.8,
within the Lockman Hole, by means of multi-object spectroscopic observations.
By using deep XMM images we have investigated the soft X-ray emission from the
Warm-Hot Intergalactic Medium (WHIM) expected to be associated with this
large-scale structure and we set a tight upper limit to its flux in the very
soft 0.2-0.4 keV band. The non-detection requires the WHIM at these redshifts
to be cooler than 0.1 keV. Combined with the WHIM emission detections at lower
redshift, our result indicates that the WHIM temperature is rapidly decreasing
with redshift, as expected in popular cosmological models.


title: GRBs-SN and SGR-X-Pulsar as blazing Jets

abstract:
  Old and recent puzzles of GRBs and SGRs find a solution with a model based on
the fast blazing of very collimated thin gamma Jets. Damped oscillating
afterglows in GRB030329 find a natural explanation assuming a very thin Jet
whose persistent activity and different angle of view maybe combined at once
with the Supernovae power and the apparent huge GRBs output. The same thin
beaming offer an understanding of the apparent SGR-Pulsar power connection. A
thin collimated precessing Gamma Jet model for both GRBs and SGRs, at their
different scaled luminosity (10^{44} - 10^{38}erg s^-1), explains the existence
of few identical energy spectra and time evolution of these sources leading to
a unified model. Their similarity with the huge precessing Jets in AGN, QSRs
and Radio-Galaxies inspires this smaller scale SGR-GRB model. The
spinning-precessing Jet explains the rare mysterious X-Ray precursors in GRBs
and SGRs events. Any large Gamma Jet off-axis beaming to the observer might
lead to the X-Flash events without any GRB signals, as the most recent
XRF030723. Its possible re-brightening would confirm the evidence of the
variable pointing of the jet in or off line towards the observer.
  Indeed a multi-precessing Jet at peak activity in all bands may explain the
puzzling X or optical re-brightening bumps found in the GRB 021004, GRB030329
and the SGR 1900+ 14 on 27 August 1998 and once again on the 18 April 2001.
Rarest micro-quasars neutron star in our galaxy as SS433, and Herbig Haro
objects and Cir-X-1 describe these thin precessing Jet imprints in the
spectacular shapes of their relic nebulae.


title: Distributions of the Baryon Fraction on Large Scales in the Universe

abstract:
  (Abridged) The nonlinear evolution of a system consisting of baryons and dark
matter is generally characterized by strong shocks and discontinuities. The
baryons slow down significantly at postshock areas of gravitational strong
shocks, which can occur in high overdense as well as low overdense regions.
Consequently, the baryon fraction would be nonuniform on large scales. We
studied these phenomena with simulation samples produced by the WENO hybrid
cosmological hydrodynamic/N-body code. We find that the baryon fraction in high
mass density regions is lower on average than the cosmic baryon fraction, and
many baryons accumulate in the regions with moderate mass density to form a
high baryon fraction phase (HBFP). In dense regions with rho>100, which are the
possible hosts for galaxy clusters, the baryon fraction can be lower than the
cosmic baryon fraction by about 10%--20% at z ~ 0. Our simulation samples show
that about 3% of the cosmic baryon budget was hidden in the HBFP at redshift
z=3, while this percentage increases to about 14% at the present day. The gas
in the HBFP cannot be detected either by Ly-alpha forests of QSO absorption
spectra or by soft X-ray background. That is, the HBFP would be missed in the
baryon budget given by current observations.


title: s Process in low-mass Asymptotic Giant Branch Stars

abstract:
  The main component of the s process is produced by low mass stars (between
1.5 and 3 Mo), when they climb for the second time the red giant branch and
experience a series of He shell flashes called thermal pulses. During the
relatively long period (10^5 yr) that elapses between two subsequent thermal
pulses, a slow neutron flux is provided by the 13C(a,n)16O reaction taking
place within a thin 13C pocket located in the He-rich and C-rich mantel of
these stars. A second, marginal, neutron burst occurs during the thermal pulse
and it is powered by the 22Ne(a,n)25Mg reaction. We review the present status
of the nucleosynthesis models of low mass AGB stars. The advance in the
knowledge of the complex coupling between convective mixing and nuclear
process, which allows the surface enrichment of C and s-process elements, is
presented, together with the hypotheses concerning the physical mechanism
driving the formation of the 13C pocket. In order to illustrate the
capabilities and the limits of the theory, an updated computation of a 2 Mo
stellar structure with solar chemical composition is reported. This model has
been obtained by including a full nuclear network (from H up to Bi, at the
termination point of the s-process path) into the stellar evolution code. The
predicted modification of the surface composition occurring during the AGB
evolution is shown. The new challenge of AGB modeling, namely the study of
C-rich and s-rich very metal-poor stars, is discussed.


title: The V-band luminosity function of galaxies in A2151

abstract:
  We present a wide field $V$-band imaging survey of approximately 1 deg$^2$
($\sim7.2 h^{-2}_{75}$ Mpc$^{2}$) in the direction of the nearby cluster of
galaxies Abell 2151 (the Hercules Cluster). The data are used to construct the
luminosity function (LF) down to $M_V \approx -14.85$, thus allowing us to
study the dwarf galaxy population in A2151 for the first time. The obtained
global LF is well described by a Schechter function with best-fit parameters
$\alpha = -1.29^{+0.09}_{-0.08}$ and $M_V^* = -21.41^{+0.44}_{-0.41}$. The
radial dependence of the LF was investigated, with the faint-end slope tending
to be slightly steeper in the outermost regions and farther away than the
virial radius. Given the presence of significant substructure within the
cluster, we also analysed the LFs in three different regions. We find that the
dwarf to giant ratio increases from the northern to the southern subcluster,
and from low to high local density environments, although these variations are
marginally significant (less than 2$\sigma$).


title:
Multi-frequency VLBA observations of compact sources from the Peacock &
  Wall catalogue

abstract:
  VLBA observations are presented for 6 compact radio sources selected from the
Peacock & Wall catalogue. From the new morphological and spectral information 2
objects that in the Peacock and Wall catalogue are flat spectrum (alpha < 0.5)
sources, appear to be double sided objects with linear sizes of the order of
one kpc. Three are core-jet sources and the last one is still an ``enigmatic''
object. These data complete the sample of small double compact sources in the
Peacock & Wall catalogue and the complete list is given.


title: Polarimetry of powerful radio galaxies from z=0 to z=4

abstract:
  The advent of sensitive polarimeters on large telescopes has led to a
revolution in our understanding of active galaxies over the last 20 years. In
the case of powerful radio galaxies the deep polarimetric measurements made
possible by the new technology have: (a) provided the most direct evidence to
support the unified schemes for powerful radio galaxies; (b) enhanced our
understanding of the colours and morphologies of radio source host galaxies at
all redshifts; and (c) provided key information about the kinematics and
geometries of the scattering regions on a sub-kpc scale.


title: Fractals vs. halos: Asymptotic scaling without fractal properties

abstract:
  Precise analyses of the statistical and scaling properties of galaxy
distribution are essential to elucidate the large-scale structure of the
universe. Given the ongoing debate on its statistical features, the development
of statistical tools permitting to discriminate accurately different spatial
patterns is highly desiderable. This is specially the case when non-fractal
distributions have power law two-point correlation functions, which are usually
signatures of fractal properties. Here we review some possible methods used in
the literature and introduce a new variable called "scaling gradient". This
tool and the conditional variance are shown to be effective in providing an
unambiguous way for such a distinction. Their application is expected to be of
outmost importance in the analysis of upcoming galaxy catalogues.


title:
Pseudo-Schwarzschild Spherical Accretion as a Classical Black Hole
  Analogue

abstract:
  We demonstrate that a spherical accretion onto astrophysical black holes,
under the influence of Newtonian or various post-Newtonian pseudo-Schwarzschild
gravitational potentials, may constitute a concrete example of classical
analogue gravity naturally found in the Universe. We analytically calculate the
corresponding analogue Hawking temperature as a function of the minimum number
of physical parameters governing the accretion flow. We study both the
polytropic and the isothermal accretion. We show that unlike in a general
relativistic spherical accretion, analogue white hole solutions can never be
obtained in such post-Newtonian systems. We also show that an isothermal
spherical accretion is a remarkably simple example in which the only one
information--the temperature of the fluid, is sufficient to completely describe
an analogue gravity system. For both types of accretion, the analogue Hawking
temperature may become higher than the usual Hawking temperature. However, the
analogue Hawking temperature for accreting astrophysical black holes is
considerably lower compared with the temperature of the accreting fluid.


title:
X-ray properties of UV-selected star forming galaxies at z~1 in the
  Hubble Deep Field North

abstract:
  We present an analysis of the X-ray emission from a large sample of
ultraviolet (UV) selected, star forming galaxies with 0.74<z<1.32 in the Hubble
Deep Field North (HDF-N) region. By excluding all sources with significant
detected X-ray emission in the 2 Ms Chandra observation we are able to examine
the properties of galaxies for which the emission in both UV and X-ray is
expected to be predominantly due to star formation. Stacking the X-ray flux
from 216 galaxies in the soft and hard bands produces significant detections.
The derived mean 2-10 keV rest-frame luminosity is 2.97+/-0.26x10^(40) erg/s,
corresponding to an X-ray derived star formation rate (SFR) of 6.0+/-0.6
Msolar/yr. Comparing the X-ray value with the mean UV derived SFR, uncorrected
for attenuation, we find that the average UV attenuation correction factor is
\~3. By binning the galaxy sample according to UV magnitude and colour,
correlations between UV and X-ray emission are also examined. We find a strong
positive correlation between X-ray emission and rest-frame UV emission. A
correlation between the ratio of X-ray-to-UV emission and UV colour is also
seen, such that L(X)/L(UV) increases for redder galaxies. Given that X-ray
emission offers a view of star formation regions that is relatively unaffected
by extinction, results such as these can be used to evaluate the effects of
dust on the UV emission from high-z galaxies. For instance we derive a
relationship for estimating UV attenuation corrections as a function of colour
excess. The observed relation is inconsistent with the Calzetti et al. (2000)
reddening law which over predicts the range in UV attenuation corrections by a
factor of ~100 for the UV selected z~1 galaxies in this sample (abridged).


title:
Dark Matter particles in the galactic halo: results and implications
  from DAMA/NaI

abstract:
  The DAMA/NaI experiment (about 100 kg highly radiopure NaI(Tl)) was proposed,
designed and realised to effectively investigate in a model independent way the
presence of a Dark Matter particle component in the galactic halo by exploiting
the annual modulation signature. With a total exposure of 107731 kg day,
collected over seven annual cycles deep underground at the Gran Sasso National
Laboratory of the I.N.F.N., it has pointed out -- at 6.3 sigma C.L. -- an
effect which satisfies all the peculiarities of the signature and neither
systematic effects nor side reactions able to mimic the signature were found.
Moreover, several (but still few with respect to the possibilities) corollary
model dependent quests for the candidate particle have been carried out. In
this paper the obtained results are summarized and some perspectives are
discussed at some extent.


title:
Ultraviolet Dust Grain Properties in Starburst Galaxies: Evidence from
  Radiative Transfer Modeling and Local Group Extinction Curves

abstract:
  This paper summarizes the evidence of the ultraviolet properties of dust
grains found in starburst galaxies. Observations of starburst galaxies clearly
show that the 2175 A feature is weak or absent. This can be the result of
radiative transfer effects (mixing the dust and stars) or due to dust grains
which do not have this feature. Spherical DIRTY radiative transfer models imply
that it is not radiative transfer effects, but other radiative transfer models
with disk/bulge geometries have found cases where it could be radiative
transfer effects. Recent work on the extinction curves in the Magellanic Clouds
and Milky Way has revealed that the traditional explanation of low metallicity
for the absence of the 2175 A feature in the Small Magellanic Cloud is likely
incorrect. The SMC has one sightline with a 2175 A feature and the Milky Way
has sightlines without this feature. In addition, where the 2175 A feature is
found to be weak or absent in both Magellanic Clouds and the Milky Way, there
is evidence for recent star formation. Taking the sum of the radiative transfer
modeling of starburst galaxies and the behavior of Local Group extinction
curves, it is likely that the dust grains in starburst galaxies intrinsically
lack the 2175 A feature.


title: The giant star forming halo associated with the radio galaxy PKS1932-46

abstract:
  We report the discovery of a giant (~160 kpc) knotty extended emission line
nebula associated with the radio galaxy PKS1932-46 at z=0.23. The 2-d long slit
spectra, obtained with VLT-FORS2 at a large angle (~63 degr) to the radio
source axis, shows that the nebula extends well beyond the radio structure and
the ionization cones of the active nucleus. This is one of the largest ionized
nebulae yet detected around a radio galaxy at any redshift. The analysis of the
ionization, morphological and kinematic properties of the knots suggests that
these are star forming objects, probably compact HII galaxies. We propose that
the giant structure is a star forming halo associated with the debris of the
merger that triggered the activity. This study reinforces the view that radio
galaxies are activated by major mergers which also trigger substantial star
formation. The star formation activity can extend on the scale of a galaxy
group, beyond the old stellar halo of the host galaxy.


title: Effects of episodic gas infall on the chemical abundances in galaxies

abstract:
  The chemical evolution of galaxies that undergo an episode of massive and
rapid accretion of metal-poor gas is investigated with models using both
simplified and detailed nucleosynthesis recipes. The rapid decrease of the
oxygen abundance during infall is followed by a slower evolution which leads
back to the closed-box relation, thus forming a loop in the N/O-O/H diagram.
For large excursions from the closed-box relation, the mass of the infalling
material needs to be substantially larger than the gas remaining in the galaxy,
and the accretion rate should be larger than the star formation rate. We apply
this concept to the encounter of high velocity clouds with galaxies of various
masses, finding that the observed properties of these clouds are indeed able to
cause substantial effects not only in low mass galaxies, but also in the
partial volumes in large massive galaxies that would be affected by the
collision. Numerical models with detailed nucleosynthesis prescriptions are
constructed. We assume star formation timescales and scaled yields that depend
on the galactic mass, and which are adjusted to reproduce the average relations
of gas fraction, oxygen abundance, and effective oxygen yield observed in
irregular and spiral galaxies. The resulting excursions in the N/O-O/H diagram
due to a single accretion event involving a high velocity cloud are found to be
appreciable, which could thus provide a contribution to the large scatter in
the N/O ratio found among irregular galaxies. Nonetheless, the N/O-O/H diagram
remains an important indicator for stellar nucleosynthesis.


title: The first turbulent combustion

abstract:
  The first turbulent combustion arises in a hot big bang cosmological model
Gibson (2004) where nonlinear exothermic turbulence permitted by quantum
mechanics, general relativity, multidimensional superstring theory, and fluid
mechanics cascades from Planck to strong force freeze out scales with gravity
balancing turbulent inertial-vortex forces. Interactions between Planck scale
spinning and non-spinning black holes produce high Reynolds number turbulence
and temperature mixing with huge Reynolds stresses driving the rapid inflation
of space. Kolmogorovian turbulent temperature patterns are fossilized as
strong-force exponential inflation stretches them beyond the scale of causal
connection ct where c is light speed and t is time. Fossil temperature
turbulence patterns seed nucleosynthesis, and then hydro-gravitational
structure formation in the plasma epoch, Gibson (1996, 2000). Evidence about
formation mechanisms is preserved by cosmic microwave background temperature
anisotropies. CMB spectra indicate hydro-gravitational fragmentation at
supercluster to galaxy masses in the primordial plasma with space stretched by
\~10^50. Bershadskii and Sreenivasan (2002, 2003) CMB multi-scaling
coefficients support a strong turbulence origin for the anisotropies prior to
the plasma epoch.


title:
Seismology of triple-mode classical Cepheids of the Large Magellanic
  Cloud

abstract:
  We interpret the three periods detected in OGLE LMC Cepheids SC3-360128 and
SC5-338399 as corresponding to the first three overtones of radial pulsations.
This interpretation imposes stringent constraints on parameters of the stars
and on their evolutionary status, which could only be the first crossing of the
instability strip. Evolutionary models reproducing measured periods exist only
in a restricted range of metallicities (Z=0.004-0.007). The models impose an
upper limit on the extent of overshooting from the convective core. Absolute
magnitude of each star is confined to a narrow interval. This allows to derive
a new estimate of the distance to the LMC. We obtain m-M ranging from 18.34mag
to 18.53mag, with a systematic difference between the two stars of about
0.13mag. The rates of period change predicted by the models are formally in
conflict with the derived observational limits, though the uncertainities of
measured dP/dt may be underestimated. If the discrepancy is confirmed, it would
constitute a significant challenge to the stellar evolution theory.


title:
Orbital Structure of Collisionless Merger Remnants: On the Origin of
  Photometric and Kinematic Properties of Elliptical and S0 Galaxies

abstract:
  We present a detailed investigation of the relation between the orbital
content of merger remnants and observable properties of elliptical and S0
galaxies. Our analysis is based on the statistical sample of collisionless
mergers of disk galaxies with different mass ratios and orbital parameters,
published by Naab & Burkert. We use the spectral method by Carpintero & Aguilar
to determine the orbital content of every remnant and correlate it with its
intrinsic shape, and its projected kinematic and photometric properties. We
discuss the influence of the bulge component and varying pericenter distances.
The two most abundant orbit classes are the minor axis tubes and the box
orbits. Their ratio seems to determine the basic properties of a remnant. On
average, the fraction of minor axis tubes increases by a factor of two from a
merger mass ratio of 1:1 to 4:1, whereas the fraction of box orbits decreases
by 10%. At a given mass the central velocity dispersion of a remnant scales
with the ratio of minor axis tubes to box orbits. Interestingly, the division
line between rotational supported systems and pressure supported objects,
$(v_{maj}/\sigma_0)^*=0.7$, turns out to coincide with a box to minor axis tube
ratio of unity. The observed $h_3$-$v/\sigma$ anti-correlation for ellipticals
can not be reproduced by collisionless merger remnants. We propose that this
can only be reconciled by an additional physical process that significantly
reduces the box orbit content. Remnants which are dominated by minor axis tube
orbits have predominantly disky projections. Boxy remnants have always a box to
minor axis tube ratio larger than one. This study will enable to identify
observed ellipticals that could have formed, in the collisionless limit, by
gas-poor disk mergers.


title: Laplacian eigenmodes for spherical spaces

abstract:
  The possibility that our space is multi - rather than singly - connected has
gained a renewed interest after the discovery of the low power for the first
multipoles of the CMB by WMAP. To test the possibility that our space is a
multi-connected spherical space, it is necessary to know the eigenmodes of such
spaces. Excepted for lens and prism space, and in some extent for dodecahedral
space, this remains an open problem. Here we derive the eigenmodes of all
spherical spaces. For dodecahedral space, the demonstration is much shorter,
and the calculation method much simpler than before. We also apply to
tetrahedric, octahedric and icosahedric spaces. This completes the knowledge of
eigenmodes for spherical spaces, and opens the door to new observational tests
of cosmic topology.
  The vector space V^k of the eigenfunctions of the Laplacian on the
three-sphere S^3, corresponding to the same eigenvalue \lambda_k = -k (k+2),
has dimension (k+1)^2. We show that the Wigner functions provide a basis for
such space. Using the properties of the latter, we express the behavior of a
general function of V^k under an arbitrary rotation G of SO(4). This offers the
possibility to select those functions of V^k which remain invariant under G.
  Specifying G to be a generator of the holonomy group of a spherical space X,
we give the expression of the vector space V_X^k of the eigenfunctions of X. We
provide a method to calculate the eigenmodes up to arbitrary order. As an
illustration, we give the first modes for the spherical spaces mentioned.


title:
VLTI/VINCI diameter constraints on the evolutionary status of delta Eri,
  xi Hya, eta Boo

abstract:
  Using VLTI/VINCI angular diameter measurements, we constrain the evolutionary
status of three asteroseismic targets: the stars $\delta$ Eri, $\xi$ Hya,
$\eta$ Boo. Our predictions of the mean large frequency spacing of these stars
are in agreement with published observational estimations. Looking without
success for a companion of $\delta$ Eri we doubt on its classification as an RS
CVn star.


title: Lessons for Asteroseismology from White Dwarf Stars

abstract:
  The interpretation of pulsation data for Sun-like stars is currently facing
challenges quite similar to those faced by white dwarf modelers ten years ago.
The observational requirements for uninterrupted long-term monitoring are
beginning to be satisfied by successful multi-site campaigns and dedicated
satellite missions. But exploration of the most important physical parameters
in theoretical models has been fairly limited, making it difficult to establish
a detailed best-fit model for a particular set of oscillation frequencies. I
review the past development and the current state of white dwarf
asteroseismology, with an emphasis on what this can tell us about the road to
success for asteroseismology of other types of stars.


title:
The first detection of [OIII] emission from high-redshift damped
  Lyman-alpha galaxies

abstract:
  We present the detection of [OIII] emission lines from the galaxies
responsible for two high-redshift z>1.75 damped Lyman-alpha (DLA) absorption
lines. These are the first detections of rest-frame optical emission lines from
high-redshift DLA galaxies. Unlike the Lyman-alpha line, the [OIII] line
provides a measure of the systemic velocity of the galaxy. We compare the
[OIII] redshifts with the velocity profile of the low-ionisation metal lines in
these two absorbers, with the goal of distinguishing between the model of
Prochaska and Wolfe of DLA absorbers as large rapidly rotating cold thick
discs, and the standard hierarchical CDM model of structure formation, in which
DLAs arise in protogalactic fragments. We find some discrepancies with the
predictions of the former model. Furthermore the image of the DLA galaxy
towards Q2206-1958 shows a complex disturbed morphology, which is more in
accord with the hierarchical picture. We use the properties of the rest-frame
optical emission lines to further explore the question posed by Moller et al.:
are high-redshift DLA galaxies Lyman-break galaxies (LBGs) selected by gas
cross section? The measured velocity dispersions of the DLA galaxies are in
agreement with this picture, while the data on the [OIII] luminosities and the
velocity differences between the Lyman-alpha and [OIII] lines are inconclusive,
as there are insufficient LBG measurements overlapping in luminosity. Finally
we estimate the star formation rates in these two DLA galaxies, using a variety
of diagnostics, and include a discussion of the extent to which the [OIII] line
is useful for this purpose. (abridged)


title: Challenges for Kinetic Unified Dark Matter

abstract:
  Given that the dark matter and dark energy in the universe affect
cosmological observables only gravitationally, their phenomenology may be
described by a single stress energy tensor. True unification however requires a
theory that reproduces the successful phenomenology of LCDM and that
requirement places specific constraints on the stress structure of the matter.
We show that a recently proposed unification through an offset quadratic
kinetic term for a scalar field is exactly equivalent to a fluid with a
closed-form barotropic equation of state plus cosmological constant. The finite
pressure at high densities introduces a cutoff in the linear power spectrum,
which may alleviate the dark matter substructure problem; we provide a
convenient fitting function for such studies. Given that sufficient power must
remain to reionize the universe, the equation of state today is nonrelativistic
with p proportional to rho^2 and a Jeans scale in the parsec regime for all
relevant densities. Structure may then be evolved into the nonlinear regime
with standard hydrodynamic techniques. In fact, the model is equivalent to the
well-studied collisional dark matter with negligible mean free path. If recent
observations of the triaxiality of dark matter halos and ram pressure stripping
in galaxy clusters are confirmed, this model will be ruled out.


title: A Kinematic Model for Gamma Ray Bursts and Symmetric Jets

abstract:
  Gamma ray bursts (GRB) occur at random points in the sky at cosmological
distances. The spectra evolve through X-ray, optical region to possibly radio
frequency. Though there are some models, the origin and time evolution of GRB
are not well understood. Extragalactic radio sources also exhibit a baffling
array of features that are poorly understood -- the core emission in
ultraviolet region, lobes in RF range, transient gamma and X-ray emissions etc.
These two phenomena appear to be very different, but the time evolution of the
core emission of radio sources is essentially the same as GRBs, though with
different time constants. Here, we present a model unifying GRB and roughly
symmetric radio sources based on light travel time effect and superluminality.
An object, moving across our field of vision at superluminal speeds, will
appear to us as two objects receding from a single point. The time evolution of
the Doppler shifted radiation of such a superluminal object bears remarkable
similarity to that of GRB and radio sources. Based on these observations, we
derive a kinematic model for radio sources and GRBs and explain the puzzling
features listed above. Our model also explains the observed blue/UV spectrum
(and its time evolution) of the core region and the RF spectrum of the lobes,
and why the radio sources appear to be associated with galactic nuclei.


title: Constraints from cosmic rays on non-systematic Lorentz violation

abstract:
  In this article we analyze the radiation loss from a high energy cosmic ray
proton propagating in a spacetime with non-systematic Lorentz violation. From
an effective field theory perspective we illuminate flaws in previous attempts
that use threshold approaches to analyze this problem. We argue that in general
such approaches are of rather limited use when dealing with non-systematic
Lorentz violating scenarios. The main issues we raise are a) the limited
applicability of threshold energy conservation rules when translation
invariance is broken and b) the large amounts of proton particle production due
to the time dependence of the fluctuations. Ignoring particle production, we
derive a constraint on the magnitude of velocity fluctuation $|v_f|<10^{-6.5}$,
much weaker than has been previously argued. However, we show that in fact
particle production makes any such constraint completely unreliable.


title: Reconciling dark energy models with f(R) theories

abstract:
  Higher order theories of gravity have recently attracted a lot of interest as
alternative candidates to explain the observed cosmic acceleration without the
need of introducing any scalar field. A critical ingredient is the choice of
the function f(R) of the Ricci scalar curvature entering the gravity Lagrangian
and determining the dynamics of the universe. We describe an efficient
procedure to reconstruct f(R) from the Hubble parameter $H$ depending on the
redshift z. Using the metric formulation of f(R) theories, we derive a third
order linear differential equation for f(R(z)) which can be numerically solved
after setting the boundary conditions on the basis of physical considerations.
Since H(z) can be reconstructed from the astrophysical data, the method we
present makes it possible to determine, in principle, what is the f(R) theory
which best reproduces the observed cosmological dynamics. Moreover, the method
allows to reconcile dark energy models with f(R) theories finding out what is
the expression of f(R) which leads to the same H(z) of the given quintessence
model. As interesting examples, we consider "quiessence" (dark energy with
constant equation of state) and the Chaplygin gas.


title:
Temperature and polarization angular power spectra of Galactic dust
  radiation at 353 GHz as measured by Archeops

abstract:
  We present the first measurement of temperature and polarization angular
power spectra of the diffuse emission of Galactic dust at 353 GHz as seen by
Archeops on 20% of the sky. The temperature angular power spectrum is
compatible with that provided by the extrapolation to 353 GHz of IRAS and DIRBE
maps using \cite{fds} model number 8. For Galactic latitudes $|b| \geq 5$ deg
we report a 4 sigma detection of large scale ($3\leq \ell \leq 8$)
temperature-polarization cross-correlation $(\ell+1)C_\ell^{TE}/2\pi = 76\pm 21
\mu\rm{K_{RJ}}^2$ and set upper limits to the $E$ and $B$ modes at $11
\mu\rm{K_{RJ}}^2$. For Galactic latitudes $|b| \geq 10$ deg, on the same
angular scales, we report a 2 sigma detection of temperature-polarization
cross-correlation $(\ell+1)C_\ell^{TE}/2\pi = 24\pm 13 \mu\rm{K_{RJ}}^2$. These
results are then extrapolated to 100 GHz to estimate the contamination in CMB
measurements by polarized diffuse Galactic dust emission. The $TE$ signal is
then $1.7\pm0.5$ and $0.5\pm0.3 \mu\rm{K^2_{CMB}}$ for $|b| \geq 5$ and 10 deg.
respectively. The upper limit on $E$ and $B$ becomes $0.2 \mu\rm{K^2_{CMB}}
(2\sigma)$. If polarized dust emission at higher Galactic latitude cuts is
similar to the one we report here, then dust polarized radiation will be a
major foreground for determining the polarization power spectra of the CMB at
high frequencies above 100 GHz.


title:
The Star Formation Rate Density of the Universe at z = 0.24 and 0.4 from
  Halpha

abstract:
  Knowledge of both the global star formation history of the universe and the
nature of individual star-forming galaxies at different look-back times is
essential to our understanding of galaxy formation and evolution. Deep redshift
surveys suggest star-formation activity increases by an order of magnitude from
z = 0 to ~1. As a direct test of whether substantial evolution in
star-formation activity has occurred, we need to measure the star formation
rate (SFR) density and the properties of the corresponding star-forming galaxy
populations at different redshifts, using similar techniques. The main goal of
this work is to extend the Universidad Complutense de Madrid (UCM) survey of
emission-line galaxies to higher redshifts. (continues)


title: SHADES: The Scuba HAlf Degree Extragalactic Survey

abstract:
  SHADES is a new, major, extragalactic sub-mm survey currently being
undertaken with SCUBA on the JCMT. The aim of this survey is to map 0.5 square
degrees of sky at a depth sufficient to provide the first, major (~300 source),
unbiased sample of bright (S(850) > 8 mJy) sub-mm sources. Combined with
extensive multi-frequency supporting observations already in hand, we aim to
measure the redshift distribution, clustering and AGN content of the sub-mm
population. Currently 40% complete, the survey is due to run until early 2006.
Here I provide some early example results which demonstrate the potential power
of our combined data set, and highlight a series of forthcoming papers which
will present results based on the current interim sample of ~130 850-micron
sources detected within the Lockman Hole and SXDF SHADES survey fields.


title:
Presolar grains from meteorites: Remnants from the early times of the
  solar system

abstract:
  This review provides an introduction to presolar grains - preserved stardust
from the interstellar molecular cloud from which our solar system formed -
found in primitive meteorites. We describe the search for the presolar
components, the currently known presolar mineral populations, and the chemical
and isotopic characteristics of the grains and dust-forming stars to identify
the grains' most probable stellar sources. Keywords: presolar grains,
interstellar dust, asymptotic giant branch (AGB) stars, novae, supernovae,
nucleosynthesis, isotopic ratios, meteorites


title:
The spectral evolution of impulsive solar X-ray flares. II.Comparison of
  observations with models

abstract:
  We study the evolution of the spectral index and the normalization (flux) of
the non-thermal component of the electron spectra observed by RHESSI during 24
solar hard X-ray flares. The quantitative evolution is confronted with the
predictions of simple electron acceleration models featuring the soft-hard-soft
behaviour. The comparison is general in scope and can be applied to different
acceleration models, provided that they make predictions for the behavior of
the spectral index as a function of the normalization. A simple stochastic
acceleration model yields plausible best-fit model parameters for about 77% of
the 141 events consisting of rise and decay phases of individual hard X-ray
peaks. However, it implies unphysically high electron acceleration rates and
total energies for the others. Other simple acceleration models such as
constant rate of accelerated electrons or constant input power have a similar
failure rate. The peaks inconsistent with the simple acceleration models have
smaller variations in the spectral index. The cases compatible with a simple
stochastic model require typically a few times 10^36 electrons accelerated per
second at a threshold energy of 18 keV in the rise phases and 24 keV in the
decay phases of the flare peaks.


title:
Interactions of Radio Galaxies and the Intra-Cluster Medium in Abell 160
  and Abell 2462

abstract:
  We present Chandra and VLA observations of two galaxy clusters, Abell 160 and
Abell 2462, whose brightest cluster galaxies (BCGs) host wide angle tailed
radio galaxies (WATs). We search for evidence of interactions between the radio
emission and the hot, X-ray emitting gas, and test various jet termination
models. We find that both clusters have cool BCGs at the cluster centre, and
that the scale of these cores ~30-40kpc for both sources) is of approximately
the same scale as the length of the radio jets. For both sources, the jet
flaring point is coincident with a steepening in the host cluster's temperature
gradient, and similar results are found for 3C465 and Hydra A. However, none of
the published models of WAT formation offer a satisfactory explanation as to
why this may be the case. Therefore it is unclear what causes the sudden
transition between the jet and the plume. Without accurate modelling, we cannot
ascertain whether the steepening of the temperature gradient is the main cause
of the transition, or merely a tracer of an underlying process.


title:
Early and late time VLT spectroscopy of SN 2001el - progenitor
  constraints for a type Ia supernova

abstract:
  We present early time high-resolution (VLT/UVES) and late time low-resolution
(VLT/FORS) optical spectra of the normal type Ia supernova, SN 2001el. The
high-resolution spectra were obtained at -9 and -2 days to allow the detection
of narrow hydrogen and/or helium emission lines from the circumstellar medium
of the SN. No such lines were detected, and we therefore use photoionisation
models to derive upper limits of 9x10^-6 Msun/yr and 5x10^-5 Msun/yr for the
mass loss rate from the progenitor system assuming velocities of 10 km/s and 50
km/s, respectively, for a wind extending to outside at least a few x 10^15 cm
away from the SN explosion site. These limits exclude a symbiotic star in the
upper mass loss rate regime from being the progenitor of SN 2001el. The low
resolution spectrum was obtained in the nebular phase of the SN, 400 days after
the maximum light, to search for any hydrogen rich gas originating from the SN
progenitor system. However, we see no signs of Balmer lines in our spectrum.
Therefore, we model the late time spectra to derive an upper limit of ~0.03
Msun for solar abundance material present at velocities lower than 1000 km/s
within the SN explosion site. According to simulations of Marietta et al.
(2000) this is less than the expected mass lost by a subgiant, red giant or
main sequence secondary star at a small binary separation as a result of the SN
explosion. Finally, we discuss the origin of high velocity Ca II lines. We see
both the CaII IR triplet and the H&K lines in the -9 days spectrum at a very
high velocity of up to 34000 km/s. The spectrum also shows a flat-bottomed Si
II `6150 A' feature similar to the one previously observed in SN 1990N at -14
days. We compare these spectral features to those observed in SNe 1984A and
1990N at even higher velocities.


title: Spectral Formation in X-Ray Pulsar Accretion Columns

abstract:
  We present the first self-consistent model for the dynamics and the radiative
transfer occurring in bright X-ray pulsar accretion columns, with a special
focus on the role of the shock in energizing the emerging X-rays. The pressure
inside the accretion column of a luminous X-ray pulsar is dominated by the
photons, and consequently the equations describing the coupled
radiative-dynamical structure must be solved simultaneously. Spectral formation
in these sources is therefore a complex, nonlinear phenomenon. We obtain the
analytical solution for the Green's function describing the upscattering of
monochromatic radiation injected into the column from the thermal mound located
near the base of the flow. The Green's function is convolved with a Planck
distribution to model the X-ray spectrum resulting from the reprocessing of
blackbody photons produced in the thermal mound. These photons diffuse through
the infalling gas and eventually escape out the walls of the column, forming
the observed X-ray spectrum. We show that the resulting column-integrated,
phase-averaged spectrum has a power-law shape at high energies and a blackbody
shape at low energies, in agreement with the observational data for many X-ray
pulsars.


title:
Nonradial mode excitation as the cause of the Blazhko effect in RR Lyrae
  stars

abstract:
  A significant fraction of RR Lyrae stars exhibits amplitude and/or phase
modulation known as the the Blazhko effect. The oscillation spectra suggest
that, at least in most of the cases, excitation of nonradial modes in addition
to the dominant radial modes is responsible for the effect. Though model
calculations predict that nonradial modes may be excited, there are problems
with explaining their observed properties in terms of finite amplitude
development of the linear instability. We propose a scenario, which like some
previous, postulates energy transfer from radial to nonradial modes, but avoids
those problems. The scenario predicts lower amplitudes in Blazhko stars. We
check this prediction with a new analysis of the Galactic bulge RR Lyrae stars
from OGLE-II database. The effect is seen, but the amplitude reduction is
smaller than predicted.


title: What controls the [O III] 5007 line strength in AGN?

abstract:
  AGN display an extreme range in the narrow emission line equivalent widths.
Specifically, in the PG quasar sample the equivalent width of the narrow [O
III] 5007 line has a range of >300, while the broad Hb line, for example, has a
range of 10 only. The strength of [O III] 5007 is modulated by the covering
factor, CF, of the narrow line region (NLR) gas, its density n_e, and
ionization parameter U. To explore which of these factors produces the observed
large range in [O III] 5007 strength, we measure the strength of the matching
narrow Hb and [O III] 4363 lines, detected in 40 out of the 87 z<0.5 PG quasars
in the Boroson & Green sample. The photoionization code CLOUDY is then used to
infer CF, n_e, and U in each object, assuming a single uniform emitting zone.
We find that the range of CF (~0.02-0.2) contributes about twice as much as the
range in both n_e and U towards modulating the strength of the [O III] 5007
line. The CF is inversely correlated with luminosity, but it is not correlated
with L_Edd as previously speculated. The single zone [O III] 5007 emitting
region is rather compact, having R=40L_44^0.45 pc. These emission lines can
also be fit with an extreme two zone model, where [O III] 4363 is mostly
emitted by a dense (n_e=10^7) inner zone at R=L_44^0.5 pc, and [O III] 5007 by
a low density (n_e=10^3) extended outer zone at R=750L_44^0.34 pc. Such an
extended [O III] 5007 emission should be well resolved by HST imaging of
luminous AGN. Further constraints on the radial gas distribution in the NLR can
be obtained from the spectral shape of the IR continuum emitted by the
associated dust.


title:
Testing Dark Energy and Light Particles via Black Hole Evaporation at
  Colliders

abstract:
  We show that collider experiments have the potential to exclude a light
scalar field as well as generic models of modified gravity as dark energy
candidates. Our mechanism uses the spectrum radiated by black holes and can
equally well be applied to determine the number of light degrees of freedom. We
obtain the grey body factors for massive scalar particles and calculate the
total emissivity. While the Large Hadron Collider (LHC) may not get to the
desired accuracy, the measurement is within reach of next generation colliders.


title:
Blazar observations above 60 GeV: the Influence of CELESTE's Energy
  Scale on the Study of Flares and Spectra

abstract:
  The CELESTE atmospheric Cherenkov detector ran until June 2004. It has
observed the blazars Mrk 421, 1ES 1426+428 and Mrk 501. We significantly
improved our understanding of the atmosphere using a LIDAR, and of the optical
throughput of the detector using stellar photometry. The new data analysis
provides better background rejection. We present our light curve for Mrk 421
for the 2002-2004 season and a comparison with X-ray data and the 2004
observation of 1ES 1426+428. The new analysis will allow a more sensitive
search for a signal from Mrk 501.


title: Andromeda IX: Properties of the Smallest M 31 Dwarf Satellite Galaxy

abstract:
  We present WIYN observations of the recently discovered And IX dwarf
spheroidal (dSph) satellite galaxy of M 31. Our data, obtained at a natural
seeing of 0.5'' and just reaching the horizontal branch level, confirm And IX
as a dSph galaxy with a distance similar to M 31. A survey for carbon stars
shows no evidence for an intermediate-age (1--10 Gyr) stellar population in And
IX. From the red giant branch we estimate a metallicity of roughly -2 dex.
Combined with the tip of the red giant branch luminosity, this results in a
distance of 735 kpc, placing And IX approximately 45 kpc from M 31. This faint
dSph follows the relations between luminosity and metallicity, and luminosity
and surface brightness defined by other Local Group dSph galaxies. The core and
tidal radii are found to be 1.35' and 5.9', respectively. We conclude that And
IX -- despite its low luminosity -- might be an ordinary Local Group dSph and
discuss implications for its formation from a once more massive, but stripped
progenitor or from an intrinsically low-mass seed.


title:
Search for Double Transit Extrasolar Planetary Systems: Another
  Transiting Planet Around OGLE-TR-111 or a False Positive Detection?

abstract:
  The search for double transit planetary systems opens new possibilities for
the transit searches and for studies of orbital stability, stellar irradiation,
and migration scenarios, among others. We explore the OGLE lightcurves of stars
with confirmed planetary companions (OGLE-TR-10, OGLE-TR-56, OGLE-TR-111,
OGLE-TR-113, and OGLE-TR-132), searching for additional transits. The most
promising candidate is OGLE-TR-111, where the photometric measurements and the
radial velocities are consistent with the presence of a second planet. If
confirmed, OGLE-TR-111 would be the first extrasolar planetary system detected
by transits. The parameters of the possible new planet OGLE-TR-111c would be:
period P = 16.0644 d, semimajor axis a = 0.12 AU, orbital inclination i = 88-89
deg, mass M = 0.7 M_J, radius R = 0.85 R_J, density \rho = 1.4 g/cm^3. If
confirmed, OGLE-TR-111c would be the smallest and densest extrasolar planet
measured todate, truly a Jovian planet, with properties intermediate between
Jupiter and Saturn, albeit with shorter period. Additional photometric and
spectroscopic data would allow to discriminate between a second transiting
planet around OGLE-TR-111 and a false positive detection.


title:
Superfluidity in the Solar Interior: Implications for Solar Eruptions
  and Climate

abstract:
  Efforts to understand unusual weather or abrupt changes in climate have been
plagued by deficiencies of the standard solar model (SSM). While it assumes
that our primary source of energy began as a homogeneous ball of hydrogen (H)
with a steady, well-behaved H-fusion reactor at its core, observations instead
reveal a very heterogeneous, dynamic Sun. As examples, the upward acceleration
and departure of H+ ions from the surface of the quiet Sun and abrupt climatic
changes, including geomagnetic reversals and periodic magnetic storms that
eject material from the solar surface are not explained by the SSM. The present
magnetic fields are probably deep-seated remnants of very ancient origin. These
could have been generated from two mechanisms. These are: a) Bose-Einstein
condensation of iron-rich, zero-spin material into a rotating, superfluid,
superconductor surrounding the solar core and/or b) superfluidity and quantized
vortices in nucleon-paired Fermions at the core.


title: The dark clump near Abell 1942: dark matter halo or statistical fluke?

abstract:
  Weak lensing surveys provide the possibility of identifying dark matter halos
based on their total matter content rather than just the luminous matter
content. On the basis of two sets of observations carried out with the CFHT,
Erben et al. (2000) presented the first candidate dark clump, i.e. a dark
matter concentration identified by its significant weak lensing signal without
a corresponding galaxy overdensity or X-ray emission.
  We present a set of HST mosaic observations which confirms the presence of an
alignment signal at the dark clump position. The signal strength, however, is
weaker than in the ground-based data. It is therefore still unclear whether the
signal is caused by a lensing mass or is just a chance alignment. We also
present Chandra observations of the dark clump, which fail to reveal any
significant extended emission.
  A comparison of the ellipticity measurements from the space-based HST data
and the ground-based CFHT data shows a remarkable agreement on average,
demonstrating that weak lensing studies from high-quality ground-based
observations yield reliable results.


title:
Irregular Mass Transfer in the Polars VV Puppis and V393 Pavonis during
  the Low State

abstract:
  The polars VV Pup and V393 Pav were observed with XMM-Newton during states of
low accretion rate with peak X-ray luminosities of ~1 x 10^30 and ~1 x 10^31
erg/s, respectively. In both polars, accretion onto the white dwarf was
extremely irregular, and the accretion rate varied by more than 1 order of
magnitude on timescales of ~1 hr. Our observations suggest that this type of
irregular accretion is a common phenomenon in polars during the low state. The
likely cause of the accretion rate fluctuations are coronal mass ejections or
solar flares on the companion star that intermittently increase the mass
transfer into the accretion stream. Our findings demonstrate that the companion
stars in cataclysmic variables possess highly active atmospheres.


title: Large-scale variations of the dust optical properties in the Galaxy

abstract:
  We present an analysis of the dust optical properties at large scale, for the
whole galactic anticenter hemisphere. We used the 2MASS Extended Source Catalog
to obtain the total reddening on each galaxy line of sight and we compared this
value to the IRAS 100 microns surface brightness converted to extinction by
Schlegel et al (1998). We performed a careful examination and correction of the
possible systematic effects resulting from foreground star contamination,
redshift contribution and galaxy selection bias. We also evaluated the
contribution of dust temperature variations and interstellar clumpiness to our
method. The correlation of the near-infrared extinction to the far-infrared
optical depth shows a discrepancy for visual extinction greater than 1 mag with
a ratio A_V(FIR) / A_V(gal) = 1.31 +- 0.06. We attribute this result to the
presence of fluffy/composite grains characterized by an enhanced far--infrared
emissivity. Our analysis, applied to half of the sky, provides new insights on
the dust grains nature suggesting fluffy grains are found not only in some very
specific regions but in all directions for which the visual extinction reaches
about 1 mag.


title: T Tauri stellar magnetic fields: He I measurements

abstract:
  We present measurements of the longitudinal magnetic field in the
circumstellar environment of seven classical T Tauri stars. The measurements
are based on high-resolution circular spectropolarimetry of the He I 5876
emission line, which is thought to form in accretion streams controlled by a
stellar magnetosphere. We detect magnetic fields in BP Tau, DF Tau and DN Tau,
and detect statistically significant fields in GM Aur and RW Aur A at one epoch
but not at others. We detect no field for DG Tau and GG Tau, with the caveat
that these objects were observed at one epoch only. Our measurements for BP Tau
and DF Tau are consistent, both in terms of sign and magnitude, with previous
studies, suggesting that the characteristics of T Tauri magnetospheres are
persistent over several years. We observed the magnetic field of BP Tau to
decline monotonically over three nights, and have detected a peak field of 4kG
in this object, the highest magnetic field yet observed in a T Tauri star. We
combine our observations with results from the literature in order to perform a
statistical analysis of the magnetospheric fields in BP Tau and DF Tau.
Assuming a dipolar field, we determine a polar field of ~3kG and a dipole
offset of 40deg for BP Tau, while DF Tau's field is consistent with a polar
field of ~-4.5kG and a dipole offset of 10deg. We conclude that many classical
T Tauri stars have circumstellar magnetic fields that are both strong enough
and sufficiently globally-ordered to sustain large-scale magnetospheric
accretion flows.


title:
Gemini Near Infrared Spectrograph observations of the central
  supermassive black hole in Centaurus A

abstract:
  The infrared spectrograph GNIRS on Gemini South unlocks new possibilities to
study the central black holes in dusty galaxies that have been inaccessible to
previous black hole studies. We exploit good near-infrared seeing to measure
the central black hole (BH) of Centaurus A (NGC 5128). We measure the stellar
kinematics of NGC 5128 using the region around the CO bandheads at 2.3 microns
and determine the black hole mass using orbit-based models. Black holes are
believed to be essential components of galaxies, and their evolutionary states
appear to be closely linked to those of their hosts. Our current knowledge does
not go much beyond this; galaxies such as NGC 5128 (an AGN and recent merger)
can further develop this knowledge. However, NGC 5128 and galaxies like it
contain large amounts of dust which hamper optical spectroscopy, making
near-infrared measurements an attractive alternative. We find a BH mass of
2.4e8 solar masses for an edge-on model, 1.8e8 solar masses for a model with
inclination of 45 degrees, and 1.5e8 solar masses for a model with inclination
of 20 degrees. We adopt the value for the edge-on model, which has
significantly lower chi^2. These estimates are consistent with a previous gas
dynamical estimate and are five to ten times higher than that predicted by the
correlation between BH mass and velocity dispersion. If NGC 5128 will
eventually follow the trend for quiescent galaxies, this result suggests that
its BH assembled first before its host component. NGC 5128 thus provides an
important example for our knowledge of central black holes; this technique can
be applied to other such galaxies to further explore this question.


title:
CO(1-0) & CO(5-4) observations of the most distant known radio galaxy at
  z=5.2

abstract:
  Using the Australia Telescope Compact Array we have detected CO(1-0) and
CO(5-4) from TNJ0924-2201 at z=5.2, the most distant radio galaxy known to
date. This is the second highest redshift detection of CO published so far. The
CO(1-0) is 250-400 km/sec wide with a peak flux density of 520 +- 115
microJy/beam whilst the CO(5-4) line emission is 200-300 km/sec wide with a
peak flux density of 7.8 +- 2.7 mJy/beam. Both transitions are spatially
unresolved but there is marginal evidence for spatial offsets between the CO
and the host galaxy; the CO(1-0) is located 28 +- 11 kpc (4.5 +- 1.7 arcsec)
north of the radio galaxy whilst the CO(5-4) is located 18 +- 8 kpc (2.8 +- 1.2
arcsec) south of the radio galaxy. Higher spatial resolution observations are
required to determine the reality of these offsets. Our result is the second
detection of CO in a high redshift galaxy without pre-selection based on a
massive dust content.


title:
Catalog of Galaxy Morphology in Four Rich Clusters: Luminosity Evolution
  of Disk Galaxies at 0.33<z<0.83

abstract:
  Hubble Space Telescope (HST) imaging of four rich, X-ray luminous, galaxy
clusters (0.33<z<0.83) is used to produce quantitative morphological
measurements for galaxies in their fields. Catalogs of these measurements are
presented for 1642 galaxies brighter than F814W(AB)=23.0 . Galaxy luminosity
profiles are fitted with three models: exponential disk, de Vaucouleurs bulge,
and a disk-plus-bulge hybrid model. The best fit is selected and produces a
quantitative assessment of the morphology of each galaxy: the principal
parameters derived being B/T, the ratio of bulge to total luminosity, the scale
lengths and half-light radii, axial ratios, position angles and surface
brightnesses of each component. Cluster membership is determined using a
statistical correction for field galaxy contamination, and a mass normalization
factor (mass within boundaries of the observed fields) is derived for each
cluster. In the present paper, this catalog of measurements is used to
investigate the luminosity evolution of disk galaxies in the rich-cluster
environment. Examination of the relations between disk scale-length and central
surface brightness suggests, under the assumption that these clusters represent
a family who share a common evolutionary history and are simply observed at
different ages, that there is a dramatic change in the properties of the small
disks (h < 2 kpc). This change is best characterized as a change in surface
brightness by about 1.5 magnitude between z=0.3 and z=0.8 with brighter disks
at higher redshifts.


title: Warm and Cold Molecular Gas in Galaxies

abstract:
  New and archival interferometric 12CO(1->0) datasets from six nearby galaxies
are combined with H_2 2.122um and H-alpha maps to explore in detail the
interstellar medium in different star-forming galaxies. We investigate the
relation between warm (H_2 at T~2000 K) and cold (CO at T~50 K) molecular gas
from 100 pc to 2 kpc scales. On these scales, the ratio of warm-to-cold
molecular hydrogen correlates with the fnu(60um)/fnu(100um) ratio, a ratio that
tracks the star formation activity level. This result also holds for the global
properties of galaxies from a much larger sample drawn from the literature. The
trend persists for over three orders of magnitude in the mass ratio, regardless
of source nuclear activity.


title: Scale Radii and Aggregation Histories of Dark Haloes

abstract:
  Relaxed dark-matter haloes are found to exhibit the same universal density
profiles regardless of whether they form in hierarchical cosmologies or via
spherical collapse. Likewise, the shape parameters of haloes formed
hierarchically do not seem to depend on the epoch in which the last major
merger took place. Both findings suggest that the density profile of haloes
does not depend on their aggregation history. Yet, this possibility is
apparently at odds with some correlations involving the scale radius r_s found
in numerical simulations. Here we prove that the scale radius of relaxed,
non-rotating, spherically symmetric haloes endowed with the universal density
profile is determined exclusively by the current values of four independent,
though correlated, quantities: mass, energy and their respective instantaneous
accretion rates. Under this premise and taking into account the inside-out
growth of haloes during the accretion phase between major mergers, we build a
simple physical model for the evolution of r_s along the main branch of halo
merger trees that reproduces all the empirical trends shown by this parameter
in N-body simulations. This confirms the conclusion that the empirical
correlations involving r_s do not actually imply the dependence of this
parameter on the halo aggregation history. The present results give strong
support to the explanation put forward in a recent paper by Manrique et al.
(2003) for the origin of the halo universal density profile.


title: Nulling Tomography with Weak Gravitational Lensing

abstract:
  We explore several strategies of eliminating (or nulling) the small-scale
information in weak lensing convergence power spectrum measurements in order to
protect against undesirable effects, for example the effects of baryonic
cooling and pressure forces on the distribution of large-scale structures. We
selectively throw out the small-scale information in the convergence power
spectrum that is most sensitive to the unwanted bias, while trying to retain
most of the sensitivity to cosmological parameters. The strategies are
effective in the difficult but realistic situations when we are able to guess
the form of the contaminating effect only approximately. However, we also find
that the simplest scheme of simply not using information from the largest
multipoles works about as well as the proposed techniques in most, although not
all, realistic cases. We advocate further exploration of nulling techniques and
believe that they will find important applications in the weak lensing data
mining.


title: Imprints of mass accretion on properties of galaxy clusters

abstract:
  A large scale SPH+N-body simulation (GADGET) of the concordance LCDM universe
is used to investigate orientation and angular momentum of galaxy clusters at
z=0 in connection with their recent accretion histories. The basic cluster
sample comprises the 3000 most massive friends-of-friends halos found in the
500 Mpc/h simulation box. Two disjoint sub-samples are constructed, using the
mass ratio of the two most massive progenitors at z=0.5 m_2 / m_1 (m_1 < m_2),
namely a recent major merger sample and a steady accretion mode sample. The
mass of clusters in the merger sample is on average ~43% larger than the mass
of the two progenitors (m_1 + m_2), whereas in the steady accretion mode sample
a smaller increase of ~25% is found. The separation vector connecting the two
most massive progenitor halos at z=0.5 is strongly correlated with the
orientation of the cluster at z=0. The angular momentum of the clusters in the
recent major merger sample tends to be parallel to orbital angular momentum of
the two progenitors, whereas the angular momentum of the steady accretion mode
sample is mainly determined by the angular momentum of the most massive
progenitor. The long range correlations for the major and the minor principal
axes of cluster pairs extend to distances of ~100 Mpc/h. Weak angular momentum
correlations are found for distances < 20 Mpc/h. Within these ranges the major
axes tend to be aligned with the connecting line of the cluster pairs whereas
minor axes and angular momenta tend to be perpendicular to this line. A
separate analysis of the two sub-samples reveals that the long range
correlations are independent of the mass accretion mode. Thus orientation and
angular momentum of galaxy clusters is mainly determined by the accretion along
the filaments independently of the particular accretion mode.


title:
Spectral Signatures of Gravitationally Confined Thermonuclear Supernova
  Explosions

abstract:
  We consider some of the spectral and polarimetric signatures of the
gravitational confined detonation scenario for Type Ia supernova explosions. In
this model, material produced by an off-center deflagration (which itself fails
to produce the explosion) forms a metal-rich atmosphere above the white dwarf
surface. Using hydrodynamical simulations, we show that this atmosphere is
compressed and accelerated during the subsequent interaction with the supernova
ejecta. This leads ultimately to the formation of a high-velocity pancake of
metal-rich material that is geometrically detached from the bulk of the ejecta.
When observed at the epochs near maximum light, this absorbing pancake produces
a highly blueshifted and polarized calcium IR triplet absorption feature
similar to that observed in several Type~Ia supernovae. We discuss the
orientation effects present in our model and contrast them to those expected in
other supernova explosion models. We propose that a large sample of
spectropolarimetric observations can be used to critically evaluate the
different theoretical scenarios.


title:
Relativistic energy shifts in Ge II, Sn II and Pb II and search for
  cosmological variation of the fine structure constant

abstract:
  Sensitivity of atomic transition frequencies to variation of the fine
structure constant $\alpha=e^2/\hbar c$ increases proportional to $Z^2$ where
$Z$ is the nuclear charge. Recently several lines of heavy ions Ge II, Sn II
and Pb II have been detected in quasar absorption spectra. We have performed
accurate many-body calculations of $\alpha^2$-dependence of transition
frequencies ($q$-coefficients) for these atoms and found an order of magnitude
increase in sensitivity in comparison with atomic transitions which were
previously used to search for temporal and spatial variation of $\alpha$ in
quasar absorption systems. An interesting feature in Pb II is highly non-linear
dependence on $\alpha^2$ due to the level pseudo-crossings.


title: Sporadically Torqued Accretion Disks Around Black Holes

abstract:
  The assumption that black hole accretion disks possess an untorqued inner
boundary, the so-called zero torque boundary condition, has been employed by
models of black hole disks for many years. However, recent theoretical and
observational work suggests that magnetic forces may appreciably torque the
inner disk. This raises the question of the effect that a time-changing
magnetic torque may have on the evolution of such a disk. In particular, we
explore the suggestion that the ``Deep Minimum State'' of the Seyfert galaxy
MCG--6-30-15 can be identified as a sporadic inner disk torquing event. This
suggestion is motivated by detailed analyses of changes in the profile of the
broad fluorescence iron line in XMM-Newton spectra. We find that the response
of such a disk to a torquing event has two phases; an initial damming of the
accretion flow together with a partial draining of the disk interior to the
torque location, followed by a replenishment of the inner disk as the system
achieves a new (torqued) steady-state. If the Deep Minimum State of
MCG--6-30-15 is indeed due to a sporadic torquing event, we show that the
fraction of the dissipated energy going into X-rays must be smaller in the
torqued state. We propose one such scenario in which Compton cooling of the
disk corona by ``returning radiation'' accompanying a central-torquing event
suppresses the 0.5-10 keV X-ray flux coming from all but the innermost regions
of the disk.


title:
A model of rotating hotspots for 3:2 frequency ratio of HFQPOs in black
  hole X-ray binaries

abstract:
  We propose a model to explain a puzzling 3:2 frequency ratio of high
frequency quasi-periodic oscillations (HFQPOs) in black hole (BH) X-ray
binaries, GRO J1655-40, GRS 1915+105 and XTE J1550-564. In our model a
non-axisymmetric magnetic coupling (MC) of a rotating black hole (BH) with its
surrounding accretion disc coexists with the Blandford-Znajek (BZ) process. The
upper frequency is fitted by a rotating hotspot near the inner edge of the
disc, which is produced by the energy transferred from the BH to the disc, and
the lower frequency is fitted by another rotating hotspot somewhere away from
the inner edge of the disc, which arises from the screw instability of the
magnetic field on the disc. It turns out that the 3:2 frequency ratio of HFQPOs
in these X-ray binaries could be well fitted to the observational data with a
much narrower range of the BH spin. In addition, the spectral properties of
HFQPOs are discussed. The correlation of HFQPOs with jets from microquasars is
contained naturally in our model.


title:
Spectral changes during six years of Scorpius X-1 monitoring with
  BeppoSAX Wide Field Cameras

abstract:
  We analyse a sample of fifty-five observations of Scorpius X-1 available in
the BeppoSAX Wide Field Camera public archive and spanning over the six years
of BeppoSAX mission life. Spectral changes are initially analysed by inspection
of colour-colour and colour-intensity diagrams, we also discuss the shift of
the Z tracks in these diagrams. Then we select two long observations for
spectral fitting analysis, a secular shift is evident between the tracks in
these observations. We finally extract spectra along the tracks and discuss the
best fit model, the parameter variations along the track and between tracks,
and their link to the accretion rate.


title: Can Gamma-Ray Bursts Be Used to Measure Cosmology? A Further Analysis

abstract:
  Three different methods of measuring cosmology with gamma-ray bursts (GRBs)
have been proposed since a relation between the $\gamma$-ray energy $E_{\gamma}
$ of a GRB jet and the peak energy $E_p$ of the $\nu F_{\nu}$ spectrum in the
burst frame was reported by Ghirlanda and coauthors. In Method I, to calculate
the probability for a favored cosmology, only the contribution of the
$E_\gamma-E_p$ relation that is already best fitted for this cosmology is
considered. We apply this method to a sample of 17 GRBs, and obtain the mass
density $\Omega_M=0.15^{+0.45}_{-0.13}$ ($1\sigma$) for a flat $\Lambda$CDM
universe. In Method II, to calculate the probability for some certain
cosmology, contributions of all the possible $E_\gamma-E_p$ relations that are
best fitted for their corresponding cosmologies are taken into account. With
this method, we find a constraint on the mass density $0.14<\Omega_M<0.69$ ($1
\sigma$) for a flat universe. In Method III, to obtain the probability for some
cosmology, contributions of all the possible $E_\gamma-E_p$ relations
associated with their unequal weights are considered. With this method, we
obtain an inspiring constraint on the mass density $0.16<\Omega_M<0.45$ ($1
\sigma$) for a flat universe, and a $\chi^2_{dof}=19.08/15=1.27$ for the
concordance model of $\Omega_M=0.27$. (abridged)


title: Seismology and activity of the F type star HD 49933

abstract:
  A 10-night asteroseismic observation programme has been conducted in January
2004 with the spectrometer Harps at the ES0 3.6-m telescope. The selected
target, the 6th magnitude F5V star HD 49933, was chosen among the prime
candidates of Corot, the European space mission dedicated to characterize
stellar oscillations mode with high precision photometry measurements. This
star shows important line profiles variations, indicating a surprisingly high
activity with respect to its low rotation rate. However, with the help of tools
developed for disentangling the signatures of activity and oscillations, we are
able to observe its oscillation spectrum in the frequency range [1.2, 2.2 mHz].
We measure the large separation (88.7+-0.4 microHz) and the maximum amplitude
(around 0.4+-0.1 m/s rms), respectively in agreement and marginal agreement
with the predicted values.


title:
Peering through the OH-forest: a new technique to remove residual sky
  features from SDSS spectra

abstract:
  The Sloan Digital Sky Survey (SDSS) currently provides by far the largest
homogeneous sample of intermediate signal-to-noise ratio (S/N) optical spectra
of galaxies and quasars. The fully automated SDSS spectroscopic reduction
pipeline has provided spectra of unprecedented quality that cover the
wavelength range 3800-9200A. However, in common with spectra from virtually all
multi-object surveys employing fibres, there remain significant systematic
residuals in many of the spectra due to the incomplete subtraction of the
strong OH sky emission lines longward of 6700A. The S/N over substantial
wavelength regions in many spectra is reduced by more than a factor of 2 over
that expected from counting statistics. We present a method to automatically
remove the sky residual signal, using a principal component analysis (PCA)
which takes advantage of the correlation in the form of the sky subtraction
residuals present in each spectrum. Application of the method results in
spectra with essentially no evidence for degradation due to the incomplete
subtraction of OH emission features. A dramatic improvement in the quality of a
substantial number of spectra, particularly those of faint objects such as the
bulk of the high-redshift quasars, is achieved. We make available IDL code and
documentation to implement the sky residual subtraction scheme on SDSS spectra
included in the public data releases. We illustrate the power of the
sky-residual subtraction scheme using samples of SDSS galaxy and quasar
spectra, presenting tests involving the near-infrared CaII triplet absorption,
metal absorption line features in damped Lyman-alpha systems and composite
spectra of high-redshift quasars.


title: The HST view of LINERs nuclei: evidence for a dual population?

abstract:
  We study a complete and distance-limited sample of 25 LINERs, 21 of which
have been imaged with the Hubble Space Telescope. In nine objects we detect an
unresolved nucleus. In order to study their physical properties, we compare the
radio and optical properties of the nuclei of LINERs with those of other
samples of local AGNs, namely Seyfert galaxies and low-luminosity radio
galaxies (LLRG). Our results show that the LINERs population is not
homogeneous, as there are two subclasses: i) the first class is similar to
LLRG, as it extends the population of radio-loud nuclei to lower luminosities;
ii) the second is similar to Seyferts, and extends the properties of
radio-quiet nuclei towards the lowest luminosities. The objects are optimally
discriminated in the plane formed by the black hole mass vs. nuclear
radio-loudness: all radio-loud LINERs have M_BH/M_sun > 10^8, while Seyferts
and radio-quiet LINERs have M_BH/M_sun < 10^8. The different nature of the
various classes of local AGN are best understood when the fraction of the
Eddington luminosity they irradiate L_o/L_Edd is plotted against the nuclear
radio-loudness parameter: Seyferts are associated with relatively {\it high}
radiative efficiencies L_o/L_Edd >~ 10^-4 (and high accretion rates onto low
mass black holes); LLRG are associated with low radiative efficiencies (and low
accretion rates onto high black hole masses); all LINERs have low radiative
efficiency (and accretion rates), and can be radio-loud or radio quiet
depending on their black hole mass.


title: White Dwarfs in Omega Centauri: Preliminary Evidence

abstract:
  We present accurate and deep multiband B,R,Halpha data for the globular
cluster Omega Cen collected with the Advanced Camera for Surveys on HST. The
photometric catalogue includes more than one million stars. By adopting severe
selection criteria we identified more than 600 bona fide White Dwarfs (WDs).
Empirical evidence suggests that a small sample of WDs are Halpha-bright. The
comparison between WD isochrones and observations shows a reasonable agreement
at fainter magnitudes and a mismatch at the brighter ones.


title: Evaporation of ion-irradiated disks

abstract:
  We calculate the evaporation of a cool accretion disk around a black hole due
to the ion-bombardment by an ion supported accretion flow (here ISAF, or
optically thin ADAF). As first suggested by Spruit & Deufel (2002), this
evaporation takes place in two stages: ion bombardment of the cool disk
(Shakura-Sunyaev disk: SSD) produces an intermediate-temperature layer on top
of the disk (`warm layer') which constitutes an independent accretion flow on
both sides of the SSD. As this warm material accretes inward of the inner
radius of the SSD, it becomes thermally unstable by lack of cooling of photons,
and evaporates into the ISAF, thereby feeding the latter. Angular momentum
conservation forces a certain fraction of the ISAF material to move outward,
where it can bombard the SSD with its hot ions. The flow geometry is derived by
computing stationary solutions of the continuity- and angular momentum
equations for the three components (ISAF, warm flow and SSD). The overall
radiative output is dominated by hard X-rays. They are produced mostly from the
warm component, rather than the ISAF. The expected time dependence and
stability of the flow, not computed here, is discussed briefly.


title: Panchromatic models of galaxies: GRASIL

abstract:
  We present here a model for simulating the panchromatic spectral energy
distribution of galaxies, which aims to be a complete tool to study the complex
multi-wavelength picture of the universe. The model take into account all
important components that concur to the SED of galaxies at wavelengths from
X-rays to the radio. We review the modeling of each component and provide
several applications, interpreting observations of galaxy of different types at
all the wavelengths.


title: Whiting 1: a new Halo Young Globular Cluster

abstract:
  We report on $BVI$ CCD photometry of a field centered in the region of the
Galactic star cluster Whiting~1 down to $V=23.0$. This cluster has never been
studied insofar, and we provide for the first time estimates of its fundamental
parameters, namely, radial extent, age, distance and reddening. Whiting~1 turns
out to be a compact star cluster with a diameter of about 1$^{\prime}$. We find
that the cluster is about 5 Gyr old and has a probable metal abundance around
[Fe/H]= -1.20. Its position at $b=-60^{o}.64$ and at a heliocentric distance of
about 45 kpc makes the cluster a rather strange object, surely not a disk old
open cluster, but perhaps the youngest halo Globular Cluster insofar known.


title:
Ovi Column Density Distribution in the Local Bubble - Results from 3D
  Adaptive Mesh Refinement Simulations

abstract:
  The Local Bubble (LB) is an X-ray emitting region extending 100 pc in radius
in the Galactic plane and 300 pc perpendicular to it, and it is embedded in a
somewhat larger H{\sc i} deficient cavity. Its origin and spectral properties
in UV, EUV and X-rays are still poorly understood. We have performed 3D high
resolution (down to 1.25 pc) hydrodynamic superbubble simulations of the LB and
Loop I superbubble in a realistic \emph{inhomogeneous} background ISM,
disturbed by supernova (SN) explosions at the Galactic rate. We can reproduce
(i) the size of the bubbles (in contrast to similarity solutions), (ii) the
interaction shell with Loop I, discovered with ROSAT, (iii) predict the merging
of the two bubbles in about 3 Myr, when the interaction shell starts to
fragment, and, (iv) the generation of blobs like the Local Cloud as a
consequence of a dynamical instability. The \ion{O}{6} column densities are
monitored and found to be in excellent agreement with \textsc{Copernicus} and
FUSE absorption line data, showing LB column densities $<1.7 \times 10^{13}
{\rm cm}^{-2}$, in contrast to other existing models.


title:
Partially ionized atmospheres of neutron stars with strong magnetic
  fields

abstract:
  We construct hydrogen atmosphere models for strongly magnetized neutron stars
in thermodynamic equilibrium, taking into account partial ionization. The
presence of bound states affects the equation of state, absorption
coefficients, and polarizability tensor of a strongly magnetized plasma.
Therefore the partial ionization influences the polarization vectors and
opacities of normal electromagnetic waves, and thus the spectra of outgoing
radiation. Here we review a model suitable for the most typical neutron-star
atmospheres and focus on the problems that remain to be solved for its
extension to other atmospheric parameters.


title: Hydrodynamic Turbulence in Accretion Disks

abstract:
  Turbulent viscosity in cold accretion disks is likely to be hydrodynamic in
origin. We investigate the growth of hydrodynamic perturbations in a small
region of a disk, which we model as a linear shear flow with Coriolis force,
between two parallel walls. Although there are no exponentially growing
eigenmodes in this system, because of the non-normal nature of the modes, it is
possible to have a large transient growth in the energy of certain
perturbations. For a constant angular momentum disk, the energy grows by more
than a factor of 1000 for a Reynolds number of only 1000, and so turbulence is
easily excited. For a Keplerian disk, the growth is more modest, and energy
growth by a factor of 1000 requires a Reynolds number of nearly a million.
Accretion disks have even larger Reynolds numbers than this. Therefore,
transient growth of perturbations could seed turbulence in such disks.


title: Depletion in post-AGB stars with a dusty disc. II

abstract:
  We present a chemical abundance analysis on the basis of high signal-to-
noise and high resolution spectra for 12 stars of our newly defined sample. The
selection criterion for the stars of this sample was their position in the `RV
Tauri' box in the [12]-[25], [25]-[60] two-colour diagram. An additional
requisite was the presence of a near-IR excess.
  We found that the photospheres of nine stars are affected by the depletion
process. Since the most likely origin of the near-IR excess is a disc, this
strongly suggests that the phenomenon of depletion and the presence of a disc
are linked. Among the depleted stars we find different depletion patterns. In
seven stars elements with a condensation temperature below 1500 K are not or
only slightly affected. Large underabundances are measured only for most
elements with a condensation temperature above 1500 K.


title:
First Results of the 74 MHz VLA-Pie Town Link. Hercules A at Low
  Frequencies

abstract:
  We present the results of the first successful observations of the Pie Town
link with the Very Large Array (VLA) at 74 MHz on Hercules A. The improvement
in resolution from 25 arcsec to 10 arcsec resolves the helical- and ring-like
features seen at higher frequencies. We also present new high dynamic range
images of this powerful radio galaxy at 325 MHz. Our low frequency observations
confirm the multiple outburst interpretation of the spectral index differences
at high frequencies. Comparison between our radio and ROSAT X-ray data does not
reveal any association between the X-ray emission from the cluster and the
radio lobes. There are no extra regions of radio emission at 74 MHz.


title:
The relationship between X-ray variability amplitude and black hole mass
  in active galactic nuclei

abstract:
  We have investigated the relationship between the 2-10 keV X-ray variability
amplitude and black hole mass for a sample of 46 radio-quiet active galactic
nuclei observed by ASCA. Thirty-three of the objects in our sample exhibited
variability over a time-scale of ~40 ks, and we found a significant
anti-correlation between excess variance and mass. Unlike most previous
studies, we have quantified the variability using nearly the same time-scale
for all objects. Moreover, we provide a prescription for estimating the
uncertainties in excess variance which accounts both for measurement
uncertainties and for the stochastic nature of the variability. We also present
an analytical method to predict the excess variance from a model power spectrum
accounting for binning, sampling and windowing effects. Using this, we modelled
the variance-mass relation assuming all objects have a universal twice-broken
power spectrum, with the position of the breaks being dependent on mass. This
accounts for the general form of the relationship but there is considerable
scatter. We investigated this scatter as a function of the X-ray photon index,
luminosity and Eddington ratio. After accounting for the dependence of excess
variance on mass, we find no significant correlation with either luminosity or
X-ray spectral slope. We do find an anti-correlation between excess variance
and the Eddington ratio, although this relation might be an artifact owing to
the uncertainties in the mass measurements. It remains to be established that
enhanced X-ray variability is a property of objects with steep X-ray slopes or
large Eddington ratios.


title: X-ray Spectroscopy of Candidate Ultracompact X-ray Binaries

abstract:
  We present high-resolution spectroscopy of the neutron star/low-mass X-ray
binaries (LMXBs) 4U 1850-087 and 4U 0513-40 as part of our continuing study of
known and candidate ultracompact binaries. The LMXB 4U 1850-087 is one of four
systems in which we had previously inferred an unusual Ne/O ratio in the
absorption along the line of sight, most likely from material local to the
binaries. However, our recent Chandra X-ray Observatory LETGS spectrum of 4U
1850-087 finds a Ne/O ratio by number of 0.22+/-0.05, smaller than previously
measured and consistent with the expected interstellar value. We propose that
variations in the Ne/O ratio due to source variability, as previously observed
in these sources, can explain the difference between the low- and
high-resolution spectral results for 4U 1850-087. Our XMM-Newton RGS
observation of 4U 0513-40 also shows no unusual abundance ratios in the
absorption along the line of sight. We also present spectral results from a
third candidate ultracompact binary, 4U 1822-000, whose spectrum is well fit by
an absorbed power-law + blackbody model with absorption consistent with the
expected interstellar value. Finally, we present the non-detection of a fourth
candidate ultracompact binary, 4U 1905+000, with an upper limit on the source
luminosity of < 1 x 10^{32} erg s^{-1}. Using archival data, we show that the
source has entered an extended quiescent state.


title: Magnetic Flux Tube Reconnection: Tunneling Versus Slingshot

abstract:
  The discrete nature of the solar magnetic field as it emerges into the corona
through the photosphere indicates that it exists as isolated flux tubes in the
convection zone, and will remain as discrete flux tubes in the corona until it
collides and reconnects with other coronal fields. Collisions of these flux
tubes will in general be three dimensional, and will often lead to
reconnection, both rearranging the magnetic field topology in fundamental ways,
and releasing magnetic energy. With the goal of better understanding these
dynamics, we carry out a set of numerical experiments exploring fundamental
characteristics of three dimensional magnetic flux tube reconnection. We first
show that reconnecting flux tubes at opposite extremes of twist behave very
differently: in some configurations, low twist tubes slingshot while high twist
tubes tunnel. We then discuss a theory explaining these differences: by
assuming helicity conservation during the reconnection one can show that at
high twist, tunneled tubes reach a lower magnetic energy state than slingshot
tubes, whereas at low twist the opposite holds. We test three predictions made
by this theory. 1) We find that the level of twist at which the transition from
slingshot to tunnel occurs is about two to three times higher than predicted on
the basis of energetics and helicity conservation alone, probably because the
dynamics of the reconnection play a large role as well. 2) We find that the
tunnel occurs at all flux tube collision angles predicted by the theory. 3) We
find that the amount of magnetic energy a slingshot or a tunnel reconnection
releases agrees reasonably well with the theory, though at the high
resistivities we have to use for numerical stability, a significant amount of
magnetic energy is lost to diffusion, independent of reconnection.


title:
Diffusion coefficient of a passive contaminant in a local MHD model of a
  turbulent accretion disc

abstract:
  We calculate the radial diffusion coefficient for a passive contaminant in an
accretion disc which is turbulent due to the action of the magnetorotational
instability. Numerical MHD simulations are used to follow the evolution of a
local patch of the disc using the shearing box formalism. A separate continuity
equation for the mass fraction of contaminant is integrated along with the MHD
system, and radial profiles of this fraction are obtained as a function of
time. Solutions of a linear diffusion equation are fitted to the numerical
measured profiles of the contaminant, treating the diffusion coefficient D as
the fitting parameter. At early times, the value of D is found to vary, however
once the contaminant is spread over scales comparable to the box size, it
saturates at a steady value. The ratio of D to the transport coefficient of
angular momentum due to shear stress is small. If D can be used as a proxy for
the turbulent magnetic diffusivity, the effective magnetic Prandtl number
P_eff=\nu/D (where \nu is the coefficient of "efective viscosity" associated
with shear stress) would be large.