title: Dark energy cosmology with generalized linear equation of state

abstract:
  Dark energy with the usually used equation of state $p=w\rho$, where
$w=const<0$ is hydrodynamically unstable. To overcome this drawback we consider
the cosmology of a perfect fluid with a linear equation of state of a more
general form $p=\alpha(\rho-\rho_0)$, where the constants $\alpha$ and $\rho_0$
are free parameters. This non-homogeneous linear equation of state provides the
description of both hydrodynamically stable ($\alpha>0$) and unstable
($\alpha<0$) fluids. In particular, the considered cosmological model describes
the hydrodynamically stable dark (and phantom) energy. The possible types of
cosmological scenarios in this model are determined and classified in terms of
attractors and unstable points by the using of phase trajectories analysis. For
the dark energy case there are possible some distinctive types of cosmological
scenarios: (i) the universe with the de Sitter attractor at late times, (ii)
the bouncing universe, (iii) the universe with the Big Rip and with the
anti-Big Rip. In the framework of a linear equation of state the universe
filled with an phantom energy, $w<-1$, may have either the de Sitter attractor
or the Big Rip.


title: Spectroscopy of Planetary Nebulae in Sextans A and Sextans B

abstract:
  Sextans A and Sextans B are two dIr galaxies situated in the outskirts of the
Local Group (LG), in which both PNe and H II regions have been detected (Jacoby
& Lesser 1981, Magrini et al. 2002, 2003). We present spectroscopic
observations of PNe and HII regions in these two galaxies (obtained with the
VLT) Preliminary results about PNe physico-chemical properties are presented.


title: Spectroscopic surveys:a different approach to data reduction

abstract:
  We present VIPGI, an automatized human supervised reduction environment,
developed within the VIRMOS project to handle VIMOS guaranteed time data. VIPGI
is now offered to the international community to be used on site in Milano and
Marseille. Born to handle the highly multiplexed MOS VIMOS data, it has been
extended to accomodate also IFU data. The widespread and extensive use of VIPGI
has suggested the idea of an integrated environment allowing users not only to
reduce, but also to organize data in logical structures, to insert results in a
database, and use any user defined plugin for data reduction, analysis and
inspection. See http://cosmos.mi.iasf.cnr.it/pandora


title: Star Formation Histories in the Local Group

abstract:
  Deep color magnitude diagrams extending to the main sequence provide the most
direct measure of the detailed star formation history in a stellar population.
With large investments of observing time, HST can obtain such data for
populations out to 1 Mpc, but its field of view is extremely small in
comparison to the size of Local Group galaxies. This limitation severely
constrains our understanding of galaxy formation. For example, the largest
galaxy in the Local Group, Andromeda, offers an ideal laboratory for studying
the formation of large spiral galaxies, but the galaxy shows substructure on a
variety of scales, presumably due to its violent merger history. Within its
remaining lifetime, HST can only sample a few sight-lines through this complex
galaxy. In contrast, a wide field imager could provide a map of Andromeda's
halo, outer disk, and tidal streams, revealing the spatially-dependent star
formation history in each structure. The same data would enable many secondary
studies, such as the age variation in Andromeda's globular cluster system,
gigantic samples of variable stars, and microlensing tracers of the galaxy's
dark matter distribution.


title:
Response to "Reanalysis of the spectrum of the z=10 galaxy ISAAC/VLT
  observations of a lensed galaxy at z=10.0" by Weatherley et al.
  (astro-ph/0407150)

abstract:
  In a recent posting of a submitted paper Weatherley et al. re-analyse the
spectroscopic data from our observations of Abell 1835 IR 1916, a galaxy we
claimed to be at redshift z=10.0 (Pello et al., 2004, A&A, 416, L35). They
conclude that the emission line is not detected in their analysis. Although
their reduction procedure is accurate and robust, there are several differences
with ours. The most important one concerns the stacking of the spectral frames.
In the case of compact target sources [here: seeing-limited object,~3 pixels
FWHM in the spectral direction, on a 1" (~7 pixels) wide slit] spectral shifts
occur between individual frames. Our reduction corrects for this effect using a
nearby strong emission line from a compact reference object, as described in
Pello et al. However, Weatherley et al. neglect this effect. This difference
turns out to be crucial. E.g. adopting their combination scheme as closely as
possible but correcting for the spectral drifts we recover the line detection.
We conclude that more work is needed to fully understand the origin of our
differences. However, their non-detection claim needs further investigation and
cannot be uphold based on the arguments presented in their original version of
the paper. More information is beeing posted on
http://webast.ast.obs-mip.fr/people/roser/z10_spectroscopy_discussion. With
this material we also invite other researchers to re-analyse independently the
ISAAC spectroscopic observations.


title:
The slowly expanding envelope of CRL618 probed with HC3N rotational
  ladders

abstract:
  Lines from HC3N and isotopic substituted species in ground and vibrationally
excited states produce crowded millimeter and submillimeter wave spectra in the
C-rich protoplanetary nebula CRL618. The complete sequence of HC3N rotational
lines from J=9-8 to J=30-29 has been observed with the IRAM 30m telescope
toward this object. Lines from a total of 15 different vibrational states
(including the fundamental), with energies up to 1100 cm^-1, have been detected
for the main HC3N isotopomer. In addition, the CSO telescope has been used to
complement this study in the range J=31-30 to J=39-38, with detections in five
of these states, all of them below 700 cm^-1. Vibrationally excited HC3N
rotational lines exhibit P-Cygni profiles at 3 mm, evolving to pure emission
lineshapes at shorter wavelengths. This evolution of the line profile shows
little dependence on the vibrational state from which they rotational lines
arise. The absorption features are formed against the continuum emission, which
has been successfully characterized in this work due to the large frequency
coverage. The HC3N column density in front of the the continuum source has been
determined by comparing the output of an array of models to the data. The best
fits are obtained for column densities in the range 2.0-3.5 10$^17 cm^-2,
consistent with previous estimates from ISO data, and TK in the range 250 to
275 K, in very good agreement with estimates made from the same ISO data.


title:
Interacting Quintessence, Cosmic Acceleration and the Coincidence
  Problem

abstract:
  Faced by recent evidence for a flat universe dominated by dark energy,
cosmologists grapple with deep cosmic enigmas such as the cosmological constant
problem, extreme fine-tuning and the cosmic coincidence problem. The extent to
which we observe the dimming of distant supernovae suggests that the cosmic
acceleration is as least as severe as in cosmological constant models.
Extrapolating this to our cosmic future implies terrifying visions of either a
cold and empty universe or an explosive demise in a ``Big Rip.'' We construct a
class of dynamical scalar field models of dark energy and dark matter. Within
this class we can explain why supernovae imply a cosmic equation of state
$w\lesssim-1$, address fine tuning issues, protect the universe from premature
acceleration and predict a constant fraction of dark energy to dark matter in
the future (thus solving the coincidence problem), satisfy the dominant energy
condition, and ensure that gravitationally bound objects remain so forever
(avoid a Big Rip). This is achieved with a string theory inspired Lagrangian
containing standard kinetic terms, exponential potentials and couplings, and
parameters of order unity.


title:
Probes of Jet-Disk-Coupling in AGN from Combined VLBI and X-Ray
  Observations

abstract:
  The formation of powerful extragalactic jets is not well understood at
present as well as the associated key question:``What makes an AGN radio
loud?''. Here we discuss how the combination of VLBI and X-ray spectroscopic
observations allows the inter-relation between the accretion flow and the
formation of relativistic jets in AGN to be explored.


title:
Testing cosmological models and understanding cosmological parameter
  determinations with metaparameters

abstract:
  Cosmological parameters affect observables in physically distinct ways. For
example, the baryon density, omega_b, affects the ionization history and also
the pressure of the pre-recombination fluid. To investigate the relative
importance of different physical effects to the determination of omega_b, and
to test the cosmological model, we artificially split omega_b into two
`metaparameters': omega_{be} which controls the ionization history and
omega_{bp} which plays the role of omega_b for everything else. In our
demonstration of the technique we find omega_b = .0229 +/- .0012 (with no
parameter splitting), omega_{bp} = .0238 +/- .0021, omega_{be}= .0150 +/- .0034
and omega_{bp}-omega_{be} = .0088 +/- .0039.


title:
A charge transfer inefficiency correction model for the Chandra Advanced
  CCD Imaging Spectrometer

abstract:
  Soon after launch, the Advanced CCD Imaging Spectrometer (ACIS), one of the
focal plane instruments on the Chandra X-ray Observatory, suffered radiation
damage from exposure to soft protons during passages through the Earth's
radiation belts. The primary effect of the damage was to increase the charge
transfer inefficiency (CTI) of the eight front illuminated CCDs by more than
two orders of magnitude. The ACIS instrument team is continuing to study the
properties of the damage with an emphasis on developing techniques to mitigate
CTI and spectral resolution degradation. We will discuss the characteristics of
the damage, the detector and the particle background and how they conspire to
degrade the instrument performance. We have developed a model for ACIS CTI
which can be used to correct each event and regain some of the lost
performance. The correction uses a map of the electron trap distribution, a
parameterization of the energy dependent charge loss and the fraction of the
lost charge re-emitted into the trailing pixel to correct the pixels in the
event island. This model has been implemented in the standard Chandra data
processing pipeline. Some of the correction algorithm was inspired by the
earlier work on ACIS CTI correction by Townsley et al. (2000; 2002). The
details of the CTI model and how each parameter improves performance will be
discussed, as well as the limitations and the possibilities for future
improvement.


title:
MOCASSIN: 3D photoionisation and dust radiative transfer modelling of
  PNe

abstract:
  We present the first 3D Monte Carlo photoionisation code to include a fully
self-consistent treatment of dust radiative transfer (RT) within the
photoionised region. This is the latest development of the recently published
pure photoionisation code MOCASSIN (Ercolano et al., 2003a) and it is currently
undergoing several benchmarking tests. The preliminary results of these tests
are presented in these conference proceedings. The new code provides the ideal
tool for the analysis of dusty ionised regions showing asymmetries and/or
density and chemical inhomogeneities


title: Eyes Wide Open - Optimising Cosmological Surveys in a Crowded Market

abstract:
  Optimising the major next-generation cosmological surveys (such as {\em SNAP,
KAOS etc...}) is a key problem given our ignorance of the physics underlying
cosmic acceleration and the plethora of surveys planned. We propose a Bayesian
design framework which (1) maximises the discrimination power of a survey
without assuming any underlying dark energy model, (2) finds the best niche
survey geometry given current data and future competing experiments, (3)
maximises the cross-section for serendipitous discoveries and (4) can be
adapted to answer specific questions (such as `is dark energy dynamical?').
Integrated Parameter Space Optimisation (IPSO) is a design framework that
integrates projected parameter errors over an entire dark energy parameter
space and then extremises a figure of merit (such as Shannon entropy gain which
we show is stable to off-diagonal covariance matrix perturbations) as a
function of survey parameters using analytical, grid or MCMC techniques. We
discuss examples where the optimisation can be performed analytically. IPSO is
thus a general, model-independent and scalable framework that allows us to
appropriately use prior information to design the best possible surveys.


title: The Missing Luminous Blue Variables and the Bistability Jump

abstract:
  We discuss an interesting feature of the distribution of luminous blue
variables on the H-R diagram, and we propose a connection with the bistability
jump in the winds of early-type supergiants. There appears to be a deficiency
of quiescent LBVs on the S Dor instability strip at luminosities between log
L/Lsun = 5.6 and 5.8. The upper boundary, is also where the
temperature-dependent S Dor instability strip intersects the bistability jump
at about 21,000 K. Due to increased opacity, winds of early-type supergiants
are slower and denser on the cool side of the bistability jump, and we
postulate that this may trigger optically-thick winds that inhibit quiescent
LBVs from residing there. We conduct numerical simulations of radiation-driven
winds for a range of temperatures, masses, and velocity laws at log L/Lsun=5.7
to see what effect the bistability jump should have. We find that for
relatively low stellar masses the increase in wind density at the bistability
jump leads to the formation of a modest to strong pseudo photosphere -- enough
to make an early B-type star appear as a yellow hypergiant. Thus, the proposed
mechanism will be most relevant for LBVs that are post-red supergiants. Yellow
hypergiants like IRC+10420 and rho Cas occupy the same luminosity range as the
``missing'' LBVs, and show apparent temperature variations at constant
luminosity. If these yellow hypergiants do eventually become Wolf-Rayet stars,
we speculate that they may skip the normal LBV phase, at least as far as their
apparent positions on the HR diagram are concerned.


title:
A Composite Extreme Ultraviolet QSO Spectrum from the Far Ultraviolet
  Spectroscopic Explorer

abstract:
  The Far Ultraviolet Spectroscopic Explorer (FUSE) has surveyed a large sample
(> 100) of active galactic nuclei in the low-redshift universe (z < 1). Its
response at short wavelengths makes it possible to measure directly the far
ultraviolet spectral properties of quasistellar objects (QSOs) and Seyfert 1
galaxies at z < 0.3. Using archival FUSE spectra, we form a composite extreme
ultraviolet (EUV) spectrum of QSOs at z < 0.67. After consideration of many
possible sources of systematic error in our analysis, we find that the spectral
slope of the FUSE composite spectrum, \alpha= -0.56^+0.38_-0.28 for F_\nu
\propto \nu^\alpha, is significantly harder than the EUV (\lambda \lesssim 1200
A) portion of the composite spectrum of QSOs with z > 0.33 formed from archival
Hubble Space Telescope spectra, \alpha=-1.76 \pm 0.12. We identify several
prominent emission lines in the \fuse composite and find that the
high-ionization O VI and Ne VIII emission lines are enhanced relative to the
HST composite. Power law continuum fits to the individual FUSE AGN spectra
reveal a correlation between EUV spectral slope and AGN luminosity in the FUSE
and FUSE + HST samples in the sense that lower luminosity AGNs show harder
spectral slopes. We find an anticorrelation between the hardness of the EUV
spectral slope and AGN black hole mass, using estimates of this quantity found
in the literature. We interpret these results in the context of the well-known
anticorrelation between AGN luminosity and emission line strength, the Baldwin
effect, given that the median luminosity of the FUSE AGN sample is an order of
magnitude lower than that of the HST sample.


title:
Complementary constraints from FR IIb radio galaxies and X-ray gas mass
  fractions in clusters on non-standard cosmological models

abstract:
  We use recent measurements of the dimensionless coordinate distances from
Fanaroff-Riley Type IIb radio galaxies and the X-ray gas mass fractions in
clusters to constrain the parameters of a non-standard cosmological model. This
work complements our recent analysis of the SN Ia data within a non-Riemannian
cosmological model. We use two independent data sets to constrain the new
density parameter $\Omega_\psi$, which is related to the non-Riemannian
structure of the underlying spacetime and supplements the field equations that
are very similar to the usual Friedmann equations of general relativity.
Thereby we place an upper limit on the presence of non-Riemannian quantities in
the late stages of the universe. The numerical results of this work also apply
to several anisotropic cosmological models which, on the level of the field
equations, exhibit a similar scaling behavior of the density parameters like
our non-Riemannian model.


title:
A Chandra Deep X-ray Exposure on the Galactic Plane and Near Infrared
  Identification

abstract:
  Using the Chandra ACIS-I instruments, we have carried out a deep X-ray
observation on the Galactic plane region at (l,b) ~ (28.5, 0.0), where no
discrete X-ray sources have been known previously. We have detected, as well as
strong diffuse emission, 274 new point X-ray sources (4 sigma confidence)
within two partially overlapping fields (~250 arcmin^2 in total) down to the
flux limit ~3 x 10^{-15} $ erg s^{-1} cm^{-2} (2 -- 10 keV) and ~ 7 x 10^{-16}
erg s^{-1} cm^{-2} (0.5 -- 2 keV). We clearly resolved point sources and the
Galactic diffuse emission, and found that ~ 90 % of the flux observed in our
field of view originates from diffuse emission. Many point sources are detected
either in the soft X-ray band (below 2 keV) or in the hard band (above 2 keV),
and only a small number of sources are detected in both energy bands.
  On the other hand, most soft X-ray sources are considered to be nearby X-ray
active stars. We have carried out a follow-up near-infrared (NIR) observation
using SOFI at ESO/NTT. Most of the soft X-ray sources were identified, whereas
only a small number of hard X-ray sources had counterparts in NIR. Using both
X-ray and NIR information, we can efficiently classify the point X-ray sources
detected in the Galactic plane. We conclude that most of the hard X-ray sources
are background Active Galactic Nuclei seen through the Milky Way, whereas
majority of the soft X-ray sources are nearby X-ray active stars.


title:
Neutrino Interactions in the Outflow from Gamma-Ray Burst Accretion
  Disks

abstract:
  We examine the composition of matter as it flows away from gamma ray burst
accretion disks, in order to determine what sort of nucleosynthesis may occur.
Since there is a large flux of neutrinos leaving the surface of the disk, the
electron fraction of the outflowing material will change due to charged current
neutrino interactions. We calculate the electron fraction in the wind using
detailed neutrino fluxes from every point on the disk and study a range of
trajectories and outflow conditions for several different accretion disk
models. We find that low electron fractions, conducive to making r-process
elements, only appear in outflows from disks with high accretion rates that
have a significant region both of trapped neutrinos and antineutrinos. Disks
with lower accretion rates that have only a significant region of trapped
neutrinos can have outflows with very high electron fractions, whereas the
lowest accretion rate disks with little trapping have outflow electrons
fractions of closer to one half.


title: Dark Matter and Background Light

abstract:
  Progress in observational cosmology over the past five years has established
that the Universe is dominated dynamically by dark matter and dark energy. Both
these new and apparently independent forms of matter-energy have properties
that are inconsistent with anything in the existing standard model of particle
physics, and it appears that the latter must be extended. We review what is
known about dark matter and energy from their impact on the light of the night
sky. Most of the candidates that have been proposed so far are not perfectly
black, but decay into or otherwise interact with photons in characteristic ways
that can be accurately modelled and compared with observational data. We show
how experimental limits on the intensity of cosmic background radiation in the
microwave, infrared, optical, ultraviolet, x-ray and gamma-ray bands put strong
limits on decaying vacuum energy, light axions, neutrinos, unstable
weakly-interacting massive particles (WIMPs) and objects like black holes. Our
conclusion is that the dark matter is most likely to be WIMPs if conventional
cosmology holds; or higher-dimensional sources if spacetime needs to be
extended.


title:
Cosmic microwave background constraints on the strong equivalence
  principle

abstract:
  We study the effect of a violation of the strong equivalence principle (SEP)
on the cosmic microwave background (CMB). Such a violation would modify the
weight of baryons in the primordial gravitational potentials and hence their
impact in the establishment of the photon-baryon plasma acoustic oscillations
before recombination. This cosmological Nordtvedt effect alters the odd peaks
height of the CMB temperature anisotropy power spectrum. A gravitational
baryonic mass density of the universe may already be inferred at the first peak
scale from the analysis of WMAP data. Experimental constraints on a primordial
SEP violation are derived from a comparison with the universe's inertial
baryonic mass density measured either in a full analysis of the CMB, or in the
framework of the standard big bang nucleosynthesis (BBN).


title: Microlensing towards LMC and M31

abstract:
  The nature and the location of the lenses discovered in the microlensing
surveys done so far towards the LMC remain unclear. Motivated by these
questions we computed the optical depth for the different intervening
populations and the number of expected events for self-lensing, using a
recently drawn coherent picture of the geometrical structure and dynamics of
the LMC. By comparing the theoretical quantities with the values of the
observed events it is possible to put some constraints on the location and the
nature of the MACHOs. Clearly, given the large uncertainties and the few events
at disposal it is not yet possible to draw sharp conclusions, nevertheless we
find that up to 3-4 MACHO events might be due to lenses in LMC, which are most
probably low mass stars, but that hardly all events can be due to self-lensing.
The most plausible solution is that the events observed so far are due to
lenses belonging to different intervening populations: low mass stars in the
LMC, in the thick disk, in the spheroid and some true MACHOs in the halo of the
Milky Way and the LMC itself. We report also on recent results of the
SLOTT-AGAPE and POINT-AGAPE collaborations on a search for microlensing events
in direction of the Andromeda galaxy, by using the pixel method. The detection
of 4 microlensing events, some likely to be due to self--lensing, is discussed.
One microlensing light curve is shown to be compatible with a binary lens. The
present analysis still does not allow us to draw conclusions on the MACHO
content of the M31 galaxy.


title: Microlensing towards the LMC

abstract:
  The nature and the location of the lenses discovered in the microlensing
surveys done so far towards the LMC remain unclear. Motivated by these
questions we computed the optical depth for the different intervening
populations and the number of expected events for self-lensing, using a
recently drawn coherent picture of the geometrical structure and dynamics of
the LMC. By comparing the theoretical quantities with the values of the
observed events it is possible to put some constraints on the location and the
nature of the MACHOs. Clearly, given the large uncertainties and the few events
at disposal it is not yet possible to draw sharp conclusions, nevertheless we
find that up to 3-4 MACHO events might be due to lenses in LMC, which are most
probably low mass stars, but that hardly all events can be due to self-lensing.
The most plausible solution is that the events observed so far are due to
lenses belonging to different intervening populations: low mass stars in the
LMC, in the thick disk, in the spheroid and some true MACHOs in the halo of the
Milky Way and the LMC itself.


title: Discovering Tau and Muon Solar Neutrino Flares above backgrounds

abstract:
  Solar neutrino flares astronomy is at the edge of its discover. High energy
flare particles (protons, alpha) whose self scattering within the solar corona
is source of a rich prompt charged pions are also source of sharp solar
neutrino "burst" (at tens-hundred MeV) produced by their pion-muon primary
decay in flight. This brief (minute) solar neutrino "burst" at largest peak
overcome by four-five order of magnitude the steady atmospheric neutrino noise
at the Earth. Later on, solar flare particles hitting the terrestrial
atmosphere may marginally increase the atmospheric neutrino flux without
relevant consequences. Largest prompt "burst" solar neutrino flare may be
detected in present or better in future largest neutrino underground neutrino
detectors. Our estimate for the recent and exceptional October - November 2003
solar flares gives a number of events above or just near unity for
Super-Kamiokande. The neutrino spectra may reflect in a subtle way the neutrino
flavour mixing in flight. A surprising tau appearance may even occur for a hard
({E}_{nu}_{mu}--> {E}_{nu}_{tau} > 4 GeV) flare spectra. A comparison of the
solar neutrino flare (at their birth place on Sun and after oscillation on the
arrival on the Earth) with other neutrino foreground is here described and it
offer an independent road map to disentangle the neutrino flavour puzzles and
its secret flavour mixing angles .


title:
R-process and alpha-elements in the Galactic disk: Kinematic
  correlations

abstract:
  Recent studies of elemental abundances in the Galactic halo and in the
Galactic disk have underscored the possibility to kinematically separate
different Galactic subcomponents. Correlations between the galactocentric
rotation velocity and various element ratios were found, providing an important
means to link different tracers of star formation and metal enrichment to the
Galactic components of different origin (collapse vs. accretion). In the
present work we determine stellar kinematics for a sample of 124 disk stars,
which we derive from their orbits based on radial velocities and proper motions
from the the literature. Our stars form a subsample of the Edvardsson et al.
(1993) sample and we concentrate on three main tracers: (i) Europium as an
r-process element is predominantly produced in Supernovae of type II. (ii)
Likewise, alpha-elements, such as Ca, Si, Mg, are synthesised in SNe II,
contrary to iron, which is being produced preferentially in SNe Ia. (iii) The
s-process element Barium is a measure of the relative contribution of AGB stars
to the Galaxy's enrichment history and has been shown to be an indicator for
distinguishing between thin and thick disk stars. All such studies reveal,
basically, that stars with low galactocentric rotational velocity tend to have
high abundances of alpha-elements and Eu, but lower abundances of, e.g., Ba.


title: New Infrared Emission Features and Spectral Variations in NGC 7023

abstract:
  We have observed the reflection nebula NGC 7023, with the Short-High module
and long-slit Short-Low and Long-Low modules of the Infrared Spectrograph on
the Spitzer Space Telescope. We also present Infrared Array Camera and
Multiband Imaging Photometer for Spitzer images of NGC 7023 at 3.6, 4.5, 8.0,
and 24 microns. We observe the aromatic emission features (AEFs) at 6.2, 7.7,
8.6, 11.3, and 12.7 microns, plus a wealth of weaker features. We find new
unidentified interstellar emission features at 6.7, 10.1, 15.8, 17.4, and 19.0
microns. Possible identifications include aromatic hydrocarbons or
nanoparticles of unknown mineralogy. We see variations in relative feature
strengths, central wavelengths, and feature widths, in the AEFs and weaker
emission features, depending on both distance from the star and nebular
position (southeast vs. northwest).


title: Redshift-Space Distortions, Pairwise Velocities and Nonlinearities

abstract:
  We derive the exact relationship, including all non-linearities, between
real-space and redshift-space two-point statistics through the pairwise
velocity distribution function. We show using numerical simulations that the
pairwise velocity PDF is strongly non-Gaussian at all scales, and explain why
this is so. We caution that a commonly used ansatz to model the redshift-space
power spectrum gives rise to an unphysical distribution of pairwise velocities,
and show that it is in general impossible to derive the distribution from
measurements of redshift-space clustering. Methods that claim to do this obtain
instead something else, whose properties we derive.
  We provide a general derivation of the large-scale limit of the
redshift-space power spectrum and show that it differs from the Kaiser formula
by terms that depend on Gaussian and non-Gaussian contributions to the velocity
dispersion of large-scale flows. We also show that the large-scale evolution of
velocity fields is not well described by linear theory and discuss how this
impacts the redshift-space power spectrum. Finally, we stress that using the
monopole of the redshift-space power as an indicator of the real-space power
spectrum shape can lead to systematic effects in the determination of
cosmological parameters; nevertheless a simple procedure is able to recover the
large-scale real-space power spectrum rather well.


title:
Near-infrared K-band Spectroscopic Investigation of Seyfert 2 Nuclei in
  the CfA and 12 Micron Samples

abstract:
  We present near-infrared K-band slit spectra of the nuclei of 25 Seyfert 2
galaxies in the CfA and 12 micron samples. The strength of the CO absorption
features at 2.3-2.4 micron produced by stars is measured in terms of a
spectroscopic CO index. A clear anti-correlation between the observed CO index
and the nuclear K-L color is present, suggesting that a featureless hot dust
continuum heated by an AGN contributes significantly to the observed K-band
fluxes in the nuclei of Seyfert 2 galaxies. After correction for this AGN
contribution, we estimate nuclear stellar K-band luminosities for all sources,
and CO indices for sources with modestly large observed CO indices. The
corrected CO indices for 10 (=40%) Seyfert 2 nuclei are found to be as high as
those observed in star-forming or elliptical (=spheroidal) galaxies. We combine
the K-band data with measurements of the L-band 3.3 micron polycyclic aromatic
hydrocarbon (PAH) emission feature, another powerful indicator for
star-formation, and find that the 3.3 micron PAH to K-band stellar luminosity
ratios are substantially smaller than those of starburst galaxies. Our results
suggest that the 3.3 micron PAH emission originates in the putative nuclear
starbursts in the dusty tori surrounding the AGNs, because of its high surface
brightness, whereas the K-band CO absorption features detected at the nuclei
are dominated by old bulge (=spheroid) stars, and thus may not be a powerful
indicator for the nuclear starbursts. We see no clear difference in the
strength of the CO absorption and PAH emission features between the CfA and 12
micron Seyfert 2s.


title: Death rate of massive stars at redshift ~0.3

abstract:
  We report the first result of a supernova search program designed to measure
the evolution of the supernova rate with redshift. To make the comparison with
local rates more significant we copied, as much as possible, the same
computation recepies as for the measurements of local rates. Moreover, we
exploited the multicolor images and the photometric redshift technique to
characterize the galaxy sample and accurately estimate the detection
efficiency.
  Combining our data with the recently published meaurements of the SN Ia rate
at different redshifts, we derived the first, direct measurement of the core
collapse supernova rate at z = 0.26 as r_cc = 1.45^{+0.55}{-0.45} h^2 SNu
[h=H_0/75]. This is a factor three {+/- 50%)} larger than the local estimate.
The increase for a look back time of "only" 2.8 Gyr is more rapid than
predicted by most of the published models of the SN rate evolution.
Core-collapse SN rates measure the death rate of massive star and, because of
the short time scale of evolution, can be translated in a measurement of the
ongoing SFR. Assuming a Salpeter IMF and the standard scenario for
core-collapse progenitors we derived to an estimate of the star formation rate
at redshift 3.1^{+1.1}{-1.0} 10^-2 h^3 M_sun yr^-1 Mpc^{-3} which compare very
well with a recent estimate based on the measurement of the Halpha luminosity
density at the same redshift.


title: Monitoring water masers in star-forming regions

abstract:
  An overview is given of the analysis of more than a decade of H2O maser data
from our monitoring program. We find the maser emission to generally depend on
the luminosity of the YSO as well as on the geometry of the SFR. There appears
to be a threshold luminosity of a few times 10**4 Lsol above and below which we
find different maser characteristics.


title:
Star Formation at Redshift One: Preliminary results from an H-alpha
  Survey

abstract:
  We present the first successful demonstration of multi-object near-infrared
spectroscopy on high redshift galaxies. Our objective is to address the true
star formation history of the universe at z~1, a crucial epoch which some have
suggested is the peak of star formation activity. By using H-alpha -the same
robust star formation indicator used at low-z - redshifted into the J- and
H-bands, we can trace star formation without the systematic uncertainties of
different calibrators, or the extreme dust extinction in the rest-UV, which
have plagued previous efforts. We are using the instrument CIRPASS (the
Cambridge Infra-Red PAnoramic Survey Spectrograph), in multi-object mode, which
has been successfully demonstrated on the Anglo-Australian Telescope (AAT) and
the William Herschel Telescope (WHT). CIRPASS has 150 fibres deployable over
\~40arcmin on the AAT and ~15arcmin on the WHT. Here we present preliminary
results from one of our fields observed with the WHT: H-alpha detections of z~1
galaxies in the Hubble Deep Field North.


title:
Line-of-sight velocity distribution corrections for Lick/IDS indices of
  early-type galaxies

abstract:
  We investigate line-of-sight velocity distribution (LOSVD) corrections for
absorption line-strength indices of early-type galaxies in the Lick/IDS system.
This system is often used to estimate basic stellar population parameters such
as luminosity weighted ages and metallicities. Using single stellar population
model spectral energy distributions by Vazdekis (1999) we find that the LOSVD
corrections are largely insensitive to changes in the stellar populations for
old galaxies (age >3 Gyr). Only the Lick/IDS Balmer series indices show an
appreciable effect, which is on the order of the correction itself.
Furthermore, we investigate the sensitivity of the LOSVD corrections to
non-Gaussian LOSVDs. In this case the LOSVD can be described by a Gauss-Hermite
series and it is shown that typical values of h_3 and h_4 observed in
early-type galaxies can lead to significant modifications of the LOSVD
corrections and thus to changes in the derived luminosity weighted ages and
metallicities. A new, simple parameterisation for the LOSVD corrections, taking
into account the h_3 and h_4 terms, is proposed and calibrations given for a
subset of the Lick/IDS indices and two additional indices applicable to old (>3
Gyr) stellar populations.


title: Monitoring lensed starlight emitted close to the Galactic Center

abstract:
  We describe the feasibility of detecting the gravitational deflection of
light emitted by stars moving under the influence of the massive object at the
Galactic center. Light emitted by a star orbiting behind the central mass has a
smaller impact parameter than the star itself, and suffers the effect of
gravitational lensing, providing a closer probe of the central mass
distribution and hence a stricter test of the black hole hypothesis. A mass of
$4.3\times 10^{6} M_{\odot}$ causes a $0.1-2\rm mas$ deviation in the apparent
position of orbiting stars projected within $10^{\circ}$ of the line of sight
to the galactic center. In addtion, we may uniquely constrain the distance to
the center of the galaxy because lensing deflections constrain the ratio
$\rg/R_{0}$ of the Schwarzschild radius to the distance to the black hole,
$R_{o}$, whereas the ratio $\rg/R_{o}^{3}$ is obtained by fitting the orbit.


title: The potential of INTEGRAL for the detection of high redshift GRBs

abstract:
  We discuss INTEGRAL's capabilities to detect a high redshift population of
Gamma-Ray Bursts (GRBs) in comparison to other high-energy missions. Emphasis
is done on the study of the relative capabilities of IBIS on board INTEGRAL
with respect to SWIFT and HETE 2 for detecting a high redshift population of
GRBs. We conclude that, if the GRB rate is proportional to the star formation
rate, INTEGRAL's capabilities for studying GRBs are complementary to the ones
of missions like SWIFT and HETE 2, specially devoted to prompt localisations of
GRBs. Whereas SWIFT and HETE 2 would detect a higher number of GRBs than
INTEGRAL, IBIS might be able to detect high redshift (z>~7) GRBs, unreachable
for SWIFT and HETE 2. We discuss the relevance of performing near-infrared
(NIR) observations of the INTEGRAL GRBs and the strategy that large class
telescopes might follow.


title:
Einstein-Rosen Bridges and the Characteristic Properties of
  Gravitational Lensing by Them

abstract:
  It is shown that Einstein-Rosen bridges (wormholes) hypothetical objects that
topologically connect separate locations in the Universe can be static
solutions of the Einstein equations. The corresponding equations for bridges
are reduced to a form convenient for their analysis and numerical solution. The
matter forming the bridge must have a sufficiently hard and anisotropic
equation of state. Our results are compared with a previously known analytic
solution for a bridge, which is a special case of the general solution in the
framework of general relativity. The deflection of photons by the bridge
(gravitational lensing) is studied.


title: The submillimeter C and CO lines in Henize 2-10 and NGC 253

abstract:
  The purpose of this paper is to describe a method for determining a cooling
template for galaxies, using nearby galaxies, and applicable to future
observations of distant galaxies. We observed two starburst galaxies (NGC 253
and Henize 2-10) with the Caltech Submillimeter Observatory in the rotational
lines of carbon monoxide 12CO(J=3-2), (J=6-5) and (J=7-6) for both, and also
12CO(J=4-3) and 13CO(J=3-2) for Henize 2-10 and in the 3P2-3P1 fine-structure
transitions of atomic carbon [CI] at 809 GHz for NGC 253. Some of these
observations have been made previously, but the present multitransition study
(including data found in the literature) is the most complete to date for the
two galaxies. From these observations, we have derived the properties of the
warm and dense molecular gas in the galaxy nuclei. We used an LTE analysis and
an LVG radiative transfer model to determine physical conditions of the
interstellar medium in both sources and predicted integrated line properties of
all CO transitions up to 12CO(15-14). A PDR model has also been used and here
the data are well fitted (within 20 %) by a model cloud with a gas density of
n(H)= 8.0 +- 1.0 * 10E5 cm-3 and an incident FUV flux of chi = 20000 for Henize
2-10. For NGC 253, we deduced n(H) = 3.0 +- 0.5 * 10E5 cm-3 and chi = 20000 for
the modelled cloud. The physical properties of warm gas and CO cooling curves
of the target galaxies are compared with those measured for the nucleus of the
Milky Way and the Cloverleaf QSO. The gas properties and CO cooling curve are
similar for the two starburst galaxies and the Cloverleaf QSO while the Milky
Way nucleus exhibits lower excitation molecular gas.


title: CO, 13CO and [CI] in Galaxy Centers

abstract:
  Measurements of [CI], (J=2-1) 13CO and (J=4-3) 12CO emission from quiescent,
starburst and active galaxy centers reveal a distinct pattern characterized by
relatively strong [CI] emission. The [CI] to 13CO emission ratio increases with
central [CI] luminosity. It is lowest in quiescent and mild starburst centers
and highest for strong starburst centers and active nuclei. Neutral C
abundances are close to, or even exceed, CO abundances. The emission is
characteristic of warm and dense gas rather than either hot tenuous or cold
very dense gas. The relative intensities of CO, [CI], [CII] and far-infrared
emission suggest that the dominant excitation mechanism in galaxy centers may
be different from that in Photon-Dominated Regions (PDRs).


title:
Scale sensitive deconvolution of interferometric images I. Adaptive
  Scale Pixel (Asp) decomposition

abstract:
  Deconvolution of the telescope Point Spread Function (PSF) is necessary for
even moderate dynamic range imaging with interferometric telescopes. The
process of deconvolution can be treated as a search for a model image such that
the residual image is consistent with the noise model. For any search
algorithm, a parameterized function representing the model such that it
fundamentally separates signal from noise will give optimal results. In this
paper, the first in a series of forthcoming papers, we argue that in general,
spatial correlation length (a measure of the scale of emission) is a stronger
separator of the signal from the noise, compared to the strength of the signal
alone. Consequently scale sensitive deconvolution algorithms result into more
noise-like residuals. We present a scale-sensitive deconvolution algorithm for
radio interferometric images, which models the image as a collection of
Adaptive Scale Pixels (Asp). Some attempts at optimizing the runtime
performance are also presented.


title:
The young pulsar PSR B0540-69.3 and its synchrotron nebula in the
  optical and X-rays

abstract:
  The young PSR B0540-69 (B0540) in the LMC is the only pulsar (except the Crab
pulsar) for which a near-UV spectrum has been obtained. However, the absolute
flux and spectral index of previously published HST/FOS data are significantly
higher than suggested by broadband groundbased UBVRI photometry. Using our
ESO/VLT/FORS1 spectral observations and HST/WFPC2 archival images we show that
the old HST and new VLT spectral data are >50% contaminated by the Pulsar Wind
Nebula (PWN) and that this is the reason for the above mentioned difference. We
find that the broadband HST spectrum for the range 3300-8000 A is clearly non-
thermal and has a negative spectral index of 1.07(+0.20/-0.19). This is dif-
ferent from the almost flat spectrum of the Crab pulsar. The PWN of B0540 shows
a clear asymmetry of the surface brightness distribution along the major axis
of the PWN torus-like structure with respect to the pulsar position, also seen
in Chandra X-ray images. This can be linked to the asymmetry of the surrounding
SN ejecta. We find no significant spectral index variation over the PWN. Using
HST archival images we estimate the proper motion of B0540 to be 4.9+/-2.3
mas/yr, i.e. a transverse velocity of 1190+/-560 km/s along the southern jet of
the PWN. This can make PSR B0540 the third pulsar with a proper motion aligned
with the jet axis of its PWN, which poses constraints on pulsar kick models. We
discuss the interstellar absorption toward B0540 including the contributions
from the Milky Way, LMC and the supernova ejecta, and compare unabsorbed multi-
wavelength spectra of B0540 and the Crab pulsar, and their PWNs. Compared with
the Crab, B0540 and its PWN show a significant depression in the optical range.


title:
An Idealized Pulsar Magnetosphere: the Relativistic Force-Free
  Approximation

abstract:
  The non-dissipative relativistic force-free condition should be a good
approximation to describe the electromagnetic field in much of the pulsar
magnetosphere, but we may plausibly expect it to break down in singular
domains. Self-consistent magnetospheric solutions are found with field lines
closing both at and within the light-cylinder. In general, the detailed
properties of the solutions may be affected critically by the physics
determining the appropriate choice of equatorial boundary condition beyond the
light-cylinder.


title:
The radio source population at high frequency: follow-up of the 15-GHz
  9C survey

abstract:
  We have carried out extensive radio and optical follow-up of 176 sources from
the 15 GHz 9th Cambridge survey. Optical identifications have been found for
155 of the radio sources; optical images are given with radio maps overlaid.
The continuum radio spectrum of each source spanning the frequency range 1.4 -
43 GHz is also given. Two flux-limited samples are defined, one containing 124
sources complete to 25 mJy and one of 70 sources complete to 60 mJy. Between
one fifth and one quarter of sources from these flux-limited samples display
convex radio spectra, rising between 1.4 and 4.8 GHz. These rising-spectrum
sources make up a much larger fraction of the radio source population at this
high selection frequency than in lower frequency surveys. We find that by using
non-simultaneous survey flux density measurements at 1.4 and 15 GHz to remove
steep spectrum objects, the efficiency of selecting objects with spectra rising
between 1.4 and 4.8 GHz (as seen in simultaneous measurements) can be raised to
49 percent without compromising the completeness of the rising spectrum sample.


title: Feedback Heating with Slow Jets in Cooling Flow Clusters

abstract:
  We propose a scenario in which a large fraction, or even most, of the gas
cooling to low temperatures of T<10^4 K in cooling flow clusters, directly
gains energy from the central black hole. Most of the cool gas is accelerated
to non-relativistic high velocities, v ~ 10^3-10^4 km/sec, after flowing
through, or close to, an accretion disk around the central black hole. A poorly
collimated wind (or double not-well collimated opposite jets) is formed.
According to the proposed scenario, this gas inflates some of the X-ray
deficient bubbles, such that the average gas temperature inside these bubbles
(cavities) in cooling flow clusters is kT_b ~< 100 keV. A large fraction of
these bubbles will be very faint, or not detectable, in the radio. The bright
rims of these weak smaller bubbles will appear as ripples. We suggest that the
X-ray ripples observed in the Perseus cluster, for example, are not sound
waves, but rather the rims of radio-faint weak bubbles which are only slightly
hotter than their environment. This scenario is incorporated into the moderate
cooling flow model; although not a necessary ingredient in that model, it
brings it to better agreement with observations. In the moderate cooling flow
model a cooling flow does exist, but the mass cooling rate is ~<10% of that in
old versions of cooling flow models.


title:
Observations and 3D photoionisation modelling of the Wolf-Rayet
  planetary nebula NGC 1501

abstract:
  Deep optical spectra of the high excitation planetary nebula NGC 1501 and its
W04 central star are presented. A recombination line abundance analysis of the
central star's emission-line spectrum yields He:C:O mass fractions of
0.36:0.48:0.16, similar to those of PG1159 stars. A detailed empirical analysis
of the nebular collisionally excited line (CEL) and optical recombination line
(ORL) spectrum is presented, together with fully three-dimensional
photoionisation modelling of the nebula. We found very large ORL-CEL abundance
discrepancy factors (ADFs) for O^2+ (32) and Ne^2+ (33). The mean value of
5100K for the T_e derived from HeI recombination lines ratios is 6000K lower
than the value of 11100K implied by the [OIII] line ratio.
  A three-dimensional photoionisation model of NGC 1501 was constructed using
the photoionisation code MOCASSIN, based on our new spectroscopic data and
using the three-dimensional electron density distribution determined from
long-slit echellograms of the nebula by Ragazzoni et al. (2001). The initial
models showed higher degrees of ionisation of heavy elements than indicated by
observations. We investigated the importance of the missing low-temperature
dielectronic recombination rates for third-row elements and have estimated
upper limits to their rate coefficients.
  Our model heavily under-predicts the optical recombination line emission. We
conclude that the presence of a hydrogen-deficient, metal-rich component is
necessary to explain the observed ORL spectrum of this object. The existence of
such knots could also provide a softening of the radiation field, via the
removal of ionising photons by absorption in the knots, thereby helping to
alleviate the over-ionisation of the heavy elements in our models.


title: On the sizes of stellar X-ray coronae

abstract:
  Spatial information from stellar X-ray coronae can be inferred by use of
scaling laws from the solar corona. This requires measurement of the physical
parameters temperature and density. We concentrate on the newly available
density measurements from line fluxes of X-ray lines measured for a large
sample of 64 grating spectra of 42 stellar coronae obtained with Chandra and
XMM-Newton. Line counts of strong H-like and He-like ions and FeXXI lines were
measured with the CORA line fitting tool by Ness and Wichmann 2002. Densities
are estimated from He-like f/i flux ratios of OVII and NeIX representing only
cooler (1-6MK) plasma components. The densities scatter between log n_e =
9.5-11 from the OVII triplet and between log n_e = 10.5-12 from the NeIX
triplet, but we caution that the latter triplet may be biased by contamination
from FeXIX and FeXXI lines. We find that low-activity stars tend to show
densities of no more than a few times 10^10cm^-3, whereas no definitive trend
is found for the more active stars. Investigating the densities of the hotter
plasma with various FeXXI line ratios, we found no consistent proof for the
presence of very high densities. This result is in line with constant pressure
in the emitting active regions. We focus on the commonly used RTV78 scaling law
to derive loop lengths from temperatures and densities assuming loop-like
structures as identical building blocks. We derive emitting volumes from direct
measurements of ion-specific emission measures and densities. Available volumes
are calculated from the loop-lengths and stellar radii. The ratios of these
volumes depict volume filling factors, which we find similar up to 0.1 for all
stages of activity for OVII and increasing for NeIX.


title: The Saas Fee Lectures on Strong Gravitational Lensing

abstract: A review of strong gravitational lensing and its astrophysical uses.


title: GRB 970228 Within the EMBH Model

abstract:
  We consider the gamma-ray burst of 1997 February 28 (GRB 970228) within the
ElectroMagnetic Black Hole (EMBH) model. We first determine the value of the
two free parameters that characterize energetically the GRB phenomenon in the
EMBH model, that is to say the dyadosphere energy, $E_{dya}=5.1\times10^{52}$
ergs, and the baryonic remnant mass $M_{B}$ in units of $E_{dya}$,
$B=M_{B}c^{2}/E_{dya}=3.0\times10^{-3}$. Having in this way estimated the
energy emitted during the beam-target phase, we evaluate the role of the
InterStellar Medium (ISM) number density (n$_{ISM}$) and of the ratio ${\cal
R}$ between the effective emitting area and the total surface area of the GRB
source, in reproducing the observed profiles of the GRB 970228 prompt emission
and X-ray (2-10 keV energy band) afterglow. The importance of the ISM
distribution three-dimensional treatment around the central black hole is also
stressed in this analysis.


title: Active Galaxies and Radiative Heating

abstract:
  There is abundant evidence that heating processes in the central regions of
elliptical galaxies has both prevented large-scale cooling flows and assisted
in the expulsion of metal rich gas. We now know that each such spheroidal
system harbors in its core a massive black hole weighing approximately 0.13% of
the mass in stars and also know that energy was emitted by each of these black
holes with an efficiency exceeding 10% of its rest mass. Since, if only 0.5% of
that radiant energy were intercepted by the ambient gas, its thermal state
would be drastically altered, it is worth examining in detail the interaction
between the out-flowing radiation and the equilibrium or inflowing gas. On the
basis of detailed hydrodynamic computations we find that relaxation
oscillations are to be expected with the radiative feedback quite capable of
regulating both the growth of the central black hole and also the density and
thermal state of the gas in the galaxy. Mechanical input of energy by jets may
assist or dominate over these radiative effects. We propose specific
observational tests to identify systems which have experienced strong bursts of
radiative heating from their central black holes.


title:
Probing the gravitational redshift effect from the relativistic jets of
  compact AGN

abstract:
  I explore a possibility to measure the gravitational redshift (GR) effect in
the gravitational field of massive central nuclei residing in active galaxies
(AGN). The activity of central nuclei is associated with the bipolar jet
ejection of relativistic plasma which produces strong radio emission. I
consider the behavior of the flux density variations of the jet plasma as a
result of GR effect from a Schwarzschild black hole, and I discuss
possibilities to detect the GR effect from the relativistic jets of compact AGN
with present and future radio facilities.


title:
Planetary Nebulae as Tracers of the Intergalactic Stellar Background: a
  Population Synthesis Theoretical Approach

abstract:
  We wish to assess the relationship between the population of planetary
nebulae (PNe) and a given parent stellar population from a theoretical point of
view. Our results rely on original population synthesis models used to estimate
the expected luminosity-specific PN density accounting for different
evolutionary scenarios and star formation histories, as observed in galaxies in
the near Universe. For a complete PN sample, we find that 1 PN/1.5E06 L(sun) a
safe (IMF-independent) lower limit to the traced global bolometric luminosity
of the parent stellar population. A tentative application to Virgo cluster data
allows us to place a lower limit at ~7% for the global B luminosity of the
cluster provided by "loose" intergalactic stars.


title:
The Number Density of 0.6 < z < 1.7 MgII Systems from CORALS:
  Observational Biases at Intermediate Redshift

abstract:
  The goal of the Complete Optical and Radio Absorption Line System (CORALS)
survey is to quantify the potential impact on QSO absorber statistics from dust
in intervening galaxies. Dust may introduce a selection bias in surveys which
are based on magnitude limited QSO samples, leading to an underestimate of
absorber number density, n(z). Here we present the results of the second phase
of the CORALS survey which extends our previous work on z > 1.8 damped Lyman
alpha systems (DLAs) to search for strong metal line systems (candidate DLAs)
in the range 0.6 < z < 1.7. We have identified 47 MgII systems with rest frame
equivalent widths EW(MgII lambda 2796) > 0.3 A in our sample of 75
radio-selected quasars. Our principal and most robust result is that the n(z)
of low redshift MgII systems determined for the CORALS survey is in excellent
agreement with that of optically-selected, magnitude limited QSO samples. The
statistically inferred number density of DLAs, n(z)=0.16^+0.08_-0.06, is
consistent with other low redshift samples, although the large 1 sigma error
bars permit up to a factor of 2.5 more DLAs in CORALS. However, confirmation of
the DLA candidates, precise evaluation of their n(z) and measurement of their
HI column densities awaits UV observations with the Hubble Space Telescope.
Finally, we report an excess of intermediate redshift MgII systems observed
towards bright QSOs which could be due to a lensing amplification bias.
However, there is also evidence that this excess could simply be due to more
sensitive EW detection limits towards brighter QSOs. We also emphasize that
absorber statistics determined from magnitude limited surveys reach a steady
value if the completeness limit is significantly fainter than the fiducial
value of the quasar luminosity function. (Abridged).


title: Black holes, cuspy atmospheres, and galaxy formation

abstract:
  In cuspy atmospheres, jets driven by supermassive black holes (BHs) offset
radiative cooling. The jets fire episodically, but often enough that the cuspy
atmosphere does not move very far towards a cooling catastrophe in the
intervals of jet inactivity. The ability of energy released on the sub-parsec
scale of the BH to balance cooling on scales of several tens of kiloparsecs
arises through a combination of the temperature sensitivity of the accretion
rate and the way in which the radius of jet disruption varies with ambient
density. Accretion of hot gas does not significantly increase BH masses, which
are determined by periods of rapid BH growth and star formation when cold gas
is briefly abundant at the galactic centre. Hot gas does not accumulate in
shallow potential wells. As the Universe ages, deeper wells form, and
eventually hot gas accumulates. This gas soon prevents the formation of further
stars, since jets powered by the BH prevent it from cooling, and it mops up
most cold infalling gas before many stars can form. Thus BHs set the upper
limit to the masses of galaxies. The formation of low-mass galaxies is
inhibited by a combination of photo-heating and supernova-driven galactic
winds. Working in tandem these mechanisms can probably explain the profound
difference between the galaxy luminosity function and the mass function of dark
halos expected in the cold dark matter cosmology.


title: The Revival of the Unified Dark Energy-Dark Matter Model ?

abstract:
  We consider the generalized Chaplygin gas (GCG) proposal for unification of
dark energy and dark matter and show that it admits an unique decomposition
into dark energy and dark matter components once phantom-like dark energy is
excluded. Within this framework, we study structure formation and show that
difficulties associated to unphysical oscillations or blow-up in the matter
power spectrum can be circumvented. Furthermore, we show that the dominance of
dark energy is related to the time when energy density fluctuations start
deviating from the linear $\delta \sim a$ behaviour.


title:
Theoretical modelling of the diffuse emission of gamma-rays from extreme
  regions of star formation: The case of Arp 220

abstract:
  Our current understanding of ultraluminous infrared galaxies suggest that
they are recent galaxy mergers in which much of the gas in the former spiral
disks, particularly that located at distances less than 5 kpc from each of the
pre-merger nuclei, has fallen into a common center, triggering a huge starburst
phenomenon. This large nuclear concentration of molecular gas has been detected
by many groups, and estimates of molecular mass and density have been made. Not
surprisingly, these estimates were found to be orders of magnitude larger than
the corresponding values found in our Galaxy. In this paper, a self-consistent
model of the high energy emission of the super-starburst galaxy Arp 220 is
presented. The model also provides an estimate of the radio emission from each
of the components of the central region of the galaxy (western and eastern
extreme starbursts, and molecular disk). The predicted radio spectrum is found
as a result of the synchrotron and free-free emission, and absorption, of the
primary and secondary steady population of electrons and positrons. The latter
is output of charged pion decay and knock-on leptonic production, subject to a
full set of losses in the interstellar medium. The resulting radio spectrum is
in agreement with sub-arcsec radio observations, what allows to estimate the
magnetic field. In addition, the FIR emission is modeled with dust emissivity,
and the computed FIR photon density is used as a target for inverse Compton
process as well as to give account of losses in the $\gamma$-ray scape.
Bremsstrahlung emission and neutral pion decay are also computed, and the
$\gamma$-ray spectrum is finally predicted. Future possible observations with
GLAST, and the ground based Cherenkov telescopes are discussed.


title:
The X-ray emission from Young Stellar Objects in the rho Ophiuchi cloud
  core as seen by XMM-Newton

abstract:
  We observed the main core F of the rho Ophiuchi cloud, an active star-forming
region located at ~140 pc, using XMM-Newton with an exposure of 33 ks. We
detect 87 X-ray sources within the 30' diameter field-of-view of the it EPIC
imaging detector array. We cross-correlate the positions of XMM-Newton X-ray
sources with previous X-ray and infrared (IR) catalogs: 25 previously unknown
X-ray sources are found from our observation; 43 X-ray sources are detected by
both XMM-Newton and Chandra; 68 XMM-Newton X-ray sources have 2MASS near-IR
counterparts. We show that XMM-Newton and Chandra have comparable sensitivity
for point source detection when the exposure time is set to ~30 ks for both. We
detect X-ray emission from 7 Class I sources, 26 Class II sources, and 17 Class
III sources. The X-ray detection rate of Class I sources is very high (64 %),
which is consistent with previous Chandra observations in this area. We propose
that 15 X-ray sources are new class III candidates, which doubles the number of
known Class III sources, and helps to complete the census of YSOs in this area.
We also detect X-ray emission from two young bona fide brown dwarfs, GY310 and
GY141, out of three known in the field of view. GY141 appears brighter by
nearly two orders of magnitude than in the Chandra observation. We extract
X-ray light curves and spectra from these YSOs, and find some of them showed
weak X-ray flares. We observed an X-ray flare from the bona fide brown dwarf
GY310. We find as in the previous Chandra observation of this region that Class
I sources tend to have higher temperatures and heavier X-ray absorptions than
Class II and III sources.


title:
Keck Adaptive Optics Imaging of 0.5<z<1 Field Galaxies from the Hubble
  Space Telescope Archive

abstract:
  We have employed natural guide star adaptive optics (AO) on the Keck II
telescope to obtain near-infrared (H and K') images of three field galaxies,
each of redshift greater than 0.5. These are among the highest-redshift
non-active disk galaxies to be imaged with AO. Each of the galaxies was chosen
because it had been observed previously with the Hubble Space Telescope (HST)
Wide Field Planetary Camera 2 (WFPC2) by others. Our AO images in the near
infrared (NIR) closely match both the depth and high spatial resolution of
those optical data. Combining the archival V and I data with our new H and K'
images potentially produces a long wavelength baseline at uniform resolution.
The NIR data probe emission well longward of the 4000-Angstrom break at these
redshifts, and provide stellar fluxes less contaminated by dust. We fit
two-dimensional galaxy bulge-plus-disk models simultaneously in all bands, and
compare stellar-population-synthesis modeling to the photometry of these
separated components. This is an initial foray into combining HST and AO
imaging to produce a high spatial-resolution multi-color dataset for a large
sample of faint galaxies. Our pilot program shows that NIR AO images from large
ground-based observatories, augmented by HST images in the optical, can in
principle provide a powerful tool for the analysis of faint field galaxies.
However, the AO data S/N will have to be increased, and AO PSFs need to be
controlled more carefully than they were here.


title: Searching for Intergalactic Shocks with the SKA

abstract:
  Strong intergalactic shocks are a natural consequence of structure formation
in the universe. These shocks are expected to deposit large fractions of their
energy in relativistic electrons (xi_e~0.05 of the thermal energy according to
supernova remnant observations) and magnetic fields (xi_B~0.01 according to
cluster halo observations). We discuss the expected synchrotron emission from
such shocks, and the observational consequences for next generation radio
telescopes such as the Square Kilometer Array. We present an analytical model,
calibrated and verified based on a hydrodynamical LCDM simulation. The
resulting signal composes a large fraction (up to a few 10%) of the
extragalactic radio background below 500 MHz. The associated angular
fluctuations, e.g. delta T_l>260(xi_e*xi_B/5*10^-4)(nu/100 MHz)^-3 K for
multipoles 400<l<2000, dominate the radio sky for frequencies<10 GHz and
angular scales 1 arcmin-1 deg (after a modest removal of point sources),
provided that xi_e*xi_B>3*10^-4. The fluctuating signal is most pronounced for
nu<500 MHz, dominating the sky there even for xi_e*xi_B=5*10^-5. We find that
the signal is easily observable by next generation telescopes such as the SKA,
and marginally observable with present telescopes. The signal may be identified
using cross-correlations with tracers of large-scale structure (e.g. gamma-ray
emission from intergalactic shocks). Detection of the signal will provide the
first identification of intergalactic shocks and of the warm-hot intergalactic
medium (believed to contain most of the baryons in the low redshift universe),
and gauge the unknown intergalactic magnetic field.


title: Fitting the HiRes Spectra and Monocular Composition

abstract:
  This paper consists of two sections. In the first section, we discuss our
fits to the latest HiRes monocular spectra. We find that the best fit for the
extragalactic component has a spectral index of $\gamma=-2.38\pm0.04$ with a
distribution of sources varying with a evolution parameter $m=2.8\pm0.3$. In
the second section, we discuss preliminary results from a new composition
measurement using HiRes monocular data. We find a predominantly light spectrum
above $10^{17.6}$ eV.


title: Scalar field "mini--MACHOs": a new explanation for galactic dark matter

abstract:
  We examine the possibility that galactic halos are collisionless ensembles of
scalar field ``massive compact halo objects'' (MACHOs). Using mass constraints
from MACHO microlensing and from theoretical arguments on halos made up of
massive black holes, as well as demanding also that scalar MACHO ensambles of
all scales do not exhibit gravothermal instability (as required by consistency
with observations of LSB galaxies), we obtain the range: $m\alt 10^{-7}
M_\odot$ or $30 M_\odot\alt m\alt 100 M_\odot$. The rather narrow mass range of
large MACHOs seems to indicate that the ensambles we are suggesting should be
probably made up of scalar MACHOs in the low mass range (``mini--MACHOs''). The
proposed model allows one to consider a non--baryonic and non--thermal
fundamental nature of dark matter, while at the same time keeping the same
phenomenology of the CDM paradigm.


title: Discovery of new 19.9-GHz methanol masers in star forming regions

abstract:
  We have used the NASA Tidbinbilla 70-m antenna to search for emission from
the 2(1)-3(0)E 19.9-GHz transition of methanol. The search was targeted towards
22 star formation regions which exhibit maser emission in the 107.0-GHz
3(1)-4(0)A+ methanol transition, as well as in the 6.6-GHz 5(1)-6(0)A+
transition characteristic of class II methanol maser sources. A total of 7
sources were detected in the 19.9-GHz transition, 6 of these being new
detections. Many of the new detections are weak (< 0.5 Jy), however, they
appear to be weak masers rather than thermal or quasi-thermal emission. We find
a strong correlation between sources which exhibit 19.9-GHz methanol masers and
those which both have the class II methanol masers projected against radio
continuum emission and have associated 6035-MHz OH masers. This suggests that
the 19.9-GHz methanol masers arise in very specific physical conditions,
probably associated with a particular evolutionary phase. In the model of
(Cragg, Sobolev & Godfrey 2002) these observations are consistent with gas
temperatures of 50 K, dust temperatures of 150-200 K and gas densities of
10^6.5-10^7.5 cm^-3.


title: Control of Star Formation in Galaxies by Gravitational Instability

abstract:
  We study gravitational instability and consequent star formation in a wide
range of isolated disk galaxies, using three-dimensional, smoothed particle
hydrodynamics simulations at resolution sufficient to fully resolve
gravitational collapse. Stellar feedback is represented by an isothermal
equation of state. Absorbing sink particles are inserted in dynamically bound,
converging regions with number density $n > 10^3$ cm$^{-3}$ to directly measure
the mass of gravitationally collapsing gas available for star formation. Our
models quantitatively reproduce not only the observed Schmidt law, but also the
observed star formation threshold in disk galaxies. Our results suggest that
the dominant physical mechanism determining the star formation rate is just the
strength of gravitational instability, with feedback primarily functioning to
maintain a roughly constant effective sound speed.


title: Formation of Globular Clusters in Galaxy Mergers

abstract:
  We present a high-resolution simulation of globular cluster formation in a
galaxy merger. For the first time in such a simulation, individual star
clusters are directly identified and followed on their orbits. We
quantitatively compare star formation in the merger to that in the unperturbed
galaxies. The merging galaxies show a strong starburst, in sharp contrast to
their isolated progenitors. Most star clusters form in the tidal features. With
a mass range of $5\times10^{5}$--$5\times 10^{6} M_{\odot}$, they are
identified as globular clusters. The merger remnant is an elliptical galaxy.
Clusters with different mass or age have different radial distributions in the
galaxy. Our results show that the high specific frequency and bimodal
distribution of metallicity observed in elliptical galaxies are natural
products of gas-rich mergers, supporting a merger origin for the ellipticals
and their globular cluster systems.


title: Initial Ionization of Compressible Turbulence

abstract:
  We study the effects of the initial conditions of turbulent molecular clouds
on the ionization structure in newly formed H_{ii} regions, using
three-dimensional, photon-conserving radiative transfer in a pre-computed
density field from three-dimensional compressible turbulence. Our results show
that the initial density structure of the gas cloud can play an important role
in the resulting structure of the H_{ii} region. The propagation of the
ionization fronts, the shape of the resulting H_{ii} region, and the total mass
ionized depend on the properties of the turbulent density field. Cuts through
the ionized regions generally show ``butterfly'' shapes rather than spherical
ones, while emission measure maps are more spherical if the turbulence is
driven on scales small compared to the size of the H_{ii} region. The
ionization structure can be described by an effective clumping factor $\zeta=<
n > \cdot < n^2>/< n>^2$, where $n$ is number density of the gas. The larger
the value of $\zeta$, the less mass is ionized, and the more irregular the
H_{ii} region shapes. Because we do not follow dynamics, our results apply only
to the early stage of ionization when the speed of the ionization fronts
remains much larger than the sound speed of the ionized gas, or Alfv\'en speed
in magnetized clouds if it is larger, so that the dynamical effects can be
negligible.


title: Doppler effect of gamma-ray bursts in the fireball framework

abstract:
  The influence of the Doppler effect in the fireball framework on the spectrum
of gamma-ray bursts is investigated. The study shows that the shape of the
expected spectrum of an expanding fireball remains almost the same as that of
the corresponding rest frame spectrum for constant radiations of the
bremsstrahlung, Comptonized, and synchrotron mechanisms as well as for that of
the GRB model. The peak flux spectrum and the peak frequency are obviously
correlated. When the value of the Lorentz factor becomes 10 times larger, the
flux of fireballs would be several orders of magnitude larger. The expansion
speed of fireballs is a fundamental factor of the enhancement of the flux of
gamma-ray bursts.


title: Mass and Spin of GRS 1915+105 Based on a Resonance Model of QPOs

abstract:
  We demonstrate that the four high-frequency QPOs observed in GRS 1915+105 can
be interpreted as the oscillation modes on disks which non-linearly and
resonantly interact with a warp. The warp is assumed to be a low-frequency
global pattern on the disk. This identification suggests that the relevant
mass, $M$, and spin, $a$, of GRS 1915+105 are, $M=13\sim 14 M_\odot$ and
$a=0\sim 0.15$


title: Intra-Day Variation of Sagittarius A* at Short Millimeter Wavelengths

abstract:
  We have performed the monitoring observations of flux density of Sagittarius
A* at short millimeter wavelengths (100 and 140 GHz bands) on seven years in
the period from 1996 to 2003 using the Nobeyama Millimeter Array (NMA). We
found intra-day variation of Sgr A* in March 2000 flare. The flux density at
the peak of the flares increases 100-200 % at 100 GHz and 200-400 % at 140 GHz
($?Delta S/S$), respectively. The two-fold increase timescale of the flare is
estimated to be about 1.5 hours at 140 GHz. The intra-day variation at
mm-wavelengths has similar increase timescale as those in the X-ray and
infrared flares but has smaller amplitude. This short timescale variability
suggests that the physical size of the emitting region is smaller than 12 AU
$?approx$ 150 Rs). The decay timescale of the flare was at most 24 hours. Such
a light curve with rapid increase and slow decay is similar to that often
observed in outburst phenomena with ejections.


title:
New colour-transformations for the Sloan photometry and revised
  metallicity calibration and equations for photometric parallax estimation

abstract:
  We evaluated new colour-transformations for the Sloan photometry by 224
standards and used them to revise both the equations for photometric parallax
estimation and metallicity calibration cited by Karaali et al. (2003). This
process improves the metallicity and absolute magnitude estimations by
[Fe/H]<=0.3 dex and M^{H}_{g} <= 0.1 mag respectively. There is a high
correlation for metallicities and absolute magnitudes derived for two systems,
UBV and Sloan, by means of the revised calibrations.


title: Gas stripping by radiation drag from an interstellar cloud

abstract:
  We perform two-dimensional hydrodynamic simulation on the gas stripping by
radiation drag from an interstellar cloud moving in uniform radiation fields.
To properly include relativistic radiation drag, the radiation hydrodynamic
equation is solved with taking into account the dilution of radiation fields by
optical depth of the cloud. As a result, it is found that the optically-thin
surface layers are effectively stripped by radiation drag from an
optically-thick gas cloud, and simultaneously stripped gas loses momentum. The
momentum loss time-scale is found to be on the order of $10^{8}$ years under
intensive radiation fields which are expected in the early phase of galaxy
evolution. The present results show that the radiation drag is an effective
mechanism to extract angular momentum from interstellar medium and allows it to
accrete onto the galactic center. The mass accretion driven by radiation drag
may lead to the formation of a central supermassive black hole.


title:
A CFH12k lensing survey of X-ray luminous galaxy clusters - I: Weak
  lensing methodology

abstract:
  We present the weak lensing methodology applied to our multi-colour imaging
survey of X-ray luminous galaxy clusters conducted with the wide field CFH12k
camera. This method, which is converting a fully reduced CFH12k image into
cluster mass constraints, is done in two steps that we explain in detail: (1)
determination of the "true" shape of faint (lensed) galaxies which involves:
object detection strategy, point spread function (PSF) determination, galaxy
shapes measurements with errors; (2) conversion of the faint galaxies catalogue
into useful mass constraints which is done by different lensing techniques
using 1D and/or 2D mass estimates. Finally, we compare the cluster mass model
to the light distribution of cluster members as observed on our imaging data.
To illustrate the method, we apply it to the well studied cluster Abell 1689
(z=0.184). In this cluster, we detect the gravitational shear signal to the
edge of the image at 3 sigma significance. The two-dimensional mass
reconstruction has a ~10 sigma significance mass peak centered on the brightest
cluster galaxy. The weak lensing constraints are well fitted by a NFW mass
profile with $M_{200} = 14.1^{+6.3}_{-4.7}\times 10^{14} M_\sun$, and $c =
3.5^{+0.5}_{-0.3}$ (chi^2=0.33), or by a power law (PL) profile with q=0.75 +-
0.07 and theta_E = 14.6"+-0.3" (chi^2=0.64). The mass-to-light ratio is found
to be almost constant with radius with a mean value of M/L_R = 150 h
(M/L)_\sun. We compare these results to other weak lensing analyses of Abell
1689 presented in the literature and find good agreements in terms of the shear
measurement as well as the final mass estimate.


title:
RR Lyrae variables in Galactic globular clusters: IV. Synthetic HB and
  RR Lyrae predictions

abstract:
  We present theoretical predictions concerning horizontal branch stars in
globular clusters, including RR Lyrae variables, as derived from synthetic
procedures collating evolutionary and pulsational constraints. On this basis,
we explore the predicted behavior of the pulsators as a function of the
horizontal branch morphology and over the metallicity range Z=0.0001 to 0.006,
revealing an encouraging concordance with the observed distribution of
fundamentalised periods with metallicity. Theoretical relations connecting
periods to K magnitudes and BV or VI Wesenheit functions are presented, both
appearing quite independent of the horizontal branch morphology only with Z
greater or equal than 0.001. Predictions concerning the parameter R are also
discussed and compared under various assumptions about the horizontal branch
reference luminosity level.


title: XMM-Newton (cross)-calibration

abstract:
  ESA's large X-ray space observatory XMM-Newton is in its fifth year of
operations. We give a general overview of the status of calibration of the five
X-ray instruments and the Optical Monitor. A main point of interest in the last
year became the cross-calibration between the instruments. A cross-calibration
campaign started at the XMM-Newton Science Operation Centre at the European
Space Astronomy Centre in collaboration with the Instrument Principle
Investigators provides a first systematic comparison of the X-ray instruments
EPIC and RGS for various kind of sources making also an initial assessment in
cross calibration with other X-ray observatories.


title: A Be star with a low nitrogen abundance in the SMC cluster NGC330

abstract:
  High-resolution UVES/VLT spectra of B12, an extreme pole-on Be star in the
SMC cluster NGC330, have been analysed using non-LTE model atmospheres to
obtain its chemical composition relative to the SMC standard star AV304. We
find a general underabundance of metals which can be understood in terms of an
extra contribution to the stellar continuum due to emission from a disk which
we estimate to be at the ~25% level. When this is corrected for, the nitrogen
abundance for B12 shows no evidence of enhancement by rotational mixing as has
been found in other non-Be B-type stars in NGC330, and is inconsistent with
evolutionary models which include the effects of rotational mixing. A second Be
star, NGC330-B17, is also shown to have no detectable nitrogen lines. Possible
explanations for the lack of rotational mixing in these rapidly rotating stars
are discussed, one promising solution being the possibility that magnetic
fields might inhibit rotational mixing.


title:
Cosmological constraints on the dark energy equation of state and its
  evolution

abstract:
  We have calculated constraints on the evolution of the equation of state of
the dark energy, w(z), from a joint analysis of data from the cosmic microwave
background, large scale structure and type-Ia supernovae. In order to probe the
time-evolution of w we propose a new, simple parametrization of w, which has
the advantage of being transparent and simple to extend to more parameters as
better data becomes available. Furthermore it is well behaved in all asymptotic
limits. Based on this parametrization we find that w(z=0)=-1.43^{+0.16}_{-0.38}
and dw/dz(z=0) = 1.0^{+1.0}_{-0.8}. For a constant w we find that -1.34 < w <
-0.79 at 95% C.L. Thus, allowing for a time-varying w shifts the best fit
present day value of w down. However, even though models with time variation in
w yield a lower chi^2 than pure LambdaCDM models, they do not have a better
goodness-of-fit. Rank correlation tests on SNI-a data also do not show any need
for a time-varying w.


title: Subgiants as probes of galactic chemical evolution

abstract:
  Chemical abundances for 23 candidate subgiant stars have been derived with
the aim at exploring their usefulness for studies of galactic chemical
evolution. High-resolution spectra from ESO CAT-CES and NOT-SOFIN covered 16
different spectral regions in the visible part of the spectrum. Some 200
different atomic and molecular spectral lines have been used for abundance
analysis of about 30 elemental species. The wings of strong, pressure-broadened
metal lines were used for determination of stellar surface gravities, which
have been compared with gravities derived from Hipparcos parallaxes and
isochronic masses. Stellar space velocities have been derived from Hipparcos
and Simbad data, and ages and masses were derived with recent isochrones. Only
12 of the stars turned out to be subgiants, i.e. on the "horizontal" part of
the evolutionary track between the dwarf- and the giant stages. The abundances
derived for the subgiants correspond closely to those of dwarf stars.
  With the possible exceptions of lithium and carbon we find that subgiant
stars show no "chemical" traces of post-main-sequence evolution and that they
are therefore very useful targets for studies of galactic chemical evolution.


title:
ISOCAM Observations of Intermediate-redshift Galaxy Clusters at 7 and 15
  microns

abstract:
  The gravitationally lensing clusters A370, A2218, A1689 and CL0024+1654 were
observed with the Infrared Space Observatory (ISO) using ISOCAM at 6.7 and 14.3
microns (hereafter 7 and 15 microns respectively). A total of 178 sources were
detected in the whole set, 70 of them being cluster objects. The spectral
energy distribution of a subset of sources was calculated using GRASIL. The
results for the total infrared luminosity and the estimation of the star
formation rate are presented for the non stellar objects for which the SED has
been determined. The majority of the cluster galaxies in A2218 are best fit by
models of quiescent ellipticals. In Cl0024+1654, most of the galaxies lying on
the Butcher-Oemler region of the colour-magnitude diagram are best fit by disk
galaxies, while those on the main sequence area have in general SEDs
corresponding to post-starburst galaxies. The population of each cluster is
compared with the field population, as well as with the population of other
clusters. A significant number of Luminous IR Galaxies (LIRGs) is detected in
CL0024+1654, while only one LIRG has been observed in total in A370, A1689, and
A2218. This result supports the link between LIRGs in clusters and recent or
ongoing cluster merger activity as well as the need for extending the
observations to the outer parts of clusters.


title:
A study of the low-frequency quasi-periodic oscillations in the X-ray
  light curves of the black hole candidate XTE J1859+226

abstract:
  We present the results of an extensive timing analysis of the 1999 outburst
of the soft X-ray transient and black hole candidate XTE J1859+226 as observed
with the Rossi X-Ray Timing Explorer. Three main different types of low
frequency (1-9 Hz) quasi-periodic oscillations (QPOs) were observed and
classified, strenghtening the general picture that is emerging for the
variability properties of black hole X-ray binaires. Rapid transitions between
different power spectral shapes were observed and their link with the count
rate was studied. Furthermore, we show that a frequency of ~6 Hz seems to hold
a particular place: one of the three QPO types we found was very stable when at
this frequency, as it happens in Z sources as well. The coherence of its
subharmonic peak was higher when the fundamental was close to 6 Hz, thus
suggesting the presence of some resonance at this frequency.


title: Late time behavior of cosmological perturbations in a single brane model

abstract:
  We present solutions for the late time evolution of cosmological tensor and
scalar perturbations in a single-Randall-Sundrum brane world model. Assuming
that the bulk is anti-de Sitter spacetime, the solutions for cosmological
perturbations are derived by summing mode functions in Poincar\'e coordinate.
The junction conditions imposed at the moving brane are solved numerically. The
recovery of 4-dimensional Einstein gravity at late times is shown by solving
the 5-dimensional perturbations throughout the infinite bulk. We also comment
on several possibilities for having deviations from 4-dimensional Einstein
gravity.


title: The INTEGRAL View of the Galactic Nucleus

abstract:
  We present the preliminary results of the observational campaign performed in
2003 to study the Galactic Nucleus with INTEGRAL. The mosaicked images obtained
with the IBIS/ISGRI coded aperture instrument in the energy range above 20 keV,
give a yet unseen view of the high-energy sources of this region in hard X and
gamma-rays, with an angular resolution of 12'. We report on the discovery of a
source, IGR J17456-2901, compatible with the instrument's point spread function
and coincident with the Galactic Nucleus Sgr A* to within 0.9'. The source is
visible up to 60-80 keV with a 20-100 keV luminosity at 8 kpc of 3 x 10E35
erg/s. Although we cannot unequivocally associate the new INTEGRAL source to
the Galactic Nucleus, this is the first report of significant hard X-ray
emission from within the inner 10' of the Galaxy and a contribution from the
galactic center supermassive black hole itself cannot be excluded. Here we
discuss the results obtained and the perspectives for future observations of
the Galactic Nucleus with INTEGRAL and other observatories


title:
The Double Pulsar System J0737-3039: Modulation of the radio emission
  from B by radiation from A

abstract:
  We have analyzed single pulses from PSR J0737-3039B, the 2.8-s pulsar in the
recently discovered double pulsar system, using data taken with the Green Bank
Telescope at 820 and 1400 MHz. We report the detection of features similar to
drifting subpulses, detectable over only a fraction of the pulse window, with a
fluctuation frequency of 0.196 cycles/period. This is exactly the beat
frequency between the periods of the two pulsars. In addition, the drifting
features have a separation within a given pulse of 23 ms, equal to the pulse
period of A. These features are therefore due to the direct influence of PSR
J0737-3039A's 44-Hz electromagnetic radiation on PSR J0737-3039B's
magnetosphere. We only detect them over a small range of orbital phases, when
the radiation from the recycled pulsar PSR J0737-3039A meets our line of sight
to PSR J0737-3039B from the side.


title: An Ab Initio Approach to the Solar Coronal Heating Problem

abstract:
  We present an ab initio approach to the solar coronal heating problem by
modelling a small part of the solar corona in a computational box using a 3D
MHD code including realistic physics. The observed solar granular velocity
pattern and its amplitude and vorticity power spectra, as reproduced by a
weighted Voronoi tessellation method, are used as a boundary condition that
generates a Poynting flux in the presence of a magnetic field. The initial
magnetic field is a potential extrapolation of a SOHO/MDI high resolution
magnetogram, and a standard stratified atmosphere is used as a thermal initial
condition. Except for the chromospheric temperature structure, which is kept
fixed, the initial conditions are quickly forgotten because the included
Spitzer conductivity and radiative cooling function have typical timescales
much shorter than the time span of the simulation. After a short initial start
up period, the magnetic field is able to dissipate 3-4 10^6 ergs cm^{-2} s^{-1}
in a highly intermittent corona, maintaining an average temperature of $\sim
10^6$ K, at coronal density values for which emulated images of the Transition
Region And Coronal Explorer(TRACE) 171 and 195 pass bands reproduce observed
photon count rates.


title: An Ab Initio approach to Solar Coronal Loops

abstract:
  Data from recent numerical simulations of the solar corona and transition
region are analysed and the magnetic field connection between the low corona
and the photosphere is found to be close to that of a potential field. The
fieldline to fieldline displacements follow a power law distribution with
typical displacements of just a few Mm. Three loops visible in emulated
Transition Region And Coronal Explorer (TRACE) filters are analysed in detail
and found to have significantly different heating rates and distributions
thereof, one of them showing a small scale heating event. The dynamical
structure is complicated even though all the loops are visible in a single
filter along most of their lengths. None of the loops are static, but are in
the process of evolving into loops with very different characteristics.
Differential Emission Measure (DEM) curves along one of the loops illustrate
that DEM curves have to be treated carefully if physical characteristics are to
be extracted.


title:
Recycled pulsars with black hole companions: the high mass analogues of
  PSR B2303+46

abstract:
  We investigate the possibility that mass transfer early in the evolution of a
massive binary can effect a reversal of the end states of the two components,
resulting in a neutron star which forms before a black hole. In this sense,
such systems would comprise the high-mass analogues of white dwarf-neutron star
systems such as PSR B2303+46. One consequence of this reversal is that a second
episode of mass transfer from the black hole progenitor star can recycle the
nascent neutron star, extending the life of the pulsar.
  An estimate of the formation rate through this channel is first performed via
a simple analytical approach, and then refined using the results of the SeBa
binary evolution package. The central role of kicks in determining the survival
rate of these binaries is clearly demonstrated. The final result is expressed
in terms of the number of field pulsars one can expect for every single neutron
star-black hole (ns,bh) binary. We also calculate this figure for black
hole-neutron star (bh,ns) systems formed through the usual channel. Assuming
kicks drawn from the distribution of Cordes & Chernoff (1998), we find an
expectation value of one (ns,bh) binary per 4 x 10^4 pulsars, and one (bh,ns)
system for every 1500 pulsars. This helps to explain why neither system has
been seen to date, though it suggests that detection of a (bh,ns) binary is
imminent.


title: The Polarization of Drifting Subpulses

abstract:
  Using new techniques based on the polarimetric fluctuation spectrum, the
fluctuation behaviour of the polarization of individual pulses is examined in
three pulsars that show drifting subpulses, allowing various aspects of the
fluctuations to be quantified for the first time. Of the three pulsars studied,
only PSR B0809+74 shows behaviour completely consistent with the superposition
of orthogonal polarization modes (OPMs), and this only at 328 MHz and in
superposition with an apparently randomly polarized component. The observed
periodic pattern is decomposed into the sum of two orthogonally polarized,
out-of-phase drift patterns, one of which shows a dramatic jump in subpulse
phase near the leading edge of the pulse window. For PSR B0320+39 and PSR
B0818$-$13, considerable periodic fluctuations away from OPM orientations are
seen, a condition that also occurs in the trailing half of the pulse in PSR
B0809+74 at 1380 MHz. In some cases the deviation is so strong that the
periodic locus of the polarization vector in the Poincar\'{e} sphere is almost
circular, in contrast to the strictly colinear states of superposed OPMs.
Several possibilities are discussed for the physical origin of these patterns.
The similarity between the subpulse patterns in one of the OPMs of PSR B0809+74
at 328 MHz to that of the total intensity signal at 1380 MHz supports a picture
of superposed, out of phase drift patterns. To explain the full range of
behaviour seen in the three pulsars, it must be possible to produce at least
three arbitrarily polarized superposed patterns. While the data do not suggest
a particular approach for the empirical decomposition of patterns into
non-orthogonally polarized components, the specific, quantitative nature of the
results should provide strong constraints for theoretically driven modelling.


title:
Methane Abundance Variations toward the Massive Protostar NGC 7538 :
  IRS9

abstract:
  Absorption and emission lines originating from the nu3 C-H stretching
manifold of gas phase CH4 were discovered in the high resolution (R=25,000)
infrared L band spectrum along the line of sight toward NGC 7538 : IRS9. These
observations provide a diagnostic of the complex dynamics and chemistry in a
massive star forming region. The line shapes resemble P Cygni profiles with the
absorption and emission components shifted by ~7 km/s with respect to the
systemic velocity. Similar velocity components were observed in CO at 4.7 um,
but in contrast to CH4, the CO shows deep absorption due to a high velocity
outflow as well as absorption at the systemic velocity due to the cold outer
envelope. It is concluded that the gas phase CH4 abundance varies by an order
of magnitude in this line of sight: it is low in the envelope and the outflow
(X[CH4]<0.4e-6), and at least a factor of 10 larger in the central core. The
discovery of solid CH4 in independent ground and space based data sets shows
that methane is nearly entirely frozen onto grains in the envelope. It thus
appears that CH4 is formed by grain surface reactions, evaporates into the gas
phase in the warm inner regions of protostellar cores and is efficiently
destroyed in shocks related to outflows.


title:
The N-point correlation functions of the first-year Wilkinson Microwave
  Anisotropy Probe sky maps

abstract:
  We compute the two-, three- and four-point correlation functions from the
Wilkinson Microwave Anisotropy Probe (WMAP) first-year data, and compare these
to a Monte Carlo ensemble of 5000 realizations, based on the best-fit WMAP
running-index spectrum of Gaussian fluctuations. The analysis is carried out in
three steps, covering small (< 72'), intermediate (< 5 degrees) and large
scales (up to 180 degrees). On the largest scales our results are consistent
with the previously reported hemisphere power asymmetries: the northern
ecliptic hemisphere is practically devoid of large scale fluctuations, while
the southern hemisphere show relatively strong fluctuations. We also detect
excess correlations in W-band difference maps as compared to the detailed noise
simulations produced by the WMAP team, possibly indicative of unknown
systematics. While unlikely to affect any temperature based results, this
effect could potentially be important for the upcoming polarization data. On
intermediate angular scales we find hints of a similar anisotropic distribution
of power as seen on the very largest scales, but not to the same extent. In
general the model is accepted on these scales. Finally, the same is also true
on the smallest scales probed in this paper.


title:
Global Test of a Quasi-Universal Gamma-Ray Burst Jet Model Through
  Monte-Carlo Simulations

abstract:
  The possibility that long gamma-ray burst (GRB) jets are structured receives
growing attention recently, and we have suggested that most GRBs and their
softer, less energetic fraternity, X-ray flashes (XRFs), can be understood
within a quasi-universal structured jet picture, given that the jet structure
for each individual burst is a Gaussian or similar function. Here we perform a
global test on such a quasi-universal Gaussian-like structured jet by comparing
Monte-Carlo simulation results with a broad spectrum of observational data.
Using the same set of input parameters as in the previous work (Zhang et al.
2004), we confront the model with more observational constraints. These
constraints include the burst redshift distribution, jet break angle
distribution, two-dimensional redshift vs. jet break angle distribution,
luminosity function, and Log N - Log P distribution. The results indicate that
the model is generally compatible with the data. This conclusion, together with
our previous tests with the observed jet break angle vs. isotropic energy and
observed peak energy vs. fluence relations, suggests that current long GRB and
XRF data are generally consistent with such a quasi-standard-energy and
quasi-standard-angle jet picture. With future homogeneous burst samples (such
as the one to be retrieved from the Swift mission), the refined GRB jet
structure can be further constrained through a global comparison between
various observed and predicted burst property distributions and relations.