title:
Separation of correlated astrophysical sources using multiple-lag data
  covariance matrices

abstract:
  This paper deals with a source separation strategy based on second-order
statistics, namely, on data covariance matrices estimated at several lags. In
general, ``blind'' approaches to source separation do not assume any knowledge
on the mixing operator; however, any prior information about the possible
structure of the mixing operator can improve the solution. Unlike ICA blind
separation approaches, where mutual independence between the sources is
assumed, our method only needs to constrain second-order statistics, and is
effective even if the original sources are significantly correlated. Besides
the mixing matrix, our strategy is also capable to evaluate the source
covariance functions at several lags. Moreover, once the mixing parameters have
been identified, a simple deconvolution can be used to estimate the probability
density functions of the source processes. To benchmark our algorithm, we used
a database that simulates the one expected from the instruments that will
operate onboard ESA's Planck Surveyor Satellite to measure the CMB anisotropies
all over the celestial sphere. The assumption was made that the emission
spectra of the galactic foregrounds can be parametrised, thus reducing the
number of unknowns for system identification to the number of the foreground
radiations. We performed separation in several sky patches, featuring different
levels of galactic contamination to the CMB, and assuming several noise levels,
including the ones derived from the Planck specifications.


title: Light pollution at the Roque de los Muchachos Observatory

abstract:
  Sky spectra were obtained from archival science frames taken with DoLoRes at
the 3.58m Telescopio Nazionale Galileo with a wavelength range ~3800 - 8000Ang
and resolution of 2.8Ang/pix and 3.6Ang/pix. Our spectra include all the
important Sodium and Mercury light pollution lines and span a wide interval of
azimuth and observing conditions, essential to disentangle environmental and
seasonal effects. New sodium and mercury lines were also detected for the first
time at the observatory. Light pollution from NaD_{5892-8} emitted by the LPS
lamps increased by a factor of 1.5 - 2 with respect to the average values of
1998. At the same time, light pollution from Hg lines decreased by ~40% and
reaches the 1998 levels only when observing toward the towns. The contribution
of NaD_{5892-8} from LPS lamps to sky background is 0.05-0.10mag at V-band and
0.07-0.12mag at R-band. Synthetic sky brightness measures calculated from our
spectra at V, B and R bands are in good agreement with those of Benn &
Ellison(1998) if we take into account that our observations were done during
2003, seven years after the last sunspot minimum. The effects of the
application of the Canary Sky Law are directly visible in the spectra as a 50%
dimming of the Hg light-polluting lines in the spectra taken after local
midnight.


title:
Ellipticals at z=0 from Self-Consistent Hydrodynamical Simulations:
  Clues on Age Effects in their Stellar Populations

abstract:
  We present results of a study of the stellar age distributions in the sample
of elliptical-like objects (ELOs) identified at z=0 in four simulations
operating in the context of a concordance cosmological model. The simulations
show that the formation of most stars in each ELO of the sample is a
consequence of violent dynamical events, either fast multiclump collapse at
high z, or mergers at lower z. This second way can explain the age spread as
well as the dynamical peculiarities observed in some ellipticals, but its
relative weight is never dominant and decreases as the ELO mass at the halo
scale, $M_{vir}$, increases, to such an extent that some recent mergers
contributing an important fraction to the total ELO mass can possibly
contribute only a small fraction of new born stars. More massive objects have
older means and narrower spreads in their stellar age distributions than less
massive ones. The ELO sample shows also a tight correlation between $M_{vir}$
and the central stellar l.o.s. velocity dispersion, $\sigma_{los}$. This gives
a trend of the means and spreads of ELO stellar populations with $\sigma_{los}$
that is consistent, even quantitatively, with the age effects observationally
detected in the stellar populations of elliptical galaxies. Therefore, these
effects can be explained as the observational manifestation of the intrinsic
correlations found in the ELO sample between $M_{vir}$ and the properties of
the stellar age distribution, on the one hand, and $M_{vir}$ and
$\sigma_{los}$, on the other hand. These correlations hint, for the first time,
at a possible way to reconcile age effects in ellipticals, and, particularly,
the increase of $\alpha / <Fe>$ ratios with $\sigma_{los}$, with the
hierarchical clustering paradigm.


title:
Dark matter distribution function from non-extensive statistical
  mechanics

abstract:
  We present an analytical and numerical study of the velocity distribution
function of self gravitating collisionless particles, which include dark matter
and star clusters. We show that the velocity distribution derived through the
Eddington's formula is identical to the analytical one derived directly from
the generalized entropy of non-extensive statistical mechanics. This implies
that self gravitating collisionless structures are to be described by
non-extensive thermo-statistics. We identify a connection between the density
slope of dark matter structures, \gamma, from \rho ~ r^{-\gamma}, and the
entropic index, q, from the generalized entropy, S_q. Our numerical result
confirms the analytical findings of earlier studies and clarifies which is the
correct connection between the density slope and the entropic index. We use
this result to conclude that from a fundamental statistical mechanics point of
view the central density slope of self gravitating collisionless dark matter
structures is not constrained, and even cored dark matter structures are
allowed with \gamma = 0. We find that the outer density slope is bounded by
\gamma= 10/3.


title: Branching ratio of Type Ib/c supernovae into GRB-supernovae

abstract:
  We study centered and decentered nucleation of black holes in core-collapse
of massive stars in binaries. By Bekenstein's gravitational-radiation recoil
mechanism, a newly nucleated black hole typically leaves the central core
prematurely. With low probability, the black hole remains centered and matures
to a high-mass black hole which spins rapidly if the binary is compact.
GRB030329/SN2003dh demonstrates that Type Ib/c supernovae are the parent
population of long GRBs, whose branching ratio is ${\cal R}=(2-4)\times
10^{-3}$. We identify ${\cal R}$ with the low probability of centered
nucleation in compact binaries. Decentered events are predicted to produce a
single short burst in gravitational radiation. Centered events are predicted to
produce a second, long-burst in gravitational radiation powered by a luminous
black hole. These signatures are of interest to LIGO, VIRGO and TAMA.


title: On the class of Oe stars

abstract:
  We present high-quality spectra of the majority of stars that have been
classified as Oe and find that their published spectral types are generally too
early, most likely due to infilling of HeI lines. As a matter of fact, all
stars classified as Oe actually fall inside the range O9-B0 with the important
exception of HD155806 (O7.5III) and perhaps HD39680 (difficult to classify, but
likely O8.5V). Observations of a sample of objects with published spectral
types in the O9-B0 range previously classified as peculiar or emission-line
stars fail to reveal any new Oe star with spectral type earlier than O9.5. Most
objects classified as peculiar in ``classical'' literature show signs of
binarity in our spectra, but no spectral anomalies. We conclude that there is
likely a real decline in the fraction of Be stars for spectral types earlier
than B0, not due to observational bias. The few Oe stars with spectral types
earlier than O9.5 deserve detailed investigation in order to provide
constraints on the physical reasons of the Be phenomenon.


title: Gamma-ray Polarimetry with Compton Telescope

abstract:
  Compton telescope is a promising technology to achieve very high sensitivity
in the soft gamma-ray band (0.1-10 MeV) by utilizing Compton kinematics.
Compton kinematics also enables polarization measurement which will open new
windows to study gamma-ray production mechanism in the universe. CdTe and Si
semiconductor technologies are key technologies to realize the Compton
telescope in which their high energy resolution is crucial for high angular
resolution and background rejection capability. We have assembled a prototype
module using a double-sided silicon strip detector and CdTe pixel detectors. In
this paper, we present expected polarization performance of a proposed mission
(NeXT/SGD). We also report results from polarization measurements using
polarized synchrotron light and validation of EGS4 MC simulation.


title: Origin of the Soft Excess in X-ray Pulsars

abstract:
  The spectra of many X-ray pulsars show, in addition to a power law, a
low-energy component that has often been modeled as a blackbody with kT ~ 0.1
keV. However the physical origin of this soft excess has remained a mystery. We
examine a sample of well-studied, bright X-ray pulsars, which have been
observed using ROSAT, ASCA, Ginga, RXTE, BeppoSAX, Chandra, and XMM-Newton. In
particular we consider the Magellanic Cloud pulsars SMC X-1, LMC X-4, XTE
J0111.2-7317, and RX J0059.2-7138 and the Galactic sources Her X-1, 4U 1626-67,
Cen X-3, and Vela X-1. We show that the soft excess is a very common if not
ubiquitous feature intrinsic to X-ray pulsars. We evaluate several possible
mechanisms for the soft emission, using theoretical arguments as well as
observational clues such as spectral shapes, eclipses, pulsations of the soft
component, and superorbital modulation of the source flux. We find that
reprocessing of hard X-rays from the neutron star by the inner region of the
accretion disk is the only process that can explain the soft excess in all the
pulsars with Lx > 10^38 ergs/s. Other mechanisms, such as emission from diffuse
gas in the system, are important in less luminous objects.


title: HI Observations of the Local Group Dwarf WLM

abstract:
  We present Australia Telescope Compact Array mosaic HI imaging of the Local
Group dwarf irregular galaxy WLM. We find an integrated flux of 149 Jy km/s and
a total HI mass of 3.2 x 10^7 solar masses. The major axis of the HI is aligned
with the stellar component of the galaxy. The overall HI distribution is
relatively smooth at our resolution and has a double peaked central core. One
of these peaks is aligned with a region found to have extinction that is
internal to WLM and we take this as possible evidence of a large molecular gas
complex in the southern half of the galaxy. The other HI peak is in close
proximity to the brightest HII regions. WLM's overall velocity field is
consistent with rigid body rotation. A rotation curve is derived, and we find a
total dynamical mass of 3.00 x 10^8 solar masses. We also performed a wide
field search, 38 arcminutes in radius, for HI companions or evidence of recent
interactions (e.g., tidal tails), and found no detections to an HI mass limit
of M_HI > 8.4 x 10^5 solar masses.


title:
Impact of Reionization on the Stellar Populations of Nearby Dwarf
  Galaxies

abstract:
  Cold dark matter models for galaxy formation predict that low-mass systems
will be the first sites of star formation. As these objects have shallow
gravitational potential wells, the subsequent growth of their stellar
populations may be halted by heating and gas loss due to reionization. This
effect has been suggested to have profoundly influenced properties of
present-day dwarf galaxies, including their stellar populations and even
survival as visible galaxies. In this Letter we draw on results from
quantitative studies of Local Group dwarf galaxy star formation histories,
especially for Milky Way satellites, to show that no clear signature exists for
a widespread evolutionary impact from reionization. All nearby dwarf galaxies
studied in sufficient detail contain ancient populations indistinguishable in
age from the oldest Galactic globular clusters. Ancient star formation activity
proceeded over several Gyr, and some dwarf spheroidal galaxies even experienced
fairly continuous star formation until just a few Gyr ago. Despite their
uniformly low masses, their star formation histories differ considerably. The
evolutionary histories of nearby dwarf galaxies appear to reflect influences
from a variety of local processes rather than a dominant effect from
reionization.


title:
The Crab Nebula and Pulsar between 500 GeV and 80 TeV: Observations with
  the HEGRA stereoscopic air Cherenkov telescopes

abstract:
  The Crab supernova remnant has been observed regularly with the stereoscopic
system of 5 imaging air Cherenkov telescopes that was part of the High Energy
Gamma Ray Astronomy (HEGRA) experiment. In total, close to 400 hours of useful
data have been collected from 1997 until 2002. The spectrum extends up to
energies of 80 TeV and is well matched by model calculations in the framework
of inverse Compton scattering of various seed photons in the nebula including
for the first time a recently detected compact emission region at
mm-wavelengths. The observed indications for a gradual steepening of the energy
spectrum in data is expected in the inverse Compton emission model.The average
magnetic field in the emitting volume is determined to be
$(161.6\pm0.8mathrm{stat}\pm18_\mathrm{sys}) \mu$G. The presence of protons in
the nebula is not required to explain the observed flux and upper limits on the
injected power of protons are calculated being as low as 20 % of the total spin
down luminosity for bulk Lorentz factors of the wind in the range of
$10^4-10^6$.The position and size of the emission region have been studied over
a wide range of energies. The position is shifted by 13\arcsec to the west of
the pulsar with a systematic uncertainty of 25\arcsec. No significant shift in
the position with energy is observed. The size of the emission region is
constrained to be less than 2\arcmin at energies between 1 and 10 TeV. Above 30
TeV the size is constrained to be less than 3\arcmin.No indications for pulsed
emission has been found and upper limits in differential bins of energy have
been calculated reaching typically 1-3 % of the unpulsed component.


title:
The Crab nebula: Linking MeV synchrotron and 50 TeV inverse Compton
  photons

abstract:
  Pulsar wind driven synchrotron nebulae are offering a unique view on the
connection of the pulsar wind and the surrounding medium. The Crab nebula is
particularly well suited for detailed studies of the different emission
regions. As inferred from the observed synchrotron emission extending beyond
MeV energies, the Crab is a unique and extreme accelerator. In the framework of
the synchrotron/inverse Compton emission model, the same electrons with
energies exceeding $10^{15}$ eV that are responsible for the MeV synchrotron
emission produce via inverse Compton scattering 10-50 TeV radiation which has
recently been observed with the HEGRA system of ground based gamma-ray
telescopes. Here we discuss the close relation of the two energy bands covered
by INTEGRAL and ground based gamma-ray telescopes. Despite the lack of
sufficient spatial resolution in both bands to resolve the emission region,
correlation of the flux measurements in the two energy bands would allow to
constrain the structure of the emission region. The emission region is expected
to be a very compact region (limited by the life-time of the electrons) near
the termination shock of the pulsar wind. We extend previous model calculations
for the nebula's emission to include an additional compact non-thermal emission
region recently detected at mm wavelengths.The overall good agreement of this
model with data constrains additional emission processes (ions in the wind,
inverse Compton from the unshocked wind) to be of little relevance.


title:
Variability in the stellar initial mass function at high mass:
  coalescence models for starburst clusters

abstract:
  A coalescence model using the observed properties of pre-stellar
condensations (PSCs) shows how an initially steep IMF that might be
characteristic of primordial cloud fragmentation can change into a Salpeter IMF
or shallower IMF in a cluster of normal density after one dynamical time, even
if the PSCs are collapsing on their own dynamical time. The model suggests that
top-heavy IMFs in some starburst clusters originate with PSC coalescence.


title:
Chandra Spatially Resolved Spectroscopic Study and Multi-Wavelength
  Imaging of the Supernova Remnant 3C 397 (G41.1-0.3)

abstract:
  (Abridged) We present a Chandra observation of the supernova remnant (SNR) 3C
397 (G41.1-0.3) obtained with ACIS-S. Previous studies of this SNR have shown
that it harbors a central X-ray `hot spot' suggestive of a compact object
associated with 3C 397. With the Chandra data, we can rule out the nature of
the hot spot as a pulsar or a pulsar wind nebula, and put an upper limit on the
flux of a hidden compact object of F (0.5--10 keV)~6E-13 erg/cm2/s. We found
two point sources in the Chandra field. We argue that none of them is
associated with 3C 397; and that the hard source, CXO J190741.2+070650, is a
newly discovered AGN. The Chandra image reveals arcseconds-scale clumps and
knots which are strongly correlated with the radio VLA image, except for the
X-ray hot spot. Our Chandra spatially resolved spectroscopic study shows that
one-component models are inadequate, and that at least two non-equilibrium
ionization thermal components are needed to fit the spectra of each selected
region. The derived average spectral parameters are consistent with the
previous global ASCA fits performed by Safi-Harb et al. (2000). However, the
hard component requires a high abundance of Fe indicating the presence of hot
Fe ejecta. When comparing the eastern with the western lobe, we find that the
column density, the brightness, and the ionization timescales are generally
higher for the western side. This result, combined with our study of the 3C397
environs at millimeter wavelengths, indicate a denser medium to the west of the
SNR. Our multi-wavelength imaging and spectral study favors the scenario where
3C 397 is a ~5,300-year old SNR expanding in a medium with a marked density
gradient, and which is likely to be encountering a molecular cloud on the
western side. We propose that 3C 397 will evolve into a mixed-morphology SNR.


title: On the vorticity of the Universe

abstract:
  Recent analyses of the first-year WMAP data claim large-scale asymmetry and
anisotropy of the CMBR fluctuations. We argue that the covariant and gauge
invariant treatment of density fluctuations formulated by Ellis and Bruni can
explain the asymmetric and anisotropic WMAP data by including the vorticity of
the Universe. It appears that the spatial gradients of the density contrast are
proportional to the vorticity of the Universe, thus allowing measurements and
quantifications of the magnitude and axis of the possible cosmological
rotation.


title:
A possible feature of thermal matter in relativistic jets of radio-loud
  quasars

abstract:
  It has been suggested that relativistic jets in quasars may contain a
considerable amount of thermal matter. In this paper, we explore the
possibility that the K-alpha line from the thermal matter may appear at tens of
keV due to a high Doppler blue-shift. In the jet comoving frame, the energy
density of photons originally emitted by the accretion disk and reflected off
the broad line region clouds dominates over that of photons of other origin. We
discuss the photoionization states of the thermal matter and find that the
irons elements are neutral. The high metallicity in quasars enhances the
possibility to detect the thermal matter in the relativistic jet in some
radio-loud quasars. A highly Doppler blue-shifted K-alpha line may be detected.
We make a rediction for 3C 273, in which the K-alpha line luminosity might be
of the order $3.0\times 10^{44}$ erg/s with an equivalent width of 2.4 keV.
Such a line could be detected in a future mission.


title:
The Additional Line Component within the Iron K\alpha Profile in
  MCG-6-30-15: Evidence for Blob Ejection?

abstract:
  The EPIC data of MCG -6-30-15 observed by XMM-Newton were analyzed for the
complexities of the iron K-alpha line. Here we report that the additional line
component (ALC) at 6.9 keV undoubtedly appears within the broad iron Kalpha;
line profile at the high state, whereas it disappears at the low state. These
state-dependent behaviors exclude several possible origins and suggest an
origin of the ALC in matter being ejected from the vicinity of the black hole.
At the low state, the newborn blob ejected from the accretion disk is so
Thomson-thick that hard X-rays are blocked from ionizing the old blobs, leading
to the disappearance of the ALC. When the blob becomes Thomson-thin as a result
of expansion, the hard X-ray will penetrate it and ionize the old ones,
emitting the ALC at the high state. The blob ejection is the key to switching
the ALC on or off.


title:
Slim Disks with Transition Regions and Applications to Microquasars and
  Narrow Line Seyfert 1 Galaxies

abstract:
  Slim disks have been received much attention because of the increasing
evidence for the super-critical accreting objects. In this paper, we make an
attempt to construct a unified model, in which the viscosity and the
dimensionless accretion rate can span rather wide ranges. We replace blackbody
radiation under diffusion approximation with a bridged formula, which accounts
for both blackbody radiation and thermal bremsstrahlung in optically-thick and
-thin cases, respectively. Thus this allows us to investigate the structures of
and the emergent spectra from slim disks in a wider parameter space, covering
transition regions from optically thick to optically thin. We show that there
is a maximum transition radius, roughly $R_{\rm tr, max}/R_g\sim 50$ when
$\dot{M}/\dot{M}_{\rm C}\sim 15$. The emergent spectra from the unified model
of the accretion disk have been calculated. A simple model of hot corona above
the slim disk is taken into account for the hard X-ray spectrum in this paper
based on Wang & Netzer (2003). We have applied the present model to the
microquasar GRS 1915+105, narrow line Seyfert 1 galaxies RE J1034+396 and Akn
564. Our model can explain well the broadband X-ray spectra of narrow line
Seyfert 1 galaxies, microquasars and possible ultra-luminous compact X-ray
sources. The present model can be widely applied to the candidates of
super-critical accreting objects.


title: Gamma-Ray Bursts Observed with the Spectrometer SPI Onboard INTEGRAL

abstract:
  The spectrometer SPI is one of the main detectors of ESA's INTEGRAL mission.
The instrument offers two interesting and valuable capabilities for the
detection of the prompt emission of Gamma-ray bursts. Within a field of view of
16 degrees, SPI is able to localize Gamma-ray bursts with an accuracy of 10
arcmin. The large anticoincidence shield, ACS, consisting of 512 kg of BGO
crystals, detects Gamma-ray bursts quasi omnidirectionally above ~70 keV. Burst
alerts from SPI/ACS are distributed to the interested community via the
INTEGRAL Burst Alert System. The ACS data have been implemented into the 3rd
Interplanetary Network and have proven valuable for the localization of bursts
using the triangulation method. During the first 8 months of the mission
approximately one Gamma-ray burst per month was localized within the field of
fiew of SPI and 145 Gamma-ray burst candidates were detected by the ACS from
which 40 % have been confirmed by other instruments.


title: The broad-band properties of the XMM-Newton Bright Serendipitous Sources

abstract:
  We present here "The XMM-Newton Bright Serendipitous Survey", a survey
program conducted by the XMM-Newton Survey Science Center. In particular we
discuss the main goals of this project, we present the sample(s) and the
current optical breakdown and we discuss some broad band spectral properties as
derived from an hardness ratio analysis of the single sources. Finally we
report the 4.5--7.5 keV Log(N$>$S)-LogS for type 1 and type 2 AGN.


title: Clean optical spectrum of the radio jet of 3C 120

abstract:
  We present integral field spectroscopy (IFS) of the central region of 3C 120.
We have modeled the nuclear and host galaxy 3D spectra using techniques
normally applied to imaging, decoupling both components, and obtained a
residual datacube. Using this residual datacube, we detected the extended
emission line region associated with the radio jet. We obtained, for the first
time, a clean spectrum of this region and found compelling evidences of a
jet-cloud interaction. The jet compresses and splits the gas cloud which is
ionized by the AGN and/or by the strong local UV photon field generated by a
shock process. We cannot confirm the detection of an extended emission line
region associated with the counter-jet reported by Axon (1989).


title:
Search for 44Ti gamma-ray line emission from GRO J0852-4642 with
  INTEGRAL/SPI

abstract:
  The gamma-ray source GRO J0852-4642, discovered by COMPTEL, is a possible
counterpart of the supernova remnant RX J0852-4622. Detection of radioactive
decay from 44Ti nuclei would proof it to be the youngest and nearest supernova
remnant known so far. During the first year of INTEGRAL core program, the Vela
region was observed twice in all for more than 2000 ks. Among other
nucleosynthesis studies, one of the most important scientific goals of this
observation is the detection of 44Ti gamma-ray lines expected at 68 keV, 78 keV
and 1157 keV. For this purpose the INTEGRAL Spectrometer (SPI), with its very
high energy resolution thanks to its germanium detector camera is the key
instrument, permitting a precise determination of gamma-ray line intensities
and profiles. The upper limit for the 78.4 keV 44Ti gamma-ray line emission
derived from the first analysis is 1.1 x 10^{-4} gamma/cm2s. This value is
mainly dominated by systematic uncertainties in the treatment of the
instrumental background. By accumulating more observation time in the next
years of the mission and by improving the background understanding, a reliable
44Ti flux for GRO J0852-4642 or an upper limit which constrains the COMPTEL
flux can be expected.


title: First results from the ATCA 18 GHz pilot survey

abstract:
  As a pilot study for the first all-sky radio survey at short wavelengths, we
have observed 1216 sq. deg. of the southern sky at 18GHz (16mm) using a novel
wide-band (3.4GHz bandwidth) analogue correlator on one baseline of the
Australia Telescope Compact Array (ATCA). We scanned a region of sky between
declination -71 and -59 degrees with an rms noise level of 15mJy. Follow-up
radio imaging of candidate sources above a 4 sigma detection limit of 60mJy
resulted in 221 confirmed detections, for which we have measured accurate
positions and flux densities. For extragalactic sources, the survey is roughly
70% complete at a flux density of 126mJy and 95% complete above 300mJy. Almost
half the detected sources lie within a few degrees of the Galactic plane, but
there are 123 sources with |b|>5 degrees which can be assumed to be
extragalactic. The differential source counts for extragalactic sources in the
range 0.1Jy < S_{18GHz} < 3Jy are well fitted by a relation of the form
n(S)=57(S/{Jy})^{-2.2\pm0.2} [Jy^-1 sr^-1], in good agreement with the 15GHz
counts published by Taylor et al. (2001) and Waldram et al. (2003). Over 70% of
the extragalactic sources have a flat radio spectrum (\alpha_{0.843}^{18}>
-0.5, S_{\nu}\propto\nu^{\alpha}), and 29% have inverted radio spectra
(\alpha_{0.843}^{18}> 0). The optical identification rate is high: 51% of the
extragalactic sources are identified with stellar objects (candidate QSOs), 22%
with galaxies and only 27% with faint optical objects or blank fields.


title: Old Galaxies in the Young Universe

abstract:
  More than half of all stars in the local Universe are found in massive
spheroidal galaxies, which are characterized by old stellar populations with
little or no current star formation. In present models, such galaxies appear
rather late as the culmination of a hierarchical merging process, in which
larger galaxies are assembled through mergers of smaller precursor galaxies.
But observations have not yet established how, or even when, the massive
spheroidals formed, nor if their seemingly sudden appearance when the Universe
was about half its present age (at redshift z \approx 1) results from a real
evolutionary effect (such as a peak of mergers) or from the observational
difficulty of identifying them at earlier epochs. Here we report the
spectroscopic and morphological identification of four old, fully assembled,
massive (>10^{11} solar masses) spheroidal galaxies at 1.6<z<1.9, the most
distant such objects currently known. The existence of such systems when the
Universe was only one-quarter of its present age, shows that the build-up of
massive early-type galaxies was much faster in the early Universe than has been
expected from theoretical simulations.


title: Neutrino signatures of supernova shock and reverse shock propagation

abstract:
  A few seconds after bounce in a core-collapse supernova, the shock wave
passes the density region corresponding to resonant neutrino oscillations with
the ``atmospheric'' neutrino mass difference. The transient violation of the
adiabaticity condition manifests itself in an observable modulation of the
neutrino signal from a future galactic supernova. In addition to the shock wave
propagation effects that were previously studied, a reverse shock forms when
the supersonically expanding neutrino-driven wind collides with the slower
earlier supernova ejecta. This implies that for some period the neutrinos pass
two subsequent density discontinuities, giving rise to a ``double dip'' feature
in the average neutrino energy as a function of time. We study this effect both
analytically and numerically and find that it allows one to trace the positions
of the forward and reverse shocks. We show that the energy dependent neutrino
conversion probabilities allow one to detect oscillations even if the energy
spectra of different neutrino flavors are the same as long as the fluxes
differ. These features are observable in the \bar\nu_e signal for an inverted
and in the \nu_e signal for a normal neutrino mass hierarchy, provided the
13-mixing angle is ``large'' (sin^2\theta_{13}\gg 10^{-5}).


title: Spectroscopy of PNe in Sextans A, Sextans B, NGC 3109 and Fornax

abstract:
  Planetary nebulae (PNe) and HII regions provide a probe of the chemical
enrichment and star formation history of a galaxy from intermediate ages to the
present day. We present the first results of NTT spectroscopy of HII regions
and/or PNe in four nearby dwarf galaxies: Sextans A, Sextans B, NGC 3109, and
Fornax. For all PNe and some of the HII regions in these galaxies we have
obtained elemental abundances via the classic Te-method based on the detection
of the [OIII] 4363 line. The oxygen abundances in three HII regions of Sextans
A are all consistent within the individual rms uncertainties. The oxygen
abundance in the PN of Sextans A is however significantly higher. This PN is
even more enriched in nitrogen and helium, implying its classification as a PN
of Type I. The presumably unaffected PN abundances of S and Ar are well below
those in the HII regions, indicating a lower metallicity at the epoch of the PN
progenitor formation. For two HII regions in Sextans B, the oxygen abundances
do not differ within the rms uncertainties. The third one is, however, twice as
metal-rich, providing evidence for the inhomogeneity of the current metallicity
distribution in Sextans B. For the PN in Sextans B we measured an O/H that is
consistent with that of the low-metallicity HII regions. For NGC 3109 our
preliminary results indicate that the oxygen abundances of PNe and HII regions
are all within a small range of $\pm$0.15 dex. For the PN in Fornax, Ne, Ar and
S abundances suggest that the ISM metallicity was $\sim$0.3 dex lower at the
epoch of the PN progenitor's formation, compared to the O/H value derived for
the PN (abridged).


title: Lens modelling and H_0 estimate in quadruply lensed systems

abstract:
  We present a numerical method to estimate the lensing parameters and the
Hubble constant H_0 from quadruply imaged gravitational lens systems. The lens
galaxy is modeled using both separable deflection potentials and constant
mass-to-light ratio profiles, while possible external perturbations have been
taken into account introducing an external shear. The model parameters are
recovered inverting the lens and the time delay ratio equations and imposing a
set of physically motivated selection criteria. We investigate correlations
among the model parameters and the Hubble constant. Finally, we apply the codes
to the real lensed quasars PG 1115+080 and RX J0911+0551, and combine the
results from these two systems to get H_0 = 56 +/- 23 km/(s Mpc). In addition,
we are able to fit to the single systems a general elliptical potential with a
non fixed angular part, and then we model the two lens systems with the same
potential and a shared H_0: in this last case we estimate H_0=49_(-11)^(+6)
km/(s Mpc).


title: The Solution of the Milne Problem for Magnetized Atmosphere

abstract:
  The numerical solution of the Milne problem for semi-infinite plane-parallel
magnetized electron atmosphere is obtained. It is assumed that magnetic field
is directed along the normal to the atmosphere. The angular dependence, the
polarization degree and positional angle of outgoing radiation are presented in
the tables for various values of the Faraday rotation parameter and the degree
of absorption q=0, 0.2 and 0.4. We assume that magnetic field B~1000000G when
one can neglect the effects of circular dichroism and take into account only
the Faraday rotation effect.


title: Self-Consistent Theory of Halo Mergers

abstract:
  The rate of merging of dark-matter halos is an absolutely essential
ingredient for studies of both structure and galaxy formation. Remarkably,
however, our quantitative understanding of the halo merger rate is still quite
limited, and current analytic descriptions based upon the extended
Press-Schechter formalism are fundamentally flawed. We show that a
mathematically self-consistent merger rate must be consistent with the
evolution of the halo abundance in the following sense: The merger rate must,
when inserted into the Smoluchowski coagulation equation, yield the correct
evolution of the halo abundance. We then describe a numerical technique to find
merger rates that are consistent with this evolution. We present results from a
preliminary study in which we find merger rates that reproduce the evolution of
the halo abundance according to Press-Schechter for power-law power spectra. We
discuss the limitations of the current approach and outline the questions that
must still be answered before we have a fully consistent and correct theory of
halo merger rates.


title: Measurements of Gamma-Ray Bursts (GRBs) with Glast

abstract:
  One of the scientific goals of the main instrument of GLAST is the study of
Gamma-Ray Bursts (GRBs) in the energy range from ~20 MeV to ~300 GeV. In order
to extend the energy measurement towards lower energies a secondary instrument,
the GLAST Burst Monitor (GBM), will measure GRBs from ~10 keV to ~25 MeV and
will therefore allow the investigation of the relation between the keV and the
MeV-GeV emission from GRBs over six energy decades. These unprecedented
measurements will permit the exploration of the unknown aspects of the
high-energy burst emission and the investigation of their connection with the
well-studied low-energy emission. They will also provide ne insights into the
physics of GRBs in general. In addition the excellent localization of GRBs by
the LAT will stimulate follow-up observations at other wavelengths which may
yield clues about the nature of the burst sources.


title:
A search for outstanding sources of PeV cosmic rays: Cassiopeia A, the
  Crab Nebula, the Monogem Ring--But how about M33 and the Virgo cluster?

abstract:
  We study arrival directions of 1.4x10^6 extensive air showers (EAS)
registered with the EAS--1000 Prototype Array in the energy range 0.1--10 PeV.
By applying an iterative algorithm that provides uniform distribution of the
data with respect to sidereal time and azimuthal angles, we find a number of
zones with excessive flux of cosmic rays (CRs) at >=3 sigma level. We compare
locations of the zones with positions of galactic supernova remnants (SNRs),
pulsars, open star clusters, and regions of ionized hydrogen and find
remarkable coincidences, which may witness in favour of the hypothesis that
certain objects of these types, including the SNRs Cassiopeia A, the Crab
Nebula, the Monogem Ring and some other, provide a noticeable contribution to
the flux of CRs in the PeV range of energies. In addition, we find certain
signs of a contribution from the M33 galaxy and a number of comparatively
nearby groups of active galactic nuclei and interacting galaxies, in particular
those in the Virgo cluster of galaxies. The results also provide some hints for
a search of possible sources of ultra-high energy (UHE) cosmic rays and support
an earlier idea that a part of both UHE and PeV CRs may originate from the same
astrophysical objects.


title: Near-IR observations of UCHII regions

abstract:
  We present adaptive-optics (AO) assisted J, H and K/K' images of 8 UCHII
regions taken with the ALFA and ADONIS AO systems at Calar Alto and La Silla
observatories. The images show details of the stellar population and the
near-IR morphology of UCHIIs with unprecedented resolution. We have searched
for the ionizing sources of the regions using near-IR photometry. The spectral
type of the ionizing and most luminous stars inferred from our photometry has
been compared with spectral type estimates from IRAS and published
radio-continuum measurements. We find that the photometric near-IR spectral
types are earlier than estimates from radio and IRAS data. This difference is
alleviated when stellar spherical models including line blanketing and stellar
winds instead of non-LTE plane-parallel models are used to derive the radio-
and IRAS-based spectral types. We also made an attempt to correlate the
properties of the near-IR ionizing population with MSX data and published CS
measurements. No correlation was found. We note that in two of the regions
(G309.92+0.48 and G61.48+0.09B1), the best candidate to ionize the region is
possibly a super-giant.


title: High energy emission from starburst galaxies

abstract:
  The star formation (SF) can be regarded as an engine powering the light
emission of spiral galaxies at several wavelengths. SF activity also plays a
significant role in the evolution of galaxies. In this thesis we focus on the
X-ray emission from processes related to star formation. Several kinds of
sources concur to X-ray emission, X-ray binaries and hot plasma being the most
important.
  We begin with a review of the infrared, radio and X-ray emission from star
forming galaxies. In the second chapter we explore the quantitative
relationships between the total X-ray, radio and infrared luminosities for a
sample of 23 star forming galaxies. It is found that linear correlations hold
between the luminosities in the above bands. In the third chapter we show, by
analyzing a sample of 11 high redshift galaxies in the Hubble Deep Field, that
the linear correlations may be extended up to z~1. In the fourth chapter we
turn to an analysis of the luminosity function and number counts of star
forming galaxies; we show that the number density of normal galaxies at faint
X-ray fluxes (10^-17 -- 10^-15 erg/s/cm2) is very well defined. The fifth
chapter offers a first insight into a different aspect of galaxy evolution,
i.e. whether is it possible to determine the metallicity enhancements in a
starburst episode. An interesting, yet problematic, picture of metal enrichment
of the interstellar matter arises from an analysis of the X-ray and near
infrared spectra of M82. Finally, a summary is offered of the work here
described.


title: Discovery of multiple shells around V838 Monocerotis

abstract:
  We report the discovery of multiple shells around the eruptive variable star
V838 Mon. Two dust shells are seen in IRAS and MSX images, which themselves are
situated in a shell of CO. This securely establishes V838 Mon as an evolved
object. We revisit the light echo, which arises from scattering off the
innermost resolved dust shell, to infer a distance to V838 Mon of >~5.5 kpc.
The dynamical timescales of the ejected shells, location in the Milky Way and
inferred luminosity are consistent with V838 Mon being a low-mass AGB star
experiencing thermal pulses of which the 2002 eruption might have sent the star
into the post-AGB phase. This scenario, however, is inconsistent with the
presence of a (young and massive) B3 V companion.


title:
Atmospheric Phase Correction Using Total Power Radiometry at the
  Submillimeter Array

abstract:
  Phase noise caused by an inhomogeneous, time-variable water vapor
distribution in our atmosphere reduces the angular resolution, visibility
amplitude and coherence time of millimeter and submillimeter wavelength
interferometers. We present early results from our total power radiometry phase
correction experiment carried out with the Submillimeter Array on Mauna Kea.
  From accurate measurements of the atmospheric emission along the lines of
sight of two elements of the array, we estimated the differential atmospheric
electrical path between them. In one test, presented here, the phase correction
technique reduced the rms phase noise at 230 GHz from 72$\degr$ to 27$\degr$
over a 20 minute period with a 2.5 second integration time. This corresponds to
a residual differential electrical path of 98 $\mu$m, or 15 $\mu$m of
precipitable water vapor, and raises the coherence in the 20 minute period from
0.45 to 0.9.


title:
Signatures of Galactic Superwinds: Inhomogeneous Metal Enrichment of the
  Lyman Alpha Forest

abstract:
  We investigate possible signatures of feedback from galactic superwinds on
the metallicity of the Lyman alpha forest, using a set of high resolution
hydrodynamic simulations of a Lambda cold dark matter model. Simulations
produce metals self-consistently, based on one single parameter, the metal
yield, which in turn is constrained by metallicity in the intra-cluster gas. We
follow metals as a separate density species. For the metallicity of Lyman alpha
clouds with column density of N_{HI}~10^{14.5}-10^{15.5}/cm^2 at z=2-4 we find
reasonable agreement between simulations, both with and without GSW, and
observations (Schaye et al). A unique signature and sensitive test of GSW is,
however, provided by lower density regions with gas density of \rho/<\rho> =
0.01-1.0 and a corresponding column density of 10^{12}-10^{14}/cm^2. Without
GSW we predict that both the mean and median metallicity of \lya clouds in this
column density range at z=2-4 should have Z<10^{3}Zsun, since these small
systems support little star formation. GSW contaminate these regions, however,
and also there is a significant fraction (~25%) of Lyman alpha clouds in this
column density range which have a high metallicity excess of 10^{-2}Zsun,
resulting in a mean metallicity of ~10^{-2}Zsun. In addition, we find that
there is a minimum in the median metallicity for clouds of
N_{HI}~10^{13}-10^{14}/cm^2 in the case with GSW, whereas without GSW the
metallicity decreases monotonically and rapidly with decreasing column density.
Finally, we predict that the ratio of secondary (e.g., N) to primary metals
(e.g., O,C) is expected to be smaller by a factor of 10 in clouds of
N_{HI}~10^{14.5}/cm^2 compared to that in large galaxies; this factor increases
to >50 for N_{HI}< 10^{13.5}/cm^2.


title: The GLAST Burst Monitor

abstract:
  The next large NASA mission in the field of gamma-ray astronomy, GLAST, is
scheduled for launch in 2007. Aside from the main instrument LAT (Large-Area
Telescope), a gamma-ray telescope for the energy range between 20 MeV and > 100
GeV, a secondary instrument, the GLAST burst monitor (GBM), is foreseen. With
this monitor one of the key scientific objectives of the mission, the
determination of the high-energy behaviour of gamma-ray bursts and transients
can be ensured. Its task is to increase the detection rate of gamma-ray bursts
for the LAT and to extend the energy range to lower energies (from ~10 keV to
\~30 MeV). It will provide real-time burst locations over a wide FoV with
sufficient accuracy to allow repointing the GLAST spacecraft. Time-resolved
spectra of many bursts recorded with LAT and the burst monitor will allow the
investigation of the relation between the keV and the MeV-GeV emission from
GRBs over unprecedented seven decades of energy. This will help to advance our
understanding of the mechanisms by which gamma-rays are generated in gamma-ray
bursts.


title: SN Ib 1990I: Clumping and Dust in the Ejecta?

abstract:
  Photometry and spectra of the type Ib SN 1990I are presented and analysed,
covering about 400 days of evolution. The presence of optical helium lines is
shown. SN 1990I seems to show higher velocities compared to a sample of type Ib
events. The nebular emission lines display a high degree of asymmetry and the
presence of fine structures. Using the [O I] 6300,64A flux, we estimate a lower
limit on the oxygen mass to fall in the range (0.7-1.35) M_solar. The oxygen
mass requires a filling factor as small as 10^{-2} on day 254, indicating a
highly clumpy distribution of the oxygen material. A blueshift of the order 600
km/s is reported in the [O I] 6300,64A after day 254. The [Ca II] 7307.5A
emission profile appears blueshifted as well at late epochs . We recover the
quasi-bolometric "BVRI" light curve of SN 1990I. The constructed bolometric
light curve shows a change of slope at late phases, with an e-folding time of
60 +/-2 d in the [50:200] d time interval, considerably faster than the one of
{56}Co decay (i.e. 111.3 d), suggesting the gamma-rays escape with lower
deposition, owing to the low mass nature of the ejecta. After day 200, an
$e$-folding time ~47 +/-2.8 d is measured. A simplified gamma-ray deposition
model is applied after adding a contribution of about 35% to the computed
pseudo-bolometric light curves to account for near-IR luminosities to estimate
the ejecta and {56}Ni masses (M({56}Ni)=0.11 M_solar and M_{ej}=3.7 M_solar).
The deficit in luminosity is estimated to be about 50% around day 308. The
observed spectral blueshift combined with the dramatic and sudden drop in the
pseudo-bolometric light curve and (B-V) colour is interpreted to be a
consequence of dust condensation in the ejecta of SN 1990I around day 250.


title: The First HET Planet: A Companion to HD 37605

abstract:
  We report the first detection of a planetary-mass companion to a star using
the High Resolution Spectrograph (HRS) of the Hobby-Eberly Telescope (HET). The
HET-HRS now gives routine radial velocity precision of 2-3 m/s for high SNR
observations of quiescent stars. The planetary-mass companion to the metal-rich
K0V star HD37605 has an orbital period of 54.23 days, an orbital eccentricity
of 0.737, and a minimum mass of 2.84 Jupiter masses. The queue-scheduled
operation of the Hobby-Eberly Telescope enabled us to discovery of this
relatively short-period planet with a total observation time span of just two
orbital periods. The ability of queue-scheduled large-aperture telescopes to
respond quickly to interesting and important results demonstrates the power of
this new approach in searching for extra-solar planets as well as in other ares
of research requiring rapid response time critical observations.


title: The GRB980425-SN1998bw Association in the EMBH Model

abstract:
  Our GRB theory, previously developed using GRB 991216 as a prototype, is here
applied to GRB 980425. We fit the luminosity observed in the 40--700 keV, 2--26
keV and 2--10 keV bands by the BeppoSAX satellite. In addition the supernova
SN1998bw is the outcome of an ``induced gravitational collapse'' triggered by
GRB 980425, in agreement with the GRB-Supernova Time Sequence (GSTS) paradigm
(\citet{lett3}). A further outcome of this astrophysically exceptional sequence
of events is the formation of a young neutron star generated by the SN1998bw
event (\citet{cospar02}). A coordinated observational activity is recommended
to further enlighten the underlying scenario of this most unique astrophysical
system.


title:
CLOVER - A new instrument for measuring the B-mode polarization of the
  CMB

abstract:
  We describe the design and expected performance of Clover, a new instrument
designed to measure the B-mode polarization of the cosmic microwave background.
The proposed instrument will comprise three independent telescopes operating at
90, 150 and 220 GHz and is planned to be sited at Dome C, Antarctica. Each
telescope will feed a focal plane array of 128 background-limited detectors and
will measure polarized signals over angular multipoles 20 < l < 1000. The
unique design of the telescope and careful control of systematics should enable
the B-mode signature of gravitational waves to be measured to a
lensing-confusion-limited tensor-to-scalar ratio r~0.005.


title:
Relativistic Binary Pulsar B1913+16: Thirty Years of Observations and
  Analysis

abstract:
  We describe results derived from thirty years of observations of PSR
B1913+16. Together with the Keplerian orbital parameters, measurements of the
relativistic periastron advance and a combination of gravitational redshift and
time dilation yield the stellar masses with high accuracy. The measured rate of
change of orbital period agrees with that expected from the emission of
gravitational radiation, according to general relativity, to within about 0.2
percent. Systematic effects depending on the pulsar distance and on poorly
known galactic constants now dominate the error budget, so tighter bounds will
be difficult to obtain. Geodetic precession of the pulsar spin axis leads to
secular changes in pulse shape as the pulsar-observer geometry changes. This
effect makes it possible to model the two-dimensional structure of the beam. We
find that the beam is elongated in the latitude direction and appears to be
pinched in longitude near its center.


title: Reanalysis of the spectrum of the z=10 galaxy

abstract:
  In a recent paper Pello et al. reported observations of a faint galaxy,
gravitationally lensed by the galaxy cluster Abell 1835. Deep J-band
spectroscopy revealed a weak emission line near 1.34 microns, detected in two
spectra with different central wavelengths. The line was interpreted as
Lyman-alpha at redshift z=10.0. This interpretation is supported by the
broad-band photometric spectral energy distribution, and by the location of the
galaxy close to the lens critical line for this redshift. We have reanalysed
the two spectra, just released from the data archive. Our analysis includes
allowance for wavelength shifts due to transverse drift of the object in the
slit. We do not detect a significant emission line at the reported location, or
nearby, at either grating setting, nor in the combined spectrum. We provide a
possible explanation for the reported detection as due to spurious positive
flux introduced in the sky-subtraction stage as a result of variable hot
pixels. We provide our final reduced 2D frame, and corresponding error array.


title:
In-flight performance and calibration of the Infrared Array Camera
  (IRAC) for the Spitzer Space Telescope

abstract:
  The Infrared Array Camera (IRAC) is one of three focal plane instruments on
board the Spitzer Space Telescope. IRAC is a four-channel camera that obtains
simultaneous broad-band images at 3.6, 4.5, 5.8, and 8.0 microns in two nearly
adjacent fields of view. We summarize here the in-flight scientific, technical,
and operational performance of IRAC.


title:
Bar Parameters From Halpha Observations: Tremaine-Weinberg method with
  Halpha velocity fields

abstract:
  The very first results of the application of the Tremaine-Weinberg (hereafter
TW) method on Halpha velocity fields are presented to find pattern speeds of
galaxies. The technique is used for a sample of four barred galaxies(NGC4321,
NGC3359, NGC6946 and NGC2903) and M51. For two of these, our results are very
similar to those obtained using the same technique but based on CO
observations. For the three other galaxies, a comparison is provided between
this observational method and numerical ones.


title: Detection of Formaldehyde Towards the Extreme Carbon Star IRC+10216

abstract:
  We report the detection of H2CO (formaldehyde) around the carbon-rich AGB
star, IRC+10216. We find a fractional abundance with respect to molecular
hydrogen of x(H2CO)= (1.3 {+1.5}{-0.8}) x 10^{-8}. This corresponds to a
formaldehyde abundance with respect to water vapor of x(H2CO)/x(H2O)=(1.1 +/-
0.2) x 10^{-2}, in line with the formaldehyde abundances found in Solar System
comets, and indicates that the putative extrasolar cometary system around
IRC+10216 may have a similar chemical composition to Solar System comets.
However, we also failed to detect CH3OH (methanol) around IRC+10216 and our
upper limit of x(CH3OH)/x(H2O) < 7.7 x 10^{-4}, (3 sigma), indicates that
methanol is substantially underabundant in IRC+10216, compared to Solar System
comets. We also conclude, based on offset observations, that formaldehyde has
an extended source in the envelope of IRC+10216 and may be produced by the
photodissociation of a parent molecule, similar to the production mechanism for
formaldehyde in Solar System comet comae. Preliminary mapping observations also
indicate a possible asymmetry in the spatial distribution of formaldehyde
around IRC+10216, but higher signal-to-noise observations are required to
confirm this finding. This study is based on observations carried out with the
IRAM 30m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and
IGN (Spain). (abridged)


title:
Complex molecules in the hot core of the low mass protostar
  NGC1333-IRAS4A

abstract:
  We report the detection of complex molecules (HCOOCH_3, HCOOH and CH_3CN),
signposts of a "hot core" like region, toward the low mass, Class 0 source
NGC1333-IRAS4A. This is the second low mass protostar where such complex
molecules have been searched for and reported, the other source being
IRAS16293-2422. It is therefore likely that compact (few tens of AUs) regions
of dense and warm gas, where the chemistry is dominated by the evaporation of
grain mantles, and where complex molecules are found, are common in low mass
Class 0 sources.Given that the chemical formation timescale is much shorter
than the gas hot core crossing time, it is not clear whether the reported
complex molecules are formed on the grain surfaces (first generation molecules)
or in the warm gas by reactions involving the evaporated mantle constituents
(second generation molecules). We do not find evidence for large differences in
the molecular abundances, normalized to the formaldehyde abundance, between the
two solar type protostars, suggesting perhaps a common origin.


title: Strange Quark Matter and Compact Stars

abstract:
  Astrophysicists distinguish between three different types of compact stars.
These are white dwarfs, neutron stars, and black holes. The former contain
matter in one of the densest forms found in the Universe which, together with
the unprecedented progress in observational astronomy, make such stars superb
astrophysical laboratories for a broad range of most striking physical
phenomena. These range from nuclear processes on the stellar surface to
processes in electron degenerate matter at subnuclear densities to boson
condensates and the existence of new states of baryonic matter--like color
superconducting quark matter--at supernuclear densities. More than that,
according to the strange matter hypothesis strange quark matter could be more
stable than nuclear matter, in which case neutron stars should be largely
composed of pure quark matter possibly enveloped in thin nuclear crusts.
Another remarkable implication of the hypothesis is the possible existence of a
new class of white dwarfs. This article aims at giving an overview of all these
striking physical possibilities, with an emphasis on the astrophysical
phenomenology of strange quark matter. Possible observational signatures
associated with the theoretically proposed states of matter inside compact
stars are discussed as well. They will provide most valuable information about
the phase diagram of superdense nuclear matter at high baryon number density
but low temperature, which is not accessible to relativistic heavy ion
collision experiments.


title:
Assessing the galaxy population out to z ~ 2 using the Hubble Deep Field
  South

abstract:
  In this work we use the Hubble Deep Field South (HDF-S) version 2 images to
assess the galaxy population out to z ~ 2. We have used two methods of
templates fitting of the spectral energy distributions to obtain photometric
redshifts and classify the objects. The Bayesian photometric redshifts gave
better results when compared with 54 spectroscopic redshifts available in the
literature. Analysis of the rest-frame colour distribution shows a bimodality
out to z ~ 1.4. We separated our sample in a blue and a red population at B-V =
0.29. At low redshifts (0.2<z<0.6), ~ 60% of the galaxies have B-V > 0.29
whereas at higher redshifts ~ 60% of the galaxies are bluer than B-V < 0.29.
Although in low numbers, a population of early-type galaxies (or heavily
obscured low redshift galaxies) is seen out to z ~ 2.


title:
The Unusual Tidal Dwarf Candidate in the Merger System NGC 3227/6: Star
  Formation in a Tidal Shock?

abstract:
  We report the discovery of active star formation in the HI cloud associated
with the interacting Seyfert system NGC 3227/NGC 3226 that was originally
identified as a candidate tidal dwarf galaxy (TDG) by Mundell et al. and that
we name J1023+1952. We present the results of broad-band BRIJHK and ultraviolet
imaging that show the HI cloud is associated with massive on-going star
formation seen as a cluster of blue knots (M_B < -15.5 mag) surrounded by a
diffuse ultraviolet halo and co-spatial with a ridge of high column density
neutral hydrogen its southern half. We also detect Ha emission from the knots
with a flux density corresponding to a star-formation rate of SFR~0.011 Msun
per yr. Although J1023+1952 spatially overlaps the edge of the disk of NGC
3227, it has a mean HI velocity 150 km/s higher than that of NGC 3227 so is
kinematically distinct; comparison of ionized and neutral gas kinematics in the
star-forming region show closely matched velocities, providing strong evidence
that the knots are embedded in J1023+1952 and do not merely lie behind in the
disk of NGC 3227, thus confirming J1023+1952 as a gas-rich dwarf galaxy. We
discuss two scenarios for the origin of J1023+1952; as a third, pre-existing
dwarf galaxy involved in the interaction with NGC 3227 and NGC 3226, or a
newly-forming dwarf galaxy condensing out of the tidal debris removed from the
gaseous disk of NGC 3227. Given the lack of a detectable old stellar
population, a tidal origin is more likely. If J1023+1952 is a bound object
forming from returning gaseous tidal tail material, we infer a dynamically
young age similar to its star-formation age, and suggests it is in the earliest
stages of TDG evolution. Whatever the origin of J1023+1952 we suggest that its
star formation is shock-triggered by collapsing tidal debris. (Abridged)


title: Dark Energy Probes in Light of the CMB

abstract:
  CMB observables have largely fixed the expansion history of the universe in
the deceleration regime and provided two self-calibrated absolute standards for
dark energy studies: the sound horizon at recombination as a standard ruler and
the amplitude of initial density fluctuations. We review these inferences and
expose the testable assumptions about recombination and reionization that
underly them. Fixing the deceleration regime with CMB observables, deviations
in the distance and growth observables appear most strongly at z=0 implying
that accurate calibration of local and CMB standards may be more important than
redshift range or depth. The single most important complement to the CMB for
measuring the dark energy equation of state at z~0.5 is a determination of the
Hubble constant to better than a few percent. Counterintuitively, with fixed
fractional distance errors and relative standards such as SNe, the Hubble
constant measurement is best achieved in the high redshift deceleration regime.
Degeneracies between the evolution and current value of the equation of state
or between its value and spatial curvature can be broken if percent level
measurement and calibration of distance standards can be made at intermediate
redshifts or the growth function at any redshift in the acceleration regime. We
compare several dark energy probes available to a wide and deep optical survey:
baryon features in galaxy angular power spectra and the growth rate from
galaxy-galaxy lensing, shear tomography and the cluster abundance.


title: Early Star Formation and Chemical Evolution in Proto-Galactic Clouds

abstract:
  We present numerical simulations to describe the evolution of pre-Galactic
clouds in a model which is motivated by cold dark matter simulations of
hierarchical galaxy formation. We adopt a SN-induced star-formation mechanism
within a model that follows the evolution of chemical enrichment and energy
input to the clouds by Type II and Type Ia supernovae. We utilize
metallicity-dependent yields for all elements at all times, and include effects
of finite stellar lifetimes. We derive the metallicity distribution functions
for stars in the clouds, their age-metallicity relation, and relative elemental
abundances for a number of alpha- and Fe-group elements. The stability of these
clouds against destruction is discussed, and results are compared for different
initial mass functions. We find that the dispersion of the metallicity
distribution function observed in the outer halo is naturally reproduced by
contributions from many clouds with different initial conditions. The predicted
relative abundances of some alpha- and Fe-group elements show reasonable
agreement with the observed values down to metallicities below [Fe/H] ~ -4 when
the iron yields are reduced relative to stellar models. The observed scatter is
also reproduced for most elements including the observed bifurcation in
[alpha/Fe] for stars with low [Fe/H]. However, the predicted dispersion may be
too large for some elements unless a limited range of progenitor masses
contributing to the abundances of these elements is assumed. The results
suggest that the low-mass end of SNeII was probably absent at the very lowest
metallicities, and that the upper mass limit for the first stars that
contributed to nucleosynthesis may be < 40 M_solar.


title:
Hot Disk Corona and Magnetic Turbulence in Radio-Quiet Active Galactic
  Nuclei: Observational Constraints

abstract:
  We compile a sample consisting of 56 radio-quiet active galactic nuclei so as
to investigate statistical properties of hot corona of accretion disks from
{\em ASCA} observations. The black-hole masses in the sample are estimated via
several popular methods and the bolometric luminosities from the
multi-wavelength continuum. This allows us to estimate the Eddington ratio
(${\cal E}\equiv L_{\rm Bol}/L_{\rm Edd}$) so that the undergoing physical
processes can be tested via hard X-ray data. We find a strong correlation
between ${\cal F}_{\rm X}\equiv L_{\rm 2-10keV}/L_{\rm Bol}$ and ${\cal E}$ as
${\cal F}_{\rm X}\propto {\cal E}^{-0.64}$ with a multivariate regression. This
indicates that the release of gravitational energy in the hot corona is
controlled by the Eddington ratio. On the other hand, the correlation between
the hard X-ray spectral index ($\Gamma$) and ${\cal E}$ depends critically on
the types of objects: $\Gamma$ is nearly constant ($\Gamma \propto {\cal E}^0$)
in broad-line Seyfert 1's (BLS1s), whereas $\Gamma \propto \log {\cal
E}^{0.18}$ in narrow-line Seyfert 1's (NLS1s), although not very significant.
We can set constraints on the forms of magnetic stress tensor on the condition
that ${\cal F}_{\rm X}$ is proportional to the fraction $f$ of gravitational
energy dissipated in the hot corona and that $f$ is proportional to magnetic
energy density in the disk. We find that the shear stress tensor
$t_{r\phi}\propto P_{\rm gas}$ is favored by the correlation in the present
sample, where $P_{\rm gas}$ is the gas pressure.


title:
H2O megamasers: Accretion disks, jet interaction, outflows or massive
  star formation?

abstract:
  The 25 years following the serendipitous discovery of megamasers have seen
tremendous progress in the study of luminous extragalactic H$_2$O emission.
Single-dish monitoring and high resolution interferometry have been used to
identify sites of massive star formation, to study the interaction of nuclear
jets with dense molecular gas and to investigate the circumnuclear environment
of active galactic nuclei (AGN). Accretion disks with radii of 0.1--3 pc were
mapped and masses of nuclear engines of order 10$^{6}$--10$^{8}$ M$_{\odot}$
were determined. So far, $\sim$50 extragalactic H$_2$O maser sources have been
detected, but few have been studied in detail.


title:
Undetected Sources Allow Transmission of the Lyman-alpha Line From
  Galaxies Prior to Reionization

abstract:
  The discovery of Lyman-alpha emission from galaxies at redshifts beyond z~6.5
should not be naively interpreted as implying that the intergalactic medium
(IGM) had been reionized at higher redsifts. We show that a cluster of faint
undetected sources around each observed galaxy generates an HII region
sufficiently large to allow transmission of the galaxy's Lyman-alpha line prior
to reionization. We also show that quasars may contribute a significant
fraction of the ionizing photons to HII regions around galaxies with a velocity
dispersion larger than ~100km/s. These contributing quasars are not usually
seen due to the small fraction of time they spend in a luminous phase.


title:
Multi-band optical micro-variability observations of the BL Lac object
  S4 0954+658

abstract:
  We have observed S4 0954+658 in the BVRI bands in 2001, and in the BI bands
in 2002. The observations resulted in almost evenly sampled light curves, 3-8
hours long, with an average sampling interval of ~5-15 min. Because of the
dense sampling and the availability of light curves in more than one optical
bands we are able to study the intra-night flux and spectral variability of the
source in detail. Significant observations were observed in all but one cases.
On average, the flux variability amplitude, on time scales of minutes/hours,
increases from ~2-3% in the I, to ~3.5-5.5% in the B band light curves. We do
not detect any flares within the individual light curves. However, there is a
possibility that the April 2001 and late May 2002 observations sample two
flares which lasted longer than ~1-3 days. The evidence is only suggestive
though, due to the limited length of the present light curves with regard to
the duration of the assumed flares. No spectral variations are detected during
the April 2001 observations. The source flux rises and decays with the same
rate, in all bands. This variability behaviour is typical of S4 0954+658, and
is attributed to geometrical effects. However, significant spectral variations
are observed in May 2002. We find that the spectrum hardens/softens as the flux
increases/decreases, respectively. Furthermore, the "hardening" rate of the
energy spectrum is faster than the rate with which the spectrum becomes
"redder" as the flux decays. We also find evidence (although of low statistical
significance) that the I band variations are delayed with respect to the B band
variations. If the May 2002 observations sample a flaring event, these results
suggest that the variations are caused by energetic processes which are
associated with the particle cooling and the source light travel time scales.


title: Trails of Solar System Minor Bodies on WFC/ACS Images

abstract:
  In this paper we analyse very short arcs of minor bodies of the Solar System
detected on Hubble Space Telescope (HST) Wide Field Channel ACS images. In
particular, we address how to constrain the Keplerian orbital elements for
minor body detections, illustrating the method for 2 objects. One of the minor
bodies left 13 successive trails, making it the most well-sampled object yet
identified in the HST archive. Most interestingly, we also address the problem
of ephemeris prediction and show that in the particular case of HST very short
arcs the confinement window for subsequent recovery is significantly reduced to
a narrow linear region, that would facilitate successive observations.


title:
Ultra-High Energy Cosmic Rays: Some General Features, and Recent
  Developments Concerning Air Shower Computations

abstract:
  We present an introductory lecture on general features of cosmic rays, for
non-experts, and some recent developments concerning cascade equations for air
shower developments.


title:
Prompt and afterglow X-ray emission from the X-Ray Flash of 2002 April
  27

abstract:
  We report on the X-ray observations of the X-ray flash (XRF) which occurred
on 2002 April 27, three days before BeppoSAX was switched off. The event was
detected with the BeppoSAX Wide Field Cameras but not with the Gamma ray Burst
Monitor. A follow-up observation with the BeppoSAX Narrow Field Instruments was
soon performed and a candidate afterglow source was discovered. We present the
results obtained. We also include the results obtained from the observations of
the XRF field with the Chandra X-ray satellite. The spectral analysis of the
prompt emission shows that the peak energy of the EF(E) spectrum is lower than
5.5 keV, with negligible spectral evolution. The X-ray afterglow spectrum is
consistent with a power law model with photon index of about 2, while the 2-10
keV flux fades as a power law with a decay index -1.33. Both these indices are
typical of GRBs. A very marginal excess around 4.5-5 keV is found in the
afterglow spectrum measured by BeppoSAX . As for many GRBs, the extrapolation
of the 2-10 keV fading law back to the time of the prompt emission is
consistent with the X-ray flux measured during the second part of the event. We
estimate a possible range of values of the redshift and discuss our results in
the light of current models of XRFs.


title: A Radio and Mid-Infrared Survey of Northern Bright-Rimmed Clouds

abstract:
  We have carried out an archival radio, optical and infrared wavelength
imaging survey of 44 Bright-Rimmed Clouds (BRCs) using the NRAO/VLA Sky Survey
(NVSS) archive, images from the Digitised Sky Survey (DSS) and the Midcourse
Space eXperiment (MSX). The data characterise the physical properties of the
Ionised Boundary Layer (IBL) of the BRCs. A total of 25 clouds display 20 cm
radio continuum emission that is associated with their bright optical rims. The
ionising photon flux illuminating these clouds, the ionised gas pressure and
the electron density of the IBL are determined. We derive internal molecular
pressures for 9 clouds using molecular line data from the literature and
compare these pressures to the IBL pressures to determine the pressure balance
of the clouds. We find three clouds in which the pressure exerted by their IBLs
is much greater than that measured in the internal molecular material. A
comparison of external pressures around the remaining clouds to a global mean
internal pressure shows that the majority of clouds can be expected to be in
pressure equilibrium with their IBLs and hence are likely to be currently
shocked by photoionisation shocks. We identify one source which shows 20 cm
emission consistent with that of an embedded high-mass YSO and confirm its
association with a known infrared stellar cluster. This embedded cluster is
shown to contain early-type B stars, implying that at least some BRCs are
intimately involved in intermediate to high mass star formation.


title:
The distances to Galactic low-mass X-ray binaries: consequences for
  black hole luminosities and kicks

abstract:
  We investigated the reported distances of Galactic black hole (BH) and
neutron star low-mass X-ray binaries (LMXBs). Comparing the distances derived
for the neutron stars CygX-2 and XTE J2123-058 using the observed Eddington
limited photospheric radius expansion bursts with the distances derived using
the observed radius and effective temperature of the companion star we find
that the latter are smaller by approximately a factor of 1.5-2. The latter
method is often employed to determine the distance to BH LMXBs. A possible
explanation for this discrepancy is that the stellar absorption lines in fast
rotating companion stars are different from those in the slowly rotating
template stars as was found before for early type stars. This could lead to a
systematic mis-classification of the spectral type of the companion star, which
in turn would yield a systematic error in the distance. We find that, using new
distances for XTE J1550-564 and V404 Cyg, the maximum outburst luminosity for
at least 5 but perhaps even 7 of the 15 BH soft X-ray transients exceeds the
Eddington luminosity for a 10 M_sun BH showing that these systems would be
classified as ultra-luminous X-ray sources had we observed them in other
Galaxies. This renders support for the idea that many ultra-luminous X-ray
sources are stellar-mass rather than intermediate-mass BHs. We find that the
rms value of the distance to the Galactic plane for BHs is consistent with that
of neutron star LMXBs. This suggests that BHs could also receive a
kick-velocity during their formation although this has to be investigated in
more detail. (Abridged).


title:
Submillimeter Observations of Titan: Global Measures of Stratospheric
  Temperature, CO, HCN, HC3N, and the Isotopic Ratios 12C/13C and 14N/15N

abstract:
  Interferometric observations of the atmosphere of Titan were performed with
the Submillimeter Array on two nights in February 2004 to investigate the
global average vertical distributions of several molecular species above the
tropopause. Rotational transitions of CO, isomers of HCN, and HC3N were
simultaneously recorded. The abundance of CO is determined to be 51+/-4 ppm,
constant with altitude. The vertical profile of HCN is dependent upon the
assumed temperature but generally increases from 30 ppb at the condensation
altitude (~83 km) to 5 ppm at ~300 km. Further, the central core of the HCN
emission is strong and can be reproduced only if the upper stratospheric
temperature increases with altitude. The isotopic ratios are determined to be
12C/13C=132+/-25 and 14N/15N=94+/-13 assuming the Coustenis & Bezard (1995)
temperature profile. If the Lellouch (1990) temperature profile is assumed the
ratios decrease to 12C/13C=108+/-20 and 14N/15N=72+/-9. The vertical profile of
HC3N is consistent with that derived by Marten et al. (2002).


title: On the evolution of star forming galaxies

abstract:
  The evolution in the comoving space density of the global average galaxy star
formation rate (SFR) out to a redshift around unity is well established. Beyond
z~1 there is growing evidence that this evolution is flat or even increasing,
contrary to early indications of a turnover. Some recent analyses of z~6
photometric dropouts are suggestive of a decline from z=3 to z~6, but there is
still very little constraint on the extent of dust obscuration at such high
redshifts. In less than a decade, numerous measurements of galaxy SFR density
spanning z=0 to as high as z~6 have rapidly broadened our understanding of
galaxy evolution, and a summary of existing SFR density measurements is
presented here. This global star formation history compilation is found to be
consistent to within factors of about three over essentially the entire range
$0<z\lesssim6$, and it can be used to constrain the evolution of the luminosity
function (LF) for star forming (SF) galaxies. The LF evolution for SF galaxies
has been previously explored using optical source counts, as well as radio
source counts at 1.4 GHz, and a well-known degeneracy between luminosity
evolution ($L\propto(1+z)^Q$) and density evolution ($\phi\propto(1+z)^P$) is
found. Combining the constraints from the global SFR density evolution with
those from the 1.4 GHz radio source counts at sub-millijansky levels allows
this degeneracy to be broken, and a best fitting evolutionary form to be
established. The preferred evolution in a $H_0=70, \Omega_M=0.3,
\Omega_\Lambda=0.7$ cosmology from these combined constraints is
$Q=2.70\pm0.60$, $P=0.15\pm0.60$.


title:
The evolutionary sequence of active galactic nuclei and galaxy formation
  revealed

abstract:
  Today, almost every galaxy spheroid contains a massive black hole: a remnant
of, and testament to, a period in its evolution when it contained an active
galactic nucleus (AGN). However, the sequence and timescales of the formation
of the black hole and surrounding spheroid of stars are completely unknown,
leaving a large gap in our knowledge of how the Universe attained its present
appearance. Here we present submillimeter observations of matched samples of
X-ray absorbed and unabsorbed AGN which have luminosities and redshifts
characteristic of the sources responsible for most of the mass in present day
black holes. Strong submillimeter emission, an isotropic signature of copious
star formation, is found only in the X-ray absorbed sample, ruling out
orientation effects as the cause of the absorption. The space density and
luminosity range of the X-ray absorbed AGN indicate that they are undergoing
the transition between a hidden growth phase and an unabsorbed AGN phase, and
implies that the X-ray absorbed period in the AGN's evolution coincides with
the formation of the galaxy spheroid.


title: The Galactic 26Al Problem and The Close Binary SNIb/c Solution?

abstract:
  The origin of the long-lived radioactive 26Al, which has been observed in the
Galactic interstellar medium from its 1.809 MeV decay gamma-ray line emission,
has been a persistent problem for over twenty years. Wolf-Rayet (WR) winds were
thought to be the most promising source, but their calculated 26Al yields are
not consistent with recent analyses of the 1.809 MeV emission from the nearest
WR star and nearby OB associations. The expected 26Al yield from the WR star
exceeds by as much as a factor of 3, that set by the 2-sigma upper limit on the
1.809 MeV emission, while the WR yields in the OB associations are only about
1/3 of that required by the 1.809 MeV emission. We suggest that a solution to
these problems may lie in 26Al from a previously ignored source: explosive
nucleosynthesis in the core collapse SNIb/c supernovae of WR stars that have
lost most of their mass to close binary companions. Recent nucleosynthetic
calculations of SNIb/c suggest that their 26Al yields depend very strongly on
the final, pre-supernova mass of the WR star, and that those with final masses
around 6 to 8 solar masses are expected to produce as much as 0.01 solar masses
of 26Al per supernova. Such binary SNIb/c make up only a small fraction of the
current SNIb/c and only about 1% of all Galactic core collapse supernovae. They
appear to be such prolific sources that the bulk of the present 26Al in the
Galaxy may come from just a few hundred close binary SNIb/c and the intense
1.809 MeV emission from nearby OB associations may come from just one or two
such supernova.


title:
Angular diameters, fluxes and extinction of compact planetary nebulae:
  further evidence for steeper extinction towards the Bulge

abstract:
  We present values for angular diameter, flux and extinction for 70 Galactic
planetary nebulae observed using narrow band filters. Angular diameters are
derived using constant emissivity shell and photoionization line emission
models. The mean of the results from these two models are presented as our best
estimate. Contour plots of 36 fully resolved objects are included and the low
intensity contours often reveal an elliptical structure that is not always
apparent from FWHM measurements. Flux densities are determined, and for both
H-alpha and O[III] there is little evidence of any systematic differences
between observed and catalogued values. Observed H-alpha extinction values are
determined using observed H-alpha and catalogued radio fluxes. H-alpha
extinction values are also derived from catalogued H-alpha and H-beta flux
values by means of an Rv dependent extinction law. Rv is then calculated in
terms of observed extinction values and catalogued H-alpha and H-beta flux
values. Comparing observed and catalogue extinction values for a subset of
Bulge objects, observed values tend to be lower than catalogue values
calculated with Rv = 3.1. For the same subset we calculate <Rv> = 2.0,
confirming that toward the Bulge interstellar extinction is steeper than Rv =
3.1. For the inner Galaxy a relation with the higher supernova rate is
suggested, and that the low-density warm ionized medium is the site of the
anomalous extinction. Lowvalues of extinction are also derived using dust
models with a turnover radius of 0.08 microns.


title:
"Mariage des Maillages": A new numerical approach for 3D relativistic
  core collapse simulations

abstract:
  We present a new 3D general relativistic hydrodynamics code for simulations
of stellar core collapse to a neutron star, as well as pulsations and
instabilities of rotating relativistic stars. It uses spectral methods for
solving the metric equations, assuming the conformal flatness approximation for
the three-metric. The matter equations are solved by high-resolution
shock-capturing schemes. We demonstrate that the combination of a finite
difference grid and a spectral grid can be successfully accomplished. This
"Mariage des Maillages" (French for grid wedding) approach results in high
accuracy of the metric solver and allows for fully 3D applications using
computationally affordable resources, and ensures long term numerical stability
of the evolution. We compare our new approach to two other, finite difference
based, methods to solve the metric equations. A variety of tests in 2D and 3D
is presented, involving highly perturbed neutron star spacetimes and
(axisymmetric) stellar core collapse, demonstrating the ability to handle
spacetimes with and without symmetries in strong gravity. These tests are also
employed to assess gravitational waveform extraction, which is based on the
quadrupole formula.


title: The generalized Roche model

abstract:
  Some exact analytical formulas are presented for the generalized Roche model
of rotating star. The gravitational field of the central core is described by
the model of two equal-mass point centers placed symmetrically at rotation axis
with the pure imaginary z coordinates. The all basic parameters of the critical
figure of the rotating massless envelope are presented in analytical form. The
existence of the concave form of the uniformly rotating liquid is shown for a
large enough angular velocity of the rotation.


title: Surprising Sun

abstract:
  Important revisions of the solar model ingredients appear after 35 years of
intense work which have led to an excellent agreement between solar models and
solar neutrino detections. We first show that the updated CNO composition
suppresses the anomalous position of the Sun in the known galactic enrichment.
The following law: He/H= 0.075 + 44.6 O/H in fraction number is now compatible
with all the indicators. We then examine the existing discrepancies between the
standard model and solar - seismic and neutrino - observations and suggest some
directions of investigation to solve them. We update our predicted neutrino
fluxes using the recent composition, new nuclear reaction rates and seismic
models as the most representative of the central plasma properties.
  We get 5.31 +- 0.6 10^6/cm^{2}/s for the total ^8B neutrinos, 66.5 SNU and
2.76 SNU for the gallium and chlorine detectors, all in remarquable agreement
with the detected values including neutrino oscillations for the last two. We
conclude that the acoustic modes and detected neutrinos see the same Sun, but
that clear discrepancies in solar modelling encourage further observational and
theoretical efforts.


title: Optical and near infrared observations of SN 1998bu

abstract:
  Infrared and optical spectra of SN 1998bu at an age of one year after
explosion are presented. The data show evidence for the radioactive decay of
56Co to 56Fe, long assumed to be the powering source for the supernova light
curve past maximum light. The spectra provide direct evidence for at least 0.4
solar masses of iron being present in the ejecta of the supernova. The fits to
the data also show that the widths of the emission lines increase with time.
Photometric measurements in the H-band show that the supernova is not fading
during the observation period. This is consistent with theoretical
expectations.


title:
High-Resolution, Wide-Field Imaging of the Galactic Center Region at 330
  MHz

abstract:
  We present a wide field, sub-arcminute resolution VLA image of the Galactic
Center region at 330 MHz. With a resolution of ~ 7" X 12" and an RMS noise of
1.6 mJy/beam, this image represents a significant increase in resolution and
sensitivity over the previously published VLA image at this frequency. The
improved sensitivity has more than tripled the census of small diameter sources
in the region, has resulted in the detection of two new Non Thermal Filaments
(NTFs), 18 NTF candidates, 30 pulsar candidates, reveals previously known
extended sources in greater detail, and has resulted in the first detection of
Sagittarius A* in this frequency range.
  A version of this paper containing full resolution images may be found at
http://lwa.nrl.navy.mil/nord/AAAB.pdf.


title:
Interpreting the High Frequency QPO Power Spectra of Accreting Black
  Holes

abstract:
  In the context of a relativistic hot spot model, we investigate different
physical mechanisms to explain the behavior of quasi-periodic oscillations
(QPOs) from accreting black holes. The locations and amplitudes of the QPO
peaks are determined by the ray-tracing calculations presented in Schnittman &
Bertschinger (2004a): the black hole mass and angular momentum give the
geodesic coordinate frequencies, while the disk inclination and the hot spot
size, shape, and overbrightness give the amplitudes of the different peaks. In
this paper additional features are added to the existing model to explain the
broadening of the QPO peaks as well as the damping of higher frequency
harmonics in the power spectrum. We present a number of analytic results that
closely agree with more detailed numerical calculations. Four primary pieces
are developed: the addition of multiple hot spots with random phases, a finite
width in the distribution of geodesic orbits, Poisson sampling of the detected
photons, and the scattering of photons from the hot spot through a corona of
hot electrons around the black hole. Finally, the complete model is used to fit
the observed power spectra of both type A and type B QPOs seen in XTE
J1550-564, giving confidence limits on each of the model parameters.


title:
Young Crab-like pulsars and luminous X-ray sources in starbursts and
  optically dull galaxies

abstract:
  Recent Chandra observations of nearby galaxies have revealed a number of
ultraluminous X-ray sources (ULXs) with super-Eddington luminosities, away from
the central regions of non-active galaxies. The nature of these sources is
still debated. We argue that a fraction of them could be young, Crab-like
pulsars, the X-ray luminosity of which is powered by rotation. We use the
pulsar birth parameters estimated from radio pulsar data to compute the
steady-state pulsar X-ray luminosity distribution as a function of the star
formation rate (SFR) in the galaxy. We find that ~10% of optically dull
galaxies are expected to have a source with L_x >~ 10^{39} erg/s, while
starbursts galaxies should each have several of these sources. We estimate that
the X-ray luminosity of a few percents of galaxies is dominated by a single
bright pulsar with L_x >~10^{39} erg/s, roughly independently of its SFR. We
discuss observational diagnostics that can help distinguish the young pulsar
population in ULXs.


title: Super-Eddington accretion rates in Narrow Line Seyfert 1 galaxies

abstract:
  Using the BH masses deduced from the empirical relation of Kaspi et al.
(2000) and assuming that the optical luminosity is provided by the accretion
disc, we show that Narrow Line Seyfert Galaxies 1 (NLS1s) accrete at
super-Eddington rates, while their luminosity stays of the order of the
Eddington limit. We take into account the possibility of a non-viscous energy
release in the gravitationally unstable region of the disc. It leads to a
smaller accretion rate and to a redder continuum than a standard disc, which
agrees better with the observations. The observed bolometric luminosities
appear to saturate at a few times the Eddington luminosity for super-Eddington
accretion rates, as predicted by slim disc models. The accretion rate stays
always of the order of a few M$_{\odot}$/yr, indicating that the growing of the
BH is mass supply limited . Since the masses of the BH increases by one order
of magnitude in a few 10$^7$ years, it could explain why NLS1s appear to not
follow the same BH - bulge relation as other galaxies. NLS1s should thus play
an important role in shaping the mass function of local BHs. We discuss the
possibility that the masses could be systematically underestimated due to an
inclination effect, and we conclude that the accretion rates could thus be
strongly overestimated, but only in a small proportion of objects.


title:
Implications of the Measured Image Size for the Radio Afterglow of GRB
  030329

abstract:
  We use data on the image size of the radio afterglow of GRB 030329 (Taylor et
al. 2004) to constrain the physical parameters of this explosion. Together with
the observed broad band spectrum, this data over-constrains the physical
parameters, thus enabling to test different GRB jet models for consistency. We
consider two extreme models for the lateral spreading of the jet: model 1 with
relativistic expansion in the local rest frame, and model 2 with little lateral
expansion as long as the jet is highly relativistic. We find that both models
are consistent with the data for a uniform external medium, while for a stellar
wind environment model 1 is consistent with the data but model 2 is disfavored
by the data. Our derivations can be used to place tighter constraints on the
dynamics and structure of GRB jets in future afterglows, following a denser
monitoring campaign for the temporal evolution of their image size.


title: The Ionizing Source of the Nucleus of NGC1097

abstract:
  We present new observations in X-ray and optical/ultraviolet of the nucleus
of NGC1097, known for the abrupt appearance of broad, double-peaked Balmer
lines in its spectrum in 1991. These new observations are used to construct the
spectral energy distribution (SED) of the central engine. From the SED we infer
that this AGN is radio-loud and has a bolometric luminosity L_Bol ~ 10^42
erg/s, implying a low Eddington ratio of L_Bol/L_Edd ~ 10^{-4}. These results
suggest that the central ionizing source is an advection-dominated accretion
flow (ADAF) in the form of an ellevated structure which photoionizes an outer
thin disk. We fit a simplified ADAF model to the SED and obtain limits on the
values of the mass accretion rate Mdot and accretion efficiency \eta, namely
Mdot/Mdot_Edd >= 10^{-3} and \eta <= 10^{-2}. We identify an energy budget
problem: if the central photoionizing source is isotropic, the covering factor
of the line-emitting portion of the thin accretion disk is ~ 6, i. e. the
central source accounts for only 20% of the energy emitted in the double-peaked
Balmer lines.


title:
Neutrino Oscillations at Supernova Core Bounce Generate the Strongest
  Gravitational-Wave Bursts

abstract:
  During the core bounce of a supernova collapse resonant active-to-active
($\nu_a \to \nu_a$), as well as active-to-sterile ($\nu_a \to \nu_s$) neutrino
($\nu$) oscillations can take place. Besides, over this phase weak magnetism
increases antineutrino ($\bar{\nu}$) mean free paths, and thus its luminosity.
Because the oscillation feeds mass-energy into the target $\nu$ species, the
large mass-squared difference between species ($\nu_a \to \nu_s$) implies a
huge amount of power to be given off as gravitational waves ($L_{\textrm{GWs}}
\sim 10^{49}erg s$^{-1}$), due to anisotropic but coherent $\nu$ flow over the
oscillation length. This anisotropy in the $\nu$-flux is driven by both the
{\it universal spin-rotation} and the spin-magnetic coupling. The new spacetime
strain estimated this way is still several orders of magnitude larger than
those from $\nu$ diffusion (convection and cooling) or quadrupole moments of
the neutron star matter. This new feature turns these bursts the more promising
supernova gravitational-wave signal that may be detected by observatories as
LIGO, VIRGO, etc., for distances far out to the VIRGO cluster of galaxies.


title: Cosmological simulations of the high-redshift radio universe

abstract:
  Using self-consistent cosmological simulations of disc galaxy formation, we
analyse the 1.4 GHz radio flux from high-redshift progenitors of present-day
normal spirals within the context of present-day and planned next-generation
observational facilities. We demonstrate that while current radio facilities
such as the Very Large Array (VLA) are unlikely to trace these progenitors
beyond redshifts z<0.2, future facilities such as the Square Kilometer Array
(SKA) will readily probe their characteristics to redshifts z<2, and are likely
to provide detections beyond z~3. We also demonstrate that the progenitors of
present-day cD galaxies can emit in excess of 10 uJy of flux at redshifts z>1,
and may be a non-negligible contributor to the micro-Jansky source counts
derived from current deep VLA cm-wave surveys.


title:
Identification and Characterization of Faint Emission Lines in the
  Spectrum of the Planetary Nebula IC 418

abstract:
  We present high signal-to-noise echelle spectra of the compact high surface
brightness, low ionization planetary nebula IC 418. These reveal 807 emission
lines down to intensities less than 10$^{-5}$ that of H$\beta$ for which we
determine widths and relative intensities. We show that line profiles are a
valuable parameter for making line identifications and in constraining the
excitation mechanism of the lines. We present evidence that indicates that many
supposed high-level recombination lines may in fact be excited by a process
other than recombination. We contend from the detection of dielectronic
recombination lines that their relatively low intensities argue against their
making a significant contribution to level populations of the heavy ions in
this object. Following similar analyses of other PNe we find that IC 418 shows
a small discrepancy in ion abundances derived from forbidden vs. recombination
lines of the heavy elements.


title:
Does regenerated emission change the high-energy signal from gamma-ray
  burst afterglows?

abstract:
  We study regenerated high-energy emission from the gamma-ray burst (GRB)
afterglows, and compare its flux with the direct component from the same
afterglow. When the intrinsic emission spectrum extends to TeV region, these
very high-energy photons are significantly absorbed by the cosmic infrared
background (CIB) radiation field, creating electron/positron pairs; since these
pairs are highly energetic, they can scatter the cosmic microwave background
radiation up to GeV energies, which may change the intrinsic afterglow light
curve in the GeV region. Using the theoretical modeling given in literature and
the reasonable choice of relevant parameters, we calculate the expected light
curve due to the regeneration mechanism. As the result, we find that the
regenerated emission could only slightly change the original light curve, even
if we take a rather large value for the CIB density, independently of the
density profile of surrounding medium, i.e., constant or wind-like profile.
This ensures us the reliable estimation of the intrinsic GRB parameters when
the high-energy observation is accessible, regardless of a large amount of
uncertainty concerning the CIB density as well as extragalactic magnetic field
strength.


title: Metallicity in the Galactic Center: The Arches cluster

abstract:
  We present a quantitative spectral analysis of five very massive stars in the
Arches cluster, located near the Galactic center, to determine stellar
parameters, stellar wind properties and, most importantly, metallicity content.
The analysis uses a new technique, presented here for the first time, and uses
line-blanketed NLTE wind/atmosphere models fit to high-resolution near-infrared
spectra of late-type nitrogen-rich Wolf-Rayet stars and OfI+ stars in the
cluster. It relies on the fact that massive stars reach a maximum nitrogen
abundance that is related to initial metallicity when they are in the WNL
phase. We determine the present-day nitrogen abundance of the WNL stars in the
Arches cluster to be 1.6% (mass fraction) and constrain the stellar metallicity
in the cluster to be solar. This result is invariant to assumptions about the
mass-luminosity relationship, the mass-loss rates, and rotation speeds. In
addition, from this analysis, we find the age of the Arches cluster to be
2-2.5Myr, assuming coeval formation.


title: Census of the Galactic Centre early-type stars using spectro-imagery

abstract:
  The few central parsecs of the Galaxy are known to contain a surprising
population of early-type stars, including at least 30 Wolf-Rayet stars and
luminous blue variables (LBV), identified thanks to their strong emission
lines. Despite the presence of emission from ionised interstellar material in
the same lines, the latest advances in spectro-imaging have made it possible to
use the absorption lines of the OB stars to characterise them as well. This
stellar population is particularly intriguing in the deep potential well of the
4 million solar mass black hole Sgr A*. We will review the properties of these
early-type stars known from spectro-imagery, and discuss possible formation
scenarios.