title:
Unexpected Dynamical Instabilities In Differentially Rotating Neutron
  Stars

abstract:
  A one-armed spiral instability has been found to develop in differentially
rotating stellar models that have a relatively stiff, $n=1$ polytropic equation
of state and a wide range of rotational energies. This suggests that such
instabilities can arise in neutron stars that are differentially, although not
necessarily rapidly, rotating. The instability seems to be directly triggered
by the presence of a corotation resonance inside the star. Our analysis also
suggests that a resonant cavity resulting from a local minimum in the radial
vortensity profile of the star plays an important role in amplifying the
unstable mode. Hence, it appears as through this instability is closely related
to the so-called ``Rossby wave instability'' \citep{LLCN99} that has been found
to arise in accretion disks. In addition to the one-armed ($m=1$) spiral mode,
we have found that higher-order ($m = 2$ and $m=3$) nonaxisymmetric modes also
can become unstable if corotation points that resonate with the
eigenfrequencies of these higher-order modes also appear inside the star. The
growth rate of each mode seems to depend on the location of its corotation
radius with respect to the vortensity profile (or on the depth of its
corotation radius inside the vortensity well). The existence of such
instabilities makes the stability criterion for differentially rotating neutron
stars non-unique. Also, the gravitational-waves emitted from such unstable
systems generally will not have a monochromatic frequency spectrum.


title:
Abundance analysis of 5 early-type stars in the young open cluster
  IC2391

abstract:
  It is unclear whether chemically peculiar stars of the upper main sequence
represent a class completely distinct from normal A-type stars, or whether
there exists a continuous transition from the normal to the most peculiar late
F- to early B-type stars. A systematic abundance analysis of open cluster
early-type stars would help to relate the observed differences of the chemical
abundances of the photospheres to other stellar characteristics, without being
concerned by possible different original chemical composition. Furthermore, if
a continuous transition region from the very peculiar to the so called normal
A-F stars exists, it should be possible to detect objects with mild
peculiarities. As a first step of a larger project, an abundance analysis of 5
F-A type stars in the young cluster IC2391 was performed using high resolution
spectra obtained with the UVES instrument of the ESO VLT. Our targets seem to
follow a general abundance pattern: close to solar abundance of the light
elements and iron peak elements, heavy elements are slightly overabundant with
respect to the sun, similar to what was found in previous studies of normal
field A-type stars of the galactic plane. We detected a weakly chemically
peculiar star, HD74044. Its element pattern contains characteristics of CP1 as
well as CP2 stars, enhanced abundances of iron peak elements and also higher
abundances of Sc, Y, Ba and Ce. We did not detect a magnetic field in this star
(detection limit was 2kG). We also studied the star SHJM2, proposed as a
pre-main sequence object in previous works. Using spectroscopy we found a high
surface gravity, which suggests that the star is very close to the ZAMS.


title: Task Force on Cosmic Microwave Background Research

abstract:
  One of the most spectacular scientific breakthroughs in past decades was
using measurements of the fluctuations in the cosmic microwave background (CMB)
to test precisely our understanding of the history and composition of the
Universe. This report presents a roadmap for leading CMB research to its
logical next step, using precision polarization measurements to learn about
ultra-high-energy physics and the Big Bang itself.


title:
The impact of meridional circulation on stellar butterfly diagrams and
  polar caps

abstract:
  Observations of rapidly rotating solar-like stars show a significant mixture
of opposite-polarity magnetic fields within their polar regions. To explain
these observations, models describing the surface transport of magnetic flux
demand the presence of fast meridional flows. Here, we link sub-surface and
surface magnetic flux transport simulations to investigate (i) the impact of
meridional circulations with peak velocities of <125m/s on the latitudinal
eruption pattern of magnetic flux tubes and (ii) the influence of the resulting
butterfly diagrams on polar magnetic field properties. Prior to their eruption,
magnetic flux tubes with low field strengths and initial cross sections below
about 300km experience an enhanced poleward deflection through meridional
flows. In particular flux tubes which originate between low and intermediate
latitudes within the convective overshoot region are strongly affected. This
latitude-dependent poleward deflection of erupting magnetic flux renders the
wings of stellar butterfly diagrams distinctively convex. The subsequent
evolution of the surface magnetic field shows that the increased number of
newly emerging bipoles at higher latitudes promotes the intermingling of
opposite polarities of polar magnetic fields. The associated magnetic flux
densities are about 20% higher than in the case disregarding the pre-eruptive
deflection, which eases the necessity for fast meridional flows predicted by
previous investigations. In order to reproduce the observed polar field
properties, the rate of the meridional circulation has to be on the order of
100m/s, and the latitudinal range from which magnetic flux tubes originate at
the base of the convective zone (<50degrees) must be larger than in the solar
case (<35degrees).


title: Statistics of Giant Radio Halos from Electron Reacceleration Models

abstract:
  The most important evidence of non-thermal phenomena in galaxy clusters comes
from Giant Radio Halos (GRHs), synchrotron radio sources extended over Mpc
scales, detected in a growing number of massive galaxy clusters. A promising
possibility to explain these sources is given by "in situ" stochastic
reacceleration of relativistic electrons by turbulence generated in the cluster
volume during merger events. Cassano & Brunetti (2005) have recently shown that
the expected fraction of clusters with GRHs and the increase of such a fraction
with cluster mass can be reconciled with present observations provided that a
fraction of 20-30 % of the turbulence in clusters is in the form of
compressible modes. In this work we extend these calculations by including a
scaling of the magnetic field strength with cluster mass. We show that the
observed correlations between the synchrotron radio power of a sample of 17
GRHs and the X-ray properties of the hosting clusters are consistent with, and
actually predicted by a magnetic field dependence on the virial mass of the
form B \propto M^b, with b>0.5 and typical micro Gauss strengths of the average
B intensity. The occurrence of GRHs as a function of both cluster mass and
redshift is obtained. The most relevant findings are that the predicted
luminosity functions of GRHs are peaked around a power P_{1.4 GHz} 10^{24}
W/Hz, and severely cut-off at low radio powers due to the decrease of the
electron reacceleration in smaller galaxy clusters. We expect a total number of
GRHs to be discovered at ~mJy radio fluxes of ~100 at 1.4 GHz. Finally, the
occurrence of GRHs and their number counts at 150 MHz are estimated in view of
the fortcoming operation of low frequency observatories (LOFAR, LWA) and
compared with those at higher radio frequencies.


title:
A Correlation Between Pre-Main Sequence Stellar Rotation Rates and IRAC
  Excesses in Orion

abstract:
  Early observations of T Tauri stars suggested that stars with evidence of
circumstellar accretion disks rotated slower than stars without such evidence,
but more recent results are not as clear. Near-IR circumstellar disk
indicators, though the most widely available, are subject to uncertainties that
can result from inner disk holes and/or the system inclination. Mid-infrared
observations are less sensitive to such effects, but until now, these
observations have been difficult to obtain. The Spitzer Space Telescope now
easily enables mid-infrared measurements of large samples of PMS stars covering
a broad mass range in nearby star-forming regions. Megeath and collaborators
surveyed the Orion Molecular Clouds (~1 Myr) with the IRAC instrument (3.6,
4.5, 5.8, 8 microns) as part of a joint IRAC and MIPS GTO program. We examine
the relationship between rotation and Spitzer mid-IR fluxes for ~900 stars in
Orion for stars between 3 and 0.1 Msun. We find in these Spitzer data the
clearest indication to date that stars with longer periods are more likely than
those with short periods to have IR excesses suggestive of disks.


title:
Evidence for chromatic X-ray light-curve breaks in Swift GRB afterglows
  and their theoretical implications

abstract:
  The power-law decay of the X-ray emission of GRB afterglows 050319, 050401,
050607, 050713A, 050802 and 050922C exhibits a steepening at about 1--4 hours
after the burst which, surprisingly, is not accompanied by a break in the
optical emission. If it is assumed that both the optical and X-ray afterglows
arise from the same outflow then, in the framework of the standard forward
shock model, the chromaticity of the X-ray light-curve breaks indicates that
they do not arise solely from a mechanism related to the outflow dynamics (e.g.
energy injection) or the angular distribution of the blast-wave kinetic energy
(structured outflows or jets). The lack of a spectral evolution accompanying
the X-ray light-curve breaks shows that these breaks do not arise from the
passage of a spectral break (e.g. the cooling frequency) either. Under these
circumstances, the decoupling of the X-ray and optical decays requires that the
microphysical parameters for the electron and magnetic energies in the forward
shock evolve in time, whether the X-ray afterglow is synchrotron or
inverse-Compton emission. For a steady evolution of these parameters with the
Lorentz factor of the forward shock and an X-ray light-curve break arising from
cessation of energy injection into the blast-wave, the optical and X-ray
properties of the above six Swift afterglows require a circumburst medium with
a r^{-2} radial stratification, as expected for a massive star origin for long
GRBs. Alternatively, the chromatic X-ray light-curve breaks may indicate that
the optical and X-ray emissions arise from different outflows. Neither feature
(evolution of microphysical parameters or the different origin of the optical
and X-ray emissions) were clearly required by pre-Swift afterglows.


title: A Chandra ACIS Observation of the X-ray Luminous SN1988Z

abstract:
  SN1988Z is the most luminous X-ray-emitting supernova, initially detected in
1995 using the ROSAT HRI with a luminosity of ~8x10^40 erg s^-1 (Fabian &
Terlevich 1996). Its high luminosity was ascribed to expansion of the blast
wave into an especially dense circumstellar medium. In this paper, we describe
a recent observation of SN1988Z using the ACIS detector on Chandra. We readily
detect SN1988Z, obtaining ~30 net counts which corresponds to a 0.2-2 keV
luminosity of ~3.2x10^39 erg s^-1. The calculated quantiles for the extracted
counts allow a broad range of temperatures, but require a temperature hotter
than 5 keV if there is no intrinsic absorption. The long term light curve
(1995-2005) declines as t^-2.6+/-0.6. This is one of the steepest X-ray light
curves. The X-ray luminosity indicates that the emitting region has a high
density (>10^5 cm^-3) and that the density profile is not consistent with a
constant mass loss stellar wind during the ~5000 years before the explosion. If
the circumstellar medium is due to progenitor mass loss, then the mass loss
rate is extremely high (~10^-3 M_sol yr^-1(v_w / 10 km s^-1)). The X-ray
results are compared with the predictions of models of SN1988Z.


title: Simulations of Cosmic Chemical Enrichment

abstract:
  Using a new numerical model for cosmic chemical evolution, we study the
influence of hypernova feedback on the star formation and metal enrichment
history of the universe. For assumptions which produce plausible results in
idealized collapse models of individual galaxies, our cosmological simulations
of the standard Lambda-CDM cosmology show a peak of the cosmic star formation
rate at z~4, with ~10% of the baryons turning into stars. We find that the
majority of stars in present-day massive galaxies formed in much smaller
galaxies at high redshifts, giving them a mean stellar age as old as 10 Gyr,
despite their late assembly times. The hypernova feedback drives galactic
outflows efficiently in low mass galaxies, and these winds eject heavy elements
into the intergalactic medium. The ejected baryon fraction is larger for less
massive galaxies, correlates well with stellar metallicity, and amounts to ~20%
of all baryons in total. The resulting enrichment history is broadly consistent
with the observed abundances of Lyman break galaxies, of damped Lyman alpha
systems, and of the intergalactic medium. The metallicity of the cold gas in
galaxies increases with galaxy mass, which is comparable to observations with a
significant scatter. The stellar mass-metallicity relation of the observed
galaxy population is well reproduced by the simulation model as a result of
mass-dependent galactic winds. However, star formation does not terminate in
massive galaxies at late times in our model, and too few dwarf galaxies are
still forming stars. These problems may be due to a lack of resolution, to
inappropriate modelling of supernova feedback, or to a neglect of other
feedback processes such as active galactic nuclei.


title: A Massive Spiral Galaxy in the Zone of Avoidance

abstract:
  We report the discovery of a very HI-massive disk galaxy, HIZOA J0836-43, at
a velocity of v_hel = 10689 km/s, corresponding to a distance of 148 Mpc
(assuming H_0=75 km/s/Mpc). It was found during the course of a systematic HI
survey of the southern Zone of Avoidance (|b| < 5 deg) with the multibeam
system at the 64m Parkes radio telescope. Follow-up observations with the
Australia Telescope Compact Array (ATCA) reveal an extended HI disk. We derive
an HI mass of 7.5 x 10^10 Msun. Using the HI radius, we estimate a total
dynamical mass of 1.4 x 10^12 Msun, similar to the most massive known disk
galaxies such as Malin 1. HIZOA J0836-43 lies deep in the Zone of Avoidance (l,
b = 262.48 deg, -1.64 deg) where the optical extinction is very high, A_B =
9.8. However, in the near-infrared wavebands, where the extinction is
considerably lower, HIZOA J0836-43 is clearly detected by both DENIS and 2MASS.
Deep AAT near-infrared (Ks and H-band) images show that HIZOA J0836-43 is an
inclined disk galaxy with a prominent bulge (scale length 2.5 arcsec or 1.7
kpc), and an extended disk (scale length 7 arcsec or 4.7 kpc) which can be
traced along the major axis out to a radius of 20 arcsec or 13.4 kpc (at 20
mag/arcsec^2 in Ks). The HI disk is much more extended, having a radius of 66
kpc at 1 Msun/pc^2. Detections in the radio continuum at 1.4 GHz and at 60
micron (IRAS) are consistent with HIZOA J0836-43 forming stars at a rate of ~35
Msun/yr. We compare the properties of HIZOA J0836-43 with those of the most
HI-massive galaxies currently known, UGC 4288, UGC 1752 and Malin 1, all of
which are classified as giant low surface brightness galaxies.


title: Hypernova Signatures in the Late Rebrightening of GRB 050525A

abstract:
  We report observations of GRB 050525A, for which a Gemini North spectrum
shows its redshift to be z = 0.606. This is the third closest long GRB
discovered by Swift. We observed its afterglow using the VLT, Gemini and TNG
telescopes to search for an associated SN. We find that the early-time light
curve is described by a broken power law with a break at t ~ 0.3 d after the
burst. About 5 d after the burst, a flattening is apparent, followed by a
further dimming. Both the magnitude and the shape of the light curve suggest
that a supernova was emerging during the late decay of the afterglow. This
supernova, dubbed SN 2005nc, had a rise time faster than SN 1998bw and a
long-lasting maximum. A spectrum obtained about 20 d (rest-frame) after the GRB
resembles the spectrum of SN 1998bw obtained close to maximum light.


title: Supernova and GRB connection: Observations and Questions

abstract:
  We review the observational status of the supernova/gamma-ray burst
connection. Present data suggest that SNe associated with GRBs form a
heterogeneous class of objects including both bright and faint hypernovae and
perhaps also `standard' Ib/c events. Evidence for association with other types
of core-collapse SNe (e.g. IIn) is much weaker. After combining the local GRB
rate with the local SN-Ibc rate and beaming estimates, we find the ratio
GRB/SNe-Ibc in the range ~0.5-4%. In most SN/GRB associations so far
discovered, the SN and GRB events appear to go off simultaneously. In some
cases data do not exclude that the SN explosion may have preceded the GRB by a
few days. Finally we discuss a number of novel questions started by recent
cases of GRB-SN associations.


title: Hypervelocity Stars. I. The Spectroscopic Survey

abstract:
  We discuss our targeted search for hypervelocity stars (HVSs), stars
traveling with velocities so extreme that dynamical ejection from a massive
black hole is their only suggested origin. Our survey, now half complete, has
successfully identified a total of four probable HVSs plus a number of other
unusual objects. Here we report the most recently discovered two HVSs: SDSS
J110557.45+093439.5 and possibly SDSS J113312.12+010824, traveling with
Galactic rest-frame velocities at least +508+-12 and +418+-10 km/s,
respectively. The other late B-type objects in our survey are consistent with a
population of post main-sequence stars or blue stragglers in the Galactic halo,
with mean metallicity [Fe/H]=-1.3 and velocity dispersion 108+-5 km/s.
Interestingly, the velocity distribution shows a tail of objects with large
positive velocities that may be a mix of low-velocity HVSs and high-velocity
runaway stars. Our survey also includes a number of DA white dwarfs with
unusually red colors, possibly extremely low mass objects. Two of our objects
are B supergiants in the Leo A dwarf, providing the first spectroscopic
evidence for star formation in this dwarf galaxy within the last ~30 Myr.


title:
uvbyCa H beta CCD Photometry of Clusters. VII. The Intermediate-Age
  Anticenter Cluster Melotte 71

abstract:
  CCD photometry on the intermediate-band uvbyCa H beta system is presented for
the anticenter, intermediate-age open cluster, Melotte 71. Restricting the data
to probable single members of the cluster using the color-magnitude diagram and
the photometric indices alone generates a sample of 48 F dwarfs on the
unevolved main sequence. The average E(b-y) = 0.148 +/- 0.003 (s.e.m.) or
E(B-V) = 0.202 +/- 0.004 (s.e.m.), where the errors refer to internal errors
alone. With this reddening, [Fe/H] is derived from both m1 and hk, using H beta
and b-y as the temperature index, with excellent agreement among the four
approaches and a final weighted average of [Fe/H] = -0.17 +/- 0.02 (s.e.m.) for
the cluster, on a scale where the Hyades has [Fe/H] = +0.12. When adjusted for
the higher reddening estimate, the previous metallicity estimates from
Washington photometry and from spectroscopy are now in agreement with the
intermediate-band result. From comparisons to isochrones of appropriate
metallicity, the cluster age and distance are determined as 0.9 +/- 0.1 Gyr and
(m-M) = 12.2 +/- 0.1 or (m-M)_0 = 11.6 +/- 0.1. At this distance from the sun,
Mel 71 has a galactocentric distance of 10.0 kpc on a scale where the sun is
8.5 kpc from the galactic center. Based upon its age, distance, and elemental
abundances, Mel 71 appears to be a less populous analog to NGC 3960.


title: Protecting Life in the Milky Way: Metals Keep the GRBs Away

abstract:
  The host galaxies of the five local, z<0.25, long-duration gamma-ray bursts,
each of which had a well-documented associated supernova, are all faint and
metal-poor compared to the population of local star-forming galaxies. We
quantify this statement by using a previous analysis of star-forming galaxies
(z<0.2) from the Sloan Digital Sky Survey to estimate the fraction of local
star formation as a function of host galaxy oxygen abundance. We find that only
a small fraction (<25%) of current star formation occurs in galaxies with
oxygen abundance 12+log(O/H)<8.6, i.e., about half that of the Milky Way.
However, all five low-z GRB hosts have oxygen abundance below this limit, in
three cases very significantly so. If GRBs traced local star formation
independent of metallicity, the probability of obtaining such low abundances
for all five hosts would be P~0.1%. We conclude that GRBs trace only
low-metallicity star formation, and that the Milky Way has been too metal rich
to host long GRBs for at least the last several billion years. This result has
implications for the potential role of GRBs in mass extinctions, for searches
for recent burst remnants in the Milky Way and other large galaxies, for
non-detections of late radio emission from local core-collapse supernovae, and
for the production of cosmic rays in the local Universe. We also find that the
isotropic energy release of these five GRBs, E_iso, steeply decreases with
increasing host oxygen abundance, suggesting an upper metallicity limit for
``cosmological'' GRBs at ~0.15 Z_solar. (Abridged)


title: The Pierre Auger Observatory progress and first results

abstract:
  The Pierre Auger Observatory was designed for a high statistics, full sky
study of cosmic rays at the highest energies. Energy, direction and composition
measurements are intended to illuminate the mysteries of the most energetic
particles in nature. The Auger Observatory utilizes a surface array together
with air fluorescence telescopes which together provide a powerful instrument
for air shower reconstruction. The southern part of the Auger Observatory, now
under construction in the Province of Mendoza, Argentina, is well over half
finished. Active detectors have been recording events for one and a half years.
Preliminary results based on this first data set are presented.


title:
Spitzer/MIPS Limits on Asteroidal Dust in the Pulsar Planetary System
  PSR B1257+1

abstract:
  With the MIPS camera on Spitzer, we have searched for far-infrared emission
from dust in the planetary system orbiting pulsar PSR 1257+12. With accuracies
of 0.05 mJy at 24 um and 1.5 mJy at 70 um, photometric measurements find no
evidence for emission at these wavelengths. These observations place new upper
limits on the luminosity of dust with temperatures between 20 and 1000 K. They
are particularly sensitive to dust temperatures of 100-200 K, for which they
limit the dust luminosity to below $3 \times 10^{-5}$ of the pulsar's spin-down
luminosity, three orders of magnitude better than previous limits. Despite
these improved constraints on dust emission, an asteroid belt similar to the
Solar System's cannot be ruled out.


title:
2D and 3D MHD Simulations of Disk Accretion by Rotating Magnetized
  Stars: Search for Variability

abstract:
  We performed 2D and full 3D magnetohydrodynamic simulations of disk accretion
to a rotating star with an aligned or misaligned dipole magnetic field. We
investigated the rotational equilibrium state and derived from simulations the
ratio between two main frequencies: the spin frequency of the star and the
orbital frequency at the inner radius of the disk. In 3D simulations we
observed different features related to the non-axisymmetry of the
magnetospheric flow. These features may be responsible for high-frequency
quasi-periodic oscillations (QPOs). Variability at much lower frequencies may
be connected with restructuring of the magnetic flux threading the inner
regions of the disk. Such variability is specifically strong at the propeller
stage of evolution.


title:
Anisotropic Thermal Conduction in Supernova Remnants: Relevance to Hot
  Gas Filling Factors in the Magnetized ISM

abstract:
  We explore the importance of anisotropic thermal conduction in the evolution
of supernova remnants via numerical simulations. The mean temperature of the
bubble of hot gas is decreased by a factor of ~3 compared to simulations
without thermal conduction, together with an increase in the mean density of
hot gas by a similar factor. Thus, thermal conduction greatly reduces the
volume of hot gas produced over the life of the remnant. This underscores the
importance of thermal conduction in estimating the hot gas filling fraction and
emissivities in high-stage ions in Galactic and proto-galactic ISMs.


title: Sunrise: Polychromatic Dust Radiative Transfer in Arbitrary Geometries

abstract:
  This paper describes Sunrise, a parallel, free Monte-Carlo code for the
calculation of radiation transfer through astronomical dust. Sunrise uses an
adaptive-mesh refinement grid to describe arbitrary geometries of emitting and
absorbing/scattering media, with spatial dynamical range exceeding 10^4, and it
can efficiently generate images of the emerging radiation at arbitrary points
in space. In addition to the monochromatic radiative transfer typically used by
Monte-Carlo codes, Sunrise is capable of propagating a range of wavelengths
simultaneously. This ``polychromatic'' algorithm gives significant improvements
in efficiency and accuracy when spectral features are calculated. Sunrise is
used to study the effects of dust in hydrodynamic simulations of interacting
galaxies, and the procedure for this is described. The code is tested against
previously published results.


title: The First VERITAS Telescope

abstract:
  The first atmospheric Cherenkov telescope of VERITAS (the Very Energetic
Radiation Imaging Telescope Array System) has been in operation since February
2005. We present here a technical description of the instrument and a summary
of its performance. The calibration methods are described, along with the
results of Monte Carlo simulations of the telescope and comparisons between
real and simulated data. The analysis of TeV $\gamma$-ray observations of the
Crab Nebula, including the reconstructed energy spectrum, is shown to give
results consistent with earlier measurements. The telescope is operating as
expected and has met or exceeded all design specifications.


title: Origin of Disc Lopsidedness in the Eridanus Group of Galaxies

abstract:
  The HI surface density maps for a sample of 18 galaxies in the Eridanus group
are Fourier analysed. This analysis gives the radial variation of the
lopsidedness in the HI spatial distribution. The lopsidedness is quantified by
the Fourier amplitude $A_1$ of the $m=1$ component normalized to the average
value. It is also shown that in the radial region where the stellar disc and HI
overlap, their $A_1$ coefficients are comparable. All the galaxies studied show
significant lopsidedness in HI. The mean value of $A_1$ in the inner regions of
the galaxies (1.5 - 2.5 scale lengths) is $\geq 0.2$. This value of $A_1$ is
twice the average value seen in the field galaxies. Also, the lopsidedness is
found to be smaller for late-type galaxies, this is opposite to the trend seen
in the field galaxies. These two results indicate a different physical origin
for disc lopsidedness in galaxies in a group environment compared to the field
galaxies. Further, a large fraction ($\sim$ 30%) shows a higher degree of
lopsidedness ($A_1 \geq 0.3$). It is also seen that the disk lopsidedness
increases with the radius as demonstrated in earlier studies, but over a radial
range that is two timeslarger than done in the previous studies. The average
lopsidedness of the halo potential is estimated to be $\sim 10$%, assuming that
the lopsidedness in HI disc is due to its response to the halo asymmetry.


title:
Shapes of Stellar Systems and Dark Halos from Simulations of Galaxy
  Major Mergers

abstract:
  Using a sample of 89 snapshots from 58 hydrodynamic binary galaxy major
merger simulations, we find that stellar remnants are mostly oblate while dark
matter halos are mostly prolate or triaxial. The stellar minor axis and the
halo major axis are almost always nearly perpendicular. This can be understood
by considering the influence of angular momentum and dissipation during the
merger. If binary mergers of spiral galaxies are responsible for the formation
of elliptical galaxies or some subpopulation thereof, these galaxies can be
expected to be oblate and inhabit their halos with the predicted shapes and
orientations. These predictions are potentially relevant to observational
studies of weak gravitational lensing, where one must stack many optically
aligned galaxies in order to determine the shape of the resulting stacked mass
distribution. The simple relationship between the dark and luminous matter
presented here can be used to guide the stacking of galaxies to minimize the
information lost.


title: Effect of r-mode instability on the evolution of isolated strange stars

abstract:
  We studied the evolution of isolated strange stars synthetically, considering
the influence of {\it r-}mode instability. Our results show that the cooling of
strange stars with non-ultra strong magnetic fields is delayed by the heating
due to the {\it r-}modes damping during million years, while the spin-down of
the stars is dominated by gravitational radiation. Especially for the strange
stars in a possible existing color-flavor locked phase, the effect of the {\it
r-}mode instability on the evolution of the stars becomes extremely important
since the viscosity, the neutrino emissivity, and the specific heat involving
paring quarks are blocked. It leads to the cooling of these color
superconducting stars is very slow, and the stars can remain high temperature
within million years differing completely from previous understanding. In this
case, a strange star in color-flavor locked phase can be located at the bottom
of its {\it r-}mode instability window for a long time, but does not spin down
to a very low frequency within hours.


title:
Lensing Effects on Gravitational Waves in a Clumpy Universe -Effects of
  Inhomogeneity on the Distance-Redshift Relation-

abstract:
  The distance-redshift relation determined by means of gravitational waves in
the clumpy universe is simulated numerically by taking into account the effects
of gravitational lensing. It is assumed that all of the matter in the universe
takes the form of randomly distributed point masses, each of which has the
identical mass $M_L$. Calculations are carried out in two extreme cases:
$\lambda\gg GM_L/c^2$ and $\lambda\ll GM_L/c^2$, where $\lambda$ denotes the
wavelength of gravitational waves. In the first case, the distance-redshift
relation for the fully homogeneous and isotropic universe is reproduced with a
small distance dispersion, whereas in the second case, the distance dispersion
is larger. This result suggests that we might obtain information about the
typical mass of lens objects through the distance-redshift relation gleaned
through observation of gravitational waves of various wavelengths. In this
paper, we show how to set limitations on the mass $M_L$ through the observation
of gravitational waves in the clumpy universe model described above.


title: Synchrotron emission from the T Tauri binary system V773 Tau A

abstract:
  The pre-main sequence binary system V773 Tau A shows remarkable flaring
activity around periastron passage. Here, we present the observation of such a
flare at a wavelength of 3 mm (90 GHz) performed with the Plateau de Bure
Interferometer. We examine different possible causes for the energy losses
responsible for the e-folding time of 2.3 hours of that flare. We exclude
synchrotron, collisional, and inverse Compton losses because they are not
consistent with observational constraints, and we propose that the fading of
the emission is due to the leakage of electrons themselves at each reflection
between the two mirror points of the magnetic structure partially trapping
them. The magnetic structure compatible with both our leakage model and
previous observations is that of a helmet streamer that, as in the solar case,
can occur at the top of the X-ray-emitting, stellar-sized coronal loops of one
of the stars. The streamer may extend up to 20 R and interact with the corona
of the other star at periastron passage, causing recurring flares. The inferred
magnetic field strength at the two mirror points of the helmet streamer is in
the range 0.12 - 125 G, and the corresponding Lorentz factor, gamma, of the
partially trapped electrons is in the range 20 < gamma < 632. We therefore rule
out that the emission could be of gyro-synchrotron nature: the derived high
Lorentz factor proves that the nature of the emission at 90 GHz from this
pre-main binary system is synchrotron radiation.
  Based on observations carried out with the IRAM Plateau de Bure
Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN
(Spain).


title:
The Star-Forming Torus and Stellar Dynamical Black Hole Mass in the
  Seyfert 1 Nucleus of NGC3227

abstract:
  We report R~4300 VLT SINFONI adaptive optics integral field K-band
spectroscopy of the nucleus of the Seyfert 1 galaxy NGC3227 at a spatial
resolution of 0.085" (7pc). We present the morphologies and kinematics of
emission lines and absorption features, and give the first derivation of a
black hole mass in a Seyfert 1 nucleus from spatially resolved stellar
dynamics. We show that the gas in the nucleus has a mean column density of
order 10^{24}-10^{25}cm^{-2} and that it is geometrically thick, in agreement
with the standard `molecular torus' scenario. We discuss which heating
processes may be responsible for maintaining the vertical height of the torus.
We have also resolved the nuclear stellar distribution, and find that within a
few parsecs of the AGN there has been an intense starburst, the most recent
episode of which began ~40Myr ago but has now ceased. The current luminosity of
stars within 30pc of the AGN, ~3x10^9L_sun, is comparable to that of the AGN.
Based on a comparison of the respective size scales, we argue that the star
formation has been occuring in the obscuring torus. Finally, we present the
first derivation of a black hole mass in a Seyfert 1 nucleus from stellar
dynamics which marginally spatially resolve the black hole's sphere of
influence. We apply Schwarzschild orbit superposition models to our full
2-dimensional data and derive the mass of the black hole, paying careful
attention to the input parameters which are often uncertain: the contribution
of the large scale bulge and its mass-to-light ratio; the recent star formation
in the nucleus and its mass-to-light ratio; the contribution of the gas mass to
the potential; and the inclination. Our models yield a 1sigma range for the
black hole mass of M_{BH} = 7x10^6-2x10^7M_sun.


title:
Empirical testing of Tsallis' Thermodynamics as a model for dark matter
  halos

abstract:
  We study a dark matter halo model from two points of view: the ``stellar
polytrope'' (SP) model coming from Tsallis' thermodynamics, and the one coming
from the Navarro-Frenk-White (NFW) paradigm. We make an appropriate comparison
between both halo models and analyzing the relations between the global
physical parameters of observed galactic disks, coming from a sample of actual
galaxies, with the ones of the unobserved dark matter halos, we conclude that
the SP model is favored over the NFW model in such a comparison.


title: Entropy considerations in constraining the mSUGRA parameter space

abstract:
  We explore the use of two criteria to constraint the allowed parameter space
in mSUGRA models. Both criteria are based in the calculation of the present
density of neutralinos as dark matter in the Universe. The first one is the
usual ``abundance'' criterion which is used to calculate the relic density
after the ``freeze-out'' era. To compute the relic density we used the
numerical public code micrOMEGAs. The second criterion applies the
microcanonical definition of entropy to a weakly interacting and
self-gravitating gas evaluating then the change in the entropy per particle of
this gas between the ``freeze-out'' era and present day virialized structures.
An ``entropy-consistency'' criterion emerges by comparing theoretical and
empirical estimates of this entropy. The main objective of our work is to
determine for which regions of the parameter space in the mSUGRA model are both
criteria consistent with the 2$\sigma$ bounds according to WMAP for the relic
density: $0.0945<\Omega_{CDM}h^2<0.1287$. As a first result, we found that for
$A_0=0$, sgn$\mu=+$, small values of tan$\beta$ are not favored; only for
tan$\beta\simeq50$ are both criteria significantly consistent.


title: UBVRI twilight sky brightness at ESO-Paranal

abstract:
  Twilight studies have proved to be important tools to analyze the atmospheric
structure with interesting consequences on the characterization of astronomical
sites. Active discussions on this topic have been recently restarted in
connection with the evaluation of Dome C, Antarctica as a potential
astronomical site and several site-testing experiments, including twilight
brightness measurements, are being prepared. The present work provides for the
first time absolute photometric measurements of twilight sky brightness for
ESO-Paranal (Chile), which are meant both as a contribution to the site
monitoring and as reference values in the analysis of other sites, including
Dome C. The UBVRI twilight sky brightness was estimated on more than 2000 FORS1
archival images, which include both flats and standard stars observations taken
in twilight, covering a Sun zenith distance range 94-112 deg. The comparison
with a low altitude site shows that Paranal V twilight sky brightness is about
30% lower, implying that some fraction of multiple scattering has to take place
at an altitude of a few km above the sea level.


title:
Power spectrum of the SDSS luminous red galaxies: constraints on
  cosmological parameters

abstract:
  In this paper we determine the constraints on cosmological parameters using
the CMB data from the WMAP experiment together with the recent power spectrum
measurement of the SDSS Luminous Red Galaxies (LRGs). Specifically, we focus on
spatially flat, low matter density models with adiabatic Gaussian initial
conditions. The spatial flatness is achieved with an additional quintessence
component whose equation of state parameter w_eff is taken to be independent of
redshift. Throughout most of the paper we do not allow any massive neutrino
contribution and also the influence of the gravitational waves on the CMB is
taken to be negligible. The analysis is carried out separately for two cases:
(i) using the acoustic scale measurements as presented in H\"utsi (2006), (ii)
using the full SDSS LRG power spectrum and its covariance matrix. We are able
to obtain a very tight constraint on the Hubble constant: H_0 = 70.8
^{+2.1}_{-2.0} km/s/Mpc, which helps in breaking several degeneracies between
the parameters and allows us to determine the low redshift expansion law with
much higher accuracy than available from the WMAP + HST data alone. The
positive deceleration parameter q_0 is found to be ruled out at 5.5 \sigma
confidence level. Finally, we extend our analysis by investigating the effects
of relaxing the assumption of spatial flatness and also allow for a
contribution from massive neutrinos.


title: Stellar Populations with ELTs

abstract:
  The star formation, mass assembly and chemical enrichment histories of
galaxies, and their present distributions of dark matter, remain encoded in
their stellar populations. Distinguishing the actual distribution functions of
stellar age, metallicity and kinematics at several locations in a range of
galaxies, sampling across Hubble types and representative environments, is the
information required for a robust description of galaxy histories. Achieving
this requires large aperture, to provide the sensitivity to reach a range of
environs and Hubble types beyond the Local Group, to provide high spatial
resolution, since the fields are crowded, and preferably with optical
performance since age-sensitivity is greatest near the main-sequence turn-off,
and metallicity-sensitivity for these warm stars is greatest in the optical.


title: The Supernova Gamma-Ray Burst Connection

abstract:
  The chief distinction between ordinary supernovae and long-soft gamma-ray
bursts (GRBs) is the degree of differential rotation in the inner several solar
masses when a massive star dies, and GRBs are rare mainly because of the
difficulty achieving the necessary high rotation rate. Models that do provide
the necessary angular momentum are discussed, with emphasis on a new single
star model whose rapid rotation leads to complete mixing on the main sequence
and avoids red giant formation. This channel of progenitor evolution also gives
a broader range of masses than previous models, and allows the copious
production of bursts outside of binaries and at high redshifts. However, even
the production of a bare helium core rotating nearly at break up is not, by
itself, a sufficient condition to make a gamma-ray burst. Wolf-Rayet mass loss
must be low, and will be low in regions of low metallicity. This suggests that
bursts at high redshift (low metallicity) will, on the average, be more
energetic, have more time structure, and last longer than bursts nearby. Every
burst consists of three components: a polar jet (~0.1 radian), high energy,
subrelativistic mass ejection (~1 radian), and low velocity equatorial mass
that can fall back after the initial explosion. The relative proportions of
these three components can give a diverse assortment of supernovae and high
energy transients whose properties may vary with redshift.


title: GMASS, Unveiling Distant Massive Galaxies with Spitzer

abstract:
  One of the main questions of galaxy formation is how and when galaxies
assembled their mass. Observations suggest that most mass assembly and star
formation occured at 1 < z < 3. However, in the same redshift range, fully
assembled old and massive galaxies co-exist with star-bursting systems still in
their assembling stage. In order to explore galaxy evolution in this critical
redshift range, we started a project called GMASS (Galaxy Mass Assembly
ultra-deep Spectroscopic Survey) based on an 145 hours ESO Large Program and
aimed at doing ultradeep spectroscopy with the VLT of a sample of high redshift
galaxies slected with IRAC/Spitzer m(4.5mu) < 23, z(phot) > 1.4) from the
GOODS-South/HUDF region. The selection at 4.5 micron is crucial to select high
redshift galaxies based on the stellar mass or objects affected by strong dust
extinction. The spectroscopic deep integration times (15 - 50 hours) are needed
to identify unambiguously the redshift and nature of these galaxies, which
redshifts are mostly in the "desert" where spectroscopy is traditionally
difficult due to the absence of strong emission lines at optical wavelengths.
The survey is almost complete and some preliminary results are presented here.


title: Testing the BH 176 and Berkeley 29 Association with GASS/Monoceros

abstract:
  It has been previously noted that the outermost open clusters in the Milky
Way seem to lie in a string-like configuration that is coincident with, and may
be associated to, the Galactic anticenter stellar structure (GASS) or the
``Monoceros Ring''. Among the clusters that have been suggested to be
associated with GASS are Berkeley 29 (Be29) and BH176, which have recently had
their proper motion determined. Matching the new proper motion determinations
to previously published radial velocities, we attempt to derive orbits for Be29
and BH176. The preliminary orbit for Be29 provides tantalizing evidence for a
non-standard formation, however better proper motions are needed to determine
whether its origin is due to normal formation or accretion.


title: Entropy perturbations and large-scale magnetic fields

abstract:
  An appropriate gauge-invariant framework for the treatment of magnetized
curvature and entropy modes is developed. It is shown that large-scale magnetic
fields, present after neutrino decoupling, affect curvature and entropy
perturbations. The evolution of different magnetized modes is then studied
across the matter-radiation transition both analytically and numerically. From
the observation that, after equality (but before decoupling) the (scalar)
Sachs-Wolfe contribution must be (predominantly) adiabatic, constraints on the
magnetic power spectra are deduced. The present results motivate the
experimental analysis of more general initial conditions of CMB anisotropies
(i.e. mixtures of magnetized adiabatic and isocurvature modes during the
pre-decoupling phase). The role of the possible correlations between the
different components of the fluctuations is partially discussed.


title:
The Impact of Starbursts and Post-Starbursts on the Photometric
  Evolution of High Redshift Galaxies

abstract:
  We present evolutionary synthesis models for galaxies of spectral types Sa
through Sd with starbursts of various strengths triggered at various redshifts
and study their photometric evolution before, during, and after their bursts in
a cosmological context. We find that bursts at high redshift, even very strong
ones, only cause a small blueing of their intrinsically blue young parent
galaxies. At lower redshift, even small bursts cause a significant blueing of
their intrinsically redder galaxies. While the burst phase is generally short,
typically a few hundred Myr in normal-mass galaxies, the postburst stage with
its red colors and, in particular the very red ones for early bursts at high
redshift, is much longer, of the order of several Gyr. Even without any dust,
which in the postburst stage is not expected to play an important role anyway,
models easily reach the colors of EROs in the redshift range z=2 through z=0.5
after starbursts at redshifts between 2 and 4. We therefore propose a third
alternative for the ERO galaxies beyond the two established ones of passive
galaxies vs. dusty starbursts: the dust-free post-(strong-)starbursts. A very
first comparison of our models to HDF data with photometric redshifts shows
that almost all of the outliers that could not be described with our chemically
consistent models for undisturbed normal galaxy types E through Sd can now be
explained very well. Galaxies in the redshift range from z=2.5 to z=0.5 that
are redder, and in some cases much redder, than our reddest undisturbed model
for a high-metallicity classical elliptical are well described by
post-starburst models after starbursts at redshifts between 2 and 4. Galaxies
bluer than our bluest low metallicity Sd model, most of which have redshifts
lower than 1, are well explained by ongoing starbursts.


title:
Single Field Inflation models allowed and ruled out by the three years
  WMAP data

abstract:
  We study the single field slow-roll inflation models that better fit the
available CMB and LSS data including the three years WMAP data: new inflation
and hybrid inflation. We study them as effective field theories in the
Ginsburg-Landau context: a trinomial potential turns out to be a simple and
well motivated model. The compute the spectral index n_s of the adiabatic
fluctuations, the ratio r of tensor to scalar fluctuations and the running
index d n_s/dln k, derive explicit formulae and provide relevant plots. In new
inflation, and for the three years WMAP central value n_s = 0.95, we predict
0.03<r<0.04 and -0.00070<d n_s/d ln k<-0.00055. In hybrid inflation, and for
n_s = 0.95, we predict r = 0.2 and dn_s/dln k=-0.001.We find in new inflation
n_s bounded from above by n_{smax} = 0.9615 and that r is a two valued function
of n_s in the interval 0.96<n_s<0.9615. In the first branch we find r<r_{max} =
0.1148.In hybrid inflation we find a critical value mu_{0 crit}^2 for the mass
parameter mu_0^2 of the field sigma coupled to the inflaton.For mu_0^2<
Lambda_0 M_{Pl}^2/192, hybrid inflation is ruled out by the WMAP three years
data since it yields n_s>1. Hybrid inflation for mu_0^2>Lambda_0 M_{Pl}^2/192
can fullfill all the present CMB+LSS data. Even if chaotic inflation predicts
n_s values compatible with the data, chaotic inflation is disfavoured since it
predicts a too high value for the ratio r=0.27. The model which best fits the
current data and which best prepares the way to the expected data r < 0.1, is
the trinomial potential with negative mass term: new inflation.


title:
On the primordial scenario for abundance variations within globular
  clusters. The isochrone test

abstract:
  Self-enrichment processes occurring in the early stages of a globular cluster
lifetime are generally invoked to explain the observed CNONaMgAl abundance
anticorrelations within individual Galactic globulars.We have tested, with
fully consistent stellar evolution calculations, if theoretical isochrones for
stars born with the observed abundance anticorrelations satisfy the
observational evidence that objects with different degrees of these anomalies
lie on essentially identical sequences in the Color-Magnitude-Diagram (CMD). To
this purpose, we have computed for the first time low-mass stellar models and
isochrones with an initial metal mixture that includes the extreme values of
the observed abundance anticorrelations, and varying initial He mass fractions.
Comparisons with 'normal' alpha-enhanced isochrones and suitable Monte Carlo
simulations that include photometric errors show that a significant broadening
of the CMD sequences occurs only if the helium enhancement is extremely large
(in this study, when Y=0.35) in the stars showing anomalous abundances. Stellar
luminosity functions up to the Red Giant Branch tip are also very weakly
affected, apart from - depending on the He content of the polluting material -
the Red Giant Branch bump region. We also study the distribution of stars along
the Zero Age Horizontal Branch, and derive general constraints on the relative
location of objects with and without abundance anomalies along the observed
horizontal branches of globular clusters.


title: Stellar populations in the nuclei of late-type spiral galaxies

abstract:
  (Abridged) As part of an ongoing effort to study the stellar nuclei of very
late-type, bulge-less spirals, we present results from a high-resolution
spectroscopic survey of nine such nuclear star clusters, undertaken with
VLT/UVES. We fit the spectra with population synthesis models and measure
Lick-type indices to determine mean luminosity-weighted ages, which range from
4.1*10^7 to 1.1*10^10 years and are insensitive to assumed metallicity or
internal extinction. The average metallicity of nuclear clusters in late-type
spirals is slightly sub-solar (<Z> = 0.015) but shows significant scatter. The
fits also show that the nuclear cluster spectra are best described by a mix of
several generations of stars. This is supported by the fact that only models
with composite stellar populations yield mass-to-light ratios that match those
obtained from dynamical measurements. The last star formation episode was on
average 34 Myr ago, while all clusters experienced some star formation in the
last 100 Myr. We thus conclude that the nuclear clusters undergo repeated
episodes of star formation. The robustness with respect to possible
contamination from the underlying galaxy disk is demonstrated by comparison to
spectra obtained with HST/STIS. Combining these results with those from Walcher
et al. (2005), we have thus shown that the stellar nuclei of these bulge-less
galaxies are massive and dense star clusters that form stars recurrently until
the present day. This unique set of properties is likely due to the central
location of these clusters in their host galaxies.


title: Red Giant stars in the Large Magellanic Cloud clusters

abstract:
  We present deep J,H,Ks photometry and accurate Color Magnitude Diagrams down
to K ~18.5, for a sample of 13 globular clusters in the Large Magellanic Cloud.
This data set combined with the previous sample of 6 clusters published by our
group gives the opportunity to study the properties of giant stars in clusters
with different ages (ranging from ~80 Myr up to ~3.5 Gyr). Quantitative
estimates of star population ratios (by number and luminosity) in the
Asymptotic Giant Branch, the Red Giant Branch and the He-clump, have been
obtained and compared with theoretical models in the framework of probing the
so-called phase transitions. The AGB contribution to the total luminosity
starts to be significant at ~200 Myr and reaches its maximum at ~5-600 Myr,
when the RGB Phase Transition is starting. At ~900 Myr the full developing of
an extended and well populated RGB has been completed. Both the occurrence of
the AGB and RGB Phase Transitions are sharp events, lasting a few hundreds Myr
only. These empirical results agree very well with the theoretical predictions
of simple stellar population models based on canonical tracks and the
fuel-consumption approach.


title:
HST/STIS Spectra of Nuclear Star Clusters in Spiral Galaxies: Dependence
  of Age and Mass On Hubble Type

abstract:
  (Abridged) We study the nuclear star clusters in spiral galaxies of various
Hubble types using spectra obtained with STIS on-board HST. We observed the
nuclear clusters in 40 galaxies, selected from two previous HST/WFPC2 imaging
surveys. The spectra provide a better separation of cluster light from
underlying galaxy light than is possible with ground-based spectra. To infer
the star formation history, metallicity and dust extinction, we fit weighted
superpositions of single-age stellar population templates to the spectra. The
luminosity-weighted age ranges from 10 Myrs to 10 Gyrs. The stellar populations
of NCs are generally best fit as a mixture of populations of different ages.
This indicates that NCs did not form in a single event, but instead they had
additional star formation long after the oldest stars formed. On average, the
sample clusters in late-type spirals have a younger luminosity-weighted mean
age than those in early-type spirals (log(age/yr) = 8.37+/-0.25 vs.
9.23+/-0.21). The average cluster masses are smaller in late-type spirals than
in early-type spirals (log(M/Msun) = 6.25+/-0.21 vs. 7.63+/-0.24), and exceed
the masses typical of globular clusters. The cluster mass correlates strongly
with both the Hubble type of the host galaxy and the luminosity of its bulge.
The latter correlation has the same slope as the well-known correlation between
supermassive black hole mass and bulge luminosity. The properties of both
nuclear clusters and black holes are therefore intimately connected to the
properties of the host galaxy.


title:
On vector mode contribution to CMB temperature and polarization from
  local strings

abstract:
  In a recent publication, we used the data from WMAP and SDSS to constrain the
primordial perturbations and to predict the B-mode polarization sourced by
cosmic string networks. We have been alerted by A. Slosar to the existence of
errors in the code we used to calculate the Cosmic Microwave Background
anisotropies from cosmic strings. Correcting the errors leads to a significant
increase in the vector mode contribution to the CMB temperature and
polarization anisotropies as well as an overall renormalization of the various
string spectra. In these notes we explain the nature of the errors and discuss
their implications for previously published constraints on cosmic strings based
on this code. The chief change in our results is that our derived limit for the
cosmic string tension is strengthened: G\mu < 1.8 (2.7) * 10^{-7} at 68 (95)%
confidence. We also note that the newly-enhanced vector mode contribution
produces a greatly-increased amplitude for B-mode polarization in the CMB which
could exceed the B-mode power produced by the lensing of primordial E-mode
polarization into B-mode polarization.


title: On mini-halo encounters with stars

abstract:
  We study, analytically and numerically, the energy input into dark matter
mini-haloes by interactions with stars. We find that the fractional energy
input in simulations of Plummer spheres agrees well with the impulse
approximation for small and large impact parameters, with a rapid transition
between these two regimes. Using the impulse approximation the fractional
energy input at large impact parameters is fairly independent of the mass and
density profile of the mini-halo, however low-mass mini-haloes experience a
greater fractional energy input in close encounters. We formulate a fitting
function which encodes these results and use it to estimate the disruption
timescales of mini-haloes, taking into account the stellar velocity dispersion
and mass distribution. For mini-haloes with mass M< {\cal O}(10^{-7} M_{\odot}
on typical orbits which pass through the disc, we find that the estimated
disruption timescales are independent of mini-halo mass, and are of order the
age of the Milky Way. For more massive mini-haloes the estimated disruption
timescales increase rapidly with increasing mass.


title: B polarization of cosmic microwave background as a tracer of strings

abstract:
  String models can produce successful inflationary scenarios in the context of
brane collisions and in many of these models cosmic strings may also be
produced. In scenarios such as KKLMMT the string contribution is naturally
predicted to be well below the inflationary signal for cosmic microwave
background (CMB) temperature anisotropies, in agreement with the existing
limits. We find that for $B$ type polarization of CMB the situation is reversed
and the dominant signal comes from vector modes generated by cosmic strings,
which exceeds the gravity wave signal from both inflation and strings. The
signal can be detected for a broad range of parameter space: future
polarization experiments may be able to detect the string signal down to the
string tension $G\mu=10^{-9}$, although foregrounds and lensing are likely to
worsen these limits. We argue that the optimal scale to search for the string
signature is at $\ell\sim 1000$, but in models with high optical depth the
signal from reionization peak at large scales is also significant. The shape of
the power spectrum allows one to distinguish the string signature from the
gravity waves from inflation, but only with a sufficiently high angular
resolution experiment


title:
Radiative recombination data for modelling dynamic finite-density
  plasmas

abstract:
  We have calculated partial final-state resolved radiative recombination (RR)
rate coefficients from the initial ground and metastable levels of all elements
up to and including Zn, plus Kr, Mo, and Xe, for all isoelectronic sequences up
to Na-like forming Mg-like. The data are archived according to the Atomic Data
and Analysis Structure (ADAS) data class adf48, which spans a temperature range
of z^2(10^1 - 10^7)K, where z is the initial ion charge. Fits to total rate
coefficients have been determined, for both the ground and metastable levels,
and those for the ground are presented here. Comparison is made both with
previous RR rate coefficients and with (background) R-matrix photoionization
cross sections. This RR database complements a DR database already produced and
both are being used to produce updated ionization balances for both (electron)
collisionally ionized and photoionized plasmas.


title:
Amplified Doppler shift observed in diffraction images as function of
  the COBE "ether drift" direction

abstract:
  We report results on an ``one-way light path'' laser diffraction experiment
as a function of the laser beam alignment relative to the Earth's velocity
vector obtained by COBE measurements of the Doppler shift in the cosmic
microwave background radiation (CMBR). An amplified Doppler shift is observed
in the diffraction images, and the effect is compatible with a ``dipole'' speed
of light anisotropy due to Earth's motion relative to the ``CMBR rest frame'',
with an amplitude of $\delta c/\bar{c}=0.00123$. This amplitude coincides with
the value of the dipole temperature anisotropy $\delta T/\bar{T}=0.00123$ of
the CMBR obtained by COBE. Our results point out that it is not possible to
neglect the preferred frame imposed by the cosmology and they are well
described by the Ether Gauge Theory (an extension of the Lorentz's ether
theory) and it satisfies the cosmological time boundary condition.


title:
Low T/|W| dynamical instabilities in differentially rotating stars:
  Diagnosis with canonical angular momentum

abstract:
  We study the nature of non-axisymmetric dynamical instabilities in
differentially rotating stars with both linear eigenmode analysis and
hydrodynamic simulations in Newtonian gravity. We especially investigate the
following three types of instability; the one-armed spiral instability, the low
T/|W| bar instability, and the high T/|W| bar instability, where T is the
rotational kinetic energy and W is the gravitational potential energy. The
nature of the dynamical instabilities is clarified by using a canonical angular
momentum as a diagnostic. We find that the one-armed spiral and the low T/|W|
bar instabilities occur around the corotation radius, and they grow through the
inflow of canonical angular momentum around the corotation radius. The result
is a clear contrast to that of a classical dynamical bar instability in high
T/|W|. We also discuss the feature of gravitational waves generated from these
three types of instability.


title:
Removing the Microlensing Blending-Parallax Degeneracy Using Source
  Variability

abstract:
  Microlensing event MACHO 97-SMC-1 is one of the rare microlensing events for
which the source is a variable star, simply because most variable stars are
systematically eliminated from microlensing studies. Using observational data
for this event, we show that the intrinsic variability of a microlensed star is
a powerful tool to constrain the nature of the lens by breaking the degeneracy
between the microlens parallax and the blended light. We also present a
statistical test for discriminating the location of the lens based on the
\chi^2 contours of the vector \Lambda, the inverse of the projected velocity.
We find that while SMC self lensing is somewhat favored over halo lensing,
neither location can be ruled out with good confidence.


title: UV Radiative Feedback on High-Redshift Proto-Galaxies

abstract:
  We use three-dimensional hydrodynamic simulations to investigate the effects
of a transient photoionizing ultraviolet (UV) flux on the collapse and cooling
of pregalactic clouds. These clouds have masses in the range 10^5 -10^7 M_sun,
form at high redshifts (z>18), are assumed to lie within the short-lived
cosmological HII regions around the first generation of stars. In addition, we
study the combined effects of this transient UV flux and a persistent
Lyman-Werner (LW) background from distant sources. In the absence of a LW
background, we find that a critical specific intensity of J_UV ~ 0.1 x 10^-21
ergs s^-1 cm^-2 Hz^-1 sr^-1 demarcates a transition from net negative to
positive feedback for the halo population. A weaker UV flux stimulates
subsequent star formation inside the fossil HII regions, by enhancing the H_2
molecule abundance. A stronger UV flux significantly delays star-formation by
reducing the gas density, and increasing the cooling time, at the centers of
collapsing halos. At a fixed J_UV, the sign of the feedback also depends
strongly on the density of the gas at the time of UV illumination. Regardless
of the whether the feedback is positive or negative, we find that once the UV
flux is turned off, its impact stars to diminish after ~30% of the Hubble time.
In the more realistic case when a LW background is present, with J_LW > 0.01 x
10^-21 ergs s^-1 cm^-2 Hz^-1 sr^-1, strong suppression persists down to the
lowest redshift (z=18) in our simulations. Finally, we find evidence that
heating and photoevaporation by the transient UV flux renders the ~10^6 M_sun
halos inside fossil HII regions more vulnerable to subsequent H_2
photo-dissociation by a LW background.


title:
The End of the Reionization Epoch Probed by Ly-alpha Emitters at z=6.5
  in the Subaru Deep Field

abstract:
  We report an extensive search for Lyman-alpha emitters (LAEs) at z=6.5 in the
Subaru Deep Field. Subsequent spectroscopy with Subaru and Keck identified
eight more LAEs, giving a total of 17 spectroscopically confirmed LAEs at
z=6.5. Based on this spectroscopic sample of 17, complemented by a photometric
sample of 58 LAEs, we have derived a more accurate Lyman-alpha luminosity
function of LAEs at z=6.5, which reveals an apparent deficit at the bright end
of ~0.75 mag fainter L*, compared with that observed at z=5.7. The difference
in the LAE luminosity functions between z=5.7 and 6.5 is significant at the
3-sigma level, which is reduced to 2-sigma when cosmic variance is taken into
account. This result may imply that the reionization of the universe has not
been completed at z=6.5. We found that the spatial distribution of LAEs at
z=6.5 was homogeneous over the field. We discuss the implications of these
results for the reionization of the universe.


title:
New observational techniques and analysis tools for wide field CCD
  surveys and high resolution astrometry

abstract:
  (Abridged) In the first part of this thesis, a general methodology for
applying image deconvolution to wide-field CCD imagery. Results show that
wavelet-based deconvolution can increase limiting magnitude up to 0.6 mag and
improve limiting resolution 1 pixel with respect to original image with no
astrometric accuracy degradation.
  In the second part, a new observational technique based on CCD fast drift
scanning has been proposed for lunar occultations (LO) and speckle
interferometry. This enables all kind of professional and high-end amateur
observatories to perform such kind of observations.
  For LO, 16 new binaries up to 2mas of projected separation were detected and
stellar diameters measurements in the 7 mas regime were obtained with that CCD
and IR subarray based techniques. A new wavelet-based LO reduction pipeline was
implemented.
  For speckle, CCD fast drift scanning technique was validated with the
observation of four binary systems with well determined orbits. The results of
separation, position angle and magnitude difference are in accordance with
published measurements. A new approach for calibrating speckle transfer
function from the binary power spectrum itself has been introduced. It does not
require point source observations, which gives a more effective use of
observation time.


title:
A Simple Two-Parameter Characterization of Gamma-Ray Burst Time
  Histories

abstract:
  A simple scheme delineates Long GRBs with similar time histories using the
Internal Luminosity Function power-law index and the spectral lag. Several
generalizations are made about time history morphologies: 1) GRBs with long
spectral lags contain fewer pulses that are broader than those found in bursts
with short spectral lags, 2) short-lag bursts with small ILF power-law indices
have many narrow pulses and are highly variable, while long-lag bursts with
small ILF power-law indices are characterized by broad, smooth pulses and have
low variability.
  GRB time history morphologies primarily identify intrinsic rather than
extrinsic characteristics based on correlations with gamma-ray luminosity,
afterglow luminosity, and numbers of pulses. These characteristics result
because internal relativistic effects due to bulk Lorentz factor are larger
than cosmological effects, and because the numbers and shapes of pulses
indicate different efficiencies and forms of GRB energy release.
  Single-pulsed GRBs are characterized either by large ILF power indices
(indicating a range of jet opening angles and Lorentz factors, with a FRED
pulse shape), or they have long lags (large jet opening angles with low Lorentz
factors, with either a FRED pulse shape or an unpeaked, smooth pulse shape).
They also have lower-luminosity afterglows than multi-pulsed GRBs. GRBs with
simple time histories are often associated with Type Ibc supernovae. This
suggests that some single-pulsed GRBs contain single, beamed blast waves that
are similar to and have characteristics that overlap with those of many
supernovae. Such a connection may not exist between multi-pulsed GRBs and
supernovae.


title:
A Strong X-Ray Flux Ratio Anomaly in the Quadruply Lensed Quasar PG
  1115+080

abstract:
  PG 1115+080 is a quadruply lensed quasar at z=1.72 whose image positions are
well fit by simple models of the lens galaxy (at z=0.31). At optical
wavelengths, the bright close pair of images exhibits a modest flux ratio
anomaly (factors of ~1.2-1.4 over the past 22 years) with respect to these same
models. We show here that as observed in X-rays with Chandra, the flux ratio
anomaly is far more extreme, roughly a factor of 6. The contrasting flux ratio
anomalies in the optical and X-ray band confirm the microlensing hypothesis and
set a lower limit on the size of the optical continuum emission region that is
\~10-100 times larger than expected from a thin accretion disk model.


title: Are short gamma-ray bursts collimated? GRB050709, a flare but no break

abstract:
  From the small sample of afterglow lightcurves of short duration gamma-ray
bursts (GRBs), the decays are rapid, roughly following a power-law in time. It
has been assumed that the afterglow emission in short GRBs is collimated in
jets in the same way as in long GRBs. An achromatic break in a short GRB
afterglow lightcurve would therefore be strong evidence in favour of
collimation in short GRBs. We examine the optical lightcurve of the afterglow
of the short GRB 050709, the only short GRB where a jet break has been claimed
from optical data. We show that (1) the decay follows a single power-law from
1.4 to 19 days after the burst and has a decay index alpha =
1.73_{-0.04}^{+0.11}, (2) that an optical flare at ~10 days is required by the
data, roughly contemporaneous with a flare in the X-ray data, and (3) that
there is no evidence for a break in the lightcurve. This means that so far
there is no direct evidence for collimation in the outflows of short GRBs. The
available limits on the collimation angles in short GRBs now strongly suggest
much wider opening angles than found in long GRBs.


title:
Ghosts, Instabilities, and Superluminal Propagation in Modified Gravity
  Models

abstract:
  We consider Modified Gravity models involving inverse powers of fourth-order
curvature invariants. Using these models' equivalence to the theory of a scalar
field coupled to a linear combination of the invariants, we investigate the
properties of the propagating modes. Even in the case for which the fourth
derivative terms in the field equations vanish, we find that the second
derivative terms can give rise to ghosts, instabilities, and superluminal
propagation speeds. We establish the conditions which the theories must satisfy
in order to avoid these problems in Friedmann backgrounds, and show that the
late-time attractor solutions are generically afflicted by superluminally
propagating tensor or scalar modes.


title: Halo Shapes, Dynamics and Environment

abstract:
  In the hierarchical structure formation model cosmic halos are supposed to
form by accretion of smaller units along anisotropic direction, defined by
large-scale filamentary structures. After the epoch of primary mass aggregation
(which depend on the cosmological model), violent relaxation processes will
tend to alter the halo phase-space configuration producing quasi-spherical
halos with a relatively smooth density profiles.
  Here we attempt to investigate the relation between halos shapes, their
environment and their dynamical state. To this end we have run a large ($L=500
h^{-1}$ Mpc, $N_{p}=512^3$ particles) N-body simulation of a flat low-density
cold dark matter model with a matter density $\Omega_{\rm
m}=1-\Omega_{\Lambda}=0.3$, Hubble constant $H_{\circ}=70$ km s$^{-1}$
Mpc$^{-1}$ and a normalization parameter of $\sigma_{8}=0.9$. The particle mass
is $m_{\rm p}\ge 7.7\times 10^{10} h^{-1} M_{\odot}$ comparable to the mass of
one single galaxy. The halos are defined using a friends-of-friend algorithm
with a linking length given by $l=0.17\bar{\nu}$ where $\bar{\nu}$ is the mean
density. This linking length corresponds to an overdensity $\rho/\rho_{\rm
mean}\simeq 200$ at the present epoch ($z=0$) and the total number of halos
with more than 130 particles ($M>3 \times 10^{13} h^{-1} M_{\odot}$) is 57524.


title:
The structure and X-ray radiation spectra of illuminated accretion disks
  in AGN. III. Modeling fractional variability

abstract:
  [abridged] Extending the work of Czerny et al. (2004), we model the
fractional variability amplitude due to distributions of hot spots co-orbiting
on the accretion disk around a supermassive black hole. From defined radial
distributions, our code samples random positions for the hot spots across the
disk. The local spot emission is computed as reprocessed radiation coming from
a compact primary source above the disk. The structure of the hot spot and the
anisotropy of the re-emission are taken into account. We compute the fractional
variability spectra expected from such spot ensembles and investigate
dependencies on the parameters describing the radial spot distribution. We
consider the fractional variability F_var with respect to the spectral mean and
also the so-called point-to-point F_pp. Our method includes relativistic
corrections for the curved space-time; the black hole angular momentum is a
free parameter and subject to the fitting procedure. We confirm that the
rms-variability spectra involve intrinsic randomness at a significant level
when the number of flares appearing during the total observation time is too
small. Furthermore, F_var is not always compatible with F_pp. For MCG -6-30-15,
we can reproduce the short-timescale variability and model the suppressed
variability in the energy range of the Kalpha line without any need to
postulate reprocessing farther away from the center. An increasing rate of
energy production by the flares toward the center of the disk, a fast rotation
of the central black hole, and considerable suppression of the primary flare
emission are required. The modeled line remains consistent with the measured
equivalent width of the iron Kalpha line complex.


title: The effect of heavy element opacity on pre-main sequence Li depletion

abstract:
  Recent 3-D analysis of the solar spectrum data suggests a significant change
of the solar chemical composition. This may affect the temporal evolution of
the surface abundance of light elements since the extension of the convective
envelope is largely affected by the internal opacity value. We analyse the
influence of the adopted solar mixture on the opacity in the convective
envelope of pre-main sequence (PMS) stars and thus on PMS lithium depletion.
The surface Li abundance depends on the relative efficiency of several
processes, some of them still not known with the required precision; this paper
thus analyses one of the aspects of this ``puzzle''. Focusing on PMS evolution,
where the largest amount of Li burning occurs, we computed stellar models for
three selected masses (0.8, 1.0 and 1.2 Msun, with Z=0.013, Y=0.27, alpha=1.9)
by varying the chemical mixture, that is the internal element distribution in
Z. We analysed the contribution of the single elements to the opacity at the
temperatures and densities of interest for Li depletion. Several mixtures were
obtained by varying the abundance of the most important elements one at a time;
we then calculated the corresponding PMS Li abundance evolution. We found that
a mixture variation does change the Li abundance: at fixed total metallicity,
the Li depletion increases when increasing the fraction of elements heavier
than O.


title: XRF 050406 late-time flattening: an inverse Compton component?

abstract:
  We investigate for possible evidence of inverse Compton (IC) emission in the
X-ray afterglow of XRF 050406. In the framework of the standard fireball model,
we show how the late-time flattening observed in the X-ray light curve between
\~10^{4} s and ~10^{6} s can be explained in a synchrotron-plus-IC scenario,
when the IC peak frequency crosses the X-ray band. We thus conclude that the
appearance of an IC component above the synchrotron one at late times
successfully accounts for these X-ray observations.


title: Search for an infrared counterpart of IGR J16358-4756

abstract:
  We report here on near infrared observations of the field around IGR
J16358-4756. The source belongs to the new class of highly absorbed X-ray
binaries discovered by IBIS/INTEGRAL. Our primary goal was to identify the
infrared counterpart of the source, previously suggested to be a LMXB and then
further reclassified as a HMXB. We have made use of Chandra observations of the
source in order to better constrain the number of possible counterparts. Using
the differential photometry technique, in observations spanning a timescale of
1 month, we found no long term variability in our observations. This is
compatible, and we suggest here, that the source is a HMXB.


title: Bayesian foreground analysis with CMB data

abstract:
  The quality of CMB observations has improved dramatically in the last few
years, and will continue to do so in the coming decade. Over a wide range of
angular scales, the uncertainty due to instrumental noise is now small compared
to the cosmic variance. One may claim with some justification that we have
entered the era of precision CMB cosmology. However, some caution is still
warranted: The errors due to residual foreground contamination in the CMB power
spectrum and cosmological parameters remain largely unquantified, and the
effect of these errors on important cosmological parameters such as the optical
depth tau and spectral index n_s is not obvious. A major goal for current CMB
analysis efforts must therefore be to develop methods that allows us to
propagate such uncertainties from the raw data through to the final products.
Here we review a recently proposed method that may be a first step towards that
goal.


title:
Gyrokinetic electron acceleration in the force-free corona with
  anomalous resistivity

abstract:
  We numerically explore electron acceleration and coronal heating by
dissipative electric fields. Electrons are traced in linear force-free magnetic
fields extrapolated from SOHO/MDI magnetograms, endowed with anomalous
resistivity ($\eta$) in localized dissipation regions where the magnetic twist
$\nabla \times \bhat$ exceeds a given threshold. Associated with $\eta > 0$ is
a parallel electric field ${\bf E} = \eta {\bf j}$ which can accelerate runaway
electrons. In order to gain observational predictions we inject electrons
inside the dissipation regions and follow them for several seconds in real
time. Precipitating electrons which leave the simulation system at height $z$ =
0 are associated with hard X rays, and electrons which escape at height $z$
$\sim$ 3$\cdot 10^4$ km are associated with normal-drifting type IIIs at the
local plasma frequency. A third, trapped, population is related to
gyrosynchrotron emission. Time profiles and spectra of all three emissions are
calculated, and their dependence on the geometric model parameters and on
$\eta$ is explored. It is found that precipitation generally preceeds escape by
fractions of a second, and that the electrons perform many visits to the
dissipation regions before leaving the simulation system. The electrons
impacting $z$ = 0 reach higher energies than the escaping ones, and
non-Maxwellian tails are observed at energies above the largest potential drop
across a single dissipation region. Impact maps at $z$ = 0 show a tendency of
the electrons to arrive at the borders of sunspots of one polarity. Although
the magnetograms used here belong to non-flaring times, so that the simulations
refer to nanoflares and `quiescent' coronal heating, it is conjectured that the
same process, on a larger scale, is responsible for solar flares.


title: The History and Future of the Local and Loop I Bubbles

abstract:
  The Local and Loop I superbubbles are the closest and best investigated
supernova (SN) generated bubbles and serve as test laboratories for
observations and theories of the interstellar medium. Since the morphology and
dynamical evolution of bubbles depend on the ambient density and pressure
distributions, a realistic modelling of the galactic environment is crucial for
a detailed comparison with observations. We have performed 3D high resolution
(down to 1.25 pc on a kpc-scale grid) hydrodynamic simulations of the Local
Bubble (LB) and the neighbouring Loop I (L1) superbubble in a realistically
evolving inhomogeneous background ISM, disturbed already by SN explosions at
the Galactic rate for 200 Myr before the LB and L1 are generated. The LB is the
result of 19 SNe occurring in a moving group, which passed through the present
day local HI cavity. We can reproduce (i) the OVI column density in absorption
within the LB in agreement with COPERNICUS and recent FUSE observations, giving
N(OVI) <2 10^{13} cm^-2 and N(OVI)<7 10^{12} cm^-2, respectively, (ii) the
observed sizes of the Local and Loop I superbubbles, (iii) the interaction
shell between LB and L1, discovered with ROSAT, (iv) constrain the age of the
LB to be 14.5+0.7/-0.4 Myr, (v) predict the merging of the two bubbles in about
3 Myr, when the interaction shell starts to fragment, (vi) the generation of
blobs like the Local Cloud as a consequence of a dynamical instability. We find
that evolving superbubbles strongly deviate from idealised self-similar
solutions due to ambient pressure and density gradients, as well as due to
turbulent mixing and mass loading. Hence, at later times the hot interior can
break through the surrounding shell, which may also help to explain the
puzzling energy "deficit" observed in LMC bubbles.


title:
Resonant Tidal Excitations of Inertial Modes in Coalescing Neutron Star
  Binaries

abstract:
  We study the effect of resonant tidal excitation of inertial modes in neutron
stars during binary inspiral. For spin frequencies less than 100 Hz, the phase
shift in the gravitational waveform associated with the resonance is small and
does not affect the matched filtering scheme for gravitational wave detection.
For higher spin frequencies, the phase shift can become significant. Most of
the resonances take place at orbital frequencies comparable to the spin
frequency, and thus significant phase shift may occur only in the
high-frequency band (hundreds of Hertz) of gravitational wave. The exception is
a single odd-paity $m=1$ mode, which can be resonantly excited for misaligned
spin-orbit inclinations, and may occur in the low-frequency band (tens of
Hertz) of gravitational wave and induce significant (>> 1 radian) phase shift.


title:
Evidence for Shocked Molecular Gas in the Galactic SNR CTB 109
  (G109.1-1.0)

abstract:
  We report the detection of molecular clouds around the X-ray bright interior
feature in the Galactic supernova remnant (SNR) CTB 109 (G109.1-1.0). This
feature, called the Lobe, has been previously suggested to be the result of an
interaction of the SNR shock wave with a molecular cloud complex. We present
new high resolution X-ray data from the Chandra X-ray Observatory and new high
resolution CO data from the Five College Radio Observatory which show the
interaction region with the cloud complex in greater detail. The CO data reveal
three clouds around the Lobe in the velocity interval -57 < v < -52 km s^-1.
The velocity profiles of 12CO at various parts of the east cloud are well fit
with a Gaussian; however, at the position where the CO cloud and the Lobe
overlap, the velocity profile has an additional component towards higher
negative velocities. The molecular hydrogen density in this part of the cloud
is relatively high (N_H2 = 1.9 x 10^20 cm^-2), whereas the foreground
absorption in X-rays (N_H = 4.5 x 10^21 cm^-2), obtained from Chandra data, is
lower than in other parts of the cloud and in the north and south cloud. These
results indicate that this cloud has been hit by the SNR blast wave on the
western side, forming the bright X-ray Lobe.


title:
On the Distance to the Bright Nonthermal Radio Sources in the Direction
  of an Extraordinarily Massive Cluster of Red Giants

abstract:
  An extraordinarily massive cluster of red supergiants has been recently
reported in the direction of the galactic coordinates $l = 25\rlap.^\circ3$; $b
= -0\rlap.^\circ2$. This cluster is associated with an X-ray source, a very
high-energy $\gamma$-ray source, and three bright non-thermal radio sources.
The \sl a priori \rm probability of these associations being only line-of-sight
coincidences is very small. However, we have analyzed VLA archive data taken
toward these three radio sources and find from their HI absorption spectra that
they are extragalactic and thus not directly associated with the galactic
cluster.


title: Age distribution of young clusters and field stars in the SMC

abstract:
  In this paper we discuss the cluster and field star formation in the central
part of the Small Magellanic Cloud. The main goal is to study the correlation
between young objects and their interstellar environment. The ages of about 164
associations and 311 clusters younger than 1 Gyr are determined using isochrone
fitting. The spatial distribution of the clusters is compared with the HI maps,
with the HI velocity dispersion field, with the location of the CO clouds and
with the distribution of young field stars. The cluster age distribution
supports the idea that clusters formed in the last 1 Gyr of the SMC history in
a roughly continuous way with periods of enhancements. The two super-shells 37A
and 304A detected in the HI distribution are clearly visible in the age
distribution of the clusters: an enhancement in the cluster formation rate has
taken place from the epoch of the shell formation. A tight correlation between
young clusters and the HI intensity is found. The degree of correlation is
decreasing with the age of the clusters. Clusters older than 300 Myr are
located away from the HI peaks. Clusters and associations younger than 10 Myr
are related to the CO clouds in the SW region of the SMC disk. A positive
correlation between the location of the young clusters and the velocity
dispersion field of the atomic gas is derived only for the shell 304A,
suggesting that the cloud-cloud collision is probably not the most important
mechanism of cluster formation. Evidence of gravitational triggered episode due
to the most recent close interaction between SMC and LMC is found both in the
cluster and field star distribution.


title:
Laboratory Testing of a Lyot Coronagraph Equipped with an Eighth-Order
  Notch Filter Image Mask

abstract:
  We have built a series of notch filter image masks that make the Lyot
coronagraph less susceptible to low-spatial-frequency optical aberrations. In
this paper, we present experimental results of their performance in the lab
using monochromatic light. Our tests show that these ``eighth-order'' masks are
resistant to tilt and focus alignment errors, and can generate contrast levels
of 2 x 10^-6 at 3 lambda/D and 6 x 10^-7 at 10 lambda/D without the use of
corrective optics such as deformable mirrors. This work supports recent
theoretical studies suggesting that eighth-order masks can provide the
Terrestrial Planet Finder Coronagraph with a large search area, high off-axis
throughput, and a practical requisite pointing accuracy.


title: Relaxation paths for single modes of vibrations in isolated molecules

abstract:
  A numerical simulation of vibrational excitation of molecules was devised,
and used to excite computational models of common molecules into a prescribed,
pure, normal vibration mode in the ground electronic state, with varying,
controlable energy content. The redistribution of this energy (either
non-chaotic or irreversible IVR) within the isolated, free molecule is then
followed in time with a view to determining the coupling strength between
modes. This work was triggered by the need to predict the general characters of
the infrared spectra to be expected from molecules in interstellar space, after
being excited by photon absorption or reaction with a radical. It is found that
IVR from a pure normal mode is very "restricted" indeed at energy contents of
one mode quantum or so. However, as this is increased, or when the excitation
is localized, our approach allows us to isolate, describe and quantify a number
of interesting phenomena, known to chemists and in non-linear mechanics, but
difficult to demonstrate experimentally: frequency dragging, mode locking or
quenching or, still, instability near a potential surface crossing, the first
step to generalized chaos as the energy content per mode is increased.


title:
Basic considerations about experimental approaches to the B-mode of the
  CMB Polarization

abstract:
  The B-mode detection of Cosmic Microwave Background polarization will require
new technological developments, able to get sensitivities at least 2 orders of
magnitude better than for the E-mode. This really ambitious goal cannot be
reached simply by either improving the present technology or by adding more
detectors to current design, at least in the frame of having a new space
mission operating within a decade. Thus, the scientific community have to take
important decisions about the most suitable technologies on which converge the
needed effort. Basically, at present two receiver families do exist: bolometric
and radiometric. Both of them are continuoulsly improving their basic
performances, but the optimal approach to B-modes may require some decisions
have to be taken in short time scale. In any case, radiometric and bolometric
receivers have to deal with some common sources of systematics as well as they
both require some cryogenics. Thus, we should expect that systematics and
cryogenics may play as watershed line in designing future experiments aimed at
measuring the B-mode of Cosmic Microwave Background.


title:
New mechanism of generation of large-scale magnetic fields in merging
  protogalactic and protostellar clouds

abstract:
  A new mechanism of generation of large-scale magnetic fields in colliding
protogalactic clouds and merging protostellar clouds is discussed. Interaction
of the colliding clouds produces large-scale shear motions which are
superimposed on small-scale turbulence. Generation of the large-scale magnetic
field is due to a ''shear-current" effect (or "vorticity-current" effect), and
the mean vorticity is caused by the large-scale shear motions of colliding
clouds. This effect causes the generation of the mean magnetic field even in a
nonrotating and nonhelical homogeneous turbulence. There is no quenching of the
nonlinear shear-current effect contrary to the quenching of the nonlinear alpha
effect, the nonlinear turbulent magnetic diffusion, etc. During the nonlinear
growth of the mean magnetic field, the shear-current effect only changes its
sign at some value of the mean magnetic field which determines the level of the
saturated mean magnetic field. Numerical study shows that the saturated level
of the mean magnetic field is of the order of the equipartition field
determined by the turbulent kinetic energy. The estimated large-scale magnetic
field for merging protogalactic clouds is about several microgauss, and for
merging protostellar clouds is of the order of several tenth of microgauss.


title: Detection Limits from the McDonald Observatory Planet Search Program

abstract:
  Based on the long-term radial-velocity surveys carried out with the McDonald
Observatory 2.7m Harlan J. Smith Telescope from 1988 to the present, we derive
upper limits to long-period giant planet companions for 31 nearby stars. Data
from three phases of the McDonald Observatory 2.7m planet-search program have
been merged together and for 17 objects, data from the pioneering
Canada-France-Hawaii Telescope (CFHT) radial-velocity program have also been
included in the companion-limits determination. For those 17 objects, the
baseline of observations is in excess of 23 years, enabling the detection or
exclusion of giant planets in orbits beyond 8 AU. We also consider the
possibility of eccentric orbits in our computations. At an orbital separation
of 5.2 AU, we can exclude on average planets of M sin i > 2.0+/-1.1 Mjup (e=0)
and M sin i > 4.0+/-2.8 Mjup (e=0.6) for 25 of the 31 stars in this survey.
However, we are not yet able to rule out "true Jupiters," i.e. planets of M sin
i ~ 1 Mjup in 5.2 AU orbits. These limits are of interest for the Space
Interferometry Mission (SIM), Terrestrial Planet Finder (TPF), and Darwin
missions which will search for terrestrial planets orbiting nearby stars, many
of which are included in this work.


title: Binary post-AGB stars and their Keplerian discs

abstract:
  In this contribution we give a progress report on our systematic study of a
large sample of post-AGB stars. The sample stars were selected on the basis of
their infrared colours and the selection criteria were tuned to discover
objects with hot dust in the system. We started a very extensive,
multi-wavelength programme which includes the analysis of our radial velocity
monitoring; our optical high-resolution spectra; our groundbased N-band
spectral data as well as the Spitzer full spectral scans; the broad-band SED
and the high spatial-resolution interferometric experiments with the VLTI. In
this contribution we highlight the main results obtained so far and argue that
all systems in our sample are indeed binaries, which are surrounded by dusty
Keplerian circumbinary discs. The discs play a lead role in the evolution of
the systems.


title:
Mapping Large-Scale Gaseous Outflows in Ultraluminous Infrared Galaxies
  with Keck II ESI Spectra: Spatial Extent of the Outflow

abstract:
  The kinematics of neutral gas and warm ionized gas have been mapped in
one-dimension across ultraluminous starburst galaxies using interstellar
absorption and emission lines, in Keck II ESI spectra. Blue-shifted absorption
is found along more of the slit than anticipated, exceeding scales of 15 kpc
across several systems. The large velocity gradient measured across some of
these outflows is inconsistent with a flow diverging from the central starburst
-- angular momentum conservation reduces the rotational velocity of an outflow
as it expands. More widespread star formation, likely triggered by the merger,
probably drives these outflows, although some models suggest the collision
itself could generate a wind by shock heating interstellar gas throughout the
disk. Young mergers with separated nuclei present the highest outflow masses,
due mainly to the larger area over which the cool gas can be detected. In a
typical ULIG, the mass carried by the cool phase of the outflow is around
10^8Msun, or a few percent of the total dynamical mass. Assuming the starburst
activity has proceeded at the observed rate for the past 10 Myr, the kinetic
energy of the cool outflows is a few percent of the supernova energy,
consistent with starbursts powering the outflows. The cool wind is expected to
be accelerated by momentum deposition, possibly from radiation pressure as well
as supernovae. Such models imply turn-around radii for the cool outflows of at
least 30 to 90 kpc. This cross-section presents a significant NaI absorption
cross section. If most L > 0.1L* galaxies pass through a luminous starburst
phase, then relics of cool outflows will create a significant redshift-path
density. Galaxy formation models should include this cool phase of the outflow
in addition to a hot wind in feedback models.


title: Primordial Black Hole Minimum Mass

abstract:
  In this paper we revisit thermodynamic constraints on primordial black hole
(PBH) formation in the early universe. Under the assumption that PBH mass is
equal to the cosmological horizon mass, one can use the 2nd Law of
Thermodynamics to put a lower limit on the PBH mass. In models of PBH
formation, however, PBHs are created at some fraction of the horizon mass. We
show that this thermodynamic constraint still holds for sub-horizon PBH
formation.


title: X-Ray Emission from the Warm Hot Intergalactic Medium

abstract:
  The number of detected baryons in the Universe at z<0.5 is much smaller than
predicted by standard big bang nucleosynthesis and by the detailed observation
of the Lyman alpha forest at red-shift z=2. Hydrodynamical simulations indicate
that a large fraction of the baryons today is expected to be in a ``warm-hot''
(10^5-10^7K) filamentary gas, distributed in the intergalactic medium. This
gas, if it exists, should be observable only in the soft X-ray and UV bands.
Using the predictions of a particular hydrodynamic model, we simulated the
expected X-ray flux as a function of energy in the 0.1-2 keV band due to the
Warm-Hot Intergalactic Medium (WHIM), and compared it with the flux from local
and high red-shift diffuse components. Our results show that as much as 20% of
the total diffuse X-ray background (DXB) in the energy range 0.37-0.925keV
could be due to X-ray flux from the WHIM, 70% of which comes from filaments at
redshift z between 0.1 and 0.6. Simulations done using a FOV of 3', comparable
with that of Suzaku and Constellation-X, show that in more than 20% of the
observations we expect the WHIM flux to contribute to more than 20% of the DXB.
These simulations also show that in about 10% of all the observations a single
bright filament in the FOV accounts, alone, for more than 20% of the DXB flux.
Red-shifted oxygen lines should be clearly visible in these observations.


title:
Improved Calculation of the Primordial Gravitational Wave Spectrum in
  the Standard Model

abstract:
  We show that the energy density spectrum of the primordial gravitational
waves has characteristic features due to the successive changes in the
relativistic degrees of freedom during the radiation era. These changes make
the evolution of radiation energy density deviate from the conventional
adiabatic evolution, \rho_r~ a^{-4}, and thus cause the expansion rate of the
universe to change suddenly at each transition which, in turn, modifies the
spectrum of primordial gravitational waves. We take into account all the
particles in the Standard Model of elementary particles. In addition,
free-streaming of neutrinos damps the amplitude of gravitational waves, leaving
characteristic features in the energy density spectrum. Our calculations are
solely based on the standard model of cosmology and particle physics, and
therefore these features must exist. Our calculations significantly improve the
previous ones which ignored these effects and predicted a smooth, featureless
spectrum.