title: Evidence for a co-moving sub-stellar companion of GQ Lup

abstract:
  We present a companion of the \le 2 Myr young classical T Tauri star GQ Lup
in the Lupus star forming region at 140 \pm 50 pc from imaging, astrometry, and
spectroscopy. With direct K-band imaging using VLT/NACO, we detected an object
6 mag fainter than GQ Lup located 0.7 arc sec west of it. Compared to images
obtained 2 to 5 years earlier with Subaru/CIAO and HST/PC, this object shares
the proper motion of GQ Lup by 5 and 7 sigma, respectively, hence it is a
co-moving companion. Its K-L' color is consistent with a spectral type early to
mid L. Our NACO K-band spectrum yields spectral type M9-L4 with H2O and CO
absorption, consistent with the new GAIA-Dusty template spectrum for log g = 2
to 3 and Teff = 2000 K with ~2 Rjup radius at ~140 pc, hence few Jupiter
masses. Using the theoretical models from Wuchterl & Tscharnuter (2003),
Burrows et al. (1997), and Baraffe et al. (2002), the mass lies between 1 and
42 Jupiter masses.


title: Primordial non-gaussianities in single field inflation

abstract:
  We calculate the three-point function for primordial scalar fluctuations in a
single field inflationary scenario where the scalar field Lagrangian is a
completely general function of the field and its first derivative. We obtain an
explicit expression for the three-point correlation function in a
self-consistent approximation scheme where the expansion rate varies slowly,
analogous to the slow-roll limit in standard, single-field inflation. The
three-point function can be written in terms of the familiar slow-roll
parameters and three new parameters which measure the non-trivial kinetic
structure of the scalar field, the departure of the sound speed from the speed
of light, and the rate of change of the sound speed.


title:
Nuclear Properties of Nearby Spiral Galaxies from Hubble Space Telescope
  NICMOS imaging and STIS Spectroscopy

abstract:
  We investigate the central regions of 23 spiral galaxies using archival
NICMOS imaging and STIS spectroscopy. The sample is taken from our program to
determine the masses of central massive black holes (MBH) in 54 nearby spiral
galaxies. Stars are likely to contribute significantly to any dynamical central
mass concentration that we find in our MBH program and this paper is part of a
series to investigate the nuclear properties of these galaxies. We use the
Nuker law to fit surface brightness profiles, derived from the NICMOS images,
to look for nuclear star clusters and find possible extended sources in 3 of
the 23 galaxies studied (13 per cent). The fact that this fraction is lower
than that inferred from optical Hubble Space Telescope studies is probably due
to the greater spatial resolution of those studies. Using R-H and J-H colors
and equivalent widths of H-alpha emission (from the STIS spectra) we
investigate the nature of the stellar population with evolutionary models.
Under the assumption of hot stars ionizing the gas, as opposed to a weak AGN,
we find that there are young stellar populations (~10-20 Myr) however these
data do not allow us to determine what percentage of the total nuclear stellar
population they form. Also, in an attempt to find any unknown AGN we use [N II]
and [S II] line flux ratios (relative to H-alpha) and find tentative evidence
for weak AGN in NGC 1300 and NGC 4536.


title: A solar active region loop compared with a 2D MHD model

abstract:
  We analyzed a coronal loop observed with the Normal Incidence Spectrometer
(NIS), which is part of the Coronal Diagnostic Spectrometer (CDS) on board the
Solar and Heliospheric Observatory (SOHO). The measured Doppler shifts and
proper motions along the selected loop strongly indicate unidirectional flows.
Analysing the Emission Measure Curves of the observed spectral lines, we
estimated that the temperature along the loop was about 380000 K. We adapted a
solution of the ideal MHD steady equations to our set of measurements. The
derived energy balance along the loop, as well as the advantages/disadvantages
of this MHD model for understanding the characteristics of solar coronal loops
are discussed.


title:
Asteroseismology of the planet-hosting star mu Arae. II. Seismic
  analysis

abstract:
  As most exoplanets host stars, HD 160691 (alias mu Ara) presents a
metallicity excess in its spectrum compared to stars without detected planets.
This excess may be primordial, in which case the star would be completely
overmetallic, or it may be due to accretion in the early phases of planetary
formation, in which case it would be overmetallic only in its outer layers. As
discussed in a previous paper (Bazot and Vauclair 2004), seismology can help
choosing between the two scenarios. This star was observed during eight nights
with the spectrograph HARPS at La Silla Observatory. Forty three p-modes have
been identified (Bouchy et al. 2005). In the present paper, we discuss the
modelisation of this star. We computed stellar models iterated to present the
same observable parameters (luminosity, effective temperature, outer chemical
composition) while the internal structure was different according to the two
extreme assumptions : original overmetallicity or accretion. We show that in
any case the seismic constraints lead to models in complete agreement with the
external parameters deduced from spectroscopy and from the Hipparcos parallax
(L and Teff). We discuss the tests which may lead to a choice between the two
typical scenarios. We show that the ``small separation'' seem to give a better
fit for the accretion case than for the overmetallic case, but in spite of the
very good data the uncertainties are still too large to conclude. We discuss
the observations which would be needed to go further and solve this question.


title: Projection effects in cluster mass estimates : the case of MS2137

abstract:
  We revisit the mass properties of the lensing cluster of galaxies MS2137-23
and assess the mutual agreement between cluster mass estimates based on
lensing, X-rays and stellar dynamics. We perform a thorough elliptical lens
modelling using arcs in the range 20<R<100kpc and weak lensing (100<R<1000kpc).
We confirm that the dark matter distribution is consistent with an NFW profile
with high concentration $c=11.7\pm0.6$. We further analyse the stellar
kinematics data of Sand etal(2004) with a detailed modelling of the los
velocity distribution of stars in the cD galaxy and quantify the small bias due
to non-Gaussianity of the LOSVD. After correction, the NFW lens model is still
unable to properly fit kinematical data and is twice as massive as suggested by
X-rays (Allen etal2001). The discrepancy between projected and tridimensional
mass estimates is studied by assuming prolate (triaxial) halos with the major
axis oriented toward the line-of-sight. This model well explains the high
concentration and the misalignement of 13 deg between stellar and dark matter
components. We then calculate the systematic and statistical uncertainties in
the relative normalization between cylindric M(< R) and spherical M(< r) mass
estimates for triaxial halos. These uncertainties prevent any attempt to couple
2D and 3D constraints without a complete tridimensional analysis. Such
asphericity/projection effects should be a major concern for comparisons
between lensing and X-rays/dynamics mass estimates.


title: Limit-cycle behavior in one-zone convective models

abstract:
  We present the results of a detailed set of one-zone models that account for
the coupling between pulsation and convection following the original
prescriptions of Stellingwerf (1986). Motivated by the arbitrary nature of the
input parameters adopted in this theoretical framework, we computed several
sequences of models that cover a substantial fraction of the parameter space
and a longer integration time. We also included a turbulent pressure term and
found that this physical mechanism plays a crucial role in the pulsation
characteristics of the models by removing the sharp discontinuities along the
light and the velocity curves showed by models that do not account for
turbulent pressure. Finally, we investigated the vibrational and the
pulsational stability of completely convective models. We consider as the most
important finding of the present work the identification of a well-defined
region in the parameter space where they approach limit-cycle stability.
Several numerical experiments performed by adopting different values of the
adiabatic exponent and of the shell thickness indicate that the coupling
between pulsation and convection is the key driving mechanism for LPVs, a
finding supported by recent theoretical predictions.


title: Is the Galactic submillimeter dust emissivity underestimated?

abstract:
  We present detailed modeling of the spectral energy distribution (SED) of the
spiral galaxies NGC 891, NGC 4013, and NGC 5907 in the far-infrared and submm
wavelengths. The model takes into account the emission produced by the diffuse
dust and the star forming HII complexes. The dust mass is constrained by
radiative transfer simulations in the optical (Xilouris et al. 1999). We find
that the submm emission predicted by our model cannot account for the observed
fluxes. Two scenarios may account for the "missing" submm flux. In the first
scenario (Popescu et al. 2000), additional dust (to that derived from the
optical, and associated with young stars) is embedded in the galaxy in the form
of a thin disk and gives rise to additional submm emission. The other scenario
investigates whether the average submm emissivity of the dust grains is higher
than the values widely used in Galactic environments. In this case, the dust
mass is equal to that derived from the optical observations, and the submm
emissivity is treated as a free parameter calculated by fitting our model to
the observed SED. We find the submm emissivity value to be ~3 times that often
used for our Galaxy. While both scenarios reproduce the observed 850 micron
surface brightness, the extra embedded dust model is not supported by the near
infrared observations. We, thus, find that the enhanced dust submm emissivity
scenario is the most plausible. [abridged]


title: The basic parameters of gamma-ray-loud blazars

abstract:
  We determined the basic parameters, such as the central black hole mass
($M$), the boosting factor (or Doppler factor) ($\delta$), the propagation
angle ($\Phi$) and the distance along the axis to the site of $\gamma$-ray
production ($d$) for 23 $\gamma$-ray-loud blazars using their available
variability timescales. In this method, the absorption effect depends on the
$\gamma$-ray energy, emission size and property of the accretion disk. Using
the intrinsic $\gamma$-ray luminosity as a fraction $\lambda$ of the Eddington
luminosity, $L^{in}_{\gamma}=\lambda L_{Ledd.}$ and the optical depth equal to
unity, we can determine the upper limit of the central black hole masses. We
found that the black hole masses range between $10^{7}M_{\odot}$ and
$10^{9}M_{\odot}$ when $\lambda$ = 0.1 and 1.0 are adopted. Since this method
is based on gamma-ray emissions and the short time-scale of the sources, it can
also be used for central black hole mass determination of high redshift
gamma-ray sources. In the case of the upper limit of black hole mass there is
no clear difference between BLs and FSRQs, which suggests that the central
black hole masses do not play an important role in the evolutionary sequence of
blazars.


title:
Hard Extended X-ray Source in the IC 443 SNR Resolved by Chandra: A Fast
  Ejecta Fragment or a New Pulsar Wind Nebula?

abstract:
  A Chandra observation of the isolated hard X-ray source XMMU
J061804.3+222732, located in the region of apparent interaction of the
supernova remnant IC 443 with a molecular cloud, resolved the complex structure
of the source in a few bright clumps embedded in an extended emission of a ~ 30
arcsec size. The X-ray spectra of the clumps and the extended emission are
dominated by a hard power-law component with a photon index of 1.2--1.4. In
addition, we see some indications of an optically thin thermal plasma of a ~
0.3 keV temperature. The observed X-ray morphology and spectra are consistent
with those expected for an isolated supernova ejecta fragment interacting with
a dense ambient medium. A possible alternative interpretation is a pulsar wind
nebula associated with either IC 443 or another SNR, G189.6+3.3.


title: Are violent events responsible of a Galaxy Morphological loop?

abstract:
  We use cosmological SPH simulations to investigate the effects of mergers and
interactions on the formation of the bulge and disc components of galactic
systems. We find that secular evolution during mergers seems to be a key
process in the formation of stable disc-bulge systems with observational
counterparts and contributes to establish the fundamental relations observed in
galaxies. Our findings suggest that the secular evolution phase couples the
formation mechanisms of the bulge and disc components. According to our
results, depending on the particular stability properties and merger
parameters, violents events could drive a morphological loop in which the
outcome could be a disc or a spheroid.


title:
The Sun as a MHD generator: application of a new heating mechanism for
  the coronal loops and closed magnetic structures

abstract:
  We investigate a possibility of heating of the loops and other closed
magnetic structures in active regions of the solar corona by the flow of solar
wind (plus other flows that may be present) across the magnetic field lines
(that are perpendicular to the flow), in a similar manner as a conventional MHD
generator works. A simple model is formulated which allows to calculate the
typical currents generated by this mechanism. This enables to make a judgement
whether the loops in solar active regions can be heated by the proposed
mechanism through the associated Ohmic dissipation. It is shown that even if
the heating region width is of the order of a few proton Larmor radii (this
effectively means that a loop is represented by {\it nano-threads}, by analogy
with the nano-flare coronal heating mechanism, with width of a few proton
Larmor radii) and the plasma flow speed is 50 km s$^{-1}$ then only about 1% of
the heating requirement of coronal loops could be met under this conjecture.
Other implications of the model, such as a predicted spatial heat distribution
along the loop as well as application of the model to the other places e.g.
chromosphere and corotating interaction region structures in the solar wind are
discussed.


title:
Correcting the influence of an asymmetric line spread function in
  2-degree Field spectrograph data

abstract:
  We investigate the role of asymmetries in the line spread function of the
2-degree field spectrograph and the variations in these asymmetries with the
CCD, the plate, the time of observation and the fibre. A data-reduction
pipeline is developed that takes these deformations into account for the
calibration and cross-correlation of the spectra. We show that, using the
emission lines of calibration lamp observations, we can fit the line spread
function with the sum of two Gaussian functions representing the theoretical
signal and a perturbation of the system. This model is then used to calibrate
the spectra and generate templates by downgrading high resolution spectra.
Thus, we can cross-correlate the observed spectra with templates degraded in
the same way. Our reduction pipeline is tested on real observations and
provides a significant improvement in the accuracy of the radial velocities
obtained. In particular, the systematic errors that were as high as ~20 km/s
when applying the AAO reduction package 2dfDR are now reduced to ~5 km/s. Even
though the 2-degree Field spectrograph is to be decommissioned at the end of
2005, the analysis of archival data and previous studies could be improved by
the reduction procedure we propose here.


title:
Rigorous luminosity function determination in presence of a background:
  theory and application to two intermediate redshift clusters

abstract:
  In this paper we present a rigorous derivation of the luminosity function
(LF) in presence of a background. Our approach is free from the logical
contradictions of assigning negative values to positively defined quantities
and avoid the use of incorrect estimates for the 68 % confidence interval
(error bar). It accounts for Poisson fluctuations ignored in previous
approaches and does not requires binning of the data. The method is extensible
to more complex situations, does not require the existence of an
environment--independent LF, and clarifies issues common to field LF
derivations. We apply the method to two clusters of galaxies at intermediate
redshift (z~0.3) with among the deepest and widest K_s observations ever taken.
Finally, we point out short-comings of flip--flopping magnitudes.


title:
A radial velocity survey of low Galactic latitude structures: I.
  Kinematics of the Canis Major dwarf galaxy

abstract:
  As part of a radial velocity survey of low Galactic latitude structures that
we undertook with the 2dF spectrograph on the AAT, we present the radial
velocities of more than 1500 Red Giant Branch and Red Clump stars towards the
centre of the Canis Major dwarf galaxy. With a mean velocity of 72\pm7 km/s at
a Heliocentric distance of 5.5 kpc and 114\pm2 km/s at 8.5 kpc, these stars
present a peculiar distance -- radial velocity relation that is unlike that
expected from thin or thick disc stars. Moreover, they belong to a
kinematically cold population with an intrinsic dispersion that may be as low
as 11_{-1}^{+3} km/s. The radial velocity distribution is used to select Canis
Major stars in the UCAC2.0 proper motion catalogue and derive proper motions in
Galactic coordinates of (\mu_l,\mu_b)= (-3.6\pm0.8 mas/yr, 1.5\pm0.4 mas/yr)
for the dwarf galaxy, which after correcting for the reflex solar motion along
this line-of-sight gives (\mu_l',\mu_b')= (-6.8\pm0.8 mas/yr, 0.8\pm0.4
mas/yr)$, corresponding to a prograde orbit with a tangential velocity of
\sim235 km/s at the average distance of \sim7.2 kpc. All these kinematic
constraints can be reproduced in simulations of the accretion of a dwarf onto
the Galactic disc. Such a process could also be responsible for the Monoceros
Ring that has recently been shown to encompass the Galactic disc. However,
without constraints on the kinematics of the tidal arms emerging from the Canis
Major dwarf, it is not yet possible to definitively prove a link between the
two structures.


title: Evolving Dark Energy with w Deviating from -1

abstract:
  Theories of evolving quintessence are constructed that generically lead to
deviations from the w = -1 prediction of non-evolving dark energy. The small
mass scale that governs evolution, m_\phi \approx 10^{-33} eV, is radiatively
stable, and the ``Why Now?'' problem is solved. These results rest crucially on
seesaw cosmology: in broad outline, fundamental physics and cosmology can be
understood from only two mass scales, the weak scale, v, and the Planck scale,
M. Requiring a scale of dark energy \rho_{DE}^{1/4} governed by v^2/M, and a
radiatively stable evolution rate m_\phi given by v^4/M^3, leads to a
distinctive form for the equation of state w(z) that follows from a cosine
quintessence potential. An explicit hidden axion model is constructed. Dark
energy resides in the potential of the axion field which is generated by a new
QCD-like force that gets strong at the scale \Lambda \approx v^2/M \approx
\rho_{DE}^{1/4}. The evolution rate is given by a second seesaw that leads to
the axion mass, m_\phi \approx \Lambda^2/f, with f \approx M.


title: Extranuclear X-ray Emission in the Edge-on Seyfert Galaxy NGC 2992

abstract:
  We found several extranuclear (r >~ 3") X-ray nebulae within 40" (6.3 kpc at
32.5 Mpc) of the nucleus of the Seyfert galaxy NGC 2992. The net X-ray
luminosity from the extranuclear sources is ~2-3 E39 erg/s (0.3-8.0 keV). The
X-ray core itself (r <~ 1") is positioned at 9:45:41.95 -14:19:34.8 (J2000) and
has a remarkably simple power-law spectrum with photon index Gamma=1.86 and
Nh=7E21 /cm2. The near-nuclear (3" <~ r <~ 18") Chandra spectrum is best
modelled by three components: (1) a direct AGN component with Gamma fixed at
1.86, (2) cold Compton reflection of the AGN component, and (3) a 0.5 keV
low-abundance (Z < 0.03 Zsolar) "thermal plasma," with ~10% of the flux of
either of the first two components. The X-ray luminosity of the 3rd component
(the "soft excess") is ~1.4E40 erg/s, or ~5X that of all of the detected
extranuclear X-ray sources. We suggest that most (~75-80%) of the soft excess
emission originates from 1" < r < 3", which is not imaged in our observation
due to severe CCD pile-up. We also require the cold reflector to be positioned
at least 1" (158 pc) from the nucleus, since there is no reflection component
in the X-ray core spectrum. Much of the extranuclear X-ray emission is
coincident with radio structures (nuclear radio bubbles and large-scale radio
features), and its soft X-ray luminosity is generally consistent with
luminosities expected from a starburst-driven wind (with the starburst scaled
from L_FIR). However, the AGN in NGC 2992 seems equally likely to power the
galactic wind in that object. Furthermore, AGN photoionization and
photoexcitation processes could dominate the soft excess, especially the
\~75-80% which is not imaged by our observations.


title: Present and Future Astrometric Study of Halo Substructure

abstract:
  We focus on how astrometric surveys might be exploited for the study of
Galactic halo substructure originating from the disruption of satellite
systems. The Sagittarius (Sgr) dwarf spheroidal tidal stream provides a useful
template to explore present and future capabilities of proper motion surveys
for finding and studying substructure as well as for using individual tidal
streams to probe the global properties of the Milky Way. The configuration of
the Sgr stream is particularly well suited for measuring the flattening of the
halo and for providing an independent means for measuring the speed of the
Local Standard of Rest. For the various proposed experiments, the required
proper motion accuracies are well within the capabilities of the Space
Interferometry Mission (SIM PlanetQuest).


title:
Effects of Cosmological Magnetic Helicity on the Cosmic Microwave
  Background

abstract:
  Cosmological magnetic fields induce temperature and polarization fluctuations
in the cosmic microwave background (CMB) radiation. A cosmological magnetic
field with current amplitude of order $10^{-9}$ G is detectable via
observations of CMB anisotropies. This magnetic field (with or without
helicity) generates vector perturbations through vortical motions of the
primordial plasma. This paper shows that magnetic field helicity induces
parity-odd cross correlations between CMB temperature and $B$-polarization
fluctuations and between $E$- and $B$-polarization fluctuations, correlations
which are zero for fields with no helicity (or for any parity-invariant
source). Helical fields also contribute to parity-even temperature and
polarization anisotropies, cancelling part of the contribution from the
symmetric component of the magnetic field. We give analytic approximations for
all CMB temperature and polarization anisotropy vector power spectra due to
helical magnetic fields. These power spectra offer a method for detecting
cosmological helical magnetic fields, particularly when combined with Faraday
rotation measurements which are insensitive to helicity.


title: The role of resonances in barred galaxies

abstract:
  The dynamics of the inner disk of many galaxies is dominated by bars. As a
result, resonances between the bar and the disk become an important factor. In
order to detect resonances, we measure angular and radial frequencies of
individual orbits in N-body models of barred galaxies. In our simulations with
several million particles, stellar disks are immersed in live halos of dark
matter. A bar forms spontaneously and interacts with the disk through
resonances. We detect 9 of them. The corotation (CR) and the inner Lindblad
resonance (ILR) are the most significant. The spatial distributions of
particles trapped at these resonances show that ILR is not localized at a given
radius. Particles trapped at ILR lie along the bar spanning a wide range of
radii. On the other hand, particles at the corotation resonance form a ring
around the corotation radius. We study how orbits evolve near corotation and
how they are trapped. When an orbit is getting trapped, it evolves strongly,
but after that there is little evolution. Those trapped orbits circulate along
the corotation ring or librate around a stable lagragian point. The same
technique is applied to study resonances in the halo. The bar interacts
strongly with the halo particles that stay close to the disk. We find the
corotation resonance and the inner Lindblad resonance for halo particles.


title: High excitation ISM and gas

abstract:
  An overview is given of ISO results on regions of high excitation ISM and
gas, i.e. HII regions, the Galactic Centre and Supernovae Remnants. IR emission
due to fine-structure lines, molecular hydrogen, silicates, polycyclic aromatic
hydrocarbons and dust are summarised, their diagnostic capabilities illustrated
and their implications highlighted.


title:
Absorption of dark matter by a supermassive black hole at the Galactic
  center: role of boundary conditions

abstract:
  The evolution of the dark matter distribution at the Galactic center is
analyzed, which is caused by the combination of gravitational scattering on
Galactic bulge stars and absorption by a supermassive black hole at the center
of the bulge. Attention is focused on the boundary condition on the black hole.
It is shown that its form depends on the energy of dark matter particles. The
modified flux of dark matter particles onto the black hole is calculated.
Estimates of the amount of dark matter absorbed show that the fraction of dark
matter in the total mass of the black hole may be significant. The density of
dark matter at the central part of the bulge is calculated. It is shown that
recently observed gamma radiation from the Galactic center can be attributed to
the annihilation of dark matter with this density.


title:
The C4 Clustering Algorithm: Clusters of Galaxies in the Sloan Digital
  Sky Survey

abstract:
  We present the "C4 Cluster Catalog", a new sample of 748 clusters of galaxies
identified in the spectroscopic sample of the Second Data Release (DR2) of the
Sloan Digital Sky Survey (SDSS). The C4 cluster--finding algorithm identifies
clusters as overdensities in a seven-dimensional position and color space, thus
minimizing projection effects which plagued previous optical clusters
selection. The present C4 catalog covers ~2600 square degrees of sky with
groups containing 10 members to massive clusters having over 200 cluster
members with redshifts. We provide cluster properties like sky location, mean
redshift, galaxy membership, summed r--band optical luminosity (L_r), velocity
dispersion, and measures of substructure. We use new mock galaxy catalogs to
investigate the sensitivity to the various algorithm parameters, as well as to
quantify purity and completeness. These mock catalogs indicate that the C4
catalog is ~90% complete and 95% pure above M_200 = 1x10^14 solar masses and
within 0.03 <=z <= 0.12. The C4 algorithm finds 98% of X-ray identified
clusters and 90% of Abell clusters within 0.03 <= z <= 0.12. We show that the
L_r of a cluster is a more robust estimator of the halo mass (M_200) than the
line-of-sight velocity dispersion or the richness of the cluster. L_r. The
final SDSS data will provide ~2500 C4 clusters and will represent one of the
largest and most homogeneous samples of local clusters.


title:
Detection of anomalous microwave emission in the Perseus molecular cloud
  with the COSMOSOMAS experiment

abstract:
  We present direct evidence for anomalous microwave emission in the Perseus
molecular cloud, which shows a clear rising spectrum from 11 to 17 GHz in the
data of the COSMOSOMAS experiment. By extending the frequency coverage using
WMAP maps convolved with the COSMOSOMAS scanning pattern we reveal a peak flux
density of 42 (+/-) 4 Jy at 22 GHz integrated over an extended area of 1.65 x
1.0 deg centered on RA = 55.4 (+/-) 0.1 deg and Dec = 31.8 (+/-) 0.1 deg
(J2000). The flux density that we measure at this frequency is nearly an order
of magnitude higher than can be explained in terms of normal galactic emission
processes (synchrotron, free-free and thermal dust). An extended IRAS dust
feature G159.6-18.5 is found near this position and no bright unresolved source
which could be an ultracompact HII region or gigahertz peaked source could be
found. An adequate fit for the spectral density distribution can be achieved
from 10 to 50 GHz by including a very significant contribution from electric
dipole emission from small spinning dust grains.


title: Late time failure of Friedmann equation

abstract:
  It is widely believed that the assumption of homogeneity is a good zero{\it
th} order approximation for the expansion of our Universe. We analyze the
correction due to subhorizon inhomogeneous gravitational fields. While at early
times this contribution (which may act as a negative pressure component) is
perturbatively subdominant, we show that the perturbative series is likely to
diverge at redshift of order 1, due to the growth of perturbations. So, the
homogeneous Friedmann equation can not be trusted at late times. We suggest
that the puzzling observations of a present acceleration of the Universe, may
just be due to the unjustified use of the Friedmann equation and not to the
presence of a Dark Energy component. This would completely solve the
coincidence problem.


title:
The Color Selection of Quasars from Redshifts 5 to 10: Cloning and
  Discovery

abstract:
  We present simulations of quasar colors, magnitudes, and numbers at redshifts
5<z<10 based on our discovery of ten new high-redshift quasars and the cloning
of lower redshift Sloan Digital Sky Survey (SDSS) quasars. The ten quasars have
redshifts ranging from z=4.7 to z=5.3 and i-magnitudes of 20.21 to 20.94. The
natural diversity of spectral features in the cloned sample allows more
realistic simulation of the quasar locus width than previously possible with
synthetic template spectra. Colors are generated for the z>6 epoch taking
advantage of the new UKIDSS near-infrared filter set, and we examine the
redshift intervals of maximum productivity, discussing color selection and
survey depth issues. On the basis of the SDSS sample, we find that the surface
density of z>4.7 quasars increases by a factor of 3X by extending 0.7
i-magnitudes deeper than the SDSS spectroscopic survey limit of i=20.2 --
correspondingly we predict a total of ~400 faint quasars in the SDSS main area
that have redshift z>4.7 and magnitudes $<20.9.


title: Dynamical One-Armed Spiral Instability in Differentially Rotating Stars

abstract:
  We investigate the dynamical one-armed spiral instability in differentially
rotating stars with both eigenmode analysis and hydrodynamic simulations in
Newtonian gravity. We find that the one-armed spiral mode is generated around
the corotation radius of the star, and the distribution of angular momentum
shifts inwards the corotation radius during the growth of one-armed spiral
mode. We also find by investigating the distribution of the canonical angular
momentum density that the low T/|W| dynamical instability for both m=1 and m=2
mode, where T is the rotational kinetic energy and W is the gravitational
potential energy, is generated around the corotation point. Finally, we discuss
the feature of gravitational waves generated from these modes.


title:
Concentration of toroidal magnetic field in the solar tachocline by
  eta-quenching

abstract:
  We show that if the turbulent magnetic diffusivity used in solar dynamos is
assumed to be 'quenched' by increasing toroidal fields, much larger amplitude
and more concentrated toroidal fields can be induced by differential rotation
from an assumed poloidal field than if there is no quenching. This
amplification and concentration mechanism is weakened and bounded by j x B
feedbacks on the differential rotation. Nevertheless, it is strong enough to
contribute to the creation of ~100 kG toroidal fields near the base of the
convection zone, perhaps in conjunction with the 'exploding flux tube' process.
Such high fields are necessary for sunspots to occur in low solar latitudes.


title:
Large Scale Cosmological Inhomogeneities, Inflation and Acceleration
  Without Dark Matter

abstract:
  We describe the universe as a local, inhomogeneous spherical bubble embedded
in a flat matter dominated FLRW universe. Generalized exact Friedmann equations
describe the expansion of the universe and an early universe inflationary de
Sitter solution is obtained. A non-perturbative expression for the deceleration
parameter q is derived that can possibly describe the acceleration of the
universe without dark energy, due to the effects associated with very long wave
length super-horizon inflationary perturbations. The suggestion by Kolbe et al.
[9] that long wave length super-horizon inflationary modes can affect a local
observable through inhomogeneities is considered in the light of our exact
inhomogeneous model.


title: Constraints on backreaction in dust universes

abstract:
  We study backreaction in dust universes using exact equations which do not
rely on perturbation theory, concentrating on theoretical and observational
constraints. In particular, we discuss the recent suggestion (in
hep-th/0503117) that superhorizon perturbations could explain present-day
accelerated expansion as a useful example which can be ruled out. We note that
a backreaction explanation of late-time acceleration will have to involve
spatial curvature and subhorizon perturbations.


title: Virtual Observatory: From Concept to Implementation

abstract:
  We review the origins of the Virtual Observatory (VO) concept, and the
current status of the efforts in this field. VO is the response of the
astronomical community to the challenges posed by the modern massive and
complex data sets. It is a framework in which information technology is
harnessed to organize, maintain, and explore the rich information content of
the exponentially growing data sets, and to enable a qualitatively new science
to be done with them. VO will become a complete, open, distributed, web-based
framework for astronomy of the early 21st century. A number of significant
efforts worldwide are now striving to convert this vision into reality. The
technological and methodological challenges posed by the information-rich
astronomy are also common to many other fields. We see a fundamental change in
the way all science is done, driven by the information technology revolution.


title: CMB Anisotropy Due to Tangled magnetic fields in re-ionized models

abstract:
  Primordial tangled cosmological Magnetic Fields source rotational velocity
perturbations of the baryon fluid, even in the post-recombination universe.
These vortical modes inturn leave a characteristic imprint on the temperature
anisotropy of the Cosmic Microwave Background (CMB), if the CMB photons can be
re-scatterred after recombination. Observations from WMAP indicate that the
Universe underwent a relatively early re-ionization ($z_{ri} \sim 15$), which
does indeed lead to a significant optical depth for re-scattering of CMB
photons after the re-ionization epoch. We compute the resulting additional
temperature anisotropies, induced by primordial magnetic fields in the
post-recombination universe. We show that in models with early re-ionization, a
nearly scale-invariant spectrum of tangled magnetic fields which redshift to a
present value of $B_0 \sim 3 \times 10^{-9}$ Gauss, produce vector mode
perturbations which in turn induce additional temperature anisotropy of about
0.3 to 0.4 $ \mu$K over very small angular scales, with $ l$ upto $\sim 10000 $
or so.


title: A Chandra Survey of Early-Type Galaxies, I: Metal Enrichment in the ISM

abstract:
  We present the first in a series of papers studying the X-ray properties of
28 early type galaxies spanning ~3 orders of magnitude in L_x. We report
emission-weighted constraints for Fe, O, Ne, Mg, Si, S and Ni. We find no
evidence of the very sub-solar Z_Fe historically reported, confirming a trend
in recent X-ray observations of bright galaxies and groups, nor do we find Z_Fe
correlates with L_x. In general we find no evidence for multi-phase ISM,
indicating multi-temperature fits found with ASCA were due to temperature
gradients Chandra can resolve. We compare the stellar Z_Fe, estimated from
simple stellar population model fits, to Z_Fe(ISM). Excepting one possible
outlier we find no evidence that the gas is much more metal-poor than the stars
and, in a few systems Z_Fe(ISM) is higher. In general the two exhibit similar
Z_Fe, which is inconsistent with both galactic wind models and recent
hierarchical chemical enrichment simulations. Adopting standard SNIa and SNII
metal yields our abundance ratio constraints imply 66+/-11% of the Fe within
the ISM was produced in SNIa, similar to the Solar neighbourhood and implying
similar enrichment histories for the ISM in a spiral and in elliptical
galaxies. Although these values are sensitive to systematic uncertainties in
the SN yields, they are in good agreement with observations of more massive
systems, indicating remarkable homology in the enrichment process operating
from cluster scales to low-to-intermediate L_x galaxies. The data also
uniformly exhibit the low Z_O/Z_Mg abundance ratios which have been reported in
some other systems. This is inconsistent with metal-production calculations in
SNII and may indicate an additional source of enrichment, such as Population
III hypernovae.(abridged)


title: Modified Newtonian Dynamics In Dimensionless Form

abstract:
  Modified Newtonian dynamics proposed that gravitational field needs
modifications when the field strength $g$ is weaker than a critical value
$g_0$. This has been shown to be a good candidate as an alternative to cosmic
dark matter. There is another way to look at this theory as a length scale
dependent theory. One will show that modification of the Newtonian field
strength depends on the mass distribution and the coordinate scale of the
system. It is useful to separate the effective gravitation field $g(r)$ into a
small scale (or short-distance)$g_s$ field and a large scale (or a
long-distance) $g_l$ field that should be helpful for a better understanding of
the underlying physics. The effective potential is also derived.


title:
The discovery of an extreme jet in Rosette that shedding light on the
  formation of free-floating brown dwarfs and giant planets

abstract:
  We report on the discovery of an optical jet with a striking morphology in
the Rosette Nebula. It could be the most extreme case known of an accretion
disk and jet system directly exposed to strong ionization fields that impose
strong effects on its disk evolution. Unlike typical optical flows, this jet
system is found to have a high excitation nature mainly due to disruptive
interaction with the violent environment. As a result, the extension of the
highly-collimated jet and possible former episodes of the degenerated
counterjet all show bow-shocked structures. Our results provide implications on
how incipience of massive stars in giant molecular clouds prevents further
generations of low-mass star formation, and offers an evolutionary solution on
how isolated substellar/planetary mass objects in regions of massive star
formation are formed.


title:
Discovery of multi-seeded multi-mode formation of embedded clusters in
  the Rosette Molecular Complex

abstract:
  An investigation based on data from the spatially complete 2MASS Survey
reveals that a remarkable burst of clustered star formation is taking place
throughout the south-east quadrant of the Rosette Molecular Cloud. Compact
clusters are forming in a multi-seeded mode, in parallel and at various places.
In addition, sparse aggregates of embedded young stars are extensively
distributed. In this study, we report the primary results and implications for
high-mass and clustered star formation in giant molecular clouds. In
particular, we incorporate for the first time the birth of medium to low-mass
stars into the scenario of sequential formation of OB clusters. Following the
emergence of the young OB cluster NGC 2244, a variety of manifestations of
forming clusters of medium to high mass appear in the vicinity of the swept-up
layer of the H{\small II} region as well as further into the molecular cloud.
The embedded clusters appear to form in a structured manner, which suggests
they follow tracks laid out by the decay of macroturbulence. We address the
possible origins of the turbulence. This leads us to propose a tree model to
interpret the neat spatial distribution of clusters within a large section of
the Rosette complex. Prominent new generation OB clusters are identified at the
root of the tree pattern.


title: Is the emerging massive cluster NGC 2244 a twin cluster?

abstract:
  We present in this paper the first near infrared study of the young open
cluster NGC 2244, which is well known for its partially embedded nature in the
Rosette Nebula. Based on the spatially complete 2 Micron All Sky Survey, the
young OB cluster indicates apparent substructures. It is surprisingly resolved
into a compact core that matches well the congregation of massive OB stars in
the optical, a satellite cluster at a distance of 6.6 pc in its west and
probably a major stellar aggregate resembling an arc in structure right below
the core. This infrared study provides various new updates on its nature of the
young open cluster, including its central position, physical scale and stellar
population. A disk fraction of $\sim 20.5\pm2.8%$ is achieved for its members
with masses above 0.8 $M_{\odot}$. NGC 2244 is hence a unique example for the
study of embedded clusters.


title: Applying Machine Learning to Catalogue Matching in Astrophysics

abstract:
  We present the results of applying automated machine learning techniques to
the problem of matching different object catalogues in astrophysics. In this
study we take two partially matched catalogues where one of the two catalogues
has a large positional uncertainty. The two catalogues we used here were taken
from the HI Parkes All Sky Survey (HIPASS), and SuperCOSMOS optical survey.
Previous work had matched 44% (1887 objects) of HIPASS to the SuperCOSMOS
catalogue.
  A supervised learning algorithm was then applied to construct a model of the
matched portion of our catalogue. Validation of the model shows that we
achieved a good classification performance (99.12% correct).
  Applying this model, to the unmatched portion of the catalogue found 1209 new
matches. This increases the catalogue size from 1887 matched objects to 3096.
The combination of these procedures yields a catalogue that is 72% matched.


title: The EUV variability of the luminous QSO HS 1700+6416

abstract:
  We report on the first observations of variations in UV (intrinsic EUV 330 A)
flux of the luminous QSO HS 1700+6416 (z=2.72) over a decade. The amplitude of
variations increases from +/-0.1 mag in the optical (R) to up to a factor of 3
at 1250 A. This is apparently an extension of the increase in amplitude of
variations towards shorter wavelengths observed with IUE in low z AGN (Paltani
& Courvoisier, 1996) to the EUV. The time-scale for variations with the largest
amplitudes is >= 1/2 yr to years. We briefly discuss the consequences of the
observed variations on the ionizing metagalactic UV background.


title:
Fluorescent Ly-alpha emission from the high-redshift intergalactic
  medium

abstract:
  We combine a high-resolution hydro-simulation of the LambdaCDM cosmology with
two radiative transfer schemes (for continuum and line radiation) to predict
the properties, spectra and spatial distribution of fluorescent Ly-alpha
emission at z~3. We focus on line radiation produced by recombinations in the
dense intergalactic medium ionized by UV photons. In particular, we consider
both a uniform background and the case where gas clouds are illuminated by a
nearby quasar. We find that the emission from optically thick regions is
substantially less than predicted from the widely used static, plane-parallel
model. The effects induced by a realistic velocity field and by the complex
geometric structure of the emitting regions are discussed in detail. We make
predictions for the expected brightness and size distributions of the
fluorescent sources.Our results account for recent null detections and can be
used to plan new observational campaigns both in the field (to measure the
intensity of the diffuse UV background) and in the proximity of bright quasars
(to understand the origin of high colum-density absorbers).


title:
Multi-seeded multi-mode formation of embedded clusters in the RMC:
  Clusters baked in swept-up shells

abstract:
  This is the first of a series of three papers on clustered star formation in
the Rosette Molecular Complex. Here we investigate star formation in the
interfacing layers between the expanding Rosette Nebula and its surrounding
cloud, based on an analysis of the spatially complete and unbiased 2MASS data.
Two medium-mass infrared clusters with ages of around 1 Myr are identified in
the south and south-east arcs of the fragmented shell. The majority of the
candidate cluster members in these radiation and pressure-confined regions are
found to be almost uniformly distributed, roughly following the compression
layers traced by the distribution of optical depth at 100 $\mu$m, and may well
develop into gravitationally unbound systems upon their emergence from the
parental cloud. These expanding shells are believed to be playing important
roles in impeding the emerging young open cluster NGC 2244 from intruding
immediately and deeply into the ambient molecular cloud, where sequential
formation of massive clusters is taking place.


title: Constraints on the sound speed of dark energy

abstract:
  We have studied constraints on the equation of state, $w$, and speed of
sound, c_s, of the dark energy from a joint analysis of data from the cosmic
microwave background, large scale structure and type-Ia supernovae. We find
that current observations have no significant sensitivity to c_s. However,
there is a slight difference between models in which there are no dark energy
perturbations and models in which dark energy behaves as a fluid. Assuming that
there are no dark energy perturbations shifts the allowed region for $w$ to
slightly higher values. At present models with and without dark energy
perturbations provide roughly equally good fits to observations, but the
difference is potentially important for future parameter estimations. Finally,
we have also performed error forecasts for future measurements of c_s.


title:
GRS 1915+105: the distance, radiative processes and energy-dependent
  variability

abstract:
  We present an exhaustive analysis of five broad-band observations of GRS
1915+105 in two variability states, chi and omega, observed simultaneously by
the PCA, HEXTE and OSSE. We find all the spectra well fitted by Comptonization
of disc blackbody photons, with very strong evidence for the presence of a
nonthermal electron component in the Comptonizing plasma. Both the energy and
the power spectra in the chi state are typical to the very high/intermediate
state of black-hole binaries. The spectrum of the omega state is characterized
by a strong blackbody component Comptonized by thermal electrons and a weak
nonthermal tail. We then calculate rms spectra (fractional variability as
functions of energy) for the PCA data. We accurately model the rms spectra by
coherent superposition of variability in the components implied by the spectral
fits, namely a less variable blackbody and more variable Comptonization. The
latter dominates at high energies, resulting in a flattening of the rms at high
energies in most of the data. This is also the case for the spectra of the QPOs
present in the chi state. Then, some of our data require a radial dependence of
the rms of the disc blackbody. We also study the distance to the source, and
find 11 kpc as the most likely value, contrary to a recent claim of a much
lower value.


title: Discovery of 10 pulsars in an Arecibo drift-scan survey

abstract:
  We present the results of a 430-MHz survey for pulsars conducted during the
upgrade to the 305-m Arecibo radio telescope. Our survey covered a total of
1147 square degrees of sky using a drift-scan technique. We detected 33
pulsars, 10 of which were not known prior to the survey observations. The
highlight of the new discoveries is PSR J0407+1607, which has a spin period of
25.7 ms, a characteristic age of 1.5 Gyr and is in a 1.8-yr orbit about a
low-mass (>0.2 Msun) companion. The long orbital period and small eccentricity
(e = 0.0009) make the binary system an important new addition to the ensemble
of binary pulsars suitable to test for violations of the strong equivalence
principle. We also report on our initially unsuccessful attempts to detect
optically the companion to J0407+1607 which imply that its absolute visual
magnitude is > 12.1. If, as expected on evolutionary grounds, the companion is
an He white dwarf, our non-detection imples a cooling age of least 1 Gyr.


title: Magnetars

abstract:
  P-stars are compact stars made of up and down quarks in beta-equilibrium with
electrons in a chromomagnetic condensate. P-stars are able to account for
compact stars like RXJ 1856.5-3754 and RXJ 0720.4-3125, stars with radius
comparable with canonical neutron stars, as well as super massive compact
objects like SgrA*. We discuss p-stars endowed with super strong dipolar
magnetic field which, following consolidated tradition in literature, are
referred to as magnetars. We show that soft gamma-ray repeaters and anomalous
X-ray pulsars can be understood within our theory. We find a well defined
criterion to distinguish rotation powered pulsars from magnetic powered
pulsars. We show that glitches, that in our magnetars are triggered by magnetic
dissipative effects in the inner core, explain both the quiescent emission and
bursts in soft gamma-ray repeaters and anomalous X-ray pulsars. We are able to
account for the braking glitch from SGR 1900+14 and the normal glitch from AXP
1E 2259+586 following a giant burst. We discuss and explain the observed anti
correlation between hardness ratio and intensity. Within our magnetar theory we
are able to account quantitatively for light curves for both gamma-ray
repeaters and anomalous X-ray pulsars. In particular we explain the puzzling
light curve after the June 18, 2002 giant burst from AXP 1E 2259+586, so that
we feel this last event as the Rosetta Stone for our theory. Finally, in
Appendix we discuss the origin of the soft emission not only for soft gamma-ray
repeaters and anomalous X-ray pulsars, but also for isolated X-ray pulsars. We
also offer an explanation for the puzzling spectral features in 1E 1207.4-5209.


title:
On the Eccentricities and Merger Rates of Double Neutron Star Binaries
  and the Creation of "Double Supernovae"

abstract:
  We demonstrate that a natural consequence of an asymmetric kick imparted to
neutron stars at birth is that the majority of double neutron star binaries
should possess highly eccentric orbits. This leads to greatly accelerated
orbital decay, due to the enormous increase in the emission of gravitational
radiation at periastron as originally demonstrated by Peters (1964). A uniform
distribution of kick velocities constrained to the orbital plane would result
in ~24% of surviving binaries coalescing at least 10,000 times faster than an
unperturbed circular system. Even if the planar kick constraint is lifted, ~6%
of bound systems still coalesce this rapidly. In a non-negligible fraction of
cases it may even be possible that the system could coalesce within 10 years of
the final supernova, resulting in what we might term a "double supernova''. For
systems resembling the progenitor of PSR J0737-3039A, this number is as high as
\~9% (in the planar kick model). Whether the kick velocity distribution extends
to the range required to achieve this is still unclear. We do know that the
observed population of binary pulsars has a deficit of highly eccentric systems
at small orbital periods. In contrast, the long-period systems favour large
eccentricities, as expected. We argue that this is because the short-period
highly eccentric systems have already coalesced and are thus selected against
by pulsar surveys. This effect needs to be taken into account when using the
scale-factor method to estimate the coalescence rate of double neutron star
binaries. We therefore assert that the coalesence rate of such binaries is
underestimated by a factor of several.


title: Applications of Bayesian model selection to cosmological parameters

abstract:
  Bayesian model selection is a tool to decide whether the introduction of a
new parameter is warranted by data. I argue that the usual sampling statistic
significance tests for a null hypothesis can be misleading, since they do not
take into account the information gained through the data, when updating the
prior distribution to the posterior. On the contrary, Bayesian model selection
offers a quantitative implementation of Occam's razor.
  I introduce the Savage-Dickey density ratio, a computationally quick method
to determine the Bayes factor of two nested models and hence perform model
selection. As an illustration, I consider three key parameters for our
understanding of the cosmological concordance model. By using WMAP 3-year data
complemented by other cosmological measurements, I show that a non-scale
invariant spectral index of perturbations is favoured for any sensible choice
of prior. It is also found that a flat Universe is favoured with odds of 29:1
over non--flat models, and that there is strong evidence against a CDM
isocurvature component to the initial conditions which is totally
(anti)correlated with the adiabatic mode (odds of about 2000:1), but that this
is strongly dependent on the prior adopted.
  These results are contrasted with the analysis of WMAP 1-year data, which
were not informative enough to allow a conclusion as to the status of the
spectral index. In a companion paper, a new technique to forecast the Bayes
factor of a future observation is presented.


title:
Sub-arcsec imaging of the AB Aur molecular disk and envelope at
  millimeter wavelengths: a non Keplerian disk

abstract:
  We present sub-arcsecond images of AB Auriga obtained with the IRAM Plateau
de Bure interferometer in the isotopologues of CO, and in continuum at 3 and
1.3 mm. Instead of being centrally peaked, the continuum emission is dominated
by a bright, asymmetric (spiral-like) feature at about 140 AU from the central
star. The large scale molecular structure suggests the AB Aur disk is inclined
between 23 and 43 degrees, but the strong asymmetry of the continuum and
molecular emission prevents an accurate determination of the inclination of the
inner parts. We find significant non-Keplerian motion, with a best fit exponent
for the rotation velocity law of 0.41 +/- 0.01, but no evidence for radial
motions. The disk has an inner hole about 70 AU in radius. The disk is warm and
shows no evidence of depletion of CO. The dust properties suggest the dust is
less evolved than in typical T Tauri disks. Both the spiral-like feature and
the departure from purely Keplerian motions indicates the AB Aur disk is not in
quasi-equilibrium. Disk self-gravity is insufficient to create the
perturbation. This behavior may be related either to an early phase of star
formation in which the Keplerian regime is not yet fully established and/or to
a disturbance of yet unknown origin. An alternate, but unproven, possibility is
that of a low mass companion located about 40 AU from AB Aur.


title: Magnetorotational Instability around a Rotating Black Hole

abstract:
  The magnetorotational instability(MRI) in the Kerr spacetime is studied on a
3+1 viewpoint. The Maxwell's equations are expressed in a circularly orbiting
observer's frame that co-rotates with matter in Keplerian orbits. There exist
large proper growth rates in MRI around a rapidly rotating black hole. The
large "centrifugal force" and the rapid variations of magnetic fields are
caused by the rotation of spacetime geometry. As the result, in the extreme
Kerr case the maximum proper growth rate at $r=r_{ms}$ becomes about twelve
times as large as that in Schwartzshield case.


title: Vigorous star formation in a bulge-dominated ERO at z = 1.34

abstract:
  We present near-IR spectroscopy of three Extremely Red Objects (EROs) using
the OHS/CISCO spectrograph at Subaru telescope. One target exhibits a strong
emission line which we identify as H-alpha at z = 1.34. Using new and existing
ground-based optical and near-IR imaging, and archival HST imaging, we argue
that this target is essentially an elliptical galaxy, with an old stellar
population of around 4E11 solar masses, but having a dust-enshrouded
star-forming component with a SFR of some 50--100 solar masses per yr. There is
no evidence that the galaxy contains an AGN. Analysis of a further two targets,
which do not exhibit any features in our near-IR spectra, suggests that one is
a quiescent galaxy in the redshift range 1.2 < z < 1.6, but that the other
cannot be conclusively categorised as either star-forming or quiescent.
  Even though our first target has many of the properties of an old elliptical,
the ongoing star formation means that it cannot have formed_all_ of its stellar
population at high redshift. While we cannot infer any robust values for the
star formation rate in ellipticals at z > 1 from this one object, we argue that
the presence of an object with such a high SFR in such a small sample suggests
that a non-negligible fraction of the elliptical galaxy population may have
formed a component of their stellar population at redshifts z ~ 1--2. We
suggest that this is evidence for ongoing star formation in the history of
elliptical galaxies.


title:
Very compact radio emission from high-mass protostars. II. Dust disks
  and ionized accretion flows

abstract:
  This paper reports 43 GHz imaging of the high-mass protostars W33A, AFGL 2591
and NGC 7538 IRS9 at 0.04'' and 0.6'' resolution. In each case, weak (~mJy),
compact (~100 AU) emission is detected, which has an elongated shape (axis
ratio ~3). For AFGL 2591 and NGC 7538 IRS9, the emission is single-peaked,
while for the highest luminosity source, W33A, a `mini-cluster' of three
sources is detected. The derived sizes, flux densities, and broad-band radio
spectra of the sources support recent models where the initial expansion of HII
regions around very young O-type stars is prevented by stellar gravity. In
these models, accretion flows onto high-mass stars originate in large-scale
molecular envelopes and become ionized close to the star. These models
reproduce our observations of ionized gas as well as the structure of the
molecular envelopes of these sources on 10^3--10^4 AU scales derived previously
from single-dish submillimeter continuum and line mapping. For AFGL 2591, the
43 GHz flux density is also consistent with dust emission from a disk seen in
near-infrared `speckle' images. However, the alignment of the 43 GHz emission
with the large-scale molecular outflow argues against an origin in a disk for
AFGL 2591 and NGC 7538 IRS9. In contrast, the outflow from W33A does not appear
to be collimated. Together with previously presented case studies of W3 IRS5
and AFGL 2136, our results indicate that the formation of stars and stellar
clusters with luminosities up to ~10^5 L0 proceeds through accretion and
produces collimated outflows as in the solar-type case, with the `additional
feature' that the accretion flow becomes ionized close to the star. Above ~10^5
L0, clusters of HII regions appear, and outflows are no longer collimated,
possibly as the result of mergers of protostars or pre-stellar cores.


title:
Studying the Variation of the Fine Structure Constant Using Emission
  Line Multiplets

abstract:
  As an extension of the method by Bahcall et al. (2004) to investigate the
time dependence of the fine structure constant, we describe an approach based
on new observations of forbidden line multiplets from different ionic species.
We obtain optical spectra of fine structure transitions in [Ne III], [Ne V], [O
III], [OI], and [SII] multiplets from a sample of 14 Seyfert 1.5 galaxies in
the low-z range 0.035 < z < 0.281. Each source and each multiplet is
independently analyzed to ascertain possible errors. Averaging over our sample,
we obtain a conservative value alpha^2(t)/\alpha^2(0) = 1.0030+-0.0014.
However, our sample is limited in size and our fitting technique simplistic as
we primarily intend to illustrate the scope and strengths of emission line
studies of the time variation of the fine structure constant. The approach can
be further extended and generalized to a "many-multiplet emission line method"
analogous in principle to the corresponding method using absorption lines. With
that aim, we note that the theoretical limits on emission line ratios of
selected ions are precisely known, and provide well constrained selection
criteria. We also discuss several other forbidden and allowed lines that may
constitute the basis for a more rigorous study using high-resolution
instruments on the next generation of 8 m class telescopes.


title: Quantitative Spectroscopy of Photospheric-Phase Type II Supernovae

abstract:
  We present first results on the quantitative spectroscopic analysis of the
photospheric-phase of Type II supernovae (SN). The analyses are based on the
non-LTE model atmosphere code, CMFGEN, of Hillier & Miller (1998). A key asset
of CMFGEN is its thorough treatment of line-blanketing due to metal species.
  From its applicability to hot star environments, the main modifications to
the source code were to allow a linear velocity law, a power-law density
distribution, an adaptive grid to handle the steep H recombination/ionization
front occurring in cooler SN models, and a routine to compute the gray
temperature structure in the presence of large velocities. In this first paper
we demonstrate the ability of CMFGEN to reproduce, with a high level of
accuracy, the UV and optical observations of a sample of well observed Type II
SN, i.e. SN1987A and SN1999em, at representative stages of their photospheric
evolution. Two principal stages of SN are modeled - that where hydrogen is
fully ionized, and that in which H is only partially ionized. We provide
detailed and accurate line identifications for our sample of epochs. We discuss
the impact on the SED of varying the density exponent, the spatial scale of the
SN, the value of Rmax and the metallicity; we illustrate the formation sites
for selected lines. Both Hydrogen Balmer and Helium lines (when present) are
very well reproduced, even for our adopted CNO-equilibrium abundance values
adequate for a massive supergiant progenitor star. NII lines are also predicted
in the blue-wing of both Hbeta and HeI 5875A, and thus not associated with
peculiar absorption/emission far above the photosphere. We finally present a
pedagogical discussion of P-Cygni profile formation and explain, e.g., the
noticeable blue-shift of Halpha in early time spectra (much abridged abstract).


title: A low-absorption disk zone at low Galactic latitude in Centaurus

abstract:
  We investigate the properties of two stellar concentrations in a
low-absorption disk zone in Centaurus, located respectively at
$\ell=306.47^{\circ}$, $b=-0.61 ^{\circ}$, and $\ell=307.01^{\circ}$, $b=-0.74
^{\circ}$. The present analysis is based mostly on 2MASS photometry, as well as
optical photometry. Based on colour-magnitude diagrams and stellar radial
density profiles, we show that these concentrations are not open star clusters.
Instead, they appear to be field stars seen through a differentially-reddened
window. We estimate that the bulk of the stars in both stellar concentrations
is located at $\sim1.5$ kpc from the Sun, a distance consistent with that of
the Sgr-Car arm in that direction. This low-absorption window allows one to
probe into distant parts of the disk besides the Sgr-Car arm, probably the
tangent part of the Sct-Cru arm, and/or the far side of the Sgr-Car arm in that
direction. The main sequence associated to the Sgr-Car arm is reddened by
$\ebv\sim0.5$, so that this window through the disk is comparable in reddening
to Baade's window to the bulge. We also investigate the nature of the open
cluster candidate Ru 166. The presently available data do not allow us to
conclude whether Ru 166 is an actual open cluster or field stars seen through a
small-scale low-absorption window.


title:
Early Re-brightenings in GRB Afterglows as Signatures of Low-to-High
  Density Boundary

abstract:
  The association of long gamma-ray bursts (GRBs) with star forming regions and
the idea of massive stars as progenitors of GRBs are widely accepted. Because
of their short lifetimes, it is very likely that massive stars are still
embedded in dense molecular clouds when they give birth to GRBs. Stellar winds
from GRB progenitors can create low-density bubbles with sizes and densities
strongly depending on the initial ambient density. A boundary between the
bubble and the dense molecular cloud must exist with the density at the
boundary increasing from that of the bubble to that of the outer cloud. We have
calculated the lightcurves of the afterglows in such environments with three
regions: the stellar wind region, the boundary, and the molecular cloud. We
show that the interaction between the cylindrical jet and the density boundary
can result in a re-brightening of the afterglow occurring as early as ~1 day
after the GRB. We compare our models with the optical afterglows of GRB970508,
GRB000301C, and GRB030226. We find that the values of our model parameters,
including the radius of the wind bubble, the densities in the bubble and in the
outer molecular cloud are within typical ranges.


title: An old quasar in a young dark energy-dominated universe?

abstract:
  Dark energy is the invisible fuel that seems to drive the current
acceleration of the Universe. Its presence, which is inferred from an
impressive convergence of high-quality observational results along with some
apparently sucessful theoretical predictions, is also supported by the current
estimates of the age of the Universe from dating of local and high-$z$ objects.
In this paper we test the viability of several dark energy scenarios in the
light of the age estimates of the high redshift ($z=3.91$) quasar APM
08279+5255. Using a chemodinamical model for the evolution of spheroids, we
first reevaluate its current estimated age, as given by Hasinger et al. (2002).
An age of 2.1 Gyr is set by the condition that Fe/O abundance ratio (normalized
to solar values) of the model reaches 3.3, which is the best fit value obtained
in the above reference. It is shown that for the currently accepted value of
the matter density parameter, most of the existing dark energy scenarios cannot
accomodate this old high redshift object unless the Hubble parameter is as low
as $H_o = 58$ $\rm{km.s^{-1}.Mpc^{-1}}$, as recently advocated by Sandage and
collaborators. Even considering less stringent age limits, only cosmological
models that predicts a considerably old Universe at high-$z$ can be compatible
with the existence of this object. This is the case of the conventional
$\Lambda$CDM scenario and some specific classes of brane world cosmologies.


title:
Stellar Populations in Ten Clump-Cluster Galaxies of the Ultra Deep
  Field

abstract:
  Color-color diagrams for the clump and interclump emission in 10
clump-cluster galaxies of the Ultra Deep Field are made from B,V,i, and z
images and compared with models to determine redshifts, star formation
histories, and galaxy masses. The clump colors suggest declining star formation
over the last ~0.3 Gy, while the interclump emission is older. The clump
luminous masses are typically 6x10^8 Msun and their diameters average 1.8 kpc.
Total galaxy luminous masses average 6.5x10^10 Msun. The distribution of axial
ratios is consistent with a thick disk geometry. The ages of the clumps are
longer than their internal dynamical times by a factor of ~8, so they are
stable clusters, but the clump densities are only ~10 times the limiting tidal
densities, so they could be deformed by tidal forces. This is consistent with
the observation that some clumps have tails. The clumps could form by
gravitational instabilities in accreting disk gas, or they could be captured as
gas-rich dwarf galaxies. Support for this second possibility comes from the
high abundance of nearly identical bare clumps in the UDF field. Several
clump-clusters have disk densities that are much larger than in local disks,
suggesting they do not survive but get converted into ellipticals by
collisions.


title:
Central Blue Clumps in Elliptical Galaxies of the Hubble Ultra Deep
  Field

abstract:
  Elliptical galaxies larger than 10 pixels in the Hubble Ultra Deep Field
(UDF) were surveyed for internal structure; 30 out of 100 in a sample of 884
morphologically classified galaxies exhibit large blue clumps near their
centers. Unsharp-masked images of the best cases are presented. The
distributions of the clumps on color-color and color-magnitude diagrams are
about the same as the distributions of isolated objects in the UDF field with
the same size, suggesting a possible accretion origin. In the few cases where
redshifts are published, the clump masses and star-formation ages were
determined from stellar evolution models, as were the galaxy masses. The clump
mass scales with galaxy mass, probably because of selection effects, and ranges
from 10^6 Msun to 10^8 Msun for galaxies with masses from 10^{9} Msun to
10^{11} Msun. The clump star formation age ranges between 10^7 yr and 2x10^8
yr. With partial evaporation and core contraction in the intervening years,
some of these clumps could resemble globular clusters today. Stars that
evaporate will contribute to the field population in the elliptical galaxy.


title: Primordial Black Holes - Recent Developments

abstract:
  Recent developments in the study of primordial black holes (PBHs) will be
reviewed, with particular emphasis on their formation and evaporation. PBHs
could provide a unique probe of the early Universe, gravitational collapse,
high energy physics and quantum gravity. Indeed their study may place
interesting constraints on the physics relevant to these areas even if they
never formed. In the "early Universe" context, particularly useful constraints
can be placed on inflationary scenarios, especially if evaporating PBHs leave
stable Planck-mass relicts. In the "gravitational collapse" context, the
existence of PBHs could provide a unique test of the sort of critical phenomena
discovered in recent numerical calculations. In the "high energy physics"
context, information may come from gamma-ray bursts (if a subset of these are
generated by PBH explosions) or from cosmic rays (if some of these derive from
evaporating PBHs). In the "quantum gravity" context, the formation and
evaporation of small black holes could lead to observable signatures in cosmic
ray events and accelerator experiments, providing there are extra dimensions
and providing the quantum gravity scale is around a TeV.


title:
Exploring Halo Substructure with Giant Stars: The Velocity Dispersion
  Profiles of the Ursa Minor and Draco Dwarf Spheroidals At Large Angular
  Separations

abstract:
  We analyze velocity dispersion profiles for the Draco and Ursa Minor (UMi)
dwarf spheroidal (dSph) galaxies based on published and new Keck HIRES spectra
for stars in the outer UMi field. Washington+DDO51 filter photometric catalogs
provide additional leverage on membership of individual stars, and beyond 0.5
King limiting radii (R_lim) identify bona fide dSph members up to 4.5 times
more efficiently than simple color-magnitude diagram selections. Previously
reported ``cold populations'' R_lim are not obvious in the data and appear only
with particular binning; more or less constant and platykurtic dispersion
profiles are characteristic of these dSphs to large radii. We report discovery
of UMi stars to at least 2.7 R_lim (i.e.,210 arcmin or 4 kpc). Even with
conservative assumptions, a UMi mass of M > 4.9 x 10^8 M_(sun) is required to
bind these stars, implying an unlikely global mass-to-light ratio of M/L > 900
(M/L)_(sun). We conclude that we have found stars tidally stripped from UMi.


title:
Gemini and Chandra observations of Abell 586, a relaxed strong-lensing
  cluster

abstract:
  We analyze the mass content of the massive strong-lensing cluster Abell 586
($z = 0.17$). We use optical data (imaging and spectroscopy) obtained with the
Gemini Multi-Object Spectrograph (GMOS) mounted on the 8-m Gemini-North
telescope, together with publicly available X-ray data taken with the
\textit{Chandra} space telescope. Employing different techniques -- velocity
distribution of galaxies, weak gravitational lensing, and X-ray spatially
resolved spectroscopy -- we derive mass and velocity dispersion estimates from
each of them. All estimates agree well with each other, within a 68% confidence
level, indicating a velocity dispersion of 1000 -- 1250 \kms. The projected
mass distributions obtained through weak-lensing and X-ray emission are
strikingly similar, having nearly circular geometry. We suggest that Abell 586
is probably a truly relaxed cluster, whose last major merger occurred more than
$\sim 4$ Gyr ago


title:
Radiative equilibrium in Monte Carlo radiative transfer using frequency
  distribution adjustment

abstract:
  The Monte Carlo method is a powerful tool for performing radiative
equilibrium calculations, even in complex geometries. The main drawback of the
standard Monte Carlo radiative equilibrium methods is that they require
iteration, which makes them numerically very demanding. Bjorkman & Wood
recently proposed a frequency distribution adjustment scheme, which allows
radiative equilibrium Monte Carlo calculations to be performed without
iteration, by choosing the frequency of each re-emitted photon such that it
corrects for the incorrect spectrum of the previously re-emitted photons.
Although the method appears to yield correct results, we argue that its
theoretical basis is not completely transparent, and that it is not completely
clear whether this technique is an exact rigorous method, or whether it is just
a good and convenient approximation. We critically study the general problem of
how an already sampled distribution can be adjusted to a new distribution by
adding data points sampled from an adjustment distribution. We show that this
adjustment is not always possible, and that it depends on the shape of the
original and desired distributions, as well as on the relative number of data
points that can be added. Applying this theorem to radiative equilibrium Monte
Carlo calculations, we provide a firm theoretical basis for the frequency
distribution adjustment method of Bjorkman & Wood, and we demonstrate that this
method provides the correct frequency distribution through the additional
requirement of radiative equilibrium. We discuss the advantages and limitations
of this approach, and show that it can easily be combined with the presence of
additional heating sources and the concept of photon weighting. However, the
method may fail if small dust grains are included... (abridged)


title: The First Generation of Star-Forming Haloes

abstract:
  We model gas cooling in high-resolution N-body simulations in order to
investigate the formation of the first generation of stars. We follow a region
of a LCDM universe especially selected to contain a rich cluster by the present
day. The properties of the dark haloes that form in these sub-solar mass
resolution simulations are presented in a companion paper by Gao et al. The
first gas clouds able to cool by molecular hydrogen line emission collapse at
extremely high redshift, z ~ 47, when the mass of the dark halo is 2.4 x 10^5
Msun/h. By z ~ 30, a substantial population of haloes are capable of undergoing
molecular hydrogen cooling although their ability to form stars is dependent on
the efficiency of feedback processes such as dissociating Lyman-Werner
radiation. The mass of the main halo grows extremely rapidly and, by z ~ 36,
its virial temperature has reached 10^4K, at which point gas cooling becomes
dominated by more effective atomic line processes. By z ~ 30, a small ``group''
of such potential galaxies will have formed unless prevented from doing so by
feedback processes. By this redshift, massive (>~ 100 Msun) population III
stars are able to ionise gas well beyond their own host halo and neighbouring
HII regions can percolate to form an ionized superbubble. Such patches would be
too widely separated to contribute significantly to reionisation at this time.
The large number density of early cooling haloes in the pre-reionised universe
raises the exciting prospect that this ultra-early generation of stars may be
observable as gamma-ray bursts or supernovae.


title:
Early photon-shock interaction in stellar wind: sub-GeV photon flash and
  high energy neutrino emission from long GRBs

abstract:
  For gamma-ray bursts (GRBs) born in a stellar wind, as the reverse shock
crosses the ejecta, usually the shocked regions are still precipitated by the
prompt MeV \gamma-ray emission. Because of the tight overlapping of the MeV
photon flow with the shocked regions, the optical depth for the GeV photons
produced in the shocks is very large. These high energy photons are absorbed by
the MeV photon flow and generate relativistic e^\pm pairs. These pairs
re-scatter the soft X-ray photons from the forward shock as well as the prompt
\gamma-ray photons and power detectable high energy emission, significant part
of which is in the sub-GeV energy range. Since the total energy contained in
the forward shock region and the reverse shock region are comparable, the
predicted sub-GeV emission is independent on whether the GRB ejecta are
magnetized (in which case the reverse shock IC and synchrotron self-Compton
emission is suppressed). As a result, a sub-GeV flash is a generic signature
for the GRB wind model, and it should be typically detectable by the future
{\em Gamma-Ray Large Area Telescope} (GLAST). Overlapping also influence
neutrino emission. Besides the 10^{15} \sim 10^{17} eV neutrino emission
powered by the interaction of the shock accelerated protons with the
synchrotron photons in both the forward and reverse shock regions, there comes
another $10^{14}$eV neutrino emission component powered by protons interacting
with the MeV photon flow. This last component has a similar spectrum to the one
generated in the internal shock phase, but the typical energy is slightly
lower.


title: Hot Cores : Probes of High-Redshift Galaxies

abstract:
  The very high rates of second generation star formation detected and inferred
in high redshift objects should be accompanied by intense millimetre-wave
emission from hot core molecules. We calculate the molecular abundances likely
to arise in hot cores associated with massive star formation at high redshift,
using several independent models of metallicity in the early Universe. If the
number of hot cores exceeds that in the Milky Way Galaxy by a factor of at
least one thousand, then a wide range of molecules in high redshift hot cores
should have detectable emission. It should be possible to distinguish between
independent models for the production of metals and hence hot core molecules
should be useful probes of star formation at high redshift.


title:
Proper Motion of H2O Masers in IRAS 20050+2720 MMS1: An AU Scale Jet
  Associated with An Intermediate-Mass Class 0 Source

abstract:
  We conducted a 4 epoch 3 month VLBA proper motion study of H$_2$O masers
toward an intermediate-mass class 0 source IRAS 20050+2720 MMS1 (d=700 pc).
  From milli-arcsecond (mas) resolution VLBA images, we found two groups of H2O
maser spots at the center of the submillimeter core of MMS1. One group consists
of more than $\sim 50$ intense maser spots; the other group consisting of
several weaker maser spots is located at 18 AU south-west of the intense group.
Distribution of the maser spots in the intense group shows an arc-shaped
structure which includes the maser spots that showed a clear velocity gradient.
The spatial and velocity structures of the maser spots in the arc-shape did not
significantly change through the 4 epochs. Furthermore, we found a relative
proper motion between the two groups. Their projected separation increased by
1.13+/-0.11 mas over the 4 epochs along a line connecting them. The spatial and
velocity structures of the intense group and the relative proper motions
strongly suggest that the maser emission is associated with a protostellar jet.
Comparing the observed LSR velocities with calculated radial velocities from a
simple biconical jet model, we conclude that the most of the maser emission are
likely to be associated with an accelerating biconical jet which has large
opening angle. The large opening angle of the jet traced by the masers would
support the hypothesis that poor jet collimation is an inherent property of
luminous (proto)stars.


title: On the origin of the drifting subpulses in radio pulsars

abstract:
  A model for the main observational characteristics of the radio emission of
pulsars with well organized drifting subpulses is presented. We propose that
drifting subpulses result from the modulation of the radio emission mechanism
due to long-wavelength drift waves in the magnetosphere. The drift waves are
generated at shorter wavelengths, and their nonlinear evolution favours
accumulation in a specific azimuthal eigenmode with an integral number, $m$, of
nodes encircling the magnetic pole. The electric field of the drift waves is
along the magnetic field lines, and this modulates the distribution for
particles and hence the radio emission mechanism. The ratio of the frequency of
the eigenmode to the rotation frequency of the star is insensitive to the
magnetic field strength and the period of rotation, and is of order unity. The
period, $P_3$, of the drifting subpulses is attributed to the mismatch between
this frequency and the nearest harmonic of the rotation frequency of the star.


title:
Asteroseismology of the planet-hosting star $\mu$ Arae. I. The acoustic
  spectrum

abstract:
  We present HARPS spectroscopy of mu Arae (HD160691) performed for studying
the origin of the metallicity excess in this planet-hosting stars. The
asteroseismologic campaign led to the previously reported discovery of a 14
earth mass planetary companion (Santos et al. 2004). The present analysis
reinforces this interpretation by excluding other possible processes for
explaining the observed Doppler variation and leads to the identification of up
to 43 p-mode oscillations with l=0-3, frequencies in the range 1.3-2.5 mHz and
amplitudes in the range 10-40 cm/s.


title:
uvby-Hbeta CCD photometry and membership segregation of the open cluster
  NGC 2548; Gaps in the Main Sequence of open clusters

abstract:
  Deep CCD photometry in the uvby-Hbeta intermediate-band system is presented
for the cluster NGC 2548 (M 48). A complete membership analysis based on
astrometric and photometric criteria is applied. The photometric analysis of a
selected sample of stars yields a reddening value of E(b-y)=0.06\pm0.03, a
distance modulus of V_0-M_V=9.3\pm0.5 (725 pc) and a metallicity of [Fe/H]=
-0.24\pm0.27. Through isochrone fitting we find an age of log t = 8.6\pm0.1
(400 Myr). Our optical photometry and JHK from 2MASS are combined to derive
effective temperatures of cluster member stars. The effective temperature
distribution along the main sequence of the cluster shows several gaps. A test
to study the significance of these gaps in the main sequence of the HR diagram
has been applied. The method is also applied to several other open clusters
(Pleiades, Hyades, NGC 1817 and M 67) to construct a sequence of metallicities
and ages. The comparison of the results of each cluster gives four gaps with
high significance (one of them, centred at 4900 K, has not been previously
reported).


title: The inflationary prediction for primordial non-gaussianity

abstract:
  We extend the \delta N formalism so that it gives all of the stochastic
properties of the primordial curvature perturbation \zeta if the initial field
perturbations are gaussian. The calculation requires only the knowledge of some
family of unperturbed universes. A formula is given for the normalisation \fnl
of the bispectrum of \zeta, which is the main signal of non-gaussianity.
Examples of the use of the formula are given, and its relation to cosmological
perturbation theory is explained.


title: Detecting a small perturbation through its non-Gaussianity

abstract:
  A highly non-gaussian cosmological perturbation with a flat spectrum has
unusual stochastic properties. We show that they depend on the size of the box
within which the perturbation is defined, but that for a typical observer the
parameters defining the perturbation `run' to compensate for any change in the
box size. Focusing on the primordial curvature perturbation, we show that an
un-correlated gaussian-squared component is bounded at around the 10% level by
the WMAP bound on the bispectrum, and we show that a competitive bound may
follow from the trispectrum when it too is bounded by WMAP. Similar
considerations apply to a highly non-gaussian isocurvature perturbation.


title:
Star counts in the Galaxy. Simulating from very deep to very shallow
  photometric surveys with the TRILEGAL code

abstract:
  We describe TRILEGAL, a new populations synthesis code for simulating the
stellar photometry of any Galaxy field. The code attempts to improve upon
several technical aspects of star count models, by: dealing with very complete
input libraries of evolutionary tracks; using a stellar spectral library to
simulate the photometry in any broad-band system; being very versatile allowing
easy changes in the input libraries and in the description of all of its
ingredients -- like the SFR, AMR, IMF, and geometry of Galaxy components. In a
previous paper (Groenewegen et al. 2002), the code was first applied to
describe the very deep star counts of the CDFS stellar catalogue. Here, we
briefly describe its initial calibration using EIS-deep and DMS star counts,
which are adequate samples to probe both the halo and the disc components of
largest scale heights (oldest ages). We then present the changes in the
calibration that were necessary to cope with some improvements in the model
input data, and the use of more extensive photometry datasets: the relatively
shallower 2MASS catalogue, which probes mostly the disc at intermediate ages,
and the immediate solar neighbourhood as sampled by Hipparcos, which contains a
somewhat larger fraction of younger stars than deeper surveys. Remarkably, the
same model calibration can reproduce well the star counts in all the
above-mentioned data sets, that span from the very deep magnitudes of CDFS
(16<R<23) to the very shallow ones of Hipparcos (V<8). Significant deviations
are found just for fields close to the Galactic Center and Plane, and for a
single set of South Galactic Pole data. The TRILEGAL code is ready to use for
the variety of wide-angle surveys in the optical/infrared that will become
available in the coming years.


title: Search templates for stochastic gravitational-wave backgrounds

abstract:
  Several earth-based gravitational-wave (GW) detectors are actively pursuing
the quest for placing observational constraints on models that predict the
behavior of a variety of astrophysical and cosmological sources. These sources
span a wide gamut, ranging from hydrodynamic instabilities in neutron stars
(such as r-modes) to particle production in the early universe. Signals from a
subset of these sources are expected to appear in these detectors as stochastic
GW backgrounds (SGWBs). The detection of these backgrounds will help us in
characterizing their sources. Accounting for such a background will also be
required by some detectors, such as the proposed space-based detector LISA, so
that they can detect other GW signals. Here, we formulate the problem of
constructing a bank of search templates that discretely span the parameter
space of a generic SGWB. We apply it to the specific case of a class of
cosmological SGWBs, known as the broken power-law models. We derive how the
template density varies in their three-dimensional parameter space and show
that for the LIGO 4km detector pair, with LIGO-I sensitivities, about a few
hundred templates will suffice to detect such a background while incurring a
loss in signal-to-noise ratio of no more than 3%.


title: Exact solution of the standard transfer problem in a stellar atmosphere

abstract:
  We come back to the analytical solution of the standard transfer problem in a
stellar atmosphere. It consists in solving the radiative transfer equation in a
homogeneous and isothermal plane-parallel atmosphere, with light scattering
taken as isotropic and monochromatic. The literature on the subject is reviewed
and the existing solution in a finite slab is improved thanks to the
introduction of non classical auxiliary functions. Eleven-figure tables of the
solution are given for typical values of the input parameters currently met in
stellar atmospheres.


title: A possible bright blue SN in the afterglow of GRB 020305

abstract:
  We report on ground-based and HST(+STIS) imaging of the afterglow and host
galaxy of the Gamma-Ray Burst (GRB) of March 5 2002. The GRB occurred in a
R=25.17+/-0.14 galaxy, which apparently is part of an interacting system. The
lightcurve of the optical afterglow shows a rebrightening, or at least a
plateau, 12--16 days after the gamma-ray event. UBVRIK' multi-band imaging of
the afterglow ~12 days after the GRB reveals a blue spectral energy
distribution (SED). The SED is consistent with a power-law with a spectral
index of \beta=-0.63+/-0.16, but there is tentative evidence for deviations
away from a power-law. Unfortunately, a spectroscopic redshift has not been
secured for GRB020305. From the SED we impose a redshift upper limit of z ~<
2.8, hence excluding the pseudo redshift of 4.6 reported for this burst. We
discuss the possibilities for explaining the lightcurve, SED and host galaxy
properties for GRB 020305. The most natural interpretation of the lightcurve
and the SED is an associated supernova (SN). Our data can not precisely
determine the redshift of the GRB. The most favoured explanation is a low
redshift (z~0.2) SN, but a higher redshift (z>0.5) SN can not be excluded. We
also discuss less likely scenarios not based on SNe, like a burst occurring in
a z=2.5 galaxy with an extinction curve similar to that of the Milky Way.


title: Testing MOND with Ultra-Compact Dwarf Galaxies

abstract:
  The properties of the recently discovered Ultra-Compact Dwarf Galaxies (UCDs)
show that their internal acceleration of gravity is everywhere above a0, the
MOdified Newtonian Dynamics (MOND) constant of gravity. MOND therefore makes
the strong prediction that no mass discrepancy should be observed for this
class of objects. This is confirmed by the few UCDs for which virial masses
were derived. We argue that UCD galaxies represent a suitable test-bench for
the theory, in the sense that even a single UCD galaxy showing evidence for
dark matter would seriously question the validity of MOND.


title:
A New Relation between GRB Rest-Frame Spectra and Energetics and Its
  Utility on Cosmology

abstract:
  We investigate the well-measured spectral and energetic properties of 20
gamma-ray bursts (GRBs) in their cosmological rest frames. We find a tight
relation between the isotropic-equivalent gamma-ray energy Eiso, the local peak
energy E'p of the \nu F_{\nu} spectrum, and the local break time t'b of the GRB
afterglow light curve, which reads Eiso*t'b\propto E'p^{1.95\pm0.08}
(\chi^2_\nu=1.40; Omega_M=0.27, Omega_Lambda=0.73). Such a power-law relation
can be understood via the high-energy radiation processes for the GRB prompt
emission accompanying the beaming effects. We then consider this relation as an
intrinsic one for the observed GRB sample, and obtain a constraint on the mass
density Omega_M=0.24^{+0.16}_{-0.12} (1\sigma) for a flat Lambda-CDM universe,
and a \chi^2_{dof}=1.33 for Omega_M\approx0.3 and Omega_Lambda\approx0.7.
Ongoing GRB observations in the Swift era are expected to confirm this relation
and make its cosmological utility progress much.


title: Stellar dynamo driven wind braking instead of disc coupling

abstract:
  Star-disc coupling is considered in numerical models where the stellar field
is not an imposed perfect dipole, but instead a more irregular self-adjusting
dynamo-generated field. Using axisymmetric simulations of the hydromagnetic
mean-field equations, it is shown that the resulting stellar field
configuration is more complex, but significantly better suited for driving a
stellar wind. In agreement with recent findings by a number of people,
star-disc coupling is less efficient in braking the star than previously
thought. Moreover, stellar wind braking becomes equally important. In contrast
to a perfect stellar dipole field, dynamo-generated stellar fields favor
field-aligned accretion with considerably higher velocity at low latitudes,
where the field is weaker and originating in the disc. Accretion is no longer
nearly periodic (as it is in the case of a stellar dipole), but it is more
irregular and episodic.


title:
The Sensitivity of Multidimensional Nova Calculations to the Outer
  Boundary Conditions

abstract:
  Multidimensional reactive flow models of accreted hydrogen rich envelopes on
top of degenerate cold white dwarfs are very effective tools for the study of
critical, non spherically symmetric, behaviors during the early stages of nova
outbursts. Such models can shed light both on the mechanism responsible for the
heavy element enrichment observed to characterize nova envelope matter and on
the role of perturbations during the early stages of ignition of the runaway.
The complexity of convective reactive flow in multi-dimensions makes the
computational model itself complex and sensitive to the details of the
numerics. In this study, we demonstrate that the imposed outer boundary
condition can have a dramatic effect on the solution. Several commonly used
choices for the outer boundary conditions are examined. It is shown that the
solutions obtained from Lagrangian simulations, where the envelope is allowed
to expand and mass is being conserved, are consistent with spherically
symmetric solutions. In Eulerian schemes which utilize an outer boundary
condition of free outflow, the outburst can be artificially quenched.


title:
The effect of a finite mass reservoir on the collapse of spherical
  isothermal clouds and the evolution of protostellar accretion

abstract:
  Motivated by recent observations which detect an outer boundary for starless
cores, and evidence for time-dependent mass accretion in the Class 0 and Class
I protostellar phases, we reexamine the case of spherical isothermal collapse
in the case of a finite mass reservoir. The presence of a core boundary results
in the generation of an inward propagating rarefaction wave. This steepens the
gas density profile from r^{-2} to r^{-3} or steeper. After a protostar forms,
the mass accretion rate \dot{M} evolves through three distinct phases: (1) an
early phase of decline in \dot{M}, which is a non-self-similar effect due to
spatially nonuniform infall in the prestellar phase; (2) for large cores, an
intermediate phase of near-constant \dot{M} from the infall of the outer part
of the self-similar density profile; (3) a late phase of rapid decline in
\dot{M} when accretion occurs from the region affected by the inward
propagating rarefaction wave. Our model clouds of small to intermediate size
make a direct transition from phase (1) to phase (3) above. Both the first and
second phase are characterized by a temporally increasing bolometric luminosity
L_bol, while L_bol is decreasing in the third (final) phase. We identify the
period of temporally increasing L_bol with the Class 0 phase, and the later
period of terminal accretion and decreasing L_bol with the Class I phase. The
peak in L_bol corresponds to the evolutionary time when 50% \pm 10% of the
cloud mass has been accreted by the protostar. This is in agreement with the
classification scheme proposed by Andre et al. (1993). We show how our results
can be used to explain tracks of envelope mass M_env versus L_bol for
protostars in Taurus and Ophiuchus. We also develop an analytic formalism which
reproduces the protostellar accretion rate.


title:
The gamma-ray giant flare from SGR1806-20: Evidence for crustal cracking
  via initial timescales

abstract:
  We report here on serendipitous observations of the intense gamma-ray flare
from SGR 1806-20 that occured on 27 December 2004. Unique data from the Cluster
and Double Star-2 satellites, designed to study the Earth's magnetosphere,
provide the first observational evidence of three separate timescales within
the early (first 100ms) phases of this class of events. These observations
reveal that, in addition to the initial very steep (<0.25ms) X-ray onset, there
is firstly a 4.9ms exponential rise timescale followed by a continued
exponential rise in intensity on a timescale of 70ms. These three timescales
are a prominent feature of current theoretical models including the timescale
(several ms) for fracture propagation in the crust of the neutron star.