title: Mass accretion histories & density profiles of LCDM clusters

abstract:
  We analyze the mass accretion histories (MAHs) and density profiles of
cluster-size halos in a flat LCDM cosmology.To fit the MAHs of all systems we
need to generalize the MAH fit found in previous systematic studies of
predominantly galactic halos.We find that the concentration of the density
distribution is tightly correlated with the halo MAH and its formation
redshift. During the early period of fast mass growth the concentration remains
roughly constant and low (~3-4), while during the slow accretion phase it
increases with decreasing redshift as 1/(1+z).We consider fits of three widely
discussed analytic density profiles.We find that there is no unique best fit
for all clusters.At the same time, if a cluster is best fit by a particular
analytic profile at z=0, the same is usually true at earlier epochs out to z ~
1-2.The local logarithmic slope of the density profiles at 3% of the virial
radius ranges from -1.2 to -2.0.In addition, the logarithmic slope becomes
shallower with decreasing radius without reaching an asymptotic value down to
the smallest resolved scale (<1% of the virial radius).During the early MAH
period of rapid mass growth the density profiles can be well described by a
single power law rho(r) ~ r^-a with a ~ 1.5-2.The relatively shallow power law
slopes result in low concentrations at these stages of evolution, as the scale
radius where the density profiles reaches the slope of -2 is at large
radii.This indicates that the inner power law like density distribution of
halos is built up during the periods of rapid mass accretion and active
merging, while the outer steeper profile is formed when the mass accretion
slows down.


title: SGRS J0515-8100: a Fat-Double giant radio galaxy

abstract:
  We present here the first detailed study of a giant radio galaxy of the
Fat-Double type. The lobes of the double radio galaxy SGRS J0515-8100 have
transverse widths that are 1.3 times their extent from the center, their
surface brightness is the lowest among known giant radio sources and the lobes
have relatively steep radio spectra. We infer that these wide lobes were
created as a result of a highly variable and intermittent jet whose axis
direction also varied significantly: the Fat-Double lobes in this giant radio
source are a result of the ejection and deposition of synchrotron plasma over a
wide range of angles over time rather than the expansion of relic lobes.
Additionally, the optical host shows evidence for an ongoing galaxy-galaxy
interaction. SGRS J0515-8100 supports the hypothesis that interactions with
companions might perturb the inner accretion disk that produces and sustains
the jets at the centers of active galactic nuclei. As a result, it appears
unnecessary to invoke black-hole coalescence to explain such morphologies,
implying that the corresponding event rates predicted for gravitational wave
detectors may be overestimates.


title:
Absolute Rate, Evolving Luminosity function, and Evolving Jet Opening
  Angle Distribution for Long Gamma-Ray Bursts

abstract:
  Using the luminosity function and the apparent GRB rate inferred from the
spectral peak energy-luminosity relation, we investigate the absolute GRB
formation rate, taking into account the effects of both the jet-luminosity
evolution and the jet opening angle evolution. In the case that there is no jet
opening angle evolution, the jet-corrected luminosity for high-redshift GRBs is
much larger than typical values for low-z (z>~1) bursts. On the other hand, if
the jet-luminosity does not evolve with time, the jet opening angle for high-z
bursts should be much smaller than that for low-z GRBs. Therefore, it is
preferable to take into account both evolution effects. We also estimate the
local GRB event rate in a galaxy of ~10^{-7}-10^{-5}/yr.


title: Dust extinction and absorption: the challenge of porous grains

abstract:
  In many models of dusty objects in space the grains are assumed to be
composite or fluffy. However, the computation of the optical properties of such
particles is still a very difficult problem. We analyze how the increase of
grain porosity influences basic features of cosmic dust -- interstellar
extinction, dust temperature, infrared bands and millimeter opacity. Porous
grains can reproduce the flat extinction across the $3 - 8 \mkm$ wavelength
range measured for several lines of sight by {\it ISO} and {\it Spitzer}.
  Porous grains are generally cooler than compact grains. At the same time, the
temperature of very porous grains becomes slightly larger in the case of the
EMT-Mie calculations in comparison with the results found from the
layered-sphere model. The layered-sphere model predicts a broadening of
infrared bands and a shift of the peak position to larger wavelengths as
porosity grows. In the case of the EMT-Mie model variations of the feature
profile are less significant. It is also shown that the millimeter mass
absorption coefficients grow as porosity increases with a faster growth
occurring for particles with Rayleigh/non-Rayleigh inclusions. As a result, for
very porous particles the coefficients given by two models can differ by a
factor of about 3.
  It is found that an increase of porosity leads to an increase of extinction
cross sections at some wavelengths and a decrease at others depending on the
grain model. However, this behaviour is sufficient to reproduce the extinction
curve in the direction of the star $\sigma$ Sco using current solar abundances.
In the case of the star $\zeta$ Oph our model requires larger amounts of carbon
and iron in the dust-phase than is available.


title: Modified SIMD architecture suitable for single-chip implementation

abstract:
  We describe a modified SIMD architecture suitable for single-chip integration
of a large number of processing elements, such as 1,000 or more. Important
differences from traditional SIMD designs are: a) The size of the memory per
processing elements is kept small. b) The processors are organized into groups,
each with a small buffer memory. Reduction operation over the groups is done in
hardware. The first change allows us to integrate a very large number of
processing elements into a single chip. The second change allows us to achieve
a close-to-peak performance for many scientific applications like
particle-based simulations and dense-matrix operations.


title: Hot One-Temperature Accretion Flows Revisited

abstract:
  The effectiveness of the thermal coupling of ions and electrons in the
context of optically thin, hot accretion flows is investigated. In the limit of
complete coupling, we focus on the one-temperature accretion flows. Based on a
global analysis, the results are compared with two-temperature accretion flow
models and with the observations of black hole sources. Many features are quite
similar. That is, hot one-temperature solutions are found to exist for mass
flow rates less than a critical value; i.e., $\dot{M}\la 10\alpha^2\dot{M}_{\rm
Edd}$, where $\dot{M}_{\rm Edd}= L_{\rm Edd}/c^2$ is the Eddington accretion
rate. At low mass flow rates, $\dot{M}\la 10^{-3}\alpha^2 \dot{M}_{\rm Edd}$,
the solution is in the advection-dominated accretion flow (ADAF) regime. But at
higher rates, radiative cooling is effective and is mainly balanced by
advective {\em heating}, placing the solution in the regime of luminous hot
accretion flow (LHAF). To test the viability of the one-temperature models, we
have fitted the spectra of the two black hole sources, Sgr A* and XTE
J1118+480, which have been examined successfully with two-temperature models.
It is found that the one-temperature models do not provide acceptable fits to
the multi-wavelength spectra of Sgr A* nor to XTE J1118+480 as a result of the
higher temperatures characteristic of the one-temperature models. It is
concluded that the thermal coupling of ions and electrons cannot be fully
effective and that a two-temperature description is required in hot accretion
flow solutions.


title:
Evidence for Gravitational Infall of Matter onto the Super-Massive Black
  Hole in the quasar PG 1211+143?

abstract:
  We report the detection of redshifted iron K-alpha absorption lines in the
Chandra LETG spectrum of the narrow-line quasar, PG 1211+143. The absorption
lines are observed at 4.22 keV and 4.93 keV in the quasar spectrum,
corresponding to 4.56 keV and 5.33 keV in the rest frame of PG 1211+143. From
Monte Carlo simulations, the chance probability of both lines being false
detections is low at 1.36e-04. Highly redshifted ionized iron K-alpha (Fe XXV
or Fe XXVI) is the most plausible identification for the lines at their
observed energies. If identified with H-like iron K-alpha at 6.97 keV, then the
relativistic velocity shifts required are 0.40c and 0.26c. The extreme
velocities can be explained by pure gravitational redshift if the matter exists
in a stable orbit within 6 gravitational radii of the black hole. This would
require a Kerr metric for the black hole. Alternatively the absorption may be
the result of matter infalling directly onto the black hole, with a maximum
observed velocity of 0.38c at 6Rg in the Schwarzschild metric. This matter may
originate in a failed outflow or jet, which does not escape the gravitational
potential of the black hole.


title:
Pah and Mid-IR Luminosities as Measures of Star-Formation Rate in
  Spitzer First Look Survey Galaxies

abstract:
  We present evidence that the 8 $\mu$m (dust) and 24 $\mu$m luminosities of
star-forming galaxies are both strongly correlated with their 1.4 GHz and
H$\alpha$ luminosities over a range in luminosity of two-to-three orders of
magnitude. At the bright end, the correlations are found to be essentially
linear over a luminosity range of about two orders of magnitude (corresponding
to star-formation rates of several-tenths to several tens of solar masses per
year). However, at the faint end, there appears to be a slope change for dwarf
galaxies, possibly due to the lower dust-to-gas ratios and lower metallicities
of the dwarfs. The correlations suggest that PAH features and mid-IR continuum
emissions are good measures of the star formation rates of galaxies, and we
present calibrations of star-formation rates based on existing radio and
H$\alpha$ relations. Our findings are based on a sample of star-forming
galaxies selected from the main field of the Spitzer First Look Survey with the
aid of spectroscopic data from the Sloan Digital Sky Survey and VLA 1.4 GHz
data.


title:
The Effect of Star Formation History on the Inferred Initial Stellar
  Mass Function

abstract:
  Peaks and lulls in the star formation rate (SFR) over the history of the
Galaxy produce plateaux and declines in the present day mass function (PDMF)
where the main-sequence lifetime overlaps the age and duration of the SFR
variation. These PDMF features can be misinterpreted as the form of the
intrinsic stellar initial mass function (IMF) if the star formation rate is
assumed to be constant or slowly varying with time. This effect applies to all
regions that have formed stars for longer than the age of the most massive
stars, including OB associations, star complexes, and especially galactic field
stars. Related problems may apply to embedded clusters. Evidence is summarized
for temporal SFR variations from parsec scales to entire galaxies, all of which
should contribute to inferred IMF distortions. We give examples of various star
formation histories to demonstrate the types of false IMF structures that might
be seen. These include short-duration bursts, stochastic histories with
log-normal amplitude distributions, and oscillating histories with various
periods and phases. The inferred IMF should appear steeper than the intrinsic
IMF over mass ranges where the stellar lifetimes correspond to times of
decreasing SFRs; shallow portions of the inferred IMF correspond to times of
increasing SFRs. If field regions are populated by dispersed clusters and
defined by their low current SFRs, then they should have steeper inferred IMFs
than the clusters. The SFRs required to give the steep field IMFs in the LMC
and SMC are determined. Structure observed in several determinations of the
Milky Way field star IMF can be accounted for by a stochastic and bursty star
formation history.


title: R modes of slowly pulsating B stars

abstract:
  We examine pulsational stability of low $m$ $r$ modes in SPB stars by
calculating fully nonadiabatic oscillations of uniformly rotating stars, where
$m$ is an integer representing the azimuthal wave number around the rotation
axis. $R$ modes are rotationally induced, non-axisymmetric, oscillation modes,
whose oscillation frequency strongly depends on the rotation frequency $\Omega$
of the star. They are conveniently classified by using two integer indices $m$
and $l^\prime\ge |m|$ that define the asymptotic oscillation frequency
$2m\Omega/[l^\prime(l^\prime+1)]$ in the limit of $\Omega\to 0$. We find low
$m$, high radial order, odd $r$ modes with $l^\prime=m$ in SPB stars are
excited by the same iron opacity bump mechanism that excites low frequency $g$
modes of the variables, when the rotation frequency $\Omega$ is sufficiently
high. No even $r$ modes with low $m$ are found to be pulsationally unstable.
Since the surface pattern of the temperature perturbation of odd modes is
antisymmetric about the equator of the star, observed photometric amplitudes
caused by the unstable odd $r$ modes with $l^\prime=m$ are strongly dependent
on the inclination angle between the axis of rotation and the line of sight.
Applying the wave-meanflow interaction formalism to nonadiabatic $r$ modes in
rapidly rotating SPB models, we find that because of the $r\phi$ component of
the Reynolds stress and the radial transport of the eddy fluctuation of density
in the rotating star, the surface rotation is accelerated by the forcing due to
the low $l^\prime=m$ unstable $r$ modes.


title: Subdwarf B binaries in the Edinburgh-Cape Survey

abstract:
  We give an update of the results of a campaign to obtain orbital solutions of
subdwarf B stars from the Edinburgh-Cape survey (Stobie et al. 1997). To date
we have obtained blue spectra of 40 subdwarf B stars from the Edinburgh-Cape
catalogue using the grating spectrograph at the 1.9m Radcliffe telescope at the
South African Astronomical Observatory. We find that 17 out of these 40 are
certain binaries with a few other objects showing radial velocity variations of
small amplitude. The binary fraction found in our sample, after correcting for
our binary detection efficiency, is 48%. We have secured the orbital parameters
for 4 of the 17 systems and narrowed down the orbits of another 7 to a small
range of periods.


title: A new scenario for the origin of galactic warps

abstract:
  Galactic warps represent an old unresolved problem, since the discovery, at
the end of the fifties, of the HI warp of the Milky Way. In this paper, we
propose a new scenario explaining a large fraction of the observed optical
warps. Based on N-body simulations, we show that realistic galactic disks,
where the dark matter is essentially distributed in a disk, are subject to
bending instabilities. S, U-shaped, as well as asymmetric warps are
spontaneously generated and in some cases are long-lived. While this scenario
presents the advantage of explaining the three observed types of warps, it also
brings new constraints on the dark matter distribution in spiral galaxies.
Finally, it gives us a unified picture of galaxies where galactic asymmetries,
like bars, spirals and warps result from gravitational instabilities.


title:
Oscillating \alpha^2-dynamos and the reversal phenomenon of the global
  geodynamo

abstract:
  A geodynamo-model based on an \alpha-effect which has been computed under
conditions suitable for the geodynamo is constructed. For a highly restricted
class of radial \alpha-profiles the linear \alpha2-model exhibits oscillating
solutions on a timescale given by the turbulent diffusion time. The basic
properties of the periodic solutions are presented and the influence of the
inner core size on the characteristics of the critical range that allows for
oscillating solutions is shown. Reversals are interpreted as half of such an
oscillation. They are rather seldom events because they can only occur if the
\alpha-profile exists long enough within the small critical range that allows
for periodic solutions. Due to strong fluctuations on the convective timescale
the probability of such a reversal is very small. Finally, a simple non-linear
mean-field model with reasonable input parameters based on simulations of
Giesecke et al. (2005) demonstrates the plausibility of the presented theory
with a long-time series of a (geo-)dynamo reversal sequence.


title: Spectral lags caused by the Doppler effect of fireballs

abstract:
  Recently, Shen et al. (2005) studied the contributions of curvature effect of
fireballs to the spectral lag and showed that the observed lags could be
accounted for by the effect. Here we check their results by performing a more
precise calculation with both the formulas presented in Shen et al. (2005) and
Qin et al. (2004). Several other aspects which were not considered in Shen et
al. (2005) are investigated. We find that in the case of ultra-relativistic
motions, both formulas are identical as long as the whole fireball surface is
concerned. In our analysis, the previous conclusion that the detected spectral
lags could be accounted for by the curvature effect is confirmed, while the
conclusion that the lag has no dependence on the radius of fireballs is not
true. We find that introducing extreme physical parameters is not the only
outlet to explain those observed large lags. Even for the larger lags
($\sim5s$) (see Norris et al. 2005), a wider local pulse ($\Delta
t_{\theta,FWHM} = 10^{7}s$) could account for it. Some conclusions not
presented in Shen et al. (2005) or those modified in our analysis are listed
below: a) lag $\propto \Gamma^{-\epsilon}$ with $\epsilon>$ 2; b) lag is
proportional to the local pulse width and the $FWHM$ of the observed light
curves; c) a large lag requires a large $\alpha_0$ and a small $\beta_0$ as
well as a large $E_{0p}$; d) when the rest frame spectrum varies with time, the
lag would become larger; e) lag decreases with the increasing of $ R_c$; f) lag
$\propto$ E within the certain energy range for a given Lorentz factor; g) lag
is proportional to the opening angle of uniform jets when $\theta_j <
0.6\Gamma^{-1}$.


title: The Luminosity Function of E/S0 Galaxies at 0.5<z<1.0

abstract:
  We measure the luminosity function of morphologically selected E/S0 galaxies
from z=0.5 to z=1.0 using deep high resolution Advanced Camera for Surveys
(ACS) imaging data. Our data extend 2 magnitudes deeper than the Deep Groth
Strip Survey (DGSS). At 0.5<z<0.75, we find M_B^*-5\log h_{0.7}=-21.1+/-0.3 and
\alpha=-0.53+/-0.2, and at 0.75<z<1.0, we find M_B^*-5\log h_{0.7}=-21.4+/-0.2.
Our morphologically selected luminosity functions are similar in both shape and
number density to other morphologically selected luminosity functions (e.g.,
DGSS), but we find significant differences to the luminosity functions of
samples selected using morphological proxies like colour or SED. The difference
is due to incompleteness from blue E/S0 galaxies, which make up to ~30% of the
sample and contamination from early-type spirals. Most of the blue E/S0
galaxies have similar structural properties to the red E/S0s and could
passively evolve to form giant red ellipticals at z=0. However, the bluest,
(U-V)_0<1.2, have much smaller Sersic parameters and would evolve into much
fainter galaxies. These may be the progenitors of dwarf ellipticals. We
demonstrate the need for both morphological and colour information to constrain
the evolution of E/S0 galaxies.


title:
Triggered massive-star formation on the borders of Galactic HII regions.
  II. Evidence for the collect and collapse process around RCW 79

abstract:
  We present SEST-SIMBA 1.2-mm continuum maps and ESO-NTT SOFI JHK images of
the Galactic HII region RCW 79. The millimetre continuum data reveal the
presence of massive fragments located in a dust emission ring surrounding the
ionized gas. The two most massive fragments are diametrically opposite each
other in the ring. The near-IR data, centred on the compact HII region located
at the south-eastern border of RCW 79, show the presence of an IR-bright
cluster containing massive stars along with young stellar objects with near-IR
excesses. A bright near- and mid-IR source is detected towards maser emissions,
1.2 pc north-east of the compact HII region centre. Additional information,
extracted from the Spitzer GLIMPSE survey, are used to discuss the nature of
the bright IR sources observed towards RCW 79. Twelve luminous Class I sources
are identified towards the most massive millimetre fragments. All these facts
strongly indicate that the massive-star formation observed at the border of the
HII region RCW 79 has been triggered by its expansion, most probably by the
collect and collapse process.


title:
Gamma-ray continuum emission from the inner Galactic region as observed
  with INTEGRAL/SPI

abstract:
  The diffuse continuum emission from the Galactic plane in the energy range
18-1000 keV has been studied using 16 Ms of data from the SPI instrument on
INTEGRAL. With such an exposure we can exploit the imaging properties of SPI to
achieve a good separation of point sources from the various diffuse components.
Using a candidate-source catalogue derived with IBIS on INTEGRAL and a number
of sky distribution models we obtained spectra resolved in Galactic longitude.
We can identify spectral components of a diffuse continuum of power law shape
with index about 1.7, a positron annihilation component with a continuum from
positronium and the line at 511 keV, and a second, roughly power-law component
from detected point sources. Our analysis confirms the concentration of
positron annihilation emission in the inner region (|l|<10), the disk
(10<|l|<30) being at least a factor 7 weaker in this emission. The power-law
component in contrast drops by only a factor 2, showing a quite different
longitude distribution and spatial origin. Detectable sources constitute about
90% of the total Galactic emission between 20 and 60 keV, but have a steeper
spectrum than the diffuse emission, their contribution to the total emission
dropping rapidly to a small fraction at higher energies. In the SPI energy
range the flux is lower than found by OSSE, probably due to the more complete
accounting for sources by SPI. The power-law emission is difficult to explain
as of interstellar origin, inverse Compton giving at most 10%, and instead a
population of unresolved point sources is proposed as a possible origin, AXPs
with their spectra hardening above 100 keV being plausible candidates. We
present a broadband spectrum of the emission.


title: Dark energy from coexistence of phases

abstract:
  We suggest that the current acceleration of the universe may be explained by
the vacuum energy of a hidden sector which is stuck in a state of equilibrium
between phases. The phases are associated to a late-time first-order phase
transition, where phase coexistence originates at a temperature $T_c \sim
10^{-3}eV$ and lasts until temperature falls below $T\sim 10^{-4}eV$. During
phase coexistence, the energy density has an effective cosmological constant
component with the observed magnitude. This scenario does not require
supercooling and may arise naturally in realistic models.


title:
The Effect of Condensates on the Characterization of Transiting Planet
  Atmospheres with Transmission Spectroscopy

abstract:
  Through a simple physical argument we show that the slant optical depth
through the atmosphere of a "hot Jupiter" planet is 35-90 times greater than
the normal optical depth. This not unexpected result has direct consequences
for the method of transmission spectroscopy for characterizing the atmospheres
of transiting giant planets. The atmospheres of these planets likely contain
minor condensates and hazes which at normal viewing geometry have negligible
optical depth, but at slant viewing geometry have appreciable optical depth
that can obscure absorption features of gaseous atmospheric species. We
identify several possible condensates. We predict that this is a general
masking mechanism for all planets, not just for HD 209458b, and will lead to
weaker than expected or undetected absorption features. Constraints on an
atmosphere from transmission spectroscopy are not the same as constraints on an
atmosphere at normal viewing geometry.


title: The Age Distribution of Massive Star Clusters in the Antennae Galaxies

abstract:
  We determine the age distribution of star clusters in the Antennae galaxies
(NGC 4038/9) for two mass-limited samples (M > 3 x 10^4 M_{\odot} and M > 2 x
10^5 M_{\odot}). This is based on integrated broadband UBVI and narrowband
H-alpha photometry from deep images taken with the Hubble Space Telescope. We
find that the age distribution of the clusters declines steeply, approximately
as dN/d\tau \propto \tau^{-1}. The median age of the clusters is ~10^7 yr,
which we interpret as evidence for rapid disruption ("infant mortality"). It is
very likely that most of the young clusters are not gravitationally bound and
were disrupted near the times they formed by the energy and momentum input from
young stars to the interstellar matter of the protoclusters. At least 20% and
possibly all stars form in clusters and/or associations, including those that
are unbound and short-lived.


title:
A Catalog of Edge-on Disk Galaxies: From Galaxies with a Bulge to
  Superthin Galaxies

abstract:
  The formation and evolution of disk-dominated galaxies is difficult to
explain, yet these objects exist. We therefore embarked on a study aimed at a
better understanding of these enigmatic objects. We used data from the SDSS DR1
in order to identify edge-on galaxies with disks in a uniform, reproducible,
automated fashion. We identified 3169 edge-on disk galaxies, which we
subdivided into disk galaxies with bulge, intermediate types, and simple disk
galaxies without any obvious bulge component. We subdivided these types further
into subclasses: Sa(f), Sb(f), Sc(f), Scd(f), Sd(f), Irr(f), where the (f)
indicates that these galaxies are seen edge-on. A number of incompleteness
effects affect our catalog, but it contains almost a factor of four more
bulgeless galaxies with prominent simple disks (flat galaxies) within the area
covered here than previous optical catalogs, which were based on the visual
selection from photographic plates. We find that approximately 15% of the
edge-on disk galaxies in our catalog are flat galaxies, demonstrating that
these galaxies are fairly common, especially among intermediate-mass
star-forming galaxies. Bulgeless disks account for roughly one third of our
galaxies when also puffy disks and edge-on irregulars are included.(Abridged)


title:
Discovery of the pre-main sequence progenitors of the magnetic Ap/Bp
  stars?

abstract:
  We report the discovery, using FORS1 at the ESO-VLT and ESPaDOnS at the CFHT,
of magnetic fields in the young A-type stars HD 101412, V380 Ori and HD 72106A.
Two of these stars (HD 101412 and V380 Ori) are pre-main sequence Herbig Ae/Be
(HAeBe) stars, while one (HD 72106A) is physically associated with a HAeBe
star. Remarkably, evidence of surface abundance spots is detected in the
spectra of HD 72106A. The magnetic fields of these objects display intensities
of order 1 kG at the photospheric level, are ordered on global scales, and
appear in approximately 10% of the stars studied. Based on these properties,
the detected stars may well represent pre-main sequence progenitors of the
magnetic Ap/Bp stars. The low masses inferred for these objects (2.6, 2.8 and
2.4 solar masses) represent additional contradictions to the hypothesis of
Hubrig et al. (2000), who claim that magnetic fields appear in
intermediate-mass stars only after 30% of their main sequence evolution is
complete. Finally, we fail to confirm claims by Hubrig et al. (2004) of
magnetic fields in the Herbig Ae star HD 139614.


title:
SDSSJ102111.02+491330.4: A Newly Discovered Gravitationally Lensed
  Quasar

abstract:
  We report follow-up observations of two gravitational lens candidates
identified in the Sloan Digital Sky Survey (SDSS) dataset. We have confirmed
that SDSS J102111.02+491330.4 is a previously unknown gravitationally lensed
quasar. This lens system exhibits two images of a $z = 1.72$ quasar, with an
image separation of $1{\farcs}14 \pm 0.04$. Optical and near-IR imaging of the
system reveals the presence of the lensing galaxy between the two quasar
images. Observations of SDSS J112012.12+671116.0 indicate that it is more
likely a binary quasar than a gravitational lens. This system has two quasars
at a redshift of $z = 1.49$, with an angular separation of $1{\farcs}49 \pm
0.02$. However, the two quasars have markedly different SEDs and no lens galaxy
is apparent in optical and near-IR images of this system. We also present a
list of 31 SDSS lens candidates which follow-up observations have confirmed are
\textit{not} gravitational lenses.


title:
Direct Measurement of Supernova Neutrino Emission Parameters with a
  Gadolinium-Enhanced Super-Kamiokande Detector

abstract:
  The time-integrated luminosity and average energy of the neutrino emission
spectrum are essential diagnostics of core-collapse supernovae. The SN 1987A
electron antineutrino observations by the Kamiokande-II and IMB detectors are
only roughly consistent with each other and theory. Using new measurements of
the star formation rate history, we reinterpret the Super-Kamiokande upper
bound on the electron antineutrino flux from all past supernovae as an excluded
region in neutrino emission parameter space. A gadolinium-enhanced
Super-Kamiokande should be able to jointly measure these parameters, and a
future megaton-scale detector would enable precision studies.


title: Spectral analysis of the Galactic e+e- annihilation emission

abstract:
  We present a spectral analysis of the e+e- annihilation emission from the
Galactic Centre region based on the first year of measurements made with the
spectrometer SPI of the INTEGRAL mission. We have found that the annihilation
spectrum can be modelled by the sum of a narrow and a broad 511 keV line plus
an ortho-Ps continuum. The broad line is detected with a flux of
(0.35+/-0.11)e-3 s-1 cm-2. The measured width of 5.4+/-1.2 keV FWHM is in
agreement with the expected broadening of 511 keV photons emitted in the
annihilation of Ps that are formed by the charge exchange process of slowing
down positrons with H atoms. The flux of the narrow line is (0.72+/-0.12)e-3
s-1 cm-2 and its width is 1.3+/-0.4 keV FWHM. The measured ortho-Ps continuum
flux yields a fraction of Ps of (96.7+/-2.2)%. To derive in what phase of the
interstellar medium positrons annihilate, we have fitted annihilation models
calculated for each phase to the data. We have found that 49(+2,-23)% of the
annihilation emission comes from the warm neutral phase and 51(+3,-2)% from the
warm ionized phase. While we may not exclude that less than 23% of the emission
might come from cold gas, we have constrained the fraction of annihilation
emission from molecular clouds and hot gas to be less than 8% and 0.5%,
respectively. We have compared our knowledge of the interstellar medium in the
bulge and the propagation of positrons with our results and found that they are
in good agreement if the sources are diffusively distributed and if the initial
kinetic energy of positrons is lower than a few MeV. Despite its large filling
factor, the lack of annihilation emission from the hot gas is due to its low
density, which allows positrons to escape this phase.


title: GRB afterglow light curves in the pre-Swift era - a statistical study

abstract:
  We present the results of a systematic analysis of the world sample of
optical/near-infrared afterglow light curves observed in the pre-Swift era by
the end of 2004. After selecting the best observed 16 afterglows with
well-sampled light curves that can be described by a Beuermann equation, we
explore the parameter space of the light curve parameters and physical
quantities related to them. In addition, we search for correlations between
these parameters and the corresponding gamma-ray data, and we use our data set
to look for a fine structure in the light curves.


title:
Three-dimensional simulations of non-stationary accretion by remnant
  black holes of compact object mergers

abstract:
  (abridged) Three-dimensional hydrodynamic simulations with an Eulerian PPM
code are presented for the time-dependent evolution of accretion tori around
nonrotating and rotating stellar-mass black holes (BHs), using a
pseudo-Newtonian gravitational potential to approximate the effects of general
relativity. The initial configurations are assumed to be remnants of binary
neutron star (NS) or NS+BH mergers and consist of a 4 solar mass BH with varied
spin, girded by a torus with a mass between 0.01 and 0.2 solar masses. The
evolution of tori without and with physical shear viscosity is simulated, using
a realistic equation of state and following the energy loss and lepton number
change due to neutrino emission by a neutrino-trapping scheme. The
time-dependent efficiency of converting rest-mass energy to neutrinos is found
to reach 10 percent, the efficiency of converting neutrino energy into a
pair-photon fireball by neutrino annihilation can reach several percent. The
rate of the latter process declines with time much less steeply than the total
neutrino luminosity, because the ongoing protonization of the torus ensures a
rather stable product of neutrino and antineutrino luminosities. The neutrino
emission increases steeply with higher viscosity, larger torus mass, and larger
BH spin in corotation with the torus. For rotation rates as expected for
post-merger BHs (a > 0.5) and reasonable values of the alpha viscosity (alpha ~
0.1), the considered tori release sufficient energy in neutrinos to account for
the energetics of the well-localized short gamma-ray bursts recently detected
by Hete and Swift, if collimation is invoked as predicted by hydrodynamic jet
simulations.


title: Spontaneous Isotropy Breaking: A Mechanism for CMB Multipole Alignments

abstract:
  We introduce a class of models in which statistical isotropy is broken
spontaneously in the CMB by a non-linear response to long-wavelength
fluctuations in a mediating field. These fluctuations appear as a gradient
locally and pick out a single preferred direction. The non-linear response
imprints this direction in a range of multipole moments. We consider two
manifestations of isotropy breaking: additive contributions and multiplicative
modulation of the intrinsic anisotropy. Since WMAP exhibits an alignment of
power deficits, an additive contribution is less likely to produce the observed
alignments than the usual isotropic fluctuations, a fact which we illustrate
with an explicit cosmological model of long-wavelength quintessence
fluctuations. This problem applies to other models involving foregrounds or
background anisotropy that seek to restore power to the CMB. Additive models
that account directly for the observed power exacerbate the low power of the
intrinsic fluctuations. Multiplicative models can overcome these difficulties.
We construct a proof of principle model that significantly improves the
likelihood and generates stronger alignments than WMAP in 30-45% of
realizations.


title:
Deep Near-Infrared Observations of L1014: Revealing the nature of the
  core and its embedded source

abstract:
  Recently, the Spitzer Space Telescope discovered L1014-IRS, a mid-infrared
source with protostellar colors, toward the heretofore "starless" core L1014.
We present deep near-infrared observations that show a scattered light nebula
extending from L1014-IRS. This nebula resembles those typically associated with
protostars and young stellar objects, tracing envelope cavities presumably
evacuated by an outflow. The northern lobe of the nebula has an opening angle
of ~100 degrees, while the southern lobe is barely detected. Its morphology
suggests that the bipolar cavity and inferred protostellar disk is not inclined
more than 30 degrees from an edge-on orientation. The nebula extends at least
8" from the source at Ks, strongly suggesting that L1014-IRS is embedded within
L1014 at a distance of 200 pc rather than in a more distant cloud associated
with the Perseus arm at 2.6 kpc. In this case, the apparently low luminosity of
L1014-IRS, 0.090 Lsun, is consistent with it having a substellar mass. However,
if L1014-IRS is obscured by a circumstellar disk, its luminosity and inferred
mass may be greater. Using near-infrared colors of background stars, we
investigate characteristics of the L1014 molecular cloud core. We determine a
mass of 3.6 Msun for regions of the core with Av > 2 magnitudes. A comparison
of the radial extinction profile of L1014 with other cores suggests that L1014
may be among the most centrally condensed cores known, perhaps indicative of
the earliest stages of brown dwarf or star formation processes.


title: High-Redshift Gamma-Ray Bursts from Population III Progenitors

abstract:
  Detection of gamma-ray bursts (GRBs) from redshifts z > 7 would open a new
window into the earliest epoch of cosmic star formation. We construct separate
star formation histories at high redshifts for normal (Pop I and II) stars, and
for predominantly massive (Pop III) stars. Based on these separate histories,
we predict the GRB redshift distribution to be observed by the {\it Swift}
mission. Regardless of whether Pop III progenitors are able to trigger GRBs, we
find that a fraction 10% of all bursts detected by {\it Swift} will originate
at z > 5. This baseline contribution is due to Pop I/II star formation which
must have extended out to high redshifts in rare massive galaxies that were
enriched by heavy elements earlier than the typical galaxies. In addition, we
consider the possible contribution of Pop III progenitors to the observable GRB
rate. Pop III stars are viable progenitors for long-duration GRBs which are
triggered by the collapsar mechanism, as long as they can lose their outer
envelope through mass transfer to a companion star in a close binary. We find
that the likelihood of Pop III binaries to satisfy the conditions required by
the collapsar mechanism could be enhanced significantly relative to Pop I/II
binaries. If Pop III binaries are common, {\it Swift} will be first observatory
to probe Pop III star formation at redshifts z > 7.


title:
SN 2005cg: Explosion Physics and Circumstellar Interaction of a Normal
  Type Ia Supernova in a Low-Luminosity Host

abstract:
  We present the spectral evolution, light curve, and corresponding
interpretation for the "normal-bright" Type Ia Supernova 2005cg discovered by
ROTSE-IIIc. The host is a low-luminosity (M_r = -16.75), blue galaxy with
strong indications of active star formation and an environment similar to that
expected for SNe Ia at high redshifts. Early-time (t ~ -10 days) optical
spectra obtained with the HET reveal an asymmetric, triangular-shaped Si II
absorption feature at about 6100 \AA with a sharp transition to the continuum
at a blue shift of about 24,000 km s^-1. By 4 days before maximum, the Si II
absorption feature becomes symmetric with smoothly curved sides. Similar Si II
profile evolution has previously been observed in other supernovae, and is
predicted by some explosion models, but its significance has not been fully
recognized. Although the spectra predicted by pure deflagration and delayed
detonation models are similar near maximum light, they predict qualitatively
different chemical abundances in the outer layers and thus give qualitatively
different spectra at the earliest phases. The Si line observed in SN 2005cg at
early times requires the presence of burning products at high velocities and
the triangular shape is likely to be formed in an extended region of slowly
declining Si abundance that characterizes delayed detonation models. The
spectra show a high-velocity Ca II IR feature that coincides in velocity space
with the Si II cutoff. This supports the interpretation that the Ca II is
formed when the outer layers of the SN ejecta sweep up about 5 x 10^-3 M_sun of
material within the progenitor system. (Abridged)


title: The Balance of Dark and Luminous Mass in Rotating Galaxies

abstract:
  A fine balance between dark and baryonic mass is observed in spiral galaxies.
As the contribution of the baryons to the total rotation velocity increases,
the contribution of the dark matter decreases by a compensating amount. This
poses a fine-tuning problem for \LCDM galaxy formation models, and may point to
new physics for dark matter particles or even a modification of gravity.


title: Spoke formation under moving plasma clouds

abstract:
  Goertz and Morfill (1983) propose that spokes on Saturn's rings form under
radially moving plasma clouds produced by meteoroid impacts. We demonstrate
that the speed at which a plasma cloud can move relative to the ring material
is bounded from above by the difference between the Keplerian and corotation
velocities. The radial orientation of new spokes requires radial speeds that
are at least an order of magnitude larger than this upper limit, thus the model
advanced by Goertz and Morfill fails to make radial spokes.


title: Accretion modes in collapsars - prospects for GRB production

abstract:
  We explore low angular momentum accretion flows onto black holes formed after
the collapse of massive stellar cores. In particular, we consider the state of
the gas falling quasi-spherically onto stellar-mass black holes in the
hypercritical regime, where the accretion rates are in the range 0.001 - 0.5
solar masses per second and neutrinos dominate the cooling. Previous studies
have assumed that in order to have a black hole switch to a luminous state, the
condition l >> r_g c, where l is the specific orbital angular momentum of the
infalling gas and r_g is the Schwarszchild radius, needs to be fulfilled. We
argue that flows in hyperaccreting, stellar mass disks around black holes are
likely to transition to a highly radiative state when their angular momentum is
just above the threshold for disk formation, l ~ 2 r_g c. In a range where l
lies between r_g c and 2 r_g c, a dwarf disk forms in which gas spirals rapidly
into the black hole due to general relativistic effects, without any help from
horizontal viscous stresses. For high rotation rates with l greater than 2 r_g
c, the luminosity is supplied by large, hot equatorial bubbles around the black
hole. The highest neutrino luminosities are obtained for l ~ 2 r_g c, and this
value of angular momentum also produces the most energetic neutrinos, and thus
also the highest energy deposition rates. Given the range of l explored in this
work, we argue that, as long as l is greater than 2 r_g c, low angular momentum
cores may in fact be better suited for producing neutrino--driven explosions
following core collapse in supernovae and gamma ray bursts.


title: Clustering of Star-forming Galaxies Near a Radio Galaxy at z=5.2

abstract:
  We present HST/ACS observations of the most distant radio galaxy known, TN
J0924-2201 at z=5.2. This radio galaxy has 6 spectroscopically confirmed Lya
emitting companion galaxies, and appears to lie within an overdense region. The
radio galaxy is marginally resolved in i_775 and z_850 showing continuum
emission aligned with the radio axis, similar to what is observed for lower
redshift radio galaxies. Both the half-light radius and the UV star formation
rate are comparable to the typical values found for Lyman break galaxies at
z~4-5. The Lya emitters are sub-L* galaxies, with deduced star formation rates
of 1-10 Msun/yr. One of the Lya emitters is only detected in Lya. Based on the
star formation rate of ~3 Msun/yr calculated from Lya, the lack of continuum
emission could be explained if the galaxy is younger than ~2 Myr and is
producing its first stars.
  Observations in V_606, i_775, and z_850 were used to identify additional
Lyman break galaxies associated with this structure. In addition to the radio
galaxy, there are 22 V-break (z~5) galaxies with z_850<26.5 (5sigma), two of
which are also in the spectroscopic sample. We compare the surface density of
2/arcmin^2 to that of similarly selected V-dropouts extracted from GOODS and
the UDF Parallel fields. We find evidence for an overdensity to very high
confidence (>99%), based on a counts-in-cells analysis applied to the control
field. The excess is suggestive of the V-break objects being associated with a
forming cluster around the radio galaxy.


title: Mergers of close primordial binaries

abstract:
  We study the production of main sequence mergers of tidally-synchronized
primordial short-period binaries. The principal ingredients of our calculation
are the angular momentum loss rates inferred from the spindown of open cluster
stars and the distribution of binary properties in young open clusters. We
compare our results with the expected number of systems that experience mass
transfer in post-main sequence phases of evolution and compute the
uncertainties in the theoretical predictions. We estimate that main-sequence
mergers can account for the observed number of single blue stragglers in M67.
Applied to the blue straggler population, this implies that such mergers are
responsible for about one quarter of the population of halo blue metal poor
stars, and at least one third of the blue stragglers in open clusters for
systems older than 1 Gyr. The observed trends as a function of age are
consistent with a saturated angular momentum loss rate for rapidly rotating
tidally synchronized systems. The predicted number of blue stragglers from main
sequence mergers alone is comparable to the number observed in globular
clusters, indicating that the net effect of dynamical interactions in dense
stellar environments is to reduce rather than increase the blue straggler
population. A population of subturnoff mergers of order 3-4% of the upper main
sequence population is also predicted for stars older than 4 Gyr, which is
roughly comparable to the small population of highly Li-depleted halo dwarfs.
Other observational tests are discussed.


title: The Secular Evolution of Disk Structural Parameters

abstract:
  We present a comprehensive series of $N$-body as well as $N$-body + SPH
simulations to study the secular evolution of the structure of disk galaxies.
Our simulations are organized in a hierarchy of increasing complexity, ranging
from rigid-halo collisionless simulations to fully live simulations with gas
and star formation. Comparisons between the different types of simulations
allow us to isolate the role of various physical mechanisms. We focus on the
evolution of systems expected in a LCDM universe.
  Our goal is to examine which structural properties of disk galaxies may
result from secular evolution rather than from direct hierarchical assembly. In
the vertical direction, we find that various mechanisms can lead to heating.
The strongest heating occurs during the vertical buckling instability of a bar.
Among the consequences of this instability is the formation of peanut-shaped
bulges which produce clear kinematic signatures when observed face-on. We find
that bars are robust structures that are not destroyed by buckling. They can be
destroyed instead by a central mass concentration but we find that this mass
needs to be a large fraction of the total mass of the disk. We then study the
evolution of stellar surface density profiles showing how angular momentum
redistribution leads to increasing central densities and disk scale lengths and
to profile breaks at large radii. The breaks in these simulations are in
excellent agreement with observed breaks, even when the evolution is purely
collisionless. Disk scale-lengths increase even when the total disk angular
momentum is conserved; thus mapping halo angular momenta to scale-lengths is
non-trivial. [Abridged]


title: UV/Optical Nuclear Activity in the gE Galaxy NGC 1399

abstract:
  Using HST/STIS, we have detected far-ultraviolet nuclear activity in the
giant elliptical galaxy NGC 1399, the central and brightest galaxy in the
Fornax I cluster. The source reached a maximum observed far-UV luminosity of
\~1.2 x 10e39 ergs/s in January 1999. It was detectable in earlier HST archival
images in 1996 (B band) but not in 1991 (V band) or 1993 (UV). It faded by a
factor of ~4x by mid-2000. The source is almost certainly associated with the
low luminosity AGN responsible for the radio emission in NGC 1399. The
properties of the outburst are remarkably similar to the UV-bright nuclear
transient discovered earlier in NGC 4552 by Renzini et al. (1995). The source
is much fainter than expected from its Bondi accretion rate (estimated from
Chandra high resolution X-ray images), even in the context of "radiatively
inefficient accretion flow" models, and its variability also appears
inconsistent with such models. High spatial resolution UV monitoring is a
valuable means to study activity in nearby LLAGNs.


title: On the Structural Differences between Disk and Dwarf Galaxies

abstract:
  Gas-rich dwarf and disk galaxies overlap in numerous physical quantities that
make their classification subjective. We report the discovery of a separation
between dwarfs and disks into two unique sequences in the mass (luminosity)
versus scale length plane. This provides an objective classification scheme for
late-type galaxies that only requires optical or near-IR surface photometry of
a galaxy. Since the baryonic Tully-Fisher relation for these samples produces a
continuous relation between baryonic mass and rotational velocity, we conclude
that the difference between dwarfs and disks must be because of their
distribution of stellar light such that dwarfs are more diffuse than disk
galaxies. This structural separation may be due to a primordial difference
between low and high mass galaxies or produced by hierarchical mergers where
disks are built up from dwarfs. Structural differences between dwarf and disk
galaxies may also be driven by the underlying kinematics where the strong
rotation in disks produces an axial symmetric object that undergoes highly
efficient star formation in contrast to the lower rotation, more disordered
motion of dwarfs that produces a diffuse, triaxial object with a history of
inefficient star formation.


title:
The Cosmological Mean Density and its Local Variations Probed by
  Peculiar Velocities

abstract:
  Peculiar velocities thoughout the region of the local supercluster are
reconstructed by two different orbit-retracing methods. The requirement of the
optimal correlation between the radial components of reconstructed velocities
and the observed peculiar velocities derived from our extensive new catalog of
distances puts stringent constraints on the values of the cosmological
parameters. Our constraints intersect those from studies of microwave
background fluctuations and statistical properties of galaxy clustering: the
ensemble of constraints are consistent with Omega_m=0.22\pm 0.02. While motions
throughout the Local Supercluster provide a measure of the mean ratio of mass
to light, there can be large local fluctuations. Our reconstruction of the
infall velocities in the immediate vicinity of the Virgo Cluster shows that
there is a mass-to-light anomaly of a factor of 3 to 6 between groups in the
general field environment and the heavily populated Virgo Cluster.


title: On the origin of anomalous velocity clouds in the Milky Way

abstract:
  We report that neutral hydrogen (HI) gas clouds, resembling High Velocity
Clouds (HVCs) observed in the Milky Way (MW), appear in MW-sized disk galaxies
formed in high-resolution Lambda Cold Dark Matter (LCDM) cosmological
simulations which include gas-dynamics, radiative cooling, star formation,
supernova feedback, and metal enrichment. Two such disk galaxies are analyzed,
and HI column density and velocity distributions in all-sky Aitoff projections
are constructed. The simulations demonstrate that LCDM is able to create
galaxies with sufficient numbers of anomalous velocity gas clouds consistent
with the HVCs observed within the MW, and that they are found within a
galactocentric radius of 150 kpc. We also find that one of the galaxies has a
polar gas ring, with radius 30 kpc, which appears as a large structure of HVCs
in the Aitoff projection. Such large structures may share an origin similar to
extended HVCs observed in the MW, such as Complex C.


title: Triggered Star Formation by Massive Stars

abstract:
  We present our diagnosis of the role that massive stars play in the formation
of low- and intermediate-mass stars in OB associations (the Lambda Ori region,
Ori OB1, and Lac OB1 associations). We find that the classical T Tauri stars
and Herbig Ae/Be stars tend to line up between luminous O stars and
bright-rimmed or comet-shaped clouds; the closer to a cloud the progressively
younger they are. Our positional and chronological study lends support to the
validity of the radiation-driven implosion mechanism, where the Lyman continuum
photons from a luminous O star create expanding ionization fronts to evaporate
and compress nearby clouds into bright-rimmed or comet-shaped clouds. Implosive
pressure then causes dense clumps to collapse, prompting the formation of
low-mass stars on the cloud surface (i.e., the bright rim) and
intermediate-mass stars somewhat deeper in the cloud. These stars are a
signpost of current star formation; no young stars are seen leading the
ionization fronts further into the cloud. Young stars in bright-rimmed or
comet-shaped clouds are likely to have been formed by triggering, which would
result in an age spread of several megayears between the member stars or star
groups formed in the sequence.


title:
Photopolarimetric observations of the new eclipsing polar CTCV
  J1928-5001

abstract:
  We report photopolarimetric observations of a new eclipsing polar (AM
Herculis system) discovered in the Calan-Tololo survey. The photometry and
polarimetry are modulated on a period of ~101 minutes. Circular polarization
variations are seen from ~-8 to +12 per cent and from ~0 to ~5 per cent in the
red and blue parts of the optical spectrum, respectively. Two linearly
polarized pulses are detected at orbital phases coinciding with the reversals
in the circular polarization. This is consistent with a magnetic field strength
of ~20 MG for the white dwarf primary, where accretion takes place at two
regions. Both accretion regions are self-occulted by the white dwarf during
parts of the orbit. We estimate some of the system's parameters from its
eclipses, which we further refine by modelling the polarimetric observations.


title:
17 new very low-mass members in Taurus. The brown dwarf deficit
  revisited

abstract:
  Recent studies of the substellar population in the Taurus cloud have revealed
a deficit of brown dwarfs (BD) compared to the Trapezium cluster population
(Briceno et al 1998; Luhman 2000; Luhman et al 2003a; Luhman 2004). However,
these works have concentrated on the highest stellar density regions of the
Taurus cloud. We have performed a large scale optical survey of this region,
covering a total area of 30 deg^2, and encompassing the densest part of the
cloud as well as their surroundings, down to a mass detection limits of 15
Jupiter Masses (MJ). In this paper, we present the optical spectroscopic
follow-up observations of 97 photometrically selected potential new low-mass
Taurus members, of which 27 are strong late-M (SpT < M4V) candidates. These
observations reveal 5 new very low mass (VLM) Taurus members and 12 new BDs.
Combining our observations with previously published results, we derive an
updated substellar to stellar ratio in Taurus of Rss =0.23 +/- 0.05. This ratio
now appears consistent with the value previously derived in the Trapezium
cluster under similar assumptions of 0.26 +/- 0.04. We find strong indication
that the relative numbers of BDs with respect to stars is decreased by a factor
2 in the central regions of the aggregates with respect to the more distributed
population. Our findings are best explained in the context of the
embryo-ejection model where brown dwarfs originate from dynamical interactions
in small N unstable multiple systems.


title:
Dark Matter-baryon segregation in the non-linear evolution of coupled
  Dark Energy model

abstract:
  The growth and virialization of spherical top-hat fluctuations, in coupled
Dark Energy models, causes segregation between Dark Matter (DM) and baryons, as
the gravitational infall into the potential well proceeds more slowly for the
baryons than for DM. As a consequence, after attaining their turn-around and
before full virialization, halos have outer layers rich of baryons.
Accordingly, a natural ambiguity exists on the definition of the virial density
contrast. In fact, when the outer baryon layers infall onto the DM-richer core,
they carry with them DM materials outside the original fluctuation; hence, no
time exists when all materials originally belonging to the fluctuation -and
only them- have virialized. Baryon-DM segregation can have various
astrophysical consequences on different length-scales. The smallest halos may
loose up to 50% of the original baryonic contents and become hardly visible.
Subhalos in cluster-size halos may loose much baryonic materials, which could
then be observed as intra-cluster light. Isolated halos, in general, can be
expected to have a baryon component richer than the cosmological proportions,
due to the cosmic enrichement of baryons lost in small halo encounters.


title: Variable stars in the globular cluster NGC 2419

abstract:
  We have used DOLORES at the TNG to obtain B,V time series photometry of NGC
2419, one of the most distant and bright clusters in the Galactic halo. These
data will be used to study its variable star population in order to check
whether the cluster could be the relic of an extragalactic system accreted by
the Milky Way.
  Using the Image Subtraction technique (Alard 2000) we have identified about
300 candidate variables, many of which are in the cluster central regions.
Several of the variables appear to be RR Lyrae stars, but we detected
variability also around the tip of the red giant branch, and in other regions
of the colour-magnitude diagram. To improve the light curve sampling and to
resolve variables in the cluster inner regions, the TNG data were combined with
HST archive data. Preliminary results are presented on the light curves from
the combined data set.


title: Dark energy and dark matter from cosmological observations

abstract:
  The present status of our knowledge about the dark matter and dark energy is
reviewed. Bounds on the content of cold and hot dark matter from cosmological
observations are discussed in some detail. I also review current bounds on the
physical properties of dark energy, mainly its equation of state and effective
speed of sound.


title: Spectroscopic distances of nearby ultracool dwarfs

abstract:
  We present updated results of spectroscopic follow-up observations of a
sample of 45 M dwarf candidates identified by Phan-Bao et al. (2003) based on
the DENIS photometry and proper motion measurements. Forty one of these are
nearby late-M dwarfs (d < 30 pc) with spectral types ranging from M5.0 to M8.5
computed from the spectral indices. One contaminant is probably an F-G main
sequence star reddened by intervening dust and three stars that were not
observed have previous classifications as M dwarfs in the literature. In this
paper, we identify three M7.5, five M8.0, one M8.5 dwarf and confirm two new
M8.0 dwarf members of the 25 pc volume.


title: From AMANDA to IceCube

abstract:
  The first string of the neoteric high energy neutrino telescope IceCube
successfully began operating in January 2005. It is anticipated that upon
completion the new detector will vastly increase the sensitivity and extend the
reach of AMANDA to higher energies. A discussion of the IceCube's discovery
potential for extra-terrestrial neutrinos, together with the prospects of new
physics derived from the ongoing AMANDA research will be the focus of this
paper. Preliminary results of the first antarctic high energy neutrino
telescope AMANDA searching in the muon neutrino channel for localized and
diffuse excess of extra-terrestrial neutrinos will be reviewed using data
collected between 2000 and 2003. Neutrino flux limits obtained with the
all-flavor dedicated UHE and cascade analyses will be described. A first
neutrino spectrum above one TeV in agreement with atmospheric neutrino flux
expectations and no extra-terrestrial contribution will be presented, followed
by a discussion of a limit for neutralino CDM candidates annihilating in the
center of the Sun.


title:
The effects of ellipticity and substructure on estimates of cluster
  density profiles based on lensing and kinematics

abstract:
  We address the question of how well the density profile of galaxy clusters
can be determined by combining strong lensing and velocity dispersion data. We
use cosmological dark matter simulations of clusters to test the reliability of
the method, producing mock catalogues of tangential and radial gravitational
arcs and simulating the radial velocity dispersion profile of the cluster
brightest central galaxy. The density profiles of the simulated clusters
closely follow the NFW form, but we find that the recovered values of the inner
slope are systematically underestimated, by about 0.4 in the mean, if the lens
is assumed to be axially symmetric. However, if the ellipticity and orientation
of the iso-contours of the cluster lensing potential are taken into account,
then the inner slopes can be recovered quite accurately for a significant
subset of the clusters whose central surface density profiles appear the most
regular. These have lensing potentials with ellipticities in the range
0.15-0.4. Further simulations projecting one cluster along many random
lines-of-sight show that, even for lower ellipticities, the central slopes are
underestimated by $\sim 10-35%$. These simulations closely mimic past
observations (see e.g. Sand et al., 2004), suggesting that existing estimates
of the central slopes may be biased towards low values. For the remaining
clusters, where the lensing potential is strongly perturbed by active merging
or by substructure, the correct determination of the inner slope requires a
more accurate model for the lens. When the halo profile is modelled by a
generalised NFW profile, we find that the inferred scale radius and
characteristic density, unlike the inner slope, are generally poorly
constrained, since there is a strong degeneracy between these two parameters.


title: Ultra High Energy Cosmic Rays from Early Decaying Primordial Black Holes

abstract:
  Origin of ultra high energy cosmic rays is an unsolved problem. Several
proposals such as Z-burst, decay of super massive matter, susy particles as a
primary, neutrino as a primary in extra dimension models exist in the
literature which try to address this issue. Many of these proposals solve the
problem of propagation of cosmic rays over cosmological distances by
introducing new physics. However these do not explain the origin of such high
energy cosmic rays. The possible astrophysics sites, such as active galactic
nuclei, are highly constrained. Here we determine whether these cosmic rays
originated from the decay of some exotic objects, such as primordial black
holes (PBHs), present in the early universe. In contrast to the usual Top Down
scenario we do not assume that this exotic object necessarily has to decay in
our astrophysical neighbourhood since we assume a beyond the standard model
scenario, where the propagation problem is absent. We consider the standard
4-dimension PBHs as well as the brane world PBHs. We find that in both cases it
is unable to produce the observed ultra high energy cosmic ray flux.


title: The outer crust of non-accreting cold neutron stars

abstract:
  The properties of the outer crust of non-accreting cold neutron stars are
studied by using modern nuclear data and theoretical mass tables updating in
particular the classic work of Baym, Pethick and Sutherland. Experimental data
from the atomic mass table from Audi, Wapstra, and Thibault of 2003 is used and
a thorough comparison of many modern theoretical nuclear models, relativistic
and non-relativistic ones, is performed for the first time. In addition, the
influences of pairing and deformation are investigated. State-of-the-art
theoretical nuclear mass tables are compared in order to check their
differences concerning the neutron dripline, magic neutron numbers, the
equation of state, and the sequence of neutron-rich nuclei up to the dripline
in the outer crust of non-accreting cold neutron stars.


title:
Oxygen abundances in planet-harbouring stars. Comparison of different
  abundance indicators

abstract:
  We present a detailed and uniform study of oxygen abundances in 155 solar
type stars, 96 of which are planet hosts and 59 of which form part of a
volume-limited comparison sample with no known planets. EW measurements were
carried out for the [O I] 6300 \AA line and the O I triplet, and spectral
synthesis was performed for several OH lines. NLTE corrections were calculated
and applied to the LTE abundance results derived from the O I 7771-5 \AA\
triplet. Abundances from [O I], the O I triplet and near-UV OH were obtained in
103, 87 and 77 dwarfs, respectively. We present the first detailed and uniform
comparison of these three oxygen indicators in a large sample of solar-type
stars. There is good agreement between the [O/H] ratios from forbidden and OH
lines, while the NLTE triplet shows a systematically lower abundance. We found
that discrepancies between OH, [O I] and the O I triplet do not exceed 0.2 dex
in most cases. We have studied abundance trends in planet host and comparison
sample stars, and no obvious anomalies related to the presence of planets have
been detected. All three indicators show that, on average, [O/Fe] decreases
with [Fe/H] in the metallicity range -0.8<[Fe/H]<0.5. The planet host stars
present an average oxygen overabundance of 0.1-0.2dex with respect to the
comparison sample.


title: OH megamasers, starburst and AGN activity in Markarian 231

abstract:
  We present MERLIN observations of OH maser and radio continuum emission from
the Ultra Luminous IR Galaxy Markarian 231. The 1665- and 1667-MHz transitions
have a combined velocity extent of 720 km/s and show a similar
position-velocity structure including a gradient of 1.7 km/s/pc from NW to SE
along the 420-pc major axis, steeper in the inner few tens of pc. The maser
distribution is modelled as a torus rotating about an axis inclined at ~45deg.
We estimate the enclosed mass density to be 320(90) Msun in a flattened
distribution, including a central unresolved mass of </=8E+06 Msun. All the
maser emission is projected against a region with a radio continuum brightness
temperature >/=1E+05 K, giving a maser gain of </=2.2. The 1667:1665-MHz line
ratio is close to the LTE ratio of 1.8 consistent with radiatively pumped,
unsaturated masers. The size of individual masing regions is in the range
0.25-4 pc with a covering factor close to unity. There are no very bright
compact masers, in contrast to galaxies such as the Seyfert 2 Markarian 273
where the masing torus is viewed nearer edge-on. The comparatively modest maser
amplification seen from Markarian 231 is consistent with its classification as
a Seyfert 1. Most of the radio continuum emission on 50-500 pc scales is
probably of starburst origin but the compact peak is 0.4 per cent polarized by
a magnetic field running north-south, similar to the jet direction on these
scales. There is no close correlation between maser and continuum intensity.
Comparisons with other data show that the jet changes direction close the
nucleus and suggest that the sub-kpc disc hosting the masers and starburst
activity is severely warped.


title:
Cosmological Evolution of Hessence Dark Energy and Avoidance of the Big
  Rip

abstract:
  Recently, many dark energy models whose equation-of-state parameter can cross
the phantom divide $w_{de}=-1$ have been proposed. In a previous paper [Class.
Quant. Grav. {\bf 22}, 3189 (2005); hep-th/0501160], we suggest such a model
named hessence, in which a non-canonical complex scalar field plays the role of
dark energy. In this work, the cosmological evolution of the hessence dark
energy is investigated. We consider two cases: one is the hessnece field with
an exponential potential, and the other is with a (inverse) power law
potential. We separately investigate the dynamical system with four different
interaction forms between hessence and background perfect fluid. It is found
that the big rip never appears in the hessence model, even in the most general
case, beyond particular potentials and interaction forms.


title:
Modeling of the heliospheric interface: multi-component nature of the
  heliospheric plasma

abstract:
  We present a new model of the heliospheric interface - the region of the
solar wind interaction with the local interstellar medium. This new model
performs a multi-component treatment of charged particles in the heliosphere.
All charged particles are divided into several co-moving types. The coldest
type, with parameters typical of original solar wind protons, is considered in
the framework of fluid approximation. The hot pickup proton components created
from interstellar H atoms and heliospheric ENAs by charge exchange, electron
impact ionization and photoionization are treated kinetically. The charged
components are considered self-consistently with interstellar H atoms, which
are described kinetically as well. To solve the kinetic equation for H atoms we
use the Monte Carlo method with splitting of trajectories, which allows us 1)
to reduce statistical uncertainties allowing correct interpretation of
observational data, 2) to separate all H atoms in the heliosphere into several
populations depending on the place of their birth and on the type of parent
protons.


title:
The IceCube Collaboration: contributions to the 29th International
  Cosmic Ray Conference (ICRC 2005), Pune, India, Aug. 2005

abstract:
  In this document we collect the 18 contributions of the IceCube Collaboration
to the 29th International Cosmic Ray Conference (ICRC 2005), Pune, India, Aug.
2005


title: Can stellar wobble in triple systems mimic a planet?

abstract:
  The first extrasolar planets have been detected by the measurement of the
wobble of the parent star. This wobble leads to the periodic modulation of
three observables: the radial velocity, the position on the sky and the time of
arrival of periodic signals. We show that the same wobble, and therefore the
same modulation of the three observables, can be due to the presence of a more
distant binary stellar companion. Thus, the observation of the wobble does not,
by itself, constitute a proof of a planet detection. In particular, astrometric
confirmation of a wobble does not necessarily provide a sufficient proof of the
existence of a planet candidate detected by radial velocity. Additional
conditions, which we discuss here, must be fulfilled. We investigate the
observed wobble for the planet candidates already detected and we find that,
for each case, a wobble due to a binary stellar companion can be excluded. But
for apparent Saturn-like planets in wide orbits, there may be an ambiguity in
future detections, especially in spaceborne astrometric missions. We conclude
that, in some cases, a definitive proof for the presence of a planet requires
further observations such as direct imaging.


title: Spectral Decomposition of Broad-Line AGNs and Host Galaxies

abstract:
  Using an eigenspectrum decomposition technique, we separate the host galaxy
from the broad line active galactic nucleus (AGN) in a set of 4666 spectra from
the Sloan Digital Sky Survey (SDSS), from redshifts near zero up to about 0.75.
The decomposition technique uses separate sets of galaxy and quasar
eigenspectra to efficiently and reliably separate the AGN and host
spectroscopic components. The technique accurately reproduces the host galaxy
spectrum, its contributing fraction, and its classification. We show how the
accuracy of the decomposition depends upon S/N, host galaxy fraction, and the
galaxy class. Based on the eigencoefficients, the sample of SDSS broad-line AGN
host galaxies spans a wide range of spectral types, but the distribution
differs significantly from inactive galaxies. In particular, post-starburst
activity appears to be much more common among AGN host galaxies. The
luminosities of the hosts are much higher than expected for normal early-type
galaxies, and their colors become increasingly bluer than early-type galaxies
with increasing host luminosity. Most of the AGNs with detected hosts are
emitting at between 1% and 10% of their estimated Eddington luminosities, but
the sensitivity of the technique usually does not extend to the Eddington
limit. There are mild correlations among the AGN and host galaxy
eigencoefficients, possibly indicating a link between recent star formation and
the onset of AGN activity. The catalog of spectral reconstruction parameters is
available as an electronic table.


title:
The gravitational wave radiation of pulsating white dwarfs revisited:
  the case of BPM 37093 and PG 1159-035

abstract:
  We compute the emission of gravitational radiation from pulsating white
dwarfs. This is done by using an up-to-date stellar evolutionary code coupled
with a state-of-the-art pulsational code. The emission of gravitational waves
is computed for a standard 0.6 solar masses white dwarf with a liquid
carbon-oxygen core and a hydrogen-rich envelope, for a massive DA white dwarf
with a partially crystallized core for which various l=2 modes have been
observed (BPM 37093) and for PG 1159-035, the prototype of the GW Vir class of
variable stars, for which several quadrupole modes have been observed as well.
We find that these stars do not radiate sizeable amounts of gravitational waves
through their observed pulsation g-modes, in line with previous studies. We
also explore the possibility of detecting gravitational waves radiated by the
f-mode and the p-modes. We find that in this case the gravitational wave signal
is very large and, hence, the modes decay very rapidly. We also discuss the
possible implications of our calculations for the detection of gravitational
waves from pulsating white dwarfs within the framework of future space-borne
interferometers like LISA.


title:
Confronting Hierarchical Clustering Models with Observations of Galaxy
  Pairs

abstract:
  We investigate the star formation activity in galaxy pairs in chemical
hydrodynamical simulations consistent with a Lambda-CDM scenario. A statistical
analysis of the effects of galaxy interactions on the star formation activity
as a function of orbital parameters shows that close encounters (r < 30 kpc/h)
can be effectively correlated with an enhancement of star formation activity
with respect to galaxies without a close companion. Our results suggest that
the stability properties of systems are also relevant in this process. We found
that the passive star forming galaxies pairs tend to have deeper potential
wells, older stellar populations, and less leftover gas than active star
forming ones. In order to assess the effects that projection and interlopers
could introduce in observational samples, we have also constructed and analysed
projected simulated catalogs of galaxy pairs. In good agreement with
observations, our results show a threshold (rp < 25 kpc/h) for interactions to
enhance the star formation activity with respect to galaxies without a close
companion. Finally, analysing the environmental effect, we detect the expected
SFR-local density relation for both pairs and isolated galaxy samples, although
the density dependence is stronger for galaxies in pairs suggesting a relevant
role for interactions in driving this relation.


title: A FADC-based Data Acquisition System for the KASCADE-Grande Experiment

abstract:
  We present the design and first test results of a new FADC-based data
acquisition (DAQ) system for the Grande array of the KASCADE-Grande experiment.
The original KASCADE experiment at the Forschungszentrum Karlsruhe, Germany,
has been extended by 37 detector stations of the former EAS-TOP experiment
(Grande array)to provide sensitivity to energies of primary particles from the
cosmos of up to $10^{18}$ eV. The new FADC-based DAQ system will improve the
quality of the data taken by the Grande array by digitizing the scintillator
signals with a 250 MHz sampling rate. events per second.
  Two Grande stations have been equipped with the FADC-based data acquisition
system and first data are shown.


title:
Fundamental parameters of Be stars located in the seismology fields of
  COROT

abstract:
  In preparation for the COROT space mission, we determined the fundamental
parameters (spectral type, temperature, gravity, vsini) of the Be stars
observable by COROT in its seismology fields (64 Be stars). We applied a
careful and detailed modeling of the stellar spectra, taking into account the
veiling caused by the envelope, as well as the gravitational darkening and
stellar flattening due to rapid rotation. Evolutionary tracks for fast rotators
were used to derive stellar masses and ages. The derived parameters will be
used to select Be stars as secondary targets (i.e. observed for 5 consecutive
months) and short-run targets of the COROT mission. Furthermore, we note that
the main part of our stellar sample is falling in the second half of the main
sequence life time, and that in most cases the luminosity class of Be stars is
inaccurate in characterizing their evolutionary status.


title: Kurucz's codes under GNU-Linux

abstract:
  We report on the latest version of our GNU-Linux port of the ATLAS - SYNTHE -
WIDTH suite of codes for the stellar atmosphere modeling. The latest version
(8.1 at the time of the workshop) of the Intel Fortran Compiler allowed for a
significantly better backward compatibility with the VMS version of the code,
thus allowing us to remove almost all the modifications we initially introduced
in order to compile the code under IFC. We now provide ported versions both of
ATLAS 9 (the ODF version of ATLAS) and ATLAS 12 (the opacity sampling version).
A comprehensive website has been created to host the ported codes, along with a
growing body of documentation and resources. Also, three mailing lists have
been created at the university of Ljubljana in order to cover general usage,
code development and ATLAS-related announcements.


title: Where are the sources of the Near Infrared Background?

abstract:
  The observed near infrared background excess over light from known galaxies
is commonly ascribed to redshifted radiation from early, very massive, PopIII
stars. We show here that this interpretation must be discarded as it largely
overpredicts the number of J-dropouts and Ly\alpha emitters in ultra deep field
searches. Independently of the detailed physics of Ly\alpha line emission,
J-dropouts limit the background excess fraction due to PopIII sources to be (at
best) < 1/24. As alternative explanations can either be rejected (e.g.
miniquasars, decaying neutrinos) or appear unlikely (zodiacal light), whereas
the reality of the excess is supported by the interpretation of the angular
fluctuations, the origin of this component remains very puzzling. We briefly
discuss possible hints to solve the problem.


title:
A study of the B and Be star population in the field of the LMC open
  cluster NGC2004 with VLT-FLAMES

abstract:
  Observations of hot stars belonging to the young cluster LMC-NGC2004 and its
surrounding region have been obtained with the VLT-GIRAFFE facilities in MEDUSA
mode. 25 Be stars were discovered; the proportion of Be stars compared to
B-type stars is found to be of the same order in the LMC and in the Galaxy
fields. 23 hot stars were discovered as spectroscopic binaries (SB1 and SB2), 5
of these are found to be eclipsing systems from the MACHO database, with
periods of a few days. About 75% of the spectra in our sample are polluted by
hydrogen (Halpha and Hgamma), [SII] and [NII] nebular lines. These lines are
typical of HII regions. They could be associated with patchy nebulosities with
a bi-modal distribution in radial velocity, with higher values (+335 kms^{-1})
preferentially seen inside the southern part of the known bubble LMC4 observed
in HI at 21 cm.


title:
Spitzer IRS spectroscopy of 3CR radio galaxies and quasars: Testing the
  unified schemes

abstract:
  With the Spitzer Space Telescope Infrared Spectrograph (IRS) we have observed
seven powerful FR2 radio galaxies and seven quasars. Both samples, the galaxies
and the quasars, are comparable in isotropic 178 MHz luminosity (10^26.5 W/Hz <
P 178MHz < 10^29.5 W/Hz) and in redshift range (0.05 < z < 1.5). We find for
both samples similar distributions in the luminosity ratios of high- to
low-excitation lines ([NeV] 14.3 mu / [NeII] 12.8 mu) and of high-excitation
line to radio power ([NeV] 24.3 \mu / P 178MHz). This solves the long debate
about the apparent difference of quasars and radio galaxies in favor of the
orientation-dependent unified schemes. Furthermore, the luminosity ratio [OIII]
500.7 nm / [OIV] 25.9 mu of most galaxies is by a factor of ten lower than that
of the quasars. This suggests that the optical emission from the central NLR is
essentially absorbed (A_V} > 3) in the powerful FR2 galaxies and that the
[OIII] 500.7 nm luminosity does not serve as isotropic tracer for testing the
unified schemes.


title:
The dust-eliminated shape of quasar spectra in the near-infrared: a
  hidden part of the big blue bump

abstract:
  The near-infrared shape of the big blue bump component in quasar spectra has
been essentially unknown. It usually cannot be observed directly, due to the
strong hot dust emission which dominates quasar spectra longward of ~1micron.
However this is quite an important part of the spectrum theoretically. At least
bare disk models provide quite a robust prediction for the overall continuum
shape in the near-infrared. Self-gravity should become important in the outer,
near-infrared emitting regions of the putative disk, possibly leaving a
signature of disk truncation in the near-infrared. We propose here that this
important part of the spectrum can be revealed for the first time by observing
polarized flux from normal quasars. At least in some polarized quasars, the
emission lines are all unpolarized and so the polarized flux should originate
interior to the broad line region, and therefore also interior to the dust
emitting region. This can then be used to eliminate the dust emission. We
present the results of near-infrared polarimetry for such three quasars
(Ton202, 4C37.43, B2 1208+32). The data for Ton202 have the highest S/N, and
the near-infrared polarized flux in this case is measured to have quite a blue
shape, nu^+0.42+-0.29 in F_nu, intriguingly consistent with the simple
multi-temperature black body, bare disk prediction of nu^+1/3. All these data,
although still with quite low S/N for the other two objects, demonstrate the
unique potential of the technique with future better data. We also present
similar data for other quasars and radio galaxies, and briefly discuss the
nature of the polarization.


title:
Spectral changes during dipping in low-mass X-ray binaries due to
  highly-ionized absorbers

abstract:
  X-ray observations have revealed that many microquasars and low-mass X-ray
binaries (LMXBs) exhibit narrow absorption features identified with resonant
absorption from Fe XXV and Fe XXVI and other abundant ions. In many well
studied systems there is evidence for blue-shifts, indicating outflowing
plasmas. We succesfully model the changes in both the X-ray continuum and the
Fe absorption features during dips from all the bright dipping LMXBs observed
by XMM-Newton (EXO 0748-676, XB 1254-690, X 1624-490, MXB 1659-298, 4U 1746-371
and XB 1916-053) as resulting primarily from an increase in column density and
a decrease in the ionization state of a highly-ionized absorber in a similar
way as was done for 4U 1323-62. This implies that the complex spectral changes
in the X-ray continua observed from the dip sources as a class can be most
simply explained primarily by changes in the highly ionized absorbers present
in these systems. There is no need to invoke unusual abundances or partial
covering of extended emission regions. Outside of the dips, the absorption line
properties do not vary strongly with orbital phase. This implies that the
ionized plasma has a cylindrical geometry with a maximum column density close
to the plane of the accretion disk. Since dipping sources are simply normal
LMXBs viewed from close to the orbital plane this implies that ionized plasmas
are a common feature of LMXBs.


title:
An Ultraviolet to Mid-Infrared Study of the Physical and Wind Properties
  of HD 164270 (WC9) and Comparison to BD+30 3639 ([WC9])

abstract:
  We present new Spitzer IRS observations of HD164270 (WC9, WR103). A
quantitative analysis of the UV, optical, near- and mid-IR spectrum of HD164270
is presented, allowing for line blanketing and wind clumping, revealing T* ~
48kK, log L/L_sun ~ 4.9, dM/dt ~ 1e-5 M_sun/yr for a volume filling factor of f
\~ 0.1. Our models predict that He is partially recombined in the outer stellar
wind, such that recent radio-derived mass-loss rates of WC9 stars have been
underestimated. We obtain C/He ~ 0.2 and O/He ~ 0.01 by number from optical
diagnostics. Mid-IR fine structure lines of [NeII] 12.8 and [SIII] 18.7micron
are observed, with [NeIII] and [SIV] absent. From these we obtain Ne/He ~
Ne^+/He = 2.2e-3 by number, 7 times higher than the Solar value (as recently
derived by Asplund et al.), and S/He ~ S^2+/He = 5.1e-5 by number. From a
comparison with similar results for other WC subtypes we conclude that WC9
stars are as chemically advanced as earlier subtypes. We consider why late WC
stars are exclusively observed in high metallicity environments. In addition,
we compare the UV/optical/mid-IR spectroscopic morphology of HD164270 with the
Planetary Nebula central star BD+30 3639 ([WC9]). Their UV and optical
signatures are remarkably similar, such that our quantitative comparisons
confirm similarities in stellar temperature, wind densities and chemistry first
proposed by Smith & Aller, in spite of completely different evolutionary
histories, with HD164270 presently a factor of ten more massive than BD+30
3639. At mid-IR wavelengths, the dust from the dense young, nebula of BD+30
3639 completely dominates its appearance, in contrast with HD164270.


title:
The chemistry of the neighbors: detailed abundances in the Sgr and CMa
  dwarf galaxies

abstract:
  We summarize the results of our ongoing investigation of the chemical
abundances in the Sagittarius Dwarf Spheroidal Galaxy (Sgr dSph) and in the
Canis Major Overdensity (CMa). 12 RGB stars were analyzed in the Sgr dSph, plus
5 in the associated globular Terzan 7, together with three CMa candidate
members. Detailed abundances have been derived for up to 23 elements from
Oxygen to Europium.


title: Slit Observations and Empirical Calculations for HII Regions

abstract:
  When analysing HII regions, a possible source of systematic error on
empirically derived physical quantities is the limited size of the slit used
for the observations. A grid of photoionization models was built through the
Aangaba code varying the ionizing radiation spectrum emitted by a stellar
cluster, as well as the gas abundance. The calculated line surface brightness
was then used to simulate slit observations and to derive empirical parameters
using the usual methods described in the literature. Depending on the fraction
of the object covered by the slit, the parameters can be different from those
obtained from observations of the whole object, an effect that is mainly
dependent on the age of the ionizing stellar cluster. The low-ionization
forbidden lines are more sensitive to the size of the area covered by the slit
than the high-ionization forbidden lines or recombination lines. Regarding the
temperature indicator T[OIII], the slit effects are small since this
temperature is derived from [OIII] lines. On the other hand, for the abundance
indicator R23, which depends also on the [OII] line, the slit effect is
slightly higher. Therefore, the systematic error due to slit observations on
the O abundance is low, being usually less than 10%, except for HII regions
powered by stellar clusters with a relative low number of ionizing photons
between 13.6 and 54.4 eV, which create a smaller O++ emitting volume. In this
case, the systematic error on the empirical O abundance deduced from slit
observations is more than 10% when the covered area is less than 50%.


title:
An Infrared Imaging Survey of the Faint Chandra Sources near the
  Galactic Centre

abstract:
  We present near-IR imaging of a sample of the faint, hard X-ray sources
discovered in the 2001 Chandra ACIS-I survey towards the Galactic Centre (GC)
(Wang et al. 2002). These ~800 discrete sources represent an important and
previously undetected population within the Galaxy. From our VLT observations
of 77 X-ray sources, we identify candidate K-band counterparts to 75% of the
Chandra sources in our sample. The near-IR magnitudes and colours of the
majority of candidate counterparts are consistent with highly reddened stars,
indicating that most of the Chandra sources are likely to be accreting binaries
at or near the GC.


title: RX J2133.7+5107 : Identification of a new long period Intermediate Polar

abstract:
  We report the first time-resolved photometric and spectroscopic optical
observations of the X-ray source RX J2133.7+5107, identified in the ROSAT
survey. A clear persistent optical light pulsation is discovered with fast
photometry at a period of P_{omega} =(570.823 +/-0.013) s which we associate
with the spin period of an accreting white dwarf. Radial velocity curves of the
strong emission lines show modulation with a period of P_{Omega} =(7.193 +/-
0.016) hr, identified as the orbital period. These observations establish that
the source is a member of the intermediate polar class (IPs) of magnetic
cataclysmic variables. With only 4 IPs with longer orbital periods, RX
J2133.7+5107 is among the widest systems. It is a unique IP with an orbital
period in the middle of the so-called (6-10)hr IP gap and it shows a
significant degree of asynchronism with a ratio P_{omega}/P_{Omega} of 0.02.
When attributed to the motion of the white dwarf, the emission lines orbital
modulation yields a mass function of f_m = (1.05 +/- 0.21) 10^{-2} Msun which,
for a probable inclination i < 45 deg and a white dwarf mass M_{wd} = (0.6-1.0)
Msun, corresponds to a secondary mass M_{s} > (0.27-0.37) Msun.


title: A Model for Patchy Reconnection in Three Dimensions

abstract:
  We show, theoretically and via MHD simulations, how a short burst of
reconnection localized in three dimensions on a one-dimensional current sheet
creates a pair of reconnected flux tubes. We focus on the post-reconnection
evolution of these flux tubes, studying their velocities and shapes. We find
that slow-mode shocks propagate along these reconnected flux tubes, releasing
magnetic energy as in steady-state Petschek reconnection. The geometry of these
three-dimensional shocks, however, differs dramatically from the classical
two-dimensional geometry. They propagate along the flux tube legs in four
isolated fronts, whereas in the two-dimensional Petschek model, they form a
continuous, stationary pair of V-shaped fronts.
  We find that the cross sections of these reconnected flux tubes appear as
teardrop shaped bundles of flux propagating away from the reconnection site.
Based on this, we argue that the descending coronal voids seen by Yohkoh SXT,
LASCO, and TRACE are reconnected flux tubes descending from a flare site in the
high corona, for example after a coronal mass ejection. In this model, these
flux tubes would then settle into equilibrium in the low corona, forming an
arcade of post-flare coronal loops.


title:
Intrinsic Absorption in the Spectrum of NGC 7469: Simultaneous Chandra,
  FUSE, and STIS Observations

abstract:
  We present simultaneous X-ray, far-ultraviolet, and near-ultraviolet spectra
of the Seyfert 1 galaxy NGC 7469 obtained with the Chandra X-Ray Observatory,
the Far Ultraviolet Spectroscopic Explorer, and the Space Telescope Imaging
Spectrograph on the Hubble Space Telescope. Previous non-simultaneous
observations of this galaxy found two distinct UV absorption components, at
-560 and -1900 km/s, with the former as the likely counterpart of the X-ray
absorber. We confirm these two absorption components in our new UV
observations, in which we detect prominent O VI, Ly alpha, N V, and C IV
absorption. In our Chandra spectrum we detect O VIII emission, but no
significant O VIII or O VII absorption. We also detect a prominent Fe K alpha
emission line in the Chandra spectrum, as well as absorption due to
hydrogen-like and helium-like neon, magnesium, and silicon at velocities
consistent with the -560 km/s UV absorber. The FUSE and STIS data reveal that
the H I and C IV column densities in this UV- and X-ray- absorbing component
have increased over time, as the UV continuum flux decreased. We use measured H
I, N V, C IV, and O VI column densities to model the photoionization state of
both absorbers self-consistently. We confirm the general physical picture of
the outflow in which the low velocity component is a highly ionized, high
density absorber with a total column density of 10^20 cm^-2, located near the
broad emission line region, although due to measurable columns of N V and C IV,
we assign it a somewhat smaller ionization parameter than found previously,
U~1. The high velocity UV component is of lower density, log N=18.6, and likely
resides farther from the central engine as we find its ionization parameter to
be U=0.08.


title: The very late-stage merger IC 4200:pre-elliptical or pre-spiral?

abstract:
  Recent observations have revealed a class of unusually HI-rich early-type
galaxies. By combining observations of their morphology, stellar populations
and neutral hydrogen we aim to understand how these galaxies fit into the
hierarchical formation paradigm. Here we present the result of our radio and
optical observations of a test case galaxy, the E/S0 IC 4200.


title: Dust in the Host Galaxies of Supernovae

abstract:
  We present Spitzer/MIPS 24 micron observations of 50 supernova host galaxies
at 0.1<z<1.7 in the Great Observatories Origins Deep Survey (GOODS) fields. We
also discuss the detection of SN host galaxies in SCUBA/850 micron observations
of GOODS-N and Spitzer/Infrared Spectrograph (IRS) 16 micron observations of
GOODS-S. About 60% of the host galaxies of both Type Ia and core-collapse
supernovae are detected at 24 microns, a detection rate which is a factor of
1.5 higher than the field galaxy population. Among the 24 micron detected
hosts, 80% have far-infrared luminosities that are comparable to or greater
than the optical luminosity indicating the presence of substantial amounts of
dust in the hosts. The median bolometric luminosity of the Type Ia SN hosts is
\~10^10.5 L_sun, very similar to that of core-collapse SN hosts. Using the high
resolution Hubble/ACS data, we have studied the variation of rest-frame
optical/ultraviolet colors within the 24 micron detected galaxies at z<1 to
understand the origin of the dust emission. The 24 micron detected galaxies
have average colors which are redder by ~0.1 mag than the 24 micron undetected
hosts while the latter show greater scatter in internal colors. This suggests
that a smooth distribution of dust is responsible for the observed mid- and
far-infrared emission. 70% of supernovae that have been detected in the GOODS
fields are located within the half-light radius of the hosts where dust
obscuration effects are significant. Although the dust emission that we detect
cannot be translated into a line of sight A_V, we suggest that the factor of
2-3 larger scatter in the peak B-V colors that is seen in the high-z Type Ia
supernova sample relative to the low-z supernovae might be partially due to the
dust that we detect in the hosts.


title:
The Excitation of Extended Red Emission: New Constraints on its Carrier
  From HST Observations of NGC 7023

abstract:
  The carrier of the dust-associated photoluminescence process causing the
extended red emission (ERE) in many dusty interstellar environments remains
unidentified. Several competing models are more or less able to match the
observed broad, unstructured ERE band. We now constrain the character of the
ERE carrier further by determining the wavelengths of the radiation that
initiates the ERE. Using the imaging capabilities of the Hubble Space
Telescope, we have resolved the width of narrow ERE filaments appearing on the
surfaces of externally illuminated molecular clouds in the bright reflection
nebula NGC 7023 and compared them with the depth of penetration of radiation of
known wavelengths into the same cloud surfaces. We identify photons with
wavelengths shortward of 118 nm as the source of ERE initiation, not to be
confused with ERE excitation, however. There are strong indications from the
well-studied ERE in the Red Rectangle nebula and in the high-|b| Galactic
cirrus that the photon flux with wavelengths shortward of 118 nm is too small
to actually excite the observed ERE, even with 100% quantum efficiency. We
conclude, therefore, that ERE excitation results from a two-step process. While
none of the previously proposed ERE models can match these new constraints, we
note that under interstellar conditions most polycyclic aromatic hydrocarbon
(PAH) molecules are ionized to the di-cation stage by photons with E > 10.5 eV
and that the electronic energy level structure of PAH di-cations is consistent
with fluorescence in the wavelength band of the ERE. Therefore, PAH di-cations
deserve further study as potential carriers of the ERE. (abridged)