title:
A rapid and dramatic outburst in Blazar 3C 454.3 during May 2005 -
  Optical and infrared observations with REM and AIT

abstract:
  The flat-spectrum radio quasar 3C 454.3 is well known to be a highly active
and variable source with outbursts occurring across the whole electromagnetic
spectrum over the last decades. In spring 2005, 3C 454.3 has been reported to
exhibit a strong optical outburst which subsequently triggered multi-frequency
observations of the source covering the radio up to gamma-ray bands. Here, we
present first results of our near-IR/optical (V, R, I, H band) photometry
performed between May 11 and August 5, 2005 with the Rapid Eye Mount (REM) at
La Silla in Chile and the Automatic Imaging Telescope (AIT) of the Perugia
University Observatory. 3C 454.3 was observed during an exceptional and
historical high state with a subsequent decrease in brightness over our 86 days
observing period. The continuum spectral behaviour during the flaring and
declining phase suggests a synchrotron peak below the near-IR band as well as a
geometrical origin of the variations e.g. due to changes in the direction of
forward beaming.


title: Weighing the young stellar discs around Sgr A*

abstract:
  It is believed that young massive stars orbiting Sgr A* in two stellar discs
on scales of 0.1-0.2 parsecs were formed either farther out in the Galaxy and
then quickly migrated inward, or in situ in a massive self-gravitating disc.
Comparing N-body evolution of stellar orbits with observational constraints, we
set upper limits on the masses of the two stellar systems. These masses turn
out to be few times lower than the expected total stellar mass estimated from
the observed young high-mass stellar population and the standard galactic IMF.
If these stars were formed in situ, in a massive self-gravitating disc, our
results suggest that the formation of low-mass stars was suppressed by a factor
of at least a few, requiring a top-heavy initial mass function (IMF) for stars
formed near sgr A*.


title:
The Tully-Fisher relation of intermediate redshift field and cluster
  galaxies from Subaru spectroscopy

abstract:
  We have carried out spectroscopic observations in 4 cluster fields using
Subaru's FOCAS multi-slit spectrograph and obtained spectra for 103 bright disk
field and cluster galaxies at $0.06 \le z \le 1.20$. Seventy-seven of these
show emission lines, and 33 provide reasonably-secure determinations of the
galaxies' rotation velocity. The rotation velocities, luminosities, colours and
emission-line properties of these galaxies are used to study the possible
effects of the cluster environment on the star-formation history of the
galaxies. Comparing the Tully-Fisher relations of cluster and field galaxies at
similar reshifts we find no measurable difference in rest-frame $B$-band
luminosity at a given rotation velocity (the formal difference is $0.18\pm0.33
$mag). The colours of the cluster emission line galaxies are only marginally
redder in rest-frame $B-V$ (by $0.06\pm0.04 $mag) than the field galaxies in
our sample. Taken at face value, these results seem to indicate that bright
star-forming cluster spirals are similar to their field counterparts in their
star-formation properties. However, we find that the fraction of disk galaxies
with absorption-line spectra (i.e., with no current star formation) is larger
in clusters than in the field by a factor of $\sim3$--5. This suggests that the
cluster environment has the overall effect of switching off star formation in
(at least) some spiral galaxies. To interpret these observational results, we
carry out simulations of the possible effects of the cluster environment on the
star-formation history of disk galaxies and thus their photometric and
spectroscopic properties. Finally, we evaluate the evolution of the rest-frame
absolute $B$-band magnitude per unit redshift at fixed rotation velocity.


title:
Photometric and spectroscopic study of the intermediate age open cluster
  NGC 3960

abstract:
  We present CCD UBVI photometry and high-resolution spectroscopy of the
intermediate age open cluster NGC 3960. The colour - magnitude diagrams (CMDs)
derived from the photometric data and interpreted with the synthetic CMD method
allow us to estimate the cluster parameters. We derive: age = 0.9 or 0.6 Gyr
(depending on whether or not overshooting from convective regions is included
in the adopted stellar models), distance (m-M)0 = 11.6 +/- 0.1, reddening
E(B-V) = 0.29 +/- 0.02, differential reddening Delta E(B-V) = 0.05 and
approximate metallicity between solar and half of solar. We obtained high
resolution spectra of three clump stars, and derived an average [Fe/H] = -0.12
(rms 0.04 dex), in very good agreement with the photometric determination. We
also obtained abundances of alpha-elements, Fe-peak elements, and of Ba. The
reddenings toward individual stars derived from the spectroscopic temperatures
and the Alonso et al. calibrations give further support to the existence of
significative variations across the cluster.


title: Na-O Anticorrelation And HB I. The Na-O anticorrelation in NGC 2808

abstract:
  We derived atmospheric parameters and elemental abundances of Fe, O and Na
for about 120 red giant stars in the Galactic globular cluster NGC 2808. Our
results are based on the analysis of medium-high resolution (R=22000-24000)
GIRAFFE spectra acquired with the FLAMES spectrograph at VLT-UT2 as a part of a
project aimed at studying the Na-O anticorrelation as a function of physical
parameters in globular clusters. We present here the anticorrelation of Na and
O abundances in NGC 2808, and we discuss the distribution function of stars
along this relation. Besides a bulk of O-normal stars, with composition typical
of field halo stars, NGC 2808 seems to host two other groups of O-poor and
super O-poor stars. In this regard, NGC 2808 is similar to M 13, the template
cluster for the Na-O anticorrelation. However, at variance with M 13, most
stars in NGC 2808 are O-rich. This might be related to the horizontal branch
morphologies which are very different in these two clusters. The average
metallicity we found for NGC 2808 is [Fe/H]=-1.10 (rms=0.065 dex, from 123
stars). We also found some evidence of a small intrinsic spread in metallicity,
but more definitive conclusions are hampered by the presence of a small
differential reddening.


title: Integration of Acoustic Detection Equipment into ANTARES

abstract:
  The ANTARES group at the University of Erlangen is working towards the
integration of a set of acoustic sensors into the ANTARES Neutrino Telescope.
With this setup, tests of acoustic particle detection methods and background
studies shall be performed. The ANTARES Neutrino Telescope, which is currently
being constructed in the Mediterranean Sea, will be equipped with the
infrastructure to accommodate a 3-dimensional array of photomultipliers for the
detection of Cherenkov light. Within this infrastructure, the required
resources for acoustic sensors are available: Bandwidth for the transmission of
the acoustic data to the shore, electrical power for the off-shore electronics
and physical space to install the acoustic sensors and to route the connecting
cables (transmitting signals and power) into the electronics containers. It
will be explained how the integration will be performed with minimal
modifications of the existing ANTARES design and which setup is foreseen for
the acquisition of the acoustic data.


title:
Binaries with total eclipses in the LMC: potential targets for
  spectroscopy

abstract:
  35 Eclipsing binaries presenting unambiguous total eclipses were selected
from a subsample of the list of Wyrzykowski et al. (2003). The photometric
elements are given for the I curve in DiA photometry, as well as approximate
Teff and masses of the components. The interest of these systems is stressed in
view of future spectroscopic observations.


title: Lithium in field Am and normal A-F-type stars

abstract:
  Preliminary abundances of lithium and a few other elements have been obtained
for 31 field Am stars with good Hipparcos parallaxes, as well as for 36 normal
A and F stars. Radial and projected rotational velocities were determined as
well. We examine the Li abundance as a function of the stellar parameters: for
normal stars, it is clearly bimodal for Teff < 7500 K, while Am-Fm stars are
all somewhat Li-deficient in this range. The most Li-deficient stars - either
Am or normal - tend to be at least slightly evolved, but the reverse is not
true.


title: New Constraints on Additional Satellites of the Pluto System

abstract:
  Observations of Pluto and its solar-tidal stability zone were made using the
Advanced Camera for Surveys' (ACS) Wide Field Channel (WFC) on the Hubble Space
Telescope on UT 2005 May 15 and UT 2005 May 18. Two small satellites of Pluto,
provisionally designated S/2005 P 1 and S/2005 P 2, were discovered, as
discussed by Weaver et al. (2006) and Stern et al. (2006a). Confirming
observations of the newly discovered moons were obtained using the ACS in the
High Resolution Channel (HRC) mode on 2006 Feb 15 (Mutchler et al. 2006). Both
sets of observations provide strong constraints on the existence of any
additional satellites in the Pluto system. Based on the May 2005 observations
using the ACS/WFC, we place a 90%-confidence lower limit of m_V = 26.8 (m_V =
27.4 for a 50%-confidence lower limit) on the magnitude of undiscovered
satellites greater than 5" (1.1x10^5 km) from Pluto. Using the 2005 Feb 15
ACS/HRC observations we place 90%-confidence lower limits on the apparent
magnitude of any additional satellites of m_V = 26.4 between 3"-5"
(6.9x10^4-1.1x10^5 km) from Pluto, m_V = 25.7 between 1"-3" (2.3x10^4-6.9x10^4
km) from Pluto, and m_V = 24. between 0.3"-1" (6.9x10^3-2.3x10^4 km) from
Pluto. The 90%-confidence magnitude limits translate into upper limits on the
diameters of undiscovered satellites of 29 km outside of 5" from Pluto, 36 km
between 3"-5" from Pluto, 49 km between 1"-3" from Pluto, and 115 km between
0.3"-1" for a comet-like albedo of p_V = 0.04. If potential satellites are
assumed to have a Charon-like albedo of p_V = 0.38, the diameter limits are 9
km, 12 km, 16 km, and 37 km, respectively.


title:
MOJAVE: Monitoring of Jets in AGN with VLBA Experiments - II.
  First-Epoch 15 GHz Circular Polarization Results

abstract:
  We report first-epoch circular polarization results for 133 active galactic
nuclei in the MOJAVE program to monitor the structure and polarization of a
flux limited sample of extra-galactic radio jets with the VLBA at 15 GHz. We
found strong circular polarization ($\geq 0.3$%) in approximately 15% of our
sample. The circular polarization was usually associated with jet cores;
however, we did find a few strong jet components to be circularly polarized.
The levels of circular polarization were typically in the range of $0.3-0.5$%
of the local Stokes-$I$. We found no strong correlations between fractional
circular polarization of jet cores and source type, redshift, EGRET detections,
linear polarization, or other observed parsec-scale jet properties. There were
differences between the circular-to-linear polarization ratios of two nearby
galaxies versus more distant quasars and BL Lac objects. We suggest this is
because the more distant sources either have (1) less depolarization of their
linear polarization, and/or (2) poorer effective linear resolution and
therefore their VLBA cores apparently contain a larger amount of linearly
polarized jet emission. The jet of 3C 84 shows a complex circular polarization
structure, similar to observations by Homan & Wardle five years earlier;
however, much of the circular polarization seems to have moved, consistent with
a proper motion of 0.06$c$. The jet of 3C 273 also has several circularly
polarized components, and we find their fractional circular polarization
decreases with distance from the core.


title: Two cosmological models, the age of the Universe, and dark energy

abstract:
  The prevailing cosmological model with the lambda-term, in which the space is
flat, is studied (section 1). The corresponding age of the Universe (t0) is
calculated (assuming a Hubble constant consistent with the measurements of the
Hubble telescope), as well as the deceleration parameter (q0). The latter is
found negative, showing an accelerating Universe, but the former is
insufficient to account for the actually estimated value. Nevertheless, with
more recent values of the parameters involved, this model actually gives a
result consistent with the estimated value. But there is a severe defect in the
prevailing model, concerning the so-called dark energy, necessary to be
introduced. Then, another model without the lambda-term, and based on the
time-symmetric theory of the author, is studied (section 3), after an
introduction to this theory (section 2). In this model the space is open, but
the overall space-time is flat. It is not accelerating (it retains a constant
rate of expansion). In this model, with q0 = 0, an age of the Universe results,
which is consistent again, within the limits of accuracy, with the estimated
value. But the great advantage of this model is that it does not require at all
the existence of the ambiguous dark energy.


title: Massive Stars in the SMC

abstract:
  In this paper we review the observational data for OB stars in the SMC
concentrating on those aspects of their spectra which provide information on
processes which may strongly influence their evolution, namely mass-loss,
rotational mixing and mass-transfer. We illustrate the very weak winds now
thought to pertain to late O-dwarfs in the SMC, using HST/STIS observations of
the main sequence in the very young cluster NGC346, briefly discussing the
quantitative results for these stars, and the difficulties involved in their
determination. We show how stars with similar luminosities can have different
luminosity classes while stars with similar spectral types and luminosity
classes can have significantly different luminosities. While the weak winds of
the dwarfs present serious difficulties for the determination of wind terminal
velocities we show that the supergiants have terminal velocities comparable to
OB supergiants in the Milky Way, agreement with theory. We also summarize
recent work demonstrating that the temperature dependence of wind terminal
velocities does not follow the widely adopted step-like approximation. Finally
we review surface compositons of OB stars in the SMC finding that 42 out of 45
OB stars with detailed surface abundances are enriched in nitrogen by a factor
\~10 or more. While these enhancements are consistent with those produced by
models with rotational mixing the rotational velocities of the sample are
significantly lower than the values predicted by the modesls, indicating a
possible problem with the evolution of angular momentum in the models or
possibly in the efficiency of mixing.


title: On Solving the Coronal Heating Problem

abstract:
  This article assesses the current state of understanding of coronal heating,
outlines the key elements of a comprehensive strategy for solving the problem,
and warns of obstacles that must be overcome along the way.


title:
Autonomous Observing and Control Systems for PAIRITEL, a 1.3m Infrared
  Imaging Telescope

abstract:
  The Peters Automated Infrared Imaging Telescope (PAIRITEL) is the first
meter-class telescope operating as a fully robotic IR imaging system. Dedicated
in October 2004, PAIRITEL began regular observations in mid-December 2004 as
part of a 1.5 year commissioning period. The system was designed to respond
without human intervention to new gamma-ray burst transients: this milestone
was finally reached on November 9, 2005 but the telescope had a number of
semi-automated sub-10 minute responses throughout early commissioning. When not
operating in Target of Opportunity mode, PAIRITEL performs a number of queue
scheduled transient monitoring campaigns. To achieve this level of automation,
we have developed communicating tools to connect the various sub-systems: an
intelligent queue scheduling database, run-time configurable observation
sequence software, a data reduction pipeline, and a master state machine which
monitors and controls all functions within and affecting the observatory.


title:
Deep Photometry of Andromeda Reveals Striking Similarities in the Tidal
  Stream and Spheroid Populations

abstract:
  We present a color-magnitude diagram (CMD) for a field in the giant tidal
stream of the Andromeda galaxy (M31). These observations, taken with the
Advanced Camera for Surveys on the Hubble Space Telescope, are 50% complete at
V~30 mag, reaching 1 mag below the oldest main-sequence turnoff. Striking
similarities between the stream and a previous spheroid CMD imply they have
very similar age and metallicity distributions, but present something of an
enigma; we speculate on possible interpretations of this result, but note that
none are without problems. Distinct multiple turnoffs, as might be expected
from pulses of star formation caused by interaction with Andromeda, are not
apparent in the stream CMD. Star formation in both fields lasted about 6
billion years, building up to relatively high metallicities and being largely
complete 6 billion years ago. The close similarity of the spheroid and stream
suggests that both may have derived from the same event; it would be worth
exploring to what extent stars in these structures are the remnants of a disk
galaxy that interacted with M31, or even were disrupted from the M31 disk
itself by the interaction.


title: Revised Pulsar Spindown

abstract:
  We address the issue of electromagnetic pulsar spindown by combining our
experience from the two limiting idealized cases which have been studied in
great extent in the past: that of an aligned rotator where ideal MHD conditions
apply, and that of a misaligned rotator in vacuum. We construct a spindown
formula that takes into account the misalignment of the magnetic and rotation
axes, and the magnetospheric particle acceleration gaps. We show that near the
death line aligned rotators spin down much slower than orthogonal ones. In
order to test this approach, we use a simple Monte Carlo method to simulate the
evolution of pulsars and find a good fit to the observed pulsar distribution in
the P-Pdot diagram without invoking magnetic field decay. Our model may also
account for individual pulsars spinning down with braking index n < 3, by
allowing the corotating part of the magnetosphere to end inside the light
cylinder. We discuss the role of magnetic reconnection in determining the
pulsar braking index. We show, however, that n ~ 3 remains a good approximation
for the pulsar population as a whole. Moreover, we predict that pulsars near
the death line have braking index values n > 3, and that the older pulsar
population has preferentially smaller magnetic inclination angles. We discuss
possible signatures of such alignment in the existing pulsar data.


title: Chandra Detection of Local Warm-Hot Gas Toward Markarian 279

abstract:
  We report the Chandra detection of OVII K\alpha absorption at z=0 in the
direction of the z=0.03 Seyfert 1 galaxy Mkn 279. The high velocity cloud
Complex C lies along this line of sight, with HI 21-cm emission and OVI 1032\AA
absorption both observed at velocities of ~ -150 km/s relative to the local
standard of rest. We present an improved method for placing limits on the
Doppler parameter and column density of a medium when only one unresolved line
can be measured; this method is applied to the OVII absorption seen here,
indicating that the OVII Doppler parameter is inconsistent with that of any
low-velocity (Galactic thick disk) or high-velocity OVI (OVI_HV) component.
Direct association of the OVII with the OVI_HV is further ruled out by the high
temperatures required to produce the observed OVI_HV/OVII ratio and the
significant velocity difference between the OVII and OVI_HV lines. If the OVII
absorption is associated with a very broad, undetected OVI component, then the
absorption must be broadened by primarily nonthermal processes. The large
velocity dispersion and possible slight redshift of the OVII absorption (as
well as limits on the absorber's temperature and density) may be indicative of
a local intergalactic medium origin, though absorption from a hot, low-density
Galactic corona cannot be ruled out.


title: What galaxies know about their nearest cluster

abstract:
  We investigate the extent to which galaxies' star-formation histories and
morphologies are determined by their clustocentric distance and their nearest
cluster's richness. We look at three tracers of star-formation history (i-band
absolute magnitude M_i, [g-r] color, and Halpha emission line equivalent width)
and two indicators of galaxy morphology (surface brightness and radial
concentration) for 52,569 galaxies in the redshift range of 0.015<z<0.068. We
find that our morphology indicators relate to the clustocentric distance only
indirectly through their relationships with stellar population and
starformation rate. Galaxies that are near the cluster center tend to be more
luminous, redder and have lower Halpha EW (ie, lower star-formation rates) than
those that lie near or outside the virial radius of the cluster. The detailed
relationships between these galaxy properties and clustocentric distance depend
on cluster richness. For richer clusters, we find that (i) the transition in
color and Halpha EW from cluster center to field values is more abrupt and
occurs closer to the cluster virial radius, and (ii) the color and Halpha EW
distributions are overall narrower than in less rich clusters. We also find
that the radial gradient seen in the luminosity distribution is strongest
around the smaller clusters and decreases as cluster richness increases. We
find there is a `characteristic distance' at around one virial radius (the
infall region) where the change with radius of galaxy property distributions is
most dramatic, but we find no evidence for infall-triggered star bursts. These
results suggest that galaxies `know' the distance to, and the size of, their
nearest cluster and they express this information in their star-formation
histories.


title: Recent Timing Studies on RXTE Observations of 4U 1538-52

abstract:
  The high mass X-ray binary pulsar 4U 1538-52 was observed between July 31 and
August 7, 2003. Using these observations, we determined new orbital epochs for
both circular and elliptical orbit models. The orbital epochs for both orbit
solutions agreed with each other and yielded an orbital period derivative
$\dot{P} / P = (0.4 \pm 1.8) \times 10^{-6}$ yr$^{-1}$. This value is
consistent with the earlier measurement of $\dot{P} / P = (2.9 \pm 2.1) \times
10^{-6}$ yr$^{-1}$ at the $1 \sigma$ level and gives only an upper limit to the
orbital period decay. Our determination of the pulse frequency showed that the
source spun up at an average rate of $2.76 \times 10^{-14}$ Hz sec$^{-1}$
between 1991 and 2003.


title: An inhomogeneous alternative to dark energy?

abstract:
  Recently, there have been suggestions that the apparent accelerated expansion
of the universe is not caused by repulsive gravitation due to dark energy, but
is rather a result of inhomogeneities in the distribution of matter. In this
work, we investigate the behaviour of a dust dominated inhomogeneous
Lemaitre-Tolman-Bondi universe model, and confront it with various
astrophysical observations. We find that such a model can easily explain the
observed luminosity distance-redshift relation of supernovae without the need
for dark energy, when the inhomogeneity is in the form of an underdense bubble
centered near the observer. With the additional assumption that the universe
outside the bubble is approximately described by a homogeneous Einstein-de
Sitter model, we find that the position of the first CMB peak can be made to
match the WMAP observations. Whether or not it is possible to reproduce the
entire CMB angular power spectrum in an inhomogeneous model without dark
energy, is still an open question.


title: Spitzer Number Counts of AGN in the GOODS fields

abstract:
  We present mid-infrared observations of AGN in the GOODS fields, performed
with the Spitzer Space Telescope. These are the deepest infrared and X-ray
fields to date and cover a total area of ~0.1 square degrees. AGN are selected
on the basis of their hard (2-8 keV) X-ray emission. The median AGN infrared
luminosity is at least 10 times larger than the median for normal galaxies with
the same redshift distribution, suggesting that the infrared emission is
dominated by the central nucleus. The X-ray to infrared luminosity ratios of
GOODS AGN, most of which are at 0.5<z<1.5, are similar to the values obtained
for AGN in the local Universe. The observed infrared flux distribution has an
integral slope of ~1.5 and there are 1000 sources per square degree brighter
than ~50 uJy at 3-6 microns. The counts approximately match the predictions of
models based on AGN unification, in which the majority of AGN are obscured.
This agreement confirms that the faintest X-ray sources, which are dominated by
the host galaxy light in the optical, are obscured AGN. Using these Spitzer
data, the AGN contribution to the extragalactic infrared background light is
calculated by correlating the X-ray and infrared catalogues. This is likely to
be a lower limit given that the most obscured AGN are missed in X-rays. We
estimate the contribution of AGN missed in X-rays, using a population synthesis
model, to be ~45% of the observed AGN contribution, making the AGN contribution
to the infrared background at most ~2-10% in the 3-24 micron range, depending
on wavelength, lower than most previous estimates. The AGN contribution to the
infrared background remains roughly constant with source flux in the IRAC bands
but decreases with decreasing flux in the MIPS 24 um band, where the galaxy
population becomes more important.


title: Obscured and Unobscured AGN Evolution and the X-ray background

abstract:
  The Great Observatories Origins Deep Survey (GOODS) combines deep HST and
Spitzer imaging with the deepest Chandra/XMM observations to probe obscured AGN
at higher redshifts than previous multiwavelength surveys. We present a
self-consistent implementation of the AGN unification paradigm, which
postulates obscured AGN wherever there are unobscured AGN, to successfully
explain the infrared, optical, and X-ray number counts of X-ray sources
detected in the GOODS fields. Assuming either a constant ratio of obscured to
unobscured AGN of 3:1 (the local value), or a ratio that decreases with
luminosity, and including Compton-thick sources, we can explain the spectral
shape and normalization of the extragalactic X-ray "background" as a
superposition of unresolved AGN, predominantly at z~0.5-1.5 and L_x~10^43-10^44
ergs/s. The possible dependence of the obscured to unobscured ratio with
redshift is not well constrained; present data allow it to decrease or increase
substantially beyond z~1.


title: The interior of the SNR RX J0852.0-4622 (Vela Jr) at radio wavelengths

abstract:
  Aim: We observed the center of the supernova remnant Vela Jr in radio
continuum in order to search for a counterpart to the compact central X-ray
source CXOU J085201.4-461753, possibly a neutron star candidate which could be
the remnant of the supernova explosion. Method: Observations were made with the
Australia Telescope Compact Array at 13 and 20 cm. Spectral indices were
obtained using flux density correlations of the data which were spatially
filtered to have the same u-v coverage. A multiwavelength search for
counterparts to the compact central X-ray source was made. Results: We compiled
a new catalogue of 31 small diameter radio sources, including the previously
known source PMN J0853-4620, listing the integrated flux densities at 20 cm
and, for half of the sources, the flux densities at 13 cm with the
corresponding spectral indices. All sources are unresolved at the present
angular resolution except for Source 18, which is clearly elongated and lies
strikingly close to CXOU J085201.4-461753. Our observations show no evidence
for the existence of a pulsar wind driven nebula associated with the point
X-ray source. Furthermore, Source 18 has a thermal spectrum with index +0.8 +/-
0.4, and appears to be the counterpart of the optical source Wray 16-30. In
spite of the absence of OIII emission lines as reported in the literature, we
find that this object could be explained as a low emission planetary nebula
belonging to the ``butterfly'' morphological class. Conclusions: We conclude
that if the radio source 18 is actually a planetary nebula, then CXOU
J085201.4-461753 is more likely to be related to it rather than to Vela Jr.


title:
The Cosmic Reionization History as Revealed by the CMB Doppler--21-cm
  Correlation

abstract:
  We show that the epoch(s) of reionization when the ionization fraction of the
universe is about half can be determined by correlating Cosmic Microwave
Background (CMB) temperature maps with 21-cm line maps at degree scales ($l\sim
100$). During reionization peculiar motion of free electrons induces the
Doppler anisotropy of the CMB, while density fluctuations of neutral hydrogen
induce the 21-cm line anisotropy. In our simplified model of inhomogeneous
reionization, a positive correlation arises as the universe reionizes whereas a
negative correlation arises as it recombines; thus, the sign of the correlation
provides information on the reionization history which cannot be obtained by
presently. The signal comes mainly from large scales (k~0.01 Mpc^-1) where
linear perturbation theory is valid and complexity due to patchy reionization
is averaged out. Since the Doppler signal comes from ionized regions and the
21-cm comes from neutral ones, the correlation has a well-defined peak(s) in
redshift when the ionization fraction of the universe is about half.
Furthermore, the cross-correlation is much less sensitive to systematic errors,
especially foreground emission, than the auto-correlation of 21-cm lines: this
is analogous to the temperature-polarization correlation of the CMB being more
immune to systematic errors than the polarization-polarization. Therefore, we
argue that the Doppler-21cm correlation provides a robust measurement of the
21-cm anisotropy, which can also be used as a diagnostic tool for detected
signals in the 21-cm data -- detection of the cross-correlation provides the
strongest confirmation that the signal is of cosmological origin. We show that
the Square Kilometer Array can easily measure the predicted correlation signal
for 1~year of survey observation.


title: Inward Motions of the Compact SiO Masers Around VX Sagittarii

abstract:
  We report Very Long Baseline Array (VLBA) observations of 43 GHz v=1, J=1-0
SiO masers in the circumstellar envelope of the M-type semi-regular variable
star VX Sgr at 3 epochs during 1999 April-May. These high-resolution VLBA
images reveal a persistent ringlike distribution of SiO masers with a projected
radius of ~3 stellar radii. The typical angular size of 0.5 mas for individual
maser feature was estimated from two-point correlation function analysis for
maser spots. We found that the apparent size scale of maser features was
distinctly smaller than that observed in the previous observations by comparing
their fractions of total power imaged. This change in the size scale of maser
emission may be related to stellar activity that caused a large SiO flare
during our observations. Our observations confirmed the asymmetric distribution
of maser emission, but the overall morphology has changed significantly with
the majority of masers clustering to the north-east of the star compared to
that lying to the south-west direction in 1992. By identifying 42 matched maser
features appearing in all the three epochs, we determined the contraction of an
SiO maser shell toward VX Sgr at a proper motion of -0.507 mas/yr,
corresponding to a velocity of about 4 km/s at a distance of 1.7 kpc to VX Sgr.
Such a velocity is on the order of the sound speed, and can be easily explained
by the gravitational infall of material from the circumstellar dust shell.


title:
Recent and Future Observations in the X-ray and Gamma-ray Bands:
  Chandra, Suzaku, GLAST, and NuSTAR

abstract:
  This paper presents a brief overview of the accomplishments of the Chandra
satellite that are shedding light on the origin of high energy particles in
astrophysical sources, with the emphasis on clusters of galaxies. It also
discusses the prospects for the new data to be collected with instruments
recently launched - such as Suzaku - or those to be deployed in the near
future, and this includes GLAST and NuSTAR.


title:
Biological Effects of Gamma-Ray Bursts: distances for severe damage on
  the biota

abstract:
  We present in this work a unified, quantitative synthesis of analytical and
numerical calculations of the effects that could be caused on Earth by a
Gamma-Ray Burst (GRB), considering atmospheric and biological implications. The
main effects of the illumination by a GRB are classified in four distinct ones
and analyzed separately, namely: direct gamma Flash, UV Flash, Ozone Layer
Depletion and Cosmic Rays. The effectiveness of each of these effects is
compared and distances for significant biological damage are given for each
one. We find that the first three effects have potential to cause global
environmental changes and biospheric damages, even if the source is located at
Galactic distances or even farther (up to 150 kpc, about five times the
Galactic diameter of 30 kpc). Instead, cosmic rays would only be a serious
threat for close sources (on the order of a few pc). As a concrete application
from a well-recorded event, the effects on the biosphere of an event identical
to the giant flare of SGR1806-20 on Dec 27, 2004 have been calculated. In spite
of not beeing a classical GRB, most of the parameters of this recent flare are
quite well-known and have been used as a calibration for our study. We find
that a giant flare impinging on Earth is not a threat for life in all practical
situations, mainly because it is not as energetic, in spite of being much more
frequent than GRBs, unless the source happens to be extremely close.


title: Probing the early universe with inflationary gravitational waves

abstract:
  Near comoving wavenumber k, the gravitational-wave background (GWB) from
inflation carries information about the physical conditions near two moments in
cosmic history: the moment when k ``left the horizon'' during inflation, and
the moment when it ``re-entered the horizon'' after inflation. We investigate
the extent to which this information can be extracted if the GWB is measured by
a combination of cosmic-microwave-background (CMB) polarization experiments on
large scales and space-based laser-interferometer experiments on small scales.
To disentangle this information, we derive a new gravitational-wave transfer
function that incorporates a number of physical effects that were treated less
accurately, less generally, or were missing altogether in previous treatments.
In particular, it incorporates: (i) dark energy with time-varying
equation-of-state w(z); (ii) tensor anisotropic stress due to free-streaming
relativistic particles in the early universe; and (iii) a variety of physical
effects that cause deviations from the standard equation-of-state w=1/3 during
the radiation era. Based on this transfer function, we consider the degree to
which the GWB can be used to test inflation and to probe the ``primordial dark
age'' between the end of inflation and the electroweak phase transition.


title: INTEGRAL/IBIS Extragalactic survey: 20-100 keV selected AGN

abstract:
  Analysis of INTEGRAL Core Program and public Open Time observations performed
up to April 2005 provides a sample of 62 active galactic nuclei in the 20-100
keV band above a flux limit of ~1.5x10^-11 erg/cm2/s. Most(42) of the sources
in the sample are Seyfert galaxies, almost equally divided between type 1 and 2
objects, 6 are blazars and 14 are still unclassified. Excluding the blazars,
the average redshift of our sample is 0.021 while the mean luminosity is Log(L)
= 43.45. We find that absorption is present in 65% of the objects with 14% of
the total sample due to Compton thick active galaxies. In agreement with both
Swift/BAT team results and 2-10 keV studies, the fraction of absorbed objects
decreases with the 20-100 keV luminosity. All Seyfert 2s in our sample are
absorbed as are 33% of Seyfert 1s. The present data highlight the capability of
INTEGRAL to probe the extragalactic gamma-ray sky and to find new and/or
absorbed active galaxies.


title:
A Close Look at the Population of Supersoft and Quasi-Soft X-Ray Sources
  Observed in M31 with XMM-Newton

abstract:
  The deepest X-ray images of M31, obtained with XMM-Newton, are examined in
this paper to derive spectral and statistical properties of the population of
the softest X-ray sources. Classifying supersoft X-ray sources (SSS) with
criteria based on the same hardness ratios defined for recent Chandra
observations, a quarter of the selected SSS turn out to be supernova remnants
(SNR). Another quarter of SSS are spatially coincident with recent classical
novae (but they are less than 10% of the nova population observed in the last
25 years). Only 3 among 15 non-SNR SSS show clear time variability, with X-ray
flux variation of more than one order of magnitude within few months. Two of
these sources display additional, smaller amplitude variability on time scales
of several minutes. Their broad band spectra and those of the novae are
approximately fit with a blackbody or white dwarf atmospheric model at
near-Eddington luminosity for the distance of M31. Two SSS appear to reach very
large, perhaps super-Eddington luminosities for part of the time, and probably
eject material in a wind until the luminosity decreases again after a few
months. One of the two objects has some characteristics in common with Ultra
Luminous X-ray Sources observed outside the Local Group. Most Quasi-Soft
Sources (QSS) are repeatedly detected. I discuss the possibilities that most
QSS may be SNR in M31, or foreground neutron stars. Two X-ray sources with both
a soft and hard component are in the positions of a recurrent nova and another
object that was tentatively classified as a symbiotic nova. These two sources
may be black hole transients.


title: Cosmic microwave background multipole alignments in slab topologies

abstract:
  Several analyses of the microwave sky maps from the Wilkinson Microwave
Anisotropy Probe (WMAP) have drawn attention to alignments amongst the
low-order multipoles. Amongst the various possible explanations, an effect of
cosmic topology has been invoked by several authors. We focus on an alignment
of the first four multipoles (\ell = 2 to 5) found by Land and Magueijo (2005),
and investigate the distribution of their alignment statistic for a set of
simulated cosmic microwave background maps for cosmologies with slab-like
topology. We find that this topology does offer a modest increase in the
probability of the observed value, but that even for the smallest topology
considered the probability of the observed value remains below one percent.


title: A Note on Crossing the Phantom Divide in Hybrid Dark Energy Model

abstract:
  Recently a lot of attention has been given to building dark energy models in
which the equation-of-state parameter $w$ can cross the phantom divide $w=-1$.
However, to our knowledge, these models with crossing the phantom divide only
provide the possibility that $w$ can cross -1. They do not answer another
question: {\em why crossing phantom divide occurs recently?} Since in many
existing models whose equation-of-state parameter can cross the phantom divide,
$w$ undulates around -1 randomly, {\em why are we living in an epoch $w<-1$?}
This can be regarded as the second cosmological coincidence problem. In this
note, we propose a possible approach to alleviate this problem within a hybrid
dark energy model.


title:
A population synthesis study on the faint X-ray sources in the Galactic
  center region

abstract:
  Context. Recent Chandra observations of the Galactic center region (GCR) have
uncovered a population of faint discrete X-ray sources. A few theoretical works
have been made to investigate the nature of these sources. Aims. We examine the
contributions and luminosity functions of various kinds of candidate objects
which are proposed either by previous authors or by ourselves. Methods. We
conduct a population synthesis calculation based on Hurley et al.'s rapid
binary evolution code. Several candidate models, i.e. wind-accreting neutron
stars, intermediate polars, low mass X-ray binaries, young pulsars and massive
stars with strong winds, are incorporated into our calculation. We also take
the geometric effect of the accretion disk into account for Roche lobe overflow
X-ray binaries. Results. Our results show that neutron star low-mass X-ray
binaries contribute significantly to the observed sources. We also point out
that wind-accreting neutron stars contribute negligibly to these sources due to
propeller effect, and the intermediate polars play a minor role in accounting
for the faint X-ray sources in both Wang et al. and Muno et al. survey. It
should be mentioned that the majority of the sources in the survey field of
Wang et al. are still beyond our expectation.


title: Gradient and dispersion analyses of the WMAP data

abstract:
  We studied the WMAP temperature anisotropy data using two different methods.
The derived signal gradient maps show regions with low mean gradients in
structures near the ecliptic poles and higher gradient values in the wide
ecliptic equatorial zone, being the result of non-uniform observational time
sky coverage. We show that the distinct observational time pattern present in
the raw (cleaned) data leaves also its imprints on the composite CMB maps.
Next, studying distribution of the signal dispersion we show that the
north-south asymmetry of the WMAP signal diminishes with galactic altitude,
confirming the earlier conclusions that it possibly reveals galactic foreground
effects. As based on these results, one can suspect that the instrumental noise
sky distribution and non-removed foregrounds can have affected some of the
analyses of the CMB signal. We show that actually the different characteristic
axes of the CMB sky distribution derived by numerous authors are preferentially
oriented towards some distinguished regions on the sky, defined by the
observational time pattern and the galactic plane orientation.


title:
Mass loss and orbital period decrease in detached chromospherically
  active binaries

abstract:
  The secular evolution of the orbital angular momentum (OAM), the systemic
mass $(M=M_{1}+M_{2})$ and the orbital period of 114 chromospherically active
binaries (CABs) were investigated after determining the kinematical ages of the
sub-samples which were set according to OAM bins. OAMs, systemic masses and
orbital periods were shown to be decreasing by the kinematical ages. The first
order decreasing rates of OAM, systemic mass and orbital period have been
determined as $\dot J = 3.48 \times 10^{-10} yr^{-1}$ per systemic OAM, $\dot M
= 1.30 \times 10^{-10} yr^{-1}$ per systemic mass and $\dot P = 3.96\times
10^{-10} yr^{-1}$ per orbital period respectively from the kinematical ages.
The ratio of $d \log J/ d \log M = 2.68$, which were derived from the
kinematics of the present sample, implies that there must be a mechanism which
amplifies the angular momentum loss $\bar A = 2.68$ times in comparison to
isotropic angular momentum loss of hypothetical isotropic wind from the
components. It has been shown that simple isotropic mass loss from the surface
of a component or both components would increase the orbital period.


title: Precession of the Super-Massive Black Hole in NGC 1275 (3C 84)?

abstract:
  The X-ray holes at the centre of the Perseus Cluster of galaxies are not all
at the same position angle with respect to the centre of the cluster. This
configuration would result if the jet inflating the bubbles is precessing, or
moving around, and the bubbles detach at different times. The orientations
which best fit the observed travel directions are an inclination of the
precession axis to the line of sight of 120 degrees and an opening angle of 50
degrees. From the timescales for the bubbles seen in the cluster, the
precession timescale, t_prec, is around 3.3x10^7 yrs. The bubbles rising up
through different parts of the cluster may have interacted with the central
cool gas, forming the whorl of cool gas observed in the temperature structure
of the cluster. The dynamics of bubbles rising in fluids is discussed. The
conditions present in the cluster are such that oscillatory motion, observed
for bubbles rising in fluids on Earth, should take place. However the timescale
for this motion is longer than that taken for the bubbles to evolve into
spherical cap bubbles, which do not undergo a path instability, so such motion
is not expected to occur.


title:
Equation of state description of the dark energy transition between
  quintessence and phantom regimes

abstract:
  The dark energy crossing of the cosmological constant boundary (the
transition between the quintessence and phantom regimes) is described in terms
of the implicitly defined dark energy equation of state. The generalizations of
the models explicitly constructed to exhibit the crossing provide the insight
into the cancellation mechanism which makes the transition possible.


title: Why is the mass function of NGC 6218 flat?

abstract:
  We have used the FORS-1 camera on the VLT to study the main sequence (MS) of
the globular cluster NGC 6218 in the V and R bands. The observations cover an
area of 3.4 x 3.4 around the cluster centre and probe the stellar population
out to the cluster's half-mass radius (r_h ~ 2.2). The colour-magnitude diagram
(CMD) that we derive in this way reveals a narrow and well defined MS extending
down to the 5 sigma detection limit at V~25, or about 6 magnitudes below the
turn-off, corresponding to stars of ~ 0.25 Msolar. The luminosity function (LF)
obtained with these data shows a marked radial gradient, in that the ratio of
lower- and higher-mass stars increases monotonically with radius. The mass
function (MF) measured at the half-mass radius, and as such representative of
the clusters global properties, is surprisingly flat. Over the range 0.4 - 0.8
Msolar, the number of stars per unit mass follows a power-law distribution of
the type dN/dm \propto m^{0}, where, for comparison, Salpeter's IMF would be
dN/dm \propto m^{-2.35}. We expect that such a flat MF does not represent the
cluster's IMF but is the result of severe tidal stripping of the stars from the
cluster due to its interaction with the Galaxy's gravitational field. Our
results cannot be reconciled with the predictions of recent theoretical models
that imply a relatively insignificant loss of stars from NGC 6218 as measured
by its expected very long time to disruption. They are more consistent with the
orbital parameters based on the Hipparcos reference system that imply a much
higher degree of interaction of this cluster with the Galaxy than assumed by
those models. Our results indicate that, if the orbit of a cluster is known,
the slope of its MF could be useful in discriminating between the various
models of the Galactic potential.


title: IR Emission from AGNs

abstract:
  Unified schemes of active galactic nuclei (AGN) require an obscuring dusty
torus around the central engine. Torus sizes of hundreds of parsecs were
deduced from early theoretical modeling efforts, but high-resolution IR
observations now show that the torus size is no more than a few parsecs. This
conflict is resolved when the clumpy nature of the torus is taken into account.
The compact torus may be best understood when identified with the dusty,
optically thick region of the wind coming off the central accretion disk.


title:
Correlated spectral and temporal changes in 3C 390.3: a new link between
  AGN and Galactic Black Hole Binaries?

abstract:
  This work presents the results from a systematic search for evidence of
temporal changes (i.e., non-stationarity) associated with spectral variations
in 3C 390.3, using data from a two-year intensive RXTE monitoring campaign of
this broad-line radio galaxy. In order to exploit the potential information
contained in a time series more efficiently, we adopt a multi-technique
approach, making use of linear and non-linear techniques. All the methods show
suggestive evidences for non-stationarity in the temporal properties of 3C
390.3 between 1999 and 2000, in the sense that the characteristic time-scale of
variability decreases as the energy spectrum of the source softens. However,
only the non-linear, "scaling index method" is able to show conclusively that
the temporal characteristics of the source do vary, although the physical
interpretation of this result is not clear at the moment. Our results indicate
that the variability properties of 3C 390.3 may vary with time, in the same way
as they do in Galactic black holes in the hard state, strengthening the analogy
between the X-ray variability properties of the two types of object. This is
the first time that such a behavior is detected in an AGN X-ray light curve.
Further work is needed in order to investigate whether this is a common
behavior in AGN, just like in the Galactic binaries, or not.


title: Simulating Star Formation and Feedback in Galactic Disk Models

abstract:
  We use a high-resolution grid-based hydrodynamics method to simulate the
multi-phase interstellar medium in a Milky Way-size quiescent disk galaxy. The
models are global and three-dimensional, and include a treatment of star
formation and feedback. We examine the formation of gravitational instabilities
and show that a form of the Toomre instability criterion can successfully
predict where star formation will occur. Two common prescriptions for star
formation are investigated. The first is based on cosmological simulations and
has a relatively low threshold for star formation, but also enforces a
comparatively low efficiency. The second only permits star formation above a
number density of 1000 cm^-3 but adopts a high efficiency. We show that both
methods can reproduce the observed slope of the relationship between star
formation and gas surface density (although at too high a rate for our adopted
parameters). A run which includes feedback from type II supernovae is
successful at driving gas out of the plane, most of which falls back onto the
disk. This feedback also substantially reduces the star formation rate.
Finally, we examine the density and pressure distribution of the ISM, and show
that there is a rough pressure equilibrium in the disk, but with a wide range
of pressures at a given location (and even wider for the case including
feedback


title:
The shaping of planetary nebula Sh 2-188 through interaction with the
  interstellar medium

abstract:
  Sh 2-188 is an example of strong interaction between a planetary nebula (PN)
and the interstellar medium (ISM). Its structure is postulated to be the result
of motion through the ISM. We present new H$\alpha$ images from the Isaac
Newton Telescope Photometric H$\alpha$ Survey of the Northern Galactic Plane
which reveal new structure. The nebula extends 15 arcmin on the sky in total.
We have developed a `triple-wind' hydrodynamical model, comprising of the
initial `slow' asymptotic giant branch (AGB) wind and the later `fast' stellar
wind plus a third wind reflecting the motion through the ISM. Simulations at
various velocities of the central star relative to the ISM indicate that a high
velocity of 125 kms is required to reproduce the observed structure. We find
most of the structure already forms during the AGB phase. The closure of the
ring arises from the slow--fast wind interaction. Most of the mass lost on the
AGB has been swept downstream, providing a potential explanation of the missing
mass problem in PNe. We report a proper motion for the central star of 30 mas
yr^-1 in the direction of the bright limb, implying a distance to the nebula of
850^{+500}_{-420} pc, consistent with a spectroscopic distances. Expansion
velocities measured from spectroscopic data are consistent with velocities
measured from the simulation. The model shows that the size of the PN was
already set during the AGB phase.


title: What best constrains galaxy evolution in the local Universe?

abstract:
  After a polemical introduction about the proper activity of an astrophysicist
facing a dominant theoretical model and many Tb of highly informative data, I
review a few recent results on the properties of galaxies in the nearby
(redshift one-tenth) Universe that directly bear on physical cosmology. In one
example, I show that there are a number of ways of measuring, or strongly
constraining, massive galaxy-galaxy major merger rates, which are predicted
with limited uncertainties in the current generation of models. In another, I
show that we can go beyond "correlations" between individual galaxy properties
and "environment". Our results show that it is galaxy star-formation
histories--not their morphologies--that are sensitive to environmental density.
I look forward to a future, perhaps not that far away, in which these results
guide a fundamental modification to our theoretical assumptions, though I fear
that the dominant paradigm may not require subversion.


title: A Parallel Adaptive P3M code with Hierarchical Particle Reordering

abstract:
  We discuss the design and implementation of HYDRA_OMP a parallel
implementation of the Smoothed Particle Hydrodynamics-Adaptive P3M (SPH-AP3M)
code HYDRA. The code is designed primarily for conducting cosmological
hydrodynamic simulations and is written in Fortran77+OpenMP. A number of
optimizations for RISC processors and SMP-NUMA architectures have been
implemented, the most important optimization being hierarchical reordering of
particles within chaining cells, which greatly improves data locality thereby
removing the cache misses typically associated with linked lists. Parallel
scaling is good, with a minimum parallel scaling of 73% achieved on 32 nodes
for a variety of modern SMP architectures. We give performance data in terms of
the number of particle updates per second, which is a more useful performance
metric than raw MFlops. A basic version of the code will be made available to
the community in the near future.


title: A Simple Method To Find All Lensed Quasars

abstract:
  We demonstrate that gravitationally lensed quasars are easily recognized
using image subtraction methods as time variable sources that are spatially
extended. For Galactic latitudes |b|>20 deg, lensed quasars dominate the
population of spatially extended variable sources, although there is some
contamination from variable star pairs, variable star-quasar pairs and binary
quasars that can be easily controlled using other information in the survey
such as the object light curves and colors. This will allow planned large-scale
synoptic surveys to find lensed quasars almost down to their detection limits
without the need for extensive follow-up observations.


title: Star Cluster Evolution with Primordial Binaries

abstract:
  Observations and theoretical work suggest that globular clusters may be born
with initially very large binary fractions. We present first results from our
newly modified Monte-Carlo cluster evolution code, which treats binary
interactions exactly via direct N-body integration. It is shown that binary
scattering interactions generate significantly less energy than predicted by
the recipes that have been used in the past to model them in approximate
cluster evolution methods. The new result that the cores of globular clusters
in the long-lived binary-burning phase are smaller than previously predicted
weakens the agreement with observations, thus implying that more than simply
stellar dynamics is at work in shaping the globular clusters we observe today.


title: Effects of neutrino-driven kicks on the supernova explosion mechanism

abstract:
  We show that neutrino-driven pulsar kicks can increase the energy of the
supernova shock. The observed large velocities of pulsars are believed to
originate in the supernova explosion, either from asymmetries in the ejecta or
from an anisotropic emission of neutrinos (or other light particles) from the
cooling neutron star. In this paper we assume the velocities are caused by
anisotropic neutrino emission and study the effects of these neutrino-driven
kicks on the supernova explosion. We find that if the collapsed star is
marginally unable to produce an explosion, the neutrino-driven mechanisms can
drive the convection to make a successful explosion. The resultant explosion is
asymmetric, with the strongest ejecta motion roughly in the direction of the
neutron star kick. This is in sharp contrast with the ejecta-driven mechanisms,
which predict the motion of the ejecta in the opposite direction. This
difference can be used to distinguish between the two mechanisms based on the
observations of the supernova remnants.


title:
FIRST-based survey of Compact Steep Spectrum sources, III. MERLIN and
  VLBI observations of subarcsecond-scale objects

abstract:
  According to a generally accepted paradigm, small intrinsic sizes of Compact
Steep Spectrum (CSS) radio sources are a direct consequence of their youth, but
in later stages of their evolution they are believed to become large-scale
sources. However, this notion was established mainly for strong CSS sources. In
this series of papers we test this paradigm on 60 weaker objects selected from
the VLA FIRST survey. They have 5-GHz flux densities in the range 150 <
S_{5GHz} < 550 mJy and steep spectra in the range 0.365 \le \nu \le 5 GHz. The
present paper is focused on sources that fulfill the above criteria and have
angular sizes in the range 0.2\arcsec - 1\arcsec. Observations of 19 such
sources were obtained using MERLIN in "snapshot" mode at 5 GHz. They are
presented along with 1.7-GHz VLBA and 5-GHz EVN follow-up snapshot observations
made for the majority of them. For one of the sources in this subsample,
1123+340, a full-track 5-GHz EVN observation was also carried out. This study
provides an important element to the standard theory of CSS sources, namely
that in a number of them the activity of their host galaxies probably switched
off quite recently and their further growth has been stopped because of that.
In the case of 1123+340, the relic of a compact "dead source" is particularly
well preserved by the presence of intracluster medium of the putative cluster
of galaxies surrounding it. The observed overabundance of compact sources can
readily be explained in the framework of the scenario of "premature" cessation
of the activity of the host galaxy nucleus. It could also explain the
relatively low radio flux densities of many such sources and, in a few cases,
their peculiar, asymmetric morphologies. We propose a new interpretation of
such asymmetries based on the light-travel time argument.


title:
Star formation and stellar populations in the Wolf-Rayet(?) luminous
  compact blue galaxy IRAS 08339+6517

abstract:
  IRAS 08339+6517 is a luminous infrared and Ly$\alpha$-emitting starburst
galaxy that possesses a dwarf companion object at a projected distance of 56
kpc. An \ion{H}{i} tidal tail has recently been detected between both galaxies,
suggesting that about 70% of the neutral gas has been ejected from them.We
present deep broad-band optical images, together with narrow band H$\alpha$ CCD
images, and optical intermediate-resolution spectroscopy of both galaxies. The
images reveal interaction features between both systems and strong H$\alpha$
emission in the inner part of IRAS 08339+6517. The chemical composition of the
ionized gas of the galaxies is rather similar. The analysis of their kinematics
also indicates interaction features and reveals an object that could be a
candidate tidal dwarf galaxy or a remnant of an earlier merger. Our data
suggest that the \ion{H}{i} tail has been mainly formed from material stripped
from the main galaxy. We find weak spectral features that could be attributed
to the presence of Wolf--Rayet stars in this starburst galaxy and estimate an
age of the most recent burst of around 4 -- 6 Myr. A more evolved underlying
stellar population, with a minimal age between 100 -- 200 Myr, is also detected
and fits an exponential intensity profile. A model which combines 85% young and
15% old populations can explain both the spectral energy distribution and the
\ion{H}{i} Balmer and \ion{He}{i} absorption lines presented in our spectrum.
The star formation rate of the galaxy is consistently derived using several
calibrations, giving a value of $\sim$9.5 \Mo yr$^{-1}$. IRAS 08339+6517 does
satisfy the criteria of a luminous compact blue galaxy, rare objects in the
local universe but common at high redshifts, being a very interesting target
for detailed studies of galaxy evolution and formation.


title: The puzzling case of 56 Pegasi: A fast rotator seen nearly face-on?

abstract:
  A spectroscopic orbit has been recently found by R. Griffin for the long
known barium star 56 Peg, which is also a strong X-ray source. This
short-period, low mass-function orbit raises several questions regarding the
history of the system. In the present paper, we show that it is not easy to
find an evolutionary history for 56 Peg which is consistent with the current
component's masses, unless one assumes that the giant is a relatively fast
rotator (a few times 10 km/s). The hypothesis of fast rotation allows us to
explain some other peculiarities of this object as well.


title: Spitzer Observations of Deeply Obscured Galactic Nuclei

abstract:
  We report on our first results from a mid-infrared spectroscopic study of ISM
features in a sample of deeply obscured ULIRG nuclei using the InfraRed
Spectrograph (IRS) on the Spitzer Space Telescope. The spectra are extremely
rich and complex, revealing absorption features of both amorphous and
crystalline silicates, aliphatic hydrocarbons, water ice and gas phase bands of
hot CO and warm C_2H_2, HCN and CO_2. PAH emission bands were found to be
generally weak and in some cases absent. The features are probing a dense and
warm environment in which crystalline silicates and water ice are able to
survive but volatile ices, commonly detected in Galactic dense molecular
clouds, cannot. If powered largely by star formation, the stellar density and
conditions of the gas and dust have to be extreme not to give rise to the
commonly detected emission features associated with starburst.


title: The design and performance of the Gaia photometric system

abstract:
  The European Gaia astrometry mission is due for launch in 2011. Gaia will
rely on the proven principles of ESA's Hipparcos mission to create an all-sky
survey of about one billion stars throughout our Galaxy and beyond, by
observing all objects down to 20th magnitude. Through its massive measurement
of stellar distances, motions and multi-colour photometry it will provide
fundamental data necessary for unravelling the structure, formation and
evolution of the Galaxy. This paper presents the design and performance of the
broad- and medium-band set of photometric filters adopted as the baseline for
Gaia. The nineteen selected passbands (extending from the ultraviolet to the
far-red), the criteria, and the methodology on which this choice has been based
are discussed in detail. We analyse the photometric capabilities for
characterizing the luminosity, temperature, gravity and chemical composition of
stars. We also discuss the automatic determination of these physical parameters
for the large number of observations involved, for objects located throughout
the entire Hertzsprung-Russell diagram. Finally, the capability of the
photometric system to deal with the main Gaia science case is outlined.


title: The Carnegie Supernova Project: The Low-Redshift Survey

abstract:
  Supernovae are essential to understanding the chemical evolution of the
Universe. Type Ia supernovae also provide the most powerful observational tool
currently available for studying the expansion history of the Universe and the
nature of dark energy. Our basic knowledge of supernovae comes from the study
of their photometric and spectroscopic properties. However, the presently
available data sets of optical and near-infrared light curves of supernovae are
rather small and/or heterogeneous, and employ photometric systems that are
poorly characterized. Similarly, there are relatively few supernovae whose
spectral evolution has been well sampled, both in wavelength and phase, with
precise spectrophotometric observations. The low-redshift portion of the
Carnegie Supernova Project (CSP) seeks to remedy this situation by providing
photometry and spectrophotometry of a large sample of supernovae taken on
telescope/filter/detector systems that are well understood and well
characterized. During a five-year program which began in September 2004, we
expect to obtain high-precision u'g'r'i'BVYJHKs light curves and optical
spectrophotometry for about 250 supernovae of all types. In this paper we
provide a detailed description of the CSP survey observing and data reduction
methodology. In addition, we present preliminary photometry and spectra
obtained for a few representative supernovae during the first observing
campaign.


title:
A New Fast Parallel Statistical Measurement Technique for Computational
  Cosmology

abstract:
  Higher order cumulants of point processes, such as skew and kurtosis, require
significant computational effort to calculate. The traditional counts-in-cells
method implicitly requires a large amount of computation since, for each
sampling sphere, a count of particles is necessary. Although alternative
methods based on tree algorithms can reduce execution time considerably, such
methods still suffer from shot noise when measuring moments on low amplitude
signals. We present a novel method for calculating higher order moments that is
based upon first top-hat filtering the point process data on to a grid. After
correcting for the smoothing process, we are able to sample this grid using an
interpolation technique to calculate the statistics of interest. The filtering
technique also suppresses noise and allows us to calculate skew and kurtosis
when the point process is highly homogeneous. The algorithm can be implemented
efficiently in a shared memory parallel environment provided a data-local
random sampling technique is used. The local sampling technique allows us to
obtain close to optimal speed-up for the sampling process on the Alphaserver
GS320 NUMA architecture.


title:
R-modes of accreting hyperon stars as persistent sources of
  gravitational waves

abstract:
  The $r$-modes of accreting neutron stars could be a detectable source of
persistent gravitational waves if the bulk viscosity of the stellar matter can
prevent a thermal runaway. This is possible if exotic particles such as
hyperons are present in the core of the star. We compute bulk viscous damping
rates and critical frequencies for $r$-modes of neutron stars containing
hyperons in the framework of relativistic mean field theory. We combine the
results of several previous calculations of the microphysics, include for the
first time the effect of rotation, and explore the effects of various
parameters on the viability of persistent gravitational wave emission. We find
that persistent emission is quite robust, although it is disfavored in stars
below 1.3--1.5 $M_\odot$ depending on the equation of state. In some cases
persistent emission is compatible with temperatures as low as $10^7$ K,
observed in some accreting neutron stars in quiescence.


title:
Selecting damped Lyman-alpha systems through CaII absorption. I: Dust
  depletions and reddening at z~1

abstract:
  We use the average E(B-V) and ZnII column densities of a sample of z~1 CaII
(3935, 3970) absorption line systems selected from the Sloan Digital Sky Survey
(SDSS DR4) to show that on average, with conservative assumptions regarding
metallicities and dust-to-gas ratios, they contain column densities of neutral
hydrogen greater than the damped Lyman-alpha (DLA) limit. We propose that
selection by CaII absorption is an effective way of identifying high column
densities of neutral hydrogen, and thus large samples of DLAs at z<1.3 from the
SDSS. The number density of strong CaII absorbers (with rest-frame equivalent
width W_3935>0.5AA), is ~20-30% that of DLAs, after correcting for the
significant bias against their detection due to obscuration of the background
quasars by dust. On average these absorbers have E(B-V)>0.1mag; the dustiest
absorbers show depletions of refractory elements at a level of the largest
depletions seen in DLAs. For the first time we can measure the dust-to-metals
ratio in a sample of absorption selected galaxies, and find values close to, or
even larger than, those observed locally. All of these properties suggest that
a substantial fraction of the CaII absorbers are more chemically evolved than
typical DLAs. From consideration of the E(B-V) distribution in our sample, and
assuming CaII absorbers represent a subset of DLAs, we calculate that dust
obscuration causes an underestimation in the number density of DLAs by at least
8-12% at these redshifts. Finally, the removal of Broad Absorption Line (BAL)
quasars from the SDSS quasar sample increases the sensitivity of the detection
of reddening by intervening absorbers. To this end, we describe a new,
automated, principal component analysis (PCA) method for identifying BAL
quasars. [abridged]


title:
Observational Constraints on the Ages of Molecular Clouds and the
  Star-Formation Timescale: Ambipolar-Diffusion--Controlled or
  Turbulence-Induced Star Formation?

abstract:
  We revisit the problem of the star formation timescale and the ages of
molecular clouds. The apparent overabundance of star-forming molecular clouds
over clouds without active star formation has been thought to indicate that
molecular clouds are "short-lived" and that star formation is "rapid". We show
that this statistical argument lacks self-consistency and, even within the
rapid star-formation scenario, implies cloud lifetimes of approximately 10 Myr.
We discuss additional observational evidence from external galaxies that
indicate lifetimes of molecular clouds and a timescale of star formation of
approximately 10 Myr . These long cloud lifetimes in conjunction with the rapid
(approximately 1 Myr) decay of supersonic turbulence present severe
difficulties for the scenario of turbulence-controlled star formation. By
contrast, we show that all 31 existing observations of objects for which the
linewidth, the size, and the magnetic field strength have been reliably
measured are in excellent quantitative agreement with the predictions of the
ambipolar-diffusion theory. Within the ambipolar-diffusion-controlled star
formation theory the linewidths may be attributed to large-scale non-radial
cloud oscillations (essentially standing large-amplitude, long-wavelength
Alfven waves), and the predicted relation between the linewidth, the size, and
the magnetic field is a natural consequence of magnetic support of
self-gravitating clouds.


title:
The Sloan-Lens ACS Survey II: stellar populations and internal structure
  of early-type lens galaxies

abstract:
  We derive Fundamental Plane parameters of 15 early-type lens galaxies
identified by the Sloan Lens ACS (SLACS) Survey. The size of the sample allows
us to investigate for the first time the distribution of lens galaxies in the
FP space. After correcting for evolution, we find that lens galaxies occupy a
subset of the local FP. The edge-on projection (approximately M vs M/L) is
indistinguishable from that of normal early-type galaxies. However -- within
the fundamental plane -- the lens galaxies appear to concentrate at the edge of
the region populated by normal early-type galaxies. We show that this is a
result of our selection procedure (approximately velocity dispersion
sigma>240km/s). We conclude that SLACS lenses are a fair sample of high
velocity dispersion early-type galaxies. By comparing the central stellar
velocity dispersion that of the best fit lens model, we find
<f_SIE>=<sigma/sigma_SIE>= =1.01+-0.02 with 0.065 rms scatter. We conclude that
within the Einstein radii the SLACS lenses are very well approximated by
isothermal ellipsoids, requiring a fine tuning of the stellar and dark matter
distribution (bulge-halo ``conspiracy''). Interpreting the offset from the
local FP in terms of evolution of the stellar mass-to-light ratio, we find for
the SLACS lenses d log M/L_B/dz=-0.69+-0.08 (rms 0.11) consistent with the rate
found for field early-type galaxies and with a scenario where most of the stars
were formed at high redshift (>2) with secondary episodes of star formation
providing less than ~10% of the stellar mass below z=1. We discuss star
formation history and structural homogeneity in the context of formation
mechanisms such as collisionless (``dry'') mergers. [Abridged]


title:
Direct Measurements of Gas Bulk Flows in the ICM of the Centaurus
  Cluster with the Chandra Satellite

abstract:
  We present the analysis of the velocity structure of the intracluster gas
near the core of Abell 3526 obtained with two off-center Chandra observations,
specifically designed to eliminate errors due to spatial variations of the
instrumental gain. We detected a significant velocity gradient along the
direction NE-SW direction, roughly perpendicular to the direction of the
incoming sub-group Cen45, in agreement with previous ASCA SIS measurements. The
presence of gas bulk velocities is observed both with and without the inclusion
of the FeK line complex in the spectral fittings. The configuration and
magnitude of the velocity gradient is consistent with near transonic
circulatory motion, either bulk or eddy-like. The velocity difference obtained
using the best calibrated central regions of ACIS-S3 is found to be
(2.4+-1.0)E03 km/s for rectangular regions 2'.4 x 3' roughly diametrically
opposed around the cluster's core. There are also indications of a high
velocity zone towards the Southern region with similar magnitudes. The
detection of velocity gradients is significant at the >99.4% confidence and
simulations show that intrachip gain fluctuations > 1800 km/s are required to
explain the velocity gradient by chance. The measurements suggest that >1% of
the total merger energy can still be bulk kinetic 0.4 Gyr after the merging
event. This is the first direct confirmation of velocity gradients in the
intracluster gas with independent instruments and indicates that strong
departure from hydrostatic equilibrium is possible even for cool clusters that
do not show obvious signs of merging.


title:
Molecular Gas, Kinematics, and OB Star Formation in the Spiral Arms of
  the Southern Milky Way

abstract:
  The rotation curve for the IV galactic quadrant, within the solar circle, is
derived from the Columbia University - U. de Chile CO(J=1-0) survey of
molecular gas. A new sampling, four times denser in longitude than in our
previous analysis, is used to compute kinematical parameters that require
derivatives w/r to galactocentric radius; the angular velocity Omega(R), the
epicyclic frequency kappa(R), and the parameters A(R) and B(R) describing,
respectively, gas shear and vorticity. The face-on surface density of molecular
gas is computed from the CO data in galactocentric radial bins for the
subcentral vicinity, the same spectral region used to derive the rotation
curve, where the two-fold ambiguity in kinematical distances is minimum. The
rate of massive star formation per unit area is derived, for the same radial
bins, from the luminosity of IRAS point-like sources with FIR colors of UC HII
regions detected in the CS(J=2-1) line. Massive star formation occurs
preferentially in three regions of high molecular gas density, coincident with
lines of sight tangent to spiral arms. The molecular gas motion in these arms
resembles that of a solid body, characterized by constant angular velocity and
by low shear and vorticity. The formation of massive stars in the arms follows
the Schmidt law, Sigma_{MSFR} is proportional to [Sigma_{gas}]^n, with an index
of n = 1.2 +- 0.2 Our results suggest that the large scale kinematics, through
shear, regulate global star formation in the Galactic disk.


title: Time Variability in the X-ray Nebula Powered by Pulsar B1509-58

abstract:
  We use new and archival Chandra and ROSAT data to study the time variability
of the X-ray emission from the pulsar wind nebula (PWN) powered by PSR B1509-58
on timescales of one week to twelve years. There is variability in the size,
number, and brightness of compact knots appearing within 20" of the pulsar,
with at least one knot showing a possible outflow velocity of ~0.6c (assuming a
distance to the source of 5.2 kpc). The transient nature of these knots may
indicate that they are produced by turbulence in the flows surrounding the
pulsar. A previously identified prominent jet extending 12 pc to the southeast
of the pulsar increased in brightness by 30% over 9 years; apparent outflow of
material along this jet is observed with a velocity of ~0.5c. However, outflow
alone cannot account for the changes in the jet on such short timescales.
Magnetohydrodynamic sausage or kink instabilities are feasible explanations for
the jet variability with timescale of ~1.3-2 years. An arc structure, located
30"-45" north of the pulsar, shows transverse structural variations and appears
to have moved inward with a velocity of ~0.03c over three years. The overall
structure and brightness of the diffuse PWN exterior to this arc and excluding
the jet has remained the same over the twelve year span. The photon indices of
the diffuse PWN and possibly the jet steepen with increasing radius, likely
indicating synchrotron cooling at X-ray energies.


title: Perspectives on Galactic Dynamics via General Relativity

abstract:
  Responses to questions, comments and criticism of our recent paper "General
Relativity Resolves.." are provided. It is emphasized that our model is
entirely natural to describe the dynamics of an axially symmetric galaxy and
that our solution, albeit idealized, contains the essence of the problem. The
discontinuity of the metric derivative on the symmetry plane is necessarily
interpreted as the effect of the mathematically idealized discontinuity of the
gradient of the density and is shown to be naturally connected to the
distributed volume density via the Gauss divergence theorem. We present
arguments to the effect that for our approximate weak field model, we can
choose the physically satisfactory mass distribution without an accompanying
singular mass surface layer. To support this contention, we modify our solution
slightly by removing the discontinuity with a region of continuous density
gradient overlapping the $z=0$ plane. The alternative of invoking a surface
layer leads to the presence of a negative mass surface layer approaching the
numerical value of the positive mass continuous region. This is in
contradiction with the assumed stationarity of the model. We find that a test
particle behaves normally as it approaches the $z=0$ plane, the acceleration
being towards the direction of this plane. This is in contradiction to the
negative mass layer hypothesis as negative mass would repel the test particle.
Thus, further support is added to the integrity of our original model.


title:
3D Numerical Experimentation on the Core Helium Flash of low-mass Red
  Giants

abstract:
  We model the core helium flash in a low-mass red giant using Djehuty, a fully
three-dimensional (3D) code. The 3D structures were generated from converged
models obtained during the 1D evolutionary calculation of a 1$\Msun$ star.
Independently of which starting point we adopted, we found that after some
transient relaxation the 3D model settled down with a briskly convecting
He-burning shell that was not very different from what the 1D model predicted.


title:
The First Spatially Resolved Mid-IR Spectra of NGC 1068 Obtained at
  Diffraction-limited Resolution with LWS at Keck I Telescope

abstract:
  We present spatially resolved mid-IR spectra of NGC 1068 with a
diffraction-limited resolution of 0.25\arcsec using the Long Wavelength
Spectrometer (LWS) at the Keck I telescope. The mid-infrared image of NGC 1068
is extended along the N-S direction. Previous imaging studies have shown the
extended regions are located inside the ionization cones indicating that the
mid-infrared emission arises perhaps from the inner regions of the narrow-line
clouds instead of the proposed dusty torus itself. The spatially resolved
mid-IR spectra were obtained at two different slit position angles, +8.0 and
-13.0 degrees across the elongated regions in the mid-IR. From these spectra,
we found only weak silicate absorption toward the northern extended regions but
strong in the nucleus and the southern extended regions. This is consistent
with a model of a slightly inclined cold obscuring torus which covers much of
the southern regions but is behind the northern extension. While a detailed
analysis of the spectra requires a radiative transfer model, the lack of
silicate emission from the northern extended regions prompts us to consider a
dual dust population model as one of the possible explanations in which a
different dust population exists in the ionization cones compared to that in
the dusty torus. Dust inside the ionization cones may lack small silicate
grains giving rise to only a featureless continuum in the northern extended
regions while dust in the dusty torus has plenty of small silicate grains to
produce the strong silicate absorption lines towards the nucleus and the
southern extended regions.


title: Template Rotation Curves for Disk Galaxies

abstract:
  A homogeneous sample of ~2200 low redshift disk galaxies with both high
sensitivity long-slit optical spectroscopy and detailed I-band photometry is
used to construct average, or template, rotation curves in separate luminosity
classes, spanning 6 magnitudes in I-band luminosity. The template rotation
curves are expressed as functions both of exponential disk scale lengths r_d
and of optical radii Ropt, and extend out to 4.5-6.5 r_d, depending on the
luminosity bin. The two parameterizations yield slightly different results
beyond Ropt because galaxies whose Halpha emission can be traced to larger
extents in the disks are typically of higher optical surface brightness and are
characterized by larger values of Ropt/r_d. By either parameterization, these
template rotation curves show no convincing evidence of velocity decline within
the spatial scales over which they are sampled, even in the case of the most
luminous systems. In contrast to some previous expectations, the fastest
rotators (most luminous galaxies) have, on average, rotation curves that are
flat or mildly rising beyond the optical radius, implying that the dark matter
halo makes an important contribution to the kinematics also in these systems.
The template rotation curves and the derived functional fits provide
quantitative constraints for studies of the structure and evolution of disk
galaxies, which aim at reproducing the internal kinematics properties of disks
at the present cosmological epoch.


title:
Afterglow spectrum of a gamma-ray burst with the highest known redshift
  z=6.295

abstract:
  Gamma-ray bursts (GRBs) and their afterglows have been proposed as an
excellent probe to study the evolution of cosmic star formation, the
reionization of the intergalactic medium, and the metal enrichment history of
the universe, since the prompt gamma-ray emission of GRBs should be detectable
out to distances z>10. Hitherto, the highest measured redshift for a GRB has
been z=4.50. Here we report the optical spectrum of the afterglow of GRB 050904
obtained 3.4 days after the burst. The spectrum shows a clear continuum at the
long wavelength end of the spectrum with a sharp cutoff at around 9000 A due to
Ly alpha absorption at a redshift of 6.3 with a damping wing. Little flux is
present in the waveband shortward of the Ly alpha break. A system of absorption
lines of heavy elements at redshift z=6.295 +- 0.002 were also detected,
yielding a precise measurement of the largest known redshift of a GRB. Analysis
of the Si II fine structure lines suggest a dense metal-enriched environment
around the GRB progenitor, providing unique information on the properties of
the gas in a galaxy when the universe was younger than one billion years.


title: Atmospheric Biomarkers and their Evolution over Geological Timescales

abstract:
  The search for life on extrasolar planets is based on the assumption that one
can screen extrasolar planets for habitability spectroscopically. The first
space born instruments able to detect as well as characterize extrasolar
planets, Darwin and terrestrial planet finder (TPF-I and TPF-C) are scheduled
to launch before the end of the next decade. The composition of the planetary
surface, atmosphere, and its temperature-pressure profile influence a
detectable spectroscopic signal considerably. For future space-based missions
it will be crucial to know this influence to interpret the observed signals and
detect signatures of life in remotely observed atmospheres. We give an overview
of biomarkers in the visible and IR range, corresponding to the TPF-C and
TPF-I/DARWIN concepts, respectively. We also give an overview of the evolution
of biomarkers over time and its implication for the search for life on
extrasolar Earth-like planets. We show that atmospheric features on Earth can
provide clues of biological activities for at least 2 billion years.


title:
RR Lyrae stars in the inner Large Magellanic Cloud: Halo-like location
  with a disk-like distribution

abstract:
  The distribution of RR Lyrae stars (RRLS) in the inner Large Magellanic Cloud
(LMC), and the structure of the halo of the LMC delineated by these stars are
studied here. RRLS identified by the OGLE II survey are used to estimate their
number density distribution in the bar region of the LMC. To find their
location, I estimated the scale-height of their distribution in the LMC using
extinction corrected average magnitudes of ab type stars. The density is found
to vary differently along and across the bar of the LMC, and the difference is
found to be statistically significant. The density distribution is found to be
elongated like the LMC bar and the position angle (PA) of the elongation is
estimated to be 112.$^o$5 $\pm$ 15.$^o$3. This value of PA is found to be same
as the PA$_{maj}$ of the bar, within the errors, estimated using red clump
stars and giants. The ellipticity of their density distribution is estimated to
be $\sim$ 0.5, very similar to the ellipticity of the bar, estimated from
giants. The above results show that majority of the population of RRLS in the
central region of the LMC are found to have the signature of the bar. This
result could mean that most of these stars are located in the disk, considering
the bar as a disk feature. On the other hand, their scale-height was found to
be 3.0$\pm 0.9$ kpc. This indicates that RRLS are located in the halo and not
in the disk. Thus these stars in the inner LMC have halo-like location and a
disk-like density distribution. I discuss some possible formation scenarios for
this puzzling combination.


title:
Probing for evolutionary links between local ULIRGs and QSOs from NIR
  spectroscopy

abstract:
  We present a study of the dynamical evolution of Ultraluminous Infrared
Galaxies (ULIRGs), merging galaxies of infrared luminosity >10^12 L_sun. During
our Very Large Telescope large program, we have obtained ISAAC near-infrared,
high-resolution spectra of 54 ULIRGs (at several merger phases) and 12 local
Palomar-Green QSOs to investigate whether ULIRGs go through a QSO phase during
their evolution. One possible evolutionary scenario is that after nuclear
coalescence, the black hole radiates close to Eddington to produce QSO
luminosities. The mean stellar velocity dispersion that we measure from our
spectra is similar (~160 km/s) for 30 post-coalescence ULIRGs and 7 IR-bright
QSOs. The black holes in both populations have masses of order 10^7-10^8 M_sun
(calculated from the relation to the host dispersion) and accrete at rates >0.5
Eddington. Placing ULIRGs and IR-bright QSOs on the fundamental plane of
early-type galaxies shows that they are located on a similar region (that of
moderate-mass ellipticals), in contrast to giant ellipticals and radio-loud
QSOs. While this preliminary comparison of the ULIRG and QSO host kinematical
properties indicates that (some) ULIRGs may undergo a QSO phase in their
evolutionary history before they settle down as ellipticals, further data on
non-IR excess QSOs are necessary to test this scenario.


title: Axisymmetric and triaxial MOND density-potential pairs

abstract:
  We present a simple method, based on the deformation of spherically symmetric
potentials, to construct explicit axisymmetric and triaxial MOND
density-potential pairs. General guidelines to the choice of suitable
deformations, so that the resulting density distribution is nowhere negative,
are presented. This flexible method offers for the first time the possibility
to study the MOND gravitational field for sufficiently general and realistic
density distributions without resorting to sophisticated numerical codes. The
technique is illustrated by constructing the MOND density-potential pair for a
triaxial galaxy model that, in the absence of deformation, reduces to the
Hernquist sphere. Such analytical solutions are also relevant to test and
validate numerical codes. Here we present a new numerical potential solver
designed to solve the MOND field equation for arbitrary density distributions:
the code is tested with excellent results against the analytic MOND triaxial
Hernquist model and the MOND razor-thin Kuzmin disk, and a simple application
is finally presented.


title: Star formation in hosts of young radio galaxies

abstract:
  We present near ultraviolet imaging with the Hubble Space Telescope Advanced
Camera for Surveys, targeting young radio galaxies (Gigahertz Peaked Spectrum
and Compact Steep Spectrum sources), in search of star formation regions in
their hosts. We find near UV light which could be the product of recent star
formation in eight of the nine observed sources. However, observations at other
wavelengths and colors are needed to definitively establish the nature of the
observed UV light. In the CSS sources 1443+77 and 1814--637 the near UV light
is aligned with and is co-spatial with the radio source, and we suggest that in
these sources the UV light is produced by star formation triggered and/or
enhanced by the radio source.


title: The Cosmological Constant in Brane Cosmology

abstract:
  This paper has been withdrawn by the second author since he is suspected by
the first author (the corresponding author) of commiting plagiarism.


title:
XMM-Newton observation of the Soft Gamma Ray Repeater SGR 1627-41 in a
  low luminosity state

abstract:
  The sky region containing the soft gamma-ray repeater SGR 1627-41 has been
observed three times with XMM-Newton in February and September 2004. SGR
1627-41 has been detected with an absorbed flux of ~9x10^{-14} erg cm^{-2}
s^{-1} (2-10 keV). For a distance of 11 kpc, this corresponds to a luminosity
of ~3x10^{33} erg s^{-1}, the smallest ever observed for a Soft Gamma Repeater
and possibly related to the long period of inactivity of this source. The
observed flux is smaller than that seen with Chandra in 2001-2003, suggesting
that the source was still fading and had not yet reached a steady quiescent
level. The spectrum is equally well fit by a steep power law (photon index
\~3.2) or by a blackbody with temperature kT~0.8 keV. We also report on the
INTEGRAL transient IGR J16358-4726 that lies at ~10' from SGR 1627-41. It was
detected only in September 2004 with a luminosity of ~4x10^{33} erg s^{-1} (for
d=7 kpc), while in February 2004 it was at least a factor 10 fainter.


title:
GMRT observations of the field of INTEGRAL X-ray sources- II (newly
  discovered hard X-ray sources)

abstract:
  We have conducted low-frequency radio observations with the Giant Metrewave
Radio Telescope (GMRT) of 40 new hard X-ray sources discovered by the INTEGRAL
satellite. This survey was conducted in order, to study radio emissions from
these sources, to provide precise position and to identify new microquasar
candidates. From our observations we find that 24 of the X-ray sources have
radio candidates within the INTEGRAL error circle. Based on the radio
morphology, variability and information available from different wavelengths,
we categorize them as seventeen Galactic sources (4 unresolved, 7 extended, 6
extended sources in diffuse region) and seven extragalactic sources (2
unresolved, 5 extended). Detailed account for seventeen of these sources was
presented in earlier paper. Based on the radio data for the remaining sources
at 0.61 GHz, and the available information from NVSS, DSS, 2MASS and NED, we
have identified possible radio counterparts for the hard X-ray sources. The
three unresolved sources, viz IGR J17303$-$0601, IGR J17464$-$3213, and IGR
J18406$-$0539 are discussed in detail. These sources have been identified as
X-ray binaries with compact central engine and variable in X-ray and in the
radio, and are most likely microquasar candidates. The remaining fourteen
sources have extended radio morphology and are either diffuse Galactic regions
or extragalactic in origin.


title: Low Frequency Radio Observations of GRS1915+105 with GMRT

abstract:
  We present the first detailed low frequency radio measurements of the
galactic microquasar GRS1915+105 with GMRT. Simultaneous observations were
carried out at 610 and 244 MHz. Our data does not show any signature of
spectral turn over even at low radio frequency of 244 MHz. We propose that
while the radio emission at high radio frequencies could predominantly come
from compact jets, the emission at lower frequency originates in the lobes at
the end of the jet which acts like a reservoir of low energy electrons.


title: Triaxial Orbit-based Models Of Elliptical Galaxies

abstract:
  We have developed an orbit-based method for constructing triaxial models of
elliptical galaxies, which fit their observed surface brightness and
kinematics. We have tested the method against analytical models with general
distribution functions. Here, we present models that fit integral-field SAURON
observations of NGC3379 and NGC4365.


title: Imaging and integral field spectroscopy of shocked H2 around G25.65+1.05

abstract:
  Near-infrared imaging of the emission from molecular hydrogen is a powerful
method for discovering outflows in star-forming regions. We present new
near-infrared images, long slit and integral field spectroscopy of the
ultra-compact HII region G25.65+1.05. These new observations reveal shocked H2
emission associated with a bipolar outflow from a young high mass star at the
centre of the source. The physical parameters of the outflow are discussed and
compared with outflows from lower mass stars.


title:
Revealing the mid-infrared emission structure of IRAS 16594-4656 and
  IRAS 07027-7934

abstract:
  TIMMI2 diffraction-limited mid-infrared images of a multipolar
proto-planetary nebula IRAS 16594-4656 and a young [WC] elliptical planetary
nebula IRAS 07027-7934 are presented. Their dust shells are for the first time
resolved (only marginally in the case of IRAS 07027-7934) by applying the
Lucy-Richardson deconvolution algorithm to the data, taken under exceptionally
good seeing conditions (<0.5"). IRAS 16594-4656 exhibits a two-peaked
morphology at 8.6, 11.5 and 11.7 microns which is mainly attributed to emission
from PAHs. Our observations suggest that the central star is surrounded by a
toroidal structure observed edge-on with a radius of 0.4" (~640 AU at an
assumed distance of 1.6 kpc) with its polar axis at P.A.~80 degrees, coincident
with the orientation defined by only one of the bipolar outflows identified in
the HST optical images. We suggest that the material expelled from the central
source is currently being collimated in this direction and that the multiple
outflow formation has not been coeval. IRAS 07027-7934 shows a bright,
marginally extended emission (FWHM=0.3") in the mid-infrared with a slightly
elongated shape along the N-S direction, consistent with the morphology
detected by HST in the near-infrared. The mid-infrared emission is interpreted
as the result of the combined contribution of small, highly ionized PAHs and
relatively hot dust continuum. We propose that IRAS 07027-7934 may have
recently experienced a thermal pulse (likely at the end of the AGB) which has
produced a radical change in the chemistry of its central star.


title:
Explosions of O-Ne-Mg Cores, the Crab Supernova, and Subluminous Type
  II-P Supernovae

abstract:
  We present results of simulations of stellar collapse and explosions in
spherical symmetry for progenitor stars in the 8-10 solar mass range with an
O-Ne-Mg core. The simulations were continued until nearly one second after core
bounce and were performed with the Prometheus/Vertex code with a variable
Eddington factor solver for the neutrino transport, including a
state-of-the-art treatment of neutrino-matter interactions. Particular effort
was made to implement nuclear burning and electron capture rates with
sufficient accuracy to ensure a smooth continuation, without transients, from
the progenitor evolution to core collapse. Using two different nuclear
equations of state (EoSs), a soft version of the Lattimer & Swesty EoS and the
significantly stiffer Wolff & Hillebrandt EoS, we found no prompt explosions,
but instead delayed explosions, powered by neutrino heating and the
neutrino-driven baryonic wind which sets in about 200 ms after bounce. The
models eject little nickel (< 0.015 solar masses), explode with an energy of
about or slightly more than 10**50 erg, and leave behind neutron stars (NSs)
with a baryonic mass near 1.36 solar masses. Different from previous models of
such explosions, the ejecta during the first second have a proton-to-baryon
ratio of Ye > 0.46, which suggests a chemical composition that is not in
conflict with galactic abundances. No low-entropy matter with Ye << 0.5 is
ejected. This excludes such explosions as sites of a low-entropy r-process. The
low explosion energy and nucleosynthetic implications are compatible with the
observed properties of the Crab supernova, and the small nickel mass supports
the possibility that our models explain some subluminous Type II-P supernovae.