title: Multi-colour Imaging of Ultra-compact Objects in the Fornax Cluster

abstract:
  Ultra-compact dwarf galaxies (UCDs) are a new type of galaxy we have
discovered in the central region of the Fornax and Virgo clusters. Unresolved
in ground-based imaging, UCDs have spectra typical of old stellar systems.
Ninety-two have been found in Fornax, making them the most numerous galaxy type
in the cluster. Here we present multicolour (u'g'r'i'z') imaging of the central
region of the Fornax Cluster using the CTIO 4m Mosaic Telescope. The
colour-magnitude relation for bright UCDs is qualitatively consistent with UCDs
being the stripped nuclei of dE,Ns. However at faint magnitudes, GCs and UCDs
cannot be distinguished by colour alone. High resolution spectroscopy to
measure their internal velocity dispersions and metallicities, is needed to
distinguish between GCs and UCDs.


title:
GRB 060121: Implications of a Short/Intermediate Duration Gamma-Ray
  Burst at High Redshift

abstract:
  Since the discovery of the first short-hard gamma-ray burst afterglows in
2005, the handful of observed events have been found to be embedded in nearby
(z < 1), bright underlying galaxies. We present multiwavelength observations of
the short-duration burst GRB 060121, which is the first observed to clearly
outshine its host galaxy (by a factor >10^2). A photometric redshift for this
event places the progenitor at a most probable redshift of z = 4.6, with a less
probable scenario of z = 1.7. In either case, GRB 060121 could be the
farthermost short-duration GRB detected to date and implies an
isotropic-equivalent energy release in gamma-rays comparable to that seen in
long-duration bursts. We discuss the implications of the released energy on the
nature of the progenitor. These results suggest that GRB 060121 may belong to a
family of energetic short-duration events, lying at z > 1 and whose optical
afterglows would outshine their host galaxies, unlike the first short-duration
GRBs observed in 2005. The possibility of GRB 060121 being an intermediate
duration burst is also discussed.


title: The Initial Mass Function of Stars

abstract:
  Observations and theory of the IMF are briefly reviewed. Slight variations
have been observed, although they are difficult to prove unambiguously. Most
detailed theoretical models reproduce the IMF, but because they use different
assumptions and conditions, there is no real convergence of explanations yet.


title:
Discovery of new Milky Way star cluster candidates in the 2MASS point
  source catalog. V. Follow-up observations of the young stellar cluster
  candidates RCW87, [BDSB2003]164 and [DBSB2003]172

abstract:
  Massive clusters are more often found in actively star forming galaxies than
in quiescent ones, similar to the Milky Way. We have carried out an extensive
survey of obscured Milky Way clusters to determine whether our Galaxy is still
forming such objects. Near-infrared spectral classification of some probable
cluster members was used to derive the distances to the cluster candidates.
Isochrone analysis of deep near-infrared color-magnitude diagrams allowed us to
obtain age and mass estimates. We report the physical parameters of three
cluster candidates:
  RCW87 is approx. 25 Myr old, located at a distance of D=7.6 Kpc in the
general direction of the Galactic center. Adding the mass of the suspected
cluster members we obtain an estimated total cluster mass of approx. 10300
solar masses. The mid-infrared photometry indicates that some next-generation
star formation is on-going in the associated HII region, probably triggered by
supernovae or stellar wind from the older stars in RCW87.
  The brightest member of [BDSB2003]164 is an O5V type star, based on our
spectroscopy. This limits the cluster age to less than a few million years. The
estimated total mass is approx. 1760 solar masses and the distance is D=3.2
Kpc.
  [DBSB2003]172 lacks central concentration and most likely this is not a
cluster but an extended star forming region.
  The high mass of RCW87 -- if confirmed -- puts this object in line with
Arches and Quintuplet, among the most young massive clusters in the Galaxy.
Further study is necessary to confirm this important result.


title: Hierarchical Formation of Galactic Clusters

abstract:
  Young stellar groupings and clusters have hierarchical patterns ranging from
flocculent spiral arms and star complexes on the largest scale to OB
associations, OB subgroups, small loose groups, clusters and cluster subclumps
on the smallest scales. There is no obvious transition in morphology at the
cluster boundary, suggesting that clusters are only the inner parts of the
hierarchy where stars have had enough time to mix. The power-law cluster mass
function follows from this hierarchical structure: n(M_cl) M_cl^-b for b~2.
This value of b is independently required by the observation that the summed
IMFs from many clusters in a galaxy equals approximately the IMF of each
cluster.


title:
On the Similarity between Cluster and Galactic Stellar Initial Mass
  Functions

abstract:
  The stellar initial mass functions (IMFs) for the Galactic bulge, the Milky
Way, other galaxies, clusters of galaxies, and the integrated stars in the
Universe are composites from countless individual IMFs in star clusters and
associations where stars form. These galaxy-scale IMFs, reviewed in detail
here, are not steeper than the cluster IMFs except in rare cases. This is true
even though low mass clusters generally outnumber high mass clusters and the
average maximum stellar mass in a cluster scales with the cluster mass. The
implication is that the mass distribution function for clusters and
associations is a power law with a slope of -2 or shallower. Steeper slopes,
even by a few tenths, upset the observed equality between large and small scale
IMFs. Such a cluster function is expected from the hierarchical nature of star
formation, which also provides independent evidence for the IMF equality when
it is applied on sub-cluster scales. We explain these results with analytical
expressions and Monte Carlo simulations. Star clusters appear to be the relaxed
inner parts of a widespread hierarchy of star formation and cloud structure.
They are defined by their own dynamics rather than pre-existing cloud
boundaries.


title: The Theory of Bodily Tides. The Models and the Physics

abstract:
  Description of tides is based on the form of dependence of the geometric lag
on the tidal frequency. Some authors assume the lag angle to be constant,
others set it to be linear in the frequency. The actual dependence of the lag
on the frequency is complicated and is determined by the planet's rheology. A
particular form of this dependence will fix the form of the frequency
dependence of the tidal quality factor Q. Since at present we know the
frequency-dependence of the quality factor, we can reverse our line of
reasoning and obtain the appropriate frequency-dependence of the lag.
Employment of a realistic frequency-dependence for Q renders considerable
changes in timescales defined by tidal dynamics.


title:
Recurrence of the blue wing enhancements in the high ionization lines of
  SDSS 1004+4112 A

abstract:
  We present integral field spectroscopic observations of the quadruple-lensed
QSO SDSS 1004+4112 taken with the fiber system INTEGRAL at the William Herschel
Telescope on 2004 January 19. In May 2003 a blueward enhancement in the high
ionization lines of SDSS 1004+4112A was detected and then faded. Our
observations are the first to note a second event of similar characteristics
less than one year after. Although initially attributed to microlensing, the
resemblance among the spectra of both events and the absence of
microlensing-induced changes in the continuum of component A are puzzling. The
lack of a convincing explanation under the microlensing or intrinsic
variability hypotheses makes the observed enhancements particularly relevant,
calling for close monitoring of this object.


title: Hierarchical Star Formation in the Spiral Galaxy NGC 628

abstract:
  The distributions of size and luminosity for star-forming regions in the
nearby spiral galaxy NGC 628 are studied over a wide range of scales using
progressively blurred versions of an image from the Hubble Space Telescope
Advanced Camera for Surveys. Four optical filters are considered for the
central region, including Halpha. Two filters are used for an outer region. The
features in each blurred image are counted and measured using SExtractor. The
cumulative size distribution is found to be a power law in all passbands with a
slope of about -1.5 over 1.8 orders of magnitudes. The luminosity distribution
is approximately a power law too, with a slope of about -1 for logarithmic
intervals of luminosity. The results suggest a scale-free nature for stellar
aggregates in a galaxy disk. Fractal models of thin disks reproduce the
projected size distribution and suggest a projected mass distribution slope of
about -0.5 for these extended regions. This mass slope converts to the observed
luminosity slope if we account for luminosity evolution and longer lifetimes in
larger regions.


title:
IRAC and MIPS Observations of the Interacting Galaxies IC 2163 and NGC
  2207: Clumpy Emission

abstract:
  IC 2163 and NGC 2207 are interacting galaxies that have been well studied at
optical and radio wavelengths and simulated in numerical models to reproduce
the observed kinematics and morphological features. Spitzer IRAC and MIPS
observations reported here show over 200 bright clumps from young star
complexes. The brightest IR clump is a morphologically peculiar region of star
formation in the western arm of NGC 2207. This clump, which dominates the
Halpha and radio continuum emission from both galaxies, accounts for ~12% of
the total 24mu m flux. Nearly half of the clumps are regularly spaced along
some filamentary structure, whether in the starburst oval of IC 2163 or in the
thin spiral arms of NGC 2207. This regularity appears to influence the clump
luminosity function, making it peaked at a value nearly a factor of 10 above
the completeness limit, particularly in the starburst oval. This is unlike the
optical clusters inside the clumps, which have a luminosity function consistent
with the usual power law form. The giant IR clumps presumably formed by
gravitational instabilities in the compressed gas of the oval and the spiral
arms, whereas the individual clusters formed by more chaotic processes, such as
turbulence compression, inside these larger-scale structures.


title: Host galaxies and environments of compact extragalactic radio sources

abstract:
  The main goal of this thesis is to study the interrelation of powerful radio
sources with their hosts. The objects of study are GPS and CSS sources. Due to
their small size, GPS/CSS sources are excellent probes of this relation.
Furthermore, their young age allows us to compare them to the larger, old radio
sources and establish a time-line evolution of this relation.
  This thesis combines imaging and spectroscopy of GPS/CSS sources at different
wavelengths, and all our studies lead to the same conclusion: the presence and
expansion of powerful radio sources clearly affect the properties and evolution
of their hosts. All chapters of the thesis find evidence of strong interaction
between the host and the radio source. Furthermore, the radio source and host
can significantly affect each others evolution. However, this influence takes
place in different ways. The influence that the host has on the radio source is
somehow indirect. However it can completely change its destiny: depending of
the contents, distribution and density of the gas, the radio source will die
early, expand and grow into the large FR sources, or remain confined inside its
host. In contrast, the influence of the radio source on its host seems to be
more direct and takes place during its expansion through the host: the radio
source will affect the kinematics and ionization of the emission line gas, and
may change the star formation history of the host.


title: Escape fraction of ionizing photons from galaxies at z=0--6

abstract:
  The escape fraction of ionizing photons from galaxies is a crucial quantity
controlling the cosmic ionizing background radiation and the reionization.
Various estimates of this parameter can be obtained in the redshift range,
z=0--6, either from direct observations or from the observed ionizing
background intensities. We compare them homogeneously in terms of the observed
flux density ratio of ionizing ($\sim900$ \AA rest-frame) to non-ionizing
ultraviolet ($\sim1500$ \AA rest-frame) corrected for the intergalactic
absorption. The escape fraction is found to increase by an order of magnitude,
from a value less than 0.01 at $z\la1$ to about 0.1 at $z\ga4$.


title: Mapping the ionizing sources with CMB polarization measurements

abstract:
  We show that the delay of structure formation from WMAP3 can not fully
account for the reduction of electron optical depth from WMAP1 to WMAP3 when
the radiative transfer effects and feedback mechanisms are took into account in
computing the reionization history of the Universe. As the ultimate limit in
constraining the reionizatin history of the Universe with Planck will be placed
by the our understanding of systematic effects and foregrounds removal, we
discuss also these aspects.


title: Nonlinear Development of Thermal Instability without External Forcing

abstract:
  Supersonic turbulent motions are the remarkable properties of interstellar
medium. Previous numerical simulations have demonstrated that the thermal
instability in a shock-compressed layer produces the supersonic turbulent
motion that does not decay. In this paper we focus on two- and
three-dimensional numerical simulations of the non-linear development of simple
thermal instability incorporating physical viscosity but without any external
forcing, in order to isolate the effects of various processes responsible for
the long-lasting turbulent motion. As the initial condition for our
simulations, we set up spatially uniform gas with thermally unstable
temperature in a box with periodic boundaries. After the linear growth stage of
the thermal instability, two-phase medium forms where cold clumps are embedded
in warm medium, and turbulent fluid flow clearly visible as translational
motions of the cold clumps does not decay in a viscous dissipation timescale.
The amplitude of the turbulent velocity increases when we reduce the Prandtl
number that is the non-dimensional ratio of kinetic viscosity to thermal
conduction: the saturation amplitude does not change when we increase the
viscosity and thermal conduction coefficients simultaneously in order to keep
the Prandtl number. This shows that the thermal conduction plays an important
role in maintaining turbulent motions against viscous dissipation. The
amplitude also increases when we increase the ratio of the computational domain
length $L$ to the cooling length $\lambda_{\rm c}$ that is defined by the
product of the cooling time and the sound speed, as long as $L \la 100
\lambda_{\rm c}$.


title:
New Chandra observations of the jet in 3C273. I. Softer X-ray than radio
  spectra and the X-ray emission mechanism

abstract:
  The jet in 3C273 is a high-power quasar jet with radio, optical and X-ray
emission whose size and brightness allow a detailed study of the emission
processes acting in it. We present deep Chandra observations of this jet and
analyse the spectral properties of the jet emission from radio through X-rays.
We find that the X-ray spectra are significantly softer than the radio spectra
in all regions of the bright part of the jet except for the first bright "knot
A", ruling out a model in which the X-ray emission from the entire jet arises
from beamed inverse-Compton scattering of cosmic microwave background photons
in a single-zone jet flow. Within two-zone jet models, we find that a
synchrotron origin for the jet's X-rays requires fewer additional assumptions
than an inverse-Compton model, especially if velocity shear leads to efficient
particle acceleration in jet flows.


title: Shedding New Light on the 3C 273 Jet with the Spitzer Space Telescope

abstract:
  We have performed infrared imaging of the jet of the quasar 3C 273 at
wavelengths 3.6 and 5.8 microns with the Infrared Array Camera (IRAC) on the
Spitzer Space Telescope. When combined with the radio, optical and X-ray
measurements, the IRAC photometry clearly shows that the optical emission is
dominated by the high-energy component of the jet, not by the radio synchrotron
component, as had been assumed to date. The high-energy component may be due to
a second synchrotron component or to IC scattering of ambient photons. In the
former case, we argue that the acceleration of protons exceeding 10^16 eV or
possibly even to 10^19 eV would be taking place in the jet. In contrast, the IC
model, into which highly relativistic Doppler beaming has to be incorporated,
requires very low-energy electrons (~ 1 MeV). The present polarization data in
the radio and optical would favor the former interpretation in the case of the
3C 273 jet. Sensitive and detailed measurements of optical polarization are
important to establish the radiation mechanism responsible for the high-energy
emission. The present study offers new clues as to the controversial origin of
the X-ray emission seen in many quasar jets.


title: The History of Galaxy Formation in Groups: An Observational Perspective

abstract:
  We present a pedagogical review on the formation and evolution of galaxies in
groups, utilizing observational information from the Local Group to galaxies at
z~6. The majority of galaxies in the nearby universe are found in groups, and
galaxies at all redshifts up to z~6 tend to cluster on the scale of nearby
groups (~1 Mpc). This suggests that the group environment may play a role in
the formation of most galaxies. The Local Group, and other nearby groups,
display a diversity in star formation and morphological properties that puts
limits on how, and when, galaxies in groups formed. Effects that depend on an
intragroup medium, such as ram-pressure and strangulation, are likely not major
mechanisms driving group galaxy evolution. Simple dynamical friction arguments
however show that galaxy mergers should be common, and a dominant process for
driving evolution. While mergers between L_* galaxies are observed to be rare
at z < 1, they are much more common at earlier times. This is due to the
increased density of the universe, and to the fact that high mass galaxies are
highly clustered on the scale of groups. We furthermore discus why the local
number density environment of galaxies strongly correlates with galaxy
properties, and why the group environment may be the preferred method for
establishing the relationship between properties of galaxies and their local
density.


title: Dark Energy: Beyond General Relativity?

abstract: 6 pages; Subm. to AIP Conf. Proceedings


title: Wind-Blown Bubbles around Evolved Stars

abstract:
  Most stars will experience episodes of substantial mass loss at some point in
their lives. For very massive stars, mass loss dominates their evolution,
although the mass loss rates are not known exactly, particularly once the star
has left the main sequence. Direct observations of the stellar winds of massive
stars can give information on the current mass-loss rates, while studies of the
ring nebulae and HI shells that surround many Wolf-Rayet (WR) and luminous blue
variable (LBV) stars provide information on the previous mass-loss history. The
evolution of the most massive stars, (M > 25 solar masses), essentially follows
the sequence O star to LBV or red supergiant (RSG) to WR star to supernova. For
stars of mass less than 25 solar masses there is no final WR stage. During the
main sequence and WR stages, the mass loss takes the form of highly supersonic
stellar winds, which blow bubbles in the interstellar and circumstellar medium.
In this way, the mechanical luminosity of the stellar wind is converted into
kinetic energy of the swept-up ambient material, which is important for the
dynamics of the interstellar medium. In this review article, analytic and
numerical models are used to describe the hydrodynamics and energetics of
wind-blown bubbles. A brief review of observations of bubbles is given, and the
degree to which theory is supported by observations is discussed.


title: On the Rayleigh-Taylor Instability of Radio Bubbles in Galaxy Clusters

abstract:
  We consider the Rayleigh-Taylor instability in the early evolution of the
rarefied radio bubbles (cavities) observed in many cooling flow clusters of
galaxies. The top of a bubble becomes prone to the Rayleigh-Taylor instability
as the bubble rises through the intra-cluster medium (ICM). We show that while
the jet is powering the inflation, the deceleration of the bubble-ICM interface
is able to reverse the Rayleigh-Taylor instability criterion. In addition, the
inflation introduces a drag effect which increases substantially the
instability growth time. The combined action of these two effects considerably
delays the onset of the instability. Later on, when the magnitude of the
deceleration drops or the jet fades, the Rayleigh-Taylor and the
Kelvin-Helmholtz instabilities set in and eventually disrupt the bubble. We
conclude that the initial deceleration and drag, albeit unable to prevent the
disruption of a bubble, may significantly lengthen its lifetime, removing the
need to invoke stabilising magnetic fields.


title: Perspectives of High Energy Neutrino Astronomy

abstract:
  This work discusses the perspectives to observe fluxes of high energy
astrophysical neutrinos with the planned km3 telescopes. On the basis of the
observations of GeV and TeV gamma-rays, and of ultra high energy cosmic rays,
it is possible to construct well motivated predictions that indicate that the
discovery of such fluxes is probable. However the range of these predictions is
broad, and the very important opening of the ``neutrino window'' on the high
energy universe is not guaranteed with the current design of the detectors. The
problem of enlarging the detector acceptance using the same (water/ice
Cherenkov) or alternative (acoustic/radio) techniques is therefore of central
importance.


title:
Weighing the Universe with Photometric Redshift Surveys and the Impact
  on Dark Energy Forecasts

abstract:
  With a wariness of Occam's razor awakened by the discovery of cosmic
acceleration, we abandon the usual assumption of zero mean curvature and ask
how well it can be determined by planned surveys. We also explore the impact of
uncertain mean curvature on forecasts for the performance of planned dark
energy probes. We find that weak lensing and photometric baryon acoustic
oscillation data, in combination with CMB data, can determine the mean
curvature well enough that the residual uncertainty does not degrade
constraints on dark energy. We also find that determinations of curvature are
highly tolerant of photometric redshift errors.


title: Modeling dark energy with a top-down approach

abstract:
  We investigate a top-down approach for modeling the dark energy where we fit
the luminosity distances directly rather than indirectly fitting the equation
of state.


title: Heavy Element Abundances in Giant Stars of 47 Tuc

abstract:
  This research forms part of an investigation into heavy element abundances in
Asymptotic Giant Branch (AGB) stars in various stellar environments. Seven
giant stars in the southern globular cluster 47 Tuc have been observed using
the Anglo-Australian Telescope. Abundances for five s- and r- process elements
have been determined: the light s-process elements, Y and Zr; the heavy
s-process elements, La and Nd; and the r-process element Eu. Mean enhancements
in the light s-process, [ls/Fe], of ~+0.6 dex and heavy s-process elements,
[hs/Fe], of ~+0.3 dex were determined for all the giant stars. There was no
statistically significant difference between the abundances determined for the
Red Giant Branch (RGB) and AGB stars in this study. The results for the RGB
stars differ from those obtained by a number of previous studies. However,
because of the similar abundance results obtained for the AGB and RGB stars in
this study we believe this provides evidence for previous enrichment of the
material from which these stars formed.


title: Characterization of jovian plasma embedded dust particles

abstract:
  As the data from space missions and laboratories improve, a research domain
combining plasmas and charged dust is gaining in prominence. Our solar system
provides many natural laboratories such as planetary rings, comet comae and
tails, ejecta clouds around moons and asteroids, and Earth's noctilucent clouds
for which to closely study plasma-embedded cosmic dust. One natural laboratory
to study electromagnetically-controlled cosmic dust has been provided by the
Jovian dust streams and the data from the instruments which were on board the
Galileo spacecraft. Given the prodigious quantity of dust poured into the
Jovian magnetosphere by Io and its volcanoes resulting in the dust streams, the
possibility of dusty plasma conditions exist. This paper characterizes the main
parameters for those interested in studying dust embedded in a plasma with a
focus on the Jupiter environment. I show how to distinguish between
dust-in-plasma and dusty-plasma and how the Havnes parameter P can be used to
support or negate the possibility of collective behavior of the dusty plasma.
The result of applying these tools to the Jovian dust streams reveals mostly
dust-in-plasma behavior. In the orbits displaying the highest dust stream
fluxes, portions of orbits E4, G7, G8, C21 satisfy the minimum requirements for
a dusty plasma. However, the P parameter demonstrates that these mild dusty
plasma conditions do not lead to collective behavior of the dust stream
particles.


title:
Helium enhancements in globular cluster stars from Asymptotic Giant
  Branch star pollution

abstract:
  Using a chemical evolution model we investigate the intriguing suggestion
that there are populations of stars in some globular clusters (e.g. NGC 2808,
omega Centauri) with enhanced levels of helium (Y from about 0.28 to 0.40)
compared to the majority of the population that presumably have a primordial
helium abundance. We assume that a previous generation of massive
low-metallicity Asymptotic Giant Branch (AGB) stars has polluted the cluster
gas via a slow stellar wind. We use two independent sets of AGB yields computed
from detailed models to follow the evolution of helium, carbon, nitrogen and
oxygen in the cluster gas using a Salpeter initial mass function (IMF) and a
number of top-heavy IMFs. In no case were we able to fit the observational
constraints, Y > 0.30 and C+N+O approximately constant. Depending on the shape
of the IMF and the yields, we either obtained Y approximately greater than 0.30
and large increases in C+N+O or Y < 0.30 and C+N+O approximately constant.
These results suggest that either AGB stars alone are not responsible for the
large helium enrichment or that any dredge-up from this generation of stars was
less than predicted by standard models.


title:
Modelling galaxy spectra in presence of interstellar dust. II. From the
  UV to the far infrared

abstract:
  In this paper, we present spectrophotometric models for galaxies of different
morphological type whose spectral energy distributions (SEDs) take into account
the effect of dust in absorbing UV-optical light and re-emitting it in the
infrared (IR). The models contain three main components: (i) the diffuse
interstellar medium (ISM) composed of gas and dust, (ii) the large complexes of
molecular clouds (MCs) in which new stars are formed and (iii) the stars of any
age and chemical composition. The galaxy models stand on a robust model of
chemical evolution taylored in such a way to match the gross properties of
galaxies of different morphological type. A simple geometrical model is adopted
for each type of galaxy. The total gas and star mass provided by the chemical
model are distributed over the whole volume by means of suitable density
profiles, one for each component and depending on the galaxy type (spheroidal,
disk and disk plus bulge). The galaxy is then split in suitable volume elements
to each of which the appropriate amounts of stars, MCs and ISM are assigned. We
derive the SEDs of galaxies of different morphological type. First the the
basic relations driving the interaction between the physical components of the
galaxy are presented. Second, the main parameters are examined and their
effects on the SED of three prototype galaxies (a disk, an elliptical and a
starburster) are highlighted. The final part of the paper is devoted to assess
the ability of our galaxy models in reproducing the SEDs of a few real galaxies
of the Local Universe.


title:
The Structure of Rapidly Rotating Late-Type Spiral Galaxies: I.
  Photometry, HI and Optical Kinematics

abstract:
  We present I-band photometry, long-slit optical spectroscopy, and new
aperture synthesis HI observations for eight late-type spirals with rotation
velocities in the range 243 km/s < V_{rot} < 308 km/s. The sample will be used
to study the structure and angular momentum of disks at the high-mass end of
the spiral galaxy population; here we discuss the basic properties of these
``fast rotators'', and derive hybrid optical/HI rotation curves for each.
Despite the presence of HI warps and low-mass companions in many systems, their
kinematics are regular and there is excellent agreement between optical and HI
tracers near the optical radius r_{opt}. At high inclinations at which
projection effects are negligible, the sample galaxies exhibit flat,
featureless rotation curves out to their last measured points at
1.7r_{opt}--3.5 r_{opt}. The intermediate inclination systems are also
consistent with a constant rotation amplitude for r > 0.5 r_{opt}. We therefore
find no evidence for declining rotation curves at the high-mass end of the
late-type spiral galaxy population. Combining our data with the compilation of
spirals with reliable outer HI kinematics from the work of Casertano & van
Gorkom, we find no convincing trends between logarithmic outer rotation curve
slopes and rotation amplitudes or surface brightnesses for galaxies with
V_{rot} > 220 km/s. Correlations between these slopes and morphological types
or disk scale lengths are also marginal in this regime.


title: Cleaning up Eta Carinae: Detection of Ammonia in the Homunculus

abstract:
  We report the first detection of ammonia in the Homunculus nebula around eta
Carinae, which is also the first detection of emission from a polyatomic
molecule in this or any other luminous blue variable (LBV) nebula. Observations
of the NH3 (J,K)=(3,3) inversion transition made with the Australia Telescope
Compact Array reveal emission at locations where infrared H2 emission had been
detected previously, near the strongest dust emission in the core of the
Homunculus. We also detect ammonia emission from the so-called ``strontium
filament'' in the equatorial disk. The presence of NH3 around eta Car hints
that molecular shells around some Wolf-Rayet stars could have originated in
prior LBV eruptions, rather than in cool red supergiant winds or the ambient
interstellar medium. Combined with the lack of any CO detection, NH3 seems to
suggest that the Homunculus is nitrogen rich like the ionized ejecta around eta
Car. It also indicates that the Homunculus is a unique laboratory in which to
study unusual molecule and dust chemistry, as well as their rapid formation in
a nitrogen-rich environment around a hot star. We encourage future observations
of other transitions like NH3 (1,1) and (2,2), related molecules like N2H+, and
renewed attempts to detect CO.


title: Aromatic Features in M101 HII Regions and Starburst Galaxies

abstract:
  The behavior of the aromatic features as a function of metallicity/radiation
field hardness in M101 HII regions and starburst galaxies is investigated using
Spitzer/IRS spectra. These spectra reveal that the 6.2, 7.8+8.6, and 11.3
micron aromatics have different dependencies on metallicity/radiation field
hardness. Specifically, the 6.2 and 7.8+8.6 micron aromatics are weak or absent
at a metallicity, 12+log(O/H), of approx. 8.0 while the 11.3 micron feature
remains relatively strong. These results apply to both the M101 HII regions and
starbursts showing that HII regions can indeed be thought of as
``mini-starbursts.'' Comparison of this work with various candidate materials
results in a good match with the annealing behavior in Quenched Carbonaceous
Composite (QCC) which is an amorphous, hydrogenated, carbonaceous solid.


title: Missing Galactic PNe: [S III] Imaging Survey

abstract:
  The total number of Galactic planetary nebulae is highly uncertain; the most
inclusive current catalog contains only ~ 1,500. We will use the PRISM
wide-field imager on the 1.83 m Perkins Telescope to conduct a pilot survey of
the Galactic plane in search of [S III] emission from planetary nebulae
obscured by dust and missed by surveys of H-alpha. We are employing the method
of Jacoby & Van de Steene, who surveyed the bulge for 9532 Angstrom [S III]
emission. In addition to seeing through more of the extinction, use of the [S
III] emission line will a priori reject the most troublesome catalog
contaminants: ultracompact H II regions.


title:
The multi-frequency angular power spectrum of the epoch of reionization
  21 cm signal

abstract:
  Observations of redshifted 21cm radiation from HI at high redshifts is an
important future probe of reionization. We consider the Multi-frequency Angular
Power Spectrum (MAPS) to quantify the statistics of the HI signal as a joint
function of the angular multipole l and frequency separation \Delta\nu. The
signal at two different frequencies is expected to get decorrelated as
\Delta\nu is increased, and quantifying this decorrelation is particularly
important in deciding the frequency resolution for future HI observations. This
is also expected to play a very crucial role in extracting the signal from
foregrounds as the signal is expected to decorrelate much faster than the
foregrounds (which are largely continuum sources) with increasing \Delta\nu. In
this paper we develop formulae relating the MAPS to different components of the
three dimensional HI power spectrum taking into account HI peculiar velocities.
We show that the flat-sky approximation provides a very good representation
over the angular scales of interest, and a final expression which is very
simple to calculate and interpret. We present results considering two models
for the HI distribution, namely, (i) DM: where the HI traces the dark matter
and (ii) PR: where the effects of patchy reionization are incorporated through
two parameters. We find that while the DM signal is largely featureless, the PR
signal peaks at the angular scales of the individual bubbles, and the signal is
considerably enhanced for large bubble size. For most cases of interest at l
\sim 100 the signal is uncorrelated beyond \Delta\nu \sim 1 MHz or even less,
whereas it occurs around \sim 0.1 MHz at l \sim 10^3. The \Delta\nu dependence
also carries an imprint of the bubble size and the bias, and is expected to be
an important probe of the reionization scenario (abridged).


title: Optical Monitoring of BL Lacertae Object OJ 287: a 40-Day Period?

abstract:
  We present the results of our optical monitoring of the BL Lacertae object OJ
287 during the first half of 2005. The source did not show large-amplitude
variations during this period and was in a relatively quiescent state. A
possible period of 40 days was derived from its light curves in three BATC
wavebands. A bluer-when-brighter chromatism was discovered, which is different
from the extremely stable color during the outburst in 1994--96. The different
color behaviors imply different variation mechanisms in the two states. We then
re-visited the optical data on OJ 287 from the OJ-94 project and found as well
a probable period of 40 days in its optical variability during the late-1994
outburst. The results suggest that two components contribute to the variability
of OJ 287 during its outburst state. The first component is the normal {\sl
blazar} variation. This component has an amplitude similar to that of the
quiescent state and also may share a similar periodicity. The second component
can be taken as a `low-frequency modulation' to the first component. It may be
induced by the interaction of the assumed binary black holes in the center of
this object. The 40-day period may be related to the helical structure of the
magnetic field at the base of the jet, or to the orbital motion close to the
central primary black hole.


title:
Imprint of Gravitational Lensing by Population III Stars in Gamma Ray
  Burst Light Curves

abstract:
  We propose a novel method to extract the imprint of gravitational lensing by
Pop III stars in the light curves of Gamma Ray Bursts (GRBs). Significant
portions of GRBs can originate in hypernovae of Pop III stars and be
gravitationally lensed by foreground Pop III stars or their remnants. If the
lens mass is on the order of $10^2-10^3M_\odot$ and the lens redshift is
greater than 10, the time delay between two lensed images of a GRB is $\approx
1$s and the image separation is $\approx 10 \mu$as. Although it is difficult to
resolve the two lensed images spatially with current facilities, the light
curves of two images are superimposed with a delay of $\approx 1$ s. GRB light
curves usually exhibit noticeable variability, where each spike is less than
1s. If a GRB is lensed, all spikes are superimposed with the same time delay.
Hence, if the autocorrelation of light curve with changing time interval is
calculated, it should show the resonance at the time delay of lensed images.
Applying this autocorrelation method to GRB light curves which are archived as
the {\it BATSE} catalogue, we demonstrate that more than half light curves can
show the recognizable resonance, if they are lensed. Furthermore, in 1821 GRBs
we actually find one candidate of GRB lensed by a Pop III star, which may be
located at redshift 20-200. The present method is quite straightforward and
therefore provides an effective tool to search for Pop III stars at redshift
greater than 10. Using this method, we may find more candidates of GRBs lensed
by Pop III stars in the data by the {\it Swift} satellite.


title:
Variable Very High Energy Gamma-ray Emission from the Microquasar LS I
  +61 303

abstract:
  Microquasars are binary star systems with relativistic radio-emitting jets.
They are potential sources of cosmic rays and laboratories for elucidating the
physics of relativistic jets. Here we report the detection of variable
gamma-ray emission above 100 gigaelectron volts from the microquasar LS I +61
303. Six orbital cycles were recorded. Several detections occur at a similar
orbital phase, suggesting the emission is periodic. The strongest gamma-ray
emission is not observed when the two stars are closest to one another,
implying a strong orbital modulation of the emission or the absorption
processes.


title: Equation of State in Numerical Relativistic Hydrodynamics

abstract:
  Relativistic temperature of gas raises the issue of the equation of state
(EoS) in relativistic hydrodynamics. We study the EoS for numerical
relativistic hydrodynamics, and propose a new EoS that is simple and yet
approximates very closely the EoS of the single-component perfect gas in
relativistic regime. We also discuss the calculation of primitive variables
from conservative ones for the EoS's considered in the paper, and present the
eigenstructure of relativistic hydrodynamics for a general EoS, in a way that
they can be used to build numerical codes. Tests with a code based on the Total
Variation Diminishing (TVD) scheme are presented to highlight the differences
induced by different EoS's.


title:
Spectral analyses of eighteen hot H-deficient (pre-) white dwarfs from
  the Sloan Digital Sky Survey Data Release 4

abstract:
  Context: The Sloan Digital Sky Survey Data Release 4 has provided spectra of
several new PG 1159 stars and DO white dwarfs. This increase in known hot
H-deficient compact objects significantly improves the statistics and helps to
investigate late stages of stellar evolution. Aims: From the optical SDSS
spectra, effective temperatures and surface gravities are derived in order to
place the observed objects in an evolutionary context. Especially the
connection between PG 1159 stars and DO white dwarfs shall be investigated.
Method: Using our non-LTE model atmospheres and applying chi^2-fitting
techniques, we determine stellar parameters and their errors. We derive total
stellar masses for the DO white dwarfs using model evolutionary tracks.
Results: We confirm three PG 1159 stars, with one showing ultra-high excitation
ion features, and one sdO which we originally classified as a PG 1159 star.
Additionally, we re-analysed the known PG 1159 star, PG 1424+535, with our new
models. Furthermore, we present the first spectral analyses of thirteen DO
white dwarfs, three of which show M-star features in their spectra, while two
display ultra-high excitation ion features.


title:
The planets capture model of V838 Monocerotis: conclusions for the
  penetration depth of the planet/s

abstract:
  V838 Mon is the prototype of a new class of objects. Understanding the nature
of its multi-stage outburst and similar systems is challenging. So far, several
scenarios have been invoked to explain this group of stars. In this work, the
planets-swallowing model for V838 Mon is further investigated, taking into
account the findings that the progenitor is most likely a massive B type star.
We find that the super-Eddington luminosity during the eruption can explain the
fast rising times of the three peaks in the optical light curve. We used two
different methods to estimate the location where the planets were consumed.
There is a nice agreement between the values obtained from the luminosities of
the peaks and from their rising time scale. We estimate that the planets were
stopped at a typical distance of one solar radius from the center of the host
giant star. The planets-devouring model seems to give a satisfying explanation
to the differences in the luminosities and rising times of the three peaks in
the optical light curve of V838 Mon. The peaks may be explained by the
consumption of three planets or alternatively by three steps in the terminal
falling process of a single planet. We argue that only the binary merger and
the planets-swallowing models are consistent with the observations of the new
type of stars defined by V838 Mon.


title: Asteroseismic signatures of helium gradients in late F-type stars

abstract:
  Element diffusion is expected to occur in all kinds of stars : according to
the relative effect of gravitation and radiative acceleration, they can fall or
be pushed up in the atmospheres. Helium sinks in all cases, thereby creating a
gradient at the bottom of the convective zones. This can have important
consequences for the sound velocity, as has been proved in the sun with
helioseismology.
  We investigate signatures of helium diffusion in late F-type stars by
asteroseismology.
  Stellar models were computed with different physical inputs (with or without
element diffusion) and iterated in order to fit close-by evolutionary tracks
for each mass. The theoretical oscillation frequencies were computed and
compared for pairs of models along the tracks. Various asteroseismic tests
(large separations, small separations, second differences) were used and
studied for the comparisons.
  The results show that element diffusion leads to changes in the frequencies
for masses larger than 1.2 Msun. In particular the helium gradient below the
convective zone should be detectable through the second differences.


title:
V4745 Sgr -- a nova above the period gap and an intermediate polar
  candidate

abstract:
  A period analysis of CCD unfiltered photometry of V4745 Sgr (Nova Sgr 2003
#1) performed during 23 nights in the years 2003 - 2005 is presented. The
photometric data are modulated with a period of 0.20782 +- 0.00003 d ($4.98768
+- 0.00072 h). Following the shape of the phased light curve and the presence
of the periodicity in all data sets with no apparent change in its value, we
interpret this periodicity as orbital in nature and this is consistent with a
cataclysmic variable above the period gap. We found a probable short-term
periodicity of 0.017238 +- 0.000037 d (24.82272 +- 0.05328 m) which we
interpret as the probable spin period of the white dwarf or the beat period
between the orbital and spin period. Therefore, we propose that nova V4745 Sgr
should be classified as an intermediate polar candidate, supporting the
proposed link between transition-oscillation novae and intermediate polars. The
mass-period relation for cataclysmic variables yields a secondary mass of about
0.52 +- 0.05 M_solar.


title: A catalogue of ULX coincidences with FIRST radio sources

abstract:
  We search for ultra luminous X-ray source (ULXs) radio counterparts located
in nearby galaxies in order to constrain their physical nature. Our work is
based on a systematic cross-identification of the most recent and extensive
available ULX catalogues and archival radio data. A catalogue of 70 positional
coincidences is reported. Most of them are located within the galaxy nucleus.
Among them, we find 11 new cases of non-nuclear ULX sources with possibly
associated radio emission.


title: New Pulsating White Dwarfs in Cataclysmic Variables

abstract:
  The number of discovered non-radially pulsating white dwarfs (WDs) in
cataclysmic variables (CVs) is increasing rapidly by the aid of the Sloan
Digital Sky Survey (SDSS). We performed photometric observations of two
additional objects, SDSS J133941.11+484727.5 (SDSS 1339), independently
discovered as a pulsator by Gansicke et al., and SDSS J151413.72+454911.9,
which we identified as a CV/ZZ Ceti hybrid. In this Letter we present the
results of the remote observations of these targets performed with the Nordic
Optical Telescope (NOT) during the Nordic-Baltic Research School at Moletai
Observatory, and follow-up observations executed by NOT in service mode. We
also present 3 candidates we found to be non-pulsating. The results of our
observations show that the main pulsation frequencies agree with those found in
previous CV/ZZ Ceti hybrids, but specifically for SDSS 1339 the principal
period differs slightly between individual observations and also from the
recent independent observation by Gansicke et al. Analysis of SDSS colour data
for the small sample of pulsating and non-pulsating CV/ZZ Ceti hybrids found so
far, seems to indicate that the r-i colour could be a good marker for the
instability strip of this class of pulsating WDs.


title:
Reconciling optical and X-ray mass estimates: the case of the elliptical
  galaxy NGC3379

abstract:
  NGC3379 is a well studied nearby elliptical for which optical investigations
have claimed a little dark matter content, or even no dark matter. Recently,
its total mass profile M(r) has been derived by exploiting Chandra observations
of its extended and X-ray emitting interstellar medium, based on the hypothesis
of hydrostatic equilibrium for the hot gas. The resulting total mass within the
effective radius Re has been claimed to be a few times larger than found by
optical studies. Here we show that part of the discrepancy can be due to an
underestimate of the optically derived mass, and the remaining discrepancy of a
factor of ~2 can be explained by deviations from hydrostatic equilibrium of the
hot gas. By using hydrodynamical simulations tailored to reproduce the observed
hot gas properties of NGC3379, and by assuming as input for the simulations the
total mass profile derived optically, we show that i) the hot gas at the
present time has X-ray properties consistent with those observed only if it is
outflowing over most of the galactic body, and ii) an overestimate of M of the
same size found in the recent X-ray analysis is recovered when assuming
hydrostatic equilibrium. We also show that the hot gas is outflowing even for a
dark matter fraction within Re as large as derived with the standard X-ray
procedure based on the hydrostatic equilibrium assumption, which shows the
unapplicability of the method for this galaxy. Finally, we find that the whole
range of dark mass amount and distribution allowed for by optical studies is
compatible with a hot gas flow with the observed X-ray properties.


title: Probable detection of H2D+ in the starless core Barnard 68

abstract:
  The presence of H2D+ in dense cloud cores underlies ion-molecule reactions
that strongly enhance the deuterium fractionation of many molecular species. We
determine the H2D+ abundance in one starless core, Barnard 68, that has a
particularly well established physical, chemical, and dynamical structure. We
observed the ortho-H2D+ ground-state line 1_10-1_11, the N2H+ J=4-3 line, and
the H13CO+ 4-3 line with the APEX telescope. We report the probable detection
of the o-H2D+ line at an intensity Tmb=0.22 +- 0.08 K and exclusively thermal
line width, and find only upper limits to the N2H+ 4-3 and H13CO+ 4-3
intensities. Within the uncertainties in the chemical reaction rates and the
collisional excitation rates, chemical model calculations and excitation
simulations reproduce the observed intensities and that of o-H2D+ in
particular.


title:
IGR J17544-2619: A new supergiant fast X-ray transient revealed by
  optical/infrared observations

abstract:
  One of the most recent discoveries of the INTEGRAL observatory is the
existence of a previously unknown population of X-ray sources in the inner arms
of the Galaxy. IGR J17544-2619, IGR J16465-4507 and XTE J1739-302 are among
these sources. Although the nature of these systems is still unexplained, the
investigations of the optical/NIR counterparts of the two last sources,
combined with high energy data, have provided evidence of them being highly
absorbed high mass X-ray binaries with blue supergiant secondaries and
displaying fast X-ray transient behaviour. In this work we present our
optical/NIR observations of IGR J17544-2619, aimed at identifying and
characterizing its counterpart. We show that the source is a high mass X-ray
binary at a distance of 2-4 kpc with a strongly absorbed O9Ib secondary, and
discuss the nature of the system.


title: Quantitative X-ray spectroscopy of massive stars

abstract:
  Radiative transfer in a clumped winds is used to describe X-ray emission line
profiles observed in the XMM-Newton RGS spectrum of the OI star Zeta Puppis. It
is shown that this X-ray spectrum can be explained as originating from a
multi-temperature collisional plasma located in the wind acceleration zone. The
X-rays are attenuated in the clumped stellar wind, which gives characteristic
profiles to the emergent lines. We specifically study the N VII emission line
in the spectrum of Zeta Pup. Long RGS exposures reveal that the N VII line
profile is structured. On the basis of our Zeta Pup atmosphere model, we rule
out the presence of N VII in the cool wind component. We suggest that the
detailed N VII line structure is due to self-absorption in the hot plasma. Wind
clumping also affects the transfer of ionizing radiation in high-mass X-ray
binaries (HMXBs). We derive analytical formulae for the ionisation parameter in
dependence on the parameters of wind clumping.


title:
Optical Counterparts of Ultra-Luminous X-ray Sources identified from
  Archival Hubble Space Telescope/WFPC2

abstract:
  We present a systematic analysis of archival HST WFPC2 ``Association'' data
sets that correlate with the Chandra positions of a set of 44 ultra-luminous
X-ray sources (ULXs) of nearby galaxies. We have improved the Chandra-HST
relative astrometry whenever possible. Disparate numbers of potential ULX
counterparts are found, and in some cases none are found. The lack of or low
number of counterparts in some cases may be due to insufficient depth in the
WFPC2 images. Particularly in late-type galaxies, the HST image in the ULX
region was often complex or crowded. We therefore address various scenarios for
the nature of the ULX since it is not known which, if any, of the sources found
are true counterparts. The optical luminosities of the sources are typically in
the range 10^4-6 L_sun. In several cases color information is available, with
the colors roughly tending to be more red in early-type galaxies. This suggests
that, in general, the (potential) counterparts found in early-type galaxies are
likely to be older stellar populations, and are probably globular clusters.
Several early-type galaxy counterparts have blue colors, which may be due to
younger stellar populations in the host galaxies, however these could also be
background sources. In spiral galaxies the sources may also be due to localized
structure in the disks rather than bound stellar systems. Alternatively some of
the counterparts in late-type galaxies may be isolated supergiant stars. The
observed X-ray/optical flux ratio is diluted by the optical emission of the
cluster in cases where the system is an X-ray binary in a cluster, particularly
in the case of a low-mass X-ray binaries in old cluster. (abridged)


title: Generation of the magnetic field in jets

abstract:
  We consider dynamo action under the combined influence of turbulence and
large-scale shear in sheared jets. Shear can stretch turbulent magnetic field
lines in such a way that even turbulent motions showing mirror symmetry become
suitable for generation of a large-scale magnetic field. We derive the integral
induction equation governing the behaviour of the mean field in jets. The main
result is that sheared jets may generate a large-scale magnetic field if shear
is sufficiently strong. The generated mean field is mainly concentrated in a
magnetic sheath surrounding the central region of a jet, and it exhibits sign
reversals in the direction of the jet axis. Typically, the magnetic field in a
sheath is dominated by the component along the jet that can reach equipartition
with the kinetic energy of particles, The field in the central region of jets
has a more disordered structure.


title:
Ammonia as a tracer of chemical equilibrium in the T7.5 dwarf Gliese
  570D

abstract:
  We present the first analysis of an optical to mid-infrared spectrum of the
T7.5 dwarf Gliese 570D with model atmospheres, synthetic spectra, and brown
dwarf evolution sequences. We obtain precise values for the basic parameters of
Gl 570D: Teff=800 - 820K, log g (cm/s^2)=5.09 - 5.23, and log L/Lsun= -5.525 to
-5.551. The Spitzer IRS spectrum shows prominent features of ammonia (NH3) that
can only be fitted by reducing the abundance of NH3 by about one order of
magnitude from the value obtained with chemical equilibrium models. We model
departures from chemical equilibrium in the atmosphere of Gl 570D by
considering the kinetics of nitrogen and carbon chemistry in the presence of
vertical mixing. The resulting model spectrum reproduces the data very well.


title: Local Group(s)

abstract:
  The properties of the galaxies of the Local Group are reviewed, followed by a
brief discussion of nearby groups. The galaxy groups in our vicinity - the M81
group, the Cen A group, and the IC 342/Maffei group - are in many respects
Local Group analogs: Their luminosity functions, galaxy content, fractional
galaxy type distribution, crossing times, masses, and zero-velocity surface
radii are similar to those of the Local Group. Also, the nearby groups usually
consist of two subgroups, some of which approach each other and may ultimately
merge to form a fossil group. These poor groups contrast with the less evolved,
loose and extended galaxy ``clouds'' such as the Scl group and the CVn I cloud.
These are characterized by long crossing times, are dominated by gas-rich,
late-type galaxies, and lack gas-deficient, low luminosity early-type dwarfs.
These clouds may be groups still in formation. The local Hubble flow derived
from the clouds and groups is very cold.


title:
Simple Magnetic Flux Balance as an Indicator of Neon VIII Doppler
  Velocity Partitioning in an Equatorial Coronal Hole

abstract:
  We present a novel investigation into the relationship between simple
estimates of magnetic flux balance and the Ne VIII Doppler velocity
partitioning of a large equatorial coronal hole observed by the Solar
Ultraviolet Measurements of Emitted Radiation spectrometer (SUMER) on the Solar
and Heliospheric Observatory (SOHO) in November 1999. We demonstrate that a
considerable fraction of the large scale Doppler velocity pattern in the
coronal hole can be qualitatively described by simple measures of the local
magnetic field conditions, i.e., the relative unbalance of magnetic polarities
and the radial distance required to balance local flux concentrations with
those of opposite polarity.


title: Oscillations of longitudinally density stratified coronal loops

abstract:
  We investigate the standing kink modes of a cylindrical model of coronal
loops. The density is stratified along the loop axis and changes
discontinuously at the surface of the cylinder. The periods and mode profiles
are studies with their deviation from those of the unstratified loops. The aim
is to extract information on the density scale heights prevailing in the solar
corona. The problem is reduced to solving a single second-order partial
differential equation for $\delta B_z(r,z)$, the longitudinal component of the
Eulerian perturbations of the magnetic field. This equation, in turn, is
separated into two second-order ordinary, differential equations in $r$ and $z$
that are, however, connected through a dispersion relation between the
frequencies and the longitudinal wave numbers. In the thin tube approximation,
the eigensolutions are obtained by a perturbation technique, where the
perturbation parameter is the density stratification parameter. Otherwise the
problem is solved numerically.


title:
Gravitational Waves from Light Cosmic Strings: Backgrounds and Bursts
  with Large Loops

abstract:
  The mean spectrum and burst statistics of gravitational waves produced by a
cosmological population of cosmic string loops are estimated using analytic
approximations, calibrated with earlier simulations. Formulas are derived
showing the dependence of observables on the string tension, in the regime
where newly-formed loops are relatively large, not very much smaller than the
horizon. Large loops form earlier, are more abundant, and generate a more
intense stochastic background and more frequent bursts than assumed in earlier
background estimates, enabling experiments to probe lighter cosmic strings of
interest to string theory. Predictions are compared with instrument noise from
current and future experiments, and with confusion noise from known
astrophysical gravitational wave sources such as stellar and massive black hole
binaries. In these large-loop models, current data from millisecond pulsar
timing already suggests that the tension is less than about $10^{-10}$, a
typical value expected in strings from brane inflation. LISA will be sensitive
to stochastic backgrounds created by strings as light as $G\mu\approx
10^{-15}$, at frequencies where it is limited by confusion noise of Galactic
stellar populations; however, for those lightest detectable strings, bursts are
rarely detectable.


title: A warped m=2 water maser disc in V778 Cyg?

abstract:
  The silicate carbon star V778 Cyg is a source of 22 GHz water maser emission
which was recently resolved by MERLIN. Observations revealed an elongated
S-like structure along which the velocities of the maser features show a linear
dependence on the impact parameter. This is consistent with a doubly-warped m=2
disc observed edge-on. Water masers and silicate dust emission (detected by
IRAS and ISO) have a common origin in O-rich material and are likely to be
co-located in the disc. We propose a detailed self-consistent model of a masing
gas-dust disc around a companion to the carbon star in a binary system, which
allows us to estimate the companion mass of 1.7 +- 0.1 M_sun, the disc radius
of 40 +-3 AU and the distance between companions of about 80 AU. Using a
dust-gas coupling model for water masing, we calculate the maser power
self-consistently, accounting for both the gas and the dust energy balances.
Comparing the simulation results with the observational data, we deduce the
main physical parameters of the masing disc, such as the gas and dust
temperatures and their densities. We also present an analysis of the stability
of the disc.


title:
Image-Subtraction Photometry of Variable Stars in the Globular Clusters
  NGC 6388 and NGC 6441

abstract:
  We have applied Alard's image subtraction method (ISIS v2.1) to the
observations of the globular clusters NGC 6388 and NGC 6441 previously analyzed
using standard photometric techniques (DAOPHOT, ALLFRAME). In this reanalysis
of observations obtained at CTIO, besides recovering the variables previously
detected on the basis of our ground-based images, we have also been able to
recover most of the RR Lyrae variables previously detected only in the analysis
of Hubble Space Telescope WFPC2 observations of the inner region of NGC6441. In
addition, we report five possible new variables not found in the analysis of
the HST observations of NGC 6441. This dramatically illustrates the
capabilities of image subtraction techniques applied to ground-based data to
recover variables in extremely crowded fields. We have also detected twelve new
variables and six possible variables in NGC 6388 not found in our previous
ground-based studies. The revised mean period for RRab stars in NGC 6388 is
0.676 day, while the mean period of RRab stars in NGC 6441 is unchanged at
0.759 day. These values are among the largest known for any galactic globular
cluster. Additional probable type II Cepheids were identified in NGC 6388,
confirming its status as a metal-rich globular cluster rich in Cepheids.


title:
HETE-2 Localizations and Observations of Four Short Gamma-Ray Bursts:
  GRBs 010326B, 040802, 051211 and 060121

abstract:
  Here we report the localizations and properties of four short-duration GRBs
localized by the High Energy Transient Explorer 2 satellite (HETE-2): GRBs
010326B, 040802, 051211 and 060121, all of which were detected by the French
Gamma Telescope (Fregate) and localized with the Wide-field X-ray Monitor (WXM)
and/or Soft X-ray Camera (SXC) instruments. We discuss eight possible criteria
for determining whether these GRBs are "short population bursts" (SPBs) or
"long population bursts" (LPBs). These criteria are (1) duration, (2) pulse
widths, (3) spectral hardness, (4) spectral lag, (5) energy Egamma radiated in
gamma rays (or equivalently, the kinetic energy E_KE of the GRB jet), (6)
existence of a long, soft bump following the burst, (7) location of the burst
in the host galaxy, and (8) type of host galaxy. In particular, we have
developed a likelihood method for determining the probability that a burst is
an SPB or a LPB on the basis of its T90 duration alone. A striking feature of
the resulting probability distribution is that the T90 duration at which a
burst has an equal probability of being a SPB or a LPB is T90 = 5 s, not T90 =
2 s, as is often used. All four short-duration bursts discussed in detail in
this paper have T90 durations in the Fregate 30-400 keV energy band of 1.90,
2.31, 4.25, and 1.97 sec, respectively, yielding probabilities P(S|T90) = 0.97,
0.91, 0.60, and 0.95 that these bursts are SPBs on the basis of their T90
durations alone. All four bursts also have spectral lags consistent with zero.
These results provide strong evidence that all four GRBs are SPBs (abstract
continues).


title:
The Sloan Digital Sky Survey Quasar Lens Search. I. Candidate Selection
  Algorithm

abstract:
  We present an algorithm for selecting an uniform sample of gravitationally
lensed quasar candidates from low-redshift (0.6<z<2.2) quasars brighter than
i=19.1 that have been spectroscopically identified in the SDSS. Our algorithm
uses morphological and color selections that are intended to identify small-
and large-separation lenses, respectively. Our selection algorithm only relies
on parameters that the SDSS standard image processing pipeline generates,
allowing easy and fast selection of lens candidates. The algorithm has been
tested against simulated SDSS images, which adopt distributions of field and
quasar parameters taken from the real SDSS data as input. Furthermore, we take
differential reddening into account. We find that our selection algorithm is
almost complete down to separations of 1'' and flux ratios of 10^-0.5. The
algorithm selects both double and quadruple lenses. At a separation of 2'',
doubles and quads are selected with similar completeness, and above (below) 2''
the selection of quads is better (worse) than for doubles. Our morphological
selection identifies a non-negligible fraction of single quasars: To remove
these we fit images of candidates with a model of two point sources and reject
those with unusually small image separations and/or large magnitude differences
between the two point sources. We estimate the efficiency of our selection
algorithm to be at least 8% at image separations smaller than 2'', comparable
to that of radio surveys. The efficiency declines as the image separation
increases, because of larger contamination from stars. We also present the
magnification factor of lensed images as a function of the image separation,
which is needed for accurate computation of magnification bias.


title:
Nonextensive entropy approach to space plasma fluctuations and
  turbulence

abstract:
  Spatial intermittency in fully developed turbulence is an established feature
of astrophysical plasma fluctuations and in particular apparent in the
interplanetary medium by in situ observations. In this situation the classical
Boltzmann-Gibbs extensive thermo-statistics, applicable when microscopic
interactions and memory are short ranged, fails. Upon generalization of the
entropy function to nonextensivity, accounting for long-range interactions and
thus for correlations in the system, it is demonstrated that the corresponding
probability distributions (PDFs) are members of a family of specific power-law
distributions. In particular, the resulting theoretical bi-kappa functional
reproduces accurately the observed global leptokurtic, non-Gaussian shape of
the increment PDFs of characteristic solar wind variables on all scales.
Gradual decoupling is obtained by enhancing the spatial separation scale
corresponding to increasing kappa-values in case of slow solar wind conditions
where a Gaussian is approached in the limit of large scales. Contrary, the
scaling properties in the high speed solar wind are predominantly governed by
the mean energy or variance of the distribution. The PDFs of solar wind scalar
field differences are computed from WIND and ACE data for different time-lags
and bulk speeds and analyzed within the nonextensive theory. Consequently,
nonlocality in fluctuations, related to both, turbulence and its large scale
driving, should be related to long-range interactions in the context of
nonextensive entropy generalization, providing fundamentally the physical
background of the observed scale dependence of fluctuations in intermittent
space plasmas.


title:
The Hubble Deep Field North SCUBA Super-map IV - Characterizing
  submillimetre galaxies using deep Spitzer imaging

abstract:
  We present SEDs, Spitzer colours, and IR luminosities for 850 micron selected
galaxies in the GOODS-N field. Using the deep Spitzer Legacy images and new
data and reductions of the VLA-HDF radio data, we find statistically secure
counterparts for 60 per cent (21/35) of our submm sample, and identify
tentative counterparts for another 12 objects. This is the largest sample of
submm galaxies with statistically secure counterparts detected in the radio and
with Spitzer. We find that in most cases the 850 micron emission is dominated
by a single 24 micron source. A composite rest-frame SED shows that the submm
sources peak at longer wavelengths than those of local ULIRGs of the same
luminosity and therefore appear to be cooler. The SEDs of submm galaxies are
also different from those of their high redshift neighbours, the near-IR
selected BzK galaxies, whose mid-IR to radio SEDs are more like those of local
ULIRGs. Using 24 micron. 850 micron and 1.4 GHz observations, we fit templates
that span the mid-IR through radio to derived the integrated IR luminosity of
the submm galaxies. By themselves, 24 micron and radio fluxes are able to
predict LIR reasonably well because they are relatively insensitive to
temperature. However, the submm flux by itself consistently overpredicts LIR
when using spectral templates which obey the local ULIRG temperature-luminosity
relation. The shorter Spitzer wavelengths sample the stellar bump at the
redshifts of the submm sources, and we find that the Spitzer photometry alone
provides a model independent estimate of the redshift. Using X-ray and mid-IR
data, only 5 per cent of our secure counterparts show strong evidence for an
active galactic nucleus dominating the IR luminosity.


title:
Determining the Nature of the SS 433 Binary Using an X-ray Spectrum
  During Eclipse

abstract:
  We test the physical model of the relativistic jets in the galactic X-ray
binary SS 433 proposed in our previous paper using additional observations from
the Chandra High Energy Transmission Grating Spectrometer. These observations
sample two new orbital/precessional phase combinations. In the observation near
orbital phase zero, the H- and He-like Fe lines from both receding and
approaching jets are comparably strong and unocculted while the He-like Si line
of the receding jet is significantly weaker than that of the approaching jet.
This condition may imply the cooler parts of the receding jet are eclipsed by
the companion. The X-ray spectrum from this observation has broader emission
lines than obtained in Paper I that may arise from the divergence of a conical
outflow or from Doppler shift variations during the observation. Using recent
optical results, along with the length of the unobscured portion of the
receding jet assuming adiabatic cooling, we calculate the radius of the
companion to be 9.6+/-1.0 R_sun, about one third of the Roche lobe radius. For
a main sequence star, this corresponds to a companion mass of 35+/-7 M_sun,
giving a primary source mass of 20+/-5 M_sun. If our model is correct, this
calculation indicates the compact object is a black hole, and accretion occurs
through a wind process. In a subsequent paper, we will examine the validity of
the adiabatic cooling model of the jets and test the mode of line broadening.


title: Cosmology with clusters of galaxies

abstract:
  In this Chapter I review the role that galaxy clusters play as tools to
constrain cosmological parameters. I will concentrate mostly on the application
of the mass function of galaxy clusters, while other methods, such as that
based on the baryon fraction, are covered by other Chapters of the book. Since
most of the cosmological applications of galaxy clusters rely on precise
measurements of their masses, a substantial part of my Lectures concentrates on
the different methods that have been applied so far to weight galaxy clusters.
I provide in Section 2 a short introduction to the basics of cosmic structure
formation. In Section 3 I describe the Press--Schechter (PS) formalism to
derive the cosmological mass function, then discussing extensions of the PS
approach and the most recent calibrations from N--body simulations. In Section
4 I review the methods to build samples of galaxy clusters at different
wavelengths. Section 5 is devoted to the discussion of different methods to
derive cluster masses. In Section 6 I describe the cosmological constraints,
which have been obtained so far by tracing the cluster mass function with a
variety of methods. Finally, I describe in Section 7 the future perspectives
for cosmology with galaxy clusters and the challenges for clusters to keep
playing an important role in the era of precision cosmology.


title:
Spatial mapping of ices in the Oph-F core: A direct measurement of CO
  depletion and the formation of CO2

abstract:
  Aims: Ices in dense star-forming cores contain the bulk of volatile molecules
apart from H2 and thus represent a large fraction of dark cloud chemistry
budget.To directly constrain the freeze-out profile of CO, the formation route
of CO2 and the carrier of the 6.8 micron band, the spatial distribution of the
CO/CO2 ice system and the 6.8 micron band carrier are measured in a nearby
dense core.
  Methods: VLT-ISAAC, ISOCAM-CVF and Spitzer-IRS archival mid-infrared (3-20
micron) spectroscopy of young stellar objects is used to construct a map of the
abundances of CO and CO2 ices in the Oph-F star-forming core, probing core
radii from 2 10^3 to 14 10^3 AU or densities from 5 10^4 to 5 10^5 cm^-3 with a
resolution of ~ 3000 AU.
  Results: The line-of-sight averaged abundances relative to water ice of both
CO and CO2 ices increase monotonously with decreasing distance to the core
center. The map traces the shape of the CO abundance profile between freeze-out
ratios of 5-60% and shows that the CO2 ice abundance increases by a factor of 2
as the CO freezes out. It is suggested that this indicates a formation route of
CO2 on a CO ice surface to produce a CO2 component dilute in CO ice, in
addition to a fraction of the CO2 formed at lower densities along with the
water ice mantle. It is predicted that the CO2 bending mode band profile should
reflect a high CO:CO2 number ratio in the densest parts of dark clouds. In
contrast to CO and CO2, the abundance of the carrier of the 6.8 micron band
remains relatively constant throughout the core. A simple freeze-out model of
the CO abundance profile is used to estimate the binding energy of CO on a CO
ice surface to 814+/-30 K.


title:
Hubble Space Telescope NICMOS Observations of T Dwarfs: Brown Dwarf
  Multiplicity and New Probes of the L/T Transition

abstract:
  We present the results of a Hubble Space Telescope NICMOS imaging survey of
22 T-type field brown dwarfs. Five are resolved as binary systems with angular
separations of 0"05-0"35, and companionship is established on the basis of
component F110W-F170M colors (indicative of CH4 absorption) and low
probabilities of background contamination. Prior ground-based observations show
2MASS 1553+1532AB to be a common proper motion binary. The properties of these
systems - low multiplicity fraction (11[+7][-3]% resolved, as corrected for
sample selection baises), close projected separations (a = 1.8-5.0 AU) and
near-unity mass ratios - are consistent with previous results for field brown
dwarf binaries. Three of the binaries have components that span the
poorly-understood transition between L dwarfs and T dwarfs. Spectral
decomposition analysis of one of these, SDSS 1021-0304AB, reveals a peculiar
flux reversal between its components, as its T5 secondary is ~30% brighter at
1.05 and 1.27 micron than its T1 primary. This system, 2MASS 0518-2828AB and
SDSS 1534+1615AB all demonstrate that the J-band brightening observed between
late-type L to mid-type T dwarfs is an intrinsic feature of this spectral
transition, albeit less pronounced than previously surmised. We also find that
the resolved binary fraction of L7 to T3.5 dwarfs is twice that of other L and
T dwarfs, an anomaly that can be explained by a relatively rapid evolution of
brown dwarfs through the L/T transition, perhaps driven by dynamic
(nonequilibrium) depletion of photospheric condensates.


title: Multi-Frequency VLBI Observations of NRAO 530

abstract:
  We report on VLBA observations of a gamma-ray bright blazar NRAO 530 at
multiple frequencies (5, 8, 15, 22, 39, 43, and 45 GHz) in 1997 and 1999. These
multi-epoch multi-frequency high-resolution VLBI images exhibit a consistent
core-dominated morphology with a bending jet to the north of the core. The
quasi-simultaneous data observed at five frequencies (5, 8, 15, 22 and 43 GHz)
in February 1997 enable us to estimate the spectra of compact VLBI components
in this highly variable source. Flat spectra are seen in central two components
(A and B), and the most compact component A with the flattest spectral index at
the south end is identified as the core.


title: Sequential Formation of Low-Mass Stars in the BRC 14 Region

abstract:
  We have carried out a deep near-infrared survey of a bright-rimmed molecular
cloud, BRC 14 (IC 1848A). The 10 sigma limiting magnitude of the survey is 17.7
mag at the K-band. Seventy-four sources are classified as young stellar object
(YSO) candidates based on the near-infrared color-color diagram. The faintest
YSO candidates may have masses of an order of tenths of the solar mass,
assuming the age of 1 Myr. We examined three values as indicators of star
formation; fraction of the YSO candidates, extinctions of all sources, and
near-infrared excesses of the YSO candidates. All indicators increase from
outside of the rim to the center of the molecular cloud, which suggests that
the formation of the low-mass stars in the BRC 14 region proceeds from outside
to the center of the cloud.


title: RR Lyrae Variables in M33. I. Evidence For a Field Halo Population

abstract:
  We present observations of RR Lyrae variables in the Local Group late-type
spiral galaxy M33. Using the Advanced Camera for Surveys on the Hubble Space
Telescope, we have identified 64 ab-type RR Lyraes in M33. We have estimated
reddenings for these stars based on their minimum light V-I colors and
metallicities based on their periods. From the distributions of these
properties, we conclude that the RR Lyraes belong to two populations - one
associated with the halo of M33 and the other with its disk. Given that RR
Lyraes are produced by populations older than ~10 Gyr, this suggests that not
only does the field halo of M33 contain an old component, but so does its disk.
This is one of the best pieces of evidence for the existence of a halo field
component in M33. Using a relation between RR Lyrae absolute magnitude and
metallicity (Mv(RR) = 0.23[Fe/H] + 0.93), we estimate a mean distance modulus
of <(m-M)o> = 24.67 +/- 0.08 for M33. This places M33 approximately 70 kpc
beyond M31 in line-of-sight distance.


title:
Parameterization of Gamma, e^+/- and Neutrino Spectra Produced by p-p
  Interaction in Astronomical Environment

abstract:
  We present the yield and spectra of stable secondary particles (gamma, e^+/-,
nu_e, nubar_e, nu_mu, and nubar_mu) of p-p interaction in parameterized
formulae to facilitate calculations involving them in astronomical
environments. The formulae are derived on the up-to-date p-p interaction model
by [Kamae05] which incorporates the logarithmically rising inelastic
cross-section, the diffraction dissociation process, and the Feynman scaling
violation. To improve fidelity to experimental data in lower energies, two
baryon resonance contributions have been added: one representing Delta(1232)
and the other multiple resonances around 1600MeV/c^2. The parametrized formulae
predict that all secondary particle spectra be harder by about 0.05 in
power-law indices than that of the incident proton and their inclusive
cross-sections be larger than those predicted by p-p interaction models based
on the Feynman scaling.


title: APEX mapping of H3O+ in the Sgr B2 region

abstract:
  The cosmic-ray ionization rate (zeta) of dense molecular clouds is a key
parameter for their dynamics and chemistry. Variations of zeta are well
established, but it is unclear if these are related to source column density or
to Galactic location. Using the APEX telescope, we have mapped the 364 GHz line
of H3O+ in the Sgr B2 region and observed the 307 GHz line at selected
positions. With the IRAM 30-m telescope we have observed the 203 GHz line of
H2O-18 at the same positions. Strong H3O+ emission is detected over a ~3x2 pc
region, indicating H3O+ column densities of 10^15 - 10^16 cm^-2 in an 18" beam.
The H3O+ abundance of ~3 x 10^-9 and H3O+/H2O ratio of ~1/50 in the Sgr B2
envelope are consistent with models with zeta ~4 x 10^-16 s^-1, 3x lower than
derived from H3+ observations toward Sgr A, but 10x that of local dense clouds.
The ionization rates of interstellar clouds thus seem to be to first order
determined by the ambient cosmic-ray flux, while propagation effects cause a
factor of ~3 decrease from diffuse to dense clouds.


title: Does simultaneous solution matter for stellar evolution codes?

abstract:
  A version of the STARS stellar evolution code has been developed that uses a
non-simultaneous solution of the equations of stellar structure and evolution.
In all other respects it is identical to the normal, fully simultaneous
version. It is therefore possible to test the dependence of the solution on how
the equations are solved. Two cases are investigated: a 5Msol and a 3Msol star,
both of metallicity Z=0.02. Prior to the asymptotic giant branch, the models
are almost identical. However once thermal pulses start, the two methods of
solution yield diverging results with the non-simultaneous technique predicting
longer interpulse periods. This is traced to difficulties associated with
hydrogen burning caused by the use of a moving mesh. It is shown that, with
careful control of the temporal resolution, the results of the simultaneous
technique can be recovered.


title:
A Spitzer Space Telescope study of SN 2002hh: an infrared echo from a
  Type IIP supernova

abstract:
  We present late-time (590-994 d) mid-IR photometry of the normal, but
highly-reddened Type IIP supernova SN 2002hh. Bright, cool, slowly-fading
emission is detected from the direction of the supernova. Most of this flux
appears not to be driven by the supernova event but instead probably originates
in a cool, obscured star-formation region or molecular cloud along the
line-of-sight. We also show, however, that the declining component of the flux
is consistent with an SN-powered IR echo from a dusty progenitor CSM. Mid-IR
emission could also be coming from newly-condensed dust and/or an ejecta/CSM
impact but their contributions are likely to be small. For the case of a CSM-IR
echo, we infer a dust mass of as little as 0.036 M(solar) with a corresponding
CSM mass of 3.6(0.01/r(dg))M(solar) where r(dg) is the dust-to-gas mass ratio.
Such a CSM would have resulted from episodic mass loss whose rate declined
significantly about 28,000 years ago. Alternatively, an IR echo from a
surrounding, dense, dusty molecular cloud might also have been responsible for
the fading component. Either way, this is the first time that an IR echo has
been clearly identified in a Type IIP supernova. We find no evidence for or
against the proposal that Type IIP supernovae produce large amounts of dust via
grain condensation in the ejecta. However, within the CSM-IR echo scenario, the
mass of dust derived implies that the progenitors of the most common of
core-collapse supernovae may make an important contribution to the universal
dust content.


title:
The U-shaped distribution of globular cluster specific frequencies in a
  biased globular cluster formation scenario

abstract:
  Using high-resolution numerical simulations, we investigate mass- and
luminosity-normalized specific frequencies (T_N and S_N, respectively) of
globular cluster systems (GCSs) in order to understand the origin of the
observed U-shaped relation between S_N and V-band magnitude (M_V) of their host
galaxies.
  We adopt a biased GC formation scenario in which GC formation is truncated in
galaxy halos that are virialized at a later redshift, z_trun. T_N is derived
for galaxies with GCs today and converted into S_N for reasonable galaxy
mass-to-light-ratios (M/L). We find that T_N depends on halo mass (M_h) in the
sense that T_N can be larger in more massive halos with M_h > 10^9 M_sun, if
z_trun is as high as 15. We however find that the dependence is too weak to
explain the observed S_N-M_V relation and the wide range of S_N in low-mass
early-type galaxies with -20.5 < M_V < -16.0 mag for a reasonable constant M/L.
The M_V-dependence of S_N for the low-mass galaxies can be well reproduced, if
the mass-to-light-ratio M_h/L_V \propto M_h^{\alpha}, where \alpha is as steep
as -1. Based on these results, we propose that the origin of the observed
U-shaped S_N-M_V relation of GCSs can be understood in terms of the bimodality
in the dependence of M_h/L_V on M_h of their host galaxies. We also suggest
that the observed large dispersionin S_N in low-mass galaxies is due partly to
the large dispersion in T_N.


title:
Low-mass star formation in R Coronae Australis: Observations of organic
  molecules with the APEX telescope

abstract:
  This paper presents new APEX submillimetre molecular line observations of
three low-mass protostars, IRS7A, IRS7B, and IRAS32, in the R Coronae Australis
molecular cloud complex. The molecular excitation analysis is performed using a
statistical equilibrium radiative transfer code. The derived beam averaged
fractional abundances vary by less than a factor of two among the three
sources, except those of H2CO and CH3OH, which show differences of about an
order of magnitude. The molecular abundances are similar to those typically
found in other star-forming regions in the Galaxy, such as the $\rho$~Oph and
Perseus molecular clouds. There is a marked difference in the kinetic
temperatures derived for the protobinary source IRS7 from H2CO (40-60 K) and
CH3OH (20 K), possibly indicating a difference in origin of the emission from
these two molecules.


title:
A Quasi-Periodic Modulation of the Radio Light Curve of the Blazar PKS
  B0048-097

abstract:
  In this letter we present the results of a wavelet analysis of the radio
light curve of the BL Lac Object PKS B0048-097 from the University of Michigan
Radio Astronomy Observatory monitoring program at 8GHz during twenty-five
years, from 1979 to 2004. The results show a remarkable periodicity of 450-470
days in the early 1980s that changed to a ~585 day periodicity in the late
1980s to early 1990s. A less pronounced ~400 day periodicity is found after
\~1995. Very-long-baseline interferometry imaging at 15GHz shows dramatic
structural changes in the usually unresolved source between two epochs, 1995.57
and 2002.38. The pronounced northward directed jet seen in the 2002 image
differs by more than 90 degrees in direction from the source structure found in
earlier epochs. These findings make PKS B0048-097 a primary target for
multi-wavelength observations and intensive radio monitoring to decipher the
blazar-variability phenomenon.


title: Dwarf novae in the Hamburg Quasar Survey: Rarer than expected

abstract:
  We report the discovery of five new dwarf novae from the Hamburg Quasar
Survey (HQS), and discuss the properties of the sample of dwarf novae in the
HQS. The orbital periods of the new dwarf novae are ~105.1 min or ~109.9 min,
114.3+-2.7 min, 92.66+-0.17 min, 272.317+-0.001 min, 258.02+-0.56 min for
HS0417+7445, HS1016+3412, HS1340+1524, HS1857+7127, and HS2214+2845,
respectively. HS1857+7127 is found to be partially eclipsing. In HS2214+2845
the secondary star of spectral type M3+-1 is clearly detected, and we estimate
the distance to the system to be d=390+-40 pc. We recorded one superoutburst of
the SU UMa system HS0417+7445. HS1016+3412 and HS1340+1524 have rare outbursts,
and their subtype is yet undetermined. HS1857+7127 frequently varies in
brightness and may be a Z Cam-type dwarf nova. HS2214+2845 is a U Gem-type
dwarf nova with a most likely cycle length of 71 d. To date, 14 new dwarf novae
have been identified in the HQS. The ratio of short-period (<3 h) to
long-period (>3 h) systems of this sample is 1.3, much smaller compared to the
ratio of 2.7 found for all known dwarf novae. The HQS dwarf novae display
typically infrequent or low-amplitude outburst activity, underlining the
strength of spectroscopic selection in identifying new CVs independently of
their variability. The spectroscopic properties of short-period CVs in the HQS
suggest that most of them are still evolving towards the minimum period. Their
total number agrees with the predictions of population models within an order
of magnitude. However, the bulk of all CVs is predicted to have evolved past
the minimum period, and those systems remain unidentified. Those post-bounce
systems may have markedly weaker Hbeta emission lines compared to the average
known short-period CVs, and probably undergo no or extremely rare outbursts.


title:
Deep Extragalactic Surveys around the Ecliptic Poles with AKARI
  (ASTRO-F)

abstract:
  AKARI (formerly ASTRO-F) is an infrared space telescope designed for an
all-sky survey at 10-180 (mu)m, and deep pointed surveys of selected areas at
2-180 (mu)m. The deep pointed surveys with AKARI will significantly advance our
understanding of galaxy evolution, the structure formation of the Universe, the
nature of the buried AGNs, and the cosmic infrared background. Here we describe
the important characteristics of the AKARI mission: the orbit, and the attitude
control system, and investigate the optimum survey area based on the updated
pre-flight sensitivities of AKARI, taking into account the cirrus confusion
noise as well as the surface density of bright stars. The North Ecliptic Pole
(NEP) is concluded to be the best area for 2-26 (mu)m deep surveys, while the
low-cirrus noise regions around the South Ecliptic Pole (SEP) are worth
considering for 50-180 (mu)m pointed surveys to high sensitivities limited by
the galaxy confusion noise. Current observational plans of these pointed
surveys are described in detail. Comparing these surveys with the deep surveys
with the Spitzer Space Telescope, the AKARI deep surveys are particularly
unique in respect of their continuous wavelength coverage over the 2-26 (mu)m
range in broad-band deep imaging, and their slitless spectroscopy mode over the
same wavelength range.


title: On the origin of the X-ray emission from Herbig Ae/Be stars

abstract:
  We performed a systematic search for Chandra archival observations of Herbig
Ae/Be stars. These stars are fully radiative and not expected to support dynamo
action analogous to their convective lower-mass counterparts, the T Tauri
stars. Their X-ray emission has remained unexplained. The superior spatial
resolution of Chandra with respect to previous X-ray instrumentation has
allowed us to examine the possible role of late-type companions in generating
the observed X-rays. In the total sample of 17 Herbig Ae/Be stars, 8 are
resolved from X-ray emitting faint companions or other unrelated X-ray bright
objects within 10". The detection fraction of Herbig Ae/Be stars is 76 %, but
lowers to 35 % if all emission is attributed to further known and unresolved
companions. The spectral analysis confirms the high X-ray temperatures (~ 20
MK) and large range of fractional X-ray luminosities (log L_x/L_star) of this
class derived from earlier studies of individual objects. Radiative winds are
ruled out as emission mechanism on basis of the high temperatures. The X-ray
properties of Herbig Ae/Be stars are not vastly different from those of their
late-type companion stars (if such are known), nor from other young late-type
stars used for comparison. Therefore, either a similar kind of process takes
place on both classes of objects, or there must be as yet undiscovered
companion stars.


title: Weak lensing survey of galaxy clusters in the CFHTLS Deep

abstract:
  AIMS: We present a weak lensing search of galaxy clusters in the 4 deg2 of
the CFHT Legacy Survey Deep. This work aims at building a mass-selected sample
of clusters. METHODS: We use the deep i' band images to perform weak lensing
mass reconstructions and to identify high convergence peaks. Thanks to the
availability of deep ugriz exposures, sources are selected from their
photometric redshifts. We also use lensing tomography to derive an estimate of
the lens redshift. After considering the raw statistics of peaks we check
whether they can be associated to a clear optical counterpart or to published
X-ray selected clusters. RESULTS: Among the 14 peaks found above a
signal-to-noise detection threshold nu=3.5, eight are secure detections with
estimated redshift 0.15<zl<0.6 and a velocity dispersion 450<sigma\_v<600 km/s.
This low mass range is accessible thanks to the high density of background
sources. We also use photometric redshifts of sources to test the effect of
contamination by source-lens clustering for clusters detection. This latter
turns out to play a minor role in our cluster sample. We study the intersection
between the shear-selected clusters and XMM/LSS X-ray clusters in the D1 field.
[ABRIDGED]


title:
Massive Star Cluster Populations in Irregulars as Probable Younger
  Counterparts of Old Metal-Rich Globular Cluster Populations in Spheroids

abstract:
  Peak metallicities of metal-rich(MR) populations of GCs belonging to
spheroids of different mass fall within the somewhat conservative
-0.7<=[Fe/H]<=-0.3 range. Indeed, if possible age effects are taken into
account,this metallicity range might become smaller. Irregulars, like the LMC,
with longer timescales of their formation and lower star formation (SF)
efficiency do not contain the old MRGCs with [Fe/H]>-1.0,but they are observed
to form populations of young/ intermediate-age massive star clusters (MSCs)
with masses exceeding 10^4 Msol. Their formation is widely believed to be
accidental process fully depending on external factors. From analysis of data
available on the populations and their hosts, including populous star clusters
in the LMC, we find that their most probable mean metallicities fall within
-0.7<=[Fe/H]<=-0.3, as the peak metallicities of MRGCs do, irrespective of
sings of interaction. Moreover, both the disk giant metallicity distribution
function (MDF) in the LMC and the MDFs for old giants in the halos of massive
spheroids exhibit significant increasing toward [Fe/H]~-0.5. That is in
agreement with a correlation found between SF activity in galaxies and their
metallicity. The formation of both the old MRGCs in spheroids and MSC
populations in irregulars probably occurs approximately at the same stage of
the host galaxies' chemical evolution and is related to the essentially
increased SF activity in the hosts around the same metallicity that is achieved
very soon in massive spheroids, later in lower-mass spheroids, and much more
later in irregulars. (Abridged)


title:
The Starburst-Interstellar Medium Interaction in NGC 1569 II.
  Small-Scale Examination of Nebular Emission, H II Region Size Distribution,
  and H II Region Luminosity Function

abstract:
  (abridged) NGC 1569 is an ideal test environment to understand the impact of
"feedback" from massive stars on the surrounding ISM. We present HST WFPC2
narrowband imagery of NGC 1569 in an attempt to understand the underlying
ionizing emission mechanisms on a 3 pc scale and to generate a H II region size
distribution and luminosity function. We use [O III]/Hbeta and [S II]/Halpha
ratio maps to find that non-photoionizing mechanisms (e.g. shocks) are
responsible for 10%+/-3% of the Halpha emission, 2.3-3.3 times larger than
results from similar galaxies. Our results for NGC 1569 indicate that these
non-photoionized areas do not lie in low surface brightness regions
exclusively. To explain this large percentage of non-photoionized emission, we
suggest that NGC 1569 is, indeed, in a post-starburst phase as previous authors
have claimed. We also derived slopes for the H II region luminosity function
(-1.00+/-0.08) and size distribution (-3.02+/-0.27). The luminosity slope,
though shallow, is similar to previous work on this galaxy and other irregular
galaxies. The size distribution slope is shallower than previous slopes found
for irregular galaxies, but our slope value fits into their confidence
intervals and vice versa.


title: Systematic effects in the sound horizon scale measurements

abstract:
  We investigate three potential sources of bias in distance estimations made
assuming that a very simple estimator of the baryon acoustic oscillation (BAO)
scale provides a standard ruler. These are the effects of the non-linear
evolution of structure, scale-dependent bias and errors in the survey window
function estimation. The simple estimator used is the peak of the smoothed
correlation function, which provides a variance in the BAO scale that is close
to optimal, if appropriate low-pass filtering is applied to the density field.
While maximum-likelihood estimators can eliminate biases if the form of the
systematic error is fully modeled, we estimate the potential effects of un- or
mis-modelled systematic errors. Non-linear structure growth using the Smith et
al. (2003) prescription biases the acoustic scale by <0.3% at z>1 under the
correlation-function estimator. The biases due to representative but simplistic
models of scale-dependent galaxy bias are below 1% at z>1 for bias behaviour in
the realms suggested by halo model calculations, which is expected to be below
statistical errors for a 1000 sq.degs. spectroscopic survey. The distance bias
due to a survey window function errors is given in a simple closed form and it
is shown it has to be kept below 2% not to bias acoustic scale more than 1% at
z=1, although the actual tolerance can be larger depending upon galaxy bias.
These biases are comparable to statistical errors for ambitious surveys if no
correction is made for them. We show that RMS photometric zero-point errors (at
limiting magnitude 25 mag) below 0.14 mag and 0.01 mag for redshift z=1 (red
galaxies) and z=3 (Lyman-break galaxies), respectively, are required in order
to keep the distance estimator bias below 1%.


title: Temperature Variations and Chemical Abundances in Planetary Nebulae

abstract:
  In this review we present a brief discussion on the observational evidence in
favor of the presence of temperature variations, and conclude that many
planetary nebulae show spatial temperature variations that are larger than
those predicted by 1D static chemically homogeneous photoionization models. To
determine accurate chemical abundances it is necessary to know the cause of
these temperature variations and several possibilities are discussed. The
importance of this problem is paramount to test the models of stellar evolution
of low and intermediate mass stars and of the chemical evolution of galaxies.
We conclude that the proper abundances for chemically homogeneous PNe are those
derived from recombination lines, while for the two-abundance nebular model the
proper heavy element abundances relative to hydrogen are those derived from
visual and UV collisionally excited lines adopting the t2 values derived from
Te([OIII]) and Te(Balmer)