title: Stability of Magnetic Equilibria in Radio Balloons

abstract:
  Current-carrying flows, in the laboratory and in astrophysical jets, can form
remarkably stable magnetic structures. Decades of experience shows that such
flows often build equilibria that reverse field directions, evolving to an MHD
Taylor state, which has remarkable stability properties. We model jets and the
magnetic bubbles they build as reversed field pinch equilibria by assuming the
driver current to be stiff in the MHD sense. Taking the jet current as rigid
and a fixed function of position, we prove a theorem: that the same, simple MHD
stability conditions guarantee stability, even after the jet turns off. This
means that magnetic structures harboring a massive inventory of magnetic energy
can persist long after the building jet current has died away. These may be the
relic radio "fossils," "ghost bubbles" or "magnetic balloons" found in
clusters. These equilibria under magnetic tension will evolve, retaining the
stability properties from that state. The remaining fossil is not a disordered
ball of magnetic fields, but a stable structure under tension, able to respond
to the slings and arrows of outside forces. Typically their Alfven speeds
greatly exceed the cluster sound speed, and so can keep out hot cluster
plasmas, leading to x-ray "ghosts." Passing shocks cannot easily destroy them,
but can energize and light them up anew at radio frequencies. Bubbles can rise
in the hot cluster plasma, perhaps detaching from the parent radio galaxy, yet
stable against Rayleigh-Taylor and other modes.


title: Planetary Nebulae as Mass Tracers in Galaxies

abstract:
  Planetary nebula are useful kinematic tracers of the stars in all galaxy
types. I review recent observationally-driven developments in the study of
galaxy mass profiles. These have yielded surprising results on spiral galaxy
disk masses and elliptical galaxy halo masses. A key remaining question is the
coupling between PNe and the underlying stellar populations.


title: The gamma-ray burst monitor for Lobster-ISS

abstract:
  Lobster-ISS is an X-ray all-sky monitor experiment selected by ESA two years
ago for a Phase A study (now almost completed) for a future flight (2009)
aboard the Columbus Exposed Payload Facility of the International Space
Station. The main instrument, based on MCP optics with Lobster-eye geometry,
has an energy passband from 0.1 to 3.5 keV, an unprecedented daily sensitivity
of 2x10^{-12} erg cm^{-2}s$^{-1}, and it is capable to scan, during each orbit,
the entire sky with an angular resolution of 4--6 arcmin. This X-ray telescope
is flanked by a Gamma Ray Burst Monitor, with the minimum requirement of
recognizing true GRBs from other transient events. In this paper we describe
the GRBM. In addition to the minimum requirement, the instrument proposed is
capable to roughly localize GRBs which occur in the Lobster FOV (162x22.5
degrees) and to significantly extend the scientific capabilities of the main
instrument for the study of GRBs and X-ray transients. The combination of the
two instruments will allow an unprecedented spectral coverage (from 0.1 up to
300/700 keV) for a sensitive study of the GRB prompt emission in the passband
where GRBs and X-Ray Flashes emit most of their energy. The low-energy spectral
band (0.1-10 keV) is of key importance for the study of the GRB environment and
the search of transient absorption and emission features from GRBs, both goals
being crucial for unveiling the GRB phenomenon. The entire energy band of
Lobster-ISS is not covered by either the Swift satellite or other GRB missions
foreseen in the next decade.


title: Spitzer IRS Spectroscopy of IRAS-Discovered Debris Disks

abstract:
  We have obtained Spitzer Space Telescope IRS 5.5 - 35 micron spectra of 59
main sequence stars that possess IRAS 60 micron excess. The spectra of five
objects possess spectral features that are well-modeled using micron-sized
grains and silicates with crystalline mass fractions 0% - 80%, consistent with
T-Tauri and Herbig AeBe stars. With the exception of eta Crv, these objects are
young with ages <50 Myr. The spectra for the majority of objects are
featureless, suggesting that the emitting grains probably have radii a > 10
micron. We have modeled the excess continua using a continuous disk with a
uniform surface density distribution, expected if Poynting-Robertson and
stellar wind drag are the dominant grain removal processes, and using a single
temperature black body, expected if the dust is located in a narrow ring around
the star. The IRS spectra of many objects are better modeled with a single
temperature black body, suggesting that the disks possess inner holes. The
distribution of grain temperatures, based on our black body fits, peaks at Tgr
= 110 - 130 K. Since the timescale for ice sublimation of micron-sized grains
with Tgr > 110 K is a fraction of a Myr, the lack of warmer material may be
explained if the grains are icy. If planets dynamically clear the central
portions of debris disks, then the frequency of planets around other stars is
probably high. We estimate that the majority of debris disk systems possess
parent body masses, MPB < 1 Mearth. The low inferred parent body masses suggest
that planet formation is an efficient process. (abridged abstract)


title:
Searching for modified gravity with baryon oscillations: from SDSS to
  wide field multiobject spectroscopy (WFMOS)

abstract:
  We discuss how the baryon acoustic oscillation (BAO) signatures in the galaxy
power spectrum can distinguish between modified gravity and the cosmological
constant as the source of cosmic acceleration. To this end we consider a model
characterized by a parameter $n$, which corresponds to the
Dvali-Gabadadze-Porrati (DGP) model if $n=2$ and reduces to the standard
spatially flat cosmological constant concordance model for $n$ equal to
infinity. We find that the different expansion histories of the modified
gravity models systematically shifts the peak positions of BAO. A preliminary
analysis using the current SDSS LRG sample indicates that the original DGP
model is disfavored unless the matter density parameter exceeds 0.3. The
constraints will be strongly tightened with future spectroscopic samples of
galaxies at high redshifts. We demonstrate that WFMOS, in collaboration with
other surveys such as Planck, will powerfully constrain modified gravity
alternatives to dark energy as the explanation of cosmic acceleration.


title: Southern GEMS Groups I: Dynamical Properties

abstract:
  Here we present an investigation of the properties of 16 nearby galaxy groups
and their constituent galaxies. The groups are selected from the Group
Evolution Multi-wavelength Study (GEMS) and all have X-ray as well as
wide-field neutral hydrogen (HI) observations. Group membership is determined
using a friends-of-friends algorithm on the positions and velocities from the
6-degree Field Galaxy Survey (6dFGS) and NASA/IPAC Extra-galactic Database
(NED). For each group we derive their physical properties using this
membership, including: velocity dispersions (sigma_v), virial masses (M_V),
total K-band luminosities (L_K(Tot)) and early-type fractions (f_early) and
present these data for the individual groups. We find that the GEMS X-ray
luminosity is proportional to the group velocity dispersions and virial masses:
L_X(r_500)\propto\sigma_v^{3.11\pm0.59} and L_X(r_500)\propto
M_V^{1.13\pm0.27}, consistent with the predictions of self-similarity between
group and clusters. We also find that M_V\propto L_K(Tot)^{2.0\pm0.9}, i.e.
mass grows faster than light and that the fraction of early-type galaxies in
the groups is correlated with the group X-ray luminosities and velocity
dispersions. We examine the brightest group galaxies (BGGs), finding that,
while the luminosity of the BGG correlates with its total group luminosity, the
fraction of group luminosity contained in the BGG decreases with increasing
total group luminosity. This suggests that BGGs grow by mergers at early times
in group evolution while the group continues to grow by accreting infalling
galaxies. (Abridged)


title: Exploring High-Velocity NH_3(6,6) Emission at the Center of our Galaxy

abstract:
  Using the NH\3 (6,6) transition, which samples dense ($\sim 10^{5}$)
molecular gas with an energy above ground of 412 K, we find hot gas at high
velocities (--142 to --210 km s$^{-1}$) associated with the central 2 pc of the
Galactic center. This material may be either infalling gas due to shocks or
tidal stripping, or possibly gas swept from the nuclear region. We identify two
high-velocity features, which we call the Southern Runner and the Cap, and
correlate these features with others detected in various molecular observations
of the Galactic center. The characteristic linewidths of the Southern Runner
and Cap, 10 -- 15 \kms, are similar to those of other hot Galactic center
clouds. The estimated H$_{2}$ masses of these clouds are 4$\times 10^{3}$
M$\sol$ and 2$\times 10^{3}$ M$\sol$, consistent with the masses of the western
streamer and northern ridge, NH\3 (6,6) emission features detected within the
central 10 pc at lower velocities. Three possible explanations for this
emission are discussed assuming that they lie at the Galactic center, including
sweeping by the supernova remnant Sgr A East, infall and/or shock from the
circumnuclear disk (CND), and stripping from the central rotating low-velocity
NH\3 (6,6) cloud.


title: Supernova Neutrinos: The Accretion Disk Scenario

abstract:
  Neutrinos from core collapse supernovae can be emitted from a rapidly
accreting disk surrounding a black hole, instead of the canonical proto-neutron
star. For Galactic events, detector count rates are considerable and in fact
can be in the thousands for Super-Kamiokande. The rate of occurrence of these
accreting disks in the Galaxy is predicted to be on the order of 10^-5 yr^-1,
yet there is little observational evidence to provide an upper limit on their
formation rate. It would therefore be useful to discriminate between neutrinos
which have been produced in a proto-neutron star and those which have been
produced accretion disks. In order to distinguish between the two scenarios,
either the time profile of the neutrino luminosity or the relative fluxes of
different neutrino flavors may be considered. There are some signals that would
clearly point to one scenario or the other.


title: X-Ray Emission from Jupiter, Saturn, and Earth: A Short Review

abstract:
  Jupiter, Saturn, and Earth - the three planets having dense atmosphere and a
well developed magnetosphere - are known to emit X-rays. Recently, Chandra
X-ray Observatory has observed X-rays from these planets, and XMM-Newton has
observed them from Jupiter and Saturn. These observations have provided
improved morphological, temporal, and spectral characteristics of X-rays from
these planets. Both auroral and non-auroral (low-latitude) 'disk' X-ray
emissions have been observed on Earth and Jupiter. X-rays have been detected
from Saturn's disk, but no convincing evidence for X-ray aurora on Saturn has
been observed. The non-auroral disk X-ray emissions from Jupiter, Saturn, and
Earth, are mostly produced due to scattering of solar X-rays. X-ray aurora on
Earth is mainly generated via bremsstrahlung from precipitating electrons and
on Jupiter via charge exchange of highlyionized energetic heavy ions
precipitating into the polar atmosphere. Recent unpublished work suggests that
at higher (>2 keV) energies electron bremsstrahlung also plays a role in
Jupiter's X-ray aurora. This paper summarizes the recent results of X-ray
observations on Jupiter, Saturn, and Earth mainly in the soft energy (~0.1-2.0
keV) band and provides a comparative overview.


title:
The Cornell High-order Adaptive Optics Survey for Brown Dwarfs in
  Stellar Systems-II: Results from Monte Carlo Population Analyses

abstract:
  In this second of a two-paper sequence, we present Monte Carlo population
simulation results of brown dwarf companion data collected during the Cornell
High-order Adaptive Optics Survey for brown dwarf companions (CHAOS). Making
reasonable assumptions of orbital parameters (random inclination, random
eccentricity and random longitude of pericentre) and age distributions, and
using published mass functions, we find that the brown dwarf companion fraction
around main sequence stars is 0.0%-9.3% for the 25-100 AU semi-major axis
region. We find a corresponding L-dwarf companion fraction of 0.0%-3.3%. We
compare our population analysis methods and results with techniques and results
presented by several other groups. In this comparison we discover that
systematic errors (most notably resulting from orbital projection effects)
occur in the majority of previously published brown dwarf companion population
estimates, leading authors to claim results not supported by the observational
data.


title: Brief outbursts in the dwarf nova V1316 Cygni

abstract:
  Several brief outbursts were detected in the dwarf nova V1316 Cyg during
2005. These events have an average amplitude of 1.4 magnitude and a duration of
<1 to 2 days. Whilst no outburst period could be confirmed, the shortest period
between detected events is 10 days. These curious brief outbursts appear to be
the normal pattern of behaviour for this system. They are of smaller amplitude
and shorter duration than normal outbursts previously reported in this star.
V1316 Cyg appears to be a very unusual system and we suggest that further
observations by both amateur and professional astronomers could yield important
information about the underlying mechanism.


title: The Birth of Quark Stars: Photon-driven Supernovae?

abstract:
  In this letter we propose a possible mechanism trying to alleviate the
current difficulty in core-collapse supernovae by forming a strange quark star
inside the collapsing core. Although the initial longtime cooling behavior of
nascent strange stars is dominated by neutrino emissions, thermal emissions
including photons and $e^\pm$ pair plasma do play a significant role in the
explosion dynamics under this picture. The key to promote a successful shock
outside a bare strange star is more likely to be the radiation pressure caused
by thermal photons rather than neutrinos in conventional models. We observed
through calculation that radiation pressure can push the overlying mantle away
through photon-electron scattering with energy (the work done by radiation
pressure) as much as ~10^{51} erg if protoquark stars are born with
temperatures higher than ~ (30-40) MeV. This result not only indicates that
strange quark stars should be bare ever since their formations, it could also
provide a possible explanation to the formation of fireballs in cosmic
long-soft $\gamma$-ray bursts associated to supernovae.


title:
Discovery of a new dwarf nova, TSS J022216.4+412259.9: WZ Sge-type dwarf
  novae breaking the shortest superhump period record

abstract:
  We report on the time-resolved CCD photometry of a newly discovered variable
star, TSS J022216.4+412259.9 during the outburst in 2005 November-December
brightening. The obtained light curves unambiguously showed 0.2-0.3 mag
modulations, which we confirmed to be the superhump observed among SU UMa-type
dwarf novae. We also performed a period search for the data obtained during the
outburst plateau phase, and revealed the existence of the two periodicities:
0.054868(98) days for the first two nights and 0.055544(26) days for the
following plateau phase. This bi-periodicity is hardly observed in usual SU
UMa-type dwarf novae, but characteristic of WZ Sge-type stars. We undoubtedly
detected a rebrightening in the post-outburst stage, which is typical of
short-period SU UMa-type dwarf novae including WZ Sge-type stars. These
observations suggests that TSS J022216.4+412259.9 may be a new WZ Sge stars
breaking the shortest superhump period of 0.05648 days for V592 Her among this
class with a known superhump period so far.


title: Gamma-ray binaries: pulsars in disguise ?

abstract:
  LS 5039 and LSI +61 303 are unique amongst high-mass X-ray binaries (HMXB)
for their spatially-resolved radio emission and their counterpart at >GeV
gamma-ray energies, canonically attributed to non-thermal particles in an
accretion-powered relativistic jet. The only other HMXB known to emit very high
energy (VHE) gamma-rays, PSR B1259-63, harbours a non-accreting millisecond
pulsar. I investigate whether the interaction of the relativistic wind from a
young pulsar with the wind from its stellar companion, as in PSR B1259-63,
constitutes a viable scenario to explain the observations of LS 5039 and LSI
+61 303. Emission would arise from the shocked pulsar wind material, which then
flows away to large distances in a comet-shape tail, reproducing on a smaller
scale what is observed in isolated, high motion pulsars interacting with the
ISM. Simple expectations for the SED are derived and are shown to depend on few
input parameters. Detailed modelling of the particle evolution is compared to
the observations from radio to TeV energies. Acceleration at the shock provides
high energy electrons that steadily emit synchrotron in X-rays and inverse
Compton scatter stellar light to gamma-rays. Electrons streaming out of the
system emit at IR frequencies and below. The overall aspect of the SEDs is
adequately reproduced for standard values of the parameters. The morphology of
the radio tail can mimic a microquasar jet. Good agreement is found with the
published VLBI map of LS 5039 and predictions are made on the expected change
in appearance with orbital phase. The pulsar wind scenario can provide a
common, viable framework to interpret the emission from all three gamma-ray
binaries.


title:
On-axis spectroscopy of the host galaxies of 20 optically luminous
  quasars at z~0.3

abstract:
  We present the analysis of a sample of 20 bright low-redshift quasars
(M_B<-23 and z < 0.35) observed spectroscopically with the VLT. The FORS1
spectra, obtained in Multi Object Spectroscopy (MOS) mode, allow to observe
simultaneously the quasars and several reference stars used to spatially
deconvolve the data. Applying the MCS deconvolution method, we are able to
separate the individual spectra of the quasar and of the underlying host
galaxy. Contrary to some previous claims, we find that luminous quasars are not
exclusively hosted by massive ellipticals. Most quasar host galaxies harbour
large amounts of gas, irrespective of their morphological type. Moreover, the
stellar content of half of the hosts is a young Sc-like population, associated
with a rather low metallicity interstellar medium. A significant fraction of
the galaxies contain gas ionized at large distances by the quasar radiation.
This large distance ionization is always associated with signs of gravitational
interactions (as detected from images or disturbed rotation curves). The
spectra of the quasars themselves provide evidence that gravitational
interactions bring dust and gas in the immediate surrounding of the super
massive black hole, allowing to feed it. The quasar activity might thus be
triggered (1) in young gas-rich spiral galaxies by local events and (2) in more
evolved galaxies by gravitational interactions or collisions. The latter
mechanism gives rises to the most powerful quasars. Finally, we derive mass
models for the isolated spiral host galaxies and we show that the most reliable
estimators of the systemic redshift in the quasar spectrum are the tips of the
Ha and Hb lines.


title:
Deficiency of large equivalent width Lyman-alpha emission in luminous
  Lyman break galaxies at z~5-6?

abstract:
  We report a deficiency of luminous Lyman break galaxies (LBGs) with a large
rest-frame equivalent width (EW_rest) of Lyman-alpha emission at z~5-6.
Combining our spectroscopic sample of LBGs at z~5 and those from the
literature, we found that luminous LBGs at z~5-6 generally show weak
Lyman-alpha emissions, while faint LBGs show a wide range of Lyman-alpha
EW_rest and tend to have strong (EW_rest >20A) Lyman-alpha emissions; i.e.,
there is a deficiency of strong Lyman-alpha emission in luminous LBGs. There
seems to be a threshold UV luminosity for the deficiency; it is M_1400 = -21.5
\~ -21.0 mag, which is close to or somewhat brighter than the M* of the UV
luminosity function at z~5 and 6. Since the large EW_rest of Lyman-alpha
emission can be seen among the faint LBGs, the fraction of Lyman-alpha emitters
in LBGs may change rather abruptly with the UV luminosity. If the weakness of
Lyman-alpha emission is due to dust absorption, the deficiency suggests that
luminous LBGs at z=5-6 tend to be in dusty and more chemically evolved
environments and started star formation earlier than faint ones, though other
causes cannot be ruled out.


title:
On the ionisation fraction in protoplanetary disks III. The effect of
  X-ray flares on gas-phase chemistry

abstract:
  Context. Recent observations of the X-ray emission from T Tauri stars in the
Orion nebula have shown that they undergo frequent outbursts in their X-ray
luminosity. These X-ray flares are characterised by increases in luminosity by
two orders of magnitude, a typical duration of less than one day, and a
significant hardening of the X-ray spectrum.
  Aims. It is unknown what effect these X-ray flares will have on the
ionisation fraction and dead-zone structure in protoplanetary disks. We present
the results of calculations designed to address this question.
  Methods. We have performed calculations of the ionisation fraction in a
standard $\alpha$-disk model using two different chemical reaction networks. We
include in our models ionisation due to X-rays from the central star, and
calculate the time-dependent ionisation fraction and dead--zone structure for
the inner 10 AU of a protoplanetary disk model.
  Results. We find that the disk response to X-ray flares depends on whether
the plasma temperature increases during flares and/or whether heavy metals
(such as magnesium) are present in the gas phase. Under favourable conditions
the outer disk dead--zone can disappear altogether,and the dead-zone located
between 0.5 < R < 2 AU can disappear and reappear in phase with the X-ray
luminosity.
  Conclusions. X-ray flares can have a significant effect on the dead-zone
structure in protoplanetary disks. Caution is required in interpreting this
result as the duration of X-ray bursts is considerably shorter than the growth
time of MHD turbulence due to the magnetorotational instability.


title: The Properties of Cataclysmic Variables In Photometric Halpha Surveys

abstract:
  We report on the properties of 71 known cataclysmic variables (CVs) in
photometric Halpha emission line surveys. Our study is motivated by the fact
that the Isaac Newton Telescope (INT) Photometric Halpha Survey of the northern
galactic plane (IPHAS) will soon provide r', i' and narrow-band Halpha
measurements down to r' \simeq 20 for all northern objects between -5 degrees <
b < +5 degrees. IPHAS thus provides a unique resource, both for studying the
emission line properties of known CVs and for constructing a new CV sample
selected solely on the basis of Halpha excess. Our goal here is to carry out
the first task and prepare the way for the second. In order to achieve this, we
analyze data on 19 CVs already contained in the IPHAS data base and supplement
this with identical observations of 52 CVs outside the galactic plane.
  Our key results are as follows: (i) the recovery rate of known CVs as Halpha
emitters in a survey like IPHAS is \simeq 70 per cent; (ii) of the \simeq 30
per cent of CVs which were not recovered \simeq 75 per cent were clearly
detected but did not exhibit a significant Halpha excess at the time of our
observations; (iii) the recovery rate depends only weakly on CV type; (iv) the
recovery rate depends only weakly on orbital period; (v) short-period dwarf
novae tend to have the strongest Halpha lines. These results imply that
photometric emission line searches provide an efficient way of constructing CV
samples that are not biased against detection of intrinsically faint,
short-period systems.


title:
X-ray Galaxy Clusters in NoSOCS: Substructure and the Correlation of
  Optical and X-ray Properties

abstract:
  We present a comparison of optical and X-ray properties of galaxy clusters in
the northern sky. We determine the recovery rate of X-ray detected clusters in
the optical as a function of richness, redshift and X-ray luminosity, showing
that the missed clusters are typically low contrast systems when observed
optically. We employ four different statistical tests to test for the presence
of substructure using optical two-dimensional data, finding that approximately
35% of the clusters show strong signs of substructure. However, the results are
test-dependent, with variations also due to the magnitude range and radius
utilized.We have also performed a comparison of X-ray luminosity and
temperature with optical galaxy counts (richness). We find that the slope and
scatter of the relations between richness and the X-ray properties are heavily
dependent on the density contrast of the clusters. The selection of
substructure-free systems does not improve the correlation between X-ray
luminosity and richness, but this comparison also shows much larger scatter
than one obtained using the X-ray temperature. In the latter case, the sample
is significantly reduced because temperature measurements are available only
for the most massive (and thus high contrast) systems. However, the comparison
between temperature and richness is very sensitive to the exclusion of clusters
showing signs of substructure. The correlation of X-ray luminosity and richness
is based on the largest sample to date ($\sim$ 750 clusters), while tests
involving temperature use a similar number of objects as previous works
($\lsim$100). The results presented here are in good agreement with existing
literature.


title:
C+O detonations in thermonuclear supernovae: Interaction with previously
  burned material

abstract:
  In the context of explosion models for Type Ia Supernovae, we present one-
and two-dimensional simulations of fully resolved detonation fronts in
degenerate C+O White Dwarf matter including clumps of previously burned
material. The ability of detonations to survive the passage through sheets of
nuclear ashes is tested as a function of the width and composition of the ash
region. We show that detonation fronts are quenched by microscopically thin
obstacles with little sensitivity to the exact ash composition. Front-tracking
models for detonations in macroscopic explosion simulations need to include
this effect in order to predict the amount of unburned material in delayed
detonation scenarios.


title: Why Do T Tauri Disks Accrete?

abstract:
  Observations of T Tauri stars and young brown dwarfs suggest that the
accretion rates of their disks scale strongly with the central stellar mass,
approximately $\mdot \propto M_*^2$. No dependence of accretion rate on stellar
mass is predicted by the simplest version of the layered disk model of Gammie
(1996), in which non-thermal ionization of upper disk layers allows accretion
to occur via the magnetorotational instability. We show that a minor
modification of Gammie's model to include heating by irradiation from the
central star yields a modest dependence of $\mdot$ upon the mass of the central
star. A purely viscous disk model could provide a strong dependence of
accretion rate on stellar mass if the initial disk radius (before much viscous
evolution has occurred) has a strong dependence on stellar mass. However, it is
far from clear that at least the most massive pre-main sequence disks can be
totally magnetically activated by X-rays or cosmic rays. We suggest that a
combination of effects are responsible for the observed dependence, with the
lowest-mass stars having the lowest mass disks, which can be thoroughly
magnetically active, while the higher-mass stars have higher mass disks which
have layered accretion and relatively inactive or ``dead'' central zones at
some radii. In such dead zones, we suggest that gravitational instabilities may
play a role in allowing accretion to proceed. In this connection, we emphasize
the uncertainty in disk masses derived from dust emission, and argue that T
Tauri disk masses have been systematically underestimated by conventional
analyses. Further study of accretion rates, especially in the lowest-mass
stars, would help to clarify the mechanisms of accretion in T Tauri stars.


title:
Estimating the Radiative Efficiency of Magnetized Accretion Disks Around
  Black Holes

abstract:
  Simulations of black hole accretion have shown that magnetic stresses are
present near and inside the innermost stable circular orbit (ISCO). This
finding suggests that such flows may be more luminous than predicted by the
standard accretion disk model. Here we apply a prescription for heat
dissipation within the simulated accretion flows to estimate their implied
radiative efficiency. We assume that dissipation is proportional to the current
density squared, and find that the resulting azimuthally-averaged and
shell-integrated radial profile is well-matched to the radial heat dissipation
profile of the standard disk model for the region outside the ISCO,
particularly when it is adjusted to account for additional stress at the ISCO.
In contrast to the standard model, however, the dissipation profile derived
from the current density continues past the ISCO and through the plunging
region. The total predicted dissipation rate is between $\simeq 30%$ and
$\simeq 100%$ greater than that predicted by the standard model, depending on
the black hole spin. Most of the additional dissipation takes place just
outside the ISCO. To predict luminosities, we assume instantaneous radiation
and zero optical depth, but allow for photon capture. The net radiative
efficiency seen by a distant observer is increased relative to the standard
model by $\simeq 25%$--80%, with the largest fractional increase for
intermediate black hole spins because the increase in dissipation from enhanced
stress that occurs for rapid spin is partially offset by the increased
likelihood that the additional photons will be captured by the hole.


title: The Influence of Large-Scale Structure on Halo Shapes and Alignments

abstract:
  Alignments of galaxy clusters (the Binggeli effect), as well as of galaxies
themselves have long been studied both observationally and theoretically. Here
we test the influence of large-scales structures and tidal fields on the shapes
and alignments of cluster-size and galaxy-size dark matter halos. We use a
high-resolution N-body simulation of a $\Lambda$CDM universe, together with the
results of Colberg et al. (2005), who identified filaments connecting pairs of
clusters. We find that cluster pairs connected by a filament are strongly
aligned with the cluster-cluster axis, whereas unconnected ones are not. For
smaller, galaxy-size halos, there also is an alignment signal, but its strength
is independent of whether the halo is part of an obvious large-scale structure.
Additionally, we find no measureable dependence of galaxy halo shape on
membership of a filament. We also quantify the influence of tidal fields and
find that these do correlate strongly with alignments of halos. The alignments
of most halos are thus caused by tidal fields, with cluster-size halos being
strongly aligned through the added mechanism of infall of matter from
filaments.


title:
Optical/near-infrared observations of the black hole candidate XTE
  J1720-318: from high-soft to low-hard state

abstract:
  Aims: To gain a better understanding of high-energy Galactic sources, we
observed the Galactic X-ray binary and black hole candidate XTE J1720-318 in
the optical and near-infrared, just after the onset of its X-ray outburst in
January, 2003. These observations were obtained with the ESO/NTT as the Target
of Opportunity, in February and April 2003. Methods: We performed an accurate
astrometry and analysed photometrical and spectroscopic observations. We then
produced a colour-magnitude diagram, looked at the overall evolution of the
multi-wavelength light curve, and analysed the spectral energy distribution.
Results: We discovered the optical counterpart in the R-band (R ~ 21.5) and
confirmed the near-infrared counterpart. We show that, for an absorption
between 6 and 8 magnitudes, XTE J1720-318 is likely to be an intermediate mass
X-ray binary located at a distance between 3 and 10 kpc, hosting a main
sequence star of spectral type between late B and early G. Our second set of
observations took place simultaneously with the third secondary outburst
present in X-ray and near-infrared light curves. The evolution of its spectral
energy distribution shows that XTE J1720-318 entered a transition from a
high-soft to a low-hard state in-between the two observations.


title: A FIRST-APM-SDSS survey for high-redshift radio QSOs

abstract:
  We selected from VLA-FIRST a sample of 94 objects starlike in SDSSS, and with
APM colour O-E>2, i.e. consistent with their being high-z QSOs. 78 candidates
were classified spectroscopically from published data (mainly SDSS) or
observations reported here. The fractions of QSOs (51/78) and z > 3 QSOs
(23/78) are comparable to those found in other photometric searches for high-z
QSOs. We confirm that O-E>2 ensures inclusion of all QSOs with 3.7 < z < 4.4.
The fraction of broad absorption line (BAL) QSOs for 2 < z < 4.4 is 27+-10 per
cent (7/26), and the estimated BAL fraction for radio loud (RL) QSOs is at
least as high as for optically selected QSOs (about 13 per cent). The high BAL
fraction and the high fraction of LoBALs in our sample are likely due to the
red colour selection. The space density of RL QSOs for 3.7 < z < 4.4, MAB (1450
A) < -26.6 and P(1.4 GHz) > 10^25.7 W Hz^(-1) is 1.7+-0.6 Gpc^(-3). Adopting a
RL fraction 13.4+-3 per cent, this corresponds to rho = 12.5+-5.6 Gpc^(-3), in
good agreement with the SDSS QSO luminosity function in Fan et al. (2001). We
note the unusual QSO FIRST 1413+4505 (z=3.11), which shows strong associated
Lyalpha absorption and an extreme observed luminosity, L about 2 x 10^(15)
solar luminosities.


title: Energy Injection in GRB Afterglow Models

abstract:
  We extend the standard fireball model, widely used to interpret gamma-ray
burst (GRB) afterglow light curves, to include energy injections, and apply the
model to the afterglow light curves of GRB 990510, GRB 000301C and GRB 010222.
We show that discrete energy injections can cause temporal variations in the
optical light curves and present fits to the light curves of GRB 000301C as an
example. A continuous injection may be required to interpret other bursts such
as GRB 010222. The extended model accounts reasonably well for the observations
in all bands ranging from X-rays to radio wavelengths. In some cases, the radio
light curves indicate that additional model ingredients may be needed.


title:
Ages and metallicities of early-type galaxies in the SDSS: new insight
  into the physical origin of the colour-magnitude and the Mg2-sigmaV relations

abstract:
  We exploit recent constraints on the ages and metallicities of early-type
galaxies in the Sloan Digital Sky Survey (SDSS) to gain new insight into the
physical origin of two fundamental relations obeyed by these galaxies: the
colour-magnitude and the Mg2-sigmaV relations. Our sample consists of 26,003
galaxies selected from the SDSS DR2 on the basis of their concentrated light
profiles, for which we have previously derived median-likelihood estimates of
stellar metallicity, light-weighted age and stellar mass. Our analysis provides
the most unambiguous demonstration to date of the fact that both relations are
primarily sequences in stellar mass and that total stellar metallicity,
alpha-elements-to-iron abundance ratio and light-weighted age all increase with
mass along the two relations. For high-mass ellipticals, the dispersion in age
is small and consistent with the error. At the low-mass end, there is a tail
towards younger ages, which dominates the scatter in colour and index strength
at fixed mass. A small, but detectable, intrinsic scatter in the
mass-metallicity relation also contributes to the scatter in the two
observational scaling relations, even at high masses. Our results suggest that
the chemical composition of an early-type galaxy is more tightly related to its
dynamical mass (including stars and dark matter) than to its stellar mass. The
ratio between stellar mass and dynamical mass appears to decrease from the
least massive to the most massive galaxies in our sample.


title:
Physical viscosity in smoothed particle hydrodynamics simulations of
  galaxy clusters

abstract:
  Most hydrodynamical simulations of galaxy cluster formation carried out to
date have tried to model the cosmic gas as an ideal, inviscid fluid, where only
a small amount of (unwanted) numerical viscosity is present, arising from
practical limitations of the numerical method employed, and with a strength
that depends on numerical resolution. However, the physical viscosity of the
gas in hot galaxy clusters may in fact not be negligible, suggesting that a
self-consistent treatment that accounts for the internal gas friction would be
more appropriate. To allow such simulations using the smoothed particle
hydrodynamics (SPH) method, we derive a novel SPH formulation of the
Navier-Stokes and general heat transfer equations and implement them in the
GADGET-2 code. We include both shear and bulk viscosity stress tensors, as well
as saturation criteria that limit viscous stress transport where appropriate.
Adopting Braginskii's parameterization for the shear viscosity of hot gaseous
plasmas, we then study the influence of viscosity on the interplay between
AGN-inflated bubbles and the surrounding intracluster medium (ICM). We find
that certain bubble properties like morphology, maximum clustercentric radius
reached, or survival time depend quite sensitively on the assumed level of
viscosity. Interestingly, the sound waves launched into the ICM by the bubble
injection are damped by physical viscosity, establishing a non-local heating
process. Finally, we carry out cosmological simulations of galaxy cluster
formation with a viscous intracluster medium. Viscosity modifies the dynamics
of mergers and the motion of substructures through the cluster atmosphere.
Substructures are generally more efficiently stripped of their gas, leading to
prominent long gaseous tails behind infalling massive halos. (Abridged)


title:
The Clustering of Luminous Red Galaxies in the Sloan Digital Sky Survey
  Imaging Data

abstract:
  We present the 3D real space clustering power spectrum of a sample of
\~600,000 luminous red galaxies (LRGs) measured by the Sloan Digital Sky Survey
(SDSS), using photometric redshifts. This sample of galaxies ranges from
redshift z=0.2 to 0.6 over 3,528 deg^2 of the sky, probing a volume of 1.5
(Gpc/h)^3, making it the largest volume ever used for galaxy clustering
measurements. We measure the angular clustering power spectrum in eight
redshift slices and combine these into a high precision 3D real space power
spectrum from k=0.005 (h/Mpc) to k=1 (h/Mpc). We detect power on gigaparsec
scales, beyond the turnover in the matter power spectrum, on scales
significantly larger than those accessible to current spectroscopic redshift
surveys. We also find evidence for baryonic oscillations, both in the power
spectrum, as well as in fits to the baryon density, at a 2.5 sigma confidence
level. The statistical power of these data to constrain cosmology is ~1.7 times
better than previous clustering analyses. Varying the matter density and baryon
fraction, we find \Omega_M = 0.30 \pm 0.03, and \Omega_b/\Omega_M = 0.18 \pm
0.04, The detection of baryonic oscillations also allows us to measure the
comoving distance to z=0.5; we find a best fit distance of 1.73 \pm 0.12 Gpc,
corresponding to a 6.5% error on the distance. These results demonstrate the
ability to make precise clustering measurements with photometric surveys
(abridged).


title:
Cosmological baryonic and matter densities from 600,000 SDSS Luminous
  Red Galaxies with photometric redshifts

abstract:
  We analyze MegaZ-LRG, a photometric-redshift catalogue of Luminous Red
Galaxies (LRGs) based on the imaging data of the Sloan Digital Sky Survey
(SDSS) 4th Data Release. MegaZ-LRG, presented in a companion paper, contains
10^6 photometric redshifts derived with ANNz, an Artificial Neural Network
method, constrained by a spectroscopic sub-sample of 13,000 galaxies obtained
by the 2dF-SDSS LRG and Quasar (2SLAQ) survey. The catalogue spans the redshift
range 0.4 < z < 0.7 with an r.m.s. redshift error ~ 0.03(1+z), covering 5,914
deg^2 to map out a total cosmic volume 2.5 h^-3 Gpc^3. In this study we use the
most reliable 600,000 photometric redshifts to present the first cosmological
parameter fits to galaxy angular power spectra from a photometric redshift
survey. Combining the redshift slices with appropriate covariances, we
determine best-fitting values for the matter and baryon densities of Omega_m h
= 0.195 +/- 0.023 and Omega_b/Omega_m = 0.16 +/- 0.036 (with the Hubble
parameter h = 0.75 and scalar index of primordial fluctuations n = 1 held
fixed). These results are in agreement with and independent of the latest
studies of the Cosmic Microwave Background radiation, and their precision is
comparable to analyses of contemporary spectroscopic-redshift surveys. We
perform an extensive series of tests which conclude that our power spectrum
measurements are robust against potential systematic photometric errors in the
catalogue. We conclude that photometric-redshift surveys are competitive with
spectroscopic surveys for measuring cosmological parameters in the simplest
vanilla models. Future deep imaging surveys have great potential for further
improvement, provided that systematic errors can be controlled.


title:
Wide-band and Air Dispersion Effecting the ABCD Algorithm of
  Phase-Recovery in Long-baseline Interferometry

abstract:
  Long-baseline interferometry detects fringes created by superposition of two
beams of light collected by two telescopes pointing into a common direction.
The external path difference generated by pointing away from the zenith is
commonly compensated by adding a variable optical path length (delay) through
air for one beam such that the optical path difference between the beams
remains close to zero near the detector.
  The ABCD formula assigns a (wrapped) phase to the amplitudes A to D of an
interference pattern shifted by multiples of 90 degrees in phase. We study the
interplay between a wide band pass of the optics and the dispersion of the air
in the compensating delay, which leads to small deviations between the ABCD
phase and the reduced, monochromatic group-delay representation of the wave
packets.
  In essence, this adds dispersion to the effects that have been discussed for
evacuated interferometers (telescopes in space) before [J. Opt. Soc. Am. A 22
(2005) 2774].


title:
Luminosity functions for galaxies and quasars in the Spitzer Wide-Area
  Infrared Extra-galactic (SWIRE) Legacy survey

abstract:
  We construct rest-frame luminosity functions at 3.6, 4.5, 5.8, 8 and 24
microns over the redshift range 0<z<2 for galaxies and 0<z<4 for optical QSOs,
using optical and infrared data from the Spitzer Wide-area InfraRed
Extragalactic survey. The 3.6 and 4.5 micron galaxy LFs show evidence for
moderate positive luminosity evolution up to z~1.5, consistent with the passive
ageing of evolved stellar populations. Their comoving luminosity density was
found to evolve passively, gradually increasing out to z~0.5-1 but flattening,
or even declining, at higher redshift. Conversely, the 24 micron galaxy LF,
which is more sensitive to obscured star formation and/or AGN activity,
undergoes strong positive evolution, with the derived IR energy density and SFR
density proportional to (1+z)^gamma with gamma=4.5^{+0.7}_{-0.6} and the
majority of this evolution occurring since z~1. Optical QSOs, however, show
positive luminosity evolution in all bands, out to the highest redshifts
(3<z<4). Modelling as L* proportional to (1+z)^gamma gave
gamma=1.3^{+0.1}_{-0.1} at 3.6 micron, gamma=1.0^{+0.1}_{-0.1} at 4.5 micron
and stronger evolution at the longer wavelengths (5.8, 8 and 24 micron), of
gamma~3. Comparison of the galaxy LFs to predictions from a semi-analytic model
based on CDM indicate that an IMF skewed towards higher mass star formation in
bursts compared to locally is preferred. As a result the currently inferred
massive star formation rates in distant sub-mm sources may require substantial
downwards revision.


title:
Masses of Astrometrically-Discovered and Imaged Binaries: G 78-28AB and
  GJ 231.1BC

abstract:
  The Stellar Planet Survey (STEPS) is an ongoing astrometric search for giant
planets and brown dwarfs around a sample of ~30 M-dwarfs. We have discovered
several low-mass companions by measuring the motion of our target stars
relative to their reference frames. The highest mass discovery thus far is G
78-28B, a companion to the M-dwarf G 78-28A. The orbital period is 4.18 +/-
0.03 y, the system mass is 0.565 +/- 0.055 Msolar, and the semi-major axis is
2.19 +/- 0.10 AU. Imaging observations with the Keck laser guide star adaptive
optics (LGSAO) and the Palomar AO instruments resolved the system and also
yielded JHK-band delta magnitudes. We use the orbital solution, light ratios,
and mass-luminosity relationships to derive component masses of MA = 0.370 +/-
0.034 Msolar and MB = 0.195 +/- 0.021 Msolar. G 78-28B is of type M4 V based
upon its colors and mass. We also discovered GJ 231.1C, a companion to GJ
231.1B, with STEPS and imaged the companion with LGSAO and Palomar AO, but the
orbital period is longer than our observing baseline; thus the system
parameters are less constrained. In GJ 231.1BC the masses are MB = 0.25 +/-
0.06 Msolar and MC =0.12 +/- 0.02 Msolar. The inferred spectral type of GJ
231.1C is M5 V. We demonstrate the results of the current state of mass
estimation techniques with our data.


title: The Formation of Globules in Planetary Nebulae

abstract:
  We discuss the formation of globules in planetary nebulae, typified by those
observed in the Helix Nebula. We show that the properties of the globules,
their number, mass, separation, and overall geometry strongly support a
scenario in which globules are formed by the fragmentation of a swept-up shell
as opposed to models in which the knots form in the AGB wind. We show that the
RT or other instabilities which lead to the break-up of shells formed in the
nebulae by fast winds or ionization fronts can produce arrays of globules with
the overall geometry and within the mass range observed. We also show that the
presence of a magnetic field in the circumstellar gas may play an important
role in controlling the fragmentation process. Using field strengths measured
in the precursor AGB envelopes, we find that close to the central star where
the fields are relatively strong, the wavelengths of unstable MRT modes are
larger than the shell dimensions, and the fragmentation of the shell is
suppressed. The wavelength of the most unstable MRT mode decreases with
increasing distance from the star, and when it becomes comparable to the shell
thickness, it can lead to the sudden, rapid break-up of an accelerating shell.
For typical nebula parameters, the model results in numerous fragments with a
mass scale and a separation scale similar to those observed. Our results
provide a link between global models of PN shaping in which shells form via
winds and ionization fronts, and the formation of small scale structures in the
nebulae.


title: Chandra Observations of the X-ray Point Source Population in NGC 4636

abstract:
  We present the X-ray point source population in the nearby Virgo elliptical
galaxy NGC 4636 from 3 Chandra/ACIS observations, totaling 193 ks, taken over 3
years. Using wavelet decomposition, we detect 318 point sources. Here, we use a
subset of the 277 sources with >10 net cts (>1.2E37 erg/s, 0.5-2 keV, >1.5
arcmin of center). Between 1.5-6 arcmin from the center, 25% are likely
background sources (AGN) and the rest are LMXBs within the galaxy, while at >6
arcmin, background sources dominate. We present a color-color diagram based on
ratios of X-ray flux, which yields a tighter source distribution, and shows a
large population of sources which are likely LMXBs and black hole candidates.
We explore short and long-term variability (over time-scales of 1 day to 3 yr):
54 sources (24%) in the common ACIS fields show significant variability between
observations. Of these, 37 are detected with >10 net counts only once and thus
may be "transient". About 10% of sources in each observation show significant
short-term variability. The cumulative luminosity function for the point
sources can be represented as a power-law of slope 1.14. Between 1.5-6 arcmin
of the center, 48 of the 129 X-ray point sources (37%) with >10 net counts are
matched with optical globular cluster (GC) candidates (matches could be as high
as 50% since many of the optical sources are AGN). 70% of matched sources are
associated with the redder GC candidates, those that are thought to have
near-solar metal abundance. The fraction of GC candidates matched with point
sources decreases with decreasing GC luminosity. The X-ray luminosities of the
matched point sources are not correlated with the luminosity or color of the
host GC candidates. Finally, we estimate an upper limit of 4.5E37 erg/s to the
current X-ray luminosity of the historical supernova SN1939A.


title:
Physical Origin of the Quadrupole Out-of-Plane Magnetic Field in
  Hall-MHD Reconnection

abstract:
  A quadrupole pattern of the out-of-plane component of the magnetic field
inside a reconnection region is seen as an important signature of the
Hall-magnetohydrodynamic (Hall-MHD) regime of reconnection. It has been first
observed in numerical simulations and just recently confirmed in the MRX
(Magnetic Reconnection Experiment) [M. Yamada, H. Ji, S. Hsu, T. Carter, R.
Kulsrud, N. Bertz, F. Jobes, Y. Ono, and F. Perkins, Phys. Plasmas 4, 1936
(1997)] and also seen in spacecraft observations of Earth's magnetosphere. In
this study, the physical origin of the quadrupole field is analyzed and traced
to a current of electrons that flows along the lines in and out of the inner
reconnection region to maintain charge neutrality. The role of the quadrupole
magnetic field in the overall dynamics of the reconnection process is
discussed. In addition, the bipolar poloidal electric field is estimated and
its effect on ion motions is emphasized.


title:
Evolution of Photosynthesis and Biospheric Oxygenation Contingent Upon
  Nitrogen Fixation?

abstract:
  How photosynthesis by Precambrian cyanobacteria oxygenated Earth's biosphere
remains incompletely understood. Here it is argued that the oxic transition,
which took place between approximately 2.3 and 0.5 Gyr ago, required a great
proliferation of cyanobacteria, and this in turn depended on their ability to
fix nitrogen via the nitrogenase enzyme system. However, the ability to fix
nitrogen was not a panacea, and the rate of biospheric oxygenation may still
have been affected by nitrogen constraints on cyanobacterial expansion.
Evidence is presented for why cyanobacteria probably have a great need for
fixed nitrogen than other prokaryotes, underscoring the importance of their
ability to fix nitrogen. The connection between nitrogen fixation and the
evolution of photosynthesis is demonstrated by the similarities between
nitrogenase and enzymes critical for the biosynthesis of (bacterio)chlorophyll.
It is hypothesized that biospheric oxygenation would not have occurred if the
emergence of cyanobacteria had not been preceded by the evolution of nitrogen
fixation, and if these organisms had not also acquired the ability to fix
nitrogen at the beginning of or very early in their history. The evolution of
nitrogen fixation also appears to have been a precondition for the evolution of
(bacterio)chlorophyll-based photosynthesis. Given that some form of chlorophyll
is obligatory for true photosynthesis, and its light absorption and chemical
properties make it a "universal pigment," it may be predicted that the
evolution of nitrogen fixation and photosynthesis are also closely linked on
other Earth- like planets.


title:
Orbital elements, masses and distance of lambda Scorpii A and B
  determined with the Sydney University Stellar Interferometer and high
  resolution spectroscopy

abstract:
  The triple system HD158926 (lambda Sco) has been observed interferometrically
with the Sydney University Stellar Interferometer and the elements of the wide
orbit have been determined. These are significantly more accurate than the
previous elements found spectroscopically. The inclination of the wide orbit is
consistent with the inclination previously found for the orbit of the close
companion. The wide orbit also has low eccentricity, suggesting that the three
stars were formed at the same time.
  The brightness ratio between the two B stars was also measured at lambda =
442nm and 700nm. The brightness ratio and colour index are consistent with the
previous classification of lambda Sco A as B1.5 and lambda Sco B as B2.
Evolutionary models show that the two stars lie on the main sequence. Since
they have have the same age and luminosity class (IV) the mass-luminosity
relation can be used to determine the mass ratio of the two stars: M_B/M_A =
0.76+/-0.04.
  The spectroscopic data have been reanalyzed using the interferometric values
for P, T, e and omega, leading to revised values for a_1sin i and the mass
function. The individual masses can be found from the mass ratio, the mass
function, spectrum synthesis and the requirement that the age of both
components must be the same: M_A = 10.4+/-1.3 Msun and M_B = 8.1+/-1.0 Msun.
  The masses, angular semimajor axis and the period of the system can be used
to determine the dynamical parallax. We find the distance to lambda Sco to be
112+/-5 pc, which is approximately a factor of two closer than the HIPPARCOS
value of 216+/-42 pc.


title: The Kinematic and Spectral Ages of the Compact Radio Source CTD 93

abstract:
  We present a study of the kinematic and spectral ages of the Gigahertz-Peaked
Spectrum (GPS) source CTD~93. Measurements of the hot spot separation over 8.5
yr show evidence of an increase. The separation rate along the source axis is
0.34$\pm0.11c$ (H$_{0}$=72 km s$^{-1}$ Mpc$^{-1}$), which results in a
kinematic age of 2200$\pm$700 yr. Assuming that two hot spots are moving apart
at equal speeds, we derive an advance speed of 0.17$\pm0.06c$. The radio lobe
spectra show a high frequency steepening, as expected if energetic electrons
lose energy by synchrotron radiation. The spectral break decreases with the
distance from the hot spot in the northern component of CTD~93. This tendency
is expected from the basic scenario of radio lobe evolution involving particle
acceleration at the hot spots, with the radio lobes populated by high energy
electrons which have leaked from the hot spots. Although a core-jet morphology
for CTD~93 has previously been proposed, these results indicate that the
morphology is similar to that of Compact Symmetric Object (CSO). From the
spectral fits in the northern component we found a break frequency of 3.7 GHz
at the edge of the lobe. The resultant spectral age is $\sim$300 yr assuming
the equipartition magnetic field. This requires the advance speed of 0.26$c$,
which shows a good agreement of the hot spot motion of 0.17$\pm0.06c$. Our
results strongly support the hypothesis that CSOs are young radio sources.


title: The acceleration of the universe and the physics behind it

abstract:
  Using a general classification of dark enegy models in four classes, we
discuss the complementarity of cosmological observations to tackle down the
physics beyond the acceleration of our universe. We discuss the tests
distinguishing the four classes and then focus on the dynamics of the
perturbations in the Newtonian regime. We also exhibit explicitely models that
have identical predictions for a subset of observations.


title:
Observation of the March Maximum in the Daemon Flux from Neos in the
  Year 2005: New Efforts and New Effects

abstract:
  The experiments of 2005 aimed at detection of low-velocity (~10-15 km s-1)
daemons falling on to the Earth's surface from Near-Earth, Almost Circular
Heliocentric Orbits (NEACHOs) have corroborated once more the existence of the
March maximum in their flux by raising its confidence level to 99.99%. In
addition, these experiments permitted us to identify several FEU-167-1-type PM
tubes, with a few times thicker inner Al coating, which appear to be capable to
detect, without any scintillator, the crossing of negatively charged daemons.
As a result, detection efficiency increases tens of times, thus raising the
measured level of the March daemon flux to f > 0.5E-7 cm-2s-1.


title: Near-infrared integral-field spectroscopy of HD209458b

abstract:
  We present first results of an exploratory study to use integral field
spectroscopy to observe extrasolar planets. We focus on transiting "Hot
Jupiters" and emphasize the importance of observing strategy and exact timing.
We demonstrate how integral field spectroscopy compares with other
spectroscopic techniques currently applied. We have tested our concept with a
time series observation of HD209458b obtained with SINFONI at the VLT during a
superior conjunction.


title:
Distribution of Matter from Singularity with Spherical Symmetry Using
  Fick Diffusion

abstract:
  A model is presented allowing calculation of energy and matter distribution
in the Universe after expansion from singularity without introduction of
expansion energy. Beginning with Fick's law of diffusion, we solve the Bessel
function for spherical systems during expansion, presuming isotropic matter
distribution in the Hubble flow. This function can be substituted with the
Associated Legendre differential equation and when solved we discover useful
parameters for those of energy and matter densities, diffusion and temperature.
Though we can follow the decline of matter density over spacetime, we cannot
suggest a precise value at singularity. This model may be useful though, as a
starting point for modeling star formation rates, SFR, galaxy formation horizon
lengths and regions devoid of matter where tracing the matter density decline
over time is important.


title: Reionisation scenarios and the temperature of the IGM

abstract:
  We examine the temperature structure of the IGM due to the passage of
individual ionisation fronts using a radiative transfer (RT) code coupled to a
particle-mesh (PM) N-body code. Multiple simulations were performed with
different spectra of ionising radiation: a power law (goes as nu^{-0.5}),
miniquasar, starburst, and a time-varying spectrum that evolves from a
starburst spectrum to a power law. The RT is sufficiently resolved in time and
space to correctly model both the ionisation state and the temperature across
the ionisation front. We find the post-ionisation temperature of the reionised
intergalactic medium (IGM) is sensitive to the spectrum of the source of
ionising radiation, which may be used to place strong constraints on the nature
of the sources of reionisation. Radiative transfer effects also produce large
fluctuations in the HeII to HI number density ratio eta. The spread in values
is smaller than measured, except for the time-varying spectrum. For this case,
the spread evolves as the spectral nature of the ionising background changes.
Large values for eta are found in partially ionised HeII as the power-law
spectrum begins to dominate the starburst, suggesting that the large eta values
measured may be indicating the onset of the HeII reionisation epoch.


title:
On the Relevance of Compton Scattering for the Soft X-ray Spectra of Hot
  DA White Dwarfs

abstract:
  We re-examine the effects of Compton scattering on the emergent spectra of
hot DA white dwarfs in the soft X-ray range. Earlier studies have implied that
sensitive X-ray observations at wavelengths $\lambda < 50$ \AA might be capable
of probing the flux deficits predicted by the redistribution of
electron-scattered X-ray photons toward longer wavelengths. We adopt two
independent numerical approaches to the inclusion of Compton scattering in the
computation of pure hydrogen atmospheres in hydrostatic equilibrium. One
employs the Kompaneets diffusion approximation formalism, while the other uses
the cross-sections and redistribution functions of Guilbert. Models and
emergent spectra are computed for stellar parameters representative of HZ 43
and Sirius B, and for models with an effective temperature $T_{\rm eff} = 100
000$ K. The differences between emergent spectra computed for Compton and
Thomson scattering cases are completely negligible in the case of both HZ 43
and Sirius B models, and are also negligible for all practical purposes for
models with temperatures as high as $T_{\rm eff} = 100 000$ K. Models of the
soft X-ray flux from these stars are instead dominated by uncertainties in
their fundamental parameters.


title:
Isophotal Shapes of Elliptical/S0 Galaxies from the Sloan Digital Sky
  Survey

abstract:
  We revisit the shapes of isophotes for elliptical (E) and lenticular (S0)
galaxies by studying 847 nearby early-type galaxies selected from the Sloan
Digital Sky Survey Data Release 4 with velocity dispersions above 200 km/s. The
IRAF task {\tt ellipse} was used to derive the deviations of the isophotes from
pure ellipses (Fourier coefficients a_3/a and a_4/a), position angles and
ellipticities as a function of radius. We show the statistical distributions of
the a_3/a and a_4/a parameters as a function of velocity dispersion, magnitude,
and colour. The a_4/a parameter is correlated with the ellipticity and absolute
Petrosian magnitude of galaxies. No significant correlation was found between
the a_4/a parameter with colour and velocity dispersion. A cross-correlation
between the FIRST survey and the SDSS data reveals a lack of powerful radio
emitters in discy E/S0s, as previously found by Bender et al. We also find that
boxy E/S0s favor denser environments while discy E/S0s favor more isolated
environments. The median values of changes in the ellipticity and position
angle between one and one and a half Petrosian half-light radii in the
isophotes are about -0.023 and 1.61 degree respectively. The average change in
the position angle is much larger, about 4.12 degree, due to an extended tail.
The change in ellipticity is weakly correlated with the ellipticity itself,
with an increasing ellipticity for galaxies with higher ellipticity as the
radius increases. The isophote parameters for the 847 galaxies are available
online.


title: Isothermal shocks in Abell 2199 and 2A 0335+096?

abstract:
  We report on a partially circular X-ray surface brightness discontinuity
found at about 55 kpc from the centre of Abell 2199 with Chandra X-ray
observatory observations. Unlike cold fronts found in other clusters, the
feature shows no significant temperature change across it but has an apparent
density jump. We therefore identify it as a weak isothermal shock associated
with the central AGN and the inflation of its radio bubbles, as found in the
Perseus cluster. We examine a similar feature at 40 kpc radius found by
Mazzotta et al in 2A 0335+096, and conclude that it too may be an isothermal
shock. The change in density if these are shocks implies a Mach number of ~1.5.
If the isothermal nature of these features is confirmed by deeper observations,
the implication is that such shocks are common in clusters of galaxies, and are
an important mechanism for the transport of energy from a central supermassive
black hole into the cluster core.


title: Time-Delay Measurement for the Quadruple Lens RX J1131-1231

abstract:
  We have measured the three time delays for the quadruple gravitational lens
RX J1131-1231 using two seasons of monitoring data. The short delays between
cusp images are A-B = 11.98 +1.52,-1.27 days and A-C = 9.61 +1.97,-1.57 days.
The long A-D delay for the counter image is not as precisely determined because
of the season gaps, but the data suggest a delay of -87 +- 8 days. The short
delays are difficult to explain using standard isothermal halo models of the
lensing potential, which instead prefer A-B and A-C delays of ~1 day for
reasonable values of the Hubble constant. Matching the cusp delays is possible
by adding a significant (~5 x 10^10 M_sun) amount of matter nearly coincident
(~0.05" South-East) with the A image. Adding such a satellite also helps
improve the quasar and lens astrometry of the model, reduces the velocity
dispersion of the main lens and shifts it closer to the Fundamental Plane. This
is suggestive of a satellite galaxy to the primary lens, but its expected
luminosity and proximity to both image A and the system's bright Einstein ring
make visual identification impossible even with the existing HST data. We also
find evidence for significant structure along the line of sight toward the
lens. Archival Chandra observations show two nearby regions of extended X-ray
emission, each with bolometric X-ray luminosities of 2-3 x 10^43 ergs/s. The
brighter region is located 153" from the lens and centered on a z=0.1
foreground cD galaxy, and the fainter and presumably more distant region is 4-5
times closer (in angular separation) to the lens and likely corresponds to the
weaker of two galaxy red sequences (which includes the lens galaxy) previously
detected at optical wavelengths.


title: Dark energy, MOND and sub-millimeter tests of gravity

abstract:
  We consider modifications of General Relativity obtained by adding the
logarithm of some curvature invariants to the Einstein-Hilbert action. These
non-linear actions can explain the late-time acceleration of the universe
giving an expansion history that differs from that of a pure cosmological
constant. We show that they also modify the Newtonian potential below a fixed
acceleration scale given by the late-time Hubble constant times the speed of
light. This is exactly what is required in MOND, a phenomenological
modification of the Newtonian potential that is capable of explaining galactic
rotation curves without the need to introduce dark matter. We show that this
kind of modification also predicts short distance deviations of Newton's law at
the sub-mm scale and an anomalous shift in the precession of the Moon's orbit
around the Earth, both effects of a size that is less than an order of
magnitude below current bounds.


title:
The Feedback-Regulated Growth of Black Holes and Bulges through Gas
  Accretion and Starbursts in Cluster Central Dominant Galaxies

abstract:
  We present an analysis of the growth of black holes through accretion and
bulges through star formation in 33 galaxies at the centers of cooling flows.
Most of these systems show evidence of cavities in the intracluster medium
(ICM) inflated by radio jets emanating from their active galactic nuclei (AGN).
We present a new and extensive analysis of X-ray cavities in these systems. We
find that AGN are energetically able to balance radiative losses (cooling) from
the ICM in more than half of our sample. Using a subsample of 17 systems, we
examine the relationship between cooling and star formation. We find that the
star formation rates are approaching or are comparable to X-ray and far UV
limits on the rates of gas condensation onto the central galaxy. The remaining
radiative losses could be offset by AGN feedback. The vast gulf between
radiative losses and the sink of cooling material, which has been the primary
objection to cooling flows, has narrowed and, in some cases, is no longer a
serious issue. Using the cavity (jet) powers, we place strong lower limits on
the rate of growth of supermassive black holes in central galaxies, and we find
that they are growing at an average rate of ~ 0.1 solar masses per year, with
some systems growing as quickly as ~ 1 solar mass per year. We find a trend
between bulge growth (star formation) and black hole growth that is
approximately in accordance with the slope of the local (Magorrian) relation
between black hole and bulge mass. However, the large scatter in the trend
suggests that bulges and black holes do not always grow in lock step.
(Abridged)


title: A Wide-Field Survey of the Globular Cluster Systems of Giant Galaxies

abstract:
  I present selected results from a wide-field CCD survey of the globular
cluster systems of giant galaxies, including showing how measurements of the
specific frequency of metal-poor globular clusters can constrain the redshift
of their formation.


title: Markov chain Monte Carlo analysis of Bianchi VII_h models

abstract:
  We have extended the analysis of Jaffe et al. to a complete Markov chain
Monte Carlo (MCMC) study of the Bianchi type ${\rm VII_h}$ models including a
dark energy density, using 1-year and 3-year Wilkinson Microwave Anisotropy
Probe (WMAP) cosmic microwave background (CMB) data. Since we perform the
analysis in a Bayesian framework our entire inference is contained in the
multidimensional posterior distribution from which we can extract marginalised
parameter constraints and the comparative Bayesian evidence. Treating the
left-handed Bianchi CMB anisotropy as a template centred upon the `cold-spot'
in the southern hemisphere, the parameter estimates derived for the total
energy density, `tightness' and vorticity from 3-year data are found to be:
$\Omega_{tot} = 0.43\pm 0.04$, $h = 0.32^{+0.02}_{-0.13}$, $\omega =
9.7^{+1.6}_{-1.5}\times 10^{-10}$ with orientation $\gamma =
{337^{\circ}}^{+17}_{-23}$). This template is preferred by a factor of roughly
unity in log-evidence over a concordance cosmology alone. A Bianchi type
template is supported by the data only if its position on the sky is heavily
restricted. The low total energy density of the preferred template, implies a
geometry that is incompatible with cosmologies inferred from recent CMB
observations. Jaffe et al. found that extending the Bianchi model to include a
term in $\Omega_{\Lambda}$ creates a degeneracy in the $\Omega_m -
\Omega_{\Lambda}$ plane. We explore this region fully by MCMC and find that the
degenerate likelihood contours do not intersect areas of parameter space that 1
or 3 year WMAP data would prefer at any significance above $2\sigma$. Thus we
can confirm that a physical Bianchi ${\rm VII_h}$ model is not responsible for
this signature.


title: X-Ray Emitting Blast Wave from the Recurrent Nova RS Ophiuchi

abstract:
  Stellar explosions such as novae and supernovae produce most of the heavy
elements in the Universe. Although the onset of novae from runaway
thermonuclear fusion reactions on the surface of a white dwarf in a binary star
system is understood[1], the structure, dynamics, and mass of the ejecta are
not well known. In rare cases, the white dwarf is embedded in the wind nebula
of a red-giant companion; the explosion products plow through the nebula and
produce X-ray emission. Early this year, an eruption of the recurrent nova RS
Ophiuchi[2,3] provided the first opportunity to perform comprehensive X-ray
observations of such an event and diagnose conditions within the ejecta. Here
we show that the hard X-ray emission from RS Ophiuchi early in the eruption
emanates from behind a blast wave, or outward-moving shock wave, that expanded
freely for less than 2 days and then decelerated due to interaction with the
nebula. The X-rays faded rapidly, suggesting that the blast wave deviates from
the standard spherical shell structure[4-6]. The early onset of deceleration
indicates that the ejected shell had a low mass, the white dwarf has a high
mass[7], and that RS Ophiuchi is a progenitor of the type of supernova integral
to studies of the expansion of the universe.


title: Cosmogenic Neutrinos from the propagation of Ultra High Energy Nuclei

abstract:
  We calculate the flux of neutrinos generated by the propagation of ultra-high
energy nuclei over cosmological distances. The propagation takes into account
the interactions with cosmic background radiations including the CMB and the
most recent estimates of higher energy (infra-red, optical, and ultra violet)
backgrounds. We assume that the composition of ultra-high energy cosmic rays
(UHECRs) at the source is the same as the observed one at low energies. This
assumption fits well the present data at the highest energies. We compare the
cosmogenic neutrino flux from mixed composition sources to pure proton sources.
We find that the neutrino flux in the mixed composition case has a high energy
peak, mainly due to photopion production off CMB photons, of similar shape and
amplitude to the proton case. At low energies both composition cases have
significant neutrino flux with a peak around 1014.5 eV due to the higher energy
backgrounds. The mixed composition case induces a higher flux of neutrinos at
energies below 1013 eV due to the neutron decay component that extends down to
low energies. Detection of diffuse neutrino fluxes at ultra high energies can
strongly constrain the source distribution of UHECR whereas fluxes at lower
energies could be used to constrain confinement of VHE and UHE cosmic rays if
combined with composition analysis from cosmic ray experiments.


title: The detection of M-dwarf UV flare events in the GALEX data archives

abstract:
  We present the preliminary results from implementing a new software tool that
enables inspection of time-tagged photon data for the astronomical sources
contained within individual GALEX ultraviolet images of the sky. We have
inspected the photon data contained within 1802 GALEX images to reveal rapid,
short-term (<500 sec) UV source variability in the form of stellar flares. The
mean associated change in NUV magnitude due to this flaring activity is
2.7+/-0.3 mag. A list of 49 new UV variable-star candidates is presented,
together with their associated Sloan Digital Sky Survey (SDSS) photometric
magnitudes. From these data we can associate the main source of these UV flare
events with magnetic activity on M-dwarf stars. Photometric parallaxes have
been determined for 32 of these sources, placing them at distances ranging from
approximately 25 to 1000pc. The average UV flare energy for these flare events
is 2.5E30 ergs, which is of a similar energy to that of U-band, X-ray and EUV
flares observed on many local M-dwarf stars. We have found that stars of
classes M0 to M5 flare with energies spanning a far larger range and with an
energy approximately 5 times greater than those of later (M6 to M8) spectral
type.


title:
Molecular Line Emission from Gravitationally Unstable Protoplanetary
  Disks

abstract:
  In the era of high resolution submillimeter interferometers, it will soon be
possible to observe the neutral circumstellar medium directly involved in gas
giant planet (GGP) formation at physical scales previously unattainable. In
order to explore possible signatures of gas giant planet formation via disk
instabilities, we have combined a 3D, non-local thermodynamic equilibrium (LTE)
radiative transfer code with a 3D, finite differences hydrodynamical code to
model molecular emission lines from the vicinity of a 1.4 M_J self-gravitating
proto-GGP. Here, we explore the properties of rotational transitions of the
commonly observed dense gas tracer, HCO+. Our main results are the following:
1. Very high lying HCO+ transitions (e.g. HCO+ J=7-6) can trace dense planet
forming clumps around circumstellar disks. Depending on the molecular
abundance, the proto-GGP may be directly imageable by the Atacama Large
Millimeter Array (ALMA). 2. HCO+ emission lines are heavily self-absorbed
through the proto-GGP's dense molecular core. This signature is nearly
ubiquitous, and only weakly dependent on assumed HCO+ abundances. The
self-absorption features are most pronounced at higher angular resolutions.
Dense clumps that are not self-gravitating only show minor self-absorption
features. 3. Line temperatures are highest through the proto-GGP at all assumed
abundances and inclination angles. Conversely, due to self-absorption in the
line, the velocity-integrated intensity may not be. High angular resolution
interferometers such as the Submillimeter Array (SMA) and ALMA may be able to
differentiate between competing theories of gas giant planet formation.


title: The infrared counterpart to the magnetar 1RXS J170849.0-400910

abstract:
  We have analyzed both archival and new infrared imaging observations of the
field of the Anomalous X-ray Pulsar 1RXS J170849.0-400910, in search of the
infrared counterpart. This field has been previously investigated, and one of
the sources consistent with the position of the AXP suggested as the
counterpart. We, however, find that this object is more likely a background
star, while another object within the positional error circle has non-stellar
colors and shows evidence for variability. These two pieces of evidence, along
with a consistency argument for the X-ray-to-infrared flux ratio, point to the
second source being the more likely infrared counterpart to the AXP.


title:
Evolution of magnetized, differentially rotating neutron stars:
  Simulations in full general relativity

abstract:
  We study the effects of magnetic fields on the evolution of differentially
rotating neutron stars, which can form in stellar core collapse or binary
neutron star coalescence. Magnetic braking and the magnetorotational
instability (MRI) both redistribute angular momentum; the outcome of the
evolution depends on the star's mass and spin. Simulations are carried out in
axisymmetry using our recently developed codes which integrate the coupled
Einstein-Maxwell-MHD equations. For initial data, we consider three categories
of differentially rotating, equilibrium configurations, which we label normal,
hypermassive and ultraspinning. Hypermassive stars have rest masses exceeding
the mass limit for uniform rotation. Ultraspinning stars are not hypermassive,
but have angular momentum exceeding the maximum for uniform rotation at the
same rest mass. We show that a normal star will evolve to a uniformly rotating
equilibrium configuration. An ultraspinning star evolves to an equilibrium
state consisting of a nearly uniformly rotating central core, surrounded by a
differentially rotating torus with constant angular velocity along magnetic
field lines, so that differential rotation ceases to wind the magnetic field.
In addition, the final state is stable against the MRI, although it has
differential rotation. For a hypermassive neutron star, the MHD-driven angular
momentum transport leads to catastrophic collapse of the core. The resulting
rotating black hole is surrounded by a hot, massive, magnetized torus
undergoing quasistationary accretion, and a magnetic field collimated along the
spin axis--a promising candidate for the central engine of a short gamma-ray
burst. (Abridged)


title: Exact versus approximate beaming formulas in Gamma-Ray Burst afterglows

abstract:
  We present the exact analytic expressions to compute, assuming the emitted
Gamma-Ray Burst (GRB) radiation is not spherically symmetric but is confined
into a narrow jet, the value of the detector arrival time at which we start to
"see" the sides of the jet, both in the fully radiative and adiabatic regimes.
We obtain this result using our exact analytic expressions for the EQuiTemporal
Surfaces (EQTSs) in GRB afterglows. We re-examine the validity of three
different approximate formulas currently adopted for the adiabatic regime in
the GRB literature. We also present an empirical fit of the numerical solutions
of the exact equations, compared and contrasted with the three above
approximate formulas. The extent of the differences is such as to require a
reassessment on the existence and entity of beaming in the cases considered in
the current literature, as well as on its consequences on the GRB energetics.


title:
The Holmberg effect of Main galaxy pairs of the SDSS Data Release 4
  (SDSS4)

abstract:
  We have investigated the Holmberg effect of Main galaxy pairs of the SDSS
Data Release 4 (SDSS4). It is found that except i-z color the color indices
between the two components of Main galaxy pairs clearly have significantly
larger correlation coefficients. Further analyses also show that the Holmberg
Effect of galaxies not only depends on the color indices but also on the
morphological type for two components of pairs.


title: Spitzer Far-Infrared Detections of Cold Circumstellar Disks

abstract:
  Observations at 70 microns with the Spitzer Space Telescope have detected
several stellar systems within 65 pc of the Sun. Of 18 presumably young systems
detected in this study, as many as 15 have 70-micron emission in excess of that
expected from their stellar photospheres. Five of the systems with excesses are
members of the Tucanae Association. The 70-micron excesses range from a factor
of ~2 to nearly 30 times the expected photospheric emission from these stars.
In contrast to the 70-micron properties of these systems, there is evidence for
an emission excess at 24 microns for only HD 3003, confirming previous results
for this star. The lack of a strong 24-micron excess in most of these systems
suggests that the circumstellar dust producing the IR excesses is relatively
cool (T_dust < 150 K) and that there is little IR-emitting material within the
inner few AU of the primary stars. Many of these systems lie close enough to
Earth that the distribution of the dust producing the IR excesses might be
imaged in scattered light at optical and near-IR wavelengths.


title: Imprint of galaxy formation and evolution on globular cluster properties

abstract:
  We discuss the origin of physical properties of globular cluster systems
(GCSs) in galaxies in terms of galaxy formation and evolution processes. Based
on numerical simulations of dynamical evolution of GCSs in galaxies, we
particularly discuss (1) the origin of radial density profiles of GCSs, (2)
kinematics of GCSs in elliptical galaxies, (3) transformation from nucleated
dwarf galaxies into GCs (e.g., omega Centauri), and (4) the origin of GCSs in
the Large Magellanic Cloud (LMC).


title: Accretion in protoplanetary disks: the imprint of core properties

abstract:
  In this Letter we present a theoretical scenario to explain the steep
correlation between disk accretion rates and stellar masses observed in
pre-main sequence stars. We show that the correlations and spread observed in
the two best studied regions, rho-Ophiuchus and Taurus, can be reproduced by a
simple model of single star formation from a rotating collapsing core and the
viscous evolution of the circumstellar disk. In this model, the rate of
rotation of the parent core sets the value of the `centrifugal radius' within
which the infalling matter is loaded onto the surface of the disk. As a
consequence, the disk accretion rate measured long after the dispersal of the
parental core bears the imprint of the initial conditions of star formation.
The observed trend results naturally if, at the onset of the collapse, cores of
all masses rotate with the same distribution of angular velocities, measured in
units of the break-up rotation rate.


title:
Astrochemical confirmation of the rapid evolution of massive YSOs and
  explanation for the inferred ages of hot cores

abstract:
  Aims. To understand the roles of infall and protostellar evolution on the
envelopes of massive young stellar objects (YSOs).
  Methods. The chemical evolution of gas and dust is traced, including infall
and realistic source evolution. The temperatures are determined
self-consistently. Both ad/desorption of ices using recent laboratory
temperature-programmed-desorption measurements are included.
  Results. The observed water abundance jump near 100 K is reproduced by an
evaporation front which moves outward as the luminosity increases. Ion-molecule
reactions produce water below 100 K. The age of the source is constrained to t
\~ 8 +/- 4 x 10^4 yrs since YSO formation. It is shown that the chemical
age-dating of hot cores at ~ few x 10^3 - 10^4 yr and the disappearance of hot
cores on a timescale of ~ 10^5 yr is a natural consequence of infall in a
dynamic envelope and protostellar evolution. Dynamical structures of ~ 350AU
such as disks should contain most of the complex second generation species. The
assumed order of desorption kinetics does not affect these results.


title:
Inflation model constraints from the Wilkinson Microwave Anisotropy
  Probe three-year data

abstract:
  We extract parameters relevant for distinguishing among single-field
inflation models from the Wilkinson Microwave Anisotropy Probe (WMAP)
three-year data set, and also from WMAP in combination with the Sloan Digital
Sky Survey (SDSS) galaxy power spectrum. Our analysis leads to the following
conclusions: 1) the Harrison--Zel'dovich model is consistent with both data
sets at a 95% confidence level; 2) there is no strong evidence for running of
the spectral index of scalar perturbations; 3) Potentials of the form V \propto
\phi^p are consistent with the data for p = 2, and are marginally consistent
with the WMAP data considered alone for p = 4, but ruled out by WMAP combined
with SDSS. We perform a "Monte Carlo reconstruction" of the inflationary
potential, and find that: 1) there is no evidence to support an observational
lower bound on the amplitude of gravitational waves produced during inflation;
2) models such as simple hybrid potentials which evolve toward an inflationary
late-time attractor in the space of flow parameters are strongly disfavored by
the data, 3) models selected with even a weak slow-roll prior strongly cluster
in the region favoring a "red" power spectrum and no running of the spectral
index, consistent with simple single-field inflation models.


title:
The Photometric and Kinematic Structure of Face-On Disk Galaxies. I.
  Sample Definition, H-alpha Integral Field Spectroscopy, and HI Line-Widths

abstract:
  We present a survey of the photometric and kinematic properties of 39 nearby,
nearly face-on disk galaxies. Our approach exploits echelle-resolution
integral-field spectroscopy of the H-alpha regions, obtained with DensePak on
the WIYN 3.5m telescope Bench Spectrograph. This data is complemented by HI
line-profiles observed with the Nancay radio telescope for 25 of these sample
galaxies. Twelve additional line-widths are available for sample galaxies from
the literature. In this paper, we introduce the goals of this survey, define
the sample selection algorithm, and amass the integral field spectroscopic data
and HI line-widths. We establish spatially-integrated H-alpha line-widths for
the sample. We test the veracity of these spatially-integrated line profiles by
convolving narrow-band imaging data with velocity field information for one of
the sample galaxies, PGC 38268, and also by comparing to HI line profiles. We
find HI and H-alpha line profiles to be similar in width but different in
shape, indicating we are observing different spatial distributions of ionized
and neutral gas in largely axisymmetric systems with flat outer
rotation-curves. We also find vertical velocity dispersions of the ionized disk
gas within several disk scale-lengths have a median value of 18 km/s and an 80%
range of 12-26 km/s. This is only a factor of ~2 larger than what is observed
for neutral atomic and molecular gas. With standard assumptions for intrinsic
and thermal broadening for H-alpha, this translates into a factor of three
range in turbulent velocities, between 8 and 25 km/s.


title:
Neutron-capture elements in the s- and r-process-rich stars: Constraints
  on neutron-capture nucleosynthesis processes

abstract:
  The chemical abundances of the very metal-poor double-enhanced stars are
excellent information for setting new constraints on models of neutron-capture
processes at low metallicity. These stars are known as s+r stars, since they
show enhancements of both s-process and r-process elements. The observed
abundance ratios for the double-enhanced stars can be explained by those of
stars that were polluted by an AGB star and subsequently accreted very
significant amounts of r-process material out of an AIC (accretion-induced
collapse) or Type 1.5 supernova. In this paper we present for the first time an
attempt to fit the elemental abundances observed in the s- and r-rich, very
metal-poor stars using a parametric model and suggest a new concept of
component coefficients to describe the contributions of the individual
neutron-capture processes to double-enhanced stars. We find that the abundance
ratios of these stars are best fitted by enrichments of s- and r-process
material. The overlap factor in the AGB stars where the observed s-process
elements were produced lies between 0.1 and 0.81. Taking into account the
dependence of the initial-final mass relations on metallicity, this wide range
of values could possibly be explained by a wide range of core-mass values of
AGB stars at low metallicity. The component coefficient of the r-process is
strongly correlated with the component coefficient of the s-process for the
double-enhanced stars. This is significant evidence that the r-process material
in double-enhanced stars comes from an AIC or Type 1.5 supernova.


title: New advances in nebular photoionisation modelling

abstract:
  The study of photoionised gas in planetary nebulae (PNe) has played a major
role achieving, over the years, a better understanding of a number of physical
processes pertinent to a broader range of fields than just PNe studies, ranging
from atomic physics to stellar evolution. Whilst empirical techniques are
routinely employed for the analysis of the emission line spectra of such
objects, the accurate interpretation of the observational data often requires
the solution of the radiative transfer (RT) problem in the nebula, via the
application of a photoionisation code.The development of the codes has been
driven by the observational constraints available, but also compromised by the
available computer power. Modern codes are faster and more flexible, with the
ultimate goal being the achievement of a description of the observations
relying on the smallest number of parameters possible. In this light, recent
developments have been focused on the inclusion of new atomic data, the
inclusion of a realistic treatment for dust grains mixed in the ionised and
photon dominated regions (PDRs) and the expansion of some codes to PDRs with
the inclusion of chemical reaction networks. Furthermore the last few years
have seen the development of fully 3D photoionisation codes based on the Monte
Carlo method. A review of the photoionisation codes currently in use is given
here, with emphasis on recent developments, including the expansion of the
models to the 3D domain, the identification of new observational constraints
and how these can be used to extract useful information from realistic
models.[Abridged]


title:
Three-Dimensional Ionisation, Dust RT and Chemical Modelling of
  Planetary Nebulae

abstract:
  The assumption of spherical symmetry is not justified for the vast majority
of PNe. The interpretation of spatially-resolved observations cannot rely
solely on the application of 1D codes, which may yield incorrect abundances
determinations resulting in misleading conclusions. The 3D photoionisation code
MOCASSIN (Monte CAarlo SimulationS of ionised Nebulae) is designed to remedy
these shortcomings. The 3D transfer of both primary and secondary radiation is
treated self-consistently without the need of approximations. The code was
benchmarked and has been applied to the study of several PNe. The current
version includes a fully self-consistent radiative transfer treatment for dust
grains mixed within the gas, taking into account the microphysics of dust-gas
interactions within the geometry-independent Monte Carlo transfer. The new code
provides an excellent tool for the self-consistent analysis of dusty ionised
regions showing asymmetries and/or density and chemical inhomogeneities. Work
is currently in progress to incorporate the processes that dominate the thermal
balance of photo-dissociation regions (PDRs), as well as the formation and
destruction processes for all the main molecular species.


title: The Dipole Anisotropy of the 2mass Redshift Survey

abstract:
  We estimate the flux weighted acceleration on the Local Group (LG) from the
near-infrared Two Micron All Sky Redshift Survey (2MRS). The near-infrared flux
weighted dipoles are very robust because they closely approximate a mass
weighted dipole, bypassing the effects of redshift distortions and require no
preferred reference frame. We use this method with the redshift information to
determine the change in dipole with distance. The LG dipole seemingly converges
by 60 Mpc/h. Assuming convergence, the comparison of the 2MRS flux dipole and
the CMB dipole provides a value for the combination of the mass density and
luminosity bias parameters Omega_m^0.6/b_L= 0.40+/-0.09.


title: Recent results from the Pierre Auger Observatory

abstract:
  The goal of the Pierre Auger Observatory is to determine the still unknown
nature and origin of ultra-high energy cosmic rays. The study of these elusive
particles probes astrophysical sites of particle acceleration as well as
fundamental interactions at energies unattainable in accelerator facilities.
Auger combines two observational techniques, a large surface array and air
fluorescence detectors, to observe the extended air showers generated in the
atmosphere by cosmic rays. This hybrid observation yields an excellent
resolution and allows for important cross-checks. The Auger South site, located
in Mendoza (Argentina), is now nearing completion, with 60% of its surface
array and three out of its four fluorescence detectors in operation. First
results on the energy spectrum measurement, the search for anisotropies in
arrival directions and the upper limit on the photon fraction are discussed.


title: The recent star formation in NGC 6822 from HST imaging

abstract:
  We present HST WFPC2 and STIS imaging of the low metallicity galaxy NGC 6822,
performed as part of a study of the young stellar populations in the galaxies
of the Local Group. Eleven WFPC2 pointings, with some overlap, cover two
regions, extending over 19'x19' and 13'x13' respectively, off the galaxy
center. One 25x25'' field observed with STIS' FUV- and NUV- MAMA, includes
Hodge's OB8 association and the HII region Hubble V. We derive the physical
parameters of the stars in the fields and the extinction by comparing the
photometry to grids of model magnitudes. The environments studied in this work
include one of the most luminous (in Halpha) HII regions in the Local Group
(Hubble V) with a compact star cluster, a typical OB association (OB15), the
sparse field population and the outskirts of NGC6822. The color-magnitude
diagrams show similar ages of few Myrs for both OB8 and OB15. The density [per
unit area] of hot massive stars in the core of the OB8 association is higher
than in OB15 by a factor of 12, while the total stellar mass formed is similar.
In both OB15 and OB8 massive star candidates are found. The average extinction
is found to vary among the three environments studied: E(B-V) = 0.22 in the
outer regions, E(B-V) = 0.27 in the fields East of the galaxy main bar, and
E(B-V) = 0.40 in the HII region Hubble V. A quantitative discussion of the
applicability of the reddening-free-index method for photometric determination
of stellar parameters is provided for the filters used in this work, based on
our grids of stellar models.


title: HI 21cm Absorption at $z \sim 2.347$ towards PKS B0438-436

abstract:
  We report the detection of redshifted HI~21cm absorption in the $z \sim
2.347$ damped Lyman-$\alpha$ absorber (DLA) towards PKS B0438-436, with the
Green Bank Telescope. This is the second-highest redshift at which 21cm
absorption has been detected in a DLA. The absorption extends over $\sim 60$
km/s and has two distinct components, at $z = 2.347477 (12)$ and $z = 2.347869
(20)$. A similar velocity structure is seen in optical metal lines, although
the peak absorption here is offset by $\sim 11$ km/s from the peak in the 21cm
line. We obtain a high spin temperature $T_s \sim (886 \pm 248) \times
(f/0.58)$ K, using a covering factor estimated from 2.3 GHz VLBI data. However,
the current data cannot rule out a low spin temperature. The non-detection of
CO 3-2 absorption places the upper limit $N_{CO} < 3.8 \times 10^{15} \times
(T_x/10)$ cm$^{-2}$ on the CO column density.


title: Substructure and the Cusp and Fold Relations

abstract:
  Gravitational lensing of a background source by a foreground galaxy lens
occasionally produces four images of the source. The cusp and the fold
relations impose conditions on the ratios of magnifications of these four-image
lenses. In this theoretical investigation, we explore the sensitivity of these
relations to the presence of substructure in the lens. Starting with a smooth
lens potential, we add varying amounts of substructure, while keeping the
source position fixed, and find that the fold relation is a more robust
indicator of substructure than the cusp relation for the images. This
robustness is independent of the detailed spatial distribution of the
substructure, as well as of the ellipticity of the lensing potential and the
presence of external shear.