title: The properties of Galactic globular cluster sub-systems

abstract:
  In this paper we compare the properties of three sub-systems of Galactic
globular clusters, which are defined according to metallicity and HB
morphology. We focus on cluster luminosities, structures, surface brightnesses
(SB) and ellipticities. It is shown that the so-called "young" halo (YH)
clusters, which may have been formed in external satellite galaxies, exhibit
characteristics clearly distinct from those of the "old" halo (OH) and
bulge/disk (BD) clusters, the majority of which are believed to be Galactic
natives. The YH clusters have properties most similar to those of clusters
belonging to several present day satellite dwarf galaxies. The OH and BD
populations have apparently been modified by destructive tidal forces in the
inner Galaxy. We estimate that the present population of Galactic natives may
only represent some two-thirds of the original population. Several low SB
clusters are highly flattened. We briefly speculate that this ellipticity may
represent the intrinsic flattening of dark matter mini-halos in which such
optically dim clusters might be embedded. Finally, we examine the distribution
of clusters on the size vs.luminosity plane. Three objects fall above the sharp
upper envelope of the main distribution on this plane: Omega Cen, M54, and NGC
2419. All three have previously, and independently, been suggested to be the
stripped cores of former dwarf galaxies. This suspicion is strengthened by the
observation that the massive cluster G1 in M31, plus a number of the most
luminous clusters in NGC 5128 also fall in the same region of the plane. All of
these objects have also previously been suggested to be the stripped cores of
now-defunct dwarf galaxies.


title:
Advances of plasma diagnostics with high-resolution spectroscopy of
  stellar coronae

abstract:
  X-ray emission from cool stars is an important tracer for stellar activity.
The X-ray luminosity reflects different levels of activity and covers four
orders of magnitude in stars of spectral types M-F. Low spectral resolution
provided by X-ray observations of stellar coronae in the past allowed the
determination of temperature distributions and elemental abundances making use
of atomic databases (listing line emissivities and bremsstrahlung continuum for
a given temperature structure). The new missions XMM-Newton and Chandra carry
X-ray gratings providing sufficient spectral resolution to measure the fluxes
of strategic emission lines. I describe the different approaches applicable to
low-resolution and high-resolution spectra, especially focusing on the new
grating spectra with X-ray lines. From only a few lines it is possible to
determine plasma temperatures and associated densities, to check for any
effects from resonant scattering, and to identify particular abundance
anomalies. Line-based temperature- and density measurements represent only a
fraction of the total plasma, but the pressure environment of different
fractions can be probed simply by selection of specific lines. Selected results
are presented covering all aspects of line-based analyses.


title: Sidebands to the lower kilohertz QPO in 4U1636-53

abstract:
  In this Paper we report on further observations of the third and fourth
kilohertz quasi-periodic oscillations (QPOs) in the power spectrum of the
low-mass X-ray binary (LMXB) 4U1636-53. These kilohertz QPOs are sidebands to
the lower kilohertz QPO. The upper sideband has a frequency 55.5+-1.7 Hz larger
than that of the contemporaneously measured lower kilohertz QPO. Such a
sideband has now been measured at a significance >6 sigma in the power spectra
of three neutron star LMXBs (4U1636-53, 4U1728-34, and 4U1608-52). We also
confirm the presence of a sideband at a frequency ~55 Hz less than the
frequency of the lower kilohertz QPO. The lower sideband is detected at a 3.5
sigma level, only when the lower kilohertz QPO frequency is between 800 and 850
Hz. In that frequency interval the sidebands are consistent with being
symmetric around the lower kHz QPO frequency. The upper limit to the rms
amplitude of the lower sideband is significant lower than that of the upper
sideband for lower kilohertz QPO frequencies >850 Hz. Symmetric sidebands are
unique to 4U1636-53. This might be explained by the fact that lower kilohertz
QPO frequencies as high as 800-850 Hz are rare for 4U1728-34 and 4U1608-52.
Finally, we also measured a low frequency QPO at a frequency of ~43 Hz when the
lower kilohertz QPO frequency is between 700-850 Hz. A similar low-frequency
QPO is present in the power spectra of the other two systems for which a
sideband has been observed. We briefly discuss the possibility that the
sideband is caused by Lense-Thirring precession.


title: X-ray properties of active M dwarfs as observed by XMM-Newton

abstract:
  We present a comparative study of X-ray emission from a sample of active M
dwarfs with spectral types \hbox{M3.5 - M4.5} using XMM-Newton observations of
two single stars, AD Leonis and EV Lacertae, and two unresolved binary systems,
AT Microscopii and EQ Pegasi. The light curves reveal frequent flaring during
all four observations. We perform a uniform spectral analysis and determine
plasma temperatures, abundances and emission measures in different states of
activity. Applying multi-temperature models with variable abundances separately
to data obtained with the EPIC and RGS detectors we are able to investigate the
consistency of the results obtained by the different instruments onboard
XMM-Newton. We find that the X-ray properties of the sample M dwarfs are very
similar, with the coronal abundances of all sample stars following a trend of
increasing abundance with increasing first ionization potential, the inverse
FIP effect. The overall metallicities are below solar photospheric ones but
appear consistent with the measured photospheric abundances of M dwarfs like
these. A significant increase in the prominence of the hotter plasma components
is observed during flares while the cool plasma component is only marginally
affected by flaring, pointing to different coronal structures. AT Mic, probably
a young pre-main-sequence system, has the highest X-ray luminosity and exhibits
also the hottest corona. While results of EQ Peg and EV Lac are presented here
for the first time, AT Mic and AD Leo have been investigated before with
different analysis approaches, allowing a comparison of the results.


title: The value of density measurements in stellar coronae

abstract:
  The grating instruments on board Chandra and XMM-Newton now allow
measurements of electron densities. These rely on the ratios of fluxes in
emission lines, where one line depends on both collisional and radiative decay
rates. The electron density is required to constrain the physical extent of the
emitting region, and large samples of measurements are of interest in the
context of trends in coronal activity. Here we discuss the important He {\sc
i}-like ions and the differences in densities that result when different
current data bases are used.


title:
Nonthermal hard X-ray excess in the cluster Abell 2256 from two epoch
  observations

abstract:
  After confirmation of the presence of a nonthermal hard X-ray excess with
respect to the thermal emission in the Coma cluster from two independent
observations, obtained using the Phoswich Detection System onboard BeppoSAX, we
present in this Letter also for Abell 2256 the results of two observations
performed with a time interval of about 2.5 yr. In both spectra a nonthermal
excess is present at a confidence level of ~3.3sigma and ~3.7sigma,
respectively. The combined spectrum obtained by adding up the two spectra
allows to measure an excess at the level of ~4.8sigma in the 20-80 keV energy
range. The nonthermal X-ray flux is in agreement with the published value of
the first observation (Fusco-Femiano et al. 2000) and with that measured by a
Rossi X-Ray Timing Explorer observation (Rephaeli & Gruber 2003).


title: X-ray Variability of Active Galactic Nuclei and the Flare Model

abstract:
  Short-term variability of X-ray spectra has been reported for several Active
Galactic Nuclei. Significant X-ray flux variations are observed within time
scales down to 10^4 -- 10^5 seconds. We discuss short variability time scales
in the framework of the X-ray flare model, which assumes the release of a large
hard X-ray flux above a small portion of the accretion disk. The resulting
observed X-ray spectrum is composed of the primary radiation as well as a
reprocessed/Compton reflection component that we model performing numerical
radiative transfer simulations. We conduct Monte-Carlo simulations of large
flare distributions across the disk including relativistic corrections of the
observed radiation and discuss general implications on AGN spectra and their
variability.


title:
Diffusion coefficient and acceleration spectrum from direct measurements
  of charged cosmic ray nuclei

abstract:
  We discuss the potentials of several experimental configurations dedicated to
direct measurements of charged cosmic ray (CR) nuclei at energies $\gsim$ 100
GeV/n. Within a two-zone propagation model for stable CRs, we calculate light
primary and secondary nuclei fluxes for different diffusion and acceleration
schemes. We show that the new detectors exploiting the long and ultra long
duration balloon flights could determine the diffusion coefficient power index
$\delta$ through the measurement of the boron-to-carbon ratio with an
uncertainty of about 10-15 %, if systematic errors are low enough. Only
space-based or satellite detectors will be able to determine $\delta$ with very
high accuracy even in the case of important systematic errors, thanks to the
higher energy reach and the less severe limitations in the exposure. We show
that no uncertainties other than those on $\delta$ affect the determination of
the acceleration slope $\alpha$, so that measures of light primary nuclei, such
as the carbon one, performed with the same experiments, will provide valuable
information on the acceleration mechanisms.


title:
Precision X-ray Timing of RX J0806.3+1527 with CHANDRA: Evidence for
  Gravitational Radiation from an Ultracompact Binary

abstract:
  RX J0806.3+1527 is a candidate double degenerate binary with possibly the
shortest known orbital period. The source shows an 100% X-ray intensity
modulation at the putative orbital frequency of 3.11 mHz (321.5 s). If the
system is a detached, ultracompact binary gravitational radiation should drive
spin-up with a magnitude of ~10-16 Hz/s. Here we describe the results of the
first phase coherent X-ray monitoring campaign on RX J0806.3+1527 with Chandra.
We obtained a total of 70 ksec of exposure in 6 epochs logarithmically spaced
over 320 days. These data conclusively show that the X-ray frequency is
increasing at a rate of 3.77 +- 0.8 x 10-16 Hz/s. Using our new ephemeris we
are able to phase up all the earlier Chandra and ROSAT data and show they are
consistent with a rate of 3.63 +- 0.06 x 10-16 Hz/s over the past decade. This
value appears consistent with that recently derived by Israel et al. largely
from monitoring of the optical modulation, and is in rough agreement with the
solutions reported initially by Hakala et al., based on ground-based optical
observations. The large spin-up is consistent with gravitational radiation
losses driving the evolution. An intermediate polar (IP) scenario where the
observed X-ray period is the spin period of an accreting white dwarf appears
less tenable. If the ultracompact scenario is correct, then the X-ray flux
cannot be powered by stable accretion which would drive the components apart,
suggesting a new type of energy source (perhaps electromagnetic) may power the
X-ray flux.


title:
On the He II Emission In Eta Carinae and the Origin of Its Spectroscopic
  Events

abstract:
  We describe and analyze Hubble Space Telescope (HST) observations of
transient emission near 4680 {\AA} in Eta Car, reported earlier by Steiner &
Damineli (2004). If, as seems probable, this is He II $\lambda$4687, then it is
a unique clue to Eta Car's 5.5-year cycle. According to our analysis, several
aspects of this feature support a mass-ejection model of the observed
spectroscopic events, and not an eclipse model. The He II emission appeared in
early 2003, grew to a brief maximum during the 2003.5 spectroscopic event, and
then abruptly disappeared. It did not appear in any other HST spectra before or
after the event. The peak brightness was larger than previously reported, and
is difficult to explain even if one allows for an uncertainty factor of order
3. The stellar wind must provide a temporary larger-than-normal energy supply,
and we describe a special form of radiative amplification that may also be
needed. These characteristics are consistent with a class of mass-ejection or
wind-disturbance scenarios, which have implications for the physical structure
and stability of Eta Car.


title:
Low-Luminosity AGN as analogues of Galactic Black Holes in the low/hard
  state: Evidence from X-ray timing of NGC 4258

abstract:
  We present a broadband power spectral density function (PSD) measured from
extensive RXTE monitoring data of the low-luminosity AGN NGC 4258, which has an
accurate, maser-determined black hole mass of 3.9+/-0.1 * 10^7 solar masses. We
constrain the PSD break timescale to be greater than 4.5 d at >90% confidence,
which appears to rule out the possibility that NGC 4258 is an analogue of black
hole X-ray binaries (BHXRBs) in the high/soft state. In this sense, the PSD of
NGC 4258 is different to those of some more-luminous Seyferts, which appear
similar to the PSDs of high/soft state X-ray binaries. This result supports
previous analogies between LLAGN and X-ray binaries in the low/hard state based
on spectral energy distributions, indicating that the AGN/BHXRB analogy is
valid across a broad range of accretion rates.


title: Early decline spectra of Nova SMC 2001 and Nova LMC 2002

abstract:
  We report results on the spectroscopic follow-up of Nova SMC 2001 and Nova
LMC 2002 carried out at La Silla. The analysis of the spectroscopic evolution
shows that these objects belong to the {\sl Fe II} class, according to the
Cerro Tololo scheme. From the line fluxes and the expansion velocities, we have
derived an approximate mass for the ejected shells of 2$\div3\times 10^{-4}
M_\odot$. The filling factor measurements ($\epsilon\sim 10^{-4}\div 10^{-1}$)
suggest a clumpy structure for the ejecta.


title: Spectroscopic metallicities for planet-host stars: extending the samples

abstract:
  We present stellar parameters and metallicities for 29 planet-host stars, as
well as for a large volume-limited sample of 53 stars not known to be orbited
by any planetary-mass companion. These stars add to the results presented in
our previous series of papers, providing two large and uniform samples of 119
planet-hosts and 94 ``single'' stars with accurate stellar parameters and
[Fe/H] estimates. The analysis of the results further confirms that stars with
planets are metal-rich when compared with average field dwarfs. Important
biases that may compromise future studies are also discussed. Finally, we
compare the metallicity distributions for single planet-hosts and planet-hosts
in multiple stellar systems. The results show that a small difference cannot be
excluded, in the sense that the latter sample is slighly overmetallic. However,
more data are needed to confirm this correlation.


title:
On the periodic clustering of cosmic ray exposure ages of iron
  meteorites

abstract:
  Two recent papers claimed to have found a periodic variation of the galactic
cosmic ray (CR) flux over the last 1-2 Gyr, using the CR exposure ages of iron
meteorites. This was attributed to higher CR flux during the passage of the
Earth through the spiral arms of the Milky Way, as suggested by models. The
derived period was 143+-10 Myrs. We perform a more detailed analysis of the CR
exposure ages on the same data set, using extensive simulation to estimate the
influence of different error sources on the significance of the periodicity
signal. We find no evidence for significant clustering of the CR exposure ages
at a 143 Myr period nor for any other period between 100 and 250 Myrs. Rather,
we find the data to be consistent with being drawn from a uniform distribution
of CR exposure ages. The different conclusion of the original studies is due to
their neglecting the influence of (i) data treatment on the statistics, (ii)
several error sources, and (iii) number statistics.


title: X-ray Emission from Hot Gas in Galaxy Mergers

abstract:
  We examine X-ray emission produced from hot gas during collisions and mergers
of disk galaxies. To study this process, we employ simulations that incorporate
cosmologically motivated disk-galaxy models and include the effects of
radiative cooling, star formation, supernova feedback, and accreting
supermassive black holes. We find that during a merger, the colliding gas in
the disks is shock-heated to X-ray-emitting temperatures. The X-ray luminosity
is spatially extended, rises during the initial stages of the merger, and peaks
when the galactic centers coalesce. When a physical model for accreting black
holes is included, the resulting feedback can drive powerful winds that
contribute significantly to the amount and metallicity of hot gas, both of
which increase the X-ray luminosity. In terms of their stellar kinematics and
structural properties, the merger remnants in our simulations resemble
elliptical galaxies. We find that the X-ray luminosities of the remnants with
B-band luminosities in the range L_B ~ 10^10 - 10^11 Lsun are consistent with
observations, while remnants with smaller or larger masses are underluminous in
X-rays. Moreover, because the majority of the merger remnants are broadly
consistent with the observed scaling relations between temperature, B-band
luminosity and X-ray luminosity we conclude that major mergers are a viable
mechanism for producing the X-ray halos of large, luminous elliptical galaxies.


title: Abundances of Na, Mg and Al in stars with giant planets

abstract:
  We present Na, Mg and Al abundances in a set of 98 stars with known giant
planets, and in a comparison sample of 41 ``single'' stars. The results show
that the [X/H] abundances (with X = Na, Mg and Al) are, on average, higher in
stars with giant planets, a result similar to the one found for iron. However,
we did not find any strong difference in the [X/Fe] ratios, for a fixed [Fe/H],
between the two samples of stars in the region where the samples overlap.
Finally, the data was used to study the Galactic chemical evolution trends for
Na, Mg and Al, and to discuss the possible influence of planets on this
evolution. The results, in general similar to the ones obtained by other
authors, show that the [X/Fe] ratios all decrease as a function of metallicity
up to solar values. While for Mg and Al this trend then becomes relatively
constant, for Na we find indications of an upturn up to [Fe/H] values close to
0.25dex. For metallicities above this value the [Na/Fe] becomes constant.


title: Cosmic Rays from Gamma Ray Bursts in the Galaxy

abstract:
  The rate of terrestrial irradiation events by galactic gamma-ray bursts
(GRBs) is estimated using recent standard-energy results. We assume that GRBs
accelerate high-energy cosmic rays, and present results of three-dimensional
simulations of cosmic rays moving in the Galactic magnetic field and diffusing
through pitch-angle scattering. An on-axis GRB extinction event begins with a
powerful prompt gamma-ray and neutron pulse, followed by a longer-lived phase
from cosmic-ray protons and neutron-decay protons that diffuse towards Earth.
Our results force a reinterpretation of reported ~ 10^{18} eV cosmic-ray
anisotropies and offer a rigorous test of the model where high-energy cosmic
rays originate from GRBs, which will soon be tested with the Auger Observatory.


title: Super-solar Metallicity in the NLS1 Galaxy Markarian 1044

abstract:
  The determination of the bulk metallicity and the abundance mixture of
various elements is very difficult in quasars and AGNs because only a few lines
are observed and the ionization correction is unknown. Most abundance studies
of AGNs assume the N/C ratio scales as metallicity (nitrogen goes as
metallicity squared) and so serves as a metallicity indicator. We present an
accurate metallicity determination of the narrow-line Seyfert 1 (NLS1) galaxy
Markarian 1044, using O VI column density measurements from the Far Ultraviolet
Spectroscopic Explorer (FUSE) together with C IV, N V, and H I from Hubble
Space Telescope (HST) observations. In this absorption line study we find that
the circumnuclear gas in Mrk 1044 has a metallicity of at least five times
solar. This is consistent with the expectation that NLS1s have a high
metallicity, similar to that found in high-redshift quasars. More surprisingly,
we find that the absorbing material requires a near-solar mixture. In other
words, the N/C is consistent with the solar ratio, and does not scale with the
metallicity. This suggests that the chemical enrichment scenario for this
object, and perhaps for AGNs in general, may be different from the traditional
model of galactic metal enrichment, at least in the high-metallicity regime.


title: The origin of intergalactic metals around Lyman-break galaxies

abstract:
  Theoretical and observational arguments suggest that the intergalactic medium
(IGM) might have been polluted with metals produced by early star formation. In
this scenario, Lyman-break galaxies (LBGs) at redshift z=3 are likely to be
surrounded by old metal bubbles, relics of an era when the characteristic mass
of galaxies was small and gas retainment more difficult. We find that
pregalactic enrichment of the IGM from 10^8-10^{10} M_sun dwarf galaxies at
6<z<12 can quantitatively explain the high cross-correlation between CIV
systems and LBGs observed at z=3. The reason is twofold. First, both LBGs and
high-z dwarfs are biased tracer of the mass distribution and form from
exceptionally high density fluctuations which are strongly clustered. Second,
the action of gravity tends to increase the spatial association between metal
bubbles and LBGs. Our analysis shows that, in order to match the abundance of
CIV systems observed at z=3, the metal bubbles generated by high-z dwarfs must
have comoving sizes of ~100 kpc. We conclude that the observed galaxy-CIV
spatial association needs not to be generated by late ``superwinds'' from LBGs.


title: A galaxy-halo model of large-scale structure

abstract:
  We present a new, galaxy-halo model of large-scale structure, in which the
galaxies entering a given sample are the fundamental objects. Haloes attach to
galaxies, in contrast to the standard halo model, in which galaxies attach to
haloes. The galaxy-halo model pertains mainly to the relationships between the
power spectra of galaxies and mass, and their cross-power spectrum. With
surprisingly little input, an intuition-aiding approximation to the
galaxy-matter cross-correlation coefficient R(k) emerges, in terms of the halo
mass dispersion. This approximation seems valid to mildly non-linear scales (k
< ~3 h/Mpc), allowing measurement of the bias and the matter power spectrum
from measurements of the galaxy and galaxy-matter power spectra (or correlation
functions). This is especially relevant given the recent advances in precision
in measurements of the galaxy-matter correlation function from weak
gravitational lensing. The galaxy-halo model also addresses the issue of
interpreting the galaxy-matter correlation function as an average halo density
profile, and provides a simple description of galaxy bias as a function of
scale.


title: Searching for Transiting Planets in Stellar Systems

abstract:
  We analyze the properties of searches devoted to finding planetary transits
by observing simple stellar systems, such as globular clusters, open clusters,
and the Galactic bulge. We develop the analytic tools necessary to predict the
number of planets that a survey will detect as a function of the parameters of
the system, the observational setup, site properties, and planet properties. We
find that the detection probability is generally maximized for I-band
observations. The signal-to-noise ratio of a planetary transit is weakly
dependent on the mass of the primary for sources with flux above the sky
background, and falls very sharply for sources below sky. Therefore the number
of detectable planets is roughly proportional to the number of stars with
fluxes above sky (and not necessarily the number of sources with photometric
error less a given threshold). In order to maximize the number of detections,
experiments should be tailored such that stars near sky are above the detection
threshold. Once this requirement is met, the number of detected planets is
relatively weakly dependent on the detection threshold, diameter of the
telescope, exposure time, seeing, age of the system, and planet radius. The
number of detected planets is a strongly decreasing function of the distance to
the system, implying that the nearest, richest clusters may prove to be optimal
targets.


title:
The effect of the 19F(alpha,p)22Ne reaction rate uncertainty on the
  yield of fluorine from Wolf-Rayet Stars

abstract:
  In the light of recent recalculations of the \el{19}{F}(alpha,p)\el{22}{Ne}
reaction rate we present results of the expected yield of \el{19}{F} from
Wolf-Rayet (WR) stars. We have computed models using the upper and lower limits
for the rate in addition to the recommended rate and hence we constrain the
uncertainty in the yield with respect to this reaction. We find a yield of
3.1x10^{-4}M_sol of \el{19}{F} with our recommended rate and a difference of a
factor of two between the yields computed with the upper and lower limits. In
comparison with previous work we find a difference in the yield of
approximately a factor of 4, connected to a different choice of mass loss.
Model uncertainties must be carefully evaluated in order to obtain a reliable
estimate of the yield of fluorine from WR stars together with its
uncertainties.


title:
On the accretion origin of a vast extended stellar disk around the
  Andromeda galaxy

abstract:
  We present the discovery of an inhomogenous, low-surface brightness, extended
disk-like structure around the Andromeda galaxy (M31) based on a large
kinematic survey of more than 2800 stars with the Keck/DEIMOS spectrograph. The
stellar structure spans radii from 15 kpc out to ~40 kpc, with detections out
to R ~ 70 kpc. The constituent stars lag the expected velocity of circular
orbits in the plane of the M31 disk by ~40 kms and have a velocity dispersion
of ~30 kms. The color range on the upper RGB shows a large spread indicative of
a population with a significant range of metallicity. The mean metallicity of
the population, measured from Ca II equivalent widths, is [Fe/H] = -0.9 +/-
0.2. The morphology of the structure is irregular at large radii, and shows a
wealth of substructures which must be transitory in nature, and are almost
certainly tidal debris. The presence of these substructures indicates that the
global entity was formed by accretion. This extended disk follows smoothly on
from the central parts of M31 disk with an exponential density law of
scale-length of 5.1 +/- 0.1 kpc, similar to that of the bright inner disk. The
population possesses similar kinematic and abundance properties over the entire
region where it is detected in the survey. We estimate that the structure
accounts for approximately 10% of the total luminosity of the M31 disk, and
given the huge scale, contains ~30% of the total disk angular momentum. This
finding indicates that at least some galactic stellar disks are vastly larger
than previously thought and are formed, at least in their outer regions,
primarily by accretion. [abridged]


title:
Early optical-IR emission from GRB 041219a: neutron-rich internal shocks
  and a mildly magnetized external reverse shock

abstract:
  Very early optical and near infrared (IR) emission was discovered
accompanying the long gamma-ray burst (GRB) 041219a. We show that the
optical/IR flash tracking the gamma-ray lightcurve during the prompt emission
could be understood as emission from neutron-rich internal shocks, as has been
suggested by Fan & Wei. The early K_s-band afterglow lightcurve after the
prompt phase could be well-modeled as the superposition of a reverse shock and
a forward shock component. The radio data also support the reverse shock
interpretation.


title:
Fluorescent Molecular Hydrogen Emission in IC 63: FUSE, HUT, and Rocket
  Observations

abstract:
  We present far-ultraviolet observations of IC 63, an emission/reflection
nebula illuminated by the B0.5IV star gamma Cassiopeia, located 1.3 pc from the
nebula. Molecular hydrogen fluorescence was detected first in IC 63 by IUE and
later at shorter wavelengths by ORFEUS. Here we present Far Ultraviolet
Spectroscopic Explorer (FUSE) observations towards three locations in the
nebula, complemented by Hopkins Ultraviolet Telescope (HUT) data on the central
nebular position. In addition, we present a sounding rocket calibration of a
FUSE spectrum of gamma Cas. Molecular hydrogen fluorescence is detected in all
three FUSE pointings. The intensity of this emission as well as the
contributions from other species are seen to vary with position. The absolute
flux calibration of the sounding rocket data allows us to reliably predict the
radiation field incident on IC 63. We use these data to test models of the
fluorescent process. Our modeling resolves the perceived discrepancy between
the existing ultraviolet observations and achieves a satisfactory agreement
with the H_2 rotational structure observed with FUSE.


title:
Power Spectrum Analysis of Far-IR Background Fluctuations in Spitzer
  Maps at 160 Microns

abstract:
  We describe data reduction and analysis of fluctuations in the Cosmic Far-IR
Background (CFIB) in large maps observed with the Multiband Imaging Photometer
for Spitzer (MIPS) instrument 160 micron detectors. We analyzed the
extragalactic First Look Survey (FLS) and the Spitzer Wide-area Infrared
Extragalactic Survey (SWIRE) Lockman Hole observations, the latter being the
largest low-cirrus mapping observation available. In the Lockman Hole map, we
measured the power spectrum of the CFIB by fitting a power law to the IR cirrus
component, the dominant foreground contaminant, and subtracting this cirrus
signal. The CFIB power spectrum at mid-high k (k ~ 0.2 - 0.5 arc min^-1) is
consistent with previous measurements of a relatively flat component. At lower
k, however, the power spectrum is clearly not flat, decreasing from our lowest
frequencies (k ~ 0.03 arc min^-1) and flattening at mid-frequencies (k ~ 0.1 -
0.2 arc min^-1). This behavior is consistent with the gross characteristics of
predictions of a source clustering signature in CFIB power spectra, and this is
the first report of such a detection.


title:
Super-critical Accretion Flows around Black Holes: Two-dimensional,
  Radiation-pressure-dominated Disks with Photon-trapping

abstract:
  The quasi-steady structure of super-critical accretion flows around a black
hole is studied based on the two-dimensional radiation-hydrodynamical (2D-RHD)
simulations. The super-critical flow is composed of two parts: the disk region
and the outflow regions above and below the disk. Within the disk region the
circular motion as well as the patchy density structure are observed, which is
caused by Kelvin-Helmholtz instability and probably by convection. The
mass-accretion rate decreases inward, roughly in proportion to the radius, and
the remaining part of the disk material leaves the disk to form outflow because
of strong radiation pressure force. We confirm that photon trapping plays an
important role within the disk. Thus, matter can fall onto the black hole at a
rate exceeding the Eddington rate. The emission is highly anisotropic and
moderately collimated so that the apparent luminosity can exceed the Eddington
luminosity by a factor of a few in the face-on view. The mass-accretion rate
onto the black hole increases with increase of the absorption opacity
(metalicity) of the accreting matter. This implies that the black hole tends to
grow up faster in the metal rich regions as in starburst galaxies or
star-forming regions.


title: High Mass Triple Systems: The Classical Cepheid Y Car

abstract:
  We have obtained an HST STIS ultraviolet high dispersion Echelle mode
spectrum the binary companion of the double mode classical Cepheid Y Car. The
velocity measured for the hot companion from this spectrum is very different
from reasonable predictions for binary motion, implying that the companion is
itself a short period binary. The measured velocity changed by 7 km/ s during
the 4 days between two segments of the observation confirming this
interpretation. We summarize "binary" Cepheids which are in fact members of
triple system and find at least 44% are triples. The summary of information on
Cepheids with orbits makes it likely that the fraction is under-estimated.


title: The same physics underlying SGRs, AXPs, and radio pulsars

abstract:
  Unexpected sign, significant magnitude and time-variation of frequency second
derivative exist not only in singular radio pulsars but also in Soft Gamma
repeaters (SGRs) and Anomalous X-ray pulsars (AXPs). This paper shows that the
these phenomena are related, and can be interpreted by a simple unified model,
long-term orbital effect. Thus many of previous ``isolated'' pulsars may be
binary pulsars, i.e., orbital period
  $P_b\approx(47, 72)$min for AXP 1E 2259+586, and $P_b\approx (20, 34)$min for
PSR J1614-5047, $P_b\approx (3.6, 6.4)$min for SGR 1900+14, and $P_b\approx
(1.5, 5.8)$min for SGR 1806-20. In addition to X-ray pulsar, 1E 1207.4-5209,
these two SGRs may be the new ultra-compact binary pulsars with orbital period
of a few minutes. There might be more binary pulsars that suitable for
gravitational wave detection than we had thought.


title: Magellanic Stream: A Possible Tool for Studying Dark Halo Model

abstract:
  We model the dynamics of Magellanic Stream with the ram-pressure scenario in
the logarithmic and power-law galactic halo models and construct numerically
the past orbital history of Magellanic clouds and Magellanic Stream. The
parameters of models include the asymptotic rotation velocity of spiral arms,
halo flattening, core radius and rising or falling parameter of rotation curve.
We obtain the best fit parameters of galactic models through the maximum
likelihood analysis, comparing the high resolution radial velocity data of HI
in Magellanic Stream with that of theoretical models. The initial condition of
the Magellanic Clouds is taken from the six different values reported in the
literature. We find that oblate and nearly spherical shape halos provide a
better fit to the observation than the prolate halos. This conclusion is almost
independent of choosing the initial conditions and is valid for both
logarithmic and power-law models.


title:
Measuring the Halo Mass of z=3 Damped Ly-alpha Absorbers from the
  Absorber-Galaxy Cross-correlation

abstract:
  [Abridged] We test the reliability of a method to measure the mean halo mass
of Damped Ly-alpha absorbers (DLAs). The method is based on measuring the ratio
of the cross-correlation between DLAs and galaxies to the auto-correlation of
the galaxies themselves ($w_{\rm dg}/w_{\rm gg}$), which is (in linear theory)
the ratio of their bias factor. This is shown to be true irrespective of the
galaxy redshift distribution, provided that one uses the same galaxies for the
two correlation functions. The method is applicable to all redshifts. Here, we
focus on z=3 DLAs and we demonstrate that the method robustly constrains the
mean DLA halo mass using smoothed particle hydrodynamics (SPH) cosmological
simulations. If we use the bias formalism of Mo & White with the DLA and galaxy
mass distributions of these simulations, we predict a bias ratio of 0.771.
Direct measurement from the simulations of $w_{\rm dg}/w_{\rm gg}$ st yields a
ratio of 0.73+/-0.08, in excellent agreement with that prediction.
Equivalently, inverting the measured correlation ratio to infer a mean DLA halo
mass yields (log. averaging, in solar units) <log(M_DLA)> =11.13+/-013, in
excellent agreement with the true value in the simulations: 11.16. The cross-
correlation method thus appears to yield a robust estimate of the average host
halo mass even though the DLAs and the galaxies occupy a broad mass spectrum of
halos, and massive halos contain multiple galaxies with DLAs. We show that the
inferred mean DLA halo mass is independent of the galaxy sub-sample used, i.e.
the cross-correlation technique is also reliable. Our results imply that the
cross-correlation length between DLAs and LBGs is predicted to be, at most,
2.85 Mpc. Future observations will soon distinguish models in which DLAs are in
low mass halos from those in which DLAs are in massive halos.


title: Anti-solar differential rotation

abstract:
  The differential rotation of anti-solar type detected by observations for
several stars may result from a fast meridional flow. The sufficiently
intensive meridional circulation may be caused by large-scale thermal
inhomogeneities or, perhaps, by tidal forcing from a companion star. First
results of simulations of the anti-solar rotation of a giant star with
magnetically induced thermal inhomogeneities are presented. Perspectives for
observational check of the theory are discussed.


title:
Oxygen isotopic ratios in galactic clouds along the line of sight
  towards Sagittarius B2

abstract:
  As an independent check on previous measurements of the isotopic abundance of
oxygen through the Galaxy, we present a detailed analysis of the ground state
rotational lines of 16OH and 18OH in absorption towards the giant molecular
cloud complex, Sagittarius B2. We have modelled the line shapes to separate the
contribution of several galactic clouds along the line of sight and calculate
16OH/18OH ratios for each of these features. The best fitting values are in the
range 320-540, consistent with the previous measurements in the Galactic Disk
but slightly higher than the standard ratio in the Galactic Centre. They do not
show clear evidence for a gradient in the isotopic ratio with galactocentric
distance. The individual 16OH column densities relative to water give ratios of
[H2O/OH]=0.6-1.2, similar in magnitude to galactic clouds in the sight lines
towards W51 and W49. A comparison with CH indicates [OH/CH] ratios higher than
has been previously observed in diffuse clouds. We estimate OH abundances of
10^-7 - 10^-6 in the line of sight features.


title: Which Massive stars are Gamma-Ray Burst Progenitors?

abstract:
  The collapsar model for gamma-ray bursts requires three essential
ingredients: a massive core, removal of the hydrogen envelope, and enough
angular momentum in the core. We study current massive star evolution models of
solar metallicity to determine which massive star physics is capable of
producing these ingredients. In particular, we investigate the role of
hydrodynamic and magnetic internal angular momentum transport and binary mass
and angular momentum transfer. We follow the evolution of rotating single stars
and of binary systems that include rotational processes for both stars.
Neglecting magnetic fields, we show that the cores of massive single stars can
maintain a high specific angular momentum when evolved with the assumption that
mean molecular weight gradients suppress rotational mixing processes. In binary
systems that undergo mass transfer during core hydrogen burning the mass
receiving star accretes large amounts of high angular momentum material,
leading to a spin-up of the core. We find, however, that this merely
compensates for the tidal angular momentum loss due to spin-orbit coupling,
which leads to synchronous rotation before the mass transfer event. Therefore
the resulting cores do not rotate faster than in single stars. We also present
models that include magnetic fields generated by differential rotation and we
consider the internal angular momentum transport by magnetic torques. We
investigate the capability of magnetic torques to efficiently pump angular
momentum into the cores of accreting stars. Despite our finding that this
mechanism works, the magnetic coupling of core and envelope after the accreting
star ends core hydrogen burning leads to slower rotation than in the
non-magnetic case.


title:
High-Resolution Molecular Line Observations of the Environment of the
  Class 0 Source B1-IRS

abstract:
  In this work we present VLA observations of the NH3, CCS, and H2O maser
emission at 1 cm from the star forming region B1-IRS (IRAS 03301+3057) with ~
5" (=1750 AU) of angular resolution. CCS emission is distributed in three
clumps around the central source. These clumps exhibit a velocity gradient from
red- to blueshifted velocities toward B1-IRS, probably due to an interaction
with the outflow from an embedded protostar. The outflow and its powering
source are traced by a reflection nebula and an associated infrared point
source detected in a 2MASS K-band image. We find that this infrared point
source is associated with water maser emission distributed in an elongated
structure (~ 450 AU size) along the major axis of the reflection nebula and
tracing the base of the outflow of the region. Ammonia emission is extended and
spatially anticorrelated with CCS. This is the first time that this kind of
anticorrelation is observed in a star forming region with such a high angular
resolution, and illustrates the importance of time-dependent chemistry on small
spatial scales. The relatively large abundance of CCS with respect to ammonia,
compared with other star forming regions, suggests an extreme youth for the
B1-IRS object (<10E+5 yr). We suggest the possibility that CCS abundance is
enhanced via shock-induced chemistry.


title:
Inferences from pulsational amplitudes and phases for multimode $\delta$
  Sct star FG Vir

abstract:
  We combine photometric and spectroscopic data on twelve modes excited in FG
Vir to determine their spherical harmonic degrees, $\ell$, and to obtain
constraints on the star model. The effective temperature consistent with the
mean colours and the pulsation data is about 7200K. In six cases, the $\ell$
identification is unique with above 80 % probability. Two modes are identified
as radial. Simultaneously with $\ell$, we determine a complex parameter $f$
which probes subphotospheric stellar layers. Comparing its values with those
derived from models assuming different treatment of convection, we find
evidence that convective transport in the envelope of this star is inefficient.


title: Friedmann cosmology on codimension 2 brane with time dependent tension

abstract:
  A solution of codimension 2 brane is found for which 4 dimensional Friedmann
cosmology is recovered on the brane with time dependent tension, in the
Einstein frame. The effective parameter $p/\rho$ of equation of state on the
brane can be quintessence like, de Sitter like or phantom like, depending on
integration constants of the solution.


title:
Spectra of black-hole binaries in the low/hard state: from radio to
  X-rays

abstract:
  We propose a jet model for the low/hard state of Galactic black-hole X-ray
sources that can explain the energy spectra from radio to X-rays. The model
assumes that i) there is a magnetic field along the axis of the jet; ii) the
electron density in the jet drops inversely proportional to distance; and iii)
the electrons in the jet follow a power law distribution function. We have
performed Monte Carlo simulations of Compton upscattering of soft photons from
the accretion disk and have found power-law high-energy spectra with
photon-number index in the range 1.5 - 2 and cutoff at a few hundred keV. The
spectrum at long wavelengths (radio, infrared, optical) is modeled to come from
synchrotron radiation of the energetic electrons in the jet. We find flat to
inverted radio spectra that extend from the radio up to about the optical band.
For magnetic field strengths of the order of 10^5-10^6G at the base of the jet,
the calculated spectra agree well in slope and flux with the observations. Our
model has the advantage over other existing models that it also explains many
of the existing timing data such as the time lag spectra, the hardening of the
power density spectra and the narrowing of the autocorrelation function with
increasing photon energy.


title:
Millimeter-wave emission during the 2003 low excitation phase of eta
  Carinae

abstract:
  In this paper we present observations of eta Carinae in the 1.3 mm and 7 mm
radio continuum, during the 2003.5 low excitation phase. The expected minimum
in the light curves was confirmed at both wavelengths and was probably due to a
decrease in the number of UV photons available to ionize the gas surrounding
the binary system. At 7 mm a very well defined peak was superimposed on the
declining flux density. It presented maximum amplitude in 29 June 2003 and
lasted for about 10 days. We show that its origin can be free-free emission
from the gas at the shock formed by wind-wind collision, which is also
responsible for the observed X-ray emission. Even though the shock strength is
strongly enhanced as the two stars in the binary system approach each other,
during periastron passage the X-ray emission is strongly absorbed and the 7 mm
observations represent the only direct evidence of this event.


title:
The application of a Trous wave filtering and Monte Carlo analysis on
  SECIS 2001 solar eclipse observations

abstract:
  8000 images of the Solar corona were captured during the June 2001 total
Solar eclipse. New software for the alignment of the images and an automated
technique for detecting intensity oscillations using multi scale wavelet
analysis were developed. Large areas of the images covered by the Moon and the
upper corona were scanned for oscillations and the statistical properties of
the atmospheric effects were determined. The a Trous wavelet transform was used
for noise reduction and Monte Carlo analysis as a significance test of the
detections. The effectiveness of those techniques is discussed in detail.


title:
Iron-line and continuum flux variations in the RXTE spectra of the
  black-hole candidate XTE J1650-500

abstract:
  We present the results of spectral fits made to 57 pointed observations of
the Galactic black hole candidate and X-ray transient XTE J1650-500, made with
the Rossi X-ray Timing Explorer in 2001 when the source was in a transition
from the hard state to the soft state. A strong and variable Fe K-alpha
emission line is detected in these spectra. The line flux varies in a
non-linear way with the hard X-ray flux, in apparent contradiction to the
predictions of simple disc reflection models. We observe a change in the
overall trend that coincides with changes in t he continuum X-ray spectrum and
the fast X-ray variability. The Fe-line flux versus hard X-ray flux variations
are consistent with the predictions of reflection models which consider high
disc-ionization states and with a model which considers gravitational
light-bending effects. Indications for an anti-correlation between the Fe-line
flux and the hard X-ray flux in the spectrally hardest observations and weak
variations in the Fe-line energy (as observed with XMM-Newton and BeppoSAX)
slightly favour the light-bending interpretation.


title:
Multiband Optical Photometry and Bolometric Light Curve of the Type Ia
  Supernova 2004S

abstract:
  We present $\rm BVR_{c}I_{c}$ broad band CCD photometry of the Type Ia
supernova SN 2004S, which appeared in the galaxy MCG-05-16-021, obtained during
2004 February 12 to March 22. Multiband and bolometric light curves constructed
using our data as well as other available data are presented. The time of B
band maximum and the peak magnitudes in different bands are obtained using the
fits of light curve and colour templates. We clearly see a strong shoulder in
$\rm R_{c}$ band and a second maximum in $\rm I_{c}$ band. SN 2004S closely
resembles SN 1992al after maximum. From the peak bolometric luminosity we
estimate the ejected mass of $\rm ^{\rm 56}Ni$ to be 0.41 $\rm M_{\odot}$.


title: The updated E_peak - E_gamma correlation in GRBs

abstract:
  The recently discovered correlation between the rest frame GRB peak spectral
energy $E_{\rm peak}$ and the collimation corrected energy $E_\gamma$ in long
GRBs is potentially very important, yet awaits confirmation from an independent
sample. It may help to shed light on the radiation mechanism of the prompt GRB
phase and on the way -- and in which form -- the energy is released from the
central engine. We here present some additional evidence for the correlation
(two new bursts) and re-derive the best-fit parameters. The tightness of the
correlation is confirmed (sigma=0.1 dex). We show that this correlation allows
us, for the first time, to use GRBs as cosmological probes to constrain the
expansion history of the universe.


title: Black Hole States: Accretion and Jet Ejection

abstract:
  The complex spectral and timing properties of the high-energy emission from
the accretion flow in black-hole binaries, together with their strong
connection to the ejection of powerful relativistic jets from the system, can
be simplified and reduced to four basic states: hard, hard-intermediate,
soft-intermediate and soft. Unlike other classifications, these states are
based on the presence of sharp state transitions. I summarize this
classification and discuss the relation between these states and the physical
components contributing to the emitted flux.


title: The lives and deaths of positrons in the interstellar medium

abstract:
  We reexamine in detail the various processes undergone by positrons in the
ISM from their birth to their annihilation using the most recent results of
positron interaction cross sections with H, H2 and He. The positrons' lives are
divided into two phases: the 'in-flight' phase and the thermal phase. The first
phase is treated with a Monte Carlo simulation that allows us to determine the
fraction of positrons that form positronium and annihilate as well as the
characteristics of the annihilation emission as a function of the medium
conditions. The second phase is treated with a binary reaction rate approach,
with cross sections adopted from experimental measurement or theoretical
calculations. An extensive search and update of the knowledge of positron
processes was thus undertaken. New reaction rates and line widths have been
obtained. We investigate the treatment of the complicated interactions between
positrons and interstellar dust grains. New reaction rates and widths of the
line resulting from the annihilation inside and outside of the grain have been
obtained. The final results of our calculations showed that dust is only
important in the hot phase of the ISM, where it dominates all other processes.
Combining the new calculations, we have constructed annihilation spectra for
each phase of the ISM, considering various grain contents, as well as an
overall combined spectrum for the ISM as a whole.


title:
Chandra Detection of the First X-ray Forest along the Line of Sight To
  Mkn 421

abstract:
  We present the first >=3.5 sigma (conservative) or >=5.8 sigma (sum of lines
significance) detection of two Warm-Hot Intergalactic Medium (WHIM) filaments
at z>0, which we find along the line of sight to the blazar Mkn 421. These
systems are detected through highly ionized resonant metal absorption in high
quality Chandra-ACIS and -HRC Low Energy Transmission Grating (LETG) spectra of
Mkn 421, obtained following our two Target of Opportunity requests during two
outburst phases.
  The two intervening WHIM systems that we detect, have OVII and NVII columns
of N(OVII)=(1.0 +/- 0.3) x 1e15 cm-2} N(NVII)=(0.8 +/- 0.4) x 1e15 cm-2, and
N(OVII)=(0.7 +/- 0.3) x 1e15 cm-2, N(NVII)=(1.4 +/- 0.5) x 1e15 cm-2
respectively.
  From the detected number of WHIM filaments along this line of sight we can
estimate the number of OVII filaments per unit redshift with columns larger
than 7e14 cm-2, dP(OVII)/dz(N(OVII)>=7e14) = 67^{+88}_{-43}, consistent, within
the large 1-sigma errors, with the hydrodynamical simulation predictions of
dP(OVII)/dz(N(OVII)>=7e14) = 30. Finally, we measure a cosmological mass
density of X-ray WHIM filaments Omega_b = 0.027^{+0.038}_{-0.019} x
10^{[O/H]_{-1}}, consistent with both model predictions and the estimated
number of 'missing' baryons at low redshift.


title:
POINT-AGAPE Pixel Lensing Survey of M31 : Evidence for a MACHO
  contribution to Galactic Halos

abstract:
  The POINT-AGAPE collaboration is carrying out a search for gravitational
microlensing toward M31 to reveal galactic dark matter in the form of MACHOs
(Massive Astrophysical Compact Halo Objects) in the halos of the Milky Way and
M31. A high-threshold analysis of 3 years of data yields 6 bright,
short--duration microlensing events, which are confronted to a simulation of
the observations and the analysis. The observed signal is much larger than
expected from self lensing alone and we conclude, at the 95% confidence level,
that at least 20% of the halo mass in the direction of M31 must be in the form
of MACHOs if their average mass lies in the range 0.5-1 M$_\odot$. This lower
bound drops to 8% for MACHOs with masses $\sim 0.01$ M$_\odot$. In addition, we
discuss a likely binary microlensing candidate with caustic crossing. Its
location, some 32' away from the centre of M31, supports our conclusion that we
are detecting a MACHO signal in the direction of M31.


title: The Kinetic Sunyaev-Zel'dovich Effect from Reionization

abstract:
  During the epoch of reionization, local variations in the ionized fraction
(patchiness) imprint arcminute-scale temperature anisotropies in the CMB
through the kinetic Sunyaev-Zel'dovich (kSZ) effect. We employ an improved
version of an analytic model of reionization devised in Furlanetto et al.(2004)
to calculate the kSZ anisotropy from patchy reionization. This model uses
extended Press-Schechter theory to determine the distribution and evolution of
HII bubbles and produces qualitatively similar reionization histories to those
seen in recent numerical simulations. We find that the angular power spectrum
of the kSZ anisotropies depends strongly on the size distribution of the HII
bubbles and on the duration of reionization. In addition, we show that upcoming
measurements of the kSZ effect should be able to distinguish between several
popular reionization scenarios. In particular, the amplitude of the patchy
power spectrum for reionization scenarios in which the IGM is significantly
ionized by Population III stars (or by mini-quasars/decaying particles) can be
larger (or smaller) by over a factor of 3 than the amplitude in more
traditional reionization histories (with temperature anisotropies that range
between 0.5 and 3 micro-Kelvin at l = 5000). We highlight the differences in
the kSZ signal between many possible reionization morphologies and discuss the
constraints that future observations of the kSZ will place on this epoch.


title: Black Holes in Galaxy Mergers: Evolution of Quasars

abstract:
  Based on numerical simulations of gas-rich galaxy mergers, we discuss a model
in which quasar activity is tied to the self-regulated growth of supermassive
black holes in galaxies. Nuclear inflow of gas attending a galaxy collision
triggers a starburst and feeds black hole growth, but for most of the duration
of the starburst, the black hole is heavily obscured by surrounding gas and
dust which limits the visibility of the quasar, especially at optical and UV
wavelengths. Eventually, feedback energy from accretion heats the gas and
expels it in a powerful wind, leaving a 'dead quasar'. Between buried and dead
phases there is a window during which the galaxy would be seen as a luminous
quasar. Because the black hole mass, radiative output, and distribution of
obscuring gas and dust all evolve strongly with time, the duration of this
phase of observable quasar activity depends on both the waveband and imposed
luminosity threshold. We determine the observed and intrinsic lifetimes as a
function of luminosity and frequency, and calculate observable lifetimes ~10
Myr for bright quasars in the optical B-band, in good agreement with empirical
estimates and much smaller than the black hole growth timescales ~100 Myr,
naturally producing a substantial population of 'buried' quasars. However,
observed and intrinsic energy outputs converge in the IR and hard X-ray bands
as attenuation becomes weaker and chances of observation greatly increase. We
obtain the distribution of column densities along sightlines in which the
quasar is seen above a given luminosity, and find that our result agrees
remarkably well with observed estimates of the column density distribution from
the SDSS for appropriate luminosity thresholds. (Abridged)


title: A Simple Model for Quintessential Inflation

abstract:
  We describe a simple toy model for quintessential inflation where a complex
scalar field described by a lagrangian with a Peccei-Quinn U(1) symmetry
spontaneously broken at a high energy scale and explicitly broken by instanton
effects at a much lower energy can account for both the early inflationary
phase and the recent accelerated expansion of the Universe. The real part of
the complex field plays the role of the inflaton whereas the imaginary part,
the "axion", is the quintessence field.


title:
Type Ia supernovae tests of fractal bubble universe with no cosmic
  acceleration

abstract:
  The unexpected dimness of Type Ia supernovae at redshifts z >~ 1 has over the
past 7 years been seen as an indication that the expansion of the universe is
accelerating. A new model cosmology, the "fractal bubble model", has been
proposed by one of us [gr-qc/0503099], based on the idea that our observed
universe resides in an underdense bubble remnant from a primordial epoch of
cosmic inflation, together with a new solution for averaging in an
inhomogeneous universe. Although there is no cosmic acceleration, it is claimed
that the luminosity distance of type Ia supernovae data will nonetheless fit
the new model, since it mimics a Milne universe at low redshifts. In this paper
the hypothesis is tested statistically against the available type Ia supernovae
data by both chi-square and Bayesian methods. While the standard model with
cosmological constant Omega_Lambda = 1-Omega_m is favoured by a Bayesian
analysis with wide priors, the comparison depends strongly on the priors chosen
for the density parameter, Omega_m. The fractal bubble model gives better
agreement generally for Omega_m<0.2. It also gives reasonably good fits for all
the range, Omega_m=0.01-0.55, allowing the possibility of a viable cosmology
with just baryonic matter, or alternatively with both baryonic matter and
additional cold dark matter.


title:
Elemental Abundance Ratios in Stars of the Outer Galactic Disk. I. Open
  Clusters

abstract:
  We summarize radial velocity studies of selected stars in the old, distant
clusters Berkeley 20, Berkeley 21, NGC 2141, Berkeley 29, and Berkeley 31.
Three members of M67 were observed similarly, and those velocities compare
extremely well with prior measures. We measured the chemical compositions of
all six clusters for [Fe/H] as well as abundances of alpha elements, iron-peak
elements, and those synthesized in either the s-process or the r-process.
  For the outer disk, the abundance gradient for [Fe/H] deviates from the trend
defined near the solar neighborhood. Rather than declining with increasing
Galactocentric distance, [Fe/H] appears to reach a "basement" at [Fe/H]=-0.5
beyond R_GC = 10 to 12kpc. We find enhanced [O/Fe], [alpha/Fe], and [Eu/Fe] in
the outer disk revealing a rapid star formation history.
  An intriguing, but tentative, conclusion is that the outer disk open cluster
abundance ratios are consistent with the outer disk being formed via a merger
event. The basement in [Fe/H] and enhanced [alpha/Fe] suggest that the outer
disk formed from a reservoir of gas with a star formation history distinct from
the solar neighborhood. The open clusters may have formed as a result of star
formation triggered by a merger event in the outer disk. The ages of the outer
disk open clusters would then be a measure of when the merger occurred.
[Abridged]


title: Models of class II methanol masers based on improved molecular data

abstract:
  The class II masers of methanol are associated with the early stages of
formation of high-mass stars. Modelling of these dense, dusty environments has
demonstrated that pumping by infrared radiation can account for the observed
masers. Collisions with other molecules in the ambient gas also play a
significant role, but have not been well modelled in the past. Here we examine
the effects on the maser models of newly available collision rate coefficients
for methanol. The new collision data does not alter which transitions become
masers in the models, but does influence their brightness and the conditions
under which they switch on and off. At gas temperatures above 100 K the effects
are broadly consistent with a reduction in the overall collision cross-section.
This means, for example, that a slightly higher gas density than identified
previously can account for most of the observed masers in W3(OH). We have also
examined the effects of including more excited state energy levels in the
models, and find that these play a significant role only at dust temperatures
above 300 K. An updated list of class II methanol maser candidates is
presented.


title:
Merging Galaxies in Goods-s: First Extragalactic Results from Keck Laser
  Adaptive Optics

abstract:
  The Center for Adaptive Optics Treasury Survey (CATS) aims to combine deep
HST images in the optical with deep Keck adaptive optics (AO) data in the
near-infrared (NIR) to study distant galaxies, AGN, and supernovae. We recently
achieved an important new milestone by securing the first Keck laser guide star
AO image of faint galaxies. Six galaxies with redshifts ranging from 0.3-1.0
were targeted in one pointing in the GOODS-S field. Two are Chandra Deep Field
South sources, XID-56 and XID-536, with complex morphologies suggestive of
recent merger activity. Substructures seen in the NIR AO image (FWHM ~ 0.1"),
including multiple tight knots in XID-56 and a double nucleus in XID-536, are
confirmed in the optical HST images. These structures are unresolved in the
best seeing-limited (FWHM ~ 0.5") NIR images. Stellar population synthesis
models of the substructures indicate that XID-56 is a gas rich merger with a
recent burst of star formation and significant amounts of dust. XID-536 appears
to be a merger of two evolved stellar populations.


title:
Geometrical Effect of Supercritical Accretion Flows: Observational
  Implications of Galactic Black-Hole Candidates and Ultraluminous X-ray
  Sources

abstract:
  We investigate the dependence of the viewing angle in supercritical accretion
flows and discuss the observational implications of galactic black-hole
candidates and ultraluminous X-ray sources. When the mass accretion rate
exceeds the critical rate, then the shape of the disk is geometrically thick
due to the enhanced radiation pressure. The model spectra of supercritical
accretion flows strongly depend on the inclination angle. Because the outer
disk blocks the emission from the disk inner region for high inclination angle.
We also find that the spectral properties of low-inclination angle and low
accretion-rate disks are very similar to those of high-inclination and high
accretion rate disks. That is, if an object has a high inclination and high
accretion rate, such a system suffers from self-occultation and the spectrum
will be extremely soft. Therefore, we cannot discriminate these differences
from spectrum shapes only. Conversely, if we use the self-occultation
properties, we could constrain the inclination angle of the system. We suggest
that some observed high temperature ultraluminous X-ray sources have near
face-on geometry, i < 40, and Galactic black hole candidate, XTE J1550-564,
possesses relatively high-inclination angles, i > 60.


title:
Interpretation of the Radio/X-ray Knots of AGN Jets within the Internal
  Shock Model Framework

abstract:
  The dynamics of relativistically moving blobs ejected out of a central AGN,
are considered. It is assumed that the collision between two blobs are
completely inelastic, such that the bulk kinetic energy lost in the collision
is used to energize electrons to relativistic energies via acceleration in
internal shocks which are formed due to the collision. These high energy
electrons which are produced on a time-scale corresponding to the collision
time-scale, cool by radiative losses due to synchrotron and Inverse Compton
processes. The model is applied to the radio/X-ray knots of several AGN. For
three of these sources we have analyzed long (> 40 ksec) Chandra observations
and report on constrains on the X-ray spectral indices. In the framework of
this model the AGN are inferred to sporadically eject relativistic blobs on
time-scales ranging from 10^{11} to 10^{12} secs for different sources. It is
shown that the collision time-scales can be longer than the age of the knot
and, hence, non-thermal electrons are continuously being injected into the
system. This continuous injection, in contrast to an instantaneous one time
injection, gives rise to a characteristic spectral break, rather than a
high-energy cutoff in the spectrum.


title:
The dynamical fingerprint of intermediate mass black holes in globular
  clusters

abstract:
  A number of observations hints for the presence of an intermediate mass black
hole (IMBH) in the core of three globular clusters: M15 and NGC 6752 in the
Milky Way, and G1, in M31. However the existence of these IMBHs is far form
being conclusive. In this paper, we review their main formation channels and
explore possible observational signs that a single or binary IMBH can imprint
on cluster stars. In particular we explore the role played by a binary IMBH in
transferring angular momentum and energy to stars flying by.


title:
Evidence for a long duration component in the prompt emission of short
  Gamma-Ray Bursts detected with BeppoSAX

abstract:
  A statistical study on the light curves of all the short Gamma-Ray Bursts
detected with the Gamma Ray Burst Monitor (GRBM) aboard BeppoSAX is reported.
Evidence for a very weak and long duration component associated with these
events in the two 1 s counters of the GRBM (40-700 keV and >100 keV) is found.
It starts a few tens of seconds before the burst and continues for about 30 s
after the burst. The overall hardness of this component is comparable with that
of the event itself. The detection of a signal before the onset time and the
similar hardness are consistent with an interpretation of the long duration
component in terms of prompt emission associated with short GRBs.


title: Observation of small scale structure using sextupole lensing

abstract:
  Weak gravitational lensing seeks to determine shear by measuring induced
quadrupole (elliptical) shapes in background galaxy images. Small impact
parameter (a few kpc) gravitational lensing by foreground core masses between 2
10^{9} and 2 10^{12} M_\odot will additionally induce a sextupole shape with
the quadrupole and sextupole minima aligned. This correlation in relative
orientation of the quadrupole and sextupole provides a sensitive method to
identify images which have been slightly curved by lensing events. A general
theoretical framework for sextupole lensing is developed which includes several
low order coefficients in a general lensing map. Tools to impute map
coefficients from the galaxy images are described and applied to the north
Hubble deep field. Instrumental PSFs, camera charge diffusion, and image
composition methods are modelled in the coefficient determination process.
Estimates of Poisson counting noise for each galaxy are used to cut galaxies
with signals too small to reliably establish curvature. Curved galaxies are
found to be spatially clumped, as would be expected if the curving were due to
small impact parameter lensing by localized ensembles of dark matter haloes.
Simulations provide an estimate of the total required lensing mass and the
acceptable mass range of the constituent haloes. The overdensities and
underdensities of visible galaxies and their locations in the Hubble foreground
is found to be consistent with our observations and their interpretation as
lensing events.


title: The AMIGA project. I. Optical characterization of the CIG catalog

abstract:
  The AMIGA project (Analysis of the Interstellar Medium of Isolated Galaxies)
is compiling a multiwavelength database of isolated galaxies that includes
optical (B and Halpha), infrared (FIR and NIR) and radio (continuum plus HI and
CO lines) properties. It involves a refinement of the pioneering Catalog of
Isolated Galaxies. This paper is the first in a series and begins with analysis
of the global properties of the nearly redshift-complete CIG with emphasis on
the Optical Luminosity Function (OLF) which we compare with other recent
estimates of the OLF for a variety of environments. The CIG redshift
distribution for n= 956 galaxies re-enforces the evidence for a bimodal
structure seen earlier in smaller samples. The peaks at redshift near 1500 and
6000km/s correspond respectively to galaxies in the local supercluster and
those in more distant large-scale components (particularly Perseus-Pisces). The
two peaks in the redshift distribution are superimposed on 50% or more of the
sample that is distributed in a much more homogeneous way. The CIG probably
represents the most homogeneous local field example that has ever been
compiled. Our derivation of the CIG OLF is consistent with other studies of the
OLF for lower density environments. This comparison via the Schechter parameter
formalization shows that: 1) M* increases with galaxy surface density on the
sky and 2) alpha shows a weaker tendency to do the same. The CIG represents the
largest and most complete foundation for studies of isolated galaxies and is
likely as close as we can come to a field sample. (Tables 1, 2 and 3 are
available in electronic form at http://www.iaa.es/AMIGA.html).


title:
Growth of Intermediate Massive Black Holes in the Hierarchical Formation
  of Small Spiral Galaxies in the High-z Universe

abstract:
  Combining a theoretical model of mass accretion onto a galactic center with a
high-resolution $N$-body/SPH simulation, we investigate the formation of an
intermediate massive black hole (IMBH) during the hierarchical formation of a
small spiral galaxy (with a total mass of $10^{10}M_{\odot}$) in the high-$z$
universe. We found that the rate of average mass accretion to the nucleus due
to the radiation drag exerted by newly formed stars in the forming galaxy is
$\approx 10^{-5}M_{\odot}$yr$^{-1}$. As a result of this accretion, an IMBH
with $\approx 10^{4}M_{\odot}$ can be formed in the center of the spiral galaxy
at $z\sim 4$. We found that a central BH coevolves with the dark matter halo
from $z\sim 15$ to $z\sim 2$. The mass ratio of the BH to the dark matter halo
is nearly constant $\approx (1-3) \times 10^{-6}$ from $z\sim 10$ to $z\sim 2$.
This is because that change in the dark matter potential enhances star
formation in the central part of the galaxy, and as a result the BH evolves due
to mass accretion via the radiation drag. Therefore, our model naturally
predicts a correlation between massive BHs and dark matter halos. Moreover, it
is found that the final BH-to-bulge mass ratio ($\approx 5\times 10^{-5}$) in a
small spiral galaxy at high-$z$ is much smaller than that in the large galaxies
($\approx 10^{-3}$). Our results also suggest that the scatter in the observed
scaling relations between the bulge mass and black hole mass are caused by a
time lag between BH growth and growth of bulge. We also predict that the X-ray
luminosity of AGN is positively correlated with the CO luminosity in the
central region. By comparing our results with the properties of Lyman break
galaxies (LBGs), it is predicted that some LBGs have massive BHs of $\approx
10^{6}-10^{7}M_{\odot}$.


title: Formation of Massive Black Holes in Globular Clusters

abstract:
  The hydrodynamic formation of massive black holes (BHs) in globular clusters
is considered. In particular, we examine the possibility of the BH formation
induced by the radiation drag that is exerted on the interstellar matter by
stellar radiation in globular clusters. The radiation drag extracts angular
momentum from interstellar gas and thus allows the gas to accrete on to the
cluster center.By incorporating the realistic chemical evolution of globular
clusters, we scrutinize the efficiency of the radiation drag to assess the
total accreted mass. As a result, we find that if a globular cluster is more
massive than $\approx 6\times 10^{6}M_{\odot}$ in the present-day stellar
component, a massive BH with $>260M_{\odot}$ can form within it. But, the
BH-to-cluster mass ratio s considerably smaller than the BH-to-bulge mass ratio
($\approx 10^{-3}$) found in galactic bulges. The results are not sensitive to
the assumed stellar initial mass function and star formation rate in the
cluster, as long as the resultant color-magnitude relation, metallicity, and
mass-to-luminosity ratio satisfy those observed in globular clusters. Hence,
the putative linear relation between BH mass and bulge mass($M_{\rm BH}-M_{\rm
bulge}$ relation) cannot be extrapolated to globular cluster systems. In the
present regime, we discuss the BH formation in M15, G1, $\omega$ Cen, the M33
nucleus, and the compact X-ray sources in M82. Finally, we argue observational
indications of the formation process of massive BHs in globular clusters. We
find that the final phase of BH growth due to the radiation drag can be
observed as ultraluminous X-ray sources (ULXs) with $\sim 10^{41}{\rm erg} {\rm
s}^{-1}$.


title: COUP census of X-ray stars in BN-KL and OMC-1S

abstract:
  We present a study of the X-ray sources detected in the vicinity of two
density peaks in the Orion Molecular Cloud 1 (OMC-1) behind the Orion Nebula
Cluster (ONC), as seen in the exceptionally deep (~10 days) exposure of the
Chandra Orion Ultradeep Project (COUP). We focus on a 40"*50" region around the
Becklin-Neugebauer object and Kleinmann-Low nebula (collectively BN-KL) and a
60"*75" region around OMC-1S, a secondary star-forming peak some 90" south of
BN-KL. Forty-three and sixty X-ray sources were detected in BN-KL and OMC-1S,
respectively, of which half and one-third, respectively, were found to be
foreground members of the ONC, while the remaining sources are identified as
obscured X-ray sources with column densities 22<log(NH)/cm^{-2})<24. All but 5
and 18 of these sources have near-infrared stellar counterparts, and 22 of
these appear to be young stellar objects (YSOs). X-ray sources are found close
to four luminous mid-IR sources namely BN, IRc3-i2, IRc2-C, and Source n; their
X-ray variability and spectral properties are typical of coronal activity in
low-mass stars rather than wind emission from massive stars, suggesting that
the X-ray emission may be arising from companions. The X-ray light curve of the
X-ray source close to BN shows a periodicity of ~8.3 days and from an X-ray
image deconvolution of the region around BN, we conclude that either BN itself
or a low mass companion with a projected separation of ~200 AU was detected. On
the other hand, no emission is seen from the bright radio Source I, held by
some to be the main source of luminosity in BN-KL. In OMC-1S, Chandra unveils a
new subcluster of seven YSOs without infrared counterparts (abridged).


title:
Energisation of interstellar media and cosmic ray production by jets
  from X-ray binaries

abstract:
  Drawing on recent estimates of the power of jets from X-ray binary systems as
a function of X-ray luminosity, combined with improved estimates of the
relevant Log(N)-Log(L_X) luminosity functions, we calculate the total energy
input to the interstellar medium (ISM) from these objects. The input of kinetic
energy to the ISM via jets is dominated by those of the black hole systems, in
contrast to the radiative input, which is dominated by accreting neutron stars.
Summing the energy input from black hole jets L_J in the Milky Way, we find
that it is likely to correspond to >1% of L_SNe, the time-averaged kinetic
luminosity of supernovae, and >5% of L_CR, the cosmic ray luminosity. Given
uncertainties in jet power estimates, significantly larger contributions are
possible. Furthermore, in elliptical galaxies with comparable distributions of
low mass X-ray binaries, but far fewer supernovae, the ratio L_J / L_SNe is
likely to be larger by a factor of ~5. We conclude that jets from X-ray
binaries may be an important, distributed, source of kinetic energy to the ISM
in the form of relativistic shocks, and as a result are likely to be a major
source of cosmic rays.


title: The impact of gas physics on strong cluster lensing

abstract:
  Previous studies of strong gravitational lensing by galaxy clusters neglected
the potential impact of the intracluster gas. Here, we compare simulations of
strong cluster lensing including gas physics at increasing levels of
complexity, i.e. with adiabatic, cooling, star-forming, feedback-receiving, and
thermally conducting gas, and with different implementations of the artificial
viscosity in the SPH simulations. Each cluster was simulated starting from the
same initial conditions such as to allow directly comparing the simulated
clusters. We compare the clusters' shapes, dynamics and density profiles and
study their strong-lensing cross sections computed by means of ray-tracing
simulations. We find that the impact of adiabatic gas depends on the amount of
turbulence that builds up, which means that the artificial viscosity plays an
important role. With the common viscosity implementation, adiabatic gas has
little effect on strong cluster lensing, while lower viscosity allows stronger
turbulence, thus higher non-thermal pressure and a generally broader gas
distribution which tends to lower lensing cross sections. Conversely, cooling
and star formation steepen the core density profiles and can thus increase the
strong-lensing efficiency considerably.


title:
The Linearity of the Wesenheit function for the Large Magellanic Cloud
  Cepheids

abstract:
  There is strong evidence that the period-luminosity (PL) relation for the
Large Magellanic Cloud (LMC) Cepheids shows a break at a period around 10 days.
Since the LMC PL relation is extensively used in distance scale studies, the
non-linearity of the LMC PL relation may affect the results based on this LMC
calibrated relation. In this paper we show that this problem can be remedied by
using the Wesenheit function in obtaining Cepheid distances. This is because
the Wesenheit function is linear although recent data suggests that the PL and
the period-colour (PC) relations that make up the Wesenheit function are not.
We test the linearity of the Wesenheit function and find strong evidence that
the LMC Wesenheit function is indeed linear. This is because the non-linearity
of the PL and PC relations cancel out when the Wesenheit function is
constructed. We discuss this result in the context of distance scale
applications. We also compare the distance moduli obtained from
mu_0=mu_V-R(mu_V-mu_I) (equivalent to Wesenheit functions) constructed with the
linear and the broken LMC PL relations, and find that the typical difference in
distance moduli is ~ +-0.03mag. Hence, the broken LMC PL relation does not
seriously affect current distance scale applications. We also discuss the
random error calculated with equation mu_0=mu_V-R(mu_V-mu_I), and show that
there is a correlation term that exists from the calculation of the random
error. The calculated random error will be larger if this correlation term is
ignored.


title: QSO Formation under Coevolution of SMBH and Bulge

abstract:
  he formation and growth of supermassive black holes (SMBHs) physically linked
with bulges are considered. We focus on the radiation hydrodynamic process for
the growth of SMBH in the optically thick starburst phase, where radiation from
bulge stars drives the mass accretion on to a galactic center through radiation
drag effect. In the present scenario, the AGN luminosity-dominant phase (QSO
phase) is preceded by the host luminosity-dominat phase, which is called
``proto-QSO phase''. In this phase, there exists the massive dusty disks within
younger bulges. Also, the proto-QSO phase is anticipated by an optically-thick
ultraluminous infrared galaxy (ULIRG) phase. Furthermore, such radiation
hydrodynamic model has been also applied to disk galaxies. It turns out that
the mass of a SMBH primarily correlates with a bulge component even in a disk
galaxy. Thus, by analogy to proto-QSOs, the BH growing phase in disk galaxies
may have massive dusty disks within younger bulges.


title:
Non-Gaussianity of one-point distribution functions in extended
  Lagrangian perturbation theory

abstract:
  We study the one-point probability distribution functions (PDFs) of the
peculiar velocity and the density fluctuation in a cosmological fluid. Within
the perturbative approach to the structure formation scenario, the effect of
``pressure'' has recently been an area of research interest. The velocity
dispersion of the cosmological fluid creates effective ``pressure'' or
viscosity terms. From this viewpoint, because the pressure reflects a nonlinear
effect of the motion of the fluid, the pressure model would include nonlinear
effects. Here we analyze the Lagrangian linear perturbation PDFs for both the
Zel'dovich approximation and the pressure model. We find that the PDFs of the
peculiar velocity remain Gaussian, even if we consider the pressure. For the
PDFs of the density fluctuation, the occurrence of non-Gaussianity depends on
the ``equation of state'' for the fluid. Therefore we distinguish the
``equation of state'' using the PDFs.


title:
A Multi-Instrument Study of the Helix Nebula Knots with the Hubble Space
  Telescope

abstract:
  We have conducted a combined observational and theoretical investigation of
the ubiquitous knots in the Helix Nebula (NGC 7293). We have constructed a
combined hydrodynamic+radiation model for the ionized portion of these knots
and have accurately calculated a static model for their molecular regions.
Imaging observations in optical emission lines were made with the Hubble Space
Telescope's STIS spectrograph, operating in a "slitless" mode, complemented by
WFPC2 images in several of the same lines. The NICMOS camera was used to image
the knots in molecular hydrogen. These observations, when combined with other
studies of molecular hydrogen and CO provide a complete characterization of the
knots. They possess dense molecular cores of densities about 1,000,000 per
cubic centimeter surrounded on the central star side by a zone of hot molecular
hydrogen. The temperature of the molecular hydrogen emitting layer defies
explanation either through detailed calculations for radiative equilibrium or
for simplistic calculations for shock excitation. Further away from the core is
the ionized zone, whose peculiar distribution of emission lines is explained by
the expansion effects of material flowing through this region. The shadowed
region behind the core is the source of most of the CO emission from the knot
and is of the low temperature expected for a radiatively heated molecular
region.


title: Varying Electromagnetic Coupling and Primordial Magnetic Fields

abstract:
  We study the effect of variations of the electromagnetic coupling on the
process of generation of primordial magnetic fields. We find that only through
a significant growth of the electromagnetic coupling minimum seed fields can be
produced. We also show that, if through some process in the early Universe the
photon acquires a mass that leads, thanks to inflation, to the generation of
primordial magnetic fields, then the influence of variations of the
electromagnetic coupling amounts essentially to the results due to the photon
effective mass alone.


title: On the Dayside Thermal Emission of Hot Jupiters

abstract:
  We discuss atmosphere models of HD209458b in light of the recent day-side
flux measurement of HD209458b's secondary eclipse by Spitzer-MIPS at 24
microns. In addition, we present a revised secondary eclipse IRTF upper limit
at 2.2 microns which places a stringent constraint on the adjacent H2O
absorption band depths. These two measurements are complementary because they
are both shaped by H2O absorption and because the former is on the Wien tail of
the planet's thermal emission spectrum and the latter is near the thermal
emission peak. A wide range of models fit the observational data, confirming
our basic understanding of hot Jupiter atmospheric physics. Although a range of
models are viable, some models at the hot and cold end of the plausible
temperature range can be ruled out. One class of previously unconsidered hot
Jupiter atmospheric models that fit the data are those with C/O >~ 1 (as
Jupiter may have), which have a significant paucity of H2O compared to solar
abundance models with C/O = 0.5. The models indicate that HD209458b is in a
situation intermediate between pure in situ reradiation and very efficient
redistribution of heat; one which will require a careful treatment of
atmospheric circulation. We discuss how future wavelength-dependent and
phase-dependent observations will further constrain the atmospheric circulation
regime. In the shorter term, additional planned measurements for HD209458b,
especially Spitzer IRAC photometry, should lift many of the model degeneracies.
Multiwavelength IR observations constrain the atmospheric structure and
circulation properties of hot Jupiters and thus open a new chapter in
quantitative extrasolar planetology.


title: Gravitational evolution of a perturbed lattice and its fluid limit

abstract:
  We apply a simple linearization, well known in solid state physics, to
approximate the evolution at early times of cosmological N-body simulations of
gravity. In the limit that the initial perturbations, applied to an infinite
perfect lattice, are at wavelengths much greater than the lattice spacing $l$
the evolution is exactly that of a pressureless self-gravitating fluid treated
in the analagous (Lagrangian) linearization, with the Zeldovich approximation
as a sub-class of asymptotic solutions. Our less restricted approximation
allows one to trace the evolution of the discrete distribution until the time
when particles approach one another (i.e. ``shell crossing''). We calculate
modifications of the fluid evolution, explicitly dependent on $l$ i.e.
discreteness effects in the N body simulations. We note that these effects
become increasingly important as the initial red-shift is increased at fixed
$l$. The possible advantages of using a body centred cubic, rather than simple
cubic, lattice are pointed out.


title: Extrasolar Carbon Planets

abstract:
  We suggest that some extrasolar planets <~ 60 Earth masses will form
substantially from silicon carbide and other carbon compounds. Pulsar planets
and low-mass white dwarf planets are especially good candidate members of this
new class of planets, but these objects could also conceivably form around
stars like the Sun. This planet-formation pathway requires only a factor of two
local enhancement of the protoplanetary disk's C/O ratio above solar, a
condition that pileups of carbonaceous grains may create in ordinary
protoplanetary disks. Hot, Neptune-mass carbon planets should show a
significant paucity of water vapor in their spectra compared to hot planets
with solar abundances. Cooler, less massive carbon planets may show
hydrocarbon-rich spectra and tar-covered surfaces. The high sublimation
temperatures of diamond, SiC, and other carbon compounds could protect these
planets from carbon depletion at high temperatures.


title: Cusps in CDM halos

abstract:
  We resolve the inner region of a massive cluster forming in a cosmological
LCDM simulation with a mass resolution of 2*10^6 Msun and before z=4.4 even
3*10^5 Msun. This is a billion times less than the clusters final virial mass
and a substantial increase over current LCDM simulations. We achieve this
resolution using a new multi-mass refinement procedure and are now able to
probe a dark matter halo density profile down to 0.1 percent of the virial
radius. The inner density profile of this cluster halo is well fitted by a
power-law rho ~ r^-gamma down to the smallest resolved scale. An inner region
with roughly constant logarithmic slope is now resolved, which suggests that
cuspy profiles describe the inner profile better than recently proposed
profiles with a core. The cluster studied here is one out of a sample of six
high resolution cluster simulations of Diemand et al. (2004) and it's inner
slope of gamma = 1.2 lies close to the sample average.


title: On the distribution of collisionless particles in local potential well

abstract:
  The distribution of collisionless particles with infinite motion in the
presence of a local potential well is discussed. Such distribution is important
for interpretation of results of dark matter searches. The relationship
n/v=const, where n and v are respectively number density and velocity of
particles, is derived for particles crossing a local potential well. The limits
of application of this relationship are specified.


title: A Catalog of Distant Compact Groups Using DPOSS

abstract:
  In this paper we present an objectively defined catalog of 459 small, high
density groups of galaxies out to z~0.2 in a region of 6260 square degrees in
the northern sky derived from the Digitized Second Palomar Observatory Sky
Survey. Our catalog extends down to r = 19.0 and has a median redshift of z_med
= 0.12, making it complementary to Hickson's catalog for the nearby universe
(z_med = 0.03). The depth and angular coverage of this catalog makes it
valuable for studies of the general characteristics of small groups of galaxies
and how galaxies evolve in and around them. We also examine the relationship
between compact groups and large scale structure.


title: The Unusual Luminosity Function of the Globular Cluster M10

abstract:
  We present the I-band luminosity function of the differentially reddened
globular cluster M10. We combine photometric analysis derived from wide-field
(23' x 23') images that include the outer regions of the cluster and
high-resolution images of the cluster core. After making corrections for
incompleteness and field star contamination, we find that the relative numbers
of stars on the lower giant branch and near the main-sequence turnoff are in
good agreement with theoretical predictions. However, we detect significant (>
6 \sigma) excesses of red giant branch stars above and below the red giant
branch bump using a new statistic (a population ratio) for testing relative
evolutionary timescales of main-sequence and red giant stars. The statistic is
insensitive to assumed cluster chemical composition, age, and main-sequence
mass function. The excess number of red giants cannot be explained by
reasonable systematic errors in our assumed cluster chemical composition, age,
or main-sequence mass function. Moreover, M10 shows excesses when compared to
the cluster M12, which has nearly identical metallicity, age, and
color-magnitude diagram morphology. We discuss possible reasons for this
anomaly, finding that the most likely cause is a mass function slope that shows
significant variations as a function of mass.


title:
IRAC Mid-Infrared Imaging of the Hubble Deep Field South: Star Formation
  Histories and Stellar Masses of Red Galaxies at z>2

abstract:
  We present deep 3.6 - 8 micron imaging of the Hubble Deep Field South with
IRAC on the Spitzer Space Telescope. We study Distant Red Galaxies (DRGs) at
z>2 selected by Js - Ks > 2.3 and compare them to a sample of Lyman Break
Galaxies (LBGs) at z=2-3. The observed UV-to-8 micron spectral energy
distributions are fit with stellar population models to constrain star
formation histories and derive stellar masses. We find that 70% of the DRGs are
best described by dust-reddened star forming models and 30% are very well fit
with old and ``dead'' models. Using only the I - Ks and Ks - 4.5 micron colors
we can effectively separate the two groups. The dead systems are among the most
massive at z~2.5 (mean stellar mass <M*> = 0.8 x 10^11 Msun) and likely formed
most of their stellar mass at z>5. To a limit of 0.5 x 10^11 Msun their number
density is ~10 x lower than that of local early-type galaxies. Furthermore, we
use the IRAC photometry to derive rest-frame near-infrared J, H, and K fluxes.
The DRGs and LBGs together show a large variation (a factor of 6) in the
rest-frame K-band mass-to-light ratios (M/L_K), implying that even a Spitzer 8
micron-selected sample would be very different from a mass-selected sample. The
average M/L_K of the DRGs is about three times higher than that of the LBGs,
and DRGs dominate the high-mass end. The M/L_K ratios and ages of the two
samples appear to correlate with derived stellar mass, with the most massive
galaxies being the oldest and having the highest mass-to-light ratios, similar
as found in the low-redshift universe.


title: A High-z Correction to the Hubble Line

abstract:
  This paper was withdrawn as it may have appeared elsewhere, although in a
different form.


title:
Photoevaporation Flows in Blister HII Regions: I. Smooth Ionization
  Fronts and Application to the Orion Nebula

abstract:
  We present hydrodynamical simulations of the photoevaporation of a cloud with
large-scale density gradients, giving rise to an ionized, photoevaporation
flow. The flow is found to be approximately steady during the large part of its
evolution, during which it can resemble a "champagne flow" or a "globule flow"
depending on the curvature of the ionization front. The distance from source to
ionization front and the front curvature uniquely determine the structure of
the flow, with the curvature depending on the steepness of the lateral density
gradient in the neutral cloud. We compare these simulations with both new and
existing observations of the Orion nebula and find that a model with a mildly
convex ionization front can reproduce the profiles of emission measure,
electron density, and mean line velocity for a variety of emitting ions on
scales of 10^{17} to 10^{18} cm. The principal failure of our model is that we
cannot explain the large observed widths of the [O I] 6300 Angstrom line that
forms at the ionization front.


title: Minimal tau approximation and simulations of the alpha effect

abstract:
  The validity of a closure called the minimal tau approximation (MTA), is
tested in the context of dynamo theory, wherein triple correlations are assumed
to provide relaxation of the turbulent electromotive force. Under MTA, the
alpha effect in mean field dynamo theory becomes proportional to a relaxation
time scale multiplied by the difference between kinetic and current helicities.
It is shown that the value of the relaxation time is positive and, in units of
the turnover time at the forcing wavenumber, it is of the order of unity. It is
quenched by the magnetic field -- roughly independently of the magnetic
Reynolds number. However, this independence becomes uncertain at large magnetic
Reynolds number. Kinetic and current helicities are shown to be dominated by
large scale properties of the flow.


title:
The Mass Function of Dark Matter Haloes in a Cosmological Model with a
  Running Primordial Power Spectrum

abstract:
  We present the first study on the mass functions of Jenkins et al (J01) and
an estimate of their corresponding largest virialized dark halos in the
Universe for a variety of dark-energy cosmological models with a running
spectral index. Compared with the PL-CDM model, the RSI-CDM model can raise the
mass abundance of dark halos for small mass halos at lower redshifts, but it is
not apparent on scales of massive mass halos. Particularly, this discrepancy
increases largely with the decrease of redshift, and the RSI-CDM model can
suppress the mass abundance on any scale of halo masses at higher redshift. As
for the largest mass of virialized halos, the spatially flat $\Lambda$CDM
models give more massive mass of virialized objects than other models for both
of PL-CDM and RSI-CDM power spectral indexs, and the RSI-CDM model can enhance
the mass of largest virialized halos for all of models considered in this
paper. So we probably distinguish the PL-CDM and RSI-CDM models by the largest
virialized halos in the future survey of cluster of galaxies.


title: The dark matter content of early-type barred galaxies

abstract:
  The dynamics of a barred galaxy depends on the pattern speed of its bar. The
only direct method for measuring the pattern speed of a bar is the
Tremaine-Weinberg technique. This method relies on the analysis of the
distribution and dynamics of the stellar component. It is best suited to
gas-poor galaxies and therefore it has been restricted to early-type barred
galaxies. On the other hand, a variety of indirect methods, which are based on
the analysis of the distribution and dynamics of the gaseous component, has
been used to measure the bar pattern speed in late-type barred galaxies. The
complete sample of galaxies for which the bar pattern speed has been directly
measured with the Tremaine-Weinberg method is given. Nearly all the measured
bars are as rapidly rotating as they can be. By comparing this result with
recent high-resolution N-body simulations of bars in cosmologically-motivated
dark matter halos, it is possible to conclude that these bars are not located
inside centrally-concentrated halos.