title: Optical studies of ultra-luminous X-ray sources in nearby galaxies

abstract:
  Optical studies of ultra-luminous X-ray sources is an essential step in
understanding the nature of these enigmatic sources, and in this paper we
report our studies of five ULXs in NGC4559, NGC5194, NGC1313 and NGC628
observed with the Hubble Space Telescope and the 6.4 Magellan/Baade telescope.
The ULX in NGC4559 is identified with four blue and red supergiants within a
$0\farcs2$ error circle, in a star forming region that is younger than
$10^{7.4}$ years. ULX-3 in NGC5194 is located on the rim of a star cluster with
a few faint stars within the $0\farcs3$ error circle, though the secondary in
this system is expected to be a low mass ($0.3M_\odot$) star below detection
limits given its two hour period. ULX-5 in NGC5194 is located on a spiral arm
with seven objects within the $0\farcs8$ error circle, which can be improved
with future observations. Both ULXs in NGC5194 are in regions younger than
$10^{7.8}$ years. The ULXs in NGC1313 and NGC628 was observed with the Baade
telescope. The ULX in NGC1313 is identified with one object with R-I color
bluer than the bluest stellar objects, indicative of non-thermal emission in
the R band, or dramatic variability between two observations, or errors in
measurements. The ULX in NGC628 is located in a bubble nebula and identified
with a few extended objects that are probably young stellar clusters. Future
observations with better spatial resolutions are needed to clarify the optical
counterparts and their nature for the ULXs in NGC1313 and NGC628.


title:
The detection of non-thermal radio continuum spokes and the study of
  star formation in the Cartwheel

abstract:
  New sensitive Very Large Array 20 cm continuum observations of the Cartwheel,
the prototypical collisional ring galaxy, were carried out with the principal
aim of tracing supernova remnants that are expected to lie in the wake of the
expanding ring and in the ring itself. We detect predominantly non-thermal
radio continuum emission from regions associated with 13 ring HII complexes.
The emission interior to the ring is confined to structures that resemble
spokes of the wheel. The spokes start near bright HII complexes, and extend to
around 6 arcsec (4 kpc) inward in the direction of the geometrical center of
the ring. There is no apparent positional coincidence between the radio
continuum and optical spokes. Radial distribution of intensity along the spokes
suggests that the past star formation rate (SFR) in the Cartwheel was much
lower than the current SFR. New Halpha observations were used to revise the
current SFR in the Cartwheel. The revised value is 18 Msun/yr, which is a
factor of 4 lower than the value reported previously, but is in good agreement
with the SFR estimated from far infrared luminosity. About 30% of the observed
20 cm continuum non-thermal emission seems to originate in processes that are
not related to star formation. Revised SFR in the Cartwheel is comparable to
that in the rest of the ring galaxies.


title:
Ultra-luminous X-ray Sources in nearby galaxies from ROSAT HRI
  observations II. statistical properties

abstract:
  The statistical properties of the ultra-luminous X-ray source (ULX)
populations extracted from the ROSAT HRI survey of X-ray point sources in
nearby galaxies in Paper I are studied to reveal connections between the ULX
phenomenon and survey galaxy properties. The $logN$--$logS$ relation is used to
calculate and remove the influence of false ULXs from the background and/or
foreground objects. Study of the luminosity functions shows that the regular
ULXs below $10^{40}$ erg/sec are an extension of the ordinary HMXB/LMXB
population below $10^{39}$ erg/sec in the late-type galaxies, and that the
extreme ULXs above $10^{40}$ erg/sec might be a different population from the
regular ULXs. This survey confirms statistically that the ULX phenomenon is
closely connected to star formation activities, since ULXs preferentially occur
in late-type galaxies rather than in early-typTwo ULX populations, the
HMXB-like ULXs as an extension of the ordinary HMXB population associated with
the young stellar population and the LMXB-like ULXs as an extension of the
ordinary LMXB population associated with the old stellar population, are both
required to account for the total ULX population. It is found that the
LMXB-like ULXs dominate the ULX population at low star formation rates, while
HMXB-like ULXs dominate at high star formation rates. However, an accurate
quantitative description of the relative fractions of HMXB-like ULXs and
LMXB-like ULXs is impossible in the current HRI survey due to the source
blending effects, and a Chandra survey of the X-ray point sources in nearby
galaxies would be required for this purpose. e galaxies, and ULXs in late-type
galaxies tend to trace the spiral arms.


title:
A Link Between the Semi-Major Axis of Extrasolar Gas Giant Planets and
  Stellar Metallicity

abstract:
  The fact that most extrasolar planets found to date are orbiting metal-rich
stars lends credence to the core accretion mechanism of gas giant planet
formation over its competitor, the disc instability mechanism. However, the
core accretion mechanism is not refined to the point of explaining orbital
parameters such as their unexpected semi-major axes and eccentricities. We
propose a model, which correlates the metallicity of the host star with the
original semi-major axis of its most massive planet, prior to migration,
considering that the core accretion scenario governs giant gas planet
formation. The model predicts that the optimum regions for planetary formation
shift inward as stellar metallicity decreases, providing an explanation for the
observed absence of long period planets in metal-poor stars. We compare our
predictions with the available data on extrasolar planets for stars with masses
similar to the mass of the Sun. A fitting procedure produces an estimate of
what we define as the Zero Age Planetary Orbit (ZAPO) curve as a function of
the metallicity of the star. The model also hints that the lack of planets
circling metal-poor stars may be partly caused by an enhanced destruction
probability during the migration process, since the planets lie initially
closer to the central stars.


title: UV Luminosity Function at z~4, 3, and 2

abstract:
  We use very deep (R_lim=27) UGRI imaging to study the evolution of the faint
end of the UV-selected galaxy luminosity function from z~4 to z~2. We find that
the number of sub-L* galaxies increases from z~4 to z~3 while the number of
bright ones appears to remain constant. We find no evidence for continued
evolution to lower redshift, z~2. If real, this differential evolution of the
luminosity function suggests that differentially comparing key diagnostics of
dust, stellar populations, etc. as a function of z and L may let us isolate the
key mechanisms that drive galaxy evolution at high redshift and we describe
several such studies currently underway.


title: Radio Emission by Particles due to Pulsar Spin

abstract:
  We present a relativistic model for the motion of charged particles in
rotating magnetic field lines projected on to a plane perpendicular to the
rotation axis. By making an approximation that the projected field lines are
straight, an analytical expression is obtained for the particle trajectory. The
motive behind developing this model is to elucidate some of the effects of
rotation in pulsar profiles. There is a significant contribution to the
curvature of particle trajectory due to the rotation of pulsar, which is in
addition to the inherent curvature of the field lines. The asymmetry in the
observed pulse shapes can be explained by considering the
aberration-retardation effects. The single sign circular polarization that has
been observed in many pulsars, might be due to the relative orientation of
sight line with respect to the particle trajectory plane.


title:
Starburst Driven Thermal and Non-thermal Structures in the Galactic
  Center Region

abstract:
  We briefly review the prominent thermal and nonthermal sources near the
Galactic center. These sources include the young stellar clusters, the Sgr B
complex as well as the large-scale nonthermal filaments and lobes. Some of the
recent radio images of this region based on VLA and Green Bank Telescope
observations are also presented. We then argue that the origin of the
large-scale features within the inner two degrees of the Galactic center is
tied to a past starburst activity in the nucleus of the Galaxy.


title:
Observation of the Ankle and Evidence for a High-Energy Break in the
  Cosmic Ray Spectrum

abstract:
  We have measured the cosmic ray spectrum at energies above $10^{17}$ eV using
the two air fluorescence detectors of the High Resolution Fly's Eye experiment
operating in monocular mode. We describe the detector, PMT and atmospheric
calibrations, and the analysis techniques for the two detectors. We fit the
spectrum to models describing galactic and extragalactic sources. Our measured
spectrum gives an observation of a feature known as the ``ankle'' near $3\times
10^{18}$ eV, and strong evidence for a suppression near $6\times 10^{19}$ eV.


title: Dark Matter in a One-dimensional Universe

abstract:
  A computer code to simulate temporal evolution of overdensities in a
one-dimensional Universe is presented for didactic purposes. The formation of
large scale structures in this one-dimensional universe can be studied both in
matter or radiation dominated eras. Since large scale structures are already
observed at z > 7, primordial dark matter overdensities delta_DM which are 90
times larger than the observed barionic delta_B in the cosmic microwave
background are required at z~1000. This makes possible non-linear gravitational
collapse at redshift z >7 and the formation of the structures. Primordial
perturbations delta_B~10^-5 do not leave the linear regime of growth without
the aid of dark matter's potential wells. This code is suitable for commercial
worksheets like MSExcel, StarOffice, or OpenOffice.


title: Astrometry and Relativity

abstract:
  General relativistic effects in astrophyiscal systems have been detected
thanks to accurate astrometric measurements. We outline some keystones of
astrometry such as stellar aberration (argument development during the years
1727-1872); Mercury's perihelion precession (1845-1916); solar disk oblateness
(1966-2001); relativistic light deflection (1916-1919); lunar geodetic
precession (1916-1988); Lense-Thirring and Pugh-Schiff precessions (1917-1959),
finally presenting the issue of the quest for a guide star for GP-B satellite
(1974-2004) as application of all previous topics.


title:
The D/H Ratio in the Interstellar Medium toward the White Dwarf
  PG0038+199

abstract:
  We determine the D/H ratio in the interstellar medium toward the DO white
dwarf PG0038+199 using spectra from the Far Ultraviolet Spectroscopic Explorer
(FUSE), with ground-based support from Keck HIRES. We employ curve of growth,
apparent optical depth and profile fitting techniques to measure column
densities and limits of many other species (H2, NaI, CI, CII, CIII, NI, NII,
OI, SiII, PII, SIII, ArI and FeII) which allow us to determine related ratios
such as D/O, D/N and the H2 fraction. Our efforts are concentrated on measuring
gas-phase D/H, which is key to understanding Galactic chemical evolution and
comparing it to predictions from Big Bang nucleosynthesis. We find column
densities log N(HI) = 20.41+-0.08, log N(DI)=15.75+-0.08 and log N(H2) =
19.33+-0.04, yielding a molecular hydrogen fraction of 0.14+-0.02 (2 sigma
errors), with an excitation temperature of 143+-5K. The high HI column density
implies that PG0038+199 lies outside of the Local Bubble; we estimate its
distance to be 297 (+164,-104)pc (1 sigma). D/[HI+2H2] toward PG0038+199 is
1.91(+0.52,-0.42) e-5 (2 sigma). There is no evidence of component structure on
the scale of Delta v > 8 km/s based on NaI, but there is marginal evidence for
structure on smaller scales. The D/H value is high compared to the majority of
recent D/H measurements, but consistent with the values for two other
measurements at similar distances. D/O is in agreement with other distant
measurements. The scatter in D/H values beyond ~100pc remains a challenge for
Galactic chemical evolution.


title:
Abundance anomalies in hot horizontal branch stars of the galactic
  globular cluster NGC 1904

abstract:
  We present abundance measurements, based on high-resolution optical
spectroscopic data obtained with the Ultraviolet and Visual Echelle
Spectrograph mounted on Kueyen (Very Large Telescope UT2), for ten stars in the
extended blue horizontal branch of the Galactic globular cluster NGC 1904
(M79). In agreement with previous findings for other clusters, we obtain normal
abundances for stars cooler than Teff ~ 11,000 K and largely anomalous
abundances for hotter stars: large He depletions, and overabundances of Fe, Ti,
Cr, P and Mn. The abundances of Mg, Si and Ca are roughly normal, in the hot
stars as well as in the cooler ones. This abundance pattern can be attributed
to the onset of diffusion and to radiation pressure in the stable atmospheres
of hot horizontal branch stars.


title: Multiple Outbursts of a Cataclysmic Variable in the Globular Cluster M22

abstract:
  We present a 4 year light curve of a cataclysmic variable in M22, based on an
analysis of accumulated data from the MOA microlensing survey. The position of
the star coincides with that of a transient event observed by HST in 1999,
originally attributed to microlensing but later suspected to be a dwarf nova
outburst. Two outburst episodes, one in 2002 and one in 2003, with $\Delta
I\sim3$ are seen in the MOA data thus confirming that the HST event was a dwarf
nova outburst. The MOA and HST data show that this dwarf nova underwent at
least three outburst episodes during 1999--2004. Further close monitoring of
this event is encouraged as future outburst episodes are expected.


title:
Hubble Space Telescope imaging of the progenitor sites of six nearby
  core-collapse supernovae

abstract:
  The search for the progenitors of six core-collapse supernovae (CCSNe) in
archival HST WFPC2 pre-explosion imaging is presented here. These SNe are
1999an, 1999br, 1999ev, 2000ds, 2000ew and 2001B. Post-explosion imaging of the
SNe, with the HST ACS/WFC, has been utilised with the technique of differential
astrometry to identify the progenitor locations on the pre-explosion imaging.
SNe 1999br, 1999ev, 2000ew and 2001B are recovered in late time imaging and an
estimate of the progenitor location on the pre-explosion imaging, with
sub-pixel accuracy, has been made. Only the progenitor of the type II-P SN
1999ev has been recovered, on pre-explosion F555W imaging, at a $4.8\sigma$
significance level. Assuming a red supergiant progenitor, the pre-explosion
observation is consistent with $M_{ZAMS}=15-18M_{\odot}$. The progenitors of
the other five SNe were below the $3\sigma$ detection threshold of the
pre-explosion observations. The detection thresholds were translated to mass
limits for the progenitors by comparison with stellar evolution models.
Pre-explosion observations of the peculiarly faint SN 1999br limit the mass of
a red supergiant progenitor to $M_{ZAMS} < 12M_{\odot}$. Analysis has been
extended, from previous studies, to include possible detections of
high-$\mathrm{T_{eff}}$, high-mass stars by conducting synthetic photometry of
model Wolf-Rayet star spectra. The mass limits for the type II-P SNe 1999an and
1999br are consistent with the previously determined mass limits for this type
of SN. The detection limits for the progenitors of the type Ibc SNe (2000ds,
2000ew and 2001B) do not permit differentiation between high-mass WR
progenitors or low mass progenitors in binaries.


title: Gravitational Imaging of CDM Substructure

abstract:
  We propose the novel method of ``gravitational imaging'' to detect and
quantify luminous and dark-matter substructure in gravitational-lens galaxies.
The method utilizes highly-magnified Einstein rings and arcs as sensitive
probes of small perturbations in the lens potential (due to the presence of
mass substructure), reconstructing the gravitational lens potential
non-parametrically. Numerical simulations show that the implemented algorithm
can reconstruct the smooth mass distribution of a typical lens galaxy -
exhibiting reasonable signal-to-noise Einstein rings - as well as compact
substructure with masses as low as M_sub~10^-3 M_lens, if present.
``Gravitational imaging'' of pure dark-matter substructure around massive
galaxies can provide a new window on the standard cold-dark-matter paradigm,
using very different physics than ground-based direct-detection experiments,
and probe the hierarchical structure-formation model which predicts this
substructure to exist in great abundance.


title:
The ACS Virgo Cluster Survey IV: Data Reduction Procedures for Surface
  Brightness Fluctuation Measurements with the Advanced Camera for Surveys

abstract:
  The Advanced Camera for Surveys (ACS) Virgo Cluster Survey is a large program
to image 100 early-type Virgo galaxies using the F475W and F850LP bandpasses of
the Wide Field Channel of the ACS instrument on the Hubble Space Telescope
(HST). The scientific goals of this survey include an exploration of the
three-dimensional structure of the Virgo Cluster and a critical examination of
the usefulness of the globular cluster luminosity function as a distance
indicator. Both of these issues require accurate distances for the full sample
of 100 program galaxies. In this paper, we describe our data reduction
procedures and examine the feasibility of accurate distance measurements using
the method of surface brightness fluctuations (SBF) applied to the ACS Virgo
Cluster Survey F850LP imaging. The ACS exhibits significant geometrical
distortions due to its off-axis location in the HST focal plane; correcting for
these distortions by resampling the pixel values onto an undistorted frame
results in pixel correlations that depend on the nature of the interpolation
kernel used for the resampling. This poses a major challenge for the SBF
technique, which normally assumes a flat power spectrum for the noise. We
investigate a number of different interpolation kernels and show through an
analysis of simulated galaxy images having realistic noise properties that it
is possible, depending on the kernel, to measure SBF distances using
distortion-corrected ACS images without introducing significant additional
error from the resampling. We conclude by showing examples of real image power
spectra from our survey.


title: Binary Disruption by Massive Black Holes in Globular Clusters

abstract:
  A massive (~10^2-10^4 Msun) black hole at the center of a globular cluster
will tidally disrupt binaries that pass sufficiently close. Such an encounter
results in the capture of one binary component by the black hole and ejection
of the other star. A 10^3 Msun black hole disrupts one binary every 1-10 Myr;
captured stars orbit with initial periods of days to decades. Although >~100
stars are captured in only 1 Gyr, the number with periods of <10 yr at any one
time is probably less than 10, regulated by stellar interactions and tidal
disruption by the black hole. Binary disruption and stellar capture should be
critically examined with detailed numerical simulations, in order to
corroborate the analytic results given here and to weigh possible observational
consequences.


title: Exploring the Nature of Weak Chandra Sources near the Galactic Centre

abstract:
  We present results from the first near-IR imaging of the weak X-ray sources
discovered in the Chandra/ACIS-I survey (Wang et al. 2002) towards the Galactic
Centre (GC). These ~800 discrete sources, which contribute significantly to the
GC X-ray emission, represent an important and previously unknown population
within the Galaxy. From our VLT observations we will identify likely IR
counterparts to a sample of the hardest sources, which are most likely X-ray
binaries. With these data we can place constraints on the nature of the
discrete weak X-ray source population of the GC.


title: The SNAP Strong Lens Survey

abstract:
  Basic considerations of lens detection and identification indicate that a
wide field survey of the types planned for weak lensing and Type Ia SNe with
SNAP are close to optimal for the optical detection of strong lenses. Such a
``piggy-back'' survey might be expected even pessimistically to provide a
catalogue of a few thousand new strong lenses, with the numbers dominated by
systems of faint blue galaxies lensed by foreground ellipticals. After
sketching out our strategy for detecting and measuring these galaxy lenses
using the SNAP images, we discuss some of the scientific applications of such a
large sample of gravitational lenses: in particular we comment on the partition
of information between lens structure, the source population properties and
cosmology. Understanding this partitioning is key to assessing strong lens
cosmography's value as a cosmological probe.


title: Relic Gravitational Waves in the Accelerating Universe

abstract:
  Observations have recently indicated that the Universe at the present stage
is in an accelerating expansion, a process that has great implications. We
evaluate the spectrum of relic gravitational waves in the current accelerating
Universe and find that there are new features appearing in the resulting
spectrum as compared to the decelerating models. In the low frequency range the
peak of spectrum is now located at a frequency $\nu_E \simeq
(\frac{\Omega_m}{\Omega_{\Lambda}})^{1/3} \nu_H$, where $\nu_H$ is the Hubble
frequency, and there appears a new segment of spectrum between $\nu_E$ and
$\nu_H$. In all other intervals of frequencies $\geq \nu_H$, the spectral
amplitude acquires an extra factor $\frac{\Omega_m}{\Omega_{\Lambda}}$, due to
the current acceleration, otherwise the shape of spectrum is similar to that in
the decelerating models. The recent WMAP result of CMB anisotropies is used to
normalize the amplitude for gravitational waves. The slope of the power
spectrum depends sensitively on the scale factor $a(\tau) \propto
|\tau|^{1+\beta}$ during the inflationary stage with $\beta=-2$ for the exact
de Sitter space. With the increasing of $\beta$, the resulting spectrum is
tilted to be flatter with more power on high frequencies, and the sensitivity
of the second science run of the LIGO detectors puts a restriction on the
parameter $\beta \leq -1.8$. We also give a numerical solution which confirms
these features.


title:
Properties of High Redshift Quasars-I: Evolution of the super-massive
  black-hole to halo mass ratio

abstract:
  In the local universe, the masses of Super-Massive Black-Holes (SMBH) appear
to correlate with physical properties of their hosts, including the mass of the
dark-matter halos. At higher redshifts, we observe the growth of SMBHs
indirectly through identification of high redshift quasars. However information
on their hosts is difficult to obtain. In this paper we determine the masses of
halos that host high redshift quasars (at z>4) by comparing the rate of growth
of quasar density with that predicted by the Press-Schechter mass function. The
host mass determined depends on how the ratio between SMBH and host halo mass
evolves with redshift. Assuming the ratio between SMBH and halo mass does not
evolve with redshift, we find a host halo mass of log(M)=11.7+/-0.3 solar
masses. Even if the quasars shine at their Eddington limit, this mass is
significantly smaller than that seen in the local universe. Indeed the
null-hypothesis, of a constant SMBH to halo mass ratio at all redshifts, can be
ruled out at greater than a 5-sigma level. SMBHs must therefore have
contributed a larger fraction to the host mass in the past. Including redshift
evolution of the SMBH to halo mass ratio, we find larger halo masses of
log(M)=12.4+/-0.3 solar masses, and a ratio between SMBH and halo mass that
increases with redshift as ~(1+z)^1.5 are required to be consistent with both
local and high redshift observations. We investigate restrictions placed on the
critical linear overdensity of quasar hosts at their epoch of virialisation and
find that it cannot exceed the traditional value of delta_c=1.69 by more than a
factor of two. Finally, we find that the high redshift quasars are hosted by
fluctuations on scales that have a variance of (delta M/M) = 2-3, corresponding
to (3-4.5)-sigma fluctuations in the density field.


title: Korean Nova Records in A.D. 1073 and A.D. 1074: R Aquarii

abstract:
  R Aqr is known to be a symbiotic binary system with an associated extended
emission nebula, possibly produced by a historic outburst. To find the
associated historic records, we searched for and compiled all 'Guest Star' and
'Peculiar Star' records in three Korean 'official' history books that cover
almost two thousand years, Samguksagi, Goryeosa, Joseonwangjosillok. In
addition to the record of A.D. 1073, previously noted by Li (1985), we have
found in Goryeosa another candidate record of A.D. 1074, which has the same
positional description as that of A.D. 1073 with an additional brightness
description. We examined various aspects of the two records and conclude that
they both are likely to be the records of outburst of R Aqr. This means that
there were two successive outbursts in A.D. 1073 and in A.D. 1074, separated by
approximately one year. Based on these records, we estimate the distance to R
Aqr to be 273 pc if the expansion of the nebula has been at a constant rate.
The brightness record of A.D. 1074 corresponds to the absolute magnitude at
outburst of M_(outburst) = -6.2 mag. ~ -5.2 mag. at this distance. The two
Korean records associated with R Aqr may provide astronomically meaningful
constraints to the outburst model of R Aqr and the formative process of its
nebulosity.


title: The Neutral Medium

abstract:
  We consider the physical conditions of the neutral medium within, and in the
environments of, galaxies. The basic physical and morphological properties of
the neutral medium within galaxy disks are now quite well-constrained.
Systematic variations in temperature and phase-balance (of cool versus warm
neutral gas) are indicated as a function of both radius and z-height.
Interestingly, the cool medium line-widths are observed to be dominated by
turbulent energy injection within cells of 10 pc to 1 kpc size. Deep new
observations reveal that 5-10% of the neutral medium is associated within an
extended halo which rotates more slowly and experiences radial inflow. Much of
this component is likely to be associated with a ``galactic fountain'' type of
phenomenon. However, compelling evidence is also accumulating for the
importance of tidal disruption of satellites as well as continuous accretion
(of both diffuse and discrete components) in fueling galaxy halos and disks.
Continued fueling is even observed on scales of 100's of kpc in galaxy
environments, where the neutral component is likely to be merely a trace
constituent of a highly ionized plasma.


title:
Are Great Disks Defined by Satellite Galaxies in Milky-Way Type Halos
  Rare in $\Lambda$CDM model?

abstract:
  We study the spatial distribution of satellite galaxies by assuming that they
follow the dark matter distribution. This assumption is supported by
semi-analytical studies based on high-resolution numerical simulations. We find
that for a Milky-Way type halo, if only a dozen satellite galaxies are
observed, then they can lie on a ``great'' disk with an rms height of about 40
kpc. The normal to the plane is roughly isotropic on the sky. These results are
consistent with the observed properties of the satellite galaxies in the Milky
Way. If, however, the satellite galaxies follow the distribution of
substructure selected by present mass, then great disks similar to the one in
the Milky Way are rare and difficult to reproduce, in agreement with the
conclusion reached by Kroupa et al. (2004).


title: Polarization in Gamma-Ray Bursts Produced by Pinch Discharge

abstract:
  Large-voltage and high-temperature plasma columns produced by pinch discharge
can generate gamma-ray flashes with energy spectra and spectral evolution
consistent with that observed in gamma-ray bursts (GRBs). The inverse Compton
scattering (ICS) during the discharge process can produce high linear
polarization. The calculation indicates that the observed polarization depends
on the angle between the observer's line-of-sight to the GRB and the direction
of the pinch discharge, but only weakly depends on observed gamma-ray energy.


title: Imaging the Low Red-shift Cosmic Web

abstract:
  The first image of a Cosmic Web, Lyman Limit System has just been made in HI
emission within the Local Group filament connecting M31 and M33. The
corresponding HI distribution function is in very good agreement with that of
the QSO absorption lines, confirming the 30-fold increase in surface area
expected between 10^19 cm^-2 and 10^17 cm^-2. The critical observational
challenge is crossing the ``HI desert'', the range of log(N_HI) from about 19.5
down to 18, over which photo-ionization by the intergalactic radiation field
produces an exponential decline in the neutral fraction from essentially unity
down to a few percent. Nature is kinder again to the HI observer below
log(N_HI) = 18, where the neutral fraction decreases only very slowly with
log(N_HI). Average spectra of the M31/M33 filament suggest a kinetic
temperature of 2x10^5 K for the parent ion population, consistent with
significant shock-heating. The brightest knot within the filament, with only a
2x10^4 K apparent temperature, is suggestive of localized cooling and
condensation. We have initiated two complimentary surveys that should lay the
groundwork for a comprehensive study of the Cosmic Web phenomenon in HI
emission. When combined with targeted optical and UV absorption line
observations, the total baryonic masses and enrichment histories of the Cosmic
Web could be determined over the complete range of environmental
over-densities.


title:
Long period variables in the globular cluster 47 Tuc: radial velocity
  variations

abstract:
  We present near infrared velocity curves for 12 long period variables (LPVs)
in the globular cluster 47 Tuc (NGC 104). New light curves are also presented
for these variables. Results are compared with the period-luminosity sequences
occupied by the LPVs in the LMC. Sequence C variables (fundamental mode
pulsators) have larger velocity amplitudes than sequence B variables (first
overtone pulsators). We show that, at similar luminosities, higher mass loss
rates are associated with larger pulsation amplitudes. One variable (V18) does
not fit the normal period luminosity sequences and it has an unusually large
amount of circumstellar dust, suggesting that it has recently undergone a
thermal pulse on the AGB. Finally, we report the discovery of three new long
period variable stars in the cluster core, all previously found to have a large
infrared excess.


title: Extragalactic Cosmic Rays and Magnetic Fields: Facts and Fiction

abstract:
  A critical discussion of our knowledge about extragalactic cosmic rays and
magnetic fields is attempted. What do we know for sure? What are our
prejudices? How do we confront our models with the observations? How can we
assess the uncertainties in our modeling and in our observations?
Unfortunately, perfect answers to these questions can not be given. Instead, I
describe efforts I am involved in to gain reliable information about
relativistic particles and magnetic fields in extragalactic space.


title: Magnetic Fields in Clusters of Galaxies

abstract:
  A brief overview about our knowledge on galaxy cluster magnetic fields is
provided. Emphasize is given to the mutual dependence of our knowledge on
relativistic particles in galaxy clusters and the magnetic field strength.
Furthermore, we describe efforts to measure magnetic field strengths,
characteristic length-scales, and power-spectra with reliable accuracy. An
interpretation of these results in terms of non-helical dynamo theory is given.
If this interpretation turns out to be correct, the understanding of cluster
magnetic fields is directly connected to our understanding of intra-cluster
turbulence.


title:
Are PAHs precursors of small hydrocarbons in Photo--Dissociation
  Regions? The Horsehead case

abstract:
  We present maps at high spatial and spectral resolution in emission lines of
C2H, c-C3H2, C4H, 12CO and C18O of the edge of the Horsehead nebula obtained
with the Plateau de Bure Interferometer (PdBI). The edge of the Horsehead
nebula is a one-dimensional Photo--Dissociation Region (PDR) viewed almost
edge-on. All hydrocarbons are detected at high signal--to--noise ratio in the
PDR where intense emission is seen both in the H2 ro-vibrational lines and in
the PAH mid--infrared bands. C18O peaks farther away from the cloud edge. Our
observations demonstrate that C2H, cC3H2 and C4H are present in UV--irradiated
molecular gas, with abundances nearly as high as in dense, well shielded
molecular cores.
  PDR models i) need a large density gradient at the PDR edge to correctly
reproduce the offset between the hydrocarbons and H2 peaks and ii) fail to
reproduce the hydrocarbon abundances. We propose that a new formation path of
carbon chains, in addition to gas phase chemistry, should be considered in
PDRs: because of intense UV--irradiation, large aromatic molecules and small
carbon grains may fragment and feed the interstellar medium with small carbon
clusters and molecules in significant amount.


title: Identification of Relativistic Effects in X-Ray Astrophysical Source

abstract:
  Precise knowledge of the features of several X-ray sources from compact
binary sources to galactic nuclei is gradually unveiling the physical
parameters of relativistic neutron stars and black holes therein. Recent
developments in theory, astrophysical models and experiments are reviewed.


title: A Study of the Type II-P Supernova 2003gd in M74

abstract:
  We present photometric and spectroscopic data of the type II-P supernova
2003gd, which was discovered in M74 close to the end of its plateau phase. SN
2003gd is the first type II supernova to have a directly confirmed red
supergiant progenitor. We compare SN 2003gd with SN 1999em, a similar type II-P
supernova, and estimate an explosion date of 18th March 2003. We determine a
reddening towards the supernova of E(B-V) = 0.14+/-0.06, using three different
methods. We also calculate three new distances to M74 of 9.6+/-2.8 Mpc,
7.7+/-1.7 Mpc and 9.6+/-2.2 Mpc. The former was estimated using the
Standardised Candle Method (SCM), for type II supernovae, and the latter two
using the Brightest Supergiants Method (BSM). When combined with existing
kinematic and BSM distance estimates, we derive a mean value of 9.3+/-1.8 Mpc.
SN 2003gd was found to have a lower tail luminosity compared to other
``normal'' type II-P SNe bringing into question the nature of this supernova.
We present a discussion concluding that this is a ``normal'' type II-P
supernova which is consistent with the observed progenitor mass of 8(+4/-2) Mo.


title: Loitering universe models in light of the CMB

abstract:
  Spatially flat loitering universe models have recently been shown to arise in
the context of brane world scenarios. Such models allow more time for structure
formation to take place at high redshifts, easing, e.g., the tension between
the observed and predicted evolution of the quasar population with redshift.
While having the desirable effect of boosting the growth of structures, we show
that in such models the position of the first peak in the power spectrum of the
cosmic microwave background anisotropies severely constrains the amount of
loitering at high redshifts.


title: Flip-flop phenomenon: observations and theory

abstract:
  In many active stars the spots concentrate on two permanent active longitudes
which are 180 degrees apart. In some of these stars the dominant part of the
spot activity changes the longitude every few years. This so-called flip-flop
phenomenon has up to now been reported in 11 stars, both single and binary
alike, and including also the Sun. To explain this phenomenon, a
non-axisymmetric dynamo mode, giving rise to two permanent active longitudes at
opposite stellar hemispheres, is needed together with an oscillating
axisymmetric magnetic field. Here we discuss the observed characteristics of
the flip-flop phenomenon and present a dynamo solution to explain them.


title: Six months of mass outflow and inclined rings in the ejecta of V1494 Aql

abstract:
  V1494 Aql was a very fast nova which reached a visual maximum of about 4.0 by
the end of 1999 December 3. We report observations from 4 to 284 days after
discovery, including sub-mm- and cm-band fluxes, a single MERLIN image, and
optical spectroscopy in the 410 to 700 nm range. The extent of the radio
continuum emission is consistent with a recent lower distance estimate of 1.6
kpc. We conclude that the optical and radio emission arises from the same
expanding ejecta. We show that these observations are not consistent with
simple kinematical spherical shell models used in the past to explain the rise
and fall of the radio flux density in these objects. The resolved remnant
structure is consistent with an inclined ring of enhanced density within the
ejecta. Optical spectroscopy indicates likely continued mass ejection for over
195 days, with the material becoming optically thin in the visible sometime
between 195 and 285 days after outburst.


title:
Dynamical evolution of intermediate mass black holes and their
  observable signatures in the nearby Universe

abstract:
  We investigate the consequences of a model of the assembly and growth of
massive black holes from primordial seeds, remnants of the first generation of
stars in a hierarchical structure formation scenario. Our model traces the
build-up of MBHs from an early epoch, and follows the merger history of dark
matter halos and their associated holes via Monte Carlo realizations of the
merger hierarchy from early times to the present time. The sequence of minor
and major mergers experienced by galactic halos in their hierarchical growth
affects the merger history of MBHs embedded in their nuclei. So, if the
formation route for the assembly of SMBHs dates back to the early universe, a
large number of BH interactions is inevitable. Binary black holes coalescence
timescales can be long enough for a third BH to fall in and interact with the
central binary. These BH triple interactions lead typically to the final
expulsion of one of the three bodies and to the recoil of the binary. Also,
asymmetric emission of gravitational waves in the last stages of the black hole
merging can give a recoil velocity to the centre of mass of the coalescing
binary. This scenario leads to the prediction of a population of intermediate
mass BHs (IMBHs) wandering in galaxy halos at the present epoch. We compute the
luminosity distribution produced by these IMBHs accreting from their
circumstellar medium. We find that in a Milky Way-sized galaxy they are unable
to account for sources with luminosities > 1e39 erg/s unless they carry a
baryonic remnant from which they are able to accrete for a long time. We also
find that, for typical spiral galaxies, the bright end of the point source
distribution correlates with the mass of the galaxy, and the most luminous
sources are expected to be found in the disk.


title:
Comment on ``The linear instability of magnetic Taylor-Couette flow with
  Hall effect''

abstract:
  In the paper we comment on (R\"udiger & Shalybkov, Phys. Rev. E. 69, 016303
(2004) (RS)), the instability of the Taylor--Couette flow interacting with a
homogeneous background field subject to Hall effect is studied. We correct a
falsely generalizing interpretation of results presented there which could be
taken to disprove the existence of the Hall--drift induced magnetic instability
described in Rheinhardt and Geppert, Phys. Rev. Lett. 88, 101103. It is shown
that in contrast to what is suggested by RS, no additional shear flow is
necessary to enable such an instability with a non--potential magnetic
background field, whereas for a curl--free one it is. In the latter case, the
instabilities found in RS in situations where neither a hydrodynamic nor a
magneto--rotational instability exists are demonstrated to be most likely
magnetic instead of magnetohydrodynamic. Further, some minor inaccuracies are
clarified.


title: An XMM-Newton Observation of Abell 2597

abstract:
  We report on a 120 ks XMM-Newton observation of the galaxy cluster Abell
2597. Results from both the European Photon Imaging Camera (EPIC) and the
Reflection Grating Spectrometer (RGS) are presented. From EPIC we obtain radial
profiles of temperature, density and abundance, and use these to derive cooling
time and entropy. We illustrate corrections to these profiles for projection
and point spread function (PSF) effects. At the spatial resolution available to
XMM-Newton, the temperature declines by around a factor of two in the central
150 kpc or so in radius, and the abundance increases from about one-fifth to
over one-half solar. The cooling time is less than 10 Gyr inside a radius of
130 kpc. EPIC fits to the central region are consistent with a cooling flow of
around 100 solar masses per year. Broad-band fits to the RGS spectra extracted
from the central 2 arcmin are also consistent with a cooling flow of the same
magnitude; with a preferred low-temperature cut-off of essentially zero. The
data appear to suggest (albeit at low significance levels below formal
detection limits) the presence of the important thermometer lines from Fe XVII
at 15, 17 Angstrom rest wavelength, characteristic of gas at temperatures ~ 0.3
keV. The measured flux in each line is converted to a mass deposition estimate
by comparison with a classical cooling flow model, and once again values at the
level of 100 solar masses per year are obtained. These mass deposition rates,
whilst lower than those of previous generations of X-ray observatories, are
consistent with those obtained from UV data for this object. This raises the
possibility of a classical cooling flow, at the level of around 100 solar
masses per year, cooling from 4 keV by more than two orders of magnitude in
temperature.


title: Magnetic domain walls of relic fermions as Dark Energy

abstract:
  We show that relic fermions of the Big Bang can enter a ferromagnetic state
if they possess a magnetic moment and satisfy the requirements of Stoner theory
of itinerant ferromagnetism. The domain walls of this ferromagnetism can
successfully simulate Dark Energy over the observable epoch spanning $\sim 10$
billion years. We obtain conditions on the anomalous magnetic moment of such
fermions and their masses. Known neutrinos fail to satisfy the requirements
thus pointing to the possibility of a new ultralight sector in Particle
Physics.


title:
Multi-wavelength observations of the 2002 outburst of GX 339-4: two
  patterns of X-ray-optical/near-infrared behavior

abstract:
  (Abridged) We report on RXTE and optical/near-infrared (nIR) observations of
the black hole transient GX 339-4, made over a time span of 8 months in 2002
and covering the initial rise and transition from a hard to a soft spectral
state. Two patterns of correlated X-ray-optical/nIR behavior were found. During
the hard state the optical/nIR and X-ray fluxes correlated well, with a nIR vs.
X-ray flux relation similar to the relation between X-ray and radio fluxes
found in previous studies of GX 339-4 and other black hole binaries. As GX
339-4 went through an intermediate state the optical/nIR fluxes decreased
rapidly and once it had entered the spectrally soft state, the optical/nIR
spectrum was much bluer and the ratio of X-ray to nIR flux was higher by a
factor of more than 10 compared to the hard state. In the spectrally soft state
nIR-changes preceded those in the X-rays by more than 2 weeks, indicating a
disk origin of the nIR. We present SEDs, including radio data, and discuss
possible sources for the optical/nIR emission. We conclude that in the hard
state this emission probably originates in the optically thin part of a jet and
that in none of the X-ray states X-ray reprocessing is the dominant source of
optical/nIR emission. Finally, comparing the light curves from the ASM and PCA
instruments, we find that the X-ray/nIR delay depends critically on the
sensitivity of the X-ray detector, with the delay inferred from the PCA (if
present at all) being a factor of 3-6 times shorter than the delay inferred
from the ASM; this may be important in interpreting previously reported
X-ray-optical/nIR lags.


title: Faint BVRI Photometric Sequences in Selected Fields

abstract:
  The results from work done to extend the Johnson-Cousins BVRI photometric
standard sequence to faint levels of V ~ 21 mag in compact fields is presented.
Such calibration and extension of sequences is necessary to fill a calibration
gap, if reliable photometry from modest aperture telescopes in space (e.g.
HST), or terrestrial telescopes with apertures exceeding 4-m is to done.
Sequences like the ones presented here, which cover a large range in brightness
as well as color, will allow photometric calibration to be done efficiently, as
well as for such work to be less prone to systematic sources of error.
Photometry of stars in approximately 10 x 10 arc-minute fields around 3
globular clusters, NGC 2419, Pal 4 and Pal 14 are presented. In each field,
several stars are measured in B, V, R and I passbands, with standard errors
less than 0.015 mag from random errors, to levels fainter than V=21 mag. The
primary context for the work presented here is that parts of these fields were
observed repeatedly by the Wide Field Planetary Camera-2 WFPC2) of the HST, and
thus these newly calibrated sequences can be used to retroactively calibrate
WFPC2 at over various times of its operating life. The sequences presented here
agree at the 0.02 mag level with other extant calibrations of these targets,
except in the I band, where there are color dependent deviations of up to 0.05
mag versus one other photometric sequence. Possible causes for this discrepancy
are examined.


title:
Uncorrelated Measurements of the Cosmic Expansion History and Dark
  Energy from Supernovae

abstract:
  We present a method for measuring the cosmic expansion history H(z) in
uncorrelated redshift bins, and apply it to current and simulated type Ia
supernova data assuming spatial flatness. If the matter density parameter
Omega_m can be accurately measured from other data, then the dark energy
density history X(z)=rho_X(z)/rho_X(0) can trivially be derived from this
expansion history H(z). In contrast to customary ``black box'' parameter
fitting, our method is transparent and easy to interpret: the measurement of
H(z)^{-1} in a redshift bin is simply a linear combination of the measured
comoving distances for supernovae in that bin, making it obvious how systematic
errors propagate from input to output.
  We find the Riess et al. (2004) ``gold'' sample to be consistent with the
``vanilla'' concordance model where the dark energy is a cosmological constant.
We compare two mission concepts for the NASA/DOE Joint Dark Energy Mission
(JDEM), the Joint Efficient Dark-energy Investigation (JEDI), and the Supernova
Accelaration Probe (SNAP), using simulated data including the effect of weak
lensing (based on numerical simulations) and a systematic bias from
K-corrections. Estimating H(z) in seven uncorrelated redshift bins, we find
that both provide dramatic improvements over current data: JEDI can measure
H(z) to about 10% accuracy and SNAP to 30-40% accuracy.


title: Stellar Bar Evolution in Cuspy and Flat-Cored Triaxial CDM Halos

abstract:
  We analyze the evolution of stellar bars in galactic disks in mildly triaxial
flat-core and cuspy CDM halos. We use tailored simulations of rigid and live
halos which include the feedback from disk/bar onto the halo in order to test
the work by El-Zant & Shlosman (2002). The latter used the Liapunov exponents
to analyze the fate of bars in analytical asymmetric halos. We find: (1) The
bar growth is similar in all rigid axisymmetric and triaxial halos. (2) Bars in
live models vertically buckle and form a pseudobulge with a boxy/peanut shape.
(3) In live axisymmetric halos, the bar strength varies little during the
secular evolution. The bar pattern speed anticorrelates with the halo core
size. The bar strength is larger for smaller disk-to-halo mass ratios within
disk radii, the bar size correlates with the halo core sizes, and the bar
pattern speeds -- with the halo central mass concentration. Bars embedded in
live triaxial halos have a starkly different fate: they dissolve on ~1.5-5 Gyr
due to the onset of chaos over continuous zones, leaving behind a weak oval
distortion. The onset of chaos is related to the halo triaxiality, the fast
rotating bar and the halo cuspiness. Before the bar dissolves, the region
outside it develops strong spiral structures, especially in the live triaxial
halos. (4) More angular momentum is absorbed by the triaxial halos as compared
to the axisymmetric models and its exchange is mediated by resonances. (5)
Cuspy halos are more susceptible than flat-core halos to having their
prolateness washed out by the bar. We analyze these results in terms of the
stability of trajectories and development of chaos. We set constraints on the
triaxiality of DM halos by comparing our predictions to recent observations of
bars out to z~1.


title:
An algorithm to detect blends with eclipsing binaries in planet transit
  searches

abstract:
  We present an algorithm that can detect blends of bright stars with fainter,
un-associated eclipsing binaries. Such systems contaminate searches for
transiting planets, in particular in crowded fields where blends are common.
Spectroscopic follow-up observations on large aperture telescopes have been
used to reject these blends, but the results are not always conclusive. Our
approach exploits the fact that a blend with a eclipsing binary changes its
shape during eclipse. We analyze original imaging data from the Optical
Gravitational Lensing Experiment (OGLE), which were used to discover planet
transit candidates. Adopting a technique developed in weak gravitational
lensing to carefully correct for the point spread function which varies both
with time and across the field, we demonstrate that ellipticities can be
measured with great accuracy using an ensemble of images. Applied to OGLE-TR-3
and OGLE-TR-56, two of the planetary transit candidates, we show that both
systems are blended with fainter stars, as are most other stars in the OGLE
fields. Moreover, while we do not detect shape change when TR-56 undergoes
transits, TR-3 exhibits a significant shape change during eclipses. We
therefore conclude that TR-3 is indeed a blend with an eclipsing binary, as has
been suggested from other lines of evidence. The probability that its shape
change is caused by residual systematics is found to be less than 0.6%. Our
technique incurs no follow-up cost and requires little human interaction. As
such it could become part of the data pipeline for any planetary transit search
to minimize contamination by blends. We briefly discuss its relevance for the
Kepler mission and for binary star detection.


title:
Strong Spatial Clustering of UV-selected Galaxies with Magnitude Ks<20.5
  and Redshift Z~2

abstract:
  We obtained deep 8.5'x8.5' near-infrared images within four high-redshift
survey fields, measured the Ks magnitudes of 300 optically selected galaxies
with spectroscopic redshift 1.8<z<2.6, and compared the spatial clustering
strength of galaxies with Ks<20.5 and Ks>20.5. We found at greater than 95%
confidence that the brighter galaxies cluster more strongly. The best-fit
correlation lengths for the bright and faint samples are 10+-3 and 4+-0.8
comoving Mpc/h, respectively (1sigma), although the unusual density of bright
QSOs in one of our survey fields may imply that the result is not
representative of the universe as a whole. Neglecting this possibility, the
correlation length for the optically selected sample with Ks<20.5 agrees well
with that reported for comparably bright near-IR-selected samples. The
differences in correlation length between optically selected and
near-IR-selected samples have been presented as evidence that the two
techniques find orthogonal populations of high-redshift galaxies. Our results
favor a more nuanced view.


title:
Stellar abundance gradients in galactic disks. I. Method and spectral
  line gradients

abstract:
  We describe the technique of absorption line imaging of galaxy disks using
the Taurus Tunable Filter on the Anglo-Australian Telescope and demonstrate its
sensitivity to the behaviour of spectral features associated with Mg and Fe.
Radial profiles of Mg2 and Fe5270 line-strengths are presented for a sample of
eight face-on spiral galaxies spanning a range of Hubble types. Signatures of
phenomena including merger-induced star formation, HII rings and galactic bars
are also reported. This study demonstrates the capacity of tunable filters to
measure Mg and Fe line-strengths across the face of spiral galaxies, which can
ultimately reveal clues about the star formation history and chemical
evolution.


title: Influence of massive planet scattering on nascent terrestrial planets

abstract:
  In most extrasolar planetary systems, the present orbits of known giant
planets admit the existence of stable terrestrial planets. Those same giant
planets, however, have typically eccentric orbits that hint at violent early
dynamics less benign for low mass planet formation. Under the assumption that
massive planet eccentricities are the end point of gravitational scattering in
multiple planet systems, we study the evolution of the building blocks of
terrestrial planets during the scattering process. We find that typically,
evolutionary sequences that result in a moderately eccentric giant planet
orbiting at a ~ 2.5 AU eject over 95% of the material initially present within
the habitable zone. Crossing orbits largely trigger the ejection, and leave the
surviving material with a wide dispersion in semi-major axis, eccentricity and
inclination. Based on these results, we predict that radial velocity follow-up
of terrestrial planet systems found by Kepler will find that these are
anti-correlated with the presence of eccentric giant planets orbiting at a few
AU.


title: Bow shocks around pulsars and neutron stars

abstract:
  Pulsar wind nebulae are now well established as important probes both of
neutron stars' relativistic winds and of the surrounding interstellar medium.
Amongst this diverse group of objects, pulsar bow shocks have long been
regarded as an oddity, only seen around a handful of rapidly moving neutron
stars. However, recent efforts at optical, radio and X-ray wavelengths have
identified many new pulsar bow shocks, and these results have consequently
motivated renewed theoretical efforts to model these systems. Here I review the
new results and ideas which have emerged on these spectacular systems, and
explain how bow shocks and "Crab-like" nebulae now form a consistent picture
within our understanding of pulsar winds.


title:
Giant Planet Formation: A First Classification of Isothermal
  Protoplanetary Equilibria

abstract:
  We present a model for the equilibrium of solid planetary cores embedded in a
gaseous nebula. From this model we are able to extract an idealized roadmap of
all hydrostatic states of the isothermal protoplanets. The complete
classification of the isothermal protoplanetary equilibria should improve the
understanding of the general problem of giant planet formation, within the
framework of the nucleated instability hypothesis. We approximate the
protoplanet as a spherically symmetric, isothermal, self-gravitating classical
ideal gas envelope in equilibrium, around a rigid body of given mass and
density, with the gaseous envelope required to fill the Hill-sphere. Starting
only with a core of given mass and an envelope gas density at the core surface,
the equilibria are calculated without prescribing the total protoplanetary mass
or nebula density. The static critical core masses of the protoplanets for the
typical orbits of 1, 5.2, and 30 AU, around a parent star of 1 solar mass are
found to be 0.1524, 0.0948, and 0.0335 Earth masses, respectively, for standard
nebula conditions (Kusaka et al. 1970). These values are much lower than
currently admitted ones primarily because our model is isothermal and the
envelope is in thermal equilibrium with the nebula. For a given core, multiple
solutions (at least two) are found to fit into the same nebula. We extend the
concept of the static critical core mass to the local and global critical core
mass. We conclude that the 'global static critical core mass' marks the meeting
point of all four qualitatively different envelope regions.


title: Detections of CO in Late-Type, Low Surface Brightness Spiral Galaxies

abstract:
  Using the IRAM 30-m telescope, we have obtained 12CO J=1-0 and 2-1 spectral
line observations toward the nuclear regions of 15 edge-on, low surface
brightness (LSB) spiral galaxies. Our sample comprises extreme late-type LSB
spirals with disk-dominated morphologies and rotational velocities V_rot<~120
km/s. We report detections of four galaxies in at least one transition
(>5sigma); for the remainder of the sample we provide upper limits on the
nuclear CO content. Adopting a standard Galactic I_CO-to-H_2 conversion factor
implies molecular gas masses of (3.3-9.8)x10**6 M_sun in the nuclear regions
(inner 1.1-1.8 kpc) of the detected galaxies. Combining our new data with
samples of late-type spirals from the literature, we find that the CO-detected
LSB spirals adhere to the same M_H2-FIR correlation as more luminous and higher
surface brightness galaxies. The amount of CO in the central regions of
late-type spirals appears to depend more strongly on mass than on central
optical surface brightness, and CO detectability declines significantly for
moderate-to-low surface brightness spirals with V_rot<~90 km/s; no LSB spirals
have so far been detected in CO below this threshold. Metallicity effects alone
are unlikely to account for this trend, and we speculate that we are seeing the
effects of a decrease in the mean fraction of a galaxy disk able to support
giant molecular cloud formation with decreasing galaxy mass.


title: The Evolution of Structure in X-ray Clusters of Galaxies

abstract:
  Using Chandra archival data, we quantify the evolution of cluster morphology
with redshift. Clusters form and grow through mergers with other clusters and
groups, and the amount of substructure in clusters in the present epoch and how
quickly it evolves with redshift depend on the underlying cosmology. Our sample
includes 40 X-ray selected, luminous clusters from the Chandra archive, and we
quantify cluster morphology using the power ratio method (Buote & Tsai 1995).
The power ratios are constructed from the moments of the X-ray surface
brightness and are related to a cluster's dynamical state. We find that, as
expected qualitatively from hierarchical models of structure formation,
high-redshift clusters have more substructure and are dynamically more active
than low-redshift clusters. Specifically, the clusters with z>0.5 have
significantly higher average third and fourth order power ratios than the lower
redshift clusters. Of the power ratios, $P_3/P_0$ is the most unambiguous
indicator of an asymmetric cluster structure, and the difference in $P_3/P_0$
between the two samples remains significant even when the effects of noise and
other systematics are considered. After correcting for noise, we apply a linear
fit to $P_3/P_0$ versus redshift and find that the slope is greater than zero
at better than 99% confidence. This observation of structure evolution
indicates that dynamical state may be an important systematic effect in cluster
studies seeking to constrain cosmology, and when calibrated against numerical
simulations, structure evolution will itself provide interesting bounds on
cosmological models.


title:
A Multi-Wavelength Study of the Western Lobe of W50 Powered by the
  Galactic Microquasar SS 433

abstract:
  W50 remains the only supernova remnant (SNR) confirmed to harbor a
microquasar: the powerful enigmatic source SS 433. Our past study of this
fascinating SNR revealed two X-ray lobes distorting the radio shell as well as
non-thermal X-rays at the site of interaction between the SS 433 eastern jet
and the eastern lobe of W50. In this paper we present the results of a 75 ksec
CHANDRA ACIS-I observation of the peak of W50-west targeted to 1) determine the
nature of the X-ray emission and 2) correlate the X-ray emission with that in
the radio and infrared domains. We have confirmed that at the site of
interaction between the western jet of SS 433 and dense interstellar gas the
X-ray emission is non-thermal in nature. The helical pattern observed in radio
is also seen with CHANDRA. No correlation was found between the infrared and
X-ray emission.


title: Plasma instabilities and magnetic-field growth in clusters of galaxies

abstract:
  We show that under very general conditions, cluster plasmas threaded by weak
magnetic fields are subject to very fast growing plasma instabilities driven by
the anisotropy of the plasma pressure (viscous stress) with respect to the
local direction of the magnetic field. Such an anisotropy will naturally arise
in any weakly magnetized plasma that has low collisionality and is subject to
stirring. The magnetic field must be sufficiently weak for the instabilities to
occur, viz., beta>Re^{1/2}. The instabilities are captured by the extended MHD
model with Braginskii viscosity. However, their growth rates are proportional
to the wavenumber down to the ion gyroscale, so MHD equations with Braginskii
viscosity are not well posed and a fully kinetic treatment is necessary. The
instabilities can lead to magnetic fields in clusters being amplified from seed
strength of ~10^{-18} G to dynamically important strengths of ~10 microG on
cosmologically trivial time scales (~10^8 yr). The fields produced during the
amplification stage are at scales much smaller than observed. Predicting the
saturated field scale and structure will require a kinetic theory of magnetized
cluster turbulence.

categories: astro-ph nlin.CD physics.plasm-ph physics.space-ph


title: Searching for Progenitors of Core-Collapse Supernovae

abstract:
  Identifying the massive progenitor stars that give rise to core-collapse
supernovae is one of the main pursuits of supernova and stellar evolution
studies. In this talk I discuss some aspects of the pursuit of these progenitor
stars in ground-based and Hubble Space Telescope images.


title:
Status of Radio and Acoustic Detection of Ultra-High Energy Cosmic
  Neutrinos and a Proposal on Reporting Results

abstract:
  Neutrino astronomy offers the possibility to perform extra-galactic
observations well beyond the photon absorption cutoff above 50 TeV. Based on
observations of cosmic rays, we already know that astrophysical sources produce
particles with at least a million times more energy than this photon cutoff.
Once discovered, either the nature of the sources themselves or the cross
sections of ultra-high energy neutrinos with terrestrial matter may reveal
exotic physical processes that are inaccessible to modern accelerators. Some of
these processes may be due to as-yet unknown physics at the grand unification
scale or beyond. Neutrino telescopes based on optical techniques currently
operating and under construction have apertures measured in several km^3-sr.
Radio and acoustic detection techniques have been demonstrated in laboratory
experiments and are currently used for instrumentation of apertures 10 to
10,000 times larger than optical techniques for neutrinos above 10 PeV. I
discuss the status of current and proposed neutrino telescope projects based on
these techniques. These telescopes have already ruled out some of the more
exotic predictions for neutrino intensity. The upcoming generation of
radio-based and acoustic-based detectors should be sensitive to cosmic
neutrinos above 1 EeV originating through the so-called GZK process. A
comparison of different neutrino telescopes using a common aperture variable
shows how they are complementary in the trade-off of volume versus threshold. I
include a proposal for how neutrino telescopes should report their
sensitivities to facilitate direct comparisons among them and to allow testing
of neutrino brightness models that appear even after publication of the
experimental results.


title:
The Black Hole Mass and Magnetic Field Correlation in Active Galactic
  Nuclei

abstract:
  The observed optical luminosity in 5100 angstorm and black hole mass
correlation is used to probe the magnetic field of black holes harbored in
active galactic nuclei(AGNs). The model is based on the assumption that the
disk is heated by energy injection due to the magnetic coupling(MC) process and
the gravitational dissipation due to accretion. The MC process can transfer
energy and angular momentum from a rotating Kerr black hole to its surrounding
disk. The relation of optical luminosity in 5100 angstorm and black hole mass
as functions of the spin and magnetic field of the black hole is modelled. The
model predicts that optical luminosity in 5100 angstorm emitted from the disk
is sensitive to the strength of the poloidal component of the magnetic field on
the BH horizon. Based on the observations of optical luminosity in 5100
angstorm for 143 AGN sources, we obtain the correlation between mass and
magnetic field of black hole. And we compared out result with the approximate
result between mass and magnetic field of black hole derived from the condition
in the standard accretion disc theory.


title:
Galaxy clustering constraints on deviations from Newtonian gravity at
  cosmological scales

abstract:
  In spite of the growing observational evidence for dark matter and dark
energy in the universe, their physical nature is largely unknown. In fact,
several authors have proposed modifications of Newton's law of gravity at
cosmological scales to account for the apparent acceleration of the cosmic
expansion. Inspired by such suggestions, we attempt to constrain possible
deviations from Newtonian gravity by means of the clustering of SDSS (Sloan
Digital Sky Survey) galaxies. To be specific, we assume a simple modification
of Newton's law with an additional Yukawa-type term characterized by the
amplitude \alpha and the length scale \lambda. Adopting spatially-flat
universes dominated by cold dark matter and/or dark energy, we solve a linear
perturbation equation for the growth of density fluctuations. In particular, we
find an exact analytic solution for the Einstein -- de Sitter case. Following
the Peacock-Dodds prescription, we compute the nonlinear power spectra of mass
fluctuations, perform a statistical comparison with the SDSS galaxy data, and
derive constraints in the \alpha-\lambda plane; for instance, we obtain the
constraints of -0.5<\alpha <0.6 and -0.8<\alpha<0.9 (99.7% confidence level)
for \lambda=5h^{-1}Mpc and 10h^{-1}Mpc, respectively. We also discuss several
future possibilities for improving our analysis.


title: Dark Energy as a Signature of Extra Dimensions

abstract:
  One of the most important and surprising discoveries in cosmology in recent
years is the realization that our Universe is dominated by a mysterious dark
energy, which leads to an accelerating expansion of space-time. A simple
generalization of the standard Friedmann-Robertson-Walker equations based on
General Relativity and the Cosmological Principles with the inclusion of a
number of closed extra dimensions reproduces the currently observed data on
dark energy, without the introduction of any cosmological constant or new
particles. In particular, with a few extra dimensions, we obtain the redshift
dependence of the deceleration parameter, the dark energy equation of state, as
well as the age of the Universe in agreement with data, with essentially no
free parameter. This model predicts that the extra dimensions have been
compactified throughout the cosmic history, and it therefore suggests that
signals from early Universe may give promising signatures of extra dimensions.


title: A model of the internal structure of Titan: first results

abstract:
  The aim of this short contribution is to report some preliminary results on a
theoretical model of the internal structure of Titan, the satellite of Saturn.
All the calculations were performed within the SK theory of dense matter. The
central pressure and temperature, as well as a possible chemical composition of
this satellite have been determinded, but they will ultimately become
verifiable only by data from the Cassini misision.


title:
A necessary condition for best fitting analytical to simulated density
  profiles in dark matter haloes

abstract:
  Generalized power-law (GPL) density profiles are compared with simulated dark
haloes (SDH) density profiles, and nonlinear least-squares fits are prescribed,
involving five parameters which specify the fitting profile (RFSM5 method).
More specifically, the validity of a necessary condition for the occurrence of
an extremal point, is related to the existence of an intersection between three
surfaces in a 3-dimension space. An application is made to a sample of 17 SDHs
on the scale of cluster of galaxies, within a flat /\CDM cosmological model. In
dealing with the averaged SDH density profile (ADP), a virial radius, equal to
the mean over the whole sample, is assigned, which allows the calculation of
the remaining parameters. The exponents of both the best fitting GPL density
profile to ADP and related averages calculated over the whole halo sample, are
far from their NFW counterparts. Values of asymptotic inner slope of fitting
logarithmic density profiles, are consistent with results from recent
high-resolution simulations.


title:
A grid of chemical evolution models as a tool to interpret spiral and
  irregular galaxies data

abstract:
  We present a generalization of the multiphase chemical evolution model
applied to a wide set of theoretical galaxies with different masses and
evolutionary rates. This generalized set of models has been computed using the
so-called Universal Rotation Curve from Persic et al (1996) to calculate the
radial mass distribution of 44 theoretical protogalaxies. This distribution is
a fundamental input which, besides its own effect on the galaxy evolution,
defines the characteristic collapse time-scale or gas infall rate onto the
disc.We have adopted 10 sets of values, between 0 and 1, for the molecular
cloud and star formation efficiencies, as corresponding to their probability
nature, for each one of the radial distributions of total mass. Thus, we have
constructed a bi-parametric grid of models, depending on those efficiency sets
and on the rotation velocity, whose results are valid in principle for any
spiral or irregular galaxy. The model results provide the time evolution of
different regions of the disc and the halo along galactocentric distance,
measured by the gas (atomic and molecular) and stellar masses, the star
formation rate and chemical abundances of 14 elements, for a total of 440
models. This grid may be used to estimate the evolution of a given galaxy for
which only present time information -- such as radial distributions of
elemental abundances, gas densities and/or star formation, which are the usual
observational constraints of chemical evolution models -- is available.


title:
Evidence for a Link Between Fe K-alpha Emission Line Strength and QPO
  Phase in a Black Hole

abstract:
  In X-ray binaries, the frequencies revealed in X-ray quasi-periodic
oscillations (QPOs) are often interpreted as characteristic frequencies in the
inner accretion disk, though the exact oscillation mechanism is unknown at
present. Broadened Fe K-alpha lines are also excellent diagnostics of the inner
accretion flow, if their broadening is indeed due to inner disk reflection.
Herein, we present two cases where the flux and equivalent width of the Fe
K-alpha emission lines in spectra of the Galactic black hole GRS 1915+105 vary
with the phase of strong 1 Hz and 2 Hz QPOs in the X-ray flux. These results
provide strong evidence that both QPOs and the Fe-alpha lines originate in the
inner disk. If the 1 Hz QPO is only a Keplerian orbital frequency, the QPO
comes from a distance of 84 +/- 26 R_Schw from the black hole; the 2 Hz QPO
implies a radius of 50 +/- 15 R_Schw. At these radii, relativistic shaping of a
disk line is inevitable. Moreover, the link holds in radio-bright and
radio-faint phases, signaling that in systems like GRS 1915+105, the Fe K-alpha
line is a disk line and not a jet line as per SS 433. A particularly
interesting possibility is that a stable warp in the inner disk, e.g. due to
Lense-Thirring precession, may produce the observed QPOs and line modulations.
More broadly, the FeK-QPO link provides an unprecedented mechanism for
revealing the inner accretion flow and relativistic regime in accreting
systems, in that it gives two measures of radius: for a given disk QPO model,
the frequency translates into a specific radius, and relativistic line models
yield radii directly.


title: Can rotation curves reveal the opacity of spiral galaxies ?

abstract:
  Long-slit optical spectra along the major axis of spiral galaxies constitute
a main source of information concerning the kinematics of galaxies. In highly
inclined spiral galaxies the long-slit spectrum is distorted by dust, which
obscures the innermost parts of the galaxy and eliminates the relevant
kinematic information. This effect however may provide information concerning
the amount and the spatial distribution of dust. Here I review previous
attempts to quantify the internal extinction of spiral galaxies using kinematic
information and I discuss the relevant theoretical models. Finally I suggest
possible directions for further studies on this subject.


title: Star Formation and Infrared Emission in Galaxies

abstract:
  The relationship between star formation and infrared emission in galaxies
will be investigated. If galaxies were simple objects and young stars were
completely covered with dust, then all the absorbed light of the young stars
would be re-emitted in the infrared and from the infrared emission of galaxies
we would infer the star formation rate (SFR) in them accurately. To show the
complexities involved in real galaxies, we will use as a case study the
late-type spiral galaxies. We will show that the heating of the dust is done
mainly by the UV radiation of the young stars and therefore the infrared
emission reveals the SFR in them. With a realistic model and its application to
a number of galaxies, tight correlations are derived between SFR and total far
infrared luminosity on one hand, and dust mass and 850 micron flux on the
other. Other diagnostics of the SFR are examined and it is shown that there is
consistency among them. Thus, the SFR for galaxies of all Hubble types has been
determined as well as for interacting starburst galaxies. Combining different
methods, the star-formation history of the universe has been determined and
will be shown. Finally, some early results from the Spitzer Space Telescope
will be presented.


title: Black hole X-ray binary jets

abstract:
  Relativistic jets powered by stellar mass black holes in X-ray binaries
appear to come in two types: steady outflows associated with hard X-ray states
and large scale discrete ejections associated with transient outbursts. We show
that the broadband radio spectrum of a `quiescent' stellar mass black hole
closely resembles that of canonical hard state sources emitting at four orders
of magnitude higher X-ray levels, suggesting that a relativistic outflow is
being formed down to at least a few 10^(-6) times the Eddington X-ray
luminosity. We further report on the discovery of a low surface brightness
radio nebula around the stellar black hole in Cyg X-1, and discuss how it can
be used as an effective calorimeter for the jet kinetic power.


title: How Special Are Dark Gamma-Ray Bursts: A Diagnostic Tool

abstract:
  We present here a comprehensive study of the optical/near-infrared (IR) upper
limits for gamma-ray bursts that have an X-ray afterglow. We have extrapolated
the X-ray afterglows to optical wavelengths based on the physics of the
fireball blast wave model (e.g. Rees & Meszaors 1992; Meszaros & Rees 1997),
and compared these results with optical upper limits for a large sample of
bursts. We find a small set of only three bursts out of a sample of 20 for
which the upper limits are not compatible with their X-ray afterglow properties
within the context of any blast wave model. This sparse sample does not allow
us to conclusively determine the cause of this optical/near-IR deficit.
Extinction in the host galaxy is a likely cause, but high redshifts and
different afterglow mechanisms might also explain the deficit in some cases. We
note that the three bursts appear to have higher than average gamma-ray peak
fluxes. In a magnitude versus time diagram the bursts are separated from the
majority of bursts with a detected optical/near-IR afterglow. However, two GRBs
with an optical afterglow (one of which is highly reddened) also fall in this
region with dark bursts, making it likely that dark bursts are at the faint end
of the set of optically detected bursts, and therefore the dark bursts likely
form a continuum with the bursts with a detected optical afterglow. Our work
provides a useful diagnostic tool for follow-up observations for potentially
dark bursts; applied to the events detected with the Swift satellite, it will
significantly increase our sample of truly dark bursts and shed light upon
their nature.


title: Satellite Infall and the Growth of Bulges of Spiral Galaxies

abstract:
  For bulges of spiral galaxies, the concentration, or Sersic index, increases
with bulge luminosity and bulge-to-disk ratio B/D (Andredakis, Peletier, &
Balcells 1995, MNRAS, 275, 874). Does this trend trace the growth of bulges via
satellite accretion? And, is satellite infall consistent with this trend?
Aguerri, Balcells, & Peletier (2001, A&A, 367, 428) investigated this question
with N-body simulations of the accretion of dense, spheroidal satellites. Here,
we expand on that work by running N-body simulations of the accretion of
satellites that have realistic densities. Satellites are modelled as disk-bulge
structures with their own dark-matter halo. A realistic density scaling with
the primary galaxy is ensured by using the Tully-Fisher relation. Our merger
models show that most satellites disrupt before reaching the center. However, a
bulge-disk decomposition of the surface density profile after the accretion
shows an increase of both the B/D and the Sersic index n of the bulge. The
increase in the mass and concentration of the inner Sersic component is due to
inward piling up of disk material due to transient bars during the satellite
orbital decay. This research is described in Eliche-Moral, Balcells, Aguerri, &
Gonzalez-Garcia, 2005 (in preparation).


title: Merging clusters of galaxies observed with XMM-Newton

abstract:
  We present results from the XMM-Newton observations of our ongoing program on
merging clusters. To date three clusters have been observed, covering the
temporal sequence from early to late stage mergers: A1750, A2065 and A3921.
Using spatially-resolved spectroscopy of discrete regions, hardness ratio and
temperature maps, we show that all three clusters display a complex temperature
structure. In the case of A1750, a double cluster, we argue that the observed
temperature structure is not only related to the ongoing merger but also to
previous merger events. A2065 seems an excellent example of a `compact merger',
i.e. when the centres of the two clusters have just started to interact,
producing a shock in the ICM. Using comparisons with numerical simulations and
complementary optical data, the highly complex temperature structure evident in
A3921 is interpreted as an off-axis merger between two unequal mass components.
These results illustrate the complex physics of merger events. The relaxation
time can be larger than the typical time between merger events, so that the
present day morphology of clusters depends not only on on-going interaction but
also on the more ancient formation history.


title: Strangeness, Cosmological Cold Dark Matter and Dark Energy

abstract:
  It is now believed that the universe is composed of a small amount of the
normal luminous matter, a substantial amount of matter (Cold Dark Matter: CDM)
which is non-luminous and a large amount of smooth energy (Dark Energy: DE).
Both CDM and DE seem to require ideas beyond the standard model of particle
interactions. In this work, we argue that CDM and DE can arise entirely from
the standard principles of strong interaction physics out of the same
mechanism.


title:
On the evolutionary status of early-type galaxies in clusters at z~0.2 -
  I. The Fundamental Plane

abstract:
  We investigate a spectroscopic sample of 48 early-type (E+S0) galaxies in the
rich cluster Abell 2390 (z=0.23) and 48 E+S0 galaxies from a previously
published survey of Abell 2218 (z=0.18). The A2390 spectra are based on Multi
Object Spectroscopy with MOSCA at the Calar Alto 3.5-m, complemented by
ground-based and HST F555W and F814W observations. Our investigation spans a
broad range in luminosity (-20.5>M_r>-23.0) and a wide FOV of 1.5x1.5 Mpc^2.
Since the A2218 and A2390 samples are very similar, we can combine them and
analyse a total of 96 E+S0 galaxies at z~0.2. We construct the Faber-Jackson
relation (FJR) for all E+S0s and detect a modest luminosity evolution. The
average offset from the local FJR in Gunn r-band is (DeltaM_r)=0.32+-0.22^m.
Less-massive galaxies show a trend for a larger evolution than more-massive
galaxies. HST/WFPC2 surface brightness profile fits were used to derive
structural parameters. For 34 E+S0 galaxies which enter the Fundamental Plane
(FP) we deduce a mild evolution in Gunn r with a zero-point offset of
0.10+-0.06, corresponding to 0.31+-0.18^m. Elliptical and lenticular galaxies
are uniformly distributed along the FP with a similar scatter of 0.1 dex. We
find little evidence for differences between the populations of ellipticals and
S0s. Lenticulars induce on average a larger evolution of 0.44+-0.18^m than
ellipticals with 0.02+-0.21^m. The M/L ratios at z=0.2 are offset by
(Deltalog(M/L_r))=-0.12+-0.06 dex compared to those of Coma. Our results can be
reconciled with a passive evolution of the stellar populations and a high
formation redshift for the bulk of the stars in E+S0 galaxies. However, our
findings are also consistent with the hierarchical formation picture for rich
clusters. [abridged]


title:
Detached binaries in the Large Magellanic Cloud. A selection of binaries
  suitable for distance determination

abstract:
  As a result of a careful selection of eclipsing binaries in the Large
Magellanic Cloud using the OGLE-II photometric database, we present a list of
98 systems that are suitable targets for spectroscopic observations that would
lead to the accurate determination of the distance to the LMC. For these
systems we derive preliminary parameters combining the OGLE-II data with the
photometry of MACHO and EROS surveys. In the selected sample, 58 stars have
eccentric orbits. Among these stars we found fourteen systems showing apsidal
motion. The data do not cover the whole apsidal motion cycle, but follow-up
observations will allow detailed studies of these interesting objects.


title: Scalar Field Oscillations Contributing to Dark Energy

abstract:
  We use action-angle variables to describe the basic physics of coherent
scalar field oscillations in the expanding universe. These analytical mechanics
methods have some advantages, like the identification of adiabatic invariants.
As an application, we show some instances of potentials leading to equations of
state with $p<-\rho/3$, thus contributing to the dark energy that causes the
observed acceleration of the universe.


title:
VLT narrow-band photometry in the Lyman continuum of two galaxies at
  z~3: Limits to the escape of ionizing flux

abstract:
  We have performed narrow-band imaging observations with the Very Large
Telescope, aimed at detecting the Lyman continuum (LC) flux escaping from
galaxies at z~3. We do not find any significant LC flux from our sample of two
galaxies in the Hubble Deep Field South, at z=3.170 and 3.275. The
corresponding lower limits on the F_{1400}/F_{900} flux density (per Hz) ratio
are 15.6 and 10.2 (3-sigma confidence level). After correction for the
intergalactic hydrogen absorption, the resulting limits on the relative escape
fraction of the LC are compared with those obtained by different approaches, at
similar or lower redshifts. One of our two objects has a relative escape
fraction lower than the detection reported by Steidel et al. in a composite
spectrum of z~3 galaxies. A larger number of objects is required to reach a
significant conclusion. Our comparison shows the potential of narrow-band
imaging for obtaining the best limit on the relative escape fraction at z~3.
Stacking a significant number of galaxies observed through a narrow-band filter
would provide constraint on the galactic contribution to the cosmic
reionization.


title: The structure of the Galactic bar

abstract:
  We present a deep near-infrared wide-angle photometric analysis of the
structure of the inner Galactic bar and central disk. The presence of a
triaxial structure at the centre of the Galaxy is confirmed, consistent with a
bar inclined at 22+/-5.5 deg from the Sun-Galactic centre line, extending to
about 2.5 kpc from the Galactic centre and with a rather small axis ratio. A
feature at l=-9.8 deg not aligned with this triaxiality suggests the existence
of a second structure in the inner Galaxy, a double triaxiality or an inner
ring. We argue that this is likely to be the signature of the end of the
Galactic bar, at about 2.5-3 kpc, which is circumscribed by an inner
pseudo-ring. No thick dust lane preceding the bar is detected, and a hole in
the disc's dust distribution inside the bar radius is inferred.


title:
Constraints on Velocity Dispersion Function of Early-type Galaxies from
  the Statistics of Strong Gravitational Lensing

abstract:
  We use the distribution of gravitationally-lensed image separations observed
in the Cosmic Lens All-Sky Survey (CLASS) and the PMN-NVSS Extragalactic Lens
Survey (PANELS), which are (nearly) complete for the image separation range
$0''.3 \le \Delta \theta \le 6''$, to constrain a model velocity dispersion
function (VF) of early-type galaxies. Assuming a current concordance
cosmological model and adopting a singular isothermal ellipsoid (SIE) model for
galactic potentials, we consider constraining both a characteristic velocity
dispersion (parameter $\sigma_*$) and the shape of the function (parameters
$\alpha$ and $\beta$; Sheth et al. 2003) for $0.3 \la z \la 1 $. If all three
parameters are allowed to vary, then none of the parameters can be tightly
constrained by the lensing data because of the small size of the sample. If we
fix the shape of the function by either the SDSS local stellar VF or an
inferred local stellar VF based on the SSRS2 galaxy sample, then the
constrained values of $\sigma_*$ are nearly equal to the corresponding stellar
values; we have $f_{\rm SIE/center} (\equiv \sigma_{*{\rm SIE}}/\sigma_{*{\rm
center}})= 0.90\pm 0.18 {\rm (SDSS)}$ or $1.04 \pm 0.19 {\rm (SSRS2)}$ assuming
non-evolution of the function between the present epoch and $z \sim 0.6$.
Finally, using only the CLASS statistical sample (Browne et al. 2003) and thus
including an absolute multiple-imaging probability, we find that the SDSS
stellar VF may have significantly underestimated the abundance of
morphologically early-type galaxies.


title: High-Latitude Molecular Clouds as gamma-ray Sources for GLAST

abstract:
  For about two decades, a population of relative small and nearby molecular
clouds has been known to exist at high Galactic latitudes. Lying more than
10$^\circ$ from the Galactic plane, these clouds have typical distances of
$\sim$150 pc, angular sizes of $\sim1^\circ$, and masses of order tens of solar
masses. These objects are passive sources of high-energy $\gamma$-rays through
cosmic ray-gas interactions. Using a new wide-angle CO survey of the northern
sky, we show that typical high-latitude clouds are not bright enough in
$\gamma$-rays to have been detected by EGRET, but that of order 100 of them
will be detectable by the Large Area Telescope (LAT) on GLAST. Thus, we predict
a new steady population of $\gamma$-ray sources at high Galactic latitudes,
perhaps the most numerous after active galactic nuclei.


title: Discovery of a Transition to Global Spin-up in EXO 2030+375

abstract:
  EXO 2030+375, a 42-second transient X-ray pulsar with a Be star companion,
has been observed to undergo an outburst at nearly every periastron passage for
the last 13.5 years. From 1994 through 2002, the global trend in the pulsar
spin frequency was spin-down. Using RXTE data from 2003 September, we have
observed a transition to global spin-up in EXO 2030+375. Although the spin
frequency observations are sparse, the relative spin-up between 2002 June and
2003 September observations, along with an overall brightening of the outbursts
since mid 2002 observed with the RXTE ASM, accompanied by an increase in
density of the Be disk, indicated by infrared magnitudes, suggest that the
pattern observed with BATSE of a roughly constant spin frequency, followed by
spin-up, followed by spin-down is repeating. If so this pattern has
approximately an 11 year period, similar to the 15 +/- 3 year period derived by
Wilson et al. (2002) for the precession period of a one-armed oscillation in
the Be disk. If this pattern is indeed repeating, we predict a transition from
spin-up to spin-down in 2005.


title: Giant Molecular Clouds in M64

abstract:
  (abridged) We investigate the properties of Giant Molecular Clouds (GMCs) in
the molecule-rich galaxy M64 (NGC 4826). In M64, the mean surface density of
molecular gas is 2N(H_2) ~ 10^22 over a 2 kpc region, equal to the surface
densities of individual GMCs in the Milky Way. We observed the J=1->0
transitions of CO, 13CO, and HCN. The line ratio W_CO/W_13CO for 200 pc < R_gal
< 800 pc is comparable to that found in the Milky Way and increases
significantly outside this region, in part due to a large contribution to the
CO emission from diffuse gas, which composes 25% of the molecular mass in the
galaxy. We developed a modified CLUMPFIND algorithm to decompose the 13CO
emission into 25 resolved clouds. The clouds have a luminosity--linewidth
relationship L ~ DV^{2.2+/-0.4}, substantially different from the Milky Way
trend reported by Solomon et al. (1987): L ~ DV^5. Similarly, the clouds have a
linewidth--size relationship of DV ~ R_e^{1.0 +/- 0.3} compared to DV ~ R_e^0.5
in the Milky Way. Estimates of the kinetic and binding energies of the clouds
suggest that the clouds are self-gravitating and significantly overpressured
with respect to the remainder of the ISM in M64. The M64 clouds have a mean
surface density at least 2.5 times larger than observed in Local Group GMCs,
and the surface density is not independent of mass as it is in the Local Group:
\Sigma_H2 ~ M^{0.7+/-0.2}. The clouds are correlated with the recombination
emission from the galaxy, implying that they are star forming; the rate is
comparable to that in other galaxies despite the increased densities of the
clouds. We note that the internal pressures of clouds in several galaxies
scales with the external pressure exerted on the clouds by the ambient ISM:
P_int ~ P_ext^{0.75+/-0.05}.


title: A Cluster of Ultrahigh Energy Cosmic Rays

abstract:
  Five ultrahigh energy cosmic rays in the combined AGASA and HiRes stereo data
are analyzed to test whether they come from a single source. The quad above 37
EeV in the 94-event high energy dataset can be analyzed without considering
magnetic dispersion. The probability that it is a chance association is 10^-3.
Assuming the source is continuous, the random magnetic deflections these UHECRs
accumulated en route from their source can be used to estimate \sqrt{B^2
\lambda D} ~ 1 nG-Mpc. A quintuplet including a HiRes event between 10 and 30
EeV is well fit with this value. Galactic magnetic deflection appears to be
smaller than in some models.


title:
Surface abundances of light elements for a large sample of early B-type
  stars - IV. The magnesium abundance in 52 stars - a test of metallicity

abstract:
  From high-resolution spectra a non-LTE analysis of the MgII 4481.2 A feature
is implemented for 52 early and medium local B stars on the main sequence (MS).
The influence of the neighbouring line AlIII 4479.9 A is considered. The
magnesium abundance is determined; it is found that log e(Mg) = 7.67 +- 0.21 on
average. It is shown that uncertainties in the microturbulent parameter Vt are
the main source of errors in log e(Mg). When using 36 stars with the most
reliable Vt values derived from OII and NII lines, we obtain the mean abundance
log e(Mg) = 7.59 +- 0.15. The latter value is precisely confirmed for several
hot B stars from an analysis of the MgII 7877 A weak line. The derived
abundance log e(Mg) = 7.59 +- 0.15 is in excellent agreement with the solar
magnesium abundance log e_sun(Mg) = 7.55 +- 0.02, as well as with the proto-Sun
abundance log e_ps(Mg) = 7.62 +- 0.02. Thus, it is confirmed that the Sun and
the B-type MS stars in our neighbourhood have the same metallicity.


title:
On the exact analytic expressions for the equitemporal surfaces in
  Gamma-Ray Burst afterglows

abstract:
  We have recently shown (see Bianco & Ruffini 2004) that marked differences
exist between the EQuiTemporal Surfaces (EQTSs) for the Gamma-Ray Burst (GRB)
afterglows numerically computed by the full integration of the equations of
motion and the ones found in the current literature expressed analytically on
the grounds of various approximations. In this Letter the exact analytic
expressions of the EQTSs are presented both in the case of fully radiative and
adiabatic regimes. The new EQTS analytic solutions validate the numerical
results obtained in Bianco & Ruffini (2004) and offer a powerful tool to
analytically perform the estimates of the physical observables in GRB
afterglows.


title: High resolution radio observations of the colliding-wind binary WR140

abstract:
  Milli-arcsecond resolution Very Long Baseline Array (VLBA) observations of
the archetype WR+O star colliding-wind binary (CWB) system WR140 are presented
for 23 epochs between orbital phases 0.74 and 0.97. At 8.4 GHz, the emission in
the wind-collision region (WCR) is clearly resolved as a bow-shaped arc that
rotates as the orbit progresses. We interpret this rotation as due to the O
star moving from SE to approximately E of the WR star, which leads to solutions
for the orbit inclination of 122+/-5 deg, the longitude of the ascending node
of 353+/-3 deg, and an orbit semi-major axis of 9.0+/-0.5 mas. The distance to
WR140 is determined to be 1.85+/-0.16 kpc, which requires the O star to be a
supergiant. The inclination implies the mass of the WR and O star to be 20+/-4
and 54+/-10 solar masses respectively. We determine a wind-momentum ratio of
0.22, with an expected half-opening angle for the WCR of 63 deg, consistent
with 65+/-10 deg derived from the VLBA observations. Total flux measurements
from Very Large Array (VLA) observations show the radio emission from WR140 is
very closely the same from one orbit to the next, pointing strongly toward
emission, absorption and cooling mechanism(s) that are controlled largely by
the orbital motion. The synchrotron spectra evolve dramatically through the
orbital phases observed, exhibiting both optically thin and optically thick
emission. We discuss a number of absorption and cooling mechanisms that may
determine the evolution of the synchrotron spectrum with orbital phase.


title: On the relativistic magnetic reconnection

abstract:
  Reconnection of the magnetic lines of force is considered in case the
magnetic energy exceeds the rest energy of the matter. It is shown that the
classical Sweet-Parker and Petschek models are generalized straightforwardly to
this case and the reconnection rate may be estimated by substituting the Alfven
velocity in the classical formulas by the speed of light. The outflow velocity
in the Sweet-Parker configuration is mildly relativistic. In the Petschek
configuration, the outflow velocity is ultrarelativistic whereas the angle
between the slow shocks is very small. Due to the strong compression, the
plasma outflow in the Petschek configuration may become strongly magnetized if
the reconnecting fields are not exactly antiparallel.


title: Cluster temperatures and non-extensive thermo-statistics

abstract:
  We propose a novel component to the understanding of the temperature
structure of galaxy clusters which does not rely on any heating or cooling
mechanism. The new ingredient is the use of non-extensive thermo-statistics
which is based on the natural generalization of entropy for systems with
long-range interactions. Such interactions include gravity and attraction or
repulsion due to charges. We explain that there is growing theoretical
indications for the need of this generalization for large cosmological
structures. The observed pseudo temperature is generally different from the
true thermodynamic temperature, and we clarify the connection between the two.
We explain that this distinction is most important in the central part of the
cluster where the density profile is most shallow. We show that the observed
pseudo temperature may differ up to a factor 2/5 from the true thermodynamic
temperature, either larger or smaller. In general the M-T and L-T relations
will be affected, and the central DM slope derived through hydrostatic
equilibrium may be either more shallow or steeper. We show how the true
temperature can be extracted correctly either from the spectrum or from the
shape of the Doppler broadening of spectral lines.