title:
A large sample of spectroscopic redshifts in the ACS-GOODS region of the
  HDF-N

abstract:
  We report the results of an extensive spectroscopic survey of galaxies in the
roughly 160 square arcminute ACS-GOODS region surrounding the HDF-N. We have
identified 787 galaxies or stars with z'<24, R<24.5, or B<25 lying in the
region. The spectra were obtained with either the DEIMOS or LRIS spectrographs
on the Keck 10m telescopes. The results are compared with photometric redshift
estimates and with redshifts from the literature, as well as with the redshifts
of a parallel effort led by a group at Keck. Our sample, when combined with the
literature data, provides identifications for 1180 sources.
  We use our results to determine the redshift distributions with magnitude, to
analyze the rest-frame color distributions with redshift and spectral type, and
to investigate the dependence of the X-ray galaxy properties on the local
galaxy density in the redshift interval z=0-1.5. We find the rather surprising
result that the galaxy X-ray properties are not strongly dependent on the local
galaxy density for galaxies in the same luminosity range.


title: Heating and deceleration of GRB fireballs by neutron decay

abstract:
  Fireballs with high energy per baryon rest mass (> 400) contain a relatively
slow neutron component. We show here that in this situation the thermal history
of fireballs is very different from the standard adiabatic cooling.


title: On Multiwavelength Emission of Large-Scale Quasar Jets

abstract:
  We discuss morphological properties of the large-scale jets in powerful radio
sources, which are now observed at radio, optical and X-ray frequencies, in
order to determine the origin of their X-ray radiation and the nature of the
particle acceleration responsible for their multiwavelength emission. We show
that modeling knots of the these objects as stationary regions of energy
dissipation within the uniform and continuous jet flow leads to several
problems. Such problems are especially pronounced if the observed X-ray
emission is due to inverse-Compton scattering of the CMB radiation. We explore
another possibility, namely that the knots represent moving and separate
portions of the jet matter, with excess kinetic power. We suggest a possible
connection between this scenario and the idea of intermittent/highly modulated
jet activity. The proposed model can explain some morphological properties of
quasar jets -- like high knot-to-interknot brightness contrasts,
frequency-independent knot profiles and almost universal extents of the knot
regions -- independently of the exact emission mechanism responsible for
producing the X-rays. In this context, we consider different possibilities for
the production of such X-ray radiation, and discuss the related issue of
particle acceleration. We conclude that the appropriate process cannot be
designated for certain yet. We suggest, however, that X-ray observations of the
jet in 3C 120 (in which intermittent jet activity is quite distinct) already
seem to support the synchrotron origin of the X-ray emission, at least in this
object.


title: A study of distant Ly-alpha emitters in overdense regions

abstract:
  Recently, we conducted a Very Large Telescope (VLT) large program to search
for forming clusters by looking for overdensities of Ly-alpha emitters around
high redshift radio galaxies. In total seven proto-clusters were discovered,
including a proto-cluster around the radio galaxy MRC 0316--257 at z ~ 3.13.
This structure has an excess of Ly-alpha emitters by a factor of 3 as compared
to the field, and the derived mass is 2-5 x 10^14 M_sun. The Ly-alpha emitters
in the proto-cluster are on average bluer than Lyman Break Galaxies (LBGs).
Also, the galaxies are faint (sub L_*) and small (half light radii < 1.7 kpc,
which is smaller than the average size of LBGs). This might indicate that, at
least a fraction of, Ly-alpha emitters could be young (~ 10^6 yr), nearly
dust-free, forming galaxies.


title: Using VLBI to Probe the Orion-KL Outflow on AU Scales

abstract:
  We present the first contemporaneous 43GHz and 86GHz VLBI images of the v=1
J=2-1 and J=1-0 SiO masers in the Orion-KL nebula. Both maser species exhibit
the same general morphology of earlier J=1-0 maser images which appear to trace
the edges of a bi-polar conical outflow. Surprisingly, the J=2-1 masers form
further from the central protostar than the J=1-0 masers, a fact not readily
explained by current SiO maser pumping models. The average magnitude of offsets
between corresponding regions of the two masing transitions is approximately
14% of the total radial extent of the SiO maser emission. This offset indicates
that each transition must trace different physical conditions.


title: The quasi-incompressible planet: some analytics

abstract:
  Exact and approximate analytical formulas are derived for the internal
structure and global parameters of the spherical non-rotating
quasi-incompressible planet. The planet is modeled by a polytrope with a small
polytropic index n << 1, and solutions of the relevant differential equations
are obtained analytically, to the second order of n.


title: On the recent star formation history of the Milky Way disk

abstract:
  We have derived the star formation history of the Milky Way disk over the
last 2 Gyr from the age distribution diagram of a large sample of open clusters
comprising more than 580 objects. By interpreting the age distribution diagram
using numerical results from an extensive library of N-body calculations
carried out during the last ten years, we reconstruct the recent star formation
history of the Milky Way disk. Our analysis suggests that superimposed on a
relatively small level of constant star formation activity mainly in small-N
star clusters, the star formation rate has experienced at least 5 episodes of
enhanced star formation lasting about 0.2 Gyr with production of larger
clusters. This cyclic behavior seems to show a period of 0.4+/-0.1 Gyr.


title: Stellar and gaseous abundances in M82

abstract:
  The near infrared (IR) absorption spectra of starburst galaxies show several
atomic and molecular lines from red supergiants which can be used to infer
reliable stellar abundances. The metals locked in stars give a picture of the
galaxy metallicity prior to the last burst of star formation. The enrichment of
the new generation of stars born in the last burst can be traced by measuring
the hot gas in the X-rays. For the first time detailed stellar abundances in
the nuclear region of the starburst galaxy M82 have been obtained. They are
compared with those of the hot gas as derived from an accurate re-analysis of
the XMM and Chandra nuclear X-ray spectra. The cool stars and the hot gas
suggest [Fe/H]=-0.35+/-0.2 dex, and an overall [Si,Mg/Fe] enhancement by 0.4
and 0.5 dex, respectively. This is consistent with a major chemical enrichment
by SNe II explosions in recursive bursts on short timescales. Oxygen is more
puzzling to interpret since it is enhanced by 0.3 dex in stars and depleted by
0.2 dex in the hot gas. None of the standard enrichment scenarios can fully
explain such a behavior when compared with the other alpha-elements.


title: Deflection of light and particles by moving gravitational lenses

abstract:
  Various authors have investigated the problem of light deflection by radially
moving gravitational lenses - with inconsistent results. In this paper we
generalize the calculations for arbitrary lens velocities and show that, to
first order in the lens velocity v, the deflection angles scales with 1-v. We
discuss the seeming inconsistency of relativistic light deflection with the
classical picture of moving test particles by generalizing the lens effect to
test particles of arbitrary velocity, including light as a limiting case. We
show that the effect of radial motion of the lens is very different for slowly
moving test particles and light and that a critical test particle velocity
exists for which the motion of the lens has no effect on the deflection angle
to first order. An interesting and not immediately intuitive result is obtained
in the limit of a highly relativistic motion of the lens towards the observer,
where the deflection angle of light reduces to zero. This phenomenon is
elucidated in terms of moving refractive media. Furthermore, we discuss the
dragging of inertial frames in the field of a moving lens and the corresponding
Lense-Thirring precession, in order to shed more light on the geometrical
effects in the surroundings of a moving mass. In a second part we discuss the
effect of transversal motion on the observed redshift of lensed sources. We
demonstrate how a simple kinematic calculation explains the effects for
arbitrary velocities of the lens and test particles. Additionally we include
the transversal motion of the source and observer to show that all three
velocities can be combined into an effective relative transversal velocity
similar to the approach used in microlensing studies.


title:
High-resolution imaging of dust shells using Keck aperture masking and
  the IOTA Interferometer

abstract:
  We present first results of an experiment to combine data from Keck aperture
masking and the Infrared-Optical Telescope Array (IOTA) to image the
circumstellar environments of evolved stars with ~20 milliarcsecond resolution.
The unique combination of excellent Fourier coverage at short baselines and
high-quality long-baseline fringe data allows us to determine the location and
clumpiness of the inner-most hot dust in the envelopes, and to measure the
diameters of the underlying stars themselves. We find evidence for large-scale
inhomogeneities in some dust shells and also significant deviations from
uniform brightness for the photospheres of the most evolved M-stars. Deviations
from spherically-symmetric mass loss in the red supergiant NML Cyg could be
related to recent evidence for dynamically-important magnetic fields and/or
stellar rotation. We point out that dust shell asymmetries, like those observed
here, can qualitatively explain the difficulty recent workers have had in
simultaneously fitting the broad-band spectral energy distributions and
high-resolution spatial information, without invoking unusual dust properties
or multiple distinct shells (from hypothetical ``superwinds''). This paper is
the first to combine optical interferometry data from multiple facilities for
imaging, and we discuss the challenges and potential for the future of this
method, given current calibration and software limitations.


title: Chain Galaxies in the Tadpole ACS Field

abstract:
  Colors and magnitudes were determined for 69 chain galaxies, 58 other linear
structures, 32 normal edge-on galaxies, and all of their large star formation
clumps in the HST ACS field of the Tadpole galaxy. Redshifts of 0.5 to 2 are
inferred from comparisons with published color-evolution models. The linear
galaxies have no red nuclear bulges like the normal disk galaxies in our field,
but the star formation clumps in each have about the same colors and
magnitudes. Light profiles along the linear galaxies tend to be flat, unlike
the exponential profiles of normal galaxies. Although the most extreme of the
linear objects look like beaded filaments, they are all probably edge-on disks
that will evolve to late Hubble type galaxies. The lack of an exponential
profile is either the result of a dust scale height that is comparable to the
stellar scale height, or an intrinsically irregular structure. Examples of
galaxies that could be face-on versions of linear galaxies are shown. They have
an irregular clumpy structure with no central bulge and with clump colors and
magnitudes that are comparable to those in the linears. Radiative transfer
solutions to the magnitudes and surface brightnesses of inclined dusty galaxies
suggest that edge-on disks should become more prominent near the detection
limit for surface brightness. The surface brightness distribution of the
edge-on galaxies in this field confirm this selection effect. The star
formation regions are much more massive than in modern galaxies, averaging up
to 10^9 Msun for kpc scales.


title:
Black holes in the real universe and their prospects as probes of
  relativistic gravity

abstract:
  Collapsed objects have definitely been observed: some are stellar-mass
objects, the endpoint of massive stars; others, millions of times more massive,
have been discovered in the cores of most galaxies. Their formation poses some
still-unanswered questions. But for relativists the key question is whether
observations can probe the metric in the strong-field domain, and test whether
it indeed agrees with the Kerr geometry predicted by general relativity.


title: Reconstructing Galaxy Histories from Globular Clusters

abstract:
  Nearly a century after the true nature of galaxies as distant "island
universes" was established, their origin and evolution remain great unsolved
problems of modern astrophysics. One of the most promising ways to investigate
galaxy formation is to study the ubiquitous globular star clusters that
surround most galaxies. Recent advances in our understanding of the globular
cluster systems of the Milky Way and other galaxies point to a complex picture
of galaxy genesis driven by cannibalism, collisions, bursts of star formation
and other tumultuous events.


title:
The origin of HI-deficiency in galaxies on the outskirts of the Virgo
  cluster. II. Companions and uncertainties in distances and deficiencies

abstract:
  The origin of the deficiency in neutral Hydrogen of 13 spiral galaxies lying
in the outskirts of the Virgo cluster is reassessed. If these galaxies have
passed through the core of the cluster, their interstellar gas should have been
lost through ram pressure stripping by the hot X-ray emitting gas of the
cluster. We analyze the positions of these HI-deficient and other spiral
galaxies in velocity-distance plots, in which we include our compilation of
velocity-distance data on 61 elliptical galaxies, and compare with simulated
velocity-distance diagrams obtained from cosmological N-body simulations. We
find that ~20% relative Tully-Fisher distance errors are consistent with the
great majority of the spirals, except for a small number of objects, whose
positions in the velocity-distance diagram suggest grossly incorrect distances,
which implies that the Tully-Fisher error distribution function has
non-gaussian wings. Moreover, we find that the distance errors may lead to an
incorrect fitting of the Tolman-Bondi solution that can generate significant
errors in the distance and especially the mass estimates of the cluster. We
suggest 4 possibilities for the outlying HI-deficient spirals (in decreasing
frequency): 1) they have large relative distance errors and are in fact close
enough (at distances between 12.7 and 20.9 Mpc from us) to the cluster to have
passed through its core and seen their gas removed by ram pressure stripping;
2) their gas is converted to stars by tidal interactions with other galaxies;
3) their gas is heated during recent mergers with smaller galaxies; and 4) they
are in reality not HI-deficient (e.g. S0/a's misclassified as Sa's).


title: Cosmic Ray Acceleration by Spiral Shocks in the Galactic Wind

abstract:
  Cosmic ray acceleration by shocks related with Slipping Interaction Regions
(SIRs) in the Galactic Wind is considered. SIRs are similar to Solar Wind
Corotating Interaction Regions. The spiral structure of our Galaxy results in a
strong nonuniformity of the Galactic Wind flow and in SIR formation at
distances of 50 to 100 kpc. SIRs are not corotating with the gas and magnetic
field because the angular velocity of the spiral pattern differs from that of
the Galactic rotation. It is shown that the collective reacceleration of the
cosmic ray particles with charge $Ze$ in the resulting shock ensemble can
explain the observable cosmic ray spectrum beyond the "knee" up to energies of
the order of $10^{17}Z$ eV. For the reaccelerated particles the Galactic Wind
termination shock acts as a reflecting boundary.


title: Physical Limits of Different Models of Cosmic Gamma-Ray Bursts

abstract:
  The present common view about GRB origin is related to cosmology, what is
based on statistical analysis, and on measurements of the redshifts in the GRB
optical afterglows of long GRB. No correlation is found between redshifts, GRB
spectrum, and total GRB fluence. Comparison of KONUS and BATSE data about
statistics and hard X-ray lines is done, and some differences are noted. Hard
gamma-ray afterglows, prompt optical spectra, hard X-ray lines measurements
could be important for farther insight into GRB origin. Possible possible
connection of short GRB with soft gamma repeaters is discussed.


title:
Simulations of spectral lines from an eccentric precessing accretion
  disc

abstract:
  Two dimensional SPH simulations of a precessing accretion disc in a q=0.1
binary system (such as XTE J1118+480) reveal complex and continuously varying
shape, kinematics, and dissipation. The stream-disc impact region and disc
spiral density waves are prominent sources of energy dissipation.The dissipated
energy is modulated on the period P_{sh} = ({P_{orb}}^{-1}-{P_{prec}}^{-1}^{-1}
with which the orientation of the disc relative to the mass donor repeats. This
superhump modulation in dissipation energy has a variation in amplitude of ~10%
relative to the total dissipation energy and evolves, repeating exactly only
after a full disc precession cycle. A sharp component in the light curve is
associated with centrifugally expelled material falling back and impacting the
disc. Synthetic trailed spectrograms reveal two distinct "S-wave" features,
produced respectively by the stream gas and the disc gas at the stream-disc
impact shock. These S-waves are non-sinusoidal, and evolve with disc precession
phase. We identify the spiral density wave emission in the trailed spectrogram.
Instantaneous Doppler maps show how the stream impact moves in velocity space
during an orbit. In our maximum entropy Doppler tomogram the stream impact
region emission is distorted, and the spiral density wave emission is
uppressed. A significant radial velocity modulation of the whole line profile
occurs on the disc precession period. We compare our SPH simulation with a
simple 3D model: the former is appropriate for comparison with emission lines
while the latter is preferable for skewed absorption lines from precessing
discs.


title: Dynamic stability of compact stars

abstract:
  After some historical remarks we discuss different criteria of dynamical
stability of stars, and properties of the critical states where dynamical
stability is lost, leading to collapse with formation of the neutron star or a
black hole. At the end some observational and theoretical problems related to
quark stars are discussed.


title: The impact of a close stellar encounter on the Edgeworth-Kuiper Belt

abstract:
  We numerically investigate the possibility that a close stellar encounter
could account for the high inclinations of the Kuiper belt, as originally
proposed by Ida, Larwood and Burkert, however we consider encounters with
pericenters within those explored by previous works. A star of mass 0.2 Msol
entering the solar system on a nearly parabolic, low inclination, retrograde
orbit with perihelion of 50 AU can scatter ~30% of the Kuiper belt into
moderate inclination (i>10 degrees) and eccentricity orbits, while leaving the
rest of the belt at low eccentricities and inclinations. This scenario provides
a possible explanation for the dichotomy of the Kuiper belt, accounting for the
scattered and classical populations, including objects with high eccentricities
and inclinations. High eccentricity objects that were not placed into resonance
with Neptune are more likely to be removed from the system by subsequent long
timescale evolution. Consequently this scenario suggests that some Plutinos
could have originally been objects in circular orbits which were scattered into
resonant high eccentricity and high inclination orbits by the stellar
encounter. Objects could have been placed into stable resonant regions with
Neptune by the encounter. However long lived regions of dynamical stability
should differ from those selected by resonance capture. This scenario predicts
the presence of objects in resonances with Neptune that are unlikely to have
been captured via Neptune's migration.


title: Massive Dark-matter halos and Evolution of Early-type Galaxies to z=1

abstract:
  (Shortened) The combination of lensing and stellar dynamics breaks the
mass-anisotropy degeneracy and provides stringent constraints on the mass
distribution in early-type (E/S0) galaxies out to z~1. We present the combined
results from the five field E/S0 lens galaxies at z=0.5-1.0 analyzed as part of
the LSD Survey. We find: (i) Constant M/L models are ruled out at >99% CL for
all five E/S0s. The projected dark-matter mass fractions inside the Einstein
(effective) radius is f_DM=0.37-0.72 (0.15-0.65) for isotropic models. (ii) The
average power-law slope of the total mass distribution is <\gamma'>=1.75+-0.10
for isotropic models with 0.20 rms scatter. The ratio between the observed
central stellar velocity dispersion and that from the best-fit SIE lens model
is <f_SIE>=<\sigma/\sigma_SIE>=0.87+-0.04 with 0.08 rms. Considering that
\gamma'>2 and f_SIE>1 have been reported for other systems, we conclude that
there is a significant intrinsic scatter in the density slopes of E/S0s (rms
\~15%). Hence, the isothermal approximation is not sufficiently accurate for
applications that depend critically on the slope of the mass density profile
(i.e. measuring H_0). (iii) The inner power-law slope of the dark-matter halo
is constrained to be <\gamma>=1.3(+0.2/-0.4) (68% CL) for the isotropic model
or an upper limit of \gamma<0.6, if the galaxies are radially anisotropic
(r_i=R_e). This is consistent with numerical simulations only for an isotropic
velocity ellipsoid and if baryonic collapse and star-formation do not steepen
dark-matter density profiles. (iv) The average stellar M/L evolves as
d\log(M_*/L_B)/dz =-0.72+-0.10, obtained via the FP. Based on lensing and
dynamics we find d\log(M_*/L_B)/dz=-0.75+-0.17, indicating that the M/L ratio
evolution for our sample of field E/S0s is faster than those in clusters.


title: The POINT-AGAPE Survey I: The Variable Stars in M31

abstract:
  The POINT-AGAPE collaboration has been monitoring M31 for three seasons with
the Wide Field Camera on the Isaac Newton Telescope. In each season, data are
taken for one hour per night for roughly sixty nights during the six months
that M31 is visible. The two fields of view straddle the central bulge,
northwards and southwards. We have calculated the locations, periods and
amplitudes of 35414 variable stars in M31 as a by-product of our microlensing
search. The variables are classified according to their period and amplitude of
variation. They are classified into population I and II Cepheids, Miras and
semi-regular long-period variables. The population I Cepheids are associated
with the spiral arms, while the central concentration of the Miras and
long-period variables varies noticeably, the stars with brighter (and shorter)
variations being much more centrally concentrated. A crucial role in the
microlensing experiment is played by the asymmetry signal. It was initially
assumed that the variable stars would not be a serious problem as their
distributions would be symmetric. We demonstrate that this assumption is not
correct. We find that differential extinction associated with the dust lanes
causes the variable star distributions to be asymmetric. The size and direction
of the asymmetry of the variable stars is measured as a function of period and
amplitude of variation. The implications of this discovery for the successful
completion of the microlensing experiments towards M31 are discussed.
(Abridged)


title:
Three-dimensional Simulations of Disk Accretion to an Inclined Dipole:
  I. Magnetospheric Flow at Different Theta

abstract:
  We present results of fully three-dimensional MHD simulations of disk
accretion to a rotating magnetized star with its dipole moment inclined at an
angle Theta to the rotation axis of the disk. We observed that matter accretes
from the disk to a star in two or several streams depending on Theta. Streams
may precess around the star at small Theta. The inner regions of the disk are
warped. The warping is due to the tendency of matter to co-rotate with inclined
magnetosphere. The accreting matter brings positive angular momentum to the
(slowly rotating) star tending to spin it up. The corresponding torque N_z
depends only weakly on Theta. The angular momentum flux to the star is
transported predominantly by the magnetic field; the matter component
contributes < 1 % of the total flux. Results of simulations are important for
understanding the nature of classical T Tauri stars, cataclysmic variables, and
X-ray pulsars.


title: Nucleosynthesis, Reionization, and the Mass Function of the First Stars

abstract:
  We critique the hypothesis that the first stars were very massive stars (VMS;
M > 140 Msun). We review the two major lines of evidence for the existence of
VMS: (1) that the relative metal abundances of extremely metal-poor Galactic
halo stars show evidence of VMS enrichment, and (2) that the high
electron-scattering optical depth (tau_e) to the CMB found by WMAP requires VMS
for reionization in a concordance LambdaCDM cosmology. The supernova yield
patterns of VMS are incompatible with the Fe-peak and r-process abundances in
halo stars. Models including Type II supernovae and/or ``hypernovae'' from
metal-free progenitors with 8 - 40 Msun can better explain the observed trends.
With a simple metal-transport model, we estimate that halo enrichment curtails
metal-free star formation after ~10^8 yr at z ~ 20. Because the ionizing photon
efficiency of metal-free stars peaks at ~120 Msun and declines at higher mass,
an IMF with a lower bound at M ~ 10 - 20 Msun and no VMS can maximize the
ionizing photon budget and still be consistent with the nucleosynthetic
evidence. An IMF devoid of low-mass stars is justified independently by models
of the formation of primordial stars. Using a semi-analytic model for H I and
He II reionization, we find that such an IMF can reproduce tau_e = 0.10 - 0.14,
consistent with the range from WMAP. We conclude, on the basis of these
results, that VMS are not necessary to meet the existing constraints commonly
taken to motivate them.


title:
Chandra Observation of the Trifid Nebula: X-ray emission from the O star
  complex and actively forming pre-main sequence stars

abstract:
  The Trifid Nebula, a young star-forming HII region, was observed for 16 hours
by the Chandra X-ray Observatory. We detected 304 X-ray sources, thirty percent
of which are hard sources and seventy percent of of which have near-infrared
counterparts. Chandra resolved the HD164492 multiple system into a number of
discrete X-ray sources. X-ray emission is detected from components HD164492A
(an O7.5III star which ionizes the nebula), B and C (a B6V star), and possibly
D (a Be star). HD164492A has a soft spectrum (kT ~ 0.5 keV) while the component
C blend shows much harder emission (kT ~ 6 keV). The soft spectrum of the O
star is similar to emission seen from other single O stars and is probably
produced by shocks within its massive stellar wind. Lack of hard emission
suggests that neither a magnetically confined wind shock nor colliding wind
emission is important in HD164492A. A dozen stars are found to have flares in
the field and most of them are pre-main sequence stars (PMS). Six sources with
flares have both optical and 2MASS counterparts. These counterparts are not
embedded and thus it is likely that these sources are in a later stage of PMS
evolution, possibly Class II or III. Two flare sources did not have any
near-IR, optical, or radio counterparts. We suggest these X-ray flare stars are
in an early pre-main sequence stage (Class I or earlier). We also detected
X-ray sources apparently associated with two massive star forming cores, TC1
and TC4. The spectra of these sources show high extinction and X-ray
luminosities of 2 - 5 x 10^{31} erg/s. If these sources are Class 0 objects, it
is unclear if their X-ray emission is due to solar-type magnetic activities as
in Class I objects, or some other mechanism.


title: Indirect search for dark matter: prospects for GLAST

abstract:
  Possible indirect detection of neutralino, through its gamma-ray annihilation
product, by the forthcoming GLAST satellite from our galactic halo, M31, M87
and the dwarf galaxies Draco and Sagittarius is studied. Gamma-ray fluxes are
evaluated for the two representative energy thresholds, 0.1 GeV and 1.0 GeV, at
which the spatial resolution of GLAST varies considerably. Apart from dwarfs
which are described either by a modified Plummer profile or by a
tidally-truncated King profiles, fluxes are compared for halos with central
cusps and cores. It is demonstrated that substructures, irrespective of their
profiles, enhance the gamma-ray emission only marginally. The expected
gamma-ray intensity above 1 GeV at high galactic latitudes is consistent with
the residual emission derived from EGRET data if the density profile has a
central core and the neutralino mass is less than 50 GeV, whereas for a central
cusp only a substantial enhancement would explain the observations. From M31,
the flux can be detected above 0.1 GeV and 1.0 GeV by GLAST only if the
neutralino mass is below 300 GeV and if the density profile has a central cusp,
case in which a significant boost in the gamma-ray emission is produced by the
central black hole. For Sagittarius, the flux above 0.1 GeV is detectable by
GLAST provided the neutralino mass is below 50 GeV. From M87 and Draco the
fluxes are always below the sensitivity limit of GLAST.


title:
Non-Linearity Corrections and Statistical Uncertainties Associated with
  Near-Infrared Arrays

abstract:
  We derive general equations for non-linearity corrections and statistical
uncertainty (variance) estimates for data acquired with near-infrared detectors
employing correlated double sampling, multiple correlated double sampling
(Fowler sampling) and uniformly-spaced continuous readout techniques. We
compare our equation for the variance on each pixel associated with Fowler
sampling with measurements obtained from data taken with the array installed in
the near-infrared cross-dispersed spectrograph (SpeX) at the NASA Infrared
Telescope Facility and find that it provides an accurate representation of the
empirical results. This comparison also reveals that the read noise associated
with a single readout of the SpeX array increases with the number of
non-destructive reads, n_r, as n_r^0.16. This implies that the {effective} read
noise of a stored image decreases as n_r^-0.34, shallower than the expected
rate of n_r^-0.5. The cause of this read noise behavior is uncertain, but may
be due to heating of the array as a result of the multiple read outs. Such
behavior may be generic to arrays that employ correlated or multiple correlated
double sampling readouts.


title:
Spectrum of Solar Type I Continuum Noise Storm in the 50 - 80 MHz band,
  and Plasma characteristics in the associated source region

abstract:
  Continuum observations of a solar noise storm in the frequency range of 50 -
80 MHz observed with the Gauribidanur radio spectrograph during 2000 September,
26 & 27, are presented here. The radio spectral index of the noise storm
continuum in the band 50 - 80 MHz is found to be ~3.65 during the above period.
The Noise Storm continuum radiation is explained as a consequence of the
non-thermal, plasma emission mechanism. The beam-density of suprathermal
electrons is estimated for the coronal plasma near the source region of storm
radiation. Supplementary evidence for the density-estimate is provided by way
of analysing the imaging data from the SXT on-board the Yohkoh spacecraft, and
the LASCO, MDI, and EIT on board the SoHO spacecraft.


title: RHESSI Observations of a Simple Large X-ray Flare on 11-03-2003

abstract:
  We present data analysis and interpretation of a simple X-class flare
observed with RHESSI on November 3, 2003. In contrast to other X-class flares
observed previously, this flare shows a very simple morphology with well
defined looptop (LT) and footpoint (FP) sources. The almost monotonic upward
motion of the LT source and increase in separation of the two FP sources are
consistent with magnetic reconnection models proposed for solar flares. In
addition, we find that the source motions are relatively slower during the more
active phases of hard X-ray emission; the emission centroid of the LT source
shifts toward higher altitudes with the increase of energy; the separation
between the LT emission centroids at two different photon energies is
anti-correlated with the FP flux. Non-uniformity of the reconnecting magnetic
fields could be a possible explanation of these features.


title:
An effect of stimulated radiation processes on radio emission from major
  planets

abstract:
  The standard theory of thermal radio emission encounters some difficulties.
The most crucial one is nonpossibility to explain the radio spectrum of Venus
in the decimeter range (Ksanfomality 1985). The radio spectra of planetary
nebulae at high frequencies also are not comfortably consistent with the
standard theory (Siodmiak & Tylenda 2001). Here we show that the account for an
induced character of radiation processes sufficiently improves the predictions
of the standard theory.


title:
Kinematic model inversions of hot star recurrent DAC data - tests
  against dynamical CIR models

abstract:
  The Discrete Absorption Components (DACs) commonly observed in the
ultraviolet lines of hot stars have previously been modelled by dynamical
simulations of Corotating Interaction Regions (CIRs) in their line-driven
stellar winds. Here we apply the kinematic DAC inversion method of Brown et al.
to the hydrodynamical CIR models and test the reliability of the results
obtained. We conclude that the inversion method is able to recover valuable
information on the velocity structure of the mean wind and to trace movement of
velocity plateaux in the hydrodynamical data, though the recovered density
profile of the stream is correct only very near to the stellar surface.


title: Kerr black holes as retro-MACHOs

abstract:
  Gravitational lensing is a well known phenomenon predicted by the General
Theory of Relativity. It is now a well-developed observational technique in
astronomy and is considered to be a fundamental tool for acquiring information
about the nature and distribution of dark matter. In particular, gravitational
lensing experiments may be used to search for black holes. It has been proposed
that a Schwarzschild black hole may act as a retro-lens (Holz & Wheeler
\cite{hw}) which, if illuminated by a powerful light source (e.g. the Sun),
deflects light ray paths to large bending angles so that the light may reach
the observer. Here, by considering the strong field limit in the deflection
angle and confining our analysis to the black hole equatorial plane, we extend
the Holz-Wheeler results to slowly spinning Kerr black holes. By considering
the Holz-Wheeler geometrical configuration for the lens, source and observer we
find that the inclusion of rotation does not substantially change the
brightness of the retro-lensing images with respect to the Schwarzschild case.
We also discuss the possibility that the next generation space-based telescopes
may detect such retro-images and eventually put limits on the rotational
parameter of the black hole.


title:
Searching for Variable Stars in the Central Part of the Globular Cluster
  M22

abstract:
  Time-series data taken with the Hubble Space Telescope of three fields
covering the central part of the globular cluster M22 have been analyzed in
search of variable objects. We report identification of 11 periodic variables
of which 8 are new discoveries. The sample includes 5 certain contact binaries
as well as 1 SX Phe star. Two objects with periods longer than 1 day are
preliminarily classified as either spotted variables of BY Dra type or
ellipsoidal variables. The most unusual of the identified variables, M22_V11,
has I_C=19.9 and is located far to the red of the main sequence in the cluster
color-magnitude diagram. It shows variability with a period as short as P=0.066
days or alternatively with P=0.132 days. We propose that it may be an
ellipsoidal variable harboring a degenerate component.


title: A New Halo Finding Method for N-Body Simulations

abstract:
  We have developed a new halo finding method, Physically Self-Bound (PSB)
group finding algorithm, which can efficiently identify halos located even at
crowded regions. This method combines two physical criteria such as the tidal
radius of a halo and the total energy of each particle to find member
particles. Two hierarchical meshes are used to increase the speed and the power
of halo identification in the parallel computing environments. First, a coarse
mesh with cell size equal to the mean particle separation $l_{\rm mean}$ is
used to obtain the density field over the whole simulation box. Mesh cells
having density contrast higher than a local cutoff threshold $\delta_{\rm LOC}$
are extracted and linked together for those adjacent to each other. This
produces local-cell groups. Second, a finer mesh is used to obtain density
field within each local-cell group and to identify halos. If a density shell
contains only one density peak, its particles are assigned to the density peak.
But in the case of a density shell surrounding at least two density peaks, we
use both the tidal radii of halo candidates enclosed by the shell and the total
energy criterion to find physically bound particles with respect to each halo.
Similar to DENMAX and HOP, the \hfind method can efficiently identify small
halos embedded in a large halo, while the FoF and the SO do not resolve such
small halos. We apply our new halo finding method to a 1-Giga particle
simulation of the $\Lambda$CDM model and compare the resulting mass function
with those of previous studies. The abundance of physically self-bound halos is
larger at the low mass scale and smaller at the high mass scale than proposed
by the Jenkins et al. (2001) who used the FoF and SO methods. (abridged)


title: Variations in Star Formation History and the Red Giant Branch Tip

abstract:
  We examine the reliability of the tip of the red giant branch (TRGB) as a
distance indicator for stellar populations with different star formation
histories (SFHs) when photometric errors and completeness corrections at the
TRGB are small. In general, the TRGB-distance method is insensitive to the
shape of the SFH except when it produces a stellar population with a
significant component undergoing the red giant branch phase transition. The
I-band absolute magnitude of the TRGB for the middle and late stages of this
transition (~1.3-1.7 Gyr) is several tenths of a magnitude fainter than the
canonical value of M_I ~ -4.0. If more than 30% of all stars formed over the
lifetime of the Universe are formed at these ages, then the distance could be
overestimated by 10-25%. Similarly, the TRGB-distance method is insensitive to
the metallicity distribution of stars formed except when the average
metallicity is greater than <[Fe/H]> = -0.3. If more than ~70% of all stars
formed have [Fe/H] > -0.3, the distance could be overestimated by ~10-45%. We
find that two observable quantities, the height of the discontinuity in the
luminosity function at the TRGB and the median (V-I)_0 at M_I = -3.5 can be
used to test if the aforementioned age and metallicity conditions are met.


title: NGC 2580 and NGC 2588: Two open clusters in the Third Galactic Quadrant

abstract:
  We present CCD broad band photometric observations in the fields of the Third
Galactic Quadrant open clusters NGC 2580 and NGC 2588 ($V(I)_C$ and $UBV(RI)_C$
respectively). From the analysis of our data we found that NGC 2580 is located
at a distance of about 4 kpc and its age is close to 160 Myr. As for NGC 2588,
it is placed at about 5 kpc from the Sun and is 450 Myr old. This means that
NGC 2588 belongs to the extension of the Perseus arm, whereas NGC 2580 is
closer to the local arm structure. The luminosity functions (LFs) have been
constructed for both clusters down to $V \sim 20$ together with their initial
mass functions (IMFs) for stars with masses above $M \sim 1-1.5 M_{\sun}$. The
IMF slopes for the most massive bins yielded values of $x \approx 1.3$ for NGC
2580 and $x \approx 2$ for NGC 2588. In the case of this latter cluster we
found evidence of a core-corona structure produced probably by dynamical
effect. In the main sequences of both clusters we detected gaps, which we
suggest could be real features.


title: Non-thermal radio emission from single hot stars

abstract:
  We present a theoretical model for the non-thermal radio emission from single
hot stars, in terms of synchrotron radiation from electrons accelerated in
wind-embedded shocks. The model is described by five independent parameters
each with a straightforward physical interpretation. Applying the model to a
high-quality observation of Cyg OB2 No. 9 (O5 If), we obtain meaningful
constraints on most parameters. The most important result is that the outer
boundary of the synchrotron emission region must lie between 500 and 2200
stellar radii. This means that shocks must persist up to that distance. We also
find that relatively weak shocks (with a compression ratio < 3) are needed to
produce the observed radio spectrum. These results are compatible with current
hydrodynamical predictions. Most of our models also show a relativistic
electron fraction that increases outwards. This points to an increasing
efficiency of the acceleration mechanism, perhaps due to multiple acceleration,
or an increase in the strength of the shocks. Implications of our results for
non-thermal X-ray emission are discussed.


title: Tracing the shock precursors in the L1448-mm/IRS3 outflows

abstract:
  We present the detection of the SiO v=0 J=2-1 and J=3-2 lines, and of the HCO
101-000 J=3/2-1/2 F=2-1 line at ambient velocities towards the molecular
outflows in L1448-mm and L1448-IRS3. This is the first detection of HCO in a
dark cloud. We have also measured lines of H13CO+, H13CN, HN13C, CH3OH, and
N2H+. While the HCO and the SiO lines have the narrowest profiles with
linewidths of 0.5 km s-1, the other lines have widths of 1km s-1. Towards
L1448-mm, all lines except those of SiO and HCO, show two distinct velocity
components centered at 4.7 and 5.2 km s-1. HCO is only observed in the 4.7 km
s-1 cloud, and SiO in the 5.2 km s-1 component. The SiO abundance is 10E-11 in
the 5.2 km s-1 clouds, one order of magnitude larger than in the 4.7 km s-1
component and in other dark clouds. The HCO abundance is 10E-11, similar to
that predicted by the ion-molecule reactions models for the quiescent gas in
dark clouds. The large change in the SiO/HCO abundance ratio (>150) from the
4.7 to the 5.2 km s-1 component, and the distribution and kinematics of the SiO
emission towards L1448-mm suggest that the ambient SiO is associated with the
molecular outflows. We propose that the narrow linewidths and the abundances of
SiO in the ambient gas are produced by the interaction of the magnetic and/or
radiative precursors of the shocks with the clumpy pre-shocked ambient gas.


title: Cluster temperature profiles and Sunyaev-Zeldovich observations

abstract:
  Galaxy clusters are not iso-thermal, and the radial temperature dependence
will affect the cluster parameters derived through the observation of the
Sunyaev-Zeldovich (SZ) effect. We show that the derived peculiar velocity will
be systematically shifted by 10-20%. For future all-sky surveys one cannot rely
on the observationally expensive X-ray observations to remove this systematic
error, but one should instead reach for sufficient angular resolution to
perform a deprojection in the SZ spectra. The Compton weighted electron
temperature is accurately derived through SZ observations.


title: Wide Field Photometry of the Galactic Globular Cluster M22

abstract:
  We present wide field photometry of the Galactic Globular Cluster M~22 in the
B, V and I passbands for more than 186,000 stars. The study is complemented by
the photometry in two narrowband filters centered on H$_{\alpha}$ and the
adjacent continuum, and by infrared J, H and K magnitudes derived from the 2
MASS survey for $\sim$2000 stars. Profiting from this huge database, we
completely characterized the evolved stellar sequences of the cluster by
determining a variety of photometric parameters, including new photometric
estimates of the mean metallicity, reddening and distance to the cluster. In
particular, from our multi-wavelength analysis, we re-examined the
long-standing metallicity spread problem in M~22. According to our dataset, we
conclude that most of the observed width of the red giant branch must be due to
differential reddening, which amounts to a maximum of $\Delta
E(B-V)\simeq0.06$, although the presence of a small metallicity spread cannot
be completely ruled out. More specifically, the maximum metallicity spread
allowed by our data is of the order of $\Delta$[Fe/H]$\simeq 0.1\div 0.2$ dex,
i.e., not much more than what allowed by the photometric errors. Finally, we
identified most of the known variable stars and peculiar objects in our field
of view. In particular, we find additional evidence supporting previous optical
identifications of the central star of the Planetary Nebula IRAS 18333-2357,
which is associated with M~22.


title: Practical Planet Prospecting

abstract:
  (Abridged) Space missions to search for exo-planets via the transit method,
such as COROT, Eddington and Kepler, will need to address problems associated
with the automated and efficient detection of planetary transits in light
curves affected by a variety of noise sources, including stellar variabilility.
Starting from a general purpose maximum likelihood approach we discuss the
links between a variety of period and transit finding methods. The natural
endpoint of this hierarchy of methods is shown to be a fast, robust and
statistically efficient least-squares algorithm based on box-shaped transits.
  This approach is predicated on the assumption of periodic transits hidden in
random noise, usually assumed to be superposed on a flat continuum with regular
continuous sampling. We next show how to generalise the transit finding method
to the more realistic scenario where complex stellar (micro) variability,
irregular sampling and long gaps in the data are all present. Tests of this
methodology on simulated Eddington light curves including realistic stellar
micro-variability, irregular sampling and data gaps, are used to quantify the
performance. In the case where transit durations are short compared to the
dominant timescales for stellar variability and data record segments, it is
possible to decouple the transit signal from the remainder.
  We conclude that even with realistic contamination from stellar variability,
irregular sampling, and gaps in the data record, it is still possible to detect
transiting planets with an efficiency close to the idealised theoretical bound.
In particular, space missions have the potential to approach the regime of
detecting earth-like planets around G2V-type stars.


title:
The Radio Continuum of the Metal-Deficient Blue Compact Dwarf Galaxy
  SBS0335-052

abstract:
  We present new Very Large Array observations at five frequencies, from 1.4 to
22GHz, of the extremely low-metallicity blue compact dwarf SBS0335-052. The
radio spectrum shows considerable absorption at 1.49GHz, and a composite
thermal+non-thermal slope. After fitting the data with a variety of models, we
find the best-fitting geometry to be one with free-free absorption
homogeneously intermixed with the emission of both thermal and non-thermal
components. The best-fitting model gives an an emission measure EM ~ 8x10^7pc
cm^{-6} and a diameter of the radio-emitting region D ~17pc. The inferred
density is n_e ~ 2000 cm^{-3}. The thermal emission comes from an ensemble of
\~9000 O7 stars, with a massive star-formation rate (>=5Msun) of 0.13-0.15
yr^{-1}, and a supernova rate of 0.006 yr^{-1}. We find evidence for ionized
gas emission from stellar winds, since the observed Bralpha line flux
significantly exceeds that inferred from the thermal radio emission. The
non-thermal fraction at 5GHz is ~0.7, corresponding to a non-thermal luminosity
of ~2x10^{20} W Hz^{-1}. We attribute the non-thermal radio emission to an
ensemble of compact SN remnants expanding in a dense interstellar medium, and
derive an equipartition magnetic field of ~0.6-1 mG, and a pressure of
\~3x10^{-8}-1x10^{-7} dyne cm^{-2}. If the radio properties of SBS0335-052 are
representative of star formation in extremely low-metallicity environments,
derivations of the star formation rate from the radio continuum in high
redshift primordial galaxies need to be reconsidered. Moreover, photometric
redshifts inferred from ``standard'' spectral energy distributions could be
incorrect.


title:
Molecular Gas in Candidate Double Barred Galaxies III. A Lack of
  Molecular Gas?

abstract:
  Most models of double-barred galaxies suggest that a molecular gas component
is crucial for maintaining long-lived nuclear bars. We have undertaken a CO
survey in an attempt to determine the gas content of these systems and to
locate double barred galaxies with strong CO emission that could be candidates
for high resolution mapping. We observed 10 galaxies in CO J=2-1 and J=3-2 and
did not detect any galaxies that had not already been detected in previous CO
surveys. We preferentially detect emission from galaxies containing some form
of nuclear activity. Simulations of these galaxies require that they contain 2%
to 10% gas by mass in order to maintain long-lived nuclear bars. The fluxes for
the galaxies for which we have detections suggest that the gas mass fraction is
in agreement with these models requirements. The lack of emission in the other
galaxies suggests that they contain as little as 7 x 10^6 solar masses of
molecular material which corresponds to < 0.1% gas by mass. This result
combined with the wide variety of CO distributions observed in double barred
galaxies suggests the need for models of double-barred galaxies that do not
require a large, well ordered molecular gas component.


title: Nitrogen abundances in Planet-harbouring stars

abstract:
  We present a detailed spectroscopic analysis of nitrogen abundances in 91
solar-type stars, 66 with and 25 without known planetary mass companions. All
comparison sample stars and 28 planet hosts were analysed by spectral synthesis
of the near-UV NH band at 3360 \AA observed at high resolution with the
VLT/UVES,while the near-IR NI 7468 \AA was measured in 31 objects. These two
abundance indicators are in good agreement. We found that nitrogen abundance
scales with that of iron in the metallicity range -0.6 <[Fe/H]< +0.4 with the
slope 1.08 \pm 0.05. Our results show that the bulk of nitrogen production at
high metallicities was coupled with iron. We found that the nitrogen abundance
distribution in stars with exoplanets is the high [Fe/H] extension of the curve
traced by the comparison sample of stars with no known planets. A comparison of
our nitrogen abundances with those available in the literature shows a good
agreement.


title:
Cosmic Ray Acceleration at Relativistic Shock Waves with a "Realistic"
  Magnetic Field Structure

abstract:
  The process of cosmic ray first-order Fermi acceleration at relativistic
shock waves is studied with the method of Monte Carlo simulations. The
simulations are based on numerical integration of particle equations of motion
in a turbulent magnetic field near the shock. In comparison to earlier studies,
a few "realistic" features of the magnetic field structure are included. The
upstream field consists of a mean field component inclined at some angle to the
shock normal with finite-amplitude sinusoidal perturbations imposed upon it.
The perturbations are assumed to be static in the local plasma rest frame.
Their flat or Kolmogorov spectra are constructed with randomly drawn wave
vectors from a wide range $(k_{min}, k_{max})$. The downstream field structure
is derived from the upstream one as compressed at the shock. We present
particle spectra and angular distributions obtained at mildly relativistic sub-
and superluminal shocks and also parallel shocks. We show that particle spectra
diverge from a simple power-law, the exact shape of the spectrum depends on
both the amplitude of the magnetic field perturbations and the wave power
spectrum. Features such as spectrum hardening before the cut-off at oblique
subluminal shocks and formation of power-law tails at superluminal ones are
presented and discussed. At parallel shocks, the presence of finite-amplitude
magnetic field perturbations leads to the formation of locally oblique field
configurations at the shock and the respective magnetic field compressions.
This results in the modification of the particle acceleration process,
introducing some features present in oblique shocks, e.g., particle reflections
from the shock. We demonstrate for parallel shocks a (nonmonotonic) variation
of the particle spectral index with the turbulence amplitude.


title: What is the Evidence for Dark Matter?

abstract:
  Newtonian mechanics indicates that galaxies and galaxy clusters are much more
massive than we would have guessed from their luminosities, with the
discrepancy being generally attributed to dark matter halos. An alternative
hypothesis is that accelerations in very weak gravitational fields are larger
than predicted by Newton's laws, and there is no need for dark matter. Even
though we do not currently have a satisfactory theory associated with this
rival hypothesis, we can ask whether any observational tests could rule it out
or prefer it over the dark matter hypothesis. Current evidence suggests that
neither hypothesis enjoys a decisive advantage over the other. If dark matter
turns out to be the correct interpretation however, then theories of galaxy
formation face some quite severe fine-tuning problems.


title: Terminal velocities of luminous, early-type SMC stars

abstract:
  Ultraviolet spectra from the Space Telescope Imaging Spectrograph (STIS) are
used to determine terminal velocities for 11 O and B-type giants and
supergiants in the Small Magellanic Cloud (SMC) from the Si IV and C IV
resonance lines. Using archival data from observations with the Goddard
High-Resolution Spectrograph and the International Ultraviolet Explorer
telescope, terminal velocities are obtained for a further five B-type
supergiants. We discuss the metallicity dependence of stellar terminal
velocities, finding no evidence for a significant scaling between Galactic and
SMC metallicities for Teff < 30,000 K, consistent with the predictions of
radiation driven wind theory for supergiant stars. A comparison of the
$v_\infty / v_{esc}$ ratio between the SMC and Galactic samples, while
consistent with the above statement, emphasizes that the uncertainties in the
distances to galactic O-stars are a serious obstacle to a detailed comparison
with theory. For the SMC sample there is considerable scatter in this ratio at
a given effective temperature, perhaps indicative of uncertainties in stellar
masses.


title:
A note on transition, turbulent length scales and transport in
  differentially rotating flows

abstract:
  In this note we address the issue of hydrodynamical instabilities in
Astrophysical rotating shear flows in the light of recent publications focused
on the possibility for differential rotation to trigger and sustain turbulence
in the absence of a magnetic field. We wish to present in a synthetic form the
major arguments in favor of this thesis along with a simple schematic scenario
of the transition to and self-sustenance of such turbulence. We also propose
that the turbulent diffusion length scale scales as the local Rossby number of
the mean flow. A new prescription for the turbulent viscosity is introduced.
This viscosity reduces to the so-called beta-prescription in the case of
velocity profiles with a constant Rossby number, which includes Keplerian
rotating flows.


title:
Detecting Population III stars through observations of near-IR cosmic
  infrared background anisotropies

abstract:
  Following the successful mapping of the last scattering surface by WMAP and
balloon experiments, the epoch of the first stars, when Population III stars
formed, is emerging as the next cosmological frontier. It is not clear what
these stars' properties were, when they formed or how long their era lasted
before leading to the stars and galaxies we see today. We show that these
questions can be answered with the current and future measurements of the
near-IR cosmic infrared background (CIB). Theoretical arguments suggest that
Population III stars were very massive and short-lived stars that formed at
$z\sim 10-20$ at rare peaks of the density field in the cold-dark-matter
Universe. Because Population III stars probably formed individually in small
mini-halos, they are not directly accessible to current telescopic studies. We
show that these stars left a strong and measurable signature via their
contribution to the CIB anisotropies for a wide range of their formation
scenarios. The excess in the recently measured near-IR CIB anisotropies over
that from normal galaxies can be explained by contribution from early
Population III stars. These results imply that Population III were indeed very
massive stars and their epoch started at $z\sim 20$ and lasted past $z\lsim
13$. We show the importance of accurately measuring the CIB anisotropies
produced by Population III with future space-based missions.


title: Molecular Gas in Spiral Galaxies

abstract:
  In this review, I highlight a number of recent surveys of molecular gas in
nearby spiral galaxies. Through such surveys, more complete observations of the
distribution and kinematics of molecular gas have become available for galaxies
with a wider range of properties (e.g., brightness, Hubble type, strength of
spiral or bar structure). These studies show the promise of both
interferometers and single-dish telescopes in advancing our general
understanding of molecular gas in spiral galaxies. In particular, I highlight
the contributions of the recent BIMA Survey of Nearby Galaxies (SONG).


title: Mass and Light in the Supercluster of galaxies : MS0302+17

abstract:
  We investigate the supercluster MS0302+17 (z~0.42) using weak lensing
analysis and deep wide field CFH12k BVR photometry. Using (B-V) - (V-R)
evolution tracks we identify supercluster early-types members. We derive a R
band weak lensing background galaxies sample. We compute the correlations
functions of light and mass and show that "light traces mass on supercluster
scales". The zeta-statistics applied in cluster centers and global correlation
analyses over the whole field converge toward the simple relation
M/L_B=300+/-30. This independently confirms the earlier results obtained by
Kaiser et al.(1998). We model dark matter halos around each galaxy by truncated
isothermal spheres and find the linear relation M L still holds. However, their
averaged halo truncation radius is s* ~< 200 kpc close to clusters cores,
whereas it reaches a lower limit of ~ 300 kpc at the periphery. This change of
s_* as function of radial distance gives indications on tidal stripping but the
lack of informations on the late-type galaxies sample prevents us to separate
contributions. Though all the data at hands are consistent with "mass is traced
by light from early-type galaxies", we are not able to describe in details the
contributions of late type galaxies. We however found it to be small.


title: Statistical Challenges in Modern Astronomy

abstract:
  Despite centuries of close association, statistics and astronomy are
surprisingly distant today. Most observational astronomical research relies on
an inadequate toolbox of methodological tools. Yet the needs are substantial:
astronomy encounters sophisticated problems involving sampling theory, survival
analysis, multivariate classification and analysis, time series analysis,
wavelet analysis, spatial point processes, nonlinear regression, bootstrap
resampling and model selection. We review the recent resurgence of
astrostatistical research, and outline new challenges raised by the emerging
Virtual Observatory. Our essay ends with a list of research challenges and
infrastructure for astrostatistics in the coming decade.


title: The 2dF Galaxy Redshift Survey: Hierarchical galaxy clustering

abstract:
  We use the two-degree field Galaxy Redshift Survey (2dFGRS) to test the
hierarchical scaling hypothesis: namely, that the $p$-point galaxy correlation
functions can be written in terms of the two point correlation function or
variance. This scaling is expected if an initially Gaussian distribution of
density fluctuations evolves under the action of gravitational instability. We
measure the volume averaged $p$-point correlation functions using a counts in
cells technique applied to a volume limited sample of 44,931 $L_*$ galaxies. We
demonstrate that $L_{*}$ galaxies display hierarchical clustering up to order
$p=6$ in redshift space. The variance measured for $L_{*}$ galaxies is in
excellent agreement with the predictions from a $\Lambda$-cold dark matter
N-body simulation. This applies to all cell radii considered,
$0.3<(R/h^{-1}{\rm Mpc})<30$. However, the higher order correlation functions
of $L_*$ galaxies have a significantly smaller amplitude than is predicted for
the dark matter for $R<10h^{-1}$Mpc. This disagreement implies that a
non-linear bias exists between the dark matter and $L_*$ galaxies on these
scales. We also show that the presence of two rare, massive superclusters in
the 2dFGRS has an impact on the higher-order clustering moments measured on
large scales.


title: The 2dF Galaxy Redshift Survey: voids and hierarchical scaling models

abstract:
  We measure the redshift space reduced void probability function (VPF) for
2dFGRS volume limited galaxy samples covering the absolute magnitude range
M_bJ-5logh=-18 to -22. Theoretically, the VPF connects the distribution of
voids to the moments of galaxy clustering of all orders, and can be used to
discriminate clustering models in the weakly non-linear regime. The reduced VPF
measured from the 2dFGRS is in excellent agreement with the paradigm of
hierarchical scaling of the galaxy clustering moments. The accuracy of our
measurement is such that we can rule out, at a very high significance, popular
models for galaxy clustering, including the lognormal distribution. We
demonstrate that the negative binomial model gives a very good approximation to
the 2dFGRS data over a wide range of scales, out to at least 20h-1Mpc.
Conversely, the reduced VPF for dark matter in a LambdaCDM universe does appear
to be lognormal on small scales but deviates significantly beyond \approx
4h-1Mpc. We find little dependence of the 2dFGRS reduced VPF on galaxy
luminosity. Our results hold independently in both the north and south Galactic
pole survey regions.


title: Post-Inflationary Curvature Perturbations

abstract:
  Curvature perturbations generated after the end of inflation are estimated
for a generic multi-field inflationary potential. The curvature perturbations
are generated by conversion of inflationary isocurvature perturbations, similar
to curvaton and inhomogeneous reheating scenarios. During inflation, the
trajectory along which the fields are rolling down will fluctuate. When
inflation ends, the fields enter the oscillatory phase along different
directions in different parts of the universe. Different oscillatory
trajectories can have different effective equations of state and reheating
rates, so that different parts of the universe will evolve differently. This
translates the isocurvature perturbations into the curvature perturbations.
  If all light fields make similar contributions to the potential energy, the
postinflationary curvature perturbations are much smaller than the standard
inflationary curvature perturbations. But if different light fields make very
different contributions to the potential energy, the postinflationary curvature
perturbations can exceed the inflationary perturbations. The characteristic
feature of postinflationary perturbations is non-Gaussianity $\sim \pm 1$.


title: Spectroscopy of Ultra-Cool Dwarfs

abstract:
  Ultra-cool dwarfs have been defined as dwarfs with spectral types of M7 or
later (Kirkpatrick, Henry, & Irwin 1997) and thus include the new L and T
spectral classes. The previous IAU report on ultra-cool dwarfs in 1999
described the optical and IR spectral features that characterize these spectral
types. In this report, I review the latest progress on the spectral
classification of ultra-cool dwarfs, which are divided into two categories: old
dwarfs in the field (>1 Gyr) and their young progenitors in the nearest
star-forming regions and open clusters (1-100 Myr). Because the former are
nearby and the latter are young, these two groups are relatively bright and
lend themselves to discovery and detailed study. Technically, the luminosity
class of young ultra-cool objects is closer to subgiant than dwarf;
nevertheless, I include them in this report on ultra-cool dwarfs.


title: Problems with the Current Cosmological Paradigm

abstract:
  We note that the standard LCDM cosmological model continues to face
fundamental problems. First, the model continues to depend wholly on two pieces
of undiscovered physics, namely dark energy and cold dark matter. Then, the
implied dark energy density is so small that it is unstable to quantum
correction and its size is fine-tuned to the almost impossible level of one
part in ~10^102; it is also difficult to explain the coincidence between the
dark energy, dark matter and baryon densities at the present day. Moreover, any
model with a positive cosmological constant also creates fundamental
difficulties for superstring theories of quantum gravity. We also review the
significant number of astrophysical observations which are now in contradiction
with the LCDM model. On the grounds that the SNIa Hubble diagram is prone to
evolutionary corrections and also that the CMB power spectrum may be
contaminated by the effects of foreground ionised gas, we argue that the
existence of such systematics could still allow more satisfactory, alternative,
models to appear. We suggest that if H_0<50kms^-1Mpc^-1 then a simpler,
inflationary model with Omega_baryon=1 might still be allowed with no need for
dark energy or cold dark matter.


title:
Diversity and Origin of 2:1 Orbital Resonances in Extrasolar Planetary
  Systems

abstract:
  (Abridged) A diversity of 2:1 resonance configurations can be expected in
extrasolar planetary systems, and their geometry can provide information about
the origin of the resonances. Assembly during planet formation by the
differential migration of planets due to planet-disk interaction is one
scenario for the origin of mean-motion resonances in extrasolar planetary
systems. The stable 2:1 resonance configurations that can be reached by
differential migration of planets with constant masses and initially coplanar
and nearly circular orbits are (1) anti-symmetric configurations with the
mean-motion resonance variables theta_1 and theta_2 (in deg.) librating about 0
and 180, respectively (as in the Io-Europa pair), (2) symmetric configurations
with both theta_1 and theta_2 librating about 0 (as in the GJ 876 system), and
(3) asymmetric configurations with theta_1 and theta_2 librating about angles
far from either 0 or 180. There are, however, stable 2:1 resonance
configurations with symmetric (theta_1 = theta_2 = 0), asymmetric, and
anti-symmetric (theta_1 = 180 and theta_2 = 0) librations that cannot be
reached by differential migration of planets with constant masses and initially
coplanar and nearly circular orbits. If real systems with these configurations
are ever found, their origin would require (1) a change in the planetary mass
ratio m_1/m_2 during migration, (2) a migration scenario involving inclination
resonances, or (3) multiple-planet scattering in crowded planetary systems. We
find that the asymmetric configurations with large e_2 and the theta_1 = 180
and theta_2 = 0 configurations have intersecting orbits and that the theta_1 =
theta_2 = 0 configurations with e_1 > 0.714 have prograde periapse precessions.


title: First Stellar Abundances in the Dwarf Irregular Galaxy Sextans A

abstract:
  We present the abundance analyses of three isolated A-type supergiant stars
in the dwarf irregular galaxy Sextans A from high-resolution spectra the UVES
spectrograph at the VLT. Detailed model atmosphere analyses have been used to
determine the stellar atmospheric parameters and the elemental abundances of
the stars. The mean iron group abundance was determined from these three stars
to be [(FeII,CrII)/H]=-0.99+/-0.04+/-0.06. This is the first determination of
the present-day iron group abundances in Sextans A. These three stars now
represent the most metal-poor massive stars for which detailed abundance
analyses have been carried out. The mean stellar alpha element abundance was
determined from the alpha element magnesium as
[alpha(MgI)/H]=-1.09+/-0.02+/-0.19. This is in excellent agreement with the
nebular alpha element abundances as determined from oxygen in the H II regions.
These results are consistent from star-to-star with no significant spatial
variations over a length of 0.8 kpc in Sextans A. This supports the nebular
abundance studies of dwarf irregular galaxies, where homogeneous oxygen
abundances are found throughout, and argues against in situ enrichment. The
alpha/Fe abundance ratio is [alpha(MgI)/FeII,CrII]=-0.11+/-0.02+/-0.10, which
is consistent with the solar ratio. This is consistent with the results from
A-supergiant analyses in other Local Group dwarf irregular galaxies but in
stark contrast with the high [alpha/Fe] results from metal-poor stars in the
Galaxy, and is most clearly seen from these three stars in Sextans A because of
their lower metallicities. The low [alpha/Fe] ratios are consistent with the
slow chemical evolution expected for dwarf galaxies from analyses of their
stellar populations.


title: The r-Process in Supernovae: Impact of New Microscopic Mass Formulas

abstract:
  The astrophysical origin of $r$-process nuclei remains a long-standing
mystery. Although some astrophysical scenarios show some promise, many
uncertainties involved in both the astrophysical conditions and in the nuclear
properties far from the $\beta$-stability have inhibited us from understanding
the nature of the $r$-process. The purpose of the present paper is to examine
the effects of the newly-derived microscopic Hartree-Fock-Bogoliubov (HFB) mass
formulas on the $r$-process nucleosynthesis and analyse to what extent a
solar-like $r$-abundance distribution can be obtained. The $r$-process
calculations with the HFB-2 mass formula are performed, adopting the
parametrized model of the prompt explosion from a collapsing O-Ne-Mg core for
the physical conditions and compared with the results obtained with the HFB-7
and droplet-type mass formulas. Due to its weak shell effect at the neutron
magic numbers in the neutron-rich region, the microscopic mass formulas (HFB-2
and HFB-7) give rise to a spread of the abundance distribution in the vicinity
of the $r$-process peaks ($A = 130$ and 195). While this effect resolves the
large underproduction at $A \approx 115$ and 140 obtained with droplet-type
mass formulas, large deviations compared to the solar pattern are found near
the third $r$-process peak. It is shown that a solar-like $r$-process pattern
can be obtained if the dynamical timescales of the outgoing mass trajectories
are increased by a factor of about 2-3, or if the $\beta$-decay rates are
systematically increased by the same factor.


title:
Constraints on Early Nucleosynthesis from the Abundance Pattern of a
  Damped Ly-alpha System at z = 2.626

abstract:
  We have investigated chemical evolution in the young universe by analysing
the detailed chemical enrichment pattern of a metal-rich galaxy at high
redshift. The recent detection of over 20 elements in the gas-phase of a damped
Lyman-alpha absorber (DLA) at z = 2.626 represents an exciting new avenue for
exploring early nucleosynthesis. Given a strict upper age of ~2.5 Gyr and a
gas-phase metallicity about one third solar, we have shown the DLA abundance
pattern to be consistent with the predictions of a chemical evolution model in
which the interstellar enrichment is dominated by massive stars with a small
contribution from Type Ia supernovae. Discrepancies between the empirical data
and the models are used to highlight outstanding issues in nucleosynthesis
theory, including a tendency for Type II supernovae models to overestimate the
magnitude of the "odd-even" effect at subsolar metallicities. Our results
suggest a possible need for supplemental sources of magnesium and zinc, beyond
that provided by massive stars.


title: Stellar Population in LLAGN.II: STIS observations

abstract:
  We present a study of the stellar population in Low Luminosity AGN (LLAGN).
Our goal is to search for spectroscopic signatures of young and intermediate
age stars, and to investigate their relationship with the ionization mechanism
in LLAGN. The method used is based on the stellar population synthesis of the
optical continuum of the innermost (20-100 pc) regions in these galaxies. For
this purpose, we have collected high spatial resolution optical (2900-5700 A)
STIS spectra of 28 nearby LLAGN that are available in the Hubble Space
Telescope archive. The analysis of these data is compared with a similar
analysis also presented here for 51 ground-based spectra of LLAGN. Our main
findings are: (1) No features due to Wolf-Rayet stars were convincingly
detected in the STIS spectra. (2) Young stars contribute very little to the
optical continuum in the ground-based aperture. However, the fraction of light
provided by these stars is higher than 10% in most of the weak-[OI] LLAGN STIS
spectra. (3) Intermediate age stars contribute significantly to the optical
continuum of these nuclei. This population is more frequent in objects with
weak than with strong [OI]. Weak-[OI] LLAGN that have young stars stand out for
their intermediate age population. (4) Most of the strong-[OI] LLAGN have
predominantly old stellar population. A few of these objects also show a
feature-less continuum that contributes significantly to the optical continuum.
These results suggest that young and intermediate age stars do not play a
significant role in the ionization of LLAGN with strong [OI]. However, the
ionization in weak-[OI] LLAGN with young and/or intermediate age population
could be due to stellar processes.


title: Triggers of magnetar outbursts

abstract:
  Bright outbursts from Soft Gamma Repeaters (SGRs) and Anomalous X-ray Pulsars
(AXPs) are believed to be caused by instabilities in ultramagnetized neutron
stars, powered by a decaying magnetic field. It was originally thought that
these outbursts were due to reconnection instabilities in the magnetosphere,
reached via slow evolution of magnetic footpoints anchored in the crust. Later
models considered sudden shifts in the crust's structure. Recent observations
of magnetars give evidence that at least some outburst episodes involve
rearrangements and/or energy releases within the star. We suggest that bursting
episodes in magnetars are episodes of rapid plastic yielding in the crust,
which trigger "swarms" of reconnection instabilities in the magnetosphere.
Magnetic energy always dominates; elastic energy released within the crust does
not generate strong enough Alfven waves to power outbursts. We discuss the
physics of SGR giant flares, and describe recent observations which give useful
constraints and clues.


title: Stellar Population in LLAGN.I: Ground-based observations

abstract:
  (Abridge): We present a spectroscopic study of the stellar populations of Low
Luminosity AGN (LLAGN). Our main goal is to determine whether the stars who
live in the innermost (100 pc-scale) regions of these galaxies are in some way
related to the emission line properties, which would imply a link between the
stellar population and the ionization mechanism. High signal to noise, ground
based long-slit spectra in the 3500--5500 A interval were collected for 60
galaxies.Our main findings are: (1) Few LLAGN have a detectable young (< 10
Myr) starburst component, indicating that very massive stars do not contribute
significantly to the optical continuum. In particular, no features due to
Wolf-Rayet stars were convincingly detected. (2) High Order Balmer absorption
lines of HI (HOBLs), on the other hand, are detected in 40% of LLAGN.
  These features, which are strongest in 100 Myr--1 Gyr intermediate age
stellar populations, are accompanied by diluted metal absorption lines and
bluer colors than other objects in the sample. (3) These intermediate age
populations are very common (50 %) in LLAGN with relatively weak [OI] emission,
but rare (10 %) in LLAGN with stronger [OI]. This is intriguing since LLAGN
with weak [OI] have been previously hypothesized to be ``transition objects''
in which both an AGN and young stars contribute to the emission-line
excitation. Massive stars, if present, are completely outshone by intermediate
age and old stars in the optical. This happens in at least a couple of objects
where independent UV spectroscopy detects young starbursts not seen in the
optical. (4) Objects with predominantly old stars span the whole range of
[OI]/Halpha values, but (5) sources with significant young and/or intermediate
age populations are nearly all (90%) weak [OI] emitters.


title:
The initial conditions of the universe: how much isocurvature is
  allowed?

abstract:
  We investigate the constraints imposed by the current data on correlated
mixtures of adiabatic and non-adiabatic primordial perturbations. We discover
subtle flat directions in parameter space that tolerate large (~60%)
contributions of non-adiabatic fluctuations. In particular, larger values of
the baryon density and a spectral tilt are allowed. The cancellations in the
degenerate directions are explored and the role of priors elucidated.


title:
Isochrone ages for field dwarfs: method and application to the
  age-metallicity relation

abstract:
  A new method is presented to compute age estimates from theoretical
isochrones using temperature, luminosity and metallicity data for individual
stars. Based on Bayesian probability theory, this method avoids the systematic
biases affecting simpler strategies, and provides reliable estimates of the age
probability distribution function for late-type dwarfs. This method is
especially relevant for G dwarfs in the 3-15 Gyr range of ages, crucial to the
study of the chemical and dynamical history of the Galaxy.
  We apply our method to the classic sample of Edvardsson et al. (1993), who
derived the age-metallicity relation (AMR) of a sample of 189 field dwarfs with
precisely determined abundances. Using new parallax, temperature and
metallicity data, our age determination for the Edvardsson et al. sample
indicates that the intrinsic dispersion in the AMR is at most 0.15 dex and
probably lower. In particular, we show that old, metal-rich objects ([Fe/H]\sim
0.0 dex, age > 5 Gyr) and young, metal-poor objects ([Fe/H]<-0.5 dex, age < 6
Gyr) in many observed AMR plots are artifacts caused by a too simple treatment
of the age determination, and that the Galactic AMR is monotonically increasing
and rather well-defined. Incidentally, our results tend to restore confidence
in the method of age determination from chromospheric activity for field
dwarfs.


title: The nature of the Lyman-alpha emission region of FDF-4691

abstract:
  In order to study the origin of the strong Lyman-alpha emission of
high-redshift starburst galaxies we observed and modeled the emission of the z
= 3.304 galaxy FDF-4691 (rest-frame EW = 103 Angstroem). The observations show
that FDF-4691 is a young starburst galaxy with a (for this redshift) typical
metallicity. The broad, double-peaked profile of the Lyman-alpha emission line
can be explained assuming a highly turbulent emission region in the inner part
of the starburst galaxy, and a surrounding extended shell of low-density
neutral gas with a normal dust/gas ratio and with Galactic dust properties. The
detection of the Lyman-alpha emission line is explained by the intrinsic broad
Lyman-alpha emission and a low HI column density of the neutral shell. A low
dust/gas ratio in the neutral shell is not needed to explain the strong
Lyman-alpha line.


title: Redshift of photons penetrating a hot plasma

abstract:
  A new interaction, plasma redshift, is derived, which is important only when
photons penetrate a hot, sparse electron plasma. The derivation of plasma
redshift is based entirely on conventional axioms of physics. When photons
penetrate a cold and dense plasma, they lose energy through ionization and
excitation, Compton scattering on the individual electrons, and Raman
scattering on the plasma frequency. But in sparse hot plasma, such as in the
solar corona, the photons lose energy also in plasma redshift. The energy loss
per electron in the plasma redshift is about equal to the product of the
photon's energy and one half of the Compton cross-section per electron. In
quiescent solar corona, this heating starts in the transition zone to the
corona and is a major fraction of the coronal heating. Plasma redshift
contributes also to the heating of the interstellar plasma, the galactic
corona, and the intergalactic plasma. Plasma redshift explains the solar
redshifts, the redshifts of the galactic corona, the cosmological redshifts,
the cosmic microwave background, and the X-ray background. The plasma redshift
explains the observed magnitude-redshift relation for supernovae SNe Ia without
the big bang, dark matter, or dark energy. There is no cosmic time dilation.
The universe is not expanding. The plasma redshift, when compared with
experiments, shows that the photons' classical gravitational redshifts are
reversed as the photons move from the Sun to the Earth. This is a quantum
mechanical effect. As seen from the Earth, a repulsion force acts on the
photons. This means that there is no need for Einstein's Lambda term. The
universe is quasi-static, infinite, and everlasting.


title: Chandra Temperature Maps for Galaxy Clusters with Radio Halos

abstract:
  We analyze Chandra temperature maps for a sample of clusters with high
quality radio halo data, to study the origin of the radio halos. The sample
includes A520, A665, A754, A773, A1914, A2163, A2218, A2319, and 1E0657-56. We
present new temperature maps for all but two of them (A520 and A754). All these
clusters exhibit distorted X-ray morphology and strong gas temperature
variations indicating ongoing mergers. Some clusters, e.g., A520, A665,
1E0657-56, exhibit the previously reported spatial correlation between the
radio halo brightness and the hot gas regions. However, it is not a general
feature. While most mergers are too messy to allow us to disentangle the
projection effects, we find clear counterexamples (e.g., A754 and A773) where
the hottest gas regions do not exhibit radio emission at the present
sensitivity level. This cannot be explained by projection effects, and
therefore argues against merger shocks -- at least those relatively weak ones
responsible for the observed temperature structure in most clusters -- as the
main mechanism for the halo generation. This leaves merger-generated turbulence
as a more likely mechanism. The two clusters with the clearest radio brightness
- temperature correlation, A520 and 1E0657-56, are both mergers in which a
small dense subcluster has just passed through the main cluster, very likely
generating turbulence in its wake. The maximum radio brightness and the hot gas
are both seen in these wake regions. On the other hand, the halos in 1E0657-56
and A665 (both high-velocity mergers) extend into the shock regions in front of
the subclusters, where no strong turbulence is expected. Thus, in high-velocity
(M=2-3) mergers, both shock and turbulence acceleration mechanisms may be
significant.


title: Modeling the disruption of the globular cluster Pal5 by Galactic tides

abstract:
  In order to understand the extended massive tidal tails of the globular
cluster Pal5, its very low mass and velocity dispersion, and its size, which is
much larger than the theoretical tidal radius, we performed more than 1000
N-body simulations. Tidal shocks at disk crossings near perigalacticon dominate
the evolution of extended low-concentration clusters, resulting in massive
tidal tails and often in a quick destruction of the cluster. The overlarge size
of Pal5 can be explained as the result of an expansion following the heating
induced by the last strong disk shock ~150Myr ago. The models can reproduce the
low observed velocity dispersion and the relative fractions of stars in the
tails and between the inner and outer parts of the tails. The tidal tails of
Pal5 show substantial structure not seen in our simulations. We argue that this
structure is probably caused by Galactic substructure, such as giant molecular
clouds, spiral arms, and dark-matter clumps.
  Clusters initially larger than their theoretical tidal limit remain so,
because, after being shocked, they settle into a new equilibrium near
apogalacticon, where they are unaffected by the perigalactic tidal field. This
implies that, contrary to previous wisdom, globular clusters on eccentric
orbits may well remain super-tidally limited and hence vulnerable to strong
disk shocks, which dominate their evolution until destruction. Our simulations
unambiguously predict the destruction of Pal5 at its next disk crossing in
\~110Myr. This corresponds to only 1% of the cluster lifetime, suggesting that
many more similar systems could once have populated the inner parts of the
Milky Way, but have been transformed into debris streams by the Galactic tidal
field. (Abridged)


title: The multiple spectroscopic and photometric periods of DI Cru (=WR 46)

abstract:
  In an effort to determine the orbital period of the star DI Cru, we made
photometric and spectroscopic observations of this object between 1996 and
2002. The star is highly variable on short (few hours) as well as on long (few
months) time-scales. The optical spectrum is rich in strong emission lines of
high ionization species. Temporal Variance Spectrum - TVS - analysis shows that
the He II 4686A line has P Cyg-like variable absorption, while NV 4603/19A
lines have a strong and broad variable component due to the continuum
fluorescence from a source (stellar atmosphere/optically thick wind) of
variable temperature. We also show that the object has variable degree of
ionization, probably caused by wind density variation. The star presents
multiple periods in radial velocity and photometry. We derived, from our data,
a main radial velocity period of 0.3319 d with an amplitude of K = 58 km/s.
When at intermediate brightness level, this period is also seen in the
photometric measurements. When the star is at bright phase, the photometric
variations do not present the same period. Photometric periods ranging from
0.154 to 0.378 d are present, consistent with observations reported by other
authors. Besides the 0.3319 d period other spectroscopic periods are also seen.
On distinct epochs, the periods are different; Marchenko et al. (2000)
interpreted the 0.3319 d period as the orbital one. Although we do not discard
this possibility, the true binary nature (e.g. long term coherence or detection
of a secondary star) has not yet been demonstrated. DI Cru is a Population I WR
object. Given the similarities (e.g. multiple periods likely due to non-radial
oscillations), it could be interpreted as a luminous counterpart of the qWR
star HD 45166.


title: Numerical coincidences and 'tuning' in cosmology

abstract:
  Fred Hoyle famously drew attention to the significance of apparent
coincidences in the energy levels of the carbon and oxygen nucleus. This paper
addresses the possible implications of other coincidences in cosmology.


title:
Simulations of planet-disc interactions using Smoothed Particle
  Hydrodynamics

abstract:
  We have performed Smoothed Particle Hydrodynamics (SPH) simulations to study
the time evolution of one and two protoplanets embedded in a protoplanetary
accretion disc. We investigate accretion and migration rates of a single
protoplanet depending on several parameters of the protoplanetary disc, mainly
viscosity and scale height. Additionally, we consider the influence of a second
protoplanet in a long time simulation and examine the migration of the two
planets in the disc, especially the growth of eccentricity and chaotic
behaviour. One aim of this work is to establish the feasibility of SPH for such
calculations considering that usually only grid-based methods are adopted. To
resolve shocks and to prevent particle penetration, we introduce a new approach
for an artificial viscosity, which consists of an additional artificial bulk
viscosity term in the SPH-representation of the Navier-Stokes equation. This
allows for an accurate treatment of the physical kinematic viscosity to
describe the shear, without the use of an artificial shear viscosity.


title: Hydrodynamical interaction between an accretion flow and a stellar wind

abstract:
  Molecular clouds in the interstellar medium suffer gravitational
instabilities that lead to the formation of one or multiple stars. A recently
formed star inside a cold cloud communicates its gravitational force to the
surrounding environment and soon an accretion flow falling into the star
develops. After their formation, all stars soon eject a wind of gas that
interacts with the external accretion flow. This interaction produces a shock
wave that evolves with time. The work presented in this article formulates a
simple prescription for the evolution of this interaction. With the aid of this
model we construct a few radio continuum maps of the source.


title: GEMS: Galaxy Evolution from Morphologies and SEDs

abstract:
  GEMS, Galaxy Evolution from Morphologies and SEDs, is a large-area (800
arcmin2) two-color (F606W and F850LP) imaging survey with the Advanced Camera
for Surveys on HST. Centered on the Chandra Deep Field South, it covers an area
of ~28'x28', or about 120 Hubble Deep Field areas, to a depth of
m_AB(F606W)=28.3 (5sigma and m_AB(F850LP)=27.1 (5sigma) for compact sources. In
its central ~1/4, GEMS incorporates ACS imaging from the GOODS project.
Focusing on the redshift range 0.2<=z<=1.1, GEMS provides morphologies and
structural parameters for nearly 10,000 galaxies where redshift estimates,
luminosities and SEDs exist from COMBO-17. At the same time, GEMS contains
detectable host galaxy images for several hundred faint AGN. This paper
provides an overview of the science goals, the experiment design, the data
reduction and the science analysis plan for GEMS.


title: Is the Local Bubble dead?

abstract:
  We give a summary of the current state of Local Bubble research, resulting
from the discussions of a dedicated panel meeting. After more than 25 years of
intense observational and theoretical work, we are still far from a coherent
picture, although a probable one emerges at the horizon. A multi-supernova
origin seems to be the best guess, with non-equilibrium cooling and soft X-ray
emission accompanying its expansion. In addition our vantage point may force us
to accept a substantial but quantitatively unknown contribution from
heliospheric emission.


title: On The Nature of the Variable Infrared Emission from Sgr A*

abstract:
  Recent infrared (IR) observations of the center of our Galaxy indicate that
the supermassive black hole source Sgr A* is strongly variable in the IR. The
timescale for the variability, $\sim 30$ min, is comparable to that of the
X-ray flares observed by {\em Chandra} and {\em XMM}, suggesting a common
physical origin. In this paper, we investigate the nature of the IR emission in
the context of models recently proposed to interpret the X-ray flares. We show
that the IR emission in Sgr A* can be well explained by nonthermal synchrotron
emission if a small fraction of the electrons in the innermost region of the
accretion flow around the black hole are accelerated {into a broken power-law
distribution}, perhaps due to transient events such as magnetic reconnection.
The model predicts differences in the variability amplitudes of flares in the
IR and X-rays, in general agreement with observations. It also predicts that
the IR emission should be linearly polarized, as has indeed been observed
during one epoch. IR and X-ray flares analogous to those observed in Sgr A* may
be detectable from other accreting SMBHs, provided $L \lsim 10^{-8} L_{EDD}$;
at higher luminosities the flaring emission is dominated by thermal
synchrotron-self Compton emission, which is likely to be less variable.


title: Evidence for Early or Efficient Black-Hole Growth

abstract:
  Mass estimates, based on scaling relationships, are presented of central
black holes in luminous quasars at a range of redshifts (z < 0.5, 1.2 ~< z ~<
6.3). The data show that very massive (about 10^9 solar masses or larger) black
holes appear already at z ~ 6, indicating that they form very early or very
fast.


title: Energy Crisis in the Superbubble DEM L 192 (N 51D)

abstract:
  Superbubbles surrounding OB associations provide ideal laboratories to study
the stellar energy feedback problem because the stellar energy input can be
estimated from the observed stellar content of the OB associations and the
interstellar thermal and kinetic energies of superbubbles are well-defined and
easy to observe. We have used DEM L 192, also known as N 51D, to carry out a
detailed case study of the energy budget in a superbubble, and we find that the
expected amount of stellar mechanical energy injected into the ISM,
(18+-5)x10^51 ergs, exceeds the amount of thermal and kinetic energies stored
in the superbubble, (6+-2)x10^51 ergs. Clearly, a significant fraction of the
stellar mechanical energy must have been converted to other forms of energy.
The X-ray spectrum of the diffuse emission from DEM L 192 requires a power-law
component to explain the featureless emission at 1.0-3.0 keV. The origin of
this power-law component is unclear, but it may be responsible for the
discrepancy between the stellar energy input and the observed interstellar
energy in DEM L 192.


title:
X-Ray and Radio Emission from UV-Selected Star Forming Galaxies at
  Redshifts 1.5<Z<3.0 in the GOODS-North Field

abstract:
  We have examined the stacked radio and X-ray emission from UV-selected
galaxies spectroscopically confirmed to lie between redshifts 1.5 < z < 3.0 in
the GOODS-North field to determine their average extinction and star formation
rates (SFRs). The X-ray and radio data are obtained from the Chandra 2 Msec
survey and the Very Large Array, respectively. There is a good agreement
between the X-ray, radio, and de-reddened UV estimates of the average SFR for
our sample of z~2 galaxies of ~50 solar masses per year, indicating that the
locally-calibrated SFR relations appear to be statistically valid from
redshifts 1.5 < z < 3.0. We find that UV-estimated SFRs (uncorrected for
extinction) underestimate the bolometric SFRs as determined from the 2-10 keV
X-ray luminosity by a factor of ~4.5 to 5.0 for galaxies over a large range in
redshift from 1.0 < z < 3.5.


title: Strong Gravitational Lensing and Dark Energy Complementarity

abstract:
  In the search for the nature of dark energy most cosmological probes measure
simple functions of the expansion rate. While powerful, these all involve
roughly the same dependence on the dark energy equation of state parameters,
with anticorrelation between its present value w_0 and time variation w_a.
Quantities that have instead positive correlation and so a sensitivity
direction largely orthogonal to, e.g., distance probes offer the hope of
achieving tight constraints through complementarity. Such quantities are found
in strong gravitational lensing observations of image separations and time
delays. While degeneracy between cosmological parameters prevents full
complementarity, strong lensing measurements to 1% accuracy can improve
equation of state characterization by 15-50%. Next generation surveys should
provide data on roughly 10^5 lens systems, though systematic errors will remain
challenging.


title:
The 2dF Galaxy Redshift Survey: higher order galaxy correlation
  functions

abstract:
  We measure moments of the galaxy count probability distribution function in
the two-degree field galaxy redshift survey (2dFGRS). The survey is divided
into volume limited subsamples in order to examine the dependence of the higher
order clustering on galaxy luminosity. We demonstrate the hierarchical scaling
of the averaged p-point galaxy correlation functions, xibar_p, up to p=6. The
hierarchical amplitudes, S_p = xibar_p/xibar_2^{p-1}, are approximately
independent of the cell radius used to smooth the galaxy distribution on small
to medium scales. On larger scales we find the higher order moments can be
strongly affected by the presence of rare, massive superstructures in the
galaxy distribution. The skewness S_3 has a weak dependence on luminosity,
approximated by a linear dependence on log luminosity. We discuss the
implications of our results for simple models of linear and non-linear bias
that relate the galaxy distribution to the underlying mass.