title:
From the Circumnuclear Disk in the Galactic Center to thick, obscuring
  tori of AGNs

abstract:
  We compare three different models of clumpy gas disk and show that the
Circumnuclear Disk (CND) in the Galactic Center and a putative, geometrically
thick, obscuring torus are best explained by a collisional model consisting of
quasi-stable, self-gravitating clouds. Kinetic energy of clouds is gained by
mass inflow and dissipated in cloud collisions. The collisions give rise to a
viscosity in a spatially averaged gas dynamical picture, which connects them to
angular momentum transport and mass inflow. It is found that CND and torus
share the same gas physics in our description, where the mass of clouds is 20 -
50 M_sun and their density is close to the limit of disruption by tidal shear.
We show that the difference between a transparent CND and an obscuring torus is
the gas mass and the velocity dispersion of the clouds. A change in gas supply
and the dissipation of kinetic energy can turn a torus into a CND-like
structure and vice versa. Any massive torus will naturally lead to sufficiently
high mass accretion rates to feed a luminous AGN. For a geometrically thick
torus to obscure the view to the center even super-Eddington accretions rates
with respect to the central black hole are required.


title:
The WHAM Northern Sky Survey and the Nature of the Warm Ionized Medium
  in the Galaxy

abstract:
  The Wisconsin H-Alpha Mapper (WHAM) has completed a velocity-resolved map of
diffuse H-alpha emission of the entire northern sky, providing the first
comprehensive picture of both the distribution and kinematics of diffuse
ionized gas in the Galaxy. WHAM continues to advance our understanding of the
physical conditions of the warm ionized medium through observations of other
optical emission lines throughout the Galactic disk and halo. We discuss some
highlights from the survey, including an optical window into the inner Galaxy
and the relationship between HI and HII in the diffuse ISM.


title:
Reionisation, chemical enrichment and seed black holes from the first
  stars: is Population III important?

abstract:
  We investigate the effects of a top-heavy stellar initial mass function on
the reionisation history of the intergalactic medium (IGM). We use cosmological
simulations that include self-consistently the feedback from ionising
radiation, H_2 dissociating radiation and supernova (SN) explosions. We find
that it is difficult to reionise the IGM at z_rei>10 with stellar sources even
after making extreme assumptions. If star formation in 10^9 M_\odot galaxies is
not suppressed by SN explosions, the optical depth to Thomson scattering is
tau_e< 0.13. If we allow for the normal energy input from SNe or if
pair-instability SNe are dominant, we find taue<0.09. Assuming normal yields
for the first stars (popIII), the mean metallicity of the IGM is already
Z/Z_\odot=2x10^-3 (10^-3<Z/Z_\odot<1 in overdense regions) when the IGM mean
ionisation fraction is less than 10%. For these reasons popIII stars cannot
contribute significantly to reionisation unless the mechanical energy input
from SNe is greatly reduced and either the metal yield or the mixing efficiency
is reduced by a factor of 1000. Both problems have a solution if popIII stars
collapse to black holes. This can happen if, having masses M_*< 130 M_\odot,
they are characterised by heavy element fall-back or if, having masses M_*>260
M_\odot, they collapse directly onto black holes without exploding as SNe.If
metal-poor stars are initially important and collapse to black holes is the
typical outcome, then the secondary emission of ionising radiation from
accretion on SN induced seed black holes, might be more important than the
primary emission. Surprisingly, including feedback effects, we estimate that a
warm dark matter scenario (with particle mass of 1.25 keV) reduces tau_e by
only approximately 10%.[abridged]


title: Chandra Phase-Resolved Spectroscopy of the Crab Pulsar

abstract:
  We present the first phase-resolved study of the X-ray spectral properties of
the Crab Pulsar that covers all pulse phases. The superb angular resolution of
the Chandra X-ray Observatory enables distinguishing the pulsar from the
surrounding nebulosity, even at pulse minimum. Analysis of the pulse-averaged
spectrum measures interstellar X-ray extinction due primarily to photoelectric
absorption and secondarily to scattering by dust grains in the direction of the
Crab Nebula. We confirm previous findings that the line-of-sight to the Crab is
underabundant in oxygen, although more-so than recently measured. Using the
abundances and cross sections from Wilms, Allen & McCray (2000) we find [O/H] =
(3.33 +/-0.25) x 10**-4. Analysis of the spectrum as a function of pulse phase
measures the low-energy X-ray spectral index even at pulse minimum -- albeit
with large statistical uncertainty -- and we find marginal evidence for
variations of the spectral index. The data are also used to set a new (3-sigma)
upper limit to the temperature of the neutron star of log T(infinity) < 6.30.


title:
The dynamical evolution of fractal star clusters: the survival of
  substructure

abstract:
  We simulate the dynamics of fractal star clusters, in order to investigate
the evolution of substructure in recently formed clusters. The velocity
dispersion is found to be the key parameter determining the survival of
substructure. In clusters with a low initial velocity dispersion, the ensuing
collapse of the cluster tends to erase substructure, although some substructure
may persist beyond the collapse phase. In clusters with virial ratios of 0.5 or
higher, initial density substructure survives for several crossing times, in
virtually all cases. Even an initially homogeneous cluster can develop
substructure, if it is born with coherent velocity dispersion. These results
suggest that the simple initial conditions used for many sophisticated $N$-body
simulations could be missing a very important and dramatic phase of star
cluster evolution.


title:
The Effects of the Sagittarius Dwarf Tidal Stream on Dark Matter
  Detectors

abstract:
  The Sagittarius dwarf tidal stream may be showering dark matter onto the
solar neighborhood, which can change the results and interpretation of WIMP
direct detection experiments. Stars in the stream may already have been
detected in the solar neighborhood, and the dark matter in the stream is
(0.3-25)% of the local density. Experiments should see an annually modulated
steplike feature in the energy recoil spectrum that would be a smoking gun for
WIMP detection. The total count rate in detectors is not a cosine curve in time
and peaks at a different time of year than the standard case.


title:
Small-Scale structure in the Galactic ISM: Implications for Galaxy
  Cluster Studies

abstract:
  Observations of extragalactic objects need to be corrected for Galactic
absorption and this is often accomplished by using the measured 21 cm HI
column. However, within the beam of the radio telescope there are variations in
the HI column that can have important effects in interpreting absorption line
studies and X-ray spectra at the softest energies. We examine the HI and
DIRBE/IRAS data for lines of sight out of the Galaxy, which show evidence for
HI variations in of up to a factor of three in 1 degree fields. Column density
enhancements would preferentially absorb soft X-rays in spatially extended
objects and we find evidence for this effect in the ROSAT PSPC observations of
two bright clusters of galaxies, Abell 119 and Abell 2142.
  For clusters of galaxies, the failure to include column density fluctuations
will lead to systematically incorrect fits to the X-ray data in the sense that
there will appear to be a very soft X-ray excess. This may be one cause of the
soft X-ray excess in clusters, since the magnitude of the effect is comparable
to the observed values.


title:
The Ensemble Photometric Variability of ~25000 Quasars in the Sloan
  Digital Sky Survey

abstract:
  Using a sample of over 25000 spectroscopically confirmed quasars from the
Sloan Digital Sky Survey, we show how quasar variability in the rest frame
optical/UV regime depends upon rest frame time lag, luminosity, rest
wavelength, redshift, the presence of radio and X-ray emission, and the
presence of broad absorption line systems. The time dependence of variability
(the structure function) is well-fit by a single power law on timescales from
days to years. There is an anti-correlation of variability amplitude with rest
wavelength, and quasars are systematically bluer when brighter at all
redshifts. There is a strong anti-correlation of variability with quasar
luminosity. There is also a significant positive correlation of variability
amplitude with redshift, indicating evolution of the quasar population or the
variability mechanism. We parameterize all of these relationships. Quasars with
RASS X-ray detections are significantly more variable (at optical/UV
wavelengths) than those without, and radio loud quasars are marginally more
variable than their radio weak counterparts. We find no significant difference
in the variability of quasars with and without broad absorption line troughs.
Models involving multiple discrete events or gravitational microlensing are
unlikely by themselves to account for the data. So-called accretion disk
instability models are promising, but more quantitative predictions are needed.


title:
X-raying Active Galaxies Found and Missed by the Sloan Digital Sky
  Survey

abstract:
  Current X-ray observatories, archival X-ray data, and the Sloan Digital Sky
Survey (SDSS) represent a powerful combination for addressing key questions
about active galactic nuclei (AGN). We describe a few selected issues at the
forefront of X-ray AGN research and the relevance of the SDSS to them. Bulk
X-ray/SDSS AGN investigations, X-ray weak AGN, red AGN, hard X-ray selected
AGN, high-redshift AGN demography, and future prospects are all briefly
discussed.


title:
Unusually Large Fluctuations in the Statistics of Galaxy Formation at
  High Redshift

abstract:
  We show that various milestones of high-redshift galaxy formation, such as
the formation of the first stars or the complete reionization of the
intergalactic medium, occurred at different times in different regions of the
universe. The predicted spread in redshift, caused by large-scale fluctuations
in the number density of galaxies, is at least an order of magnitude larger
than previous expectations that argued for a sharp end to reionization. This
cosmic scatter in the abundance of galaxies introduces new features that affect
the nature of reionization and the expectations for future probes of
reionization, and may help explain the present properties of dwarf galaxies in
different environments. The predictions can be tested by future numerical
simulations and may be verified by upcoming observations. Current simulations,
limited to relatively small volumes and periodic boundary conditions, largely
omit cosmic scatter and its consequences. In particular, they artificially
produce a sudden end to reionization, and they underestimate the number of
galaxies by up to an order of magnitude at redshift 20.


title: The Star Formation Rate and Dense Molecular Gas in Galaxies

abstract:
  (abridged) HCN luminosity Lhcn is a tracer of DENSE molecular gas, n(H_2) >~
3x10^4 cm^{-3}, associated with star-forming giant molecular cloud (GMC) cores.
We present the results and analysis of our survey of HCN emission from 65
infrared galaxies including 9 ultraluminous infrared galaxies (ULIGs,
Lir>10^{12}Lsun), 22 luminous infrared galaxies (LIGs,
10^{11}<Lir<~10^{12}Lsun) and 34 normal spiral galaxies with lower IR
luminosity (most are large spiral galaxies). We have measured the global HCN
line luminosity and the observations are reported in Gao and Solomon (2003,
Paper I). This paper analyzes the relationships between the total far-IR
luminosity a tracer of the star formation rate, the global HCN line luminosity
a measure of the total DENSE molecular gas content, and the CO luminosity a
measure of the total molecular content. We find a tight linear correlation
between the IR and HCN luminosities Lir and Lhcn (in the log-log plot) with a
correlation coefficient R=0.94. The IR--HCN linear correlation is valid over 3
orders of magnitude including ULIGs. The direct consequence of the linear
IR--HCN correlation is that the star formation law in terms of DENSE molecular
gas content has a power law index of 1.0. The global star formation rate is
linearly proportional to the mass of dense molecular gas in normal spiral
galaxies, LIGs, and ULIGs. This is strong evidence in favor of star formation
as the power source in ultraluminous galaxies since the star formation in these
galaxies appears to be normal and expected given their high mass of dense
star-forming molecular gas.


title:
Multi-wavelength Observations of the Gas-rich Host Galaxy of PDS 456: a
  New Challenge for the ULIRG-to-QSO Transition Scenario

abstract:
  We report new K-band, radio continuum, and CO (1-0) imaging observations and
850 micron photometric observations of PDS 456, the most luminous QSO in the
local universe (z<0.3). The 0.6'' resolution K-band image obtained using the
Keck telescope shows three compact K~16.5 (M(K)~ -21) sources at a projected
distance of ~10 kpc to the southwest, and the host galaxy of PDS 456 may be
interacting or merging with one or more companions. The observations using the
OVRO millimeter array has revealed a narrow CO (1-0) line (FWHM = 181 km/s)
centered at z=0.1849, and 9 x 10^9 solar mass of molecular gas mass is
inferred. Radio continuum luminosity is nearly an order of magnitude larger
than expected from its FIR luminosity, and the radio source, unresolved by the
2" beam of the VLA, is dominated by the AGN activity. Our 850 micron
photometric observations suggest that the cold dust content of the host galaxy
is less than one half of the amount in Arp 220. Its SED has both a QSO-like and
a ULIRG-like nature, and the observed IR, X-ray, and gas properties suggest
that the AGN activity dominates its luminosity. ULIRGs and IR QSOs form a broad
continuous track in the ``star formation efficiency'' plot in the manner
consistent with the ULIRG-QSO transition scenario, relating the evolution in
the dust processed luminosity with the available fuel (gas and dust) supply.
However, the location of PDS 456 is clearly offset from the apparent track
traced by the ULIRGs and IR QSOs on this plot, and PDS 456 appears to be a
rare, exceptional object, and the duration of the physical process governing
its present properties must be short compared with the length of the luminous
QSO phase.


title: HCN Survey of Normal Spiral, IR-luminous and Ultraluminous Galaxies

abstract:
  We report systematic HCN J=1-0 (and CO) observations of a sample of 53
infrared (IR) and/or CO-bright and/or luminous galaxies, including seven
ultraluminous infrared galaxies, nearly 20 luminous infrared galaxies, and more
than a dozen of the nearest normal spiral galaxies. This is the largest and
most sensitive HCN survey of galaxies to date. All galaxies observed so far
follow the tight correlation between the IR luminosity $L_{\rm IR}$ and the HCN
luminosity $L_{\rm HCN}$ initially proposed by Solomon, Downes, & Radford,
which is detailed in a companion paper. We also address here the issue of HCN
excitation. There is no particularly strong correlation between $L_{\rm HCN}$
and the 12$\mu$m luminosity; in fact, of all the four \IRAS bands, the 12$\mu$m
luminosity has the weakest correlation with the HCN luminosity. There is also
no evidence of stronger HCN emission or a higher ratio of HCN and CO
luminosities $L_{\rm HCN}/L_{\rm CO}$ for galaxies with excess 12$\mu$m
emission. This result implies that mid-IR radiative pumping, or populating, of
the J=1 level of HCN by a mid-IR vibrational transition is not important
compared with the collisional excitation by dense molecular hydrogen.
Furthermore, large velocity gradient calculations justify the use of HCN J=1-0
emission as a tracer of high-density molecular gas ($\approxgt 3\times
10^4/\tau$ cm$^{-3}$) and give an estimate of the mass of dense molecular gas
from HCN observations. Therefore, $L_{\rm HCN}$ may be used as a measure of the
total mass of dense molecular gas, and the luminosity ratio $L_{\rm HCN}/L_{\rm
CO}$ may indicate the fraction of molecular gas that is dense.


title: Why is the Universe Accelerating?

abstract:
  The universe appears to be accelerating, but the reason why is a complete
mystery. The simplest explanation, a small vacuum energy (cosmological
constant), raises three difficult issues: why the vacuum energy is so small,
why it is not quite zero, and why it is comparable to the matter density today.
I discuss these mysteries, some of their possible resolutions, and some issues
confronting future observations.


title: Optical Properties of Complex Dust Grains

abstract:
  Dust particles in space may appear as clusters of individual grains. The
morphology of these clusters could be of a fractal or more compact nature. To
investigate how the cluster morphology influences the calculated extinction of
different clusters in the wavelength range 0.1 - 100 micron, we have preformed
extinction calculations of three-dimensional clusters consisting of identical
touching spherical particles arranged in three different geometries:
prefractal, simple cubic and face-centered cubic. In our calculations we find
that the extinction of prefractal and compact clusters are of the same order of
magnitude. For the calculations, we have performed an in-depth comparison of
the theoretical predictions of extinction coefficients of multi-sphere clusters
derived by rigorous solutions, on the one hand, and popular discrete-dipole
approximations, on the other. This comparison is essential if one is to assess
the degree of reliability of model calculations made with the discrete-dipole
approximations, which appear in the literature quite frequently without an
adequate accounting of their validity.


title: Cosmological acceleration, varying couplings, and Lorentz breaking

abstract:
  Many candidate fundamental theories contain scalar fields that can acquire
spacetime-varying expectation values in a cosmological context. Such scalars
typically obey Lorentz-violating effective dispersion relations. We illustrate
this fact within a simple supergravity model that also exhibits the observed
late-time cosmological acceleration and implies varying electromagnetic
couplings.


title: Power Spectrum Normalisation and the Non-Gaussian Halo Model

abstract:
  The normalisation of the matter power spectrum, sigma_8, is an essential
ingredient to predict the phenomenology of the low redshift universe. It has
been measured using several methods, such as X-ray cluster counts, weak lensing
and the cosmic microwave background, which have yielded values ranging from 0.7
to 1.0. While these differences could be due to systematic effects, they could
also be due to physics beyond the standard LambdaCDM model. An obvious
possibility is the presence of non-Gaussian initial fluctuations in the density
field. To study the impact of non-Gaussianity on each of these methods, we use
a generalised halo model to compute cluster counts and the non-linear power
spectrum for non-Gaussian models. Assuming scale invariance, the upper-limits
on non-Gaussianity from the WMAP CMB experiment correspond to roughly a 4%
shift in sigma_8 as measured from cluster counts and about 2% shift through
weak lensing. This is not enough to account for the current internal and mutual
discrepancies between the different methods, unless non-Gaussianity is strongly
scale dependent. A comparison between future X-ray surveys with a two fold
improvement in cluster mass calibration and future cosmic shear surveys with
400 deg^2 will be required to constrain non-Gaussianity on small scales with a
precision matching that of the current CMB constraints on larger scales. Our
results argue for the presence of systematics in the current cluster and cosmic
shear surveys, or to non-standard physics other than non-Gaussianity.


title:
The DEEP Groth Strip Survey VII: The Metallicity of Field Galaxies at
  0.26<z<0.82 and the Evolution of the Luminosity-Metallicity Relation

abstract:
  Using spectroscopic data from the Deep Extragalactic Evolutionary Probe
(DEEP) Groth Strip survey (DGSS), we analyze the gas-phase oxygen abundances in
the warm ionized medium for 64 emission-line field galaxies in the redshift
range 0.26<z<0.82. Oxygen abundances relative to hydrogen range between
8.4<12+log(O/H)<9.0 with typical internal plus systematic measurement
uncertainties of 0.17 dex. The 64 DGSS galaxies collectively exhibit an
increase in metallicity with B-band luminosity. DGSS galaxies in the highest
redshift bin (z=0.6-0.82) are brighter, on average, by ~1 mag at fixed
metallicity compared to the lowest DGSS redshift bin (z=0.26-0.40) and brighter
by up to ~2.4 mag compared to local (z<0.1) emission-line field galaxies.
Alternatively, DGSS galaxies in the highest redshift bin (z=0.6-0.82) are, on
average, 40% (0.15 dex) more metal-poor at fixed luminosity compared to local
(z<0.1) emission-line field galaxies. For 0.6<z<0.8 galaxies, the offset from
the local L-Z relation is greatest for objects at the low-luminosity (M_B>-19)
end of the sample and vanishingly small for objects at the high-luminosity end
of the sample (M_B ~ -22). Simple galaxy evolution models can produce
reasonable agreement with observations for low-mass galaxies when least two of
the following are true: 1) low-mass galaxies have lower effective chemical
yields than massive galaxies, 2) low-mass galaxies assemble on longer
timescales than massive galaxies, 3) low-mass galaxies began the assembly
process at a later epoch than massive galaxies. (abridged)


title:
GBT Discovery of Two Binary Millisecond Pulsars in the Globular Cluster
  M30

abstract:
  We report the discovery of two binary millisecond pulsars in the
core-collapsed globular cluster M30 using the Green Bank Telescope (GBT) at 20
cm. PSR J2140-2310A (M30A) is an eclipsing 11-ms pulsar in a 4-hr circular
orbit and PSR J2140-23B (M30B) is a 13-ms pulsar in an as yet undetermined but
most likely highly eccentric (e>0.5) and relativistic orbit. Timing
observations of M30A with a 20-month baseline have provided precise
determinations of the pulsar's position (within 4" of the optical centroid of
the cluster), and spin and orbital parameters, which constrain the mass of the
companion star to be m_2 >~ 0.1Msun. The position of M30A is coincident with a
possible thermal X-ray point source found in archival Chandra data which is
most likely due to emission from hot polar caps on the neutron star. In
addition, there is a faint (V_555 ~ 23.8) star visible in archival HST F555W
data that may be the companion to the pulsar. Eclipses of the pulsed radio
emission from M30A by the ionized wind from the compact companion star show a
frequency dependent duration (\propto\nu^{-\alpha} with \alpha ~ 0.4-0.5) and
delay the pulse arrival times near eclipse ingress and egress by up to 2-3 ms.
Future observations of M30 may allow both the measurement of post-Keplerian
orbital parameters from M30B and the detection of new pulsars due to the
effects of strong diffractive scintillation.


title:
Formation of omega Centauri from an ancient nucleated dwarf galaxy in
  the young Galactic disc

abstract:
  We first present a self-consistent dynamical model in which $\omega$ Cen is
formed from an ancient nucleated dwarf galaxy merging with the first generation
of the Galactic thin disc in a retrograde manner with respect to the Galactic
rotation. Our numerical simulations demonstrate that during merging between the
Galaxy and the $\omega$ Cen's host dwarf with $M_{\rm B}$ $\simeq$ -14 mag and
its nucleus mass of $10^7$ $M_{\odot}$, the outer stellar envelope of the dwarf
is nearly completely stripped whereas the central nucleus can survive from the
tidal stripping because of its compactness. The developed naked nucleus has a
very bound retrograde orbit around the young Galactic disc, as observed for
$\omega$ Cen, with its apocenter and pericenter distances of $\sim$ 8 kpc and
$\sim$ 1 kpc, respectively. The Galactic tidal force can induce radial inflow
of gas to the dwarf's center and consequently triggers moderately strong
nuclear starbursts in a repetitive manner. This result implies that efficient
nuclear chemical enrichment resulting from the later starbursts can be closely
associated with the origin of the observed relatively young and metal-rich
stars in $\omega$ Cen. Dynamical heating by the $\omega$ Cen's host can
transform the young thin disc into the thick disc during merging.


title: LMC Bar: Evidence for a warped bar

abstract:
  The geometry of the LMC bar is studied using the de-reddened mean magnitudes
of the red clump stars ($I_0$) from the OGLE II catalogue. The value of $I_0$
is found to vary in the east-west direction such that both the east and the
west ends of the bar are closer to us with respect to the center of the bar.
The maximum observed variation has a statistical significance of more than 7.6
$\sigma$ with respect to the maximum value of random error. The variation in
$I_0$ indicates the presence of warp in the bar of LMC. The warp and the
structures seen in the bar indicate that the bar could be a dynamically
disturbed structure.


title: Galaxy threshing and the origin of intracluster stellar objects

abstract:
  We numerically investigate dynamical evolution of non-nucleated dwarf
elliptical/spiral galaxies (dE) and nucleated ones (dE,Ns) in clusters of
galaxies in order to understand the origin of intracluster stellar objects,
such as intracluster stars (ICSs), GCs (ICGCs), and ``ultra-compact dwarf''
(UCDs) recently discovered by all-object spectroscopic survey centred on the
Fornax cluster of galaxies. We find that the outer stellar components of a
nucleated dwarf are removed by the strong tidal field of the cluster, whereas
the nucleus manages to survive as a result of its initially compact nature. The
developed naked nucleus is found to have physical properties (e.g., size and
mass) similar to those observed for UCDs. We also find that the UCD formation
processes does depend on the radial density profile of the dark halo in the
sense that UCDs are less likely to be formed from dwarfs embedded in dark
matter halos with central `cuspy' density profiles. Our simulations also
suggest that very massive and compact stellar systems can be rapidly and
efficiently formed in the central regions of dwarfs through the merging of
smaller GCs. GCs initially in the outer part of dE and dE,Ns are found to be
stripped to form ICGCs.


title: V445 Puppis -- Helium nova on a massive white dwarf

abstract:
  The 2000 outburst of V445 Puppis shows unique properties, such as absence of
hydrogen, enrichment of helium and carbon, slow development of the light curve
with a small amplitude that does not resemble any classical novae. This object
has been suggested to be the first example of helium novae. We calculate
theoretical light curves of helium novae and reproduce the observational light
curve of V445 Pup. Modeling indicates a very massive white dwarf (WD), more
massive than 1.3 Msun. The companion star is possibly either a helium star or a
helium-rich main-sequence star. We estimate the ignition mass as several times
10^{-5} Msun, the corresponding helium accretion rate as several times 10^{-7}
Msun yr^{-1}, and the recurrence period as several tens of years. These values
suggest that the WD is growing in mass and ends up either a Type Ia supernova
or an accretion induced collapse to a neutron star.


title: Evolution of galaxies in triaxial halos with figure rotation

abstract:
  Firstly, we demonstrate that unusually large outer HI spiral arms observed in
NGC 2915 can form in an extended gas disk embedded in a massive triaxial dark
matter halo with slow figure rotation, through the strong gravitational torque
of the rotating halo. Secondly, we show that the figure rotation of a triaxial
dark matter halo can influence dynamical evolution of disk galaxies by using
fully self-consistent numerical simulations. We particularly describe the
formation processes of ``halo-triggered'' bars in thin galactic disks dominated
by dark matter halos with figure rotation and discuss the origin of stellar
bars in low luminosity, low surface brightness (LSB) disk galaxies. Thirdly, we
provide several implications of the present numerical results in terms of
triggering mechanism of starbursts in galaxies and stellar bar formation in
high redshifts.


title: Position-sensitive detector for the 6-meter optical telescope

abstract:
  The Position-Sensitive Detector (PSD) for photometrical and spectral
observation on the 6-meter optical telescope of the Special Astrophysical
Observatory (Russia) is described. The PSD consists of a position-sensitive
tube, amplifiers of output signals, analog-to-digital converters (ADC) and a
digital logic plate, which produces a signal for ADC start and an external
strob pulse for reading information by registration system. If necessary, the
thermoelectric cooler can be used. The position-sensitive tube has the
following main elements: a photocathode, electrodes of inverting optics, a
block of microchannel plates (MCP) and a position-sensitive collector of
quadrant type. The main parameters of the PSD are the diameter of the sensitive
surface is 25 mm, the spatial resolution is better than 100 (\mu)m in the
centre and a little worse on the periphery; the dead time is near 0.5 (\mu)s;
the detection quantum efficiency is defined by the photocathode and it is not
less than 0.1, as a rule; dark current is about hundreds of cps, or less, when
cooling. PSD spectral sensitivity depends on the type of photocathode and input
window material. We use a multialkali photocathode and a fiber or UV-glass,
which gives the short- wave cut of 360 nm or 250 nm, respectively.


title:
The Multicolor Panoramic Photometer-Polarimeter with high time
  resolution based on the PSD

abstract:
  Multicolor Panoramic Photometer-Polarimeter (MPPP) with a time resolution of
1 microsecond has been built based on a PSD and used at the 6-meter telescope
in SAO (Russia). The device allows registration of the photon fluxes in four
photometric bands simultaneously and finding values of 3 Stokes parameters.
MPPP consists of Position-Sensitive Detector (PSD), acquisition MANIA-system,
polarization unit and a set of dichroic filters. MPPP gives a possibility of
detecting photons in 2 pupils with a size of 10 - 15 arc sec centered on the
object and comparison star positions simultaneously. The first half of the
object photon flux passes through the phase rotating plate and polarizer, and
the second one through the polarizer alone. MPPP registers in each of the 4
filters four images of the object with different orientations of polarization
plane and one image of a comparison star. It allows measuring instantaneous
Stokes parameters. The main astrophysical problems to be solved with MPPP are
as follows: investigation of optical pulsars; study of GRB phenomenon in the
optical range; searching for single black holes; study of fast variability of
X-ray binaries. As an illustration of MPPP use, the results of observations at
the 6-meter telescope of Crab pulsar and soft gamma repeater are presented.


title: A large X-ray flare from the Herbig Ae star V892 Tau

abstract:
  We report the XMM-Newton observation of a large X-ray flare from the Herbig
Ae star V892 Tau. The apparent low mass companion of V892 Tau, V892 Tau NE, is
unresolved by XMM-Newton. Nevertheless there is compelling evidence from
combined XMM-Newton and Chandra data that the origin of the flare is the Herbig
Ae star V892 Tau. During the flare the X-ray luminosity of V892 Tau increases
by a factor of ~15, while the temperature of the plasma increases from kT ~ 1.5
keV to kT ~ 8 keV. From the scaling of the flare event, based on hydrodynamic
modeling, we conclude that a 500 G magnetic field is needed in order to confine
the plasma. Under the assumptions that a dynamo mechanism is required to
generate such a confining magnetic field and that surface convection is a
necessary ingredient for a dynamo, our findings provide indirect evidence for
the existence of a significant convection zone in the stellar envelope of
Herbig Ae stars.


title: The XMM-2df Cluster Survey

abstract:
  We present the results from a shallow (2-10 ksec) XMM/2dF survey. Our survey
covers 18 XMM fields ($\sim 5 {\rm deg}^2$) previously spectroscopically
followed up with the Anglo-Australian telescope 2-degree field facility. About
half of the fields are also covered by the Sloan Digital Sky Survey (SDSS). We
are searching for extended sources using the XMM SAS maximum likelihood
algorithm in the 0.3-2 keV band and we have detected 14 candidate clusters down
to a flux of $\sim2\times10^{-14} cgs$. Our preliminary results show that: i)
the redshift distribution peaks at relatively high redshifts ($\sim0.4$) as
expected from the Rosati et al. $\Phi(L)$, ii) some of our X-ray clusters
appear to have optical counterparts.


title: Generality of inflation in closed FRW models

abstract:
  We investigate the generality of inflation in closed FRW models for a wide
class of quintessence potentials. It is shown that inflation is not suppressed
for most of them for a wide class of their parameters. This allows us to decide
if inflation is common even in case of a closed universe.


title: Recycling of ghost galaxies: The origin of giant HI ring around NGC 1533

abstract:
  We propose that the giant HI ring recently discovered by HIPASS for S0 galaxy
NGC 1533 is formed by unequal-mass merging between gas-rich LSB (low surface
brightness: ``ghost'') galaxies and HSB disks. The NGC 1533 progenitor HSB
spiral is transformed into a barred S0 during merging and the outer HI gas disk
of the LSB is transformed into the giant HI ring. We also discuss two different
possibilities for the origin of isolated star-forming regions (``ELdot''
objects) in the giant gas ring.


title: Non-linear perturbations in scalar-tensor cosmologies

abstract:
  Can local fluctuations of a ``Quintessence'' scalar field play a dynamical
role in the gravitational clustering and cosmic structure formation process? We
address this question in the general framework of scalar-tensor theories of
gravity. Non-linear energy density perturbations, both in the scalar field and
matter component, and linear metric perturbations are accounted for in the
perturbed Einstein's equations. We derive the Newtonian limit of the relevant
equations for clustering in scalar-tensor cosmologies. We then specialize to
non-linear perturbations of the ``Extended Quintessence'' model of Dark Energy;
in such a model, a non-minimally coupled scalar field is thought to be
responsible for driving the present accelerated phase of the Universe
expansion. The interplay between Dark Energy and Dark Matter is displayed in
the equations governing the growth of structure in the Universe.


title: Inferring information about rotation from stellar oscillations

abstract:
  The first part of this paper aims at illustrating the intense scientific
activity in the field of stellar rotation although, for sake of shortness, we
cannot be exhaustive nor give any details. The second part is devoted to the
rotation as a pertubation effect upon oscillation frequencies. The discussion
focuses on one specific example: the p-modes frequency small separation which
provides information about properties of the stellar inner layers. It is shown
that the small separation can be affected by rotation at the level of 0.1-0.2
microHz for a 1.4 Mo model rotating with an equatorial velocity of 20 km/s at
the surface. This is of the same order of magnitude as the expected precision
on frequencies with a 3 months observation and must therefore be taken into
account. We show however that it is possible to recover the small separation
free of these contaminating effects of rotation, provided enough high quality
data are available as will be with space seismic missions such as Eddington.


title: Physical restrictions on the models of gamma-ray bursts

abstract:
  The present common view about GRB origin is related to cosmology. There are
two evidences in favor of this interpretation. The first is connected with
statistics, the second is based on measurements of the redshifts in the GRB
optical afterglows. Redshifts in optical afterglows had been observed only in
long GRB. 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 and polarization measurements could be very important
for farther insight into GRB origin.
  Possibility of galactic origin of short GRB is discussed as well as their
possible connection with soft gamma repeaters.


title: ISGRI: the INTEGRAL Soft Gamma-Ray Imager

abstract:
  For the first time in the history of high energy astronomy, a large CdTe
gamma-ray camera is operating in space. ISGRI is the low-energy camera of the
IBIS telescope on board the INTEGRAL satellite. This paper details its design
and its in-flight behavior and performances. Having a sensitive area of 2621
cm$^2$ with a spatial resolution of 4.6 mm, a low threshold around 12 keV and
an energy resolution of $\sim$ 8% at 60 keV, ISGRI shows absolutely no signs of
degradation after 9 months in orbit. All aspects of its in-flight behavior and
scientific performance are fully nominal, and in particular the observed
background level confirms the expected sensitivity of 1 milliCrab for a 10$^6$s
observation.


title: The age of the oldest Open Clusters

abstract:
  We determine ages of 71 old Open Clusters by a two-step method: we use
main-squence fitting to 10 selected clusters, in order to obtain their
distances, and derive their ages from comparison with our own isochrones used
before for Globular Clusters. We then calibrate the morphological age indicator
delta(V), which can be obtained for all remaining clusters, in terms of age and
metallicity. Particular care is taken to ensure consistency in the whole
procedure. The resulting Open Cluster ages connect well to our previous
Globular Cluster results. From the Open Cluster sample, as well as from the
combined sample, questions regarding the formation process of Galactic
components are addressed. The age of the oldest open clusters (NGC6791 and
Be17) is of the order of 10 Gyr. We determine a delay by 2.0+-1.5 Gyr between
the start of the halo and thin disk formation, whereas thin and thick disk
started to form approximately at the same time. We do not find any significant
age-metallicity relationship for the open cluster sample. The cumulative age
distribution of the whole open cluster sample shows a moderately significant
(~2sigma level) departure from the predictions for an exponentially declining
dissolution rate with timescale of 2.5 Gyr. The cumulative age distribution
does not show any trend with galactocentric distance, but the clusters with
larger height to the Galactic plane have an excess of objects between 2-4 and 6
Gyr with respect to their counterpart closer to the plane of the Galaxy.


title: A superburst from 4U 1254-690

abstract:
  We report the detection with the BeppoSAX Wide Field Cameras of a superburst
from 4U 1254-690. The superburst is preceded by a normal type-I X-ray burst,
has a decay time that is the longest of all eight superbursts detected so far
and a peak luminosity that is the lowest. Like for the other seven superbursts,
the origin is a well-known type-I X-ray burster with a persistent luminosity
level close to one tenth of the Eddington limit. Based on WFC data of all
persistently bright X-ray bursters, the average rate of superbursts is
0.51+/-0.25 per year per persistently bright X-ray burster. Some systems may
have higher superburst rates. For all superbursters, we present evidence for a
pure helium layer which is burnt in an unstable as well as a stable manner.


title:
Monitoring of the Central Region of the Globular Cluster M15 = NGC 7078:
  New Variable Stars

abstract:
  We obtained a series of more than two hundred R-band CCD images for the
crowded central (115"x77") region of the metal-poor globular cluster M15 with
an angular resolution of 0.5"-0.9" in most images. Optimal image subtraction
was used to identify variable stars. Brightness variations were found in 83
stars, 55 of which were identified with known cluster variables and the
remaining 28 are candidates for new variables. Two of them are most likely SX
Phe variables. The variability type of two more stars is incertain. The
remaining stars were tentatively classified as RR Lyrae variables. A
preliminary analysis of published data and our results shows that the
characteristics of RR Lyrae variables in the densest part (r<35") of the
cluster probably change. More specifically, the maximum of the period
distribution of first- and second-overtone (RR1, RR2) pulsating stars shifts
toward shorter periods; i.e., there is an increase in the fraction of stars
pulsating with periods < 0.3d and a deficiency of stars with 0.35d-0.40d. The
ratio of the number of these short-period RR Lyrae variables to the number of
fundamental-tone (RR0) pulsating variables changes appreciably. We found and
corrected the error of transforming the coordinates of variables V128-155 in
M15 to the coordinate system used in the catalog of variable stars in globular
clusters.


title:
XMM-Newton confirmation of a warm absorber in the z=4.4 blazar PMN
  J0525-3343

abstract:
  We present the analysis and results from a series of XMM-Newton observations
of the distant blazar PMN J0525-3343, at a redshift of 4.4. The X-ray spectrum
shows a spectral flattening below ~1 keV confirming earlier results from ASCA
and BeppoSAX. The spectrum is well fitted by a power-law continuum with either
a spectral break or absorption; no sharp features are apparent in the spectrum.
No variability is seen in the individual lightcurves although there is evidence
of small longer term variations (~ months in the blazar frame) in both flux and
(0.1-2.4)/(2-10) keV flux ratio. Very low levels of optical-UV extinction and
the lack of any evidence of a Lyman-limit system at the quasar redshift rule
out neutral absorption and we argue that the most plausible explanation is the
presence of a warm, ionized absorber. Very strong C IV absorption in the
optical spectrum already implies the presence of highly ionized material along
the line of sight. Warm absorber models using the photoionization code CLOUDY
are consistent with both the X-ray and C IV data, yielding a column density
\~10^(22.3-22.5) cm^-2 and ionization parameter ~10^(0.8-1.2) erg cm s^-1.


title: Astroparticle Theory: Some New Insights into High Energy Cosmic Rays

abstract:
  Some new developments obtained in the last few years concerning the
propagation of high energy cosmic rays are discussed. In particular, it is
shown how the inclusion of drift effects in the transport diffusion equations
leads naturally to an explanation for the knee, for the second knee and for the
observed behavior of the composition and anisotropies between the knee and the
ankle. It is shown that the trend towards a heavier composition above the knee
has significant impact on the predicted neutrino fluxes above $10^{14}$ eV. The
effects of magnetic lensing on the cosmic rays with energies above the ankle
are also discussed, analyzing the main features of the different regimes that
appear between the diffusive behavior that takes place at lower energies and
the regime of small deflections present at the highest ones.


title: What do astrophysics and the world's oldest profession have in common?

abstract:
  In the present paper I want to tell of my impressions about the world of
research in astrophysics, which I know from close observation. I see with
certain pessimism the actual state of astrophysics, as well as of other
sciences with similar problems. There are many charms in the profession, as
many charms as in love, but not when they are in the service of mercantile
aims.


title: Internal Kinematics of Microstructures and Implications

abstract:
  High resolution images at different wavelengths show the common presence of
structures and microstructures in planetary nebulae (PNe), which are not well
incorporated to the existing models for the formation of these objects. We
summarize how studies of the internal kinematics, combined with the information
provided by high resolution images, may help to establish the nature and
possible origin of the observed structures as well as to provide information
about the physical processes involved in the formation and evolution of PNe.


title: Multiple Point-Symmetric Ejections in IC 4634

abstract:
  We present a spatio-kinematical study of the planetary nebula (PN) IC 4634
which has experienced several episodes of point-symmetric ejections oriented at
different directions. The nebula displays two S-shaped low-ionization arcs that
are probably related to two relatively recent point-symmetric ejections, the
outer S-shaped arc representing a beautiful example of a bow-shock resolved in
a PN. We report here the discovery of an arc-like string of knots at larger
distances from IC 4634 central star that represents a much earlier
point-symmetric ejection.


title:
A Sample of X-Ray active extragalactic Sources suitable for NIR Adaptive
  Optics Observations

abstract:
  Recent X-ray surveys have now resolved most of the X-ray background (XRB)
into discrete sources. While this represents a break- through in the
understanding of the XRB, the astrophysical nature of these sources still
remains mysterious. In this article we present a sample of X-ray/optically
selected extragalactic objects which are suitable for adaptive optics
observations in the near infrared (NIR) at highest angu- lar resolution. The
sample is based on a cross-correlation of the Sloan Digital Sky Survey and the
ROSAT All Sky Survey. The NIR properties can help to disentangle the nature of
the X-ray bright, partially absorbed and spectroscopically passive background
objects and their hosts.


title: Potential Variations in the Interstellar N I Abundance

abstract:
  We present Far Ultraviolet Spectroscopic Explorer (FUSE) and Space Telescope
Imaging Spectrograph observations of the weak interstellar N I doublet at 1160
Angstroms toward 17 high-density sight lines [N(Htot)>=10^21 cm^-2]. When
combined with published data, our results reveal variations in the fractional N
I abundance showing a systematic deficiency at large N(Htot). At the FUSE
resolution (~20 km s^-1), the effects of unresolved saturation cannot be
conclusively ruled out, although O I at 1356 Angstroms shows little evidence of
saturation. We investigated the possibility that the N I variability is due to
the formation of N_2 in our mostly dense regions. The 0-0 band of the c'_4
^1Sigma^+_u - X ^1Sigma^+_g transition of N_2 at 958 Angstroms should be easily
detected in our FUSE data; for 10 of the denser sight lines, N_2 is not
observed at a sensitivity level of a few times 10^14 cm^-2. The observed N I
variations are suggestive of an incomplete understanding of nitrogen chemistry.
  Based on observations made with the NASA-CNES-CSA Far Ultraviolet
Spectroscopic Explorer, which is operated for NASA by the Johns Hopkins
University under NASA contract NAS 5-32985, and the NASA/ESA Hubble Space
Telescope, obtained from the Multimission Archive at the Space Telescope
Science Institute, which is operated by the Association of Universities for
Research in Astronomy, Inc., under the NASA contract NAS 5-26555.


title: Imaging and Spectroscopy of the Planetary Nebula NGC 6778

abstract:
  We present narrow-band images and long-slit echelle spectra of the planetary
nebula (PN) NGC 6778. The data show this PN as bipolar, with a very prominent
low-excitation equatorial toroid, high-excitation lobes and two pairs of
collimated outflows. Morphologically, the pairs of outflows are different from
each other; one is linear and oriented along the bipolar axis, the other
presents an S-shape with changing orientations. Besides the different
morphology, both pairs of collimated outflows present radial velocities
increasing with distance from the central star and share a common origin in
bright knots at the tips of the shell.


title: Monitoring The Evolution of SNR 1987A with Chandra

abstract:
  We report on the results of our monitoring program of SNR 1987A with the
Chandra X-Ray Observatory. The high resolution images and the spectra from the
latest Chandra data suggest that the blast wave has reached the dense inner
ring in the western side of the SNR, as well as in the east. The observed soft
X-ray flux is increasing more rapidly than ever, and the latest flux is four
times brighter than three years ago.


title: Decaying particles and the reionization history of the Universe

abstract:
  We investigate the possibility that the Universe is reionized by the decay
products of heavy particles. In particular we study under which circumstances
this decay may produce a significant reionization at high redshift ($z \simeq
20$), as requested by the WMAP result.Extra sources of reionization at high
redshifts increase the recombination rate. As a result, the number density of
decaying particles required to produce a high level of ionization at $z \simeq
10-20$ is significantly higher ($\simeq 300$ times) than previously estimated.
Moreover, the ionization produced by decay particles implies a high optical
depth even if the maximum level of ionization ever produced is of the order of
$10^{-2}$. In order to match the cosmic microwave background polarization power
spectrum, other significant sources of reionization are needed at low redshift.
Decaying particles producing a ionization fraction $x \simeq 0.5$ at $z \simeq
20$ would imply an optical depth much too high to fit the cosmic microwave
background spectra at $l \ge 30$. For decay times $t_{dec} < 2 \times 10^{16}
{\rm s}$, recent cosmic microwave background and large scale structure data
limits the primordial abundance of the decaying particles to $\Omega_x \le 21
\times 10^{-9} (1+z)^3$ at 95 % C.L., and favors long decay times. The data do
not favor this reionization model versus the instantaneous reionization one. We
also find that the decay of these heavy particles significantly heats up the
medium, bringing the expected $y$ distortion to unobservable levels.


title: The Distribution of Dark Matter in Galaxies: the Core Radius Issue

abstract:
  I review the up-to-date status on the properties of the Dark Matter density
distribution around Galaxies. The rotation curves of spirals all conform to a
same Universal profile which can be uniquely decomposed as the sum of an
exponential thin stellar disk and a dark halo with a flat density core.
  From dwarfs to giants galaxies, the halos embedding the stellar component
feature a constant density region of size $r_0$ and value $\rho_0$, which are
inversely correlated. The fine structure of dark halos in the region of the
stellar disk has been derived for a number of low--luminosity disk galaxies:
the halo circular velocity increases almost linearly with radius out to the
edge of the stellar disk, implying, up there, an almost constant dark matter
density. This sets a serious discrepancy between the cuspy density distribution
predicted by N-body simulations of $\Lambda$CDM cosmology, and those actually
detected around galaxies. The small scatter around the Fundamental Plane (FP)
of elliptical galaxies constraints the distribution of dark and luminous matter
in these systems. The measured central velocity dispersion $\sigma_0$ in the FP
is linked to both photometric and dynamical properties of luminous and dark
matter. As a consequence, the well-known features of the FP imply that, inside
the effective radius $R_e$, the stellar spheroid must dominate over the dark
matter, in contrast with $\Lambda$CDM predictions.


title: Abundances in stars with exoplanets

abstract:
  Extensive spectroscopic studies of stars with and without planets have
concluded that stars hosting planets are significantly more metal-rich than
those without planets. More subtle trends of different chemical elements begin
to appear as the number of detected extrasolar planetary systems continues to
grow. I review our current knowledge concerning the observed abundance trends
of various chemical elements in stars with exoplanets and their possible
implications.


title: Lithium in stars with exoplanets

abstract:
  We present a comparison of the lithium abundances of stars with and without
planetary-mass companions. New lithium abundances are reported in 79 planet
hosts and 38 stars from a comparison sample. When the Li abundances of planet
host stars are compared with the 157 stars in the sample of field stars of Chen
et al. (2001) we find that the Li abundance distribution is significantly
different, and that there is a possible excess of Li depletion in planet host
stars with effective temperatures in the range 5600--5850 K, whereas we find no
significant differences in the temperature range 5850--6350 K. We have searched
for statistically significant correlations between the Li abundance of parent
stars and various parameters of the planetary companions. We do not find any
strong correlation, although there are may be a hint of a possible gap in the
Li distribution of massive planet host stars.


title: Space Studies of the Black-Drop Effect at a Mercury Transit

abstract:
  Transits of Mercury and Venus across the face of the Sun are rare. The 20th
century had 15 transits of Mercury and the 21st century will have 14, the two
most recent occuring on 15 November 1999 and 7 May 2003. We report on our
observations and analyses of a black-drop effect at the 1999 and 2003 transits
of Mercury seen in high spatial resolution optical imaging with NASA's
Transition Region and Coronal Explorer (TRACE) spacecraft. We have separated
the primary contributors to this effect, solar limb darkening and broadening
due to the instrumental point spread function, for the 1999 event. The
observations are important for understanding historical observations of
transits of Venus, which in the 18th and 19th centuries were basic for the
determination of the scale of the solar system. Our observations are in
preparation for the 8 June 2004 transit of Venus, the first to occur since
1882. Only five transits of Venus have ever been seen -- in 1639, 1761, 1769,
1874, and 1882. These events occur in pairs, whose members are separated by 8
years, with an interval between pairs of 105 or 122 years. Nobody alive has
ever seen a transit of Venus.


title: The Association of PSR B1757-24 and the SNR G5.4-1.2

abstract:
  The association of PSR B1757-24 and the supernova remnant (SNR) G5.4-1.2 was
recently questioned by Thorsett et al. (2002) on the basis of proper motion
measurements of the pulsar and the "incorrect" orientation of the vector of
pulsar transverse velocity [inferred from the orientation of the
cometary-shaped pulsar wind nebula (PWN)]. We showed, however, that the
association could be real if both objects are the remnants of an off-centred
cavity supernova (SN) explosion.


title: Characterising stellar micro-variability for planetary transit searches

abstract:
  (abridged) A method for simulating light curves containing stellar
micro-variability for a range of spectral types and ages, based on
parameter-by-parameter scaling of a multi-component fit to the solar irradiance
power spectrum (from VIRGO/PMO6 data), and scaling laws derived from ground
based observations of various stellar samples, is presented.
  We observe a correlation in the Sun between the amplitude of the power
spectrum on weeks timescales and the BBSO Ca II K-line index of chromospheric
activity. On the basis of this evidence, the chromospheric activity level,
predicted from rotation period and B-V colour estimates according to the
relationship first introduced by Noyes(1983) and Noyes et al. (1984), is used
to predict the variability power on weeks time scale. The rotation period is
estimated on the basis of a fit to the distribution of rotation period versus
$B-V$ observed in the Hyades and the Skumanich (1972) spin-down law. The
characteristic timescale of the variability is also scaled according to the
rotation period.
  We use this model to estimate the impact of the target star type and age on
the detection capability of missions such as Eddington and Kepler. K stars are
found to be the most promising targets, while the performance drops
significantly for stars earlier than G and younger than 2.0 Gyr. Simulations
also show that \emph{Eddington} should detect terrestrial planets orbiting
solar-age stars in most of the habitable zone for G2 types and all of it for K0
and K5 types.


title: Superimposed Oscillations in the WMAP Data?

abstract:
  The possibility that the cosmic variance outliers present in the recently
released WMAP multipole moments are due to oscillations in the primordial power
spectrum is investigated. Since the most important contribution to the WMAP
likelihood originates from the outliers at relatively small angular scale
(around the first Doppler peak), special attention is paid to these in contrast
with previous studies on the subject which have concentrated on the large
scales outliers only (i.e. the quadrupole and octupole). As a physically
motivated example, the case where the oscillations are of trans-Planckian
origin is considered. It is shown that the presence of the oscillations causes
an important drop in the WMAP chi square of about fifteen. The F-test reveals
that such a drop has a probability less than 0.06% to occur by chance and can
therefore be considered as statistically significant.


title: Near-Infrared Integral Field Spectroscopy of Star-Forming Galaxies

abstract:
  The Palomar Integral Field Spectrograph was used to probe a variety of
environments in nine nearby galaxies that span a range of morphological types,
luminosities, metallicities, and infrared-to-blue ratios. For the first time,
near-infrared spectroscopy was obtained for nuclear or bright HII regions in
star-forming galaxies over two spatial dimensions (5.7"x10.0") in the [FeII]
(1.257um), [FeII] (1.644um), Paschen beta (1.282um), H2 (2.122um), and Brackett
gamma (2.166um) transition lines. These data yield constraints on various
characteristics of the star-forming episodes in these regions, including their
strength, maturity, spatial variability, and extinction. The HII regions stand
out from the nuclei. Unlike observations of nuclear regions, HII region
near-infrared observations do not show a spatial coincidence of the line and
continuum emission; the continuum and line maps of HII regions usually show
distinct and sometimes spatially-separated morphologies. Gauging from Paschen
beta and Brackett gamma equivalent widths and luminosities, the HII regions
have younger episodes of star formation than the nuclei and more intense
radiation fields. Near-infrared line ratio diagnostics suggest that HII regions
have "purer" starbursting properties. The correlation between ionizing photon
density and mid-infrared color is consistent with the star formation activity
level being higher for HII regions than for nuclei. And though the
interpretation is complicated, on a purely empirical basis the HII regions show
lower Fe1+ abundances than nuclei by an order of magnitude.


title: STIS Spectroscopy of PKS 0405-123

abstract:
  We present results for QSO PKS 0405-123 (z=0.574, V=14.9), as part of a STIS
Investigation Definition Team (IDT) key project to study weak Ly-alpha forest
systems at low z. We detect 59 (47) Ly-alpha absorbers at 4.0 sigma
significance to an 80% completeness limit of column density log N(HI)=13.3
(13.1) for Doppler parameter V_Dop=40 km/s over 0.002<z<0.423 (0.020<z<0.234).
We find 4 intervening O VI systems, useful for studies of hot intergalactic
gas. We do not distinguish between metal and Ly-alpha-only systems in the
following analysis. The redshift density is consistent with previous
measurements for log N(HI)>=14.0, but exhibits twice as many systems at
13.1<log N(HI)<14.0 compared to the mean number density of lines at z<0.07
toward 15 extragalactic objects. The difference possibly arises from cosmic
variance. The Doppler parameter distribution has <V_Dop>=48 +- 21 km/s; line
blending possibly inflates the value. We find evidence for Ly-alpha-Ly-alpha
clustering in our sample on a scale of Delta v<=250 km/s, and there is evidence
for a void at 0.032<z<0.081 with probability of occurrance P=0.0005. We find
line-of-sight velocity correlations of up to 250 km/s between Ly-alpha
absorbers with log N(HI)>=13.1 and 45 galaxies taken from the literature and
unpublished data at 0<z<0.47; the transverse distances cover up to 1.5 /h_70
Mpc in the local frame. The Ly-alpha-galaxy clustering is stronger for higher
log(N(HI) systems.


title: Re-Analysis of Polarization in the Gamma-ray flux of GRB 021206

abstract:
  (abridged) A previous analysis of the Reuven Ramaty High Energy Solar
Spectroscopic Imager observation of GRB 021206 found that the gamma-ray flux
was 80+/-20 polarized. We re-examine this data and find no signal that can be
interpreted as due to polarization. First, we find that the number of
scattering events suitable for measuring polarization -- having been scattered
from one detector to another, with a count produced in both -- is considerably
lower than estimated by Coburn and Boggs (2003; CB03), by a factor of 10. The
signal-to-noise of the data-set is thus too low to produce a detection, even
from a 100% polarized source. Nonetheless, we develop a polarization-detection
analysis limited in sensitivity only by Poisson noise, which does not require a
space-craft mass model to detect polarization, as in CB03. We find no signal
which might be interpreted as due to polarization. Separately, we reproduce the
CB03 signal and show that it is not due to polarization. Rather, the CB03
signal is consistent with the previously-neglected systematic uncertainty in
the ``null lightcurve'' used for detection. Due to the low signal-to-noise
ratio of the RHESSI data, our Poisson noise-limited analysis results in an
upper limit consistent with 100%-polarization of the gamma-ray flux from GRB
021206. Thus, no observational constraint on the polarization of GRB 021206 can
be derived from these data.


title: High Resolution Optics & Detector Systems for Hard X-rays

abstract:
  We describe development of hard x-ray focusing optics telescopes at the
National Space Science and Technology Center (NSSTC).


title: Dust in the High Redshift Universe

abstract:
  This paper reviews the dust content of the high redshift (z > 2) universe.
Studies of the various "species" in the high-z "zoo" show that almost all have
strong evidence for containing dust. The one exception, where the evidence is
not yet convincing, is in quasar absorption line systems, particularly those
with low column density. These may not even be associated with galaxies. The
high-z galaxy types which do show evidence for dust are all strongly star
forming. Hence, as seen locally, star formation and dust in the distant
universe are also strongly correlated. It is beyond debate that star formation
at z ~ 3 is dominated by dusty systems who emit most of their bolometric flux
in the rest-frame FIR. What is not clear is whether these systems are totally
invisible at shorter wavelengths, or whether a large fraction are visible in
the rest-frame UV as Lyman Break Galaxies. The issue may not be settled until
the sub-mm background is definitively resolved.


title:
An ultraviolet-selected galaxy redshift survey - III: Multicolour
  imaging and non-uniform star formation histories

abstract:
  (abridged) We present panoramic u' and optical ground-based imaging
observations of a complete sample of low-redshift (0<z<0.4) galaxies selected
in the ultraviolet (UV) at 2000A using the balloon-borne FOCA instrument of
Milliard et al. This survey is highly sensitive to newly-formed massive stars,
and hence to actively star-forming galaxies. We use the new data to further
investigate the stellar population and star formation properties of this
sample. When combined with our earlier spectroscopic surveys, these new data
allow us to compare star-formation measures derived from aperture-corrected Ha
line fluxes, UV(2000A) and u'(3600A) continuum fluxes on a galaxy-by-galaxy
basis. As expected from our earlier studies, we find broad correlations between
the dust-corrected star-formation diagnostics, though the scatter is larger
than that from observational errors, with significant offsets from trends
expected according to simple star-formation history (SFH) models. Varying
metallicities and/or initial mass functions seem unable to explain the observed
discrepancies. We investigate the star-formation properties further by
modelling the observed spectroscopic and photometric properties of the galaxies
in our survey. Nearly half of the galaxies surveyed possess features that
appear incompatible with simple constant or smoothly declining SFHs, favouring
instead irregular or temporally-varying SFHs. We demonstrate how this can
reconcile the majority of our observations, and determine empirical corrections
to calculate intrinsic star formation rates from measures based on UV (or u')
observations alone. We discuss the broader implications of our finding that a
significant fraction of star-forming galaxies have complex SFHs, particularly
in the context of recent determinations of the cosmic SFH.


title: X-ray Spectroscopy of Thermally Emitting Neutron Stars

abstract:
  I describe recent high-resolution X-ray spectroscopy of surface emission from
nearby, thermally emitting neutron stars. I focus on RX J0720.4-3125, RX
J1308.6+2127, and RX J1605.3+3249, all of which have similar temperature, but
differ in the presence and strength of absorption features in their spectra. I
discuss possible causes for the absorption we see in two sources, and conclude
that it may be proton cyclotron line absorption, but weakened due to the
strong-field quantum electrodynamics effect of vacuum resonance mode
conversion.


title: Kinetics of Particles in Relativistic Collisionless Shocks

abstract:
  Charged plasma particles form an anisotropic counter-streaming distribution
at the front of a shock. In the near- and ultra-relativistic regimes, Weibel
(or two-stream) instability produces near-equipartition, chaotic, small-scale
magnetic fields. The fields introduce effective collisions and "thermalize" the
plasma particles via pitch-angle scattering. The properties of jitter radiation
emitted by accelerated electrons from these small-scale fields are markedly
different from synchrotron spectra. Here we theoretical summary and the results
of recent numerical 3D PIC plasma kinetic simulations. The relation of the
obtained results to the theory of gamma-ray bursts is outlined.


title: Extragalactic Sources of TeV Gamma Rays: A Summary

abstract:
  The development of techniques whereby gamma rays of energy 100 GeV and above
can be studied from the ground, using indirect, but sensitive, techniques has
opened up a new area of high energy photon astronomy. The most exciting result
that has come from these is the detection of highly variable fluxes of TeV
gamma rays from the relativistic jets in nearby AGN. The recent detection of
signals from a starburst galaxy and from a radio galaxy opens the possibility
that the extragalactic emission of TeV gamma rays is a ubiquitous phenomenon.
Here we attempt to summarize the properties of the sources detected so far.


title: Effects of Planetesimal Dynamics on the Formation of Terrestrial Planets

abstract:
  Formation of terrestrial planets by agglomeration of planetesimals in
protoplanetary disks sensitively depends on the velocity evolution of
planetesimals. We describe a novel semi-analytical approach to the treatment of
planetesimal dynamics incorporating the gravitational scattering by massive
protoplanetary bodies. Using this method we confirm that planets grow very
slowly in the outer Solar System if gravitational scattering is the only
process determining planetesimal velocities, making it hard for giant planets
to acquire their massive gaseous envelopes within less than 10 Myr. We put
forward several possibilities for alleviating this problem.


title: Very Large Array Observations of Winds from Massive Stars

abstract:
  The classical model for free-free emission from ionized stellar winds is
based on the assumption of a stationary, isotropic and homogeneous wind.
However, since there exist objects whose wind behaviour deviates from the
standard model, during the last decade these assumptions have been questioned.
In this work, we present results for 3 bright sources: P Cyg, Cyg OB2 No.12 and
WR 147. These objects have been reported to possess winds that deviate from the
basic assumptions. We have obtained flux densities, sizes, spectral indices and
mass loss rates for each of the targets. These parameters allow us to analyze
possible asymmetries, inhomogeneities and time variations in the flux
densities. These features confirm the nonclassical behaviour of these winds.


title: Palomar Testbed Interferometer Observations of Young Stellar Objects

abstract:
  We present observations of a sample of Herbig AeBe stars, as well as the FU
Orionis object V1057 Cygni. Our K-band (2.2 microns) observations from the
Palomar Testbed Interferometer (PTI) used baselines of 110m and 85m, resulting
in fringe spacings of 4 mas and 5 mas, respectively. Fringes were obtained for
the first time on V1057 Cygni as well as V594 Cas. Additional measurements were
made of MWC147, while upper limits to visibility-squared are obtained for
MWC297, HD190073, and MWC614. These measurements are sensitive to the
distribution of warm, circumstellar dust in these sources. If the circumstellar
infrared emission comes from warm dust in a disk, the inclination of the disk
to the line of sight implies that the observed interferometric visibilities
should depend upon hour angle. Surprisingly, the observations of Millan-Gabet,
Schloerb, and Traub 2001 (hereafter MST) did not show significant variation
with hour angle. However, limited sampling of angular frequencies on the sky
was possible with the IOTA interferometer, motivating us to study a subset of
their objects to further constrain these systems.


title: Galactic metallicity distribution from open clusters

abstract:
  We have compiled two new Galactic open cluster catalogues. The first one has
119 objects with age, distance and metallicity data, while the second one has
144 objects with both absolute proper motion and radial velocity data, of which
45 clusters also with metallicity data available. An iron radial gradient of
about $-0.063\pm$0.008 \dexkpc is obtained from our sample. By dividing
clusters into age groups, we show that iron gradient was steeper in the past. A
disk age-metallicity relation could very probably exist based on the current
sample.


title:
An Unbiassed Census of Active Galactic Nuclei in the Two Micron All Sky
  Survey

abstract:
  (Abridged) We present an unbiassed near-IR selected AGN sample, covering
12.56 square degrees down to K ~ 15.5, selected from the Two Micron All Sky
Survey (2MASS). Our only selection effect is a moderate color cut (J-K>1.2)
designed to reduce contamination from galactic stars. We observed both
point-like and extended sources. Using the brute-force capabilities of the 2dF
multi-fiber spectrograph on the Anglo-Australian Telescope, we obtained spectra
of 65% of the target list: an unbiassed sub-sample of 1526 sources.
  80% of the 2MASS sources in our fields are galaxies, with a median redshift
of 0.15. The remainder are K- and M-dwarf stars.
  Seyfert-2 Galaxies are roughly three times more common in this sample than in
optically selected galaxy samples (once corrections have been made for the
equivalent width limit and for different aperture sizes).
  We find 14 broad-line (Type-1) AGNs, giving a surface density down to K<15
comparable to that of optical samples down to B=18.5. Half of our Type-1 AGNs
could not have been found by normal color selection techniques. In all cases
this was due host galaxy light contamination rather than intrinsically red
colors.
  We conclude that the Type-1 AGN population found in the near-IR is not
dramatically different from that found in optical samples. There is no evidence
for a large population of AGNs that could not be found at optical wavelengths,
though we can only place very weak constraints on any population of dusty
high-redshift QSOs.


title:
Physical properties of DLA metallicity and neutral hydrogen column
  density

abstract:
  We investigate some basic properties of Damped Lyman alpha systems based on
the Semi-Analytical model of disk galaxy formation theory. We derive the DLA
metallicity, column density, number density, gas content and cosmic star
formation rate by assuming that disks form at the center of dark halos, and the
modelled DLAs are selected by Monte Carlo simulation according to the
distributions of halo properties. We find that DLA hosts are dominated by small
galaxies and biased to extended galaxies. In terms of model results, DLAs could
naturally arise in a $\Lambda$CDM universe from radiatively cooled gas in dark
matter halos. However, model predicts a reverse correlation between metallicity
and the column density when compared with observations, regardless of the
proposed observational bias. We argue that this could be resulted from the
model limitations, or the inadequacy of Schmidt-type star formation mode at
high redshift, or/and the diversities of DLA populations.


title: Structured, Dynamo Driven Stellar and Disc Winds

abstract:
  Considerable progress has been made in understanding the hydrodynamics, but
only to a certain extent the magnetohydrodynamics, of shaping bipolar outflows
forming protoplanetary nebulae (PPNs) and planetary nebulae (PNs). In
particular, Blackman et al. (2001b,2001a) point out two problems related to the
formation of PNs and PPNs, regarding the formation of multipolar structures and
the origin of the nebulae. They propose a solution by giving a
semi-quantitative physical model which should be investigated by numerical
simulations.


title:
Direct measurement of the size and shape of the present-day stellar wind
  of Eta Carinae

abstract:
  We present new high angular resolution observations at near-IR wavelengths of
the core of the Luminous Blue Variable Eta Carinae, using NAOS-CONICA at the
VLT and VINCI at the VLT Interferometer (VLTI). The latter observations provide
spatial information on a scale of 5 milli-arcsec or ~11 AU at the distance of
Eta Carinae. The present-day stellar wind of Eta Carinae is resolved on a scale
of several stellar radii. Assuming spherical symmetry, we find a mass loss rate
of 1.6x10^{-3} M_sun/yr and a wind clumping factor of 0.26. The VLTI data taken
at a baseline of 24 meter show that the object is elongated with a de-projected
axis ratio of approximately 1.5; the major axis is aligned with that of the
large bi-polar nebula that was ejected in the 19th century. The most likely
explanation for this observation is a counter-intuitive model in which stellar
rotation near the critical velocity causes enhanced mass loss along the
rotation axis. This results from the large temperature difference between pole
and equator in rapidly rotating stars. Eta Carinae must rotate in excess of 90
per cent of its critical velocity to account for the observed shape. The large
outburst may have been shaped in a similar way. Our observations provide strong
support for the existence of a theoretically predicted rotational instability,
known as the Omega limit.


title: Recent Constraints on Models of Quintessence

abstract:
  We perform a comparison of the WMAP measurements with the predictions of
quintessence cosmological models of dark energy. We consider a wide range of
quintessence models, including: a constant equation-of-state; a
simply-parametrized, time-evolving equation-of-state; a class of models of
early quintessence; scalar fields with an inverse-power law potential. We also
provide a joint fit to the CBI and ACBAR CMB data, and the type 1a supernovae.


title:
Amount of intergalactic dust: constraints from distant supernovae and
  thermal history of intergalactic medium

abstract:
  This paper examines the allowed amount of IG (intergalactic) dust, which is
constrained by extinction and reddening of distant SNe and thermal history of
IGM (intergalactic medium) affected by dust photoelectric heating. Based on the
observational cosmic star formation history, we find an upper bound of $\chi$,
the mass ratio of the IG dust to the total metal in the Universe, as $\chi\la
0.1$ for $10 {\rm \AA} \la a \la 0.1 \micron$ and $\chi\la 0.1(a/0.1
\micron)^{-1}$ for $0.1 \micron\la a\la1\micron$, where $a$ is a characteristic
grain size of the IG dust. This upper bound of $\chi\sim0.1$ suggests that the
dust-to-metal ratio in the IGM is smaller than the current Galactic value. The
corresponding allowed density of the IG dust increases from $\sim10^{-34}$ g
cm$^{-3}$ at $z=0$ to $\sim10^{-33}$ g cm$^{-3}$ at $z\sim1$, and keeps almost
the value toward higher redshift. This causes IG extinction of $\la 0.2$ mag at
the observer's $B$-band for $z\sim 1$ sources and that of $\la 1$ mag for
higher redshift sources. Furthermore, if $E(B-V)\sim 0.1$ mag at the observer's
frame against $z\ga1$ sources is detected, we can conclude that a typical size
of the IG dust is $\la 100$ \AA. The 2175 \AA absorption feature of small
graphite may be found as a local minimum at $z\sim2.5$ in a plot of the
observed $E(B-V)$ as a function of the source redshift. Finally, the IGM mean
temperature at $z\la1$ can be still higher than $10^{4}$ K, provided the size
of the IG dust is $\la100$ \AA.


title: The observers' view of (very) long X-ray bursts: they are super!

abstract:
  In many X-ray point sources on the sky, the X-ray emission arises because
hydrogen and/or helium is accreted onto a neutron star from a nearby donor
star. When this matter settles on the neutron star surface, it will undergo
nuclear fusion. For a large range of physical parameters the fusion is
unstable. The resulting thermo-nuclear explosions last from seconds to minutes.
They are observed as short flares in X-rays and are called `type I X-ray
bursts'. Recently, hours-long X-ray flares have been found in seven X-ray burst
sources with the BeppoSAX/WFC, RXTE/ASM and RXTE/PCA. They have similar
properties to the usual X-ray bursts, except they last for two or three orders
of magnitude longer (hence they are referred to as `superbursts'). This can not
be understood in the context of the standard nuclear-fusion picture mentioned
above. Instead, the superbursts are thought to be related to the unstable
burning of the leftovers from the hydrogen and/or helium fusion. I will discuss
the observational properties of these superbursts.


title: Accretion onto the neutron star in Be/X-ray binaries

abstract:
  We study accretion onto the neutron star in Be/X-ray binaries, using a 3D SPH
code and the data imported from a high resolution simulation by Okazaki et al.\
(2002) for a coplanar system with a short period ($P_{\rm orb}=24.3 \rm d$) and
moderate eccentricity $(\rm{e=0.34})$. We find that a time-dependent accretion
disk is formed around the neutron star in Be/X-ray binaries. The disk shrinks
after the periastron passage of the Be star and restores its radius afterwards.
Our simulations show that the truncated Be disk model for Be/X-ray binaries is
consistent with the observed X-ray behavior.


title: Two formation paths for cluster dwarf galaxies?

abstract:
  A surprising result of our recent spectroscopic survey of galaxies in the
Coma cluster has been the discovery of a possible bimodal distribution in the
metallicities of faint galaxies at $M_B>-17$. We identified a group of dwarfs
with luminosity-weighted metallicities around solar and a group with [M/H]
around -1.5. A metallicity bimodality among galaxies of similar luminosities is
unexpected and suggests that faint cluster galaxies could be an heterogeneous
population that formed through more than one evolutionary path, possibly as a
consequence of the cluster environment.


title: Do we really observe a bow shock in N157B...?

abstract:
  I present a model of a pulsar wind interacting with its associated supernova
remnant. I will use the model to argue that one can explain the morphology of
the pulsar wind nebula inside N157B, a supernova remnant in the Large
Magellanic Cloud, without the need for a bow shock interpretation. The model
uses a hydrodynamics code which simulates the evolution of a pulsar wind
nebula, when the pulsar is moving at a high velocity (1000 km/sec) through the
expanding supernova remnant. The simulation shows three different stages of the
pulsar wind nebula: the supersonic expansion stage, the subsonic expansion
stage and the bow shock stage. The last stage occurs when the head of the
pulsar wind nebula, containing the active pulsar, deforms into a bow shock, due
to the motion of the pulsar becoming supersonic. I will argue that the pulsar
wind nebula inside N157B is currently in the second stage of its evolution,
i.e. the expansion of the pulsar wind nebula is subsonic and there is no bow
shock around the pulsar wind bubble. The strongly off-centered position of the
pulsar with respect to its pulsar wind nebula is naturally explained by the
result of the interaction of the reverse shock with the pulsar wind nebula, as
the simulation bears out.


title:
The dependence of the sub-stellar IMF on the initial conditions for star
  formation

abstract:
  Abridged: We have undertaken a series of hydrodynamical simulations of
multiple star formation in small turbulent molecular clouds. Our goal is to
determine the sensitivity of the properties of the resulting stars and brown
dwarfs to variations in the initial conditions imposed. In this paper we report
on the results obtained by applying two different initial turbulent velocity
fields. The slope of the turbulent power-law spectrum alpha is set to -3 in
half of the calculations and to -5 in the other half. We find that, whereas the
stellar mass function seems to only be weakly dependent on the value of alpha,
the sub-stellar mass function turns out to be more sensitive to the initial
slope of the velocity field. We argue that, since the role of turbulence is to
create substructure from which gravitational instabilities may grow, variations
in other initial conditions that also determine the fragmentation process are
likely to affect the shape of the sub-stellar mass function as well. The
absence of many planetary mass `free-floaters' in our simulations, especially
in the mass range 1-10 MJ, suggests that, if these objects are abundant, they
are likely to form by similar mechanisms to those thought to operate in
quiescent accretion discs, instead of via instabilities in gravitationally
unstable discs. Finally, we find that multiple and single stars share
comparable kinematical properties, both populations being able to attain
velocities in the range 1-10 km/s. From these values we draw the conclusion
that only low-mass star-forming regions such as Taurus-Auriga or Ophiuchus,
where the escape speed is low, might have suffered some depletion of its single
and binary stellar population.


title: Low light level CCDs and visibility parameter estimation

abstract:
  Recently, low light level charge coupled devices (L3CCDs) capable of on-chip
gain have been developed, leading to sub-electron effective readout noise,
allowing for the detection of single photon events. Optical interferometry
usually requires the detection of faint signals at high speed and so L3CCDs are
an obvious choice for these applications. Here we analyse the effect that using
an L3CCD has on visibility parameter estimation (amplitude and triple product
phase), including situations where the L3CCD raw output is processed in an
attempt to reduce the effect of stochastic multiplication noise introduced by
the on-chip gain process. We establish that under most conditions, fringe
parameters are estimated accurately, whilst at low light levels, a bias
correction which we determine here, may need to be applied to the estimate of
fringe visibility amplitude. These results show that L3CCDs are potentially
excellent detectors for astronomical interferometry at optical wavelengths.


title: A Key to Pulsar Wind Bubble Morphologies: HD simulations

abstract:
  We present a model of a pulsar-driven supernova remnant, by using a
hydrodynamics code, which simulates the evolution of a pulsar wind nebula when
the pulsar is moving at a high velocity through its expanding supernova
remnant. The simulation shows four different stages of the pulsar wind nebula:
the supersonic expansion stage, the reverse shock interaction stage, the
subsonic expansion stage and ultimately the bow shock stage. Due to the high
velocity of the pulsar, the position of the pulsar is located at the head of
the pulsar wind bubble, after the passage of the reverse shock. The resulting
morphology of the pulsar wind bubble is therefore similar to the morphology of
a bow shock pulsar wind nebula. We show how to distinguish these two different
stages, and apply this method to the SNR G327.1-1.1, for which we argue that
there is no bow shock around its pulsar wind nebula.


title:
H_2-bearing damped Lyman-alpha systems as tracers of cosmological
  chemical evolution

abstract:
  The chemical abundances in damped Lyman-alpha systems (DLAs) show more than 2
orders of magnitude variation at a given epoch, possibly because DLAs arise in
a wide variety of host galaxies. This could significantly bias estimates of
chemical evolution. We explore the possibility that DLAs in which H_2
absorption is detected may trace cosmological chemical evolution more reliably
since they may comprise a narrower set of physical conditions. The 9 known H_2
absorption systems support this hypothesis: metallicity exhibits a faster, more
well-defined evolution with redshift than in the general DLA population. The
dust-depletion factor and, particularly, H_2 molecular fraction also show rapid
increases with decreasing redshift. We comment on possible observational
selection effects which may bias this evolution. Larger samples of H_2-bearing
DLAs are clearly required and may constrain evolution of the UV background and
DLA galaxy host type with redshift.


title:
Probing the atmosphere of a solar-like star by galactic microlensing at
  high magnification

abstract:
  We report a measurement of limb darkening of a solar-like star in the very
high magnification microlensing event MOA 2002-BLG-33. A 15 hour deviation from
the light curve profile expected for a single lens was monitored intensively in
V and I passbands by five telescopes spanning the globe. Our modelling of the
light curve showed the lens to be a close binary system whose centre-of-mass
passed almost directly in front of the source star. The source star was
identified as an F8-G2 main sequence turn-off star. The measured stellar
profiles agree with current stellar atmosphere theory to within ~4% in two
passbands. The effective angular resolution of the measurements is <1
micro-arcsec. These are the first limb darkening measurements obtained by
microlensing for a Solar-like star.


title: A Resonant-Mode Model of Pulsar Radio Emission

abstract:
  It is argued that the polar gap and flux tube in the pulsar magnetosphere act
as a resonant cavity/waveguide system which is excited by oscillations in the
primary beam current and accelerating potential. The modes will be converted,
probably scattered, to produce radio beams in the frequency range of those
observed.


title: Early Quintessence and the CMB

abstract:
  We examine the cosmic microwave background (CMB) anisotropy for signatures of
early quintessence dark energy -- a non-negligible quintessence energy density
during the recombination and structure formation eras. In contrast to a
$\Lambda$CDM cosmology, early quintessence leads to a larger suppression of
structure growth. Because of this influence on the clustering of dark matter
and the baryon-photon fluid, we may expect to find trace signals in the CMB and
the mass fluctuation power spectrum. In detail, we demonstrate that suppressed
clustering power on small length-scales, as suggested by the combined Wilkinson
Microwave Anisotropy Probe (WMAP) / CMB / large scale structure data set, is
characteristic of early quintessence.


title: Cosmology with the lyman-alpha forest in the WMAP era

abstract:
  In the WMAP era of high precision cosmology an accurate determination of the
matter power spectrum from lyman-alpha forest data becomes crucial. When
combining the matter power spectrum derived from CMB experiments with that
inferred from lyman-alpha absorption an evidence for a running spectral index
and a primordial index n < 1 arises (Verde et al. 2003). In this talk, I will
describe some results obtained from a sample of 27 high resolution and high
signal-to-noise quasar spectra (the LUQAS sample) and I will address possible
systematic errors that can affect the estimate of the flux power spectrum.


title: Highlights of the HETE-2 Mission

abstract:
  The HETE-2 mission has been highly productive. It has observed more than 250
GRBs so far. It is currently localizing 25 - 30 GRBs per year, and has
localized 43 GRBs to date. Twenty-one of these localizations have led to the
detection of X-ray, optical, or radio afterglows, and as of now, 11 of the
bursts with afterglows have redshift determinations. HETE-2 has also observed
more than 45 bursts from soft gamma-ray repeaters, and more than 700 X-ray
bursts. HETE-2 has confirmed the connection between GRBs and Type Ic
supernovae, a singular achievement and certainly one of the scientific
highlights of the mission so far. It has provided evidence that the
isotropic-equivalent energies and luminosities of GRBs may be correlated with
redshift; such a correlation would imply that GRBs and their progenitors evolve
strongly with redshift. Both of these results have profound implications for
the nature of GRB progenitors and for the use of GRBs as a probe of cosmology
and the early universe. HETE-2 has placed severe constraints on any X-ray or
optical afterglow of a short GRB. It has made it possible to explore the
previously unknown behavior optical afterglows at very early times, and has
opened up the era of high-resolution spectroscopy of GRB optical afterglows. It
is also solving the mystery of "optically dark" GRBs, and revealing the nature
of X-ray flashes (XRFs).


title:
A survey for water maser emission towards planetary nebulae. New
  detection in IRAS 17347-3139

abstract:
  We report on a water maser survey towards a sample of 27 planetary nebulae
(PNe) using the Robledo de Chavela and Medicina single-dish antennas, as well
as the Very Large Array (VLA). Two detections have been obtained: the already
known water maser emission in K 3-35, and a new cluster of masers in IRAS
17347-3139. This low rate of detections is compatible with the short life-time
of water molecules in PNe (~100 yr). The water maser cluster at IRAS 17347-3139
are distributed on a ellipse of size ~ 0.2" x 0.1", spatially associated with
compact 1.3 cm continuum emission (simultaneously observed with the VLA). From
archive VLA continuum data at 4.9, 8.4, and 14.9 GHz, a spectral index alpha =
0.76 +- 0.03 is derived for this radio source, which is consistent with either
a partially optically thick ionized region or with an ionized wind. However,
the latter scenario can be ruled out on mass-loss considerations, thus
indicating that this source is probably a young PN. The spatial distribution
and the radial velocities of the water masers are suggestive of a rotating and
expanding maser ring, tracing the innermost regions of a torus formed at the
end of the AGB phase. Given that the 1.3 cm continuum emission peak is located
near one of the tips of the major axis of the ellipse of masers, we speculate
on a possible binary nature of IRAS 17347-3139, where the radio continuum
emission could belong to one of the components and the water masers would be
associated with a companion.


title:
Radioquiet isolated neutron stars: old and young, nearby and far away,
  dim and very dim

abstract:
  We briefly discuss the evolutionary path and observational appearance of
isolated neutron stars (INSs) focusing on radioquiet objects. There are many
reasons to believe that these sources are extremely elusive once the star
surface has cooled down: their high spatial velocities, the long propeller
stage and/or the very low accretion efficiency. We describe recent population
synthesis models of close-by young INSs, highlighting the major difficulties
encountered in the past by these simulations in reproducing the observed
properties of known sources. As we show, a likely possibility is that most of
the INSs in the Solar proximity are young (less than few Myrs) neutron stars
born in the Gould Belt. To stay hot enough and sustain X-ray emission for a
time $\approx 1$ Myr, they probably need to be low- to medium-massive, with $M$
less than$\sim 1.35 M_\odot$.


title: GRB941017: A Case Study of Neutrino Production in Gamma Ray Bursts

abstract:
  GRB941017, a gamma-ray burst of exceptional fluence, has recently been shown
to have a high-energy component which is not consistent with the standard
fireball phenomenology. If this component is the result of photomeson
interactions in the burst fireball, it provides new and compelling support for
substantial high-energy neutrino fluxes from this and similar sources. In this
letter, we consider what impact this new information has on the neutrino
spectra of gamma-ray bursts and discuss how this new evidence impacts the
prospects for detection of such events in next generation neutrino telescopes.


title: The Nature of the Massive Young Stars in W75 N

abstract:
  We have observed the W75 N massive star forming region in SiO(J=2-1 & J=1-0)
at 3" - 5" resolution and in 6 cm, 2 cm, and 7 mm continuum emission at 1.4" -
0.2" resolution. The abundance ratio of [SiO]/[H2] is roughly 5-7 x 10^-11
which is typical for what is expected in the ambient component of molecular
clouds with active star formation. The SiO morphology is diffuse and centered
on the positions of the ultracompact HII regions - no collimated, neutral jet
was discovered. The ionized gas surrounding the protostars have emission
measures ranging from 1-15 x 10^6 pc cm^-6, densities from 0.4-5 x 10^4 cm^-3,
and derived spectral types of the central ionizing stars ranging from B0.5 to
B2. Most of the detected sources have spectral indicies which suggest optically
thin to moderately optically thick HII regions produced by a central ionizing
star. The spread in ages between the oldest and youngest early-B protostars in
the W75 N cluster is 0.1-5 x 10^6 years. This evolutionary timescale for W75 N
is consistent with that found for early-B stars born in clusters forming more
massive stars (Mstar > 25 Msun).


title: The Warped Gas and Dust Lane in NGC 3718

abstract:
  We present the first observations of molecular line emission in NGC 3718 with
the IRAM 30m and the Plateau de Bure Interferometer. This galaxy is an
impressive example for a strongly warped gas disk harboring an active galactic
nucleus (AGN). An impressive dust lane is crossing the nucleus and a warp is
developing into a polar ring. The molecular gas content is found to be typical
of an elliptical galaxy with a relatively low molecular gas mass content
(~4*10^8 Msun). The molecular gas distribution is found to warp from the inner
disk together with the HI distribution. The CO data were also used to improve
the kinematic modeling in the inner part of the galaxy, based on the so-called
"tilted ring"-model. The nature of NGC 3718 is compared with its northern sky
``twin'' Centaurus A and the possible recent swallowing of a small-size
gas-rich spiral is discussed.


title: IRAS 23385+6053: a candidate protostellar massive object

abstract:
  We present the results of a multi-line and continuum study towards the source
IRAS 23385+6053,performed with the IRAM-30m telescope, the Plateau de Bure
Interferometer, the Very Large Array Interferometer and the James Clerk Maxwell
Telescope. The new results confirm our earlier findings, namely that IRAS
23385+6053 is a good candidate high-mass protostellar object, precursor of an
ultracompact H$_{II}$ region. The source is roughly composed of two regions: a
molecular core $\sim0.03\div0.04$ pc in size, with a temperature of $\sim40$ K
and an H$_{2}$ volume density of the order of 10$^{7}$ cm$^{-3}$, and an
extended halo of diameter $\leq$0.4 pc, with an average kinetic temperature of
$\sim 15$ K and H$_{2}$ volume density of the order of 10$^{5}$ cm$^{-3}$. The
core temperature is much smaller than what is typically found in molecular
cores of the same diameter surrounding massive ZAMS stars. We deduce that the
core luminosity is between 150 and $1.6\times10^{4}L_{\odot}$, and we believe
that the upper limit is near the ``true'' source luminosity. Moreover, by
comparing the H$_{2}$ volume density obtained at different radii from the IRAS
source, we find that the halo has a density profile of the type $n_{\rm
H_{2}}\propto r^{-2.3}$. This suggests that the source is gravitationally
unstable. Finally, we demonstrate that the temperature at the core surface is
consistent with a core luminosity of $10^3 L_{\odot}$ and conclude that we
might be observing a protostar still accreting material from its parental
cloud, whose mass at present is $\sim 6 M_{\odot}$.