title: The cosmological constant and the paradigm of adiabaticity

abstract:
  We discuss the value of the cosmological constant as recovered from CMB and
LSS data and the robustness of the results when general isocurvature initial
conditions are allowed for, as opposed to purely adiabatic perturbations. The
Bayesian and frequentist statistical approaches are compared. It is shown that
pre-WMAP CMB and LSS data tend to be incompatible with a non-zero cosmological
constant, regardless of the type of initial conditions and of the statistical
approach. The non-adiabatic contribution is constrained to be < 40% (2sigma
c.l.).


title: A second glance at SN 2002ap and the M74 field with XMM-Newton

abstract:
  We have re-observed the field of M74 in January 2003 with XMM-Newton, 11
months after the X-ray detection of SN 2002ap. From a comparison of the two
XMM-Newton observations we obtain more accurate values for the X-ray luminosity
and colours of the source five days after the event, and a limit on its decline
rate. We compare its X-ray behaviour (prompt soft X-ray emission, relatively
low luminosity) with that of other Type Ic SNe, and speculate that SN 2002ap
may share some physical properties (low mass-loss rate and high-velocity
stellar wind from the progenitor star) with the candidate hypernova/GRB
progenitor SN 1998bw, but with a lower (non-relativistic) speed of the ejecta.
We suggest that the X-ray emission observed in 2002 is likely to come from the
radiatively-cooling reverse shock, at a temperature kT ~ 0.8 keV, and that this
soft component was already detected 5 d after the event because the absorbing
column density of the cool shell between the forward and reverse shocks was
only ~ 10^{20} cm^{-2}, ie, the shell was optically thin in the soft X-ray
band. The new XMM-Newton data also allowed us to continue monitoring two bright
variable sources in M74 that had reached peak luminosities > 10^{39} erg s^{-1}
in previous XMM-Newton and Chandra observations. Finally, we used two Chandra
observations from 2001 to investigate the luminosity and colour distribution of
the X-ray source population of M74, typical of moderately-active late-type
spirals.


title:
Tests of Quantum Gravity and Large Extra Dimensions Models Using High
  Energy Gamma Ray Observations

abstract:
  Observations of the multi-TeV spectra of the nearby BL Lac objects Mkn 421
and Mkn 501 exhibit the high energy cutoffs predicted to be the result of
intergalactic annihilation interactions, primarily with IR photons having a
flux level as determined by various astronomical observations. After correcting
for such intergalactic absorption, these spectra can be explained within the
framework of synchrotron self-Compton emission models. Stecker & Glashow have
shown that the existence of this annihilation via electron-positron pair
production puts strong constraints on Lorentz violation. Such constraints have
important implications for quantum gravity models and large extra dimension
models. We also discuss the implications of observations of high energy
gamma-rays from the Crab Nebula on constraining quantum gravity models.


title: An improved gamma-ray limit on the density of PBHs

abstract:
  Gamma-rays are, with antiprotons, a very efficient way to derive upper limits
on the density of evaporating black holes. They have been successfully used in
the last decades to severely constrain the amount of Primordial Black Holes
(PBHs) in our Universe. This article suggests a little refinement, based on the
expected background, to improve this limit by a factor of three. The resulting
value is : Omega_PBH < 3.3E-9.


title: An XMM-Newton hard X-ray survey of ULIRGs

abstract:
  XMM-Newton observations of 10 ULIRGs are reported. The aim is to investigate
in hard X-rays a complete ULIRG sample selected from the bright IRAS 60$\mu$m
catalogue. All sources are detected in X-rays, 5 of which for the first time.
These observations confirm that ULIRGs are intrinsically faint X-rays sources,
their observed X-ray luminosities being typically L(2-10 keV)<1E42-43 erg/s,
whereas their bolometric luminosities are L>1E45 erg/s. In all sources we find
evidence for thermal emission from hot plasma with kT~0.7keV, dominating the
X-ray spectra below 1keV, and likely associated with a nuclear or circumnuclear
starburst. This thermal emission appears uncorrelated with the FIR luminosity,
suggesting that,in addition to the ongoing rate of star formation, other
parameters may also affect it. The soft X-ray emission appears to be extended
on a scale of ~30kpc for Mkn231 and IRAS19254-7245, possible evidence of
galactic superwinds. In these 2 sources, in IRAS20551-4250 and IRAS23128-5919
we find evidence for the presence of hidden AGNs, while a minor AGN
contribution may be suspected also in IRAS20100-4156. In particular, we have
detected a strong Fe line at 6.4keV in the spectrum of IRAS19254-7245 and a
weaker one in Mkn231, suggestive of deeply buried AGNs. For the other sources,
the X-ray luminosities and spectral shapes are consistent with hot thermal
plasma and X-ray binary emissions of mainly starburst origin. We find that the
2-10keV luminosities in these sources, most likely due to high-mass X-ray
binaries, are correlated with L_FIR: both luminosities are good indicators of
the current global SFR in the galaxy. The composite nature of ULIRGs is then
confirmed, with hints for a predominance of the starburst over the AGN
phenomenon in these objects.


title:
A CCD Study of High Latitude Galactic Structure: Testing the Model
  Parameters

abstract:
  We interpret published CCD UBVI data to deduce the stellar density
distribution and metallicity distribution function in the region from 2-8 kpc
from the Galactic Plane, and compare our results to several star count models.
A feature of extant star count models is degeneracy between the adopted scale
heights of the thin and thick disks, and their local normalisation. We
illustrate the utility of this small data set, and future larger sets (e.g.
SDSS), by explicitly considering consistency between the derived density laws,
and the implied solar neighbourhood luminosity function. Our data set, from
Hall et al.(1996) (l=52, b=-39) contains 566 stars, selected to be consistent
with stellar loci in colour-colour diagrams. Our analysis supports the
parameterisation of the recent SDSS galaxy model of Chen et al.(2001), except
in preferring the stellar halo axis ratio to be 0.84. Photometric
metal-abundances have been derived for 329 stars using a new calibration. The
vertical distance-dependent metallicity distribution function, if parameterised
by a single mean value, can be described by a metallicity gradient -0.2$
dex/kpc for the thin disk and thick disk, and -0.1$ dex/kpc for the inner halo.
The data are however better described as the sum of three discrete distribution
functions, each of which has a small or zero internal gradient. The changing
mix of thin disk, thick disk and halo populations with distance from the plane
generates an illusion of a smooth gradient.


title: The Spatial Distribution of Fluorescent H$_2$ Near T Tau

abstract:
  New subarcsecond FUV observations of T Tau with HST/STIS show spatially
resolved structures in the 2"x2" area around the star. The structures show in
multiline emission of fluorescent H_2 pumped by Lyman alpha. One emission
structure follows the cavity walls observed around T Tau N in scattered light
in the optical. A temperature greater or equal to 1000K is required to have
enough population in the H_2 to produce the observed fluorescent lines; in the
cool environment of the T Tau system, shock heating is required to achieve this
temperature at distances of a few tens of AU. Fluorescent H_2 along the cavity
wall represents the best evidence to date for the action of low-density,
wide-opening-angle outflows driving cavities into the molecular medium at
scales smaller than 100 AU. A southern region of emission consists of two arcs,
with shape and orientation similar to the arcs of H_2 2.12 microns and
forbidden line emission crossing the outflow associated with the embedded
system T Tau S. This region is located near the centroid of forbidden line
emission at the blueshifted lobe of the N-S outflow.


title: Polarization asymmetry in CSS sources: evidence of AGN fuel?

abstract:
  The compact steep spectrum and gigahertz peaked spectrum sources are widely
believed to be young radio sources, with ages <10^6 yr. If the activity in the
nucleus is fuelled by the supply of gas, one might find evidence of this gas by
studying the structural and polarization characteristics of CSS sources as
these evolve through this gas. We present polarization observations of a sample
of CSS sources, and combine our results with those available in the literature,
to show that CSS sources are more asymmetric in the polarization of the outer
lobes compared with the more extended ones. We suggest that this could be
possibly due to interaction of the jets with infalling material, which fuels
the radio source. We also investigate possible dependence of the polarization
asymmetry of the lobes on redshift, since this might be affected by more
interactions and mergers in the past. No such dependence is found for the CSS
sources, suggesting that the environments on the CSS scales are similar at
different redshifts. However, the polarization asymmetry of the
oppositely-directed lobes is larger at higher redshifts for the more extended
sources, possibly reflecting the higher incidence of interactions in the past.


title:
Bright stars and an inactive disk in Sgr A* and other dormant galaxy
  centers. I. The optically thick disk

abstract:
  Cold inactive disks are believed to exist in Low Luminosity AGN (LLAGN). They
may also exist in the nuclei of inactive galaxies and in the center of our own
Galaxy. These disks would then be embedded in the observed dense nuclear
stellar clusters. Making the simplest assumption of an optically thick disk, we
explore several ways to detect the disk presence through its interaction with
the cluster. First of these is the eclipses of close bright stars by the disk.
The second is the increase in the infrared flux of the disk due to illumination
of its surface by such stars during close passages. Finally the surface
brightness of the star cluster should show an anisotropy that depends on the
inclination angle of the disk. We apply the first two of the methods to Sgr A*,
the super massive black hole in our Galactic Center. Using the orbital
parameters of the close star S2, we strongly rule out a disk optically thick in
the near infrared unless it has a relatively large inner hole. For disks with
no inner holes, we estimate that the data permit a disk with infrared optical
depth no larger than about 0.01. Such a disk could also be responsible for the
detected 3.8 microns excess in the spectrum of S2. The constraints on the disk
that we obtain here can be reconciled with the disk parameters needed to
explain the observed X-ray flares if dust particles in the disk have sizes
greater than ~ 30 microns. The destruction of small dust particles by strong UV
heating and shocks from star passages through the disk, and grain growth during
"quiescent" times, are mentioned as possible mechanisms of creating the unusual
grain size distribution. (...)


title:
Precision era of the kinetic Sunyaev-Zeldovich effect: simulations,
  analytical models and observations and the power to constrain reionization

abstract:
  The kinetic SZ effect, which is the dominant CMB source at arc-minute scales
and $\nu \sim 217$ Ghz, probes the ionized gas peculiar momentum up to the
epoch of reionization and is a sensitive measure of the reionization history.
We ran high resolution self-similar and $\Lambda$CDM hydro simulations and
built an analytical model to study this effect. Our model reproduces the
$\Lambda$CDM simulation results to several percent accuracy, passes various
tests against self-similar simulations, and shows a wider range of
applicability than previous analytical models. Our model in its continuous
version is free of simulation limitations such as finite simulation box and
finite resolution and allows an accurate prediction of the kinetic SZ power
spectrum $C_l$. For the WMAP cosmology, we find $l^2C_l/(2\pi)\simeq 0.91
\times 10^{-12} [(1+z_{\rm reion})/10]^{0.34}(l/5000)^{0.23-0.015(z_{\rm
reion}-9)}$ for the reionization redshift $6<z_{\rm reion}<20$ and
$3000<l<9000$. The corresponding temperature fluctuation is several $\mu$K at
these ranges. The dependence of $C_l$ on the reionization history allows an
accurate measurement of the reionization epoch. For the Atacama cosmology
telescope experiment, $C_l$ can be measured with $\sim 1%$ accuracy. $C_l$
scales as $(\Omega_b h)^2 \sigma_8^{4\sim 6}$. Given cosmological parameters,
ACT would be able to constrain $z_{\rm reion}$ with several percent accuracy.
Some multi-reionization scenarios degenerate in the primary CMB temperature and
TE measurement can be distinguished with $\sim 10 \sigma$ confidence.


title: Multiwavelength Spectrum of the Black Hole XTE J1118+480 in Quiescence

abstract:
  We present an X-ray/UV/optical spectrum of the black hole primary in the
X-ray nova XTE J1118+480 in quiescence at L_x = 4 x 10^{-9} of the Eddington
luminosity. The Chandra, HST and MMT spectroscopic observations were performed
simultaneously on 2002 January 12 UT. Because this 4.1-hr binary is located at
b = 62 deg, the transmission of the ISM is very high (e.g., 70% at 0.3 keV). We
present many new results for the quiescent state, such as the first far-UV
spectrum and evidence for an 0.35 mag orbital modulation in the near-UV flux.
However, the centerpiece of our work is the multiwavelength spectrum of XTE
J1118+480, which we argue represents the canonical spectrum of a stellar-mass
black hole radiating at L_x = 4 x 10^{-8.5} of the Eddington luminosity. This
spectrum is comprised of two apparently disjoint components: a hard X-ray
spectrum with a photon index Gamma = 2.02 +/- 0.16, and an optical/UV continuum
that resembles a 13,000 K disk blackbody spectrum punctuated by several strong
emission lines. We present a model of the source in which the accretion flow
has two components: (1) an X-ray-emitting interior region where the flow is
advection-dominated, and (2) a thin, exterior accretion disk with a truncated
inner edge (R_tr ~ 10^4 Schwarzschild radii) that is responsible for the
optical/UV spectrum. For D = 1.8 kpc, the luminosity of the X-ray component is
L_x = 3.5 x 10^{30} erg/s (0.3-7 keV); the bolometric luminosity of the
optical/UV component is 20 times greater.


title: Anthropic predictions for neutrino masses

abstract:
  It is argued that small values of the neutrino masses may be due to anthropic
selection effects. If this is the case, then the combined mass of the three
neutrino species is expected to be ~1eV, neutrinos causing a non-negligible
suppression of galaxy formation.


title:
Internal Dynamics, Structure and Formation of Dwarf Elliptical Galaxies:
  II. Rotating Versus Non-Rotating Dwarfs

abstract:
  We present spatially-resolved internal kinematics and stellar chemical
abundances for a sample of dwarf elliptical (dE) galaxies in the Virgo Cluster
observed with Keck/ESI. We find that 4 out of 17 dEs have major axis rotation
velocities consistent with rotational flattening, while the remaining dEs have
no detectable major axis rotation. Despite this difference in internal
kinematics, rotating and non-rotating dEs are remarkably similar in terms of
their position in the Fundamental Plane, morphological structure, stellar
populations, and local environment. We present evidence for faint underlying
disks and/or weak substructure in a fraction of both rotating and non-rotating
dEs, but a comparable number of counter-examples exist for both types which
show no evidence of such structure. Absorption-line strengths were determined
based on the Lick/IDS system (Hbeta, Mgb, Fe5270, Fe5335) for the central
region of each galaxy. We find no difference in the line-strength indices, and
hence stellar populations, between rotating and non-rotating dE galaxies. The
best-fitting mean age and metallicity for our 17 dE sample are 5 Gyr and Fe/H =
-0.3 dex, respectively, with rms spreads of 3 Gyr and 0.1 dex. The majority of
dEs are consistent with solar alpha/Fe abundance ratios. By contrast, the
stellar populations of classical elliptical galaxies are, on average, older,
more metal rich, and alpha-enhanced relative to our dE sample. The local
environments of both dEs types appear to be diverse in terms of their proximity
to larger galaxies in real or velocity space within the Virgo Cluster. Thus,
rotating and non-rotating dEs are remarkably similar in terms of their
structure, stellar content, and local environments, presenting a significant
challenge to theoretical models of their formation. (abridged)


title: The AGN content of the z=0.83 cluster MS1054-0321

abstract:
  We present a survey of X-ray point sources in a 91 ksec Chandra ACIS-S
observation of the z=0.83 cluster MS1054-0321. We detect 47 X-ray sources
within the 8.3 arcmin by 8.3 arcmin field, of which two are immediately
confirmed from pre-existing spectroscopy to be at the redshift of the cluster.
At fluxes brighter than S_(0.5 - 8 keV) = 5 x 10^{-15} erg s^{-1} cm^{-2} we
find a ~ 2 sigma excess compared to predictions from field surveys, consistent
with an excess of approximately 6 AGN. If these sources are associated with the
cluster, they too are AGN with luminosities of order L_(0.5 - 8 keV) ~ 10^{43}
erg s^{-1}. Combined with the identification of 7 cluster AGN from deep radio
observations (Best et al. 2002), these observations suggest significantly
enhanced AGN activity in MS1054-03 compared to local galaxy clusters.
Interestingly, the excess of X-ray detected AGN is found at radial distances of
between 1 and 2 Mpc, suggesting they may be associated with infalling galaxies.
The radio AGN are seen within the inner Mpc of the cluster and are largely
undetected in the X-ray, suggesting they are either intrinsically less luminous
and/or heavily obscured.


title:
On the use of fractional Brownian motion simulations to determine the 3D
  statistical properties of interstellar gas

abstract:
  Based on fractional Brownian motion (fBm) simulations of 3D gas density and
velocity fields, we present a study of the statistical properties of
spectro-imagery observations (channel maps, integrated emission, and line
centroid velocity) in the case of an optically thin medium at various
temperatures. The power spectral index gamma_W of the integrated emission is
identified with that of the 3D density field (gamma_n) provided the medium's
depth is at least of the order of the largest transverse scale in the image,
and the power spectrum of the centroid velocity map is found to have the same
index gamma_C as that of the velocity field (gamma_v). Further tests with
non-fBm density and velocity fields show that this last result holds, and is
not modified either by the effects of density-velocity correlations. A
comparison is made with the theoretical predictions of Lazarian & Pogosyan
(2000).


title: Fourier space intermittency of the small-scale turbulent dynamo

abstract:
  The small-scale turbulent dynamo in the high Prandtl number regime is
described in terms of the one-point Fourier space correlators. The second order
correlator of this kind is the energy spectrum and it has been previously
studied in detail. We examine the higher order k-space correlators which
contain important information about the phases of the magnetic wavepackets and
about the dominant structures of the magnetic turbulence which cause
intermittency. In particular, the fourth-order correlators contain information
about the mean-square phase difference between any two components of the
magnetic field in a plane transverse to the wavevector. This can be viewed as a
measure of the magnetic field's polarization. Examining this new quantity, the
magnetic field is shown to become plane polarized in the Kazantsev-Kraichnan
model at large time, corresponding to a strong deviation from Gaussianity. We
derive a closed equation for the generating function of the Fourier correlators
and find the large-time asymptotic solutions of these correlators at all
orders. The time scaling of these solutions implies the magnetic field has
log-normal statistics, whereas the wavenumber scaling indicates that the field
is dominated by intermittent fluctuations at high k.


title:
Emission line widths and QSO black hole mass estimates from the 2dF QSO
  Redshift Survey

abstract:
  We have used composite spectra generated from more than 22000 QSOs observed
in the course of the 2dF and 6dF QSO Redshift Surveys to investigate the
relationship between the velocity width of emission lines and QSO luminosity.
We find that the velocity width of the broad emission lines Hbeta, Hgamma,
MgII, CIII] and CIV are correlated with the continuum luminosity, with a
significance of more than 99 per cent. Of the major narrow emission lines
([OIII] 5007, [OII] 3727, NeIII 3870 and NeV 3426) only [OIII] exhibits a
significant correlation between line width and luminosity. Assuming that the
gas is moving in Keplerian orbits and that the radius of the broad line region
is related to the QSO continuum luminosity, we use the velocity widths of the
broad lines to derive average black hole masses for the QSOs contributing to
the composite spectra. The resultant QSO mass-luminosity relationship is
consistent with M ~ L^0.97+-0.16. We find that the correlation between line
width and redshift, if present, must be weak, and only CIV shows significant
evidence of evolution. This enables us to constrain the redshift evolution of
the black hole mass-luminosity ratio to be ~(1+z)^beta with beta ~< 1, much
less than the ~(1+z)^3 evolution seen in QSO luminosity evolution. Assuming
that the motion of the broad line region gas is Keplerian and that its radius
depends on the QSO luminosity, our models indicate that the observed weak
redshift dependence is too small for the observed QSO luminosity function to be
due to the evolution of a single long-lived population of sources.


title: Transition Region Emission From Very Low Mass Stars

abstract:
  We present results from our cycle 10 HST program to search for transition
region emission in very low-mass, main-sequence stars in the spectral range
M7-M9. Our program is aimed at 1) detecting emission; and 2) distinguishing
between flaring and quiescent origin for the emission. We have obtained
HST/STIS time series observations of three active, very low mass stars (VB 8,
VB 10, and LHS 2065) which show persistent activity in transition region lines
including Si IV, C IV, He II. Emission in transition region lines appears to be
variable between exposures, but is always observed. A strong flare was also
observed in one 10 minute exposure on VB 10. Our results indicate that active,
very low-mass stars maintain a persistent quiescent chromosphere and transition
region that is similar to those observed in active, earlier type M dwarfs, in
contrast to suggestions that these low-mass, main-sequence stars exhibit only
relatively strong flares and no quiescent emission.


title: Meteors And Showers A Millennium Ago

abstract:
  Meteors can be classified into either sporadic meteors or showery meteors. We
compile the meteor records in the astronomical archives in the Chronicle of the
Koryo dynasty (918-1392), and investigate the spatial distribution of meteor
streams along the orbit of the Earth from the 10th century to the 14th century.
We see that meteors from meteor streams signalize themselves over noisy
sporadic meteors, and that the seasonal activity of sporadic meteors was
apparently regular. We discover the presence of a few meteor streams by
analysing about 700 meteors in the Koryo period. We also compile the records of
meteor showers and storms in the chronicles of Korea, Japan, China, Arab, and
Europe, and compare their appearance dates with those of showers obtained
above, as well as with the modern observations. We confirm that the three sets
of data are in agreement with each other. The representative meteor showers are
the Perseids, the Leonids, and the $\eta$-Aquarids/Orionids pair formed by
Halley's comet. The other weak or relic meteor streams are also observable but
uncertain. Hence, we witness the regularity of meteor activity, which is seen
to persist for a millennium.


title: The Magnetar Fields

abstract: We discuss the nature of evolution of the magnetic field in Magnetars.


title: Of Neutrinos and Magnetars

abstract:
  We discuss the nature of neutrino propagation in the presence of strong
magnetic fields of Magnetars.


title: Clusters and Superclusters in the Las Campanas Redshift Survey

abstract:
  Two-dimensional high-resolution density field of galaxies of the Las Campanas
Redshift Survey (LCRS) with a smoothing length 0.8 Mpc/h is used to extract
clusters and groups of galaxies, and a low-resolution field with a smoothing
length 10 Mpc/h to find superclusters of galaxies. Properties of these density
field (DF) clusters and superclusters are studied and compared with the
properties of Abell clusters and superclusters, and LCRS loose groups. We
calculate the DF-cluster luminosity function, and show that most luminous
clusters in high-density environments are about ten times brighter than most
luminous clusters in low-density environments. We present a catalogue of
DF-superclusters and show that superclusters that contain Abell clusters are
richer and more luminous than superclusters without Abell clusters. A pdf file
of the paper with high-resolution figures is available in Tartu Observatory
web-site (http://www.aai.ee/~maret/cosmoweb.html)


title: Cloning Dropouts: Implications for Galaxy Evolution at High Redshift

abstract:
  The evolution of high redshift galaxies in the two Hubble Deep Fields, HDF-N
and HDF-S, is investigated using a cloning technique that replicates z~ 2-3 U
dropouts to higher redshifts, allowing a comparison with the observed B and V
dropouts at higher redshifts (z ~ 4-5). We treat each galaxy selected for
replication as a set of pixels that are k-corrected to higher redshift,
accounting for resampling, shot-noise, surface-brightness dimming, and the
cosmological model. We find evidence for size evolution (a 1.7x increase) from
z ~ 5 to z ~ 2.7 for flat geometries (Omega_M+Omega_LAMBDA=1.0). Simple scaling
laws for this cosmology predict that size evolution goes as (1+z)^{-1},
consistent with our result. The UV luminosity density shows a similar increase
(1.85x) from z ~ 5 to z ~ 2.7, with minimal evolution in the distribution of
intrinsic colors for the dropout population. In general, these results indicate
less evolution than was previously reported, and therefore a higher luminosity
density at z ~ 4-5 (~ 50% higher) than other estimates. We argue the present
technique is the preferred way to understand evolution across samples with
differing selection functions, the most relevant differences here being the
color cuts and surface brightness thresholds (e.g., due to the (1+z)^4 cosmic
surface brightness dimming effect).


title: On the detection of pre-low-mass X-ray binaries

abstract:
  We explore the population of candidate pre-low-mass X-ray binaries in which a
neutron star accretes mass from the wind of a low-mass companion (mass < 2Msun)
in the framework of a binary population synthesis study. The simulated
accretion-luminosity distribution shows a primary peak close to 1e31 erg/s and
a secondary peak near 1e28 erg/s. The relative contribution of the two peaks
depends primarily on the magnitude of the kick velocity imparted to the neutron
star at birth. The secondary peak is negligible for average kick velocities
larger than 200 km/s, but becomes dominant for average kick velocities smaller
than 50 km/s. Regardless of the relative contributions of the two peaks, our
calculations suggest that pre-low-mass X-ray binaries may provide a
non-negligible contribution to the population of discrete low-luminosity X-ray
sources in the Galaxy.


title: Two body relaxation in CDM simulations

abstract:
  N-body simulations of the hierarchical formation of cosmic structures suffer
from the problem that the first objects to form always contain just a few
particles. Although relaxation is not an issue for virialised objects
containing millions of particles, collisional processes will always dominate
within the first structures that collapse. First we quantify how the relaxation
varies with resolution, softening, and radius within isolated equilibrium and
non-equilibrium cuspy haloes. We then attempt to determine how this numerical
effect propagates through a merging hierarchy by measuring the local relaxation
rates of each particle throughout the hierarchical formation of a dark matter
halo. The central few percent of the final structures - a region which one
might naively think is well resolved at the final time since the haloes
contains about 10^6 particles - suffer from high degrees of relaxation. It is
not clear how to interpret the effects of the accumulated relaxation rate, but
we argue that it describes a region within which one should be careful about
trusting the numerical results. Substructure haloes are most affected by
relaxation since they contain few particles at a constant energy for the entire
simulation. We show that relaxation will flatten a cusp in just a few mean
relaxation times of a halo. We explore the effect of resolution on the degree
of relaxation and we find that increasing N slowly reduces the degree of
relaxation proportional to N^{-0.25} rather than proportional to N. Simulated
with the same relative mass resolution (i.e. equal numbers of particles)
cluster mass objects suffer significantly more relaxation than galaxy mass
objects since they form relatively late and therefore more of the particles
spend more time in small N haloes.


title: Detection of type-2 quasars in the radio galaxies B3 0731+438 and 3C 257

abstract:
  We present XMM-Newton observations and spectral fitting of two highly
redshift, [OIII]-luminous, narrow-line radio galaxies, B3 0731+438 and 3C 257.
Their X-ray continua are well fitted by a partial covering model with
intrinsically unabsorbed and absorbed powerlaw components. The spectral models
indicate that both objects harbour highly obscured nuclei, with N_H ~ 0.5 - 2 x
10^23 cm^-2. Correcting for this absorption we find large intrinsic
luminosities in the range L_X ~ 0.2 - 1 x 10^45 erg/s. Thus, both sources are
type-2 quasars.


title:
Modelling the two point correlation function of galaxy clusters in the
  Sloan Digital Sky Survey

abstract:
  We study the clustering properties of the recently compiled SDSS cluster
catalog using the two point correlation function in redshift space. We divide
the total SDSS sample into two richness subsamples, roughly corresponding to
Abell $R\ge 0$ and APM clusters, respectively. If the two point correlations
are modeled as a power law, $\xi(r)=(r_{\circ}/r)^{\gamma}$, then the
best-fitting parameters for the two subsamples are
$r_{\circ}=20.7^{+4.0}_{-3.8} h^{-1}$ Mpc with $\gamma=1.6^{+0.4}_{-0.4}$ and
$r_{\circ}=9.7^{+1.2}_{-1.2}$ with $\gamma=2.0^{+0.7}_{-0.5} h^{-1}$ Mpc,
respectively. Our results are consistent with the dependence of cluster
richness to the cluster correlation length. Finally, comparing the SDSS cluster
correlation function with that predictions from three flat cosmological models
($\Omega_{\rm m}=0.3$) with dark energy (quintessence), we estimate the cluster
redshift space distortion parameter $\beta \simeq \Omega_{\rm
m}^{0.6}/b_{\circ}$ and the cluster bias at the present time. For the
$\Lambda$CDM case we find $\beta=0.2^{+0.029}_{-0.016}$, which is in agreement
with the results based on the large scale cluster motions.


title:
Thermal X-ray emission from shocked ejecta in Type Ia Supernova
  Remnants. Prospects for explosion mechanism identification

abstract:
  The explosion mechanism behind Type Ia supernovae is a matter of continuing
debate. The diverse attempts to identify or at least constrain the physical
processes involved in the explosion have been only partially successful so far.
In this paper we propose to use the thermal X-ray emission from young supernova
remnants originated in Type Ia events to extract relevant information
concerning the explosions themselves. We have produced a grid of thermonuclear
supernova models representative of the paradigms currently under debate: pure
deflagrations, delayed detonations, pulsating delayed detonations and
sub-Chandrasekhar explosions, using their density and chemical composition
profiles to simulate the interaction with the surrounding ambient medium and
the ensuing plasma heating, non-equilibrium ionization and thermal X-ray
emission of the ejecta. Key observational parameters such as electron
temperatures, emission measures and ionization time scales are presented and
discussed. We find that not only is it possible to identify the explosion
mechanism from the spectra of young Type Ia Supernova Remnants, it is in fact
necessary to take the detailed ejecta structure into account if such spectra
are to be modeled in a self-consistent way. Neither element line flux ratios
nor element emission measures are good estimates of the true ratios of ejected
masses, with differences of as much as two or three orders of magnitude for a
given model. Comparison with observations of the Tycho SNR suggests a delayed
detonation as the most probable explosion mechanism. Line strengths, line
ratios, and the centroid of the Fe Kalpha line are reasonably well reproduced
by a model of this kind.


title:
A search for Low Surface Brightness galaxies in the near-infrared II.
  Arecibo HI line observations

abstract:
  A total of 367 Low Surface Brightness galaxies detected in the 2MASS all-sky
near-infrared survey have been observed in the 21 cm HI line using the Arecibo
telescope. All have a K_s-band mean central surface brightness, measured within
a 5 arcsec radius, fainter than 18 mag/arcsec^(2). We present global HI line
parameters for the 107 clearly detected objects and the 21 marginal detections,
as well as upper limits for the undetected objects. The 107 clear detections
comprise 15 previously uncatalogued objects and 36 with a PGC entry only.


title:
A Variable Ultraluminous Supersoft X-ray Source in "The Antennae":
  Stellar-Mass Black Hole or White Dwarf?

abstract:
  The chandra monitoring observations of The Antennae (NGC 4038/39) have led to
the discovery of a variable, luminous, supersoft source (SSS). This source is
only detected at energies below 2 keV and, in 2002 May, reached count rates
comparable to those of the nine ultraluminous X-ray sources (ULXs) detected in
these galaxies. Spectral fits of the SSS data give acceptable results only for
a $\sim$100--90 eV blackbody spectrum with an intrinsic absorption column of
$N_{\rm H} \sim 2-3 \times 10^{21} \rm cm^{-2}$. For a distance of 19 Mpc, the
best-fit observed luminosity increases from 1.7$\times 10^{38}$\ergs in 1999
December to 8.0$\times 10^{38}$\ergs in 2002 May. The intrinsic,
absorption-corrected best-fit luminosity reaches 1.4$\times 10^{40}$ \ergs in
2002 May. The assumption of unbeamed emission would suggest a black hole of
$\ga$100\msun. However, if the emission is blackbody at all times, as suggested
by the steep soft spectrum, the radiating area would have to vary by a factor
of $\sim10^3$, inconsistent with gravitational energy release from within a few
Schwarzschild radii of a black hole. Viable explanations for the observed
properties of the SSS are provided by anisotropic emission from either an
accreting nuclear-burning white dwarf or an accreting stellar-mass black hole.


title: Cirrus models for local and high z SCUBA galaxies

abstract:
  We present a model for the UV to submillimeter emission from stars embedded
in the general interstellar dust in galaxies (the 'infrared cirrus' component).
Such emission is characterized by relatively low optical depths of dust and by
cool (< 30 K) dust temperatures. The model incorporates the stellar population
synthesis model of Bruzual & Charlot and the dust model of Siebenmorgen &
Krugel which includes the effects of small grains/PAHs. We apply the model to
fit the optical to submillimeter spectral energy distributions (SEDs) of nearby
galaxies which are dominated by cirrus emission and find that our simple model
is quite adequate to explain the observed SEDs.
  We also, more controversially, apply this cirrus model to the SEDs of high
redshift sources detected in blank field submillimeter surveys with SCUBA.
Surprisingly, an excellent fit is found for many of these sources, with typical
values for the optical depth A_V and the surface brightness of the stellar
radiation field psi being only a factor 2-3 higher than for nearby galaxies.
This increase is not unreasonable given the expected evolution of dust optical
depth in currently favoured star-formation history models.
  We conclude that the tendency to interpret the high-z SCUBA galaxies as very
highly obscured starbursts may be premature and that these galaxies may be more
closely linked to optically selected high redshift galaxies than previously
assumed.


title:
The Cosmic Microwave Background and Helical Magnetic Fields: the tensor
  mode

abstract:
  We study the effect of a possible helicity component of a primordial magnetic
field on the tensor part of the cosmic microwave background temperature
anisotropies and polarization. We give analytical approximations for the tensor
contributions induced by helicity, discussing their amplitude and spectral
index in dependence of the power spectrum of the primordial magnetic field. We
find that an helical magnetic field creates a parity odd component of gravity
waves inducing parity odd polarization signals. However, only if the magnetic
field is close to scale invariant and if its helical part is close to maximal,
the effect is sufficiently large to be observable. We also discuss the
implications of causality on the magnetic field spectrum.


title: Magnetic Rotator Winds and Keplerian Disks of Hot Stars

abstract:
  We consider rotating magnetic stars with winds and disks. We establish a
theorem that relates the angular velocity of a disk region with no meridional
motion to the angular velocity of the star. Also, we show that for a given
value of the magnetic field strength, if the rotation rate is too high or the
flow velocity into the shock boundary is too low, a Keplerian disk region will
not be formed. We develop a model for the formation of disks in magnetic
rotators through the processes of fill-up and diffusion into Keplerian orbits.
At the end of the fill-up stage the density of the disk increases significantly
and the magnetic force in the disk becomes negligible. We derive analytical
expressions for the inner and outer radii of Keplerian disks in terms of the
stellar rotation rate. A disk can form if the meridional component Bm of the
field at the stellar surface is larger than a minimum value. The radial extent
of the Keplerian region becomes larger for larger values of Bm and is largest
when Bm equals an optimal value. The strengths of the minimum fields required
for Keplerian disk formation in B-type stars varies from order 1G to 10G. In
O-type stars they must be of order 500G. Also, we suggest that the stellar
magnetic fields may be affected by rotationally driven meridional circulation
leading to some of the the observed variations of disks with time.


title: Does the small CMB quadrupole moment suggest new physics?

abstract:
  Motivated by WMAP's confirmation of an anomalously low value of the
quadrupole moment of the CMB temperature fluctuations, we investigate the
effects on the CMB of cutting off the primordial power spectrum P(k) at low
wave numbers. This could arise, for example, from a break in the inflaton
potential, a prior period of matter or radiation domination, or an oscillating
scalar field which couples to the inflaton. We reanalyze the full WMAP
parameter space supplemented by a low-k cutoff for P(k). The temperature
correlations by themselves are better fit by a cutoff spectrum, but including
the TE temperature-polarization spectrum reduces this preference to a 1.4 sigma
effect. Inclusion of large scale structure data does not change the conclusion.
If taken seriously, the low-k cutoff is correlated with optical depth so that
reionization occurs even earlier than indicated by the WMAP analysis.


title: Optimal Weak Lensing Skewness Measurements

abstract:
  Weak lensing measurements are entering a precision era to statistically map
the distribution of matter in the universe. The most common measurement has
been of the variance of the projected surface density of matter, which
corresponds to the induced correlation in alignments of background galaxies.
This measurement of the fluctuations is insensitive to the total mass content,
like using waves on the ocean to measure its depths. But when the depth is
shallow as happens near a beach, waves become skewed. Similarly, a measurement
of skewness in the projected matter distribution directly measures the total
matter content of the universe. While skewness has already been convincingly
detected, its constraint on cosmology is still weak. We address optimal
analyses for the CFHT Legacy Survey in the presence of noise. We show that a
compensated Gaussian filter with a width of 2.5 arc minutes optimizes the
cosmological constraint, yielding $\Delta \Omega_m/\Omega_m\sim 10%$. This is
significantly better than other filters which have been considered in the
literature. This can be further improved with tomography and other
sophisticated analyses.


title:
New constraints on space-time Planck scale fluctuations from established
  high energy astronomy observations

abstract:
  The space-time metric is widely believed to be subject to stochastic
fluctuations induced by quantum gravity at the Planck scale. This work is based
on two different phenomenological approaches being currently made to this
topic, and theoretical models which describe this phenomenon are not dealt with
here. By using the idea developed in one of these two approaches in the
framework of the other one, it is shown that the constraints on the nature of
Planck scale space-time fluctuations already set by the observation of
electrons and gamma-rays with energies above 15 TeV are much stronger than have
been shown so far. It is concluded that for the kind of Planck scale
fluctuations implied by several models, including the most naive one, to be
consistent with the observations, the transformation laws between different
reference frames must be modified in order to let the Planck scale be
observer-independent.


title: Dynamical Stability of Earth-Like Planetary Orbits in Binary Systems

abstract:
  This paper explores the stability of an Earth-like planet orbiting a solar
mass star in the presence of an outer-lying intermediate mass companion. The
overall goal is to estimate the fraction of binary systems that allow
Earth-like planets to remain stable over long time scales. We numerically
determine the planet's ejection time $\tauej$ over a range of companion masses
($M_C$ = 0.001 -- 0.5 $M_\odot$), orbital eccentricities $\epsilon$, and
semi-major axes $a$. This suite of $\sim40,000$ numerical experiments suggests
that the most important variables are the companion's mass $M_C$ and periastron
distance $\rmin$ = $a(1-\epsilon)$ to the primary star. At fixed $M_C$, the
ejection time is a steeply increasing function of $\rmin$ over the range of
parameter space considered here (although the ejection time has a distribution
of values for a given $\rmin$). Most of the integration times are limited to 10
Myr, but a small set of integrations extend to 500 Myr. For each companion
mass, we find fitting formulae that approximate the mean ejection time as a
function of $\rmin$. These functions can then be extrapolated to longer time
scales. By combining the numerically determined ejection times with the
observed distributions of orbital parameters for binary systems, we estimate
that (at least) 50 percent of binaries allow an Earth-like planet to remain
stable over the 4.6 Gyr age of our solar system.


title:
RXTE, ROSAT and ASCA Observations of G347.3-0.5 (RX J1713.7-3946):
  Probing Cosmic Ray Acceleration by a Galactic Shell-Type Supernova Remnant

abstract:
  (Abridged) We present an analysis of the X-ray spectrum of the Galactic
shell-type supernova remnant (SNR) G347.3-0.5 (RX J1713.7-3946). By performing
a joint spectral analysis of data from observations made of G347.3-0.5 using
the ROSAT PSPC, the ASCA GIS and the RXTE PCA, we have fit the spectra of
particular regions of this SNR (including the bright northwestern and
southwestern rims, the northeastern rim and the interior diffuse emission) over
the approximate energy range of 0.5 through 30 keV. Based on the parameters of
the best fit to the spectra using the SRCUT model, we estimate the maximum
energy of cosmic-ray electrons accelerated by the rims of G347.3-0.5 to be
19-25 TeV, assuming a magnetic field strength of 10 microGauss. We present a
broadband (radio to gamma-ray) photon energy flux-spectrum for the northwestern
rim of the SNR, using a synchrotron-inverse Compton model with a variable
magnetic field strength to fit the spectrum. Our fit derived from this model
yields a maximum energy of only 8.8 TeV for the accelerated cosmic-ray
electrons and a magnetic field strength of 150 microGauss. However, our derived
ratio of volumes for TeV emission and X-ray emission (approximately 1000) is
too large to be physically acceptable. We argue that neither non-thermal
bremsstrahlung nor neutral pion decay can adequately describe the TeV emission
from this rim, and therefore the physical process responsible for this emission
is currently uncertain. Finally, we compare the gross properties of G347.3-0.5
with other SNRs known to possess X-ray spectra dominated by non-thermal
emission.


title: The Variable Light Curve of GRB 030329: The Case for Refreshed Shocks

abstract:
  GRB 030329 is unique in many aspects. It has a very low redshift for a GRB,
$z=0.1685$, and is therefore very bright and easy to monitor, making it the
most well studied afterglow to date. It shows a supernova bump in the light
curve, with a spectrum very similar to SN 1998bw, thus establishing with much
better confidence the connection between GRBs and core collapse SNe. There are
also two important physical characteristics that make this burst especially
interesting, aside from its remarkably low redshift. First, unlike most GRB
afterglows, the light curve of GRB 030329 shows a very large variability a few
days after the burst. These fluctuations show a roughly constact amplitude, and
a constant duration $\Delta t$, while $\Delta t/t$ decreases with time $t$.
Second, its $\gamma$-ray energy output and X-ray luminosity at $10 $hr are a
factor of $\sim 20$ and $\sim 30$, respectively, below the average value around
which most GRBs are narrowly clustered. We consider several interpretations for
the variability in the light curve, in the context of different physical
mechanisms, and find that the most likely cause is refreshed shocks, i.e. slow
shells that are ejected from the source and catch up with the afterglow shock
at late times. In GRB 030329 this happens after the jet break, which implies an
approximately constant duration $\Delta t$ of the bumps, in agreement with the
observations. This interpretation also explains the anomalously low initial
energy of this burst, as the total energy of the afterglow shock is increased
by a factor of $\sim 10$ due to the refreshed shocks, thus bringing the total
energy output close to the average value for all GRBs.


title: How Massive Are BALQSO Winds?

abstract:
  We are involved in a program to derive properties of broad absorption line
(BAL) winds in quasars using combined UV and X-ray observations.
  A major obstacle is large uncertainties in the derived BAL column densities
because of partial coverage of the background light source. In this preliminary
report, we circumnavigate those uncertainties by making a simple assumption --
that the relative metal abundances are roughly solar. In this case, the PV
1118,1128 multiplet should have at least 500 times lower optical depth than CIV
1549,1551. Nonetheless, a PV BAL is present in at least half of the
well-measured BALQSOs we studied. We conclude that the strong lines of abundant
species like CIV are typically very optically thick. The total BAL column
densities are N_H > 10^22 cm^-2 (for solar overall metallicity), and they might
be comparable to the X-ray absorbers, of order 10^23 cm^-2, if the BAL gas is
sufficiently ionized. If the column densities in outflowing BAL gas are, in
fact, as large as the X-ray absorbers, it would present a serious challenge to
models of radiatively-driven BAL winds.


title: A Class of Interstellar OH Masers Associated with Protostellar Outflows

abstract:
  Using the Very Large Array, we have detected weak OH maser emission near the
Turner-Welch protostellar source in the W3 OH region. Unlike typical
interstellar OH masers, which are associated with ultra-compact HII regions,
our measured positions and proper motions (from Very Long Baseline
Interferometry) indicate that these OH masers are associated with a bipolar
outflow traced by strong H2O masers. These OH masers may be part of a class of
interstellar OH masers that are associated with very young stars which have yet
to, or may never, create ultra-compact HII regions. This class of OH masers
appears to form near the edges of very dense material (within which H2O masers
form), where total densities drop precipitously and interstellar UV radiation
is sufficient to dissociate the H2O molecules. Observations of this class of OH
masers may be an important way to probe the distribution of this important
molecule in interstellar shocks at arcsecond resolution or better.


title: A correlation of the cosmic microwave sky with large scale structure

abstract:
  We cross correlate the large-scale cosmic microwave background (CMB) sky
measured by WMAP with two probes of large-scale structure at z ~ 1. The hard
X-ray background, measured by the HEAO-1 satellite, is positively correlated
with the WMAP data at the 2.5-3.0 sigma level. The number counts of radio
galaxies in the NVSS survey are also correlated at a slightly weaker level
(2.-2.5 sigma). These correlations appear to arise from both hemispheres on the
sky and are resilient to changes in the levels of masking of the Galaxy and
point sources, suggesting that foregrounds are not responsible for the signal.
The implication is that some of the observed CMB fluctuations arise at low
redshifts. The level of the correlations is consistent with that expected for
the cosmological constant (Omega_Lambda = 0.72) concordance model resulting
from the integrated Sachs-Wolfe effect. Thus, we may be observing dark energy's
effect on the growth of structure.


title:
Self-Similar Hot Accretion onto a Spinning Neutron Star: Matching the
  Outer Boundary Conditions

abstract:
  Medvedev & Narayan have described a hot accretion flow onto a spinning
neutron star in which the gas viscously brakes the spin of the star. Their
self-similar solution has the surprising property that the density, temperature
and angular velocity of the gas at any radius are completely independent of the
outer boundary conditions. Hence, the solution cannot be matched to a general
external medium. We resolve this paradoxical situation by showing that there is
a second self-similar solution which bridges the gap between the original
solution and the external medium. This new solution has an extra degree of
freedom which permits it to match general outer boundary conditions. We confirm
the main features of the analytical results with a full numerical solution.


title: Dynamical Formation of Close Binary Systems in Globular Clusters

abstract:
  We know from observations that globular clusters are very efficient catalysts
in forming unusual short-period binary systems or their offspring, such as
low-mass X-ray binaries (LMXBs; neutron stars accreting matter from low-mass
stellar companions), cataclysmic variables (CVs; white dwarfs accreting matter
from stellar companions), and millisecond pulsars (MSPs; rotating neutron stars
with spin periods of a few ms). Although there has been little direct evidence,
the overabundance of these objects in globular clusters has been attributed by
numerous authors to the high densities in the cores, which leads to an increase
in the formation rate of exotic binary systems through close stellar
encounters. Many such close binary systems emit X-radiation at low luminosities
(L_x < 10^{34} erg/s) and are being found in large numbers through observations
with the Chandra X-ray Observatory. Here we present conclusive observational
evidence for a link between the number of close binaries observed in X-rays in
a globular cluster and the stellar encounter rate of the cluster. We also make
an estimate of the total number of LMXBs in globular clusters in our Galaxy.


title: The elemental abundance pattern in a galaxy at z=2.626

abstract:
  The discovery of metal-poor stars (where metal is any element more massive
than helium) has enabled astronomers to probe the chemical enrichment history
of the Milky Way. More recently, element abundances in gas inside high-redshift
galaxies has been probed through the absorption lines imprinted on the spectra
of background quasars, but these have typically yielded measurements of only a
few elements. Furthermore, interpretation of these abundances is complicated by
the fact that differential incorporation of metals into dust can produce an
abundance pattern similar to that expected from nucleosynthesis by massive
stars. Here we report the observation of over 25 elements in a galaxy at
z=2.626. With these data, we can examine nucleosynthetic processes independent
of the uncertainty arising from depletion. We find that the galaxy was enriched
mainly by massive stars (M > 15 solar masses) and propose that it is the
progenitor of a massive, elliptical galaxy. The detailed abundance patterns
suggest that boron is produced through processes that act independently of
metallicity, and may require alternative mechanisms for the nucleosynthesis of
germanium.


title:
Building Self-Consistent Triaxial Galaxy Models Using Schwarzschild's
  Method

abstract:
  We use Schwarzschild's orbit superposition method to build self-consistent
models of elliptical galaxies with scale-free potentials. Our exhaustive study
of all physical shapes and central densities for galaxies with scale-free
potentials establishes a relationship between the presence of chaos and
self-consistency. The extent and the onset of chaos is studied by varying
parameters of the model which are believed to be its inducers, such as the
steepness of the central density cusp, flatness and triaxiality. We show that
gravitational scattering of the central density cusp plays a dominant role in
restricting the shapes of elliptical galaxies.


title: Gravitational Lensing by Cosmic Strings in the Era of Wide-Field Surveys

abstract:
  Motivated by the recent claim for gravitational lensing by a cosmic string,
we reinvestigate the probability of finding such an event with upcoming
wide-field surveys. If an observed lensing event is suspected to be due to a
string, observations of the vicinity of the event in a circle of diameter L
centered on the observed lens should reveal several additional lensing events.
For a string located nearby (z\lesssim 0.5), we find that observations in a
region of size \approx 1 arcmin^2 will see \sim 100 objects, of which \sim 5
would be lensed by the string, compared to \sim 0.1 lensed by conventional
sources.


title: Power-law expansion in k-essence cosmology

abstract:
  We study spatially flat isotropic universes driven by k-essence. It is shown
that Friedmann and k-field equations may be analytically integrated for
arbitrary k-field potentials during evolution with a constant baryotropic
index. It follows that there is an infinite number of dynamically different
k-theories with equivalent kinematics of the gravitational field. We show that
there is a large "window" of stable solutions, and that the dust-like behaviour
separates stable from unstable expansion. Restricting to the family of power
law solutions, it is argued that the linear scalar field model, with constant
function F, is isomorphic to a model with divergent speed of sound and this
makes them less suitable for cosmological modeling than the non-linear k-field
solutions we find in this paper.


title: Cosmological Results from High-z Supernovae

abstract:
  The High-z Supernova Search Team has discovered and observed 8 new supernovae
in the redshift interval z=0.3-1.2. These independent observations, confirm the
result of Riess et al. (1998a) and Perlmutter et al. (1999) that supernova
luminosity distances imply an accelerating universe. More importantly, they
extend the redshift range of consistently observed SN Ia to z~1, where the
signature of cosmological effects has the opposite sign of some plausible
systematic effects. Consequently, these measurements not only provide another
quantitative confirmation of the importance of dark energy, but also constitute
a powerful qualitative test for the cosmological origin of cosmic acceleration.
We find a rate for SN Ia of 1.4+/-0.5E-04 h^3/Mpc^3/yr at a mean redshift of
0.5. We present distances and host extinctions for 230 SN Ia. These place the
following constraints on cosmological quantities: if the equation of state
parameter of the dark energy is w=-1, then H0 t0 = 0.96+/-0.04, and O_l - 1.4
O_m = 0.35+/-0.14. Including the constraint of a flat Universe, we find O_m =
0.28+/-0.05, independent of any large-scale structure measurements. Adopting a
prior based on the 2dF redshift survey constraint on O_m and assuming a flat
universe, we find that the equation of state parameter of the dark energy lies
in the range -1.48<w<-0.72 at 95% confidence. If we further assume that w>-1,
we obtain w<-0.73 at 95% confidence. These constraints are similar in precision
and in value to recent results reported using the WMAP satellite, also in
combination with the 2dF redshift survey.


title: Nucleosynthesis in Early Stars

abstract:
  We present preliminary results of stellar structure and nucleosynthesis
calculations for some early stars. The study (still in progress) seeks to
explore the expected chemical signatures of second generation low- and
intermediate-mass stars that may have formed out of a combination of Big Bang
and Pop III (Z=0) supernovae material. Although the study is incomplete at this
stage, we find some important features in our models. The initial chemical
composition of these early stars is found to be significantly different to that
given by just scaling the solar composition. The most notable difference is the
lack of nitrogen. This should not affect the structural evolution significantly
as nitrogen will be quickly produced through the CNO cycle due to the presence
of carbon (and oxygen). It should however effect the nucleosynthetic yields. We
also find that our very low metallicity five solar-mass model, with
[Fe/H]=-4.01, does not reach the RGB - it goes directly to the helium burning
phase. It does not experience the first dredge-up either. This is not a new
finding but it will have an effect on the surface chemical evolution of the
stars and should alter the nucleosynthetic yields that we are currently
calculating. Our higher metallicity stars, with a globular cluster composition
at [Fe/H]= -1.40, do experience all the standard phases of evolution but also
have significantly higher surface temperatures and luminosities compared to
solar metallicity stars. Their internal temperatures are also higher which
should again effect the final nucleosynthetic yields.


title:
The Column Density Distribution Function at z=0 from HI Selected
  Galaxies

abstract:
  We have measured the column density distribution function, f(N), at z=0 using
21-cm HI emission from galaxies selected from a blind HI survey. f(N) is found
to be smaller and flatter at z=0 than indicated by high-redshift measurements
of Damped Lyman-alpha (DLA) systems, consistent with the predictions of
hierarchical galaxy formation. The derived DLA number density per unit
redshift, dn/dz =0.058, is in moderate agreement with values calculated from
low-redshift QSO absorption line studies. We use two different methods to
determine the types of galaxies which contribute most to the DLA cross-section:
comparing the power law slope of f(N) to theoretical predictions and analysing
contributions to dn/dz. We find that comparison of the power law slope cannot
rule out spiral discs as the dominant galaxy type responsible for DLA systems.
Analysis of dn/dz however, is much more discriminating. We find that galaxies
with log M_HI < 9.0 make up 34% of dn/dz; Irregular and Magellanic types
contribute 25%; galaxies with surface brightness > 24 mag arcsec^{-2} account
for 22% and sub-L* galaxies contribute 45% to dn/dz. We conclude that a large
range of galaxy types give rise to DLA systems, not just large spiral galaxies
as previously speculated.


title: Mg and Al Yields from Low and Intermediate Mass AGB stars

abstract:
  We investigate the production of aluminium and the heavy magnesium isotopes
in asymptotic giant branch models. We evolve models with a wide range in
initial mass (between 1 and 6Msun), and composition (Z=0.02, 0.008, 0.004). We
evolve the models from the pre-main sequence, through all intermediate stages
including the core helium flash, to near the end of the thermally-pulsing AGB
phase. We performed detailed nucleosynthesis calculations from which we
determine for the first time, the production of the magnesium and aluminium
isotopes as a function of the stellar mass and composition. From our models, we
calculate stellar yields suitable for galactic chemical evolution models. The
most massive AGB models produce the neutron-rich magnesium isotopes, and also
produce Al-26 in substantial quantities via hot bottom burning. We note that
the calculations are subject to many uncertainties, such as the modelling of
the third dredge up, mass-loss and nuclear reaction rates.


title:
The issue of aliasing in PSR B0943+10 I Limitations of the physical
  model

abstract:
  Deshpande and Rankin (DR1999, DR2001) claim that the frequency of the very
narrow feature, in the spectrum of radio flux variations of PSR B0943+10, is an
alias of its actual value. For this, they need to interpret the narrow feature
as a very stable pattern of drifting sub pulses on the polar cap of this
pulsar, within the framework of the Ruderman and Sutherland (1975) model. This
paper discusses several factors within the same framework, that may perturb a
very steady pattern of drifting sub pulses, leading to a broadening of the
spectral feature. One should be cautious in (1) identifying such very narrow
spectral features with a very stable pattern of drifting sub pulses, and (2)
use this picture to resolve the issue of aliasing in PSR B0943+10.


title: The issue of aliasing in PSR B0943+10 II Signal processing arguments

abstract:
  Deshpande and Rankin (DR1999, DR2001) claim that the frequency of the very
narrow feature, in the spectrum of radio flux variations of PSR B0943+10, is an
alias of its actual value. They also claim to have detected an amplitude
modulation on the above phase modulation. This paper argues that both these
claims are unjustified.


title: Simulating a White Dwarf-dominated Galactic Halo

abstract:
  Observational evidence has suggested the possibility of a Galactic halo which
is dominated by white dwarfs (WDs). While debate continues concerning the
interpretation of this evidence, it is clear that an initial mass function
(IMF) biased heavily toward WD precursors (1 < m/Msol < 8), at least in the
early Universe, would be necessary in generating such a halo. Within the
framework of homogeneous, closed-box models of Galaxy formation, such biased
IMFs lead to an unavoidable overproduction of carbon and nitrogen relative to
oxygen (as measured against the abundance patterns in the oldest stars of the
Milky Way). Using a three-dimensional Tree N-body smoothed particle
hydrodynamics code, we study the dynamics and chemical evolution of a galaxy
with different IMFs. Both invariant and metallicity-dependent IMFs are
considered. Our variable IMF model invokes a WD-precursor-dominated IMF for
metallicities less than 5% solar (primarily the Galactic halo), and the
canonical Salpeter IMF otherwise (primarily the disk). Halo WD density
distributions and C,N/O abundance patterns are presented. While Galactic haloes
comprised of ~5% (by mass) of WDs are not supported by our simulations, mass
fractions of ~1-2% cannot be ruled out. This conclusion is consistent with the
present-day observational constraints.


title: Scalar perturbation spectra from warm inflation

abstract:
  We present a numerical integration of the cosmological scalar perturbation
equations in warm inflation. The initial conditions are provided by a
discussion of the thermal fluctuations of an inflaton field and thermal
radiation using a combination of thermal field theory and thermodynamics. The
perturbation equations include the effects of a damping coefficient $\Gamma$
and a thermodynamic potential $V$. We give an analytic expression for the
spectral index of scalar fluctuations in terms of a new slow-roll parameter
constructed from $\Gamma$. A series of toy models, inspired by spontaneous
symmetry breaking and a known form of the damping coefficient, lead to a
spectrum with $n_s>1$ on large scales and $n_s<1$ on small scales.


title:
The proper motion and energy distribution of the isolated neutron star
  RX J0720.4-3125

abstract:
  ESO 4m class telescope and VLT deep imaging of the isolated neutron star RX
J0720.4-3125 reveals a proper motion of mu = 97 +/-12 mas/yr and a blue U-B
color index. We show that a neutron star atmosphere model modified to account
for a limited amount of hydrogen on the star's surface can well represent both
the optical and X-ray data without invoking any additional components. The
large proper motion almost completely excludes the possibility that accretion
from interstellar medium is the powering mechanism of the X-ray emission. It
also implies that the proposed spin down is entirely due to magnetic dipole
losses. RX J0720.4-3125 is thus a very likely middle aged cooling neutron star.
Its overall properties are quite similar to some of the long period radio
pulsars recently discovered, giving further support to the idea that RX
J0720.4-3125 may be a pulsar whose narrow radio beam does not cross the Earth.


title: H_2 absorption in a dense interstellar filament in the Milky Way halo

abstract:
  We investigate interstellar absorption from molecular hydrogen (H_2) and
metals in an intermediate-velocity cloud (IVC) in the direction of the LMC star
Sk -68 80 (HD 36521), based on data from the Far Ultraviolet Spectroscopic
Explorer (FUSE) satellite. H_2 absorption from the Lyman- and Werner bands is
detected in 30 lines at radial velocities v=+50 km/s in this IVC that is
presumably located in the Milky Way halo. We obtain a total logarithmic H_2
column density of log N(H_2)=16.6 (0.5) along with a very low Doppler parameter
of b=1.5 km/s. The presence of molecular material in this cloud is suprising,
given the fact that the OI column density (log N(OI)=14.8 (0.1)) implies a very
low neutral gas column density of ~10^{18} cm^-2 (assuming a solar oxygen
abundance). If the H_2 column density represents its abundance in a
formation-dissociation equilibrium, the data imply that the molecular gas
resides in a small, dense filament at a volume density of ~800 cm^-3 and a
thickness of only 41 Astronomical Units (AU). The molecular filament possibly
corresponds to the tiny-scale atomic structures (TSAS) in the diffuse
interstellar medium observed in high-resolution optical data, HI 21cm
absorption, and in CO emission.


title:
Collisional depolarization and transfer rates of spectral lines by
  atomic hydrogen. II: application to d states of neutral atoms

abstract:
  The theory of collisional depolarization of spectral lines by atomic hydrogen
(Derouich et al. \cite{derouich1}) is extended to $d$ $(l$=2) atomic levels.
Depolarization rates, polarization and population transfer rates are calculated
and results are given as a function of the temperature. Cross sections as a
function of the effective quantum number for a relative velocity of 10
$\textrm{km s}^{-1}$ are also given together with velocity exponents $\lambda$,
if \textbf{they exist}, on the assumption that the cross section varies with
velocity as $v^{-\lambda}$. A discussion of our results is presented.


title: Phantom scalar fields result in inflation rather than Big Rip

abstract:
  There exists a variety of exact solutions of the scalar field Einstein
equations, allowing for ``phantom regions'' with the negative kinetic field
term. These regions can be cut out, their boundaries being sewn together in
such a way that neither the scale factor (along with its first two derivatives)
nor density or pressure will experience a jump. Such a domain surgery
eliminates the ``Big Rip'' scenario, substituting for it the standard
inflation.


title: Double Inflation and the Low CMB Quadrupole

abstract:
  Recent released WMAP data show a low value of quadrupole in the CMB
temperature fluctuations, which confirms the early observations by COBE. In
this paper we consider a model of two inflatons with different masses,
$V(\phi_1,\phi_2)={1\over 2}m_1^2\phi_1^2 + {1 \over 2} m_2^2 \phi_2^2$,
$m_1>m_2$ and study its effects on CMB of suppressing the primordial power
spectrum $P(k)$ at small $k$. Inflation is driven in this model firstly by the
heavier inflaton $\phi_1$, then the lighter field $\phi_2$. But there is no
interruption in between. We numerically calculate the scalar and tensor power
spectra with mode by mode integrations, then fit the model to WMAP temperature
correlations TT and the TE temperature-polarization spectra. Our results show
that with $m_1\sim 10^{14}$ GeV and $m_2\sim 10^{13}$ GeV, this model solves
the problems of flatness {\it etc.} and the CMB quadrupole predicted can be
much lower than the standard power-law $\Lambda$CDM model.


title:
Explosive Disruption of Polytropes: a One Dimensional Hydrodynamic
  Calculation

abstract:
  We study explosions of stars using a one-dimensional Lagrangian hydrodynamics
code. We calculate how much mass is liberated as a function of the energy of
explosion for a variety of pre-explosion stellar structures and for equations
of state with a range of radiation-to-gas pressure ratios. The results show
that simple assumptions about the amount of mass lost in an explosion can be
quite inaccurate, and that even one-dimensional stars exhibit a rich
phenomenology. The mass loss fraction rises from about 50 to 100 per cent as a
function of the explosion energy in an approximately discontinuous manner.
Combining our results with those of other, more realistic models, we suggest
that Nova Scorpii (J1655-40) may have experienced significant mass fallback
because the explosion energy was less than the critical value. We infer that
the original progenitor was less than twice the mass of today's remnant.


title: Neighboring Galaxies' Influence on Rotation Curve Asymmetry

abstract:
  The rotation velocity asymmetry v observed in spiral galaxy HI rotation
curves linearly correlates with the effective potential force from the 10
closest neighboring galaxies normalized for the test particle mass and the
gravitational constant. The magnitude of the potential force from a close
galaxy is proportional to the luminosity of the close galaxy and inversely
proportional to the square of the distance from the close galaxy to the target
galaxy. The correlation coefficient is 0.99 and F test is 0.99. Also, the slope
of the rotation curve in the disk region of a galaxy from rising to flat to
declining is qualitatively correlated with increasing asymmetry and, hence, to
the net force from other galaxies. The result is based on a sample of nine
spiral galaxies with published Cepheid distances and rotation curves and with a
wide range of characteristics. These relationships are interesting not only for
their predictive power but also because (1) they suggest a galaxy's dynamics
and the shape of its rotation curve are related to the potential energy and
distance of neighboring galaxies, (2) they suggest a rising rotation curve in
the disk region is intrinsic, (3) they suggest the Tully-Fisher relationship's
assumption that the mass to intrinsic luminosity ratio is constant among
galaxies is valid, and (4) they are inconsistent with MOND, dark matter, and
the Linear Potential Model.


title:
Measuring Global Galaxy Metallicities Using Emission Line Equivalent
  Widths

abstract:
  We develop a prescription for estimating the interstellar medium oxygen
abundances of distant star-forming galaxies using the ratio EWR_{23} formed
from the equivalent widths of the [O II] 3727, [O III] 4959,5007 and Hbeta
nebular emission lines. This EWR_{23} approach essentially identical to the
widely-used R_{23} method of Pagel et. al (1979). Using data from three
spectroscopic surveys of nearby galaxies, we conclude that the emission line
equivalent width ratios are a good substitute for emission line flux ratios in
galaxies with active star formation. The RMS dispersion between EWR_{23} and
the reddening-corrected R_{23} values is sigma(log(R_{23})) < 0.08 dex. This
dispersion is comparable to the emission-line measurement uncertainties for
distant galaxies in many spectroscopic galaxy surveys, and is smaller than the
uncertainties of sigma(O/H) ~ 0.15 dex inherent in strong-line metallicity
calibrations. Because equivalent width ratios are, to first order, insentitive
to interstellar reddening, emission line equivalent width ratios may actually
be superior to flux ratios when reddening corrections are not available. The
EWR_{23} method presented here is likely to be most useful for statistically
estimating the mean metallicities for large samples of galaxies to trace their
chemical properties as a function of redshift or environment. The approach
developed here is used in a companion paper (Kobulnicky et. al 2003) to measure
the metallicities of star-forming galaxies at z=0.2-0.8 in the Deep
Extragalactic Evolutionary Probe spectroscopic survey of the Groth Strip.


title:
The DEEP Groth Strip Survey XII: 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
for 56 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
uncertainties of 0.17 dex. The 56 DGSS galaxies collectively exhibit a
correlation between B-band luminosity and metallicity, i.e., an L-Z relation.
Subsets of DGSS galaxies binned by redshift also exhibit L-Z correlations but
with different zero points. Galaxies in the highest redshift bin (z=0.6-0.82)
are brighter by ~1 mag compared to the lowest redshift bin (z=0.26-0.40) and
brighter by ~1-2 mag compared to local (z<0.1) field galaxies. This 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). Thus, both the slope and zero
point of the L-Z relation appear to evolve. Either the least-luminous DGSS
field galaxies have faded by 1--2 mag due to decreasing levels of star
formation, or they have experienced an increase in the mean metallicity of the
interstellar medium by factors of 1.3--2 (0.1-0.3 dex). The relatively greater
degree of luminosity and metallicity evolution seen among the lower luminosity
(sub L*) galaxies in the last 8 Gyr implies either a more protracted assembly
process, or a more recent formation epoch compared to more luminous L*
galaxies. (abridged)


title: Generalized Uncertainty Principle and Dark Matter

abstract:
  There have been proposals that primordial black hole remnants (BHRs) are the
dark matter, but the idea is somewhat vague. Recently we argued that the
generalized uncertainty principle (GUP) may prevent black holes from
evaporating completely, in a similar way that the standard uncertainty
principle prevents the hydrogen atom from collapsing. We further noted that the
hybrid inflation model provides a plausible mechanism for production of large
numbers of small black holes. Combining these we suggested that the dark matter
might be composed of Planck-size BHRs. In this paper we briefly review these
arguments, and discuss the reheating temperature as a result of black hole
evaporation.


title:
Extraplanar Emission-Line Gas in Edge-On Spiral Galaxies. I. Deep
  Emission-Line Imaging

abstract:
  The extraplanar diffuse ionized gas (eDIG) in 17 nearby, edge-on disk
galaxies is studied using deep Taurus Tunable Filter Halpha and [N II] lambda
6583 images and conventional interference filter Halpha + [N II] lambda 6548,
6583 images which reach flux levels generally below about 1 x 10^{-17} erg
s^{-1} cm^{-2} arcsec^{-2}. [N II] lambda 6583/Halpha excitation maps are
available for 10 of these objects. All but one galaxy in the sample exhibit
eDIG. The contribution of the eDIG to the total Halpha luminosity is relatively
constant, of order 12 +/- 4%. The Halpha scale height of the eDIG derived from
a two-exponential fit to the vertical emission profile ranges from 0.4 kpc to
17.9 kpc, with an average of 4.3 kpc. This average value is noticeably larger
than the eDIG scale height measured in our Galaxy and other galaxies. This
difference in scale height is probably due in part to the lower flux limits of
our observations. A quantitative analysis of the topology of the eDIG confirms
that several galaxies in the sample have a highly structured eDIG morphology.
The distribution of the eDIG emission is often correlated with the locations of
the H II regions in the disk. A strong correlation is found between the star
formation rate (IR luminosity) per unit disk area and the extraplanar ionized
mass, providing further support for a strong connection between the disk and
eDIG components in these galaxies. The excitation maps confirm that the [N
II]/Halpha ratios are systematically higher in the eDIG than in the disk. More
detail is given in Paper II. (abridged)


title:
The Katzman Automatic Imaging Telescope Gamma-Ray Burst Alert System,
  and Observations of GRB 020813

abstract:
  We present the technical details of the gamma-ray burst (GRB) alert system of
the Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory, and the
successful observations of the GRB 020813 optical afterglow with this system.
KAIT responds to GRB alerts robotically, interrupts its pre-arranged program,
and takes a sequence of images for each GRB alert. A grid-imaging procedure is
used to increase the efficiency of the early-time observations. Different
sequences of images have been developed for different types of GRB alerts. With
relatively fast telescope slew and CCD readout speed, KAIT can typically
complete the first observation within 60 s after receiving a GRB alert,
reaching a limiting magnitude of $\sim 19$.
  Our reduction of the GRB 020813 data taken with KAIT shows that unfiltered
magnitudes can be reliably transformed to a standard passband with a precision
of $\sim$5%, given that the color of the object is known. The GRB 020813
optical afterglow has an exceptionally slow early-time power-law decay index,
though other light-curve parameters and the optical spectral index are fairly
typical of GRBs.


title:
On the Origin of Lyman-$\alpha$ Blobs at High Redshift: Kinematic
  Evidence for a Hyperwind Galaxy at z = 3.1

abstract:
  We present deep optical spectroscopy of an extended Ly$\alpha$ emission-line
blob located in an over-dense region at redshift $z \approx 3.1$; `blob 1' of
Steidel et al. (2000). The origin of such Ly$\alpha$ blobs has been debated for
some time; two of the most plausible models are (1) that it comes from a
dust-enshrouded, extreme starburst galaxy with a large-scale galactic outflow
(superwind/hyperwind) or (2) that it is the cooling radiation of proto-galaxies
in dark matter halos. Examination of the kinematic properties of the Ly$\alpha$
emission-line gas should allow us to determine its nature. With this
motivation, we performed optical spectroscopy of `blob 1' using the Subaru
Telescope, and found that its kinematic properties can be well explained in
terms of superwind activity.


title: Magnetically Arrested Disk: An Energetically Efficient Accretion Flow

abstract:
  We consider an accretion flow model originally proposed by Bisnovatyi-Kogan &
Ruzmaikin (1974), which has been confirmed in recent 3D MHD simulations. In the
model, the accreting gas drags in a strong poloidal magnetic field to the
center such that the accumulated field disrupts the axisymmetric accretion flow
at a relatively large radius. Inside the disruption radius, the gas accretes as
discrete blobs or streams with a velocity much less than the free-fall
velocity. Almost the entire rest mass energy of the gas is released as heat,
radiation and mechanical/magnetic energy. Even for a non-rotating black hole,
the efficiency of converting mass to energy is of order 50% or higher. The
model is thus a practical analog of an idealized engine proposed by Geroch and
Bekenstein.


title: Planet finding prospects for the Space Interferometry Mission

abstract:
  The Space Interferometry Mission (SIM) will make precise astrometric
measurements that can be used to detect planets around nearby stars. We have
simulated SIM observations and estimated the ability of SIM to detect planets
with given masses and orbital periods and measure their orbital elements. We
combine these findings with an estimate of the mass and period distribution of
planets determined from radial velocity surveys to predict the number and
characteristics of planets SIM would likely find. Our predictions are based on
extrapolating the mass distribution of known extrasolar planets by up to a
factor of 100. This extrapolation provides the best prediction we can make of
the actual number of planets that SIM will detect and characterize, but may
substantially over- or underestimate the frequency of Earth-mass planets,
especially if these form by a different mechanism than giant planets. We find
that SIM is likely to detect 1-5 planets with masses less than 3 M_Earth
(depending on mission parameters). SIM would measure masses and orbits with 30%
accuracy for 0-2 of these planets, but is unlikely to measure orbits with 10%
accuracy for more than one of them. SIM is likely to detect 5-25 planets with
mass less than 20 M_Earth, measure masses and orbits with 30% accuracy for 2-12
of these, and measure masses and orbits with 10% accuracy for 2-8 such planets.
SIM is likely to find 25-160 planets of all masses, depending on the observing
strategy and mission lifetime.


title: Phase Separation in Giant Planets: Inhomogeneous Evolution of Saturn

abstract:
  We present the first models of Jupiter and Saturn to couple their evolution
to both a radiative-atmosphere grid and to high-pressure phase diagrams of
hydrogen with helium and other admixtures. We find that prior calculated phase
diagrams in which Saturn's interior reaches a region of predicted helium
immiscibility do not allow enough energy release to prolong Saturn's cooling to
its known age and effective temperature. We explore modifications to published
phase diagrams that would lead to greater energy release, and propose a
modified H-He phase diagram that is physically reasonable, leads to the correct
extension of Saturn's cooling, and predicts an atmospheric helium mass fraction
Y_atmos = 0.185, in agreement with recent estimates. We also explore the
possibility of internal separation of elements heavier than helium, and find
that, alternatively, such separation could prolong Saturn's cooling to its
known age and effective temperature under a realistic phase diagram and heavy
element abundance (in which case Saturn's Y_atmos would be solar but heavier
elements would be depleted). In none of these scenarios does Jupiter's interior
evolve to any region of helium or heavy-element immiscibility: Jupiter evolves
homogeneously to the present day. We discuss the implications of our
calculations for Saturn's primordial core mass.


title: Taurus Tunable Filter -- seven years of observing

abstract:
  The Taurus Tunable Filter (TTF) has now been in regular use for seven years
on the Anglo-Australian Telescope. The instrument was also used for three years
(1996--1999) on the William Herschel Telescope. We present a brief review of
the different applications in order to illustrate the versatility of tunable
filters in optical/IR spectrophotometric imaging. Tunable filters are now
planned or are under development for 6-10m class telescopes which ensures their
use for years to come.


title: Physics of Structure Formation in the Universe

abstract:
  In recent years, unprecedented progress in observational cosmology has
revealed a great deal of information about the formation and evolution of
structures in the universe. This, in turn, has raised many challenging issues
for the theorists. In the thesis, we have addressed two such key issues,
namely, (a) the formation of baryonic structures and (b) the nature of dark
matter and dark energy and the limitations in determining their nature from
observations. The main results from the thesis are: (i) The baryons in the
intergalactic medium at redshifts z \sim 2.5 can be modelled (both analytically
and semi-analytically) by accounting for the non-linearities in the density
field through lognormal approximation. Our results agree with observations, and
can be used for constraining parameters related to the baryons. (ii) A simple
model based on baryon conservation, along with observational estimates of
cosmic star formation rate, correctly predicts the abundance of damped
Lyman-alpha systems in the universe. (iii) The redshift distribution of gamma
ray bursts can, in principle, be used for studying the physical conditions of
the universe before reionization epoch (which is otherwise a difficult task).
(iv) It might be possible that the dark matter and dark energy arise from the
same scalar field, provided the equation of state has a dependence on the
length scale. The possibility of using the kinematical and geometrical
measurements (such as supernova observations) for determining the nature and
evolution of the dark energy is discussed.


title: The Critical Rotation of Strange Stars and Rapidly Rotating Pulsars

abstract:
  We utilize the bulk viscosity of interacting strange quark matter to
reevaluate the damping time scale. The presence of medium effect of bulk
viscosity leads to a stronger damping of r-modes, which can be over an order of
magnitude for realistic parameters. We find that the r-mode instability window
is narrowed due to the medium effect, and hence when a pulsar reaches the
instability window it will only slow down by gravitational wave emission to a
period of 1.78msec instead of 2.5msec given by early estimate. As a theoretical
upper rotation limit of pulsars, the period of 1.78msec is very close to the
two most rapidly spinning pulsars known, with periods of about 1.6msec.


title:
On the possible role of massive neutrinos in cosmological structure
  formation

abstract:
  In addition to the problem of galaxy formation, one of the greatest open
questions of cosmology is represented by the existence of an asymmetry between
matter and antimatter in the baryonic component of the Universe. We believe
that a net lepton number for the three neutrino species can be used to
understand this asymmetry. This also implies an asymmetry in the
matter-antimatter component of the leptons. The existence of a nonnull lepton
number for the neutrinos can easily explain a cosmological abundance of
neutrinos consistent with the one needed to explain both the rotation curves of
galaxies and the flatness of the Universe. Some propedeutic results are
presented in order to attack this problem.


title: SDSS J1650+4251: A New Gravitational Lens

abstract:
  We report that the Sloan Digital Sky Survey quasar SDSS J165043.44+425149.3
is gravitationally lensed into two images, based on observations obtained with
the WIYN 3.5 m telescope at the Kitt Peak National Observatory. The lensed
quasar, at a redshift of z=1.54, appears as two images separated by 1.2" with
B-band magnitudes of 17.8 and 20.0. The lensing galaxy is clearly detected in
I-band images obtained in 0.3" seeing, after point spread function subtraction
of the two quasar images. A strong metal-line absorption system is also
identified in the unresolved SDSS spectrum of the double quasar, suggesting a
plausible lens redshift of z=0.58. The UBRI flux ratios of the pair vary
significantly from 8.5:1 in the blue to 5.4:1 in the red, a difference of 0.5
magnitudes, and may indicate the presence of microlensing in one or both quasar
components. The predicted differential time delay between quasar images is on
the order of one month, assuming the intervening absorption system is due to
the lensing galaxy.


title: Some Thoughts on the Quantum Theory of de Sitter Space

abstract:
  This is a summary of two lectures I gave at the Davis Conference on Cosmic
Inflation. I explain why the quantum theory of de Sitter (dS) space should have
a finite number of states and explore gross aspects of the hypothetical quantum
theory, which can be gleaned from semiclassical considerations. The constraints
of a self-consistent measurement theory in such a finite system imply that
certain mathematical features of the theory are unmeasurable, and that the
theory is consequently mathematically ambiguous. There will be a universality
class of mathematical theories all of whose members give the same results for
local measurements, within the {\it a priori} constraints on the precision of
those measurements, but make different predictions for unmeasurable quantities,
such as the behavior of the system on its Poincare recurrence time scale. A toy
model of dS quantum mechanics is presented.


title: Particle Physics and Cosmology

abstract:
  In the first Lecture, the Big Bang and the Standard Model of particle physics
are introduced, as well as the structure of the latter and open issues beyond
it. Neutrino physics is discussed in the second Lecture, with emphasis on
models for neutrino masses and oscillations. The third Lecture is devoted to
supersymmetry, including the prospects for discovering it at accelerators or as
cold dark matter. Inflation is reviewed from the viewpoint of particle physics
in the fourth Lecture, including simple models with a single scalar inflaton
field: the possibility that this might be a sneutrino is proposed. Finally, the
fifth Lecture is devoted to topics further beyond the Standard Model, such as
grand unification, baryo- and leptogenesis - that might be due to sneutrino
inflaton decays - and ultra-high-energy cosmic rays - that might be due to the
decays of metastable superheavy dark matter particles.


title:
Flat cosmological models with massive scalar field in gauge theories of
  gravity

abstract:
  Solutions of gravitational equations of gauge theories of gravity in
homogeneous isotropic world with massive scalar field are investigated in the
case of flat cosmological models. Special attention is dedicated to general
behavior of solutions on contraction stage. It is shown, that on expansion
stage inflationary solutions are generic feature of the model. At the same time
on contraction stage an effective equation of state is similar to the case of
massless scalar field $p=\rho$ at the beginning of evolution and tends to the
equation of ultrarelativistic gas $p=\rho/3$. The Hubble parameter tends to
some negative value on contraction stage, depending on the mass of the scalar
field. Nonsingular solutions in this model are unstable.


title:
Quantifying dust and the ultraviolet radiation-density in the local
  universe

abstract:
  A sample of local galaxies for which far infrared and uv fluxes are available
is used to estimate the characteristic dust extinction in galaxies and to test
whether standard dust properties are plausible. Assuming galaxies can be
characterized by a single dust optical depth (certainly not valid for galaxies
with a dominant starburst component), the infrared excess and ultraviolet
colours of local galaxies are found to be consistent with normal Milky Way
dust, with a mean value for E(B-V) of 0.16. A significant fraction of the dust
heating is due to older, lower mass stars, and this fraction increases towards
earlier galaxy types.
  Analysis of F_fir/F_uv versus uv colour diagrams for starburst galaxies in
terms of a simple screen dust model does not support a Calzetti (1999) rather
than a Milky Way extinction law, though the absence of the expected strong 2200
A feature in several galaxies with IUE spectra does show that more detailed
radiative transfer models are needed, probably with non-spherical geometry.
  A simple treatment in which the 100/60 mu flux-ratio is used to subtract the
optically thick starburst contribution to the far infrared radiation results in
lower extinction estimates for the optically thin cirrus component, with a mean
E(B-V) of 0.10
  The uv luminosity density, corrected for dust extinction, is derived and a
value for the local mean star-formation rate inferred. This is consistent with
previous estimates from uv surveys and from H-alpha surveys.


title: Clusters of Galaxies in the SDSS

abstract:
  I review here past and present research on clusters and groups of galaxies
within the Sloan Digital Sky Survey (SDSS). In particular, I discuss the C4
algorithm which is designed to search for clusters within a 7-dimensional
data-space, i.e., simultaneous in both color & space. The C4 catalog has a well
defined selection function based on mock SDSS galaxy catalogs constructed from
the Hubble Volume simulation, and is >90% complete, with <10% contamination,
for halos with M200 > 10^14 Msolar at z<0.14. Furthermore, the observed summed
r-band luminosity of C4 clusters is linearly related to M200 with <30% scatter
at any given halo mass. I also briefly review the selection and observation of
Luminous Red Galaxies (LRGs) and demonstrate that these galaxies have a similar
clustering strength as clusters and groups of galaxies. I outline a new
collaboration planning to obtain redshifts for 10,000 LRGs at 0.4<z<0.7 using
the SDSS photometric data and the AAT 2dF instrument. Finally, I review the
role of clusters and groups of galaxies in the study of galaxy properties as a
function of environment. In particular, I discuss the ``SFR--Density'' and
``Morphology--Radius'' relations for the SDSS and note that both of these
relationships have a critical density (or ``break'') at a projected local
galaxy density of ~1 h_75^2 Mpc^-2 (or between 1 to 2 virial radii). One
possible physical mechanism to explain this observed critical density is the
stripping of warm gas from the halos of in-falling spiral galaxies, thus
leading to a slow strangulation of star-formation in these galaxies. This
scenario is consistent with the recent discovery (within the SDSS) of an excess
of ``Passive'' or ``Anemic'' spiral galaxies located within the in-fall regions
of C4 clusters.


title: History of the Local Group

abstract:
  It is suggested that M31 was created by the early merger, and subsequent
violent relaxation, of two or more massive metal-rich ancestral galaxies within
the core of the Andromeda subgroup of the Local Group. On the other hand the
evolution of the main body of the Galaxy appears to have been dominated by the
collapse of a single ancestral object, that subsequently evolved by capturing a
halo of small metal-poor companions. It remains a mystery why the globular
cluster systems surrounding galaxies like M33 and the LMC exhibit such striking
differences in evolutionary history. It is argued that the first generation of
globular clusters might have been formed nearly simultaneously in all
environments by the strong pressure increase that accompanied cosmic
reionization. On the other hand subsequent generations of globulars may have
formed during starbursts that were triggered by collisions and mergers of gas
rich galaxies.


title: The origin of the Fe K features in Markarian 205 and Markarian 509

abstract:
  We examine the 3-10 keV EPIC spectra of Mrk 205 and Mrk 509 to investigate
their Fe K features. The most significant feature in the spectra of both
objects is an emission line at 6.4 keV. The spectra can be adequately modelled
with a power law and a relatively narrow (sigma < 0.2 keV) Fe K alpha emission
line. Better fits are obtained when an additional Gaussian emission line,
relativistic accretion-disk line, or Compton reflection from cold material, is
added to the spectral model. We obtain similar goodness of fit for any of these
three models, but the model including Compton reflection from cold material
offers the simplest, physically self-consistent solution, because it only
requires one reprocessing region. Thus the Fe K spectral features in Mrk 205
and Mrk 509 do not present strong evidence for reprocessing in the inner,
relativistic parts of accretion disks.