title:
The Apparent Host Galaxy of PKS 1413+135: HST, ASCA and VLBA
  Observations

abstract:
  PKS 1413+135 (z=0.24671) is one of very few radio-loud AGN with an apparent
spiral host galaxy. Previous authors have attributed its nearly exponential
infrared cutoff to heavy absorption but have been unable to place tight limits
on the absorber or its location in the optical galaxy. In addition, doubts
remain about the relationship of the AGN to the optical galaxy given the
observed lack of re-emitted radiation. We present new HST, ASCA and VLBA
observations which throw significant new light on these issues. The HST
observations reveal an extrremely red color (V-H = 6.9 mag) for the active
nucleus of PKS 1413+135, requiring both a spectral turnover at a few microns
due to synchrotron aging and a GMC-sized absorber. We derive an intrinsic
column N_H = 4.6^{+2.1}_{-1.6} times 10^{22}cm^{-2} and covering fraction f =
0.12^{+0.07}_{-0.05}. As the GMC is likely in the disk of the optical galaxy,
our sightline is rather unlikely (P ~ 2 times 10^{-4}). The properties of the
GMC typical of GMCs in our own galaxy. The HI absorber appears centered 25
milliarcseconds away from the nucleus, while the X-ray and nearly all of the
molecular absorbers must cover the nucleus, implying a complicated geometry and
cloud structure, with a molecular core along our line of sight to the nucleus.
Interestingly, the HST/NICMOS data require the AGN to be decentered relative to
the optical galaxy by 13 +/- 4 milliarcseconds. This could be interpreted as
suggestive of an AGN location far in the background compared to the optical
galaxy, but it can also be explained by obscuration and/or nuclear structure,
which is more consistent with the observed lack of multiple images.


title: Clusters of galaxies in the local universe

abstract:
  We use a matched filter algorithm to find and study clusters in both N-body
simulations artificially populated with galaxies and the 2MASS survey. In
addition to numerous checks of the matched filter algorithm, we present results
on the halo multiplicity function and the cluster number function. For a subset
of our identified clusters we have information on X-ray temperatures and
luminosities which we cross-correlate with optical richness and galaxy velocity
dispersions. With all quantities normalized by the spherical radius
corresponding to a mass overdensity of Delta_M=200 or the equivalent galaxy
number overdensity of Delta_N=200Omega^{-1}~666, we find that the number of
L>L_* galaxies in a cluster of mass M_{200} is log N_{*666} = (1.44 +/-
0.17)+(1.10 +/- 0.09)log(M_{200}h/10^{15}Msun) where the uncertainties are
dominated by the scatter created by three choices for relating the observed
quantities to the cluster mass. The region inside the virial radius has a
K-band cluster mass-to-light ratio of (M/L)_K=(116 +/- 46)h which is
essentially independent of cluster mass. Integrating over all clusters more
massive than M_{200}=10^{14}Msun/h, the virialized regions of clusters contain
~7% of the local stellar luminosity, quite comparable to the mass fraction in
such objects in currently popular LambdaCDM models.


title: Structural Parameters and Dynamical Masses for Globular Clusters in M33

abstract:
  Using high-dispersion spectra from the HIRES echelle spectrograph on the Keck
I telescope, we measure velocity dispersions for 4 globular clusters in M33.
Combining the velocity dispersions with integrated photometry and structural
parameters derived from King-Michie model fits to WFPC2 images, we obtain
mass-to-light ratios for the clusters. The mean value is M/LV = 1.53 +/- 0.18,
very similar to the M/LV of Milky Way and M31 globular clusters. The M33
clusters also fit very well onto the fundamental plane and binding energy -
luminosity relations derived for Milky Way GCs. Dynamically and structurally,
the four M33 clusters studied here appear virtually identical to Milky Way and
M31 GCs.


title: The Roles of Small Telescopes in a Virtual Observatory Environment

abstract:
  The advent of the Virtual Observatory (VO) concept signals a pradigm shift in
the way astronomy will be done in the era of information abundance and
ubiquitous networking. Small telescopes will be playing a number of essential
roles in this new research environment, probably contributing a major portion
of all data taken in astronomy, both as surveying instruments, and as follow-up
facilities. In this review we describe the VO concept and its background, and
how small telescopes will fit in this emergent way of doing astronomy in the
21st century.


title:
Predictions of the High-Energy Emission from BL Lac objects: The Case of
  W Comae

abstract:
  Spectral fitting of the radio through hard X-ray emission of BL Lac objects
has previously been used to predict their level of high-energy (GeV - TeV)
emission. In this paper, we point out that such spectral fitting can have very
large uncertainties with respect to predictions of the VHE emission. This is
demonstrated with the example of W Comae. We show that the best currently
available contemporaneous optical - X-ray spectrum of W Comae still allows for
a large range of possible parameters, resulting in drastically different > 40
GeV fluxes. We find that all acceptable leptonic-model fits to the optical -
X-ray emission of W Comae predict a cut-off of the high-energy emission around
~ 100 GeV. We suggest that detailed measurements and analysis of the soft X-ray
variability of W Comae may be used to break the degeneracy in the choice of
possible fit parameters, and thus allow a more reliable prediction of the VHE
emission from this object. Using the available soft X-ray variability measured
by BeppoSAX, we predict a > 40 GeV flux from W Comae of ~ (0.4 - 1) * 10^{-10}
photons/(cm^2 s) with no significant emission at E > 100 GeV for a leptonic jet
model. We compare our results concerning leptonic jet models with detailed
predictions of the hadronic Synchrotron-Proton Blazar model. This hadronic
model predicts > 40 GeV fluxes very similar to those found for the leptonic
models, but results in > 100 GeV emission which should be clearly detectable
with future high-sensitivity instruments like VERITAS. Thus, we suggest this
object as a promising target for VHE gamma-ray and co-ordinated broadband
observations to distinguish between leptonic and hadronic jet models for
blazars.


title: Ring Nebulae around Massive Stars throughout the HR Diagram

abstract:
  Massive stars evolve across the HR diagram, losing mass along the way and
forming a variety of ring nebulae. During the main sequence stage, the fast
stellar wind sweeps up the ambient interstellar medium to form an interstellar
bubble. After a massive star evolves into a red giant or a luminous blue
variable, it loses mass copiously to form a circumstellar nebula. As it evolves
further into a WR star, the fast WR wind sweeps up the previous mass loss and
forms a circumstellar bubble. Observations of ring nebulae around massive stars
not only are fascinating, but also are useful in providing templates to
diagnose the progenitors of supernovae from their circumstellar nebulae. In
this review, I will summarize the characteristics of ring nebulae around
massive stars throughout the HR diagram, show recent advances in X-ray
observations of bubble interiors, and compare supernovae's circumstellar
nebulae with known types of ring nebulae around massive stars.


title: Magnetic Pressure-Density Correlation in Compressible MHD Turbulence

abstract:
  We discuss magnetic pressure and density fluctuations in strongly turbulent
isothermal MHD flows in "1+2/3" dimensions. We first consider "simple"
nonlinear MHD waves, which allow us show that the slow and fast modes have
different asymptotic dependences of the magnetic pressure B^2 vs. rho. For the
slow mode, B^2 ~= c_1-c_2 rho, while for the fast mode, B^2 ~= rho^2. We also
perform a perturbative analysis to investigate Alfven wave pressure, recovering
previous results that B^2 ~= rho^gamma_e, with gamma_e ~= 2, 3/2 and 1/2 at
respectively large, moderate and low M_a. This variety of scalings implies that
a single polytropic description of magnetic pressure is not possible in
general, since the relation between B^2 and rho depends on which mode dominates
the density fluctuation production, which in turn depends on the angle between
the magnetic field and the direction of wave propagation, and on the Alfvenic
Mach number M_a. Typically, at small M_a, the slow mode dominates, and B is
ANTIcorrelated with rho. At large M_a, both modes contribute to density
fluctuation production, and the magnetic pressure decorrelates from density,
exhibiting a large scatter, which however decreases towards higher densities.
In this case, the unsystematic behavior of the magnetic pressure causes the
density PDF to generally maintain the lognormal shape corresponding to
non-magnetic isothermal turbulence, except when the slow mode dominates, in
which case the PDF develops an excess at low densities. Our results are
consistent with the low values and apparent lack of correlation between the
magnetic field strength and density in surveys of the lower-density molecular
gas, and also with the recorrelation apparently seen at higher densities, if
M_a is relatively large there.


title:
Witnessing the Hierarchical Assembly of the Brightest Cluster Galaxy in
  a Cluster at z=1.26

abstract:
  We have obtained a new high-resolution K'-band image of the central region of
the rich X-ray cluster RX J0848.9+4452 at z=1.26. We found that the brightest
cluster galaxy (BCG) in the cluster is clearly separated into two distinct
objects. Whereas the optical to near-infrared colors of the objects are
consistent with the predictions of passive evolution models for galaxies formed
at high redshift, the luminosities of the two galaxies are both considerably
fainter than predicted by passive evolution of BCG's in low and intermediate
redshift clusters. We argue that this is evidence of an on-going merger of
normal cluster ellipticals to form the dominant galaxy in the core of RX
J0848.9+4452. The two galaxies appear to point towards the nearby cluster ClG
J0848+4453 and are aligned with the outer X-ray contour of their parent
cluster, supporting a model of BCG formation by collimated infall along the
surrounding large-scale structure.


title: The YY Isochrones for alpha-element Enhanced Mixtures

abstract:
  We present a new set of isochrones in which the effect of the alpha-element
enhancement is fully incorporated. These isochrones are an extension of the
already published set of YY Isochrones (Yi et al. 2001: Paper 1), constructed
for the scaled-solar mixture. As in Paper 1, helium diffusion and convective
core overshoot have been taken into account.The range of chemical compositions
covered is 0.00001 < Z < 0.08. The models were evolved from the
pre-main-sequence stellar birthline to the onset of helium burning in the core.
The age range of the full isochrone set is 0.1 -- 20 Gyr, while younger
isochrones of age 1 -- 80 Myr are also presented up to the main-sequence
turn-off. Combining this set with that of Paper 1 for scaled-solar mixture
isochrones, we provide a consistent set of isochrones which can be used to
investigate populations of any value of alpha-enhancement. We confirm the
earlier results of Paper 1 that inclusion of alpha-enhancement effects further
reduces the age estimates of globular clusters by approximately 8 percent if
[alpha/Fe]=+0.3. It is important to note the metallicity dependence of the
change in age estimates (larger age reductions in lower metallicities). This
reduces the age gap between the oldest metal-rich and metal-poor Galactic
stellar populations and between the halo and the disk populations. The
isochrone tables, together with interpolation routines have been made available
via internet; http://www.astro.yale.edu/demarque/yyiso.html
http://www-astro.physics.ox.ac.uk/~yi/yyiso.html
http://csaweb.yonsei.ac.kr/~kim/yyiso.html


title: Cosmic Expansion and Ho: A Retro- and Pro-Spective Note

abstract:
  Attempts to measure extragalactic distances over the last 90 years are
briefly described. It follows a short history of the discovery of the expansion
of space. Reasons are discussed for the decrease of the Hubble constant from
Ho~500 originally to Ho<~60 at present. Remaining problems with Cepheids as
local distance calibrators are outlined.


title:
WhiteDwarf.org - Establishing a permanent endowment for the Whole Earth
  Telescope

abstract:
  White Dwarf Research Corporation is a 501(c)(3) non-profit organization
dedicated to scientific research and public education on topics relevant to
white dwarf stars. It was founded in 1999 in Austin, Texas to help fulfill the
need for an alternative research center where scarce funding dollars could be
used more efficiently, and to provide a direct link between astronomers who
study white dwarf stars and the general public. Due to its administrative
simplicity, WDRC can facilitate the funding of multi-institutional and
international collaborations, provide seamless grant portability, minimize
overhead rates, and actively seek non-governmental funding sources. I describe
the motivation for, and current status of, one of the long-term goals of WDRC:
to establish a permanent endowment for the operation of the Whole Earth
Telescope. I pay particular attention to fund-raising efforts through the
website at http://WhiteDwarf.org/donate/


title: GAIA and the Extragalactic Distance Scale

abstract:
  The local (v<1200kms) and the cosmic expansion field out to 30000kms-1 are
characterized by Ho=58. While the random error is small (+-2), it may still be
affected by systematic errors as large as 10%. The local expansion is outlined
by Cepheids and by Cepheid-calibrated TF distances of a complete sample of
field galaxies and by nearby groups and clusters; the cosmic expansion is
defined by Cepheid-calibrated SNeIa. The main source of systematic errors are
therefore the shape and the zero point of the P-L relation of Cepheids and its
possible dependence on metallicity. GAIA will essentially eliminate these error
sources. Another source of systematic error is due to the homogenization of
SNeIa as to decline rate Delta m_15 and color (B-V). GAIA will discover about
half of the 2200 SNeIa which will occur during a four-year lifetime within
10000kms. For many of them ground-based follow-up will provide useful
photometric parameters (and spectra), which will allow to fix the dependence of
the SNeIa luminosity on Delta m_15 and (B-V) with high accuracy. At the same
time they will yield exquisite distances to an corresponding number of field
galaxies. - GAIA will also revolutionize the very local distance scale by
determining fundamental distances of the companion galaxies of the Milky Way
and even of some spirals in- and possibly outside the Local Group from their
rotation curves seen in radial velocities and proper motions. Moreover, GAIA
will obtain trigonometric parallaxes of RR Lyrae stars, of red giants defining
the TRGB, of stars on the ZAMS, of White Dwarf defining their cooling sequence,
and of globular clusters, and determine the metallicity dependence of these
distance indicators. It will thus establish a self-controlling network of
distance indicators within the Local Group and beyond.


title:
BeppoSAX observations of the EXS 1737.9-2952 region II: Analysis of
  sources

abstract:
  (Abridged) Spectral and time variability analysis of the region of the hard
X-ray transient EXS 1737.9-2952 near the Galactic Centre (GC), using data from
the Narrow Field Instruments of BeppoSAX is reported. The main results are the
MECS spectra of the 10 identified sources. Fluxes obtained with spectral fits
are 1.7-4.8E-12 erg / cm2 s. The absorption is in the range N_H=0.5-6.7E22 /
cm2, indicating that the sources are at least at the distance of the GC, and
thus have L_x > 2-5E34 erg/s (2-10 keV). A powerlaw with photon index 1.1-1.8
generally gives a fair fit, but a strong iron line (at 6-7 keV) is evident for
5 sources and exists at lower confidence in the others. The fits indicate
differences in line position in the range 6.1-7.0 keV suggesting that the
ionisation state and/or emission mechanism may not be the same in all sources.
The time-binned data indicates that two sources are variable on a time scale of
hours at confidence > 99.99%, and one at 99.67%. These sources could be
low-mass X-ray binaries. The other sources are most probably X-ray binaries or
SNRs. A MECS spectrum from a subfield including 8 of the new sources and a
major contribution of diffuse emission yielded a fairly good fit to a power-law
spectrum with photon index 1.3 and a strong iron line at 6.8 keV. Another field
with only residual emission and no point sources yielded spectral parameters
close to the diffuse emission near GC observed by other investigators, except
for the high interstellar absorption. The PDS spectrum of the same region is
more difficult to interpret due to lack of spatial resolution and a larger FOV
that contains the bright hard X-ray source 1E1740.7-2942. The source for the
hard X-ray transient EXS 17137.9-2952 cannot be identified from the present
observations.


title: Magnetic fields in the absence of spiral density waves - NGC 4414

abstract:
  We present three-frequency VLA observations of the flocculent spiral galaxy
NGC 4414 made in order to study the magnetic field structure in absence of
strong density wave flows. NGC 4414 shows a regular spiral pattern of observed
polarization B-vectors with a radial component comparable in strength to the
azimuthal one. The average pitch angle of the magnetic field is about
20$\degr$, similar to galaxies with a well-defined spiral pattern. This
provides support for field generation by a turbulent dynamo without significant
``contamination'' from streaming motions in spiral arms. While the stellar
light is very axisymmetric, the magnetic field structure shows a clear
asymmetry with a stronger regular field and a smaller magnetic pitch angle in
the northern disk. Extremely strong Faraday rotation is measured in the
southern part of the disk, becoming Faraday thick at 6cm. The distribution of
Faraday rotation suggests a mixture of axisymmetric and higher-mode magnetic
fields. The strong Faraday effects in the southern region suggest a much
thicker magnetoionic disk and a higher content of diffuse ionized gas than in
the northern disk portion. An elongation of the 20cm total power emission is
also seen towards the South. Although NGC 4414 is currently an isolated spiral,
the asymmetries in the polarized radio emission may be sensitive tracers of
previous encounters, including weak interactions which would chiefly affect the
diffuse gas component without generating obvious long-term perturbations in the
optical structure.


title: Environment Shaping Galaxies: Spectroscopy of Cluster Galaxies

abstract:
  In this paper I present some recent and new results regarding the effects of
the cluster environment on the star formation history of galaxies. Three main
aspects are discussed: the differences in the stellar population ages of
cluster ellipticals and S0 galaxies; the comparison of the spectroscopic
properties of galaxies in distant clusters and in Coma; and the incidence and
properties of faint post-starburst/post-starforming galaxies in the Coma
cluster.


title: Antimatter from primordial black holes

abstract:
  Antiprotons and antideuterons are considered as probes to look for primordial
black holes in our Galaxy. I give a brief overview of the latest developments
on the subject.


title:
Exploring the spectral properties of faint hard X-ray sources with
  XMM-Newton

abstract:
  We present a spectroscopic study of 41 hard X-ray sources detected
serendipitously with high significance (> 5 sigma in the 2-10 keV band) in
seven EPIC performance/verification phase observations. The large collecting
area of EPIC allows us to explore the spectral properties of these faint hard
X-ray sources with 2< F_{2-10} < 80 x 10^{-14} erg cm^{-2}s^{-1} even though
the length of the exposures are modest (~ 20 ks). Optical identifications are
available for 21 sources of our sample. Using a simple power law plus Galactic
absorption model we find an average value of the photon index Gamma ~ 1.6-1.7,
broadly consistent with recent measurements made at similar fluxes with ASCA
and with Chandra stacked spectral analyses. We find that 31 out of 41 sources
are well fitted by this simple model and only eight sources require absorption
in excess of the Galactic value. Interestingly enough, one third of these
absorbed sources are broad line objects, though with moderate column densities.
Two sources in the sample are X-ray bright optically quiet galaxies and show
flat X-ray spectra. Comparing our observational results with those expected
from standard synthesis models of the cosmic X-ray background (CXB) we find a
fraction of unabsorbed to absorbed sources larger than predicted by theoretical
models at our completeness limit of F_{2-10} ~ 5 x 10^{-14} erg cm^{-2}s^{-1}.
The results presented here illustrate well how wide-angle surveys performed
with EPIC on board XMM-Newton allow population studies of interesting and
unusual sources to be made as well as enabling constraints to be placed on some
input parameters for synthesis models of the CXB.


title: Orbital migration and the frequency of giant planet formation

abstract:
  We present a statistical study of the post-formation migration of giant
planets in a range of initial disk conditions. For given initial conditions we
model the evolution of giant planet orbits under the influence of disk,
stellar, and mass loss torques. We determine the mass and semi-major axis
distribution of surviving planets after disk dissipation, for various disk
masses, lifetimes, viscosities, and initial planet masses. The majority of
planets migrate too fast and are destroyed via mass transfer onto the central
star. Most surviving planets have relatively large orbital semi-major axes of
several AU or larger. We conclude that the extrasolar planets observed to date,
particularly those with small semi-major axes, represent only a small fraction
(~25% to 33%) of a larger cohort of giant planets around solar-type stars, and
many undetected giant planets must exist at large (>1-2 AU) distances from
their parent stars. As sensitivity and completion of the observed sample
increases with time, this distant majority population of giant planets should
be revealed. We find that the current distribution of extrasolar giant planet
masses implies that high mass (more than 1-2 Jupiter masses) giant planet
formation must be relatively rare. Finally, our simulations imply that the
efficiency of giant planet formation must be high: at least 10% and perhaps as
many as 80% of solar-type stars possess giant planets during their pre-main
sequence phase. These predictions, including those for pre-main sequence stars,
are testable with the next generation of ground- and space-based planet
detection techniques


title:
Automated Stellar Spectral Classification and Parameterization for the
  Masses

abstract:
  Stellar spectroscopic classification has been successfully automated by a
number of groups. Automated classification and parameterization work best when
applied to a homogeneous data set, and thus these techniques primarily have
been developed for and applied to large surveys. While most ongoing large
spectroscopic surveys target extragalactic objects, many stellar spectra have
been and will be obtained. We briefly summarize past work on automated
classification and parameterization, with emphasis on the work done in our
group. Accurate automated classification in the spectral type domain and
parameterization in the temperature domain have been relatively easy. Automated
parameterization in the metallicity domain, formally outside the MK system, has
also been effective. Due to the subtle effects on the spectrum, automated
classification in the luminosity domain has been somewhat more difficult, but
still successful. In order to extend the use of automated techniques beyond a
few surveys, we present our current efforts at building a web-based automated
stellar spectroscopic classification and parameterization machine. Our proposed
machinery would provide users with MK classifications as well as the
astrophysical parameters of effective temperature, surface gravity, mean
abundance, abundance anomalies, and microturbulence.


title: Primordial Alchemy: From The Big Bang To The Present Universe

abstract:
  Of the light nuclides observed in the universe today, D, 3He, 4He, and 7Li
are relics from its early evolution. The primordial abundances of these relics,
produced via Big Bang Nucleosynthesis (BBN) during the first half hour of the
evolution of the universe provide a unique window on Physics and Cosmology at
redshifts of order 10^10. Comparing the BBN-predicted abundances with those
inferred from observational data tests the consistency of the standard model of
cosmology over ten orders of magnitude in redshift, constrains the baryon and
other particle content of the universe, and probes both Cosmology and Physics
beyond their current standard models. These lectures are intended to introduce
students, both of theory and observation, to those aspects of the evolution of
the universe relevant to the production and evolution of the light nuclides
from the Big Bang to the present. The current observational data is reviewed
and compared with the BBN predictions and the implications for cosmology (e.g.,
universal baryon density) and particle physics (e.g., relativistic energy
density) are discussed. While this comparison reveals the stunning success of
the standard model(s), there are currently some challenges which leave open the
door for more theoretical and observational work with potential implications
for astronomy, cosmology, and particle physics.


title: The Chandra HETGS and RXTE view of GRS 1915+105

abstract:
  The Chandra AO1 HETGS observation of the micro-quasar GRS 1915+105 in the low
hard state reveals (1) neutral K absorption edges from Fe, Si, Mg, and S in
cold gas, and (2) highly ionized (Fe XXV and Fe XXVI) absorption attributed to
a hot disk, disk wind, or corona. The neutral edges reveal anomalous Si and Fe
abundances which we attribute to surrounding cold material in/near the
environment of GRS 1915+105. We also point out the exciting possibility for the
first astrophysical detection of XAFS attributed to material in interstellar
grains. We place constraints on the ionization parameter, temperature, and
hydrogen equivalent number density of the absorber near the accretion disk
based on the detection of the H- and He-like Fe absorption. Observed spectral
changes in the ionized lines which track the light curve point to changes in
both the ionizing flux and density of the absorber, supporting the presence of
a flow. Details can be found in Lee et al., 2002, ApJ., 567, 1102


title:
Testing intermediate-age stellar evolution models with VLT photometry of
  LMC clusters. I. The data

abstract:
  This is the first of a series of three papers devoted to the calibration of a
few parameters of crucial importance in the modeling of the evolution of
intermediate-mass stars, with special attention to the amount of convective
core overshoot. To this end we acquired deep V and R photometry for three
globular clusters of the Large Magellanic Cloud (LMC), namely NGC 2173, SL 556
and NGC 2155, in the age interval 1-3 Gyr. In this first paper, we describe the
aim of the project, the VLT observations and data reduction, and we make
preliminary comparisons of the color-magnitude diagrams with both Padova and
Yonsei-Yale isochrones. Two following papers in this series present the results
of a detailed analysis of these data, independently carried out by members of
the Yale and Padova stellar evolution groups. This allows us to compare both
sets of models and discuss their main differences, as well as the systematic
effects that they would have to the determination of the ages and metallicities
of intermediate-age single stellar populations.


title: Massive black hole remnants of the first stars in galactic haloes

abstract:
  We investigate the possibility that present-day galactic haloes contain a
population of massive black holes (MBHs) that form by hierarchical merging of
the black hole remnants of the first stars. Some of the MBHs may be large
enough or close enough to the centre of the galactic host that they merge
within a Hubble time. We estimate to what extent this process could contribute
to the mass of the super-massive black holes (SMBHs) observed in galactic
centres today. Many MBHs will not reach the centre of the main halo, however,
but continue to orbit within satellite subhaloes. Using a semi-analytical
approach that explicitly accounts for dynamical friction, tidal disruption and
encounters with the galactic disk, we follow the dynamics of the satellites and
their MBHs and determine the abundance and distribution of MBHs in present-day
haloes of various masses. Considering two different accretion scenarios we also
compute the bolometric luminosity function for the MBHs.


title: Radio Emission from SN 1988Z and Very Massive Star Evolution

abstract:
  We present observations of the radio emission from the unusual SN 1988Z made
with the VLA from 385 to 4,438 days after explosion. SN 1988Z is the most
distant radio supernova ever detected. The radio light curves are
well-described by a model involving the blastwave interacting with a
high-density circumstellar cocoon, which consists almost entirely of clumps or
filaments. However, at age ~ 1750 days the SN declines much more rapidly than
expected, without a change in absorption parameters. This is due to a change in
the number density of circum- stellar clumps without a change in the average
properties of each clump. This also represents a change in the presupernova
stellar wind properties ~ 10,000 yr before explosion. A massive wind (Mdot >~
10^{-4} Msun/yr) and very high ZAMS mass, ~ 20--30 Msun, is implied for the SN
progenitor, similar to what is likely the case for SNe 1986J and 1998bw.


title:
Soft X-ray properties of a high redshift sample of QSOs observed with
  ROSAT

abstract:
  In order to study systematically the soft X-ray emission of Active Galactic
Nuclei (AGNs) at medium to high redshifts, we have analyzed ROSAT PSPC and HRI
data of QSOs at 0.26<z<3.43 selected from the second deepest ROSAT PSPC survey
carried out in 1991-1993 by McHardy et al. (1998). Our sample of 22 type 1 QSOs
is nearly complete above a flux limit of 1.4e-14 erg cm^{-2} s^{-1} in the
0.1-2 keV band. Of these, nine QSOs show long term (~ 2 yr) X-ray variability
by a factor of 1.5-3.5. Significant excess absorption above the Galactic column
is seen in three QSOs. The soft X-ray photon index of the QSOs ranges from 1.4
to 3.7. Three QSOs have steep soft X-ray spectra (Gamma_X > 3.0), one of which
is a narrow-line QSO - a high luminosity version of narrow-line Seyfert 1
galaxies. The average photon index (<Gamma_X>) is 2.40+/-0.09 (with a
dispersion of 0.57) in the 0.1-2 keV band. The average QSO spectra in four
redshift bins flatten from an average photon index of <Gamma_X> ~ 2.53 at 0.25
< z < 1 to <Gamma_X> ~ 2 at 2 < z < 3.4. The flattening of the average photon
index can be understood in terms of the redshift effect of the mean intrinsic
QSO spectrum consisting of two components - a soft X-ray excess and a power-law
component. We have also studied optical spectra of 12 of the 22 QSOs.


title: Cosmology with the Sunyaev-Zel'dovich Effect

abstract:
  The Sunyaev-Zel'dovich effect (SZE) provides a unique way to map the
large-scale structure of the universe as traced by massive clusters of
galaxies. As a spectral distortion of the cosmic microwave background, the SZE
is insensitive to the redshift of the galaxy cluster, making it well-suited for
studies of clusters at all redshifts, and especially at reasonably high
redshifts (z > 1) where the abundance of clusters is critically dependent on
the underlying cosmology. Recent high signal-to-noise detections of the SZE
have enabled interesting constraints on the Hubble constant and the matter
density of the universe using small samples of galaxy clusters. Upcoming SZE
surveys are expected to find hundreds to thousands of new galaxy clusters, with
a mass selection function that is remarkably uniform with redshift. In this
review we provide an overview of the SZE and its use for cosmological studies
with emphasis on the cosmology that can, in principle, be extracted from SZE
survey yields. We discuss the observational and theoretical challenges that
must be met before precise cosmological constraints can be extracted from the
survey yields.


title: ISO-LWS observations of C+ and O lines in absorption toward SgrB2

abstract:
  High spectral resolution ISO-LWS observations of the [OI] 63.2 and 145.5
microns and [CII] 157.7 microns fine structure lines are presented for the
center of the Sagittarius B2 complex (SgrB2). Both the [OI] 63.2 microns and
the [CII] 157.7 microns lines are detected in absorption. Using observations of
the CO isotopes and of the HI lines, absorption components can be associated
with many clouds along the Sgr B2 line of sight. From these data, we were able
to disentangle three different layers, as predicted by PDR models, which
contain atomic oxygen. We derive lower limits for the column densities of C and
O. The fact that the [CII] 157.7 microns line is detected in absorption implies
that the main cooling line of the interstellar medium can be optically thick
especially in the direction of large star-forming complexes or in the nuclei of
galaxies. This could partially account for the deficiency in the [CII] 157.7
microns line which has been recently found toward infrared bright galaxies in
ISO data.


title:
Development of Atmospheric Monitoring System at Akeno Observatory for
  the Telescope Array Project

abstract:
  We have developed an atmospheric monitoring system for the Telescope Array
experiment at Akeno Observatory. It consists of a Nd:YAG laser with an
alt-azimuth shooting system and a small light receiver. This system is
installed inside an air conditioned weather-proof dome. All parts, including
the dome, laser, shooter, receiver, and optical devices are fully controlled by
a personal computer utilizing the Linux operating system.
  It is now operated as a back-scattering LIDAR System. For the Telescope Array
experiment, to estimate energy reliably and to obtain the correct shower
development profile, the light transmittance in the atmosphere needs to be
calibrated with high accuracy.
  Based on observational results using this monitoring system, we consider this
LIDAR to be a very powerful technique for Telescope Array experiments. The
details of this system and its atmospheric monitoring technique will be
discussed.


title: High Velocity Clouds and the Local Group

abstract:
  It was proposed by Blitz et al. (1999) that High Velocity Clouds (HVCs) are
remnants of Local Group formation and the average distance of HVCs is 1 Mpc,
which is the result of a simple dynamical calculation leading to match the
observed HVCs distributions. However, in this paper, we clearly show that
fitting the observed HVCs distributions by a dynamical calculation cannot
provide any constraints on the average distance of HVCs.
  With our choices of initial conditions, the observational results in Wakker &
van Woerden (1991) are produced in our simulations for the models of both
Galactic and extragalactic origins. Moreover, because Zwaan & Briggs (2000)
reported that they failed to locate any extragalactic counterparts of the Local
Group HVCs in a blind HI 21-cm survey of extragalactic groups, we propose to
use ``remnants of galactic disc formation'' as the modification for the picture
of ``remnants of galaxy group formation'' in Blitz et al. (1999) and thus
reduce the possible average distances of HVCs to be about or less than a few
hundred kpc.


title:
A Chandra observation of the interacting pair of galaxies NGC 4485/NGC
  4490

abstract:
  (Abridged) We report the results of a 20 ks Chandra ACIS-S observation of the
interacting galaxy pair NGC 4485/4490. A total of 29 discrete X-ray sources are
found coincident with NGC 4490, but only one is found within NGC 4485. The
sources range in observed X-ray luminosity from ~ 2 x 10^37 to ~ 4 x 10^39
erg/s. Extensive diffuse X-ray emission is detected coincident with the disk of
NGC 4490, and in the tidal tail of NGC 4485, which appears to be thermal in
nature and hence the signature of a hot ISM in both galaxies. However, the
diffuse component accounts for only ~ 10% of the total X-ray luminosity of the
system (2 x 10^40 erg/s, 0.5 - 8 keV), which arises predominantly in a handful
of the brightest discrete sources. This diffuse emission fraction is unusually
low for a galaxy pair that has many characteristics that would lead it to be
classified as a starburst system, possibly as a consequence of the small
gravitational potential well of the system. The discrete source population, on
the other hand, is similar to that observed in other starburst systems,
possessing a flat luminosity function slope of ~ -0.6 and a total of six
ultraluminous X-ray sources (ULX). Five of the ULX are identified as probable
black hole X-ray binary systems, and the sixth (which is coincident with a
radio continuum source) is identified as an X-ray luminous supernova remnant.
The ULX all lie in star-formation regions, providing further evidence of the
link between the ULX phenomenon and active star formation. Importantly, this
shows that even in star forming regions, the ULX population is dominated by
accreting systems. We discuss the implications of this work for physical models
of the nature of ULX, and in particular how it argues against the
intermediate-mass black hole hypothesis.


title:
Circular Polarization of Water Masers in the Circumstellar Envelopes of
  Late Type Stars

abstract:
  We present circular polarization measurements of circumstellar H_2O masers.
The circular polarization detected in the (6_{16}-5_{23}) rotational transition
of the H_{2}O maser can be attributed to Zeeman splitting in the intermediate
temperature and density regime. The magnetic fields are derived using a
general, LTE Zeeman analysis as well as a full radiative transfer method
(non-LTE), which includes a treatment of all hyperfine components
simultaneously as well as the effects of saturation and unequal populations of
the magnetic substates. The differences and relevances of these interpretations
are discussed extensively. The field strengths are compared with previous
detections of the magnetic field on the SiO and OH masers. We show that the
magnetic pressure dominates the thermal pressure by a factor of 20 or more.


title:
Astrometry of the stellar image of U Her amplified by the circumstellar
  22 GHz water masers

abstract:
  The 22 GHz H_2O masers in the circumstellar envelope of the Mira variable
star U Her have been observed with MERLIN using a phase referencing technique
to determine accurate astrometric positions. The positions were compared with
the optical positions obtained with the Hipparcos satellite to an accuracy of
18 mas. The absolute radio position of the brightest H_2O maser spot is found
to match the optical position, indicating that this spot is the stellar image
amplified by the maser screen in front of it. The occurrence of an amplified
image in the 22 GHz maser can be used to accurately determine the positions of
the H_2O with respect to the star as well as with respect to the SiO and OH
masers. Our observations seem to indicate that the star is not in the centre of
the distribution of maser spots, which has been interpreted as a ring.


title:
Stellar Atmosphere and Accretion Disk Models for the Hot Component in
  Symbiotic Stars

abstract:
  We describe our NLTE codes which allow the computation of synthetic spectra
of hot stars and accretion disks. They can be combined to compute ionizing
fluxes from the hot component in symbiotic stars.


title:
Numerical simulation of the surface flow of a companion star in a close
  binary system

abstract:
  We simulate numerically the surface flow of a gas-supplying companion star in
a semi-detached binary system. Calculations are carried out for a region
including only the mass-losing star, thus not the mass accreting star. The
equation of state is that of an ideal gas characterized by a specific heat
ratio gamma, and the case with gamma=5/3 is mainly studied. A system of eddies
appears on the surface of the companion star: an eddy in the low pressure
region near the L1 point, one around the high pressure at the north pole, and
one or two eddies around the low pressure at the opposite side of the L1 point.
Gas elements starting near the pole region rotate clockwise around the north
pole (here the binary system rotates counter-clockwise as seen from the north
pole). Because of viscosity, the gas drifts to the equatorial region, switches
to the counter-clockwise eddy near the L1 point and flows through the L1 point
to finally form the L1 stream. The flow field in the L1 region and the
structure of the L1 stream are also considered.


title: The Morphology of 9 Radio-selected Faint Galaxies from deep HST Imaging

abstract:
  Using the HST WFPC2 we perform deep I-band imaging of 9 radio-selected (limit
14 microJanskys at 8.5 GHz) faint galaxies from Roche, Lowenthal and Koo
(2002). Two are also observed in V. Six of the galaxies have known redshifs of
0.4<z<1.0. Radial intensity profiles indicate that 7 are disk galaxies and 2
are bulge-dominated. Four of the six with redshifts have a high optical surface
brightness compared to typical disk galaxies. Two of the 9 galaxies are in
close interacting pairs, another two are very asymmetric and three have large,
luminous rings resembling the collisional starburst rings in the Cartwheel
galaxy. In most of these galaxies the high radio luminosities are probably the
result of interaction-triggered starbursts. The mixture of observed
morphologies suggests that enhanced radio luminosities often persist for >0.2
Gyr, to a late stage of the interaction. One of these 9 galaxies may be an
exception in that it is a large red elliptical and its strong radio emission is
more likely to be from an obscured AGN.


title: The EUVE point of view of AD Leo

abstract:
  All the Extreme Ultraviolet Explorer (EUVE) observations of AD Leo, totalling
1.1 Ms of exposure time, have been employed to analyze the corona of this
single M dwarf. The light curves show a well defined quiescent stage, and a
distribution of amplitude of variability following a power law with a ~-2.4
index. The flaring behavior exhibits much similarity with other M active stars
like FK Aqr or YY Gem, and flares behave differently from late type active
giants and subgiants. The Emission Measure Distribution (EMD) of the summed
spectrum, as well as that of quiescent and flaring stages, were obtained using
a line-based method. The average EMD is dominated by material at log T(K)~6.9,
with a second peak around log T(K)~6.3, and a large increase in the amount of
material with log T(K)>~7.1 during flares, material almost absent during
quiescence. The results are interpreted as the combination of three families of
loops with maximum temperatures at log T(K)~6.3, ~6.9 and somewhere beyond log
T(K)>~7.1. A value of the abundance of [Ne/Fe]=1.05+-0.08 was measured at log
T(K)~5.9. No significative increment of Neon abundance was detected between
quiescence and flaring states.


title:
Fine Structure in the Circumstellar Environment of a Young, Solar-like
  Star: the Unique Eclipses of KH 15D

abstract:
  Results of an international campaign to photometrically monitor the unique
pre-main sequence eclipsing object KH 15D are reported. An updated ephemeris
for the eclipse is derived that incorporates a slightly revised period of 48.36
d. There is some evidence that the orbital period is actually twice that value,
with two eclipses occurring per cycle. The extraordinary depth (~3.5 mag) and
duration (~18 days) of the eclipse indicate that it is caused by circumstellar
matter, presumably the inner portion of a disk. The eclipse has continued to
lengthen with time and the central brightness reversals are not as extreme as
they once were. V-R and V-I colors indicate that the system is slightly bluer
near minimum light. Ingress and egress are remarkably well modeled by the
passage of a knife-edge across a limb-darkened star. Possible models for the
system are briefly discussed.


title:
Magnetic field strengths in the hotspots and lobes of three powerful
  FRII radio sources

abstract:
  We have made deep Chandra observations of three powerful FRII radio sources:
two quasars (3C263 and 3C351) and one radio galaxy (3C330). X-ray emission from
hotspots and lobes, as well as from the active nucleus, is detected in each
source.
  We model the hotspots' synchrotron spectra using VLA, BIMA and HST data. In
3C263 and 3C330, the hotspots' X-ray emission is at a level consistent with
being synchrotron self-Compton (SSC) emission, with a hotspot magnetic field
close to the equipartition value. In the two hotspots of 3C351, however, an SSC
origin for the X-rays would require the magnetic field strength to be an order
of magnitude below the equipartition value in our models: in addition, there
are offsets between the radio, optical and X-ray emission from the secondary
hotspot which are hard to explain in a simple SSC model. We discuss the
emission mechanisms that may be responsible for these observations.
  On our preferred model, the X-ray emission from the radio lobes of the three
sources is due to inverse-Compton scattering of the microwave background
radiation. If this is the case, the magnetic field strengths in the lobes are
typically about a factor 2 below the equipartition values, assuming uniform
lobe electron and magnetic field distributions.
  We detect extended X-ray emission, which we attribute to a cluster/group
environment, around 3C263 and 3C330. This detection allows us to show that the
lobes are close to pressure balance with their surroundings, as long as no
non-radiating particles contribute to the internal pressure of the lobes.


title:
Rotational Broadening Measurement for the Neutron Star X-Ray Transient
  XTE J2123-058

abstract:
  We used optical spectroscopy of the neutron star X-ray transient XTE
J2123-058 to measure the rotational broadening of the binary companion's
stellar absorption lines and determined that the companion's projected
rotational velocity is vsini = 121 (+21)(-29) km/s. This value is considerably
larger than the measurements of vsini obtained previously for three other
neutron star systems where the values are between 34 and 65 km/s. The larger
value is likely due to the combination of high binary inclination and short (6
hr) orbital period for XTE J2123-058. Along with previously measured
parameters, the rotational broadening measurement allowed us to determine the
binary parameters, including the ratio of the neutron star mass to the
companion mass, q = M_1/M_2 = 2.7 (+1.3)(-0.9), the neutron star mass, M_1 =
1.46 (+0.30)(-0.39) solar masses, and the companion mass, M_2 = 0.53
(+0.28)(-0.39) solar masses, assuming a Roche lobe filling companion
synchronously rotating with the binary orbit. These values are consistent with
a previous measurement where the H alpha emission line was used to determine
the semiamplitude of the neutron star's radial velocity curve (K_1). It is a
significant result that the two methods give consistent values. We also report
the first measurement of the XTE J2123-058 companion's radius. Assuming
synchronous rotation, we obtain R_2 = 0.62 (+0.11)(-0.15) solar radii, which is
in-line with that expected for a late K-type star on or close to the main
sequence. Finally, we report the first precise spectroscopic determination of
the binary orbital period (P_orb = 21442.3 +/- 1.8 seconds).


title: The evolution of a warped disc around a Kerr black hole

abstract:
  We consider the evolution of a warped disc around a Kerr black hole, under
conditions such that the warp propagates in a wavelike manner. This occurs when
the dimensionless effective viscosity, alpha, that damps the warp is less than
the characteristic angular semi-thickness, H/R, of the disc. We adopt
linearized equations that are valid for warps of sufficiently small amplitude
in a Newtonian disc, but also account for the apsidal and nodal precession that
occur in the Kerr metric. Through analytical and time-dependent studies, we
confirm the results of Demianski & Ivanov, and of Ivanov & Illarionov, that
such a disc takes on a characteristic warped shape. The inner part of the disc
is not necessarily aligned with the equator of the hole, even in the presence
of dissipation. We draw attention to the fact that this might have important
implications for the directionality of jets emanating from discs around
rotating black holes.


title: GMRT and VLA observations of HI and OH from the Seyfert galaxy Mrk 1

abstract:
  We present Giant Meterwave Radio Telescope (GMRT) observations of the HI 21
cm line and Very Large Array (VLA) observations of the OH 18 cm line from the
Seyfert 2 galaxy Mrk 1. HI emission is detected from both Mrk 1 and its
companion NGC 451. The HI emission morphology and the velocity field of Mrk 1
are disturbed. We speculate that the nuclear activities of Mrk 1 are triggered
by tidal interactions. We have also detected two-component HI 21 cm line and
the OH 18 cm line in absorption toward the nucleus of Mrk 1 at blueshifted
velocities with respect to its systemic velocity indicating an outflow of
atomic and molecular gas. The profile of the OH absorption is qualitatively
similar to that of the HI absorption. The higher velocity components of the HI
and OH (1667 MHz) absorption lines are blueshifted from the O[III]5007,
O[I]6300, and the systemic velocity by ~ 100 km s^{-1}, but are consistent with
the O[II]3727 velocity. We explain these velocity discrepancies as due to shock
ionization of a region which is pushed forward due to shocks in front of the
radio nucleus thereby giving apparent blueshift to HI, OH, and O[II]
velocities. The optical depth ratios tau{HI}/tau{OH1667} of both the components
of the HI and OH absorption are ~3, indicating their origin in dense molecular
clouds. Using OH/A_{v} values for the Galactic molecular clouds, we obtain 9 <
A_{v} < 90 toward the line of sight of Mrk 1.


title: A High Resolution Picture of the Intracluster Gas

abstract:
  Chandra has significantly advanced our knowledge of the processes in the
intracluster gas. The discovery of remarkably regular ``cold fronts'', or
contact discontinuities, in merging clusters showed that gas dynamic
instabilities at the boundaries between the moving gases are often suppressed,
most likely by specially structured magnetic fields.
  Cold fronts are not limited to mergers -- Chandra observed them in the cores
of more than 2/3 of the cooling flow clusters, where they often divide the cool
central and the hotter ambient gas phases. The natural state of the low-entropy
central gas in clusters thus appears to be to slosh subsonically in the central
potential well, with several interesting implications. Hydrostatic equilibrium
is not reached and the hydrostatic total mass estimates cannot be valid at
small radii (r<100 kpc). The kinetic energy dissipated by the sloshing gas may
be sufficient to compensate for radiative cooling. In the absence of a recent
merger, the cause of such sloshing is unclear. It might be related to the
mechanical energy generated by the central AGN, evidence of which (the bubbles)
is also observed by Chandra in a large fraction of the cooling flow clusters.
  Heat conduction across cold fronts is suppressed completely. In the bulk of
the gas, it is reduced by a factor of ~10 or more relative to the classic
value, as shown by merger temperature maps. A spatial correlation between the
gas temperature maps and the radio halo maps is observed in several mergers,
which may provide clues for the relativistic particle acceleration mechanisms.


title: Ground-Based Optical Deep Pencil Beam Surveys

abstract:
  The initial results of the Deep Lens Survey (http://dls.bell-labs.com) to
identify possible brown dwarfs and extremely metal poor red halo subdwarfs near
the hydrogen burning limit are presented. Individual deep CCD high galactic
latitude survey fields appear to offer a low probability of discovering field
BD's, but taken collectively offer an opportunity to begin addressing questions
regarding the scale height and distribution of these objects. In all
likelihood, the very depth of such surveys will greatly increase our knowledge
of the coolest extreme halo objects, which currently are known in far fewer
numbers than T dwarfs. Ultimately, the large volume surveyed by the Large
Synoptic Survey Telescope will identify vast numbers of such objects, providing
a more complete picture of their spatial distribution.


title: Angular Radii of Stars via Microlensing

abstract:
  We outline a method by which the angular radii of giant and main sequence
stars in the Galactic bulge can be measured to a few percent accuracy. The
method combines ground-based photometry of caustic-crossing bulge microlensing
events, with a handful of precise astrometric measurements of the lensed star
during the event, to measure the angular radius of the source, theta_*. Dense
photometric coverage of one caustic crossing yields the crossing timescale dt.
Less frequent coverage of the entire event yields the Einstein timescale t_E
and the angle phi of source trajectory with respect to the caustic. The
photometric light curve solution predicts the motion of the source centroid up
to an orientation on the sky and overall scale. A few precise astrometric
measurements therefore yield theta_E, the angular Einstein ring radius. Then
the angular radius of the source is obtained by theta_*=theta_E(dt/t_E)
sin(phi). We argue that theta_* should be measurable to a few percent accuracy
for Galactic bulge giant stars using ground-based photometry from a network of
small (1m-class) telescopes, combined with astrometric observations with a
precision of ~10 microarcsec to measure theta_E. We find that a factor of ~50
times fewer photons are required to measure theta_E to a given precision for
binary-lens events than single-lens events. Adopting parameters appropriate to
the Space Interferometry Mission (SIM), ~7 min of SIM time is required to
measure theta_E to ~5% accuracy for giant sources in the bulge. For
main-sequence sources, theta_E can be measured to ~15% accuracy in ~1.4 hours.
With 10 hrs of SIM time, it should be possible to measure theta_* to ~5% for
\~80 giant stars, or to 15% for ~7 main sequence stars. A byproduct of such a
campaign is a significant sample of precise binary-lens mass measurements.


title:
Narrow-line Seyfert 1 Galaxies from the Sloan Digital Sky Survey Early
  Data Release

abstract:
  We present a sample of 150 narrow-line Seyfert 1s (NLS1s) found within the
Sloan Digital Sky Survey Early Data Release (EDR), only two of which were
previously identified as such. This substantially increases the known number of
NLS1s, and provides a basic method by which to identify many more with
subsequent releases of SDSS data. With its large size and homogeneous,
well-defined selection criteria, this sample will help alleviate two major
problems which have plauged NLS1 research in the past; namely, their relative
rarity and significant differences in selection algorithms between the known
samples. 45 of these SDSS-selected NLS1s are detected at energies of 0.1-2 keV
in the ROSAT All-Sky Survey (RASS), and are found to have ultrasoft X-ray
spectra with photon indices of Gamma >~ 2, in agreement with previous results
for NLS1s. However, about 10-20 of those NLS1s that were not detected by ROSAT
have optical properties very similar to the detected objects, and so should
also have been detected by the RASS. This may be due to either significant
intrinsic absorption in many NLS1s, or a significant sub-class of NLS1s that
have uncharacteristic, intrinsically flatter (hence harder) X-ray spectral
energy distributions.


title:
On the Low and High Frequency Correlation in Quasi-Periodic Oscillations
  Among White Dwarfs, Neutron Star and Black Hole Binaries

abstract:
  We interpret the correlation over five orders of magnitude between high
frequency and low frequency in a quasi-periodic oscillations (QPO) found by
Psaltis, Belloni & van der Klis (1999) for black hole (BH), neutron star (NS)
systems and then extended by Mauche (2002) to white dwarf (WD) binaries. We
argue that the observed correlation is a natural consequence of the Keplerian
disk flow adjustment to the innermost sub-Keplerian boundary conditions near
the central object. In the framework of the transition layer model the high
frequency is related to the Keplerian frequency at the outer (adjustment)
radius and the low frequency is related to the magnetoacoustic oscillation (MA)
frequency. Using a relation between the MA frequency the magnetic and gas
pressure and the density and the hydrostatic equilibrium condition in the disk
we infer a linear correlation the Keplerian frequency and the MA frequency. We
estimate the magnetic field strength near the TL outer radius for BHs NSs and
WDs. The fact that the observed high-low frequency correlation over five orders
of magnitude is valid for BHs, NSs, and down to WDs strongly rules out
relativistic models for QPO phenomena. We come to the conclusion that the QPOs
observations indicate the adjustment of the geometrically thin disk to
sub-Keplerian motion near the central object. This effect is a common feature
for a wide class of systems, starting from white dwarf binaries up to black
hole binaries.


title: Analysis of H2 Emission from Mira B in UV Spectra from HST

abstract:
  We analyze Ly-alpha fluoresced H2 lines observed in the UV spectrum of Mira
B. We identify 13 different sequences fluoresced by 13 different H2 transitions
within the Ly-alpha line. The observed H2 line ratios within these sequences
imply significant line opacity, so we use a Monte Carlo radiative transfer code
to model the line ratios, correcting for opacity effects. We find the observed
line ratios can best be reproduced by assuming that the H2 is fluoresced in a
layer between the observer and Mira B with a temperature and column density of
T=3600 K and log N(H2)=17.3, respectively. The strengths of H2 absorption
features within the Ly-alpha line are roughly consistent with this temperature
and column. We use the total flux fluoresced within the 13 sequences to infer
the Ly-alpha profile seen by the H2. In order to explain differences between
the shape of this and the observed profile, we have to assume that the observed
profile suffers additional interstellar (or circumstellar) H I Ly-alpha
absorption with a column density of about log N(H I)=20.35. We also have to
assume that the observed profile is about a factor of 2.5 lower in flux than
the profile seen by the H2, and a couple possible explanations for this
behavior are presented. Several lines of evidence lead us to tentatively
attribute the fluoresced emission to H2 that is heated in a photodissociation
front within Mira A's wind a few AU from Mira B, although it is possible that
interaction between the winds of Mira A and B may also play a role in heating
the H2. We estimate a Mira B mass loss rate of 5e-13 solar masses per year and
a terminal velocity of 250 km/s, based on wind absorption features in the Mg II
h & k lines. We note, however, that the wind is variable and IUE Mg II spectra
suggest significantly higher mass loss rates during the IUE era.


title:
Elemental Abundances and Ionization States within the Local Interstellar
  Cloud Derived from HST and FUSE Observations of the Capella Line of Sight

abstract:
  We use ultraviolet spectra of Capella from the Hubble Space Telescope (HST)
and Far Ultraviolet Spectroscopic Explorer (FUSE) satellites to study
interstellar absorption lines from the Local Interstellar Cloud (LIC).
Measurements of these lines are used to empirically determine the ionization
states of carbon, nitrogen, and silicon in the LIC, for comparison with the
predictions of theoretical photoionization models. We find that the observed
ionization states are consistent with previously published photoionization
predictions. Total abundances are determined for the elements mentioned above,
and others, for comparison with solar abundances. Magnesium, aluminum, silicon,
and iron are all depleted by at least a factor of 10 toward Capella. The
abundances of carbon, nitrogen, and oxygen are essentially solar, although the
error bars are large enough to also allow depletions of about a factor of 2 for
these elements.


title: Multiple black holes in galactic bulges

abstract:
  We study the number and interaction rates of supermassive black holes in
galactic bulges as predicted by hierarchical models of galaxy formation in
which the spheroidal components of galaxies are formed by mergers. In bright
ellipticals, the number of events that can eject a central supermassive binary
black hole is large. Central binaries must therefore merge in less than a
Hubble time -- otherwise there will be too much scatter in the M-sigma relation
and too many off-center galactic nuclei. We propose that binary black holes are
able to merge during the major gas accretion events that trigger QSO activity
in galaxies. If this is the case, less than 10 percent of faint ellipticals and
40 percent of bright ellipticals are predicted to harbour binary black holes
with near equal masses at their centres. This binary may be ejected away from
the centre of the galaxy or even into intergalactic space in up to 20 percent
of the most luminous ellipticals. The number of low mass black holes that can
interact with the central object is predicted to be a strong function of galaxy
luminosity. In most faint ellipticals, no black holes fall into the centre of
the galaxy after the last major gas accretion event, but in the most luminous
ellipticals, an average of 10 low mass black holes interact with the central
supermassive object after this time. It is expected that stars will be ejected
from galaxy cores as these low mass-ratio binaries harden. Multiple black holes
in galactic bulges thus provide a natural explanation for the strong systematic
trends in the observed central density profiles of ellipticals as a function of
luminosity.


title:
OVRO CMB Anisotropy Measurement Constraints on Flat-Lambda and Open CDM
  Cosmogonies

abstract:
  We use Owens Valley Radio Observatory (OVRO) cosmic microwave background
(CMB) anisotropy data to constrain cosmological parameters. We account for the
OVRO beamwidth and calibration uncertainties, as well as the uncertainty
induced by the removal of non-CMB foreground contamination. We consider open
and spatially-flat-Lambda cold dark matter cosmogonies, with
nonrelativistic-mass density parameter Omega_0 in the range 0.1--1,
baryonic-mass density parameter Omega_B in the range (0.005--0.029)h^{-2}, and
age of the universe t_0 in the range (10--20) Gyr. Marginalizing over all
parameters but Omega_0, the OVRO data favors an open (spatially-flat-Lambda)
model with Omega_0 ~= 0.33 (0.1). At the 2 sigma confidence level model
normalizations deduced from the OVRO data are mostly consistent with those
deduced from the DMR, UCSB South Pole 1994, Python I-III, ARGO, MAX 4 and 5,
White Dish, and SuZIE data sets.


title: Structure Function Scaling of a 2MASS Extinction Map of Taurus

abstract:
  We compute the structure function scaling of a 2MASS extinction map of the
Taurus molecular cloud complex. The scaling exponents of the structure
functions of the extinction map follow the Boldyrev's velocity structure
function scaling of supersonic turbulence. This confirms our previous result
based on a spectral map of 13CO J=1-0 covering the same region and suggests
that supersonic turbulence is important in the fragmentation of this
star--forming cloud.


title:
A New Empirical Method of Estimation of the Far-Infrared Flux of
  Galaxies

abstract:
  We propose a new empirical method to estimate the total far-infrared flux of
galaxies from the spectral energy distribution (SED) at wavelengths lambda
shorter than 100 microns. It is difficult to derive the total far-infrared
luminosity from only the IRAS data, though it is one of the most important
properties of galaxies. Observations by Infrared Telescope in Space (IRTS)
indicate that the SED of the diffuse emission from the Galactic plane in this
wavelength region can be derived from the 60 microns to 100 microns color. This
empirical SED relation was improved in order to obtain a better fit to the
Galactic plane data for I(60 microns)/I(100 microns) > 0.6, and applied to 96
IRAS galaxies for which ISOPHOT and KAO data are available at lambda > 100
microns. As a result, the empirical relation describes well the far-infrared
(FIR) SED for a majority of the galaxies. Additionally, the total FIR flux for
lambda longer than 40 microns is derived from the flux densities at 60 and 100
microns by using this model. For the 96 IRAS galaxies, the uncertainty in the
total far-infrared flux of the present method is 26%. The present method is
more accurate than the previous one widely used to derive the total infrared
flux from the IRAS 60 and 100 microns data.


title: Simulating the formation of cosmic structure

abstract:
  A timely combination of new theoretical ideas and observational discoveries
has brought about significant advances in our understanding of cosmic
evolution. Computer simulations have played a key role in these developments by
providing the means to interpret astronomical data in the context of physical
and cosmological theory. In the current paradigm, our Universe has a flat
geometry, is undergoing accelerated expansion and is gravitationaly dominated
by elementary particles that make up cold dark matter. Within this framework,
it is possible to simulate in a computer the emergence of galaxies and other
structures from small quantum fluctuations imprinted during an epoch of
inflationary expansion shortly after the Big Bang. The simulations must take
into account the evolution of the dark matter as well as the gaseous processes
involved in the formation of stars and other visible components. Although many
unresolved questions remain, a coherent picture for the formation of cosmic
structure in now beginning to emerge. In this paper, I review a selection of
recent results obtained from simulations of the cosmic large-scale structure
and galaxy formation and compare them with observational data, including
results from the ``2dF Galaxy Redshift Survey.''


title:
Weak gravitational lensing: reducing the contamination by intrinsic
  alignments

abstract:
  Intrinsic alignments of galaxies can mimic to an extent the effects of shear
caused by weak gravitational lensing. Previous studies have shown that for
shallow surveys with median redshifts z_m = 0.1, the intrinsic alignment
dominates the lensing signal. For deep surveys with z_m = 1, intrinsic
alignments are believed to be a significant contaminant of the lensing signal,
preventing high-precision measurements of the matter power spectrum. In this
paper we show how distance information, either spectroscopic or photometric
redshifts, can be used to down-weight nearby pairs in an optimised way, to
reduce the errors in the shear signal arising from intrinsic alignments.
Provided a conservatively large intrinsic alignment is assumed, the optimised
weights will essentially remove all traces of contamination. For the Sloan
spectroscopic galaxy sample, residual shot noise continues to render it
unsuitable for weak lensing studies. However, a dramatic improvement for the
slightly deeper Sloan photometric survey is found, whereby the intrinsic
contribution, at angular scales greater than 1 arcminute, is reduced from about
80 times the lensing signal to a 10% effect. For deeper surveys such as the
COMBO-17 survey with z_m = 0.6, the optimisation reduces the error from a
largely systematic 220% error at small angular scales to a much smaller and
largely statistical error of only 17% of the expected lensing signal. We
therefore propose that future weak lensing surveys be accompanied by the
acquisition of photometric redshifts, in order to remove fully the unknown
intrinsic alignment errors from weak lensing detections.


title:
Evolution of Brown Dwarf Atmospheres: Investigating Physical Parameters
  from Near-IR Spectra

abstract:
  We obtained near-infrared spectra of a sample of very low mass objects as a
function of age in order to investigate the temperature and surface gravity
sensitivity of several features in the J and K bands.


title:
Corrections to the Fine Structure Constant in D-dimensional Space from
  the Generalized Uncertainty Principle

abstract:
  In this letter we compute the corrections to the fine structure constant in
D-dimensional space. These corrections stem from the generalized uncertainty
principle. We also discuss in three-space dimension.


title: The accelerating universe in brane-world cosmology

abstract:
  The standard Friedmann universe embedded in a five dimensional and constant
curvature bulk is examined without any a priori junction condition between the
brane and the bulk. A geometrical explanation for the accelerated expansion of
the universe is derived by using a minimum set of assumptions consistent with
the brane-world program. It is shown that the extrinsic curvature of the brane
can be associated to the dark energy which presumably drives the universe
expansion.


title:
Luminous early-type field galaxies at z ~ 0.4 - II. Star-formation
  history and space density

abstract:
  We present a combined photometric and spectroscopic analysis of the star
formation history and space density of a sample of 485 luminous, M_V - 5 log h
< -20.5, field early-type galaxies at redshifts 0.3 < z < 0.6. The observed
b_Jori colours as a function of redshift, mean absorption line strengths and
[OII] 3727 emission properties are used to constrain the star formation history
of the galaxies. The mean star formation history of the early-type galaxy
sample is consistent with an old (z_f>1), passively evolving
luminosity-weighted stellar population. Twenty-one percent of the sample
possess detectable [OII] 3727 emission consistent with a low level (<1
M_solar/yr) of on-going star formation. Parametric and non-parametric estimates
of the space density of the sample are derived. The integrated luminosity
density at z ~ 0.4, allowing only for passive luminosity evolution, is in
excellent agreement with the local, (<z> = 0.1), luminosity density of
early-type galaxies. Overall, the sample properties are consistent with a
galaxy formation scenario in which the majority of luminous field early-type
galaxies formed at redshifts z>1 and have largely evolved passively since the
formation epoch.


title:
The ^12C(alpha,gamma)^16O Nuclear Reaction Rate from Asteroseismology of
  the DBV White Dwarf CBS 114

abstract:
  We have identified seven independent pulsation modes in the helium-atmosphere
variable (DBV) white dwarf star CBS 114, based on 65 hours of time-resolved CCD
photometry from the 0.75-m telescope at SAAO. We interpret these pulsations as
non-radial g-modes with the same spherical degree l=1, as suggested by the mean
period spacing of 37.1+/-0.7 seconds. We use a genetic-algorithm-based fitting
method to find the globally optimal model parameters, including the stellar
mass (M_* = 0.73 M_sun), the effective temperature (T_eff = 21,000 K), the mass
of the atmospheric helium layer (log[M_He/M_*] = -6.66), and the central oxygen
mass fraction (X_O = 0.61). The latter value implies a rate for the
^12C(alpha,gamma)^16O reaction near S_300 = 180 keV b, consistent with
laboratory measurements.


title:
VLT observations of metal-rich extra galactic HII regions. I. Massive
  star populations and the upper end of the IMF

abstract:
  We have obtained high quality FORS1/VLT optical spectra of 85 disk HII
regions several nearby spiral galaxies. Our sample of metal-rich HII regions
with metallicities close to solar and higher reveal the presence of Wolf-Rayet
(WR) stars in 27 objects from the blue WR bump and 15 additional candidate WR
regions. This provides for the first time a large set of metal-rich WR regions.
  Approximately half of the WR regions also show broad CIV emission attributed
to WR stars of the WC subtype (...). The WR regions show quite clear trends
between their observed WR features and the Hbeta emission line. Detailed
synthesis models are presented to understand/interpret these observations.
(...)
  The availability of a fairly large sample of metal-rich WR regions allows us
to improve existing estimates of the upper mass cut-off of the IMF in a robust
way and independently of detailed modeling: from the observed maximum Hbeta
equivalent width of the WR regions we derive a LOWER LIMIT for M_up of 60-90
Msun in the case of a Salpeter slope and larger values for steeper IMF slopes.
  From our direct probe of the massive star content we conclude that there is
at present no evidence for systematic variations of the upper mass cut-off of
the IMF in metal-rich environments, in contrast to some claims based on
indirect nebular diagnostics. (abridged abstract)


title: The massive star IMF

abstract:
  We review our current knowledge on the IMF in nearby environments, massive
star forming regions, super star clusters, starbursts and alike objects from
studies of integrated light, and discuss the various techniques used to
constrain the IMF.
  In most cases, including UV-optical studies of stellar features and
optical-IR analysis of nebular emission, the data is found to be compatible
with a "universal" Salpeter-like IMF with a high upper mass cut-off over a
large metallicity range.
  In contrast, near-IR observations of nuclear starbursts and LIRG show
indications of a lower M_up and/or a steeper IMF slope, for which no alternate
explanation has yet been found. Also, dynamical mass measurements of seven
super star clusters provide so far no simple picture of the IMF.
  Finally we present recent results of a direct stellar probe of the upper end
of the IMF in metal-rich HII regions, showing no deficiency of massive stars at
high metallicity, and determining a lower limit on M_up of >~ 60--90 Msun.


title:
Sensitivity of the Auger Observatory to ultra high energy photon
  composition through inclined showers

abstract:
  We report a calculation of the expected rate of inclined air showers induced
by ultra high energy cosmic rays to be obtained by the Auger Southern
Observatory assuming different mass compositions. We describe some features
that can be used to distinguish photons at energies as high as 10$^{20}$ eV.
The discrimination of photons at such energies will help to test some models of
the origin of ultra-high-energy cosmic rays.


title:
A comprehensive study of reported high metallicity giant HII regions.
  II. Ionising stellar populations

abstract:
  The ionising stellar populations of eleven HII regions in the spiral
galaxies: NGC628, NGC925, NGC1232 and NGC1637, all of them reported to have
solar or oversolar abundances according to empirical calibrations, have been
analysed using stellar population synthesis models. Four of the observed
regions in the sample, show features which indicate the presence of a
population of Wolf-Rayet (WR) stars with ages between 2.3 and 4.1 Myr. This
population is sufficient to explain the emission line spectrum of the low
metallicity region H13 in NGC628. This is not the case for the rest of the
regions for which a second ionising population is required to simultaneously
reproduce both the WR features and the emission line spectrum. For two of the
regions showing WR features, no consistent solution is found, since the
population containing WR stars produces a spectral energy distribution which is
too hard to explain the emission of the gas. Several solutions are proposed to
solve this problem.


title:
New algorithms and technologies for the un-supervised reduction of
  Optical/IR images

abstract:
  This paper presents some of the main aspects of the software library that has
been developed for the reduction of optical and infrared images, an integral
part of the end-to-end survey system being built to support public imaging
surveys at ESO. Some of the highlights of the new library are: unbiased
estimates of the background, critical for deep IR observations; efficient and
accurate astrometric solutions, using multi-resolution techniques; automatic
identification and masking of satellite tracks; weighted co-addition of images;
creation of optical/IR mosaics, and appropriate management of multi-chip
instruments. These various elements have been integrated into a system using
XML technology for setting input parameters, driving the various processes,
producing comprehensive history logs and storing the results, binding them to
the supporting database and to the web. The system has been extensively tested
using deep images as well as images of crowded fields (e.g. globular clusters,
LMC), processing at a rate of 0.5 Mega-pixels per second using a DS20E ALPHA
computer with two processors. The goal of this presentation is to review some
of the main features of this package.


title: Evidence for chemical evolution in the spectra of high redshift galaxies

abstract:
  Using a sample of 57 VLT FORS spectra in the redshift range 1.37<z<3.40
(selected mainly from the FORS Deep Field survey) and a comparison sample with
36 IUE spectra of local (z ~ 0) starburst galaxies we derive CIV and SiIV
equivalent width values and estimate metallicities of starburst galaxies as a
function of redshift. Assuming that a calibration of the CIV equivalent widths
in terms of the metallicity based on the local sample of starburst galaxies is
applicable to high-z objects, we find a significant increase of the average
metallicities from about 0.16 Z_sun at the cosmic epoch corresponding to z ~
3.2 to about 0.42 Z_sun at z ~ 2.3. A significant further increase in
metallicity during later epochs cannot be detected in our data. Compared to the
local starburst galaxies our high-redshift objects tend to be overluminous for
a fixed metallicity. Our observational results are in good agreement with
published observational data by other authors and with theoretical predictions
of the cosmic chemical evolution.


title:
Chandra Observations and Optical Identification of Hard X-ray Sources
  Discovered with ASCA

abstract:
  We present the first results of the Chandra and optical follow-up
observations of hard X-ray sources detected in the ASCA Medium Sensitivity
Survey (AMSS). Optical identifications are made for five objects. Three of them
show either weak or absent optical narrow emission lines and are at low
redshift <z>~0.06. One of them is a broad line object at z=0.910 and one is a
z=0.460 object with only narrow lines. All the narrow line objects show strong
evidence for absorption in their X-ray spectra. Their line ratios are
consistent with a Seyfert II/LINER identification as are the line widths. The
three low redshift objects have the colors of normal galaxies and apparently
the light is dominated by stars. This could be due to the extinction of the
underlying nuclear continuum by the same matter that absorbs X-rays and/or due
to the dilution of the central source by starlight. These results suggest that
X-ray sources that appear as ``normal'' galaxies in optical and near-IR bands
significantly contribute to the hard X-ray background. This population of
objects has a high space density and probably dominates the entire population
of active galaxies.


title: SuperWASP: Wide Angle Search for Planets

abstract:
  SuperWASP is a fully robotic, ultra-wide angle survey for planetary transits.
Currently under construction, it will consist of 5 cameras, each monitoring a
9.5 x 9.5 deg field of view. The Torus mount and enclosure will be fully
automated and linked to a built-in weather station. We aim to begin
observations at the beginning of 2003.


title: Can clocks really run backwards?

abstract:
  In an apparently unexplored region of relativistic spacetime, a simple
thought experiment demonstrates that conjoined Lorentz transformations predict
a proper clock at rest will run backwards and that prediction violates the
logical principle of causality. Shown first in a modification of the standard
clock paradox thought experiment, this fault carries over to finite
accelerations of the moving observer. After re-examination of the standard
clock paradox, a logical fault was also found in the concept of spacetime. A
two-dimensional treatment of the Earth orbit predicts that our astronomers
should measure proper time on distant variable objects in our own Galaxy as
impossibly running backwards on approach-then-recede trajectories. The
excellent record of relativity aside, we still have much new physics to learn
about our spatially three-dimensional universe. It is suggested that space is
not a freely stretching medium but is something that is substantive and is
being produced.


title: Phase Mapping as a Powerful Diagnostic of Primordial Non-Gaussianity

abstract:
  The identification and extraction of non-Gaussian signals is one of the main
cosmological challenges facing future experimental measurements of the cosmic
microwave background temperature pattern. We present a generalized statistical
measure based on a novel technique representation of Fourier phases using the
return map. We show that this method is both robust and powerful in comparison,
for example, with morphological measures.


title:
Old stellar Galactic disc in near-plane regions according to 2MASS:
  scales, cut-off, flare and warp

abstract:
  We have pursued two different methods to analyze the old stellar population
near the Galactic plane, using data from the 2MASS survey. The first method is
based on the isolation of the red clump giant population in the color-magnitude
diagrams and the inversion of its star counts to obtain directly the density
distribution along the line of sight. The second method fits the parameters of
a disc model to the star counts in 820 regions. Results from both independent
methods are consistent with each other. The qualitative conclusions are that
the disc is well fitted by an exponential distribution in both the
galactocentric distance and height. There is not an abrupt cut-off in the
stellar disc (at least within R<15 kpc). There is a strong flare (i.e. an
increase of scale-height towards the outer Galaxy) which begins well inside the
solar circle, and hence there is a decrease of the scale-height towards the
inner Galaxy. Another notable feature is the existence of a warp in the old
stellar population whose amplitude is coincident with the amplitude of the gas
warp.
  It is shown for low latitude stars (mean height: |z|~300 pc) in the outer
disc (galactocentric radius R>6 kpc) that: the scale-height in the solar circle
is h_z(R_sun)=3.6e-2 R_sun, the scale-length of the surface density is h_R=0.42
R_sun and the scale-length of the space density in the plane (i.e. including
the effect of the flare) is H=0.25 R_sun. The variation of the scale-height due
to the flare follows roughly a law h_z(R) =~ h_z(R_sun) exp
[(R-R_\odot)/([12-0.6R(kpc)] kpc)] (for R<~15 kpc; R_sun=7.9 kpc). The warp
moves the mean position of the disc to a height z_w=1.2e-3 R(kpc)^5.25
sin(phi+(5 deg.)) pc (for R<~13 kpc; R_sun=7.9 kpc).


title: Cepheid, Tully-Fisher and SNIa Distances

abstract:
  We first discuss why the uncomfortable fine-tuning of the parameters of the
Lambda-CDM cosmological model provides continuing, strong motivation to
investigate Hubble's Constant. Then we review evidence from the HST Key Project
that there is a significant scale error between raw Cepheid and Tully-Fisher
distances. An analysis of mainly HST Distance Scale Key Project data shows a
correlation between host galaxy metallicity and the rms scatter around the
Cepheid P-L relation, which may support a recent suggestion that the P-L
metallicity dependence is stronger than expected. If Cepheids do have a
significant metallicity dependence then the Tully-Fisher scale error increases
and the distances of the Virgo and Fornax clusters extend to more than 20Mpc,
decreasing the value of Ho. Finally, if the Cepheids have a metallicity
dependence then so do Type Ia Supernovae since the metallicity corrected
Cepheid distances to eight galaxies with SNIa would then suggest that the SNIa
peak luminosity is fainter in metal poor galaxies, with important implications
for SNIa estimates of qo as well as Ho.


title: X-Ray Spectral Variability Signatures of Flares in BL Lac Objects

abstract:
  We are presenting a detailed parameter study of the time-dependent electron
injection and kinematics and the self-consistent radiation transport in jets of
intermediate and low-frequency peaked BL Lac objects. Using a time-dependent,
combined synchrotron-self-Compton and external-Compton jet model, we study the
influence of variations of several essential model parameters, such as the
electron injection compactness, the relative contribution of synchrotron to
external soft photons to the soft photon compactness, the electron-injection
spectral index, and the details of the time profiles of the electron injection
episodes giving rise to flaring activity. In the analysis of our results, we
focus on the expected X-ray spectral variability signatures in a region of
parameter space particularly well suited to reproduce the broadband spectral
energy distributions of intermediate and low-frequency peaked BL Lac objects.
We demonstrate that SSC- and external-Compton dominated models for the
gamma-ray emission from blazars are producing significantly different
signatures in the X-ray variability, in particular in the soft X-ray light
curves and the spectral hysteresis at soft X-ray energies, which can be used as
a powerful diagnostic to unveil the nature of the high-energy emission from BL
Lac objects.


title:
Limits on the Short Term Variability of Sagittarius A* in the
  Near-Infrared

abstract:
  The recent detection of a 3-hr X-ray flare by the Chandra Observatory has
raised the possibility of enhanced emission over a broad range of wavelengths
from Sgr A*, the suspected 2.6 x 10^6 solar mass black hole at the Galactic
Center, during a flaring event. We have, therefore, reconstructed 3-hr data
sets from 2 micron speckle and adaptive optics images (theta_core = 50 - 100
mas) obtained with the W. M. Keck 10-m telescopes between 1995 and 2001. In 25
separate observations, no evidence of any significant excess emission
associated with Sgr A* was detected. The lowest of our detection limits gives
an observed limit for the quiescent state of Sgr A* of 0.09+/-0.005 mJy, or,
equivalently, a dereddened value of 2.0+/-0.1 mJy, which is a factor of 2 lower
than the best previously published quiescent value. Under the assumption that
there are random 3-hr flares producing both enhanced X-ray and near-infrared
emission, our highest limit constrains the variable state of Sgr A* to <0.8 mJy
(observed) or 19 mJy (dereddened). These results suggest that the model favored
by Markoff et al. (2001), in which the flare is produced through local heating
of relativistic particles surrounding Sgr A* (e.g., a sudden magnetic
reconnection event), is unlikely, because it predicts peak 2 micron emission of
300 mJy, well above our detection limit.


title: On angular momentum transport in convection-dominated accretion flows

abstract:
  Convection-dominated accretion flow (CDAF) is a promising model to explain
underluminous accreting black holes in X-ray binaries and galactic nuclei. I
discuss effects of angular momentum transport in viscous hydrodynamical and MHD
CDAFs. In hydrodynamical CDAFs, convection transports angular momentum inward,
and this together with outward convection transport of thermal energy determine
the radial structure of the flow. In MHD CDAFs, convection can transport
angular momentum either inward or outward, depending on properties of
turbulence in rotating magnetized plasma, which are not fully understood yet.
Direction of convection angular momentum transport can affect the law of
rotation of MHD CDAFs.


title:
Two Rare Magnetic Cataclysmic Variables with Extreme Cyclotron Features
  Identified in the Sloan Digital Sky Survey

abstract:
  Two newly identified magnetic cataclysmic variables discovered in the Sloan
Digital Sky Survey (SDSS), SDSSJ155331.12+551614.5 and SDSSJ132411.57+032050.5,
have spectra showing highly prominent, narrow, strongly polarized cyclotron
humps with amplitudes that vary on orbital periods of 4.39 and 2.6 hrs,
respectively. In the former, the spacing of the humps indicates the 3rd and 4th
harmonics in a magnetic field of ~60 MG. The narrowness of the cyclotron
features and the lack of strong emission lines imply very low temperature
plasmas and very low accretion rates, so that the accreting area is heated by
particle collisions rather than accretion shocks. The detection of rare systems
like these exemplifies the ability of the SDSS to find the lowest accretion
rate close binaries.


title: Multiple Collimated Outflows in the Proto-planetary Nebula GL 618

abstract:
  We present narrow-band H-alpha, [S II], and [O I] Hubble Space Telescope
images of the young planetary nebula GL 618. This object is a compact, bipolar
nebula that is currently undergoing the transition from asymptotic giant branch
star to planetary nebula. Our images confirm the presence of at least three
highly collimated outflows emanating from the central regions of GL 618. We
also detect H-alpha emission close to the central dust lane and in an extended
scattered light halo. The three outflows are occurring simultaneously in this
object, as opposed to being the result of a precessing jet. We derive an
inclination for the brightest outflow in the East lobe of 39 degrees. This
differs from the previous estimate of 45 degrees. In addition, our results
indicate that the outflows seen in GL 618 are probably not coplanar. Line
strengths derived from the narrow-band images indicate a shock velocity in the
range of 40 - 100 km/s. Based on the shock velocity we estimate that the age of
the outflows is less than 500 years. The outflows seen in the optical images of
GL 618 are related to features seen in near-IR, CO and CS maps of this object.
This relationship indicates that the outflows are playing a major role in the
morphological evolution of this young planetary nebula, interacting with and
shaping the neutral envelope surrounding GL 618. We discuss the implications of
these jets and their interaction with the neutral envelope in the context of
current models of planetary nebula formation.


title:
Measurement of the Flux of Ultrahigh Energy Cosmic Rays from Monocular
  Observations by the High Resolution Fly's Eye Experiment

abstract:
  We have measured the cosmic ray spectrum above 10^17.2 eV using the two air
fluorescence detectors of the High Resolution Fly's Eye observatory operating
in monocular mode. We describe the detector, photo-tube and atmospheric
calibrations, as well as the analysis techniques for the two detectors. We fit
the spectrum to a model consisting of galactic and extra-galactic sources.


title: Matter fields from a decaying background Lambda vacuum

abstract:
  We suggest an alternative framework for interpreting the current state of the
visible universe. Our approach is based on a dynamical ``Cosmological
Constant'' and the starting point is that a decaying vacuum produces matter. As
we point out, such a dynamical Lambda is not incompatible with the general
requirements of general relativity. By assuming inflation and big bang
nucleosynthesis we can solve for the present fractional densities of matter
Omega_{m,0} and vacuum Omega_{Lambda, 0} in terms of only one parameter which
we call the vacuum domination crossing redshift, z_c. We put constraints on z_c
to obtain a universe that is presently vacuum dominated and with characteristic
densities consistent with observations. The model points to the possible
existence of newly formed dark matter in the inter-cluster voids. We argue that
some of this matter could be accreting onto clusters through the latter's long
range gravitational potentials. If so, then cluster dark matter halos may not
manifest clear cut-offs in their radial density profiles. Furthermore, if a
substantial amount of this newly produced matter has already drained onto the
clusters, then the CMB power spectrum may favor lower dark matter density
values than is currently observed bound in the clusters. A final feature of our
approach relates to the combined effect of the matter production by a decaying
vacuum and the different rates at which matter and the vacuum will dilute with
the scale factor. Such combination may create conditions for a universe in
which the vacuum and matter densities dilute and evolve towards comparable
amplitudes. In this sense the model offers a natural and conceptually simple
explanation to the Coincidence Problem.


title: Can Hydrostatic Cores Form Within Isothermal Molecular Clouds?

abstract:
  Under the assumptions that molecular clouds are nearly spatially and
temporally isothermal and that the density peaks (``cores'') within them are
formed by turbulent fluctuations, we argue that cores cannot reach a
hydrostatic (or magneto-static) state as a consequence of their formation
process. In the non-magnetic case, stabilization requires a Bonnor-Ebert
truncation at a finite radius, which is not feasible for a single-temperature
flow, unless it amounts to a shock, which is clearly a dynamical feature.
Instead, in this case, cores must be dynamical entities that can either be
pushed into collapse, or else ``rebound'' towards the mean pressure and density
as the parent cloud. Nevertheless, rebounding cores are delayed in their
re-expansion by their own self-gravity. We give a crude estimate for the
re-expansion time as a function of the closeness of the final compression state
to the threshold of instability, finding typical values $\sim 1$ Myr, i.e., of
the order of a few free-fall times. Our results support the notion that not all
cores observed in molecular clouds need to be on route to forming stars, but
that instead a class of ``failed cores'' should exist, which must eventually
re-expand and disperse, and which can be identified with observed starless
cores. In the magnetic case, recent observational and theoretical work suggests
that all cores are critical or supercritical, and are thus qualitatively
equivalent to the non-magnetic case. Our results support the notion that the
entire star formation process is dynamical, with no intermediate hydrostatic
stages.


title: Challenges for Cluster Analysis in a Virtual Observatory

abstract:
  There has been an unprecedented and continuing growth in the volume, quality,
and complexity of astronomical data sets over the past few years, mainly
through large digital sky surveys. Virtual Observatory (VO) concept represents
a scientific and technological framework needed to cope with this data flood.
We review some of the applied statistics and computing challenges posed by the
analysis of large and complex data sets expected in the VO-based research. The
challenges are driven both by the size and the complexity of the data sets
(billions of data vectors in parameter spaces of tens or hundreds of
dimensions), by the heterogeneity of the data and measurement errors, the
selection effects and censored data, and by the intrinsic clustering properties
(functional form, topology) of the data distribution in the parameter space of
observed attributes. Examples of scientific questions one may wish to address
include: objective determination of the numbers of object classes present in
the data, and the membership probabilities for each source; searches for
unusual, rare, or even new types of objects and phenomena; discovery of
physically interesting multivariate correlations which may be present in some
of the clusters; etc.


title: Deconvolution With a Spatially-Variant PSF

abstract:
  Application of deconvolution algorithms to astronomical images is often
limited by variations in PSF structure over the domain of the images. One major
difficulty is that Fourier methods can no longer be used for fast convolutions
over the entire images. However, if the PSF is modeled as a sum of orthogonal
functions that are individually constant in form over the images, but whose
relative amplitudes encode the PSF spatial variability, then separation of
variables again allows global image operations to be used. This approach is
readily adapted to the Lucy-Richardson deconvolution algorithm. Use of the
Karhunen-Loeve transform allows for a particularly compact orthogonal expansion
of the PSF. These techniques are demonstrated on the deconvolution of
Gemini/Hokupa'a adaptive optics images of the galactic center.


title:
Grating X-ray Spectroscopy of High-Velocity Outflows from Active
  Galaxies

abstract:
  X-ray absorption and emission lines now serve as powerful diagnostics of the
outflows from active galaxies. Detailed X-ray line studies of outflows have
recently been enabled for a significant number of active galaxies via the
grating spectrometers on Chandra and XMM-Newton. We will review some of the
recent X-ray findings on active galaxy outflows from an observational
perspective. We also describe some future prospects. X-ray absorption lines
from H-like and He-like ions of C, N, O, Ne, Mg, Al, Si, and S are often seen.
A wide range of ionization parameter appears to be present in the absorbing
material, and inner-shell absorption lines from lower ionization ions, Fe
L-shell lines, and Fe M-shell lines have also been seen. The X-ray absorption
lines are typically blueshifted relative to the systemic velocity by a few
hundred km s^{-1}, and they often appear kinematically consistent with UV
absorption lines of C IV, N V, and H I. The X-ray absorption lines can have
complex profiles with multiple kinematic components present as well as filling
of the absorption lines by emission-line photons. A key remaining uncertainty
is the characteristic radial location of the outflowing gas; only after this
quantity is determined will it be possible to calculate reliably the amount of
outflowing gas and the kinetic luminosity of the outflow.