title: Primordial magnetic fields and CP violation in the sky

abstract:
  It has been argued that electroweak baryogenesis generates a left-handed
primordial magnetic field. The helicity density of the primordial magnetic
field today is estimated to be $\sim 10^2 n_b$ where $n_b\sim 10^{-6}$ /cm$^3$
is the present cosmological baryon number density. With certain assumptions
about the inverse cascade the field strength at recombination is $\sim
10^{-13}$ G on a coherence scale $\sim 10^{-4}$ pc. Here I discuss the various
assumptions made in obtaining these estimates and the concomitant open issues.


title:
The Lyman-alpha forest of a Lyman Break Galaxy: VLT Spectra of
  MS1512-cB58 at z=2.724

abstract:
  The high redshift galaxy MS1512-cB58 (z=2.724, m_V=20.64) has been observed
with the very efficient high resolution echelle spectrograph VLT/UVES. Although
this is a very challenging observational program for a Southern hemisphere
telescope (the galaxy is located at +36 deg declination), high resolution
spectra (FWHM ~ 26 km/s) have revealed, with unprecedented detail along a
galaxy sight line, the Lyman-alpha forest due to intervening clouds in the
intergalactic medium (IGM). The mean depression D_A due to IGM absorption
blueward of the galaxy Ly-alpha wavelength and the number density dn/dz of
Ly-alpha clouds have been compared with equivalent results obtained for QSO
sight lines at similar redshifts. Our results indicate a possible excess of
absorption close to the galaxy. The mean depression at ~ 150 h_65^-1 Mpc
comoving (Omega_m=0.3, Omega_Lambda=0.7) from the galaxy is D_A=0.36+/-0.03, to
be compared with 0.22+/-0.04, expected from a best fit to QSO sight lines. In
the same region (z=2.610), the number density of lines with HI column density
in excess of 10^14 atoms/cm2 is also about 3 sigma larger than expected. This
high density region is at least 60 h_65^-1 Mpc comoving wide, but the large
Ly-alpha absorption of the galaxy itself prevents us from detecting a possible
structure extending down to the galaxy. This excess of Ly-alpha clouds is
suggestive of two possible scenarios. One is the presence of a super cluster of
Ly-alpha clouds not associated with cB58. The other is a high density of gas
associated with the environment of cB58. Indeed, a hint of the complexity of
cB58 and possibly its environment is given by the huge velocity range (almost
1000 km/s) between the optical emission of star forming regions and UV
absorption of its interstellar medium.


title:
Large Equivalent width Lyman-alpha line emission at z=4.5: young
  galaxies in a young universe

abstract:
  The Large Area Lyman Alpha survey has found ~ 150 Lyman-alpha emitters at
z=4.5. While stellar models predict a maximum Lyman-alpha equivalent width (EW)
of 240 angstrom, 60% of the Lyman-alpha emitters have EWs exceeding this value.
We attempt to model the observed EW distribution by combining stellar
population models with an extrapolation of Lyman break galaxy luminosity
function at z=4, incorporating observational selection effects and Malmquist
bias. To reproduce the high EWs seen in the sample we need to postulate a
stellar initial mass function (IMF) with extreme slope alpha = 0.5 (instead of
2.35); zero metallicity stars; or narrow-lined active galactic nuclei. The
models also reveal that only 7.5-15% of galaxies need show Lyman-alpha emission
to explain the observed number counts. This raises the possibility that either
star-formation in high redshift galaxies is episodic or the Lyman-alpha
galaxies we are seeing are the youngest 7.5-15% and that Lyman-alpha is
strongly quenched by dust at about 10 Mega-years of age.


title:
Photometric Observations of Omega Centauri: Multi-Wavelength
  Observations of Evolved Stars

abstract:
  We present multi-wavelength observations of the northern population of Omega
Cen from the main-sequence turn-off to high on the red giant branch. We show
that the best information about the metallicity and age of the stars can be
gained from combining vby, B-I and V-I colors (in the absence of spectroscopy).
We confirm our results for the main-sequence turn-off stars: there is at least
a
  3 Gyr age spread. We use proper motion studies to confirm cluster membership
at and above the level of the horizontal branch, and we show that the age
spread is maintained amongst stars from the subgiant branch through the red
giants. The available evidence suggests that Omega Cen is the core of a
disrupted dwarf galaxy.


title:
Inflation with a constant ratio of scalar and tensor perturbation
  amplitudes

abstract:
  The single scalar field inflationary models that lead to scalar and tensor
perturbation spectra with amplitudes varying in direct proportion to one
another are reconstructed by solving the Stewart-Lyth inverse problem to
next-to-leading order in the slow-roll approximation.
  The potentials asymptote at high energies to an exponential form,
corresponding to power law inflation, but diverge from this model at low
energies, indicating that power law inflation is a repellor in this case. This
feature implies that a fine-tuning of initial conditions is required if such
models are to reproduce the observations. The required initial conditions might
be set through the eternal inflation mechanism.
  If this is the case, it will imply that the spectral indices must be nearly
constant, making the underlying model observationally indistinguishable from
power law inflation.


title:
The Star Formation Rate Intensity Distribution Function--Implications
  for the Cosmic Star Formation Rate History of the Universe

abstract:
  We address the effects of cosmological surface brightness dimming on
observations of faint galaxies by examining the distribution of "unobscured"
star formation rate intensities versus redshift. We use the star formation rate
intensity distribution function to assess the ultraviolet luminosity density
versus redshift, based on our photometry and photometric redshift measurements
of faint galaxies in the HDF and the HDF--S WFPC2 and NICMOS fields. We find
that (1) previous measurements have missed a dominant fraction of the
ultraviolet luminosity density of the universe at high redshifts by neglecting
cosmological surface brightness dimming effects, which are important at
redshifts larger than z = 2, (2) the incidence of the highest intensity star
forming regions increases monotonically with redshift, and (3) the ultraviolet
luminosity density plausibly increases monotonically with redshift through the
highest redshifts observed. By measuring the spectrum of the luminosity density
versus redshift, we also find that (4) previous measurements of the ultraviolet
luminosity density at redshifts z < 2 must be reduced by a factor 2 to allow
for the spectrum of the luminosity density between rest-frame wavelengths 1500
and 2800 A. And by comparing with observations of high-redshift damped
Lyman-alpha absorption systems detected toward background QSOs, we further find
that (5) the distribution of star formation rate intensities matches the
distribution of neutral hydrogen column densities at redshifts z = 2 through 5,
which establishes a quantitative connection between high-redshift galaxies and
high column density gas and suggests that high-redshift damped Lyman-alpha
absorption systems trace lower star formation rate intensity regions of the
same galaxies detected in star light in the HDF and HDF--S.


title:
High Energy Radiation Generated at Boundary Shear Layers of Relativistic
  Jets

abstract:
  A simple model of cosmic ray electron acceleration at the jet boundary
(Ostrowski 2000) yields a power-law particle energy distribution of
ultrarelativistic electrons with an energy cut-off growing with time and
finally, a growing particle bump at the energy, where energy gains equal
radiation losses. For such electron distribution, in tens-of-kpc scale jets, we
derived the observed time varying spectra of synchrotron and inverse-Compton
radiation, including comptonization of synchrotron and cosmic microwave
background photons. Slowly varying spectral index along the jet in the
`low-frequency' spectral range is a natural consequence of boundary layer
acceleration. Variations of the high energy bump of the electron distribution
can give rise to anomalous behaviour in X-ray band in comparison to the lower
frequencies.


title: Tracing Cosmic Evolution with an XMM Serendipitous Cluster Survey

abstract:
  This paper describes updated predictions, as a function of the underlying
cosmological model, for a serendipitous galaxy cluster survey that we plan to
conduct with the {\em XMM-Newton} X-ray Satellite. We have included the effects
of the higher than anticipated internal background count rates and have
expanded our predictions to include clusters detected at 3 sigma. Even with the
enhanced background levels, we expect the XCS to detect sufficient clusters at
z>1 to differentiate between open and flat cosmological models. We have
compared the XCS cluster redshift distribution to those expected from the XMM
Slew Survey and the ROSAT Massive Cluster Survey (MACS) and find them to be
complementary. We conclude that the future existence of the XCS should not
deter the launch of a dedicated X-ray survey satellite.


title:
High resolution Chandra HETG and RXTE observations of GRS 1915+105 : A
  hot disk atmosphere & cold gas enriched in Iron and Silicon

abstract:
  The time-averaged 30 ks Chandra HETGS observation of the micro-quasar GRS
1915+105 in the low hard state reveals for the first time in this source
neutral K absorption edges from Fe, Si, Mg, & S. Ionized resonance absorption
from H-, and He-like Fe (XXV, XXVI), Ca XX and possibly emission from neutral
Fe Kalpha and ionized Fe XXV (forbidden, or the resonance emission component of
a P-Cygni profile) are also seen. We report the tentative detection of the
first astrophysical signature of XAFS in the photoelectric edge of Si (and
possibly Fe and Mg), attributed to material in grains. The large column
densities measured from the neutral edges reveal anomalous Si and Fe
abundances. Scenarios for which the anomalous abundances can be attributed to
surrounding cold material associated with GRS 1915+105 and/or that the
enrichment may signify either a highly unusual supernova/hypernova, or external
supernova activity local to the binary are discussed. We attribute the ionized
features to a hot disk, disk-wind, or corona environment. These features allow
for constraints on the ionization parameter (log xi > 4.15), temperature (T >
2.4 x 10^6 K), and hydrogen equivalent number density (n > 10^{12} cm^{-3}) for
this region. Variability studies with simultaneous RXTE data show that the
light curve count rate tracks changes in the disk blackbody and the power-law
flux. Spectral changes in the Chandra data also track the behavior of the light
curve, and may point to changes in both the ionizing flux and density of the
absorber. A 3.69 Hz QPO and weak first harmonic is seen in the RXTE data.


title:
The Silent Majority - Jets and Radio Cores from Low-Luminosity Black
  Holes

abstract:
  They are weak, they are small, and they are often overlooked, but they are
numerous and an ubiquitous sign of accreting black holes: compact radio cores
and jets in low-power AGN. Here I summarize our work concerning these radio
cores and jets in recent years, specifically focusing on the large population
of low-luminosity AGN. Special attention is also given to Sgr A*, the
supermassive black hole candidate at the Galactic Center, whose radio
properties are reviewed in more detail. This source exhibits a submm-bump,
possibly from an ultra-compact region around the black hole which should allow
imaging of the event horizon of the black hole in the not too distant future. A
jet model is proposed which explains the basic feature of Sgr A*: its slightly
inverted radio spectrum, the submm-bump, the lack of extended emission, and the
X-ray emission. This model also works for famous sources like M81*, NGC4258, or
GRS1915+105 based on the argument that radio cores are jets whose emission can
be scaled with the accretion power over many orders of magnitude. This scaling
is corroborated by the detection of many Sgr A*-like radio cores in nearby
Low-Luminosity AGN (LLAGN), some of which show jet structures on the VLBI (Very
Long Baseline Interferometry) scale. These cores confirm an AGN origin of about
half of the known low-luminosity AGN classified as LINERs and dwarf-Seyferts.
It is argued that in fact most of the compact radio emission at centimeter
waves in LLAGN is produced by a compact radio jet and not an Advection
Dominated Accretion Flow (ADAF). In general one can say that compact radio
cores are a genuine feature of AGN, allowing one to precisely pinpoint black
holes in many galaxies - not only in luminous quasars.


title:
The X-ray Spectra of Black Hole X-ray Novae in Quiescence as Measured by
  Chandra

abstract:
  We present Chandra observations of black hole X-ray novae V404 Cyg, A0620-00,
GRO J1655-40 and XTE J1550-564 in quiescence. Their quiescent spectra can be
well fitted by a power-law model with slope $\alpha \sim 2$. While a coronal
(Raymond-Smith) model is also a statistically acceptable representation of the
spectra, the best fit temperatures of these models is $\sim 5$ times higher
than that seen in active stellar coronae. These four spectra of quiescent X-ray
novae are all consistent with that expected for accretion via an
advection-dominated accretion flow (ADAF) and inconsistent with that expected
from a stellar corona. This evidence for continued accretion in quiescence
further strengthens the case for the existence of event horizons in black
holes. Both A0620-00 and GRO J1655-40 were fainter than in previous
observations, while V404 Cyg was more luminous and varied by a factor of 2 in a
few ksec. A reanalysis of the X-ray data for XTE J1550-564 shows that (like
V404 Cyg and A0620-00) its luminosity exceeds the maximum prediction of the
coronal model by a large factor. The 0.3-7 keV luminosity of the four sources
studied ranges from $\sim 10^{30}-10^{33}$ erg/s.


title: Large Scale Structure at z=1.2 Outlined by MgII Absorbers

abstract:
  The largest known structure in the high redshift universe is mapped by at
least 18 quasars and spans ~5 deg x 2.5 deg on the sky, with a quasar spatial
overdensity of 6-10 times above the mean. This large quasar group provides an
extraordinary laboratory ~100 x 200 x 200 h^-3 comoving Mpc^3 in size (q0=0.5,
Lambda=0, H0=100h km/s/Mpc) covering 1.20<z<1.39 in redshift. One approach to
establish how LQGs relate to mass (galaxy) enhancements is to probe their gas
content and distribution via background quasars. We have found the large quasar
group to be associated with 11 MgII absorption systems at 1.2<z<1.4;
0.02%--2.05% of simulations with random MgII redshifts match or exceed this
number in that redshift interval, depending on the normalization method used.
The minimal spanning tree test also supports the existence of a structure of
MgII absorbers coincident with the LQG, and additionally indicates a foreground
structure populated by MgII absorbers and quasars at z~0.8. Finally, we find a
tendency for MgII absorbers in general to correlate with field quasars (i.e.
quasars both inside and outside of the LQG) at a projected scale length on the
sky of 9/h Mpc and a velocity difference |Delta v|=3000 to 4500 km/s. While the
correlation is on a scale consistent with observed galaxy-AGN distributions,
the nonzero velocity offset could be due to the "periphery effect", in which
quasars tend to populate the outskirts of clusters of galaxies and metal
absorption systems, or to peculiar velocity effects.


title: Active Optics in Modern, Large Optical Telescopes

abstract:
  Active optics is defined as the control of the shape and the alignment of the
components of an optical system at low temporal frequencies. For modern large
telescopes with flexible monolithic or segmented primary mirrors and also
flexible structures this technique is indispensable to reach a performance
which is either diffraction limited for an operation in space or limited by the
atmosphere for an operation on the ground. This article first describes the
theory of active optics, both of the wavefront analysis and the correction
mechanisms, then the design of three representative active optics systems, two
in telescopes of the four and eight meter class with meniscus mirrors and one
in a telescope with a segmented primary mirror, and, finally, presents
practical experience with these active optics systems.


title:
Dark matter halos around elliptical galaxies: how reliable is the
  stellar kinematical evidence ?

abstract:
  Hierarchical models of galaxy formation and various observational evidence
suggest that elliptical galaxies are, like disk galaxies, embedded in massive
dark matter halos. Stellar kinematics are considered the most important tracer
for this dark halo at a few effective radii. Using detailed modeling
techniques, several authors have recently presented stellar kinematical
evidence of a dark halo for a number of elliptical galaxies. In these modeling
techniques, dust attenuation (absorption and scattering of starlight by dust
grains) has not been taken into account. Nevertheless, elliptical galaxies
contain a significant amount of interstellar dust, which affects all observable
quantities, including the observed kinematics. We constructed a set of
dynamical models for elliptical galaxies, in which dust attenuation is included
through a Monte Carlo technique. We find that a dust component, shallower than
the stellar distribution and with an optical depth of order unity, affects the
observed kinematics significantly, in the way that it mimics the presence of a
dark halo. If such dust distributions are realistic in elliptical galaxies, we
are faced with a new mass-dust degeneracy. Taking dust into account in
dynamical modeling procedures will hence reduce or may even eliminate the need
for a dark matter halo at a few effective radii.


title: Type 1 AGN and their Link to ULIRGS

abstract:
  Increasing observational evidence supports a picture for a close link among
AGN phenomenum, star-formation processes and galaxy formation. Since the
physical phenomena related to the onset of both AGN and star formation are very
likely characterized by a strong far infrared (FIR) emission it becomes
mandatory to investigate the FIR energy domain. However, because of their
faintness in the FIR energy range, very little is known about the FIR
properties of type 1 AGN, and type 2 AGN, which are supposed to be missed in
classical searches, still lack definition and samples. Our aim is to
investigate the FIR properties of optically selected type 1 AGN, compare them
to Ultraluminous Infrared Galaxies (ULIRGs) and derive some general
characteristics of the population. Expectations for future surveys are also
presented.


title: The VST telescope control software in the ESO VLT environment

abstract:
  The VST (VLT Survey Telescope) is a 2.6 m Alt-Az telescope to be installed at
Mount Paranal in Chile, in the European Southern Observatory (ESO) site. The
VST is a wide-field imaging facility planned to supply databases for the ESO
Very Large Telescope (VLT) science and carry out stand-alone observations in
the UV to I spectral range. This paper will focus mainly on control software
aspects, describing the VST software architecture in the context of the whole
ESO VLT control concept. The general architecture and the main components of
the control software will be described.


title: VST telescope dynamic analisys and position control algorithms

abstract:
  The VST (VLT Survey Telescope) is a 2.6 m class Alt-Az telescope to be
installed on Cerro Paranal in the Atacama desert, Northern Chile, in the
European Southern Observatory (ESO) site. The VST is a wide-field imaging
facility planned to supply databases for the ESO Very Large Telescope (VLT)
science and carry out stand-alone observations in the UV to I spectral range.
So far no telescope has been dedicated entirely to surveys; the VST will be the
first survey telescope to start the operation, as a powerful survey facility
for the VLT observatory. This paper will focus on the axes motion control
system. The dynamic model of the telescope will be analyzed, as well as the
effect of the wind disturbance on the telescope performance. Some algorithms
for the telescope position control will be briefly discussed.


title: Extended HI disks in dust-lane elliptical galaxies

abstract:
  We present the results of HI observations of five dust-lane ellipticals with
the Australia Telescope Compact Array. Two galaxies (NGC 3108 and NGC 1947) are
detected, and sensitive upper limits are obtained for the other three. In the
two detected galaxies, the HI is distributed in a regular, extended and warped
disk-like structure of low surface brightness. Adding data from the literature,
we find that several more dust-lane ellipticals have regular HI structures.
This HI is likely to be a remnant of accretions/mergers which took place a
considerable time ago, and in which a significant fraction of the gas survived
to form a disk. The presence of regular HI structures suggests that some
mergers lead to galaxies with extended low surface brightness density gas
disks. These gas disk will evolve very slowly and these elliptical galaxies
will remain gas rich for a long period of time. (abridged)


title: Active optics control of the VST telescope with the CAN field-bus

abstract:
  The VST (VLT Survey Telescope) is a 2.6 m class Alt-Az telescope to be
installed at Mount Paranal in the Atacama desert, Chile, in the European
Southern Observatory (ESO) site. The VST is a wide-field imaging facility
planned to supply databases for the ESO Very Large Telescope (VLT) science and
carry out stand-alone observations in the UV to I spectral range. This paper
will focus on the distributed control system of active optics based on CAN bus
and PIC microcontrollers. Both axial and radial pads of the primary mirror will
be equipped by astatic lever supports controlled by microcontroller units. The
same CAN bus + microcontroller boards approach will be used for the temperature
acquisition modules.


title: Integration of the VIMOS control system

abstract:
  The VIRMOS consortium of French and Italian Institutes (PI: O. Le Fevre,
co-PI: G. Vettolani) is manufacturing two wide field imaging multi-object
spectrographs for the European Southern Observatory Very Large Telescope (VLT),
with emphasis on the ability to carry over spectroscopic surveys of large
numbers of sources: the VIsible Multi-Object Spectrograph, VIMOS, and the Near
InfraRed Multi-Object Spectrograph, NIRMOS. There are 52 motors to be
controlled in parallel in the spectrograph, making VIMOS a complex machine to
be handled. This paper will focus on the description of the control system,
designed in the ESO VLT standard control concepts, and on some integration
issues and problem solving strategies.


title:
N-band Observations of He 2-10: Unveiling the Dusty Engine of a
  Starburst Galaxy

abstract:
  To better understand the early stages of massive star cluster evolution we
have obtained J,H,K', and N (10.8 micron) images of the nuclear region of the
starburst galaxy He 2-10. The N-band images were obtained with the Gemini North
telescope and reveal four of the five enshrouded clusters, or "ultradense HII
regions" (UDHIIs), recently discovered in radio maps. None of these sources
appears in either the optical HST images or the near-infrared images. They
comprise about 60% of the total N-band flux from He 2-10 and, we suspect, a
similar fraction of the total far infrared flux measured by IRAS. The inferred
spectra of the UDHIIs are very similar to those of Galactic ultracompact HII
regions and we have modeled the UDHIIs under the assumption that they are
"scaled-up" versions of these objects. The bolometric luminosity of the
brightest UDHII is estimated to be ~2x10^9 L_sun, and the total mass of the
dust and gas is ~10^7 M_sun. The mass of the enshrouded stellar cluster must be
> 2.5x10^6 M_sun and the age must be < 4.8x10^6 yr. All of the stellar clusters
within the UDHIIs must have ages less than about 5x10^6 yr and masses greater
than about 5x10^5 M_sun. The logarithmic ratios of the radio to far infrared
flux densities for the individual UDHIIs, and He 2-10 as a whole, are
significantly larger than the average for normal galaxies, but comparable to
those for ultraluminous infrared galaxies. Large ratios for some starburst
galaxies may indicate that a significant fraction of the far infrared flux
arises from UDHIIs. If all of the far infrared flux from He 2-10 and other
starbursts is produced by heavily obscured regions, the observed correlation
between UV continuum slope and infrared-to-ultraviolet flux ratio in starbursts
cannot be due primarily to UV reprocessing by dust in a foreground screen.


title: Radiative cooling in SPH hydrodynamical simulations of X-ray clusters

abstract:
  The results from hydrodynamical TREESPH simulations of galaxy clusters are
used to investigate the dependence of the final cluster X-ray properties upon
the numerical resolution and the assumed star formation models for the cooled
gas. When cold gas particles are allowed to convert into stars the final gas
profiles show a well defined core radius and the temperature profiles are
nearly flat. Final X-ray luminosities are found to be numerically stable, with
uncertainties of a factor 2.


title: The evolution of the Tully-Fisher relation of spiral galaxies

abstract:
  We present the B-band Tully-Fisher relation (TFR) of 60 late-type galaxies
with redshifts 0.1-1. The galaxies were selected from the FORS Deep Field with
a limiting magnitude of R=23. Spatially resolved rotation curves were derived
from spectra obtained with FORS2 at the VLT. High-mass galaxies with v_max>=150
km/s show little evolution, whereas the least massive systems in our sample are
brighter by about 1-2 mag compared to their local counterparts. For the entire
distant sample, the TFR slope is flatter than for local field galaxies
(-5.77+-0.45 versus -7.92+-0.18). Thus, we find evidence for evolution of the
slope of the TFR with redshift on the 3-sigma level. This is still true when we
subdivide the sample into three redshift bins. We speculate that the flatter
tilt of our sample is caused by the evolution of luminosities and an additional
population of blue galaxies at z>=0.2. The mass dependence of the TFR evolution
also leads to variations for different galaxy types in magnitude-limited
samples, suggesting that selection effects can account for the discrepant
results of previous TFR studies on the luminosity evolution of late-type
galaxies.


title:
Photometric properties of Stellar Populations in GGCs: a
  multi-wavelength approach

abstract:
  Globular star clusters are extremely important astrophysical objects since
(1) they are prime laboratories for testing stellar evolution; (2) they are
``fossils'' from the epoch of galaxy formation, and thus important cosmological
tools; (3) they serve as test particles for studying the dynamics of the
Galaxy; (4) information on individual stars can provide constrains for stellar
dynamic models; (5) they are the largest aggregates in which all post Main
Sequence (MS) stars can be individually observed, and thus serve as fiducial
templates for all the studies of the integrated light from distant stellar
systems. In the framework of a long-term project devoted to a multi-band study
of stellar populations in Galactic Globular Clusters I present a set of recent
results of a systematic study of (1) the Red Giant Branch in the near-IR (J,K)
and in the optical bands; (2) the Horizontal Branch and Blue Stragglers stars
from mid- and far-UV observations obtained with HST.


title: The formerly X-ray reflection-dominated Seyfert~2 galaxy NGC6300

abstract:
  In this paper, a BeppoSAX observation of the bright Seyfert 2 galaxy NGC6300
is presented. The rapidly variable emission from the active nucleus is seen
through a Compton-thin (NH ~ 3x10^23 atomoms/cm/cm) absorber. A
Compton-reflection component with an unusually high reflection fraction (R ~
4.2), and the comparison with a reflection-dominated spectrum measured by RXTE
two and half years earlier suggest that NGC6300 belongs to the class of
"transient" AGN, undergoing long and repeated periods of low-activity. The
spectral transition provides support to the idea that Compton-thick and
Compton-thin X-ray absorbers in Seyfert 2 galaxies are decoupled, the former
being most likely associated with the "torus", whereas the latter is probably
located at much larger distances.


title: The Field population towards NGC 6553

abstract:
  We analyze the colour magnitude diagram of the field population in the
direction of the bulge cluster NGC 6553 to discuss the stellar field component
projected towards the cluster. In particular we investigate the nature of a
peculiar feature, called ``red flare'' which appears as a faint turnoff,
located 2 magnitudes about below the turnoff of the cluster, with a sparse
trace of a sub-giant branch just above. A detailed modeling shows that the red
flare is consistent with the expected location of the turnoff and sub-giant
branch of the bulge population, once that the appropriate metallicity range and
spatial distribution of the bulge stars are adopted. From the data, hints can
be derived about the spatial shape and the basic stellar parameters of the
bulge.


title:
A new, cleaner colour-magnitude diagram for the metal-rich globular
  cluster NGC 6528

abstract:
  Using two epochs of observations with HST/WFPC2 we obtain the stellar proper
motions for all stars in the field. The proper motions are used to separate the
bulge from the cluster stars. The stellar sequences in the resulting colour-
magnitude diagram (CMD) are better defined than in any previously published
CMD. Using alpha-enhanced stellar isochrones we find NGC 6528 to have a
probable age of 11+-2 Gyrs, this is the first attempt to establish the absolute
age for NGC6528. Previous studies have only compared the fiducial ridge line
for the cluster to that of other globular clusters of similar metallicities.
Mainly the comparisons have been with regards to NGC6553 and 47Tuc. With the
new metallicity determinations for individual stars in both NGC6553 and NGC6528
it is now clear that 47Tuc (at -0.71 dex) has a significantly lower metallicity
than NGC6528 and NGC6553 and is thus not a suitable comparison cluster as
regards differential age determinations. A comparison with the fiducial line
for NGC6553 confirms results in earlier studies, e.g. Ortolani et al. (1995),
that the two clusters indeed have very similar ages. From the measured
velocities both the proper motion of the cluster and the velocity dispersion in
the Galactic bulge are found. NGC 6528 is found to have a proper motion
relative to the Galactic bulge of mu_l=0.006 and mu_b=0.044 arcsec per century.
Using stars with ~14 < V < 19 (i.e. the red giant branch and horizontal branch)
we find, for the Galactic bulge, sigma_l= 0.33 +- 0.03 and sigma_b= 0.25 +-
0.02 arcsec per century. This give sigma_l/sigma_b=1.32 +- 0.16, consistent
both with previous proper motion studies of K giants in the Galactic bulge as
well as with predictions by models of the kinematics of bulge stars.


title: Infrared Light Curves of Mira Variable Stars from COBE DIRBE Data

abstract:
  We have used the COBE DIRBE database to derive near- and mid-infrared light
curves for a well-defined sample of 38 infrared-bright Mira variable stars, and
compared with optical data from the AAVSO. In general, the 3.5 micron and 4.9
micron DIRBE bandpasses provide the best S/N light curves, with S/N decreasing
with wavelength at longer wavelengths. At 25 microns, good light curves are
only available for ~10 percent of our stars, and at wavelengths >= 60 microns,
extracting high quality light curves is not possible. The amplitude of
variability is typically less in the near-infrared than in the optical, and
less in the mid-infrared than in the near-infrared, with decreasing amplitude
with increasing wavelength. On average, there are 0.20 +/- 0.01 magnitudes
variation at 1.25 microns and 0.14 +/- 0.01 magnitudes variation at 4.9 micron
for each magnitude variation in V. The observed amplitudes are consistent with
results of recent theoretical models of circumstellar dust shells around Mira
variables. For a few stars in our sample, we find clear evidence of time lags
between the optical and maxima of phase ~ 0.05 - 0.13, with no lags in the
minima. For three stars, mid-infrared maximum appears to occur slightly before
that in the near-infrared,but after optical maximum. We find three examples of
secondary maxima in the rising portions of the DIRBE light curves, all of which
have optical counterparts in the AAVSO data, supporting the hypothesis that
they are due to shocks rather than newly-formed dust layers. We find no
conclusive evidence for rapid (hours to days) variations in the infrared
brightnesses of these stars.


title:
A Correlation between Galaxy Light Concentration and Supermassive Black
  Hole Mass

abstract:
  We present evidence for a strong correlation between the concentration of
bulges and the mass of their central supermassive black hole (M_bh) -- more
concentrated bulges have more massive black holes. Using C_{r_e}(1/3) from
Trujillo, Graham & Caon (2001b) as a measure of bulge concentration, we find
that log (M_bh/M_sun) = 6.81(+/-0.95)C_{r_e}(1/3) + 5.03(+/-0.41). This
correlation is shown to be marginally stronger (Spearman's r_s=0.91) than the
relationship between the logarithm of the stellar velocity dispersion and log
M_bh (Spearman's r_s=0.86), and has comparable, or less, scatter (0.31 dex in
log M_bh), which decreases to 0.19 dex when we use only those galaxies whose
supermassive black hole's radius of influence is resolved and remove one well
understood outlying data point).


title:
Study of the Cir X--1 Broad Band Spectrum at Orbital Phases Close to the
  Apoastron

abstract:
  We report on the results of a BeppoSAX (1.8--200 keV) observation of the
peculiar X-ray binary source Circinus X--1 (Cir X--1) at the orbital phases
between 0.61 and 0.63. We find that three components are needed to fit the
broad band spectrum: a blackbody component, at a temperature of $\sim 0.6$ keV,
a Comptonized component, with a seed-photon temperature of $\sim 1.2$ keV,
electron temperature of $\sim 6$ keV and optical depth of $\sim 1.7$, and a
power-law component dominating the spectrum at energies higher than 20 keV. We
interpret the blackbody as the emission from the accretion disk, while the
Comptonized component probably comes from a corona surrounding the inner part
of the system. This spectrum is different from that observed at the periastron
(Iaria et al. 2001a) because of the presence of the blackbody component. We
discuss the implications of this difference and the presence of the power-law
component.


title:
FUSE Observations of Possible Infalling Planetesimals in the 51 Ophiuchi
  Circumstellar Disk

abstract:
  We present the first observations of the circumstellar (CS) disk system 51
Ophiuchi with the Far Ultraviolet Spectroscopic Explorer. We detect several
absorption lines arising from the unusual metastable atomic species NI (2D), NI
(2P), and SII (2D). These levels lie 1.8 - 3.6 eV above the ground level and
have radiative decay lifetimes of 2 days or less, indicating that the lines
arise from warm CS gas. The high S/N FUSE spectra, obtained six days apart,
also show time-variable absorption features arising from NI, NII, OI (1D), and
FeIII, which are redshifted with respect to the stellar velocity. The resolved
redshifted absorption extends over many tens of km/s (40 for NI, 100 for NII,
65 for OI, and 84 for FeIII). We calculate column densities for all the
variable infalling CS gasses, using the apparent optical depth method. The
FeIII and NII infalling gasses must be produced through collisional ionization,
and the ionization fraction of nitrogen suggests a gas temperature between
20000 and 34000 K. The infalling gas shows a peculiar, non-solar composition,
with nitrogen and iron more abundant than carbon. We also set upper limits on
the line-of-sight column densities of molecular hydrogen and carbon monoxide.
These observations strengthen the connection between 51 Oph and the older
debris-disk system Beta Pictoris, and indicate that there may be infalling
planetesimals in the 51 Oph system.


title: A Multiwavelength Study of Stephan's Quintet

abstract:
  Stephan's Quintet (SQ) is a compact group that we find in an atypical moment
when a high velocity intruder is passing through it. The intrusion is
particularly interesting because a previous intruder had stripped most of the
gas from the group members. This debris field was shocked in the ongoing
collision with the new intruder. This evolutionary history agrees well with
observations and explains how a strongly interacting system can show low levels
of star formation. We present new multiwavelength data including previously
unpublished ROSAT X-ray, Ha interference filter/FP, ISO MIR/FIR and radio line
and continuum images. These observations and previously published data provide
new insights as well as support for some previous hypotheses. 1) FP and HI
velocities allow us to unambiguously distinguish between gas associated with SQ
and the new intruder.
  2) Most detected emission regions are found in the remnant ISM of the NI
which allows us to infer its size and present physical state. 3) The few
emission regions associated with the stripped ISM of SQ include the best
candidate tidal dwarf galaxy. 4) Multiwavelength data suggest that strong
MIR/FIR emission from the Seyfert 2 nucleus of NGC7319 comes from dust heated
directly by a power-law continuum rather than a starburst. 5) The
correspondance between extended X-ray/radio continuum/forbidden optical
emission confirms the existence of a large scale shock in SQ.


title:
A High Angular Resolution Multiplicity Survey of the Open Clusters alpha
  Persei and Praesepe

abstract:
  Two hundred and forty-two members of the Praesepe and alpha Persei clusters
ranging from B (~5Msun) to early-M (~0.5 Msun) have been surveyed with high
angular resolution imaging. The 39 binary and 1 quadruple systems detected
encompass separations from 0".053 to 7".28; 28 of the systems are new
detections and there are 9 candidate substellar companions. The main results
from the survey are: * Over the projected separation range of 26-581 AU and
magnitude differences of DeltaK < 4.0 mag, the companion star fraction (CSF)
for alpha Persei is 0.09 +/- 0.03 and for Praesepe is 0.10 +/- 0.03. This
fraction is consistent with the field G-dwarf value, implying that there is not
a systematic decline in multiplicity with age on timescales of at 4 +1/-1.5 AU,
significantly smaller value than both the field G-dwarf and the nearby T Tauri
distributions. A simple population synthesis model suggests that the G-dwarf
binary population is a combination of ~30% dark cloud and ~70% giant molecular
cloud systems. * An exploration of the binary star properties reveals a cluster
CSF that increases with decreasing target mass and a cluster mass ratio
distribution that rises more sharply for higher mass stars, but is independent
of binary separation. These observational trends are consistent with several
models of capture in small clusters and simulations of accretion following
fragmentation in a cluster environment. * Among the cluster A stars, there is a
higher fraction of binaries in the subset with X-ray detections, consistent
with the hypothesis that lower mass companions are the true source of X-ray
emission. * In alpha Persei, the rotational velocities for solar-type binaries
with separations less that 60 AU the rotational evolution of young stars.


title:
Understanding the nature of the optically faint radio sources and their
  connection to the submillimeter population

abstract:
  We present a sample of 43 submillimeter sources detected (at >3 sigma), drawn
from our program to follow-up optically faint radio sources with SCUBA. These
sources already have associated radio and in many cases optical
identifications, and many are also detected at 450 microns. We compare these
with 12 submillimeter sources drawn from the literature, which were discovered
in blank field mapping campaigns, but also have radio detections. We then use
this total sample (55 sources) to study and model the evolution of dusty
galaxies. A correlation is observed in the sub-mm/radio color-magnitude
diagram, which can be modeled by strong luminosity evolution. The selection
effects of the radio/optical pre-selection technique are determined from the
models, and a corrected redshift distribution is constrained using a range of
model assumptions. The temperature/redshift effects on the 450 microns detected
subset of our sample are studied in relation to the models, and prospects for
improved measurements in the shorter sub-mm wavelength windows (450 microns and
350 microns) are explored.


title:
Reliability of the dark matter clustering in cosmological N-body
  simulation on scales below the mean separation length of particles

abstract:
  We critically examine the reliability of the dark matter clustering in
high-resolution cosmological $N$-body simulations on scales below the mean
separation length of particles. The particle discreteness effect imposes the
two fundamental limitations on those scales; the lack of the initial
fluctuation power and the finite mass resolution. We address this problem
applying the dark halo approach and are able to discuss separately how those
two limitations affect the dark matter clustering in $N$-body simulations at
early epochs. We find that limitations of the dark matter clustering are
primarily determined by the mass of particles. By a detailed comparison with
three major cosmological simulations, we also find that in order to reproduce a
proper amplitude of the dark matter clustering on small scales, halos with a
characteristic nonlinear mass, $M_{\rm NL}(z)$ defined by $\sigma_R(M_{\rm NL};
z)=1$, must be resolved in the simulation. This leads to a critical redshift
$z_{\rm crit}$ determined by $M_{\rm NL}(z_{\rm crit})=n_{\rm halo} m_{\rm
part}$ where $n_{\rm halo}$ is the number of particles necessary to resolve the
typical nonlinear mass halo ($\sim 10$). We conclude that, at least as far as
the two-point correlation functions are concerned, the dark matter clustering
in high-resolution $N$-body simulations on scales below the mean particle
separation is reliable down to the gravitational force resolution length only
for $z<z_{\rm crit}$, while it is strongly affected by the finite mass
resolution for $z>z_{\rm crit}$.


title: Cosmic Microwave Background Anisotropy in models with Quintessence

abstract:
  We study the Cosmic Microwave Background (CMB) anisotropies produced by
cosine-type quintessence models. In our analysis, effects of the adiabatic and
isocurvature fluctuations are both taken into account. For purely adiabatic
fluctuations with scale invariant spectrum, we obtain a stringent constraint on
the model parameters using the CMB data from COBE, BOOMERanG and MAXIMA.
Furthermore, it is shown that isocurvature fluctuations have significant
effects on the CMB angular power spectrum at low multipoles in some parameter
space, which may be detectable in future satellite experiments. Such a signal
may be used to test the cosine-type quintessence models.


title: The Gravitational Lens B1608+656: I. V, I, and H-band HST Imaging

abstract:
  We present a multi-wavelength analysis of high-resolution observations of the
quadruple lens B1608+656 from the HST archive, acquired with WFPC2 through
filters F606W (V-band) and F814W (I-band), and with NIC1 in filter F160W
(H-band).
  In the three bands, the observations show extended emission from the four
images of the source in a ring-like configuration that surrounds the two,
resolved, lensing galaxies. B1608+656 was discovered as a double-lobed radio
source, and later identified as a post-starburst galaxy in the optical. Based
on photometry and optical spectroscopy we estimate that the stellar population
of the source has an age of $\sim$ 500 Myr. This provides a model for the
spectrum of the source that extends over spectral regions where no observations
are available, and is used to generate Tiny Tim PSFs for the filters.
Deconvolutions performed with the Lucy-Richardson method are presented, and the
limitations of these restorations is discussed. V$-$I and I$-$H color maps show
evidence of extinction by dust associated with one of the lensing galaxies, a
late type galaxy presumably disrupted after its close encounter with the other
lens, an elliptical galaxy. The extinction affects the two lens galaxies and
two of the four multiple images. The diagnostic of wavelength-dependent effects
in the images shows that corrections for contamination with light from the
lenses, extinction, and PSF convolution need to be applied before using the
extended structure in the images as a constraint on lens models. We will
present the restoration of the images in a subsequent paper.


title:
Collimated Energy-Momentum Extraction from Rotating Black Holes in
  Quasars and Microquasars Using the Penrose Mechanism

abstract:
  For almost four decades, since the discovery of quasars, mounting
observational evidence has accumulated that black holes indeed exist in nature.
In this paper, I present a theoretical and numerical (Monte Carlo) fully
relativistic 4-D analysis of Penrose scattering processes (Compton at radii
between the marginally stable, marginally bound orbits and
gamma-gamma-->$e^-e^+$ pair production at the photon orbit) in the ergosphere
of a supermassive Kerr (rotating) black hole. These model calculations
surprisingly reveal that the observed high energies and luminosities of quasars
and other active galactic nuclei (AGNs), the collimated jets about the polar
axis, and the asymmetrical jets (which can be enhanced by relativistic Doppler
beaming effects) all are inherent properties of rotating black holes. From this
analysis, it is shown that the Penrose scattered escaping relativistic
particles exhibit tightly wound coil-like cone distributions (highly collimated
vortical jet distributions) about the polar axis, with helical polar angles of
escape varying from $0.5^o$ to $30^o$ for the highest energy particles. It is
also shown that the gravitomagnetic (GM) field, which causes the dragging of
inertial frames, exerts a force acting on the momentum vectors of the incident
and scattered particles, causing the particle emission to be asymmetrical above
and below the equatorial plane, thus appearing to break the equatorial
reflection symmetry of the Kerr metric. This energy-momentum extraction model
can be applied to any size black hole, irrespective of the mass, and therefore
applies to microquasars as well.


abstract:
  Recycling strange stars to millisecond periods is studied within the
framework of general relativity. We employ equations of state of strange quark
matter based on the MIT Bag Model, with massive strange quarks and lowest order
QCD interactions. The presence of the crust of normal matter is taken into
account, with a bottom density assumed to be equal to the neutron-drip one. The
calculations are performed by solving the exact 2-D equations for rigidly
rotating stationary configurations in general relativity. Evolutionary tracks
of accreting strange stars are computed, and their dependence on the initial
strange star mass and on the fraction of the angular momentum transferred to
the star from the infalling matter, is studied. The differences between
recycling strange stars and neutron stars are pointed out.


title:
Cosmic Temperature Decline in the Course of the Evolution of the
  Universe

abstract:
  At the early stage of the Universe-evolution there were no stars and no
galaxies, but only a uniform hot plasma consisting of free electrons and free
nuclei. The Universe temperature was determined by the Stefan-Boltzmann law of
thermodynamics and the general relativistic cosmological theory. At the present
time one has the background cosmic radiation with the temperature of 2.73K. We
calculate how much of the early Universe energy has gone to matter and other
forms of energy, so as to leave us with a background radiation of only 2.73K.


title: X-ray and optical monitoring of the peculiar source 4U 1700+24/V934 Her

abstract:
  (Abridged) We report on ASCA and BeppoSAX observations of the X-ray source 4U
1700+24 and on (quasi-)simultaneous spectroscopy of its optical counterpart,
V934 Her, from the Loiano 1.5-meter telescope. Archival ROSAT and RXTE data as
well as the RXTE ASM light curve of 4U 1700+24 are also analyzed along with a
1985 EXOSAT pointing. The optical spectra are typical of a M2 III star; a
revised distance to the object of ~400 pc is inferred. While these spectra do
not show either any change between the two epochs or any peculiar feature, the
X-ray spectra reveal a complex and long-term variable shape, with a clear soft
excess. The X-ray spectral properties of the source are best described by a
thermal Comptonization spectrum plus a soft energy(<1 keV) excess, which can be
modeled with a blackbody emission with kT_BB ~ 1 keV; the latter component is
not detected at the lowest source flux levels. The ratio between the two
components varies substantially with the source flux. The X-ray emission from
the object appears to become harder as its luminosity increases, and the RXTE
data acquired during an outburst occurred during Fall 1997 display a hard tail
detected up to 100 keV. Apart from erratic shot-noise variability on timescales
of tens to thousands of seconds, no significant pulsations or QPOs are found
from the timing analysis of the X-ray light curves. With the new distance
determination, the 2-10 keV X-ray luminosity range spanned in the considered
observations lies between ~2x10^32 and ~1x10^34 erg/s. All this allows us to
suggest a scenario consisting of a wide binary system in which a neutron star
accretes matter from the wind of an M giant.


title: Anomalous scattering of highly dispersed pulsars

abstract:
  We report multifrequency measurements of scatter broadening times for nine
highly dispersed pulsars over a wide frequency range (0.6 -- 4.9 GHz). We find
the scatter broadening times to be larger than expected and to scale with
frequency with an average power-law index of $3.44\pm 0.13$, i.e. significantly
less than that expected from standard theories. Such possible discrepancies
have been predicted very recently by Cordes & Lazio.


title: Can Structure Formation Influence the Cosmological Evolution?

abstract:
  The backreaction of structure formation influences the cosmological evolution
equation for the homogenous and isotropic average metric. In a cold dark matter
universe this effect leads only to small corrections unless a substantial
fraction of matter is located in regions where strong gravitational fields
evolve in time. A``cosmic virial theorem'' states that the sum of gravitational
and matter pressure vanishes and therefore relates the average kinetic energy
to a suitable average of the Newtonian potential. In presence of a scalar
``cosmon'' field mediating quintessence, however, cosmology could be modified
if local cosmon fluctuations grow large. We speculate that this may trigger the
accelerated expansion of the universe after the formation of structure.


title:
Absolute dimensions of the M-type eclipsing binary YY Geminorum (Castor
  C): a challenge to evolutionary models in the lower main-sequence

abstract:
  We present new spectroscopic observations of the detached late-type
double-lined eclipsing binary YY Gem, a member of the Castor sextuple system
and one of the benchmarks for the comparison between observations and stellar
evolution theory in the lower main-sequence. In addition, we have re-analyzed
existing light curves in several passbands using modern techniques that account
for the conspicuous presence of spots. This, combined with the spectroscopy,
has yielded a very precise determination of the absolute dimensions of the
components, which are virtually identical to each other. We obtain mean values
of M=0.5992+/-0.0047 Mo, R=0.6191+/-0.0057 Ro, and Teff=3820+/-100 K. Both the
mass and the radius determinations are good to better than 1%. A re-analysis of
the Hipparcos transit data for Castor AB has yielded an improved parallax for
the system of 66.90+/-0.63 mas. With this, we have estimated the age (~370 Myr)
and metal abundance ([Fe/H]~0.0) of YY Gem from isochrone fits to Castor A and
B. We have compared the observations of YY Gem with a large number of recent
theoretical calculations, and we show that all models underestimate the radius
by up to 20%, and most overestimate the effective temperature by 150 K or more.
Both of these trends are confirmed by observations of another similar system in
the Hyades cluster (V818 Tau). Consequently, theoretical ages for relatively
low-mass objects such as T Tauri stars derived from the H-R diagram may be
considerably biased. If the radius is used directly as a measure of evolution,
ages could be underestimated by as much as a factor of 10 in this mass regime.
In view of these discrepancies, absolute ages from essentially all current
models for the lower main sequence must be viewed with at least some measure of
skepticism. (abridged)


title: Combined multi-frequency map for point source substraction

abstract:
  A method is proposed for combining multi-frequency maps in order to produce a
catalogue of extragalactic point sources using data from future high-precision
satellite experiments. We have found the optimal way for combining maps at
different frequencies in order to maximize the signal (point sources) to noise
(rest of the signal) ratio. Our approach is a natural multi-frequency
generalization of the band-pass filter introduced by Tegmark and de
Oliveira-Costa (1998). We show that combination of different frequency maps
gives us the possibility of creating a more complete catalogue of point
sources.


title:
Galaxy colours in high redshift X-ray selected clusters - I: Blue galaxy
  fractions in eight clusters

abstract:
  We present initial results from a wide-field, multi-colour imaging project,
designed to study galaxy evolution in X-ray selected clusters at intermediate
(z~0.25) and high redshifts (z~0.5). In this paper we give blue galaxy
fractions from eight X-ray selected clusters, drawn from a combined sample of
three X-ray surveys. We find that all the clusters exhibit excess blue galaxy
populations over the numbers observed in local systems, though a large scatter
is present in the results. We find no significant correlation of blue fraction
with redshift at z>0.2 although the large scatter could mask a positive trend.
We also find no systematic trend of blue fraction with X-ray luminosity. We
show that the blue fraction is a function of (a) radius within a cluster, (b)
absolute magnitude and (c) the passbands used to measure the colour. We find
that our blue fractions (f_b) from galaxy colours close to restframe (U-B),
f_b~0.4, are systematically higher than those from restframe (B-V) colours,
f_b~0.2. We conclude this effect is real, may offer a partial explanation of
the widely differing levels of blue fraction found in previous studies and may
have implications for biases in optical samples selected in different bands.
  While the increasing blue fraction with radius can be interpreted as evidence
of cluster infall of field galaxies, the exact physical processes which these
galaxies undergo is unclear. We estimate that, in the cores of the more massive
clusters, galaxies should be experiencing ram--pressure stripping of galactic
gas by the intra--cluster medium. The fact that our low X-ray luminosity
systems show a similar blue fraction as the high luminosity systems, as well as
a significant blue fraction gradient with radius, implies other physical
effects are also important.


title: Theories of Gamma-Ray Bursts

abstract:
  The gamma ray burst phenomenon is reviewed from a theoretical point of view,
with emphasis on the fireball shock scenario of the prompt emission and the
longer wavelenght afterglow. Recent progress and issues are discussed,
including spectral-temporal evolution, localizations, jets, spectral lines,
environmental and cosmological aspects, as well as some prospects for future
experiments in both electromagnetic and non-electromagnetic channels.


title: Near-infrared micro-variability of radio-loud quasars

abstract:
  We observed three AGN from the Parkes Half-Jansky Flat-spectrum Sample at
near-infrared (NIR) wavelengths to search for micro-variability. In one source,
the blue quasar PKS 2243-123, good evidence for NIR micro-variability was
found. In the other two sources, PKS 2240-260 and PKS 2233-148, both BL
Lacertae objects, no such evidence of variability was detected. We discuss the
implications of these observations for the various mechanisms that have been
proposed for micro-variability.


title:
The Spectrum of the Th-Ar Hollow-Cathode Lamp Used with the 2dcoude
  Spectrograph

abstract:
  We have produced an atlas of the Th-Ar hollow-cathode lamp used with the
2dcoude spectrograph at McDonald Observatory. The atlas covers from 3611.9 to
10596.4 A at a resolving power of 52,000. We have determined the wavelenghts of
1483 emission lines in the spectrum with a median precision of 0.00023 A. A
web-based interface is offered for interactive visualization of segments of the
atlas or spectral orders.


title:
Clues about the Star Formation History of the M31 Disk from WFPC2
  Photometry

abstract:
  Over the past several years, the Hubble Space Telescope (HST) has acquired
many broad-band images of various regions in the M31 disk. I have obtained 27
such fields from the HST data archive in order to produce color-magnitude
diagrams (CMDs) of the stellar populations contained within these areas of the
disk. I have attempted to reproduce these CMDs using theoretical stellar
evolution models in conjunction with statistical tools for determining the star
formation history which best fits the observations. The wide range of
extinction values within any given field makes the data difficult to accurately
reproduce; nevertheless, I have managed to find star formation histories which
roughly reproduce the data. These statistically determined star formation
histories reveal that, like the disk of the Galaxy, the disk of M31 contains
very few old metal-poor stars. The histories also suggest that the star
formation rate of the disk as a whole has been low over the past ~1 Gyr.


title: The Parallax and Proper Motion of RX J1856.5-3754 Revisited

abstract:
  RX J1856.5-3754, a bright soft X-ray source believed to be the nearest
thermally emitting neutron star, has commanded and continues to command intense
interest from X-ray missions. One of the main goals is to determine the radius
of this neutron star. An integral part of the determination is an accurate
parallax. Walter (2001) analyzed Hubble Space Telescope (HST) data and derived
a parallax, pi=16.5+/-2.3 mas. Combining this distance with the angular radius
derived from blackbody fits to observations of RX J1856.5-3754 with ROSAT,
EUVE, HST, Pons et al. (2001) derived an observed radius ("radiation radius"),
R_{infty}= 7 km. This value is smaller than the radii calculated from all
proposed equations-of-state (EOS) of dense baryonic matter (Haensel 2001).
Here, we have analyzed the same HST data and find pi=7+/-2 mas. We have
verified our result using a number of different, independent techniques, and
find the result to be robust. Adopting our parallax, the radius of RX
J1856.5-3754 is R_{infty}=15+/-6 km. This radius falls squarely in the range of
radii, 12--16 km, expected from calculations of neutron star structure for
different equations of state. With additional HST observations, the parallax
estimate can be improved to the point by which the inferred radius can
constrain the choice of EOS.


title: Thickening of galactic disks through clustered star formation

abstract:
  (Abridged) The building blocks of galaxies are star clusters. These form with
low-star formation efficiencies and, consequently, loose a large part of their
stars that expand outwards once the residual gas is expelled by the action of
the massive stars. Massive star clusters may thus add kinematically hot
components to galactic field populations. This kinematical imprint on the
stellar distribution function is estimated here by calculating the velocity
distribution function for ensembles of star-clusters distributed as power-law
or log-normal initial cluster mass functions (ICMFs). The resulting stellar
velocity distribution function is non-Gaussian and may be interpreted as being
composed of multiple kinematical sub-populations. The notion that the formation
of star-clusters may add hot kinematical components to a galaxy is applied to
the age--velocity-dispersion relation of the Milky Way disk to study the
implied history of clustered star formation, with an emphasis on the possible
origin of the thick disk.


title:
Gravothermal Collapse of Self-Interacting Dark Matter Halos and the
  Origin of Massive Black Holes

abstract:
  A central supermassive black hole (SMBH) with a mass $10^6-10^9 M_\odot$
appears to be a common feature in nearby galaxies and the likely power source
in quasars and active galactic nuclei. We demonstrate that the formation of a
central black hole is a natural and inevitable consequence of the gravothermal
catastrophe in a self-interacting dark matter (SIDM) halo. Through gravothermal
evolution driven by collisional relaxation, an SIDM halo will form a massive
inner core whose density and velocity dispersion will increase secularly in
time. Eventually, the inner core arrives at a relativistic radial instability
and undergoes dynamical collapse to a black hole. The initial mass of the black
hole will be $10^{-8}-10^{-6}$ of the total mass of the halo. We show that if
at formation the overdensity in the SIDM halo is not too large, SMBHs in the
observed mass range can form directly in very massive halos following core
collapse. Alternatively, with large overdensities, moderate mass halos undergo
core collapse to form central seed black holes of intermediate mass, and these
holes can then merge and/or accrete to reach the SMBH range. Forming SMBHs by
core collapse in SIDM halos requires no baryons, no prior epoch of star
formation and no other mechanism of forming black holes seeds.


title: Polarized Foregrounds Power Spectra vs CMB

abstract:
  We briefly review our work about the polarized foreground contamination of
the Cosmic Microwave Background maps. We start by summarizing the main
properties of the polarized cosmological signal, resulting in "electric" (E)
and "magnetic" (B) components of the polarization tensor field on the sky. Then
we describe our present understanding of sub-degree anisotropies from Galactic
synchrotron and from extra-Galactic point sources. We discuss their
contamination of the cosmological E and B modes.


title: Cold dust in late-type Virgo Cluster galaxies

abstract:
  We have statistically analyzed the spatially integrated far-infrared (FIR)
emissions of the complete volume- and luminosity-limited sample of late-type
(later than S0) Virgo cluster galaxies measured using the Infrared Space
Observatory (ISO) by Tuffs et al. (2002) in bands centered on 60, 100 and 170
microns. 30 out of 38 galaxies detected at all three wavelengths contain a cold
dust emission component, present within all morphological types of late-type
systems ranging from early giant spirals to Blue Compact Dwarfs (BCDs), and
which could not have been recognized by IRAS. The temperatures of the cold dust
were found to be broadly distributed, with a median of 18 K, some 8-10 K lower
than would have been predicted from IRAS. The derived total dust masses are
correspondingly increased by factors of typically 6 - 13. A particularly
significant result concerns the low dust temperatures (ranging down to less
than 10 K) and large dust masses associated with the Im and BCD galaxies in our
sample. We propose two scenarios to account for the FIR characteristics of
these systems.


title: Chemical inhomogeneities and pulsation

abstract:
  Major improvements in models of chemically peculiar stars have been achieved
in the past few years. With these new models it has been possible to test
quantitatively some of the processes involved in the formation of abundance
anomalies and their effect on stellar structure. The models of metallic A (Am)
stars have shown that a much deeper mixing has to be present to account for
observed abundance anomalies. This has implications on their variability, which
these models also reproduce qualitatively. These models also have implications
for other chemically inhomogeneous stars such as HgMn B stars which are not
known to be variable and lambda Bootis stars which can be. The study of the
variability of chemically inhomogeneous stars can provide unique information on
the dynamic processes occurring in many types of stars in addition to modeling
of the evolution of their surface composition.


title: Injection of Radioactivities into the Forming Solar System

abstract:
  Meteorite studies have revealed the presence of short-lived radioactivities
in the early solar system. The current data suggests that the origin of at
least some of the radioactivities requires contribution from recent
nucleosynthesis at a stellar site. This sets a strict time limit on the time
available for the formation of the solar system and argues for the theory of
the triggered origin of the solar system. According to this scenario, the
formation of our planetary system was initiated by the impact of an
interstellar shock wave on a molecular cloud core. The shock wave originated
from a nearby explosive stellar event and carried with it radioactivities
produced in the stellar source. In addition to triggering the collapse of the
molecular cloud core, the shock wave also deposited some of the freshly
synthesized radioactivities into the collapsing system. The radioactivities
were then incorporated into the first solar system solids, in this manner
leaving a record of the event in the meteoritic material. The viability of the
scenario can be investigated through numerical simulations studying the
processes involved in mixing shock wave material into the collapsing system.
The high-resolution calculations presented here show that injection occurs
through Rayleigh-Taylor instabilities, the injection efficiency is
approximately 10%, and temporal and spatial heterogeneities in the abundances
of the radioactivities existed at the time of their arrival in the forming
solar system.


title: Abundances of 30 elements in 23 metal-poor stars

abstract:
  We report the abundances of 30 elements in 23 metal-poor ([Fe/H] <-1.7)
giants. These are based on 7774 equivalent widths and spectral synthesis of 229
additional lines. Hyperfine splitting is taken into account when appropriate.
Our choice of model atmospheres has the most influence on the accuracy of our
abundances. We consider the effect of different model atmospheres on our
results. In addition to the random errors in Teff, log g, and microturbulent
velocity, there are several sources of systematic error. These include using
Teff determined from FeI lines rather than colors, ignoring NLTE effects on the
FeI/FeII ionization balance, using models with solar [alpha/Fe] ratios and
using Kurucz models with overshooting. Of these, only the use of models with
solar [alpha/Fe] ratios had a negligible effect. However, while the absolute
abundances can change by > 0.10 dex, the relative abundances, especially
between closely allied atoms such as the rare earth group, often show only
small (<0.03 dex) changes. We found that some strong lines of FeI, MnI and CrI
consistently gave lower abundances by ~0.2 dex, a number larger than the quoted
errors in the gf values. After considering a model with depth-dependent
microturbulent velocity and a model with hotter temperatures in the upper
layers, we conclude that the latter did a better job of resolving the problem
and agreeing with observational evidence for the structure of stars. The error
analysis includes the effects of correlation of Teff, log g, and microturbulent
velocity errors, which is crucial for certain element ratios, such as [Mg/Fe].
The abundances presented here are being analyzed and discussed in a separate
series of papers.


title:
Observations of T-Tauri Stars using HST-GHRS: II. Optical and Near UV
  lines

abstract:
  We have analyzed GHRS data of eight Classical T Tauri stars (CTTSs) and one
Weak T Tauri star (WTTS). The GHRS data consist of an spectral range 40 A wide
centered on 2800 A. For 4 of the CTTS we have nearly simultaneous optical
observations which contain Halpha, Hbeta, HeI, NaD, and the CaII infrared
triplet. The MgII resonance doublet is the strongest feature in the 2800 A
range. This line has a fairly wide and symmetric emission component (~200 to
\~300 km/s for the CTTSs), with a narrow central absorption and a wide
blueshifted absorption superimposed to it. The narrow central absorption width
and equivalent width are inconsistent with being due only to ISM clouds
described in the literature, which lead us to conclude that it is partially due
to non-LTE processes in the emission line region itself. The emission profile
closely follows Halpha. Its large width in CTTS cannot be due to the Stark
effect and we suggest that it is due to supersonic turbulence. All the stars
show blueshifted absorptions that are evidence of outflows (terminal velocities
\~300 km/s), with multiple flows observed in two stars. We show evidence that
the wind is not spherical, with wind signatures being stronger for lower
inclinations at a given accretion rate. We briefly compare other optical lines
with the hot transition region lines observed in CTTS.


title:
Early-type Galaxy Distances from the Fundamental Plane and Surface
  Brightness Fluctuations

abstract:
  We compare two methods for deriving distances to early-type galaxies:
fundamental plane (FP) and surface brightness fluctuations (SBF) distances for
170 galaxies. A third set of distances is provided by predictions derived from
the density field of the IRAS redshift survey. Overall there is good agreement.
However, several nearby, low-luminosity, mainly S0 galaxies have systematically
low FP distances; we conclude that this is at least partly due to recent star
formation and consequently low mass-to-light ratios. The tie between the
Cepheid-calibrated SBF distances (Mpc) and the far-field calibrated FP
distances (km/s) yields a Hubble constant H_0 = 68 +/- 3 km/s/Mpc, while the
comparison between SBF and the IRAS-reconstructed distances yields H_0 = 74 +/-
2 (internal errorbars). Possible explanations for the marginal inconsistency
include systematic errors in the redshift survey completeness estimates or in
the FP aperture corrections, but at this point, the best estimate of H_0 from
early-type galaxies may be a simple average of the above two estimates. After
revising the SBF distances to be in agreement with the final set of Key Project
Cepheid distances, we conclude H_0 = 73 +/- 4 +/- 11, where the second errorbar
represents the total systematic uncertainty in the distance zero point. We also
discuss the recently introduced "fluctuation star count" parameter Nbar as a
less demanding alternative to (V-I) for calibrating SBF distances. The
Nbar-calibrated SBF method is akin to a hybrid SBF-FP distance indicator, and
we find that the use of Nbar actually improves the SBF distances. Further study
of Nbar would provide useful constraints for elliptical galaxy formation
models. (abridged)


title:
Evolution of the Ionizing Background and the Epoch of Reionization from
  the Spectra of z~6 Quasars

abstract:
  We study the process of cosmic reionization and estimate the ionizing
background in the IGM using the Lyman series absorption in the spectra of the
four quasars at 5.7<z<6.3 discovered by the SDSS. We derive the evolution of
the ionizing background at high redshifts, using both semi-analytic techniques
and cosmological simulations to model the density fluctuations in the IGM. The
existence of the complete Ly alpha Gunn-Peterson trough in the spectrum of the
z=6.28 quasar SDSS 1030+0524 indicates a photoionization rate Gamma_{-12} at
z~6 lower than 0.08, at least a factor of 6 smaller than the value at z~3. The
Ly beta and Ly gamma Gunn-Peterson troughs give an even stronger limit
Gamma_{-12}<0.02 due to their smaller oscillator strengths, indicating that the
ionizing background in the IGM at z~6 is more than 20 times lower than that at
z~3. Meanwhile, the volume-averaged neutral hydrogen fraction increases from
10^{-5} at z~3 to >10^{-3} at z~6. At this redshift, the mass-averaged neutral
hydrogen fraction is larger than 1%; the mildly overdense regions (delta > 3)
are still mostly neutral and the comoving mean free path of ionizing photons is
shorter than 8 Mpc. Comparison with simulations of cosmological reionization
shows that the observed properties of the IGM at z~6 are typical of those in
the era at the end of the overlap stage of reionization when the individual HII
regions merge. Thus, z~6 marks the end of the reionization epoch. The redshift
of reionization constrains the small scale power of the mass density
fluctuations and the star forming efficiency of the first generation of
objects.


title: Age Estimates for Globular Clusters in NGC 1399

abstract:
  We present high signal-to-noise Keck spectra for 10 globular clusters
associated with the giant Fornax elliptical NGC 1399, and compare measured line
indices with current stellar population models. Our data convincingly
demonstrate, for the first time, that at least some of the clusters in a giant
elliptical galaxy have super-solar abundance ratios, similar to the host
galaxy. From Hbeta line-strengths the majority of clusters have ages of ~11
Gyrs (within 2sigma), which is similar to the luminosity-weighted stellar age
of NGC 1399. Two of the clusters (which also reveal enhanced abundance ratios)
show significantly higher Hbeta values than the others. It remains unclear
whether this is due to young (~2 Gyr) ages, or extremely old (> 15 Gyr) ages
with a warm blue horizontal branch. However a conflict with current
cosmological parameters is avoided if the young age is favored. Either
alternative indicates a complicated age distribution among the metal-rich
clusters and sets interesting constraints on their chemical enrichment at late
epochs.


title: Detection of Galaxy Spin Alignments in the PSCz Shear Field

abstract:
  We report the first direct observational evidence for alignment of galaxy
spin axes with the local tidal shear field. We measure quantitatively the
strength of this directional correlation of disk galaxies from the Tully
catalog with the local shear field reconstructed from PSCz galaxies. We
demonstrate that the null hypothesis of random galaxy alignments relative to
the shear frame can be ruled out more than 99.98 % confidence. The observed
intrinsic correlation averaged over the censored samples that have detected
non-zero signals is measured in terms of the alignment parameter 'a=0.17 +/-
0.04', which includes only statistical errors of the censored data, but not the
cosmic variance error. The reconstruction procedure is likely to underestimates
'a' systematically. Our result is consistent with the linear tidal torque
model, and supports the idea that the present galaxy spins may be used as a
probe of primordial tidal shear and mass density fields. The intrinsic
alignments of galaxy spins dominate over weak gravitational lensing for shallow
surveys such like SDSS, while it should be negligible for deeper surveys at z ~
1.


title: The origin of primary nitrogen in galaxies

abstract:
  We investigate the role of stellar axial rotation on the nitrogen
nucleosynthesis at low metallicities Z. For this purpose, we have calculated
models with initial masses between 2 and 60 M$_\odot$ at Z=0.00001 from the
zero age sequence to the phase of thermal pulses for models below or equal to 7
M$_\odot$, and up to the end of central C--burning for the more massive stars.
The models include all the main physical effects of rotation. We show that
intermediate mass stars with rotation naturally reproduce the occurrence and
amount of primary nitrogen in the early star generations in the Universe. We
identify two reasons why rotating models at low Z produce primary $^{14}$N: 1)
Since the stars lose less angular momentum, they rotate faster. Simultaneously,
they are more compact, thus differential rotation and shear mixing are
stronger. 2) The H--burning shell has a much higher temperature and is thus
closer to the core, which favours mixing between the two.


title: The luminosity dependence of clustering

abstract:
  The PSCz redshift survey and the ongoing Two-Degree Field Galaxy Redshift
Survey (2dFGRS) are used to look for luminosity dependence of galaxy clustering
by measuring the two point correlation functions for sub-samples of the
surveys.
  An analysis of the PSCz survey finds that galaxies with cooler colours are
more strongly clustered than warmer galaxies. Between 1 and 10 Mpc/h it is
found that the redshift-space correlation function, is a factor of about 1.5
larger for the cooler galaxies. This is consistent with the suggestion that
hotter galaxies have higher star formation rates and correspond to later type
galaxies which are known to be less clustered than earlier types. There is a
very weak luminosity dependence of clustering with the more luminous galaxies
being less clustered than fainter galaxies, but the trend has a low statistical
significance.
  Results from the 2dFGRS reveal a strong dependence of clustering on intrinsic
galaxy luminosity. The most luminous galaxies are more strongly clustered by a
factor of 2.5 than L* galaxies, in qualitative agreement with analytic models
of galaxy formation.


title:
A photometric and spectroscopic study of dwarf and giant galaxies in the
  Coma cluster - V. Dependence of the spectroscopic properties on location in
  the cluster

abstract:
  We investigate the radial dependence of the spectroscopic properties, in
particular the Mg2, <Fe> and H beta spectroscopic indices, in a sample of
galaxies spanning a wide range of absolute luminosity in the Coma cluster.
  After allowing for the magnitude dependence of these indices, we find a
significant gradient in Mg2, in the sense that galaxies in the core of the
cluster have stronger Mg2. We find only weak gradients in <Fe> and H beta.
Using the model grids presented in an earlier paper in this series, we
attribute the Mg2 gradient to changes in metal abundance. One possible
mechanism to create this abundance gradient is pressure confinement by the
intracluster medium of material from Supernova driven winds early in the
history of the galaxies.


title: Spectroscopy of faint emission line nebulae

abstract:
  Based on results obtained with FORS1 in long-slit mode we demonstrate the
power of the VLT for the spectroscopy of faint emission line nebulae such as
the gaseous halos of diffuse ionized gas (DIG) in spiral galaxies. It is shown
that VLT spectra of DIG allow us to address the ionization and excitation
processes for the interstellar medium on galactic scales and that in the future
more detailed kinematical studies of DIG could help to constrain the origin of
the observed thick H+ layer in galaxies. The currently available
instrumentation with regard to this application is compared to other possible
designs and efficiencies for integral field spectrographs, in particular
Fabry-Perot systems.


title: Steady-State Eternal Inflation

abstract:
  Since the advent of inflation, several theorems have been proven suggesting
that although inflation can (and generically does) continue eternally into the
future, it cannot be extended eternally into the past to create a
``steady-state'' model with no initial time. Here we provide a construction
that circumvents these theorems and allows a self-consistent, geodesically
complete, and physically sensible steady-state eternally inflating universe,
based on the flat slicing of de Sitter space. This construction could be used
as the background space-time for creation events that form big-bang-like
regions, and hence could form the basis for a cosmology that is compatible with
observations and yet which avoids an initial singularity or beginning of time.


title:
The distribution of emission measure, and of heating budget, among the
  loops in the corona

abstract:
  The aim of this paper is to validate a methodology for connecting the
emission measure of individual solar coronal loops to the integrated emission
measure of the entire solar corona, and using this connection to deduce the
energetic properties of the corona, and then to show how this methodology can
be applied to observations of solar-like stellar coronae. The solar validation
is carried out by using spatially resolved X-ray observations of the Sun
obtained from the Yohkoh satellite. This work is a further step in our effort
to place the "solar-stellar connection" on a quantitative footing. In
particular, we show how this analysis procedure can be used in the context of
archival Einstein, ROSAT and EUVE data, as well as Chandra and XMM Newton data,
as a complementary analysis tool to existing multi-thermal component models.


title: The X-ray -- radio alignment in the z = 2.2 radio galaxy PKS 1138--262

abstract:
  We present high resolution X-ray observations of the narrow line radio galaxy
PKS 1138-262 at z = 2.156 with the ACIS-S detector on the Chandra observatory.
These observations show that the X-ray emission from 1138-262 is dominated by
emission from the AGN with a (rest frame) 2 to 10 keV luminosity of 4x10^{45}
erg/s. The relative X-ray and radio properties of the AGN in 1138-262 are
similar to those seen for the AGN in the archetype powerful radio galaxy Cygnus
A. Between 10% and 25% (depending on energy) of the X-ray emission from
1138--262 is spatially extended on scales of 10'' to 20''. The extended X-ray
emission is elongated, with a major axis aligned with that of the radio source.
While the X-ray and radio emissions are elongated on similar scales and
position angles, there is no one-to-one correspondence between the radio and
X-ray features in the source. The most likely origin for the extended X-ray
emission in 1138-262 is thermal emission from shocked gas, although we cannot
rule-out a contribution from inverse Compton emission. If the emission is from
hot gas, the gas density is 0.05 cm^{-3} and the gas mass is 2.5x10^{12}
M_solar. The pressure in this hot gas is adequate to confine the radio emitting
plasma and the optical line emitting gas. We set an upper limit of 1.5x10^{44}
erg/s to the 2 to 10 keV luminosity of any normal cluster atmosphere associated
with 1138-262. No emission was detected from any of the Ly alpha emitting
galaxies in the (proto-) cluster around 1138-262, outside of the Ly alpha halo
of 1138-262 itself, to a 2 to 10keV luminosity limit of 1.2x10^{43}erg/s.


title: Matter Power Spectrum from the Lyman-Alpha Forest: Myth or Reality?

abstract:
  We investigate possible systematic errors in the recent measurement of the
matter power spectrum from the Lyman-alpha forest by Croft et al. (2001). We
find that for a large set of prior cosmological models the Croft et al. result
holds quite well, with systematic errors being comparable to random ones, when
a dependence of the recovered matter power spectrum on the cosmological
parameters at z~3 is taken into account. We find that peculiar velocities cause
the flux power spectrum to be smoothed over about 100-300 km/s, dependng on
scale. Consequently, the recovered matter power spectrum is a smoothed version
of the underlying true power spectrum. Uncertainties in the recovered power
spectrum are thus correlated over about 100-300 km/s. As a side effect, we find
that residual fluctuations in the ionizing background, while having almost no
effect on the recovered matter power spectrum, significantly bias estimates of
the baryon density from the Lyman-alpha forest data. We therefore conclude that
the Croft et al. result provides a powerful new constraint on cosmological
parameters and models of structure formation.


title: Modified Median Statistics and Type Ia Supernova Data

abstract:
  The median statistic has recently been discussed by Gott \textit{et al.} as a
more reliable alternative to the standard $\chi^2$ likelihood analysis, in the
sense of requiring fewer assumptions about the data and being almost as
constraining. We apply this statistic to the currently available combined
dataset of 92 distant type Ia supernovae, and also to a mock SNAP-class
dataset. We find that the performances of the modified median and $\chi^2$
statistics are comparable, particularly in the latter case. We further extend
the work of Gott \textit{et al.} by modifying the median statistic to account
for the number and size of sequences of consecutive points above or below the
median. We also comment on how the performance of the statistic depends on the
choice of free parameters that one is estimating.


title: How Lumpy is the Milky Way's Dark Matter Halo?

abstract:
  CDM simulations predict that there are hundreds of lumps of with masses
greater than 10e7 solar masses in the Milky Way halo. However, we know of only
a dozen dwarf satellites close to this mass. Are these lumps simply lacking in
stars or is there a fundamental flaw in our most popular cosmology? By studying
the tidal debris of known satellites we can potentially address this question.
In this paper, we quantify the the effects of the dark matter lumps on tidal
tails. The lumps scatter stars in the tidal tails from their original orbits
producing a distinctive signature. We simulate debris evolution in smooth and
lumpy halos potentials and use our simulations to motivate and test a
statistical measure of the degree of scattering apparent in the angular
position and radial velocity measurement of debris stars - the ``scattering
index''. We find that the scattering index can in general distinguish between
the levels of substructure predicted by CDM cosmologies and smooth Milky Way
models, but that the sensitivity of the debris depends on the orientation of
the parent satellite's orbit relative to the largest lumps orbits.
  We apply our results to the carbon star stream associated with the
Sagittarius dwarf galaxy (Sgr) and find that these stars appear to be more
scattered than we expect for debris orbiting in a smooth halo. However, the
degree of scattering is entirely consistent with that expected due to the
influence of the Large Magellanic Cloud, which is on an orbit that intersects
Sgr's own. We conclude that the current data is unable to constrain CDM models.
Nevertheless, our study suggests that future data sets of debris stars
associated with other Milky Way satellites could provide strong constraints on
CDM models.


title:
A Fast, Accurate and Robust Algorithm For Transferring Radiation in
  Three-Dimensional Space

abstract:
  We have developed an algorithm for transferring radiation in
three-dimensional space. The algorithm computes radiation source and sink terms
using the Fast Fourier Transform (FFT) method, based on a formulation in which
the integral of any quantity (such as emissivity or opacity) over any volume
may be written in the classic convolution form. The algorithm is fast with the
computational time scaling as N (log N)^2, where N is the number of grid points
of a simulation box, independent of the number of radiation sources.
Furthermore, in this formulation one can naturally account for both local
radiation sources and diffuse background as well as any extra external sources,
all in a self-consistent fashion. Finally, the algorithm is completely stable
and robust.
  While the algorithm is generally applicable, we test it on a set of problems
that encompass a wide range of situations in cosmological applications,
demonstrating that the algorithm is accurate. These tests show that the
algorithm produces results that are in excellent agreement with analytic
expectations in all cases. In particular, radiation flux is guaranteed to
propagate in the right direction, with the ionization fronts traveling at the
correct speed with an error no larger than one cell for all the cases tested.
The total number of photons is conserved in the worst case at 10% level and
typically at 1-5% level over hundreds of time steps. As an added advantage, the
accuracy of the results depends weakly on the size of the time step, with a
typical cosmological hydrodynamic time step being sufficient.


title: Spectroscopic and Variability Surveys for AGN in the Groth Survey Strip

abstract:
  Preliminary results are presented for a spectroscopic survey of the Groth
Survey Strip (GSS), a 40 by 3.5 arcminute region of the sky imaged with HST,
for which several hundred galaxy spectra have been obtained as part of the DEEP
project (http://deep.ucolick.org). At least 6 broad-line AGNs (primarily
Seyfert 1s) have been detected as well as several narrow-line Seyfert 2
candidates. The Seyfert galaxies detected in our survey have integrated
absolute magnitudes extending to M(B)~-17.5, probing fainter magnitudes and
higher redshifts than existing optical spectroscopic surveys. We also discuss a
variability study of the GSS using the original HST images from 1994 and new
images obtained in 2001. The high resolution obtained with HST allows us to
isolate and measure variable galactic nuclei too faint to be detected from the
ground, reaching nuclear magnitudes of M(B)~-16 in galaxies to z=0.8. The
combination of these techniques provides a powerful probe of the population of
low-luminosity AGNs at moderate redshifts.


title: Spectra of the Expansion Stage of X-Ray Bursts

abstract:
  We present an analytical theory of thermonuclear X-ray burst atmosphere
structure. Newtonian gravity and diffusion approximation are assumed.
Hydrodynamic and thermodynamic profiles are obtained as a numerical solution of
the Cauchy problem for the first-order ordinary differential equation. We
further elaborate a combined approach to the radiative transfer problem which
yields the spectrum of the expansion stage of X-ray bursts in analytical form
where Comptonization and free-free absorption-emission processes are accounted
for and tau ~ r^{-2} opacity dependence is assumed. Relaxation method on an
energy opacity grid is used to simulate radiative diffusion process in order to
match analytical form of spectrum, which contains free parameter, to energy
axis. Numerical and analytical results show high similarity. All spectra
consist of a power-law soft component and diluted black-body hard tail. We
derive simple approximation formulae usable for mass-radius determination by
observational spectra fitting.


title:
Capabilities of the NASA/IPAC Extragalactic Database (NED) in the Era of
  a Global Virtual Observatory

abstract:
  We review the capabilities of the NASA/IPAC Extragalactic Database (NED,
http://ned.ipac.caltech.edu) for information retrieval and knowledge discovery
in the context of a globally distributed virtual observatory. Since its
inception in 1990, NED has provided astronomers world-wide with the results of
a systematic cross-correlation of catalogs covering all wavelengths, along with
thousands of extragalactic observations culled from published journal articles.
NED is continuously being expanded and revised to include new catalogs and
published observations, each undergoing a process of cross-identification to
capture the current state of knowledge about extragalactic sources in a
panchromatic fashion. In addition to assimilating data from the literature, the
team is incrementally folding in millions of observations from new large-scale
sky surveys such as 2MASS, NVSS, APM, and SDSS. At the time of writing the
system contains over 3.3 million unique objects with 4.2 million
cross-identifications. We summarize the recent evolution of NED from its
initial emphasis on object name-, position-, and literature-based queries into
a research environment that also assists statistical data exploration and
discovery using large samples of objects. Newer capabilities enable "Web
mining" of entries in geographically distributed astronomical archives that are
indexed by object names and positions in NED, sample building using constraints
on redshifts and object types, and an image archive. A pilot study demonstrates
how NED is being used in conjunction with linked survey archives to
characterize the properties of galaxy classes to form a training set for
machine learning algorithms. Opportunities for tighter integration of NED
capabilities into data mining tools for astronomy archives are also discussed.


title: Turbulent Compressibilty of Protogalactic Gas

abstract:
  The star formation rate in galaxies should be related to the fraction of gas
that can attain densities large enough for gravitational collapse. In galaxies
with a turbulent interstellar medium, this fraction is controlled by the
effective barotropic index $gamma = dlog P/dlog (rho)$ which measures the
turbulent compressibility. When the cooling timescale is smaller than the
dynamical timescale, gamma can be evaluated from the derivatives of cooling and
heating functions, using the condition of thermal equilibrium. We present
calculations of gamma for protogalaxies in which the metal abundance is so
small that H_2 and HD cooling dominates. For a heating rate independent of
temperature and proportional to the first power of density, the turbulent gas
is relatively "hard", with $gamma >= 1$, at large densities, but moderately
"soft", $gamma <= 0.8$, at densities below around $10^4 cm^(-3)$. At low
temperatures the density probability distribution should fall ra pidly for
densities larger than this value, which corresponds physically to the critical
density at which collisional and radiative deexcitation rate s of HD are equal.
The densities attained in turbulent protogalaxies thus depend on the relatively
large deuterium abundance in our universe. We expect the same physical effect
to occur in higher metallicity gas with different coolants. The case in which
adiabatic (compressional) heating due to cloud collapse dominates is also
discussed, and suggests a criterion for the maximum mass of Population III
stars.


title: Str{\"o}mgren Color-Temperature Relations for Cool Stars

abstract:
  A new extensive grid of synthetic Str{\"o}mgren colors and bolometric
corrections is presented for F-M type dwarf and giant stars having 3000K $\leq$
T$_{\rm{eff}}$ $\leq$ 8000K, 0.0 $\leq$ log $g$ $\leq$ 5.0, and -3.0 $\leq$
[Fe/H] $\leq$ 0.5. These purely theoretical colors are placed on the
observational system using color calibrations derived from $uvby$ photometry of
nearby field stars having $Hipparcos$ parallaxes and effective temperatures
determined by the infrared flux method. Modern isochrones transformed to the
observed plane using the resultant color-temperature relations are able to
reproduce the $uvby$ color-magnitude diagrams of several open and globular
clusters (notably M 67, M 92, and 47 Tuc) quite satisfactorily.


title: CMB and Inflation: the report from Snowmass 2001

abstract:
  Astrophysical observations provide the best evidence of physics beyond the
particle physicists' standard model. Over the past decade, the case has
solidified for inflation, dark energy, dark matter and massive neutrinos. In
this report we focus on inflation and dark energy as constrained by the
CMB--first the evidence from current observations and then what we can expect
to learn in the future. High energy physicists can contribute to the succesful
realization of this future, both observationally and theoretically.


title:
The Relation between Near-Infrared Luminosity of RGB Bumps and
  Metallicity of Galactic Globular Clusters

abstract:
  Using photometric data from the 2MASS second incremental release point source
catalog we constructed Ks vs. (J-Ks) color-magnitude diagrams (CMDs) of
Galactic globular clusters (GGCs) for which the JKs photometric data have been
made available up to now. On the CMDs of 13 GGCs we identified RGB bump
features and derived luminosities of bumps in Ks and in absolute Ks for 11 of
them. We reconfirm the relation between abolute Ks magnitude of bump and
metallicity [Fe/H]CG97 or [M/H] such that the luminosity of bump becomes
brighter as metallicity [Fe/H]CG97 or [M/H] decreases. This result is similar
to that obtained by Ferraro et al. (1999) for the relation between abolute V
magnitude of bump and [M/H] based on observations of 47 GGCs which were
conducted in the optical region (V vs. (B-V) CMDs). Our results show the same
trend as those found by Ferraro et al. (2000) for the relations between abolute
Ks magnitude of bump and metallicity [Fe/H]CG97 and [M/H] derived from
observations of 8 GGCs in the same near-infrared (K vs. (J-K) CMDs). Combining
with the data of Ferraro et al. (2000), we derive a robust relation for the
metal-dependent luminosities of the bumps.


title:
The Gravitational Lens -- Galaxy Group Connection: I. Discovery of a
  Group Coincident with CLASS B0712+472

abstract:
  Previous observations of the environments of the lensing galaxies in
gravitational lens systems suggest that many of the lensing galaxies are
associated with small groups of galaxies. As a result, we have begun a
coordinated program to study the local environments of all known gravitational
lens systems. In this paper, we present results on the gravitational lens
system CLASS B0712+472, which has previously measured source and lens redshifts
of (z_l,z_s) = (0.4060,1.339). Although we have not found a galaxy group
associated with the primary lensing galaxy, we have found a foreground group
which is spatially coincident with the lens system. Based on multi-object
spectroscopy taken at the Keck 10-m telescope, we have confirmed ten group
members with a mean redshift of <z> = 0.2909. The resulting velocity dispersion
and estimated virial mass are 306(+110/-58) km/s and 3.0(+2.2/-1.2) x 10^13
h^-1 M_sun, respectively, for (Omega_m,Omega_Lambda) = (0.2,0.0). The dynamical
properties of this moderate-redshift group are completely consistent with the
range of values found in nearby groups of galaxies. Five of the group members
are red, elliptical-like galaxies, while the remaining five are active,
star-forming galaxies. Based on the spectroscopic results and the
publically-available HST imaging of nine group members, we find that the
early-type fraction is 40%. We estimate that the effect of this foreground
group on the gravitational lensing potential of B0712+472 is small, producing
an external shear which is only a few percent, although the shear could be
larger if the group centroid is significantly closer to the lens system than it
appears to be.