title: The REFLEX Galaxy Cluster Survey IV: The X-ray Luminosity Function

abstract:
  The X-ray galaxy cluster sample from the REFLEX Cluster Survey, which covers
the X-ray brightest galaxy clusters detected in the ROSAT All-Sky Survey in the
southern sky, is used to construct the X-ray luminosity function of clusters in
the local Universe. With 452 clusters detected above an X-ray flux-limit of 3
10^(-12) erg s^(-1) cm^(-2) in 4.24 sr of the sky, this sample is the most
comprehensive X-ray cluster sample with a well documented selection function,
providing the best current census of the local X-ray galaxy cluster population.
In this paper we discuss the construction of the luminosity function, the
effects of flux measurement errors and of variations with sample region and we
compare the results to those from previous surveys.


title:
Gravitational wave production: A strong constraint on primordial
  magnetic fields

abstract:
  We compute the gravity waves induced by anisotropic stresses of stochastic
primordial magnetic fields. The nucleosynthesis bound on gravity waves is then
used to derive a limit on the magnetic field amplitude as function of the
spectral index. The obtained limits are extraordinarily strong: If the
primordial magnetic field is produced by a causal process, leading to a
spectral index $n\ge 2$ on super horizon scales, galactic magnetic fields
produced at the electroweak phase transition or earlier have to be weaker than
$B_\la \le 10^{-27}$Gauss! If they are induced during an inflationary phase
(reheating temperature $T\sim 10^{15}$GeV) with a spectral index $n\sim 0$, the
magnetic field has to be weaker than $B_\la \le 10^{-39}$Gauss! Only very red
magnetic field spectra, $n\sim -3$ are not strongly constrained. We also find
that a considerable amount of the magnetic field energy is converted into
gravity waves. The gravity wave limit derived in this work rules out most of
the proposed processes for primordial seeds for the large scale coherent
magnetic fields observed in galaxies and clusters.


title: CMB constraints on spatial variations of the vacuum energy density

abstract:
  In a recent article, a simple `spherical bubble' toy model for a spatially
varying vacuum energy density was introduced, and type Ia supernovae data was
used to constrain it. Here we generalize the model to allow for the fact that
we may not necessarily be at the centre of a region with a given set of
cosmological parameters, and discuss the constraints on these models coming
from Cosmic Microwave Background Radiation data. We find tight constraints on
possible spatial variations of the vacuum energy density for any significant
deviations from the centre of the bubble and we comment on the relevance of our
results.


title: Chandra finds X-ray jets are common in low-power radio galaxies

abstract:
  We present results for the first three low-power radio galaxies from the B2
bright sample to have been observed with Chandra. Two have kpc-scale radio
jets, and in both Chandra resolves jet X-ray emission, and detects soft X-ray
core emission and an X-ray emitting galaxy-scale atmosphere of luminosity a few
10^41 ergs s^-1. These are the first detections of X-ray jets in low-power
radio galaxies more distant than Cen A and M 87. The cooling time of the
galaxy-scale gas implies mass infall rates of order one solar mass per year.
The gas pressure near the jets is comparable to the minimum pressure in the
jets, implying that the X-ray emitting gas may play an important role in jet
dynamics. The third B2 radio galaxy has no kpc-scale radio jet, and here only
soft X-ray emission from the core is detected. The ratio of X-ray to radio flux
is similar for the jets and cores, and the results favour a synchrotron origin
for the emission. kpc-scale radio jets are detected in the X-ray in ~7 ks
exposures with Chandra more readily than in the optical via HST snapshot
surveys.


title:
Cosmological magnetic fields from photon coupling to fermions and bosons
  in inflation

abstract:
  We consider several gauge invariant higher dimensional operators that couple
gravity, gauge fields and scalar or fermionic fields and thus break conformal
invariance. In particular, we consider terms that break conformal invariance by
the photon coupling to heavy and light fermions. While the coupling to heavy
fermions typically do not induce significant magnetic fields, the coupling to
light fermions may produce observable magnetic fields when there are a few
hundred light fermions. Next we consider Planck scale modifications of the
kinetic gauge terms of the form f(phi) F_{mu nu} F^{mu nu} and h(psi) F_{mu nu}
\~F^{mu nu}, where f and h are functions of scalar and pseudoscalar fields phi,
psi, and F_{mu nu}, ~F^{mu nu} are the gauge field strength and its dual,
respectively. For a suitable choice of f sufficiently strong magnetic fields
may be produced in inflation to be potentially observable today. The
pseudoscalar coupling may lead to birefringence in inflation, but no observable
magnetic field amplification. Finally, we show that the photon coupling to
metric perturbations produces by far too weak fields to be of cosmological
interest.


title: ASCA observations of massive medium-distant clusters of galaxies. II

abstract:
  We have selected seven medium-distant clusters of galaxies (z ~ 0.1 - 0.3)
for multi-wavelength observations with the goal of investigating their
dynamical state. Following Paper I (Pierre et al. 1999) which reported the ASCA
results about two of them, we present here the analysis of the ASCA
observations of the other five clusters; RXJ1023.8-2715 (A3444),
RXJ1031.6-2607, RXJ1050.5-0236 (A1111), RXJ1203.2-2131(A1451), and
RXJ1314.5-2517. Except for RXJ1031.6, whose X-ray emission turned out to be
dominated by an AGN, the ASCA spectra are well fitted by a one-temperature thin
thermal plasma model. We compare the temperature-luminosity relation of our
clusters with that of nearby ones (z<0.1). Two clusters, RXJ1050.5 and
RXJ1023.8, show larger luminosities than the bulk of clusters at similar
temperatures, which suggests the presence of a cooling flow. The temperature
vs. iron-abundance relationship of our sample is consistent with that of nearby
clusters.


title:
New Analyses of Star-to-Star Abundance Variations Among Bright Giants in
  the Mildly Metal-Poor Globular Cluster M5

abstract:
  We present a chemical composition analysis of 36 giant stars in the mildly
metal-poor globular cluster M5 (NGC 5904). The analysis makes use of high
resolution data acquired at the Keck I telescope as well as a re-analysis of
high resolution spectra acquired for an earlier study at Lick Observatory. We
employed two analysis techniques: one, adopting standard spectroscopic
constraints, and two, adopting an analysis consistent with the non-LTE precepts
as recently described by Thevenin & Idiart. The abundance ratios we derive for
magnesium, silicon, calcium, scandium, titanium, vanadium, nickel, barium and
europium in M5 show no significant abundance variations and the ratios are
comparable to those of halo field stars. However, large variations are seen in
the abundances of oxygen, sodium and aluminum, the elements that are sensitive
to proton-capture nucleosynthesis. In comparing the abundances of M5 and M4
(NGC 6121), another mildly metal-poor globular cluster, we find that silicon,
aluminum, barium and lanthanum are overabundant in M4 with respect to what is
seen in M5, confirming and expanding the results of previous studies. In
comparing the abundances between these two clusters and others having
comparable metallicities, we find that the anti-correlations observed in M5 are
similar to those found in more metal-poor clusters, M3, M10 and M13, whereas
the behavior in M4 is more like that of the more metal-rich globular cluster
M71. We conclude that among stars in Galactic globular clusters, there is no
definitive ``single'' value of [el/Fe] at a given [Fe/H] for at least some
alpha-capture, odd-Z and slow neutron-capture process elements, in this case,
silicon, aluminum, barium and lanthanum.


title:
The Galaxy Correlation Function in the CNOC2 Redshift Survey: Dependence
  on Color, Luminosity and Redshift

abstract:
  We examine how the spatial correlation function of galaxies from the CNOC2
Field Galaxy Redshift Survey depends on galaxy color, luminosity and redshift.
The projected correlation function w_p is determined for volume-limited samples
of objects with 0.12 < z < 0.51 and evolution-compensated Rc absolute
magnitudes M < -20, over the comoving projected separation range 0.04 Mpc/h <
r_p < 10 Mpc/h. Our sample consists of 2937 galaxies which are classified as
being either early- or late-type objects according to their spectral energy
distribution (SED), determined from UBVRcIc photometry. For simplicity, galaxy
SEDs are classified independently of redshift: our classification scheme
therefore does not take into account the colour evolution of galaxies.


title: Cold Dark Matter Halos Must Burn

abstract:
  High-quality optical rotation curves for a sample of low-luminosity spirals
evidence that the dark halos around galaxies are inconsistent with the output
of proper CDM simulations. In fact, dark halos enveloping stellar disks are
structures with approximately a constant density out to the optical edges. This
is in strong disagreement with the characteristic rho(r) ~ r^(-1.5) CDM regime
and severely challenges the "standard" CDM theory, also because the halo
density appears to be heated up, at gross variance with the hierarchical
evolution of collision-free particles.


title: Missing Link Found? --- The ``runaway'' path to supermassive black holes

abstract:
  Observations of stellar kinematics, gas dynamics and masers around galactic
nuclei have now firmly established that many galaxies host central supermassive
black holes (SMBHs) with masses in the range $10^6 \sim 10^9$M$_{\odot}$.
However, how these SMBHs formed is not well understood. One reason for this
situation is the lack of observations of intermediate-mass BHs (IMBHs), which
could bridge the gap between stellar-mass BHs and SMBHs. Recently, this missing
link (i.e., an IMBH) has been found in observations made by the ASCA and the
Chandra of the central region of the starburst galaxy M82 \citep{MT99, PG99,
MT01, Ka01}. Subsequent observations by SUBARU have revealed that this IMBH
apparently coincides with a young compact star cluster. Based on these
findings, we suggest a new formation scenario for SMBHs. In this scenario,
IMBHs first form in young compact star clusters through runaway merging of
massive stars. While these IMBHs are forming, the host star clusters sink
toward the galactic nucleus through dynamical friction, and upon evaporation
deposit their IMBHs near the galactic center. The IMBHs then form binaries and
eventually merge via gravitational radiation, forming an SMBH.


title: Where are the high velocity clouds?

abstract:
  Recent observations of high velocity clouds (HVCs) have revealed compression
fronts and tail shaped features of HI suggesting that they are interacting with
external medium. We perform 3-D hydro-dynamical simulations of HVCs moving
through a diffuse hot gaseous component, investigating the behaviour of both
extra-galactic dark matter dominated HVCs and nearby pure gas clouds that may
be accreting onto the Galactic disk via a Galactic fountain. Both scenarios can
give rise to similar features as observed if the external medium has a density
$>10^{-4}$ cm$^{-3}$. Observations suggest that this may be too high for a hot
ionised halo or intergalactic gas and supports the Galactic fountain origin, a
model that can also account for the high fraction of HVCs with tails and
asymmetrical morphologies.


title: Bright X-Ray Sources in M31 Globular Clusters

abstract:
  We have conducted Chandra observations of ~2560 square arcmin (~131 kpc^2) of
of M31, and find that the most luminous X-ray sources in our fields are in
globular clusters (GCs). Of the 28 GC X-ray sources in our fields, 17 are newly
discovered. Approximately 1/3 of all the sources have L_x([0.5-7] keV) >
10^{37} ergs/s; approximately 1/10 of all the sources have L_x([0.5-7] keV)
close to or above 10^{38} erg/s. The most luminous source, in the globular
cluster Bo 375, is consistently observed to have L_x greater than 2 x 10^{38}
ergs/s.
  (1) We present data on the spectra and/or light curves of the 5 most luminous
M31 GC sources.
  (2)We explore possible explanations for the high X-ray luminosities of the
brightest sources. These include that the X-ray sources may be composites, the
radiation we receive may be beamed, metallicity effects could be at work, or
the sources may be accreting black holes. We weigh each of these possibilities
against the data. In addition, we introduce a neutron star model in which mass
transfer proceeds on the thermal time scale of the donor star. Our model can
produce luminosities of several times 10^{38} ergs/s, and leads to a set of
well-defined predictions.
  (3) We compute the X-ray luminosity function and the distribution of counts
in wavebands that span the range of energies to which Chandra is sensitive. We
find the peak X-ray luminosity is higher and that systems with L_x > 10^{37}
ergs/s constitute a larger fraction of all GC sources than in the MW.
  (4) We study the possible reasons for this difference between M31 and
Galactic GC X-ray sources and identify three promising explanations.


title:
The CORALIE survey for southern extrasolar planets V: 3 new extrasolar
  planets

abstract:
  We report the detection of 3 new planetary companions orbiting the solar-type
stars GJ 3021, HD 52265 and HD 169830 using radial-velocity measurements taken
with the CORALIE echelle spectrograph. All these planetary companions have
longer orbital periods than the 51 Peg-like objects. The orbits are fairly
eccentric. The minimum masses of these planets range from 1 to 3.3 M_Jup. The
stars have spectral types from F8V to G6V. They are metal-rich. We also present
our radial-velocity measurements for three solar-type stars known to host
planetary companions iota Hor (HD 17051), HD 210277 and HD 217107.


title: HD 80606 b, a planet on an extremely elongated orbit

abstract:
  We report the detection of a planetary companion orbiting the solar-type star
HD 80606, the brighter component of a wide binary with a projected separation
of about 2000 AU. Using high-signal spectroscopic observations of the two
components of the visual binary, we show that they are nearly identical. The
planet has an orbital period of 111.8 days and a minimum mass of 3.9 M_Jup.
With e=0.927, this planet has the highest orbital eccentricity among the
extrasolar planets detected so far. We finally list several processes this
extreme eccentricity could result from.


title:
Broad-band Observations and Modeling of the Shell-Type Supernova Remnant
  G347.3-0.5

abstract:
  The supernova remnant G347.3--0.5 emits a featureless power-law in X-rays,
thought to indicate shock-acceleration of electrons to high energies. We here
produce a broad-band spectrum of the bright NW limb of this source by combining
radio observations from the Australia Telescope Compact Array (ATCA), X-ray
observations from the Advanced Satellite for Cosmology and Astrophysics (ASCA),
and TeV gamma-ray observations from the CANGAROO imaging Cerenkov telescope. We
assume this emission is produced by an electron population generated by
diffusive shock acceleration at the remnant forward shock. The nonlinear
aspects of the particle acceleration force a connection between the widely
different wavelength bands and between the electrons and the unseen ions,
presumably accelerated simultaneously with the electrons. This allows us to
infer the relativistic proton spectrum and estimate ambient parameters such as
the supernova explosion energy, magnetic field, matter density in the emission
region, and efficiency of the shock acceleration process. We find convincing
evidence that the shock acceleration is efficient, placing >25% of the shock
kinetic energy flux into relativistic ions. Despite this high efficiency, the
maximum electron and proton energies, while depending somewhat on assumptions
for the compression of the magnetic field in the shock, are well below the
observed `knee' at about 10^{15} eV in the Galactic cosmic-ray spectrum.


title:
The Las Campanas/AAT Rich Cluster Survey I: Precision and Reliability of
  the Photometric Catalogue

abstract:
  The Las Campanas Observatory and Anglo--Australian Telescope Rich Cluster
Survey (LARCS) is a panoramic imaging and spectroscopic survey of an X-ray
luminosity-selected sample of 21 clusters of galaxies at 0.07<z<0.16. CCD
imaging was obtained in B and R of typically 2-degree wide regions centred on
the 21 clusters, and the galaxy sample selected from the imaging is being used
for an on-going spectroscopic survey of the clusters with the 2dF spectrograph
on the Anglo-Australian Telescope. This paper presents the reduction of the
imaging data and the photometric analysis used in the survey. Based on an
overlapping area of 12.3 square degrees, we compare the CCD-based LARCS
catalogue with the photographic-based galaxy catalogue used for the input to
the 2dF Galaxy Redshift Survey (2dFGRS) from the APM, to the completeness of
the GRS/APM catalogue, b_J=19.45. This comparison confirms the reliability of
the photometry across our mosaics and between the clusters in our survey. This
comparison also provides useful information about the properties of the
GRS/APM. The stellar contamination in the GRS/APM galaxy catalogue is confirmed
to be around 5-10 percent, as originally estimated. However, using the superior
sensitivity and spatial resolution in the LARCS survey, we find evidence for
four distinct populations of galaxies that are systematically omitted from the
GRS/APM catalogue. The characteristics of the `missing' galaxy populations are
described, reasons for their absence examined and the impact they will have on
the conclusions drawn from the 2dF Galaxy Redshift Survey are discussed.


title: Orbits of Globular Clusters in the Outer Galaxy: NGC 7006

abstract:
  We present a proper motion study of the distant globular cluster NGC 7006
based on the measurement of 25 photographic plates spanning a 40-year interval.
The absolute proper motion determined with respect to extragalactic objects is
(-0.96, -1.14) +- (0.35, 0.40) mas/yr. The total space velocity of NGC 7006 in
a Galactocentric rest frame is 279 km/s, placing the cluster on one of the most
energetic orbits (Ra =102 kpc) known to date for clusters within 40-kpc from
the Galactic center. We compare the orbits of four clusters that have
apocentric radii larger than 80 kpc (NGC 5466, NGC 6934, NGC 7006 and Pal 13)
with those of Galactic satellites with well-measured proper motions. These
clusters have orbits that are highly eccentric and of various inclinations with
respect to the Galactic plane. In contrast, the orbits of the Galactic
satellites are of low to moderate eccentricity and highly inclined. Based on
orbit types, chemical abundances and cluster parameters, we discuss the
properties of the hypothetical host systems of the remote globular clusters in
the Searle-Zinn paradigm. It is apparent that clusters such as NGC 5466, NGC
6934 and NGC 7006 formed in systems that more likely resemble the Fornax dSph,
rather than the Sagittarius dSph. We also discuss plausible causes for the
difference found so far between the orbit type of outer halo clusters and that
of Galactic satellites and for the tentative, yet suggestive phase-space
scatter found among outer halo clusters.


title: Non-uniform extinction in young open star clusters

abstract:
  The extinction law and the variation of colour excess with position,
luminosity as well as spectral class in young open star clusters NGC 663,
NGC869, NGC 884, NGC 1502, NGC 1893, NGC 2244, NGC 2264, NGC 6611, Tr 14, Tr
15,Tr 16, Coll 228, Tr 37 and Be 86 have been studied. The difference in the
minimum and maximum values of E(B-V) of cluster members has been considered as
a measure of the presence of non-uniform gas and dust inside the clusters. Its
value ranges from 0.22 to 1.03 mag in clusters under study, which indicates
that non-uniform extinction is present in all the clusters. It has been noticed
for the first time in NGC 1502 and Tr 37. It is also found that the
differential colour excess in open clusters, which may be due to the presence
of gas and dust, decreases systematically with the age of clusters indicating
that matter is used either in star formation or blown away by hot stars or
both. There is no uniformity in the variation of E(B-V) with either position or
spectral class or luminosity.


title:
Structure, mass and distance of the Virgo cluster from a Tolman-Bondi
  model

abstract:
  We have applied a relativistic Tolman-Bondi model of the Virgo cluster to a
sample of 183 galaxies with measured distances within a radius of 8 degrees
from M87. We find that the sample is significantly contaminated by background
galaxies which lead to too large a cluster mean distance if not excluded. The
Tolman-Bondi model predictions, together with the HI deficiency of spiral
galaxies, allows one to identify these background galaxies. One such galaxy is
clearly identified among the 6 calibrating galaxies with Cepheid distances. As
the Tolman-Bondi model predicts the expected distance ratio to the Virgo
distance, this galaxy can still be used to estimate the Virgo distance, and the
average value over the 6 galaxies is 15.4 +- 0.5 Mpc.
  Well-known background groups of galaxies are clearly recovered, together with
filaments of galaxies which link these groups to the main cluster, and are
falling into it. No foreground galaxy is clearly detected in our sample.
Applying the B-band Tully-Fisher method to a sample of 51 true members of the
Virgo cluster according to our classification gives a cluster distance of 18.0
+- 1.2 Mpc, larger than the mean Cepheid distance.
  Finally, the same model is used to estimate the Virgo cluster mass, which is
M = 1.2 10^{15} Msun within 8 degrees from the cluster center (2.2 Mpc radius),
and amounts to 1.7 virial mass.


title: Time at the Beginning

abstract:
  Age consistency for the Universe today has been an important cosmological
test. Even more powerful consistency tests at times as early as 10^{-32} sec
lie ahead in the precision era of cosmology. I outline tests based upon cosmic
microwave background (CMB) anisotropy, big-bang nucleosynthesis (BBN), particle
dark matter, phase transitions, and inflation. The ultimate cosmic timescale --
the fate of the Universe -- will be in doubt until the mystery of the dark
energy is unraveled.


title:
Spectropolarimetry of a Complete Infrared Selected Sample of Seyfert 2
  Galaxies

abstract:
  We report the results of a spectropolarimetric survey of a complete far
infrared selected sample of Seyfert 2 galaxies. We have found polarized broad
Halpha emission in one new source, NGC5995. In the sample as a whole, there is
a clear tendency for galaxies in which we have detected broad Halpha in
polarized light to have warm mid--far infrared colours (F(60um)/F(25um)<4), in
agreement with our previous results. However, a comparison of the optical,
radio and hard x-ray properties of these systems leads us to conclude that this
is a secondary consequence of the true mechanism governing our ability to see
scattered light from the broad line region. We find a strong trend for galaxies
showing such emission to lie above a critical value of the relative luminosity
of the active core to the host galaxy (as measured from the [OIII] 5007A
equivalent width) which varies as a function of the obscuring column density as
measured from hard x-ray observations. The warmth of the infrared colours is
then largely due to a combination of the luminosity of the active core, the
obscuring column and the relative importance of the host galaxy in powering the
far infrared emission, and not solely orientation as we inferred in our
previous paper. Our data may also provide an explanation as to why the most
highly polarized galaxies, which appear to have tori that are largely edge-on,
are also the most luminous and have the most easily detectable scattered broad
Halpha.


title:
Partial Averaging and Resonance Trapping in a Restricted Three-Body
  System

abstract:
  Based on the value of the orbital eccentricity of a particle and also its
proximity to the exact resonant orbit in a three-body system, the Pendulum
Approximation (Dermott & Murray 1983) or the Second Fundamental Model of
Resonance (Andoyer 1903; Henrard & Lemaitre 1983) are commonly used to study
the motion of that particle near its resonance state. In this paper, we present
the method of partial averaging as an analytical approach to study the
dynamical evolution of a body near a resonance. To focus attention on the
capabilities of this technique, a restricted, circular and planar three-body
system is considered and the dynamics of its outer planet while captured in a
resonance with the inner body is studied. It is shown that the first-order
partially averaged system resembles a mathematical pendulum whose librational
motion can be viewed as a geometrical interpretation of the resonance capture
phenomenon. The driving force of this pendulum corresponds to the gravitational
attraction of the inner body and its contribution, at different resonant
states, is shown to be proportional to e^s, where s is the order of the
resonance and e is the orbital eccentricity of the outer planet. As examples of
such systems, the cases of (1:1), (1:2) and (1:3) resonances are discussed and
the results are compared with known planetary systems such as the
Sun-Jupiter-Trojan asteroids.


title:
Optical spectroscopy and photometry of the isolated neutron star RX
  J1856.5-3754

abstract:
  We present spectroscopy and imaging with the Very Large Telescope (VLT) of
the neutron star RX J1856.5-2754. Little is known about the nature of this
source other than that it is a nearby hot neutron star. Our VLT spectrum does
not show any strong emission or absorption features. With considerable care to
photometric calibration, we obtain photometric measurements over the optical
and ultra-violet (UV) using our VLT observations and a detailed analysis of
archival {\em Hubble Space Telescope} data. We find that the entire optical to
UV spectral energy distribution is well described by a slightly reddened
Rayleigh-Jeans tail ($f_\lambda=(2.96\pm0.06)\times10^{-19}
(\lambda/5000\un{\AA})^{-4} 10^{-0.4(0.12\pm0.05)(A_\lambda/A_V-1.138)}
\un{erg}\un{s^{-1}}\un{cm^{-2}}\un{\AA^{-1}}$, where $A_\lambda/A_V$ is the
reddening curve; implied $V=25.58\pm0.02$). The reddening is consistent with
the interstellar absorption inferred from X-ray spectroscopy. The simplest
explanation for this Rayleigh-Jeans emission is that the optical-UV radiation
arises from thermal emission from the surface of the neutron star. The high
degree to which the data conform to the Rayleigh-Jeans tail significantly
limits contributions from other sources of emission. In particular, our
observations are inconsistent with the presence of an accretion disk and also
strongly constrain the amount of magnetospheric emission from this enigmatic
neutron star.


title: Effects of CSPN Models on PNe Shell Modeling

abstract:
  Modeling planetary nebulae (PNe) shells using different ionizing spectra for
a hot central star (CSPN) of evolved PNe, we found that especially a blackbody
model leads to wrong nebular diagnostics and abundances.


title: The orbit of the brown dwarf binary Gl 569B

abstract:
  We present photometric, astrometric and spectroscopic observations of the
nearby (9.8 pc) low-mass binary Gl 569Bab (in turn being a companion to the
early-M star Gl 569A), made with the Keck adaptive optics facility. Having
observed Gl 569Bab since August 1999, we are able to see orbital motion and to
determine the orbital parameters of the pair. We find the orbital period to be
892 +/- 25 days, the semi-major axis to be 0.90 +/- 0.02 AU, the eccentricity
to be 0.32 +/- 0.02 and the inclination of the system to be 34+/- 3 degrees
(1-sigma). The total mass is found to be 0.123 (-0.022/+0.027) Msun (3-sigma).
In addition, we have obtained low resolution (R=1500-1700) near-infrared
spectra of each of the components in the J- and K-bands. We determine the
spectral types of the objects to be M8.5V (Gl 569Ba) and M9V (Gl 569Bb) with an
uncertainty of half a subclass. We also present new J- and K-band photometry
which allows us to accurately place the objects in the HR diagram. Most likely
the binary system is comprised of two brown dwarfs with a mass ratio of 0.89
and with an age of approximately 300 Myr.


title: Halo Substructure and Disk Heating in a Lambda CDM Universe

abstract:
  We examine recent suggestions that substructure in cold dark matter (CDM)
halos may be in conflict with the presence of thin, dynamically fragile stellar
disks. N-body simulations of an isolated disk/bulge/halo model of the Milky Way
that includes several hundred dark matter satellites with masses, densities and
orbits derived from high-resolution cosmological CDM simulations indicate that
substructure at $z=0$ plays only a minor dynamical role in the heating of the
disk over several Gyrs. This is because the orbits of satellites in present-day
CDM halos seldom take them near the disk, where their tidal effects are
greatest. Unless the effects of substructure are very different at earlier
times, our models suggest that substructure might not preclude virialized CDM
halos from being acceptable hosts of thin stellar disks like that of the Milky
Way.


title:
Response to Technical Comments regarding the paper "Direct Detection of
  Galactic Halo Dark Matter"

abstract:
  We reply to the criticism of Gibson & Flynn and of Graff regarding "Direct
detection of galactic halo dark matter" by Oppenheimer et al. (2001) (Science,
Vol. 292, p. 698), which reported on the discovery of a significant population
of halo white dwarfs found in our South Galactic Cap survey. None of their
arguments against our claims withstand close scrutiny.


title:
The SNR G106.3+2.7 and its Pulsar Wind Nebula: relics of triggered star
  formation in a complex environment

abstract:
  We propose that the pulsar nebula associated with the pulsar J2229+6114 and
the supernova remnant (SNR) G106.3+2.7 are the result of the same supernova
explosion. The whole structure is located at the edge of an HI bubble with
extended regions of molecular gas inside. The radial velocities of both the
atomic hydrogen and the molecular material suggest a distance of 800 pc. At
this distance the SNR is 14 pc long and 6 pc wide. Apparently the bubble was
created by the stellar wind and supernova explosions of a group of stars in its
center which also triggered the formation of the progenitor star of G106.3+2.7.
The progenitor star exploded at or close to the current position of the pulsar,
which is at one end of the SNR rather than at its center. The expanding shock
wave of the supernova explosion created a comet shaped supernova remnant by
running into dense material and then breaking out into the inner part of the HI
bubble. A synchrotron nebula with a shell-like structure (the ``Boomerang'') of
length 0.8 pc was created by the pulsar wind interacting with the dense ambient
medium. The expanding shock wave created an HI shell of mass 0.4 Msun around
this nebula by ionizing the atomic hydrogen in its vicinity.


title:
Dark matter in Draco and the Local Group: Implications for direct
  detection experiments

abstract:
  We use a cosmological simulation of the Local Group to make quantitative and
speculative predictions for direct detection experiments. Cold dark matter
(CDM) halos form via a complex series of mergers, accretion events and violent
relaxation which precludes the formation of significant caustic features
predicted by axially symmetric collapse. The halo density profiles are combined
with observational constraints on the galactic mass distribution to constrain
the local density of cold dark matter to lie in the range 0.18 <~
rho_CDM(R_solar)/GeV cm^-3 <~ 0.30. In velocity space, coherent streams of dark
matter from tidally disrupted halos fill the halo and provide a tracer of the
merging hierarchy. The particle velocities within triaxial CDM halos cannot be
approximated by a simple Maxwellian distribution and is radially biased at the
solar position. The detailed phase space structure within the solar system will
depend on the early merger history of the progenitor halos and the importance
of major mergers over accretion dominated growth. We follow the formation of a
``Draco'' sized dSph halo of mass 10^8M_solar with several million particles
and high force accuracy. Its internal structure and substructure resembles that
of galactic or cluster mass halos: the density profile has a singular central
cusp and it contains thousands of sub-halos orbiting within its virial radius
demonstrating a self-similar nature to collisionless dark matter
sub-clustering. The singular cores of substructure halos always survive
complete tidal disruption although mass loss is continuous and rapid.
Extrapolating wildly to earth mass halos with velocity dispersion of 1 m s^-1
(roughly equal to the free streaming scale for neutralinos) we find that most
of the dark matter may remain attached to bound subhalos. (Abridged)


title: The Milky Way as the Ultimate Extragalactic Source

abstract:
  The GAIA satellite will observe the Galaxy and its closest satellites in
great detail. This should allow (i) dating past events of dwarf galaxies
merging or interacting with the Galaxy, and much improved orbital parameters of
the nine dwarf spheroidals and the Magellanic Clouds and (ii) dating of active
galactic nucleus (AGN) phases of the Galaxy several Gigayears in the past, by
detecting coeval star formation (e.g. open star clusters) that occurred along
kpc scale Galactic jets. Both predictions (i) and (ii) of past history will be
highly valuable for searching for or excluding topologically lensed images of
the Milky Way at high redshift.


title:
Lens Model Degeneracy and Cosmological Tests by Strong Gravitational
  Lensing

abstract:
  We estimate the sensitivity of lensing observables to the parameters in the
lens model (isothermal sphere/Navarro-Frenk-White profile) parameters and to
cosmological parameters. We find that the observables are primarily dependent
on the lens model parameters, while the dependence on cosmological parameters
is minor (especially so for the dark energy parameters). We demonstrate the
lens model degeneracy by deriving both the projected mass density profile and
the circular velocity profile. We also identify a possible source of the
problem of fitting the averaged mass profile of CL 0024+1654 with the
Navarro-Frenk-White profile.


title: A Supernova Brane Scan

abstract:
  We consider a `brane-world scenario' recently introduced by Dvali, Gabadadze
and Porrati, and subsequently proposed as an alternative to a cosmological
constant in explaining the current acceleration of the universe. We show that,
contrary to these claims, this proposal is already strongly disfavoured by the
available Type Ia Supernovae, Cosmic Microwave Background and cluster data.


title: HST/WFPC2 Imaging of the QDOT Ultraluminous Infrared Galaxy Sample

abstract:
  We present HST WFPC2 V band imaging for 23 Ultraluminous Infrared Galaxies
taken from the QDOT redshift survey. The fraction of sources observed to be
interacting is 87%. Most of the merging systems show a number of compact
`knots', whose colour and brightness differ substantially from their immediate
surroundings. Colour maps for nine of the objects show a non-uniform colour
structure. Features include blue regions located towards the centres of merging
systems which are likely to be areas of enhanced star formation, and compact
red regions which are likely to be dust shrouded starbursts or AGN. The host
galaxies of the QSOs in the sample were found to be either interacting systems
or ellipticals. Our data shows no evidence that ULIRGs are a simple transition
stage between galaxy mergers and QSOs. We propose an alternative model for
ULIRGs based on the morphologies in our sample and previous N-body simulations.
Under this model ULIRGs as a class are much more diverse than a simple
transition between galaxy merger and QSO. The evolution of IR power source and
merger morphology in ULIRGs is driven solely by the local environment and the
morphologies of the merger progenitors.


title:
Investigation of clustering of galaxies, clusters and superclusters by
  the method of correlation Gamma-function

abstract:
  Using the apparatus of correlation Gamma-function (``conditional density''),
we have analyzed spatial clustering of objects from several different samples
of galaxies, clusters and superclusters. On small scales the distribution of
objects obeys a power law drop of density with a power index of 0.9--1.5. On a
scale of ~30 Mpc for independent samples of bright galaxies and clusters of
galaxies we have detected a pronounced break in the slope of the Gamma-function
with a power index decreasing to ~0.3. The clustering is much less pronounced
in the region from 40 to 100 Mpc, and there is reason to suppose that the
distribution of objects changes to homogeneous on scales larger than 100 Mpc.
This is indicated by the slope of the Gamma-function close to 0 for a sample of
rich clusters of galaxies up to 250 Mpc.
  The slope of the Gamma-function prior to the break, which characterizes the
degree of clustering of matter, changes essentially and in a complex manner
when passing to brighter (massive) objects. This suggests that the large-scale
structure of the visible Universe even on small scales is considerably more
complex than the fractal distribution described by one dimension (monofractal).


title:
New neighbours. III. 21 new companions to nearby dwarfs, discovered with
  adaptive optics

abstract:
  We present some results of a CFHT adaptive optics search for companions to
nearby dwarfs. We identify 21 new components in solar neighbourhood systems, of
which 13 were found while surveying a volume-limited sample of M dwarfs within
12pc. We are obtaining complete observations for this subsample, to derive
unbiased multiplicity statistics for the very-low-mass disk population.
Additionally, we resolve for the first time 6 known spectroscopic or
astrometric binaries, for a total of 27 newly resolved companions. A fair
fraction of the new binaries has favourable parameters for accurate mass
determinations. The newly resolved companion of Gl120.1C had an apparent
spectroscopic minimum mass in the brown-dwarf range (Duquennoy & Mayor 1991)
and it contributed to the statistical evidence that a few percent of solar type
stars might have close-in brown-dwarf companions. We find that Gl~120.1C
actually is an unrecognised double-lined spectroscopic pair. Its
radial-velocity amplitude had therefore been strongly underestimated by
Duquennoy & Mayor, and it does not truly belong to their sample of single-lined
systems with minimum spectroscopic mass below the substellar limit. We also
present the first direct detection of Gl~494B, an astrometric brown-dwarf
candidate. Its luminosity does straddle the substellar limit, and it is a brown
dwarf if its age is less than 300Myr. A few more years of observations will
ascertain its mass and status from first principles.


title:
Multi--dimensional Cosmological Radiative Transfer with a Variable
  Eddington Tensor Formalism

abstract:
  We present a new approach to numerically model continuum radiative transfer
based on the Optically Thin Variable Eddington Tensor (OTVET) approximation.
Our method insures the exact conservation of the photon number and flux (in the
explicit formulation) and automatically switches from the optically thick to
the optically thin regime. It scales as N logN with the number of hydrodynamic
resolution elements and is independent of the number of sources of ionizing
radiation (i.e. works equally fast for an arbitrary source function).
  We also describe an implementation of the algorithm in a Soften Lagrangian
Hydrodynamic code (SLH) and a multi--frequency approach appropriate for
hydrogen and helium continuum opacities. We present extensive tests of our
method for single and multiple sources in homogeneous and inhomogeneous density
distributions, as well as a realistic simulation of cosmological reionization.


title:
FUSE Observations of Cooling Flow Gas in the Galaxy Clusters A1795 and
  A2597

abstract:
  We present far-ultraviolet spectroscopy of the cores of the massive cooling
flow clusters Abell 1795 and 2597 obtained with FUSE. As the intracluster gas
cools through 3x10^5 K, it should emit strongly in the OVI 1032,1038 resonance
lines. We report the detection of OVI 1032 emission in A2597, with a line flux
of 1.35 +/- 0.35x10^-15 erg/cm2/s, as well as detection of emission from CIII
977. A marginal detection of CIII 977 emission is also reported for A1795.
These observations provide evidence for a direct link between the hot (10^7 K)
cooling flow gas and the cool (10^4 K) gas in the optical emission line fients.
Assuming simple cooling flow models, the OVI line flux in A2597 corresponds to
a mass deposition rate of ~40 Msun/yr within the central 36 kpc. Emission from
OVI 1032 was not detected in A1795, with an upper limit of 1.5x10^-15
erg/cm2/s, corresponding to a limit on the mass cooling flow rate of Mdot(28
kpc) < 28 Msun/yr. We have considered several explanations for the lack of
detection of OVI emission in A1795 and the weaker than expected flux in A2597,
including extinction by dust in the outer cluster, and quenching of thermal
conduction by magnetic fields. We conclude that a turbulent mixing model, with
some dust extinction, could explain our OVI results while also accounting for
the puzzling lack of emission by FeXVII in cluster cooling flows.


title: Astrophysical significance of the anisotropic kinetic alpha effect

abstract:
  The generation of large scale flows by the anisotropic kinetic alpha (AKA)
effect is investigated in simulations with a suitable time-dependent space- and
time-periodic anisotropic forcing lacking parity invariance. The forcing
pattern moves relative to the fluid, which leads to a breaking of the Galilean
invariance as required for the AKA effect to exist. The AKA effect is found to
produce a clear large scale flow pattern when the Reynolds number, R, is small
as only a few modes are excited in linear theory. In this case the
non-vanishing components of the AKA tensor are dynamically independent of the
Reynolds number. For larger values of R, many more modes are excited and the
components of the AKA tensor are found to decrease rapidly with increasing
value of R. However, once there is a magnetic field (imposed and of sufficient
strength, or dynamo-generated and saturated) the field begins to suppress the
AKA effect, regardless of the value of R. It is argued that the AKA effect is
unlikely to be astrophysically significant unless the magnetic field is weak
and R is small.


title: Magnetic Energy of the Intergalactic Medium from Galactic Black Holes

abstract:
  A quantitative analysis of two radio source samples having opposite extremes
of ambient gas density leads to important new conclusions about the magnetic
energy in the IGM. We conclude that giant sources in rarefied IGM environments,
which contain magnetic energies E_B ~ 10^60-61 ergs, can be viewed as important
"calorimeters" of the minimum energy a black hole (BH) accretion disk system
injects into the IGM. In contrast to the radiation energy released by BH
accretion, most of the magnetic energy is "trapped" initially in a volume, up
to ~10^73 cm^3, around the host galaxy. But since these large, Mpc scale radio
lobes are still overpressured after the AGN phase, their subsequent expansion
and diffusion will magnetize a large fraction of the entire IGM. This suggests
that the energy stored in intergalactic magnetic fields will have a major, as
yet underestimated effect on the evolution of subsequently forming galaxies.
Comparison with the second sample, consisting of sources within 150 kpc of rich
cluster cores, shows that the minimum magnetic energy E_B can be a strongly
variable fraction of the inferred accretion energy E_acc, and that it depends
on the ambient IGM environment. AGNs inject significant energy as PdV work on
the thermal ICM gas, and their magnetic energy, even ignoring the contribution
from stellar and starburst outflows, is sufficient to account for that recently
found beyond the inner cores of galaxy clusters. Other loss processes in the
course of the lobe expansion are considered. We conclude that the aggregate IGM
magnetic energy derived purely from galactic black holes since the first epoch
of significant galaxy BH formation is sufficiently large that it will have an
important influence on the process of both galaxy and visible structure
formation on scales up to ~ 1Mpc.


title:
The growth of galaxies in cosmological simulations of structure
  formation

abstract:
  We use hydrodynamic simulations to examine how the baryonic components of
galaxies are assembled, focusing on the relative importance of mergers and
smooth accretion in the formation of ~L_* systems. In our primary simulation,
which models a (50\hmpc)^3 comoving volume of a Lambda-dominated cold dark
matter universe, the space density of objects at our (64-particle) baryon mass
resolution threshold, M_c=5.4e10 M_sun, corresponds to that of observed
galaxies with L~L_*/4. Galaxies above this threshold gain most of their mass by
accretion rather than by mergers. At the redshift of peak mass growth, z~2,
accretion dominates over merging by about 4:1. The mean accretion rate per
galaxy declines from ~40 M_sun/yr at z=2 to ~10 M_sun/yr at z=0, while the
merging rate peaks later (z~1) and declines more slowly, so by z=0 the ratio is
about 2:1. We cannot distinguish truly smooth accretion from merging with
objects below our mass resolution threshold, but extrapolating our measured
mass spectrum of merging objects, dP/dM ~ M^a with a ~ -1, implies that
sub-resolution mergers would add relatively little mass. The global star
formation history in these simulations tracks the mass accretion rate rather
than the merger rate. At low redshift, destruction of galaxies by mergers is
approximately balanced by the growth of new systems, so the comoving space
density of resolved galaxies stays nearly constant despite significant mass
evolution at the galaxy-by-galaxy level. The predicted merger rate at z<~1
agrees with recent estimates from close pairs in the CFRS and CNOC2 redshift
surveys.


title: Convective and Rotational Stability of a Dilute Plasma

abstract:
  The stability of a dilute plasma to local convective and rotational
disturbances is examined. A subthermal magnetic field and finite thermal
conductivity along the field lines are included in the analysis. Stability
criteria similar in form to the classical H{\o}iland inequalities are found,
but with angular velocity gradients replacing angular momentum gradients, and
temperature gradients replacing entropy gradients. These criteria are
indifferent to the properties of the magnetic field and to the magnitude of the
thermal conductivity. Angular velocity gradients and temperature gradients are
both free energy sources; it is not surprising that they are directly relevant
to the stability of the gas. Magnetic fields and thermal conductivity provide
the means by which these sources can be tapped. Previous studies have generally
been based upon the classical H{\o}iland criteria, which are inappropriate for
magnetized, dilute astrophysical plasmas. In sharp contrast to recent claims in
the literature, the new stability criteria demonstrate that marginal flow
stability is not a fundamental property of accreting plasmas thought to be
associated with low luminosity X-ray sources.


title: Evolution of Dusty Disks in Nearby Young Stellar Groups

abstract:
  Given their proximity and age differences, nearby groups of young stars are
valuable laboratories for investigations of disk evolution and diversity. The
estimated 10-Myr age of groups like the TW Hydrae Association provides a strong
constraint on disk evolution timescales and fills a significant gap in the age
sequence between 1-Myr-old T Tauri stars in molecular clouds and 50-Myr-old
nearby open clusters. I review the results of recent and on-going studies of
dusty disks in three nearby groups --TW Hya, $\eta$ Cha and MBM 12-- that
suggest rapid evolution of inner disks. However, it is unlikely that there is a
universal evolutionary timescale for protoplanetary disks, especially when the
influence of companion stars is taken into account.


title: FUSE Observations of Warm Absorbers in AGN

abstract:
  In a survey of the UV-brightest AGN using the Far Ultraviolet Spectroscopic
Explorer (FUSE), we commonly find associated absorption in the O VI 1032,1038
resonance doublet. Of 34 Type I AGN observed to date with z < 0.15, 16 show
detectable O VI absorption. Most absorption systems show multiple components
with intrinsic widths of ~100 km/s spread over a blue-shifted velocity range of
less than 1000 km/s. With the exception of three galaxies (Ton S180, Mrk 478,
and Mrk 279), those galaxies in our sample with existing X-ray or longer
wavelength UV observations also show C IV absorption and evidence of a soft
X-ray warm absorber. In some cases, a UV absorption component has physical
properties similar to the X-ray absorbing gas, but in others there is no clear
physical correspondence between the UV and X-ray absorbing components.


title:
Molecular gas and dust in NGC4550: A galaxy with two counterrotating
  stellar disks

abstract:
  We report the detection of 1 10^7 M_sun of molecular gas in the central
region of the S0/E7 galaxy NGC4550, inferred from observations of CO(1-0)
emission. Dust is detected in HST WFPC2 images and found to be asymmetrically
distributed around the nucleus, only extending to a galactocentric distance of
7'' (600 pc). The shape of the CO emission profile is consistent with a
molecular gas distribution following the dust. The distribution of the dust and
gas in the center could be the result of an m=1 instability, which is the
fastest growing unstable mode in counterrotating stellar disks. On a global
scale the molecular gas in NGC4550 is stable against gravitational collapse but
nevertheless star formation appears to be ongoing with normal star formation
efficiency and gas consumption time scales. The stellar velocity dispersion in
NGC4550 resembles that of elliptical galaxies. It is therefore likely that a
hot X-ray emitting plasma limits the lifetime of the molecular gas, that must
arise from a recent (<1 Gyr) accretion event.


title: NewtonPlus: Approximating Relativistic Effects in Supernova Simulations

abstract:
  We propose an approximation to full relativity that captures the main
gravitational effects of dynamical importance in supernovae. The conceptual
link between this formalism and the Newtonian limit is such that it could
likely be implemented relatively easily in existing multidimensional Newtonian
gravitational hydrodynamics codes employing a Poisson solver. As a test of the
formalism's utility, we display results for rapidly rotating (and therefore
highly deformed) neutron stars.


title: Study of corrections to the dust model via perturbation theory

abstract:
  This work reports on the application of the Eulerian perturbation theory to a
recently proposed model of cosmological structure formation by gravitational
instability (astro-ph/0009414). Its physical meaning is discussed in detail and
put in perspective of previous works. The model incorporates in a systematic
fashion corrections to the popular dust model due to multistreaming and, more
generally, the small-scale, virialized degrees of freedom. It features a
time-dependent length scale L(t) estimated to be L/r0 ~ 0.1 (r0(t) is the
nonlinear scale, at which the density variance =1). The model provides a new
angle on the dust model and allows to overcome some of its limitations. Thus,
the scale L(t) works as a physically meaningful short-distance cutoff for the
divergences appearing in the perturbation expansion of the dust model when
there is too much initial power on small scales. The model also incorporates
the generation of vorticity by tidal forces; according to the perturbational
result, the filtered vorticity for standard CDM initial conditions should be
significant today only at scales below ~ 1 Mpc/h.


title: Nuclear Aspects of the s- and n-Processes in Massive Stars

abstract:
  In order to study the processes creating intermediate and heavy nuclei in
massive stars it is necessary to provide neutron capture cross sections and
reaction rates close to stability and for moderately unstable neutron-rich
nuclei. Furthermore, one has to know the efficiency of neutron-releasing
reactions in the main evolutionary phases of a massive star. We present
simulations of the nucleosynthesis in a 15 and 25 solar mass star, for the
first time followed completely from main sequence hydrogen burning until the
type II supernova explosion including all nuclides up to Bi. Theoretical
reaction rates were calculated with the NON-SMOKER code, providing a complete
library of Hauser-Feshbach cross sections and rates for nuclear and
astrophysical applications. Experimental rates at stability were taken from
different sources. The impact of uncertainties in the rates on nucleosynthesis
are illustrated by two examples, the reactions 62Ni(n,gamma)63Ni and
22Ne(alpha,n)25Mg.


title:
The effects of relativistic bulk motion of X-ray flares in the corona on
  the iron Kalpha line in Seyfert 1 galaxies

abstract:
  We study the effects of the bulk motion of X-ray flares on the shape and
equivalent width of the iron Kalpha line from an untruncated cold disk around a
Kerr black hole using fully relativistic calculations. The flares are located
above a cold accretion disk -- either on or off the rotation axis. For on- or
off-axis flares, the upward/outward bulk motion causes a reduction of the iron
Kalpha line width. To a distant observer with a low inclination angle (\theta_o
\simlt 30deg.), larger upward/outward bulk velocities decrease the extension of
the red wing, with little change in the location of the blue `edge'. In
contrast, an observer at a large inclination angle (e.g. \theta_o=60deg.) sees
both the red wing and the blue `edge' change with the bulk velocity. The
equivalent width of the iron Kalpha line decreases rapidly with increasing bulk
velocity of flares. However, the `narrower' line profiles observed in some
objects (e.g. IC4329A and NGC4593) are difficult to produce using the
out-flowing magnetic flare model with an appropriate equivalent width unless
the X-ray emission is concentrated in an outer region with a radius of several
tens of r_g=GM/c^2 or more. An important result is that the iron Kalpha line
intensity is found to be constant even though the continuum flux varies
significantly, which is true for out-flowing magnetic flares with different
bulk velocities but similar intrinsic luminosities when located close to the
central black hole. We find that fluctuations in the bulk velocities of
out-flowing low-height flares located at the inner region (r\simlt 15r_g) can
account for a constant iron Kalpha line and significant continuum variation as
observered in MCG-6-30-15 and NGC5548. (Abridged)


title:
A Possible Explanation for the "Parallel Tracks" Phenomenon in Low-Mass
  X-Ray Binaries

abstract:
  An explanation is proposed for the fact that in LMXBs the correlation between
most observable X-ray spectral and timing parameters (such as kHz QPO
frequency) on the one hand, and Lx on the other, while generally good in a
given source on a time scale of hours, is absent both on longer time scales and
between sources. This leads to parallel tracks in plots of such parameters vs.
Lx. Where previous explanations require at least two time-variable independent
parameters, e.g. Mdot through the disk and through a radial inflow, one is in
fact sufficient if the systemic response to time variations in this variable
has both a prompt and a time-averaged component. I explore a scenario in which
most observable spectral and timing parameters to first order depend on disk
accretion rate normalized by its own long-term average rather than on any
individual Mdot; Lx just depends on total Mdot. Thus, parameters can be
uncorrelated to Mdot, yet vary in response to Mdot variations. Numerical
simulations of the model describing the dependence of kHz QPO frequency on Lx,
which observationally is characterized by a striking pattern of parallel tracks
both in individual sources and between sources, reproduce the observations
remarkably well. A physical interpretation involving a radial inflow with a
rate that derives through a time averaging process from the disk accretion
rate, and an inner disk radius that depends on the balance between the
accretion through the disk and the total luminosity seems particularly
promising. The consequences of this idea for our understanding of states and
tracks in LMXBs are discussed, and the applicability of the idea to black-hole
candidates, where the observational situation is more complex, is briefly
addressed.


title:
The relationship between the X-ray variability and the central black
  hole mass

abstract:
  We assembled a sample of Seyfert 1 galaxies, QSOs and Low-Luminosity Active
Galactic Nuclei (LLAGNs) observed by ASCA, whose central black hole masses have
been measured. We found that the X-ray variability (which is quantified by the
``excess variance'' sigma^2_{rms}) is significantly anti-correlated with the
central black hole mass, and there likely exists a linear relationship
sigma^2_{rms}\propto M^{-1}_{bh}. This can be interpreted that the short
time-scale X-ray variability is caused by some global coherent variations in
the X-ray emission region which is scaled by the size of the central black
hole. Hence, the central black hole mass is the driving parameter of the
previously established relation between X-ray variability and luminosity. This
findings favor the hypothesis that the Narrow Line Seyfert 1 galaxies and QSOs
harbor smaller black holes than the broad line objects, and can also easily
explain the observational fact that high redshift QSOs have greater variability
than local AGNs at a given luminosity. Further investigations are needed to
confirm our findings, and a large sample X-ray variability investigation can
give constraints on the physical mechanism and evolution of AGNs.


title: Galaxy Halo Occupation at High Redshift

abstract:
  We discuss how current and future data on the clustering and number density
of z~3 Lyman-break galaxies (LBGs) can be used to constrain their relationship
to dark matter haloes. We explore a three-parameter model in which the number
of LBGs per dark halo scales like a power-law in the halo mass: N(M) =
(M/M_1)^S for M>M_m. Here, M_m is the minimum mass halo that can host an LBG,
M_1 is a normalization parameter, associated with the mass above which haloes
host more than one observed LBG, and S determines the strength of the mass
dependence. We show how these three parameters are constrained by three
observable properties of LBGs: the number density, the large-scale bias, and
the fraction of objects in close pairs. Given these three quantities, the three
unknown model parameters may be estimated analytically, allowing a full
exploration of parameter space. As an example, we assume an LCDM cosmology and
consider the observed properties of a recent sample of spectroscopically
confirmed LBGs. We find that the favored range for our model parameters is M_m
= (0.4-8)x10^10 Msun/h, M_1 = (6-10)x10^12 Msun/h, and 0.9 < S < 1.1. The
preferred region in M_m expands by an order of magnitude and slightly shallower
slopes are acceptable if the allowed range of bias is permitted to span all
recent observational estimates. We also discuss how the observed clustering of
LBGs as a function of luminosity can be used to constrain halo occupation,
although due to current observational uncertainties we are unable to reach any
strong conclusions. Our methods and results can be used to constrain more
realistic models that aim to derive the occupation function N(M) from first
principles, and offer insight into how basic physical properties affect the
observed properties of LBGs.


title: Are Stars with Planets Polluted?

abstract:
  We compare the metallicities of stars with radial velocity planets to the
metallicity of a sample of field dwarfs. We confirm recent work indicating that
the stars-with-planet sample as a whole is iron rich. However, the lowest mass
stars tend to be iron poor, with several having [Fe/H]<-0.2, demonstrating that
high metallicity is not required for the formation of short period Jupiter-mass
planets. We show that the average [Fe/H] increases with increasing stellar mass
(for masses below 1.25 solar masses) in both samples, but that the increase is
much more rapid in the stars-with-planet sample. The variation of metallicity
with stellar age also differs between the two samples. We examine possible
selection effects related to variations in the sensitivity of radial velocity
surveys with stellar mass and metallicity, and identify a color cutoff
(B-V>0.48) that contributes to but does not explain the mass-metallicity trend
in the stars-with-planets sample. We use Monte Carlo models to show that adding
an average of 6.5 Earth masses of iron to each star can explain both the
mass-metallicity and the age-metallicity relations of the stars-with-planets
sample. However, for at least one star, HD 38529, there is good evidence that
the bulk metallicity is high. We conclude that the observed metallicities and
metallicity trends are the result of the interaction of three effects;
accretion of about 6 Earth masses of iron rich material, selection effects, and
in some cases, high intrinsic metallicity.


title: The [O III]4363 Emitting Region Obscured by Dusty Tori

abstract:
  The emission-line flux ratio of [O III]4363/[O III]5007 is a useful
diagnostic for the ionization mechanism and physical properties of narrow-line
regions in active galactic nuclei. However, it is known that simple
photoionization models underpredict this ratio. In this contribution, we report
on some pieces of evidence that a large fraction of the [O III]4363 emission
arises from the dense gas, which can be obscured by dusty tori. Taking this
dense component into account, we show that the flux ratio of [O III]4363/[O
III]5007 can be explained by two-component photoionization models.


title: Dark Matter Equation of Motion and Density Profiles

abstract:
  Cold dark matter simulations appear to disagree with the observations on
small distance scales. Here we consider a modified description of CDM particles
which is implied by a new fundamental theory: In this picture, the dark matter
is composed of supersymmetric WIMPs, but they are scalar bosons with an
unconventional equation of motion. The modified dynamics leads to much weaker
gravitational binding, and therefore to a reduced tendency to form small clumps
and central cusps.


title: Clusters in extragalactic HII regions and their modelling

abstract:
  This review deals with properties of very young (< 10-20 Myr) stellar
clusters which are in the nebular phase and are embedded in photoionized
regions (classical extragalactic HII regions (RHIIs) or starburst galaxies).
Based on the analysis of the integrated light of these clusters at the UV and
optical wavelengths, different techniques are discussed that allow to estimate
in consistent the stellar content and the evolutionary state of the ionizing
clusters.


title:
Parasitic Light in NGST instruments: the accuracy of photometric
  redshifts and the effect of filter leaks in the visible and near IR camera

abstract:
  A detailed analysis of NGST multiband photometry applied to the reference
case of the study of high-redshift galaxies has been carried out with
simulations based on galaxy SEDs derived from the currently available empirical
and model templates and on plausible standard filter-sets. In order to
correctly identify star forming galaxies in the redshift range 5<z<9 and
early-type galaxies above z>2 and avoid confusion with other SEDs it is
mandatory to have photometric information in optical bands, besides a standard
IR filter-set like F110 F160 K L M. In particular by adding the V606, I814 and
z-Gunn filters a good discrimination is obtained above z>5 for star forming
galaxies and z>1 for early-types. The case for an extension of the NGST
wavelength domain to the optical range is therefore strongly supported by this
analysis. The effects of leaks in the filter blocking have also been
investigated. In spite of rather pessimistic assumptions (a constant leak at a
level of 10^{-4} of the peak transmission over the whole spectral range or a
leak of Gaussian shape placed at 1.5 times the effective wavelength of the
filter with an amplitude of 10^{-3} of the peak transmission and a width of 5%
of the central wavelength) the effects are not dramatic: the accuracy of the
determination of photometric redshifts with a standard V606 I814 z-Gunn F110
F160 K L M filter set does not significantly deteriorate for a sample limited
to M_AB~30. In the range 5.5<z<12.5 a rather high accuracy with a typical error
|z_sim-z_phot|<=0.2 is achieved. With the filter blocking achieved by the
present standard technology, extended and continuous spectral coverage appears
to be the driving factor to maximize the scientific output.


title:
Gravitational wave background from coalescing compact stars in eccentric
  orbits

abstract:
  Stochastic gravitational wave background produced by a stationary coalescing
population of binary neutron stars in the Galaxy is calculated. This background
is found to constitute a confusion limit within the LISA frequency band up to a
limiting frequency $\NUlim{}\sim 10^{-3}$ Hz, leaving the frequency window
$\sim 10^{-3}$--$10^{-2}$ Hz open for the potential detection of cosmological
stochastic gravitational waves and of signals involving massive black holes out
to cosmological distances.


title: Implications of Neutron Decoupling in Short Gamma Ray Bursts

abstract:
  Roughly half of the observed gamma-ray bursts (GRBs) may arise from the
shocking of an ultra-relativistic shell of protons with the interstellar medium
(ISM). Any neutrons originally present in the GRB fireball may, depending on
the characteristics of the central engine, dynamically decouple as the fireball
accelerates. This leads to outflow consisting of separate fast proton and slow
neutron components. We derive detailed implications of neutron decoupling for
the observed lightcurves of short bursts. We show that the collision of a
neutron decayed shell with a decelerating outer shell is expected to result in
an observable second peak in the GRB lightcurve. There may be substantial
optical emission associated with such an event, so the upcoming Swift satellite
may be able to place constraints on models for short bursts. We also discuss
interesting inferences about central engine characteristics allowed by existing
BATSE data and a consideration of neutron decoupling.


title: Turbulent Dynamo in Asymptotic Giant Branch Stars

abstract:
  Using recent results on the operation of turbulent dynamos, we show that a
turbulent dynamo can amplify a large scale magnetic field in the envelopes of
asymptotic giant branch (AGB) stars. We propose that a slow rotation of the AGB
envelope can fix the symmetry axis, leading to the formation of an axisymmetric
magnetic field structure. Unlike solar-type alpha-omega dynamos, the rotation
has only a small role in amplifying the toroidal component of the magnetic
field. The large-scale magnetic field is strong enough for the formation of
magnetic cool spots on the AGB stellar surface. The spots can regulate dust
formation, hence mass loss rate, leading to axisymmetric mass loss and the
formation of elliptical planetary nebulae (PNe). Despite its role in forming
cool spots, the large scale magnetic field is too weak to play a dynamic role
and directly influence the wind from the AGB star. We find other problems in
models where the magnetic field plays a dynamic role in shaping the AGB winds,
and argue that they cannot explain the formation of nonspherical PNe.


title: A Model for the Strings of Eta Carinae

abstract:
  We propose a model based on ionization shadows to explain the formation of
the long and narrow strings of Eta Carinae. Five strings are known, all located
along the symmetry axis outside the Homunculus. The model assumes that each
string is formed in a shadow behind a dense clump near the symmetry axis. The
surrounding gas is ionized first, becomes much hotter, and compresses the gas
in the shadow. This leads to the formation of a radial, dense, long, and narrow
region, i.e., a string. Later the neutral material in the strings is ionized,
and becomes brighter. Still later it re-expands, and we predict that in about
200 years the strings will fade. The condition for the model to work is that
the ionization front, due to the diffuse ionizing recombination radiation of
the surrounding gas, proceeds into the shadow at a velocity slower than the
compression speed. From that we get a condition on the mass loss rate of the
mass loss episode that formed the strings, which should be less than 10^{-4}
Mo/year. The model can also explain the strings in the planetary nebula NGC
6543.


title: Homogenization of the Stellar Population along Late-Type Spiral Galaxies

abstract:
  We present a study of the broadband UBV color profiles for 257 Sbc barred and
non-barred galaxies. In our sample, the color gradients are negative (reddish
inward) in approximately 59% of the objects, are almost null in 27%, and are
positive in 14%, considering only the face-on galaxies, which represent
approximately 51% of the sample. We have also found that barred galaxies are
over-represented among the objects having null or positive gradients,
indicating that bars act as a mechanism of homogenization of the stellar
population. A correlation between the total and bulge colors was found, which
is a consequence of an underlying correlation between the colors of bulges and
disks found by others. Moreover, the mean total color is the same irrespective
of the gradient regime, while bulges are bluer in galaxies with null or
positive gradients, which indicates an increase of the star formation rate in
the central regions of these objects. We found no correlation between color and
O/H abundance gradients. We discuss this result considering a picture in which
bars are a relatively fast recurrent phenomenon. These results are not
compatible with a pure classical monolithic scenario for bulge and disk
formation. On the contrary, they favor a scenario where both these components
are evolving in a correlated process, in which stellar bars play a crucial
role.(Abridged)


title:
Observing the planet formation time-scale by ground-based direct imaging
  of planetary companions to young nearby stars: Gemini/Hokupa'a image of TWA-5

abstract:
  Many extra-solar planets and a few planetary systems have been found
indirectly by small periodic radial velocity variations around old nearby
stars. The orbital characteristics of most of them are different from the
planets in our solar system. Hence, planet formation theories have to be
revised. Therefore, observational constraints regarding young planets would be
very valuable. We have started a ground-based direct imaging search for giant
planets in orbit around young nearby stars. Here, we will motivate the sample
selection and will present our direct imaging observation of the very low-mass
(15 to 40 Jupiter masses) brown dwarf companion TWA-5 B in orbit around the
nearby young star TWA-5 A, recently obtained with the 36-element
curvature-sensing AO instrument Hokupa'a of the University of Hawai'i at the
8.3m Gemini-North telescope on Mauna Kea. We could achieve a FWHM of 64 mas and
25 % Strehl. We find significance evidence for orbital motion of B around A.


title: First detection of ammonia in M82

abstract:
  We report the detection of the (J,K) = (1,1), (2,2), and (3,3) inversion
lines of ammonia (NH3) towards the south--western molecular lobe in M82. The
relative intensities of the ammonia lines are characterized by a rotational
temperature of T_rot=29+/-5 K which implies an average kinetic temperature of
T_kin~60 K. A Gaussian decomposition of the observed spectra indicates
increasing kinetic temperatures towards the nucleus of M82, consistent with
recent findings based on CO observations. The observations imply a very low NH3
abundance relative to H2, X(NH3)~5x10^(-10). We present evidence for a
decreasing NH3 abundance towards the central active regions in M82 and
interpret this abundance gradient in terms of photodissociation of NH3 in PDRs.
The low temperature derived here from NH3 also explains the apparent
underabundance of complex molecules like CH_3OH and HNCO, which has previously
been reported.


title:
Constraints on the Lyman continuum radiation from galaxies: first
  results with FUSE on Mrk 54

abstract:
  We present Far Ultraviolet Spectroscopic Explorer observations of the
star-forming galaxy Mrk 54 at z = 0.0448. The Lyman continuum radiation is not
detected above the HI absorption edge in our Galaxy. An upper limit is
evaluated by comparison with the background measured in regions of the detector
adjacent to the observed spectrum. A spectral window of 16 A, reasonably free
of additional HI Lyman series line absorption is used. No correction is needed
for molecular hydrogen absorption in our Galaxy but a foreground extinction of
0.29 mag is accounted for. An upper limit of 6.15 10^{-16} erg/cm^2/s/A is
obtained for the flux at ~ 900 A in the rest frame of Mrk 54. By comparison
with the number of ionizing photons derived from the H-alpha flux, this limit
translates into an upper limit of f_esc < 0.062 for the fraction of Lyman
continuum photons that escape the galaxy without being absorbed by interstellar
material. This limit compares with the limits obtained in three other nearby
galaxies and is compatible with the escape fractions predicted by models.
  The upper limits obtained in nearby galaxies contrasts with the detection of
Lyman continuum flux in the composite spectrum of Lyman-break galaxies at z ~
3.4. The difficulties and implications of a comparison are discussed.


title: NGC 3603 - a Local Template for Massive Young Clusters

abstract:
  We present a study of the star cluster associated with the massive Galactic
HII region NGC3603 based on near-IR broad-- and narrowband observations taken
with ISAAC/VLT under excellent seeing conditions (<0.4''). We discuss
color-color diagrams and address the impact of the high UV flux on the disk
evolution of the low-mass stars.


title:
Global Emission Line Trends in Spiral Galaxies: The Reddening and
  Metallicity Sequences

abstract:
  We have explored the emission line trends in the integrated spectra of normal
spiral galaxies of the Nearby Field Galaxy Survey, in order to investigate the
relationships between dust extinction, metallicity and some macroscopic
properties of spiral galaxies. We found a very strong correlation between the
Hbeta and Halpha equivalent widths, implying that the difference between the
extinction of the stellar and the nebular light depends only on the intrinsic
colours of the galaxies, being larger for redder galaxies. The usual
metallicity indicator for giant HII regions ([OIII]4959,5007 + [OII]3726,3729)/
Hbeta is not appropriate for integrated spectra of spiral galaxies, probably
due to metallicity gradients. Much better qualitative metallicity indicators
are found to be [NII]6584/[OII]3726,3729 and [NII]6584/Halpha, the latter
having the advantage of being independent of reddening and being applicable
also for galaxies with weak emission lines. With these indicators, we find that
the nebular extinction as derived from the Balmer decrement strongly correlates
with the effective metallicity of the emission line regions. The overall
metallicity of the emission line regions is much better correlated with galaxy
colours than with morphological types. A Principal Component Analysis on a 7-D
parameter space showed that the variance is produced, in first place, by the
metallicity and parameters linked to the stellar populations, and, in second
place, by the surface brightness, which is linked to the dynamical history of
the galaxies. The absolute magnitude, related to the mass of the galaxy, comes
only in the third place.


title: Deep ROSAT-HRI observation of the elliptical galaxy NGC 1399

abstract:
  We present the preliminary results of a deep (167 ks) ROSAT HRI observation
of the cD galaxy NGC1399 in the Fornax cluster. We find, in agreement with
previous observations, an extended (41 Kpc adopting a distance of 19 Mpc)
gaseous halo with a luminosity of L_X=(4.41\pm 0.04)x10^{41} erg/s. The 5
arcsec resolution of the data allows us to detect a very complex and asymmetric
structure of the halo with respect to the optical galaxy. Moreover the analysis
of the radial structure reveals the presence of a multi-component profile not
consistent with a simple King model over the whole 40 Kpc. We do not detect the
presence of a central source and pose an upper limit to the luminosity of a
possible active nucleus. Due to the length of the observation, comparable to
that of a deep survey, we detect a large number of sources within the HRI FOV,
in slight excess with respect to the estimates based on previous surveys. We
study the flux distribution of the sources, their temporal behaviour and their
spatial distribution with respect to the central galaxy.


title: XMM-Newton Observation of the Black Hole Microquasar GRS 1758-258

abstract:
  The XMM-Newton X-ray observatory pointed the galactic black hole candidate
and microquasar GRS 1758-258 in September 2000 for about 10 ks during a program
devoted to the scan of the Galactic Center regions. Preliminary results from
EPIC MOS camera data are presented here. The data indicate that the source
underwent a state transition from its standard low-hard state to an
intermediate state. For the first time in this source the ultra-soft component
of the accretion disk, which black hole binaries display in intermediate or
high-soft states, was clearly detected and measured thanks to the high spectral
capabilities of XMM-Newton.


title: A complete sample of Seyfert galaxies selected at 1/4 keV

abstract:
  We have used the ROSAT Bright Source Catalogue to extract a complete sample
of sources selected in the band from 0.1-0.4 keV. This 1/4 keV-selected sample
is comprised of 54 Seyfert galaxies, 25 BL Lacertae objects, 4 clusters and 27
Galactic stars or binaries. Seyfert-type galaxies with ``ultrasoft'' X-ray
spectra can very often be classed optically as Narrow-line Seyfert 1s (NLS1s).
Such objects are readily detected in 1/4 keV surveys; the sample reported here
contains 20 NLS1s, corresponding to a 40% fraction of the Seyferts. Optical
spectra of the Seyfert galaxies were gathered for correlative analysis, which
confirmed the well-known relations between X-ray slope and optical spectral
properties (e.g., [O III]/H-beta ratio; Fe II strength, H-beta width). The
various intercorrelations are most likely driven, fundamentally, by the shape
of the photoionising continuum in Seyfert nuclei. We argue that a steep X-ray
spectrum is a better indicator of an ``extreme'' set of physical properties in
Seyfert galaxies than is the narrowness of the optical H-beta line. (Abridged)


title:
Searching for additional heating - [OII] emission in the diffuse ionized
  gas of NGC891, NGC4631 and NGC3079

abstract:
  We present spectroscopic data of ionized gas in the disk--halo regions of
three edge-on galaxies, NGC 891, NGC 4631 and NGC 3079, covering a wavelength
range from [\ion{O}{2}] $\lambda$3727\AA to [\ion{S}{2}] $\lambda$6716.4\AA.
The inclusion of the [\ion{O}{2}] emission provides new constraints on the
properties of the diffuse ionized gas (DIG), in particular, the origin of the
observed spatial variations in the line intensity ratios. We used three
different methods to derive electron temperatures, abundances and ionization
fractions along the slit. The increase in the [\ion{O}{2}]/H$\alpha$ line ratio
towards the halo in all three galaxies requires an increase either in electron
temperature or in oxygen abundance. Keeping the oxygen abundance constant
yields the most reasonable results for temperature, abundances, and ionization
fractions. Since a constant oxygen abundance seems to require an increase in
temperature towards the halo, we conclude that gradients in the electron
temperature play a significant role in the observed variations in the optical
line ratios from extraplanar DIG in these three spiral galaxies.


title:
A Brief History of Astronomical Brightness Determination Methods at
  Optical Wavelengths

abstract:
  In this brief article I review the history of astronomical photometry,
touching on observations made by the ancient Chinese, Hipparchus and Ptolemy,
the development of the concept (and definition) of magnitude, the endeavors of
Argelander and Zoellner, work at Harvard at the end of the 19th century, and
the development of photography, photomultipliers, and CCD's and their
application to astronomy.


title: Results and plans of the CRESST dark matter search

abstract:
  Data taken by CRESST in 2000 with a cryogenic detector system based on 262 g
sapphire crystals is used to place limits on WIMP dark matter in the Galactic
Halo. The detector is especially sensitive for low-mass WIMPS with
spin-dependent cross sections and improves on existing limits in this region.
CRESST is now preparing for a second phase, which will use a 10 kg detector
consisting of 300 g CaWO4 crystals with simultaneous detection of phonons and
scintillation light to reduce background.


title:
Are Clusters Standard Candles? Galaxy Cluster Scaling Relations With the
  Sunyaev-Zeldovich Effect

abstract:
  An extensive sample of galaxy clusters will be available in the coming years,
detected through their Sunyaev-Zeldovich effect (SZE). We use a semi-analytic
model to study the scientific yield of combining SZE data with X-ray and
optical follow-up observations. If clusters at a given redshift z_o can be
identified with virialized, spherical halos, they populate a well-defined
"fundamental plane" (FP) in the parameter space of the three observables:
virial temperature (T), total Sunyaev-Zeldovich flux decrement (DS), and
angular size (theta). The location and orientation of the FP, as well as its
redshift-evolution, are sensitive to both the internal evolution of clusters,
and to the underlying cosmological parameters. We show that if clusters are not
standard candles (e.g. due to feedback, or energy injection), then this can be
inferred from the FP. Likewise, we study the dependence of the FP on the
cosmological parameters h, sigma_8, and Omega_0, and quantify constraints on
these parameters. We also show that in the absence of any non-gravitational
effects, the scatter in the the (DS-T) plane is significantly smaller than in
either the (theta-T) or the (theta-DS) planes. As a result, the (DS-T) relation
can be an exceptionally sensitive probe of both cluster physics and
cosmological parameters, and a comparison of the amount of scatter in these
three scaling relations will serve as a test of the origin (cosmological vs.
stochastic) of the scatter.


title: Natural Quintessence with Gauge Coupling Unification

abstract:
  We show that a positive accelerating universe can be obtained simply by the
dynamics of a non-abelian gauge group. It is the condensates of the chiral
fields that obtain a negative power potential, below the condensation scale,
and allow for a quintessence interpretation of these fields. The only free
parameters in this model are $N_c$ and $N_f$ and the number of dynamically
gauge singlet bilinear fields $\phi$ generated below the condensation scale. We
show that it is possible to have unification of all coupling constants,
including the standard and non standard model couplings, while having an
acceptable phenomenology of $\phi$ as the cosmological constant. This is done
without any fine tuning of the initial conditions. The problem of coincidence
(why the universe has only recently started an accelerating period) is not
solved but it is put at the same level as what the particle content of the
standard model is.


title:
Bremsstrahlung of Flavor-Degenerate Pairs by Neutrinos in the Nuclear
  Field

abstract:
  Neutrino Bremsstrahlung of flavor-degenerate pairs in the field of a nucleus
is of potential importance for neutrino astrophysics and is representative of a
class of processes connecting leptonic electroweak sectors to real or virtual
photons. We focus on first generation flavor production by both electron and
muon neutrinos and present Standard Model cross sections and distributions for
lead and iron nuclei. The results (of order 10-41 cm2 for electron neutrino -
lead collisions at 100 MeV) have been fitted to empirical formulae that can be
used to estimate backgrounds to neutrino detection experiments and flux
normalizations. A compact form of the matrix element obtained by analytic
reduction is used to explain the distributions. The V-A limits of the cross
sections are shown to agree with published work from the pre-neutral current
era. Event signatures and the possible roles of these processes in stellar and
laboratory neutrino physics are discussed. Cross sections are compared with
those for neutrino-electron scattering for neutrino spectra corresponding to
typical supernovae temperatures.


title: The spectrum of HD46223

abstract:
  The spectrum of HD46223 was established from the optical to the far UV and
normalized by the spectrum of a non reddened star of same spectral type. The
resulting spectrum is separated into two components. One is the direct
starlight. The second is an additional component of light scattered at small
angles.
  In the optical the spectrum is dominated by direct starlight which decreases
exponentially due to the linear extinction.
  Scattered light begins to be noticeable in the near-UV. The near-UV rise of
the scattered light is interrupted in the bump region. The wavelength
dependence of the scattered light is established in the far-UV, where scattered
light dominates the extinction curve. A 1/lambda^4 dependence is found, proving
the presence of grains small compared to UV wavelengths.
  The mathematic expressions of the different components mentionned above give
a good fit to the extinction curve in the direction of the star. On a
mathematic standpoint the fit can be completed by a Lorentzien for the 2200Ang.
bump region. The physical interpretation of the bump may be more difficult to
achieve since the paper shows the possibility that only scattered light is
extinguished in the bump region.
  Consequences for the grain size distribution which is necessary to explain
the different aspects of scattering in interstellar clouds, for the value of
Rv, and problems raised by this interpretation of the spectrum of HD46223, are
considered at the end of this paper.


title: Scattered starlight contamination in the spectrum of reddened stars

abstract:
  The comparison, undertaken in preceding papers, of the UV observations of
nebulae and of reddened stars reveals contradictory aspects of interstellar
extinction. The aim of this paper is to understand the implications hidden
behind the apparent contradictions. The questions treated will be: how can
small grains with an isotropic phase function make an appreciable contribution
in the UV spectrum of a star? Why are small grains not observed in the spectrum
of a nebula? How much of starlight can be scattered by large grains in the
forward direction?


title:
The standard theory of extinction and the spectrum of stars with very
  little reddening

abstract:
  This paper examines the relationship between spectra of stars of same
spectral type with extremely low reddenings.
  According to the standard theory, the relationship between the spectrum of
stars with same spectral type and small, but different reddenings should be
different in the optical and in the UV.
  This difference is not observed: the ratio of the spectra of two stars in
directions where the reddening is large enough to be detected and low enough
not to give a noticeable 2200Ang. bump is an exponential of 1/lambda from the
near-infrared to the far-UV.
  This result is in conformity with the ideas introduced in preceding papers:
the exponential optical extinction extends to the UV, and the spectrum of stars
with enough reddening is contaminated by light scattered at close angular
distance from the stars.
  An application will be the determination of the spectrum of a non-reddened
star from the spectrum of a star of same spectral type with little reddening.


title:
TTauri Stars in the Large Magellanic Cloud: a combined HST and VLT
  effort

abstract:
  The combination of the unprecedented spatial resolution attainable with WFPC2
on board HST and of the large collecting area of the VLT makes it possible to
study in detail the low mass pre-Main Sequence stars in galaxies other than our
own.
  Here we present the results of our studies of two star forming environments
in our closest galactic neighbor, the Large Magellanic Cloud: the region around
Supernova 1987A and the double cluster NGC 1850.


title: Four years of Ulysses dust data: 1996 to 1999

abstract:
  The Ulysses spacecraft is orbiting the Sun on a highly inclined ellipse ($ i
= 79^{\circ}$, perihelion distance 1.3 AU, aphelion distance 5.4 AU). Between
January 1996 and December 1999 the spacecraft was beyond 3 AU from the Sun and
crossed the ecliptic plane at aphelion in May 1998. In this four-year period
218 dust impacts were recorded with the dust detector on board. We publish and
analyse the complete data set of both raw and reduced data for particles with
masses $\rm 10^{-16} g$ to $\rm 10^{-8}$ g. Together with 1477 dust impacts
recorded between launch of Ulysses and the end of 1995 published earlier
\cite{gruen1995c,krueger1999b}, a data set of 1695 dust impacts detected with
the Ulysses sensor between October 1990 and December 1999 is now available. The
impact rate measured between 1996 and 1999 was relatively constant with about
0.2 impacts per day. The impact direction of the majority of the impacts is
compatible with particles of interstellar origin, the rest are most likely
interplanetary particles. The observed impact rate is compared with a model for
the flux of interstellar dust particles. The flux of particles several
micrometers in size is compared with the measurements of the dust instruments
on board Pioneer 10 and Pioneer 11 beyond 3 AU (Humes 1980, JGR, 85,
5841--5852, 1980). Between 3 and 5 AU, Pioneer results predict that Ulysses
should have seen five times more ($\rm \sim 10 \mu m$ sized) particles than
actually detected.


title:
Near Infrared Faint Galaxies in the Subaru Deep Field: Comparing the
  Theory with Observations for Galaxy Counts, Colors, and Size Distributions to
  K=24.5

abstract:
  Galaxy counts in the K band, (J-K)-colors, and apparent size distributions of
faint galaxies in the Subaru Deep Field (SDF) down to K~24.5 were studied in
detail. Special attention has been paid to take into account various selection
effects including the cosmological dimming of surface brightness, to avoid any
systematic bias which may be the origin of controversy in previously published
results. We also tried to be very careful about systematic model uncertainties;
we present a comprehensive surveys of these systematic uncertainties and
dependence on various parameters. We found that the pure luminosity evolution
(PLE) model is well consistent with all the SDF data down to K~22.5, without
any evidence for number or size evolution in a low-density, Lambda-dominated
flat universe which is now favored by various cosmological observations. If the
popular Lambda-dominated universe is taken for granted, our result then gives a
strong constraint on the number evolution of giant elliptical or early-type
galaxies to z~1-2 which must be met by any models in the hierarchically
clustering universe, since such galaxies are the dominant population in this
magnitude range (K<~22.5). In the fainter magnitude range of K>~22.5, we found
a slight excess of observed counts over the prediction of the PLE model when
elliptical galaxies are treated as a single population. We suggest that this
discrepancy reflects some number evolution of dwarf galaxies and/or the
distinct populations of giant and dwarf elliptical galaxies which have been
known for local elliptical galaxies.


title: Theoretical Modeling of Starburst Galaxies

abstract:
  We have modeled a large sample of infrared starburst galaxies using both the
PEGASE v2.0 and STARBURST99 codes to generate the spectral energy distribution
of the young star clusters. PEGASE utilizes the Padova group tracks while
STARBURST99 uses the Geneva group tracks, allowing comparison between the two.
We used our MAPPINGS III code to compute photoionization models which include a
self-consistent treatment of dust physics and chemical depletion. We use the
standard optical diagnostic diagrams as indicators of the hardness of the EUV
radiation field in these galaxies. These diagnostic diagrams are most sensitive
to the spectral index of the ionizing radiation field in the 1-4 Rydberg
region. We find that warm infrared starburst galaxies contain a relatively hard
EUV field in this region. The PEGASE ionizing stellar continuum is harder in
the 1-4 Rydberg range than that of STARBURST99. As the spectrum in this regime
is dominated by emission from Wolf-Rayet (W-R) stars, this difference is most
likely due to the differences in stellar atmosphere models used for the W-R
stars. We believe that the stellar atmospheres in STARBURST99 are more
applicable to the starburst galaxies in our sample, however they do not produce
the hard EUV field in the 1-4 Rydberg region required by our observations. The
inclusion of continuum metal blanketing in the models may be one solution.
Supernova remnant (SNR) shock modeling shows that the contribution by
mechanical energy from SNRs to the photoionization models is << 20%. The models
presented here are used to derive a new theoretical classification scheme for
starbursts and AGN galaxies based on the optical diagnostic diagrams.


title: The spectral energy distribution of self-gravitating protostellar disks

abstract:
  The long wavelength emission of protostellar objects is commonly attributed
to a disk of gas and dust around the central protostar. In the first stages of
disk accretion or in the case of high mass protostars, the disk mass is likely
to be sufficiently large, so that the disk self-gravity may have an impact on
the dynamics and the emission properties of the disk. In this paper we describe
the spectral energy distribution (SED) produced by a simple, non-flaring,
self-gravitating accretion disk model. Self-gravity is included in the
calculation of the rotation curve of the disk and in the energy balance
equation, as a term of effective heating related to Jeans instability. In order
to quantify in detail the requirements on the mass of the disk and on the
accretion rate posed on the models by realistic situations, we compare the SEDs
produced by these models with the observed SEDs of a small sample of
well-studied protostellar objects. We find that relatively modest disks - even
lighter than the central star - can lead to an interesting fit to the infrared
SED of the FU Orionis objects considered, while in the case of T Tauri stars
the required parameters fall outside the range suggested as acceptable by the
general theoretical and observational scenario. On the basis of the present
results, we may conclude that the contribution of a self-gravitating disk is
plausible in several cases (in particular, for FU Orionis objects) and that, in
the standard irradiation dominated disk scenario, it would help softening the
requirements encountered by Keplerian accretion models.


title:
Chandra Limits on X-ray Emission Associated with the Supermassive Black
  Holes in Three Giant Elliptical Galaxies

abstract:
  Elliptical galaxy nuclei are the sites of the largest black holes known, but
typically show little or no nuclear activity. We investigate this extreme
quiescence using Chandra X-ray Observatory observations of the giant elliptical
galaxies NGC 1399, NGC 4472, and NGC 4636. The unique Chandra imaging power
enables us to place upper limits of 7.3, 15 and 28 X 10^-9 the Eddington
luminosity for the 0.1-1 billion solar mass black holes in NGC 1399, NGC 4472,
and NGC 4636, respectively. The corresponding radiative efficiencies in this
band are 4.1, 24, and 620 X 10^-6 using Bondi accretion rates derived from the
Chandra hot interstellar gas surface brightness profiles. These limits are
inconsistent with basic advection-dominated accretion flow (ADAF) models for
NGC 1399 and NGC 4472, indicating accretion onto the black hole at 10% of the
Bondi rate.


title: Galaxy populations from Deep ISO Surveys

abstract:
  I discuss some of the main extra-galactic field surveys which have been
undertaken by the Infrared Space Observatory (ISO). I review the findings from
the source counts analysies and then examine some of the more recent detailed
investigations into the explicit nature of the populations that make up these
source counts.


title: FIRST Extra-Galactic Surveys: Practical Considerations

abstract:
  We discuss some of the practical considerations that need to be made in the
design of extra-galactic field surveys using FIRST. We investigate the various
limitations that confusion noise imposes on possible FIRST surveys and the
benefits of super resolution or decconvolution techniques. We consider the
possible sizes and depths of survey fields in order to meet many of the
scientific objectives of the FIRST mission. In particular we discuss the
factors that need to be taken into account in selecting the survey fields. The
final choice of fields will be influenced by the location of other surveys that
are currently being planned; so it is vital that the FIRST community begin
debating this issue now. We conclude that a substantial survey of order of 100
square degrees is likely to be sited in the region of the SIRTF Legacy survey,
SWIRE.