title: An Accretion-Induced X-ray Flare in Sgr A*

abstract:
  The recent detection of a three-hour X-ray flare from Sgr A* by Chandra
provides very strong evidence for a compact emitting region near this
supermassive black hole at the Galactic center. Sgr A*'s mm/sub-mm spectrum and
polarimetric properties, and its quiescent-state X-ray flux density, are
consistent with a model in which low angular momentum gas captured at large
radii circularizes to form a hot, magnetized Keplerian flow within tens of
Schwarzschild radii of the black hole's event horizon. In Sgr A*'s quiescent
state, the X-ray emission appears to be produced by self-Comptonization (SSC)
of the mm/sub-mm synchrotron photons emitted in this region. In this paper, we
show that the prominent X-ray flare seen in Sgr A* may be due to a sudden
enhancement of accretion through the circularized flow. Depending on whether
the associated response of the anomalous viscosity is to increase or decrease
in tandem with this additional injection of mass, the X-ray photons during the
outburst may be produced either via thermal bremsstrahlung (if the viscosity
decreases), or via SSC (if the viscosity increases). However, the latter
predicts a softer X-ray spectrum than was seen by Chandra, so it appears that a
bremsstrahlung origin for the X-ray outburst is favored. A strong correlation
is expected between the mm/sub-mm and X-ray fluxes when the flare X-rays are
produced by SSC, while the correlated variability is strongest between the
sub-mm/far-IR and X-rays when bremsstrahlung emission is dominant during the
flare. In addition, we shows that future coordinated multi-wavelength
observations planned for the 2002 and 2003 cycles may be able to distinguish
between the accretion and jet scenarios.


title: Line Emission from Cooling Accretion Flows in the Nucleus of M31

abstract:
  The recent Chandra X-ray observations of the nucleus of M31, combined with
earlier VLA radio and HST UV spectral measurements, provide the strictest
constraints on the nature of accretion onto the supermassive black hole (called
M31* hereafter) in this region. One of the two newly-detected sources within
roughly an arcsec of M31* may be its X-ray counterpart. If not, the X-ray flux
from the nucleus must be even lower than inferred previously. Some uncertainty
remains regarding the origin of the UV excess from the compact component known
as P2. In our earlier analysis, we developed a unified picture for the
broadband spectrum of this source. Contrary to the `standard' picture in which
the infalling plasma attains temperatures in excess of 10^{10} K near the event
horizon, the best fit model for M31*, under the assumption that the UV
radiation is in fact produced by this source, appears to correspond to a cool
branch solution, arising from strong line cooling inside the capture radius.
Starting its infall with a temperature of about 10^6 K in the post-shock
region, the plasma cools down efficiently to about 10^4 K toward smaller radii.
An important prediction of this model is the appearance of a prominent UV spike
from hydrogen line emission. In this paper we model this line emission with
significantly greater accuracy, using the algorithm CLOUDY, and to correctly
take into account the attenuation along the line of sight. We predict a
spectrum with several additional prominent emission lines that can be used to
verify the model with future high-resolution observations.


title:
Keck Spectroscopy and HST Imaging of GRB 000926: Probing a Host Galaxy
  at z = 2. 038

abstract:
  We present early-time Keck spectroscopic observations and late-time Hubble
Space Telescope (HST) imaging of GRB 000926. The HST images show a small offset
between the optical transient and the compact host galaxy. Combined with the
large equivalent widths measured for metallic absorption lines by the Keck
Echellette Spectrograph and Imager (ESI) and the Low-Resolution Imaging
Spectrometer (LRIS), this indicates that the GRB exploded near the center of
its host. The ESI spectroscopy reveals two absorption systems centered at z =
2.0379 \pm 0.0008 with a velocity separation of 168 km s^{-1}, which we
interpret as being due to individual clouds in the host galaxy. The ratios of
chromium to zinc equivalent widths indicates the host is depleted in dust
relative to local values to a similar degree as damped Lyman alpha systems at
the same redshift. Further, the two clouds appear to have similar relative
metal abundance and dust to gas ratio. If one cloud is associated with the GRB
site, this implies the explosion did not significantly alter the surrounding
environment.


title: Thermal Conduction in Clusters of Galaxies

abstract:
  We estimate the thermal conductivity of a weakly collisional magnetized
plasma with chaotic magnetic field fluctuations. When the fluctuation spectrum
extends over two or more decades in wave-vector, we find that thermal
conduction is very efficient; the conduction coefficient is only a factor ~5
below the classical Spitzer estimate. We suggest that conduction could play a
significant role in cooling flows in clusters of galaxies.


title: Radial Color Gradients in K+A Galaxies in Distant Clusters of Galaxies

abstract:
  Galaxies in rich clusters with z $\gtrsim$ 0.3 are observed to have a higher
fraction of photometrically blue galaxies than their nearby counterparts. This
raises the important question of what environmental effects can cause the
termination of star formation between z $\approx$ 0.3 and the present. The star
formation may be truncated due to ram-pressure stripping, or the gas in the
disk may be depleted by an episode of star formation caused by some external
perturbation. To help resolve this issue, surface photometry was carried out
for a total of 70 early-type galaxies in the cluster Cl1358+62, at z $\sim$
0.33, using two-color images from the Hubble Archive. The galaxies were divided
into two categories based on spectroscopic criteria: 24 are type K+A (e.g.,
strong Balmer lines, with no visible emission lines), while the remaining 46
are in the control sample with normal spectra. Radial color profiles were
produced to see if the K+A galaxies show bluer nuclei in relation to their
surrounding disks. Specifically, a linear gradient was fit to the radial color
profile of each galaxy. We find that the K+A galaxies on average tend to have
slightly bluer gradients towards the center than the normals. A
Kolmogorov-Smirnov two-sample test has been applied to the two sets of color
gradients. The result of the test indicates that there is only a $\sim$2%
probability that the K+A and normal samples are drawn from the same parent
distribution. There is a possible complication from a trend in the apparent
magnitude vs. color gradient relation, but overall our results favor the
centralized star formation scenario as an important process in the evolution of
galaxies in dense clusters.


title:
Variability of Soft X-ray Spectral Shape: Narrow-Line Seyfert 1 Galaxies
  versus Broad-Line Seyfert 1 Galaxies

abstract:
  In order to understand how the soft X-ray spectra vary we present the
Hardness Ratio 1 versus Count Rates (HR1-CTs) correlation of 8 Narrow-line
Seyfert 1 Galaxies (NLS1s) and 14 Broad-line Seyfert1 Galaxies (BLS1s) obtained
during the ROSAT PSPC pointing observations. According to our criteria, six of
the NLS1s show a positive HR1-CTs correlation, and seven of the BLS1s display
an anti-correlation of HR1 versus CTs. The other 2 NLS1s and 7 BLS1s do not
show a clear HR1-CTs correlation. From these we can see that the NLS1s
statistically show a different spectral shape variability with flux change from
the BLS1s: the spectra of NLS1s become harder as total flux increases while
those of BLS1s soften. We attribute the different spectral variations to a
strong stable 'soft excess' in NLS1s, while it is weak in BLS1s. For two types
of objects, the power law component similarly becomes softer with increasing
intensity. These imply that the soft excess originates from the Big Blue Bump
and power law emission is from Compton upscattering of UV or Soft X-ray
photons. Our results are consistent with what is widely accepted that NLS1s
have smaller black hole masses and higher accretion rates than BLS1s.


title: A new source detection algorithm using FDR

abstract:
  The False Discovery Rate (FDR) method has recently been described by Miller
et al (2001), along with several examples of astrophysical applications. FDR is
a new statistical procedure due to Benjamini and Hochberg (1995) for
controlling the fraction of false positives when performing multiple hypothesis
testing. The importance of this method to source detection algorithms is
immediately clear. To explore the possibilities offered we have developed a new
task for performing source detection in radio-telescope images, Sfind 2.0,
which implements FDR. We compare Sfind 2.0 with two other source detection and
measurement tasks, Imsad and SExtractor, and comment on several issues arising
from the nature of the correlation between nearby pixels and the necessary
assumption of the null hypothesis. The strong suggestion is made that
implementing FDR as a threshold defining method in other existing
source-detection tasks is easy and worthwhile. We show that the constraint on
the fraction of false detections as specified by FDR holds true even for highly
correlated and realistic images. For the detection of true sources, which are
complex combinations of source-pixels, this constraint appears to be somewhat
less strict. It is still reliable enough, however, for a priori estimates of
the fraction of false source detections to be robust and realistic.


title:
Chemical composition of red horizontal branch stars in the thick disk of
  the Galaxy

abstract:
  High-resolution spectra of 13 core helium-burning stars in the thick disk of
the Galaxy have been obtained with the SOFIN spectrograph on the Nordic Optical
Telescope to investigate abundances of up to 22 chemical elements. Abundances
of carbon were studied using the C_2 Swan (0,1) band head at 5635.5 A. The
wavelength interval 7980-8130 A with strong CN features was analysed in order
to determine nitrogen abundances and 12C/13C isotope ratios. The oxygen
abundances were determined from the O I line at 6300 A. Abundances in the
investigated stars suggest that carbon is depleted by about 0.3 dex, nitrogen
is enhanced by more than 0.4 dex and oxygen is unaltered. The 12C/13C ratios
are lowered and lie between values 3 and 7 which is in agreement with "cool
bottom processing" predictions (Boothroyd & Sackmann 1999). The C/N ratios in
the investigated stars are lowered to values between 0.7 and 1.2 which is less
than present day theoretical predictions and call for further studies of
stellar mixing processes. Abundance ratios of O, Mg, Eu and other heavy
chemical elements to iron in the investigated stars show a pattern
characteristic of thick disk stars. The results provide evidence that the thick
disk population has a distinct chemical history from the thin disk. The onset
of the bulk of SN Ia is suggested to appear around [Fe/H] = -0.6 dex.


title: GAW (Gamma Air Watch): a novel imaging Cherenkov telescope

abstract:
  GAW (Gamma Air Watch) is a new imaging Cherenkov telescope designed for
observation of very high-energy gamma-ray sources. GAW will be equipped with a
3 meter diameter Fresnel lens as light collector and with an array of 300
multi-anode photomultipliers at the focal plane. The pixel size will be 4
arcmin wide for a total field of view of 10.5 degrees. Whith respect to the
planned imaging Cherenkov telescopes (CANGAROO III, HESS, MAGIC, VERITAS) GAW
follows a different approach for what concerns both the optical system and the
detection working mode: the Cherenkov light collector is a single acrylic flat
Fresnel lens (instead of mirrors) that allows to achieve wide field of view;
the photomultipliers operate in single photoelectron counting mode (instead of
charge integration). The single photoelectron counting mode allows to reach a
low energy threshold of ~200 GeV, in spite of the relatively small dimension of
the GAW optic system.


title: The spin evolution of nascent neutron stars

abstract:
  The loss of angular momentum due to unstable r-modes in hot young neutron
stars has been proposed as a mechanism for achieving the spin rates inferred
for young pulsars. One factor that could have a significant effect on the
action of the r-mode instability is fallback of supernova remnant material. The
associated accretion torque could potentially counteract any gravitational-wave
induced spin-down, and accretion heating could affect the viscous damping rates
and hence the instability. We discuss the effects of various external agents on
the r-mode instability scenario within a simple model of supernova fallback on
to a hot young magnetized neutron star. We find that the outcome depends
strongly on the strength of the star's magnetic field. Our model is capable of
generating spin rates for young neutron stars that accord well with initial
spin rates inferred from pulsar observations. The combined action of r-mode
instability and fallback appears to cause the spin rates of neutron stars born
with very different spin rates to converge, on a timescale of about a year. The
results suggest that stars with magnetic fields $\le10^{13}$ G could emit a
detectable gravitational wave signal for perhaps several years after the
supernova event. Stars with higher fields (magnetars) are unlikely to emit a
detectable gravitational wave signal via the r-mode instability. The model also
suggests that the r-mode instability could be extremely effective in preventing
young neutron stars from going dynamically unstable to the bar-mode.


title: HD 174005: another binary classified as lambda Boo

abstract:
  We demonstrate that HD 174005, a star recently classified as belonging to the
lambda Boo group, is in reality a double lined spectroscopic binary; at some
phases, the observed composite spectrum may be similar to that of a single star
with weak metal lines.


title:
Bulk viscosity in superfluid neutron star cores. III. Effects of
  $\Sigma^-$ hyperons

abstract:
  Bulk viscosity of neutron star cores containing hyperons is studied taking
into account non-equilibrium weak process $n+n \rightleftharpoons p+\Sigma^-$.
Rapid growth of the bulk viscosity within the neutron star core associated with
switching on new reactions (modified Urca process, direct Urca process, hyperon
reactions) is analyzed. The suppression of the bulk viscosity by superfluidity
of baryons is considered and found out to be very important.


title: STIS spectroscopy of newborn massive stars in SMC N81

abstract:
  Using Hubble Space Telescope observations with STIS, we study the main
exciting stars of N81, a high excitation compact Hii region in the Small
Magellanic Cloud (SMC). These far UV observations are the first spectroscopic
measurements of stars in such a region and reveal features characteristic of an
O6-O8 stellar type. The astonishing weakness of their wind profiles and their
sub-luminosity (up to ~ 2 mag fainter in Mv than the corresponding dwarfs) make
these stars a unique stellar population in the Magellanic Clouds. Our analysis
suggests that they are probably in the Hertzsprung-Russell diagram locus of a
particularly young class of massive stars, the so-called Vz luminosity class,
as they are arriving on the zero age main sequence.


title: A search for starlight reflected from upsilon And's innermost planet

abstract:
  In data from three clear nights of a WHT/UES run in 2000 Oct/Nov, and using
improved Doppler tomographic signal-analysis techniques, we have carried out a
deep search for starlight reflected from the innermost of upsilon And's three
planets. We place upper limits on the planet's radius R_p as functions of its
projected orbital velocity K_p ~ 139 sin i km/sec for various assumptions about
the wavelength-dependent geometric albedo spectrum p(\lambda) of its
atmosphere. For a grey albedo p we find R_p \sqrt{p} < 0.98 R_Jup with 0.1
percent false-alarm probability (4-sigma). For a Sudarsky et al (2000) Class V
model atmosphere, the mean albedo in our 380-676 nm bandpass is <p> ~ 0.42,
requiring R_p < 1.51 R_Jup, while an (isolated) Class IV model with <p> ~ 0.19
requires R_p < 2.23 R_Jup. The star's v sin{i} ~ 10 km/sec and estimated
rotation period P_{rot} ~ 10 d suggest a high orbital inclination i ~ 70-80
degrees. We also develop methods for assessing the false-alarm probabilities of
faint candidate detections, and for extracting information about the albedo
spectrum and other planetary parameters from faint reflected-light signals.


title: Origin of the galaxy morphology

abstract:
  In the current most plausible Cold Dark Matter (CDM) cosmology, larger clumps
increase their mass by the progressive merger of smaller clumps. During the
evolution, a several merger events, e.g., many minor and a few major merger
events, strongly affect the morphology of galaxies as assumed in semi-analytic
models. With our physically most detailed high resolution SPH models, we try to
tackle the origin of the galaxy morphology. We compute the evolution of 50
over-density peaks in SCDM cosmology and analyzed the obtained properties of
the model. We have obtained many different types of star formation history. As
a preliminary result, we found the relation between the morphology of the model
galaxies and their star formation history. Also we present the global star
formation history and metal enrichment history as a function of the redshift,
which are obtained by the summing the whole results.


title: X-ray Spectroscopy of QSOs with Broad Ultraviolet Absorption Lines

abstract:
  For the population of QSOs with broad ultraviolet absorption lines, we are
just beginning to accumulate X-ray observations with enough counts for spectral
analysis at CCD resolution. From a sample of eight QSOs [including four Broad
Absorption Line (BAL) QSOs and three mini-BAL QSOs] with ASCA or Chandra
spectra with more than 200 counts, general patterns are emerging. Their
power-law X-ray continua are typical of normal QSOs with Gamma~2.0, and the
signatures of a significant column density [N_H~(0.1-4)x10^{23} cm^{-2}] of
intrinsic, absorbing gas are clear. Correcting the X-ray spectra for intrinsic
absorption recovers a normal ultraviolet-to-X-ray flux ratio, indicating that
the spectral energy distributions of this population are not inherently
anomalous. In addition, a large fraction of our sample shows significant
evidence for complexity in the absorption. The subset of BAL QSOs with broad
MgII absorption apparently suffers from Compton-thick absorption completely
obscuring the direct continuum in the 2-10 keV X-ray band, complicating any
measurement of their intrinsic X-ray spectral shapes.


title: On the statistics of the gravitational field

abstract:
  In this paper we extend Chandrasekhar and von Neumann's analysis of the
statistics of the gravitational field to systems in which particles (e.g.
stars, galaxies) are not homogeneously distributed. We derive a distribution
function W(F,d F/dt) giving the joint probability that a test particle is
subject to a force F and an associated rate of change of F given by d F/dt. We
calculate the first moment of d F/dt to study the effects of inhomogenity on
dynamical friction.


title:
High-resolution HI Mapping of NGC 4038/9 ("The Antennae") and its Tidal
  Dwarf Galaxy Candidates

abstract:
  We present new VLA C+D-array HI observations and optical and NIR imaging of
the well known interacting system NGC 4038/9, ``The Antennae''. The radio data
reveal a wealth of gaseous sub-structure both within the main bodies of the
galaxies and along the tidal tails. In agreement with previous HI studies, we
find that the northern tail has HI along its outer length, but none along its
base. We suggest that the HI at the base of this tail has been ionized by
massive stars in the disk of NGC 4038. The gas in the southern tail has a
bifurcated structure, with one filament lying along the optical tail and
another running parallel to it but with no optical counterpart. The two
filaments join just before the location of several star forming regions near
the end of the tail. The HI velocity field at the end of the tail is dominated
by strong velocity gradients which suggest that at this location the tail is
bending away from us. We delineate and examine two regions within the tail
previously identified as possible sites of a so-called ``tidal dwarf galaxy''
condensing out of the expanding tidal material. The tail velocity gradients
mask any clear kinematic signature of a self-gravitating condensation in this
region. A dynamical analysis suggest that there is not enough mass in gas alone
for either of these regions to be self-gravitating. Conversely, if they are
bound they require a significant contribution to their dynamical mass from
evolved stars or dark matter. (Abridged)


title: Constraints On the Size Evolution of Brightest Cluster Galaxies

abstract:
  We measure the luminosity profiles of 16 brightest cluster galaxies (BCGs) at
$0.4 < z < 0.8$ using high resolution F160W NICMOS and F814W WFPC2 HST imaging.
The heterogeneous sample is drawn from a variety of surveys: seven from
clusters in the Einstein Medium Sensitivity Survey, five from the Las Campanas
Distant Cluster Survey and its northern hemisphere precursor, and the remaining
four from traditional optical surveys. We find that the surface brightness
profiles of all but three of these BCGs are well described by a standard de
Vaucouleurs ($r^{1/4}$) profile out to at least $\sim2r_{e}$ and that the
biweight-estimated NICMOS effective radius of our high redshift BCGs ($r_{e} =
8.3\pm 1.4$ kpc for $H_{0} = 80$ km s$^{-1}$ Mpc$^{-1}$, $\Omega_{m} = 0.2,
\Omega_\Lambda = 0.0$) is $\sim 2$ times smaller than that measured for a local
BCG sample. If high redshift BCGs are in dynamical equilibrium and satisfy the
same scaling relations as low redshift ones, this change in size would
correspond to a mass growth of a factor of 2 since $z \sim 0.5$. However, the
biweight-estimated WFPC2 effective radius of our sample is 18 $\pm $ 5.1 kpc,
which is fully consistent with the local sample. While we can rule out mass
accretion rates higher than a factor of 2 in our sample, the discrepancy
between our NICMOS and WFPC2 results, which after various tests we describe
appears to be physical, does not yet allow us to place strong constraints on
accretion rates below that level.


title: New neighbours: IV. 30 DENIS late-M dwarfs between 15 and 30 parsecs

abstract:
  We present 30 new nearby (d<30 pc) red dwarf candidates, with estimated
spectral types M6 to M8. 26 were directly selected from the DENIS database, and
another 4 were first extracted from the LHS catalogue and cross-identified with
a DENIS counterpart. Their proper motions were measured on the MAMA measuring
machine from plates spanning 13 to 48 years, and are larger than 0.1 arcsec/yr,
ruling out the possibility that they are giants. Their distances were estimated
from the DENIS colours and IR colour-magnitude relations and range between 15
and 30 pc.


title:
The Masses, Ancestors and Descendents of Extremely Red Objects:
  Constraints from Spatial Clustering

abstract:
  Wide field near-infrared (IR) surveys have revealed a population of galaxies
with very red optical$-$IR colors, which have been termed ``Extremely Red
Objects'' (EROs). Modeling suggests that such red colors (R-K > 5) could be
produced by galaxies at z>~1 with either very old stellar populations or very
high dust extinction. Recently it has been discovered that EROs are strongly
clustered. Are these objects the high-redshift progenitors of present day giant
ellipticals (gEs)? Are they already massive at this epoch? Are they the
descendents of the $z\sim3$ Lyman Break Galaxies (LBG), which have also been
identified as possible high redshift progenitors of giant ellipticals? We
address these questions within the framework of the Cold Dark Matter paradigm
using an analytic model that connects the number density and clustering or bias
of an observed population with the halo occupation function (the number of
observed galaxies per halo of a given mass). We find that EROs reside in
massive dark matter halos, with average mass <M> > 1E13/h100 Msun. The
occupation function that we derive for EROs is very similar to the one we
derive for z=0, L>L* early type galaxies, whereas the occupation function for
LBGs is skewed towards much smaller host halo masses (<M> ~ 1E11 to 1E12/h100
Msun. We then use the derived occupation function parameters to explore the
possible evolutionary connections between these three populations.


title: The core structure of presolar graphite onions

abstract:
  Of the ``presolar particles'' extracted from carbonaceous chondrite
dissolution residues, i.e. of those particles which show isotopic evidence of
solidification in the neighborhood of other stars prior to the origin of our
solar system, one subset has an interesting concentric
graphite-rim/graphene-core structure. We show here that single graphene sheet
defects in the onion cores (e.g. cyclopentane loops) may be observable edge-on
by HREM. This could allow a closer look at models for their formation, and in
particular strengthen the possibility that growth of these assemblages proceeds
atom-by-atom with the aid of such in-plane defects, under conditions of growth
(e.g. radiation fluxes or grain temperature) which discourage the graphite
layering that dominates subsequent formation of the rim.


title:
Solution of the radiative transfer equation in the separable
  approximation

abstract:
  A method for the fast and accurate solution of the radiative transfer
equation in plane-parallel media with coherent isotropic scattering is
presented. This largely analytical approach uses the formalism of meromorphic
functions in order to obtain the total solution, i.e. the angle and depth
variation of the radiation field. A discretization of space and angle
coordinates is not required. For the further application in the accretion disks
a particular case of a finite slab whose the midplane is the symmetry plane is
considered.


title: A Bayesian non-parametric method to detect clusters in Planck data

abstract:
  We show how one may expect a significant number of SZ detections in future
Planck data without any of the typical assumptions needed in present component
separation methods, such as about the power spectrum or the frequency
dependence of any of the components, circular symmetry or a typical scale for
the clusters. We reduce the background by subtracting an estimate of the point
sources, dust and CMB. The final SZE map is estimated in Fourier space. The
catalogue of returned clusters is complete above flux 200 mJy (353 GHz) while
the lowest flux reached by our method is about 70 mJy (353 GHz). We predict a
large number of detections (about 9000) in 4/5 of the sky. This large number of
SZ detections will allow a robust and consistent analysis of the evolution of
the cluster population with redshift and will have important implications for
determining the best cosmological model.


title:
The Interacting Dwarf Galaxy NGC 3077: The Interplay of Atomic and
  Molecular Gas with Violent Star Formation

abstract:
  We present a comprehensive multi-wavelength study of the nearby interacting
dwarf galaxy NGC3077 (member of the M81 triplet). High resolution VLA HI
observations show that most of the atomic gas (~90%) around NGC3077 is situated
in a prominent tidal arm with a complex velocity structure. Little HI (~5 x
10^7 M_sun) is associated with NGC3077 itself. High resolution OVRO
observations of the molecular component (CO) reveal the presence of 16
molecular complexes near the center of NGC3077 (total mass: ~1.6 x 10^6 M_sun).
A virial mass analysis of the individual complexes yields a lower CO-to-H_2
conversion factor in NGC3077 than the Galactic value - a surprising result for
a dwarf galaxy. The total (atomic and molecular) gas content in the centre of
NGC3077 is displaced from the stellar component of NGC3077 -- this implies that
not only the gas at large galactocentric radii is affected by the interaction
within the triplet but also the center. We speculate that the starburst
activity of NGC3077 was triggered by this redistribution of gas in the center.
Some of these supershells are surrounded by neutral hydrogen. In a few cases,
the rims of the ionized supershells are associated with dust absorption. The
most prominent star forming region in NGC3077 as probed by Pa-alpha
observations is hidden behind a dust cloud which is traced by the molecular
complexes. Correcting for extinction we derive a star forming rate of 0.05
M_sun year^-1, i.e. given the reservoir in atomic and molecular gas in NGC3077,
star formation may proceed at a similar rate for a few 10^8 years. The
efficiency to form stars out of molecular gas in NGC3077 is similar to that in
M82.


title:
X-ray properties of the microquasar GRS 1915+105 during a variability
  class transition

abstract:
  We present a detailed X-ray study of the microquasar GRS 1915+105 during a
variability class transition observed in 2000 June with the PPCs of the Indian
X-ray Astronomy Experiment. We supplement this observation with data from the
RXTE archives. The source made a transition from a steady low-hard state to a
regular oscillatory behaviour in the light curve known as bursts or class `rho'
(Belloni et al. 2000) between 2000 May 11 and 17 and reverted back to the
low-hard state on 2000 June 27. A gradual change in the burst recurrence time
from about 75 s to about 40 s was observed which then increased to about 120 s
during the ~ 40 days of class `rho'. The regular bursts disappeared from the
X-ray light curves and the class transition was observed to occur within 1.5
hours on 2000 June 27 with the PPCs. A correlation is found between the
observed QPO frequency at 5-8 Hz in the quiescent phase and the average X-ray
intensity of the source during the class `rho'. We notice a strong similarity
between the properties of the source during the class `rho' and those during
the oscillatory phase of the observations of class `alpha'. From the timing and
spectral analysis, it is found that the observed properties of the source over
tens of days during the class `rho' are identical to those over a time scale of
a few hundreds of seconds in the class `alpha'. Examining the light curves from
the beginning of the RXTE/PCA and RXTE/ASM observations, it is found that the
change of state from radio-quiet low-hard state to high state occurs through
the X-ray classes `rho' and `alpha' which appear together during the state
transition. It is further inferred that the source switches from low-hard state
to the class `rho' through the intermediate class `alpha'.


title: Value of the Cosmological Constant in the Cosmological Relativity Theory

abstract:
  It is shown that the cosmological relativity theory prdicts the value Lambda
= 1.934 x 10^-35 s^-2 for the cosmological constant. This value of Lambda is in
exellent agreement with the measurements recently obtained by the High-Z
Supernova Team and the Supernova Cosmology Project.


title: Formation of a Proto-Quasar from Accretion Flows in a Halo

abstract:
  We present a detailed model for the formation of massive objects at the
centers of galaxies. The effects of supernovae heating and the conditions of
gas loss are revisited. The escape time of the gas is compared with the cooling
time, which provides an additional condition not previously considered. Its
consequences for the allowed mass range of the halo is calculated. It is shown
that sufficient gas is retained to form massive dark objects and quasars even
for moderately massive halos but a decline is expected at low redshifts.
Subsequently, a gaseous disk forms with a radial extent of a ~kpc, spun up by
tidal torques and magnetized by supernovae fields with fields strengths of
$10-100 \mu G$. In a model of a self-similar accretion flow in an initially
dominant halo, it is shown that for typical halo parameters, about $10^8
M_\odot$ accretes via small magnetic stresses (or alternatively by self-gravity
induced instability or by alpha viscosity) in $10^8$ years into a compact
region. A model of a self-gravitating evolution of a compact magnetized disk,
which is relevant when a significant fraction of the disk mass falls in, is
presented, and it has a rapid collapse time scale of a million years. The two
disk solutions, one for accretion in an imposed halo potential and the other
for self-gravitating disk, obtained here, have general utility and can be
adapted to other contexts like protostellar disks as well.


title: The Orthogonal Gaseous Kinematical Decoupling in the Sa Spiral NGC 2855

abstract:
  We present major and minor-axis kinematics of stars and ionized gas as well
as narrow and broad-band surface photometry of the Sa spiral NGC 2855. In the
nuclear regions of this unbarred and apparently undisturbed spiral galaxy the
gas is rotating perpendicularly to the galaxy disk. We suggest that this
kinematically-decoupled component is the signature of an acquisition process in
the history of this galaxy.


title:
The Mauna Kea Observatories Near-Infrared Filter Set. II. Specifications
  for a New JHKL'M' Filter Set for Infrared Astronomy

abstract:
  We present a description of a new 1--5 $\mu$m filter set similar to the
long-used JHKLM filter set derived from that of Johnson. The new Mauna Kea
Observatories Near-Infrared (MKO-NIR) filter set is designed to reduce
background noise, improve photometric transformations from observatory to
observatory, provide greater accuracy in extrapolating to zero air mass, and
reduce the color dependence in the extinction coefficient in photometric
reductions. We have also taken into account the requirements of adaptive optics
in setting the flatness specification of the filters. A complete technical
description is presented to facilitate the production of similar filters in the
future.


title:
The Mauna Kea Observatories Near-Infrared Filter Set. I: Defining
  Optimal 1-5 $\mu$m Bandpasses

abstract:
  A new MKO-NIR infrared filter set is described, including techniques and
considerations given to designing a new set of bandpasses that are useful at
both mid- and high-altitude sites. These filters offer improved photometric
linearity and in many cases reduced background, as well as preserve good
throughput within the JHKLM atmospheric windows. MKO-NIR filters have already
been deployed with a number of instruments around the world as part of a filter
consortium purchase to reduce the unit cost of filters. Through this effort we
hope to establish, for the first time, a single standard set of infrared
fitlers at as many observatories as possible.


title:
Feasibility of Probing Dark Energy with Strong Gravitational Lensing
  Systems -- Fisher-Matrix Approach --

abstract:
  We assess the feasibility of probing dark energy with strong gravitational
lensing systems. The capability of the method, which depends on the accuracy
with which the lensing systems are modeled, is quantitatively investigated
using the Fisher-matrix formalism. We show that this method might place useful
constraints on the density parameter and the redshift evolution of the dark
energy by combining it with a constraint from supernova measurements. For this
purpose, the lens potential needs to be precisely reconstructed. We determine
the required quality of data. We also briefly discuss the optimal strategy to
constrain the cosmological parameters using gravitational lensing systems.


title: Cosmological constraint from QSO spatial power spectrum

abstract:
  In this paper we consider constraints on the cosmological density parameters
from the spatial power spectrum of QSOs. We first review an analytic approach
to the spatial power spectrum of QSOs, then we compare the result of the
analytic approach with a preliminary result of the power spectrum from the
two-degree Field QSO redshift (2QZ) survey. From a simple chi^2 test, we show
that a finite baryon fraction better explains observation of the QSO power
spectrum, which might suggest a possible detection of the baryonic oscillations
in the QSO power spectrum.


title:
Galaxy Population in a Cluster of Galaxies around the Radio Galaxy 3C
  324 at z=1.2

abstract:
  We discuss the properties of galaxies around the radio galaxy 3C 324 at z=1.2
based on BVRIK' multi-band imaging data. We have applied a photometric-redshift
technique to objects in the 3C 324 field, and identified 35 objects as
plausible cluster members. We have found that red and luminous members are
concentrated in a small region enclosed by a circle of 40" radius (0.33 Mpc at
z=1.2 for \Omega_0=0.3, \lambda_0=0.7, H_0=70km/s/Mpc cosmology) from the 3C
324 galaxy. The 3C 324 cluster is probably much more compact in size compared
with the local clusters. We constructed a K'-band luminosity function of the
cluster members and fit a Schechter function, and found the characteristic
magnitude to be K*_{AB}=20.2+-0.6. This value is consistent with the
extrapolation of the pure passive evolution seen for z<1 clusters. We have
identified eight bright galaxies which form a red color-magnitude sequence. The
slope of the sequence is consistent with the passive evolution model down to
K'_{AB}<22; we also found that there is no clear age variation in these bright
red galaxies. However, seven out of these eight galaxies exhibit a significant
excess in the rest UV light with respect to the passive evolution model. This
may suggest that the massive early-type galaxies in this high-redshift cluster
are still forming stars to some extent. We have confirmed a truncation of the
color-magnitude sequence at K'_{AB}\sim22; faint passively-evolving galaxies
may not yet be present in this cluster at z\sim1.2. The overall color
distribution of the cluster members, selected by the photometric redshift
technique, is found to be very broad. We derived the fraction of blue galaxies
in this cluster following a


title:
Galaxy Clusters: Cosmic High-Energy Laboratories to Study the Structure
  of Our Universe

abstract:
  This contribution illustrates the study of galaxy clusters as astrophysical
laboratories as well as probes for the large-scale structure of the Universe.
Using the REFLEX Cluster Survey, the measurement of the statistics of the
large-scale structure on scales up to 500 $h^{-1}$ Mpc is illustrated. The
results clearly favour a low density Universe. Clusters constitute, in
addition, well defined astrophysical laboratory environments in which some very
interesting large-scale phenomena can be studied. As an illustration we show
some spectacular new XMM X-ray spectroscopic results on the thermal structure
of cooling flows and the interaction effects of AGN with this hot intracluster
medium. The X-ray observations with XMM-Newton show a lack of spectral evidence
for large amounts of cooling and condensing gas in the centers of galaxy
clusters believed to harbour strong cooling flows. To explain these findings we
consider the heating of the core regions of clusters by jets from a central
AGN. We find that the power output the AGN jets is well sufficient. The
requirements such a heating model has to fulfill are explored and we find a
very promising scenario of self-regulated Bondi accretion of the central black
hole.


title: CMD's, RR Lyrae's, clump stars and reddening in the LMC

abstract:
  We present new B, V, I photometry in the standard Johnson-Cousins photometric
system of two regions near the bar of the Large Magellanic Cloud (LMC), one of
which is very close to LMC field used for the "Coimbra test on the synthetic
CMD techniques". The two areas contain 128 RR Lyrae variables and more than
8000 clump stars. Once combined with Clementini et al. 2001 (astro-ph/0007471)
photometry the new data-set allows us to get (i) accurate CMD's down to V~23
mag, (ii) full coverage of the B and V light variation for more than 80% of the
RR Lyrae's, (iii) a very precise estimate of the LMC RR Lyrae's average
apparent luminosity, (iv) an accurate estimate of the I luminosity of the LMC
clump stars, and (v) an independent evaluation of the reddening in these
regions of the LMC using the pulsational properties of the RR Lyrae's in our
sample. A detailed comparison is made between our, OGLE II and MACHO
photometries. We discuss the impact of our new results on the distance to the
LMC and on the "short" and "long" distance scale controversy.


title: Temperature fluctuations in the intergalactic medium

abstract:
  The temperature of the low-density intergalactic medium is set by the balance
between adiabatic cooling resulting from the expansion of the universe, and
photo-heating by the UV-background. We have analysed the Lyman-alpha forest of
eleven high-resolution quasar spectra using wavelets, and find strong evidence
of a marked jump in the temperature at the mean density, T_0, of 60 per cent
around a redshift z=3.3, which we attribute to reionization of HeliumII. The
jump can be seen in all three of our spectra that straddle redshift 3.3, at a
significance of 99 per cent. Below z=3.1, our results are consistent with a
smooth cooling down of the universe, as expected when adiabatic expansion
dominates over photo-heating by a UV-background from QSOs and galaxies. We find
no evidence of thermal fluctuations on scales greater than 5000 km/s larger
than 50 per cent, which could be detected by our method, suggesting that the
IGM follows a reasonably well-defined temperature-density relation. We
demonstrate that the mean wavelet amplitude scales inversely with T_0 and
calibrate the relation with hydrodynamical simulations. We find T_0= 12000K at
z>3.6. Such high temperature suggest that Hydrogen reionization occured
relatively recent.


title: Damping of inhomogeneities in neutralino dark matter

abstract:
  The lightest supersymmetric particle, most likely the neutralino, might
account for a large fraction of dark matter in the Universe. We show that the
primordial spectrum of density fluctuations in neutralino cold dark matter
(CDM) has a sharp cut-off due to two damping mechanisms: collisional damping
during the kinetic decoupling of the neutralinos at O(10 MeV) and free
streaming after last scattering of neutralinos. The cut-off in the primordial
spectrum defines a minimal mass for CDM objects in hierarchical structure
formation. For typical neutralino and sfermion masses the first gravitationally
bound neutralino clouds have masses above 10^(-6) M_\odot.


title:
Modelling surface magnetic field evolution on AB Doradus due to
  diffusion and surface differential rotation

abstract:
  From Zeeman Doppler images of the young, rapidly-rotating K0 dwarf AB
Doradus, we have created a potential approximation to the observed radial
magnetic field and have evolved it over 30 days due to the observed surface
differential rotation, meridional flow and various diffusion rates. Assuming
that the dark polar cap seen in Doppler images of this star is caused by the
presence of a unipolar field, we have shown that the observed differential
rotation will shear this field to produce the observed high-latitude band of
unidirectional azimuthal field. By cross-correlating the evolved fields each
day with the initial field we have followed the decay with time of the
cross-correlation function. Over 30 days it decays by only 10 percent. This
contrasts with the results of Barnes et al (1998), who show that on this
timescale the spot distribution of He699 is uncorrelated. We propose that this
is due to the effects of flux emergence changing the spot distributions.


title: The optical afterglow and host galaxy of GRB 000926

abstract:
  In this paper we illustrate with the case of GRB 000926 how Gamma Ray Bursts
(GRBs) can be used as cosmological lighthouses to identify and study star
forming galaxies at high redshifts. The optical afterglow of the burst was
located with optical imaging at the Nordic Optical Telescope 20.7 hours after
the burst. Rapid follow-up spectroscopy allowed the determination of the
redshift of the burst and a measurement of the host galaxy HI-column density in
front of the burst. With late-time narrow band Ly-alpha as well as broad band
imaging, we have studied the emission from the host galaxy and found that it is
a strong Ly-alpha emitter in a state of active star formation.


title: Detecting filaments at z=3

abstract:
  We present the detection of a filament of Ly-alpha emitting galaxies in front
of the quasar Q1205-30 at z=3.04 based on deep narrow band imaging and
follow-up spectroscopy obtained at the ESO NTT and VLT. We argue that Ly-alpha
selection of high redshift galaxies with relatively modest amounts of observing
time allows the detection and redshift measurement of galaxies with
sufficiently high space densities that we can start to map out the large scale
structure at z=2-3 directly. Even more interesting is it that a 3D map of the
filaments will provide a new cosmological test for the value of the
cosmological constant, Omega_Lambda.


title:
Kinetic equilibrium of iron in the atmospheres of cool dwarf stars II.
  Weak Fe I lines in the solar spectrum

abstract:
  NLTE line formation calculations of FeI in the solar atmosphere are extended
to include weak optical lines. Previously established atomic models are used to
discriminate between different ways of treating collisional interaction
processes. To derive a common solar FeI abundance from both strong and weak
lines, fine-tuning of the microturbulence velocity parameter and the van-der-
Waals damping constants is required. The solar FeI abundances based on all
available f-values are dominated by the large scatter already found for the
stronger lines. In particular the bulk of the data from the work of May et al.
and O'Brian et al. is not adequate for accurate abundance work. Based on
f-values measured by the Hannover and Oxford groups alone, the FeI LTE
abundances are eps(FeI,Sun)=7.57 for the empirical and eps(FeI,Sun) = 7.48 ...
7.51 for the line-blanketed solar model. The solar Fe ionization equilibrium
obtained for different atomic and atmospheric models rules out NLTE atomic
models with a low efficiency of hydrogen collisions. At variance with Paper I,
it is now in better agreement with laboratory FeII f-values for all types of
line-blanketed models. Our final model assumptions consistent with a single
unique solar Fe abundance eps(Fe,Sun) = 7.48 ... 7.51 calculated from NLTE line
formation are (a) a line-blanketed solar model atmosphere, (b) an iron model
atom with hydrogen collision rates 0.5 < S_H < 5 times the standard value to
compensate for the large photoionization cross-sections, (c) a microturbulence
velocity xi = 1.0 kms, (d) van-der-Waals damping parameters decreased by
Delta(log C6) = -0.10...-0.15 as compared to Anstee & O'Mara's calculations,
depending on S_H, (e) FeII f-values as published by Schnabel et al., and (f)
FeI f-values published by the Hannover and Oxford groups.


title:
Gravitational Wave Induced Rotation of the Plane of Polarization of
  Pulsar Signals

abstract:
  We derive in this an expression for the rotation of plane of polarization, of
an electromagnetic wave, induced by the field of a gravitational wave
propagating along the same direction $\approx \f{G\mu d^2\Omega^4}{3\o}$, $\o$
and $\Omega$ being their respective frequencies using the geometrical optics
limit of the wave equation for fields. Estimating the effect for the case of
pulses from binary pulsars, one finds it too small to be observable, there
could be other sources like inspiralling binary or an asymmetric neutron star
where the effect could be in the observable region.


title: Rotation of the solar interior

abstract:
  Helioseismology has allowed us to infer the rotation in the greater part of
the solar interior with high precision and resolution. The results show
interesting conflicts with earlier theoretical expectations, indicating that
the the Sun is host to complex dynamical phenomena, so far hardly understood.
This has important consequences for our ideas about the evolution of stellar
rotation, as well as for models for the generation of the solar magnetic field.
Here we provide an overview of our current knowledge about solar rotation, much
of it obtained from observations from the SOHO spacecraft, and discuss the
broader implications.


title:
The hard X-ray emission from the complex SNR MSH 15-52 observed by
  BeppoSAX

abstract:
  We present the results of a BeppoSAX observation of the Supernova Remnant MSH
15-52, associated with the pulsar PSR B1509-58, and discuss its main
morphological and spectroscopic properties in the 1.6--200 keV energy range
(MECS and PDS instruments). The two main structures of the remnant, the
Southern Nebula, the plerion centered on the pulsar, and the Northern Nebula,
are clearly visible in the MECS, with the former showing a much a harder
spectrum. Furthermore, a diffuse extended emission surrounds the whole remnant
up to ~ 17' from the center. Non-thermal flux is detected in the PDS up to 200
keV as well, and it appears that also in this energy range the emission is not
concentrated in the central region around the pulsar. These data imply that the
plerion extends up to a few tens of parsecs from the pulsar.


title: Energy generation in stars

abstract:
  It is a current opinion that thermonuclear fusion is the main source of the
star activity. It is shown below that this source is not unique. There is
another electrostatic mechanism of the energy generation which accompanies
thermonuclear fusion. Probably, this approach can solve the solar neutrino
problem.


title:
The X-ray virial relations for relaxed lensing clusters observed with
  Chandra

abstract:
  We examine the relations linking mass, X-ray temperature and bolometric
luminosity for a sample of luminous, relatively relaxed clusters of galaxies
observed with the Chandra Observatory, for which independent confirmation of
the mass results is available from gravitational lensing studies. Within radii
corresponding to a fixed overdensity Delta = 2500 with respect to the critical
density at the redshifts of the clusters, the observed temperature profiles,
scaled in units of T_2500 and r_2500, exhibit an approximately universal form
which rises within r~0.3 r_2500 and then remains approximately constant out to
r_2500. We obtain best-fit slopes for the mass-temperature and
temperature-luminosity relations consistent with the predictions from simple
scaling arguments i.e. M_2500 \propto T_2500^{3/2} and L_2500 \propto
T_2500^{2}, respectively. We confirm the presence of a systematic offset of ~40
per cent between the normalizations of the observed and predicted
mass-temperature relations for both SCDM and LambdaCDM cosmologies.


title: Probing the Mass Distribution with IRAS Galaxies

abstract:
  We present the results of three independent analyses in which we show that
IRAS galaxies faithfully trace the underlying distribution the mass in the
local universe. In the first analysis we compare the mass and the galaxy
density fields and show that they are consistent within 60 $h^{-1}$Mpc. In the
second one we show that the tidal velocity field of the Mark III catalog is
consistent with the tidal velocity field predicted from the distribution of
IRAS galaxies, hence indicating that IRAS galaxies trace the mass distribution
well beyond 60 $h^{-1}$Mpc. Finally, a third analysis aimed at determining the
mean biasing relation of IRAS galaxies showed no appreciable deviations from
the linear biasing prescription.


title:
The Optical Gravitational Lensing Experiment. Difference Image Analysis
  of LMC and SMC data. The Method

abstract:
  We describe the Difference Image Analysis (DIA) algorithms and software used
to analyze four years (1997-2000) of OGLE-II photometric monitoring of the
Magellanic Clouds, the calibration, the photometric error analysis, and the
search for variable stars. A preliminary analysis of photometric errors is
based on the field LMC_SC2. A full catalog of about 70,000 variable stars will
be presented in a separate publication.


title:
Constraints on the Ultra High Energy Photon flux using inclined showers
  from the Haverah Park array

abstract:
  We describe a method to analyse inclined air showers produced by ultra high
energy cosmic rays using an analytical description of the muon densities. We
report the results obtained using data from inclined events
(60^{\circ}<\theta<80^{\circ}) recorded by the Haverah Park shower detector for
energies above 10^19 eV. Using mass independent knowledge of the UHECR spectrum
obtained from vertical air shower measurements and comparing the expected
horizontal shower rate to the reported measurements we show that above 10^19 eV
less than 48 % of the primary cosmic rays can be photons at the 95 % confidence
level and above 4 X 10^19 eV less than 50 % of the cosmic rays can be photonic
at the same confidence level. These limits place important constraints on some
models of the origin of ultra high-energy cosmic rays.


title:
Broad and shifted iron-group emission lines in gamma-ray bursts as tests
  of the hypernova scenario

abstract:
  In the hypernova/collapsar model of gamma-ray bursts, it is natural that
radiation is emitted by the inner engine for some time after the burst. This
has been discussed as a possible source of the X-ray line emission observed in
some afterglows. We show here that the natural geometry of a hypernova
  --a source of radiation at the bottom of a deep funnel-- has very significant
consequences for the shape and central energy of the observed emission lines:
the lines acquire a very broad scattering wing on the low-energy side and a
characteristic second peak one Compton wavelength away from the initial energy,
due to the once- and twice-scattered photons. We suggest that this explains the
large width of the observed lines. Furthermore, the downscattering lowers the
central line energy (by up to 1 keV in the source rest frame, before the lines
become unrecognizable), so that the observed line energies can become
consistent with originating from cobalt and nickel, as expected in few-day-old
supernova ejecta.


title: The Origin of Spatial Intermittency in the Galaxy Distribution

abstract:
  The dynamical equations describing the evolution of a self-gravitating fluid
can be rewritten in the form of a Schrodinger equation coupled to a Poisson
equation determining the gravitational potential. This approach has a number of
interesting features, many of which were pointed out in a seminal paper by
Widrow & Kaiser (1993). In particular we show that this approach yields an
elegant reformulation of an idea due to Jones (1999) concerning the origin of
lognormal intermittency in the galaxy distribution.


title: Large-Scale Environmental Effects of the Cluster Distribution

abstract:
  Using the APM cluster distribution we find interesting alignment effects: (1)
Cluster substructure is strongly correlated with the tendency of clusters to be
aligned with their nearest neighbour and in general with the nearby clusters
that belong to the same supercluster, (2) Clusters belonging in superclusters
show a statistical significant tendency to be aligned with the major axis
orientation of their parent supercluster. Furthermore we find that dynamically
young clusters are more clustered than the overall cluster population. These
are strong indications that cluster develop in a hierarchical fashion by
merging along the large-scale filamentary superclusters within which they are
embedded.


title:
Astrometric radial velocities III. Hipparcos measurements of nearby star
  clusters and associations

abstract:
  Radial motions of stars in nearby moving clusters are determined from
accurate proper motions and trigonometric parallaxes, without any use of
spectroscopy. Assuming that cluster members share the same velocity vector
(apart from a random dispersion), we apply a maximum-likelihood method on
astrometric data from Hipparcos to compute radial and space velocities (and
their dispersions) in the Ursa Major, Hyades, Coma Berenices, Pleiades, and
Praesepe clusters, and for the alpha Persei, Scorpius-Centaurus, and `HIP
98321' associations. The radial motion of the Hyades cluster is determined to
within 0.47 km/s (standard error), and that of its individual stars to within
0.6 km/s. For other clusters, Hipparcos data yield astrometric radial
velocities with typical accuracies of a few km/s. A comparison of these
astrometric values with spectroscopic radial velocities in the literature shows
a good general agreement and, in the case of the best-determined Hyades
cluster, also permits searches for subtle astrophysical differences, such as
evidence for enhanced convective blueshifts of F-dwarf spectra, and decreased
gravitational redshifts in giants. Similar comparisons for the Scorpius OB2
complex indicate some expansion of its associations, albeit slower than
expected from their ages. As a by-product from the radial-velocity solutions,
kinematically improved parallaxes for individual stars are obtained, enabling
Hertzsprung-Russell diagrams with unprecedented accuracy in luminosity. For the
Hyades (parallax accuracy 0.3 mas), its main sequence resembles a thin line,
possibly with wiggles in it.


title:
Peculiar Velocity Reconstruction with Fast Action Method: Tests on Mock
  Redshift Surveys

abstract:
  We present extensive tests of the Fast Action Method (FAM) for recovering the
past orbits of mass tracers in an expanding universe from their redshift-space
coordinates at the present epoch. The tests focus on the reconstruction of
present-day peculiar velocities using mock catalogs extracted from high
resolution $N$-body simulations. The method allows for a self-consistent
treatment of redshift-space distortions by direct minimization of a modified
action for a cosmological gravitating system. When applied to ideal, volume
limited catalogs, FAM recovers unbiased peculiar velocities with a 1-D, 1\sigma
error of ~220 km/s, if velocities are smoothed on a scale of 5 Mpc/h.
Alternatively, when no smoothing is applied, FAM predicts nearly unbiased
velocities for objects residing outside the highest density regions. In this
second case the 1\sigma$error decreases to a level of ~150 km/s. The
correlation properties of the peculiar velocity fields are also correctly
recovered on scales larger than 5 Mpc/h. Similar results are obtained when FAM
is applied to flux limited catalogs mimicking the IRAS PSCz survey. In this
case FAM reconstructs peculiar velocities with similar intrinsic random errors,
while velocity-velocity correlation properties are well reproduced beyond
scales of ~8 Mpc/h. We also show that FAM provides better velocity predictions
than other, competing methods based on linear theory or Zel'dovich
approximation. These results indicate that FAM can be successfully applied to
presently available galaxy redshift surveys such as IRAS PSCz.


title:
Possible Infrared Counterparts to the Soft Gamma-Ray Repeater SGR
  1806-20

abstract:
  We report the discovery of possible infrared counterparts to SGR 1806-20. We
use archival {\it Chandra} observations to determine the location of SGR
1806-20 to $<1 \arcsec$ accuracy. We then locate 2 infrared objects within this
error circle in K-band ($2.2 \mu$m) images of this field. Based on the X-ray
absorption towards SGR 1806-20 and the extinction towards the nearby star
cluster, we discuss the likelihood of association for the possible
counterparts, and the implications for SGR 1806-20's physical properties and
origins.


title:
On the crosscorrelation between Gravitational Wave Detectors for
  detecting association with Gamma Ray Bursts

abstract:
  Crosscorrelation of the outputs of two Gravitational Wave (GW) detectors has
recently been proposed [1] as a method for detecting statistical association
between GWs and Gamma Ray Bursts (GRBs). Unfortunately, the method can be
effectively used only in the case of stationary noise. In this work a different
crosscorrelation algorithm is presented, which may effectively be applied also
in non-stationary conditions for the cumulative analysis of a large number of
GRBs. The value of the crosscorrelation at zero delay, which is the only one
expected to be correlated to any astrophysical signal, is compared with the
distribution of crosscorrelation of the same data for all non-zero delays
within the integration time interval. This background distribution is gaussian,
so the statistical significance of an experimentally observed excess would be
well-defined.
  Computer simulations using real noise data of the cryogenic GW detectors
Explorer and Nautilus with superimposed delta-like signals were performed, to
test the effectiveness of the method, and theoretical estimates of its
sensitivity compared to the results of the simulation. The effectiveness of the
proposed algorithm is compared to that of other cumulative techniques, finding
that the algorithm is particularly effective in the case of non-gaussian noise
and of a large (100-1000s) and unpredictable delay between GWs and GRBs.


title: The Formation of Ultra-Compact Dwarf Galaxies

abstract:
  Recent spectroscopic observations of galaxies in the Fornax-Cluster reveal
nearly unresolved `star-like' objects with red-shifts appropriate to the
Fornax-Cluster. These objects have intrinsic sizes of about 100 pc and absolute
B-band magnitudes in the range -14 < M_B < -11.5 mag and lower limits for the
central surface brightness mu_B > 23 mag/arcsec^2 (Phillipps et al. 2001), and
so appear to constitute a new population of ultra-compact dwarf galaxies
(UCDs). Such compact dwarfs were predicted to form from the amalgamation of
stellar super-clusters (Kroupa 1998), which are rich aggregates of young
massive star clusters (YMCs) that can form in collisions between gas-rich
galaxies. Here we present the evolution of super-clusters in a tidal field. The
YMCs merge on a few super-cluster crossing times. Super-clusters that are
initially as concentrated and massive as knot~S in the interacting Antennae
galaxies (Whitmore et al. 1999) evolve to merger objects that are long-lived
and show properties comparable to the newly discovered UCDs. Less massive
super-clusters resembling knot 430 in the Antennae may evolve to omega-Cen-type
systems. Low-concentration super-clusters are disrupted by the tidal field,
dispersing their surviving star clusters while the remaining merger objects
rapidly evolve into the mu_B-M_B region populated by low-mass Milky-Way dSph
satellites.


title: Resolving the compact HII regions in N160A with HST

abstract:
  Using high-resolution imaging with the Hubble Space Telescope, we study the
Large Magellanic Cloud HII region N160A and uncover several striking features
of this complex massive star-forming site. The two compact high excitation HII
blobs (HEBs) A1 and A2 are for the first time resolved and their stellar
content and morphology is revealed. A1, being of higher excitation, is powered
by a single massive star whose strong wind has created a surrounding bubble. A2
harbors several exciting stars enshrouded inside large quantities of dust. The
whole N160A nebula is energized by three star clusters for which we obtain
photometry and study their color-magnitude diagram. The HII region is
particularly dusty, with extinction values reaching an A_v~2.5 mag in the
visible, and it is separated from the molecular cloud by an outstanding
ionization front. A previously detected infrared young stellar object is also
accurately located with respect to the HII region.


title:
The Optical Gravitational Lensing Experiment. Difference Image Analysis
  of LMC and SMC data. The Catalog

abstract:
  We present the first edition of a catalog of variable stars found in the
Magellanic Clouds using OGLE-II data obtained during four years: 1997-2000. The
catalog covers about 7 square degrees of the sky - 21 fields in the Large
Magellanic Cloud and 11 fields in the Small Magellanic Cloud. All variables
were found with the Difference Image Analysis (DIA) software. The catalog is
divided into two sections. The DC section contains FITS reference images
(obtained by co-adding 20 best frames for each field) and profile photometry
(DoPHOT) of all variable stars on those images. The AC section contains flux
variations and magnitudes of detected variable stars obtained with DIA as well
as with DoPHOT. The results are available in electronic form via FTP and
through WWW interface from the OGLE internet archive. Typically, there are
about 400 I-band data points and about 30 V and B-band data points for over
68,000 variables. A detailed analysis and classification of variable stars will
be presented elsewhere. The FTP catalog contains approximately 2Gbytes of data.


title:
Probability distribution of density fluctuations in the non-linear
  regime

abstract:
  We present a general procedure for obtaining the present density fluctuation
probability distribution given the statistics of the initial conditions. The
main difficulties faced with regard to this problem are those related to the
non-linear evolution of the density fluctuations and those posed by the fact
that the fields we are interested in are the result of filtering an underlying
field with structure down to scales much smaller than that of filtering. The
solution to the latter problem is discussed here in detail and the solution to
the former is taken from a previous work.
  We have checked the procedure for values of the rms density fluctuation as
large as 3/2 and several power spectra and found that it leads to results in
excellent agreement with those obtained in numerical simulations. We also
recover all available exact results from perturbation theory.


title:
Transient Absorption Features in GRBs and Their Implications for GRB
  Progenitors

abstract:
  The recent detection of a transient absorption feature in the prompt emission
of GRB 990705 has sparked multiple attempts to fit this feature in terms of
photoelectric absorption or resonance scattering out of the line of sight to
the observer. However, the physical conditions required to reproduce the
observed absorption feature turn out to be rather extreme compared to the
predictions of current GRB progenitor models. In particular, strong clumping of
ejecta from the GRB progenitor seems to be required. Using detailed 3D
hydrodynamic simulations of supernova explosions as a guideline, we have
investigated the dynamics and structure of pre-GRB ejecta predicted in various
GRB progenitor models. Based on our results, combined with population synthesis
studies relevant to the He-merger model, we estimate the probability of
observing X-ray absorption features as seen in GRB 990705 to << 1 %.
Alternatively, if the supranova model is capable of producing highly collimated
long-duration GRBs, it may be a more promising candidate to produce observable,
transient X-ray absorption features.


title: A study of the gravitational wave form from pulsars II

abstract:
  We present analytical and numerical studies of the Fourier transform (FT) of
the gravitational wave (GW) signal from a pulsar, taking into account the
rotation and orbital motion of the Earth. We also briefly discuss the
Zak-Gelfand Integral Transform. The Zak-Gelfand Integral Transform that arises
in our analytic approach has also been useful for Schrodinger operators in
periodic potentials in condensed matter physics (Bloch wave functions).


title: Distorted HI Gas in the Widely Separated LIRG Arp 256

abstract:
  We present new interferometric HI and CO (1-0) observations of the luminous
infrared source, Arp 256. Arp 256 consists of two spiral galaxies in an early
stage of merging, with a projected nuclear separation of 29 kpc (54") and an
infrared luminosity of 2.0E11 L_sun. Despite the large separation of the
galaxies' nuclei and mildly disrupted stellar components, the HI disks are
found to be strongly disrupted, and the southern galaxy in Arp 256 shows an
elevated star formation efficiency, which is consistent with a nuclear
starburst. Both of these results run contrary to expectations, posing
interesting questions on the physical mechanisms involved in stimulating star
formation during an interaction.


title: Astrometry Survey Missions Beyond the Magnitude Limit

abstract:
  Three planned astrometry survey satellites, FAME, DIVA, and GAIA, all aim at
observing magnitude-limited samples. We argue that substantial additional
scientific opportunities are within the reach of these mission if they devote a
modest fraction of their catalogs to selected targets that are fainter than
their magnitude limits. We show that the addition of ~10^6 faint (R>15) targets
to the 40 10^6 object FAME catalog can improve the precision of the reference
frame by a factor 2.5, to 7 micro-as/yr, increase Galactocentric distance at
which halo rotation can be precisely (2 km/s) measured by a factor 4, to 25
kpc, and increase the number of late M dwarfs, L dwarfs, and white dwarfs with
good parallaxes by an order of magnitude. In most cases, the candidate quasars,
horizontal branch stars, and dim dwarfs that should be observed to achieve
these aims are not yet known. We present various methods to identify candidates
from these classes, and assess the efficiencies of these methods. The analysis
presented here can be applied to DIVA with modest modifications. Application to
GAIA should be deferred until the characteristics of potential targets are
better constrained.


title: The Sloan Digital Sky Survey Quasar Catalog I. Early Data Release

abstract:
  We present the first edition of the Sloan Digital Sky Survey (SDSS) Quasar
Catalog. The catalog consists of the 3814 objects (3000 discovered by the SDSS)
in the initial SDSS public data release that have at least one emission line
with a full width at half maximum larger than 1000 km/s, luminosities brighter
than M_i^* = -23, and highly reliable redshifts. The area covered by the
catalog is 494 square degrees; the majority of the objects were found in SDSS
commissioning data using a multicolor selection technique. The quasar redshifts
range from 0.15 to 5.03. For each object the catalog presents positions
accurate to better than 0.2" rms per coordinate, five band (ugriz) CCD-based
photometry with typical accuracy of 0.05 mag, radio and X-ray emission
properties, and information on the morphology and selection method. Calibrated
spectra of all objects in the catalog, covering the wavelength region 3800 to
9200 Angstroms at a spectral resolution of 1800-2100, are also available. Since
the quasars were selected during the commissioning period, a time when the
quasar selection algorithm was undergoing frequent revisions, the sample is not
homogeneous and is not intended for statistical analysis.


title: The Origin of Cosmic Rays and the Diffuse Galactic Gamma-Ray Emission

abstract:
  Cosmic-ray interactions with interstellar gas and photons produce diffuse
gamma-ray emission. In this talk we will review the current understanding of
this diffuse emission and its relationship to the problem of the origin of
cosmic rays. We will discuss the open issues and what progress might be
possible with GLAST, which is planned for launch in 2006.


title: Globular Cluster Systems in Four BCGs: A262, A3560, A3565 and A3742

abstract:
  We have used deep I-band (F814W) images from the HST archive to study the
globular cluster systems around the brightest cluster galaxies (BCGs) in Abell
262, 3560, 3565 and 3742. Three of these BCGs have inner dust lanes and
peculiar structural features which indicate past histories of low-level
interaction and accretion. The deep I-band WFPC2 images have photometric limits
which, for all four galaxies, reach near or just beyond the GCLF turnover
point. Their specific frequencies are 8.24 \pm 1.65, 4.66 \pm 0.93, 2.58 \pm
0.52 and 2.62 \pm 0.52 respectively, all within a factor of two of the normal
range for giant ellipticals. We obtain new estimates of the GCLF turnover
magnitudes, which are shown to be consistent with an adopted Hubble constant of
H_0 ~ 70 km s^{-1} Mpc^{-1} on the ``Hubble diagram'' of GCLF turnover apparent
magnitude versus redshift, on a distance scale where the fundamental GCLF
calibrator E galaxies (M87 and others) in Virgo are at d=16 Mpc.


title:
Bar-driven dark halo evolution: a resolution of the cusp--core
  controversy

abstract:
  Simulations predict that the dark matter halos of galaxies should have
central cusps, while those inferred from observed galaxies do not have cusps.
We demonstrate, using both linear perturbation theory and n-body simulations,
that a disk bar, which should be ubiquitous in forming galaxies, can produce
cores in cuspy CDM dark matter profiles within five bar orbital times.
Simulations of forming galaxies suggest that one of Milky Way size could have a
10 kpc primordial bar; this bar will remove the cusp out to approximately 5 kpc
in approximately 1.5 gigayears, while the disk only loses approximately 8% of
its original angular momentum. An inner Lindblad-like resonance couples the
rotating bar to orbits at all radii through the cusp, transferring the bar
pattern angular momentum to the dark matter cusp, rapidly flattening it. This
resonance disappears for profiles with cores and is responsible for a
qualitative difference in bar driven halo evolution with and without a cusp.
This bar induced evolution will have a profound effect on the structure and
evolution of almost all galaxies. Hence, both to understand galaxy formation
and evolution and to make predictions from theory it is necessary to resolve
these dynamical processes. Unfortunately, correctly resolving these important
dynamical processes in ab initio calculations of galaxy formation is a daunting
task, requiring at least 4,000,000 halo particles using our SCF code, and
probably requiring many times more particles when using noisier tree, direct
summation, or grid based techniques, the usual methods employed in such
calculations.


title:
Evolution of a 3 \msun star from the main sequence to the ZZ Ceti stage:
  the role played by element diffusion

abstract:
  The purpose of this paper is to present new full evolutionary calculations
for DA white dwarf stars with the major aim of providing a physically sound
reference frame for exploring the pulsation properties of the resulting models
in future communications. Here, white dwarf evolution is followed in a
self-consistent way with the predictions of time dependent element diffusion
and nuclear burning. In addition, full account is taken of the evolutionary
stages prior to the white dwarf formation. In particular, we follow the
evolution of a 3 \msun model from the zero-age main sequence (the adopted
metallicity is Z=0.02) all the way from the stages of hydrogen and helium
burning in the core up to the thermally pulsing phase. After experiencing 11
thermal pulses, the model is forced to evolve towards its white dwarf
configuration by invoking strong mass loss episodes. Further evolution is
followed down to the domain of the ZZ Ceti stars on the white dwarf cooling
branch. Emphasis is placed on the evolution of the chemical abundance
distribution due to diffusion processes and the role played by hydrogen burning
during the white dwarf evolution. Furthermore, the implications of our
evolutionary models for the main quantities relevant for adiabatic pulsation
analysis are discussed. Interestingly, the shape of the Ledoux term is markedly
smoother as compared with previous detailed studies of white dwarfs. This is
translated into a different behaviour of the Brunt-Vaisala frequency.


title:
The Chandra High Energy Transmission Grating Spectrometer probes the
  dusty warm absorber in the Seyfert 1 galaxy MCG--6-30-15

abstract:
  The Chandra HETGS spectra of the Seyfert 1 galaxy MCG--6-30-15 show numerous
narrow, unresolved (FWHM < 200 km/s) absorption lines from a wide range of
ionization states of N, O, Mg, Ne, Si, S, Ar, and Fe. The initial analysis of
these data, presented in Lee et al. (2001), shows that a dusty warm absorber
model adequately explains the spectral features > 0.48 keV (< 26 A). We
attribute previous reports of an apparently highly redshifted O VII edge to the
neutral Fe L absorption complex and the O VII resonance series (by transitions
higher than He $\gamma$; He $\alpha,\beta,\gamma$ are also seen at lower
energies). The implied dust column density needed to explain the FeI L edge
feature agrees with that obtained from earlier reddening studies, which had
already concluded that the dust should be associated with the ionized absorber
(given the relatively lower observed X-ray absorption by cold gas). Our
findings contradict the interpretation of Branduardi-Raymont et al. (2001),
based on XMM-Newton RGS spectra, that this spectral region is dominated by
highly relativistic soft X-ray line emission originating near the central black
hole. Here we review these issues pertaining to the soft X-ray spectral
features as addressed by Lee et al., (2001). (Details found in Lee et al.,
2001, ApJ., 554, L13)


title:
Detecting Outer Planets in Edge-On Orbits: Combining Radial Velocity and
  Astrometric Techniques

abstract:
  The astrometric and radial velocity techniques of extra-solar planet
detection attempt to detect the periodic reflex motion of the parent star by
extracting this periodic signal from a time-sampled set of observations. The
extraction is generally accomplished using periodogram analysis or the
functionally equivalent technique of Least Squares fitting of sinusoids. In
this paper, we use a Frequentist approach to examine the sensitivity of Least
Squares technique when applied to a combination of radial velocity and
astrometric observations. We derive a semi-analytical expression for the
sensitivity and show that the combined approach yields significantly better
sensitivity than either technique on its own. We discuss the ramifications of
this result to upcoming astrometric surveys with FAME, the Keck Interferometer,
and SIM.


title:
The Impact of an Extra Background of Relativistic Particles on the
  Cosmological Parameters derived from Microwave Background Anisotropies

abstract:
  Recent estimates of cosmological parameters derived from Cosmic Microwave
Background (CMB) anisotropies are based on the assumption that we know the
precise amount of energy density in relativistic particles in the universe,
$\omega_{rel}$, at all times. There are, however, many possible mechanisms that
can undermine this assumption. In this paper we investigate the effect that
removing this assumption has on the determination of the various cosmological
parameters. We obtain fairly general bounds on the redshift of equality,
$z_{eq}= \omega_{m}/\omega_{rel}=3100_{-400}^{+600}$. We show that
$\omega_{rel}$ is nearly degenerate with the amount of energy in matter,
$\omega_m$, and that its inclusion in CMB parameter estimation also affects the
present constraints on other parameters such as the curvature or the scalar
spectral index of primordial fluctuations. This degeneracy has the effect of
limiting the precision of parameter estimation from the MAP satellite, but it
can be broken by measurements on smaller scales such as those provided by the
Planck satellite mission.


title:
New Observations of the Interstellar Medium in the Lyman Break Galaxy MS
  1512-cB58

abstract:
  We present the results of a detailed study of the interstellar medium of MS
1512-cB58, an L* Lyman break galaxy at z = 2.7276, based on new spectral
observations obtained with the Echelle Spectrograph and Imager on the Keck II
telescope at 58 km/s resolution. We focus in particular on the chemical
abundances and kinematics of the interstellar gas and our main findings are as
follows. Even at this relatively early epoch, the ISM of this galaxy is already
highly enriched in elements released by Type II supernovae; the abundances of
O, Mg, Si, P, and S are all about 2/5 of their solar values. In contrast, N and
the Fe-peak elements Mn, Fe, and Ni are underabundant by a factor of about 3.
Based on current ideas of stellar nucleosynthesis, these results can be
understood if most of the metal enrichment in cB58 has taken place within the
last 300 million years, the timescale for the release of N from intermediate
mass stars. cB58 appears to be an example of a galaxy in the process of
converting its gas into stars on a few dynamical timescales; quite possibly we
are witnessing the formation of a galactic bulge or an elliptical galaxy. The
energetic star formation activity has stirred the interstellar medium to high
velocities of up to 1000 km/s. The net effect is a bulk outflow of the ISM at a
speed of 255 km/s and at a rate which exceeds the star formation rate. It is
unclear whether this gas will be lost or retained by the galaxy. We point out
that the chemical and kinematic properties of cB58 are markedly different from
those of most damped Lyman alpha systems at the same redshift.


title: 2-point Correlation Function of HI-selected Galaxies

abstract:
  The 2-point spatial correlation function (CF), $\xi(s)$, has been used to
study the clustering of the galaxies in the preliminary version of the HIPASS
Bright Galaxy Catalogue (HIPASS BGC), which includes the 1,000 HI brightest
galaxies in the Southern sky. This is the first time the CF has been used to
analyse an HI-selected sample. The CF is well described by a power law,
$\xi(s)\sim(s/s_0)^{-\gamma}$, with slope $\gamma\sim1.7$ and correlation
length $s_0\sim3.55$ $h^{-1}$ Mpc using Peebles estimator. However, when the
Hamilton estimator is used, the CF is fit with $\gamma\sim2.19$ and
$s_0\sim3.37$ $h^{-1}$ Mpc. Note that, these HI-selected galaxies show less
clustering than optically-selected surveys which have a correlation length
$s_0\sim$ 5.5 $h^{-1}$ Mpc or larger.


title: Variability of Soft X-ray Spectral Shape in Blazars Observed by ROSAT

abstract:
  In paper 1 (Cheng et al. 2001) we have shown that the soft X-ray spectra of
two types of Seyfert 1 galaxies statistically vary differently with increasing
intensity. In order to understand how the spectrum of blazars changes, the
spectral shape variability of 18 blazars observed by ROSAT/PSPC mode are
studied by presenting the correlation of Hardness Ratio 1 versus Count Rates
(HR1-CTs). According to our criteria, 10 blazars show a positive HR1-CTs
relation, and only 2 blazars display an anti-correlation of HR1 versus CTs. The
rest 6 blazars do not indicate any clear correlation. From these we can see
that most blazars of our sample statistically show a hardening spectrum during
overall flux increase, though some vary randomly. By investigating the photon
index of these objects and different radiation theories, we argue that the
dominance of the synchrotron or inverse Compton emission in the soft X-ray band
may interpret the dichotomy of spectral variability well, and that different
spectral variations might represent a sequence of synchrotron peaked frequency.


title:
Afterglow Light Curve Modulated by a Highly Magnetized Millisecond
  Pulsar

abstract:
  We investigate consequences of a continuously energy-injecting central engine
of gamma-ray burst (GRB) afterglow emission, assuming that a highly magnetized
pulsar is left beaming in the core of a GRB progenitor. Beaming and continuous
energy-injection are natural consequences of the pulsar origin of GRB
afterglows. Whereas previous studies have considered continuous
energy-injection from a new-born pulsar to interpret the deviation of afterglow
light curves of GRBs from those with the simple power law behavior, a beaming
effect, which is one of the most important aspects of pulsar emissions, is
ignored in earlier investigations. We explicitly include the beaming effect and
consider a change of the beaming with time due to a dynamical evolution of a
new-born pulsar. We show that the magnitude of the afterglow from this fireball
indeed first decreases with time, subsequently rises, and declines again. One
of the most peculiar optical afterglows light curve of GRB 970508 can be
accounted for by continuous energy injection with beaming due to a highly
magnetized new-born pulsar. We discuss implications on such observational
evidence for a pulsar.


title:
EXPORT: optical photometry and polarimetry of Vega-type and pre-main
  sequence stars

abstract:
  This paper presents optical UBVRI broadband photo-polarimetry of the EXPORT
sample obtained at the 2.5m Nordic Optical Telescope. The database consists of
multi-epoch photo-polarimetry of 68 pre-main-sequence and main-sequence stars.
An investigation of the polarization variability indicates that 22 objects are
variable at the 3sigma level in our data. All these objects are pre-main
sequence stars, consisting of both T Tauri and Herbig Ae/Be objects while the
main sequence, Vega type and post-T Tauri type objects are not variable. The
polarization properties of the variable sources are mostly indicative of the
UXOR-type behaviour; the objects show highest polarization when the brightness
is at minimum. We add seven new objects to the class of UXOR variables (BH Cep,
VX Cas, DK Tau, HK Ori, LkHa 234, KK Oph and RY Ori). The main reason for their
discovery is the fact that our data-set is the largest in its kind, indicating
that many more young UXOR-type pre-main sequence stars remain to be discovered.
The set of Vega-like systems has been investigated for the presence of
intrinsic polarization. As they lack variability, this was done using indirect
methods, and apart from the known case of BD +31.643, the following stars were
found to be strong candidates to exhibit polarization due to the presence of
circumstellar disks: 51 Oph, BD +31.643C, HD 58647 and HD 233517.


title:
A reanalysis of the luminosities of clusters of galaxies in the EMSS
  sample with 0.3 < z < 0.6

abstract:
  The X-ray luminosities of the Einstein Extended Medium Sensitivity Survey
(EMSS) clusters of galaxies with redshifts 0.3<z<0.6 are remeasured using ROSAT
PSPC data. It is found that the new luminosities are on average 1.18 +/- 0.08
times higher than previously measured but that this ratio depends strongly on
the X-ray core radii we measure. For the clusters with small core radii, in
general we confirm the EMSS luminosities, but for clusters with core radii >250
kpc (the constant value assumed in the EMSS), the new luminosities are 2.2 +/-
0.15 times the previous measurements. The X-ray luminosity function (XLF) at
0.3<z<0.6 is recalculated and is found to be consistent with the local XLF. The
constraints on the updated properties of the 0.3<z<0.6 EMSS sample, including a
comparison with the number of clusters predicted from local XLFs, indicate that
the space density of luminous, massive clusters has either not evolved or has
increased by a small factor ~2 since z=0.4. The implications of this result are
discussed in terms of constraints on the cosmological parameter Omega_0.


title:
Meridional flow and differential rotation by gravity darkening in fast
  rotating solar-type stars

abstract:
  An explanation is presented for the rather strong total surface differential
rotation of the observed very young solar-type stars like AB Dor and PZ Tel.
Due to its rapid rotation a nonuniform energy flux leaves the stellar core so
that the outer convection zone is nonuniformly heated from below. Due to this
`gravity darkening' of the equator a meridional flow is created flowing
equatorwards at the surface and thus accelerating the equatorial rotation. The
effect linearly grows with the normalized pole-equator difference, \epsilon, of
the heat-flux at the bottom of the convection zone. A rotation rate of about 9
h leads to \epsilon=0.1 for a solar-type star. In this case the resulting
equator-pole differences of the angular velocity at the stellar surface,
\delta\Omega, varies from unobservable 0.005/day to the (desired) value of 0.03
day$^{-1}$ when the dimensionless diffusivity factors $c_\nu$ and c_\chi vary
between 1 and 0.1 (standard value c_\nu \simeq c_\chi \simeq 0.3, see Table 1.)
In all cases the related temperature differences between pole and equator at
the surface are unobservably small.
  The (clockwise) meridional circulation which we obtain flows opposite to the
(counterclockwise) circulation appearing as a byproduct in the \Lambda-theory
of the nonuniform rotation in outer convection zones. The consequences of this
situation for those dynamo theories of stellar activity are discussed which
work with the meridional circulation as the dominant magnetic-advection effect
in latitude to produce the solar-like form of the butterfly diagram.
  Key words: Hydrodynamics, Star: rotation, Stars: pre-main sequence, Stellar
activity


title: Relic Black Holes In Galactic Nuclei

abstract:
  We discuss the link between the observations of distant quasars and those of
massive dark objects in the cores of many local galaxies. We show how the
formation of early black holes gives rise to the luminosity function of high z
quasars, while it imprints into their dark local relics a related shape of the
mass-dispersion correlation. We propose that in its lower section the
correlation slope will tell the (otherwise uncertain) strenght of the feedback
effect from the quasar radiation on the host galaxies.


title: A new calibration of the RGB Tip as a Standard Candle

abstract:
  We have obtained an accurate estimate of the absolute I magnitude of the Tip
of the Red Giant Branch (M_I(TRGB)) for the globular cluster Omega Cen, based
{\em (a)} on the largest photometric database ever assembled for a globular, by
Pancino et al. (2000), and {\em (b)} on a direct distance estimate for \omen,
recently obtained by Thompson et al.(2001) from a detached eclipsing binary.
The derived value M_I(TRGB) = -4.04\pm 0.12 provides, at present, the most
accurate empirical zero-point for the calibration of the \mtip -- [Fe/H]
relation, at [Fe/H] ~ -1.7.


title: The Crab Nebula at 850 microns

abstract:
  Observations of the Crab Nebula at 850 micron made with the "Submillimetre
Common-User Bolometer Array" (SCUBA) on the James Clerk Maxwell Telescope are
presented. A variety of chop-throws and scanning directions was used in these
observations, to well sample structure over a range of scales and directions.
The resulting image, which was restored using a MEM algorithm, has a resolution
of 17 arcsec, and has been compared with a 20-cm VLA image of the Crab Nebula
to study spectral index variations. The 850-micron and 20-cm images are very
similar, implying that there is little variation in spectral index across the
face of the remnant between these wavelengths.


title: Cluster detection from surface-brightness fluctuations in SDSS data

abstract:
  Galaxy clusters can be detected as surface brightness enhancements in
smoothed optical surveys. This method does not require individual galaxies to
be identifiable, and enables clusters to be detected out to surprisingly high
redshifts, as recently demonstrated by the Las Campanas Distant Cluster Survey
(LCDCS). Here, we investigate redshift limits for cluster detection in the
Sloan Digital Sky Survey (SDSS). Calibrating assumptions about the surface
brightness profile, the mass-to-light ratio, and the spectral energy
distribution of galaxy clusters using available observational data, we show
that it should be possible to detect galaxy groups out to redshifts of ~0.5,
and massive galaxy clusters out to redshifts of ~1.2 in summed r'+i'+z' SDSS
data. Redshift estimates can be derived from the SDSS magnitudes of brightest
cluster members out to redshifts near unity. Over the area of sky it covers,
SDSS should find >~98% of the clusters detectable by the Planck satellite
through the thermal Sunyaev-Zel'dovich effect. The few Planck clusters not
detected in SDSS will almost all be at z>~1.2.


title:
The relative abundances of ellipticals and starbursts among the
  Extremely Red Galaxies

abstract:
  We present J band observations of a complete sample of 57 red galaxies
selected to have K<20 and R-K>5.3. We use the Pozzetti and Mannucci (2000)
prescriptions, based on the R-K and J-K colours, to separate the two dominant
populations, old ellipticals and dusty starbursts. We find that both
populations are present in the current sample and have similar abundances, and
discuss the uncertainties in this result. Galactic stars comprise about 9% of
the objects. The starburst galaxies of the present sample are found to give a
contribution to the cosmic star formation density similar to the Lyman-break
galaxies.


title: Spectral analysis of water vapour in cool stars

abstract:
  M star spectra, at wavelengths beyond 1.35 $\mu$m, are dominated by water
vapour yet terrestrial water vapour makes it notoriously difficult to make
accurate measurement from ground-based observations. We have used the short
wavelength spectrometer on the Infrared Space Observatory at four wavelength
settings to cover the 2.5--3.0 $\mu$m region for a range of M stars. The
observations show a good match with previous ground-based observations and with
synthetic spectra based on the Partridge & Schwenke (1997) line list though not
with the SCAN (Jorgensen et al. 2001) line list. We used a least-squared
minimisation technique to systematically find best fit parameters for the
sample of stars. The temperatures that we find indicate a relatively hot
temperature scale for M dwarfs. We consider that this could be a consequence of
problems with the Partridge & Schwenke linelist which leads to synthetic
spectra predicting water bands which are too strong for a given temperature.
Such problems need to be solved in the next generation of water vapour line
lists which will extend the calculation of water vapour to higher energy levels
with the good convergence necessary for reliable modelling of hot water vapour.
Then water bands can assume their natural role as the primary tool for the
spectroscopic analysis of M stars.


title:
Cosmic Background dipole measurements with Planck-High Frequency
  Instrument

abstract:
  This paper discusses the Cosmic Background (CB) dipoles observations in the
framework of the Planck mission. Dipoles observations can be used in three
ways: (i) It gives a measurement of the peculiar velocity of our Galaxy which
is an important observation in large scale structures formation model. (ii)
Measuring the dipole can give unprecedent information on the monopole (that can
be in some cases hard to obtain due to large foreground contaminations). (iii)
The dipole can be an ideal absolute calibrator, easily detectable in
cosmological experiments. Following the last two objectives, the main goal of
the work presented here is twofold. First, we study the accuracy of the
Planck-HFI calibration using the Cosmic Microwave Background (CMB) dipole
measured by COBE as well as the Earth orbital motion dipole. We show that we
can reach for HFI, a relative calibration between rings of about 1% and an
absolute calibration better than 0.4% for the CMB channels (in the end, the
absolute calibration will be limited by the uncertainties on the CMB
temperature). We also show that Planck will be able to measure the CMB dipole
direction at better than 1.7 arcmin and improve on the amplitude. Second, we
investigate the detection of the Cosmic Far-Infrared Background (FIRB) dipole.
Measuring this dipole could give a new and independent determination of the
FIRB for which a direct determination is quite difficult due to Galactic dust
emission contamination. We show that such a detection would require a Galactic
dust emission removal at better than 1%, which will be very hard to achieve.


title:
The potential of near-infrared high-resolution studies on the field of
  galaxies in the young universe

abstract:
  So far, high resolution techniques on the one hand provide morphological
information on bright nearby objects. On the other hand, telescopes with large
collecting areas allow us to detect very faint and distant objects, but not to
obtain a spatial resolution which is sufficient for detailed morphological
studies. Currently, the construction of large optical and infrared
interferometers like the Keck Interferometer, the Very Large Telescope
Interferometer (VLTI) and the Large Binocular Telescope Interferometer (LBTI)
is in progress. These instruments will simultaneously provide larger collecting
areas and higher spatial resolutions than current instruments. Thus, they might
enable for the first time near-infrared studies of galaxies in the young
universe with an absolute spatial resolution as available today only for the
closest galaxies. Using recent results in the field of high resolution studies
of nearby galaxies, a rough idea of what might be expected to be observed is
given. The concepts of the forthcoming interferometers is reviewed and
technical aspects that are essential for observations of distant galactic
centers are discussed. An outlook is given on which observational tasks can be
addressed to these instruments and how the results will increase our knowledge
in the field of the evolution of galaxies and the universe.


title: GAIA: Understanding the Galaxy

abstract:
  The GAIA Observatory, ESA's Cornerstone 6 mission, addresses the origin and
evolution of our Galaxy, and a host of other scientific challenges. GAIA will
provide unprecedented positional and radial velocity measurements with the
accuracies needed to produce a stereoscopic and kinematic census of about one
billion stars in our Galaxy and throughout the Local Group, about one per cent
of the Galactic stellar population. Combined with astrophysical information for
each star, provided by on-board multi-colour photometry, these data will have
the precision and depth necessary to address the three key questions which
underlie the GAIA science case:
  When did the stars in the Milky Way form?
  When and how was the Milky Way assembled?
  What is the distribution of dark matter in our Galaxy?


title:
ISO spectroscopy of compact HII regions in the Galaxy. II Ionization and
  elemental abundances

abstract:
  Based on the ISO spectral catalogue of compact HII regions by Peeters et al.
(2001), we present a first analysis of the hydrogen recombination and atomic
fine-structure lines originated in the ionized gas. The sample consists of 34
HII regions located at galactocentric distances between Rgal = 0 and 15 kpc.
The SWS HI recombination lines between 2 and 8 mum are used to estimate the
extinction law at these wavelengths for 14 HII regions. An extinction in the K
band between 0 and $\sim$ 3 mag. has been derived. The fine-structure lines of
N, O, Ne, S and Ar are detected in most of the sources. Most of these elements
are observed in two different ionization stages probing a range in ionization
potential up to 41 eV. The ISO data, by itself or combined with radio data
taken from the literature, is used to derive the elemental abundances relative
to hydrogen. The present data thus allow us to describe for each source its
elemental abundance, its state of ionization and to constrain the properties of
the ionizing star(s).