title:
On the origin of the O and B-type stars with high velocities II Runaway
  stars and pulsars ejected from the nearby young stellar groups

abstract:
  We use milli-arcsecond accuracy astrometry (proper motions and parallaxes)
from Hipparcos and from radio observations to retrace the orbits of 56 runaway
stars and nine compact objects with distances less than 700 pc, to identify the
parent stellar group. It is possible to deduce the specific formation scenario
with near certainty for two cases. (i) We find that the runaway star zeta
Ophiuchi and the pulsar PSR J1932+1059 originated about 1 Myr ago in a
supernova explosion in a binary in the Upper Scorpius subgroup of the Sco OB2
association. The pulsar received a kick velocity of about 350 km/s in this
event, which dissociated the binary, and gave zeta Oph its large space
velocity. (ii) Blaauw & Morgan and Gies & Bolton already postulated a common
origin for the runaway-pair AE Aur and mu Col, possibly involving the massive
highly-eccentric binary iota Ori, based on their equal and opposite velocities.
We demonstrate that these three objects indeed occupied a very small volume
\sim 2.5Myr ago, and show that they were ejected from the nascent Trapezium
cluster.
  We identify the parent group for two more pulsars: both likely originate in
the 50 Myr old association Per OB3, which contains the open cluster alpha
Persei. At least 21 of the 56 runaway stars in our sample can be linked to the
nearby associations and young open clusters. These include the classical
runaways 53 Arietis (Ori OB1), xi Persei (Per OB2), and lambda Cephei (Cep
OB3), and fifteen new identifications, amongst which a pair of stars running
away in opposite directions from the region containing the lambda Ori cluster.
Other currently nearby runaways and pulsars originated beyond 700 pc, where our
knowledge of the parent groups is very incomplete.


title: Observations of Lyman-alpha Absorption in a Triple Quasar System

abstract:
  We have obtained follow-up observations of the quasar pair LBQS 0107-025A,B
and new observations of the nearby quasar LBQS 0107-0232 with the Hubble Space
Telescope Faint Object Spectrograph. Extended wavelength coverage of LBQS
0107-025A and B using the G270H grating was also obtained. This triple system
is unique in providing sensitivity to coherent Ly-alpha absorption on
transverse scales of approximately 1 Mpc at z < 1. Monte Carlo simulations were
used to establish the confidence level for matches between absorption features
in different lines of sight as a function of velocity separation. Pairwise,
there are 8, 9, and 12 lines that match between spectra. Three instances of
matches between all three lines of sight were found with velocity separations
of less than 550 kms^-1. Two of the pairings have coincident lines within
|Delta v| < 200 kms^-1 that would occur with less than 10% probability by
chance. Taking into account the equivalent widths of the lines, one of these
triple coincidences is significant at the 99.99% confidence level, based on
Monte Carlo simulations with random line placements. Matches with strong lines
preferentially have small velocity separations. These same simulations are used
to demonstrate that the distribution of matches for a population of absorbers
randomly distributed in velocity space is peaked toward |Delta v| = 0, which
has implications for the statistical significance of matches. One of the triple
coincidences appears to be a strong absorber with a sheet-like, but
inhomogeneous, geometry and a coherence length approaching or exceeding 1 Mpc.


title: Cluster Surveys

abstract:
  I review some of the current efforts to create unbiased samples of galaxy
clusters. Readers are referred elsewhere for general wide area sky surveys and
redshift surveys, and for Sunyaev-Zeldovich, radio, infrared and submm surveys,
some of which were not designed to search primarily for clusters. My focus will
be on optical and X-ray samples and on high redshift clusters.


title:
Parallax and Kinematics of PSR B0919+06 from VLBA Astrometry and
  Interstellar Scintillometry

abstract:
  Results are presented from a long-term astrometry program on PSR B0919+06
using the NRAO Very Long Baseline Array. With ten observations (seven epochs)
between 1994--2000, we measure a proper motion of 18.35 +/- 0.06 mas/yr in RA,
86.56 +/- 0.12 mas/yr in Dec, and a parallax of 0.83 +/- 0.13 mas (68%
confidence intervals). This yields a pulsar distance of 1.21 +/- 0.19 kpc,
making PSR B0919+06 the farthest pulsar for which a trigonometric parallax has
been obtained, and the implied pulsar transverse speed is 505 +/- 80 km/s.
Combining the distance estimate with interstellar scintillation data spanning
20 years, we infer the existence of a patchy or clumpy scattering screen along
the line of sight in addition to the distributed electron density predicted by
models for the Galaxy, and constrain the location of this scattering region to
within about 250 parsecs of the Sun. Comparison with the lines of sight towards
other pulsars in the same quadrant of the Galaxy permits refinement of our
knowledge of the local interstellar matter in this direction.


title:
Far infrared observations of the southern Galactic star forming complex
  around IRAS 09002-4732

abstract:
  The Galactic star forming region in the southern sky, associated with IRAS
09002-4732 has been mapped simultaneously in two far infrared bands (148 & 209
um), with ~ 1' angular resolution. Fifteen sources including IRAS 08583-4719,
08589-4714, 09002-4732 and 09014-4736 have been detected, some of which are
well resolved. Taking advantage of similar beams in the two bands, a reliable
dust temperature [T(148/209)] map has been obtained, which detects colder dust
(< 30 K) in this region. The HIRES processed IRAS maps at 12, 25, 60 & 100 um
have also been used for comparison. The optical depth maps at 200 um & 100 um,
generated from these FIR data quantify the spatial distribution of the dust.
The diffuse emission from this entire region has been found to be 35 % of the
total FIR luminosity. The slope of the IMF in the mass range 4-16 M_sun has
been estimated to be -1.25^+0.75_-0.65 for this star forming complex.
  Radiative transfer models have been explored to fit available observations of
the 4 IRAS sources and extract various physical parameters for corresponding
dust-gas clouds. Whereas a constant radial density distribution is favoured in
IRAS 08583-4719, 08589-4714 & 09002-4732, the r^-1 law is inferred for IRAS
09014-4736. The dust composition is found to be similar (Silicate dominated) in
all the 4 sources. The luminosity per unit mass is found to be in the narrow
range of 44-81 L_sun/M_sun for these star forming regions.


title:
Probing the Inner Region of Cyg X-1 in the Low/Hard State through its
  X-ray Broad Band Spectrum

abstract:
  We present the broad band X-ray spectrum of Cyg X-1 in the low/hard state as
observed by the instruments on board of BeppoSAX. The spectrum spans from 0.1
to 200 keV, allowing the total accretion luminosity to be observed, rather than
extrapolated, corresponding to ~2 per cent of the Eddington limit for a 10
Solar mass black hole. The broad bandpass allows us to determine the continuum
shape with great accuracy. Simple models of Compton up-scattering of seed
photons from the accretion disk do not adequately match the spectrum. At low
energies an additional continuum component is required, giving a complex soft
excess which extends up to ~4 keV, in line with previous results from ASCA.
Moreover we clearly detect a reflected component from the accretion disk which
is smeared, probably because of relativistic and Doppler effects. The
reflecting material is not strongly ionized and does not subtend a large solid
angle as seen from the corona. The inner radius of the disk, that depends on
the inclination of the system, is most probably between 10 and 70 gravitational
radii (Rg). An unsmeared reprocessed component, probably originating from the
companion star or the outer disk, could also be present. In this case, the
inner radius of the disk, as inferred from the smeared reflection, is smaller,
between 6 and 20 Rg.


title: Constraints on the redshift of reionization from CMB data

abstract:
  We use the recent CMB power spectrum measurement by the Maxima experiment
(Hanany et al. 2000) to constrain the redshift of reionization z_re. This
becomes possible by combining the CMB data with cosmological parameters from
various independent measurements, including Big Bang Nucleosynthesis (BBN) and
X-ray cluster data. Most notably, our results provide a robust lower bound on
z_re. We find that z_re>15 (8) at the 68% (95%) confidence level, unless the
Hubble constant is larger than 75 km/s/Mpc.


title:
Axisymmetry in proto-planetary nebulae: using imaging polarimetry to
  investigate envelope structure

abstract:
  We use ground-based imaging polarimetry to detect and image the dusty
circumstellar envelopes of a sample of proto-planetary nebulae (PPNe) at
near-infrared wavelengths. We detect extended (up to 9 arcsec diameter)
circumstellar envelopes around 15 out of 16 sources with a range of
morphologies including bipolars and shells. The distribution of scattered light
in combination with its polarization (up to 40 per cent) provides unambiguous
evidence for axisymmetry in 14 objects showing this to be a common trait of
PPNe. We suggest that the range of observed envelope morphologies results from
the development of an axisymmetric dust distribution during the superwind phase
at the end of the AGB. We identify shells seen in polarized light with
scattering from these superwind dust distributions which allows us to provide
constraints on the duration of the superwind phase. In one object (IRAS
19475+3119) the circumstellar envelope has a two-armed spiral structure which
we suggest results from the interaction of the mass losing star with a binary
companion.


title: The Globular Cluster System in the Outer Regions of NGC 4472

abstract:
  We have undertaken a study of the globular cluster (GC) systems of a large
sample of elliptical and spiral galaxies in order to test predictions of galaxy
formation models. Here we present results for the giant Virgo elliptical NGC
4472 (M49). The galaxy was observed in 3 filters (BVR) using the Mosaic Imager
on the Kitt Peak 4-m telescope. Our images roughly double the radial coverage
of previous CCD observations of NGC 4472. We have combined the Mosaic data with
spectroscopic data and HST data in order to fully characterize the level of
contamination in our GC sample. The radial profile of the GC system is fit
fairly well by a de Vaucouleurs law out to 17 arc minutes (~80 kpc), but the
profile falls slightly below the de Vaucouleurs law between 17 and 23 arc
minutes. The bimodal color distribution observed in past studies appears in our
data. We find a small metallicity gradient in the inner 8 arc minutes of the GC
system due to the increasing ratio of blue to red clusters. The gradient
vanishes, however, when the entire radial extent of the data is taken into
account. We estimate a total of 5,900 GCs in NGC 4472 out to 23 arc minutes,
yielding a specific frequency of 3.6+/-0.6 within this radius. This value is
smaller than that found by previous studies of NGC 4472. We examine the
implications of these results with regard to predictions made by four galaxy
formation models, and find that all four models have at least one inconsistency
with the data. [abridged]


title: Dust in active nuclei. II. Powder or gravel?

abstract:
  In a companion paper, Maiolino et al. (2000) presented various observational
evidences for "anomalous" dust properties in the circumnuclear region of AGNs
and, in particular, the reduced E(B-V)/N_H and Av/N_H ratios, the absence of
the silicate absorption feature in mid-IR spectra of Sy2s and the absence of
the carbon dip in UV spectra of reddened Sy1s. In this paper we discuss various
explanations for these facts.
  The observational constraints favor a scenario where coagulation, catalyzed
by the high densities in the circumnuclear region, yields to the formation of
large grains. The resulting extinction curve is featureless, flatter than
Galactic and the E(B-V)/N_H and Av/N_H ratios are significantly reduced. These
results should warn about an unappropriate use of the standard Galactic
extinction curve and Av/N_H ratio when dealing with the extreme gas conditions
typical of the circumnuclear clouds of AGNs.
  We also investigated alternative scenarios for the observed anomalous
properties of dust in AGNs. Some of these scenarios might explain some of the
observed properties for a few objects, but they generally fail to account for
all of the observational constraints obtained for the large sample of AGNs
studied in these works.


title: Chemical abundances in cool metal rich disk dwarf stars

abstract:
  The present study of spectra of twelve metal-rich cool dwarf stars, carefully
selected in order to cover a range of temperatures (~4400 - 6000 K), is a
follow up on Feltzing & Gustafsson (1998, A&AS 129, 237) with the aim to
understand the apparent over-ionization and anomalous elemental abundances
found by them for the K dwarf stars in their sample. Our method of analysis
employs synthetic spectra of the full spectrum both to constrain the continuum
level and to derive abundances. It is shown that by using this method and
imposing a strict excitation equilibrium (possible to do because of the care in
selection of observed Fe I lines) we are able to show that metal-rich K dwarf
stars do not show anomalous stellar abundances, as indicated in Feltzing &
Gustafsson (1998), and can, with reasonable efforts, be analyzed in order to
increase the number of metal-rich stars with useful chemical abundances. With
abundance analysis by means of spectrum synthesis and assuming Local
Thermodynamic Equilibrium (LTE) the abundances of Na, Si, Ca, Sc, Ti, V, Cr,
Fe, Co, Ni, and Nd have been derived. Also ionization balance is satisfied for
Fe and Cr after correcting the stellar effective temperatures such that both
ionization and excitation equilibrium were satisfied. In addition, spectra from
five cool dwarf stars of the Feltzing & Gustafsson (1998) sample have been
analyzed with the methods used in this work. They show essentially the same
abundance patterns as the new stars in this sample.


title: Magnetic lensing of ultra high energy cosmic rays

abstract:
  We discuss several effects due to lensing of ultra high energy cosmic rays by
the regular component of the galactic magnetic field. Large flux magnification
around caustics can be a significant source of clustering in the arrival
directions of UHECRs of comparable energy. We also discuss lensing effects in a
hypothetical galactic magnetic wind model recently proposed to explain the
extremely high energy cosmic rays so far observed as originating from a single
source (M87). This model implies large flux magnifications, which reduce the
power requirements on the source, and a significant asymmetry in the expected
flux between the north and south galactic hemispheres.


title: Neutrino-Driven Jets and Rapid-Process Nucleosynthesis

abstract:
  We have studied whether the jet in a collapse-driven supernova can be a key
process for the rapid-process (r-process) nucleosynthesis. We have examined the
features of a steady, subsonic, and rigidly rotating jet in which the
centrifugal force is balanced by the magnetic force. As for the models in which
the magnetic field is weak and angular velocity is small, we found that the
r-process does not occur because the final temperature is kept to be too high
and the dynamical timescale becomes too long when the neutrino luminosities are
set to be high. Even if the luminosities of the neutrinos are set to be low,
which results in the low final temperature, we found that the models do not
give a required condition to produce the r-process matter. Furthermore, the
amount of the mass outflow seems to be too little to explain the solar-system
abundance ratio in such low-luminosity models. As for the models in which the
magnetic field is strong and angular velocity is large, we found that the
entropy per baryon becomes too small and the dynamical timescale becomes too
long. This tendency is, of course, a bad one for the production of the
r-process nuclei. As a conclusion, we have to say that it is difficult to cause
a successful r-process nucleosynthesis in the jet models in this study.


title:
The Contribution of EUV from Clusters of Galaxies to the Cosmic Ionizing
  Background

abstract:
  Recent observations with the Extreme Ultraviolet Explorer (EUVE) suggest that
at least some clusters of galaxies are luminous sources of extreme ultraviolet
(EUV) radiation. It is not clear yet whether EUV emission is a general feature
of clusters; for the purposes of limiting the contribution to the background
radiation, we assume that it is true of most clusters. Assuming that the source
of the EUV emission is inverse Compton (IC) scattering of the Cosmic Microwave
Background photons by relativistic electrons, we construct a simple model for
the expected average emission from clusters as a function of their mass and the
redshift of interest. Press-Schechter theory is used to determine the abundance
of clusters of various masses as a function of redshift. We determine the
amount of background radiation produced by clusters. The total mean intensity,
spectrum, and the ionization rates for HI and HeII are determined at present
and at a variety of redshifts. Because clusters form by the merger of smaller
subclusters, the amount of EUV background radiation should be larger at present
than in the past. We compare our results to the ionizing background expected
from quasars. We find that while clusters do contribute a significant EUV
background, it is less than a percent of that expected from quasars.


title: Weak Lensing Determination of the Mass in Galaxy Halos

abstract:
  We detect the weak gravitational lensing distortion of 450,000 background
galaxies (20<R<23) by 790 foreground galaxies (R<18) selected from the Las
Campanas Redshift Survey (LCRS). This is the first detection of weak lensing by
field galaxies of known redshift, and as such permits us to reconstruct the
shear profile of the typical field galaxy halo in absolute physical units
(modulo H_0), and to investigate the dependence of halo mass upon galaxy
luminosity. This is also the first galaxy-galaxy lensing study for which the
calibration errors are negligible. Within a projected radius of 200 \hkpc, the
shear profile is consistent with an isothermal profile with circular velocity
164+-20 km/s for an L* galaxy, consistent with typical disk rotation at this
luminosity. This halo mass normalization, combined with the halo profile
derived by Fischer et al (2000) from lensing analysis SDSS data, places a lower
limit of (2.7+-0.6) x 10^{12}h^{-1} solar masses on the mass of an L* galaxy
halo, in good agreement with satellite galaxy studies. Given the known
luminosity function of LCRS galaxies, and the assumption that $M\propto
L^\beta$ for galaxies, we determine that the mass within 260\hkpc of normal
galaxies contributes $\Omega=0.16\pm0.03$ to the density of the Universe (for
$\beta=1$) or $\Omega=0.24\pm0.06$ for $\beta=0.5$. These lensing data suggest
that $0.6<\beta<2.4$ (95% CL), only marginally in agreement with the usual
$\beta\approx0.5$ Faber-Jackson or Tully-Fisher scaling. This is the most
complete direct inventory of the matter content of the Universe to date.


title:
Discovery of a 270 Hz X-Ray Burst Oscillation in the X-Ray Dipper 4U
  1916-053

abstract:
  We report the discovery of a highly coherent oscillation in a type-I X-ray
burst observed from 4U 1916-053 by the Rossi X-ray Timing Explorer (RXTE). The
oscillation was most strongly detected approx. 1 s after the burst onset at a
frequency of 269.3 Hz, and it increased in frequency over the following 4
seconds of the burst decay to a maximum of around 272 Hz. The total measured
drift of 3.58 +/- 0.41 Hz (1 sigma) represents the largest fractional change in
frequency (1.32 +/- 0.15 %) yet observed in any burst oscillation. If the
asymptotic frequency of the oscillation is interpreted in terms of a decoupled
surface burning layer, the implied neutron star spin period is around 3.7 ms.
However, the expansion of the burning layer required to explain frequency drift
during the burst is around 80 m, substantially larger than expected
theoretically (assuming rigid rotation). The oscillation was not present in the
persistent emission before the burst, nor in the initial rise. When detected
its amplitude was 6-12% (RMS) with a roughly sinusoidal profile. The burst
containing the oscillation showed no evidence for photospheric radius
expansion, while at least 5 of the other 9 bursts observed from the source by
RXTE during 1996 and 1998 did. No comparable oscillations were detected in the
other bursts. A pair of kilohertz quasi-periodic oscillations (QPOs) has been
previously reported from this source with a mean separation of 348 +/- 12 Hz.
4U 1916-053 is the first example of a source where the burst oscillation
frequency is significantly smaller than the frequency separation of the kHz
QPOs.


title: The Puzzle of the Lyman Continuum Polarization of QSOs

abstract:
  Recent spectropolarimetry of QSOs has revealed a surprising rise in
polarization in the Lyman continuum of several objects. We discuss several
recent attempts to interpret this feature, including the role of Lyman limit
absorption in PG 1222+228. We present new theoretical results involving
electron scattering in a hot corona or wind above an accretion disk, and
polarization resulting from the relativistic returning radiation. These
mechanisms can lead to potentially observable polarization at short
wavelengths, but neither has quantitative success in fitting the observed Lyman
continuum polarization rises. A renewed capability for ultraviolet
spectropolarimetry from space is urgently needed to provide further clues to
the nature of this phenomenon.


title:
Performance characteristics of the new Keck Observatory echelle
  spectrograph and imager

abstract:
  The Echelle Spectrograph and Imager (ESI) is a multipurpose instrument which
has been delivered by the Instrument Development Laboratory of Lick Observatory
for use at the Cassegrain focus of the Keck II telescope. ESI saw first light
on August 29, 1999. The optical performance of the instrument has been measured
using artificial calibration sources and starlight. Measurements of the average
image FWHM in echelle mode are 22 microns (0.22 arcseconds), 16 to 18 microns
(0.16 to 0.18 arcseconds) in broad band imaging mode, and comparable in the
low-dispersion prismatic mode (LDP). Images on the sky, under best seeing
conditions show FWHM sizes of 34 microns (0.34 arcseconds). Maximum
efficiencies are measured to be 30% for echelle and anticipated to be greater
than 38% for low dispersion prismatic mode including atmospheric, telescope and
detector losses. In this paper we describe the instrument and its
specifications. We discuss the testing that led to the above conclusions.


title: HI Observations of Giant Low Surface Brightness Galaxies

abstract:
  We have used the Nancay Radio Telescope to obtain new global HI data for 16
giant low surface brightness (LSB) galaxies. Our targets have optical
luminosities and disk scale lengths at the high end for spiral galaxies
(L_B~10^10 Lsun and h_r>~6 kpc for H_0=75 km/s/Mpc), but they have diffuse
stellar disks, with mean disk surface brightnesses ~1 magnitude or more fainter
than normal giant spirals. Thirteen of the galaxies previously had been
detected in HI by other workers, but the published HI observations were either
confused, resolved by the telescope beam, of low signal-to-noise, or showed
significant discrepancies between different authors. For the other 3 galaxies,
no HI data were previously available. Several of the galaxies were resolved by
the Nancay 3.6' E-W beam, so global parameters were derived from multiple-point
mapping observations. Typical HI masses for our sample are ~10^10 Msun, with
M_HI/L_B=0.3-1.7 (in solar units). All of the observed galaxies have published
optical surface photometry, and we have compiled key optical measurements for
these objects from the literature. We frequently find significant variations
among physical parameters of giant LSB galaxies reported by various workers.


title: The Dwarf Galaxy Population of the Dorado group down to Mv=-11

abstract:
  We present V and I CCD photometry of suspected low-surface brightness dwarf
galaxies detected in a survey covering ~2.4 deg^2 around the central region of
the Dorado group of galaxies. The low-surface brightness galaxies were chosen
based on their sizes and magnitudes at the limiting isophote of 26.0V\mu. The
selected galaxies have magnitudes brighter than V=20 (Mv=-11 for an assumed
distance to the group of 17.2 Mpc), with central surface brightnesses \mu0>22.5
V mag/arcsec^2, scale lengths h>2'', and diameters > 14'' at the limiting
isophote. Using these criteria, we identified 69 dwarf galaxy candidates. Four
of them are large very low-surface brightness galaxies that were detected on a
smoothed image, after masking high surface brightness objects. Monte Carlo
simulations performed to estimate completeness, photometric uncertainties and
to evaluate our ability to detect extended low-surface brightness galaxies show
that the completeness fraction is, on average, > 80% for dwarf galaxies with
$-17<M_{V}<-10.5$ and 22.5<\mu0<25.5 V mag/arcsec^2, for the range of sizes
considered by us (D>14''). The V-I colors of the dwarf candidates vary from
-0.3 to 2.3 with a peak on V-I=0.98, suggesting a range of different stellar
populations in these galaxies. The projected surface density of the dwarf
galaxies shows a concentration towards the group center similar in extent to
that found around five X-ray groups and the elliptical galaxy NGC1132 studied
by Mulchaey and Zabludoff (1999), suggesting that the dwarf galaxies in Dorado
are probably physically associated with the overall potential well of the
group.


title: K band Spectroscopy of Ultraluminous Infrared Galaxies: The 2 Jy Sample

abstract:
  We present near-infrared spectroscopy for a complete sample of 33
ultraluminous infrared galaxies at a resolution of R\approx 1000. Most of the
wavelength range from 1.80-2.20 microns in the rest frame is covered, including
the Pa-alpha and Br-gamma hydrogen recombination lines, and the molecular
hydrogen vibration-rotation 1-0 S(1) and S(3) lines. Other species, such as He
I, [Fe II], and [Si VI] appear in the spectra as well, in addition to a number
of weaker molecular hydrogen lines. Nuclear extractions for each of the
individual galaxies are presented here, along with spectra of secondary nuclei,
where available. The Pa-alpha emission is seen to be highly concentrated on the
nuclei, typically with very little emision extending beyond a radius of 1 kpc.
Signatures of active nuclei are rare in the present sample, occurring in only
two of the 33 galaxies. It is found that visual extinctions to the nuclei via
the Pa-alpha/Br-gamma line ratio in excess of 10 magnitudes are relatively
common among ULIRGs, and that visual extinctions greater than 25 mag are
necessary to conceal a QSO emitting half the total bolometric luminosity. The
vibration-rotation lines of molecular hydrogen appear to be predominantly
thermal in origin, with effective temperatures generally around 2200 K. The
relative nuclear velocities between double nucleus ULIRGs are investigated,
through which it is inferred that the maximum deprojected velocity difference
is about 200 km/s. This figure is lower than the velocities predicted by
physical models of strong interactions/mergers of large, gas-rich galaxies.


title: The outer-halo globular cluster NGC 6229. IV. Variable stars

abstract:
  We present time-series B, V photometry of NGC 6229, obtained with the purpose
of providing the first extensive CCD variability study of this cluster. As a
result, we were able to obtain periods for all NGC 6229 variables, with the
exception of five stars from the Borissova et al. (1997) candidate list located
very close to the cluster center. Two variable stars suspected by Carney,
Fullton, & Trammell (1991) are first-overtone RR Lyrae (RRc) stars, whereas
seven of the 12 candidates from Borissova et al. (1997) are confirmed variables
-- three of them being fundamental RR Lyrae (RRab) pulsators, two
first-overtone pulsators, one eclipsing binary (most likely an Algol system)
and one bright star whose variability status could not be satisfactorily
determined. A new image subtraction method (ISM) suggested by Alard (1999) has
been employed which, together with the Welch & Stetson (1993) technique, has
allowed us to discover twelve new RR Lyrae variables in the cluster, for which
ephemerides are provided. Ten of these are RRab's, whereas the other two are
RRc's. As originally suggested by Mayer (1961), NGC 6229 is clearly an
Oosterhoff type I globular cluster. We also confirm that V8 is a Population II
Cepheid of the W Virginis type, and suspect that this is the case for V22 as
well.
  The physical properties of the NGC 6229 RR Lyrae population are compared
against those of M3 (NGC 5272) using several different methods, including a
standard period-shift analysis. Possible differences between these two clusters
are discussed.


title: Quintessence Energy and Dissipation

abstract:
  The combined effect of a dissipative fluid and quintessence energy can
simultaneously drive an accelerated expansion phase at the present time and
solve the coincidence problem of our current Universe. A solution compatible
with the observed cosmic acceleration is succinctly presented.


title: Ion $H_2^+$ can dissociate in a strong magnetic field

abstract:
  In framework of a variational method the molecular ion $H_2^+$ in a magnetic
field is studied. An optimal form of the vector potential corresponding to a
given magnetic field (gauge fixing) is chosen variationally. It is shown that
for any magnetic field strength as well as for any orientation of the molecular
axis the system $(ppe)$ possesses a minimum in the potential energy. The stable
configuration always corresponds to elongation along the magnetic line.
However, for magnetic fields $B \gtrsim 5\times 10^{11} G$ and some
orientations the ion $H_2^+$ becomes unstable decaying to $H{-atom} + p$.


title: Stability of Toomre-Hayashi Disk

abstract:
  We investigate stability of Toomre-Hayashi model for a self-gravitating,
rotating gas disk. The rotation velocity, $ v_\phi $, and sound speed, $ c
_{\rm s} $, are spatially constant in the model. We show that the model is
unstable against an axisymmetric perturbation irrespectively of the values of $
v_\phi $ and $ c_{\rm s} $. When the ratio, $ v_\phi / c_{\rm s} $, is large,
the model disk is geometrically thin and unstable against an axisymmetric
perturbation having a short radial wavelength, i.e., unstable against
fragmentation. When $ v_\phi / c_{\rm s} $ is smaller than 1.20, it is unstable
against total collapse. Toomre-Hayashi model of $ 1.7 \la v_\phi / c_{\rm s}
\la 3 $ was thought to be stable against axisymmetric perturbations in earlier
studies in which only radial motion was taken into account. Thus, the
instability of Toomre-Hayashi model having a medium $ v_\phi / c_{\rm s} $ is
due to not change in the surface density but that in the disk height. We also
find that the singular isothermal perturbation is stable against non-spherical
peturbations.


title: Inflationary perturbations near horizon crossing

abstract:
  We study the behaviour of inflationary density perturbations in the vicinity
of horizon crossing, using numerical evolution of the relevant mode equations.
We explore two specific scenarios. In one, inflation is temporarily ended
because a portion of the potential is too steep to support inflation. We find
that perturbations on super-horizon scales can be modified, usually leading to
a large amplification, because of entropy perturbations in the scalar field.
This leads to a broad feature in the power spectrum, and the slow-roll and
Stewart--Lyth approximations, which assume the perturbations reach an
asymptotic regime well outside the horizon, can fail by many orders of
magnitude in this regime. In the second scenario we consider perturbations
generated right at the end of inflation, which re-enter shortly after inflation
ends --- such perturbations can be relevant for primordial black hole
formation.


title: Radio Properties of REX BL Lacs and Galaxies

abstract:
  Detailed VLA observations have been gathered for a number of sources
classified as either BL Lacs or galaxies, derived from the REX survey. We focus
in particular on the sources identified by us, for which we have in hand
homogeneous optical data, to study in more detail than allowed by the NVSS the
radio properties of these sources in the framework of AGN unified models.


title: The Sunyaev-Zeldovich MITO Project

abstract:
  Compton scattering of the cosmic microwave background radiation by electrons
in the hot gas in clusters of galaxies - the Sunyaev-Zeldovich effect - has
long been recognized as a uniquely important feature, rich in cosmological and
astrophysical information. We briefly describe the effect, and emphasize the
need for detailed S-Z and X-ray measurements of nearby clusters in order to use
the effect as a precise cosmological probe. This is the goal of the MITO
project, whose first stage consisted of observations of the S-Z effect in the
Coma cluster. We report the results of these observations.


title: Non-spherical core collapse supernovae and nucleosynthesis

abstract:
  Motivated by observations of supernova SN 1987A, various authors have
simulated Rayleigh-Taylor (RT) instabilities in the envelopes of core collapse
supernovae (for a review, see Mueller 1998). The non-radial motion found in
these simulations qualitatively agreed with observations in SN 1987A, but
failed to explain the extent of mixing of newly synthesized 56Ni
quantitatively. Here we present results of a 2D hydrodynamic simulation which
re-addresses this failure and covers the entire evolution of the first 5 hours
after core bounce.


title: The EMSS Radio Loud Quasar Sample

abstract:
  We construct the first X-ray selected sample of radio-loud quasars from the
EMSS survey. The X-ray selection allows us to explore the properties of
radio-loud quasars 10-100 weaker than classical samples in the radio band.
There are no radio-loud quasars whose synchrotron peak reaches the UV-soft
X-ray band at these (radio) flux levels (as occurs for BL Lac objects selected
in the X-ray band), but they appear to have comparatively stronger optical-UV
emission. We suggest that this can be ascribed to a significant contribution
from a quasi-thermal optical-UV component, emerging due to the comparatively
weak non-thermal emission. The detection of sources at low radio fluxes also
shows the presence of a large population of steep spectrum quasars, and the
lack of the predicted turnover in the quasar counts.


title:
Distribution and Kinematics of Molecular Gas in Barred Spiral Galaxies.
  I. NGC 3504

abstract:
  We present the results of the CO mapping observations of the barred spiral
galaxy NGC3504 with the Nobeyama 45-m telescope. The distribution of the
molecular gas shows offset ridges which correspond to the distribution of HII
regions along the bar. The velocity perpendicular to the bar decreases abruptly
at the ridge. The velocity change implies that the molecular gas changes the
direction of its motion to parallel to the bar at the ridge. Since the position
angle of the major axis of the bar and the line of nodes are almost the same in
NGC 3504, an upper limit to the pattern speed of the bar can be derived
directly from the radial velocity. The resultant upper limit is 41 km/s/kpc
which is much smaller than that derived with an assumption that the corotation
radius is located at the end of the bar (77 km/s/kpc). The corotaion radius
derived from our upper limit is more than two times larger than the length of
the semi-major axis of the bar in NGC 3504.


title:
The Role of Clustering of Sub-Clumps in Bright Elliptical Galaxy
  Formation from a Low-Spin Seed Galaxy

abstract:
  We reveal the role of clustering of sub-clumps, which is expected in the cold
dark matter (CDM) universe, in forming a bright elliptical galaxy (BEG) from a
low-spin seed galaxy.
  This can be done by comparing the evolution of a low-spin seed galaxy
including small-scale density fluctuations expected in the CDM universe
  (Model 1) with that of a completely uniform one (Model 2), using numerical
experiments.
  We show that Model 2 cannot reproduce the properties of BEGs and forms a disk
which is too compact and too bright due to the conservation of the
initial-small angular momentum.
  In Model 1 clustering of the sub-clumps caused by initial small-scale density
fluctuations leads to angular momentum transfer from the baryon component to
the dark matter and consequently a nearly spherical system supported by random
motions is formed.
  Moreover the collisionless property of the stars formed in the sub-clumps
prevents the dissipative contraction of the system, leading to a large measured
half-light radius.
  As a result, the end-product is quite well reproduces the observed properties
of BEGs, such as the de Vaucouleurs light-profile, typical color and
metallicity gradients, the large half-light radius, the small ratio of the
rotational velocity to the velocity dispersion (V/\sigma). We conclude that the
clustering of sub-clumps, i.e., the hierarchical clustering, plays a crucial
role in the formation of BEGs from a low-spin seed galaxy.


title: Orientation effects on bent extragalactic jets

abstract:
  We have investigated how varying several parameters affects the results of a
collision between an extragalactic jet and a dense, intergalactic cloud,
through a series of hydrodynamic simulations. We have produced synthetic radio
images for comparison with observations. These show that a variety of
structures may be produced from simple jet-cloud collisions. Moderate Mach
numbers and density contrasts are needed to produce observable bends. We
investigate the effect of viewing from various angles on the appearance of such
sources.


title: Can we look inside a dynamo?

abstract:
  For a simple spherically symmetric mean-field dynamo model we investigate the
possibility of determining the radial dependence of the coefficient $\alpha$.
Growth rates for different magnetic field modes are assumed to be known by
measurement. An evolutionary strategy (ES) is used for the solution of the
inverse problem. Numerically, we find quite different $\alpha$-profiles giving
nearly the same eigenvalues. The ES is also applied to find functions
$\alpha(r)$ yielding zero growth rates for the lowest four magnetic field
modes. Additionally, a slight modification of the ES is utilized for an
''energetic'' optimization of $\alpha^2$-dynamos. The consequences of our
findings for inverse dynamo theory and for the design of future dynamo
experiments are discussed.


title:
Two New Ejecta-Dominated Galactic Supernova Remnants: G337.2-0.7 and
  G309.2-0.6

abstract:
  We present the analysis of new X-ray observations of two Galactic radio
supernova remnants (SNRs), G337.2-0.7 and G309.2-0.6. Both remnants exhibit
line-rich thermal spectra that require highly non-solar elemental abundance
ratios. In each case, Si and S are unequivocally overabundant compared to solar
based purely on the measured equivalent width of the K$\alpha$ line complex.
Detailed nonequilibrium ionization spectral analysis of these remnants, using a
single temperature, single ionization age model, confirm the overabundances,
yielding Si, S and Ar abundances many times their solar values: 3 to 5 times
solar for G337.2-0.7 and greater than 3 to 10 times solar for G309.2-0.6. We
also find that for both remnants, Ne and Mg are underabundant relative to Si,
and for G309.2-0.6, Ca and Fe as well are relatively underabundant. This is the
first detection of metal-rich, non-solar abundance material in these remnants,
identifying them as young ejecta-dominated SNRs. Further support for their
youth comes from the distances that we estimate from the fitted column
densities (less than 15 kpc for G337.2-0.7, and $4 \pm 2$ kpc for G309.2-0.6).
  From the implied sizes of the remnants at these distances we infer relatively
young ages (2000 to 4500 years for G337.2-0.7, and 700 to 4000 years for
G309.2-0.6). Finally we note that no compact object has yet been found within
G337.2-0.7, but an X-ray point source is evident within the radio shell of
G309.2-0.6, although its nature remains unknown.


title: Object Classification in Astronomical Multi-Color Surveys

abstract:
  We present a photometric method for identifying stars, galaxies and quasars
in multi-color surveys, which uses a library of >65000 color templates. The
method aims for extracting the information content of object colors in a
statistically correct way and performs a classification as well as a redshift
estimation for galaxies and quasars in a unified approach. For the redshift
estimation, we use an advanced version of the MEV estimator which determines
the redshift error from the redshift dependent probability density function.
  The method was originally developed for the CADIS survey, where we checked
its performance by spectroscopy. The method provides high reliability (6 errors
among 151 objects with R<24), especially for quasar selection, and redshifts
accurate within sigma ~ 0.03 for galaxies and sigma ~ 0.1 for quasars.
  We compare a few model surveys using the same telescope time but different
sets of broad-band and medium-band filters. Their performance is investigated
by Monte-Carlo simulations as well as by analytic evaluation in terms of
classification and redshift estimation. In practice, medium-band surveys show
superior performance. Finally, we discuss the relevance of color calibration
and derive important conclusions for the issues of library design and choice of
filters. The calibration accuracy poses strong constraints on an accurate
classification, and is most critical for surveys with few, broad and deeply
exposed filters, but less severe for many, narrow and less deep filters.


title: EROs and the formation epoch of field ellipticals

abstract:
  A comparison is presented between the observed surface density of extremely
red objects (EROs) and the densities of red high-z elliptical galaxies
predicted by Pure Luminosity Evolution (PLE) and by some CDM hierarchical
models. The analysis is based on the widest field survey for EROs available to
date (covering in total $\sim$850 arcmin^2), and it takes into account the
effects of ERO clustering. Good agreement is found between the observed surface
densities of EROs and those predicted by PLE models for ellipticals selected
using the same color and luminosity thresholds. Since there is evidence that
the bulk of EROs are passively evolving ellipticals, this result implies that
most field ellipticals were fully assembled at least by $z\sim$2.5. Existing
hierarchical models predict instead a surface density of red ellipticals that
is much smaller than that of the EROs.


title: High Speed Phase-Resolved 2-d UBV Photometry of the Crab pulsar

abstract:
  We report a phase-resolved photometric and morphological analysis of UBV data
of the Crab pulsar obtained with the 2-d TRIFFID high speed optical photometer
mounted on the Russian 6m telescope. By being able to accurately isolate the
pulsar from the nebular background at an unprecedented temporal resolution (1
\mu s), the various light curve components were accurately fluxed via
phase-resolved photometry. Within the $UBV$ range, our datasets are consistent
with the existing trends reported elsewhere in the literature. In terms of flux
and phase duration, both the peak Full Width Half Maxima and Half Width Half
Maxima decrease as a function of photon energy. This is similarly the case for
the flux associated with the bridge of emission. Power-law fits to the various
light curve components are as follows; \alpha = 0.07 \pm 0.19 (peak 1), \alpha
= -0.06 \pm 0.19 (peak 2) and \alpha = -0.44 \pm 0.19 (bridge) - the
uncertainty here being dominated by the integrated CCD photometry used to
independently reference the TRIFFID data. Temporally, the main peaks are
coincident to \le 10 \mu s although an accurate phase lag with respect to the
radio main peak is compromised by radio timing uncertainties. The plateau on
the Crab's main peak was definitively determined to be \leq 55 \mu s in extent
and may decrease as a function of photon energy. There is no evidence for
non-stochastic activity over the light curves or within various phase regions,
nor is there evidence of anything akin to the giant pulses noted in the radio.
Finally, there is no evidence to support the existence of a reported 60 second
modulation suggested to be as a consequence of free precession.


title:
CCD Photometry of the Globlular Cluster NGC 5986 and its
  Post-Asymptotic-Giant-Branch and RR Lyrae Stars

abstract:
  We have obtained new CCD BV photometry of the little-studied southern
Galactic globular cluster NGC 5986, including light curves of 5 of its RR Lyrae
variables. The cluster's red giant branch bump is detected for the first time
at V = 16.47 +- 0.03. We derive a reddening and true distance modulus of E(B-V)
= 0.29 +- 0.02 and (m-M)_0 = 15.15 +- 0.10, respectively. The cluster's
color-magnitude diagram reveals a mostly blue horizontal branch, like that of
M13 or M2, and quite unlike M3; yet all of these clusters have nearly identical
metallicities ([Fe/H]_CG97 = -1.35). We show that the RR Lyrae variables in NGC
5986 are about 0.2 mag brighter on average than those in M3, an important
exception to the often-employed, universal M_V(RR)--[Fe/H] relation. Finally,
we note that NGC 5986 contains two luminous stars with spectral types A-F,
which are likely to be post-asymptotic-giant-branch (PAGB) objects. The V-band
luminosity function (LF) of such yellow PAGB stars is a promising standard
candle. We suggest that the LF is sharply peaked at M_V(PAGB) = -3.28 +- 0.07.


title: What Makes the Sun Tick? - The Origin of the Solar Cycle

abstract:
  In contrast to the situation with the geodynamo, no breakthrough has been
made in the solar dynamo problem for decades. Since the appearance of
mean-field electrodynamics in the 1960's, the only really significant advance
was in the field of flux tube theory and flux emergence calculations. These new
results, together with helioseismic evidence, have led to the realization that
the toroidal magnetic flux giving rise to activity phenomena must be stored and
presumably generated below the convection zone proper, in what I will call the
DOT (Dynamo-Overshoot-Tachoclyne) layer. The only segment of the problem we can
claim to basically understand is the transport of flux from this layer to the
surface. On the other hand, as reliable models for the DOT layer do not exist
we are clueless concerning the precise mechanisms responsible for
toroidal/poloidal flux conversion and for characteristic migration patterns
(extended butterfly diagram) and periodicities. Even the most basic result of
mean-field theory, the interpretation of the butterfly diagram as an
alpha-omega dynamo wave, has been questioned. This review therefore will
necessarily ask more questions than give answers. Some of these key questions
are
  - Structure of the DOT layer
  - alpha-quenching and distributed dynamo
  - High-latitude migration patterns and their interpretation
  - The ultimate fate of emerged flux


title: The Wisconsin H-Alpha Mapper Northern Sky Survey

abstract:
  The Wisconsin H-Alpha Mapper (WHAM) has completed a survey in Balmer Alpha of
the entire Northern sky above declination -30 deg. This survey provides the
first calibrated, velocity-resolved map of the H-Alpha emission from the
Galaxy. With one-degree spatial resolution, 12 km s^{-1} velocity resolution,
and sensitivity to features as faint as 0.1 R (EM ~ 0.2 cm^{-6} pc), this
survey provides the deepest maps of the ionized content of the Galaxy to date.
In addition to probing the detailed kinematic structure of the Warm Ionized
Medium and the vertical structure of the ionized content in spiral arms,
initial results include the discovery of several faint, extended (d > 1\deg) H
II regions and the first map of the ionized component of an intermediate
velocity cloud.


title: Rotation of the Disk of the Large Magellanic Cloud

abstract: This paper has been withdrawn


title:
Discovery of an Extended Dust Emission around IRAS 18576+0341 (AFGL
  2298) at 10.3 and 18.0 microns: a New Luminous Blue Variable Candidate?

abstract:
  We report detection of an extended mid-infrared emission from \iras
18576+0341 (AFGL 2298). The object shows a dusty circumstellar shell that has
diameter of $\age 7\arcsec$ at 10.3 and 18.0 $\um$. The dust nebula shows two
emission peaks concentrically elongated and symmetrically oriented on the
opposite sides of the third, central peak, which appears to be the central star
of the system. The observed mid-infrared morphology indicates that the
circumstellar dust shell has an equatorially-enhanced material distribution,
which is a common signature of stellar objects that have experienced mass loss.
Radiative transfer model calculations suggest that the central star is an
extremely bright ($\lstar = 10^{6.4} \lsun$) star at a distance of about 10
kpc: this object is best described as a new luminous blue variable candidate.
The circumstellar dust shell seems to have been generated by an
equatorially-enhanced mass loss process with ${\dot M} \ge 6.8 \times 10^{-6}
\msun$ yr$^{-1}$ and ${\dot M}_{\rm pole}/{\dot M}_{\rm eq} \sim 0.5$.


title: The Morphology of Extremely Red Objects

abstract:
  We briefly discuss our survey of Extremely Red Objects (EROs) with HST/NICMOS
and deep ground-based images and summarize its results. We use the
high-resolution NICMOS images to sub-divide EROs into morphological classes,
tentatively arguing that about 60 % of EROs (18 out of 30) are early-type
galaxies. About 20 % (6 out of 30 objects) appear to be flattened disk systems.
Another 10 % (3 out of 30) have an irregular morphology. Thus, combining disk
and irregular systems, our data are compatible with 30 % of EROs being dusty
starbursts. A small fraction (3 out of 30) appear point-like even on the HST
images and could therefore be either compact high redshift galaxies or stars in
the Milky Way halo.


title: Sub-mm imaging of a proto-cluster region at z=3.09

abstract:
  We have used the Submillimetre Common-User Bolometer Array (SCUBA) detector
on the James Clerk Maxwell Telescope (JCMT) to measure bright sub-mm emission
associated with a recently discovered extensive (>100/h kpc) and highly
luminous, `blob' of Ly-alpha emission at z=3.09. The blob lies within a known
large overdensity of optical sources in the z=3.07-3.11 range, and is centered
on a locally overdense peak within this region. The best explanation for the
copious sub-mm emission is a dust obscured continuum source, which may produce
the ionizing flux for the Ly-alpha cloud. Cooling gas explanations are
plausible but excessively complicated, and the 450/850 micron ratio rules out a
significant fraction of the signal arising from the Sunyaev-Zel'dovich
increment. At least two additional ~10 mJy sub-mm detections in the SCUBA map,
with a surface density significantly higher than in blank field surveys,
suggests that they may be associated with the z=3.09 structure. A SCUBA
`photometry' observation of a second nearby Ly-alpha blob tentatively detects a
weaker sub-mm counterpart.


title: Ages of A-type Vega-like stars from uvby$\beta$ Photometry

abstract:
  We have estimated the ages of a sample of A-type Vega-like stars by using
Str\"{o}mgren \emph{uvby$\beta} photometric data and theoretical evolutionary
tracks. We find that 13 percent of these A stars have been reported as
Vega-like stars in the literature and that the ages of this subset run the
gamut from very young (50~Myr) to old (1~Gyr), with no obvious age difference
compared to those of field A stars. We clearly show that the fractional IR
luminosity decreases with the ages of Vega-like stars.


title: On the Mass-Donating Star in GRS 1915+105

abstract:
  We present an analysis of constraints on the companion mass for the Galactic
microquasar GRS 1915+105. Using the known inclination angle and stability of
the jet axis, we can rule out massive ($M_s \ga 3 M_{\sun}$) companions with
orbital axes not aligned with the jet axis. For an aligned orbital axis, we
constrain the ratio of the stellar radius to the binary semi-major axis to be
$R_s/a <0.342$, based on the lack of X-ray eclipses. We then show that these
constraints together with the X-ray luminosity, approximate black hole mass,
and observations of the X-ray absorbing column density towards GRS 1915+105
rule out accretion via stellar wind from a massive companion, implying that
accretion occurs via Roche-lobe overflow. In that case, the constraint on
$R_s/a$ rules out any companion with $M_s > 19.4 M_{\sun}$ for a black hole
mass of $M_{BH} \simeq 30 M_{\sun}$. The lack of significant X-ray reprocessing
in the infrared from GRS 1915+105 also provides constraints on the mass and
temperature range of a Roche-lobe-filling mass donor.


title:
Galaxy-QSO Correlation induced by Weak Gravitational Lensing arising
  from Large-Scale Structure

abstract:
  Observational evidence shows that gravitational lensing induces an angular
correlation between the distribution of galaxies and much more distant QSOs. We
use weak gravitational lensing theory to calculate this angular correlation,
updating previous calculations and presenting new results exploring the
dependence of the correlation on the large-scale structure. We study the
dependence of the predictions on a variety of cosmological models, such as cold
dark matter models, mixed dark matter models, and models based on quintessence.
We also study the dependence on the assumptions made about the nature of the
primordial fluctuation spectrum: adiabatic, isocurvature and power spectra
motivated by the cosmic string scenario are investigated. Special attention is
paid to the issue of galaxy biasing, which is fully incorporated. We show that
different mass power spectra imply distinct predictions for the angular
correlation, and therefore the angular correlation provides an extra source of
information about cosmological parameters and mechanisms of structure
formation. We compare our results with observational data and discuss their
potential uses. In particular, it is suggested that the observational
determination of the galaxy-QSO correlation may be used to give an independent
measurement of the mass power spectrum.


title:
The importance of anisotropic interstellar turbulence and
  molecular-cloud magnetic mirrors for galactic cosmic-ray propagation

abstract:
  Recent studies suggest that when magnetohydrodynamic (MHD) turbulence is
excited by stirring a plasma at large scales, the cascade of energy from large
to small scales is anisotropic, in the sense that small-scale fluctuations
satisfy the inequality k_parallel << k_perp, where k_parallel and k_perp are,
respectively, the components of a fluctuation's wave vector parallel and
perpendicular to the background magnetic field. Such anisotropic fluctuations
are very inefficient at scattering cosmic rays. Results based on the
quasilinear approximation for scattering of cosmic rays by anisotropic MHD
turbulence are presented and explained. The important role played by
molecular-cloud magnetic mirrors in confining and isotropizing cosmic rays when
scattering is weak is also discussed.


title: Auto-Correlation Functions and Solar Cycle Predictability

abstract:
  Starting from the traditional definition of auto-correlation function we can
introduce a new quantity, based on the wavelet formalism, called local wavelet
auto-correlation function, which contains more information about the
correlation properties on a given signal on different scales. The application
of this formalism to the temporal variations of solar activity, from the
monthly time series of sunspot numbers, allows to derive some interesting
information about the correlation properties of different periodicities present
in the signal and in particular the correlation characteristics of the main 11
years Schwabe cycle. The scale selectivity, allowed by the local wavelet
auto-correlation function, can give interesting information about the range of
reliable predictions reachable through deterministic predictive models.


title: Charge densities above pulsar polar caps

abstract:
  The ability of the neutron star surface to supply all or only part of the
charges filling the pulsar magnetosphere is crucial for the physics prevailing
within it, with direct consequences for the possible formation of pair creation
regions. We evaluate the conditions for $e^-$ emission from pulsar surfaces for
a simple Goldreich-Julian geometry taking both thermal and field emission
processes into account. Using recently published estimates for the equation of
state at the neutron star's surface, we show, that for a large range of $T_{\rm
surf}, B$ and $P$, the liberated charges will fully screen the accelerating
B-parallel electric field ${\rm E_\|}$. For surface temperatures $T_{\rm
surf}<2\cdot 10^5 $K a balance between field emission of electrons and
shielding of the field will occur. Even in the overidealised case of $T_{\rm
surf}=0$ one can expect a prodigious supply of electrons which will weaken the
accelerating ${\rm E_\|}$. We calculated the motion of electrons along selected
polar field lines numerically for the low temperature, field emission scenario
yielding their Lorentz factors as well as the produced radiation densities.
Inverse Compton and later curvature losses are seen to balance the acceleration
by the residual electric fields. We found that the conditions for magnetic pair
production are not met anywhere along the field lines up to a height of 1500
pulsar radii. We did not {\it a priori} assume an "inner gap", and our
calculations did not indicate the formation of one under realistic physical
conditions without the introduction of further assumptions.


title:
A New Model for the Evolution of Light Elements in an Inhomogeneous
  Galactic Halo

abstract:
  We present predictions of the evolution of the light elements, Li, Be, and B,
in the early epochs of the Galactic halo, using a model of supernova-induced
chemical evolution based on contributions from supernovae (SNe) and cosmic rays
(CRs). The most important prediction from our model is that the abundances of
light elements in extremely metal-poor stars might be used as age indicators in
the very early stages of an evolving halo population, at times when metallicity
in most stars are dominated by local metal enrichment due to nearby SN events,
and is poorly correlated with age. Our results show that the best ``cosmic
clock'' is the $^6$Li abundance. We have derived relationships among various
cosmic-ray parameters. Although our model is successful for certain sets of
cosmic-ray parameters, larger energy should be absorbed by energetic particles
from each SN than required to the current situation of Galactic disk. We
discuss an alternative hypothesis of AGN activity in the early Galaxy as
another possible accelerator of CRs.


title: Superconducting Superfluids in Neutron Stars

abstract:
  For treatment of the layers below the crust of a neutron star it is useful to
employ a relativistic model involving three independently moving constituents,
representing superfluid neutrons, superfluid protons, and degenerate negatively
charged leptons. A Kalb Ramond type formulation is used here to develop such a
model for the specific purpose of application at the semi macroscopic level
characterised by lengthscales that are long compared with the separation
between the highly localised and densely packed proton vortices of the
Abrikosov type lattice that carries the main part of the magnetic flux, but
that are short compared with the separation between the neutron vortices.


title: Dynamical Evolution of Clusters

abstract:
  We consider a sample of about 50 distant galaxy clusters at z>0.15 (<z> about
0.3), each cluster having at least 10 galaxies with available redshift in the
literature. We select member galaxies, analyze the velocity dispersion
profiles, and evaluate in a homogeneous way cluster velocity dispersions and
virial masses. We apply the same procedures already recently applied on a
sample of nearby clusters (z<0.15) in order to properly analyze the possible
dynamical evolution of galaxy clusters. We do not find any significant
difference between nearby and distant clusters. In particular, we consider the
galaxy spatial distribution, the shape of the velocity dispersion profile, and
the relations between velocity dispersion and X-ray luminosity and temperature.
Our results imply little dynamical evolution in the range of redshift spanned
by our cluster sample, and suggest that the typical redshift of cluster
formation is higher than that of the sample we analyze.


title:
Evolution of globular cluster systems in elliptical galaxies. II.
  Power-law initial mass function

abstract:
  We have studied the evolution of globular cluster systems (GCS) in elliptical
galaxies with a power-law initial GCS mass function (GCMF) ($f(M) \propto
M^{-\alpha}$) similar to that predicted by some theoretical studies of globular
clusters formation and to that of young cluster systems observed in merging
galaxies. We have carried out a survey over a large number of different host
galaxies and we have considered different values for the index, $\alpha$, of
the initial power-law GCMF ($\alpha=1.5,1.8,2.0$); we show the dependence of
the main GCS final properties (mean mass and dispersion of the final GCMF,
fraction of surviving clusters, radial gradient of the GCMF parameters) on the
structure of the host galaxy and on the slope of the initial GCMF. For a
subsample of host galaxies with values of effective masses and radii equal to
those determined using observational data for a number of giant, normal and
dwarf galaxies our results show that the relation between the final GCMF
properties and those of the host galaxies as well as the dependence of the
final GCMF parameters on the galactocentric distance within individual galaxies
differ from those observed in old GCS: the values of the final GCS mean mass
are in general smaller (4.2 < log M_final < 5.0) than those observed and the
galaxy-to-galaxy dispersion of logM_final is larger than that reported by
observational analyses. The results are compared with those of a companion
paper in which we investigated the evolution of GCS with a log-normal initial
GCMF and in which the final GCS properties were perfectly consistent with
observations.


title: Neutron Stars with a Stable, Light Supersymmetric Baryon

abstract:
  If a light gluino exists, the lightest gluino-containing baryon, the \OSO, is
a possible candidate for self-interacting dark matter. In this scenario, the
simplest explanation for the observed ratio $\Omega_{dm}/\Omega_b \approx 6-10$
is that $m_{S^0} \sim 900$\MeVcs; this is not at present excluded by particle
physics. Such an \OSO could be present in neutron stars, with hyperon formation
serving as an intermediate stage. We calculate equilibrium compositions and
equation of state for high density matter with the \OSO, and find that for a
wide range of parameters the properties of neutron stars with the \OSO are
consistent with observations. In particular, the maximum mass of a nonrotating
star is $1.7-1.8 M_\odot$, and the presence of the \OSO is helpful in
reconciling observed cooling rates with hyperon formation.


title:
Planck LFI: Comparison Between Galaxy Straylight Contamination and other
  Systematic Effects

abstract:
  The straylight contamination due to the Galactic emission (GSC, Galaxy
Straylight Contamination) entering at large angles from the antenna centre
direction may be one of the most critical sources of systematic effects in
observations of the cosmic microwave background (CMB) anisotropies by future
satellite missions like {\sc Planck} and MAP. We describe here different
methods to evaluate the impact of this effect and compare it with other
systematics of instrumental and astrophysical origin. The contributions within
few degrees from the beam centre dominate the GSC near the Galaxy plane. The
antenna sidelobes at intermediate and large angles from the beam centre
dominate the GSC at medium and high Galactic latitudes. We find a GSC peak at
$\sim 15\mu$K and a GSC angular power spectrum above that of the white noise
for multipoles $\ell \lsim 10$ albeit smaller than that of CMB anisotropies by
a factor larger than $\sim 10$. Although the GSC is largest at low Galactic
latitudes, the contamination produced by far pattern features at medium and
high Galactic latitudes, peaking at $\sim 4\mu$K, has to be carefully
investigated, because the combination of low amplitude of Galaxy emission in
those regions with the extremely good nominal {\sc Planck} sensitivity
naturally makes high Galactic latitude areas the targets for unprecedentedly
precise estimation of cosmological CMB anisotropy.


title:
The use of the NEXTGEN model atmospheres for cool giants in a light
  curve synthesis code

abstract:
  We have written a light curve synthesis code that makes direct use of model
atmosphere specific intensities, in particular the NEXTGEN model atmosphere
grid for cool giants (T_eff <= 6800 K and log(g) <= 3.5, Hauschildt et al.
1999). We point out that these models (computed using spherical geometry)
predict a limb darkening behaviour that deviates significantly from a simple
linear or two-parameter law (there is less intensity at the limb of the star).
The presence of a significantly nonlinear limb darkening law has two main
consequences. First, the ellipsoidal light curve computed for a tidally
distorted giant using the NEXTGEN intensities is in general different from the
light curve computed using the same geometry but with the black body
approximation and a one- or two-parameter limb darkening law. In most cases the
light curves computed with the NEXTGEN intensities have deeper minima than
their black body counterparts. Thus the light curve solutions for binaries with
a giant component obtained with models with near linear limb darkening (either
black body or plane-parallel model atmosphere intensities) are biased.
Observations over a wide wavelength range (i.e. both the optical and infrared)
are particularly useful in discriminating between models with nearly linear
limb darkening and the NEXTGEN models. Second, we show that rotational
broadening kernels for Roche lobe filling (or nearly filling) giants can be
significantly different from analytic kernels due to a combination of the
nonspherical shape of the star and the radical departure from a simple limb
darkening law. As a result, geometrical information inferred from V_rot*sin(i)
measurements of cool giants in binary systems are likewise biased.


title:
Euler, Hipparcos and the five dwarfs : Reconstructing star formation
  histories in the Local Group

abstract:
  The unprecedented quality of recent colour-magnitude diagrams of resolved
stellar populations in nearby galaxies requires state-of-the-art techniques to
infer the star formation histories which gave rise to the observed
distributions. We have developed a maximum likelihood technique, which coupled
to a variational calculus allows us to make a robust, non-parametric
reconstruction of the evolution of the star formation rate. A full Bayesian
analysis is also applied to assess whether the best solutions found are also
good fits to the data. Applying this new method to WFPC2 observations of five
dSph galaxies of the Local Group, we find a wide variety of star formation
histories, with no particular epoch being dominant. In the case of the solar
neighbourhood observed by Hipparcos we infer, with an unprecedented resolution
of 50 Myr, its star formation history over the past 3 Gyr. The surprising
regularity of star formation episodes separated by some 0.5 Gyr could be
interpreted as the result of interactions with two spiral arms or the Galactic
bar. These bursts possibly trigger the formation of massive star clusters which
slowly dissolve into the galactic field.


title: The minor axis outflow of NGC 2146

abstract:
  X-ray and optical observations have shown that the supernova explosions and
stellar winds of the starburst in NGC 2146 produce an outflow of hot material
along the minor axis. This outflow is expected to have a more or less conical
shape, on either side of the galactic plane, and cone walls of cooler material
where the outflow is in shock contact with halo gas. We attempt to determine
the geometry (diameter at the base and opening angle) and the physical
parameters (velocity and density) of the material in the cone walls from the
optical emission line and radio observations presented here, and from published
X-ray, radio, and optical observations. We compare the outflow of NGC 2146 with
the outflow of M 82.


title:
Forces on Dust Grains Exposed to Anisotropic Interstellar Radiation
  Fields

abstract:
  Grains exposed to anisotropic radiation fields are subjected to forces due to
the asymmetric photon-stimulated ejection of particles. These forces act in
addition to the ``radiation pressure'' due to absorption and scattering. Here
we model the forces due to photoelectron emission and the photodesorption of
adatoms. The ``photoelectric'' force depends on the ambient conditions relevant
to grain charging. We find that it is comparable to the radiation pressure when
the grain potential is relatively low and the radiation spectrum is relatively
hard. The calculation of the ``photodesorption'' force is highly uncertain,
since the surface physics and chemsitry of grain materials are poorly
understood at present. For our simple yet plausible model, the photodesorption
force dominates the radiation pressure for grains with size >~0.1 micron
exposed to starlight from OB stars. We find that the anisotropy of the
interstellar radiation field is ~10% in the visible and ultraviolet. We
estimate size-dependent drift speeds for grains in the cold and warm neutral
media and find that micron-sized grains could potentially be moved across a
diffuse cloud during its lifetime.


title: The Assembly and Evolution of Spiral Disks

abstract:
  We explore how the growth rate of spiral disks can be measured via analyses
of the scatter in the Tully-Fisher (TF) relation of local and intermediate
redshift galaxies. As an initial step, we show it is possible to construct a
low-dispersion TF relation for nearly face-on, nearby spirals. We find these
spiral disks are non-circular, (a mean ellipticity of 6%), which accounts for
about 0.1 mag of the intrinsic scatter in the nearby TF relation of even the
most ``normal'' looking spirals. If this ellipticity is induced by matter
accretion, we expect to find greater disk ellipticity or disturbance in the
past. We find evidence that more extreme outliers of the intermediate-redshift
TF relation are more morphologically and kinematically disturbed. Whether this
effect reflects a redshift trend or selection bias of local samples needs to be
addressed.


title: N-band Imaging of Seyfert Nuclei and the MIR-X-ray correlation

abstract:
  We present new mid-infrared (N-band) images of a sample of eight nearby
Seyfert galaxies. In all of our targets, we detect a central unresolved source,
which in some cases has been identified for the first time. In particular, we
have detected the mid-infrared emission from the active nucleus of NGC 4945,
which previously remained undetected at any wavelength but hard X-rays. We also
detect circumnuclear extended emission in the Circinus galaxy along its major
axis, and find marginal evidence for extended circumnuclear emission in NGC
3281.
  The high spatial resolution (1.7") of our data allows us to separate the flux
of the nuclear point sources from the extended circumnuclear starburst (if
present). We complement our sample with literature data for a number of
non-active starburst galaxies, and relate the nuclear N-band flux to published
hard (2-10 kev) X-ray fluxes. We find tight and well-separated correlations
between nuclear N-band flux and X-ray flux for both Seyfert and starburst
nuclei which span over 3 orders of magnitude in luminosity. We demonstrate that
these correlations can be used as a powerful classification tool for galactic
nuclei.
  For example, we find strong evidence against NGC 1808 currently harbouring an
active Seyfert nucleus based on its position in the mid-infrared-X-ray diagram.
On the other hand, we confirm that NGC 4945 is in fact a Seyfert 2 galaxy.


title:
Convective proton and He3 ingestion into helium burning: Nucleosynthesis
  during a post-AGB thermal pulse

abstract:
  A thermal pulse during the post-AGB phase of stellar evolution may lead to a
unique mode of light element nucleosynthesis. The stage is set by the ingestion
of the unprocessed envelope material into the hot He-flash convection zone
below. If the temperature is sufficiently large and the C12 abundance high
enough (e.g. T_8 > 0.8, X(C12) ~ 0.4 and X(H) ~ 1E-3) protons react faster with
C12 and form C13 than destroying Be7 The latter forms by alpha-capture of He3
after an initial reduction of the He3 abundance to about 3E-5 X(He4) by the ppI
reaction He3(He3,2p)He4 (for T_8 ~ 1). All He3 is burned within minutes to
weeks depending on the temperature. Be7 is now present at about the previously
mentioned level of He3. Its further fate is determined by the reactions
Be7(e-,nu)Li7 and the alpha-capture reactions of Be7 and Li7. These captures
lead to the production of Be11 which in turn is finally destroyed by
Be11(alpha,n)N14$. The details of this mechanism of light element production in
real stars is expected to be fairly dependent on the description of mixing.


title: Standard Cosmic Ray Energetics and Light Element Production

abstract:
  The recent observations of Be and B in metal poor stars has led to a
reassessment of the origin of the light elements in the early Galaxy. At low it
is metallicity ([O/H] < -1.75), it is necessary to introduce a production
mechanism which is independent of the interstellar metallicity (primary). At
higher metallicities, existing data might indicate that secondary production is
dominant. In this paper, we focus on the secondary process, related to the
standard Galactic cosmic rays, and we examine the cosmic ray energy
requirements for both present and past epochs. We find the power input to
maintain the present-day Galactic cosmic ray flux is about 1.5e41 erg/s = 5e50
erg/century. This implies that, if supernovae are the sites of cosmic ray
acceleration, the fraction of explosion energy going to accelerated particles
is about 30%, a value which we obtain consistently both from considering the
present cosmic ray flux and confinement and from the present 9Be and 6Li
abundances. Using the abundances of 9Be (and 6Li) in metal-poor halo stars, we
extend the analysis to show the effect of the interstellar gas mass on the
standard galactic cosmic ray energetic constraints on models of Li, Be, and B
evolution. The efficiency of the beryllium production per erg may be enhanced
in the past by a factor of about 10; thus the energetic requirement by itself
cannot be used to rule out a secondary origin of light elements. Only a clear
and undisputable observational determination of the O-Fe relation in the halo
will discriminate between the two processes. (abridged)


title: The Expansion of the X-ray Remnant of Tycho's Supernova (SN1572)

abstract:
  Two ROSAT high resolution images separated by nearly five years have been
used to determine the expansion of the X-ray remnant of Tycho's supernova
(SN1572). The current expansion rate averaged over the entire remnant is
$0.124\pm0.011$ % per yr, which, when combined with the known age of the
remnant, determines the mean expansion parameter $m$, defined as $R\propto
t^m$, to be $0.54\pm0.05$. There are significant radial and azimuthal
variations of the X-ray expansion rate. The radial expansion in particular
shows highly significant evidence for the more rapid expansion of the forward
blast wave as compared to the reverse-shocked ejecta, an effect that has not
been seen previously. The expansion parameter varies from $m=0.71\pm0.06$ at
the outermost edge of Tycho's supernova remnant (SNR) to a value of
$m=0.34\pm0.10$ on the inside edge of the bright rim of emission. These values
are consistent with the rates expected for a remnant with constant density
ejecta evolving into a uniform interstellar medium during the ejecta-dominated
phase of evolution. Based on the size, age, and X-ray expansion rates, I obtain
values for the explosion energy and ambient density of $E\approx 4-5\times
10^{50} \rm ergs$ and $n_0 \approx 0.35-0.45 \rm cm^{-3}$. As is also the case
for Cas A and Kepler's SNR, the X-ray expansion rate of Tycho's SNR appears to
be significantly higher than the radio expansion rate. In the case of Tycho's
SNR, however, the difference between radio and X-ray expansion rates is clearly
associated with the motion of the forward shock.


title: On the Kinematics of GRB980425 and its association with SN1998bw

abstract:
  In this paper I put forward a model in which GRB980425 is both associated
with SN1998bw and is also a standard canonical (long; ~seconds) gamma-ray
burst. Herein it is argued that if gamma-ray bursts are relativistic jets with
the fastest moving material at the core, then the range of observed jet
inclinations to the line-of-sight produces a range in the observed properties
of GRBs, i.e. the lag-luminosity relationship. In particular, if the jet
inclination is high enough, the observed emitter will move slowly enough to
render relativistic beaming ineffective, thus distinguishing the jet from
apparent isotropic emission. Thus we expect a break in the lag-luminosity
relationship. I propose that GRB980425 defines that break. The position of this
break gives important physical parameters such as the Lorentz factor
(\gamma_max ~ 1000), the jet opening angle (~1 degree), and thus the beaming
fraction (~10^-4). Estimates of burst rates are consistent with observation. If
correct, this model is evidence in favor of the collapsar mode as the
progenitor of cosmological, long gamma-ray bursts.


title: Liquid Xenon for a Very Sensitive WIMP Search

abstract:
  We describe the research and development efforts of the UCLA Torino group to
develop a large, powerful, discriminating WIMP detector. We also discuss the
possible amplifications of the WIMP signal. The first real detector, ZEPLIN II,
is being prepared for the UKDMC Boulby Mine Laboratory.


title: ASCA Observation of an X-Ray-Luminous Active Nucleus in Markarian 231

abstract:
  We have obtained a moderately long (100 kilosecond) ASCA observation of the
Seyfert 1 galaxy Markarian 231, the most luminous of the local ultraluminous
infrared galaxy (ULIRG) population. In the best-fitting model we do not see the
X-ray source directly; the spectrum consists of a scattered power-law component
and a reflection component, both of which have been absorbed by a column N_H
\approx 3 X 10^(22)/cm^2. About 3/4 of the observed hard X-rays arise from the
scattered component, reducing the equivalent width of the iron K alpha line.
The implied ratio of 1-10 keV X-ray luminosity to bolometric luminosity,
L_x/L_bol \sim 2%, is typical of Sy 1 galaxies and radio-quiet QSOs of
comparable bolometric luminosities, and indicates that the bolometric
luminosity is dominated by the AGN. Our estimate of the X-ray luminosity also
moves Mrk 231 in line with the correlations found for AGN with extremely strong
Fe II emission. A second source separated by about 2 arcminutes is also clearly
detected, and contributes about 25% of the total flux.


title: Full-sky correlations of peaks in the microwave background

abstract:
  We compute precise predictions for the two-point correlation function of
local maxima (or minima) in the temperature of the microwave background, under
the assumption that it is a random gaussian field. For a given power spectrum
and peak threshold there are no adjustable parameters, and since this analysis
does not make the small-angle approximation of Heavens & Sheth (1999), it is
essentially complete. We find oscillatory features which are absent in the
temperature autocorrelation function, and we also find that the small-angle
approximation to the peak-peak correlation function is accurate to better than
0.01 on all scales. These high-precision predictions can form the basis of a
sensitive test of the gaussian hypothesis with upcoming all-sky microwave
background experiments MAP and Planck, affording a thorough test of the
inflationary theory of the early Universe. To illustrate the effectiveness of
the technique, we apply it to simulated maps of the microwave sky arising from
the cosmic string model of structure formation, and compare with the bispectrum
as a non-gaussian discriminant. We also show how peak statistics can be a
valuable tool in assessing and statistically removing contamination of the map
by foreground point sources.


title: NICMOS Observations of Low-Redshift Quasar Host Galaxies

abstract:
  We have obtained Near-Infrared Camera and Multi-Object Spectrometer images of
16 radio quiet quasars observed as part of a project to investigate the
``luminosity/host-mass limit.'' The limit results were presented in McLeod,
Rieke, & Storrie-Lombardi (1999). In this paper, we present the images
themselves, along with 1- and 2-dimensional analyses of the host galaxy
properties. We find that our model-independent 1D technique is reliable for use
on ground-based data at low redshifts; that many radio-quiet quasars live in
deVaucouleurs-law hosts, although some of the techniques used to determine host
type are questionable; that complex structure is found in many of the hosts,
but that there are some hosts that are very smooth and symmetric; and that the
nuclei radiate at ~2-20% of the Eddington rate based on the assumption that all
galaxies have central black holes with a constant mass fraction of 0.6%.
Despite targeting hard-to-resolve hosts, we have failed to find any that imply
super-Eddington accretion rates.


title:
Molecular Gas and the Modest Star Formation Efficiency in the
  ``Antennae'' Galaxies: Arp~244=NGC 4038/39

abstract:
  (abridged) We report here a factor of 5.7 higher total CO flux in Arp~244
(the ``Antennae'' galaxies) than that previously accepted in the literature
(thus a total molecular gas mass of 1.5x10$^{10}$ Msun), based on our fully
sampled CO(1-0) observations at the NRAO 12m telescope. Our observations show
that the molecular gas peaks predominately in the disk-disk overlap region
between the nuclei, similar to the far-infrared (FIR) and mid-infrared (MIR)
emission. The bulk of the molecular gas is forming into stars with a normal
star formation efficiency (SFE) L_{IR}/M(H_2) \approx 4.2 Lsun/Msun, same as
that of giant molecular clouds in the Galactic disk. Additional supportive
evidence is the extremely low fraction of the dense molecular gas in Arp~244,
revealed by our detections of the HCN(1-0) emission.
  We estimate the local SFE indicated by the ratio map of the radio continuum
to CO(1-0) emission. Remarkably, the local SFE stays roughly same over the bulk
of the molecular gas distribution. Only some localized regions show the highest
radio-to-CO ratios that we have identified as the sites of the most intense
starbursts with SFE >~ 20 Lsun/Msun. These starburst regions are confined
exclusively in the dusty patches seen in the HST images near the CO and FIR
peaks where presumably the violent starbursts are heavily obscured.
Nevertheless, recent large-scale star formation is going on throughout the
system, yet the measured level is more suggestive of a moderate starburst (SFE
>~ 10 Lsun/Msun) or a weak to normal star formation (SFE ~ 4 Lsun/Msun). The
overall starburst from the bulk of the molecular gas is yet to be initiated as
most of the gas further condenses into kpc scale in the final coalescence.


title:
Diffraction Limited Imaging of High Redshift Galaxies with Adaptive
  Optics

abstract:
  The major cornerstone of future ground-based astronomy is imaging and
spectroscopy at the diffraction limit using adaptive optics. To exploit the
potential of current AO systems, we have begun a survey around bright stars to
study intermediate redshift galaxies at high resolution. Using ALFA to reach
the diffraction limit of the 3.5-m telescope at Calar Alto allows us to study
the structure of distant galaxies in the near-infrared at scales of 100-150 pc
for z=0.05 and at scales 1.0-1.5 kpc at z=1. In this contribution we present
the initial results of this project, which hint at the exciting prospects
possible with the resolution and sensitivity available using an AO camera on
the 8-m class VLT.


title:
Spiral and irregular galaxies in the Hubble Deep Field North -
  Comparison with early types and implications for the global SFR density

abstract:
  We analyze a morphologically-selected complete sample of 52 late-type (spiral
and irregular) galaxies in the Hubble Deep Field North with total K-magnitudes
brighter than K=20.47. This sample exploits in particular the ultimate imaging
quality achieved by HST in this field, allowing us to clearly disentangle the
galaxy morphologies, based on accurate profiles of the surface brightness
distributions. Our purpose was to investigate systematic differences between
the two classes, as for colours, redshift distributions and ages of the
dominant stellar populations. This sample appears to miss significantly
galaxies above z=1.4 (in a similar way as an early-type galaxy sample
previously studied by us), a fact which may be explained as a global decline of
the underlying mass function for galaxies at these high redshifts. Differences
between early and late-types are apparent -particularly in the colour
distributions and the evolutionary star-formation (SF) rates per unit volume-,
although the complication in spectro-photometric modelling introduced by
dust-extinction in the gas-rich systems prevents us to reach conclusive results
on the single sources. However, we find that an integrated quantity like the
comoving star-formation rate density (SFR(t)) as a function of redshift is much
less affected by these uncertainties: by combining this with the previously
studied early-type galaxy sample, we find a shallower dependence of SFR(t) on z
between z=0.2 and z=1.5 than found by Lilly et al. (1995).


title:
Envelope tomography of long-period variable stars: I. The Schwarzschild
  mechanism and the Balmer emission lines

abstract:
  This paper is the first one in a series devoted to the study of the dynamics
of the atmospheres of long-period variable stars. Results from a two-month-long
monitoring of the Mira variables RT Cyg and X Oph around maximum light with the
ELODIE spectrograph at the Haute-Provence Observatory are presented. The
monitoring covers phases 0.80 to 1.16 for RT Cyg and phases 0.83 to 1.04 for X
Oph. The cross-correlation profile of the spectrum of RT Cyg with a K0 III mask
confirms that the absorption lines of RT Cyg in the optical domain appear
double around maximum light. No line doubling was found in the optical spectrum
of X Oph around maximum light, indicating that this feature is not common to
all long-period variables. This paper also presents the application to RT Cyg
of a new tomographic technique deriving the velocity field across the
atmosphere by cross-correlating the optical spectrum with numerical masks
constructed from synthetic spectra and probing layers of increasing depths.
This technique reveals that both the temporal evolution of the line doubling,
and its variation with depth in the atmosphere of RT Cyg, are consistent with
the ``Schwarzschild scenario''. This scenario relates the temporal evolution of
the red and blue peaks of the double absorption lines to the progression of a
shock wave in the atmosphere. The temporal evolution of the Balmer Halpha, H
beta, Hgamma and Hdelta emission lines around maximum light is also presented
for RT Cyg and X Oph. The velocity variations of Halpha and of the absorption
lines are discussed in the framework of two competing models for the formation
of Balmer emission lines in long-period variable stars.


title:
Comparison of Parallaxes from Eclipsing Binaries Method with Hipparcos
  Parallaxes

abstract:
  The parallaxes determined by Lacy (1979) by means of eclipsing binaries
method are compared with the Hipparcos parallaxes for 19 systems. The residual
scatter of the distance moduli inferred from eclipsing binaries method - after
allowing for known errors as given by Lacy and Hipparcos - is equal to 0.18
mag. It decreases to 0.08 mag when obviously not fitting semi-detached systems
and systems with chromospheric activity of components are removed from the
sample.


title: Biconical Outflow in the Seyfert Galaxy NGC 2992

abstract:
  We report on a detailed kinematic study of the galactic-scale outflow in the
Seyfert galaxy NGC 2992. The TAURUS-2 Imaging Fabry-Perot Interferometer was
used on the Anglo-Australian 3.9-m telescope to derive the two-dimensional
velocity field of the Halpha-emitting gas over the central arcminute of NGC
2992. The complete two-dimensional coverage of the data combined with simple
kinematic models of rotating axisymmetric disks allows us to differentiate the
outflowing material from the line-emitting material associated with the
galactic disk. The kinematics of the disk component out to R = 3.0 kpc are well
modeled by pure circular rotation. The outflow component is distributed into
two wide cones with opening angle of 125 -- 135 degrees and extending 2.8 kpc
(18") on both sides of the nucleus at nearly right angles to the disk kinematic
major axis. The outflow on the SE side of the nucleus is made of two distinct
kinematic components interpreted as the front and back walls of a cone. The
azimuthal velocity gradient in the back-wall component reflects residual
rotational motion which indicates either that the outflowing material was
lifted from the disk or that the underlying galactic disk is contributing
slightly to this component. A single outflow component is detected in the NW
cone. The most likely energy source for this outflow is a hot bipolar thermal
wind powered on sub-kpc scale by the AGN and diverted along the galaxy minor
axis by the pressure gradient of the ISM in the host galaxy. The data are not
consistent with a starburst-driven wind or a collimated outflow powered by
radio jets. (abridged)


title: Blank field submm sources, failed stars, and the dark matter

abstract:
  I discuss the possibility that a significant fraction (possibly a third) of
the faint SCUBA sources are not in fact high redshift galaxies, but actually
local cold dark dusty gas clouds emitting only in the submm, with a temperature
around 7K. I show that the observational constraints on such a population -
dynamical limits on missing matter, the FIR-mm background, and the absence of
gross high-latitude extinction features - constrains the mass of such objects
to be in the range 0.1 - 10 Jupiter masses. The characteristics deduced are
closely similar to those of the objects proposed by Walker and Wardle (1998) to
explain halo dark matter. However, such objects, if they explain a large
fraction of the SCUBA sources, cannot extend through the halo without greatly
exceeding the FIR-mm background. Instead, I deduce the characteristic distance
of the SCUBA sources to be around 100 pc, consistent with being drawn from a
disk population with a scale height of few hundred parsecs. Regardless of the
dark matter problem, the possible existence of such compact sub-stellar but
non-degenerate objects is intriguing. They may be seen as "failed stars",
representing an alternative end-point to brown dwarfs. It is possible that they
greatly outnumber both stars and brown dwarfs. The nearest such object could be
a fraction of a parsec away. Several relatively simple observations could
critically test this hypothesis.


title: Distance to the RR Lyrae Star V716 Monocerotis

abstract:
  We present high quality BVRI CCD photometry of the variable star V716
Monocerotis (= NSV 03775). We confirm it to be an RR Lyrae star of variability
type ab (i.e. a fundamental mode pulsator), and determine its metallicity
([Fe/H] = -1.33 +/- 0.25), luminosity (Mv = 0.80 +/- 0.06), and foreground
reddening (E(B-V) = 0.05-0.17) from the Fourier components of its light curve.
These parameters indicate a distance of 4.1 +/- 0.3 kpc, placing V716 Mon near
the plane of the Galaxy well outside the solar circle. This research was
conducted as part of the 1999 Research Experiences for Undergraduates (REU) and
Practicas de Investigacion en Astronomia (PIA) Programs at Cerro Tololo
Inter-American Observatory (CTIO).


title: On the streaming motions of haloes and galaxies

abstract:
  A simple model of how objects of different masses stream towards each other
as they cluster gravitationally is described. The model shows how the mean
streaming velocity of dark matter particles is related to the motions of the
parent dark matter haloes. It also provides a reasonably accurate description
of how the pairwise velocity dispersion of dark matter particles differs from
that of the parent haloes. The analysis is then extended to describe the
streaming motions of galaxies. This shows explicitly that the streaming motions
measured in a given galaxy sample depend on how the sample was selected, and
shows how to account for this dependence on sample selection. In addition,we
show that the pairwise dispersion should also depend on sample type. Our model
predicts that, on small scales, redshift space distortions should affect red
galaxies more strongly than blue.


title:
Aromatic Hydrocarbons, Diamonds, and Fullerenes in Interstellar Space:
  Puzzles to be Solved by Laboratory and Theoretical Astrochemistry

abstract:
  New research is presented, and previous research is reviewed, on the emission
and absorption of interstellar aromatic hydrocarbons. Emission from aromatic
hydrocarbons dominate the mid-infrared emission of many galaxies, including our
own Milky Way galaxy. Only recently have aromatic hydrocarbons been observed in
absorption in the interstellar medium, along lines of sight with high column
densities of interstellar gas and dust. Much work on interstellar aromatics has
been done, with astronomical observations and laboratory and theoretical
astrochemistry. In many cases the predictions of laboratory and theoretical
work are confirmed by astronomical observations, but in other cases clear
discrepancies exist which provide problems to be solved by a combination of
astronomical observations, laboratory studies, and theoretical studies. The
emphasis of this paper will be on current outstanding puzzles concerning
aromatic hydrocarbons which require further laboratory and theoretical
astrochemistry to resolve. This paper will also touch on related topics where
laboratory and theoretical astrochemistry studies are needed to explain
astrophysical observations, such as a possible absorption feature due to
interstellar "diamonds" and the search for fullerenes in space.


title: Complex Phase Lag Behaviors of the 0.5 - 10 Hz QPOs in GRS 1915+105

abstract:
  Through studying the hard lags between the soft (3.3 - 5.8 keV) and hard
(13.0 - 41.0 keV) photons of the 0.5 - 10 Hz QPOs in GRS 1915+105, we have
classified them into three types: 0.5 - 2.0 Hz QPOs, 2.0 - 4.5 Hz QPOs, and 4.5
- 10 Hz QPOs. They are closely related to different temporal and spectral
states. The first type of QPOs (0.5 - 2 Hz) have positive hard lags at both the
QPO fundamental and first harmonic frequencies. These QPOs were observed in the
quiescent soft state. The second type of QPOs (2 - 4.5 Hz), which were also
detected in the quiescent soft state, have opposite signs of hard lags at the
QPO fundamental and first harmonic frequencies. The third type (4.5 - 10 Hz),
which showed up in medium soft quiescent/out-burst states, do not have
significant higher harmonic peaks. There is a smooth transition between these
three types of QPO behaviors. We did not detect 0.5 - 10 Hz QPOs in the very
soft state. We discuss some of the implications of these results.


title: Automatic Shell Detection in CGPS Data

abstract:
  A numerical code aiming at the automatic detection of spherical expanding HI
shells in radio data-cubes is presented. The following five shell parameters
are allowed to vary within a specified range: angular radius, expansion
velocity and three center coordinates (galactic coordinates l and b, and
systemic radial velocity V). We discuss several factors which can reduce the
sensitivity of the shell detection: the presence of noise (both instrumental
and "structural"), the fragmentation and asphericity of the shell and the
inhomogeneity of the background and/or foreground emission. The code is tested
on four objects: two HII regions and two early B stars. We use HI data from the
Canadian Galactic Plane Survey. In all four cases the evidence for an expanding
HI shell is found.