title:
Redshift-Distance Survey of Early-Type Galaxies: Circular Aperture
  Photometry

abstract:
  We present R-band CCD photometry for 1332 early-type galaxies, observed as
part of the ENEAR survey of peculiar motions using early-type galaxies in the
nearby Universe. Circular apertures are used to trace the surface brightness
profiles, which are then fit by a two-component bulge-disk model. From the fits
we obtain the structural parameters required to estimate galaxy distances using
the D_n-sigma and Fundamental Plane relations. We find that about 12% of the
galaxies are well represented by a pure r^{1/4} law while 87% are best fit by a
two component model. There are 356 repeated observations of 257 galaxies
obtained during different runs that are used to derive statistical corrections
and bring the data to a common system. We also use these repeated observations
to estimate our internal errors. The accuracy of our measurements are tested by
the comparison of 354 galaxies in common with other authors. Typical errors in
our measurements are 0.011 dex for log{D_n}, 0.064 dex for log{r_e}, 0.086 mag
arcsec^{-2} for <{mu_e}> and 0.09 for m_{R_C}, comparable to those estimated by
other authors. The photometric data reported here represent one of the largest
high-quality and uniform all-sky samples currently available for early-type
galaxies in the nearby universe, especially suitable for peculiar motion
studies.


title: The circumstellar envelope of the C-rich post-AGB star HD 56126

abstract:
  We present a detailed study of the circumstellar envelope of the
post-asymptotic giant branch ``21 micron object'' HD 56126. We build a detailed
dust radiative transfer model of the circumstellar envelope in order to derive
the dust composition and mass, and the mass-loss history of the star. To model
the emission of the dust we use amorphous carbon, hydrogenated amorphous
carbon, magnesium sulfide and titanium carbide. We present a detailed
parametrisation of the optical properties of hydrogenated amorphous carbon as a
function of H/C content. The mid-infrared imaging and spectroscopy is best
reproduced by a single dust shell from 1.2 to 2.6 arcsec radius around the
central star. This shell originates from a short period during which the
mass-loss rate exceeded 10^(-4) M_sun/yr. We find that the strength of the
``21'' micron feature poses a problem for the TiC identification. The low
abundance of Ti requires very high absorption cross-sections in the ultraviolet
and visible wavelength range to explain the strength of the feature. Other
nano-crystalline metal carbides should be considered as well. We find that
hydrogenated amorphous carbon in radiative equilibrium with the local radiation
field does not reach a high enough temperature to explain the strength of the
3.3-3.4 and 6-9 micron hydrocarbon features relative to the 11-17 micron
hydrocarbon features. We propose that the carriers of these hydrocarbon
features are not in radiative equilibrium but are transiently heated to high
temperature. We find that 2 per cent of the dust mass is required to explain
the strength of the ``30'' micron feature, which fits well within the measured
atmospheric abundance of Mg and S. This further strengthens the MgS
identification of the ``30'' micron feature.


title:
Core dissolution and the dynamics of massive stars in young stellar
  clusters

abstract:
  We investigate the dynamical effects of rapid gas expulsion from the core of
a young stellar cluster. The aims of this study are to determine 1) whether a
mass-segregated core survives the gas expulsion and 2) the probable location of
any massive stars that have escaped from the core. Feedback from massive stars
is expected to remove the gas from the core of the cluster first, as that is
where most massive stars are located. We find that gas expulsion has little
effect on the core for a core star formation efficiency, of greater than 50%.
For lower values of star formation efficiency down to 20%, a reduced core
survives containing the majority of the massive stars while some of them are
dispersed into the rest of the cluster. In fact we find that ejected stars
migrate from radial to tangential orbits due to stellar encounters once they
leave the core. Thus, the location of massive stars outside of the core does
not exclude their forming in the dense cluster core. Few massive stars are
expected to remain in the core for a star formation efficiency lower than 20%.


title: What Shapes the Luminosity Function of Galaxies?

abstract:
  We investigate the physical mechanisms that shape the luminosity function.
Beginning with the mass function of dark matter halos, we show how gas cooling,
photoionization, feedback, merging and thermal conduction affect the shape of
the luminosity function. We consider three processes whereby supernovae can
affect the forming galaxy: (1) reheating of disk gas to the halo temperature;
(2) expansion of the diffuse halo gas; (3) expulsion of cold disk gas from the
halo. While feedback of form (1) is able to flatten the faint end of the
luminosity function, this alone does not produce the sharp cut-off observed at
large luminosities. Feedback of form (2) is also unable to solve this problem.
The relative paucity of very bright galaxies can only be explained if cooling
in massive halos is strongly suppressed. Conduction is a promising mechanism,
but an uncomfortably high efficiency is required to suppress cooling to the
desired level. If, instead, superwinds are responsible for the lack of bright
galaxies, then the total energy budget required to obtain a good match to the
galaxy luminosity function greatly exceeds the energy available from supernova
explosions. The mechanism is only viable if the formation of central
supermassive black holes play a crucial role in limiting the amount of stars
that form in the host galaxy. (abridged)


title: Early Reionization by the First Galaxies

abstract:
  Large-scale polarization of the cosmic microwave background measured by the
WMAP satellite requires a mean optical depth to Thomson scattering, tau_e ~
0.17. The reionization of the universe must therefore have begun at relatively
high redshift. We have studied the reionization process using supercomputer
simulations of a large and representative region of a universe which has
cosmological parameters consistent with the WMAP results. Our simulations
follow both the radiative transfer of ionizing photons and the formation and
evolution of the galaxy population which produces them. A previously published
model with a standard stellar IMF, with a moderate photon escape fraction from
galaxies and with ionizing photon production as expected for zero metallicity
stars produces tau_e = 0.104, which is within 1.0 to 1.5-sigma of the ``best''
WMAP value. Values up to 0.16 can be produced by taking larger escape fractions
or a top heavy IMF. The data do not require a separate populations of
``miniquasars'' or of stars forming in objects with total masses below 10^9
M_sun. Reconciling such early reionization with the observed Gunn-Peterson
troughs in z>6 quasars may be challenging. Possible resolutions of this problem
are discussed.


title: PSR B1929+10 revisited in X-ray

abstract:
  We performed timing and spectral analysis for PSR B1929+10, one of the oldest
(about 10^7 years) of the ordinary pulsars detected in X-rays, using archival
ROSAT, ASCA and RXTE data. Pulsed emission was detected at a more than five
sigma level for combined ROSAT PSPC and unpublished HRI data. Our pulse profile
is in agreement with that obtained by Yancopoulos et al. (1994; ROSAT PSPC) but
now with better statistics. An investigation of the behaviour of the pulsed
signal as a function of energy, based on PSPC data, provides indications that
the pulsed fraction is changing with energy. The most important new result from
this work is derived from the spectral analysis=2E We found that the combined
ROSAT PSPC and ASCA GIS spectrum can satisfactorily be described by a power-law
as well as by a double black-body model but not by a single black-body model,
as was presented earlier by Yancopoulos et al. (1994; ROSAT) and Wang et al.
(1997; ASCA). Fitting the combined ROSAT/ASCA 0.1 - 10 keV spectrum by a
power-law model we obtain a photon index of 2.54 +/- 0.12 and a neutral
Hydrogen column density N_H towards the source of 9.8_{-1.0}^{+1.4} x 10^20
cm^-2. For a double black-body fit our results are: T_1 = 2.0_{-0.05}^{+0.05} x
10^6 K, T_2 = 6.9_{-0.35}^{+0.23} x 10^6 K, and N_H = 4.43_{-1.12}^{+2.08} x
10^20 cm^-2. In both cases the derived N_H value is higher than that adopted in
earlier works, but our result is consistent with the larger distance estimate
of 331 +/- 10 pc from new parallax measurements performed by Brisken et al.
(2002) and with the Hydrogen distribution measured in the direction of the
pulsar (Frisch & York, 1983). No significant pulsed signal is found in the RXTE
data.


title: Primordial Nucleosynthesis in the New Cosmology

abstract:
  Big bang nucleosynthesis (BBN) and the cosmic microwave background (CMB)
anisotropies independently predict the universal baryon density. Comparing
their predictions will provide a fundamental test on cosmology. Using BBN and
the CMB together, we will be able to constrain particle physics, and predict
the primordial, light element abundances. These future analyses hinge on new
experimental and observational data. New experimental data on nuclear cross
sections will help reduce theoretical uncertainties in BBN's predictions. New
observations of light element abundances will further sharpen BBN's probe of
the baryon density. Observations from the MAP and PLANCK satellites will
measure the fluctuations in the CMB to unprecedented accuracy, allowing the
precise determination of the baryon density. When combined, this data will
present us with the opportunity to perform precision cosmology.


title: The iron $K_\alpha$-line diagnostics of a rotational black hole metric

abstract:
  The original idea to show the spacetime geometry using few geodesics was
developed by Johnson and Ruffini (1974). We used this idea to interpret the
observational data for rotating BH's. We developed the imitation approach to
simulate a propagation of radiation near BH's. An important problem for this
approach is the diagnostics of a black hole metric using X-ray observational
data of the iron $K_\alpha$-line.
  Observations of Seyfert galaxies in X-ray region reveal the broad emissiion
lines in their spectra, which can arise in inner parts of accretion disks,
where the effects of General Relativity (GR) must be counted. A spectrum of a
solitary emission line (the $K_\alpha$-line of iron, for example) of a hot spot
in Kerr accretion disk is simulated, depending on the radial coordinate $r$ and
the angular momentum $a=J/M$ of a black hole, under the assumption of an
equatorial circular motion of a hot spot. Using results of numerical
simulations it is shown that the characteristic two-peak line profile with the
sharp edges arises at a large distance, (about $r \approx (3-10)r_g$). The
inner regions emit the line, which is observed with one maximum and extremely
broad red wing. High accuracy future spectral observations, being carried out,
could detect the angular momentum $a$ of the black hole. We analyzed the
different parameters of problems on the observable shape of this line and
discussed some possible kinds of these shapes. The total number of geodesics is
about $10^9$ (to simulate possible shapes of the $K_\alpha$-line), so the
number is great enough, especially in comparison with few geodesics in the
original paper by Johnson and Ruffini (1974).


title: Supermassive black holes in radio-loud AGN

abstract:
  In this review the correlations between host galaxy properties and black-hole
mass determined from nearby quiescent galaxies are briefly discussed, before
proceeding to investigate their application to active galactic nuclei (AGN).
The recent advances in estimating the black-hole masses of AGN are then
reviewed, followed by an examination of the connection between black-hole mass
and radio luminosity.


title: Weak Homology of Bright Elliptical Galaxies

abstract:
  Studies of the Fundamental Plane of early-type galaxies, from small to
intermediate redshifts, are often carried out under the guiding principle that
the Fundamental Plane reflects the existence of an underlying mass-luminosity
relation for such galaxies, in a scenario where elliptical galaxies are
homologous systems in dynamical equilibrium. Here I will re-examine the issue
of whether empirical evidence supports the view that significant systematic
deviations from strict homology occur in the structure and dynamics of bright
elliptical galaxies. In addition, I will discuss possible mechanisms of
dynamical evolution for these systems, in the light of some classical
thermodynamical arguments and of recent N-body simulations for stellar systems
under the influence of weak collisionality.


title: The Black Hole Masses of High-Redshift Quasars

abstract:
  A reliable method for estimating the black-hole masses of high-redshift
quasars would provide crucial new information for understanding the nature and
cosmological evolution of quasars. In this proceedings we summarize the results
of our recent paper (McLure & Jarvis 2002) which provides a virial black-hole
mass estimator based on rest-frame UV observables, thereby allowing reliable
black-hole mass estimates to be obtained out to redshifts of $z\sim2.5$ from
optical spectra alone.


title:
The luminosity function of the Large Magellanic Cloud globular cluster
  NGC 1866

abstract:
  We present {\it Hubble Space Telescope} {\it V,I} photometry of the central
region of the LMC cluster NGC 1866, reaching magnitudes as faint as V=27 mag.
We find evidence that the cluster luminosity function shows a strong dependence
on the distance from the cluster center, with a clear deficiency of low
luminosity stars in the inner region. We discuss a {\it global} cluster
luminosity function as obtained from stars in all the investigated region,
which appears in impressive agreement with the prediction from a Salpeter mass
distribution. We also revisit the use of NGC 1866 as a probe for determining
the efficiency of core overshooting, and conclude that a definitive answer to
this question is not possible from this cluster.


title:
Electron capture rates on nuclei and implications for stellar core
  collapse

abstract:
  Supernova simulations to date have assumed that during core collapse electron
captures occur dominantly on free protons, while captures on heavy nuclei are
Pauli-blocked and are ignored. We have calculated rates for electron capture on
nuclei with mass numbers A=65-112 for the temperatures and densities
appropriate for core collapse. We find that these rates are large enough so
that, in contrast to previous assumptions, electron capture on nuclei dominates
over capture on free protons. This leads to significant changes in core
collapse simulations.


title: Does Transparent Hidden Matter Generate Optical Scintillation?

abstract:
  Stars twinkle because their light goes through the atmosphere. The same
phenomenon is expected when the light of extra-galactic stars goes through a
Galactic -- disk or halo -- refractive medium. Because of the large distances
involved here, the length and time scales of the optical intensity fluctuations
resulting from the wave distortions are accessible to the current technology.
In this paper, we discuss the different possible scintillation regimes and we
focus on the so-called strong diffractive regime that is likely to produce
large intensity contrasts. The critical relationship between the source angular
size and the intensity contrast in optical wavelengths is also discussed in
detail. We propose to monitor small extra-galactic stars every $\sim 10
\mathrm{s}$ to search for intensity scintillation produced by molecular
hydrogen clouds. We discuss means to discriminate such hidden matter signal
from the foreground effects on light propagation. Appropriate observation of
the scintillation process described here should allow one to detect column
density stochastic variations in Galactic molecular clouds of order of $\sim
3\times 10^{-5} \mathrm{g/cm^2}$, that is $10^{19} \mathrm{molecules/cm^2}$ per
$\sim 10 000 \mathrm{km}$ transverse distance.


title:
Dark matter distribution in the Coma cluster from galaxy kinematics:
  breaking the mass-anisotropy degeneracy

abstract:
  We study velocity moments of elliptical galaxies in the Coma cluster using
Jeans equations. The dark matter distribution in the cluster is modelled by a
generalised formula based upon the results of cosmological N-body simulations.
Its inner slope (cuspy or flat), concentration, and mass within the virial
radius are kept as free parameters, as well as the velocity anisotropy, assumed
independent of position. We show that the study of line-of-sight velocity
dispersion alone does not allow to constrain the parameters. By a joint
analysis of the observed profiles of velocity dispersion and kurtosis we are
able to break the degeneracy between the mass distribution and velocity
anisotropy. We determine the dark matter distribution at radial distances
larger than 3% of the virial radius and we find that the galaxy orbits are
close to isotropic. Due to limited resolution, different inner slopes are found
to be consistent with the data and we observe a strong degeneracy between the
inner slope $\alpha$ and concentration $c$: the best-fitting profiles have the
two parameters related with $c=19 - 9.6 \alpha$. Our best-fitting NFW profile
has concentration $c=9$, which is 50% higher than standard values found in
cosmological simulations for objects of similar mass. The total mass within the
virial radius of $2.9 h_{70}^{-1}$ Mpc is $1.4 \times 10^{15} h_{70}^{-1}
M_{\sun}$ (with 30% accuracy), 85% of which is dark. At this distance from the
cluster centre, the mass-to-light ratio in the blue band is $351 h_{70}$ solar
units. The total mass within the virial radius leads to estimates of the
density parameter of the Universe, assuming that clusters trace the
mass-to-light ratio and baryonic fraction of the Universe, with $\Omega_0=0.29
\pm 0.1$.


title:
The Measurement of the Light Deflection from Jupiter: Theoretical
  Interpretation

abstract:
  Equations of light, propagating from quasar to observer on earth, are
integrated in the time-dependent gravitational field of the solar system by
making use of either retarded or advanced solutions of the Einstein field
equations. This technique allows to separate explicitly the effects associated
with the propagation of gravity from those associated with light in the
integral expression for the relativistic time delay of light. We prove that the
relativistic correction to the Shapiro time delay discovered by Kopeikin (ApJ,
556, L1, 2001) changes sign if one retains direction of the light propagation
but replaces retarded with advanced solution of the gravitational field
equations. Hence, this correction is due to the propagation of gravity and
allows to measure its speed. Relativistic VLBI experiment conducted by Fomalont
and Kopeikin in September 2002 proves that the propagation of gravitational
field is characterized by the retarded potentials.


title: Parametric Dwarf Spheroidal Tidal Interaction

abstract:
  The time dependent tidal interaction of the Local Group Dwarf Spheroidal (dS)
Galaxies with the Milky Way (MW) can fundamentally affect their dynamical
properties. The model developed here extends earlier numerical descriptions of
dS-MW tidal interactions. We explore the dynamical evolution of dS systems in
circular or elliptical MW orbits in the framework of a parametric oscillator.
An analytic model is developed and compared with more general numerical
solutions and N-body simulation experiments.


title: Stability of Triple Star Systems with Highly Inclined Orbits

abstract:
  It is well established that certain detached eclipsing binary stars exhibit
apsidal motions whose value is in disagreement with with calculated deviations
from Keplerian motion based on tidal effects and the general theory of
relativity. Although many theoretical senarios have been demonstrated to bring
calculations into line with observations, all have seemed unlikely for various
reasons. In particular, it has been established that the hypothesis of a third
star in an orbit almost perpendicular to the orbital plane of the close binary
system can explain the anomalous motion in at least some cases. The stability
of triple star systems with highly inclined orbits has been in doubt, however.
  We have found conditions which allow the long term stability of such systems
so that the third body hypothesis now seems a likely resolution of the apsidal
motion problem. We apply our stability criteria to the cases of AS Cam and DI
Her and recommend observations at the new Keck interferometer which should be
able to directly observe the third bodies in these systems.


title: Constraints on the cosmic neutrino background

abstract:
  The radiative component of the Universe has a characteristic impact on both
large scale structure (LSS) and the cosmic microwave background radiation
(CMB). We use the recent WMAP data, together with previous CBI data and 2dF
matter power spectrum, to constrain the effective number of neutrino species
$N_{eff}$ in a general Cosmology. We find that $N_{eff}=4.31$ with a 95 per
cent C.L. $1.6 \le N_{eff} \le 7.1$. If we include the $H_0$ prior from the HST
project we find the best fit $N_{eff}=4.08$ and $1.90 \le N_{eff} \le 6.62$ for
95 per cent C.L. The curvature we derive is still consistent with flat, but
assuming a flat Universe from the beginning implies a bias toward lower
$N_{eff}$, as well as artificially smaller error bars. Adding the Supernovae
constraint doesn't improve the result. We analyze and discuss the degeneracies
with other parameters, and point out that probes of the matter power spectrum
on smaller scales, accurate independent $\sigma_8$ measurements, together with
better independent measurement of $H_0$ would help in breaking the
degeneracies.


title:
Subaru Deep Survey. IV. Discovery of a Large-Scale Structure at Redshift
  \simeq 5

abstract:
  We report the discovery of a large-scale structure of Lyman alpha emitters
(LAEs) at z=4.86 based on wide-field imaging with the prime-focus camera
(Suprime-Cam) on the Subaru telescope. We observed a 25' x 45' area of the
Subaru Deep Field in a narrow band (NB, lambdaC=7126 A and FWHM=73 A) together
with R and i'. We isolate from these data 43 LAE candidates down to NB=25.5 mag
using color criteria. Follow-up spectroscopy of five candidates suggests the
contamination by low-z objects to be ~ 20%. We find that the LAE candidates are
clustered in an elongated region on the sky of 20 Mpc in width and 50 Mpc in
length at z=4.86, which is comparable in size to present-day large-scale
structures (we adopt H0=70 km/s/Mpc, Omega0=0.3, lambda0=0.7). This elongated
region includes a circular region of 12 Mpc radius of higher surface
overdensity (delta=2), which may be the progenitor of a cluster of galaxies.
Assuming this circular region to be a sphere with a spatial overdensity of 2,
we compare our observation with predictions by Cold Dark Matter models. We find
that an Omega0=0.3 flat model with sigma8=0.9 predicts the number of such
spheres consistent with the observed number (one sphere in our survey volume)
if the bias parameter of LAEs is b \simeq 6. This value suggests that the
typical mass of dark haloes hosting LAEs at z \simeq 5 is of the order of 10^12
Msolar. Such a large mass poses an interesting question about the nature of
LAEs.


title: PSR B1929+10 Revisited in X-Rays

abstract:
  This article has been withdrawn because it was submitted twice
unintentionally.


title: Magnetically powered prompt radiation and flow acceleration in GRB

abstract:
  The physics of GRB powered by a magnetic energy flux is reviewed. Magnetic
fields are natural for transmitting the energy from the central compact object
to the small amount of baryons required for a GRB. When dissipation of the flux
of magnetic energy by reconnection inside the flow is taken into account, the
magnetic model assumes several more convincing properties. For baryon loading
typical of observed GRB, most of the dissipation takes place just outside
photosphere, so that prompt emission is produced efficiently, and the magnetic
field strength in this region is high, resulting in efficient synchrotron
emission. Remarkably, the dissipation also causes very efficient acceleration
of the bulk flow. This effect is illustrated with a classical hydrodynamic
equivalent. In this context, the distinction between the flux of magnetic
energy $cB^2/8\pi$ and the Poynting flux $cB^2/4\pi$ is important, and an
interpretation of the Poynting flux as a `magnetic enthalpy flux' illuminating.
Numerical and analytical results for flow acceleration and the relative
contribution of photospheric (thermal) and nonthermal emission as functions of
the asymptotic bulk Lorentz factor are given. The transition between X-ray
flashes and true GRB is predicted at $\Gamma\approx 100$.


title: Consequences of Gravitational Tunneling Radiation

abstract:
  Gravitational tunneling radiation (GTR) from a black hole is similar to
electric field emission of electrons from a metal. There is always a second
body to give the gravitational barrier of a black hole a finite rather than
infinite width so that a particle can escape by tunneling. Thus GTR may be
emitted from black holes in a process differing from that of Hawking radiation
(HR) with broad ranging astrophysical ramifications. HR of an "isolated" black
hole is an abstraction which has not been detected in three decades, and which
may not exist. GTR is beamed, in contrast to HR, which is isotropic. Little
black holes may account for much of the dark matter of the universe, and hence
the anomalous rotation of spiral galaxies, as well as contribute to the
accelerated expansion of the universe. The absence of HR permits the existence
of little black hole gravitationally bound atoms with quantized orbits and
quantized gravitational radiation. Since some theories speculate that the early
universe may have existed in n-dimensional space, certain results will be
presented both for general n-space and for the 3-space in which we live. An
inconsistency between quantum mechanics and the equivalence principle is
demonstrated. It is shown that angular momentum cannot be quantized in the
usual manner in 4-space, with possible consequences for Kaluza-Klein theory. An
hypothesis is presented for reducing the enormously too-large vacuum zero-point
energy. String theory may be impacted by the finding that atoms are not
energetically stable in higher than 3-space. GTR avoids the black hole lost
information paradox.


title:
In ISM Modeling, The Devil is in the Details: You Show Me Your OVI and
  I'll Show You Mine

abstract:
  The three sections of this paper illustrate the importance of rationalizing
ISM theory and modeling with the observational information.


title:
Estimates of Confusion and Gravitational Lensing Limits in
  Sunyaev-Zel'dovich Increment Measurements

abstract:
  We present estimates of the confusion limit of measurements of the
Sunyaev-Zel'dovich effect (SZ) increment near its peak intensity based on Monte
Carlo simulations of sub-millimetre observations of galaxy clusters.
Specifically, we evaluate the contribution of gravitational lensing of high
redshift background sources by a target cluster to its inferred SZ signal. We
find that the background confusion limit is 0.6 mJy per beam without any
lensing. With gravitational lensing, the confusion limit increases to 0.9 mJy
per beam. Removing bright sources in the gravitationally lensed fields
decreases the confusion limit to 0.7 mJy per beam, essentially background
levels. These limits are found by removing exceptionally poor fits to the
expected SZ profile, which are due to the different structure of the SZ and
lensing angular profiles.
  We conclude that experiments designed to measure the SZ increment must have
high enough angular resolution to identify background point sources while
surveying enough of the sky to determine the SZ profile. Observations of the SZ
increment with SCUBA, which has sufficient sensitivity and resolution for the
task, should be straight forward.


title: Interferometric Observations of the T Tauri Stars in the MBM 12 Cloud

abstract:
  We have carried out a millimeter interferometric continuum survey toward 7
YSOs in the MBM 12 cloud. Thermal emissions associated with 2 YSOs were
detected above the 3-$\sigma$ level at 2.1 mm, and one also showed a 1.3 mm
thermal emission. Another object was marginally detected at 2.1 mm. Spectral
energy distributions of the YSOs are well fitted by a simple power-law disk
model. Masses of the circumstellar disks are estimated to be an order of $0.05
M_{\sun}$. The circumstellar disks in the MBM 12 cloud have properties in
common with the disks in nearby star-forming regions, in terms of disk
parameters such as a disk mass, as well as an infrared excess.


title:
The Halpha Luminosity Function and Star Formation Rate at z~0.24 Based
  on Subaru Deep Imaging Data

abstract:
  We have carried out a deep imaging survey for H$\alpha$ emitting galaxies at
$z\approx$0.24 using a narrowband filter tuned with the redshifted line. The
total sky area covered is 706 arcmin$^2$ within a redshift range from 0.234 to
0.252 ($\delta z$=0.018). This corresponds to a volume of 3.9$\times10^3$
Mpc$^3$ when $\Omega_{\rm matter}=0.3$, $\Omega_\Lambda=0.7$, and
$H_{\mathrm{0}}$=70 km s$^{-1}$ Mpc$^{-1}$ are adopted. We obtain a sample of
348 H$\alpha$ emitting galaxies whose observed emission-line equivalent widths
are greater than 12 \AA. We find an extinction-corrected H$\alpha$ luminosity
density of $10^{39.65^{+0.08}_{-0.12}}$ ergs s$^{-1}$ Mpc$^{-3}$. Using the
Kennicutt relation between the H$\alpha$ luminosity and star formation rate,
the star formation rate density in the covered volume is estimated as
$0.036^{+0.006}_{-0.012}$ $M_{\sun}$ yr$^{-1}$ Mpc$^{-3}$. This value is higher
by a factor of 3 than the local SFR density.


title: Relativistic Singular Isothermal Toroids

abstract:
  We construct self-similar, axisymmetric, time-independent solutions to
Einstein's field equations for an isothermal gas with a flat rotation curve in
the equatorial plane. The metric scales as $ds^2 \to a^2 ds^2$ under the
transformation $r\to a r$ and $t \to a^{1-n} t$, where $n$ is a dimensionless
measure of the strength of the gravitational field. The solution space forms a
two-parameter family characterized by the ratios of the isothermal sound speed
and the equatorial rotation speed to the speed of light. The isodensity
surfaces are toroids, empty of matter along the rotation axis. Unlike the
Newtonian case, the velocity field is not constant on a cylindrical radius. As
the configuration rotates faster, an ergoregion develops in the form of the
exterior of a cone centered about the rotation axis. The sequence of solutions
terminates when frame dragging becomes infinite and the ergocone closes onto
the axis. The fluid velocity of the last solution has finite value in the
midplane but reaches the speed of light on the axis.


title:
Gemini observations of Wolf-Rayet Stars in the Local Group Starburst
  Galaxy IC10

abstract:
  We present Gemini-N GMOS and CFHT MOS spectroscopy of Wolf-Rayet candidates
in the Local Group dwarf galaxy IC10 that were previously identified by Massey
et al. and Royer et al. From the present spectroscopic survey, the WC/WN ratio
for IC10 remains unusually high, given its low metallicity, although none of
the WC9 stars suspected from narrow-band imaging are confirmed. Our
spectroscopy confirms 9 newly discovered Wolf-Rayet candidates from Royer et
al., whilst spectral types of 14 Wolf-Rayet stars previously observed by Massey
& Armandroff are refined here. In total, there are 26 spectroscopically
confirmed Wolf-Rayet stars in IC~10. All but one of the fourteen WC stars are
WC4-6 stars, the exception being # 10 from Massey et al., a broad-lined,
apparently single WC7 star. There are a total of eleven WN stars, which are
predominantly early WN3-4 stars, but include a rare WN10 star, #8 from Royer et
al. #5 from Massey et al. is newly identified as a transition WN/C star.
Consequently, the WC/WN ratio for IC10 is 14/11=1.3, unusually high for a
metal-poor galaxy. Re-evaluating recent photometric data of Massey & Holmes, we
suggest that the true WC/WN ratio may not be as low as 0.3. Finally, we present
ground-based finding charts for all confirmed WR stars, plus HST/WFPC2 charts
for twelve cases.


title: Unusual Subpulse Modulation in PSR B0320+39

abstract:
  We report on an analysis of the drifting subpulses of PSR B0320+39 that
indicates a sudden step of ~180 degrees in subpulse phase near the centre of
the pulse profile. The phase step, in combination with the attenuation of the
periodic subpulse modulation at pulse longitudes near the step, suggests that
the patterns arise from the addition of two superposed components of nearly
opposite drift phase and differing longitudinal dependence. We argue that since
there cannot be physical overlap of spark patterns on the polar cap, the drift
components must be associated with a kind of ``multiple imaging'' of a single
polar cap ``carousel'' spark pattern. One possibility is that the two
components correspond to refracted rays originating from opposite sides of the
polar cap. A second option associates the components with emission from two
altitudes in the magnetosphere.


title: Dust emission from young outflows: the case of L1157

abstract:
  We present new high-sensitivity 1.3 mm bolometer observations of the young
outflow L1157. These data show that the continuum emission arises from four
distinct components: a circumstellar disk, a protostellar envelope, an extended
flattened envelope --the dense remnant of the molecular cloud in which the
protostar was formed--, and the outflow itself, which represents ~20% of the
total flux. The outflow emission exhibits two peaks that are coincident with
the two strong shocks in the southern lobe of L1157. We show that the mm
continuum is dominated by thermal dust emission arising in the high velocity
material. The spectral index derived from the new 1.3 mm data and 850 mu
observations from Shirley et al. (2000), is ~5 in the outflow, significantly
higher than in the protostellar envelope (~3.5). This can be explained by an
important line contamination of the 850 mu map, and/or by different dust
characteristics in the two regions, possibly smaller grains in the post-shocks
regions of the outflow. Our observations show that bipolar outflows can present
compact emission peaks which must not be misinterpreted as protostellar
condensations when mapping star forming regions.


title: Doppler Tomograms from Hydrodynamical Models of Dwarf Nova Disks

abstract:
  We present three-dimensional models of accretion disks in U Gem - like
systems and calculate their Doppler tomograms. The tomograms are based on two
different assumptions concerning the origin of line emission from the disk. The
assumption of lines originating due to irradiation of the surface layer of the
disk by the central source leads to a better agreement with observations. We
argue that fully three-dimensional modelling is necessary to properly interpret
the observed tomograms.


title: An inflation model with large variations in spectral index

abstract:
  Recent fits of cosmological parameters by the Wilkinson Microwave Anisotropy
Probe (WMAP) measurement favor a primordial scalar spectrum with varying index.
This result, if stands, could severely constrain inflation model buildings.
Most extant slow-roll inflation models allow for only a tiny amount of scale
variations in the spectrum. We propose in this paper an extra-dimensional
inflation model which is natural theoretically and can generate the required
variations of the spectral index as implied by the WMAP for suitable choices of
parameters.


title: Field and cluster RR Lyrae stars as stellar tracers

abstract:
  We present an overview on pulsation properties of RR Lyrae stars in the
Galaxy and in Local Group dwarf galaxies. We discuss the key information that
RR Lyrae might provide on their parent population, and in particular on their
metallicity distribution.


title:
MSX Mid Infrared Imaging of Massive Star Birth Environments. I:
  Ultracompact HII Regions

abstract:
  We present mid-IR 21micron images of a sample of radio selected Ultracompact
HII (UCHII) regions, obtained with the Midcourse Space Experiment (MSX). All,
with one possible exception, are detected at mid-IR wavelengths, sampling the
warm dust emission of the cocoons of the OB star central exciting sources. Many
of the UCHII regions have nearby (up to a few pc distant) companion dust
emission sources, which represent other potential star birth sites. In some
objects the companion dominates the IRAS point source catalogue entry for the
UCHII region. We compare the mid- and far-IR dust emission, measuring the
embedded hot star luminosity, with published UCHII radio emission, measuring
the Lyman continuum luminosity. We find a spectral type dependence, as
predicted by the standard model of an ultracompact ionized hydrogen region,
surrounded by a natal dust shell, with some scatter, which can be understood by
consideration of: 1) dust absorption of some fraction of the emitted Lyman
continuum photons; 2) fainter companion stars within the UCHII region; 3) the
structure of the UCHII regions differing from star to star. Overall, the higher
spatial resolution offered by MSX alleviates difficulties often encountered by
comparison of IRAS far-IR fluxes with radio derived ionizing fluxes for UCHII
regions.


title:
Methods and results of the IGEC search for burst gravitational waves in
  the years 1997--2000

abstract:
  This paper presents the results of the observations of the detectors
participating in the International Gravitational Event Collaboration (IGEC)
from 1997 to 2000 and reviews the data analysis methods. The analysis is
designed to search for coincident excitations in multiple detectors. The data
set analysed in this article covers a longer period and is more complete than
that given in previous reports. The current analysis is more accurate for
determining the false dismissal probability for a time coincidence search and
it optimizes the search with respect to a target amplitude and direction of the
signal. The statistics of the accidental coincidences agrees with the model
used for drawing the results. The observations of this IGEC search are
consistent with no detection of gravitational wave burst events. A new
conservative upper limit has been set on the rate of gravitational wave bursts
with Fourier component H > 2 10^{-21}Hz^{-1}, both for searches with and
without a filter for the Galactic Center direction. This study confirms that
the false alarm rate of the observation can be negligible when at least three
detectors are operating simultaneously.


title: Signatures of Protons in UHECR

abstract:
  We demonstrate that the energy spectra of Ultra High Energy Cosmic Rays
(UHECR) as observed by AGASA, Fly's Eye, HiRes and Yakutsk detectors, have the
imprints of UHE proton interaction with the CMB radiation as the dip centered
at $E\sim 1\times 10^{19}$ eV, beginning of the GZK cutoff, and very good
agreement with calculated spectrum shape. This conclusion about proton
composition agrees with recent HiRes data on elongation rate that support the
proton composition at $E\geq 1\times 10^{18}$ eV. The visible bump in the
spectrum at $E \sim 4\times 10^{19}$ eV is not caused by pile-up protons, but
is an artifact of multiplying the spectrum by $E^3$. We argue that these data,
combined with small-angle clustering and correlation with AGN (BL Lacs), point
to the AGN model of UHECR origin at energies $E \leq 1\times 10^{20}$ eV. The
events at higher energies and the excess of the events at $E \geq 1\times
10^{20}$ eV, which is observed by AGASA (but absent in the HiRes data) must be
explained by another component of UHECR, e.g. by UHECR from superheavy dark
matter.


title: On the maximum rotational frequency of neutron and hybrid stars

abstract:
  We construct self-consistent equilibrium sequences of general relativistic,
rotating neutron star models. Special emphasis in put on the determination of
the maximum rotation frequency of such objects. Recently proposed models for
the equation of state of neutron star matter are employed, which are derived by
describing the hadronic phase within the many-body Brueckner--Bethe--Goldstone
formalism, and the quark matter phase within the MIT bag model using a density
dependent bag constant. We find that the rotational frequencies of neutron
stars with deconfined quark phases in their cores rival those of absolutely
stable, self-bound strange quark matter stars. This finding is of central
importance for the interpretation of extremely rapidly rotating pulsars, which
are the targets of present pulsar surveys.


title:
RX J0513.9-6951: The first example of accretion wind evolution, a key
  evolutionary process to Type Ia supernovae

abstract:
  A new self-sustained model for long-term light curve variations of RX
J0513.9-6951 is proposed based on an optically thick wind model of
mass-accreting white dwarfs (WDs). When the mass accretion rate to a WD exceeds
the critical rate of \sim 1 x 10^{-6} M_\sun yr^{-1}, optically thick strong
winds begin to blow from the WD so that a formation of common envelope is
avoided. The WD can accrete and burn hydrogen-rich matter atop the WD at the
critical rate. The excess matter transferred to the WD above the critical rate
is expelled by winds. This is called the accretion wind evolution. This
ejection process, however, occurs intermittently because the mass transfer is
attenuated by strong winds: the strong winds collide with the secondary surface
and strip off the very surface layer of the secondary. The matter stripped-off
is lost from the binary system. Properly formulating this mass stripping effect
and the ensuing decay of mass transfer rate, we are able to reproduce, in a
self-sustained manner, the transition between the optical high/X-ray off and
optical low/X-ray on states of RX J0513.9-6951. Thus RX J0513.9-6951 is the
first example of the accretion wind evolution, which is a key evolutionary
process in a recently developed evolutionary path to Type Ia supernovae.


title: HD 112914 : A nearby one solar mass binary system

abstract:
  In paper 167 of his serie published in The Observatory, Griffin presented the
spectroscopic orbit of HD 112914, a late main sequence star. He also noticed
that this star, also known as HIP 63406, was one of the few for which the
DMSA/O Annex of the Hipparcos Catalogue derived an orbit prior to any
spectroscopic one. Albeit in agreement with each others, the astrometric orbit
was however determined with rather large uncertainties. Here, we have
reanalysed the Hipparcos Intermediate Astrometric Data (IAD) using
Griffin'spectroscopic orbit to obtain a much more precise astrometric orbit.
Several parameters of the HD 112914 system are now well constrained.


title:
Clausius' Virial vs. Total Potential Energy in the dynamics of a
  two-component system

abstract:
  In a gravitational virialized bound system built up of two components, one of
which is embedded in the other, the Clausius' virial energy of one subcomponent
is not, in general, equal to its total potential energy, as occurs in a single
system without external forces. This is the main reason for the presence, in
the case of two non-coinciding concentric spheroidal subsystems, of a minimum
(in absolute value) in the Clausius' virial of the inner component B, when it
assumes a special configuration characterized by a value of its semi-major axis
we have named "tidal radius". The physical meaning, connected with its
appearance, is to introduce a scale length on the gravity field of the inner
subsystem, which is induced from the outer one. Its relevance in the galaxy
dynamics has been stressed by demonstrating that some of the main features of
the Fundamental Plane may follow as consequence of its existence. More physical
insight into the dynamics of a two component system may be got by looking at
the location of this scale length inside the plots of the potential energies of
each subsystem and of the whole system and by also taking into account the
trend of the anti-symmetric residual-energy, that is the difference between the
tidal and the interaction-energy of each component. Some thermodynamical
arguments related to the inner component are also added to prove as special is
the "tidal radius configuration". Moreover the role of the divergency at the
center of the two subsystems in obtaining this scale length is considered. For
the sake of simplicity the analysis has been performed in the case of a frozen
external component even if this constraint does not appear to be too relevant
in order to preserve the main results.


title: The 1.2 Millimeter Image of the beta Pictoris Disk

abstract:
  We present millimeter imaging observations in the 1200 micron continuum of
the disk around beta Pictoris. With the 25 arcsec beam, the beta Pic disk is
unresolved perpendicularly to the disk plane (< 10 arcsec), but slightly
resolved in the northeast-southwest direction (26 arcsec). Peak emission is
observed at the stellar position. A secondary maximum is found 1000 AU along
the disk plane in the southwest, which does not positionally coincide with a
similar feature reported earlier at 850 micron. Arguments are presented which
could be seen in support of the reality of these features. The observed
submm/mm emission is consistent with thermal emission from dust grains, which
are significantly larger than those generally found in the interstellar medium,
including mm-size particles, and thus more reminiscent of the dust observed in
protostellar disks. Modelling the observed scattered light in the visible and
the emission in the submm/mm provides evidence for the particles dominating the
scattering in the visible/NIR and those primarily responsible for the thermal
emission at longer wavelengths belonging to different populations.


title: Multi-Messenger Astronomy: Cosmic Rays, Gamma-Rays, and Neutrinos

abstract:
  Although cosmic rays were discovered a century ago, we do not know where or
how they are accelerated. There is a realistic hope that the oldest problem in
astronomy will be solved soon by ambitious experimentation: air shower arrays
of 10,000 kilometer-square area, arrays of air Cerenkov telescopes and
kilometer- scale neutrino observatories. Their predecessors are producing
science. We will review the highlights:
  - Cosmic rays: the highest energy particles and the GZK cutoff, the search
for cosmic accelerators and the the Cygnus region, top-down mechanisms: photons
versus protons?
  - TeV-energy gamma rays: blazars, how molecular clouds may have revealed
proton beams, first hints of the diffuse infrared background?
  - Neutrinos: first results and proof of concept for technologies to construct
kilometer-scale observatories.


title:
Evidence of a cyclotron feature in the spectrum of the anomalous X-ray
  pulsar 1RXS J170849-400910

abstract:
  We report the results of a long observation of the anomalous X-ray pulsar
1RXS J170849-400910 obtained with the BeppoSAX satellite in August 2001. The
best-fit phase-averaged spectrum was an absorbed power law plus blackbody
model, with photon index Gamma~2.4 and a blackbody temperature of kT_bb~0.4
keV. We confirm the presence of significant spectral variations with the
rotational phase of the pulsar. In the spectrum corresponding to the rising
part of the pulse we found an absorption-like feature at ~8.1 keV (a
significance of 4 sigma), most likely due to cyclotron resonant scattering. The
centroid energy converts to a magnetic field of 9x10^11 G and 1.6x10^15 G in
the case of electrons and protons, respectively. If confirmed, this would be
the first detection of a cyclotron feature in the spectrum of an anomalous
X-ray pulsar.


title:
On the energy determination of extensive air showers through the
  fluorescence technique

abstract:
  The determination of the shower development in air using fluorescence yield
is subject to corrections due to the angular spread of the particles in the
shower. This could introduce systematic errors in the energy determination of
an extensive air shower through the fluorescence technique.


title:
Dwarfs after Mergers? The case of NGC520, NGC772, Arp141, NGC3226/7,
  NGC3656 and Arp299

abstract:
  We present results from a survey of dwarf galaxy candidates in the vicinity
of strongly interacting galaxies. The goal of the survey was a test of the
hypothesis that massive condensations of stars and HI in tidal tails of large
interacting galaxies may be a significant source of independent,
self-gravitating dwarf galaxies. These so called tidal dwarf galaxies (TDG) can
be expected to resemble the blue luminous knots found in tidal tails, but also
might appear as redder, evolved systems if formed much before they are being
observed. For the present study, a homogeneous subsample of 6 fields was
selected from the catalog of extended objects in fields around 15 strongly
interacting galaxies by Deeg et al. (1998). Criteria for the subsample were:
similar redshifts of the central interacting galaxies, and photometric
completeness of the extended objects in V and R. The number density of these
TDG candidates was compared with expected background galaxy densities. Within
the statistical errors, background galaxies account for most, if not all of the
extended objects. There is no evidence for a substantial locally formed dwarf
galaxy population. Thus, we conclude that field galaxy-galaxy interactions are
likely to result in the formation of only a few long-lived TDG.


title: XMM-NEWTON High Resolution Spectroscopy of NGC 5548

abstract:
  We analyze a 137 ks exposure X-ray spectrum of the Seyfert 1 galaxy NGC 5548
obtained with the XMM-Newton Reflection Grating Spectrometer. Due to the long
exposure time, the spectrum is of higher statistical quality than the previous
observations of this AGN. Therefore, we detect for the first time in NGC 5548
inner-shell transitions from O III to O VI ions, and the Unresolved Transition
Array of M-shell iron. The warm absorber found from this X-ray observation
spans three orders of magnitude in ionization parameter. We detect O III, which
is as lowly ionized as the warm absorber detected in the UV band, to Fe XXIV.
For O VI the column density determined from our X-ray data is an order of
magnitude larger than the column density measured in previous UV observations.
We conclude that there is substantially more low ionized material than
previously deduced from UV observations. However, only a few percent of the
warm absorber detected in the X-rays is lowly ionized. A 99.9 % significant
increase in the derived absorbing column density with higher ionization states
is observed. The outflow velocities determined from the X-ray absorption lines
are consistent with those deduced from the UV lines, evidence, together with
the detection of O VI, that the X-ray and UV warm absorber are different
manifestations of the same phenomenon. From a simple mass conservation
argument, we indicate that our data set is consistent with an outflow with
small opening angle formed due to instabilities in the accretion disk. Possible
due to uncertainties in the radiative transport mechanism, an apparent deviant
iron to oxygen abundance is detected. No strong relativistically broadened
emission lines of O VIII, N VII and C VI were detected.


title: Quasar Elemental Abundances at High Redshifts

abstract:
  We examine rest-frame ultraviolet spectra of 70 high redshift quasars (z>3.5)
to study the chemical enrichment history of the gas closely related to the
quasars, and thereby estimate the epoch of first star formation. The fluxes of
several ultraviolet emission lines were investigated within the framework of
the most recent photoionization models to estimate the metallicity of the gas
associated with the high-z quasars. Standard photoionization parameters and the
assumption of secondary nitrogen enrichment indicate an average abundance of
Z/Z_sol = 4 to 5 in the line emitting gas. Assuming a time scale of t_evol =
0.5 - 0.8 Gyrs for the chemical enrichment of the gas, the first major star
formation for quasars with z>=4 should have started at a redshift of z_f = 6 -
8, corresponding to an age of the universe of several 10^8 yrs (H_o = 65
km/s/Mpc, Omega_M = 0.3, Omega_Lambda = 0.7). We note that this also appears to
be the era of re-ionization of the universe. Finally, there is some evidence
for a positive luminosity - metallicity relation in this high redshift quasar
sample.


title: CIW Cosmology Symposium: Conference Summary -- Observations

abstract:
  I review the major concordances and controversies of the meeting concerning
observations. Cosmologists are nearing agreement on the global cosmological
parameters of the Universe. A few parameters still have large error bars,
notably Omega_mat, but most of these windows will close soon with upcoming
accurate observations of the CMB. The major era of chasing the major
cosmological parameters is now closing. Understanding galaxy formation in all
its messy detail will continue to occupy cosmologists for some time to come.
Development of highly accurate standard candles,such as inspiraling black
holes, holds out hope for understanding Lambda, whether it is truly constant or
evolving. This is the major prospective contribution from cosmology to
fundamental physics in the next generation. I close with a discussion of
anthropic cosmology. Anthropic reasoning has been shown to be correct at least
three times in the history of cosmology. Applying it now leads us to take
seriously the prospect of other universes, a notion that should be pursued
seriously by theoreticians.


title: A high resolution foreground cleaned CMB map from WMAP

abstract:
  We perform an independent foreground analysis of the WMAP maps to produce a
cleaned CMB map (available online) useful for cross-correlation with, e.g.,
galaxy and X-ray maps. We use a variant of the Tegmark & Efstathiou (1996)
technique that is completely blind, making no assumptions about the CMB power
spectrum, the foregrounds, WMAP detector noise or external templates. Compared
with the foreground-cleaned internal linear combination map produced by the
WMAP team, our map has the advantage of containing less non-CMB power (from
foregrounds and detector noise) outside the Galactic plane. The difference is
most important on the the angular scale of the first acoustic peak and below,
since our cleaned map is at the highest (13') rather than lowest (49') WMAP
resolution. We also produce a Wiener filtered CMB map, representing our best
guess as to what the CMB sky actually looks like, as well as CMB-free maps at
the five WMAP frequencies useful for foreground studies.
  We argue that our CMB map is clean enough that the lowest multipoles can be
measured without any galaxy cut, and obtain a quadrupole value that is slightly
less low than that from the cut-sky WMAP team analysis. This can be understood
from a map of the CMB quadrupole, which shows much of its power falling within
the Galaxy cut region, seemingly coincidentally. Intriguingly, both the
quadrupole and the octopole are seen to have power suppressed along a
particular spatial axis, which lines up between the two, roughly towards (l,b)
\~ (-110,60) in Virgo.


title: Tidal Effects in Clusters of Galaxies

abstract:
  High-redshift clusters of galaxies show an over-abundance of spirals by a
factor of 2-3, and the corresponding under-abundance of S0 galaxies, relative
to the nearby clusters. This morphological evolution can be explained by tidal
interactions with neighboring galaxies and with the hierarchically growing
cluster halo. The efficiency of tidal interactions depends on the size and
structure of the cluster, as well as on the epoch of its formation. I simulate
the formation and evolution of Virgo-type clusters in three cosmologies: a
critical density model Omega_0=1, an open model Omega_0=0.4, and a flat model
Omega_0=0.4 with a cosmological constant. The orbits of identified halos are
traced with a high temporal resolution (~10^7 yr). Halos with low relative
velocities merge only shortly after entering the cluster; after virialization
mergers are suppressed. The dynamical evolution of galaxies is determined by
the tidal field along their trajectories. The maxima of the tidal force do not
always correspond to closest approach to the cluster center. They are produced
to a large extent by the local density structures, such as the massive galaxies
and the unvirialized remnants of infalling groups of galaxies. Collisions of
galaxies are intensified by the substructure, with about 10 encounters within
10 kpc per galaxy in the Hubble time. These very close encounters add an
important amount (10-50%) of the total heating rate. The integrated effect of
tidal interactions is insufficient to transform a spiral galaxy into an
elliptical, but can produce an S0 galaxy. Overall, tidal heating is stronger in
the low Omega_0 clusters.


title: Dynamical Evolution of Galaxies in Clusters

abstract:
  Tidal forces acting on galaxies in clusters lead to a strong dynamical
evolution. In order to quantify the amount of evolution, I run self-consistent
N-body simulations of disk galaxies for a variety of models in the
hierarchically forming clusters. The tidal field along the galactic orbits is
extracted from the simulations of cluster formation in the Omega_0=1;
Omega_0=0.4; and Omega_0=0.4, Omega_Lambda=0.6 cosmological scenarios. For
large spiral galaxies with the rotation speed of 250 km/s, tidal interactions
truncate massive dark matter halos at 30 +- 6 kpc, and thicken stellar disks by
a factor 2 to 3, increasing Toomre's parameter to Q > 2 and halting star
formation. Low density galaxies, such as the dwarf spheroidals with the
circular velocity of 20 km/s and the extended low surface brightness galaxies
with the scale length of 10-15 kpc, are completely disrupted by tidal shocks.
Their debris contribute to the diffuse intracluster light. The tidal effects
are significant not only in the core but throughout the cluster and can be
parametrized by the critical tidal density. The tidally-induced evolution
results in the transformation of the infalling spirals into S0 galaxies and in
the depletion of the LSB population. In the low Omega_0 cosmological models,
clusters form earlier and produce stronger evolution of galaxies.


title:
Polarimetric variations of binary stars. V. Pre-main-sequence
  spectroscopic binaries located in Ophiuchus and Scorpius

abstract:
  We present polarimetric observations of 7 pre-main-sequence (PMS)
spectroscopic binaries located in the rho Oph and Upper Sco star forming
regions (SFRs). The average observed polarizations at 7660A are between 0.5%
and 3.5%. After estimates of the interstellar polarization are removed, all
binaries have an intrinsic polarization above 0.4%. Two binaries,
NTTS162814-2427 and NTTS162819-2423S, present high levels of intrinsic
polarization between 1.5% and 2.1%. All 7 PMS binaries have a statistically
variable or possibly variable polarization. Combining these results with our
previous sample of binaries located in the Tau, Aur and Ori SFRs, 68% of the
binaries have an intrinsic polarization above 0.5%, and 90% of the binaries are
polarimetrically variable or possibly variable. NTTS160814-1857,
NTTS162814-2427, and NTTS162819-2423S are clearly polarimetrically variable.
The first two also exhibit phase-locked variations over ~10 and ~40 orbits
respectively. NTTS160905-1859 shows periodic variations that are not
phased-locked and only present for short intervals of time. The amplitudes of
the variations reach a few tenths of a percent. The high-eccentricity system
NTTS162814-2427 shows single-periodic variations, in agreement with our
previous numerical simulations. Non-periodic events introduce stochastic noise
that partially masks the periodic variations and prevents the Brown, McLean, &
Emslie (1978) formalism from finding a reasonable estimate of the inclination.


title:
Development of Silicon Strip Detectors for a Medium Energy Gamma-ray
  Telescope

abstract:
  We report on the design, production, and testing of advanced double-sided
silicon strip detectors under development at the Max-Planck-Institute as part
of the Medium Energy Gamma-ray Astronomy (MEGA) project. The detectors are
designed to form a stack, the "tracker," with the goal of recording the paths
of energetic electrons produced by Compton-scatter and pair-production
interactions. Each layer of the tracker is composed of a 3 x 3 array of 500
micron thick silicon wafers, each 6 cm x 6 cm and fitted with 128 orthogonal p
and n strips on opposite sides (470 micron pitch). The strips are biased using
the punch-through principle and AC-coupled via metal strips separated from the
strip implant by an insulating oxide/nitride layer. The strips from adjacent
wafers in the 3 x 3 array are wire-bonded in series and read out by 128-channel
TA1.1 ASICs, creating a total 19 cm x 19 cm position-sensitive area. At 20
degrees C a typical energy resolution of 15-20 keV FWHM, a position resolution
of 290 microns, and a time resolution of ~1 microsec is observed.


title: Effect of Clouds on Apertures of Space-based Air Fluorescence Detectors

abstract:
  Space-based ultra-high-energy cosmic ray detectors observe fluorescence light
from extensive air showers produced by these particles in the troposphere.
Clouds can scatter and absorb this light and produce systematic errors in
energy determination and spectrum normalization. We study the possibility of
using IR remote sensing data from MODIS and GOES satellites to delimit clear
areas of the atmosphere. The efficiency for detecting ultra-high-energy cosmic
rays whose showers do not intersect clouds is determined for real, night-time
cloud scenes. We use the MODIS SST cloud mask product to define clear pixels
for cloud scenes along the equator and use the OWL Monte Carlo to generate
showers in the cloud scenes. We find the efficiency for cloud-free showers with
closest approach of three pixels to a cloudy pixel is 6.5%, exclusive of other
factors. We conclude that defining a totally cloud-free aperture reduces the
sensitivity of space-based fluorescence detectors to unacceptably small levels.


title:
Radio Observations of Two Isolated Neutron Stars, RXJ0720.4-3125 and RX
  J0806.4-4132

abstract:
  Radio observations of two isolated neutron stars, RXJ0720.4-3125 and RX
J0806.4-4132, have been made with the Australia Telescope Compact Array at a
frequency of 1.4 GHz. No continuum emission is detected from either object with
a 3 sigma upper limit of 0.2 mJy. The data were also folded synchronously with
the known rotation periods of 8.4 and 11.4 s respectively. No pulsed emission
was detected. If the pulse duty cycle is small, the upper limit on pulsed
emission can be reduced still further to 0.04 mJy. The best evidence seems to
indicate that the isolated neutron stars detected by ROSAT all-sky survey are
relatively young objects, born with a very high magnetic field.


title: Thermal Conduction in Magnetized Turbulent Gas

abstract:
  Using numerical methods, we systematically study in the framework of ideal
MHD the effect of magnetic fields on heat transfer within a turbulent gas. We
measure the rates of passive scalar diffusion within magnetized fluids and make
the comparisons a) between MHD and hydro simulations, b) between different MHD
runs with different values of the external magnetic field (up to the energy
equipartition value), c) between thermal conductivities parallel and
perpendicular to magnetic field. We do not find apparent suppression of
diffusion rates by the presence of magnetic fields, which implies that magnetic
fields do not suppress heat diffusion by turbulent motions.


title: Grand Unified Inflation Confronts WMAP

abstract:
  In a class of realistic four and five dimensional supersymmetric grand
unified models, the scalar spectral index is found to be $n_s=0.98 (\pm 0.01)$,
in excellent agreement with the values determined by several previous
experiments and most recently by the Wilkinson Microwave Anisotropy Probe
(WMAP). The models predict $dn_s/d{\rm ln}k\sim 10^{-3}$ and a negligible
tensor-to-scalar ratio $r\sim 10^{-8}$. A new five dimensional supersymmetric
SO(10) model along these is presented in which inflation is associated with the
breaking of SO(10) to SU(5) at scale $M$, with $\delta T/T\propto (M/M_{\rm
Planck})^2$, so that $M\simeq 10^{16}$ GeV. The inflaton decay leads to the
observed baryon asymmetry via leptogenesis. We also discuss how the monopole
problem is solved without the use of non-renormalizable terms.


title: Early Quintessence in Light of WMAP

abstract:
  We examine the cosmic microwave background (CMB) anisotropy for signatures of
early quintessence dark energy -- a non-negligible quintessence energy density
during the recombination and structure formation eras. Only very recently does
the quintessence overtake the dark matter and push the expansion into
overdrive. Because the presence of early quintessence exerts an influence on
the clustering of dark matter and the baryon-photon fluid, we may expect to
find trace signals in the CMB and the mass fluctuation power spectrum. In
detail, we demonstrate that suppressed clustering power on small length-scales,
as suggested by the combined Wilkinson Microwave Anisotropy Probe (WMAP) / CMB
/ large scale structure data set, is characteristic of early quintessence. We
identify a set of concordant models, and map out directions for further
investigation of early quintessence.


title: Phantom Energy and Cosmic Doomsday

abstract:
  Cosmologists have long wondered whether the Universe will eventually
re-collapse and end with a Big Crunch, or expand forever, becoming increasingly
cold and empty. Recent evidence for a flat Universe, possibly with a
cosmological constant or some other sort of negative-pressure dark energy, has
suggested that our fate is the latter. However, the data may actually be
pointing toward an astonishingly different cosmic end game. Here, we explore
the consequences that follow if the dark energy is phantom energy, in which the
sum of the pressure and energy density is negative. The positive phantom-energy
density becomes infinite in finite time, overcoming all other forms of matter,
such that the gravitational repulsion rapidly brings our brief epoch of cosmic
structure to a close. The phantom energy rips apart the Milky Way, solar
system, Earth, and ultimately the molecules, atoms, nuclei, and nucleons of
which we are composed, before the death of the Universe in a ``Big Rip''.


title: A spectroscopic search for faint secondaries in cataclysmic variables

abstract:
  The secondary in cataclysmic variables (CV's) is usually detected by
cross-correlation of the CV spectrum with that of a K or M dwarf template, to
produce a radial velocity curve. Although this method has demonstrated its
power, it has its limits in the case of noisy spectra, such as are found when
the secondary is faint. A method of co-adding spectra, called skew mapping, has
been proposed in the past. Gradually, examples of its application are being
published. Nonetheless, so far no journal article has described the technique
in detail. To answer this need, this paper explores in detail the capabilities
of skew mapping when determining the amplitude of the radial velocity for faint
secondaries. It demonstrates the method's power over techniques that are more
conventional, when the signal-to-noise (s/n) ratio is poor. The paper suggests
an approach to assessing the quality of results. This leads in the case of the
investigated objects to a first tier of results, where we find K2=127+-23 km/s
for SY Cnc, K2=144+-18 km/s for RW Sex, and K2=262+-14 km/s for UX UMa. These
we believe to be the first direct determinations of K2 for these objects.
Furthermore, we also obtain K2=263+-30 km/s for RW Tri, close to a skew mapping
result obtained elsewhere. In the first three cases, we use these results to
derive the mass of the white dwarf companion. A second tier of results includes
UU Aqr, EX Hya, and LX Ser, for which we propose more tentative values of K2.
Clear failures of the method are also discussed (EF Eri, VV Pup, SW Sex).


title:
Arrival Distribution of Ultra-High Energy Cosmic Rays: Prospects for the
  Future

abstract:
  We predict the arrival distribution of UHECRs above $4 \times 10^{19}$ eV
with the event number expected by future experiments in the next few years. We
perform event simulations with the source model which is adopted in our recent
study and can explain the current AGASA observation. At first, we calculate the
harmonic amplitude and the two point correlation function for the simulated
event sets. We find that significant anisotropy on large angle scale will be
observed when $\sim 10^3$ cosmic rays above $4 \times 10^{19}$ eV are detected
by future experiments. The statistics of the two point correlation function
will also increase. The angle scale at which the events have strong correlation
with each other corresponds to deflection angle of UHECR in propagating in the
EGMF, which in turn can be determined by the future observations. We further
investigate the relation between the number of events clustered at a direction
and the distance of their sources. Despite the limited amount of data, we find
that the C2 triplet events observed by the AGASA may originate from the source
within 100 Mpc. Merger galaxy Arp 299 (NGC 3690 + IC 694) is the best candidate
for their source. If data accumulate, the UHECR sources within $\sim 100$ Mpc
can be identified from observed event clusterings significantly. This will
provide some kinds of information about poorly known parameters which influence
the propagation of UHECRs, such as extragalactic and galactic magnetic field,
chemical composition of observed cosmic rays. Also, we will reveal their origin
with our method to identify the sources of UHECR. Finally, we predict the
arrival distribution of UHECRs above $10^{20}$ eV, which is expected to be
observed if the current HiRes spectrum is correct, and discuss their
statistical features and implications.


title: Inverse Compton X-rays from the radio galaxy 3C 219

abstract:
  We report the results from a Chandra observation of the powerful nearby
(z=0.1744) radio galaxy 3C 219. We find evidence for non-thermal X-ray emission
from the radio lobes which fits fairly well with a combination of inverse
Compton scattering of Cosmic Microwave Background radiation and of nuclear
photons with the relativistic electrons in the lobes. The comparison between
radio synchrotron and IC emission yields a magnetic field strength
significantly lower (about a factor 3) than that calculated under minimum
energy conditions; the source energetics is then dominated by the relativistic
particles.


title: Galaxy Clustering and Dark Energy

abstract:
  We study the evolution of galaxy clustering in various cosmological models
with quintessence. We investigate how the analytical predictions vary with
change of dark energy equation of state $w_X$. Comparing these predictions
against available data we discuss to what extent the problems of galaxy biasing
can be modelled. This will be key in constraining the dark energy equation of
state with future galaxy surveys. We use a compilation of various surveys to
study the number density and amplitude of galaxy clustering from observations
of the local universe at $z \sim 0$ to that of the Lyman break galaxies and
Ly-$\alpha$ emitters at $z \sim 4.9$. We find that there is a degeneracy
between the dark energy equation of state and the way galaxies populate dark
matter haloes; objects are more biased in models with more negative values of
dark energy equation of state $w_X$.
  We conclude that, while future all sky CMB observations will determine
cosmological parameters with unprecedented precision, and cross correlation of
weak lensing experiments and galaxy surveys will provide a cleaner and accurate
picture of bias associated with collapsed objects, the rate of growth of large
scale structure in such surveys can potentially constrain the equation of state
of dark energy and the potential of the scalar field associated with
quintessence. In particular, we show that the abundance and spatial
distribution of galaxy clusters at intermediate redshifts strongly depend on
the dark energy equation of state. When accurate measurement of galaxy
clustering at high-redshit becomes possible, it will provide constraints on
dark energy that are independent and complementary to type Ia supernova
studies.


title:
The Galactic disk mass function: reconciliation of the HST and nearby
  determinations

abstract:
  We derive and parametrize the Galactic mass function (MF) below 1 $\msol$
characteristic of both single objects and binary systems. We resolve the long
standing discrepancy between the MFs derived from the HST and from the nearby
luminosity functions, respectively. We show that this discrepancy stemmed from
{\it two} cumulative effects, namely (i) incorrect color-magnitude determined
distances, due a substantial fraction of M dwarfs in the HST sample belonging
to the metal-depleted, thick-disk population, as corrected recently by Zheng et
al. and (ii) unresolved binaries. We show that both the nearby and HST MF for
unresolved systems are consistent with a fraction $\sim $50% of M-dwarf
binaries, with the mass of both the primaries and the companions originating
from the same underlying single MF. This implies that $\sim$30% of M dwarfs
should have an M dwarf companion and $\sim$20% should have a brown dwarf
companion, in agreement with recent determinations. The present calculations
show that the so-called "brown-dwarf desert" should be reinterpreted as a lack
of high mass-ratio $(m_2/m_1\la 0.1$) systems, and does not preclude a
substantial fraction of brown dwarfs as companions of M dwarfs or for other
brown dwarfs.


title: The M_BH - L_rad Relation for Flat-Spectrum Quasars

abstract:
  In this proceedings we summarize our recent letter (Jarvis & McLure 2002)
where we suggested that by correcting for the inevitable effects of
inclination, the black-hole masses of flat-spectrum quasars (FSQ) with
intrinsically powerful radio jets are confined, virtually exclusively, to M_BH
>10^{8} Msolar. After considering realistic Doppler boosting factors, many of
the FSQ would be more accurately classified as radio-intermediate or radio-quie
t quasars. This range in radio luminosity suggests that the FSQ are fully
consistent with an upper boundary on radio power of the form L_5GHz
proportional to M_BH^2.5.


title:
Spectroscopy of the near-nuclear regions of Cygnus A: estimating the
  mass of the supermassive black hole

abstract:
  We use a combination of high spatial resolution optical and near-IR
spectroscopic data to make a detailed study of the kinematics of the NLR gas in
the near-nuclear regions of the powerful, FRII radio galaxy Cygnus A
(z=0.0560), with the overall goal of placing limits on the mass of any
supermassive black hole in the core. Our K-band infrared observations (0.75
arcsec seeing) -- taken with NIRSPEC on the Keck II telescope -- show a smooth
rotation pattern across the nucleus in the Paschen alpha and H_2 emission lines
along a slit position (PA180) close to perpendicular to the radio axis,
however, there is no evidence for such rotation along the radio axis (PA105).
Higher spatial resolution observations of the [OIII]5007 emission line -- taken
with STIS on the Hubble Space Telescope (HST) -- confirm the general rotation
pattern of the gas in the direction perpendicular to the radio axis, and
provide evidence for steep velocity gradients within a radius of 0.1 arcsec of
the core. The circular velocities measured from both the Keck and HST data lead
to an estimate of the mass of the supermassive black hole of 2.5+/-0.7x10^9
solar masses. For the host galaxy properties of Cygnus A, this mass is
consistent with the global correlations between black hole mass and host galaxy
properties deduced for non-active galaxies. Therefore, despite the extreme
power of its radio source and the quasar-like luminosity of its AGN, the black
hole in Cygnus A is not unusually massive considering theluminosity of its host
galaxy. Indeed, the estimated mass of the black hole in Cygnus A is similar to
that inferred for the supermassive black hole in the FRI radio galaxy M87,
despite the fact that the AGN and radio jets of Cygnus A are 2 -- 3 orders of
magnitude more powerful.


title: The host galaxies of flat-spectrum quasars

abstract:
  We present the results of deep VLT-ISAAC Ks-band imaging of four z~1.5
flat-spectrum quasars selected from the Parkes half-Jansky flat spectrum
sample. We find that the hosts of these flat-spectrum quasars are consistent
with lying on the K-z Hubble relation for radio galaxies. This implies that the
flat-spectrum quasar hosts fall in line with the expectations from orientation
based unified schemes and also that they contain black holes of similar mass.
Moreover, the width of the Hbeta broad emission line in these objects tends to
be narrower than in their misaligned (low-frequency selected quasar)
counterparts, implying that the width of the Hbeta broad emission line depends
on source inclination, at least for radio-loud quasars, in line with previous
studies.


title: VLT observations of the highly ionized nebula around Brey2

abstract:
  We present the first high resolution HeII 4686 images of the high excitation
nebula around the WR star Brey 2 in the LMC. This nebula presents a striking
morphology: a small arc-like feature some 3.6pc in radius is particularly
prominent in the HeII 4686 line. We further discover a previously unknown faint
HeII emission that extends over an area of 22*17 pc^2. An even fainter HeII
emission is apparently associated with the interstellar bubble blown by the
progenitor of Brey2. The total HeII flux corresponds to an ionizing flux of
4*10^{47} photons/s. Halpha, [OIII], and HeI 5876 images and long-slit spectra
are also examined in this letter, enabling us to investigate the detailed
physical properties at various locations of the nebula.


title: X-ray line emission from a fragmented stellar wind

abstract:
  We discuss X-ray line formation in dense O star winds. A random distribution
of wind shocks is assumed to emit X-rays that are partially absorbed by cooler
wind gas. The cool gas resides in highly compressed fragments oriented
perpendicular to the radial flow direction. For fully opaque fragments, we find
that the blueshifted part of X-ray line profiles remains flat-topped even after
severe wind attenuation, whereas the red part shows a steep decline. These
box-type, blueshifted profiles resemble recent Chandra observations of the O3
star zeta Pup. For partially transparent fragments, the emission lines become
similar to those from a homogeneous wind.


title:
The Munich Near-Infrared Cluster Survey (MUNICS) - V. The evolution of
  the rest-frame K-band and J-band galaxy luminosity functions to z ~ 0.7

abstract:
  We present spectroscopic follow-up observations of galaxies from the Munich
Near-Infrared Cluster Survey (MUNICS). MUNICS is a wide-field medium-deep
K'-band selected survey covering 1 square degree in the near-infrared K' and J
pass-bands, and 0.35 square degrees in I, R, V, and - recently completed - B.
The spectroscopic sample comprises observations of objects down to a limit of
K' < 17.5 in five survey fields (0.17 square degrees in total), and a sparsely
selected deeper sample (K' < 19.0) constructed in one of the survey patches
(0.03 square degrees). Here we describe the selection procedure of objects for
spectroscopic observations, the observations themselves, the data reduction,
and the construction of the spectroscopic catalogue containing roughly 500
galaxies with secure redshifts. Furthermore we discuss global properties of the
sample like its distribution in colour-redshift space, the accuracy of redshift
determination, and the completeness function of the data. We derive the
rest-frame K'-band luminosity function of galaxies at median redshifts of z =
0.2, z = 0.4, and z = 0.7. We find evidence for mild evolution of magnitudes
(-0.70 mag) and number densities (35 per cent) to redshift one. Furthermore, we
present the rest-frame J-band luminosity function of galaxies at these
redshifts, the first determination of this quantity at higher redshifts, with a
behaviour similar to the K-band luminosity function.


title: Optical and radio behaviour of the BL Lacertae object 0716+714

abstract:
  Eight optical and four radio observatories have been intensively monitoring
the BL Lac object 0716+714 in the last years: 4854 data points have been
collected in the UBVRI bands since 1994, while radio light curves extend back
to 1978. Many of these data are presented here for the first time. The
long-term trend shown by the optical light curves seems to vary with a
characteristic time scale of about 3.3 years, while a longer period of 5.5-6
years seems to characterize the radio long-term variations. In general, optical
colour indices are only weakly correlated with brightness. The radio flux
behaviour at different frequencies is similar, but the flux variation amplitude
decreases with increasing wavelength. The radio spectral index varies with
brightness (harder when brighter), but the radio fluxes seem to be the sum of
two different-spectrum contributions: a steady base level and a harder-spectrum
variable component. Once the base level is removed, the radio variations appear
as essentially achromatic, similarly to the optical behaviour. Flux variations
at the higher radio frequencies lead the lower-frequency ones with week-month
time scales. The behaviour of the optical and radio light curves is quite
different, the broad radio outbursts not corresponding in time to the faster
optical ones and the cross-correlation analysis indicating only weak
correlation with long time lags. However, minor radio flux enhancements
simultaneous with the major optical flares can be recognized, which may imply
that the mechanism producing the strong flux increases in the optical band also
marginally affects the radio one.


title: What determines the strength and the slowdown rate of bars ?

abstract:
  Isolated barred galaxies evolve by redistributing their angular momentum,
which, emitted by material in the inner disc at resonance with the bar, can be
absorbed by resonant material in the outer disc, or in the halo. The amount of
angular momentum that can be emitted/absorbed at a given resonance depends on
the distribution function of the emitting/absorbing material. It thus depends
not only on the amount of material on resonant orbits, but also on the velocity
dispersion of that material. As it loses angular momentum, the bar becomes
stronger and it also rotates slower. Thus the strength of the bar and the
decrease of its pattern speed with time are set by the amount of angular
momentum exchanged within the galaxy, which, in turn, is regulated by the mass
distribution and the velocity dispersion of the material in the disc and
spheroidal components. Correlations between the pattern speed of the bar, its
strength and the angular momentum absorbed by the spheroid (halo plus bulge)
argue strongly that it is the amount of angular momentum exchanged that
determines the strength and the slowdown rate of the bar. The decrease of the
bar pattern speed with time should not be used to set constraints on the
halo-to-disc mass ratio, since it depends also on the velocity dispersion of
the halo and disc material.


title:
The radio flaring behaviour of GRO J1655-40: an analogy with
  extragalactic radio sources?

abstract:
  At radio frequencies, the current evidence for the microquasar-quasar
connection is based on imaging observations showing that relativistic
outflows/jets are found in both classes of objects. Some microquasars also
display superluminal motion, further strengthening the view that microquasars
are in fact Galactic miniatures of quasars. Here we demonstrate that this
connection can be extended to incorporate timing and spectral observations. Our
argument is based on the striking similarity found in the radio flaring
behaviour of the Galactic superluminal source GRO J1655-40 and of the
extragalactic sources, such as the blazar 3C 273. We find that the variability
of GRO J1655-40 can be explained within the framework of the successful
generalised shock model for compact radio sources in which the radio emission
arises from shocked plasma in relativistic jets. Specifically, the
multifrequency flare amplitudes, time delays and radio polarization position
angle measurements are consistent with the predictions of the growth stage of
this model.


title: Angular momentum redistribution and the evolution and morphology of bars

abstract:
  Angular momentum exchange is a driving process for the evolution of barred
galaxies. Material at resonance in the bar region loses angular momentum which
is taken by material at resonance in the outer disc and/or the halo. By losing
angular momentum, the bar grows stronger and slows down. This evolution
scenario is backed by both analytical calculations and by $N$-body simulations.
The morphology of the bar also depends on the amount of angular momentum
exchanged.


title: The fundamental definition of 'radial velocity'

abstract:
  Accuracy levels of metres per second require the fundamental concept of
'radial velocity' for stars and other distant objects to be examined, both as a
physical velocity, and as measured by spectroscopic and astrometric techniques.
Aiming at definitions that are unambiguous at accuracy levels of 1 m/s, we
analyse different concepts of radial velocity and their interrelations. We
distinguish between the geometrically defined 'kinematic radial velocity' and
'astrometric radial velocity' on one hand, and the spectroscopically defined
'barycentric radial-velocity measure' on the other. The last two concepts are
defined by recent resolutions adopted by the International Astronomical Union
(IAU), the motives and consequences of which are explained in this paper.


title: Extragalactic Astronomy with the VLTI: a new window on the Universe

abstract:
  Interferometry in the optical and near infrared has so far played a marginal
role in Extragalactic Astronomy. Active Galactic Nuclei are the brightest and
most compact extragalactic sources, nonetheless only a very limited number
could be studied with speckle interferometry and none with long baseline
interferometry. The VLTI will allow the study of moderately faint extragalactic
objects with very high spatial resolution thus opening a new window on the
universe. With this paper we focus on three scientific cases to show how AMBER
and MIDI can be used to tackle open issues in extragalactic astronomy.


title: Neutrinos From Individual Gamma-Ray Bursts in the BATSE Catalog

abstract:
  We calculate the neutrino emission from individual gamma-ray bursts observed
by the BATSE detector on the Compton Gamma-Ray Observatory. Neutrinos are
produced by photoproduction of pions when protons interact with photons in the
region where the kinetic energy of the relativistic fireball is dissipated
allowing the acceleration of electrons and protons. We also consider models
where neutrinos are predominantly produced on the radiation surrounding the
newly formed black hole. From the observed redshift and photon flux of each
individual burst, we compute the neutrino flux in a variety of models based on
the assumption that equal kinetic energy is dissipated into electrons and
protons. Where not measured, the redshift is estimated by other methods. Unlike
previous calculations of the universal diffuse neutrino flux produced by all
gamma-ray bursts, the individual fluxes (compiled at
http://www.arcetri.astro.it/~dafne/grb/) can be directly compared with
coincident observations by the AMANDA telescope at the South Pole. Because of
its large statistics, our predictions are likely to be representative for
future observations with larger neutrino telescopes.


title:
Gamma-ray burst early optical afterglows: implications for the initial
  Lorentz factor and the central engine

abstract:
  Early optical afterglows have been observed from GRB 990123, GRB 021004, and
GRB 021211, which reveal rich emission features attributed to reverse shocks.
It is expected that Swift will discover many more early afterglows. Here we
investigate in a unified manner both the forward and the reverse external shock
emission components, and introduce a straightforward recipe for directly
constraining the initial Lorentz factor of the fireball using early optical
afterglow data. The scheme is largely independent of the shock microphysics. We
identify two types of combinations of the reverse and forward shock emission,
and explore their parameter regimes. We also discuss a possible diagnostic for
magnetized ejecta. There is evidence that the central engine of GRB 990123 is
strongly magnetized.


title:
Hubble Space Telescope Observations of Binary Very-Low-Mass Stars and
  Brown Dwarfs

abstract:
  We present analysis of Hubble Space Telescope images of 82 nearby field
late-M and L dwarfs. We resolve 13 of these systems into double M/L dwarf
systems and identify an additional possible binary. Combined with previous
observations of 20 L dwarfs, we derive an observed binary fraction for
ultracool dwarfs of 17+4-3%, where the statistics included systems with
separations in the range 1.6-16 A.U. We argue that accounting for biases and
incompleteness leads to an estimated binary fraction 15+-5% in the range 1.6-16
A.U. No systems wider than 16 A.U. are seen, implying that the wide companion
frequency is less than 1.7%; the distribution of orbital separation is peaked
at ~2-4 A.U. and differs greatly from the G dwarf binary distribution. Indirect
evidence suggests that the binary fraction is ~5+-3% for separations less than
1.6 A.U. We find no evidence for differences in the binary fraction between
stellar late-M and L dwarfs and substellar L dwarfs. We note, however, that the
widest (>10 A.U.) systems in our sample are all of earlier (M8-L0) spectral
type; a larger sample is needed determine if this is a real effect. One system
with a spectral type of L7 has a secondary that is fainter in the HST F814W
filter but brighter in F1042M; we argue that this secondary is an early-T
dwarf.


title: Diffusion in supersonic, turbulent, compressible flows

abstract:
  We investigate diffusion in supersonic, turbulent, compressible flows.
Supersonic turbulence can be characterized as network of interacting shocks. We
consider flows with different rms Mach numbers and where energy necessary to
maintain dynamical equilibrium is inserted at different spatial scales. We find
that turbulent transport exhibits super-diffusive behavior due to induced bulk
motions. In a comoving reference frame, however, diffusion behaves normal and
can be described by mixing length theory extended into the supersonic regime.


title: Variability of sub-mJy radio sources

abstract:
  We present 1.4 GHz VLA observations of the variability of radio sources in
the Lockman Hole region at the level of > 100 uJy on timescales of 17 months
and 19 days. These data indicate that the areal density of highly variable
sources at this level is < 0.005 arcmin^{-2}. We set an upper limit of 2% to
the fraction of 50 to 100uJy sources that are highly variable (> 50%). These
results imply a lower limit to the beaming angle for GRBs of 1deg, and give a
lower limit of 200 arcmin^2 to the area that can be safely searched for GRB
radio afterglows before confusion might become an issue.


title: Surprisingly Little O VI Emission Arises in the Local Bubble

abstract:
  This paper reports the first study of the O VI resonance line emission (1032,
1038 Angstroms) originating in the Local Bubble (or Local Hot Bubble)
surrounding the solar neighborhood. In spite of the fact that O VI absorption
within the Local Bubble has been observed, no resonance line emission was
detected during our 230 ksec Far Ultraviolet Spectroscopic Explorer observation
toward a ``shadowing'' filament in the southern Galactic hemisphere. As a
result, tight 2 sigma upper limits are set on the intensities in the 1032 and
1038 Angstrom emission lines: 500 and 530 photons cm^{-2} s^{-1} sr^{-1},
respectively. These values place strict constraints on models and simulations.
They suggest that the O VI-bearing plasma and the X-ray emissive plasma reside
in distinct regions of the Local Bubble and are not mixed in a single plasma,
whether in equilibrium with T ~ 10^6 K or highly overionized with T ~ 4 to 6 x
10^4 K. If the line of sight intersects multiple cool clouds within the Local
Bubble, then the results also suggest that hot/cool transition zones differ
from those in current simulations. With these intensity upper limits, we
establish limits on the electron density, thermal pressure, pathlength, and
cooling timescale of the O VI-bearing plasma in the Local Bubble. Furthermore,
the intensity of O VI resonance line doublet photons originating in the
Galactic thick disk and halo is determined (3500 to 4300 photons cm^{-2} s^{-1}
sr^{-1}), and the electron density, thermal pressure, pathlength, and cooling
timescale of its O VI-bearing plasma are calculated. The pressure in the
Galactic halo's O VI-bearing plasma (3100 to 3800 K cm^{-3}) agrees with model
predictions for the total pressure in the thick disk/lower halo. We also report
the results of searches for other emission lines.


title: The Behaviour of the Optical and X-ray Emission from Scorpius X-1

abstract:
  In 1970, Hiltner & Mook reported the results of the first multiyear study of
the optical emission from Sco X-1. They found that the Sco X-1 B-magnitude
histograms changed from year to year. Subsequent multi-wavelength campaigns
confirmed the variable nature of these optical histograms and also found that
the X-ray and optical emissions were only correlated when Sco X-1 was brighter
than about B = 12.6. Models had suggested that the optical emission from this
source arose from X-rays reprocessed in an accretion disk surrounding the
central neutron star. It was therefore difficult to explain why the optical and
X-ray fluxes were not more closely correlated. In 1994 and 1995, two new
simultaneous optical and X-ray campaigns on Sco X-1 were conducted with the
Burst and Transient Source Experiment on the Compton Gamma Ray Observatory and
the 1 m Yale telescope at Cerro Tololo Inter-American Observatory. Using these
data and models by Psaltis, Lamb & Miller, it is now possible to provide a
qualitative picture of how the X-ray and optical emissions from Sco X-1 are
related. Differences in the B-magnitude histograms are caused by variations in
the mass accretion rate and the relatively short time period usually covered by
optical investigations. The tilted Gamma pattern seen in plots of the
simultaneous X-ray and optical emission from Sco X-1 arises from (1) the nearly
linear relation between the optical B magnitude and the mass accretion rate in
the range 13.3 > B > 12.3 and an asymptotic behaviour in the B magnitude
outside this range, and (2) a double-valued relation between the X-ray emission
and mass accretion rate along the normal branch and the lower flaring branch of
this source.


title: Substructure in the Andromeda Galaxy Globular Cluster System

abstract:
  In the most prominent current scenario of galaxy formation, galaxies form
hierarchically through the merger of smaller systems. Such mergers could leave
behind dynamical signatures which may linger long after the event. In
particular, the globular cluster system (GCS) of a merging satellite galaxy may
remain as a distinct sub-population within the GCS of a massive galaxy. Using
the latest available globular cluster velocities and metallicities, we present
the results of a search for grouping in the GCS of our nearest large spiral
galaxy neighbor, M31. A modified friends-of-friends algorithm is used to
identify a number of possible merger remnants in projected position, radial
velocity and [Fe/H] parameter space. Numerical simulations are used to check
that such merger remnants are indeed plausible over the timescales of interest.
The identification of stellar streams associated with these groups is required
in order to confirm that they represent merger remnants.


title:
Chandra discovery of the intracluster medium around UM425 at redshift
  1.47

abstract:
  We report on a discovery of a candidate cluster of galaxies at redshift
z=1.47 based on Chandra observations in the field of quasars UM425 A & B. We
detect with high significance diffuse emission due the intracluster hot gas
around the quasar pair. This is the second highest redshift cluster candidate
after 3C294 at z=1.786. The diffuse emission is elliptical in shape with about
17" extent. If indeed at z=1.47, this corresponds to a physical size of 140
h_{70}^{-1} Kpc and 2--10 keV luminosity of about 3 times 10^{43} erg/s. The
cluster is unlikely to be the long sought gravitational lens invoked to explain
unusual brightness of UM425 A and the close quasar pair. Coexistence of the
quasars with the cluster suggests a link of activity to cluster environment.
The unusual brightness of UM425 A may then be due to a higher accretion rate.
We also comment briefly on the X-ray spectra of UM 425 A & B which also happen
to be broad absorption line quasars. We argue that present evidence suggests
that the quasars are just a pair and not lensed images of the same quasar.