title: Gravitational Instabilities in Disks with Radiative Cooling

abstract:
  Previous simulations of self-gravitating protostellar disks have shown that,
once developed, gravitational instabilities are enhanced by cooling the disk
constantly during its evolution (Pickett et al. 2002). These earlier
calculations included a very simple form of volumetric cooling, with a constant
cooling time throughout the disk, which acted against the stabilizing effects
of shock heating. The present work incorporates more realistic treatments of
energy transport. The initial disk model extends from 2.3 to 40 AU, has a mass
of 0.07 Msun and orbits a 0.5 Msun star. The models evolve for a period of over
2500 years, during which extensive spiral arms form. The disks structure is
profoundly altered, transient clumps form in one case, but no permanent bound
companion objects develop.


title: How Common are Engines in Ib/c Supernovae?

abstract:
  The association of gamma-ray bursts (GRBs) and core-collapse supernovae (SNe)
of Type Ib and Ic was motivated by the detection of SN1998bw in the error box
of GRB980425 and the now-secure identification of a SN1998bw-like event in the
cosmological GRB030329. The bright radio emission from SN1998bw indicated that
it possessed some of the unique attributes expected of GRBs, namely a large
reservoir of energy in (mildly) relativistic ejecta and variable energy input.
Here we discuss the results of a systematic program of radio observations of
most reported Type Ib/c SNe accessible to the Very Large Array, designed to
determine the fraction of Type Ib/c SNe driven by an engine. We conclude that:
(i) the incidence of such events is low, <3%, and (ii) there appears to be a
clear dichotomy between the majority of hydrodynamic explosions (SNe) and
engine-driven explosions (GRBs)


title:
The Diversity of Cosmic Explosions: Gamma-Ray Bursts and Type Ib/c
  Supernovae

abstract:
  The death of massive stars and the processes which govern the formation of
compact remnants are not fully understood. Observationally, this problem may be
addressed by studying different classes of cosmic explosions and their energy
sources. Here we discuss recent results on the energetics of gamma-ray bursts
(GRBs) and Type Ib/c Supernovae (SNe Ib/c). In particular, radio observations
of GRB030329, which allow us to undertake calorimetry of the explosion, reveal
that some GRBs are dominated by mildly relativistic ejecta such that the total
explosive yield of GRBs is nearly constant, while the ultra-relativistic output
varies considerably. On the other hand, SNe Ib/c exhibit a wide diversity in
the energy contained in fast ejecta, but none of those observed to date (with
the exception of SN1998bw) produced relativistic ejecta. We therefore place a
firm limit of 3% on the fraction of SNe Ib/c that could have given rise to a
GRB. Thus, there appears to be clear dichotomy between hydrodynamic (SNe) and
engine-driven (GRBs) explosions


title:
High-Energy Neutrinos Produced by Interactions of Relativistic Protons
  in Shocked Pulsar Winds

abstract:
  We have estimated fluxes of neutrinos and gamma-rays that are generated from
decays of charged and neutral pions from a pulsar surrounded by supernova
ejecta in our galaxy, including an effect that has not been taken into
consideration, that is, interactions between high energy cosmic rays themselves
in the nebula flow, assuming that hadronic components are the energetically
dominant species in the pulsar wind. Bulk flow is assumed to be randomized by
passing through the termination shock and energy distribution functions of
protons and electrons behind the termination shock are assumed to obey the
relativistic Maxwellians. We have found that fluxes of neutrinos and gamma-rays
depend very sensitively on the wind luminosity, which is assumed to be
comparable to the spin-downluminosity. In the case where B=10^{12}G and P=1ms,
neutrinos should be detected by km^3 high-energy neutrino detectors such as
AMANDA and IceCube. Also, gamma-rays should be detected by Cherenkov telescopes
such as CANGAROO and H.E.S.S. as well as by gamma-ray satellites such as GLAST.
On the other hand, in the case where B=10^{12}G and P=5ms, fluxes of neutrinos
and gamma-rays will be too low to be detected even by the next-generation
detectors. However, even in the case where B=10^{12}G and P=5ms, there is a
possibility that very high fluxes of neutrinos may be realized at early stage
of a supernova explosion (t \le 1yr), where the location of the termination
shock is very near to the pulsar. We also found that there is a possibility
that protons with energies \sim 10^5 GeV in the nebula flow may interact with
the photon field from surface of the pulsar and produce much pions, which
enhances the intensity of resulting neutrinos and gamma-rays.


title:
Apparent Deviations from Keplerian Acceleration for Stars Around the
  Supermassive Black Hole at the Galactic Center

abstract:
  We show that the time-dependent Doppler effect should induce measureable
deviations of the time history of the projected orbit of a star around the
supermassive black hole in the Galactic center (SgrA*) from the expected
Keplerian history. In particular, the line-of-sight acceleration of the star
generates apparent acceleration of its image along its velocity vector on the
sky, even if its actual Keplerian acceleration in this direction vanishes. The
excess apparent acceleration simply results from the transformation of time
between the reference frames of the observer and the star. Although the excess
acceleration averages to zero over a full closed orbit, it could lead to
systematic offsets of a few percent in estimates of the dynamical mass or
position of the black hole that rely on partially sampled orbits with
pericentric distances of ~100AU. Deviations of this magnitude from apparent
Keplerian dynamics of known stars should be detectable by future observations.


title: The Turbulent Star Formation Model. Outline and Tests

abstract:
  We summarize the current status of the turbulent model of star formation in
turbulent molecular clouds. In this model, clouds, clumps and cores form a
hierarchy of nested density fluctuations caused by the turbulence, and either
collapse or re-expand. Cores that collapse can be either internally sub- or
super-sonic. The former cannot further fragment, and can possibly be associated
with the formation of a single or a few stars. The latter, instead, can undergo
turbulent fragmentation during their collapse, and probably give rise to a
cluster of bound objects. The star formation efficiency is low because only a
small fraction of the density fluctuations proceed to collapse. Those that do
not may constitute a class of ``failed'' cores that can be associated with the
observed starless cores. ``Synthetic'' observations of cores in numerical
simulations of non-magnetic turbulence show that a large fraction of them have
subsonic internal velocity dispersions, can be fitted by Bonnor-Ebert column
density profiles, and exhibit ``coherence'' (an apparent independence of
linewidth with column density near the projected core centers), in agreement
with observed properties of molecular cloud cores.


title: Physical interpretation of the UV/X-ray variability behavior of NGC 7469

abstract:
  We present a re-analysis of the simultaneous 30 day IUE/XTE observation of
NGC 7469 done in 1996. Our main progress, in comparison to previous spectral
analysis, is to adopt and fit directly to the data a detailed Comptonization
model. This firstly allows to fit simultaneously the data from the UV to the
hard X-ray band in a self-consistent way and secondly it gives direct
constraints on the physical parameters of the disc-corona system. Our results
are completely consistent with a slab geometry where all the observed UV
emission is supposed to cross the corona but more photon-starved geometries
also give acceptable fits. Whatever the geometry is, the UV seed photon
emission appears to be dominated by the reprocessing of the X-rays. We also
found very interesting correlations between the different model parameters, the
most important one being the anticorrelation between the corona temperature and
the UV flux. Such an anticorrelation is clearly inconsistent with a fixed
disc-corona configuration and suggests a variation of the geometry of the
system. We also find a correlation between the corona optical depth and the
X-ray flux which may reflect processes linked to the corona formation. During
the observations, NGC 7469 appears to accrete near its Eddington limit. This
source could then be an example of magnetically dominated disc-corona system as
recently proposed by Merloni (2003).


title: Masers : High resolution probes of massive star formation

abstract:
  Astrophysical masers are one of the most readily detected signposts of
high-mass star formation. Their presence indicates special conditions, probably
indicative of a specific evolutionary phase. Masers also represent the ultimate
high-resolution probe of star formation with the potential to reveal
information on the kinematics and physical conditions within the region at
milli-arcsecond resolution. To date this potential has largely remained
unfulfilled, however, recent advances suggest that this will soon change. The
key to unlocking the potential of masers lies in identifying where they fit
within the star formation jigsaw puzzle. I will review recent high resolution
observations of OH, water and methanol maser transitions and what they reveal.
I also briefly discuss how multi-transition observations of OH and methanol
masers are being used to constrain maser pumping models and through this
estimate the physical conditions in the masing region.


title:
A multicolor CCD photometric study of the open clusters NGC 2866, Pismis
  19, Westerlund 2, ESO96-SC04, NGC 5617 and NGC 6204

abstract:
  Accurate and deep BVI CCD photometry is presented for the core regions of six
southern compact open clusters (supplemented in one case by U and R bands).
These clusters generally have only scanty photometric data published, in some
case only photoelectric or photographic. Together with adoption of modern
reference isochrones, this has allowed us to derive improved values for their
distance, reddening, age and main sequence morphology.


title:
A Proposal to Search for Transparent Hidden Matter Using Optical
  Scintillation

abstract:
  It is proposed to search for scintillation of extragalactic sources through
the last unknown baryonic structures. Appropriate observation of the
scintillation process described here should allow one to detect column density
stochastic variations in cool 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: Time variation of G and \alpha within models with extra dimensions

abstract:
  We derive the formulae for the time variation of the gravitational "constant"
G and of the fine structure "constant" \alpha in various models with extra
dimensions and analyze their consistency with the available observational data
for distant supernovae. We find that the reported variation of \alpha
translates into a small variation of G that makes distant supernovae to appear
brighter, in contradiction with recent observations of high z supernovae. The
significance of these results within the framework of some cosmological
scenarios is also discussed. We find, however, that the magnitude of the effect
is not large enough to safely discard the models with extra dimensions studied
here.


title:
Contamination of Cluster Radio Sources in the Measurement of the Thermal
  Sunyaev-Zel'dovich Angular Power Spectrum

abstract:
  We present a quantitative estimate of the confusion of cluster radio halos
and galaxies in the measurement of the angular power spectrum of the thermal
Sunyaev-Zel'dovich (SZ) effect. To achieve the goal, we use a purely analytic
approach to both radio sources and dark matter of clusters by incorporating
empirical models and observational facts together with some theoretical
considerations. It is shown that the correction of cluster radio halos and
galaxies to the measurement of the thermal SZ angular power spectrum is no more
than 20% at $l>2000$ for observing frequencies $\nu>30$ GHz. This eliminates
the concern that the SZ measurement may be seriously contaminated by the
existence of cluster radio sources.


title: The evolutionary properties of intermediate-mass stars

abstract:
  We briefly review the main problems related to the computation of the
evolution of intermediate-mass stars: the treatment of turbulent convection and
the occurrence of blue loops during the core He-burning phase. It is shown
that, in order to obtain more accurate and reliable stellar models for this
class of stars, one has to consider all possible theoretical and observational
constraints. This includes observations of low-mass stars to constrain the
treatment of envelope convection, and the analysis of the pulsational behaviour
of Cepheid stars.


title: HMXB, ULX and star formation

abstract:
  Based on recent X-ray observations of the Milky Way, Magellanic Clouds and
nearby starburst galaxies we study population of high mass X-ray binaries,
their connection with ultra-luminous X-ray sources and relation to the star
formation. Although more subtle SFR dependent effects are likely to exist, the
data in the lg(Lx)~36-40.5 luminosity range are broadly consistent with
existence of a ``universal'' luminosity function of HMXBs, which can be roughly
described as a power law with differential slope of ~1.6 and a cutoff at
lg(Lx)~40.5. The ULX sources found in many starburst galaxies occupy the high
luminosity end of this single slope power law distribution, whereas its low
luminosity part is composed of ``ordinary'' high mass X-ray binaries, observed,
e.g. in the Milky Way and Magellanic Clouds.
  As the normalization of the ``universal'' luminosity function is proportional
to the star formation rate, the number and/or the collective X-ray luminosity
of HMXBs can be used to measure the current value of SFR in the host galaxy.
Distant (unresolved) starburst galaxies observed by Chandra at redshifts of
z~0.2-1.3 obey the same Lx-SFR relation as local galaxies, indicating that the
ULXs at these redshifts were not significantly more luminous than those found
in nearby galaxies.


title: Tracing a Z-track in the M31 X-ray Binary RX J0042.6+4115

abstract:
  Four XMM-Newton observations of the core of M31, spaced at 6 month intervals,
show that the brightest point X-ray source, RX J0042.6+4115, has a 0.4-10 keV
luminosity of ~5 10^38 erg/s, and exhibits significant variability in intensity
and X-ray spectrum over a time scale of ~100 s including hard flares; such
behaviour is only observed in Z-sources and transient blackhole binaries in our
Galaxy. The lightcurves, X-ray spectra and hardness-intensity data from the
four XMM-Newton observations all strongly suggest that it is a Z-source,
bringing the total number of known Z-sources to nine.


title:
Simultaneous visible and infrared spectro-polarimetry of a solar
  internetwork region

abstract:
  We present the first simultaneous infrared (IR) and visible
spectro-polarimetric observations of a solar internetwork region. The Fe I
lines at 6301.6 A, 6302.5 A, 15648 A, and 15652 A were observed, with a lag of
only 1 min, using highly sensitive spectro-polarimeters operated in two
different telescopes (VTT and THEMIS at the Observatorio del Teide). Some 30%
of the observed region shows IR and visible Stokes V signals above noise. These
polarization signals indicate the presence of kG magnetic field strengths
(traced by the visible lines) co-existing with sub-kG fields (traced by the
infrared lines). In addition, one quarter of the pixels with signal have
visible and IR Stokes V profiles with opposite polarity. We estimate the
probability density function of finding each longitudinal magnetic field
strength in the region. It has a tail of kG field strengths that accounts for
most of the (unsigned) magnetic flux of the region.


title: The Luminosity Function of Void Galaxies in the Sloan Digital Sky Survey

abstract:
  (Abridged) The Sloan Digital Sky Survey now extends over a large enough
region that galaxies in low density environments can be detected. Rojas et al.
have developed a technique to extract more than 1000 void galaxies with delta
rho/rho < -0.6 on scales r>7 h^{-1} Mpc from the SDSS. In this paper, we
present the luminosity function of these galaxies and compare it to that of
galaxies at higher densities. We obtain a measurement of the void galaxy
luminosity function over the range -21.5<M_r*<-14.5 in the SDSS r-band. The
void galaxy luminosity function (LF) is well fit by a Schechter function with
values of Phi*=(0.19 +- 0.04)*0.01 h^3 Mpc^{-3}, M_r* - 5logh=-19.74 +- 0.11
and alpha=-1.18 +- 0.13, where as the LF of the wall galaxy has Schechter
function parameters Phi*=(1.42 +- 0.03)*0.01 h^3 Mpc^{-3}, M_r* - 5logh=-20.62
+- 0.08 and alpha=-1.19 +- 0.07. The fainter value of M_r* is consistent with
the work of Rojas et al.who found that void galaxies were fainter than galaxies
at higher densities but the value of alpha is very similar to that of galaxies
at higher densities. To investigate this further, the LF of wall and void
galaxies as a function of density is considered. Only the wall galaxies in the
highest density regions have a shallower faint end slope. The LF of the void
galaxies is also compared to the LF of the wall galaxies with similar
properties to the void galaxies. The LF of the bluest, Sersic index n<2 and
EW(Halpha)>5A wall galaxies is very similar in shape to that of the void
galaxies, with only slightly brighter M_r* values and similar values of alpha.
The value of alpha ~ -1.2 found from the void galaxy LF is shallower that that
found from CDM models, suggesting that voids are not filled with a large
population of dwarf galaxies.


title: Sunyaev-Zel'dovich Effects from Quasars in Galaxies and Groups

abstract:
  The energy fed by active galactic nuclei to the surrounding diffuse baryons
changes their amount, temperature, and distribution; so in groups and in member
galaxies it affects the X-ray luminosity and also the Sunyaev-Zel'dovich
effect. Here we compute how the latter is enhanced by the transient blastwave
driven by an active quasar, and is depressed when the equilibrium is recovered
with a depleted density. We constrain such depressions and enhancements with
the masses of relic black holes in galaxies and the X-ray luminosities in
groups. We discuss how all these linked observables can tell the quasar
contribution to the thermal history of the baryons pervading galaxies and
groups.


title:
Binaries discovered by the SPY project. III. HE2209-1444: a massive,
  short period double degenerate

abstract:
  In the course of our search for double degenerate (DD) binaries as potential
progenitors of type Ia supernovae with the UVES spectrograph at the ESO VLT
(ESO SN Ia Progenitor surveY - SPY) we discovered HE2209-1444 to be a
double-lined system consisting of two DA white dwarfs. From the analysis of the
radial velocity curve we determined the period of the system to be P = 6h 38m
47s. The semi-amplitudes for both individual components are 109 km/s each. A
model atmosphere analysis enabled us to derive individual temperatures for both
components (8490 K and 7140 K, resp.) and masses of 0.58 Msol for each
component. The total mass of the system is 1.15 +/- 0.07 Msol. The system will
loose angular momentum due to gravitational wave radiation and therefore will
merge within 5 Gyrs -- less than a Hubble time. HE2209-1444 is the second
massive, short period double degenerate detected by SPY. Its total mass is
about 20 % below the Chandrasekhar mass limit and therefore it does not qualify
as a potentional SN Ia progenitor. However, together with our previous
detections it supports the view that Chandrasekhar mass systems do exist.


title:
Applications of Gas Imaging Micro-Well Detectors to an Advanced Compton
  Telescope

abstract:
  We present a concept for an Advanced Compton Telescope (ACT) based on the use
of pixelized gas micro-well detectors to form a three-dimensional electron
track imager. A micro-well detector consists of an array of individual
micro-patterned proportional counters opposite a planar drift electrode. When
combined with thin film transistor array readouts, large gas volumes may be
imaged with very good spatial and energy resolution at reasonable cost. The
third dimension is determined from the drift time of the ionization electrons.
The primary advantage of this approach is the excellent tracking of the Compton
recoil electron that is possible in a gas volume. Such good electron tracking
allows us to reduce the point spread function of a single incident photon
dramatically, greatly improving the imaging capability and sensitivity. The
polarization sensitivity, which relies on events with large Compton scattering
angles, is particularly enhanced. We describe a possible ACT implementation of
this technique, in which the gas tracking volume is surrounded by a CsI
calorimeter, and present our plans to build and test a small prototype over the
next three years.


title: The XMM-Newton hard band wide angle Survey

abstract:
  We present the preliminary findings of our XMM-Newton Survey performed in the
hard band [7-11] keV. The survey covers nearly 30 squares degrees for a total
of 112 fields observed. We detected in the [7-11] keV band, down to a limit
flux of about 3*10^(-14) erg cm^(-2) s^(-1) a total of 45 sources, 30% of which
show strongly absorption. A detailed spectral characterization of these sources
allows us to constraint the local N_H distribution.


title: GRB 011121: A collimated outflow into wind-blown surroundings

abstract:
  We discover a break in the GRB 011121 afterglow light curve after 1.3 days,
which implies an initial jet opening angle of about 9 deg. The SED during the
first four days is achromatic, and supports the jet origin of this break. The
SED during the supernova bump can be best represented by a black body with a
temperature of 6000 K. The deduced parameters for the decay slope as well as
the spectral index favor a wind scenario, i.e. an outflow into a circum-burst
environment shaped by the stellar wind of a massive GRB progenitor. Due to its
low redshift of z=0.36, GRB 011121 has been the best example for the
GRB-supernova connection until GRB 030329, and provides compelling evidence for
a circum-burster wind region expected to exist if the progenitor was a massive
star.


title: Mass and Angular Momentum Transfer in the Massive Algol Binary RY Persei

abstract:
  We present an investigation of H-alpha emission line variations observed in
the massive Algol binary, RY Per. We give new radial velocity data for the
secondary based upon our optical spectra and for the primary based upon high
dispersion UV spectra. We present revised orbital elements and an estimate of
the primary's projected rotational velocity (which indicates that the primary
is rotating 7 times faster than synchronous). We use a Doppler tomography
algorithm to reconstruct the individual primary and secondary spectra in the
region of H-alpha, and we subtract the latter from each of our observations to
obtain profiles of the primary and its disk alone. Our H-alpha observations of
RY Per show that the mass gaining primary is surrounded by a persistent but
time variable accretion disk. The profile that is observed outside-of-eclipse
has weak, double-peaked emission flanking a deep central absorption, and we
find that these properties can be reproduced by a disk model that includes the
absorption of photospheric light by the band of the disk seen in projection
against the face of the star. We developed a new method to reconstruct the disk
surface density distribution from the ensemble of H-alpha profiles observed
around the orbit, and this method accounts for the effects of disk occultation
by the stellar components, the obscuration of the primary by the disk, and flux
contributions from optically thick disk elements. The resulting surface density
distribution is elongated along the axis joining the stars, in the same way as
seen in hydrodynamical simulations of gas flows that strike the mass gainer
near trailing edge of the star. This type of gas stream configuration is
optimal for the transfer of angular momentum, and we show that rapid rotation
is found in other Algols that have passed through a similar stage.


title: Cold Dark Matter's Small Scale Crisis Grows Up

abstract:
  The Cold Dark Matter (CDM) theory predicts a wealth of substructure within
dark halos. These predictions match observations of galaxy clusters like the
nearby Virgo cluster. However, CDM has a "small scale crisis" since galaxies
dominate the halo with little substructure while the model predicts that
galaxies should be scaled versions of galaxy clusters with abundant
substructure. Compared to CDM predictions, the Milky Way and Andromeda are
"missing" objects with velocity dispersions $\sigma \geq 10$ km s$^{-1}$. The
energy scale of these missing satellites is low enough that stellar winds and
supernovae might remove gas and suppress the formation of their luminous
stellar components. Here, we show that the small scale crisis persists in
fossil groups that have masses of up to 40% of the nearby Virgo cluster of
galaxies. Fossil groups are missing satellites with luminosities that occur at
the predicted frequency in the Virgo cluster. Moreover, the "missing galaxies"
in fossil groups are nearly as luminous as the Milky Way with a velocity
dispersion $\sigma \leq$ 150 km s$^{-1}$.


title:
Ultraviolet Line Emission from Metals in the Low-Redshift Intergalactic
  Medium

abstract:
  We use a high-resolution cosmological simulation that includes hydrodynamics,
multiphase star formation, and galactic winds to predict the distribution of
metal line emission at z~0 from the intergalactic medium (IGM). We focus on two
ultraviolet doublet transitions, OVI 1032,1038 and CIV 1548,1551. Emission from
filaments with moderate overdensities is orders of magnitude smaller than the
background, but isolated emission from enriched, dense regions with
T~10^5-10^5.5 K and characteristic sizes of 50-100 kpc can be detected above
the background. We show that the emission from these regions is substantially
greater when we use the metallicities predicted by the simulation (which
includes enrichment through galactic winds) than when we assume a uniform IGM
metallicity. Luminous regions correspond to volumes that have recently been
influenced by galactic winds. We also show that the line emission is clustered
on scales ~1 h^-1 Mpc. We argue that although these transitions are not
effective tracers of the warm-hot intergalactic medium, they do provide a route
to study the chemical enrichment of the IGM and the physics of galactic winds.


title:
The relationship between the X-ray and radio components in the Compact
  Steep Spectrum Quasar 3C 48

abstract:
  We combine results from ROSAT, Chandra, and multifrequency VLBA observations
of the Compact Steep Spectrum quasar 3C 48. We infer that the X-ray spectrum of
the nucleus is made up of a soft, variable, steep-spectrum component, and
harder, power-law emission of slope consistent with the 1 GHz radio spectrum.
The similarity of 3C 48's X-ray to radio ratio to that seen in core-dominated
radio-loud quasars leads us to examine the possibility that the harder X-ray
emission is inverse Compton radiation from the radio source, which is more than
99% resolved in our VLBA data. The weak (3 sigma) evidence that we find for a
proper motion of 0.5\pm0.2c in a compact radio component about 0.05 arcsec from
the core implies that if this component has a highly relativistic bulk motion,
it is at a very small angle to the line of sight. However, stringent
requirements on the jet opening angle make it unlikely that all the X-ray
emission is from a fast jet which sees boosted Cosmic Microwave Background
emission and emits beamed X-rays in the observer's frame. If the unusual radio
structures are intrinsically one-sided and unbeamed, the inverse Compton
mechanism can provide an appreciable fraction of the X-ray emission if the
magnetic field strength is a factor of six to ten below that which gives equal
energy in radiating relativistic particles and magnetic fields and roughly
minimizes the total energy in the source. It remains possible that the
unresolved X-ray emission arises from close to the central engine, either as an
embedded blazar or associated with the accretion processes. (Slightly
abridged).


title:
Spectroscopic Gravitational Lensing and Limits on the Dark Matter
  Substructure in Q2237+0305

abstract:
  Spatially resolved spectroscopic data from the CIRPASS integral field unit
(IFU) on Gemini are used to measure the gravitational lensing of the 4-image
quasar Q2237+0305 on different size scales. A method for measuring the
substructure present in the lens using observations at multiple wavelengths is
demonstrated to be very effective and independent of many of the degeneracies
inherent in previous methods. The magnification ratios of the QSO's narrow line
region (NLR) and broad line region (BLR) are measured and found to be disagree
with each other and with the published radio and mid-infrared magnification
ratios. The disagreement between the BLR ratios and the radio/mid-infrared
ratios is interpreted as microlensing by stars in the lens galaxy of the BLR
The disagreement between the radio/mid-infrared ratios and the NLR ratios is
interpreted as a signature of substructure on a larger scale, possibly the
missing small scale structure predicted by the standard cold dark matter (CDM)
model. Certain combinations of the radial profile and the substructure surface
densities are ruled out using extensive lensing simulations. A substructure
mass scale as large as 10^8 M is strongly disfavored while 10^4 M is too small
if the radio and mid-infrared emission regions have the expected sizes of ~10
pc. The standard elliptical isothermal lens mass profile is not compatible with
a substructure surface density of < 280 M/pc^2 at the 95% confidence level.
This is 4-7% of the galaxy's surface density (depending on which image position
is used to evaluate this). The required substructure surface density at the
required mass scale is high in comparison with the present expectations within
the CDM model.


title:
The Accelerating Universe and Dark Energy: Evidence from Type Ia
  Supernovae

abstract:
  The measured luminosity distances of Type Ia supernovae (SNe Ia) as a
function of redshift have shown that the expansion of the Universe is currently
accelerating, probably due to the presence of repulsive dark energy such as
Einstein's cosmological constant (Lambda). From about 200 SNe Ia, we find that
H_0t_0 = 0.96 +/ 0.04, and Omega_Lambda - 1.4 Omega_M = 0.35 +/- 0.14.
Combining our data with the results of large-scale structure surveys, we find a
best fit for Omega_M and Omega_Lambda of 0.28 and 0.72, respectively --
essentially identical to the recent WMAP results (and having comparable
precision). The sum of the densities, ~1.0, agrees with extensive measurements
of the cosmic microwave background radiation, including WMAP, and coincides
with the value predicted by most inflationary models for the early Universe. A
number of possible systematic effects (dust, SN evolution) thus far do not seem
to eliminate the need for Omega_Lambda > 0. Recently, analyses of SNe Ia at z =
1.0-1.7 provide further support for current acceleration, and give tentative
evidence for an early epoch of deceleration. The dynamical age of the Universe
is 13.1 +/- 1.5 Gyr, consistent with the ages of globular star clusters and
with the WMAP result of 13.7 +/- 0.2 Gyr. Current projects include the search
for additional SNe Ia at z > 1 to confirm the early deceleration, and the
measurement of a few hundred SNe Ia at z = 0.2-0.8 to determine the equation of
state of the dark energy, w = P/(rho c^2).


title: Pulsar bow shocks as probes of warm neutral gas

abstract:
  Pulsars have mean space velocities >~500 km/s. The consequent ram pressure
results in tight confinement of the star's energetic wind, driving a bow shock
into the surrounding medium. Pulsar bow shocks have long been regarded as a
curiosity, but new optical and X-ray observations are both rapidly expanding
the sample of such sources, and are offering new ways to probe the interaction
between pulsars and their environments. Here we discuss some of these new
results, and explain how these data can be used to probe the density and
structure of neutral gas in the interstellar medium.


title: Chandra Detections of Two Quiescent Black Hole X-Ray Transients

abstract:
  Using the Chandra X-ray Observatory, we have detected the black hole
transients V4641 Sgr and XTE J1859+226 in their low luminosity, quiescent
states. The 0.3-8 keV luminosities are (4.0^(+3.3)_(-2.4))E31 (d/7 kpc)^2 erg/s
and (4.2^(+4.8)_(-2.2))E31 (d/11 kpc)^2 erg/s for V4641 Sgr and XTE J1859+226,
respectively. With the addition of these 2 systems, 14 out of the 15 transients
with confirmed black holes (via compact object mass measurements) now have
measured quiescent luminosities or sensitive upper limits. The only exception
is GRS 1915+105, which has not been in quiescence since its discovery in 1992.
The luminosities for V4641 Sgr and XTE J1859+226 are consistent with the median
luminosity of 2E31 erg/s for the systems with previous detections. Our analysis
suggests that the quiescent X-ray spectrum of V4641 Sgr is harder than for the
other systems in this group, but, due to the low statistical quality of the
spectrum, it is not clear if V4641 Sgr is intrinsically hard or if the column
density is higher than the interstellar value. Focusing on V4641 Sgr, we
compare our results to theoretical models for X-ray emission from black holes
in quiescence. Also, we obtain precise X-ray positions for V4641 Sgr and XTE
J1859+226 via cross-correlation of the X-ray sources detected near our targets
with IR sources in the 2 Micron All-Sky Survey catalog.


title: The 3-Dimensional Structure of HH 32 from GMOS IFU Spetroscopy

abstract:
  We present new high resolution spectroscopic observations of the Herbig-Haro
object HH 32 from System Verification observations made with the GMOS IFU at
Gemini North Observatory. The 3D spectral data covers a 8''.7 x 5''.85 spatial
field and 4820 - 7040 Angstrom spectral region centered on the HH~32 A knot
complex. We show the position-dependent line profiles and radial velocity
channel maps of the Halpha line, as well as line ratio velocity channel maps of
[OIII]5007/Halpha, [OI]6300/Halpha, [NII]6583/Halpha, [SII](6716+6730)/Halpha
and [SII]6716/6730. We find that the line emission and the line ratios vary
significantly on spatial scales of ~1'' and over velocities of ~50 km/s. A
``3/2-D'' bow shock model is qualitatively successful at reproducing the
general features of the radial velocity channel maps, but it does not show the
same complexity as the data and it fails to reproduce the line ratios in our
high spatial resolution maps. The observations of HH 32 A show two or three
superimposed bow shocks with separations of ~3'', which we interpret as
evidence of a line of sight superposition of two or three working surfaces
located along the redshifted body of the HH 32 outflow.


title:
An Attempt to Probe the Radio Jet Collimation Regions in NGC 4278, NGC
  4374 (M84), and NGC 6166

abstract:
  NRAO Very Long Baseline Array (VLBA) observations of NGC 4278, NGC 4374
(M84), NGC 6166, and M87 (NGC 4486) have been made at 43 GHz in an effort to
image the jet collimation region. This is the first attempt to image the first
three sources at 43 GHz using Very Long Baseline Interferometry (VLBI)
techniques. These three sources were chosen because their estimated black hole
mass and distance implied a Schwarzschild radius with large angular size,
giving hope that the jet collimation regions could be studied. Phase
referencing was utilize for the three sources because of their expected low
flux densities. M87 was chosen as the calibrator for NGC 4374 because it
satisfied the phase referencing requirements: nearby to the source and
sufficiently strong. Having observed M87 for a long integration time, we have
detected its sub-parsec jet, allowing us to confirm previous high resolution
observations made by Junor, Biretta & Livio, who have indicated that a wide
opening angle was seen near the base of the jet. Phase referencing successfully
improved our image sensitivity, yielding detections and providing accurate
positions for NGC 4278, NGC 4374 and NGC 6166. These sources are point
dominated, but show suggestions of extended structure in the direction of the
large-scale jets. However, higher sensitivity will be required to study their
sub-parsec jet structure.


title: Probing the Spacetime Around Sgr A* with Radio Pulsars

abstract:
  The supermassive black hole at the Galactic center harbors a bound cluster of
massive stars that should leave neutron-star remnants. Extrapolating from the
available data, we estimate that 100-1000 radio pulsars may presently orbit Sgr
A* with periods of <~100 yr. Optimistically, 1-10 of the most luminous of these
pulsars may be detectable with current telescopes in periodicity searches at
frequencies near 10 GHz, where the effects of interstellar scattering are
alleviated. Long-term timing observations of such a pulsar would clearly reveal
its Keplerian motion, and possibly show the effects of relativistic gravity. We
briefly discuss how pulsar timing can be used to study the dynamical and
interstellar environment of the central black hole, and speculate on the
prospects for astrometric observations of an orbiting pulsar.


title:
Imaging X-ray, Optical, and Infrared Observations of the Transient
  Anomalous X-ray Pulsar XTE J1810-197

abstract:
  We report X-ray imaging, timing, and spectral studies of XTE J1810-197, a
5.54s pulsar discovered by Ibrahim et al. (2003) in recent RXTE observations.
In a set of short exposures with the Chandra HRC camera we detect a strongly
modulated signal (55+/-4% pulsed fraction) with the expected period located at
(J2000) 18:09:51.08, -19:43:51.7, with a uncertainty radius of 0.6 arcsec (90%
C.L.). Spectra obtained with XMM-Newton are well fitted by a two-component
model that typically describes anomalous X-ray pulsars (AXPs), an absorbed
blackbody plus power law with parameters kT = 0.67+/-0.01 keV, Gamma=3.7+/-0.2,
N_H=(1.05+/-0.05)E22 cm^-2, and Fx(0.5-10 keV) = 3.98E-11 ergs/cm2/s.
Alternatively, a 2T blackbody fit is just as acceptable. The location of CXOU
J180951.1-194351 is consistent with a point source seen in archival Einstein,
Rosat, & ASCA images, when its flux was nearly two orders-of-magnitude fainter,
and from which no pulsations are found. The spectrum changed dramatically
between the "quiescent" and "active" states, the former can be modeled as a
softer blackbody. Using XMM timing data, we place an upper limit of 0.03 lt-s
on any orbital motion in the period range 10m-8hr. Optical and infrared images
obtained on the SMARTS 1.3m telescope at CTIO show no object in the Chandra
error circle to limits V=22.5, I=21.3, J=18.9, & K=17.5. Together, these
results argue that CXOU J180951.1-194351 is an isolated neutron star, one most
similar to the transient AXP AX J1844.8-0256. Continuing study of XTE J1810-197
in various states of luminosity is important for understanding and possibly
unifying a growing class of isolated, young neutron stars that are not powered
by rotation.


title: Phantom Cosmic Dynamics: Tracking Attractor and Cosmic Doomsday

abstract:
  We study the dynamics of phantom model and give the conditions for potentials
to admit tracking attractor, de Sitter attractor and big rip attractor.
Especially, we show that phantom models with exponential and inverse power law
potentials do not admit the tracking attractor solution. The "tachyonic"
stability of the system at/near the attractors as well as the quantum stabiltiy
have been studied.


title: The Dyer-Roeder relation in a universe with particle production

abstract:
  We have obtained analytical exact solutions of the Dyer-Roeder equation in a
cosmological model where creation of particles occurs at the expenses of the
gravitational field. We discussed the influences of inhomogeneities in the path
of a light beam on the apparent diameter of astrophysical objects and consider
both redshift independent as redshift dependent distributions of the
inhomogeneities.


title: GRB 020813: polarization in the case of a smooth optical decay

abstract:
  We present the results of a VLT polarimetric monitoring campaign of the GRB
020813 optical afterglow carried out in three nights, from 0.88 to 4.20 days
after the gamma-ray event. The mean values of the degree of linear polarization
(P) and its position angle (Theta) resulting from our campaign are
<P>=1.18+/-0.10% and Theta = 148.7+/-2.3 deg after correcting for Galactic
interstellar polarization. Our VLT data set is most naturally described by a
constant degree of linear polarization and position angle, nonetheless a slow
Theta evolution cannot be entirely ruled out by our data. The VLT monitoring
campaign did not reveal either a significant Theta rotation respect to the Keck
spectropolarimetric observations performed ~0.25 days after the GRB (Barth et
al. 2003). However, <P> is a factor of two lower than the polarization degree
measured from Keck. Additionally, the VLT polarization data allowed us to
construct an accurate V-band light curve. The V-band photometric data revealed
a smooth light curve with a break located between the last Keck and our first
VLT polarimetric measurement, 0.33 < t_(break, V) < 0.88 days after the GRB.
The typical magnitude fluctuations of the VLT V-band lightcurve are 0.003 mag,
0.010 mag and 0.016 mag for our three observing nights, respectively. We
speculate that the stability of Theta might be related to the smoothness of the
light curve.


title:
WIYN Open Cluster Study. XVII. Astrometry and Membership to V=21 in NGC
  188

abstract:
  We present techniques for obtaining presision astrometry using old
photographic plates from assorted large-aperture reflectors in combination with
recent CCD Mosaic Imager frames. At the core of this approach is a
transformation of plate/CCD coordinates into a previously constructed
astrometric reference frame around the open cluster NGC 188. Our primary result
is a new catalog of proper motions and positions for 7812 objects down to V=21
in the 0.75 square degree area around NGC 188. The precision for well-measured
stars is 0.15 mas/yr for proper motions and 2 mas for positions on the system
of the Tycho-2 catalog. The sum of membership probabilities indicates that NGC
188 contains 1050 stars down to V=21. Comprehensive lists of the candidate blue
stragglers and red giants substantially enlarge the number of such stars known
in NGC 188. We have also obtained a small correction to the proper motions from
the mean `motion' of background galaxies. (Abridged)


title:
Extinction in the Galaxy from surface brightnesses of ESO-LV galaxies:
  determination of A_R/A_B ratio

abstract:
  A new method for the determination of the extinction in our Galaxy is
proposed. The method uses surface brightnesses of external galaxies in the B
and R bands. The observational data have been taken from the ESO-LV galaxy
catalogue. As a first application of our model we derive the ratio of R band to
B band extinction. We introduce two methods for computing the ratio which give:
0.62 $\pm$ 0.05 (the first method) and 0.64 $\pm$ 0.06 (the second method)
which is in agreement with the recent literature value of 0.61. This agreement
confirms the validity and efficiency of our model and is an independent
verification for the standard value of the "total to selective extinction". The
method of extinction determination introduced in this paper will be explored in
subsequent publications.


title:
Extinction in the Galaxy from surface brightnesses of ESO-LV galaxies:
  testing 'standard' extinction maps

abstract:
  The relative extinction in the Galaxy computed with our new method
(Choloniewski and Valentijn 2003, CV) is compared with three patterns:
Schlegel, Finkbeiner and Davis (1998, SFD), Burstein and Heiles (1978, BH) and
the cosecans law. It is shown that extinction of SFD is more reliable then that
of BH since it stronger correlates with our new extinction. The smallest
correlation coeffcient have been obtained for the cosecans law. Linear
regression analysis show that SFD overestimate the extinction by a factor of
1.4.
  Our results clearly indicate that there is non-zero extinction at the
Galactic South pole and that the extinction near the Galactic equator
($|b|<40^o$) is significantly larger in the Southern hemisphere than in the
Northern.


title: Dynamo-Driven Outflows in Pre-Planetary Nebulae

abstract:
  The plethora of asymmetric planetary nebulae and the curiously high momenta
of pre-planetary nebula outflows suggest that rotational energy is extracted
from the engines. Magneto-rotational outflows driven by dynamos might be
operating therein. I summarize scenarios involving (a) an isolated AGB star and
(b) a binary. The efficacy of (a) requires re-establishing differential
rotation over the AGB star's lifetime, whereas (b) delivers the angular
momentum at the end of the AGB phase when needed, and may involve turbulent
disks. Both can produce fields that drive outflows of the required mechanical
luminosity and momentum, though weak points and open questions require further
study.


title: The Host Galaxy of GRB 990712

abstract:
  We present a comprehensive study of the z=0.43 host galaxy of GRB 990712,
involving ground-based photometry, spectroscopy, and HST imaging. The
broad-band UBVRIJHKs photometry is used to determine the global spectral energy
distribution (SED) of the host galaxy. Comparison with that of known galaxy
types shows that the host is similar to a moderately reddened starburst galaxy
with a young stellar population. The estimated internal extinction in the host
is Av=0.15+/-0.1 and the star-formation rate (SFR) from the UV continuum is
1.3+/-0.3 M_sun/yr, (not corrected for the effects of extinction). Other galaxy
template spectra than starbursts failed to reproduce the observed SED. We also
present VLT spectra leading to the detection of Halpha from the GRB host
galaxy. A SFR of 2.8+/-0.7 M_sun/yr, is inferred from the Halpha line flux, and
the presence of a young stellar population is supported by a large equivalent
width. Images from HST/STIS show that the host has two separate knots, which
could be two distinct star-forming regions.


title:
Screw instability of the magnetic field connecting a rotating black hole
  with its surrounding disk

abstract:
  Screw instability of the magnetic field connecting a rotating black hole (BH)
with its surrounding disk is discussed based on the model of the coexistence of
the Blandford-Znajek (BZ) process and the magnetic coupling (MC) process
(CEBZMC). A criterion for the screw instability with the state of CEBZMC is
derived based on the calculations of the poloidal and toroidal components of
the magnetic field on the disk. It is shown by the criterion that the screw
instability will occur, if the BH spin and the power-law index for the
variation of the magnetic field on the disk are greater than some critical
values. It turns out that the instability occurs outside some critical radii on
the disk. It is argued that the state of CEBZMC always accompanies the screw
instability. In addtition, we show that the screw instability contributes only
a small fraction of magnetic extraction of energy from a rotating BH.


title: Galaxy Formation and Baryonic Dark Matter

abstract:
  The $\Lambda$CDM scenario to form galaxies encounters many problems when
confronted with observations, namely the prediction of dark matter cusps in all
galaxies, and in particular in dwarf irregulars, dominated by dark matter, or
the low angular momentum and consequent small size of galaxy disks, or the high
predicted number of small systems. We will consider the hypothesis that the
baryonic dark matter could be in the form of gas and could be continuously
involved in the galaxy formation scenario. Through cold gas accretion all along
a galaxy life, angular momentum could be increased, galaxy disks could be more
dominated by baryons than previously thought, and small systems could merge
more frequently.


title: Cosmology calculations almost without general relativity

abstract:
  The Friedmann equation is derived for a Newtonian universe. Changing mass
density to energy density gives exactly the Friedmann equation of general
relativity. Accounting for work done by pressure then yields the two Einstein
equations that govern the expansion of the universe. Descriptions and
explanations of radiation pressure and vacuum pressure are added to complete a
basic kit of cosmology tools. It provides a basis for teaching cosmology to
undergraduates in a way that quickly equips them to do basic calculations. This
is demonstrated with calculations involving: characteristics of the expansion
for densities dominated by radiation, matter, or vacuum; the closeness of the
density to the critical density; how much vacuum energy compared to matter
energy is needed to make the expansion accelerate; and how little is needed to
make it stop. Travel time and luninosity distance are calculated in terms of
the redshift and the densities of matter and vacuum energy, using a scaled
Friedmann equation with the constant in the curvature term determined by
matching with the present values of the Hubble parameter and energy density.
General relativity is needed only for the luminosity distance, to describe how
the curvature of space, determined by the energy density, can change the
intensity of light by changing the area of the sphere to which the light has
spread. Thirty-one problems are included.


title:
An Extended Star Formation History for the Galactic Center from Hubble
  Space Telescope/NICMOS Observations

abstract:
  We present Hubble Space Telescope (HST) Near-Infrared Camera and Multiobject
Spectrometer (NICMOS) observations as evidence that continuous star formation
has created much of the central stellar cusp of the Galaxy. The data are the
deepest ever obtained for a Galactic Center (GC) population, being $>$50%
complete for \mnk$<19.3$, or initial stellar masses $\gtrsim$2 \Msun. We use
Geneva and Padova stellar evolution models to produce synthetic luminosity
functions for burst and continuous star formation scenarios, finding that the
observations are fit best by continuous star formation at a rate that is
consistent with the recent star formation activity that produced the three
massive young clusters in the central 50 \pc. Further, it is not possible to
fit the observations with ancient burst models, such as would be appropriate
for an old population like that in Baade's Window or NGC6528.


title: Some Aspects of Galactic Cosmic Ray Acceleration

abstract:
  I give a synopsis of two aspects of the Galactic Cosmic Ray (GCR)
acceleration problem: the importance of the medium energy gamma-ray window, and
several specific astrophysical sources which merit further investigation.


title: Speckle interferometry of the HAeBe star V376 Cas

abstract:
  We report H- and K'-band speckle interferometric observations of the HAeBe
star V376 Cas. Our observations show that the object is partially resolved. The
visibility curves suggest three separate components: a large scattering
envelope visible only in the H band, a component approximately 100 mas in
radius, and a component with a Gaussian HWHM of approximately 8+/-3 mas,
corresponding to approximately 5 AU at 600 pc distance, which contributes most
of the flux. We compare the smallest structure to the radius of dust
sublimation in the radiation field of the star and find that the radius is
approximately six times larger than that expected. This may indicate that the
inner regions of the system are in fact obscured by a flaring circumstellar
disk or torus seen close to edge-on.


title: Adaptive Optics in Star Formation

abstract:
  Over the past ten years, the concept of adaptive optics has evolved from
early experimental stages to a standard observing tool now available at almost
all major optical and near-infrared telescope facilities. Adaptive optics will
also be essential in exploiting the full potential of the large
optical/infrared interferometers currently under construction. Both
observations with high-angular resolution and at high contrast, and with a high
point source sensitivity are facilitated by adaptive optics. Among the areas
which benefit most from the use of adaptive optics are studies of the
circumstellar environment (envelopes, disks, outflows), substellar companions
and multiple systems, and dense young stellar populations. This contribution
highlights some of the recent advances in star formation studies facilitated by
adaptive optics, and gives a brief tutorial on optimized observing and data
reduction strategies.


title:
A HST Census of Nuclear Star Clusters in Late-Type Spiral Galaxies: II.
  Cluster Sizes and Structural Parameter Correlations

abstract:
  We investigate the structural properties of nuclear star clusters in
late-type spiral galaxies. More specifically, we fit analytical models to HST
images of 39 nuclear clusters in order to determine their effective radii after
correction for the instrumental point spread function. We use the results of
this analysis to compare the luminosities and sizes of nuclear star clusters to
those of other ellipsoidal stellar systems, in particular the Milky Way
globular clusters. Our nuclear clusters have a median effective radius of r_e =
3.5 pc, with 50% of the sample falling between 2.4 pc < r_e < 5.0 pc. This
narrow size distribution is statistically indistinguishable from that of
Galactic globular clusters, even though the nuclear clusters are on average 4
magnitudes brighter than the old globulars. We discuss some possible
interpretations of this result. From a comparison of nuclear cluster
luminosities with various properties of their host galaxies, we confirm that
more luminous galaxies harbor more luminous nuclear clusters. It remains
unclear whether this correlation mainly reflects the influence of galaxy size,
mass, and/or star formation rate. Since the brighter galaxies in our sample
typically have stellar disks with a higher central surface brightness, nuclear
cluster luminosity also correlates with this property of their hosts. On the
other hand, we find no evidence for a correlation between the presence of a
nuclear star cluster and the presence of a large-scale stellar bar.


title:
Galactic mass distribution without dark matter or modified Newtonian
  mechanics

abstract:
  Given the dimensions (including thickness) of a galaxy, and its rotation
profile, a method is shown that finds the mass and density distributions in the
defined envelope that will cause that rotation profile with near-exact speed
matches. Newton's law is unchanged. Surface-light intensity and dark matter are
not needed. Results are presented in dimensionless plots allowing easy
comparisons of galaxies. As compared with the previous version of this paper
the methods are the same, but some data are presented in better dimensionless
parameters, Also the part on thickness representation is simpified and
extended, the contents are rearranged to have a logical buildup in the problem
development, and more examples are added.


title: Spatially resolved X-ray spectroscopy of cooling clusters of galaxies

abstract:
  We present spatially resolved X-ray spectra taken with the EPIC cameras of
XMM-Newton of a sample of 17 cooling clusters and three non-cooling clusters
for comparison. The deprojected spectra are analyzed with a multi-temperature
model, independent of any a priori assumptions about the physics behind the
cooling and heating mechanisms. All cooling clusters show a central decrement
of the average temperature, most of them of a factor of ~2. At each radius
within the cooling region the gas is non-isothermal. The differential emission
measure distribution peaks near the maximum (ambient) temperature, and steeply
declines towards lower temperatures, proportional to T^3, or alternatively a
cut-off at about a quarter to half of the maximum temperature. In general, we
find a poor correlation between radio flux of the central galaxy and the
temperature decrement of the cooling flow. This is interpreted as evidence that
except for a few cases heating by a central AGN is not the most common cause of
weak cooling flows. We investigate the role of heat conduction by electrons and
find that the theoretically predicted conductivity rates are not high enough to
balance radiation losses. The differential emission measure distribution has
remarkable similarities with the predictions from coronal magnetic loop models.
Also the physical processes involved (radiative cooling, thermal conduction
along the loops, gravity) are similar for clusters loops and coronal loops. If
coronal loop models apply to clusters, we find that a few hundred loops per
scale height should be present. The typical loop sizes deduced from the
observed emission measure distribution are consistent with the characteristic
magnetic field sizes deduced from Faraday rotation measurements.


title: Surface r Modes and Burst Oscillations of Neutron Stars

abstract:
  We study the $r$-modes propagating in steadily mass accreting, nuclear
burning, and geometrically thin envelopes on the surface of rotating neutron
stars. For the modal analysis, we construct the envelope models which are fully
radiaitive or have a convective region. As the angular rotation frequency
$\Omega$ is increased, the oscillation frequency $\omega$ of the $r$-modes in
the thin envelopes deviates appreciably from the asymptotic frequency
$\omega=2m\Omega/l^\prime(l^\prime+1)$ defined in the limit of $\Omega\to 0$,
where $\omega$ is the frequency observed in the corotating frame of the star,
and $m$ and $l^\prime$ are the indices of the spherical harmonic function
$Y_{l^\prime}^m$ representing the angular dependence of the modes. We find that
the fundamental $r$-modes in the convective models are destabilized by strong
nuclear burning in the convective region. Because of excessive heating by
nuclear buring, the corotating-frame oscillation frequency $\omega$ of the
$r$-modes in the convective models becomes larger, and hence the inertial-frame
oscillation frequency $|\sigma|$ becomes smaller, than those of the
corresopnding $r$-modes in the radiative models, where $\sigma=\omega-m\Omega$
is negative for the $r$-modes of positive $m$. We find that the relative
frequency change $f=-(\sigma_{conv}-\sigma_{rad})/\sigma_{rad}$ is always
positive and becomes less than $\sim$0.01 for the fundamental $r$-modes of
$l^\prime>|m|+1$ at $|\sigma_{rad}|/2\pi\sim$300Hz for $m=1$ or at
$|\sigma_{rad}|/2\pi\sim$600Hz for $m=2$, where $\sigma_{conv}$ and
$\sigma_{rad}$ denote the oscillation frequencies for the convective and the
radiative envelope models, respectively.


title:
A common trend in the chemical evolution of Local Group dwarf
  spheroidals and Damped Ly-alpha systems

abstract:
  We compare chemical abundances of Local Group dwarf spheroidals, obtained
from recent UVES/VLT observations, and of high redshift Damped Lyman alpha
systems (DLAs), corrected for dust effects. We focus, in particular, on the
abundance ratio between alpha-capture elements and iron, alpha/Fe, a well known
indicator of chemical evolution. Comparison of the data in the plane alpha/Fe
versus Fe/H shows a remarkable similarity between the dwarf spheroidals and the
DLAs, suggestive of a common trend in their chemical evolution. At any given
metallicity these two distinct types of astronomical targets show alpha/Fe
ratios systematically lower than those of Milky Way stars. In terms of chemical
evolution models, this suggests that, on average, dSph galaxies and DLA systems
are characterized by lower, or more episodic, star formation rates than the
Milky Way.


title: FUSE observations of the HI interstellar gas of IZw18

abstract:
  We present the analysis of FUSE observations of the metal-deficient dwarf
galaxy IZw18. We measured column densities of HI, NI, OI, ArI, SiII, and FeII.
The OI/HI ratio (log(OI/HI)=-4.7^{+0.8}_{-0.6}) is consistent with the O/H
ratio observed in the HII regions (all uncertainties are 2-sigma). If the
oxygen is depleted in the HI region compared to the HII regions, the depletion
is at most 0.5dex. This is also consistent with the log(O/H) ratios ~-5
measured with FUSE in the HI regions of other blue compact dwarf galaxies. With
log(NI/OI)=-2.4^{+0.6}_{-0.8}, the measured NI/OI ratio is lower than expected
for primary nitrogen. The determination of the NII column density is needed to
discriminate between a large ionization of NI or a possible nitrogen
deficiency. The neutral argon is also apparently underabundant, indicating that
ionization into ArII is likely important. The column densities of the other
alpha-chain elements SiII and ArI favor the lower edge of the permitted range
of OI column density, log(N(OI))~16.3.


title:
Australia Telescope Compact Array imaging of circumstellar HCN line
  emission from R Scl

abstract:
  We present radio-interferometric observations of HCN J=1-0 line emission from
the carbon star R Scl, obtained with the interim 3-mm receivers of the
Australia Telescope Compact Array. The emission is resolved into a central
source with a Gaussian FWHM of ~1 arcsec, which we identify as the present mass
loss envelope. Using a simple photodissociation model and constraints from
single-dish HCN spectra, we argue that the present mass-loss rate is low, ~2 x
10^{-7} Msol/yr, supporting the idea that R Scl had to experience a brief
episode of intense mass loss in order to produce the detached CO shell at ~10
arcsec radius inferred from single-dish observations. Detailed radiative
transfer modelling yields an abundance of HCN relative to H_2, of ~10^{-5} in
the present-day wind. There appears to be a discrepancy between model results
obtained with higher transition single-dish data included and those from the
J=1-0 interferometer data alone, in that the interferometer data suggest a
smaller envelope size and larger HCN abundance than the single-dish data. The
lack of HCN in the detached shell is consistent with the rapid
photodissociation of HCN into CN as it expands away from the star.


title: Helium-rich EHB Stars in Globular Clusters

abstract:
  Recent UV observations of the most massive Galactic globular clusters show a
significant population of hot stars below the zero-age HB (``blue hook''
stars), which cannot be explained by canonical stellar evolution. Stars which
suffer unusually large mass loss on the red giant branch and thus experience
the helium-core flash while descending the white dwarf cooling curve could
populate this region. They should show higher temperatures than the hottest
canonical HB stars and their atmospheres should be helium-rich and probably
C/N-rich. We have obtained spectra of blue hook stars in omega Cen and NGC 2808
to test this possibility. Our analysis shows that the blue hook stars in these
clusters reach effective temperatures well beyond the hot end of the canonical
EHB and have higher helium abundances than canonical EHB stars. These results
support the hypothesis that the blue hook stars arise from stars which ignite
helium on the white dwarf cooling curve.


title: Cosmic Irony: SETI Optimism from Catastrophes?

abstract:
  Classical arguments for skepticism regarding the Search for ExtraTerrestrial
Intelligence (SETI) are critically examined. It is suggested that the emerging
class of "phase transition" astrobiological models can simultaneously account
for all available astrophysical and biological evidence, explain several
unresolved puzzle in Earth sciences, and rationally justify current and future
SETI projects. In particular, the hypothesis of Annis that local gamma-ray
bursts drive the astrobiological phase transition deserves to be further
quantitatively elucidated. Some epistemological and ethical ramifications of
such a model are briefly discussed.


title: A Comment on Tectonics and the Future of Life on Terrestrial Planets

abstract:
  It is argued that the tight interconnection between biological,
climatological, and geophysical factors in the history of the terrestrial
biosphere can teach us something of wider importance regarding the general
astrobiological evolution of planets in the Galactic habitable zone of the
Milky Way. Motivated by a recent debate on the future of Earth's biosphere, we
suggest an additional reason why the impact of plate tectonics on the
biological evolution is significant on the global Galactic level.


title: Numerical study of halo concentrations in dark-energy cosmologies

abstract:
  We study the concentration parameters, their mass dependence and redshift
evolution, of dark-matter halos in different dark-energy cosmologies with
constant and time-variable equation of state, and compare them with "standard''
Lambda-CDM and OCDM models. We find that previously proposed algorithms for
predicting halo concentrations can be well adapted to dark-energy models. When
centred on the analytically expected values, halo concentrations show a
log-normal distribution with a uniform standard deviation of ~0.2. The
dependence of averaged halo concentrations on mass and redshift permits a
simple fit of the form (1+z) c=c0 (M/M0)^a, with a~-0.1 throughout. We find
that the cluster concentration depends on the dark energy equation of state at
the cluster formation redshift z_{coll} through the linear growth factor
D_+(z_{coll}). As a simple correction accounting for dark-energy cosmologies,
we propose scaling c0 from Lambda-CDM with the ratio of linear growth factors,
c0 -> c0 D_+(z_{coll})/D_{+,Lambda-CDM}(z_{coll}).


title: The Research Productivity of Small Telescopes and Space Telescopes

abstract:
  We present statistics on the research productivity of astronomical
telescopes. These were compiled by finding papers in which new data were
presented, noting which telescopes were used, and then counting the number of
papers, number of pages, and other statistics. The journals used were the
Astronomical Journal, the Astrophysical Journal (including the Letters and
Supplements), and the Publications of the Astronomical Society of the Pacific.
We also compiled citations from the Science Citation Index.
  This work was designed to be similar to that of Trimble (1995), except that
more recent journals (from 1995) and citations (from 1998) were used. We also
did not restrict our sample to large telescopes only: we included all
telescopes from which new data were presented, the smallest of which was a
0.1-m. The data were gathered by first-year work-study undergraduates, who were
instructed to include data for all telescopes for which they found new data
were included in the journals. A by-product of this research was therefore the
relative productivity of ground-based versus space telescopes, and the relative
productivity of radio and other telescopes across the spectrum, versus optical
telescopes.


title:
Photometry of Be Stars in the vicinity of COROT primary targets for
  asteroseismology

abstract:
  We present differential photometry of Be stars close to potential COROT
primary targets for asteroseismology. Several stars are found to be short
period variables. We propose them to be considered as secondary targets in the
COROT asteroseismology fields.


title: Pre-suprenova evolution of rotating massive stars

abstract:
  The Geneva evolutionary code has been modified to study the advanced stages
(Ne, O, Si burnings) of rotating massive stars. Here we present the results of
four 20 solar mass stars at solar metallicity with initial rotational
velocities of 0, 100, 200 and 300 km/s in order to show the crucial role of
rotation in stellar evolution. As already known, rotation increases mass loss
and core masses (Meynet and Maeder 2000). A fast rotating 20 solar mass star
has the same central evolution as a non-rotating 26 solar mass star. Rotation
also increases strongly net total metal yields. Furthermore, rotation changes
the SN type so that more SNIb are predicted (see Meynet and Maeder 2003 and N.
Prantzos and S. Boissier 2003). Finally, SN1987A-like supernovae progenitor
colour can be explained in a single rotating star scenario.


title: The variable quiescence of Cen X-4

abstract:
  Cen X-4 is one of the best studied low-mass neutron star transients in
quiescence. Thanks to XMM-Newton large throughput, Cen X-4 was observed at the
highest signal to noise ever. This allowed us to disclose rapid (>100 s), large
(45+/-7 rms in the 10^{-4}-1 Hz range) intensity variability, especially at low
energies. In order to highlight the cause of this variability, we divided the
data into intensity intervals and fit the resulting spectra with the canonical
model for neutron star transients in quiescence, i.e. an absorbed power law
plus a neutron star atmosphere. The fit is consistent with a variable column
density plus variability in (at least) one of the spectral models. Variations
in the neutron star atmosphere might suggest that accretion onto the neutron
star surface is occuring in quiescence; variations in the power law tail should
support the view of an active millisecond radio pulsar emitting X-rays at the
shock between a radio pulsar wind and inflowing matter from the companion star.


title:
Interpretation of the Global Anisotropy in the Radio Polarizations of
  Cosmologically Distant Sources

abstract:
  We present a detailed statistical study of the observed anisotropy in radio
polarizations from distant extragalactic objects. This anisotropy was earlier
found by Birch (1982) and reconfirmed by Jain and Ralston (1999) in a larger
data set. A very strong signal was seen after imposing the cut
$|RM-\bar{RM}|>6$ rad/m$^2$, where $RM$ is the rotation measure and $\bar{RM}$
its mean value. In this paper we show that there are several indications that
this anisotropy cannot be attributed to bias in the data.
  We also find that a generalized statistic shows a very strong signal in the
entire data without imposing the RM dependent cut. Finally we argue that an
anisotropic background pseudoscalar field can explain the observations.


title: MgS in detached shells around carbon stars. Mining the mass-loss history

abstract:
  We investigate the dust composition of detached shells around carbon stars,
with a focus to understand the origin of the cool magnesium-sulfide (MgS)
material around warm carbon stars, which has been detected around several of
these objects. We build a radiative transfer model of a carbon star surrounded
by an expanding detached shell of dust. The shell contains amorphous carbon
grains and MgS grains. We find that a small fraction of MgS dust (2% of the
dust mass) can give a significant contribution to the IRAS 25 micron flux.
However, the presence of MgS in the detached shell cannot be inferred from the
IRAS broadband photometry alone but requires infrared spectroscopy. We apply
the model to the detached-shell sources R Scl and U Cam, both exhibiting a cool
MgS feature in their ISO/SWS spectra. We use the shell parameters derived for
the molecular shell, using the CO submillimetre maps. The models, with MgS
grains located in the detached shell, explain the MgS grain temperature, as
derived from their ISO spectra, very well. This demonstrates that the MgS
grains are located at the distance of the detached shell, which is a direct
indication that these shells originate from a time when the stellar photosphere
was already carbon-rich. In the case of R Scl, the IRAS photometry is
simultaneously explained by the single shell model. In the case of U Cam, the
IRAS photometry is under predicted, pointing to a contribution from cooler dust
located even further away from the star than the molecular shell. We present a
simple diagnostic to constrain the distance of the shell using the profile of
the MgS emission feature. The emission feature shifts to longer wavelength with
decreasing grain temperature. One can therefore infer a temperature and a
corresponding distance to the star from the observed profile. (abridged)


title: AGB star in the Magellanic Clouds & in other members of the Local Group

abstract:
  Results obtained in the Magellanic Clouds using the latest near-IR DENIS
survey are briefly revised. This sets the base to a similar study of AGB stars
in other galaxies of the Local Group and in particular in NGC6822.


title:
HI metal enrichment from massive star--forming regions: sudden or
  delayed?

abstract:
  It now becomes possible to perform multiphase studies of the ISM from hot to
molecular phases. HI and HII in star--forming gas-rich galaxies seem to exhibit
differences in their metal composition in the sense that HII is less enriched
in nitrogen, argon and possibly oxygen than the HII ionized gas. This
observational evidence needs to be confirmed on larger sample and yet remains
difficult to intepret. We review some possible interpretations. If, on the
other hand, metals remain for a long time in hot gas they might ultimately cool
down and mix with the original interstellar medium rather than being expelled
into the intergalactic medium.


title:
Formalism and quality of a proper motion link with extragalactic objects
  for astrometric satellite missions

abstract:
  The accuracy of the link of the proper motion system of astrometric satellite
missions like AMEX and GAIA is discussed. Monte-Carlo methods were used to
simulate catalogues of positions and proper motions of quasars and galaxies to
test the link. The main conclusion is, that future satellite missions like GAIA
may be ``self-calibrated'' by their measurements of QSOs, while additional
measurements from radio stars or HST-data are needed to calibrate the less deep
reaching astrometric satellite missions of AMEX type.


title: HI and CO in Blue Compact Dwarf Galaxies: Haro 2 and Haro 4

abstract:
  We present VLA HI imaging of two blue compact dwarf (BCD) galaxies, Haro 2
and Haro 4, and of the spiral galaxy Haro 26, which is projected some 22' SW of
Haro 4. We also show a map of the CO(1-0) distribution of Haro 2 obtained with
the OVRO millimeter array, as well as derive an upper limit for CO(2-1)
emission from Haro 4 obtained with the CSO. The HI data of Haro 2 reveal that
the kinematical major axis lies perpendicular to the photometric major axis,
indicating that the atomic hydrogen rotates about the major axis of the galaxy.
This confirms earlier indications based on CCD photometry that Haro 2 is a
dust-lane dE rather than a dIrr. We propose that the present neutral and
molecular ISM configuration is due to recent gas accretion or a merger. The HI
distribution and dynamics of Haro 4 and the neighboring spiral Haro 26 suggest
that they are currently undergoing a tidal interaction, reinforcing the notion
that interactions play an important role in triggering the star formation
witnessed in Blue Compact Galaxies.


title: Wien Fireball Model of Relativistic Outflows in Active Galactic Nuclei

abstract:
  We study steady and spherically symmetric outflows of pure electron-positron
pair plasma as a possible acceleration mechanism of relativistic jets up to the
bulk Lorentz factor of greater than 10. These outflows are initiated by the
``Wien fireball'', which is optically thick to Compton scattering but thin to
absorption and in a Wien equilibrium state between pairs and photons at a
relativistic temperature.


title: Mean-field dynamo action in protoneutron stars

abstract:
  We have investigated the turbulent mean-field dynamo action in protoneutron
stars that are subject to convective and neutron finger instabilities. While
the first one develops mostly in the inner regions of the star, the second one
is favoured in the outer regions, where the Rossby number is much smaller and a
mean-field dynamo action is more efficient. By solving the mean-field induction
equation we have computed the critical spin period below which no dynamo action
is possible and found it to be ~1 s for a wide range of stellar models. Because
this critical period is substantially longer than the characteristic spin
period of very young pulsars, we expect that a mean-field dynamo will be
effective for most protoneutron stars.


title: VINCI / VLTI observations of Main Sequence stars

abstract:
  Main Sequence (MS) stars are by far the most numerous class in the Universe.
They are often somewhat neglected as they are relatively quiet objects (but
exceptions exist), though they bear testimony of the past and future of our
Sun. An important characteristic of the MS stars, particularly the solar-type
ones, is that they host the large majority of the known extrasolar planets.
Moreover, at the bottom of the MS, the red M dwarfs pave the way to
understanding the physics of brown dwarfs and giant planets. We have measured
very precise angular diameters from recent VINCI/VLTI interferometric
observations of a number of MS stars in the K band, with spectral types between
A1V and M5.5V. They already cover a wide range of effective temperatures and
radii. Combined with precise Hipparcos parallaxes, photometry, spectroscopy as
well as the asteroseismic information available for some of these stars, the
angular diameters put strong constraints on the detailed models of these stars,
and therefore on the physical processes at play.


title:
Non-linear evolution of the cosmological background density field as
  diagnostic of the cosmological reionization

abstract:
  We present constraints on the cosmological and reionization parameters based
on the cumulative mass function of the Ly-alpha systems.
  We find that the analysis of the cumulative mass function of the Ly-alpha
systems indicates a reionization redshift z_r=24.2\+-4 (68%CL) in agreement
with the value found on the basis of the WMAP anisotropy measurements, setting
constraints on the amplitude of the density contrast, sigma_8=0.91+-0.04
(68\CL), similar to those derived from the X-ray cluster temperature function.
  Our joint analysis of Ly-alpha cumulative mass function and WMAP anisotropy
measurements shows that the possible current identification of a running of the
slope, dn_s/dlnk \ne 0, at k_p=0.05Mpc^-1 (multipole l of about 700) is mainly
an effect of the existing degeneracy in the amplitude-slope plane at this
scale, the result being consistent with the absence of running, the other
constraints based on WMAP data remaining substantially unchanged.
  Finally, we evaluate the progress on the determination the considered
parameters achievable by using the final temperature anisotropy data from WMAP
and from the forthcoming Planck satellite that will significantly improve the
sensitivity and reliability of these results.
  This work has been done in the framework of the Planck LFI activities.


title:
Star formation in gaseous galaxy halos: VLT-spectroscopy of extraplanar
  HII-regions in NGC55

abstract:
  We present first deep VLT-spectra of a new class of compact extraplanar
objects located in the disk-halo interface of the edge-on spiral galaxy NGC55.
Their spectra reveal continuum emission from stars and show typical
emission-lines as observed in ordinary disk HII-regions. Similar to the Diffuse
Ionized Gas (DIG) the prominent ionization stage of oxygen is O+, whereas the
corresponding one for low metallicity HII-regions is O++. A comparison with
CLOUDY model simulations reveals that the ionization mechanism of these compact
objects is most likely photoionization by late OB stars (O9.5 to B0). Further
analysis of diagnostic diagrams unambiguously confirms the HII-region
character. This raises the question whether these extraplanar HII-regions
(EHRs) originated from the prominent extraplanar gas of this galaxy or have
just been expelled from the disk into the halo. From hydrodynamical
considerations ejection from the disk can be ruled out. Therefore, these
objects must have formed within the halo. Compared to the average abundance of
the central disk HII-region (45% Z_solar) both EHRs reveal substantially lower
[O/H] abundances of about 10% Z_solar. We could establish for the first time
strong differences in the metal content along the minor axis of this galaxy.
Oxygen appears to be less abundant in the halo by about a factor of 4. Since
both EHRs are located above the central part of NGC55, it appears likely, that
their formation was triggered by star formation activity in the disk below. In
this environment the molecular gas clouds out of which EHRs have formed can
survive and collapse only in the period between two successive bursts of star
formation.


title: Molecular gas in the galaxy M83. I - The molecular gas distribution

abstract:
  We present CO(1-0) and CO(2-1) Swedish-ESO Submillimetre Telescope (SEST)
observations of the barred spiral galaxy M83 (NGC5236). The maps cover the
entire optical disk. The CO emission is strongly peaked toward the nucleus,
which breaks up into two separate components in the CO(2-1) data due to the
higher spatial resolution. Emission from the bar is strong, in particular on
the leading edges of the bar. The molecular gas arms are clearly resolved and
can be traced for more than 360\degr . Emission in the inter-arm regions is
detected. The average CO CO(2-1)/CO(1-0) line ratio is 0.77. The ratio is lower
than this on the spiral arms and higher in the inter-arm regions. The arms show
regularly spaced concentrations of molecular gas, Giant Molecular Associations
(GMA's), whose masses are of the order 10^7 Msun. The total molecular gas mass
is estimated to be 3.9*10^9 Msun. This mass is comparable to the total HI mass,
but H_2 dominates in the optical disk. In the disk, H_2 and HI show very
similar distributions, including small scale clumping. We compare the molecular
gas distribution with those of other star formation tracers, such as B and
H_alpha images.


title: The ROSAT North Ecliptic Pole Survey: The Optical Identifications

abstract:
  The X-ray data around the North Ecliptic Pole (NEP) of the ROSAT All Sky
Survey have been used to construct a contiguous area survey consisting of a
sample of 445 individual X-ray sources above a flux of ~2x10^-14 erg cm^-2 s^-1
in the 0.5-2.0 keV energy band. The NEP survey is centered at RA (2000) = 18h
00m, DEC(2000) = +66deg 33arcmin and covers a region of 80.7 sq. deg at a
moderate Galactic latitude of b = 29.8deg. Hence, the NEP survey is as deep and
covers a comparable solid angle to the ROSAT serendipitous surveys, but is also
contiguous. We have identified 99.6% of the sources and determined redshifts
for the extragalactic objects. In this paper we present the optical
identifications of the NEP catalog of X-ray sources including basic X-ray data
and properties of the sources. We also describe with some detail the optical
identification procedure. The classification of the optical counterparts to the
NEP sources is very similar to that of previous surveys, in particular the
Einstein Extended Medium Sensitivity Survey (EMSS). The main constituents of
the catalog are active galactic nuclei (~49%), either type 1 or type 2
according to the broadness of their permitted emission lines. Stellar
counterparts are the second most common identification class (~34%). Clusters
and groups of galaxies comprise 14%, and BL Lacertae objects 2%. One non-AGN
galaxy, and one planetary nebula have also been found. The NEP catalog of X-ray
sources is a homogeneous sample of astronomical objects featuring complete
optical identification.


title: The dual dust chemistry - binarity connection

abstract:
  Accumulating evidence points to a binary nature for the Wolf-Rayet ([WC])
central stars, a group that constitutes about 15% of all central stars of
planetary nebula. From ISO observations, a dual dust chemistry (oxygen- and
carbon-rich) has been shown to be almost exclusively associated with [WC]
central stars, a fact that could be explained by O-rich dust residing in a
disk, while the C-rich dust being more widely distributes. HST/STIS space
resolved spectroscopy of the [WC10] central star CPD-568032, is interpreted as
revealing a dust disk or torus around the central star. This, together with
CPD-568032's variable lightcurve is taken as an indirect indication of
binarity. Finally, we present here, for the first time, preliminary results
from a radial velocity survey of central stars. Out of 18 stars with excellent
data at least 8 are radial velocity variables. If these turn out to be
binaries, it is likely that the central star binary fraction is as high as
about 50%.


title:
Metallic fingers and metallicity excess in exoplanets host stars : the
  accretion hypothesis revisited

abstract:
  While the metallicity excess observed in the central stars of planetary
systems is confirmed by all recent observations, the reason for this excess is
still a subject of debate : is it primordial, is it the result of accretion or
both? The basic argument against an accretion origin is related to the masses
of the outer convective zones which vary by more than one order of magnitude
among the considered stars while the observed overabundances of metals are
similar. We show here that in previous discussions a fundamental process was
forgotten : thermohaline convection induced by the inverse mu-gradient.
"Metallic fingers" may be created which dilute the accreted matter inside the
star. Introducing this effect may reconcile the overabundances expected in case
of accretion with the observations in stars of different masses.


title: Cooling Flows and Radio Mini-Halos in Clusters of Galaxies

abstract:
  We apply to radio mini-halo candidates a model for electron re-acceleration
in cooling flows (Gitti, Brunetti & Setti 2002). In agreement with the basic
idea of the model, we find that the power required for the re-acceleration of
the electron population is only a small fraction of the maximum power that can
be extracted from the cooling flow (as estimated on the basis of the standard
model). Observationally, we notice that the strongest radio mini-halos are
found in association with the most powerful cooling flows, and that cooling
flow powers are orders of magnitude larger than the integrated radio power.
Possible effects of new Chandra and XMM-Newton estimates of $\dot{M}$ on this
trend are considered: we conclude that even if earlier derived cooling rates
were overestimated, cooling flow powers are still well above the radio powers
emitted by mini-halos.


title: The HII Regions of the Damped Lyman alpha Absorber SBS 1543+593

abstract:
  We report new imaging and spectroscopic observations of the damped Ly alpha
(DLA) galaxy SBS 1543+593, a nearby dwarf galaxy whose stellar disk is
intersected by the sightline to the bright background QSO HS 1543+5921. Hubble
Space Telescope imaging observations with WFPC2 in the F450W and F702W bands
are used to measure the DLA galaxy's properties and compile a catalog of its
(candidate) HII regions. Ground-based long-slit spectroscopy of the brightest
HII region in the galaxy yields estimates of the star formation rate (SFR) and
of chemical abundances in the galaxy's interstellar medium. We find that SBS
1543+593 exhibits a SFR $\approx 0.006 h^{-2}_{70} M_{\odot}$ yr$^{-1}$, or a
SFR per unit area of $\approx 1.4 \times 10^{-4} h^{-2}_{70} M_\odot$ yr$^{-1}$
kpc$^{-2}$. We derive gas-phase abundances in the ionized gas of $12 + \log
{\rm (O/H)} = 8.2 \pm 0.2$, which is about 1/3 of the solar value, and $\log
{\rm (N/O)} = -1.40^{+0.2}_{-0.3}$. These values are consistent with the
morphologial appearance of SBS 1543+593, an Sm dwarf of $M_B -5 \log h_{70} =
-16.8\pm0.2$ and of intermediate surface brightness. SBS 1543+593 is the first
{\it bona fide} DLA for which abundances have been measured using emission-line
diagnostics. When compared with future, high-resolution, ultraviolet
spectroscopy, our results should prove key for interpreting abundance
determinations in high redshift DLAs.


title: The First Direct Supernova/GRB Connection: GRB 030329/SN 2003dh

abstract:
  Observations of gamma-ray burst (GRB) afterglows have yielded tantalizing
hints that supernovae (SNe) and GRBs are related. The case had been
circumstantial, though, relying on irregularities in the light curve or the
colors of the afterglow. I will present observations of the optical afterglow
of GRB 030329. The early spectra show a power-law continuum, consistent with
other GRB afterglows. After approximately one week, broad peaks in the spectrum
developed that were remarkably similar to those seen in the spectra of the
peculiar Type Ic SN 1998bw. This is the first direct, spectroscopic
confirmation that at least some GRBs arise from SNe.


title:
Surveying the Inner Halo of the Galaxy with 2MASS-Selected Horizontal
  Branch Candidates

abstract:
  We use 2MASS photometry to select blue horizontal branch (BHB) candidates
covering the sky |b|>15 deg. A 12.5<J<15.5 sample of BHB stars traces the thick
disk and inner halo to d<9 kpc, with a density comparable to that of M giant
stars. We base our sample selection strategy on the Century Survey Galactic
Halo Project, a survey that provides a complete, spectroscopically-identified
sample of blue stars to a similar depth as the 2MASS catalog. We show that a
-0.20<(J-H)_0<0.10, -0.10<(H-K)_0<0.10 color-selected sample of stars is 65%
complete for BHB stars, and is composed of 47% BHB stars. We apply this
photometric selection to the full 2MASS catalog, and see no spatial
overdensities of BHB candidates at high Galactic latitude |b|>50 deg. We insert
simulated star streams into the data and conclude that the high Galactic
latitude BHB candidates are consistent with having no ~5 deg wide star stream
with density greater than 0.33 objects deg^-2 at the 95% confidence level. The
absence of structure suggests there have been no major accretion events in the
inner halo in the last few Gyr. However, at low Galactic latitudes a two-point
angular correlation analysis reveals structure on angular scales <1 deg. This
structure is apparently associated with stars in the thick disk, and has a
physical scale of 10-100 pc. Interestingly, such structures are expected by
cosmological simulations that predict the majority of the thick disk may arise
from accretion and disruption of satellite mergers.


title:
Hubble Space Telescope Observations of cD Galaxies and their Globular
  Cluster Systems

abstract:
  We have used WFPC2 on the Hubble Space Telescope to obtain F450W and F814W
images of four cD galaxies (NGC 541 in Abell 194, NGC 2832 in Abell 779, NGC
4839 in Abell 1656 and NGC 7768 in Abell 2666) in the range 5400 < cz < 8100 km
s^{-1}. For NGC 541, the HST data are supplemented by ground-based B and I
images obtained with the FORS1 on the VLT. We present surface brightness and
color profiles for each of the four galaxies, confirming their classification
as cD galaxies. Isophotal analyses reveal the presence of subarcsecond-scale
dust disks in the nuclei of NGC 541 and NGC 7768. Despite the extreme nature of
these galaxies in terms of spatial extent and luminosity, our analysis of their
globular cluster systems reveals no anomalies in terms of specific frequencies,
metallicity gradients, average metallicities, or the metallicity offset between
the globulars and the host galaxy. We show that the latter offset appears
roughly constant at \Delta [Fe/H] ~ 0.8 dex for early-type galaxies spanning a
luminosity range of roughly four orders of magnitude. We combine the globular
cluster metallicity distributions with an empirical technique described in a
series of earlier papers to investigate the form of the protogalactic mass
spectrum in these cD galaxies. We find that the observed GC metallicity
distributions are consistent with those expected if cD galaxies form through
the cannibalism of numerous galaxies and protogalactic fragments which formed
their stars and globular clusters before capture and disruption. However, the
properties of their GC systems suggest that dynamical friction is not the
primary mechanism by which these galaxies are assembled. We argue that cDs
instead form rapidly, via hierarchical merging, prior to cluster virialization.


title:
The Redshift Distribution of Type-Ia Supernovae: Constraints on
  Progenitors and Cosmic Star Formation History

abstract:
  We use the redshift distribution of type-Ia supernovae (SNe) discovered by
the Supernova Cosmology Project to constrain the star formation history (SFH)
of the Universe and SN Ia progenitor models. Given some of the recent
determinations of the SFH, the observed SN Ia redshift distribution indicates a
long (>~1 h^-1 Gyr) mean delay time between the formation of a stellar
population and the explosion of some of its members as SNe Ia. For example, if
the Madau et al. (1998) SFH is assumed, the delay time tau is constrained to be
tau > 1.7 (tau > 0.7) h^-1 Gyr at the 95%(99%) confidence level (CL). SFHs that
rise at high redshift, similar to those advocated by Lanzetta et al. (2002),
are inconsistent with the data at the 95% CL unless tau > 2.5 h^-1 Gyr. Long
time delays disfavor progenitor models such as edge-lit detonation of a white
dwarf accreting from a giant donor, and the carbon core ignition of a white
dwarf passing the Chandrasekhar mass due to accretion from a subgiant. The SN
Ia delay may be shorter, thereby relaxing some of these constraints, if the
field star formation rate falls, between z=1 and the present, less sharply than
implied, e.g., by the original Madau plot. We show that the discovery of larger
samples of high-z SNe Ia by forthcoming observational projects should yield
strong constraints on the progenitor models and the SFH. In a companion paper
(astro-ph/0309797), we demonstrate that if SNe Ia produce most of the iron in
galaxy clusters, and the stars in clusters formed at z~2, the SN Ia delay time
must be lower than 2 Gyr. If so, then the Lanzetta et al. (2002) SFH will be
ruled out by the data presented here.


title:
The Type-Ia Supernova Rate in z < 1 Galaxy Clusters: Implications for
  Progenitors and the Source of Cluster Iron

abstract:
  The iron mass in galaxy clusters is about 6 times larger than could have been
produced by core-collapse supernovae (SNe), assuming the stars in the cluster
formed with a standard initial mass function (IMF). SNe Ia have been proposed
as the alternative dominant iron source. Different SN Ia progenitor models
predict different ``delay functions'' between the formation of a stellar
population and the explosion of some of its members as SNe Ia. We use our
previous measurements of the cluster SN Ia rate at high redshift to constrain
SN Ia progenitor models and the star-formation epoch in clusters. The low
observed rate of cluster SNe Ia at z ~ 0 - 1 means that, if SNe Ia produced the
observed amount of iron, they must have exploded at even higher z. This puts a
>95% upper limit on the mean SN Ia delay time of tau <2 Gyr (<5 Gyr) if the
stars in clusters formed at redshift z<2 (z<3), assuming Ho=70 km/s/Mpc. In a
companion paper (astro-ph/0309796), we show that, for some current versions of
cosmic (field) star formation history (SFH), observations of field SNe Ia place
a lower bound on the delay time, tau>3 Gyr. If these SFHs are confirmed, the
entire range of tau will be ruled out. Cluster enrichment by core-collapse SNe
from a top-heavy IMF will then remain the only viable option.


title:
Discovery of a faint R-band drop-out: a strongly reddened lensed star
  forming galaxy at z=1.68

abstract:
  We report the discovery of an unusual emission line galaxy at redshift z=1.68
found from near-IR imaging and spectroscopic observations with ISAAC/VLT of a
faint gravitationally lensed R-band drop-out behind the lensing cluster Abell
1835. From the emission lines of [O_III], and H_beta this galaxy shows a
moderate to high excitation and line equivalent widths typical of relatively
metal-poor HII galaxies. Its apparent J magnitude translates to an absolute
B-band magnitude M_B ~ -16.4 once corrected for a gravitational magnification
of 1.8 magnitudes. This makes it one of the faintest intermediate redshift
galaxiesknown so far. From the presence of emission lines and the available
VRIJHK photometry we determine constraints on its dominant stellar population.
The only viable fit found is for a fairly young (~ 6-9 Myr) burst suffering
from a considerable extinction (A_v ~ 1.2-1.8 mag). We find that this object
resembles strongly HII galaxies and intermediate redshift compact emission line
galaxies, albeit suffering from a larger extinction than usual. We also discuss
the possible contamination introduced by such R-band drop-out galaxies in
searches for z > 5 galaxies.


title:
A close look at the state transitions of Galactic black hole transients
  during outburst decay

abstract:
  We characterize the evolution of spectral and temporal properties of several
Galactic black hole transients during outburst decay using the data from well
sampled PCA/\rxte observations close to the transition to the low/hard state.
We find several global patterns of evolution for spectral and temporal
parameters before, during, and after the transition. We show that the changes
in temporal properties (sudden increase or decrease in the rms amplitude of
variability) are much sharper than the changes in the spectral properties, and
it is much easier to identify a state transition with the temporal properties.
  The spectral index shows a drop 3-5 days before the transition for some of
our sources. The ratio of the power-law flux to the total flux in the 3-25 keV
band increases close to the transition, which may mean that the system must be
dominated by the coronal emission for the transition to occur. We also show
that the power-law flux shows a sharp change along with the temporal properties
during the transitions which may indicate a threshold transition volume for the
corona. The evolution of the spectral and temporal properties after the
transition is consistent with the idea that the inner accretion disk moves away
from the black hole. Based on the evolution of spectral and temporal parameters
and changes during the transitions, we discuss possible scenarios of how the
transition is happening.