title:
Hot Interstellar Gas and Stellar Energy Feedback in the Antennae
  Galaxies

abstract:
  We have analyzed Chandra archival observations of the Antennae galaxies to
study the distribution and physical properties of its hot interstellar gas.
Eleven distinct diffuse X-ray emission regions are selected according to their
underlying interstellar structures and star formation activity. The X-ray
spectra of these regions are used to determine their thermal energy contents
and cooling timescales. Young star clusters in these regions are also
identified and their photometric measurements are compared to evolutionary
stellar population synthesis models to assess their masses and ages. The
cluster properties are then used to determine the stellar wind and supernova
energies injected into the ISM. Comparisons between the thermal energy in the
hot ISM and the expected stellar energy input show that young star clusters are
sufficient to power the X-ray-emitting gas in some, but not all, active star
formation regions. Super-star clusters, with masses >= 1x10^5 M_sol, heat the
ISM, but the yield of hot interstellar gas is not directly proportional to the
cluster mass. Finally, there exist diffuse X-ray emission regions which do not
show active star formation or massive young star clusters. These regions may be
powered by field stars or low-mass clusters formed within the last ~100 Myr.


title: Black-Hole Mass Measurements

abstract:
  The applicability and apparent uncertainties of the techniques currently
available for measuring or estimating black-hole masses in AGNs are briefly
summarized.


title:
Structure of Disk Dominated Galaxies: II. Color Gradients and Stellar
  Population Models

abstract:
  (Abridged) We investigate optical and near-IR color gradients in a sample of
172 low-inclination galaxies spanning Hubble types S0--Irr. The colors are
compared to stellar population synthesis models from which luminosity-weighted
average ages and metallicities are determined. We explore the effects of
different underlying star formation histories and additional bursts of star
formation. Our results are robust in a relative sense under the assumption that
our galaxies shared a similar underlying star formation history and that no
bursts involving more than ~10% of the galaxy mass have occurred in the past
1-2 Gyr. We find strong correlations in age and metallicity with Hubble-type,
rotational velocity, total magnitude, and central surface brightness in the
sense that earlier-type, faster rotating, more luminous, and higher surface
brightness galaxies are older and more metal-rich, suggesting an early and more
rapid star formation history for these galaxies. The increasing trends with
rotational velocity and total magnitude level off for V_rot > 120 km/s and M_K
< -23 mag respectively. This effect is stronger for metallicity (than age)
which could reflect a threshold potential above which all metals are retained
and thus metallicity saturates at the yield. Trends in gradients with galaxy
parameters are compared with model predictions: these trends do not agree with
predictions of semi-analytic models of hierarchical galaxy formation, possibly
due to the effect of bar-induced radial flows. The observed trends are in
agreement with chemo-spectrophotometric models of spiral galaxy evolution based
on CDM-motivated scaling laws but none of the hierarchical merging
characteristics, implying a strong dependence of the star formation history of
spiral galaxies on the galaxy potential and halo spin parameter.


title: A Strategy for Finding Near Earth Objects with the SDSS Telescope

abstract:
  We present a detailed observational strategy for finding Near Earth Objects
(NEOs) with the Sloan Digital Sky Survey (SDSS) telescope. We investigate
strategies in normal, unbinned mode as well as binning the CCDs 2x2 or 3x3,
which affects the sky coverage rate and the limiting apparent magnitude. We
present results from 1 month, 3 year and 10 year simulations of such surveys.
For each cadence and binning mode, we evaluate the possibility of achieving the
Spaceguard goal of detecting 90% of 1 km NEOs (absolute magnitude H <= 18 for
an albedo of 0.1). We find that an unbinned survey is most effective at
detecting H <= 20 NEOs in our sample. However, a 3x3 binned survey reaches the
Spaceguard Goal after only seven years of operation. As the proposed large
survey telescopes (PanStarss; LSST) are at least 5-10 years from operation, an
SDSS NEO survey could make a significant contribution to the detection and
photometric characterization of the NEO population.


title:
A Survey of Star-Forming Galaxies in the z=1.4-2.5 `Redshift Desert':
  Overview

abstract:
  We present the first results of a large-scale survey, using the UV/blue
sensitive LRIS-B spectrograph on the Keck I telescope, of galaxies in the
redshift interval 1.4<z<2.5, often called the `redshift desert' because of
historical difficulties in spectroscopically identifying galaxies in that
range. We introduce two samples of star forming galaxies, `BX' galaxies at
<z>=2.20+/-0.32 and `BM' galaxies at <z>=1.70+/-0.34; currently we have
spectroscopically confirmed 749 of the former and 114 of the latter. We also
present initial results of deep near-IR photometry and spectroscopy, from which
we show that z~2 galaxies are significantly redder in their optical/IR colors
compared to similarly UV-selected galaxies at z~3, but that the characteristics
of their galaxy-scale outflows are quite similar. We illustrate by example the
information which can be deduced on the stellar populations, metallicities, and
kinematics of `redshift desert' galaxies from easily accessible rest-frame
far-UV and rest-frame optical spectra. Far from being hostile to observations,
the universe at z~2 is uniquely suited to providing information on the
astrophysics of star-forming galaxies and the intergalactic medium, and the
relationship between the two [abridged].


title: HST Observations of the Main Sequence of M4

abstract:
  This paper presents new results from a photometric study of the main-sequence
stars in M4, the closest globular cluster to the sun. Multi-field, multi-epoch
observations at approximately 1, 2, and 6 core-radii were obtained with the
WFPC2 camera on the HST. The multi-epoch observations allowed us to clean the
data on the basis of proper motion. In all the fields the cluster main sequence
can be traced to at least V = 27.0 but there remains a trail of stars to the
limit of the data near V = 30 in the deepest outer field. There is no evidence
that we have reached the end of the hydrogen burning main sequence in any of
our fields, however, there is some indication that very few stars remain to be
detected in the deepest data.
  The scatter about the cluster main sequence yields a surprisingly small and
variable binary fraction; f_b = 2% in the inner parts of the cluster falling to
the 1% range outside. For the currently visible main sequence stars, the
cluster mass function is very flat (alpha =0.1) in the outer field and flattens
further in the inner fields suggesting well developed mass segregation. The
observed variation in the mass function is broadly consistent with isotropic,
multi-mass Michie-King models. Because we have a large sample of white dwarfs
in the outer field we are able to show that the cluster IMF above 0.8Msun was
considerably steeper than the present day mass function for low mass stars.
  Two appendicies are included in this contribution; a detailed discussion of
the techniques used to reduce the data and a direct comparison between the
cluster stars and those belonging to the inner spheroid of the Galaxy yielding
a Galactocentric distance of 7.5+/-0.6 kpc.


title:
Morphological Classification of Galaxies by Shapelet Decomposition in
  the Sloan Digital Sky Survey II: Multiwavelength Classification

abstract:
  We describe the application of the `shapelet' linear decomposition of galaxy
images to multi-wavelength morphological classification using the $u,g,r,i,$
and $z$-band images of 1519 galaxies from the Sloan Digital Sky Survey. We
utilize elliptical shapelets to remove to first-order the effect of inclination
on morphology. After decomposing the galaxies we perform a principal component
analysis on the shapelet coefficients to reduce the dimensionality of the
spectral morphological parameter space. We give a description of each of the
first ten principal component's contribution to a galaxy's spectral morphology.
We find that galaxies of different broad Hubble type separate cleanly in the
principal component space. We apply a mixture of Gaussians model to the
2-dimensional space spanned by the first two principal components and use the
results as a basis for classification. Using the mixture model, we separate
galaxies into three classes and give a description of each class's physical and
morphological properties. We find that the two dominant mixture model classes
correspond to early and late type galaxies, respectively. The third class has,
on average, a blue, extended core surrounded by a faint red halo, and typically
exhibits some asymmetry. We compare our method to a simple cut on $u-r$ color
and find the shapelet method to be superior in separating galaxies.
Furthermore, we find evidence that the $u-r=2.22$ decision boundary may not be
optimal for separation between early and late type galaxies, and suggest that
the optimal cut may be $u-r \sim 2.4$.


title: Gemini imaging of QSO host galaxies at z~2

abstract:
  We present results of a Gemini adaptive optics (AO) imaging program to
investigate the host galaxies of typical QSOs at z~2. Our aim is to study the
host galaxies of typical, L*_qso QSOs at the epoch of peak QSO and star
formation activity. The large database of faint QSOs provided by the 2dF QSO
Redshift Survey allows us to select a sample of QSOs at z=1.75-2.5 which have
nearby (<12 arcsecond separation) bright stars suitable for use as AO guide
stars. We have observed a sample of 9 QSOs. The images of these sources have AO
corrected full-width at half-maximum of between 0.11 and 0.25 arcseconds. We
use multiple observations of point spread function (PSF) calibration star pairs
in order to quantify any uncertainty in the PSF. We then factored these
uncertainties into our modelling of the QSO plus host galaxy. In only one case
did we convincingly detect a host (2QZ J133311.4+001949, at z=1.93). This host
galaxy has K=18.5+-0.2 mag with a half-light radius, r_e=0.55+-0.1'',
equivalent to ~3L*_gal assuming a simple passively evolving model. From
detailed simulations of our host galaxy modelling process, we find that for
four of our targets we should be sensitive to host galaxies that are equivalent
to ~2L*_gal (passively evolved). Our non-detections therefore place tight
constraints on the properties of L*_qso QSO host galaxies, which can be no
brighter (after allowing for passive evolution) than the host galaxies of
L*_qso AGN at low redshift, although the QSOs themselves are a factor of ~50
brighter. This implies that either the fueling efficiency is much greater at
high redshift, or that more massive black holes are active at high redshift.


title: HST Observations of the White Dwarf Cooling Sequence of M4

abstract:
  We investigate in detail the white dwarf cooling sequence of the globular
cluster Messier 4. In particular we study the influence of various systematic
uncertainties, both observational and theoretical, on the determination of the
cluster age from the white dwarf cooling sequence. These include uncertainties
in the distance to the cluster and the extinction along the line of sight, as
well as the white dwarf mass, envelope and core compositions and the white
dwarf --main sequence mass relation. We find that fitting to the full
two-dimensional colour-magnitude diagram offers a more robust method for age
determination than the traditional method of fitting the one-dimensional white
dwarf luminosity function.
  After taking into account the various uncertainties, we find a best fit age
of 12.1 Gyr, with a 95% lower limit of 10.3 Gyr. We also perform fits using two
other sets of cooling models from the literature. The models of Chabrier et al
(2000) yield an encouragingly similar result, although the models of Salaris et
al (2000) do not provide as good a fit. Our results support our previous
determination of a delay between the formation of the Galactic halo and the
onset of star formation in the Galactic disk.


title: An Erupting Classical Nova in a Globular Cluster of M87

abstract:
  Only one certain classical nova eruption has ever been detected inside a
globular cluster - nova 1860 A.D. (T Sco) in M80. During a survey of M87 we
have detected an erupting star coincident (to within 0.08 pixels) with a
globular cluster of that giant elliptical galaxy. We are able to discount
variables in the foreground or background of M87. The light curve and color of
the erupting star match those expected for a nova at the distance of M87. The
chance superposition of an M87 field nova on the globular cluster is very
unlikely but cannot be completely ruled out.Our detection hints at a globular
cluster nova frequency $f \sim .004$ novae/cluster/year, much higher than
previous observations have suggested.


title: Optical Selection of Galaxies at Redshifts 1<z<3

abstract:
  Few galaxies have been found between the redshift ranges z < ~1 probed by
magnitude-limited surveys and z > ~3 probed by Lyman-break surveys. Comparison
of galaxy samples at lower and higher redshift suggests that large numbers of
stars were born and the Hubble sequence began to take shape at the intermediate
redshifts 1<z<3, but observational challenges have prevented us from observing
the process in much detail. We present simple and efficient strategies that can
be used to find large numbers of galaxies throughout this important but
unexplored redshift range. All the strategies are based on selecting galaxies
for spectroscopy on the basis of their colors in ground-based images taken
through a small number of optical filters: GRi for redshifts 0.85<z<1.15, GRz
for 1<z<1.5, and UGR for 1.4<z<2.1 and 1.9<z<2.7. The performance of our
strategies is quantified empirically through spectroscopy of more than 2000
galaxies at 1<z<3.5. We estimate that more than half of the UV-luminosity
density at 1<z<3 is produced by galaxies that satisfy our color-selection
criteria. Our methodology is described in detail, allowing readers to devise
analogous selection criteria for other optical filter sets.


title:
Concerning the White Dwarf Cooling Age of M4: A Response to the Paper by
  De Marchi et al. on "A Different Interpretation of Recent HST Observations"

abstract:
  We respond to the paper by De Marchi, Paresce, Straniero and Moroni (2003) on
the white dwarf cooling age of M4. The authors question the data analysis and
interpretation that led to the conclusions in Hansen et al. (2002). In their
paper, De Marchi et al. are unable to obtain photometry as deep as ours from
the same data set and therefore assert that only a lower limit to the white
dwarf cooling age for this cluster of approximately 9 Gyr can be obtained.
  In this short contribution we show that shortcomings in the data analysis and
reduction techniques of De Marchi et al. are responsible for their inability to
reach the photometry limits that our study reports. In a forthcoming paper in
which the complete techniques for age determination with white dwarfs are laid
out, we demonstrate that their method of fitting the luminosity function gives
a spuriously low white dwarf cooling age.


title: Are there thin accretion disks?

abstract:
  Total and internal energy requirements set constraints on the allowable
temperature on the disk. In a gas pressure dominated disk, they lead to a
cooling rate that decreases with temperature. These findings are used to show
that the flow is mildly supersonic, with the azimuthal Mach number moderately
exceeding one in a large extent of the disk. Only in the narrow outermost
region, of about 12% of the disk extent, the Mach number greatly exceeds one.
It is also shown that, under most favorable conditions, radiation can, at the
most, transport 20% of the heat produced, close to the inner radius. Far away,
under the same conditions, this efficiency can rise to 100%. This result
depends only on boundary conditions, being independent of the accretion rate
and mass of the central object.The geometrical thin disk approximation is
violated everywhere in the disk, except in the narrow region where, under the
unlikely assumption of thermodynamical equilibrium or, at least, local
equilibrium, the flow is indeed supersonic.


title: The Fate of Luminous Compact Blue Galaxies: An Environmental Approach

abstract:
  Luminous Compact Blue Galaxies (LCBGs) are a heterogeneous class which
dominate an intermediate phase of galaxy evolution. These sources account for
the majority of the star formation between 0.3<z<1, yet the identity of their
present-day counterparts is an open question. An environmental dependence to
their evolution may provide the answer. We have undertaken the first census of
LCBGs in intermediate-redshift clusters using broad and narrow-band images from
the WIYN Long Term Variability Study. Several key clusters are in the southern
sky. The Southern African Large Telescope's (SALT) Prime Focus Imaging
Spectrograph (PFIS), with a field of view matching our WIYN data, will allow us
to determine several fundamental characteristics of cluster LCBGs, including
(1) star formation rates (SFR) and metallicities from low dispersion
Mulit-Object Spectroscopy (MOS); (2) dynamical masses from line-widths measured
via high dispersion MOS; and (3) cluster velocity dispersions of LCBGs relative
to other cluster emission-line galaxies via Fabry-Perot imaging or MOS. We
tentatively connect these distant galaxies with their local, evolved
counterparts, and discuss how PFIS observations will enable us to make the
physical distinction between LCBGs in clusters and the field.


title:
The Global Baroclinic Instability in Accretion Disks. II: Local Linear
  Analysis

abstract:
  This paper contains a local linear stability analysis for accretion disks
under the influence of a global radial entropy gradient beta = - d log T / d
log r for constant surface density. Numerical simulations suggested the
existence of an instability in two- and three-dimensional models of the solar
nebula. The present paper tries to clarify, quantify, and explain such a global
baroclinic instability for two-dimensional flat accretion disk models. As a
result linear theory predicts a transient linear instability that will amplify
perturbations only for a limited time or up to a certain finite amplification.
This can be understood as a result of the growth time of the instability being
longer than the shear time which destroys the modes which are able to grow. So
only non-linear effects can lead to a relevant amplification. Nevertheless, a
lower limit on the entropy gradient ~beta = 0.22 for the transient linear
instability is derived, which can be tested in future non-linear simulations.
This would help to explain the observed instability in numerical simulations as
an ultimate result of the transient linear instability, i.e. the Global
Baroclinic Instability.


title: On the oxygen abundance of HE0107-5240

abstract:
  We have determined the oxygen abundance of HE0107-5240 from UV-OH lines
detected in VLT/UVES spectra. Using a plane-parallel LTE model atmosphere, we
derive [O/Fe] = +2.4, and a similar analysis of CD -38 245 yields [O/Fe] =
+1.0. We estimate systematic errors due to 3D effects to be in the order of 0.3
to 0.4 dex. That is, our derived O abundances are likely overestimates: effects
from thermal inhomogeneities due to convection may require that the abundances
should be reduced by 0.3-0.4 dex or even more. Radial velocity data for
HE0107-5240 based on high-resolution spectra show that over a time span of 373
days the radial velocity was constant at 44.5 km/s, with a 1 sigma scatter of
the measurements of 0.5 km/s. However, it can not yet be ruled out that
HE0107-5240 is a very long period and/or low amplitude binary. These results
provide new constraints on scenarios for the origin of the abundance pattern of
HE0107-5240. In particular, it seems unlikely that the large overabundances of
CNO have been produced in a medium-mass AGB star which later evolved to a white
dwarf. The oxygen abundance of HE0107-5240 is significantly smaller than the
prediction of Umeda & Nomoto (2003) from calculated yields of a ~25 solar mass
Population III star exploding as a supernova of low explosion energy (E_exp = 3
x 10^50 erg) with mixing and fallback. The scenario of Limongi et al. (2003),
involving two Population III supernovae, predicts an oxygen abundance of [O/Fe]
= +4.1 for HE0107-5240, in strong contradiction with the observed value. In
conclusion, none of the above mentioned scenarios, in their present
realizations, can satisfactorly explain the abundance pattern of HE0107-5240.


title: N-body simulations of stars escaping from the Orion nebula

abstract:
  We study the dynamical interaction in which the two single runaway stars AE
Aurigae and mu Columbae and the binary iota Orionis acquired their unusually
high space velocity. The two single runaways move in almost opposite directions
with a velocity greater than 100 km/s away from the Trapezium cluster. The star
iota Ori is an eccentric (e=0.8) binary moving with a velocity of about 10 km/s
at almost right angles with respect to the two single stars. The kinematic
properties of the system suggest that a strong dynamical encounter occurred in
the Trapezium cluster about 2.5 Myr ago. Curiously enough, the two binary
components have similar spectral type but very different masses, indicating
that their ages must be quite different. This observation leads to the
hypothesis that an exchange interaction occurred in which an older star was
swapped into the original iota Orionis binary. We test this hypothesis by a
combination of numerical and theoretical techniques, using N-body simulations
to constrain the dynamical encounter, binary evolution calculations to
constrain the high orbital eccentricity of iota Orionis and stellar evolution
calculations to constrain the age discrepancy of the two binary components. We
find that an encounter between two low eccentricity (0.4<e<0.6) binaries with
comparable binding energy, leading to an exchange and the ionization of the
wider binary, provides a reasonable solution to this problem.


title: The origin of intergalactic thermonuclear supernovae

abstract:
  The population synthesis method is used to study the possibility of
explaining the appreciable fraction (20^+12_15%) of the intergalactic (no-host)
type Ia supernovae observed in galaxy clusters (Gal-Yam ete al. 2003) by binary
whote dwarf merginngs in the cores of globular clusters. In a typical globular
cluster, the number of merging double white dwarfs is fount to be smaller than
10^{-13} per year per average cluster star during the entire evolution of the
cluster, which is a factor of 3 higher than in a Milky-Way-type galaxy. From 5
to 30% of the merging white dwarfs are dynamically expelled from the cluster
with barycenter velocities up to 150 km/s. SN Ia explosions during the mergers
of binary white dwarfs in dense star clusters may account for \sim 1% of the
total rate of SN Ia in the central parts of galaxy clusters if the baryon mass
fraction in such star clusters is \sim 0.3%.


title:
Determining the Location of the Tip of the Red Giant Branch in Old
  Stellar Populations: M33, Andromeda I & II

abstract:
  The absolute bolometric luminosity of the point of core Helium ignition in
old, metal poor, red-giant stars is of roughly constant magnitude, varying only
very slightly with mass or metallicity. It can thus be used as a standard
candle. Here, we review the main difficulties in measuring this location in any
real dataset and develop an empirical approach to optimise it for tip of the
red giant branch (TRGB) analysis. We go on to present a new algorithm for the
identification of the TRGB in nearby metal poor stellar systems. Our method
uses a least-squares fit of a data-adaptive slope to the luminosity function in
1 magnitude windows. This finds the region of the luminosity function that
shows the most significant decline in star counts as we go to brighter
magnitudes; the base of this decline is attributed as the location of the tip.
This technique then allows for the determination of realistic uncertainties
which reflect the quality of the luminosity function used, but which are
typically ~0.02 mags rms + ~ 0.03 mags systematic, a significant improvement
upon previous methods that have used the tip as a standard candle. Finally, we
apply our technique to the Local Group spiral galaxy M33 and the dwarf galaxies
And I & II, and derive distance modulii of 24.50 +/- 0.06 (794 +/- 23 kpc),
24.33 +/- 0.07 (735 +/- 23 kpc) and 24.05 +/- 0.06 (645 +/- 19 kpc)
respectively. The result for M33 is in excellent agreement with the Cepheid
distances to this galaxy, and makes the possibility of a significant amount of
reddening in this object unlikely.


title: Globular Clusters as Probes of Galaxy Evolution: NGC 5128

abstract:
  We present the results of our analysis of the photometric data of globular
clusters in the elliptical galaxy NGC 5128 (Cen A). We show that the integrated
colour U-B can be an effective metallicity indicator for simple stellar
populations. This is because it is sensitive to metallicity via the opacity
effect but relatively insensitive to the effective main sequence turn-off
temperature of the population (and thus to age) when Teff ~ 7000-12000K, that
is, when the Balmer Jump is strong. This flat U-B vs Teff relation is a result
of the fact that the blueing effect of the optical continuum with increasing
temperature is temporarily stopped by the Balmer Jump which becomes greater
with temperature in this range. In this study we use U-B and B-V as metallicity
and age indicators, respectively. We first show that the use of the U-B vs B-V
two-colour diagram roughly yields the metallicities and ages of the Milky Way
globular clusters independently determined, and then apply the technique to the
clusters in NGC 5128. There is a large range in U-B, which corresponds to
[Fe/H] of -2.0 through over +0.3. The large uncertainties from the data and the
models currently prevent us from pinning down their ages and metallicities.
Although a constant age for all these clusters cannot be ruled out, there is a
hint of the metal-rich clusters being younger. Significance of these results
and caveats of the analysis are discussed.


title:
Galaxy Pairs in the 2dFGRS II. Effects of interactions on star formation
  in groups and clusters

abstract:
  We analyse the effects of galaxy interactions on star formation in groups and
clusters of galaxies with virial masses in the range $10^{13} - 10 ^{15}
M_{\odot}$. We find a trend for galaxy-galaxy interactions to be less efficient
in triggering star formation in high density regions in comparison with
galaxies with no close companion.
  However, we obtain the same relative projected distance and relative radial
velocity thresholds for the triggering of significant star formation activity
($r_p \sim 25 h^{-1} $ kpc and $\Delta V \sim 100 {\rm km s^{-1}}$) as found in
the field. Thus, the nature of star formation driven by galaxy interactions is
nearly independent of environment, although there is a general lower level of
star formation activity in massive systems. The above results reflect, on one
hand, the local nature of star formation induced by tidal interactions and, on
the other, the role played by the internal properties of galaxies. By using a
2dFGRS mock catalog we estimate the contamination by spurious pairs finding
that the statistics are cleary dominated by real pairs. We also found the
behaviour of the trends to be robust against the use of more restrictive
relative velocity thresholds.(Abridged)


title: Thermal conduction in cosmological SPH simulations

abstract:
  Thermal conduction in the intracluster medium has been proposed as a possible
heating mechanism for offsetting central cooling losses in rich clusters of
galaxies. In this study, we introduce a new formalism to model conduction in a
diffuse ionised plasma using smoothed particle hydrodynamics (SPH), and we
implement it in the parallel TreePM/SPH-code GADGET-2. We consider only
isotropic conduction and assume that magnetic suppression can be described in
terms of an effective conductivity, taken as a fixed fraction of the
temperature-dependent Spitzer rate. We also account for saturation effects in
low-density gas. Our formulation manifestly conserves thermal energy even for
individual and adaptive timesteps, and is stable in the presence of small-scale
temperature noise. This allows us to evolve the thermal diffusion equation with
an explicit time integration scheme along with the ordinary hydrodynamics. We
use a series of simple test problems to demonstrate the robustness and accuracy
of our method. We then apply our code to spherically symmetric realizations of
clusters, constructed under the assumptions of hydrostatic equilibrium and a
local balance between conduction and radiative cooling. While we confirm that
conduction can efficiently suppress cooling flows for an extended period of
time in these isolated systems, we do not find a similarly strong effect in a
first set of clusters formed in self-consistent cosmological simulations.
However, their temperature profiles are significantly altered by conduction, as
is the X-ray luminosity.


title:
Detection of oxygen and carbon in the hydrodynamically escaping
  atmosphere of the extrasolar planet HD209458b

abstract:
  Four transits of the planet orbiting the star HD209458 were observed with the
STIS spectrograph on board HST. The wavelength domain (1180-1710A) includes HI
as well as CI, CII, CIV, NV, OI, SI, SiII, SiIII and SiIV lines. During the
transits, absorptions are detected in HI, OI and CII (5+/-2%, 13+/-4.5% and
7.5+/-3.5%, respectively). No absorptions are detected for other lines. The 5%
mean absorption over the whole HI Lyman alpha line is consistent with the
previous detection at higher resolution (Vidal-Madjar et al. 2003). The
absorption depths in OI and CII show that oxygen and carbon are present in the
extended upper atmosphere of HD209458b. These species must be carried out up to
the Roche lobe and beyond, most likely in a state of hydrodynamic escape.


title:
65 Cybele in the thermal infrared: Multiple observations and
  thermophysical analysis

abstract:
  We investigated the physical and thermal properties of 65 Cybele}, one of the
largest main-belt asteroids. Based on published and recently obtained thermal
infrared observations, including ISO measurements, we derived through
thermophysical modelling (TPM) a size of 302x290x232 km (+/- 4 %) and an
geometric visible albedo of 0.050+/-0.005. Our model of a regolith covered
surface with low thermal inertia and "default" roughness describes the
wavelengths and phase angle dependent thermal aspects very well. Before/after
opposition effect and beaming behaviour can be explained in that way. We found
a constant emissivity of 0.9 at wavelengths up to about 100 micron and lower
values towards the submillimetre range, indicating a grain size distribution
dominated by 200 micron particle sizes. The spectroscopic analysis revealed an
emissivity increase between 8.0 and 9.5 micron. We compared this emissivity
behaviour with the Christiansen features of carbonaceous chondrite meteorites,
but a conclusive identification was not possible. A comparison between the
Standard Thermal Model (STM) and the applied TPM clearly demonstrates the
limitations and problems of the STM for the analysis of multi-epoch and
-wavelengths observations. While the TPM produced a unique diameter/albedo
solution, the calculated STM values varied by +/-30 % and showed clear trends
with wavelength and phase angle. Cybele can be considered as a nice textbook
case for the thermophysical analysis of combined optical and thermal infrared
observations.


title: The Nonradially-Pulsating Primary of the Cataclysmic Variable GW Librae

abstract:
  The dwarf nova GW Librae is the first cataclysmic variable discovered to have
a primary in a white dwarf instability strip, making it the first multi-mode,
nonradially-pulsating star known to be accreting. The primaries of CVs,
embedded in hot, bright accretion discs, are difficult to study directly.
Applying the techniques of asteroseismology to GW Librae could therefore give
us an unprecedented look at a white dwarf that has undergone ~10^9 years of
accretion. However, an accreting white dwarf may have characteristics
sufficiently different from those of single pulsating white dwarfs to render
the standard models of white dwarf pulsations invalid for its study. This paper
presents amplitude spectra of GW Lib from a series of observing campaigns
conducted during 1997, 1998 and 2001. We find that the dominant pulsation modes
cluster at periods near 650, 370 and 230 s, which also appear in linear
combinations with each other. GW Lib's pulsation spectrum is highly unstable on
time-scales of months, and exhibits clusters of signals very closely spaced in
frequency, with separations on the order of a few microHz.


title:
Time-dependent evolution of quasi-spherical, self-gravitating accretion
  flow

abstract:
  A self-similar solution for time evolution of quasi-spherical,
self-gravitating accretion flows is obtained under the assumption that the
generated heat by viscosity is retained in the flow. The solutions are
parameterized by the ratio of the mass of the accreting gas to the central
object mass and the viscosity coefficient. While the density and the pressure
are obtained simply by solving a set of ordinary differential equations, the
radial and the rotational velocities are presented analytically. Profiles of
the density and the rotational velocities show two distinct features. Low
density outer accreting flow with relatively flat rotation velocity, surrounds
an inner high density region. In the inner part, the rotational velocity
increases from the center to a transition radius where separates the inner and
outer portions. We show that the behaviour of the solutions in the inner region
depends on the ratio of the heat capacities, $\gamma$, and the viscosity
coefficient, $\alpha$.


title: Core-Collapse Supernovae at the Threshold

abstract:
  Recent progress in modeling core-collapse supernovae is summarized and set in
perspective. Two-dimensional simulations with state-of-the-art treatment of
neutrino transport still fail to produce powerful explosions, but evidence is
presented that they are very close to success.


title: Cosmic metal production and the mean metallicity of the Universe

abstract:
  By means of detailed chemo-photometric models for elliptical, spiral and
irregular galaxies, we evaluate the cosmic history of the production of
chemical elements as well as the metal mass density of the present-day
universe. We then calculate the mean metal abundances for galaxies of different
morphological types, along with the average metallicity of galactic matter in
the universe (stars, gas and intergalactic medium). For the average metallicity
of galaxies in the local universe, we find Z_gal= 0.0175, i.e. close to the
solar value. We find the main metal production in spheroids (ellipticals and
bulges) to occur at very early times, implying an early peak in the metal
production and a subsequent decrease. On the other hand, the metal production
in spirals and irregulars is always increasing with time. We perform a
self-consistent census of the baryons and metals in the local universe finding
that, while the vast majority of the baryons lies outside galaxies in the
inter-galactic medium (IGM), 52 % of the metals (with the exception of the
Fe-peak elements) is locked up in stars and in the interstellar medium. We
estimate indirectly the amount of baryons which resides in the IGM and we
derive its mean Fe abundance, finding a value of X_Fe,IGM=0.05 X_Fe,sun. We
believe that this estimate is uncertain by a factor of 2, owing to the
normalization of the local luminosity function. This means that the Fe
abundance of 0.3 solar inferred from X-ray observations of the hot
intra-cluster medium (ICM) is higher than the average Fe abundance of the
inter-galactic gas in the field.


title:
Brightness suppression of relativistic radio jets of quasars: The role
  of the lower electron energy cut-off

abstract:
  Although the possibility of a low energy cut-off (LEC) of the relativistic
electron population (E_{min} ~ 0.1 GeV) in the different components of radio
galaxies has been discussed in the literature, from both theoretical and
observational viewpoints, its possible role in causing a distinct spectral
flattening, and thus reducing the apparent brightness temperature of the radio
nucleus, has thus far not been explicitly discussed. Here we point out that
such an effect may in fact be quite significant for the parsec-scale,
superluminal emission regions associated with the inner radio jets. This is
because the observed frequency of the spectral turnover arising from the LEC
increases linearly with the bulk Doppler factor (\delta) of the jet flow,
whereas the frequency of synchrotron self-absorption (the well known cause of
spectral flattening and turnover at low frequencies) shows a mild decrease as
\delta rises. For an observationally relevant range of source parameters, we
investigate here the role of the LEC. We argue that some statistical trends
revealed by the recent VLBI surveys can in fact be understood in terms of
effects arising from LEC, including the faster superluminal motion found in the
VLBI surveys at higher frequencies, and the apparent inability of most radio
cores to even attain the brightness temperatures consistent with the
equipartition condition. We also point out some possible implications of the
LEC for X-ray observations of the kiloparsec scale relativistic jets of
quasars.


title: The orbital resonance model for twin peak kHz QPOs

abstract:
  Many Galactic black hole and neutron star sources in low X-ray mass binaries
show QPOs (quasi periodic oscillations) in their observed X-ray fluxes, i.e.
peaks in the Fourier variability power spectra. Pairs of twin peaks are
observed, and in black-hole systems their frequencies (upp), (down) are in
rational ratios. For example, in all four microquasars with twin peaks
observed, (upp):(down) = 3:2. The rational ratios have been postulated in a
model that explained twin peak QPOs as a non-linear resonance between modes of
accretion disk oscillations. For those microquasars where the mass of the X-ray
source is known, we determine the black-hole spin, following from the observed
QPO frequencies within various models of resonance.


title: Future Probes of the Neutron Star Equation of State Using X-ray Bursts

abstract:
  Observations with NASA's Rossi X-ray Timing Explorer (RXTE) have resulted in
the discovery of fast (200 - 600 Hz), coherent X-ray intensity oscillations
(hereafter, "burst oscillations") during thermonuclear X-ray bursts from 12 low
mass X-ray binaries (LMXBs). It is now beyond doubt that these oscillations
result from spin modulation of the thermonuclear burst flux from the neutron
star surface. Among the new timing phenomena revealed by RXTE the burst
oscillations are perhaps the best understood, in the sense that many of their
properties can be explained in the framework of this relatively simple model.
Because of this, detailed modelling of burst oscillations can be an extremely
powerful probe of neutron star structure, and thus the equation of state (EOS)
of supra-nuclear density matter. The new discoveries have spurred much new
theoretical work on thermonuclear burning and propagation on neutron stars, so
that in the near future it is not unreasonable to think that detailed physical
models of the time dependent flux from burning neutron stars will be available
for comparison with the observed pulse profiles from a future, large collecting
area X-ray timing observatory. In addition, recent high resolution burst
spectroscopy with XMM/Newton suggests the presence of redshifted absorption
lines from the neutron star surface during bursts. This leads to the
possibility of using large area, high spectral resolution measurements of X-ray
bursts as a precise probe of neutron star structure. In this work I will
explore the precision with which constraints on neutron star structure, and
hence the dense matter EOS, can be made with the implementation of such
programs.


title: Masses of Stellar Black Holes and Testing Theories of Gravitation

abstract:
  We analyze the mass distribution of stellar black holes derived from the
light and radial velocity curves of optical stars in close binary systems using
dynamical methods. The systematic errors inherent in this approach are
discussed. These are associated primarily with uncertainties in models for the
contribution from gaseous structures to the optical brightness of the systems
under consideration. The mass distribution is nearly flat in the range
4-15M_sun. This is compared with the mass distribution for black holes in
massive close binaries, which can be manifest as ultraluminous X-ray sources
(L_x > 10^39 erg/s) observed in other galaxies. If the X-ray luminosities of
these objects correspond to the Eddington limit, the black-hole mass
distribution should be described by a power law, which is incompatible with the
flat shape derived dynamically from observations of close binaries in our
Galaxy. One possible explanation of this discrepancy is the rapid evaporation
of stellar-mass black holes predicted in recent multi-dimensional models of
gravity. This hypothesis can be verifed by measuring the stellar black-hole
mass spectrum or finding isolated or binary black holes with masses below
3M_sun.


title: The Zeeman effect in the G band

abstract:
  We investigate the possibility of measuring magnetic field strength in G-band
bright points through the analysis of Zeeman polarization in molecular CH
lines. To this end we solve the equations of polarized radiative transfer in
the G band through a standard plane-parallel model of the solar atmosphere with
an imposed magnetic field, and through a more realistic snapshot from a
simulation of solar magneto-convection. This region of the spectrum is crowded
with many atomic and molecular lines. Nevertheless, we find several instances
of isolated groups of CH lines that are predicted to produce a measurable
Stokes V signal in the presence of magnetic fields. In part this is possible
because the effective Land\'{e} factors of lines in the stronger main branch of
the CH A$^{2}\Delta$--X$^{2}\Pi$ transition tend to zero rather quickly for
increasing total angular momentum $J$, resulting in a Stokes $V$ spectrum of
the G band that is less crowded than the corresponding Stokes $I$ spectrum. We
indicate that, by contrast, the effective Land\'{e} factors of the $R$ and $P$
satellite sub-branches of this transition tend to $\pm 1$ for increasing $J$.
However, these lines are in general considerably weaker, and do not contribute
significantly to the polarization signal. In one wavelength location near 430.4
nm the overlap of several magnetically sensitive and non-sensitive CH lines is
predicted to result in a single-lobed Stokes $V$ profile, raising the
possibility of high spatial-resolution narrow-band polarimetric imaging. In the
magneto-convection snapshot we find circular polarization signals of the order
of 1% prompting us to conclude that measuring magnetic field strength in
small-scale elements through the Zeeman effect in CH lines is a realistic
prospect.


title: The magnetic field of pulsars and the gravito-magnetic theory

abstract:
  Many authors have considered a gravitational origin of the magnetic field of
celestial bodies. Especially, the so-called Wilson-Blackett formula has been
investigated, both theoretically and observationally. It appeared possible to
deduce this formula from general relativity, e. g., by application of a special
interpretation of gravito-magnetic theory. More consequences of the latter
theory for pulsars will be considered in this work. As an example, the standard
quadrupolar charge density for pulsars can be deduced from the gravito-magnetic
theory. Moreover, a new magnetic dipole moment from electromagnetic origin is
found, generated in the basic magnetic field from gravito-magnetic origin. In
general, for thirteen accreting, slowly rotating, binary pulsars the agreement
between the observed magnetic field and the gravito-magnetic prediction is
better than between the observed value and the value from the standard magnetic
dipole radiation model. At present, an analogous comparison for five isolated
pulsars appears to be difficult. For a sample of 100 pulsars the averaged
(gravito-)magnetic field, extracted from the magnetic dipole spin-down model,
is in fair agreement with the gravito-magnetic prediction. Unfortunately, the
(gravito-)magnetic field has not yet directly been measured. Finally, it is
found that the first and second order braking indices only depend on the
magnetic field from electromagnetic origin.


title:
High Spatial Resolution Optical and Radio Imagery of the Circumbinary
  Environment

abstract:
  In this review, I concentrate on describing observations of spatially
resolved emission in symbiotic stars at sub-arcsecond scales. In some of the
closer objects, the highest resolutions discussed here correspond to linear
dimensions similar to the supposed binary separation. A total of 17 stars well
accepted as symbiotics are now observed to show sub-arcsecond structure, almost
twice the number at the time of the last review in 1987. Furthermore, we now
have access to HST imagery to add to radio interferometry. From such
observations we can derive fundamental parameters of the central systems,
investigate the variation of physical parameters across the resolved nebulae
and probe the physical mechanisms of mass loss and interactions between ejecta
and the circumstellar medium.
  Suggestions for future work are made and the potential of new facilities in
both the radio and optical domains is described. This review complements that
by Corradi (this volume) which mainly considers the larger scale emission from
the ionized nebulae of these objects.


title: Thermal Conduction in Simulated Galaxy Clusters

abstract:
  We study the formation of clusters of galaxies using high-resolution
hydrodynamic cosmological simulations that include the effect of thermal
conduction with an effective isotropic conductivity of 1/3 the classical
Spitzer value. We find that, both for a hot ($T_{\rm ew}\simeq 12$ keV) and
several cold ($T_{\rm ew}\simeq 2$ keV) galaxy clusters, the baryonic fraction
converted into stars does not change significantly when thermal conduction is
included. However, the temperature profiles are modified, particularly in our
simulated hot system, where an extended isothermal core is readily formed. As a
consequence of heat flowing from the inner regions of the cluster both to its
outer parts and into its innermost resolved regions, the entropy profile is
altered as well. This effect is almost negligible for the cold cluster, as
expected based on the strong temperature dependence of the conductivity. Our
results demonstrate that while thermal conduction can have a significant
influence on the properties of the intra--cluster medium of rich galaxy
clusters, it appears unlikely to provide by itself a solution for the
overcooling problem in clusters, or to explain the current discrepancies
between the observed and simulated properties of the intra--cluster medium.


title: Observational tests of the galaxy formation process

abstract:
  The mutual feedback between star formation and nuclear activity in large
spheroidal galaxies may be a key ingredient to overcome several difficulties
plaguing current semi-analytic models for galaxy formation. We discuss some
observational implications of the model by Granato et al. (2003) for the
co-evolution of galaxies and active nuclei at their centers and stress the
potential of the forthcoming surveys of the Sunyaev-Zeldovich effect on
arcminute scales, down to $\mu$K levels, to investigate the early galaxy
formation phases, difficult to access by other means.


title:
An X-Ray Pulsar, Metal-rich Ejecta, and Shocked Ambient Medium in the
  Supernova Remnant G292.0+1.8

abstract:
  We report the discovery of pulsed X-ray emission from the compact object CXOU
J112439.1-591620 within the Galactic supernova remnant G292.0+1.8 using the
High Resolution Camera on the Chandra X-Ray Observatory. The X-ray period is
consistent with the extrapolation of the radio period and spindown rate of PSR
J1124-5916. The X-ray pulse is single peaked and broad. There is no optical
counterpart to a limit of M_V ~ 26. The pressure in the pulsar wind nebula is
considerably less than that in the reverse-shock-heated ejecta and
circumstellar medium, indicating that the reverse shock has not yet begun to
interact with the nebula.


title:
X-Ray Observations of the Most Massive DLS Shear-Selected Galaxy
  Clusters

abstract:
  We report on preliminary results of our X-ray survey of the most massive
clusters currently identified from the Deep Lens Survey (DLS). The DLS cluster
sample is selected based on weak lensing shear, which makes it possible for the
first time to study clusters in a baryon-independent way. In this article we
present X-ray properties of a subset of the shear-selected cluster sample.


title:
Angular Momentum Transport by Internal Gravity Waves II- Pop II stars
  from the Li plateau to the horizontal branch

abstract:
  This paper is the second in a series where we examine the generation and
filtering of internal gravity waves in stars and the consequences of wave
induced transport of angular momentum at various stages of the stellar
evolution.
  Here we concentrate on Pop II dwarf stars and we focus in particular on the
differential properties of internal gravity waves as a function of the stellar
mass. We show that, for the range of masses corresponding to the lithium
plateau, gravity waves are fully efficient and should thus lead to a
quasi-solid rotation state, similar to that of the Sun. In the slightly more
massive progenitors of currently observed horizontal branch star however,
internal wave generation is not efficient on the main sequence, and large
internal differential rotation can thus be maintained. This leads to a natural
explanation of the large rotational velocities measured on the horizontal
branch in some globular clusters.


title: A survey of extended radio jets with Chandra and HST

abstract:
  We present the results from an X-ray and optical survey of a sample of 17
radio jets in AGN performed with Chandra and HST. The sample was selected from
the radio and is unbiased toward detection at shorter wavelengths, but
preferentially it includes beamed sources. We find that X-ray emission is
common on kpc-scales, with over half radio jets exhibiting at least one X-ray
knot on the Chandra images. The distributions of the radio-to-X-ray and
radio-to-optical spectral indices for the detected jets are similar to the
limits for the non-detections,suggesting all bright radio jets have X-ray
counterparts which will be visible in longer observations. Comparing the radio
and X-ray morphologies shows that the majority of the X-ray jets have
structures that closely map the radio. Analysis of the SED of the jet knots
suggest the knots in which the X-ray and radio morphologies track each other
produce X-rays by IC scattering of the Cosmic Microwave Background. The
remaining knots produce X-rays by the synchrotron process. Spectral changes are
detected along the jets, with the ratio of the X-ray-to-radio and
optical-to-radio flux densities decreasing from the inner to the outer regions.
This suggests the presence of an additional contribution to the X-ray flux in
the jet's inner part, either from synchrotron or IC of the stellar light.
Alternatively, in a pure IC/CMB scenario, the plasma decelerates as it flows
from the inner to the outer regions. Finally, the X-ray spectral indices for
the brightest knots are flat, indicating that the bulk of the luminosity of the
jets is emitted at GeV energies, and raising the interesting possibility of
future detections with GLAST.


title: A Frequency Glitch in an Accreting Pulsar

abstract:
  Frequency glitches have been observed so far only in radio pulsars and
anomalous X-ray pulsars. Here we present evidence of a glitch in a neutron star
accreting from a Be companion. The transient KS 1947+300 reappeared in 2000
October as a moderately strong X-ray source that exhibited 18.7 s pulsations,
leading to an identification with the BATSE source GRO J1948+32, last detected
in 1994. We have analyzed Rossi X-ray Timing Explorer observations taken during
the 2000-01 outburst, as well as additional observations taken during a smaller
outburst in July 2002. Orbital Doppler shifts are apparent in the temporal
variation of the pulse frequency. A joint fit of the RXTE data together with
BATSE measurements from an outburst in 1994 yields the orbital period P_orb =
40.415+/-0.010 d, the projected orbital radius a_x sin i = 137+/-3 lt-s, and
the eccentricity e = 0.033+/-0.013. This degree of eccentricity is unexpectedly
low for such a wide orbit. Pulse timing results also show that the intrinsic
pulse frequency increased from 53.30 to 53.47 mHz at a rate approximately
proportional to the X-ray flux. This is about the degree of spin up expected
from the accretion torques that must be present when the X-ray luminosity
reaches ~10^38 ergs/s. On one occasion during the 2000-01 outburst, the pulse
frequency increased by ~1.8x10^-6 Hz in less than approximately 10 hr over and
above the mean trend seen around that time, without any indication of a
correspondingly large increase in X-ray flux. The fractional change in
frequency of 3.7x10^-5 during this event is significantly larger than the
values observed in the glitches in radio pulsars and anomalous X-ray pulsars.
We discuss other similarities and differences between these events.


title: The Gaseous Trail of the Sagittarius Dwarf Galaxy

abstract:
  A possible gaseous component to the stream of debris from the Sagittarius
dwarf galaxy is presented. We identify 4 - 10 x 10^6 Msun of neutral hydrogen
along the orbit of the Sgr dwarf in the direction of the Galactic anticenter
(at 36 kpc, the distance to the stellar debris in this region). This is 1-2% of
the estimated total mass of the Sgr dwarf. Both the stellar and gaseous
components have negative velocities, but the gaseous component extends to
higher negative velocities. If associated, this gaseous stream was most likely
stripped from the main body of the dwarf 0.2 - 0.3 Gyr ago during its current
orbit after a passage through a diffuse edge of the Galactic disk with a
density > 10^{-4} cm^{-3}. This gas represents the dwarf's last source of star
formation fuel and explains how the galaxy was forming stars 0.5-2 Gyr ago.


title: Non-thermal particles in the intergalactic and intracluster medium

abstract:
  I present a review of nonthermal processes in the large scale structure of
the universe. After examining the properties of cosmological shock waves and
their role as particle accelerators, I discuss the main observational facts,
from radio to \gr and describe the processes that are thought be responsible
for the observed nonthermal emissions. Finally, I emphasize the important role
of $\gamma$-ray astronomy for the progress in the field. Non detections (upper
limits) at these photon energies have already allowed us to draw important
conclusions. Future observations will tell us more about the physical
conditions in the intracluster medium, physics of shocks dissipation, aspects
of CR acceleration.


title:
Are dust shell models well-suited to explain interferometric data of
  late-type stars in the near-infrared?

abstract:
  Recently available near-infrared interferometric data on late-type stars show
a strong increase of diameter for asymptotic giant branch (AGB) stars between
the K (2.0 - 2.4 \mu m) and L (3.4 - 4.1 \mu m) bands. Aiming at an explanation
of these findings, we chose the objects \alpha Orionis (Betelgeuse), SW
Virginis, and R Leonis, which are of different spectral types and stages of
evolution, and which are surrounded by circumstellar envelopes with different
optical thicknesses. For these stars, we compared observations with spherically
symmetric dust shell models. Photometric and 11 \mu m interferometric data were
also taken into account to further constrain the models. -- [...] -- We
conclude that AGB models comprising a photosphere and dust shell, although
consistent with SED data and also interferometric data in K and at 11 \mu m,
cannot explain the visibility data in L; an additional source of model opacity,
possibly related to a gas component, is needed in L to be consistent with the
visibility data.


title: Metagalactic Ultraviolet Flux from Cosmic Structure Formation

abstract:
  The contribution to the ultraviolet background (UVB) from thermal emission
due to gas shock heated during cosmic structure formation is assessed with an
updated version of Press-Schechter (Sheth & Tormen 1999) formalism. The
calculation is consistent with empirical estimates based on the observed
properties of galaxies and the observed cosmic star formation history. The bulk
of the radiation turns out to be produced by objects in the mass range 10^{11-
13} M_solar, i.e. large galaxies and small groups. When compared to more
conventional components (QSOs, stellar) it is found that near 1 Ry, thermal
emission is comparable to stellar contributions and amounts to about 10 %, 20 %
and 35 % of the total flux at redshifts of 3, 4.5 and higher, respectively;
more importantly, near the ionization threshold for HeII, the thermal
contribution is comparable to the QSO intensity already at redshift ~3 and
dominates at redshifts above 4. In addition, thermal photons alone are enough
to produce and sustain HeII reionization already at z~6. Finally, the observed
Gunn-Peterson effect at high redshifts (3<z<6) constrains the escape fraction
of ionizing photons from galaxies to less than a few percent.


title: Relativistic Poynting Jets from Accretion Disks

abstract:
  A model is developed for relativistic Poynting jets from the inner region of
a disk around a rotating black hole. The disk is initially threaded by a
dipole-like magnetic field. The model is derived from the special relativistic
equation for a force-free electromagnetic field. The ``head'' of the Poynting
jet is found to propagate outward with a velocity which may be relativistic.
The Lorentz factor of the head (Gamma) is found to be dependent on the magnetic
field strength close to the black hole, B_0, the density of the external medium
n_ext, and on the ratio R=r_0/r_g >1, where r_g is the gravitational radius of
the black hole, and r_0 is the radius of the O-point of the initial dipole
field threading the disk. For conditions pertinent to an active galactic
nuclei, Gamma is approximately equal to 8 (10/R)^(1/3) (B_0/10^3 Gauss)^(1/3)
(1/cm^3/n_ext)^(1/6). This model offers an explanation for the observed Lorentz
factors which are of the order of 10 for the parsec-scale radio jets measured
with very long baseline interferometry.


title: Water Absorption From Line-of-Sight Clouds Toward W49A

abstract:
  We have observed 6 clouds along the line-of-sight toward W49A using the
Submillimeter Wave Astronomy Satellite (SWAS) and several ground-based
observatories. The ortho-H2O 1-0 and OH (1665 and 1667 MHz) transitions are
observed in absorption, whereas the low-J CO, 13CO, and C18O lines, as well as
the [CI] 1-0 transition, are seen in emission. By using both the o-H218O and
o-H2O absorption lines, we are able to constrain the column-averaged o-H_2O
abundances in each line-of-sight cloud to within about an order of magnitude.
Assuming the standard N(H2)/N(CO) ratio of 10^4, we find N(o-H2O)/N(H2) = 8.1 x
10^-8 - 4 x 10^-7 for three clouds with optically thin water lines. In three
additional clouds, the H$_2$O lines are saturated so we have used observations
of the H218O ground-state transition to find upper limits to the water
abundance of 8.2x 10^-8 - 1.5x10^-6. We measure the OH abundance from the
average of the 1665 and 1667 MHz observations and find N(OH)/N(H2) = 2.3x10^-7
- 1.1x10^-6. The o-H2O and OH abundances are similar to those determined for
line-of-sight water absorption features towards W51 and Sgr B2 but are higher
than those seen from water emission lines in molecular clouds. However, the
clouds towards W49 have lower ratios of OH relative to H2O column densities
than are predicted by simple models which assume that dissociative
recombination is the primary formation pathway for OH and H2O. Building on the
work of Neufeld et al. (2002), we present photo-chemistry models including
additional chemical effects, which can also explain the observed OH and H2O
column densities as well as the observed H2O/CO abundance ratios.


title:
Evolution of Disk Galaxies in the GOODS-South Field: Number Densities
  and Size Distribution

abstract:
  We examine the evolution of the sizes and number densities of disk galaxies
using the high resolution images obtained by the Great Observatories Origins
Deep Survey (GOODS) with the Advanced Camera for Surveys (ACS) on the Hubble
Space Telescope (HST). The multiwavelength (B,V,i,z) images allow us to
classify galaxies based on their rest-frame B-band morphologies out to redshift
z = 1.25. In order to minimize the effect of selection biases, we confine our
analysis to galaxies which occupy the region of magnitude-size plane where the
survey is almost 90% complete at all redshifts. The observed size distribution
is consistent with a log-normal distribution as seen for the disk galaxies in
the local Universe and does not show any significant evolution over the
redshift range 0.25 < z < 1.25. We find that the number densities of disk
galaxies remains fairly constant over this redshift range, although a modest
evolution by a factor of four may be possible within the 2-sigma uncertainties.


title: Optical, UV, and EUV Oscillations of SS Cygni in Outburst

abstract:
  I provide a review of observations in the optical, UV (HST), and EUV (EUVE
and Chandra LETG) of the rapid periodic oscillations of nonmagnetic,
disk-accreting, high mass-accretion rate cataclysmic variables (CVs), with
particular emphasis on the dwarf nova SS Cyg in outburst. In addition, I drawn
attention to a correlation, valid over nearly six orders of magnitude in
frequency, between the frequencies of the quasi-periodic oscillations (QPOs) of
white dwarf, neutron star, and black hole binaries. This correlation identifies
the high frequency quasi-coherent oscillations (so-called ``dwarf nova
oscillations'') of CVs with the kilohertz QPOs of low mass X-ray binaries
(LMXBs), and the low frequency and low coherence QPOs of CVs with the
horizontal branch oscillations (or the broad noise component identified as
such) of LMXBs. Assuming that the same mechanisms produce the QPOs of white
dwarf, neutron star, and black hole binaries, this correlation has important
implications for QPO models.


title: Study of the Bipolar Nebula IRAS 19312+1950. I. Mapping Observations

abstract:
  IRAS 19312+1950 is an SiO maser source that exhibits a prominent bipolar
nebulosity. Mapping observations of this object were made in the CO J=1--0,
13CO J=1--0, C18O J=1--0, CS J=2--1, and HCN J=1--0 lines and in the 150 GHz
continuum band. Near-infrared imaging observations were also made in the J, H,
and K-bands. The line profiles of the 12CO and HCN spectra consist of a weak
broad component with a line width of about 50 km/s and a strong narrow
component of the width of about 3 km/s. The profiles of the 13CO, C18O, and CS
lines have only the narrow component. Both of the components have an intensity
peak at the IRAS position. The narrow component was clearly resolved with a
15'' telescope beam. The spectral energy distribution of this object exhibits a
doubly peaked profile between 1 and 25 micron. The 150 GHz continuum flux
density was found to be 0.07 Jy, which is consistent with the flux density
predicted by the expanding envelope model with a mass loss rate of ~10^{-4}
M_sun/y at a distance of 2.5 kpc. We argue that the broad component originates
from the expanding envelope of this object, and that the hot dust cloud, which
is the source of the narrow component, is also physically associated with this
object. Though the present observations do not preclude the possibility of a
young stellar object, we argue that it is less plausible. We conclude that IRAS
19312+1950 is an AGB/post-AGB star that is evolved from a massive progenitor.


title: PV Ceph: Young Star Caught Speeding?

abstract:
  Three independent lines of evidence imply that the young star PV Ceph is
moving at roughly 20 km/s through the interstellar medium. The first, and
strongest, suggestion of motion comes from the geometry of the HH knots in the
"giant" Herbig-Haro (HH) flow associated with PV Ceph. Bisectors of lines drawn
between pairs of knots at nearly equal distances from PV Ceph imply an E-W
motion of the source, and a plasmon model fit to the knot positions gives a
good fit of 22 km/s motion for the star. The second bit of damning evidence
comes from a redshifted "trail" of molecular gas, pointing in the same E-W
direction implied by the HH knot geometry. The third exhibit we offer in
accusing PV Ceph of speeding involves the tilt apparent in the high-velocity
molecular jet now emanating from the star. This tilt is best explained if the
true, current, jet direction is N-S, as it is in HST images, and the star is
moving at roughly 20 km/s. Tracing the motion of PV Ceph backward in time, to
the nearest cluster from which it might have been ejected, we find that it is
very likely to have been thrown out of the massive star-forming cluster NGC
7023 (more than 10 pc away). We propose that PV Ceph was ejected, at a speed
large enough to escape NGC 7023, at least 100,000 years ago, but that it did
not enter the molecular cloud in which it now finds itself until more like
35,000 years ago. Our calculations show that the currently-observable molecular
outflow associated with PV Ceph is about 10,000 years old, so that the flow has
had plenty of time to form while in its current molecular cloud. But, the
question of what PV Ceph was doing, and what gas/disk it took along with it in
the time it was traveling through the low-density region between NGC 7023 and
its current home is an open question.


title: The evolution of irradiated planets. Application to transits

abstract:
  Extending the theory we derived recently for HD209458b to different cases of
strongly irradiated gaseous exoplanets, we have calculated the consistent
evolution of the new transiting planet, OGLE-TR-56b, for its recently revised
mass determination. The theory is shown to successfully reproduce the observed
radius, for the proper age of the system. We also examine the dissipation of
kinetic energy at the planet's internal adiabat due to atmospheric winds, and
place constraints on the efficiency of this process. We show that a fraction
$\sim 0.1$ -- 0.5% of the incident flux transformed into thermal energy
deposited at the adiabatic level can accommodate the observed radii of both
OGLE-TR-56b and HD209458b. The present theory yields quantitative predictions
on the evolution of the emergent spectrum and fundamental properties of
hot-jupiters. The predictions for radius, luminosity, temperature as a function
of the planet's mass and orbital distance can be used as benchmarks for future
detections of transit planets.


title:
Ion-Ion Correlation Effect on the Neutrino-Nucleus Scattering in
  Supernova Cores

abstract:
  We calculate the ion-ion correlation effect on the neutrino-nucleus
scattering in supernova cores, which is an important opacity source for the
neutrinos and plays a vital role in the supernova explosion. In order to
calculate the ion-ion correlation effect we use the results of the improved
hypernetted-chain method calculations of the classical one-component plasma. As
in the preceding studies on this effect, we find a dramatic decrease of the
effective neutrino-nucleus scattering cross section for relatively low energy
neutrinos with E < 20MeV. As a matter of fact, our calculation shows a much
more dramatic reduction of the effective neutrino-nucleus scattering cross
section for the low energy neutrinos with E < 10MeV than the results of
Horowitz. Therefore, the ion-ion correlation effect will be more important than
has hitherto been recognized. We present an accurate analytic fitting formula
that summarizes our numerical results. This fitting formula will facilitate the
application of the present results to the supernova explosion simulations.


title:
White dwarf envelopes: further results of a non-local model of
  convection

abstract:
  We present results of a fully non-local model of convection for white dwarf
envelopes. We show that this model is able to reproduce the results of
numerical simulations for convective efficiencies ranging from very inefficient
to moderately efficient; this agreement is made more impressive given that no
closure parameters have been adjusted in going from the previously reported
case of A-stars to the present case of white dwarfs; for comparison, in order
to match the peak convective flux found in numerical simulations for both the
white dwarf envelopes discussed in this paper and the A-star envelopes
discussed in our previous work requires changing the mixing length parameter of
commonly used local models by a factor of 4. We also examine in detail the
overshooting at the base of the convection zone, both in terms of the
convective flux and in terms of the velocity field: we find that the flux
overshoots by approximately 1.25 H_P and the velocity by approximately 2.5 H_P.
Due to the large amount of overshooting found at the base of the convection
zone the new model predicts the mixed region of white dwarf envelopes to
contain at least 10 times more mass than local mixing length theory (MLT)
models having similar photospheric temperature structures. This result is
consistent with the upper limit given by numerical simulations which predict an
even larger amount of mass to be mixed by convective overshooting. Finally, we
attempt to parametrise some of our results in terms of local MLT-based models,
insofar as is possible given the limitations of MLT


title: Prospects for X-ray Studies of Galaxy Clusters with Astro-E2/XRS

abstract:
  The Astro-E2 high resolution X-Ray Spectrometer (XRS) is expected to provide
a major enhancement in study of clusters of galaxies. Astro-E2 is the fifth
Japanese X-ray astronomy observatory, which is scheduled for launch in early
2005. The XRS instrument, developed under a Japan-US collaboration, is an X-ray
microcalorimeter with a capability of observing extended objects, and a high
energy resolution of about 6 eV at 6 keV. The spectral resolving power is 20
times higher than CCDs over the 0.5-10 keV energy band. We have obtained
several new results of clusters with Chandra and XMM, which show that
high-resolution imaging spectroscopy can clarify some outstanding questions.
New sciences from Astro-E2 include the first clear measurement of gas
velocities, determination of ion and electron temperatures, and electron
densities based on the resolved line features. We will describe the XRS
instrument design, and present simulations of the expected performance.


title:
Properties and nature of Be stars XXIII. Long-term variations and
  physical properties of kappa Dra

abstract:
  We present an analysis of new spectroscopic observations of the bright Be
star kappa Dra obtained at the Ondrejov observatory during 1992 - 2003 and UBV
photometric observations secured at several observatories. The fundamental
stellar parameters have been obtained from a comparison with a grid of NLTE
model atmospheres. The best fit was found for Teff=14000K, log g = 3.5, and v
sin i = 170km/s. These values together with a Hipparcos parallax lead to a
stellar mass M=4.8+-0.8 M_solar and radius R=6.4+-0.5 R_solar. Long-term
variations of kappa Dra were analysed using measurements of equivalent widths,
central intensities, peak intensities of emission lines and emission peak
velocity differences for H-alpha, H-beta, H-gamma, H-delta, and some helium,
silicon, and iron lines. It turned out that the previously reported period of
23 years in the variation of the emission strength is probably a cyclic, not a
strictly periodic phenomenon. An attempt to find out a period from all
available records of the H-beta emission strength led to a value of 8044+-167
days (22.0 years) but the phase plots show that each cycle has a different
shape and length. For the moment, the nature and origin of the disk around
kappa Dra still remains unknown. From the comparison of the electronic spectra
obtained at different phases of the long-term cycle and synthetic spectra it
appears that there are no detectable changes in the photospheric part of the
Balmer lines related to variations in the Balmer emission strength which could
be attributed to an extended photosphere corresponding to inner parts of the
disk, optically thick in continuum.


title:
Optical photometry and spectral classification in the field of the open
  cluster NGC 6996 in the North America Nebula

abstract:
  We present and discuss broad band CCD $UBV(I)_C$ photometry and low
resolution spectroscopy for stars in the region of the open cluster NGC 6996,
located in the North America Nebula. The new data allow us to tightly constrain
the basic properties of this object. We revise the cluster size, which in the
past has been significantly underestimated. The width of the Main Sequence is
mainly interpreted in terms of differential reddening, and indeed the stars'
color excess $E_{B-V}$ ranges from 0.43 to 0.65, implying the presence of a
significant and evenly distributed dust component. We cross-correlate our
optical photometry with near infrared from 2MASS, and by means of spectral
classification we are able to build up extinction curves for an handful of
bright members. We find that the reddening slope and the total to selective
absorption ratio $R_V$ toward NGC 6996 are anomalous. Moreover the reddening
corrected colors and magnitudes allow us to derive estimates for the cluster
distance and age, which turn out to be $760 \pm 70 pc$ ($V_{0}-M_{V} = 9.4 \pm
0.2$) and $\sim 350$ Myr, respectively. Basing on our results, we suggest that
NGC 6996 is located in front of the North America Nebula, and does not seem to
have any apparent relationship with it.


title: Binaries in the Hipparcos data: Keep digging

abstract:
  Among the 120 000 objects in the Hipparcos catalogue, only 235 were fitted
with an orbital model. Besides these 235 original astrometric binaries, most
Hipparcos entries with a known spectroscopic orbit (extrasolar planet or
stellar companion) have now been re-processed, as part of the on-going
construction of the 9th Catalogue of Spectroscopic Binary Orbits (SB9,
available at http://sb9.astro.ulb.ac.be). The pitfalls and successes of this
re-processing are discussed in various contexts, like (i) orbital inclinations:
the holy grail for extrasolar planets (ii) searching for binaries without a
priori knowledge of their spectroscopic orbital elements, and application to
barium stars (iii) why not all SB9 entries yield acceptable astrometric
solutions? The lessons learned from this study are useful to devise the best
possible binary-detection and orbit-determination algorithms for future
astrometric missions like GAIA.


title: SB2 and eclipsing binaries with GAIA and RAVE

abstract:
  The expected performance of GAIA satellite on eclipsing binaries is reviewed
on the basis of (a) combined Hipparcos and ground-based observations mimicking
GAIA data harvest, and (b) accurate simulations using the latest instrument
model. It is found that for a large majority of the 16000 SB2 eclipsing
binaries that GAIA will discover at magnitudes V<13, the orbital solutions and
physical parameters will be derived with formal accuracies better than 2%. For
the same stars the GAIA parallax errors will be about 5 micro-arcsec, i.e. an
error of 0.5% at 1 kpc, which will allow to iteratively refine of the
parameters and physics used in orbital modeling. The detectability of SB2
binaries by the already up and running spectral survey RAVE is discussed. It is
found that all F-to-M SB2 binaries showing a velocity separation >=35 km/sec
and a luminosity ratio >=0.5 will be recognized as such.


title: Flaring vs. self-shadowed disks: the SEDs of Herbig Ae/Be stars

abstract:
  Isolated Herbig Ae stars can be divided into two groups (Meeus et al. 2001):
those with an almost flat spectral energy distribution in the mid-infrared
(`group I'), and those with a strong decline towards the far-infrared (`group
II'). In this paper we show that the group I vs. II distinction can be
understood as arising from flaring vs. self-shadowed disks. We show that these
two types of disks are natural solutions of the 2-D radiation-hydrostatic
structure equations. Disks with high optical depth turn out to be flaring and
have a strong far-IR emission, while disks with an optical depth below a
certain threshold drop into the shadow of their own puffed-up inner rim and are
weak in the far-IR. In spite of not having a directly irradiated surface layer,
self-shadowed disks still display dust features in emission, in agreement with
observations of group II sources. We propose an evolutionary scenario in which
a disk starts out with a flaring shape (group I source), and then goes through
the process of grain growth, causing the optical depth of the disk to drop and
the disk to become self-shadowed (group II source). We show that this scenario
predicts that the (sub-)millimeter slope of the disk changes from steep (small
grains) to Rayleigh-Jeans-like (large grains) in the early stages of evolution,
so that all group II sources are expected to have Rayleigh-Jeans-like slopes,
while some group I sources may still have steep (sub-)millimeter slopes.


title:
Seyferts on the edge: polar scattering and orientation-dependent
  polarization in Seyfert 1 nuclei

abstract:
  We have identified 12 Seyfert 1 galaxies that exhibit optical polarization
spectra similar to those of Seyfert 2 galaxies in which polarized broad-lines
are detected. We present new spectropolarimetric observations of 3 of them: Was
45, Mrk 231 and NGC 3227. These objects appear to be polarized as a result of
far-field scattering in the polar illumination cones of the circum-nuclear
torus. We estimate that they represent between 10 and 30 per cent of the
Seyfert 1 population; they are found amongst all the main spectroscopic
sub-types, including narrow-line Seyfert 1 galaxies. We have shown elsewhere
that Seyfert 1 nuclei more commonly have polarization characteristics that can
be attributed to scattering by a compact 'equatorial' scattering region located
inside the torus. We propose that both equatorial and polar scattering regions
are present in all Seyfert galaxies and argue that the observed range of
polarization properties can be broadly understood as an orientation effect. In
this scheme, polar-scattered Seyfert 1 galaxies represent the transition
between unobscured (the majority of type 1) and obscured (type 2) Seyferts.
They are viewed through the upper layers of the torus and are thus subject to
moderate extinction (Av ~1-4 mag) sufficient to suppress polarized light from
the equatorial scattering region, but not the broad wings of the Balmer lines.
The orientation of the polarization position angle relative to the radio source
is broadly consistent with the two-component scattering model. More generally,
we find that amongst Seyferts 1 galaxies, parallel, perpendicular and
intermediate orientations of the polarization PA relative to the radio axis
occur roughly in the proportions 2:1:1.


title: He-D3 Polarization observed in Prominences

abstract:
  Spectro-polarimetric measurements of the D3-HeI 5876 A line profile in 35
prominences have been performed in 2003 with the Gregory-Coud\'e Telescope in
Locarno. Two different experimental techniques (ZIMPOL and Beam-exchange
method) have been successfully employed to determine all four Stokes
components. Both give compatible results. The preliminary results as well as
the measurement techniques are reported.


title: XMM-Newton EPIC & OM observations of Her X-1 over the 35 day beat period

abstract:
  We present the results of a series of XMM-Newton EPIC and OM observations of
Her X-1, spread over a wide range of the 35 day precession period. We confirm
that the spin modulation of the neutron star is weak or absent in the low state
- in marked contrast to the main or short-on states. During the states of
higher intensity, we observe a substructure in the broad soft X-ray modulation
below ~1keV, revealing the presence of separate peaks which reflect the
structure seen at higher energies. The strong fluorescence emission line at
~6.4keV is detected in all observations (apart from one taken in the middle of
eclipse), with higher line energy, width and normalisation during the main-on
state. In addition, we report the detection of a second line near 7keV in 10 of
the 15 observations taken during the low-intensity states of the system. This
feature is rather weak and not significantly detected during the main-on state,
when the strong continuum emission dominates the X-ray spectrum. Spin resolved
spectroscopy just after the rise to the main-on state shows that the variation
of the Fe Kalpha line at 6.4 keV is correlated with the soft X-ray emission.
This confirms our past finding based on the XMM-Newton observations made
further into the main-on state, and indicates the common origin for the thermal
component and the Fe Kalpha line detected at these phases. We also find that
the normalisation of the 6.4keV line during the low state is correlated with
the binary orbital phase, having a broad maximum centered near phi_(orbit) ~
0.5. We discuss these observations in the context of previous observations,
investigate the origin of the soft and hard X-rays and consider the emission
site of the 6.4keV and 7keV emission lines.


title:
The evolution of the Milky Way from its earliest phases : constraints on
  stellar nucleosynthesis

abstract:
  We computed the evolution of the abundances of O, Mg, Si, Ca, K, Ti, Sc, Ni,
Mn, Co, Fe and Zn in the Milky Way. We made use of the most widely adopted
nucleosynthesis calculations and compared the model results with observational
data with the aim of imposing constraints upon stellar yields. In order to fit
at best the data in the solar neighborhood, when adopting the Woosley and
Weaver (1995) yields for massive stars and the Iwamoto et al. (1999) ones for
type Ia SNe, it is required that: i) the Mg yields should be increased in stars
with masses from 11 to 20 M_sun and decreased in masses larger than 20 M_sun.
The Mg yield should be also increased in SNe Ia. ii) The Si yields should be
slightly increased in stars above 40 M_sun, whereas those of Ti should be
increased between 11 and 20 M_sun and above 30 M_sun. iii) The Cr and Mn yields
should be increased in stars with masses in the range 11-20 M_sun, iv) the Co
yields in SNe Ia should be larger and smaller in stars in the range 11-20
M_sun, v) the Ni yield from type Ia SNe should be decreased, vi) the Zn yield
from type Ia SNe should be increased. vii) The yields of O (metallicity
dependent SN models), Ca, Fe,
  Ni, and Zn (the solar abundance case) in massive stars from Woosley and
Weaver (1995) are the best to fit the abundance patterns of these elements
since they do not need any change. We adopted also the yields by Nomoto et al.
(1997) and Limongi and Chieffi (2003) for massive stars and discussed the
corrections required in these yields in order to fit the observations. Finally,
the small spread in the [el/Fe] ratios in the metallicity range from
[Fe/H]=-4.0 up to -3.0 dex (Cayrel et al. 2003) is a clear sign that the halo
of the Milky Way was well mixed even in the earliest phases of its evolution.


title: The FORS Deep Field Spectroscopic Survey

abstract:
  We present a catalogue and atlas of low-resolution spectra of a well defined
sample of 341 objects in the FORS Deep Field. All spectra were obtained with
the FORS instruments at the ESO VLT with essentially the same spectroscopic
set-up. The observed extragalactic objects cover the redshift range 0.1 to 5.0.
98 objects are starburst galaxies and QSOs at z > 2. Using this data set we
investigated the evolution of the characteristic spectral properties of bright
starburst galaxies and their mutual relations as a function of the redshift.
Significant evolutionary effects were found for redshifts 2 < z < 4. Most
conspicuous are the increase of the average C IV absorption strength, of the
dust reddening, and of the intrinsic UV luminosity, and the decrease of the
average Ly alpha emission strength with decreasing redshift. In part the
observed evolutionary effects can be attributed to an increase of the
metallicity of the galaxies with cosmic age. Moreover, the increase of the
total star-formation rates and the stronger obscuration of the starburst cores
by dusty gas clouds suggest the occurrence of more massive starbursts at later
cosmic epochs.


title: A multifrequency analysis of radio variability of blazars

abstract:
  We have carried out a multifrequency analysis of the radio variability of
blazars, exploiting the data obtained during the extensive monitoring programs
carried out at the University of Michigan Radio Astronomy Observatory (UMRAO,
at 4.8, 8, and 14.5 GHz) and at the Metsahovi Radio Observatory (22 and 37
GHz). Two different techniques detect, in the Metsahovi light curves, evidences
of periodicity at both frequencies for 5 sources (0224+671, 0945+408, 1226+023,
2200+420, and 2251+158). For the last three sources consistent periods are
found also at the three UMRAO frequencies and the Scargle (1982) method yields
an extremely low false-alarm probability. On the other hand, the 22 and 37 GHz
periodicities of 0224+671 and 0945+408 (which were less extensively monitored
at Metsahovi and for which we get a significant false-alarm probability) are
not confirmed by the UMRAO database, where some indications of ill-defined
periods about a factor of two longer are retrieved. We have also investigated
the variability index, the structure function, and the distribution of
intensity variations of the most extensively monitored sources. We find a
statistically significant difference in the distribution of the variability
index for BL Lac objects compared to flat-spectrum radio quasars (FSRQs), in
the sense that the former objects are more variable. For both populations the
variability index steadily increases with increasing frequency. The
distribution of intensity variations also broadens with increasing frequency,
and approaches a log-normal shape at the highest frequencies. We find that
variability enhances by 20-30% the high frequency counts of extragalactic
radio-sources at bright flux densities, such as those of the WMAP and Planck
surveys.


title: Blue straggler production in globular clusters

abstract:
  Recent HST observations of a large sample of globular clusters reveal that
every cluster contains between 40 and 400 blue stragglers. The population does
not correlate with either stellar collision rate (as would be expected if all
blue stragglers were formed via collisions) or total mass (as would be expected
if all blue stragglers were formed via the unhindered evolution of a subset of
the stellar population). In this paper, we support the idea that blue
stragglers are made through both channels. The number produced via collisions
tends to increase with cluster mass. In this paper we show how the current
population produced from primordial binaries decreases with increasing cluster
mass; exchange encounters with third, single, stars in the most massive
clusters tend to reduce the fraction of binaries containing a primary close to
the current turn-off mass. Rather their primaries tend to be somewhat more
massive (~1-3 M_sun) and have evolved off the main sequence, filling their
Roche lobes in the past, often converting their secondaries into blue
stragglers (but more than 1 Gyr or so ago and thus they are no longer visible
as blue stragglers). We show that this decline in the primordial blue straggler
population is likely to be offset by the increase in the number of blue
stragglers produced via collisions. The predicted total blue straggler
population is therefore relatively independent of cluster mass, thus matching
the observed population. This result does not depend on any particular assumed
blue straggler lifetime.


title: Characteristic Scales in Galaxy Formation

abstract:
  Recent data, e.g. from SDSS and 2dF, reveal a robust bi-modality in the
distribution of galaxy properties, with a characteristic transition scale at
stellar mass M_*~3x10^{10} Msun (near L_*), corresponding to virial velocity
V~100 km/s. Smaller galaxies tend to be blue disks of young populations. They
define a "fundamental line" of decreasing surface brightness, metallicity and
velocity with decreasing M_*, which extends to the smallest dwarf galaxies.
Galaxies above the critical scale are dominated by red spheroids of old
populations, with roughly constant high surface brightens and metallicity, and
they tend to host AGNs. A minimum in the virial M/L is obtained at the same
magic scale. This bi-modality can be the combined imprint of several different
physical processes. On smaller scales, disks are built by cold flows, and
supernova feedback is effective in regulating star formation. On larger scales,
the infalling gas is heated by a virial shock and star formation can be
suppressed by AGN feedback. Another feedback mechanism -- gas evaporation due
to photo-ionization -- may explain the existence of totally dark halos below
V~30 km/s. The standard cooling barriers are responsible for the loose upper
and lower bounds for galaxies: 10 < V < 300 km/s.


title: On the spherical collapse model in dark energy cosmologies

abstract:
  We study the spherical collapse model in dark energy cosmologies, in which
dark energy is modelled as a minimally coupled scalar field. We first follow
the standard assumption that dark energy does not cluster on the scales of
interest. Investigating four different popular potentials in detail, we show
that the predictions of the spherical collapse model depend on the potential
used. We also investigate the dependence on the initial conditions. Secondly,
we investigate in how far perturbations in the quintessence field affect the
predictions of the spherical collapse model. In doing so, we assume that the
field collapses along with the dark matter. Although the field is still
subdominant at the time of virialisation, the predictions are different from
the case of a homogeneous dark energy component. This will in particular be
true if the field is non--minimally coupled. We conclude that a better
understanding of the evolution of dark energy in the highly non--linear regime
is needed in order to make predictions using the spherical collapse model in
models with dark energy.


title: Mirage: a new iterative Map-Making code for CMB experiments

abstract:
  A major goal of CMB experiments is to obtain highly sensitive CMB maps in
order to extract Spherical Harmonic Power Spectrum (SHPS) and cosmological
parameters with unprecedented accuracy. We present a new map-making code
(Mirage), based on a two-phase iterative algorithm, involving low frequency
drift treatment, Butterworth high-pass filtering and conjugate gradient method.
This work was strongly motivated by Archeops CMB experiment data analysis. We
believe that Archeops was a good test bench for the future Planck Surveyor data
analysis, and Mirage was designed in order to be used for Planck data
processing with minimal work. A strong feature of Mirage is that it handles
experimental problems in data, such as holes in data stream, bright sources,
and galaxy side effects, without jeopardising speed. The other advantage is its
processing speed, allowing to run Monte Carlo simulations of Archeops data
processing on a single processor workstation overnight. Algorithms are
explained. Systematic effects on SHPS are investigated on various simulated
data, including typical Archeops observational systematics.
  This code is available at adress http://www-dapnia.cea.fr/Telechargement/
  Preprint with full resolution figures is available at
http://www-dapnia.cea.fr/Doc/Publications/Archives/dapnia-03-378.pdf


title: A survey for low luminosity quasars at redshift z~5

abstract:
  We present the results of a multi-colour (VIZ) survey for low luminosity
(M_B<-23.5) quasars with z~5 using the 12K CCD mosaic camera on CFHT. The
survey covers 1.8deg^2 to a limiting magnitude of m_z=22.5(Vega), about two
magnitudes fainter than the SDSS quasar survey. 20 candidates were selected by
their VIZ colours and spectra for 15 of these were obtained with GMOS on the
Gemini North telescope. A single quasar with z=4.99 was recovered, the
remaining candidates are all M stars.
  The detection of only a single quasar in the redshift range accessible to the
survey (4.8<5.2) is indicative of a possible turn over in the luminosity
function at faint quasar magnitudes, and a departure from the form observed at
higher luminosities (in agreement with quasar lensing observations by Richards
etal (2003)). However, the derived space densitys, of quasars more luminous
than M_B(Vega)<-23.5, of 2.96x10^-7 Mpc^-3 is consistent at the 65% confidence
level with extrapolation of the quasar luminosity function as derived by Fan
etal (2001a) at m_i<19.6(Vega).


title: Citation measures and impact within astronomy

abstract:
  By utilising the inbuilt citation counts from NASA's astrophysics data system
(ADS) I derive how many citations refereed articles receive as a function of
time since publication. After five years, one paper in a hundred has
accumulated 91 or more citations, a figure which rises to 145 citations after
ten years. By adding up the number of citations active researchers have
received over the past five years I have estimated their relative impact upon
the field both for raw citations and citations weighted by the number of
authors per paper.


title:
A Radio Outburst Nearly Coincident with the Large X-ray Flare from Sgr
  A* on 2002-10-03

abstract:
  A large radio outburst from Sgr A* was observed during the VLA weekly
monitoring program at 2 cm, 1.3 cm and 7 mm, nearly coincident with the
brightest X-ray flare detected to date with the XMM-Newton X-ray Observatory on
2002-10-03. The flux density of 1.9$\pm$0.2 Jy measured at 7 mm exceeds the
mean value (1.00$\pm$0.01 Jy) by a factor of $\sim 2$, one of the two highest
increases observed during the past three years (June 2000-October 2003), while
less significant increases in flux densities were observed at 1.3 cm and 2 cm.
The radio observation started 13.5 hrs after the onset of the X-ray flare
(which had occurred over a 45 min duration) and continued for 1.3 hrs. During
the observation, there was no significant ($<3\sigma$) change in the radio flux
densities at all the three wavelengths, indicating that the radio outburst
varied on a timescale of $>1$hr. A spectral index of $\alpha=2.4^{+0.3}_{-0.6}$
(${\rm S \propto\nu^\alpha}$) was derived for the outburst component,
consistent with an optically thick nonthermal synchrotron source. These results
suggest that energetic electrons responsible for the radio outburst might be
produced via a process associated with the X-ray flare, then transported to
large radii, producing the observed radio outburst. The observation is the
first evidence for a correlated variation in the radio and X-ray emissions from
Sgr A*.


title:
Dark and luminous matter connections. Towards understanding galaxy
  evolution

abstract:
  In this review we outline the major points of ab-initio cosmological models
focusing on some galaxy evolution unresolved problems. In particular our
knowledge of the star formation rate which leads galaxy evolution, i.e.
luminosity, colors and dust enrichment, is still very poor. Smoothed particle
hydrodynamic simulations including chemo-photometric evolutionary population
synthesis models of isolated collapsing systems endowed with triaxial dark
matter halos, gas and the star formation switched on, are a useful tool to shed
light on several open questions. This approach, which allows a greater particle
resolution than a fully consistent cosmological scenario, gives us important
insights into connections between dark and luminous matter. Both the initial
properties of the halo, as so as its geometry and dynamical state, and total
mass of the system, drive the galaxy formation and evolution. In our simple
framework spiral galaxies arise only in systems with both a total mass less
than 1.e12 solar masses and a critical value of the baryonic-to-total-mass
ratio, around its cosmological value, 0.1. For the same value of such a ratio
more massive systems host more luminous and redder galaxies, as a consequence
of the stronger burst of star formation arising into their halos earlier on.
Moreover the star formation does not switch on in the less massive DM halos so
that the critical mass to entail a luminous system is 1.e11 solar masses. For a
given total mass, higher values of the baryonic-to-total-mass ratio provide
galaxies with lower rotational support so that no constraints to the total mass
of the system hosting an elliptical galaxy have been derived.