title:
Recent Achievements on the development of the Herschel/PACS Bolometer
  arrays

abstract:
  A new type of bolometer arrays sensitive in the Far Infrared and
Submillimeter range has been developped and manufactured by CEA/LETI/SLIR and
will be integrated in the PACS instrument onboard the Herschel Space
Observatory (launch date 2008). The main innovations are their collective
manufacturing technique (production of 3-side buttable 16x16 arrays) and their
high mapping efficiency (large format detector and instantaneous Nyquist
sampling). Their measured NEP is 2x10^-16 W/Hz^-0.5 and their thermometric
passband about 4-5 Hz. In this paper we describe CEA bolometers and present the
results obtained during the last test campaign.


title: A 110 MG cyclotron harmonic in the optical spectrum of RX J1554.2+2721

abstract:
  We report the detection of a 110 MG cyclotron harmonic in the SDSS-spectrum
of the magnetic cataclysmic variable (MCV) RX J1554.2+2721. This feature was
noted earlier by others but remained unexplained. The wide spectral coverage of
the new spectrum together with the earlier detection of a Zeeman split Ly-a
line in a field of 144 MG makes the identification almost unambiguous. We
propose to explain the non-conforming UV-optical photospheric temperature of
the white dwarf by an as yet unobserved cyclotron component in the ultraviolet
which also could significantly contribute to the overall energy balance of the
accretion process.


title: Variation of atmospheric depth profile on different time scales

abstract:
  The vertical profile of atmospheric depth is an important element in
extensive air shower studies. The depth of shower maximum is one of the most
important characteristics of the shower. In the fluorescence technique of
shower detection, the geometrical reconstruction provides the altitude of
shower maximum, so that an accurate profile of atmospheric depth is needed to
convert this altitude to the depth of shower maximum. In this paper the
temporal variation of experimentally measured profiles of atmospheric depth at
different sites is studied and implications for shower reconstruction are
shown. The atmospheric profiles vary on time scales from hours to years. It is
shown that the daily variation of the profile is as important as its seasonal
variation and should be accounted for in air shower studies. For precise shower
reconstruction, the daily profiles determined locally at the site of the air
shower detector are recommended.


title:
Giant Pulses -- the Main Component of the Radio Emission of the Crab
  Pulsar

abstract:
  The paper presents an analysis of dual-polarization observations of the Crab
pulsar obtained on the 64-m Kalyazin radio telescope at 600 MHz with a time
resolution of 250 ns. A lower limit for the intensities of giant pulses is
estimated by assuming that the pulsar radio emission in the main pulse and
interpulse consists entirely of giant radio pulses; this yields estimates of
100 Jy and 35 Jy for the peak flux densities of giant pulses arising in the
main pulse and interpulse, respectively. This assumes that the normal radio
emission of the pulse occurs in the precursor pulse. In this case, the
longitudes of the giant radio pulses relative to the profile of the normal
radio emission turn out to be the same for the Crab pulsar and the millisecond
pulsar B1937+21, namely, the giant pulses arise at the trailing edge of the
profile of the normal radio emission. Analysis of the distribution of the
degree of circular polarization for the giant pulses suggests that they can
consist of a random mixture of nanopulses with 100% circular polarization of
either sign, with, on average, hundreds of such nanopulses within a single
giant pulse.


title: The X-ray nuclei of intermediate-redshift radio sources

abstract:
  We present a Chandra and XMM-Newton spectral analysis of the nuclei of the
radio galaxies and radio-loud quasars from the 3CRR sample in the redshift
range 0.1 < z < 0.5. In the range of radio luminosity sampled by these objects,
mostly FRIIs, it has been clear for some time that a population of radio
galaxies (`low-excitation radio galaxies') cannot easily participate in models
that unify narrow-line radio galaxies and broad-line objects. We show that
low-excitation and narrow-line radio galaxies have systematically different
nuclear X-ray properties: while narrow-line radio galaxies universally show a
heavily absorbed nuclear X-ray component, such a heavily absorbed component is
rarely found in sources classed as low-excitation objects. Combining our data
with the results of our earlier work on the z<0.1 3CRR sources, we discuss the
implications of this result for unified models, for the origins of mid-infrared
emission from radio sources, and for the nature of the apparent FRI/FRII
dichotomy in the X-ray. The lack of direct evidence for accretion-related X-ray
emission in FRII LERGs leads us to argue that there is a strong possibility
that some, or most, FRII LERGs accrete in a radiatively inefficient mode.
However, our results are also consistent with a model in which the accretion
mode is the same for low- and high-excitation FRIIs, with the lower accretion
luminosities in FRII LERGs attributed instead to more efficient radio
luminosity production in those objects.


title: The Hubble flow around the CenA / M83 galaxy complex

abstract:
  We present HST/ACS images and color-magnitude diagrams for 24 nearby galaxies
in and near the constellation of Centaurus with radial velocities V_LG < 550
km/s. Distances are determined based on the luminosities of stars at the tip of
the red giant branch that range from 3.0 Mpc to 6.5 Mpc. The galaxies are
concentrated in two spatially separated groups around Cen A (NGC 5128) and M 83
(NGC 5236). The Cen A group itself has a mean distance of 3.76 +/-0.05 Mpc, a
velocity dispersion of 136 km/s, a mean harmonic radius of 192 kpc, and an
estimated orbital/virial mass of (6.4 - 8.1) x 10^12 M_sun. This elliptical
dominated group is found to have a relatively high mass-to-light ratio: M/L_B =
125 M_sun/L_sun. For the M 83 group we derived a mean distance of 4.79 +/-0.10
Mpc, a velocity dispersion of 61 km/s, a mean harmonic radius of 89 kpc, and
estimated orbital/virial mass of (0.8 - 0.9) x 10^12 M_sun. This spiral
dominated group is found to have a relatively low M/L_B = 34 M_sun/L_sun. The
radius of the zero-velocity surface around Cen A lies at R_0 = 1.40 +/-0.11
Mpc, implying a total mass within R_0 of M_T = (6.0 +/-1.4) x 10^12 M_sun. This
value is in good agreement with the Cen A virial/orbital mass estimates and
provides confirmation of the relatively high M/L_B of this elliptical-dominated
group. The centroids of both the groups, as well as surrounding field galaxies,
have very small peculiar velocities, < 25 km/s, with respect to the local
Hubble flow with H_0 = 68 km/s/Mpc.


title: Gauge Freedom in Orbital Mechanics

abstract:
  In orbital and attitude dynamics the coordinates and the Euler angles are
expressed as functions of the time and six constants called elements. Under
disturbance, the constants are endowed with time dependence. The Lagrange
constraint is then imposed to guarantee that the functional dependence of the
perturbed velocity on the time and constants stays the same as in the
undisturbed case. Constants obeying this condition are called osculating
elements. The constants chosen to be canonical are called Delaunay elements, in
the orbital case, or Andoyer elements, in the spin case. (As some Andoyer
elements are time dependent even in the free-spin case, the role of constants
is played by their initial values.) The Andoyer and Delaunay sets of elements
share a feature not readily apparent: in certain cases the standard equations
render them non-osculating. In orbital mechanics, elements furnished by the
standard planetary equations are non-osculating when perturbations depend on
velocities. To preserve osculation, the equations must be amended with extra
terms that are not parts of the disturbing function. In the case of Delaunay
parameterisation, these terms destroy canonicity. So under velocity-dependent
disturbances, osculation and canonicity are incompatible. (Efroimsky and
Goldreich 2003, 2004) Similarly, the Andoyer elements turn out to be
non-osculating under angular-velocity-dependent perturbation. Amendment of only
the Hamiltonian makes the equations render nonosculating elements. To make them
osculating, more terms must enter the equations (and the equations will no
longer be canonical). In practical calculations, is often convenient to
deliberately deviate from osculation by substituting the Lagrange constraint
with a condition that gives birth to a family of nonosculating elements.

categories: astro-ph math.DS nlin.CD physics.class-ph


title: Disks around Young O-B (Proto)Stars: Observations and Theory

abstract:
  Disks are a natural outcome of the star formation process in which they play
a crucial role. Luminous, massive stars of spectral type earlier than B4 are
likely to be those that benefit most from the existence of accretion disks,
which may significantly reduce the effect of radiation pressure on the
accreting material. The scope of the present contribution is to review the
current knowledge about disks in young high-mass (proto)stars and discuss their
implications. The issues of disk stability and lifetime are also discussed. We
conclude that for protostars of less than ~20 solar masses, disks with mass
comparable to that of the central star are common. Above this limit the
situation is unclear and there are no good examples of proto O4-O8 stars
surrounded by accretion disks: in these objects only huge, massive, toroidal,
non-equilibrium rotating structures are seen. It is clear on the other hand
that the observed disks in stars of 10-20 solar masses are likely to be
unstable and with short lifetimes.


title:
The GOODS-MUSIC sample: a multicolour catalog of near-IR selected
  galaxies in the GOODS-South field

abstract:
  We present a high quality multiwavelength (from 0.3 to 8.0 micron) catalog of
the large and deep area in the GOODS Southern Field covered by the deep near-IR
observations obtained with the ESO VLT. The catalog is entirely based on public
data: in our analysis, we have included the F435W, F606W, F775W and F850LP ACS
images, the JHKs VLT data, the Spitzer data provided by IRAC instrument (3.6,
4.5, 5.8 and 8.0 micron), and publicly available U-band data from the 2.2ESO
and VLT-VIMOS. We describe in detail the procedures adopted to obtain this
multiwavelength catalog. In particular, we developed a specific software for
the accurate "PSF-matching" of space and ground-based images of different
resolution and depth (ConvPhot), of which we analyse performances and
limitations. We have included both z-selected, as well as Ks-selected objects,
yielding a unique, self-consistent catalog. The largest fraction of the sample
is 90% complete at z~26 or Ks~23.8 (AB scale). Finally, we cross-correlated our
data with all the spectroscopic catalogs available to date, assigning a
spectroscopic redshift to more than 1000 sources. The final catalog is made up
of 14847 objects, at least 72 of which are known stars, 68 are AGNs, and 928
galaxies with spectroscopic redshift (668 galaxies with reliable redshift
determination). We applied our photometric redshift code to this data set, and
the comparison with the spectroscopic sample shows that the quality of the
resulting photometric redshifts is excellent, with an average scatter of only
0.06. The full catalog, which we named GOODS-MUSIC (MUltiwavelength Southern
Infrared Catalog), including the spectroscopic information, is made publicly
available, together with the software specifically designed to this end.


title:
The Clustering Evolution of Distant Red Galaxies in the GOODS-MUSIC
  Sample

abstract:
  We use the GOODS-MUSIC sample, a catalog of ~3000 Ks-selected galaxies based
on VLT and HST observation of the GOODS-South field with extended
multi-wavelength coverage (from 0.3 to 8 micron) and accurate estimates of the
photometric redshifts to select 179 DRGs with J-Ks>1.3 in an area of 135 sq.
arcmin. We first show that the J-Ks>1.3 criterion selects a rather
heterogeneous sample of galaxies, going from the targeted high-redshift
luminous evolved systems, to a significant fraction of lower redshift (1<z<2)
and less luminous dusty starbursts. These low-redshift DRGs are significantly
less clustered than higher-z DRGs. With the aid of extreme and simplified
theoretical models of clustering evolution we show that it is unlikely that the
two samples are drawn from the same population observed at two different stages
of evolution. High-z DRGs likely represent the progenitors of the more massive
and more luminous galaxies in the local Universe and might mark the regions
that will later evolve into structures of intermediate mass, like groups or
small galaxy clusters. Low-z DRGs, on the other hand, will likely evolve into
slightly less massive field galaxies.


title: The Structure and Evolution of Young Stellar Clusters

abstract:
  We examine the properties of embedded clusters within 1 kiloparsec using new
data from the Spitzer Space Telescope, as well as recent results from 2MASS and
other ground-based near-infrared surveys. We use surveys of entire molecular
clouds to understand the range and distribution of cluster membership, size and
surface density. The Spitzer data demonstrate clearly that there is a continuum
of star- forming environments, from relative isolation to dense clusters. The
number of members of a cluster is correlated with the cluster radius, such that
the average surface density of clusters having a few to a thousand members
varies by a factor of only a few. The spatial distributions of
Spitzer-identified young stellar objects frequently show elongation, low
density halos, and sub-clustering. The spatial distributions of protostars
resemble the distribution of dense molecular gas, suggesting that their
morphologies result directly from the fragmentation of the natal gas. We also
examine the effects of the cluster environments on star and planet formation.
Although Far-UV and Extreme-UV radiation from massive stars can truncate disks
in a few million years, fewer than half of the young stars in our sample
(embedded clusters within 1 kpc) are found in regions of strong FUV and EUV
fields. Typical volume densities and lifetimes of the observed clusters suggest
that dynamical interactions are not an important mechanism for truncating disks
on solar system size scales.


title:
Polars Changing State: Multiwavelength Long Term Photometry and
  Spectroscopy of QS Tel, V834 Cen, and BL Hyi

abstract:
  Long term optical and near-infrared photometric and blue spectroscopic
observations were obtained for QS Tel, V834 Cen, and BL Hyi. The optical light
curves of all three polars displayed large magnitude changes during our
observations. These same high/low state transitions were also apparent in
near-infrared JHK photometry, though with decreased amplitude. The color of the
polar with respect to its state was examined and found not to be a good
indicator of the instantaneous state. During low to high state transitions, a
nearly constant magnitude difference was observed in all three polars. This
$\Delta$m value was found to be consistent with the level expected to occur if
accretion onto the white dwarf reached the Eddington luminosity during the high
state. The high state Balmer decrement was measured for each star and used to
estimate that the temperature of the emission line forming region was ~12,000K
with N$_H$ near 12.8 dex. No relationship between the Balmer emission line
strength and the white dwarf magnetic field strength was seen, in contrast to a
good correlation between these two parameters observed for UV emission lines.


title:
New Gamma Cas-like objects: X-ray and optical observations of SAO49725
  and HD161103

abstract:
  A growing number of early Be stars exhibit unusually hard X-ray spectra and
luminosities intermediate between those typical of early type stars and those
emitted by most Be/X-ray binaries in quiescence. We report on XMM-Newton and
optical observations of two such Be stars, SAO 49725 and HD 161103. The nature
of the hard-thermal X-ray emission is discussed in the light of the models
proposed for Gamma Cas, magnetic disc-star interaction or accretion onto a
compact companion object - neutron star or white dwarf. These two new objects
added to similar cases discovered in XMM-Newton surveys point at the emergence
of a new class of Gamma Cas analogs.


title:
Cross-correlation between WMAP and 2MASS: non-Gaussianity induced by SZ
  effect

abstract:
  We study the SZ-effect-induced non-Gaussianity in the cosmic microwave
background (CMB) fluctuation maps. If a CMB map is contaminated by the SZ
effect of galaxies or galaxy clusters, the CMB maps should have similar
non-Gaussian features as the galaxy and cluster fields. Using the WMAP data and
2MASS galaxy catalog we show that the non-Gaussianity of the 2MASS galaxies is
imprinted on WMAP maps. The signature of non-Gaussianity can be seen with the
4^{th} order cross correlation between the wavelet variables of the WMAP maps
and 2MASS clusters. The intensity of the 4^{th} order non-Gaussian features is
found to be consistent with the contamination of the SZ effect of 2MASS
galaxies. We also show that this non-Gaussianity can not be seen by the high
order auto-correlation of the WMAP. This is because the SZ signals in the
auto-correlations of the WMAP data generally is weaker than the WMAP-2MASS
cross correlations by a factor f^2, which is the ratio between the powers of SZ
effect map and the CMB fluctuations on the scale considered. Therefore, the
ratio of high order auto-correlations of CMB maps to cross-correlations of the
CMB maps and galaxy field would be effective to constrain the powers of SZ
effect on various scales.


title:
Revealing the Jet Structure of GRB 030329 with High Resolution
  Multicolor Photometry

abstract:
  We present multicolor optical observations of the nearby (z=0.1685) GRB
030329 obtained with the same instrumentation over a time period of 6 hours for
a total of an unprecedented 475 quasi-simultaneous BVR observations. The
achromatic steepening in the optical, which occurs at t~0.7 days, provides
evidence for a dynamic transition of the source, and can be most readily
explained by models in which the GRB ejecta are collimated into a jet. Since
the current state-of-the-art modeling of GRB jets is still flawed with
uncertainties, we use these data to critically assess some classes of models
that have been proposed in the literature. The data, especially the smooth
decline rate seen in the optical afterglow, are consistent with a model in
which GRB 030329 was a homogeneous, sharp-edged jet, viewed near its edge
interacting with a uniform external medium, or viewed near its symmetry axis
with a stratified wind-like external environment. The lack of short timescale
fluctuations in the optical afterglow flux down to the 0.5 per cent level puts
stringent constraints on possible small scale angular inhomogeneities within
the jet or fluctuations in the external density.


title:
Spectral Modeling of SNe Ia Near Maximum Light: Probing the
  Characteristics of Hydro Models

abstract:
  We have performed detailed NLTE spectral synthesis modeling of 2 types of 1-D
hydro models: the very highly parameterized deflagration model W7, and two
delayed detonation models. We find that overall both models do about equally
well at fitting well observed SNe Ia near to maximum light. However, the Si II
6150 feature of W7 is systematically too fast, whereas for the delayed
detonation models it is also somewhat too fast, but significantly better than
that of W7. We find that a parameterized mixed model does the best job of
reproducing the Si II 6150 line near maximum light and we study the differences
in the models that lead to better fits to normal SNe Ia. We discuss what is
required of a hydro model to fit the spectra of observed SNe Ia near maximum
light.


title: The radio SNR G65.1+0.6 and its associated pulsar J1957+2831

abstract:
  New images of the radio Supernova Remnant (SNR) G65.1+0.6 are presented,
based on the 408 MHz and 1420 MHz continuum emission and the HI-line emission
data of the Canadian Galactic Plane Survey (CGPS). A large shell-like structure
seen in the 2695 MHz Effelsberg map appears to have nonthermal spectral index.
HI observations show structures associated with the SNR G65.1+0.6 in the radial
velocity range of -20 to -26 km$/$s and suggest a distance of 9.2 kpc for the
SNR. The estimated Sedov age for G65.1+0.6 is 4 - 14 x10E4 yr. The pulsar (PSR)
J1957+2831 is possibly associated with G65.1+0.6, with consistent distance and
kinematic age estimate, but different characteristic age than the SNR. The
EGRET source 3EG J1958+2909 and gamma-ray source 2CG 065+00 are also near the
eastern edge of the SNR but do not agree in position with the pulsar and are
likely not associated with the SNR. The SNR's flux densities at 408 MHz
(8.6+-0.8 Jy), 1420 MHz (4.9+-0.5 Jy) and 2695 MHz (3.3+-0.5 Jy) have been
corrected for flux densities from compact sources within the SNR. The
integrated flux density based spectral index between 1420 MHz and 408 MHz is
0.45+-0.11 and agrees with the T-T plot spectral index of 0.34+-0.20. The
nearby SNR DA495 has a T-T plot spectral index of 0.50+-0.01.


title:
Turbulence driven diffusion in protoplanetary disks - chemical effects
  in the outer disk

abstract:
  The dynamics and chemistry of protostellar disks are likely to be intricately
linked, with dynamical processes altering the chemical composition, and
chemistry, in turn, controlling the ionization structure and hence the ability
of the magneto-rotational instability to drive the disk turbulence. Here we
present the results from the first chemical models of the outer regions (R >
100 AU) of protoplanetary disks to consider the effects of turbulence driven
diffusive mixing in the vertical direction. We show that vertical diffusion can
greatly affect the column densities of many species, increasing them by factors
of up to two orders of magnitude. Previous disk models have shown that disks
can be divided into three chemically distinct layers, with the bulk of the
observed molecular emission coming from a region between an atomic/ionic layer
on the surface of the disk and the midplane regoin where the bulk of molecules
are frozen onto grains. Diffusion retains this three layer structure, but
increases the depth of the molecular layer by bringing atoms and atomic ions
form by photodissociation in the surface layers into the shielded molecular
layer where molecules can reform. For other species, notably NH3 and N2H+, the
column densities are relatively unaffected by diffusion. These species peak in
abundance near the midplane where most other molecules are heavily depleted,
rather than in the molecular layer above. Diffusion only affects the abundances
of those molecules with peak abundances in the molecular layer. We find that
diffusion does not affect the ionization fraction of the disk. We compare the
calculated column densities to observations of DM Tau, LkCa 15 and TW Hya and
find good agreement for many molecules with a diffusion coefficient of 1e18
cm^2 s^-1.


title:
24-micron Detections of Disks around Very Low-mass Stars and Brown
  Dwarfs in IC 348: Grain Growth/Settling and Inner Holes?

abstract:
  We present observations of six late-type members of the young cluster IC 348
detected at 24 microns with the Multiband Imaging Photometer for Spitzer(MIPS).
At least four of the objects are probably substellar. Combining these data with
ground-based optical and near-infrared photometry and complementary
observations with the Infrared Array Camera (IRAC), we have modeled the
spectral energy distributions using detailed models of irradiated accretion
disks. We are able to fit the observations with models using a range of maximum
grain sizes from ISM-type dust to grains as large as 1 millimeter. Two objects
show a lack of excess emission at wavelengths shortward of 5.8-8 microns but
significant excess at longer wavelengths, indicative of large optically thin or
evacuated inner holes. Our models indicate a inner hole of radius ~ 0.5-0.9 AU
for the brown dwarf L316; this is the first brown dwarf with evidence for an
AU-scale inner disk hole. We examine several possible mechanisms for the inner
disk clearing in this case, including photoevaporation and planet formation.


title: Correlation Statistics of Quantized Noiselike Signals

abstract:
  I calculate the statistics of correlation of two digitized noiselike signals,
which are drawn from complex Gaussian distributions, sampled, quantized,
correlated, and averaged. Averaged over many such samples, the correlation r
approaches a Gaussian distribution. The mean and variance of r fully
characterize the distribution of r. The mean corresponds to the reproducible
part of the measurement, and the variance corresponds to the random part, or
noise. I investigate the case of nonnegligible covariance rho between the
signals. Noise in the correlation can increase or decrease, depending on
quantizer parameters, when rho increases. This contrasts with the correlation
of continuously valued or unquantized signals, for which the noise in phase
with rho increases with increasing rho, and noise out of phase decreases.
Indeed, for some quantizer parameters, I find that the correlation of quantized
signals provides a more accurate estimate of rho than would correlation without
quantization. I present analytic results in exact form and as polynomial
expansions, and compare these mathematical results with results of computer
simulations.


title: The Size-Frequency Distribution of Dormant Jupiter Family Comets

abstract:
  We estimate the total number and the slope of the size frequency distribution
(SFD) of dormant Jupiter Family Comets (JFCs) by fitting a one-parameter model
to the known population. We first select 61 Near Earth Objects (NEOs) that are
likely to be dormant JFCs because their orbits are dynamically coupled to
Jupiter (Bottke et al, 2002). Then, from the numerical simulations of Levison &
Duncan (1997), we construct an orbit distribution model for JFCs in the NEO
orbital element space. We assume an orbit independent SFD for all JFCs, the
slope of which is our unique free parameter. Finally, we compute observational
biases for dormant JFCs using a calibrated NEO survey simulator (Jedicke et al.
2003). By fitting the biased model to the data, we estimate that there are ~75
dormant JFCs with H<18 in the NEO region and that the slope of their cumulative
SFD is -1.5 +/- 0.3. Our slope for the SFD of dormant JFCs is very close to
that of active JFCs as determined by Weissman and Lowry (2003). Thus, we argue
that when JFCs fade they are likely to become dormant rather than to disrupt
and that the fate of faded comets is size independent. Our results imply that
the size distribution of the JFC progenitors - the scattered disk
trans-Neptunian population - either (i) has a similar and shallow SFD or (i')
is slightly steeper and physical processes acting on the comets in a
size-dependent manner creates the shallower active comet SFD. Our measured
slope, typical of collisionally evolved populations with a size dependent
impact strength (Benz and Asphaug 1999), suggests that scattered disk bodies
reached collisional equilibrium inside the proto-planetary disk prior to their
removal from the planetary region.


title: Very High Energy Neutrinos Originating from Kaons in Gamma-Ray Bursts

abstract:
  We simulate neutrino production in a gamma-ray burst (GRB) with the most
detailed method to date. We show that the highest energy neutrinos from GRBs
mainly come from kaons. Although there is little chance to detect such
neutrinos, attempts of detection are very important to prove physical
conditions in GRBs.


title: A High Resolution Search for Dark-Matter Axions

abstract:
  We have performed a high resolution search for galactic halo axions in cold
flows using a microwave cavity detector. The analysis procedure and other
details of this search are described. No axion signal was found in the mass
range 1.98-2.17 micro-eV. We place upper limits on the density of axions in
local discrete flows based on this result.


title: Parametrizations of the Dark Energy Density and Scalar Potentials

abstract:
  We develop a theoretical method of constructing the scalar (quintessence or
phantom) potential directly from the dimensionless dark energy function X(z),
the dark energy density in units of its present value. We apply our method to
two parametrizations of the dark energy density, the quiessence-Lambda ansatz
and the generalized Chaplygin gas model, and discuss some features of the
constructed potentials.


title: Placing Confidence Limits on Polarization Measurements

abstract:
  The determination of the true source polarization given a set of measurements
is complicated by the requirement that the polarization always be positive.
This positive bias also hinders construction of upper limits, uncertainties,
and confidence regions, especially at low signal-to-noise levels. We generate
the likelihood function for linear polarization measurements and use it to
create confidence regions and upper limits. This is accomplished by integrating
the likelihood function over the true polarization (parameter space), rather
than the measured polarization (data space). These regions are valid for both
low and high signal-to-noise measurements.


title: Off-Line, Multi-Detector Intensity Interferometers I: Theory

abstract:
  Stellar amplitude interferometry is limited by the need to have optical
distances fixed and known to a fraction of the wavelength. We suggest reviving
intensity interferometry, which requires hardware which is many orders of
magnitude less accurate, at the cost of more limited sensitivity. We present an
algorithm to use the very high redundancy of a uniform linear array to increase
the sensitivity of the instrument by more than a hundredfold. When using an
array of 100 elements, each almost 100m in diameter, and conservative
technological improvements, we can achieve a limiting magnitude of about
mb=14.4. Digitization, storage, and off-line processing of all the data will
also enable interferometric image reconstruction from a single observation run,
and application of various algorithms at any later time. Coronagraphy,
selectively suppressing only the large scale structure of the source, can be
achieved by specific aperture shapes. We conclude that after three decades of
abandonment optical intensity interferometry deserves another review.


title:
Off-Line, Multi-Detector Intensity Interferometers II: Implications and
  Applications

abstract:
  Intensity interferometry removes the stringent requirements on mechanical
precision and atmospheric corrections that plague all amplitude interferometry
techniques at the cost of severely limited sensitivity. A new idea we recently
introduced, very high redundancy, alleviates this problem. It enables the
relatively simple construction (~1cm mechanical precision) of a ground-based
astronomical facility able to transform a two-dimensional field of point-like
sources to a three-dimensional distribution of micro-arcsec resolved systems,
each imaged in several optical bands. Each system will also have its high
resolution residual timing, high quality (inside each band) spectra and light
curve, emergent flux, effective temperature, polarization effects and perhaps
some thermodynamic properties, all directly measured. All the above attributes
can be measured in a single observation run of such a dedicated facility. We
conclude that after three decades of abandonment optical intensity
interferometry deserves another review, also as a ground-based alternative to
the science goals of space interferometers.


title: Observed Planetary Nebulae as Descendants of Interacting Binary Systems

abstract:
  We examine recent studies on the formation rate of planetary nebulae and find
this rate to be about one-third of the formation rate of white dwarfs. This
implies than only about one-third of all planetary nebulae that evolve to form
white dwarfs are actually bright enough to be observed. This finding
corresponds with the claim that it is necessary for a binary companion to
interact with the asymptotic giant branch stellar progenitor for the descendant
planetary nebulae to be bright enough to be detected. The finding about the
formation rate also strengthens De Marco's conjecture that the majority of
observed planetary nebulae harbor binary systems. In other words, single stars
almost never form observed planetary nebulae.


title: Dark Energy: Mystery of the Millennium

abstract:
  Nearly seventy per cent of the energy density in the universe is unclustered
and exerts negative pressure. This conclusion -- now supported by numerous
observations -- poses the greatest challenge for theoretical physics today. I
discuss this issue with special emphasis on the cosmological constant as the
possible choice for the dark energy. Several curious features of a universe
with a cosmological constant are described and some possible approaches to
understand the nature of the cosmological constant are reviewed. In particular,
I show how some of the recent ideas, related to a thermodynamic route to
gravity, allow us to: (i) create a paradigm in which the bulk value of
cosmological constant is irrelevant and (ii) obtain the correct, observed,
value for the cosmological constant from vacuum fluctuations in a region
confined by the deSitter horizon.


title: Impact of a non-Gaussian density field on Sunyaev-Zeldovich observables

abstract:
  The main statistical properties of the Sunyaev-Zeldovich (S-Z) effect - the
power spectrum, cluster number counts, and angular correlation function - are
calculated and compared within the framework of two density fields which differ
in their predictions of the cluster mass function at high redshifts. We do so
for the usual Press and Schechter mass function, which is derived on the basis
of a Gaussian density fluctuation field, and for a mass function based on a
chi^2 distributed density field. These three S-Z observables are found to be
very significantly dependent on the choice of the mass function. The different
predictions of the Gaussian and non-Gaussian density fields are probed in
detail by investigating the behaviour of the three S-Z observables in terms of
cluster mass and redshift. The formation time distribution of clusters is also
demonstrated to be sensitive to the underlying mass function. A
semi-quantitative assessment is given of its impact on the concentration
parameter and the temperature of intracluster gas.


title:
Modeling the Structure of Hot Star Disks: a Critical Evaluation of the
  Viscous Decretion Scenario

abstract:
  We present self-consistent solutions for the disk structure of classical Be
stars. Our disk model is hydrostatically supported in the vertical direction
and the radial structure is governed by viscosity ($\alpha$-disks). We perform
three-dimensional non-LTE Monte Carlo simulations to calculate simultaneously
both the equilibrium temperature and Hydrogen level populations and to solve
self-consistently for the density structure of the disk. We discuss the general
properties of the solution for the disk structure and test our model against
observations of $\delta$ Scorpii. Our results confirm that a viscous decretion
disk model is consistent with these observations.


title: Refining the fundamental plane of accreting black holes

abstract:
  The idea of a unified description of supermassive and stellar black holes has
been supported by the extension of the empirical radio/X-ray correlation from
X-ray binaries to active galactic nuclei through the inclusion of a mass term.
This has lead to the so-called fundamental plane of black hole activity in the
black hole mass, radio and X-ray luminosity space. Two incarnations of this
fundamental plane have so far been suggested using different underlying models
and using two different samples of accreting black holes. We present revised
samples for both studies together with a refined statistical analysis using
measured errors of the observables. This method is used to compare the two
samples, discuss selection effects, and infer parameters for the fundamental
plane in a homogeneous way. We show that strongly sub-Eddington objects in a
state equivalent to the low/hard state of X-ray binaries follow the fundamental
plane very tightly; the scatter is comparable to the measurement errors.
However, we find that the estimated parameters depend strongly on the
assumptions made on the sources of scatter and the relative weight of the
different AGN classes in the sample. Using only hard state objects, the
fundamental plane is in agreement with the prediction of a simple uncooled
synchrotron/jet model for the emitted radiation. Inclusion of high-state
objects increases the scatter and moves the correlation closer to a disk/jet
model. This is qualitatively consistent with a picture where low-state objects
are largely dominated by jet emission while high-state objects have a strong
contribution from an accretion disk.


title: The Search For Primordial Tensor Modes

abstract:
  We review the prospects for detecting tensor modes generated during inflation
by CMB polarization experiments and by searching for a stochastic gravitational
wave background with laser interferometers in space. We tackle the following
two questions: (i) what does inflation predict for the tensor fluctuations?
(ii) is it really worth building experiments that can cover only a small range
of tensor amplitudes?


title: Resolving the nature of the Rosette HH1 jet facing strong UV dissipation

abstract:
  The Rosette HH1 jet is a collimated flow immersed in the strong UV radiation
field of the Rosette Nebula. We investigate the physical properties of the
Rosette HH1 jet using high-quality narrow-band images and high-dispersion
spectroscopy. The new images show that the axis of the jet is not precisely
aligned with the star near the base of the jet. The high resolution of the
spectra allows us to accurately determine the contributions from the \ion{H}{2}
region, jet, and star. The appoaching and receding sides of the expanding shell
of the Rosette Nebula are at heliocentric velocities of 13 and 40 km s$^{-1}$,
while the jet reaches a maximum velocity offset at a heliocentric velocity of
$-$30 km s$^{-1}$. The [\ion{S}{2}] doublet ratios indicate an electron density
of $\sim$1000 cm$^{-3}$ in the jet and $\le$100 cm$^{-3}$ in the \ion{H}{2}
region. With a careful subtraction of the nebular and jet components, we find
the stellar H$\alpha$ line is dominated by a broad absorption profile with
little or no emission component, indicating a lack of substantial circumstellar
material. The circumstellar material has most likely been photo-evaporated by
the strong UV radiation field in the Rosette Nebula. The evaporation time scale
is 10$^3$ -- 10$^4$ yr. The Rosette HH1 jet source provides evidence for an
accelerated evolution from a CTTS to a WTTS due to the strong UV radiation
field; therefore, both CTTSs and WTTSs can be spatially mixed in regions with
massive star formation.


title:
Self-similar solutions for the interaction of relativistic ejecta with
  an ambient medium

abstract:
  We find self-similar solutions to describe the interaction of spherically
symmetric ejecta expanding at relativistic speeds with an ambient medium having
a power law density distribution. Using this solution, the time evolution of
the Lorentz factor of the outer shock is derived as a function of the explosion
energy, the mass of the ejecta, and parameters for the ambient medium. These
solutions are an ultra-relativistic version of the solutions for the
circumstellar interaction of supernova ejecta obtained by Chevalier and
extensions of the relativistic blast wave solutions of Blandford & Mckee.


title: 350 Micron Dust Emission from High Redshift Quasars

abstract:
  We report detections of six high-redshift (1.8 < z < 6.4), optically
luminous, radio-quiet quasars at 350 micron, using the SHARC II bolometer
camera at the Caltech Submillimeter Observatory. Our observations double the
number of high-redshift quasars for which 350 micron photometry is available.
By combining the 350 micron measurements with observations at other
submillimeter/millimeter wavelengths, for each source we have determined the
temperature of the emitting dust (ranging from 40 to 60 K) and the far-infrared
luminosity (0.6 to 2.2 x 10(13) Lo). The combined mean spectral energy
distribution (SED) of all high-redshift quasars with two or more rest frame
far-infrared photometric measurements is best fit with a greybody with
temperature of 47 +- 3 K and a dust emissivity power-law spectral index of beta
= 1.6 +- 0.1. This warm dust component is a good tracer of the starburst
activity of the quasar host galaxy. The ratio of the far-infrared to radio
luminosities of infrared luminous, radio-quiet high-redshift quasars is
consistent with that found for local star-forming galaxies.


title: Solar System Binaries

abstract:
  The discovery of binaries in each of the major populations of minor bodies in
the solar system is propelling a rapid growth of heretofore unattainable
physical information. The availability of mass and density constraints for
minor bodies opens the door to studies of internal structure, comparisons with
meteorite samples, and correlations between bulk- physical and surface-spectral
properties. The number of known binaries is now more than 70 and is growing
rapidly. The relative sizes and separations of binaries in the different minor
body populations point to more than one mechanism for forming bound pairs.
Collisions appear to play a major role in the Main Belt. Rotational and/or
tidal fission may be important in the Near Earth population. For the Kuiper
Belt, capture in multi-body interactions may be the preferred formation
mechanism. High angular resolution observations from space and from the ground
are critical for detection of the relatively distant binaries in the Main Belt
and the Kuiper Belt. Radar has been the most productive method for detection of
Near Earth binaries. Lightcurve analysis is an independent technique that is
capable of exploring phase space inaccessible to direct observations. Finally,
spacecraft flybys have played a crucial paradigm-changing role with discoveries
that unlocked this now-burgeoning field.


title:
CHANDRA ACIS Spectroscopy of N157B -- A Young Composite Supernova
  Remnant in a Superbubble

abstract:
  We present Chandra ACIS observations of N157B, a young supernova remnant
located in the 30 Doradus star-formation region of the LMC. This remnant
contains the most energetic pulsar known (PSR J0537-6910), which is surrounded
by a bright nonthermal nebula that likely represents a toroidal pulsar wind
terminal shock observed edge-on. We confirm the non-thermal nature of the
comet-shaped X-ray emission feature and show that the spectral steepening of
this feature away from the pulsar is quantitatively consistent with synchrotron
cooling of shocked pulsar wind particles flowing downstream at a bulk velocity
close to the speed of light. Around the cometary nebula we unambiguously detect
a thermal component, which accounts for about 1/3 of the total 0.5 - 10 keV
flux from the remnant. This thermal component is distributed among various
clumps of metal-enriched plasma embedded in the low surface brightness
X-ray-emitting diffuse gas. The relative metal enrichment pattern suggests that
the mass of the supernova progenitor is >~ 20M_sun. A comparison of the X-ray
data with HST optical images suggests that the explosion site is close to a
dense cloud, against which a reflection shock is launched. The interaction
between this reflection shock and the nebula has likely produced both its
cometary shape and the surrounding thermal emission enhancement. SNR N157B is
apparently expanding into the hot low-density interior of a surrounding
superbubble formed by the young OB association LH99, as revealed by Spitzer
mid-infrared images. This scenario naturally explains the exceptionally large
sizes of both the thermal and nonthermal components as well as the lack of an
outer shell of the SNR. These results provide a rare glimpse into the SNR
structure and evolution in a region of recent star-formation.


title: On the origin of rR_1 ring structures in barred galaxies

abstract:
  We propose a new theory for the formation of rR_1 ring structures, i.e. for
ring structures with both an inner and an outer ring, the latter having the
form of ``8''. We propose that these rings are formed by material from the
stable and unstable invariant manifolds associated with the Lyapunov orbits
around the equilibrium points of a barred galaxy. We discuss the shape and
velocity structure of the rings thus formed and argue that they are in
agreement with the observed properties of rR_1 structures.


title:
A deep kinematic survey of planetary nebulae in the Andromeda Galaxy
  using the Planetary Nebula Spectrograph

abstract:
  We present a catalogue of positions, magnitudes and velocities for 3300
emission-line objects found by the Planetary Nebula Spectrograph in a survey of
the Andromeda Galaxy, M31. Of these objects, 2615 are found likely to be
planetary nebulae (PNe) associated with M31. Initial results from this survey
include: the likely non-existence of Andromeda VIII; a universal PN luminosity
function, with the exception of a small amount of obscuration, and a small
offset in normalization between bulge and disk components; very faint
kinematically-selected photometry implying no cut-off in the disk to beyond 4
scalelengths and no halo population in excess of the bulge out to 10 effective
bulge radii; disk kinematics that show significant dispersion and asymmetric
drift out to large radii, consistent with a warm flaring disk; and no sign of
any variation in kinematics with PN luminosity, suggesting that PNe arise from
a fairly uniform population of old stars.


title:
Analysing the atolls: X-ray spectral transitions of accreting neutron
  stars

abstract:
  We systematically analyze all the available X-ray spectra of disc accreting
neutron stars (atolls and millisecond pulsars) from the RXTE database. We show
that while these all have similar spectral evolution as a function of mass
accretion rate, there are also subtle differences. There are two different
types of hard/soft transition, those where the spectrum softens at all
energies, leading to a diagonal track on a colour-colour diagram, and those
where only the higher energy spectrum softens, giving a vertical track. The
luminosity at which the transition occurs is correlated with this spectral
behaviour, with the vertical transition at L/L_Edd ~0.02 while the diagonal one
is at ~0.1. Superimposed on this is the well known hysteresis effect, but we
show that classic, large scale hysteresis occurs only in the outbursting
sources, indicating that its origin is in the dramatic rate of change of mass
accretion rate during the disc instability. We show that the long term mass
accretion rate correlates with the transition behaviour, and speculate that
this is due to the magnetic field being able to emerge from the neutron star
surface for low average mass accretion rates. While this is not strong enough
to collimate the flow except in the millisecond pulsars, its presence may
affect the inner accretion flow by changing the properties of the jet.


title: Can single O stars produce non-thermal radio emission?

abstract:
  We present a model for the non-thermal radio emission from presumably single
O stars, in terms of synchrotron emission from relativistic electrons
accelerated in wind-embedded shocks. These shocks are associated with an
unstable, chaotic wind. The main improvement with respect to earlier models is
the inclusion of the radial dependence of the shock velocity jump and
compression ratio, based on 1D hydrodynamical simulations. The decrease of the
velocity jump and the compression ratio as a function of radius produces a
rapidly decreasing synchrotron emissivity. This effectively prohibits the
models from reproducing the spectral shape of the observed non-thermal radio
emission. We investigate a number of "escape routes" by which the
hydrodynamical predictions might be reconciled with the radio observations.
Although these escape routes reproduce the observed spectral shape, none of
these escape routes are physically plausible. In particular, re-acceleration by
feeding an electron distribution through a number of shocks, is in
contradiction with current hydrodynamical simulations. These hydrodynamical
simulations have their limitations, most notably the use of 1D. At present, it
is not feasible to perform 2D simulations of the wind out to the distances
required for synchrotron-emission models. Based on the current hydrodynamic
models, we suspect that the observed non-thermal radio emission from O stars
cannot be explained by wind-embedded shocks associated with the instability of
the line-driving mechanism. The most likely alternative mechanism is
synchrotron emission from colliding winds. That would imply that all O stars
with non-thermal radio emission should be members of binary or multiple
systems.


title: Evidence for rotation-induced mixing in evolved intermediate mass stars

abstract:
  Many observational results seem to indicate more efficient mixing processes
in intermediate mass stars (5-20 M$_{\odot}$) than the expected by the standard
models. These processes are usually thought to be caused by stellar rotation.
Our recent analysis of 19 evolved intermediate mass stars has found them to
display different efficiencies of internal mixing. The comparison of these
results, and others from the literature, with rotating and non-rotating stellar
evolutionary models led us to find, for the first time, an important
correlation between stellar mass and the [N/C] ratio; the kind of correlation
expected to be produced by a rotation-induced mixing.


title: Studying the Nature of Dark Energy with Galaxy Clusters

abstract:
  We report on the status of our effort to constrain the nature of dark energy
through the evolution of the cluster mass function. Chandra temperature
profiles for 31 clusters from a local cluster sample are shown. The X-ray
appearance of the proto supermassive binary black hole at the center of the
cluster Abell 400 is described. Preliminary weak lensing results obtained with
Megacam@MMT for a redshift z=0.5 cluster from a distant cluster sample are
given.


title: The INTEGRAL Galactic Bulge monitoring program

abstract:
  The Galactic Bulge region is a rich host of variable high-energy point
sources. These sources include bright and relatively faint X-ray transients,
X-ray bursters, persistent neutron star and black-hole candidate binaries,
X-ray pulsars, etc.. We have a program to monitor the Galactic Bulge region
regularly and frequently with the gamma-ray observatory INTEGRAL. As a service
to the scientific community the high-energy light curves of all the active
sources as well as images of the region are made available through the WWW. We
show the first results of this exciting new program.


title: Measurement of the specific activity of Ar-39 in natural argon

abstract:
  We report on the measurement of the specific activity of Ar-39 in natural
argon. The measurement was performed with a 2.3-liter two-phase (liquid and
gas) argon drift chamber. The detector was developed by the WARP Collaboration
as a prototype detector for WIMP Dark Matter searches with argon as a target.
The detector was operated for more than two years at Laboratori Nazionali del
Gran Sasso, Italy, at a depth of 3,400 m w.e. The specific activity measured
for Ar-39 is 1.01 +/- 0.02(stat) +/- 0.08(syst) Bq per kg of natural Ar.


title: Dust flow in gas disks in the presence of embedded planets

abstract:
  We study the dynamics of gas and dust in a protoplanetary disk in the
presence of embedded planets. We investigate the conditions for dust-gap
formation in terms of particle size and planetary mass. We also monitor the
amount of dust that is accreted by the planet relative to the amount of gas,
which is an important parameter in determining the enrichment of solids in
giant planets compared to the solid content of the central star. We use a new
two-fluid hydrodynamics code to solve the flow equations for both gas and dust.
For the gas, we use a Godunov-type scheme with an approximate Riemann solver
(the Roe solver). The dust is treated as a pressureless fluid by essentially
the same numerical method as is used for the gas. We find that it only takes a
planet of 0.05 Jupiter masses to open up a gap in a disk with a significant
population of mm-sized particles. Dust particles larger than 150 micron
participate in gap formation. We also find that the formation of the gap
severely slows down dust accretion compared to that in the gas. Therefore, it
is not possible to enrich a newly formed giant planet in solids, if these
solids are contained in particles with sizes from 150 micron to approximately
10 cm.


title: Radio Recombination Lines in Galactic HII Regions

abstract:
  We report radio recombination line (RRL) and continuum observations of a
sample of 106 Galactic HII regions made with the NRAO 140 Foot radio telescope
in Green Bank, WV. We believe this to be the most sensitive RRL survey ever
made for a sample this large. Most of our source integration times range
between 6 and 90 hours which yield typical r.m.s. noise levels of 1.0--3.5
milliKelvins. Our data result from two different experiments performed,
calibrated, and analyzed in similar ways. A CII survey was made at 3.5 cm
wavelength to obtain accurate measurements of carbon radio recombination lines.
When combined with atomic (CI) and molecular (CO) data, these measurements will
constrain the composition, structure, kinematics, and physical properties of
the photodissociation regions that lie on the edges of HII regions. A second
survey was made at 3.5 cm wavelength to determine the abundance of 3He in the
interstellar medium of the Milky Way. Together with measurements of the 3He+
hyperfine line we get high precision RRL parameters for H, 4He, and C. Here we
discuss significant improvements in these data, with both longer integrations
and newly observed sources.


title:
Balmer and Paschen jump temperature determinations in low-metallicity
  emission-line galaxies

abstract:
  We have used the Balmer and Paschen jumps to determine the temperatures of
the H+ zones of a total sample of 47 H II regions. The Balmer jump was used on
MMT spectrophotometric data of 22 low-metallicity H II regions in 18 blue
compact dwarf (BCD) galaxies and of one H II region in the spiral galaxy M101.
The Paschen jump was used on spectra of 24 H II emission-line galaxies selected
from the Data Release 3 of the Sloan Digital Sky Survey (SDSS). To derive the
temperatures, we have used a Monte Carlo technique varying the electron
temperature in the H+ zone, the extinction of the ionized gas and that of the
stellar population, the relative contribution of the ionized gas to the total
emission and the star formation history to fit the spectral energy distribution
of the galaxies. For the MMT spectra, the fit was done in the wavelength range
of 3200 - 5200A which includes the Balmer discontinuity, and for the SDSS
spectra, in the wavelength range of 3900 - 9200A which includes the Paschen
discontinuity. We find for our sample of H II regions that the temperatures of
the O+2 zones determined from the nebular to auroral line intensity ratio of
doubly ionized oxygen [O III] (4959+5007)/4363 do not differ, in a statistical
sense, from the temperatures of the H+ zones determined from fitting the Balmer
and Paschen jumps and the SEDs. We cannot rule out small temperature
differences of the order of 3-5%.


title:
Testing grain surface chemistry : a survey of deuterated formaldehyde
  and methanol in low-mass Class 0 protostars

abstract:
  Context : Despite the low cosmic abundance of deuterium (D/H ~ 1e-5), large
degrees of deuterium fractionation in molecules are observed in star forming
regions with enhancements that can reach 13 orders of magnitude, which current
models have difficulties to account for.
  Aims : Multi-isotopologue observations are a very powerful constraint for
chemical models. The aim of our observations is to understand the processes
forming the observed large abundances of methanol and formaldehyde in low-mass
protostellar envelopes (gas-phase processes ? chemistry on the grain surfaces
?) and better constrain the chemical models. Methods : Using the IRAM 30m
single-dish telescope, we observed deuterated formaldehyde (HDCO and D2CO) and
methanol (CH2DOH, CH3OD, and CHD2OH) towards a sample of seven low-mass class 0
protostars. Using population diagrams, we then derive the fractionation ratios
of these species (abundance ratio between the deuterated molecule and its main
isotopologue) and compare them to the predictions of grain chemistry models.
Results : These protostars show a similar level of deuteration as in
IRAS16293-2422, where doubly-deuterated methanol -- and even triply-deuterated
methanol -- were first detected. Our observations point to the formation of
methanol on the grain surfaces, while formaldehyde formation cannot be fully
pined down. While none of the scenarii can be excluded (gas-phase or grain
chemistry formation), they both seem to require abstraction reactions to
reproduce the observed fractionations.


title:
A Testable the Stochastic Acceleration Model for Flares in Sagittarius
  A*

abstract:
  The near-IR and X-ray flares in Sagittarius A* are believed to be produced by
relativistic electrons via synchrotron and synchrotron self-Comptonization,
respectively. These electrons are likely energized by turbulent plasma waves
through second-order Fermi acceleration that, in combination with the radiative
cooling processes, produces a relativistic Maxwellian distribution in the
steady state. This model has four principal parameters, namely the magnetic
field B, the electron density n and temperature \gamma_c mec2, and the size of
the flare region R. In the context of stochastic acceleration, the quantities
Rn^1/2B and \gamma_cRn should remain nearly constant in time. Therefore,
simultaneous spectroscopic observations in the NIR and X-ray bands can readily
test the model, which, if proven to be valid, may be used to determine the
evolution of the plasma properties during an eruptive event with spectroscopic
observations in either band or simultaneous flux density measurements in both
bands. The formulae can be applied to other isolated or confined systems, where
electrons are accelerated to relativistic energies by plasma wave turbulence
and produce most of the emission via synchrotron processes.


title: Stochastic Acceleration in the Galactic Center HESS Source

abstract:
  Stochastic acceleration of electrons interacting resonantly with a turbulent
magnetic field in a small accretion torus appears to be the likely mechanism
responsible for much of Sagittarius A*'s millimeter and shorter wavelength
spectrum. The longer wavelength radiation is produced at larger radii by
electrons either diffusing from smaller scales or accelerated in situ. An
important prediction of this model is the ejection of a significant flux of
relativistic protons from a magnetic-field-dominated acceleration site into the
wind-shocked medium surrounding the black hole. Recently, several air Cerenkov
telescopes, notably HESS, have detected TeV emission from the Galactic center,
with characteristics hinting at a p-p-induced pion decay process for the
\gamma-ray emission. Given (1) the size of this acceleration region measured in
the radio band and (2) the wind-injected ISM mapped with Chandra using the
diffuse X-rays, it is feasible to test the idea that protons accelerated within
\~20 Schwarzschild radii of the black hole produce the TeV emission farther
out. We show a fraction of TeV protons scattering about once within ~3 pc of
Sagittarius A* and the proton power (~10^37 erg s^-1) produced in concert with
the 7 mm radio emission matches the TeV luminosity well. This model explains
why the TeV source does not vary on a timescale of a year or less. The particle
cascade generated by the p-p scatterings also produces bremsstrahlung, inverse
Compton, and synchrotron emission at longer wavelengths from secondary
particles. We compare these with current measurements and demonstrate that
GLAST will detect this source during its one-year all-sky survey.


title: Star Formation in Space and Time: The Orion Nebula Cluster

abstract:
  We examine the pattern of star birth in the Orion Nebula Cluster (ONC), with
the goal of discerning the cluster's formation mechanism. Outside of the
Trapezium, the distribution of stellar masses is remarkably uniform, and is not
accurately described by the field-star initial mass function. The deconvolved,
three-dimensional density of cluster members peaks at the Trapezium stars,
which are truly anomalous in mass. Using theoretical pre-main-sequence tracks,
we confirm the earlier finding that star formation has accelerated over the
past 10 Myr. We further show that the rate of acceleration has been the same
for all masses. Thus, there is no correlation between stellar age and mass,
contrary to previous claims. Finally, the acceleration has been spatially
uniform throughout the cluster. Our reconstruction of the parent molecular
cloud spawning the cluster shows that it had a mass of 6700 solar masses prior
to its destruction by the Trapezium. If the cloud was supported against
self-gravity by mildly dissipative turbulence, then it contracted in a
quasi-static, but accelerating manner. We demonstrate this contraction
theoretically through a simple energy argument. The mean turbulent speed
increased to its recent value, which is reflected in the present-day stellar
velocity dispersion. The current ONC will be gravitationally unbound once cloud
destruction is complete, and is destined to become a dispersing OB association.
We hypothesize that similarly crowded groups seen at the centers of distant OB
associations are also unbound, and do not give rise to the Galactic population
of open clusters. Finally, accelerating star formation implies that most clumps
within giant molecular complexes should have relatively low formation activity.
Sensitive infrared surveys could confirm this hypothesis.


title: Relativistic Iron lines at high redshifts

abstract:
  The shape and the intensity of the 6.4 keV iron line bring unique information
on the geometrical and physical properties of the supermassive black hole and
the surrounding accreting gas at the very center of Active Galactic Nuclei.
While there are convincing evidences of a relativistically broadened iron line
in a few nearby bright objects, their properties at larger distances are
basically unknown. We have searched for the presence of iron line by fully
exploiting Chandra observations in the deep fields. The line is clearly
detected in the average spectra of about 250 sources stacked in several
redshift bins over the range z=0.5-4.0. We discuss their average properties
with particular enphasys on the presence and intensity of a broad component.


title: Scalar potential model of the CMB radiation temperature

abstract:
  A derivation of a theoretical, time average, cosmic microwave background
(CMB), Planckian temperature V of the universe remains a challenge. A scalar
potential model (SPM) that resulted from considerations of galaxy cells is
applied to deriving a value for V. The heat equation is solved for a cell with
the boundary conditions of SPM Source and Sink characteristics, with simplified
cell characteristics, and with zero initial temperature. The universe is a
collection of cells. The CMB radiation is black body radiation with the cells
acting as radiators and absorbers. Conventional thermodynamics is applied to
calculate V = 2.718 K. The temperature and matter content of cells are finely
controlled by a feedback mechanism. Because time is required for matter to flow
from Sources to Sinks, the radiation temperature of cells cycles about V after
an initial growth phase. If the universe is like an ideal gas in free expansion
and is not in thermal equilibrium, then the pressure and volume follow the
measured CMB temperature vm = 2.725 K. Therefore, increasing vm >V equates to
an expansion pressure on matter and expanding volume.


title:
An upper limit on anomalous dust emission at 31 GHz in the diffuse cloud
  [LPH96]201.663+1.643

abstract:
  [LPH96]201.663+1.643, a diffuse H{\sc ii} region, has been reported to be a
candidate for emission from rapidly spinning dust grains. Here we present
Cosmic Background Imager (CBI) observations at 26-36 GHz that show no evidence
for significant anomalous emission. The spectral index within the CBI band, and
between CBI and Effelsberg data at 1.4/2.7 GHz, is consistent with optically
thin free-free emission. The best-fitting temperature spectral index from 2.7
to 31 GHz, $\beta=-2.06 \pm 0.03$, is close to the theoretical value,
$\beta=-2.12$ for $T_{e}=9100$ K. We place an upper limit of 24% ~ (2\sigma)
for excess emission at 31 GHz as seen in a $6\arcmin$ FWHM beam. Current
spinning dust models are not a good fit to the spectrum of LPH96. No polarized
emission is detected in the CBI data with an upper limit of 2% on the
polarization fraction.


title:
Constraints from the Old Quasar APM 08279+5255 on Two Classes of
  $\Lambda($t$)$-Cosmologies

abstract:
  The viability of two different classes of $\Lambda(t)$CDM cosmologies is
tested by using the APM 08279+5255, an old quasar at redshift $z = 3.91$. In
the first class of models, the cosmological term scales as $\Lambda(t)\sim
R^{-n}$. The particular case $n=0$ describes the standard $\Lambda$CDM model
whereas $n=2$ stands for the Chen and Wu model. For an estimated age of 2 Gyr,
it is found that the power index has a lower limit $n> 0.21$, whereas for 3 Gyr
the limit is $n > 0.6$. Since $n$ can not be so large as $\sim 0.81$, the
$\Lambda$CDM and Chen and Wu models are also ruled out by this analysis. The
second class of models is the one recently proposed by Wang and Meng which
describes several $\Lambda(t)$CDM cosmologies discussed in the literature. By
assuming that the true age is 2 Gyr it is found that the $\epsilon$ parameter
satisfies the lower bound $\epsilon > 0.11$, while for 3 Gyr, a lower limit of
$\epsilon > 0.52$ is obtained. Such limits are slightly modified when the
baryonic component is included.


title: Extended HI Rotation Curve and Mass Distribution of M31

abstract:
  New HI observations of Messier 31 (M31) obtained with the Effelsberg and
Green Bank 100-m telescopes make it possible to measure the rotation curve of
that galaxy out to ~35 kpc. Between 20 and 35 kpc, the rotation curve is nearly
flat at a velocity of ~226 km/s. A model of the mass distribution shows that at
the last observed velocity point, the minimum dark-to-luminous mass ratio is
\~0.5 for a total mass of 3.4 10^11 Msol at R < 35 kpc. This can be compared to
the estimated MW mass of 4.9 10^11 Msol for R < 50 kpc.


title:
A new cosmic microwave background constraint to primordial gravitational
  waves

abstract:
  Primordial gravitational waves (GWs) with frequencies > 10^{-15} Hz
contribute to the radiation density of the Universe at the time of decoupling
of the cosmic microwave background (CMB). The effects of this GW background on
the CMB and matter power spectra are identical to those due to massless
neutrinos, unless the initial density-perturbation amplitude for the
gravitational-wave gas is non-adiabatic, as may occur if such GWs are produced
during inflation or some post-inflation phase transition. In either case,
current observations provide a constraint to the GW amplitude that competes
with that from big-bang nucleosynthesis (BBN), although it extends to much
lower frequencies (~10^{-15} Hz rather than the ~10^{-10} Hz lower limit from
BBN): at 95% confidence-level, Omega_gw h^2 < 6.9 x 10^{-6} for homogeneous
(i.e., non-adiabatic) initial conditions. Future CMB experiments, like Planck
and CMBPol, should allow sensitivities to Omega_gw h^2 < 1.4 x 10^{-6} and
Omega_gw h^2 < 5 x 10^{-7}, respectively.


title:
Merger of binary neutron stars to a black hole: Disk mass, short
  gamma-ray bursts, and quasinormal mode ringing

abstract:
  Three-dimensional simulations for the merger of binary neutron stars (BNSs)
are performed in the framework of full general relativity. We pay particular
attention to the black hole (BH) formation case and to the resulting mass of
the surrounding disk for exploring possibility for formation of the central
engine of short-duration gamma-ray bursts. Hybrid equations of state (EOSs) are
adopted mimicking realistic, stiff nuclear EOSs, for which the maximum allowed
gravitational mass of cold and spherical neutron stars (NSs), M_sph, is larger
than 2M_sun. For the simulations, we focus on BNSs of the ADM mass M>2.6M_sun.
For M>M_thr, the merger results in prompt formation of a BH irrespective of the
mass ratio Q_M with 0.65<Q_M<1. The value of M_thr is approximately written as
1.3-1.35M_sph for the chosen EOSs. For the BH formation case, we evolve the
spacetime using a BH excision technique and determine the mass of a
quasistationary disk surrounding the BH. The disk mass steeply increases with
decreasing the value of Q_M for given ADM mass and EOS. For M<M_thr, the
outcome is a hypermassive neutron star (HMNS) of a large ellipticity. If the
HMNS collapses to a BH after the longterm angular momentum transport, the disk
mass may be >0.01M_sun. Gravitational waves (GWs) are computed in terms of a
gauge-invariant wave extraction technique. In the formation of the HMNS,
quasiperiodic GWs of frequency (3-3.5kHz) are emitted. The effective amplitude
of GWs can be >5x10^{-21} at a distance of 50 Mpc. For the BH formation case,
the BH excision technique enables a longterm computation and extraction of
ring-down GWs associated with a BH quasinormal mode. It is found that the
frequency and amplitude are 6.5-7kHz and 10^{-22} at a distance of 50Mpc for
M=2.7-2.9M_sun.


title: Cosmic Voids and Galaxy Bias in the Halo Occupation Framework

abstract:
  (Abridged) We investigate the power of void statistics to constrain galaxy
bias and the amplitude of dark matter fluctuations. We use the halo occupation
distribution (HOD) framework to describe the relation between galaxies and dark
matter. After choosing HOD parameters that reproduce the mean space density
n_gal and projected correlation function w_p measured for galaxy samples with
M_r<-19 and M_r<-21 from the Sloan Digital Sky Survey (SDSS), we predict the
void probability function (VPF) and underdensity probability function (UPF) of
these samples by populating the halos of a large, high-resolution N-body
simulation. If we make the conventional assumption that the HOD is independent
of large scale environment at fixed halo mass, then models constrained to match
n_gal and w_p predict nearly identical void statistics, independent of the
scatter between halo mass and central galaxy luminosity or uncertainties in HOD
parameters. Models with sigma_8=0.7 and sigma_8=0.9 also predict very similar
void statistics. However, the VPF and UPF are sensitive to environmental
variations of the HOD in a regime where these variations have little impact on
w_p. For example, doubling the minimum host halo mass in regions with large
scale (5 Mpc/h) density contrast delta<-0.65 has a readily detectable impact on
void probabilities of M_r<-19 galaxies, and a similar change for delta<-0.2
alters the void probabilities of M_r<-21 galaxies at a detectable level. The
VPF and UPF provide complementary information about the onset and magnitude of
density- dependence in the HOD. By detecting or ruling out HOD changes in low
density regions, void statistics can reduce systematic uncertainties in the
cosmological constraints derived from HOD modeling, and, more importantly,
reveal connections between halo formation history and galaxy properties.


title:
Time-dependent force-free pulsar magnetospheres: axisymmetric and
  oblique rotators

abstract:
  Magnetospheres of many astrophysical objects can be accurately described by
the low-inertia (or "force-free") limit of MHD. We present a new numerical
method for solution of equations of force-free relativistic MHD based on the
finite-difference time-domain (FDTD) approach with a prescription for handling
spontaneous formation of current sheets. We use this method to study the
time-dependent evolution of pulsar magnetospheres in both aligned and oblique
magnetic geometries. For the aligned rotator we confirm the general properties
of the time-independent solution of Contopoulos et al. (1999). For the oblique
rotator we present the 3D structure of the magnetosphere and compute, for the
first time, the spindown power of pulsars as a function of inclination of the
magnetic axis. We find the pulsar spindown luminosity to be L = (mu^2
Omega^4/c^3) (1+ sin^2(alpha)) for a star with the dipole moment "mu", rotation
frequency "Omega", and magnetic inclination angle "alpha". We also discuss the
effects of current sheet resistivity and reconnection on the structure and
evolution of the magnetosphere.


title:
Prospects for detecting Dark Matter with neutrino telescopes in
  Intermediate Mass Black Holes scenarios

abstract:
  Current strategies of indirect Dark Matter detection with neutrino telescopes
are based on the search for high-energy neutrinos from the Solar core or from
the center of the Earth. Here, we propose a new strategy based on the detection
of neutrinos from Dark Matter annihilations in 'mini-spikes' around
Intermediate Mass Black Holes. Neutrino fluxes, in this case, depend on the
annihilation cross-section of Dark Matter particles, whereas solar and
terrestrial fluxes are sensitive to the scattering cross-section off nucleons,
a circumstance that makes the proposed search complementary to the existing
ones. We discuss the prospects for detection with upcoming under-water and
under-ice experiments such as ANTARES and IceCube, and show that several, up to
many, sources could be detected with both experiments. A kilometer scale
telescope in the Mediterranean appears to be ideally suited for the proposed
search.


title: Physics of Cosmic Reionization

abstract:
  The study of cosmic reionization has acquired increasing significance over
the last few years because of various reasons. On the observational front, we
now have good quality data of different types at high redshifts (quasar
absorption spectra, radiation backgrounds at different frequencies, cosmic
microwave background polarization, Ly-alpha emitters and so on). Theoretically,
the importance of the reionization lies in its close coupling with the
formation of first cosmic structures, and there have been numerous progresses
in modelling the process. In this article, we review the current status of our
understanding of the physical processes governing the cosmic reionization based
on available observational data.


title: The Bound Mass of Substructures in Dark Matter Halos

abstract:
  We present a new definition of subhalos in dissipationless dark matter N-body
simulations, based on the coherent identification of their dynamically bound
constituents. Whereas previous methods of determining the energetically bound
components of a subhalo ignored the contribution of all the remaining particles
in the halo (those not geometrically or dynamically associated with the
subhalo), our method allows for all the forces, both internal and external,
exerted on the subhalo. We demonstrate, using the output of a simulation at
different timesteps, that our new method is more accurate at identifying the
bound mass of a subhalo. We then compare our new method to previously adopted
means of identifying subhalos by applying each to a sample of 1838 virialized
halos extracted from a high resolution cosmological simulation. We find that
the subhalo distributions are similar in each case, and that the increase in
the binding energy of a subhalo from including all the particles located within
it is almost entirely balanced by the losses due to the external forces; the
net increase in the mass fraction of subhalos is roughly 10%, and the extra
substructures tending to reside in the inner parts of the system. Finally, we
compare the subhalo populations of halos to the sub-subhalo populations of
subhalos, finding the two distributions to be similar. This is a new and
interesting result, suggesting a self-similarity in the hierarchy substructures
within cluster mass halos.


title: Evolution of the Reverse Shock Emission from SNR 1987A

abstract:
  We present new (2004 July) G750L and G140L Space Telescope Imaging
Spectrograph (STIS) data of the H-alpha and Ly-alpha emission from supernova
remnant (SNR) 1987A. With the aid of earlier data, from Oct 1997 to Oct 2002,
we track the local evolution of Ly-alpha emission and both the local and global
evolution of H-alpha emission. In addition to emission which we can clearly
attribute to the surface of the reverse shock, we also measure comparable
emission, in both H-alpha and Ly-alpha, which appears to emerge from supernova
debris interior to the surface. New observations taken through slits positioned
slightly eastward and westward of a central slit show a departure from
cylindrical symmetry in the H-alpha surface emission. Using a combination of
old and new observations, we construct a light curve of the total H-alpha flux,
F, from the reverse shock, which has increased by a factor ~ 4 over about 8
years. However, due to large systematic uncertainties, we are unable to discern
between the two limiting behaviours of the flux - F ~ t (self-similar
expansion) and F ~ t^5 (halting of the reverse shock). Such a determination is
relevant to the question of whether the reverse shock emission will vanish in
less than about 7 years (Smith et al. 2005). Future deep, low- or
moderate-resolution spectra are essential for accomplishing this task.


title:
Monte Carlo Study of Detector Concepts for the MAX Laue Lens Gamma-Ray
  Telescope

abstract:
  MAX is a proposed Laue lens gamma-ray telescope taking advantage of Bragg
diffraction in crystals to concentrate incident photons onto a distant
detector. The Laue lens and the detector are carried by two separate satellites
flying in formation. Significant effort is being devoted to studying different
types of crystals that may be suitable for focusing gamma rays in two 100 keV
wide energy bands centered on two lines which constitute the prime
astrophysical interest of the MAX mission: the 511 keV positron annihilation
line, and the broadened 847 keV line from the decay of 56Co copiously produced
in Type Ia supernovae. However, to optimize the performance of MAX, it is also
necessary to optimize the detector used to collect the source photons
concentrated by the lens. We address this need by applying proven Monte Carlo
and event reconstruction packages to predict the performance of MAX for three
different Ge detector concepts: a standard coaxial detector, a stack of
segmented detectors, and a Compton camera consisting of a stack of strip
detectors. Each of these exhibits distinct advantages and disadvantages
regarding fundamental instrumental characteristics such as detection efficiency
or background rejection, which ultimately determine achievable sensitivities.
We conclude that the Compton camera is the most promising detector for MAX in
particular, and for Laue lens gamma-ray telecopes in general.


title: Dust settling in local simulations of turbulent protoplanetary disks

abstract:
  In this paper, we study the effect of MHD turbulence on the dynamics of dust
particles in protoplanetary disks. We vary the size of the particles and relate
the dust evolution to the turbulent velocity fluctuations. We performed
numerical simulations using two Eulerian MHD codes, both based on finite
difference techniques: ZEUS--3D and NIRVANA. These were local shearing box
simulations incorporating vertical stratification. Both ideal and non ideal MHD
simulations with midplane dead zones were carried out. The codes were extended
to incorporate different models for the dust as an additional fluid component.
Good agreement between results obtained using the different approaches was
obtained. The simulations show that a thin layer of very small dust particles
is diffusively spread over the full vertical extent of the disk. We show that a
simple description obtained using the diffusion equation with a diffusion
coefficient simply expressed in terms of the velocity correlations accurately
matches the results. Dust settling starts to become apparent for particle sizes
of the order of 1 to 10 centimeters for which the gas begins to decouple in a
standard solar nebula model at 5.2 AU. However, for particles which are 10
centimeters in size, complete settling toward a very thin midplane layer is
prevented by turbulent motions within the disk, even in the presence of a
midplane dead zone of significant size. These results indicate that, when
present, MHD turbulence affects dust dynamics in protoplanetary disks. We find
that the evolution and settling of the dust can be accurately modelled using an
advection diffusion equation that incorporates vertical settling. The value of
the diffusion coefficient can be calculated from the turbulent velocity field
when that is known for a time of several local orbits.


title: Sky surveys and deep fields of ground-based and space telescopes

abstract:
  Selected results obtained in major observational sky surveys (DSS, 2MASS,
2dF, SDSS) and deep field observations (HDF, GOODS, HUDF, etc.) are reviewed.
Modern surveys provide information on the characteristics and space
distribution of millions of galaxies. Deep fields allow one to study galaxies
at the stage of formation and to trace their evolution over billions of years.
The wealth of observational data is altering the face of modern astronomy: the
formulation of problems and their solutions are changing and all the previous
knowledge, from planetary studies in the solar system to the most distant
galaxies and quasars, is being revised.


title:
The effect of dust obscuration in RR Tel on optical and IR long-term
  photometry and Fe II emission lines

abstract:
  Infrared and optical photometric and spectroscopic observations of the
symbiotic nova RR Tel are used to study the effects and properties of dust in
symbiotic binaries containing a cool Mira component, as well as showing
"obscuration events" of increased absorption, which are typical for such Miras.
A set of photometric observations of the symbiotic nova RR Tel in different
wavelength bands - visual from 1949 to 2002 and near-infrared (JHKL) from 1975
to 2002 - are presented. The variability due to the normal Mira pulsation was
removed from the JHKL data, which were then compared with the AAVSO visual
light curve. The changes of the Fe II emission line fluxes during the 1996-2000
obscuration episode were studied in the optical spectra taken with the
Anglo-Australian telescope.
  We discuss the three periods during which the Mira component was heavily
obscured by dust as observed in the different wavelength bands. A change in the
correlations of J with other infrared magnitudes was observed with the colour
becoming redder after JD2446000. Generally, J-K was comparable, while K-L was
larger than typical values for single Miras. A distance estimate of 2.5 kpc,
based on the IR data, is given. A larger flux decrease for the permitted than
for the forbidden Fe II lines, during the obscuration episode studied, has been
found. There is no evidence for other correlations with line properties, in
particular with wavelength, which suggests obscuration due to separate
optically thick clouds in the outer layers.


title:
Star Cluster Evolution: From young massive star clusters to old
  globulars

abstract:
  Young, massive star clusters are the most notable and significant end
products of violent star-forming episodes triggered by galaxy collisions,
mergers, and close encounters. The question remains, however, whether or not at
least a fraction of the compact YMCs seen in abundance in extragalactic
starbursts, are potentially the progenitors of globular cluster (GC)-type
objects. However, because of the lack of a statistically significant sample of
similar nearby objects we need to resort to either statistical arguments or to
the painstaking approach of case by case studies of individual objects in more
distant galaxies. Despite the difficulties inherent to addressing this issue
conclusively, an ever increasing body of observational evidence lends support
to the scenario that GCs, which were once thought to be the oldest building
blocks of galaxies, are still forming today.


title: The dust envelope of the pre-planetary nebula IRAS19475+3119

abstract:
  We present the spectral energy distribution (SED) of the pre-planetary
nebula, IRAS 19475+3119 (I19475), from the optical to the far-infrared. We
identify emission features due to crystalline silicates in the ISO SWS spectra
of the star. We have fitted the SED of I19475 using a 1-D radiative transfer
code, and find that a shell with inner and outer radii of 8.8X10^{16} and
4.4X10^{17}cm, and dust temperatures ranging from about 94K to 46K provide the
best fit. The mass of this shell is greater than/equal to
1[34cm^{2}g^{-1}/kappa(100micron)][delta/200]M_Sun, where kappa(100micron) is
the 100micron dust mass absorption coefficient (per unit dust mass), and delta
is the gas-to-dust ratio. In agreement with results from optical imaging and
millimeter-wave observations of CO emission of I19475, our model fits support
an r^{-3} density law for its dust shell, with important implications for the
interaction process between the fast collimated post-AGB winds and the dense
AGB envelopes which results in the observed shapes of PPNs and PNs. We find
that the observed JCMT flux at sub-millimeter wavelengths (850micron) is a
factor ~ 2 larger than our model flux, suggesting the presence of large dust
grains in the dust shell of I19475 which are not accounted for by our adopted
standard MRN grain size distribution.


title:
Tracking quintessence by cosmic shear - Constraints from VIRMOS-Descart
  and CFHTLS and future prospects

abstract:
  Dark energy can be investigated in two complementary ways, by considering
either general parameterizations or physically well-defined models. Following
the second route, we explore the constraints on quintessence models where the
acceleration is driven by a slow-rolling scalar field. The analysis focuses on
cosmic shear, combined with supernovae Ia and CMB data. Using a Boltzmann code
including quintessence models and the computation of weak lensing observables,
we determine several two-point shear statistics. The non-linear regime is
described by two different mappings. The likelihood analysis is based on a grid
method. The data include the "gold set" of supernovae Ia, the WMAP-1 year data
and the VIRMOS-Descart and CFHTLS-deep and -wide data for weak lensing. This is
the first analysis of high-energy motivated dark energy models that uses weak
lensing data. We explore larger angular scales, using a synthetic realization
of the complete CFHTLS-wide survey as well as next space-based missions
surveys. Two classes of cosmological parameters are discussed: i) those
accounting for quintessence affect mainly geometrical factors; ii) cosmological
parameters specifying the primordial universe strongly depend on the
description of the non-linear regime. This dependence is addressed using wide
surveys, by discarding the smaller angular scales to reduce the dependence on
the non-linear regime. Special care is payed to the comparison of these
physical models with parameterizations of the equation of state. For a flat
universe and a quintessence inverse power law potential with slope alpha, we
obtain alpha < 1 and Omega_Q=0.75^{+0.03}_{-0.04} at 95% confidence level,
whereas alpha=2^{+18}_{-2}, Omega_Q=0.74^{+0.03}_{-0.05} when including
supergravity corrections.


title: On the limit cycle instability in magnetized accretion discs

abstract:
  Observational evidence accumulated over the past decade indicates that
accretion discs in X-ray binaries are viscously stable unless they accrete very
close to the Eddington limit. This is at odds with the most basic standard
accretion disc theory, but could be explained by either having the discs to be
much cooler whereby they are not radiation pressure dominated, or by a more
sophisticated viscosity law. Here we argue that the latter is taking place in
practice, on the basis of a stability analysis that assumes that the
magneto-rotational-instability (MRI) responsible for generating the turbulent
stresses inside the discs is also the source for a magnetically dominated
corona. We show that observations of stable discs in the high/soft states of
black hole binaries, on the one hand, and of the strongly variable microquasar
GRS 1915+105 on the other, can all be explained if the magnetic turbulent
stresses inside the disc scale proportionally to the geometric mean of gas and
total pressure with a constant of proportionality (viscosity parameter) having
a value of a few times 10^{-2}. Implications for bright AGN are also briefly
discussed


title:
Spitzer and JCMT Observations of the Active Galactic Nucleus in the
  Sombrero Galaxy (NGC 4594)

abstract:
  We present Spitzer 3.6-160 micron images, Spitzer mid-infrared spectra, and
JCMT SCUBA 850 micron images of the Sombrero Galaxy (NGC 4594), an Sa galaxy
with a 10^9 M_solar low luminosity active galactic nucleus (AGN). The brightest
infrared sources in the galaxy are the nucleus and the dust ring. The spectral
energy distribution of the AGN demonstrates that, while the environment around
the AGN is a prominent source of mid-infrared emission, it is a relatively weak
source of far-infrared emission, as had been inferred for AGN in previous
research. The weak nuclear 160 micron emission and the negligible polycyclic
aromatic hydrocarbon emission from the nucleus also implies that the nucleus is
a site of only weak star formation activity and the nucleus contains relatively
little cool interstellar gas needed to fuel such activity. We propose that this
galaxy may be representative of a subset of low ionization nuclear emission
region galaxies that are in a quiescent AGN phase because of the lack of gas
needed to fuel circumnuclear star formation and Seyfert-like AGN activity.
Surprisingly, the AGN is the predominant source of 850 micron emission. We
examine the possible emission mechanisms that could give rise to the 850 micron
emission and find that neither thermal dust emission, CO line emission,
bremsstrahlung emission, nor the synchrotron emission observed at radio
wavelengths can adequately explain the measured 850 micron flux density by
themselves. The remaining possibilities for the source of the 850 micron
emission include a combination of known emission mechanisms, synchrotron
emission that is self-absorbed at wavelengths longer than 850 microns, or
unidentified spectral lines in the 850 micron band.


title:
The SAURON project - VII. Integral-field absorption and emission-line
  kinematics of 24 spiral galaxy bulges

abstract:
  (Abridged) We present observations of the stellar and gas kinematics for a
representative sample of 24 Sa galaxies obtained with our custom-built
integral-field spectrograph SAURON operating on the William Herschel Telescope.
Our maps typically cover the bulge dominated region. We find a significant
fraction of kinematically decoupled components (12/24), many of them displaying
central velocity dispersion minima. They are mostly aligned and co-rotating
with the main body of the galaxies, and are usually associated with dust discs
and rings detected in unsharp-masked images. Almost all the galaxies in the
sample (22/24) contain significant amounts of ionised gas which, in general, is
accompanied by the presence of dust. The kinematics of the ionised gas is
consistent with circular rotation in a disc co-rotating with respect to the
stars. The distribution of mean misalignments between the stellar and gaseous
angular momenta in the sample suggest that the gas has an internal origin. The
[OIII]/Hbeta ratio is usually very low, indicative of current star formation,
and shows various morphologies (ring-like structures, alignments with dust
lanes or amorphous shapes). The star formation rates in the sample are
comparable with that of normal disc galaxies. Low gas velocity dispersion
values appear to be linked to regions of intense star formation activity. We
interpret this result as stars being formed from dynamically cold gas in those
regions. In the case of NGC5953, the data suggest that we are witnessing the
formation of a kinematically decoupled component from cold gas being acquired
during the ongoing interaction with NGC5954.


title: Is space expanding in the Friedmann universe models?

abstract:
  The interpretation of the expanding universe as an expansion of space has
recently been challenged. From the geodesic equation in Friedmann universe
models and the empty Milne model, we argue that a Newtonian or special
relativistic analysis is not applicable on large scales, and the general
relativistic interpretation in terms of expanding space has the advantage of
being globally consistent. We also show that the cosmic redshift, interpreted
as an expansion effect, containts both the Doppler effect and the gravitational
frequency shift.


title: Far-IR Detection Limits II: Probing Confusion including Source Confusion

abstract:
  We present a comprehensive analysis for the determination of the confusion
levels for the current and the next generation of far-infrared surveys assuming
three different cosmological evolutionary scenarios. We include an extensive
model for diffuse emission from infrared cirrus in order to derive absolute
sensitivity levels taking into account the source confusion noise due to point
sources, the sky confusion noise due to the diffuse emission, and instrumental
noise. We use our derived sensitivities to suggest best survey strategies for
the current and the future far-infrared space missions Spitzer, AKARI
(ASTRO-F), Herschel, and SPICA. We discuss whether the theoretical estimates
are realistic and the competing necessities of reliability and completeness. We
find the best estimator for the representation of the source confusion and
produce predictions for the source confusion using far-infrared source count
models. From these confusion limits considering both source and sky confusions,
we obtain the optimal, confusion limited redshift distribution for each
mission. Finally, we predict the Cosmic Far-Infrared Background (CFIRB) which
includes information about the number and distribution of the contributing
sources.


title: Metallicity dependence of some parameters of Cepheids

abstract:
  Dependence of phenomenological properties of Cepheids on the heavy element
abundance is studied. It is found that the amplitude of the pulsation depends
on the metallicity of the stellar atmosphere.


title: The GL 569 Multiple System

abstract:
  We report the results of high spectral and angular resolution infrared
observations of the multiple system GL 569 A and B that were intended to
measure the dynamical masses of the brown dwarf binary believed to comprise GL
569 B. Our analysis did not yield this result but, instead, revealed two
surprises. First, at age ~100 Myr, the system is younger than had been reported
earlier. Second, our spectroscopic and photometric results provide support for
earlier indications that GL 569 B is actually a hierarchical brown dwarf triple
rather than a binary. Our results suggest that the three components of GL 569 B
have roughly equal mass, ~0.04 Msun.


title: Deep 1.4 GHz VLA Observations of the Radio Halo and Relic in Abell 2256

abstract:
  We present deep VLA observations of the merging galaxy cluster Abell 2256.
This cluster is known to possess diffuse steep spectrum radio relic emission in
the peripheral regions. Our new observations provide the first detailed image
of the central diffuse radio halo emission in this cluster. The radio halo
extends over more than 800 kpc in the cluster core, while the relic emission
covers a region of ~1125 x 520 kpc. A spectral index map of the radio relic
shows a spectral steepening from the northwest toward the southeast edge of the
emission, with an average spectral index between 1369 MHz and 1703 MHz of -1.2
across the relic. Polarization maps reveal high fractional polarization of up
to 45% in the relic region with an average polarization of 20% across the relic
region. The observed Faraday rotation measure is consistent with the Galactic
estimate and the dispersion in the rotation measure is small, suggesting that
there is very little contribution to the rotation measure of the relic from the
intracluster medium. We use these Faraday properties of the relic to argue that
it is located on the front side of the cluster.


title: A photoionized Herbig-Haro object in the Orion nebula

abstract:
  The spectra of Herbig Haro objects are usually characteristic of ionization
and excitation in shock-heated gas, whether an internal shock in an unsteady
outflow or a bow shock interface with the interstellar medium. We examine the
eastern-most shock -- the leading optically visible shock -- of a Herbig Haro
outflow (HH 529) seen projected on the face of the Orion Nebula, using deep
optical echelle spectroscopy, showing that the spectrum of this gas is
consistent with photoionization by $\theta^1$ Ori C. By modeling the emission
lines, we determine a gas-phase abundance of Fe which is consistent with the
depleted (relative to solar) abundance found in the Orion nebula -- evidence
for the presence of dust in the nebula and therefore in the Herbig Haro
outflow. The spectrum also allows for the calculation of temperature
fluctuations, $t^2$, in the nebula and the shock. These fluctuations have been
used to explain discrepancies between abundances obtained from recombination
lines versus those obtained from collisionally-excited lines, although to date
there has not been a robust theory for how such large fluctuations ($t^2 >
0.02$) can exist.


title: Variable Unidentified Emission Near 6307 AA in Eta Carinae

abstract:
  We have discovered a conspicuous unidentified variable feature near 6307 AA
in the spectrum of Eta Carinae which is spatially unresolved from the central
star and its wind (r < 200--300 AU). It is significant for two reasons: such
prominent unidentified lines are now rare in this object, and this feature
varies strongly and systematically. It exhibits a combination of
characteristics which, so far as we know are unique in Eta Carinae's spectrum.
It may provide insights into the recurrent spectroscopic events and the star's
long-term brightening.