title: Chandra Observations of Associates of $\eta$ Car: II. Spectra

abstract:
  The low resolution X-ray spectra around $\eta$ Car covering Tr 16 and part of
Tr 14 have been extracted from a Chandra CCD ACIS image. Various analysis
techniques have been applied to the spectra based on their count rates. The
spectra with the greatest number of counts (HD 93162 = WR 25, HD 93129AB, and
HD 93250) have been fit with a wind model, which uses several components with
different temperatures and depths in the wind. Weaker spectra have been fit
with Raymond-Smith models. The weakest spectra are simply inter-compared with
strong spectra. In general, fits produce reasonable parameters based on
knowledge of the extinction from optical studies and on the range of
temperatures for high and low mass stars. Direct comparisons of spectra confirm
the consistency of the fitting results and also hardness ratios for cases of
unusually large extinction in the clusters. The spectra of the low mass stars
are harder than the more massive stars. Stars in the sequence evolving from the
main sequence (HD 93250) through the system containing the O supergiant (HD
93129AB) and then through the Wolf-Rayet stage (HD93162), presumably ending in
the extreme example of $\eta$ Car, share the property of being unusually
luminous and hard in X-rays. For these X-ray luminous stars, their high mass
and evolutionary status (from the very last stages of the main sequence and
beyond) is the common feature. Their binary status is mixed, and magnetic
status is still uncertain.


title:
A Realistic Determination of the Error on the Primordial Helium
  Abundance: Steps Toward Non-Parametric Nebular Helium Abundances

abstract:
  Currently there are two significantly different observational determinations
of the primordial helium abundance, and, if only statistical errors in He4
abundance determinations are considered, the discrepancies between the
observational determinations and the value favored by the WMAP results are
significant. Here we examine in detail some likely sources of systematic
uncertainties which may resolve the differences between the two determinations.
We conclude that the observational determination of the primordial helium
abundance is completely limited by systematic errors and that these systematic
errors have not been fully accounted for in any published observational
determination of the primordial helium abundance. In principle, the observed
metal-poor HII region spectra should be analyzed in a non-parametric way, such
that the HII region physical conditions and the helium abundance are derived
solely from the relative flux ratios of the helium and hydrogen emission lines.
In practice, there are very few HII region spectra with the quality that allow
this, so that most analyses depend on assumed ranges or relationships between
physical parameters, resulting in parametric solutions with underestimated
error bars. A representative result of our analysis yields Y_p = 0.249 \pm
0.009. However, given that most of the spectra analyzed to date do not
significantly constrain the primordial helium abundance, we argue in favor a
range of allowed values of 0.232 le Y_p le 0.258. [abstract abridged]


title: The Angular Power Spectrum of the First-Year WMAP Data Reanalysed

abstract:
  We measure the angular power spectrum of the WMAP first-year temperature
anisotropy maps. We use SpICE (Spatially Inhomogeneous Correlation Estimator)
to estimate Cl's for multipoles l=2-900 from all possible cross-correlation
channels. Except for the map-making stage, our measurements provide an
independent analysis of that by Hinshaw etal (2003). Despite the different
methods used, there is virtually no difference between the two measurements for
l < 700 ; the highest l's are still compatible within 1-sigma errors. We use a
novel intra-bin variance method to constrain Cl errors in a model independent
way. When applied to WMAP data, the intra-bin variance estimator yields
diagonal errors 10% larger than those reported by the WMAP team for 100 < l <
450. This translates into a 2.4 sigma detection of systematics since no
difference is expected between the SpICE and the WMAP team estimator window
functions in this multipole range. With our measurement of the Cl's and errors,
we get chi^2/d.o.f. = 1.042 for a best-fit LCDM model, which has a 14%
probability, whereas the WMAP team obtained chi^2/d.o.f. = 1.066, which has a
5% probability. We assess the impact of our results on cosmological parameters
using Markov Chain Monte Carlo simulations. From WMAP data alone, assuming
spatially flat power law LCDM models, we obtain the reionization optical depth
tau = 0.145 +/- 0.067, spectral index n_s = 0.99 +/- 0.04, Hubble constant h =
0.67 +/- 0.05, baryon density Omega_b h^2 = 0.0218 +/- 0.0014, cold dark matter
density Omega_{cdm} h^2 = 0.122 +/- 0.018, and sigma_8 = 0.92 +/- 0.12,
consistent with a reionization redshift z_{re} = 16 +/- 5 (68% CL).


title: Conditional Cumulants in Weakly Non-linear Regime

abstract:
  Conditional cumulants form a set of unique statistics which represent a
sensible compromise between N-point correlation functions and cumulants
measured from moments of counts in cells. They share accurate edge corrected
estimators with $N$-point correlation functions, yet, they are as
straightforward to measure and interpret as counts in cells. The conditional
cumulants have three equivalent views as i) degenerate N-point correlation
functions ii) or integrated monopole moments of the bispectrum iii) they are
closely related to neighbour counts. We compute the predictions of weakly
non-linear perturbation theory for conditional cumulants and compare them with
measurements in simulations, both in real and redshift space. We find excellent
agreement between theory and simulations, especially on scales >~20Mpc. Due to
their advantageous statistical properties and well understood dynamics, we
propose conditional cumulants as tools for high precision cosmology. Potential
applications include constraining bias and redshift distortions from galaxy
redshift surveys


title: Re-defining the Empirical ZZ Ceti Instability Strip

abstract:
  We use the new ZZ Ceti stars (hydrogen atmosphere white dwarf variables;
DAVs) discovered within the Sloan Digital Sky Survey (Mukadam et al. 2004) to
re-define the empirical ZZ Ceti instability strip. This is the first time since
the discovery of white dwarf variables in 1968 that we have a homogeneous set
of spectra acquired using the same instrument on the same telescope, and with
consistent data reductions, for a statistically significant sample of ZZ Ceti
stars. The homogeneity of the spectra reduces the scatter in the spectroscopic
temperatures and we find a narrow instability strip of width ~950K, from
10850--11800K. We question the purity of the DAV instability strip as we find
several non-variables within. We present our best fit for the red edge and our
constraint for the blue edge of the instability strip, determined using a
statistical approach.


title: Angular Clustering of Galaxies at 3.6 micron from the SWIRE survey

abstract:
  We present the first analysis of large-scale clustering from the Spitzer
Wide-area InfraRed Extragalactic legacy survey: SWIRE. We compute the angular
correlation function of galaxies selected to have 3.6 micron fluxes brighter
than 32 muJy in three fields totaling two square degrees in area. In each field
we detect clustering with a high level of significance. The amplitude and slope
of the correlation function is consistent between the three fields and is
modeled as $w(theta)=A\theta^{1-\gamma}$ with $A=(0.6\pm0.3)\times10^{-3},
\gamma=2.03\pm0.10$. With a fixed slope of $\gamma=1.8$, we obtain an amplitude
of $A=(1.7\pm0.1)\times10^{-3}$. Assuming an equivalent depth of K~18.7 mag we
find our errors are smaller but our results are consistent with existing
clustering measurements in K-band surveys and with stable clustering models. We
estimate our median redshift $z\simeq 0.75$ and this allows us to obtain an
estimate of the three-dimensional correlation function $\xi(r)$, for which we
find $r_0=4.4\pm0.1 h^{-1}$ Mpc.


title: Baryons and weak lensing power spectra

abstract:
  We provide a simple toy model to elucidate the effects of baryonic cooling on
predictions of the convergence power spectrum in weak gravitational lensing.
Our model suggests that the effects of baryonic cooling on dark matter halo
profiles can alter the dark matter power spectrum at k~10 h/Mpc and lead to
percent level changes in the convergence angular power spectrum at wavenumbers
of several thousand. These effects would be measurable with planned weak
lensing surveys and will impact constraints on cosmological parameters.


title: Mid-Infrared Galaxy Morphology Along the Hubble Sequence

abstract:
  The mid-infrared emission from 18 nearby galaxies imaged with the IRAC
instrument on Spitzer Space Telescope samples the spatial distributions of the
reddening-free stellar photospheric emission and the warm dust in the ISM.
These two components provide a new framework for galaxy morphological
classification, in which the presence of spiral arms and their emission
strength relative to the starlight can be measured directly and with high
contrast. Four mid-infrared classification methods are explored, three of which
are based on quantitative global parameters (colors, bulge-to-disk ratio)
similar to those used in the past for optical studies; in this limited sample,
all correlate well with traditional B-band classification. We suggest reasons
why infrared classification may be superior to optical classification.


title: Number Counts At 3 < lambda < 10 um From the Spitzer Space Telescope

abstract:
  Infrared source counts at wavelengths 3 < lambda < 10 um cover more than 10
magnitudes in source brightness, four orders of magnitude in surface density,
and reach an integrated surface density of 10^5 sources/deg^2. At m<14 mag,
most of the sources are Galactic stars, in agreement with models. After removal
of Galactic stars, galaxy counts are consistent with what few measurements
exist at nearby wavelengths. At 3.6 and 4.5 um, the galaxy counts follow the
expectations of a Euclidean world model down to ~16 mag and drop below the
Euclidean curve for fainter magnitudes. Counts at these wavelengths begin to
show decreasing completeness around magnitude 19.5. At 5.8 and 8 um, the counts
relative to a Euclidean world model show a large excess at bright magnitudes.
This is probably because local galaxies emit strongly in the aromatic dust
(``PAH'') features. The counts at 3.6 um resolve <50% of the Cosmic Infrared
Background at that wavelength.


title: Acceleressence: Dark Energy from a Phase Transition at the Seesaw Scale

abstract:
  Simple models are constructed for "acceleressence" dark energy: the latent
heat of a phase transition occurring in a hidden sector governed by the seesaw
mass scale v^2/M_Pl, where v is the electroweak scale and M_Pl the
gravitational mass scale. In our models, the seesaw scale is stabilized by
supersymmetry, implying that the LHC must discover superpartners with a
spectrum that reflects a low scale of fundamental supersymmetry breaking.
Newtonian gravity may be modified by effects arising from the exchange of
fields in the acceleressence sector whose Compton wavelengths are typically of
order the millimeter scale. There are two classes of models. In the first class
the universe is presently in a metastable vacuum and will continue to inflate
until tunneling processes eventually induce a first order transition. In the
simplest such model, the range of the new force is bounded to be larger than 25
microns in the absence of fine-tuning of parameters, and for couplings of order
unity it is expected to be \approx 100 microns. In the second class of models
thermal effects maintain the present vacuum energy of the universe, but on
further cooling, the universe will "soon" smoothly relax to a matter dominated
era. In this case, the range of the new force is also expected to be of order
the millimeter scale or larger, although its strength is uncertain. A firm
prediction of this class of models is the existence of additional energy
density in radiation at the eV era, which can potentially be probed in
precision measurements of the cosmic microwave background. An interesting
possibility is that the transition towards a matter dominated era has occurred
in the very recent past, with the consequence that the universe is currently
decelerating.


title:
HAT Variability Survey in the High Stellar Density "Kepler Field" with
  Millimagnitude Image Subtraction Photometry

abstract:
  The Hungarian-made Automated Telescope network (HATnet) is an ongoing project
to detect transiting extra-solar planets using small aperture (11 cm diameter),
robotic telescopes. In this paper we present the results from using image
subtraction photometry to reduce a crowded stellar field observed with one of
the HATnet telescopes (HAT-5). This field was chosen to overlap with the
planned Kepler mission. We obtained I-band light curves for 98,000 objects in a
8.3x8.3 square degree field of view, near the Galactic plane in the
constellations Cygnus and Lyra. These observations include 788 5-minute
exposures over 30 days. For the brightest stars (I~8.0) we achieved a precision
of 3.5 millimagnitudes, falling to 0.1 magnitudes at the faint end (I~14). From
these light curves we identify 1617 variable stars, of which 1439 are newly
discovered. The fact that nearly 90% of the variables were previously
undetected further demonstrates the vast number of variables yet to be
discovered even among fairly bright stars in our Galaxy. We also discuss some
of the most interesting cases. These include: V1171 Cyg, a triple system with
the inner two stars in P=1.462 day period eclipsing orbit and the outer star a
P=4.86 day Cepheid; HD227269, an eccentric eclipsing system with a P=4.86 day
period that also shows P=2.907 day pulsations; WW Cyg, a well studied eclipsing
binary; V482 Cyg, an RCB star; and V546 Cyg, a PV Tel Variable. We also detect
a number of small amplitude variables, in some cases with full amplitude as low
as 10 mmag.


title: Dark Matter Search with Direction Sensitive Scintillator

abstract:
  A direction sensitive dark matter detector using organic crystals is being
developed. It exploits the anisotropic scintillation efficiency of organic
crystals with respect to the direction of nuclear recoils relative to
crystallographic axes. A variation of about 7% was observed in the
scintillation efficiency of carbon recoils in a stilbene crystal for recoil
energies of 30 keV to 1 MeV. We have performed a pilot experiment at Kamioka to
prove the feasibility of this method.


title: Self lensing effects for compact stars and their mass-radius relation

abstract:
  During the last couple of years astronomers and astrophysicists have been
debating on the fact whether the so called `strange stars' - stars made up of
strange quark matter, have been discovered with the candidates like SAX
J1808.4-3658, 4U 1728-34, RX J1856.5-3754, etc. The main contention has been
the estimation of radius of the star for an assumed mass of ~ 1.4 M_sun and to
see whether the point overlaps with the graphs for the neutron star equation of
state or whether it goes to the region of stars made of strange matter equation
of state. Using the well established formulae from general relativity for the
gravitational redshift and the `lensing effect' due to bending of photon
trajectories, we, in this letter, relate the parameters M and R with the
observable parameters, the redshift z and the radiation radius R_\infty, thus
constraining both M and R for specific ranges, without any other arbitrariness.
With the required inputs from observations, one ought to incorporate the
effects of self lensing of the compact stars which has been otherwise ignored
in all of the estimations done so far. Nonetheless, these effect of self
lensing makes a marked difference and constraints on the M-R relation.


title:
The R Coronae Borealis stars - carbon abundances from forbidden carbon
  lines

abstract:
  Spectra of several R Coronae Borealis (RCB) stars at maximum light were
examined for the [C I] 9850 A and 8727 A absorption lines. The 9850 A line is
variously blended with a Fe II and CN lines but positive identifications of the
[C I] line are made for R CrB and SU Tau. The 8727 A line is detected in the
spectrum of the five stars observed in this wavelength region. Carbon
abundances are derived from the [C I] lines using the model atmospheres and
atmospheric parameters used by Asplund et al. (2000).
  Although the observed strength of a C I line is constant from cool to hot RCB
stars, the strength is weaker than predicted by an amount equivalent to a
factor of four reduction of a line's gf-value. Asplund et al. dubbed this 'the
carbon problem' and discussed possible solutions.
  The [C I] 9850 A line seen clearly in R CrB and SU Tau confirms the magnitude
of the carbon problem revealed by the C I lines. The [C I] 8727 A line measured
in five stars shows an enhanced carbon problem. The gf-value required to fit
the observed [C I] 8727 A line is a factor of 15 less than the well-determined
theoretical gf-value. We suggest that the carbon problem for all lines may be
alleviated to some extent by a chromospheric-like temperature rise in these
stars. The rise far exceeds that predicted by our non-LTE calculations, and
requires a substantial deposition of mechanical energy.


title: Cooling of a New Born Compact Star with QCD Phase Transition

abstract:
  We study the cooling behaviour of an isolated strange quark star, using an
equation of state derived from perturbative QCD up to second order in strong
coupling constant, and we compare it with that of a neutron star. After an
initial rapid cooling, a quark star may undergo the QCD phase transition to
become a neutron star. We propose several signatures for such a scenario: a
large amount of energy can be released due to latent heat, a long duration
$\gamma$-ray source, and a second neutrino burst after a supernova explosion.


title:
The collimation--corrected GRB energies correlate with the peak energy
  of their $\nu F_{\nu}$ spectrum

abstract:
  We consider all bursts with known redshift and $\nu F_\nu$ peak energy,
$E^{obs}_{peak}$. For a good fraction of them an estimate of the jet opening
angle is available from the achromatic break of their afterglow light curve.
This allows the derivation of the collimation--corrected energy of the bursts,
$E_\gamma$. The distribution of the values of $E_\gamma$ is more spread with
respect to previous findings, covering about two orders of magnitude. We find a
surprisingly tight correlation between $E_\gamma$ and the source frame
$E_{peak}$: $E^{obs}_{peak}(1+z) \propto E_\gamma^{0.7}$. This correlation can
shed light on the still uncertain radiation processes for the prompt GRB
emission. More importantly, if the small scatter of this newly found
correlation will be confirmed by forthcoming data, it will be possible to use
it for cosmological purposes.


title:
Light Propagation in Inhomogeneous Universes. IV. Strong Lensing and
  Environmental Effects

abstract:
  We study the gravitational lensing of high-redshift sources in a LCDM
universe. We have performed a series of ray-tracing experiments, and selected a
subsample of cases of strong lensing (multiple images, arcs, and Einstein
rings). For each case, we identify a massive galaxy that is primarily
responsible for lensing, and studied how the various density inhomogeneities
along the line of sight (other galaxies, background matter) affect the
properties of the image. The matter located near the lensing galaxy, and
physically associated with it, has a small effect. The background matter
increases the magnification by a few percents at most, while nearby galaxies
can increase it by up to about 10 percent. The effect on the image separation
is even smaller. The only significant effect results from the random alignment
of physically unassociated galaxies, which can increase the magnification by
factors of several, create additional images, and turn arcs into rings. We
conclude that the effect of environment on strong lensing in negligible in
general, and might be important only in rare cases. We show that our conclusion
does not depend on the radial density profile of the galaxies responsible for
lensing.


title:
Obscured and unobscured active galactic nuclei in the Spitzer Space
  Telescope First Look Survey

abstract:
  Selection of active galactic nuclei (AGN) in the infrared allows the
discovery of AGN whose optical emission is extinguished by dust. In this paper,
we use the Spitzer Space Telescope First Look Survey (FLS) to assess what
fraction of AGN with mid-infrared luminosities comparable to quasars are missed
in optical quasar surveys due to dust obscuration. We begin by using the Sloan
Digital Sky Survey (SDSS) database to identify 54 quasars within the 4 deg^2
extragalactic FLS. These quasars occupy a distinct region in mid-infrared color
space by virtue of their strong, red, continua. This has allowed us to define a
mid-infrared color criterion for selecting AGN candidates. About 2000 FLS
objects have colors consistent with them being AGN, but most are much fainter
in the mid-infrared than the SDSS quasars, which typically have 8 micron flux
densities, S(8.0), ~1 mJy. We have investigated the properties of the 43
objects with S(8.0) >= 1 mJy satisfying our AGN color selection. This sample
should contain both unobscured quasars, and AGN which are absent from the SDSS
survey due to extinction in the optical. After removing 16 known quasars, three
probable normal quasars, and eight spurious or confused objects from the
initial sample of 43, we are left with 16 objects which are likely to be
obscured quasars or luminous Seyfert-2 galaxies. This suggests the numbers of
obscured and unobscured AGN are similar in samples selected in the mid-infrared
at S(8.0)~1 mJy.


title: Photometry of Irregular Satellites of Uranus and Neptune

abstract:
  We present BVR photometric colors of six Uranian and two Neptunian irregular
satellites, collected using the Magellan Observatory (Las Campanas, Chile) and
the Keck Observatory, (Manua Kea, Hawaii). The colors range from neutral to
light red, and like the Jovian and the Saturnian irregulars (Grav et al. 2003)
there is an apparent lack of the extremely red objects found among the Centaurs
and Kuiper belt objects.
  The Uranian irregulars can be divided into three possible dynamical families,
but the colors collected show that two of these dynamical families, the Caliban
and Sycorax-clusters, have heterogeneous colors. Of the third possible family,
the 168-degree cluster containing two objects with similar average inclinations
but quite different average semi-major axis, only one object (U XXI Trinculo)
was observed. The heterogeneous colors and the large dispersion of the average
orbital elements leads us to doubt that they are collisional families. We favor
single captures as a more likely scenario. The two neptunians observed (N II
Nereid and S/2002 N1) both have very similar neutral, sun-like colors. Together
with the high collisional probability between these two objects over the age of
the solar system (Nesvorny et al. 2003, Holman et al. 2004), this suggests that
S/2002 N1 be a fragment of Nereid, broken loose during a collision or cratering
event with an undetermined impactor.


title: Early reionization by cosmic strings revisited

abstract:
  Measurements of the CMB temperature anisotropy and the
temperature-polarization cross correlation by WMAP suggest a reionization
redshift of $z \sim 17 \pm 5$. On the other hand, observations of high redshift
galaxies indicate a presence of a significant fraction of neutral hydrogen at
redshift $z\sim 6-7$. We show that cosmic strings with tensions well within,
but not far from, current observation bounds could cause early star formation
at a level sufficient to explain the high reionization redshift.


title:
Constraining the mass distribution of galaxies using galaxy-galaxy
  lensing in clusters and in the field

abstract:
  We present a maximum-likelihood analysis of galaxy-galaxy lensing effects in
galaxy clusters and in the field. The aim is to determine the accuracy and
robustness of constraints that can be obtained on galaxy halo properties in
both environments - the high density cluster and the low density field. This
paper is theoretically motivated, therefore, we work exclusively with simulated
data (nevertheless defined to match observations) to study the accuracy with
which input parameters for mass distributions for galaxies can be extracted. We
model galaxies in the cluster and the field using a wide range of mass
profiles: the truncated pseudo isothermal elliptical mass distribution, the
Navarro, Frenk and White profile, and a Power Law model with a core radius. We
find that independent of the choice of profile the mean mass of galaxies (of
the order of 10^{12}Mo) can be estimated to within 15% from ground-based data
and with an error of less than 10% with space observations. Additionally robust
constraints can be obtained on the mean slope of the mass profile. The two
standard parameters that characterise galaxy halo models, the central velocity
dispersion and the truncation radius can also be retrieved reliably from the
maximum-likelihood analysis. Furthermore, going beyond the usual formulation,
we propose a re-parameterisation of the mass models that allows us to put yet
stronger constraints on the aperture mass of a galaxy halo (with less than 10%
error). The gain in signal to noise using space observations, expected for
instance with the proposed SNAP satellite compared to ground based data in
terms of accuracy of retrieving input parameters is highly significant.


title: Cosmic Rays in the 'Knee'-Region - Recent Results from KASCADE -

abstract:
  Recent results from the KASCADE experiment on measurements of cosmic rays in
the energy range of the knee are presented. Emphasis is placed on energy
spectra of individual mass groups as obtained from sophisticated unfolding
procedures applied to the reconstructed electron and truncated muon numbers of
EAS. The data show a knee-like structure in the energy spectra of light
primaries (p, He, C) and an increasing dominance of heavy ones (A>20) towards
higher energies. This basic result is robust against uncertainties of the
applied interaction models QGSJET and SIBYLL. Slight differences observed
between experimental data and EAS simulations provide important clues for
improvements of the interaction models. The data are complemented by new limits
on global anisotropies in the arrival directions of CRs and by upper limits on
point sources. Astrophysical implications for discriminating models of maximum
acceleration energy vs galactic diffusion/drift models of the knee are
discussed based on this data. To improve the reconstruction quality and
statistics around 10^17 eV, KASCADE has recently been extended by a factor 10
in area. The status and expected performance of the new experiment
KASCADE-Grande is presented.


title: Efficient simulations of gas-grain chemistry in interstellar clouds

abstract:
  Chemical reactions on dust grains are of crucial importance in interstellar
chemistry because they produce molecular hydrogen and various organic
molecules. Due to the submicron size of the grains and the low flux, the
surface populations of reactive species are small and strongly fluctuate. Under
these conditions rate equations fail and the master equation is needed for
modeling these reactions. However, the number of equations in the master
equation grows exponentially with the number of reactive species, severely
limiting its feasibility. Here we present a method which dramatically reduces
the number of equations, thus enabling the incorporation of the master equation
in models of interstellar chemistry.


title:
SBS 0335-052 E and W: implications of new broad-band and H-alpha
  photometry

abstract:
  We present the results of deep multicolour CCD imaging with the 6-m telescope
of the pair of extremely metal-deficient gas-rich dwarf galaxies SBS 0335-052 E
and W. The total magnitudes in U,B,V,R,I bands and the integrated fluxes of
H-alpha emission are measured for both galaxies, and their integrated colours
are derived. The analysis of their surface brightness (SB) distributions is
performed with the use of the azimuthally-averaged SB profiles. The latter were
modeled by the central Gaussian component and the underlying exponential
`disk', mainly contributing in the outermost, very low SB regions. The colours
of these LSB components are used to estimate the age of the oldest visible
stellar population. For the interpretation of the observed LSB colours their
contamination by the nebular emission of ionized gas is accounted for by the
use of the distribution of H-alpha flux. We compare the derived `gas-free'
colours with the colours predicted by the evolution synthesis models from the
PEGASE.2 package, considering three SF histories: a) instantaneous starburst,
b) continuous star formation with constant SFR, c) continuous exponentially
fading SF (e-fold time of 3 Gyr). We conclude that the `gas-free' colours of
the LSB component of the E galaxy can be best consistent with the instantaneous
starburst population (ages of less than ~100 Myr). Models with continuous SF
give less consistent results, but can be considered as acceptable. For such
scenarios, the `gas-free' colours require ages of less than ~400 Myr. For the W
galaxy, the situation is in general similar. But the colour (V-R) appears to be
quite red and implies a significantly older component. We briefly discuss the
possible evolution sequence between SBS 0335-052, HI 1225+01 and other
extremely metal-deficient galaxies based on the merger scenario.


title: Cosmological Feedback from High-Redshift Dwarf Galaxies

abstract:
  We model how repeated supernova explosions in high-redshift dwarf starburst
galaxies drive superbubbles and winds out of the galaxies. We compute the
efficiencies of metal and mass ejection and energy transport from the galactic
potentials, including the effect of cosmological infall of external gas. The
starburst bubbles quickly blow out of small, high-redshift, galactic disks, but
must compete with the ram pressure of the infalling gas to escape into
intergalactic space. We show that the assumed efficiency of the star formation
rate dominates the bubble evolution and the metal, mass, and energy feedback
efficiencies. With star formation efficiency f*=0.01, the ram pressure of
infall can confine the bubbles around high-redshift dwarf galaxies with
circular velocities v_c>52 km/s. We can expect high metal and mass ejection
efficiencies, and moderate energy transport efficiencies in halos with
v_c~30-50 km/s and f*~0.01 as well as in halos with v_c~100 km/s and f*>>0.01.
Such haloes collapse successively from 1-2 sigma peaks in LambdaCDM Gaussian
density perturbations as time progresses. These dwarf galaxies can probably
enrich low and high-density regions of intergalactic space with metals to
10^-3-10^-2 Zsun as they collapse at z~8 and z<5 respectively. They also may be
able to provide adequate turbulent energy to prevent the collapse of other
nearby halos, as well as to significantly broaden Lyman-alpha absorption lines
to v_rms~20-40 km/s. We compute the timescales for the next starbursts if gas
freely falls back after a starburst, and find that, for star formation
efficiencies as low as f*<0.01, the next starburst should occur in less than
half the Hubble time at the collapse redshift. This suggests that episodic star
formation may be ubiquitous in dwarf galaxies.


title: Extremely Red Objects in The Lockman Hole

abstract:
  We investigate Extremely Red Objects (EROs) using near- and mid-infrared
observations in five passbands (3.6 to 24 micron) obtained from the Spitzer
Space Telescope, and deep ground-based R and K imaging. The great sensitivity
of the IRAC camera allows us to detect 64 EROs in only 12 minutes of IRAC
exposure time, by means of an R-[3.6] color cut (analogous to the traditional
red R-K cut). A pure infrared K-[3.6] red cut detects a somewhat different
population and may be more effective at selecting z > 1.3 EROs. We find 17% of
all galaxies detected by IRAC at 3.6 or 4.5 micron to be EROs. These
percentages rise to about 40% at 5.8 micron, and about 60% at 8.0 micron. We
utilize the spectral bump at 1.6 micron to divide the EROs into broad redshift
slices using only near-infrared colors (2.2/3.6/4.5 micron). We conclude that
two-thirds of all EROs lie at redshift z > 1.3. Detections at 24 micron imply
that at least 11% of 0.6 < z < 1.3 EROs and at least 22% of z > 1.3 EROs are
dusty star-forming galaxies.


title: Deficit of Ultrahigh Energy Extensive Air Showers

abstract:
  Arrival directions of extensive air showers by using world data are
considered. It is shown that distributions of showers in zenith angle at
E>10^{19}eV and E>4.10^{19}eV differ from each other. On this basis the
conclusions are made: the estimation of the energy of inclined showers at
E>4.10^{19}eV at Yakutsk and AGASA arrays is incorrect; the cosmic ray spectrum
is not break up and most likely continued up to E=10^{20}eV and higher. It is
found that ultrahigh energy cosmic rays are, probably, superheavy nuclei.


title: IRAC Observations of Planetary Nebulae

abstract:
  We present the initial results from the Infrared Array Camera (IRAC) imaging
survey of planetary nebulae (PN). The IRAC colors of PN are red, especially
when considering the 8.0 micron band. Emission in this band is likely due to
contributions from two strong molecular hydrogen lines and an [Ar III] line in
that bandpass. IRAC is sensitive to the emission in the halos as well as in the
ionized regions that are optically bright. In NGC 246, we have observed an
unexpected ring of emission in the 5.8 and 8.0 micron IRAC bands not seen
previously at other wavelengths. In NGC 650 and NGC 3132, the 8.0 micron
emission is at larger distances from the central star compared to the optical
and other IRAC bands, possibly related to the molecular hydrogen emission in
that band and the tendency for the molecular material to exist outside of the
ionized zones. In the flocculi of the outer halo of NGC 6543, however, this
trend is reversed, with the 8.0 micron emission bright on the inner edges of
the structures. This may be related to the emission mechanism, where the
molecular hydrogen is possibly excited in shocks in the NGC 6543 halo, whereas
the emission is likely fluorescently excited in the UV fields near the central
star.


title: Magnetically Regulated Star Formation in Turbulent Clouds

abstract:
  We investigate numerically the combined effects of supersonic turbulence,
strong magnetic fields and ambipolar diffusion on cloud evolution leading to
star formation. We find that, in clouds that are initially magnetically
subcritical, supersonic turbulence can speed up star formation, through
enhanced ambipolar diffusion in shocks. The speedup overcomes a major objection
to the standard scenario of low-mass star formation involving ambipolar
diffusion, since the diffusion time scale at the average density of a molecular
cloud is typically longer than the cloud life time. At the same time, the
strong magnetic field can prevent the large-scale supersonic turbulence from
converting most of the cloud mass into stars in one (short) turbulence crossing
time, and thus alleviate the high efficiency problem associated with the
turbulence-controlled picture for low-mass star formation. We propose that
relatively rapid but inefficient star formation results from supersonic
collisions of somewhat subcritical gas in strongly magnetized, turbulent
clouds. The salient features of this shock-accelerated, ambipolar
diffusion-regulated scenario are demonstrated with numerical experiments.


title: The Infrared Array Camera (IRAC) for the Spitzer Space Telescope

abstract:
  The Infrared Array Camera (IRAC) is one of three focal plane instruments in
the Spitzer Space Telescope. IRAC is a four-channel camera that obtains
simultaneous broad-band images at 3.6, 4.5, 5.8, and 8.0 microns. Two nearly
adjacent 5.2x5.2 arcmin fields of view in the focal plane are viewed by the
four channels in pairs (3.6 and 5.8 microns; 4.5 and 8 microns). All four
detector arrays in the camera are 256x256 pixels in size, with the two shorter
wavelength channels using InSb and the two longer wavelength channels using
Si:As IBC detectors. IRAC is a powerful survey instrument because of its high
sensitivity, large field of view, and four-color imaging. This paper summarizes
the in-flight scientific, technical, and operational performance of IRAC.


title: Galaxy evolution in clusters up to z=1.0

abstract:
  We present a combined study of the colour-magnitude relation, colour
distribution and luminosity function of a sample of 24 clusters at redshifts
0.3<z<1. The sample is largely composed of X-ray selected/detected clusters.
Most of the clusters at redshifts z<0.6 display X-ray luminosity or richness
typical of poor clusters or groups, rather than the more typical, massive
clusters studied in literature at redshifts z>~0.3. All our clusters, including
groups, display a colour-magnitude relation consistent with a passively
evolving stellar population formed at a redshift z_f>~2, in accordance with
observed galaxy populations in more massive clusters studied at comparable
redshifts. Colours and luminosity functions show that the cluster galaxy
population is consistent with the presence of at least two components: old
systems formed at high redshift that have evolved passively from that epoch,
together with a galaxy population displaying more recent star formation. The
former population forms at ~2< z_f <~5, the latter at redshifts z<1. A model in
which stars do not evolve is clearly rejected by both by the colour of reddest
galaxies and by the characteristic luminosity m* measures. All clusters (with
one possible exception) are detected independently by an almost three
dimensional optical search employing sky position and colour - this despite the
primary X-ray selection and low X-ray flux/optical richness displayed by the
majority of the sample.


title: Gas flows, star formation and galaxy evolution

abstract:
  In the first part of this article we show how observations of the chemical
evolution of the Galaxy: G- and K-dwarf numbers as functions of metallicity,
and abundances of the light elements, D, Li, Be and B, in both stars and the
interstellar medium (ISM), lead to the conclusion that metal poor HI gas has
been accreting to the Galactic disc during the whole of its lifetime, and is
accreting today at a measurable rate, ~2 Msun per year across the full disc.
Estimates of the local star formation rate (SFR) using methods based on stellar
activity, support this picture. The best fits to all these data are for models
where the accretion rate is constant, or slowly rising with epoch. We explain
here how this conclusion, for a galaxy in a small bound group, is not in
conflict with graphs such as the Madau plot, which show that the universal SFR
has declined steadily from z=1 to the present day. We also show that a model in
which disc galaxies in general evolve by accreting major clouds of low
metallicity gas from their surroundings can explain many observations, notably
that the SFR for whole galaxies tends to show obvious variability, and
fractionally more for early than for late types, and yields lower dark to
baryonic matter ratios for large disc galaxies than for dwarfs. In the second
part of the article we use NGC 1530 as a template object, showing from
Fabry-Perot observations of its Halpha emission how strong shear in this
strongly barred galaxy acts to inhibit star formation, while compression acts
to stimulate it.


title: Kinematics of the Ionised Gas in the Spiral Galaxy NGC 2403

abstract:
  We present a study of the kinematics of the ionised gas in the nearby spiral
galaxy NGC 2403 using deep long-slit spectra obtained with the 4.2-m William
Herschel Telescope. The data show the presence of a halo component of ionised
gas that is rotating more slowly than the gas in the disk. The kinematics of
this ionised halo gas is similar to that of the neutral halo gas. On small
scales, broad line profiles (up to 300 km/s wide) indicate regions of fast
outflows of ionised gas. We discuss these new results in the context of
galactic fountain models.


title: The distance duality relation from X-ray and SZ observations of clusters

abstract:
  X-ray and Sunyaev-Zel'dovich data of clusters of galaxies enable to construct
a test of the distance duality relation between the angular and luminosity
distances. We argue that such a test on large cluster samples may be of
importance while trying to distinguish between various models of dark energy.
The analysis of a data set of 18 clusters shows no significant violation of
this relation. The origin and amplitude of systematic effects and the
possibility to increase the precision of this method are discussed.


title:
The optical-near-infrared colour of the host galaxies of BL Lacertae
  objects

abstract:
  We present H-band imaging of 23 low redshift (z < 0.3) BL Lac objects that
were previously investigated by us in the R-band. For all the observed objects,
the host galaxy is well represented by an elliptical model, with average scale
length R(e) = 7.2 +- 3.6 kpc and average absolute magnitude M(H) = -25.9 +-
0.6. BL Lac hosts are therefore luminous elliptical galaxies indistinguishable
from those of low redshift radio galaxies and inactive ellipticals. The
best-fit H-band Kormendy relation of mu(e) = 3.7 log r(e) (kpc) + 14.8 mag
arcsec^-2 agrees with that obtained for normal ellipticals and radio galaxies.
This similarity indicates that all massive elliptical galaxies can experience
nuclear activity without significant perturbation of their global structure.
The new observations are combined with literature data of 18 objects, and this
extended sample is used to investigate the optical-NIR colour and colour
gradient properties of the host galaxies of BL Lacs and to perform a direct
comparison with other elliptical galaxies with and without nuclear activity.
The optical/near-infrared colour (R-H = 2.2 +- 0.4) and colour gradient
(Delta(R-H)/Delta(log r) = -0.38 +- 0.60) distributions of the BL Lac hosts are
much wider than those for normal ellipticals with old stellar populations, and
many BL Lacs have bluer hosts and/or steeper colour gradients than those in
normal ellipticals. The blue colours are most likely caused by a young stellar
population, and indicates a link between star formation caused by an
interaction/merging event and the onset of the nuclear activity. However, the
lack of obvious signs of interaction may require a significant time delay
between the event with associated SF episodes and the onset of nuclear
activity.


title:
Extended X-ray emission at high redshifts: radio galaxies versus
  clusters

abstract:
  Most old distant radio galaxies should be extended X-ray sources due to
inverse Compton scattering of Cosmic Microwave Background (CMB) photons. Such
sources can be an important component in X-ray surveys for high redshift
clusters, due to the increase with redshift of both the CMB energy density and
the radio source number density. We estimate a lower limit to the space density
of such sources and show that inverse Compton scattered emission may dominate
above redshifts of one and X-ray luminosities of 10^44 erg/s, with a space
density of radio galaxies > 10^-8 Mpc^-3. The X-ray sources may last longer
than the radio emission and so need not be associated with what is seen to be a
currently active radio galaxy.


title: Modification of the field theory and the dark matter problem

abstract:
  We present a Modification of the Field Theory in which the topology of space
can vary. We show that in MOFT particles lose their point-like character and
acquire a specific distribution in space, i.e., each point source is surrounded
with a halo which carries charges of all sorts. From the dynamical standpoint
such halos can be described by the presence of dark matter or fictitious
particles. We show that in MOFT fermions obey a generalized statistics and at
scales $r>r_{\min}$ violate the Pauli principle (more than one fermion can
occupy the same quantum state). We also demonstrate that in this range the
stable equilibrium state corresponds to the fractal distribution of baryons and
due to the presence of fictitious particles predicted by MOFT this distribution
is consistent with observational limits on $\Delta T/T$. The concept of
fictitious particles is then used to explain the origin of the diffuse
component in the X-ray background and the origin of scalar Higgs fields. Thus,
we show that MOFT allows to relate the rest mass spectrum of elementary
particles with cosmological parameters. In conclusion we discuss some open
problems in MOFT.


title: Deep mid-infrared observations of Lyman-break galaxies

abstract:
  As part of the In-Orbit Checkout activities for the Spitzer Space Telescope,
the IRAC team carried out a deep observation (average integration time ~8
hours) of a field surrounding the bright QSO HS 1700+6416. This field contains
several hundred z~3 Lyman-break galaxy candidates, and we report here on their
mid-infrared properties, including the IRAC detection rate, flux densities and
colors, and the results of fitting population synthesis models to the optical,
near-infrared, and IRAC magnitudes. The results of the model-fitting show that
previous optical/near-infrared studies of LBGs were not missing large, hidden
old stellar populations. The LBG candidates' properties are consistent with
those of massive, star-forming galaxies at z~3. Other IRAC sources in the same
field have similar properties, so IRAC selection may prove a promising method
of finding additional high-redshift galaxies.


title: Summary of the XXXIX Rencontres de Moriond

abstract:
  This conference covered dark matter particle properties and searches, lensing
by dark matter, and dark matter distributions in galaxies and clusters; dark
energy phenomenology and theoretical models; surveys of structure and galaxy
formation, large scale simulations and neutrino cosmology; astronomy and star
formation; cosmic rays; cosmic microwave background; inflation in the
primordial universe, cosmic strings, brane cosmology, and the fine-structure
constant.


title: IRAC Observations of M81

abstract:
  IRAC images of M81 show three distinct morphological constituents: a smooth
distribution of evolved stars with bulge, disk, and spiral arm components; a
clumpy distribution of dust emission tracing the spiral arms; and a pointlike
nuclear source. The bulge stellar colors are consistent with M-type giants, and
the disk colors are consistent with a slightly younger population. The dust
emission generally follows the blue and ultraviolet emission, but there are
large areas that have dust emission without ultraviolet and smaller areas with
ultraviolet but little dust emission. The former are presumably caused by
extinction, and the latter may be due to cavities in the gas and dust created
by supernova explosions. The nucleus appears fainter at 8 um than expected from
ground-based 10 um observations made four years ago.


title:
Oscillator strengths for transitions to Rydberg levels in
  $^{12}C^{16}O$, $^{13}C^{16}O$ and $^{13}C^{18}O$ between 967 and 972 A

abstract:
  Absorption oscillator strengths have been determined from high-resolution
spectra in the 967-972 \AA region of three CO isotopomers for transitions to
the Rydberg levels 4{\it p$\pi$}(0), 3{\it d$\pi$}(1) and 4{\it p$\sigma$}(0),
as well as to the mixed {\it E(6)} level recently characterized by Eidelsberg
et al. (2004). Synchrotron radiation from the Super-ACO electron storage ring
at Orsay (LURE) was used as a light source. Oscillator strengths were extracted
from the recorded spectra by least-squares fitting of the experimental profiles
with synthetic spectra taking into account the homogeneous and heterogeneous
interactions of the four levels. Column densities were derived from fits to the
3{\it p$\pi$}(0) absorption band whose oscillator strength is well established.
These are the first reported measurements for $^{13}$C$^{18}$O. For
$^{12}$C$^{16}$O, our results are consistent with the larger values obtained in
the most recent laboratory and astronomical studies.


title: Processed and unprocessed ices in circumstellar disks

abstract:
  We present 3-5 micron VLT-ISAAC spectroscopy searching for evidence of
methanol ices in edge-on disks of young embedded stars. Examples include the
disks of L1489 IRS in Taurus and CRBR 2422.8-3423 in Ophiuchus, the last of
which has the highest column density of solid CO known toward a YSO. We find no
unambiguous evidence for abundant methanol in the observed disks, but give
strict upper limits. Several additional low-mass sources in the Serpens and
Chameleon molecular clouds exhibit abundant solid methanol, although it is not
clear if the ice is associated with a disk or with the envelope. These are the
first detections of solid methanol in the circumstellar environments of
embedded young low-mass stars providing evidence that complex molecular species
previously observed only in the solid state toward high-mass star forming
regions are also present near solar-type young stars. The constraints on the
formation mechanisms of methanol and the chemical evolution of ices as the
material is incorporated into circumstellar disks are discussed.


title:
VLT-ISAAC 3-5 micron spectroscopy of low-mass young stellar objects:
  prospects for CRIRES

abstract:
  We present results from an extensive spectroscopic survey in the 3-5 micron
wavelength region of low-mass young stellar objects using VLT-ISAAC. Medium
resolution spectra (R ~ 1000-10000) of young embedded stars in the mid-infrared
allow for detailed studies of ro-vibrational lines from molecular gas,
interstellar ices and Polycyclic Aromatic Hydrocarbons (PAHs). By taking
advantage of this wide range of molecular tracers available within a few
spectral settings, the survey has helped to constrain the chemical evolution of
cold molecular material in low-mass star forming regions as well as the physics
of disks surrounding protostars. In this contribution, we will review the
various spectral diagnostics of molecular material, which require ground-based
high resolution infrared spectroscopy. The importance of a high resolution
spectroscopic capability as will be offered by CRIRES is discussed in the
context of the physics and chemistry of low-mass star formation.


title: New Constraints on Varying Alpha

abstract:
  I briefly present some current theoretical motivations for time or space
variations of the fundamental constants of nature and review current key
observational results. I focus on the fine-structure constant, and particularly
on measurements using quasars and the cosmic microwave background. I also
compare various observational results to the simplest model-building
expectations.


title: Polynomial Interpretation of Multipole Vectors

abstract:
  Copi, Huterer, Starkman and Schwarz introduced multipole vectors in a tensor
context and used them to demonstrate that the first-year WMAP quadrupole and
octopole planes align at roughly the 99.9% confidence level. In the present
article the language of polynomials provides a new and independent derivation
of the multipole vector concept. Bezout's Theorem supports an elementary proof
that the multipole vectors exist and are unique (up to rescaling). The
constructive nature of the proof leads to a fast, practical algorithm for
computing multipole vectors. We illustrate the algorithm by finding exact
solutions for some simple toy examples, and numerical solutions for the
first-year WMAP quadrupole and octopole. We then apply our algorithm to Monte
Carlo skies to independently re-confirm the estimate that the WMAP quadrupole
and octopole planes align at the 99.9% level.


title: Mid-Infrared Spectra of Dust Debris Around Main-Sequence Stars

abstract:
  We report spectra obtained with the Spitzer Space Telescope in the wavelength
range between 14 microns and 35 microns of 19 nearby main-sequence stars with
infrared excesses. The six stars with strong dust emission show no recognizable
spectral features, suggesting that the bulk of the emitting particles have
diameters larger than 10 microns. If the observed dust results from collisional
grinding of larger solids, we infer minimum masses of the parent body
population between 0.004 of the Earth's mass and 0.06 of the Earth's mass.
  We estimate grain production rates of 10 Gg/s around lambda Boo and HR 1570;
selective accretion of this matter may help explain their peculiar surface
abundances. There appear to be inner truncations in the dust clouds at 48 AU,
11 AU, 52 AU and 54 AU around HR 333, HR 506, HR 1082 and HR 3927,
respectively.


title: Be/X-ray stars and candidates: catalogue

abstract:
  Here we present a compilation of data on Be/X-ray binaries. On the whole we
include 90 objects into our catalogue. Brief comments on each object are
provided.


title:
Spitzer 24micron Observations of Optical/Near-IR Selected Extremely Red
  Galaxies: Evidence for Assembly of Massive Galaxies at z~1-2 ?

abstract:
  We carried out the direct measurement of the fraction of dusty sources in a
sample of extremely red galaxies with (R - Ks) > 5.3mag and Ks < 20.2mag, using
24um data from the Spitzer Space Telescope. Combining deep 24um, Ks- and R-band
data over an area of 64sq.arcmin in ELAIS N1, we find that 50%+-6% of our ERO
sample have measurable 24um flux above the 3sigma flux limit of 40uJy. This
flux limit corresponds to a SFR of 12Msun/yr at z~1. The 24um-detected EROs
have 24-to-2.2 and 24-to-0.7um flux ratios consistent with infrared luminous,
dusty sources at z>1, and an order of magnitude too red to be explained by an
infrared quiescent spiral or a pure old stellar population at any redshift.
Keck optical spectroscopy of a sample of similarly selected EROs in the FLS
field suggests that most of the EROs in ELAIS N1 are probably at z~1. The mean
24um flux (167uJy) of the 24um-detected ERO sample roughly corresponds to the
total infrared luminosity of (3-10)x10^(11)Lsun at z=1-1.5, which is similar to
that of local LIRGs and ULIGs. The corresponding SFR is ~(50-170)Msun/yr. If
the time scale of this starbursting phase is on the order of 10^8yr as inferred
for the local LIRGs and ULIGs, the lower limit on the masses of these
24um-detected EROs is (5-20)x10^9Msun. It is plausible that some of the
starburst EROs are in the midst of violent transformation to become massive
early type galaxies at the epoch of z ~ 1-2.


title:
Extragalactic Source Counts at 24 Microns in the Spitzer First Look
  Survey

abstract:
  We present the Spitzer MIPS 24 micron source counts in the Extragalactic
First Look Survey main, verification and ELAIS-N1 fields. Spitzer's increased
sensitivity and efficiency in large areal coverage over previous infrared
telescopes, coupled with the enhanced sensitivity of the 24 micron band to
sources at intermediate redshift, dramatically improve the quality and
statistics of number counts in the mid-infrared. The First Look Survey
observations cover areas of, respectively, 4.4, 0.26 and 0.015 sq.deg. and
reach 3-sigma depths of 0.11, 0.08 and 0.03 mJy. The extragalactic counts
derived for each survey agree remarkably well. The counts can be fitted by a
super-Euclidean power law of index alpha=-2.9 from 0.2 to 0.9 mJy, with a
flattening of the counts at fluxes fainter than 0.2 mJy. Comparison with
infrared galaxy evolution models reveals a peak's displacement in the 24 micron
counts. This is probably due to the detection of a new population of galaxies
with redshift between 1 and 2, previously unseen in the 15 micron deep counts.


title:
Constraints on Scalar-Field Dark Energy from Galaxy Cluster Gas Mass
  Fraction versus Redshift

abstract:
  We use the Allen et al. (2004) Chandra measurements of x-ray gas mass
fraction of 26 rich clusters to place constraints on the scalar-field dark
energy model with inverse power law potential energy density. The constraints
are consistent with, and typically more constraining than, those from other
cosmological tests, and mildly favor the Einstein cosmological constant limit
of the dark energy model.


title:
Characterization of Extragalactic 24micron Sources in the Spitzer First
  Look Survey

abstract:
  In this Letter, we present the initial characterization of extragalactic 24um
sources in the Spitzer First Look Survey (FLS) by examining their counterparts
at 8um and R-band. The color-color diagram of 24-to-8 vs. 24-to-0.7um is
populated with 18,734 sources brighter than the 3sigma flux limit of 110uJy,
over an area of 3.7sq.degrees. The 24-to-0.7um colors of these sources span
almost 4 orders of magnitudes, while the 24-to-8um colors distribute at least
over 2 orders of magnitudes. In addition to identifying ~30% of the total
sample with infrared quiescent, mostly low redshift galaxies, we also found
that: (1) 23% of the 24um sources (~1200/sq.degrees) have very red 24-to-8 and
24-to-0.7 colors and are probably infrared luminous starbursts with
L(IR)>3x10^(11)Lsun at z>1. In particular, 13% of the sample (660/sq.degrees)
are 24um detected only, with no detectable emission in either 8um or R-band.
These sources are the candidates for being ULIRGs at z>2. (2) 2% of the sample
(85/sq.degrees) have colors similar to dust reddened AGNs, like Mrk231 at
z~0.6-3. (3) We anticipate that some of these sources with extremely red colors
may be new types of sources, since they can not be modelled with any familiar
type of spectral energy distribution. We find that 17% of the 24um sources have
no detectable optical counterparts brighter than R limit of 25.5mag. Optical
spectroscopy of these optical extremely faint 24um sources would be very
difficult, and mid-infrared spectroscopy from the Spitzer would be critical for
understanding their physical nature (Abridged).


title: Radiation from condensed surface of magnetic neutron stars

abstract:
  Recent observations show that the thermal X-ray spectra of many isolated
neutron stars are featureless and in some cases (e.g., RX J1856.5-3754) well
fit by a blackbody. Such a perfect blackbody spectrum is puzzling since
radiative transport through typical neutron star atmospheres causes noticeable
deviation from blackbody. Previous studies have shown that in a strong magnetic
field, the outermost layer of the neutron star may be in a condensed solid or
liquid form because of the greatly enhanced cohesive energy of the condensed
matter. The critical temperature of condensation increases with the magnetic
field strength, and can be as high as 10^6 K (for Fe surface at B \sim 10^{13}
G or H surface at B \sim a few times 10^{14} G). Thus the thermal radiation can
directly emerge from the degenerate metallic condensed surface, without going
through a gaseous atmosphere. Here we calculate the emission properties
(spectrum and polarization) of the condensed Fe and H surfaces of magnetic
neutron stars in the regimes where such condensation may be possible. For a
smooth condensed surface, the overall emission is reduced from the blackbody by
less than a factor of 2. The spectrum exhibits modest deviation from blackbody
across a wide energy range, and shows mild absorption features associated with
the ion cyclotron frequency and the electron plasma frequency in the condensed
matter. The roughness of the solid condensate (in the Fe case) tends to
decrease the reflectivity of the surface, and make the emission spectrum even
closer to blackbody. We discuss the implications of our results for
observations of dim, isolated neutron stars and magnetars.


title:
The Colors of Dwarf Elliptical Galaxy Globular Cluster Systems, Nuclei
  and Stellar Halos

abstract:
  We present the results of a Hubble Space Telescope WFPC2 F555W and F814W
survey of 69 dwarf elliptical galaxies (dEs) in the Virgo and Fornax Clusters
and Leo Group. The $V-I$ colors of the dE globular clusters, nuclei, and
underlying field star populations are used to trace the dE star-formation
histories. We find that the dE globular cluster candidates are as blue as the
metal-poor globular clusters of the Milky Way. The observed correlation of the
dE globular cluster systems' $V-I$ color with the luminosity of the host dE is
strong evidence that the globular clusters were formed within the the halos of
dEs and do not have a pre-galactic origin. Assuming the majority of dE clusters
are old, the mean globular cluster color- host galaxy luminosity correlation
implies a cluster metallicity $-$ galaxy luminosity relation of $Z_{GC} \propto
L_B^{0.22 \pm 0.05}$, which is significantly shallower than the field star
metallicity - host galaxy luminosity relationship observed in Local Group
dwarfs ($Z_{FS} \propto L^{0.4}$). The dE stellar envelopes are $0.1-0.2$
magnitudes redder in $V-I$ than their globular clusters and nuclei. This color
offset implies separate star-formation episodes within the dEs for the clusters
and field stars, while the very blue colors of two dE nuclei trace a third
star-formation event in those dEs less than a Gyr ago.


title: IRAC Colors of Young Stellar Objects

abstract:
  We compare the infrared colors predicted by theoretical models of
protostellar envelopes and protoplanetary disks with initial observations of
young stellar objects made with the Infrared Array Camera (IRAC) on the Spitzer
Space Telescope (Werner et al. 2004, Fazio et al. 2004). Disk and envelope
models characterized by infall and/or accretion rates found in previous studies
can quantitatively account for the range of IRAC colors found in four young
embedded clusters: S 140, S 171, NGC 7129, and Cep C. The IRAC color-color
diagram ([3.6]-[4.5] vs. [5.8]-[8.0]) can be used to help to distinguish
between young stars with only disk emission and protostars with circumstellar
envelopes.


title:
Cross-correlation of CMB with large-scale structure: weak gravitational
  lensing

abstract:
  We present the results of a search for gravitational lensing of the cosmic
microwave background (CMB) in cross-correlation with the projected density of
luminous red galaxies (LRGs). The CMB lensing reconstruction is performed using
the first year of Wilkinson Microwave Anisotropy Probe (WMAP) data, and the
galaxy maps are obtained using the Sloan Digital Sky Survey (SDSS) imaging
data. We find no detection of lensing; our constraint on the galaxy bias
derived from the galaxy-convergence cross-spectrum is $b_g=1.81\pm 1.92$
($1\sigma$, statistical), as compared to the expected result of $b_g\sim 1.8$
for this sample. We discuss possible instrument-related systematic errors and
show that the Galactic foregrounds are not important. We do not find any
evidence for point source or thermal Sunyaev-Zel'dovich effect contamination.


title: Tidal Acceleration of Ultrarelativistic Particles

abstract:
  We investigate the motion of free relativistic particles relative to the
ambient medium around a gravitationally collapsed system. If the relative speed
exceeds a critical value given by c/sqrt(2), the gravitational tidal effects
exhibit novel features that are contrary to Newtonian expectations. In
particular, ultrarelativistic jet clumps moving freely outward along the
rotation axis strongly decelerate with respect to the ambient medium, while
ultrarelativistic particles strongly accelerate in directions normal to the jet
axis. The implications of these direct consequences of general relativity for
jets in microquasars and the origin of the high-energy cosmic rays are briefly
mentioned.


title: IRAC Imaging of Lockman Hole

abstract:
  IRAC imaging of a 4'7x4'7 area in the Lockman Hole detected over 400 galaxies
in the IRAC 3.6 micron and 4.5 micron bands, 120 in the 5.8 micron, and 80 in
the 8 micron bandin 30 minutes of observing time. Color-color diagrams suggest
that about half of these galaxies are at redshifts 0.6<z<1.3 with about a
quarter at higher redshifts (z>1.3). We also detect IRAC counterparts for 6 of
the 7 SCUBA sources and all 9 XMM sources in this area. The detection of the
counterparts of the SCUBA sources and galaxies at z>1.3 demonstrates the
ability of IRAC to probe the universe at very high redshifts.


title: The HI Content of Compact Groups of Galaxies

abstract:
  The HI content of Hickson Compact Groups in the southern hemisphere is
measured using data from the HI Parkes All Sky Survey (HIPASS), and dedicated
observations using the narrowband filter on the Multibeam instrument on the
Parkes telescope. The expected HI mass of these groups was estimated using the
luminosity, diameter and morphological types of the member galaxies, calibrated
from published data. Taking careful account of non-detection limits, the
results show that the compact group population that has been detected by these
observations has an HI content similar to that of galaxies in the reference
field sample. The upper limits for the undetected groups lie within the normal
range; improvement of these limits will require a large increase in
sensitivity.


title: Initial Results from The Spitzer Young Stellar Cluster Survey

abstract:
  We report initial results from IRAC observations of four young stellar
clusters. These regions are part of a larger Spitzer survey of 31 young stellar
groups and clusters within 1 kpc of the Sun. In each of the four clusters,
there are between 39 and 85 objects with colors inconsistent with reddened
stellar photospheres. We identify these objects as young stars with significant
emission from circumstellar dust. Applying an analysis developed in a companion
paper (Allen et al. 2004), we classify these objects as either pre-main
sequence stars with disks (class II) or protostellar objects (class I). These
show that the sites of recent star formation are distributed over multi-parsec
size scales. In two clusters, Cepheus C and S140, we find protostars embedded
in filamentary dark clouds seen against diffuse emission in the IRAC bands.


title: TreePM Method for Two-Dimensional Cosmological Simulations

abstract:
  We describe the two-dimensional TreePM method in this paper. The 2d TreePM
code is an accurate and efficient technique to carry out large two-dimensional
N-body simulations in cosmology. This hybrid code combines the 2d Barnes and
Hut Tree method and the 2d Particle-Mesh method. We describe the splitting of
force between the PM and the Tree parts. We also estimate error in force for a
realistic configuration. Finally, we discuss some tests of the code.


title: ESO215-G?009: An Extreme HI-Rich Dwarf Irregular Galaxy

abstract:
  We present deep BVRI band images and HI line observations of the nearby, low
surface brightness galaxy ESO215-G?009 which were obtained with the ANU 2.3-m
Telescope and the Australia Telescope Compact Array, respectively. ESO215-G?009
was selected from the HIPASS Bright Galaxy Catalog because it has the second
highest HI mass-to-light ratio of the galaxies with measured B band apparent
magnitudes. We find that it is an isolated dwarf irregular galaxy with an old
stellar population. We place an upper limit on the current star formation rate
of ~2.5 x 10^-3 M_sun/yr. The extended HI disk shows regular rotation (v_rot =
51 +/- 8 km/s), and at a column density of ~5.0 x 10^19 atoms/cm^2 can be
traced out to over six times the Holmberg radius of the stellar component
(radius at mu_B = 26.6 mag/arcsec^2). After foreground star subtraction, we
measure a B band apparent magnitude of 16.13 +/- 0.07 mag within a radius of
80". The HI flux density is 122 +/- 4 Jy km/s within a radius of 370". Given a
Galactic extinction of A_B = 0.95 +/- 0.15 mag, we derive an HI mass-to-light
ratio of 22 +/- 4 M_sun/L_sun for ESO215-G?009. To our knowledge this is the
highest ratio for a galaxy to be confirmed by accurate measurement to date.


title: Observations of Cold Dust in Nearby Elliptical Galaxies

abstract:
  Spectral energy distribution (SED) analyses, that include new millimeter (mm)
to far-infrared (FIR) observations, obtained with continuum instruments on the
Nobeyama and James Clerk Maxwell Telescopes and Infrared Space Observatory
(ISO), are presented for seven, nearby (< 45Mpc) FIR-bright elliptical
galaxies. These are analyzed together with archival FIR and short-wave radio
data obtained from the NASA/IPAC Extragalactic Database (NED). The radio to
infrared SEDs are best fit by power-law plus greybody models of dust residing
in the central galactic regions within 2.4kpc diameter and with temperatures
between about 21 and 28K, emissivity index approximately 2, and masses from
about 0.16 to 1.9 million solar masses. The emissivity index is consistent with
dust constituting amorphous silicate and carbonaceous grains previously modeled
for stellar-heated dust observed in the Galaxy and other nearby extragalactic
sources. Using updated dust absorption coefficients for this type of dust, dust
masses are estimated that are similar to those determined from earlier FIR data
alone, even though the latter results implied hotter dust temperatures. Fluxes
and masses that are consistent with the new FIR and submm data are estimated
for dust cooler than 20K within the central galactic regions. Tighter physical
constraints for such cold, diffuse dust (if it exists) with low surface
brightness, will need sensitive FIR-submm observations with the Spitzer Space
Telescope, SCUBA2, or ALMA.


title: The unfriendly ISM in the radio galaxy 4C12.50 (PKS 1345+12)

abstract:
  The radio source 4C12.50 has often been suggested to be a prime candidate for
the link between ultraluminous infrared galaxies and young radio galaxies. A
VLBI study of the neutral hydrogen in the nuclear regions of this object shows
that most of the gas detected close to the systemic velocity is associated with
an off-nuclear cloud (~50 to 100 pc from the radio core) with a column density
of ~10^22 T_spin/100 K) cm^(-2) and an HI mass of a few times 10^5 to 10^6
M_sun. We consider a number of possibilities to explain the results. In
particular, we discus the possibility that this cloud indicates the presence of
a rich and clumpy interstellar medium in the centre, likely left over from the
merger that triggered the activity and that this medium influences the growth
of the radio source. The location of the cloud -- at the edge of the northern
radio jet/lobe -- suggests that the radio jet might be interacting with a gas
cloud. This interaction could be responsible for bending the young radio jet.
The velocity profile of the gas is relatively broad (~150$ km/s) and we
interpret this as kinematical evidence for interaction of the radio plasma with
the cloud. We also consider the model where the cloud is part of a broader
circumnuclear structure. Only a limited region of this structure would have
sufficient background radio brightness and large enough column depth in neutral
gas to obtain detectable HI absorption against the counterjet. The VLBI study
of the neutral hydrogen in 4C12.50 suggests that HI detected near the systemic
velocity (as it is often the case in radio galaxies) may not necessarily be
connected with a circumnuclear disk or torus (as is very often assumed) but
instead could be a tracer of the large-scale medium that surrounds the active
nucleus and that may influence the growth of the young radio source.


title: A Tale of Two Distances

abstract:
  There are two basic ways to measure physical distances in cosmology: One
based on standard candles and one based on standard rulers. Comparing current
data for each method allows us to rule out axion-photon mixing and
dust-extinction as the sources of supernova dimming and generally protects the
case for cosmic acceleration from attacks based on loss of photons. The
combined data constrains the energy densities in a LCDM model to 0.19 < Omega_m
< 0.32 and 0.47 < Omega_Lambda < 0.82 (at 2\sigma) without recourse to any
further data sets. Future data will improve on these limits and allow us to
place constraints on more exotic physics.


title:
Mapping stationary axisymmetric phase-space distribution functions by
  orbit libraries

abstract:
  This is the first of a series of papers dedicated to unveil the mass
composition and dynamical structure of a sample of flattened early type
galaxies in the Coma cluster. We describe our modifications to the
Schwarzschild code of Richstone et al. (in preparation). Applying a Voronoi
tessellation in the surface of section we are able to assign accurate
phase-space volumes to individual orbits and to reconstruct the full
three-integral phase-space distribution function (DF) of any axisymmetric orbit
library. Two types of tests have been performed to check the accuracy with
which DFs can be represented by appropriate orbit libraries. First, by mapping
DFs of spherical gamma-models and flattened Plummer models on to the library we
show that the resulting line-of-sight velocity distributions and internal
velocity moments of the library match those directly derived from the DF to a
precision better than that of present day observational errors. Second, by
fitting libraries to the projected kinematics of the same DFs we show that the
distribution function reconstructed from the fitted library matches the input
DF to a rms of about 15 per cent over a region in phase-space covering 90 per
cent of the mass of the library. The achieved accuracy allows us to implement
effective entropy-based regularisation to fit real, noisy and spatially
incomplete data.


title: XMM-Newton Observations of the Be/X-ray transient A0538-66 in quiescence

abstract:
  We present XMM-Newton observations of the recurrent Be/X-ray transient
A0538-66, situated in the Large Magellanic Cloud, in the quiescent state.
Despite a very low luminosity state of (5-8)E33 ergs/s in the range 0.3-10 keV,
the source is clearly detected up to ~8 keV. and can be fitted using either a
power law with photon index alpha=1.9+-0.3 or a bremsstrahlung spectrum with
kT=3.9+3.9-1.7 keV. The spectral analysis confirms that the off-state spectrum
is hard without requiring any soft component, contrary to the majority of
neutron stars observed in quiescence up to now.


title: PAHs contribution to the infrared output energy of the Universe at z~2

abstract:
  We present an updated phenomenological galaxy evolution model to fit the
Spitzer 24, 70 and 160 microns number counts as well as all the previous mid
and far infrared observations. Only a minor change of the co-moving luminosity
density distribution in the previous model (Lagache, Dole, Puget 2003),
combined with a slight modification of the starburst template spectra mainly
between 12 and 30 microns, are required to fit all the data available. We show
that the peak in the MIPS 24 micron counts is dominated by galaxies with
redshift between 1 and 2, with a non negligible contribution from the z>2
galaxies (~30% at S=0.2 mJy). The very close agreement between the model and
number counts at 15 and 24 microns strikingly implies that (1) the PAHs
(Policyclic Aromatic Hydrocarbons) features remain prominent in the redshift
band 0.5 to 2.5 and (2) the IR energy output has to be dominated by ~3 10^11 Lo
to ~3 10^12 Lo galaxies from redshift 0.5 to 2.5. Combining Spitzer with the
Infrared Space Observatory (ISO) deep cosmological surveys gives for the first
time an unbiased view of the infrared Universe from z=0 to z=2.5.


title: The extended star formation history of omega Centauri

abstract:
  For the first time, the abundances of a large sample of subgiant and turn-off
region stars in omega Centauri have been measured, the data base being medium
resolution spectroscopy from FORS2 at the VLT. Absolute iron abundances were
derived for about 400 member stars from newly defined line indices with an
accuracy of +/-0.15 dex. The abundances range between -2.2<[Fe/H]<-0.7 dex,
resembling the large metallicity spread found for red giant branch stars. The
combination of the spectroscopic results with the location of the stars in the
colour magnitude diagram has been used to estimate ages for the individual
stars. Whereas most of the metal-poor stars are consistent with a single old
stellar population, stars with abundances higher than [Fe/H]=-1.3 dex are
younger. The total age spread in omega Cent is about 3 Gyr. The monotonically
increasing age-metallicity relation seems to level off above [Fe/H]=-1.0 dex.
Whether the star formation in omega Cen occured continuously or rather
episodically has to be shown by combining more accurate abundances with highest
quality photometry.


title: Dark Energy in Chains

abstract:
  Dark energy affects the CMB through its perturbations and affects both CMB
and Sn-Ia through its background evolution. Using recent CMB and Sn-Ia data
sets, together with the most general parameterization of the dark energy
equation of state available, we find that today w < -0.8 (2 sigma). We also
find that the value of the normalization of the power spectrum on cluster
scales, sigma8, can be used to discriminate between dynamical models of dark
energy (Quintessence models) and a cosmological constant model (Lambda CDM).


title:
High Energy Large Area Surveys: optically obscured AGN and the history
  of accretion

abstract:
  Hard X-ray, large area surveys are a fundamental complement of ultra-deep,
pencil beam surveys in obtaining a more complete coverage of the L-z plane,
allowing to find luminous QSO in wide z ranges. Furthermore, results from these
surveys can be used to make reliable predictions about the luminosity (and
hence the redshift) of the sources in the deep surveys which have optical
counterparts too faint to be observed with the present generation of optical
telescopes. This allows us to obtain accurate luminosity functions on wide
luminosity and redshift intervals.


title:
Submillimeter Array multiline observations of the massive star-forming
  region IRAS 18089-1732

abstract:
  Submillimeter Array (SMA) observations of the high-mass star-forming region
IRAS 18089-1732 in the 1 mm and 850 $\mu$m band with 1 GHz bandwidth reveal a
wealth of information. We present the observations of 34 lines from 16
different molecular species. Most molecular line maps show significant
contributions from the outflow, and only few molecules are confined to the
inner core. We present and discuss the molecular line observations and outline
the unique capabilities of the SMA for future imaging line surveys at high
spatial resolution.


title: Far Infrared Source Counts at 70 and 160 microns in Spitzer Deep Surveys

abstract:
  We derive galaxy source counts at 70 and 160 microns using the Multiband
Imaging Photometer for Spitzer (MIPS) to map the Chandra Deep Field South
(CDFS) and other fields. At 70 microns, our observations extend upwards about 2
orders of magnitude in flux density from a threshold of 15 mJy, and at 160
microns they extend about an order of magnitude upward from 50 mJy. The counts
are consistent with previous observations on the bright end. Significant
evolution is detected at the faint end of the counts in both bands, by factors
of 2-3 over no-evolution models. This evolution agrees well with models that
indicate most ofthe faint galaxies lie at redshifts between 0.7 and 0.9. The
new Spitzer data already resolve about 23% of the Cosmic Far Infrared
Background at 70 microns and about 7% at 160 microns.


title: Confusion in the infrared: Spitzer and beyond

abstract:
  We use the source counts measured with the Multiband Imaging Photometer for
Spitzer (MIPS) at 24, 70, and 160 microns to determine the 5-sigma confusion
limits due to extragalactic sources: 56 micro-Jy, 3.2 and 40 mJy at 24, 70 and
160 microns, respectively. We also make predictions for confusion limits for a
number of proposed far infrared missions of larger aperture (3.5 to 10m
diameter).


title:
Nature of two massive protostellar candidates: IRAs 21307+5049 and IRAS
  22172+5549

abstract:
  We present observations of continuum and molecular lines towards the
protostar candidates IRAS 21307+5049 and IRAS 22172+5549. Single-dish maps in
the 12CO(2--1), C18O(2--1), HCO+(1--0) lines and sub-mm continuum are compared
with interferometric maps in the 12CO(1--0) line and 3 mm continuum, and with
mid- and near-infrared images. A plausible interpretation of our data based on
the continuum maps and spectral energy distributions is that two components are
present: a compact molecular core, responsible for the continuum emission at
wavelengths longer than ~25 \mum, and a cluster of stars located close to the
center of the core, but not spatially coincident with it, responsible for the
emission at shorter wavelengths. The core is approximately located at the
center of the associated molecular outflow, detected for both sources in the
12CO(1--0) and (2--1) lines. The cores have masses of ~50 M_{\odot}, and
luminosities of ~10^{3} L_{\odot}. The outflows parameters are consistent with
those typically found in high-mass young stellar objects. Our results support
the hypothesis that in these sources the luminosity is dominated by accretion
rather than by nuclear burning. We conclude that the sources embedded inside
the cores are likely protostars with mass ~5-8 M_{\odot}.


title:
Internal kinematics of spiral galaxies in distant clusters. Part II.
  Observations and data analysis

abstract:
  We have conducted an observing campaign with FORS at the ESO-VLT to explore
the kinematical properties of spiral galaxies in distant galaxy clusters. Our
main goal is to analyse transformation- and interaction processes of disk
galaxies within the special environment of clusters as compared to the
hierarchical evolution of galaxies in the field. Spatially resolved MOS-spectra
have been obtained for seven galaxy clusters at 0.3<z<0.6 to measure rotation
velocities of cluster members. For three of the clusters, Cl0303+17, Cl0413-65,
and MS1008-12, for which we presented results including a TF-diagram in Ziegler
et al. 2003, we describe here in detail the observations and data analysis.
Each of them was observed with two setups of the standard FORS MOS-unit.With
typical exposure times of >2 hours we reach an S/N>5 in the emission lines
appropriate for the deduction of the galaxies' internal rotation velocities
from [OII], Hbeta, or [OIII] profiles. Preselection of targets was done on the
basis of available redshifts as well as from photometric and morphological
information gathered from own observations, archive data, and from the
literature. Emphasis was laid on the definition of suitable setups to avoid the
typical restrictions of the standard MOS unit for this kind of observations. In
total we assembled spectra of 116 objects of which 50 turned out to be cluster
members. Position velocity diagrams, finding charts as well as tables with
photometric, spectral, and structural parameters of individual galaxies are
presented.


title: A Study of Prompt Emission Mechanisms in Gamma-Ray Bursts

abstract:
  The principal paradigm for the prompt emission of gamma-ray bursts invokes
diffusive acceleration at shocks internal to the dynamic ultrarelativistic
outflow. This paper explores expectations for burst emission spectra arising
from shock acceleration theory in the limit of particles cooling much slower
than their acceleration. Parametric fits to burst spectra obtained by the
Compton Gamma-Ray Observatory (CGRO) are explored for the cases of the
synchrotron, inverse Compton and synchrotron self-Compton radiation mechanisms,
using a linear combination of thermal and non-thermal electron populations.
These fits demand that the preponderance of electrons that are responsible for
the prompt emission reside in an intrinsically non-thermal population, strongly
contrasting particle distributions obtained from acceleration simulations. This
implies a potential conflict for acceleration scenarios where the non-thermal
electrons are drawn directly from a thermal gas. It is also found that the CGRO
data preclude effective spectroscopic discrimination between the synchrotron
and inverse Compton mechanisms. This situation may be resolved with future
missions probing gamma-ray bursts, namely Swift and GLAST. However, the
synchrotron self-Compton (SSC) spectrum is characteristically too broad near
the $\nu F_{\nu}$ peak to viably account for bursts such as GRB 910601, GRB
910814 and GRB 990123. It is concluded that the SSC mechanism may be generally
incompatible with differential burst spectra steeper than around $E^{-2.5}$
above the peak, unless the synchrotron component is strongly self-absorbed.


title:
Primordial non-Gaussianity: local curvature method and statistical
  significance of constraints on f_NL from WMAP data

abstract:
  We test the consistency of estimates of the non-linear coupling constant
f_{NL} using non-Gaussian CMB maps generated by the method described in
(Liguori, Matarrese and Moscardini 2003). This procedure to obtain non-Gaussian
maps differs significantly from the method used in previous works on estimation
of f_{NL}. Nevertheless, using spherical wavelets, we find results in very good
agreement with (Mukherjee and Wang 2004), showing that the two ways of
generating primordial non-Gaussian maps give equivalent results. Moreover, we
introduce a new method for estimating the non-linear coupling constant from CMB
observations by using the local curvature of the temperature fluctuation field.
We present both Bayesian credible regions (assuming a flat prior) and proper
(frequentist) confidence intervals on f_{NL}, and discuss the relation between
the two approaches. The Bayesian approach tends to yield lower error bars than
the frequentist approach, suggesting that a careful analysis of the different
interpretations is needed. Using this method, we estimate
f_{NL}=-10^{+270}_{-260} at the 2\sigma level (Bayesian) and
f_{NL}=-10^{+310}_{-270} (frequentist). Moreover, we find that the wavelet and
the local curvature approaches, which provide similar error bars, yield
approximately uncorrelated estimates of f_{NL} and therefore, as advocated in
(Cabella et al. 2004), the estimates may be combined to reduce the error bars.
In this way, we obtain f_{NL}=-5\pm 85 and f_{NL}=-5\pm 175 at the 1\sigma and
2\sigma level respectively using the frequentist approach.


title:
Analysis of Two Scenarios for the Early Optical Emission of the GRB
  Afterglows 990123 and 021211

abstract:
  The optical light-curves of GRB afterglows 990123 and 021211 exhibit a steep
decay at 100--600 seconds after the burst, the decay becoming slower after
about 10 minutes. We investigate two scenarios for the fast decaying early
optical emission of these GRB afterglows. In the reverse-forward shock
scenario, this emission arises in the reverse shock crossing the GRB ejecta,
the mitigation of the light-curve decay occurring when the forward shock
emission overtakes that from the reverse shock. Both a homogeneous and
wind-like circumburst medium are considered. In the wind-bubble scenario, the
steeply decaying, early optical emission arises from the forward shock
interacting with a 1/r^2 bubble, with a negligible contribution from the
reverse shock, the slower decay starting when the blast wave reaches the bubble
termination shock and enters a homogeneous region of the circumburst medium.
  We determine the shock microphysical parameters, ejecta kinetic energy, and
circumburst density which accommodate the radio and optical measurements of the
GRB afterglows 990123 and 021211. We find that, for a homogeneous medium, the
radio and optical emissions of the afterglow 990123 can be accommodated by the
reverse-forward shock scenario if the microphysical parameters behind the two
shocks differ substantially. A wind-like circumburst medium also allows the
reverse-forward shocks scenario to account for the radio and optical properties
of the afterglows 990123 and 021211, but the required wind densities are at
least 10 times smaller than those of Galactic Wolf-Rayet stars. The wind-bubble
scenario requires a variation of the microphysical parameters when the
afterglow fireball reaches the wind termination shock, which seems a contrived
feature.


title: Sub-millimeter detections of Spitzer Space Telescope galaxy populations

abstract:
  We present sub-millimeter statistical detections of galaxies discovered in
the 5'x5' Spitzer Early Release Observations (to 4-15 microJy 5 sigma at 3.6-8
microns, 170 microJy at 24 microns) through a stacking analysis of our
reanalysed SCUBA 8mJy survey maps, and a Spitzer identification of a new
sub-millimeter point source in the 8mJy survey region. For sources detected at
5.8 or 8 microns (154 and 111 sources respectively), we detect positive skews
in the sub-millimeter flux distributions at 99.2-99.8% confidence using
Kolmogorov-Smirnov tests, at both 850 microns and 450 microns. We also
marginally detect the Spitzer 24 micron galaxies at 850 microns at 97%
confidence, and place limits on the mean sub-millimeter fluxes of the 3.6 and
4.5 micron sources. Integrating the sub-millimeter fluxes of the Spitzer
populations, we find the 5.8 micron galaxies contribute 0.12 +/- 0.05 nW/m^2/sr
to the 850 micron background, and 2.4 +/- 0.7 nW/m^2/sr to the 450 micron
background; similar contributions are made by the 8 micron-selected sample. We
infer that the populations dominating the 5.8 and 8 micron extragalactic
background light also contribute around a quarter of the 850 micron background
and the majority of the 450 micron background.


title: 24 micron Properties of X-ray Selected AGN

abstract:
  We examine the 24 micron to X-ray color of 157 X-ray--selected AGN as a
function of X-ray obscuration and optical classification in the Chandra Deep
Field South. The sample consists of the Chandra hard--band detections with hard
flux >10^-15 erg/s/cm^2. A deep 24 micron mosaic obtained with Spitzer provides
mid--infrared fluxes for the sample. Since obscured AGN locally have higher 24
micron / 2-8 keV ratios than unobscured AGN, and since X-ray background models
predict a large population of obscured AGN, we expect to find many X-ray--hard,
IR--bright AGN. Instead, we find that the 24 micron to X-ray flux ratio does
not depend on X-ray hardness in the full sample, nor does it differ between
narrow--line and broad--line AGN. We identify 5 nearly Compton--thick AGN, and
find they have similar 24 micron to X-ray flux ratios compared to the full
sample. We consider AGN in the narrow redshift spikes at z~0.7; for these AGN,
there is some evidence that the flux ratio increases with X-ray hardness. The
redshift slice also shows an odd trend, which is also prominent in the full
sample: a group of X-ray--hard AGN with very low 24 micron to X-ray flux
ratios.


title:
The Far- and Mid-Infrared/Radio Correlations in the Spitzer
  Extragalactic First Look Survey

abstract:
  Using the SPITZER SPACE TELESCOPE and the VLA, we present the first DIRECT
evidence that the well-known far-infrared/radio correlation is valid to
cosmologically significant redshift. We also confirm, with improved statistics
compared with previous surveys, a similar result for the Mid-IR/radio
correlation. We explore the dependence of monochromatic q_{24} and q_{70} on z.
The results were obtained by matching Spitzer sources at 24 and 70 microns with
VLA 1.4 GHz micro-Jy radio sources obtained for the SPITZER FLS. Spectroscopic
redshifts have been obtained for over 500 matched IR/radio sources using
observations at WIYN, Keck and archival SDSS data extending out to z > 2. We
find that q_{24} shows significantly more dispersion than q_{70}. By comparing
the observed fluxes at 70, 24 and 4.5 microns with a library of SED templates,
we find that the larger dispersion in q_{24} is predictable in terms of
systematic variations in SED shape throughout the population. Although the
models are not able to encompass the full range of observed behavior (both the
presence of either extremely flat or extremely steep IR SEDs), the fitting
parameters were used to `k-correct' the higher-z galaxies which resulted in a
reduced scatter in q. For comparison, we also corrected these data using the
SED for M82. The results for 24 and 70 microns provide strong consistent
evidence for the universality of the mid-IR/radio and far-IR/radio correlations
out to redshifts of at least z = 1.


title: The Missing X-ray Background

abstract:
  The fraction of the hard X-ray background (XRB) resolved into individual
sources by the deep Chandra and XMM-Newton surveys strongly depends on the
adopted energy range and decreases with increasing energy. As a consequence,
the nature of the sources of the even harder (>10 keV) XRB remains
observationally poorly constrained. I will briefly discuss the need for X-ray
observations above 10 keV.


title:
Massive galaxies in cosmological simulations: UV-selected sample at
  redshift z=2

abstract:
  We study the properties of galaxies at z=2 in a Lambda CDM universe, using
two different types of hydrodynamic simulation methods (Eulerian TVD and SPH)
and a spectrophotometric analysis in the Un, G, R filter set. The simulated
galaxies at z=2 satisfy the color-selection criteria proposed by Adelberger et
al. (2004) when we assume Calzetti extinction with E(B-V)=0.15. We find that
the number density of simulated galaxies brighter than R<25.5 at z=2 is about
2e-2 h^3/Mpc^3, roughly one order of magnitude larger than that of Lyman break
galaxies at z=3. The most massive galaxies at z=2 have stellar masses >~1e11
Msun, and their observed-frame G-R colors lie in the range 0.0<G-R<1.0. They
typically have been continuously forming stars with a rate exceeding 30 Msun/yr
over a few Gyrs from z=10 to z=2, although the TVD simulation indicates a more
sporadic star formation history than the SPH simulations. Of order half of
their stellar mass was already assembled by z~4. The reddest massive galaxies
at z=2 with G-R >= 1.0 and Mstar>1e10 Msun/h finished the build-up of their
stellar mass by z~3. Interestingly, our study suggests that the majority of the
most massive galaxies at z=2 should be detectable at rest-frame UV wavelengths,
contrary to some recent claims made on the basis of near-IR studies of galaxies
at the same epoch, provided the median extinction is less than E(B-V)<0.3.
However, our results also suggest that the fraction of stellar mass contained
in galaxies that pass the color-selection criteria could be as low as 50% of
the total stellar mass in the Universe at z=2. Our simulations suggest that the
missing stellar mass is contained in fainter (R>25.5) and intrinsically redder
galaxies. Our results do not suggest that hierarchical galaxy formation fails
to account for the massive galaxies at z>=1. (abridged)


title: The z>4 Quasar Population Observed by Chandra and XMM-Newton

abstract:
  The current status of our Chandra and XMM-Newton project on high-redshift
(z>4) quasars is briefly reviewed. We report the main results obtained in the
last few years for the detected quasars, along with a few (~10%) intriguing
cases where no detection has been obtained with Chandra snapshot observations.


title: Dark Matter Subhaloes in Numerical Simulations

abstract:
  We use cosmological LCDM numerical simulations to model the evolution of the
substructure population in sixteen dark matter haloes with resolutions of up to
seven million particles within the virial radius. The combined substructure
circular velocity distribution function (VDF) for hosts of 10^11 to 10^14 Msun
at redshifts from zero to two or higher has a self-similar shape, is
independent of host halo mass and redshift, and follows the relation:
dn/dv=(1/8)(v_cmax/v_cmax,host)^-4. Halo to halo variance in the VDF is a
factor of roughly two to four. At high redshifts, we find preliminary evidence
for fewer large substructure haloes (subhaloes). Specific angular momenta are
significantly lower for subhaloes nearer the host halo centre where tidal
stripping is more effective. The radial distribution of subhaloes is marginally
consistent with the mass profile for r >~ 0.3r_vir, where the possibility of
artificial numerical disruption of subhaloes can be most reliably excluded by
our convergence study, although a subhalo distribution that is shallower than
the mass profile is favoured. Subhalo masses but not circular velocities
decrease toward the host centre. Subhalo velocity dispersions hint at a
positive velocity bias at small radii. There is a weak bias toward more
circular orbits at lower redshift, especially at small radii. We additionally
model a cluster in several power law cosmologies of P ~ k^n, and demonstrate
that a steeper spectral index, n, results in significantly less substructure.


title: The 24 Micron Source Counts in Deep Spitzer Surveys

abstract:
  Galaxy source counts in the infrared provide strong constraints on the
evolution of the bolometric energy output from distant galaxy populations. We
present the results from deep 24 micron imaging from Spitzer surveys, which
include approximately 50,000 sources to an 80% completeness of 60 uJy. The 24
micron counts rapidly rise at near-Euclidean rates down to 5 mJy, increase with
a super-Euclidean rate between 0.4 - 4 mJy, and converge below 0.3 mJy. The 24
micron counts exceed expectations from non-evolving models by a factor >10 at
0.1 mJy. The peak in the differential number counts corresponds to a population
of faint sources that is not expected from predictions based on 15 micron
counts from ISO. We argue that this implies the existence of a previously
undetected population of infrared-luminous galaxies at z ~ 1-3. Integrating the
counts to 60 uJy, we derive a lower limit on the 24 micron background intensity
of 1.9 +/- 0.6 nW m-2 sr-1 of which the majority (~ 60%) stems from sources
fainter than 0.4 mJy. Extrapolating to fainter flux densities, sources below 60
uJy contribute 0.8 {+0.9/-0.4} nW m-2 sr-1 to the background, which provides an
estimate of the total 24 micron background of 2.7 {+1.1/-0.7} nW m-2 sr-1.