title: Galactic Collapsed Objects

abstract:
  Our Galaxy contains some 10^8 to 10^9 collapsed objects (neutron stars and
black holes). Our knowledge of them is based on less than 2000 objects
identified as radio pulsars, members of X-ray binaries and magnetars. In this
review I shall briefly discuss some of their properties such as masses,
magnetic fields and rotation.


title: The stability of decelerating shocks revisited

abstract:
  We present a new method for analyzing the global stability of the Sedov-von
Neumann-Taylor self-similar solutions, describing the asymptotic behavior of
spherical decelerating shock waves, expanding into ideal gas with density
\propto r^{-\omega}. Our method allows to overcome the difficulties associated
with the non-physical divergences of the solutions at the origin. We show that
while the growth rates of global modes derived by previous analyses are
accurate in the large wave number (small wavelength) limit, they do not
correctly describe the small wave number behavior for small values of the
adiabatic index \gamma. Our method furthermore allows to analyze the stability
properties of the flow at early times, when the flow deviates significantly
from the asymptotic self-similar behavior. We find that at this stage the
perturbation growth rates are larger than those obtained for unstable
asymptotic solutions at similar [\gamma,\omega]. Our results reduce the
discrepancy that exists between theoretical predictions and experimental
results.


title:
Modeling star formation in dwarf spheroidal galaxies: a case for
  extended dark matter halos

abstract:
  We propose a simple model for the formation of dwarf spheroidal galaxies, in
which stars are assumed to have formed from isothermal gas in hydrostatic
equilibrium inside extended dark matter halos. After expelling the leftover
gas, the stellar system undergoes a dynamical relaxation inside the dark matter
halo. These models can adequately describe the observed properties of three
(Draco, Sculptor, and Carina) out of four Galactic dwarf spheroidal satellites
studied in this paper. We suggest that the fourth galaxy (Fornax), which cannot
be fitted well with our model, is observed all the way to its tidal radius. Our
best fitting models have virial masses of ~10^9 M_Sun, halo formation redshifts
consistent with the age of oldest stars in these dwarfs, and shallow inner dark
matter density profiles (with slope gamma -0.5...0). The inferred temperature
of gas is ~10^4 K. In our model, the "extratidal" stars observed in the
vicinity of some dwarf spheroidal galaxies are gravitationally bound to the
galaxies and are a part of the extended stellar halos. The inferred virial
masses make Galactic dwarf spheroidals massive enough to alleviate the "missing
satellites" problem of LCDM cosmologies.


title:
Radial and vertical epicyclic frequencies of Keplerian motion in the
  field of Kerr naked singularities - comparison with the black hole case and
  possible instability of naked singularity accretion discs

abstract:
  Relativistic Keplerian orbital frequency and related epicyclic frequencies
play an important role in physics of accretion discs orbiting Kerr black holes
and can by resonant or trapping effects explain quasiperiodic oscillations
observed in microquasars. Because of growing theoretical evidence on possible
existence of naked singularities, we discuss behaviour of the fundamenal
orbital frequencies for Keplerian motion in the field of Kerr naked
singularities, primarily in order to find phenomena that could observationally
distinguish a hypothetical naked singularity from black holes. Some
astrophysically important consequences are sketched, namely the existence of
strong resonant frequency for all Kerr naked singularities, with radial and
vertical epicyclic frequencies being equal at well defined radius.


title:
Iron K Features in the Quasar E 1821+643: Evidence for Gravitationally
  Redshifted Absorption?

abstract:
  We report a Chandra high-energy grating detection of a narrow, redshifted
absorption line superimposed on the red wing of a broad Fe K line in the
$z=0.297$ quasar E1821+643. The absorption line is detected at a confidence
level, estimated by two different methods, in the range ~2-3 sigma. Although
the detection significance is not high enough to exclude a non-astrophysical
origin, accounting for the absorption feature when modeling the X-ray spectrum
implies that the Fe-K emission line is broad, and consistent with an origin in
a relativistic accretion disk. Ignoring the apparent absorption feature leads
to the conclusion that the Fe-K emission line is narrower, and also affects the
inferred peak energy of the line (and hence the inferred ionization state of
Fe). If the absorption line (at ~6.2 keV in the quasar frame) is real, we argue
that it could be due to gravitationally redshifted Fe XXV or Fe XXVI resonance
absorption within ~10-20 gravitational radii of the putative central black
hole. The absorption line is not detected in earlier low-energy grating
observations, but is not unequivocally ruled out by these data. The Chandra
high-energy grating Fe K emission line is consistent with an origin
predominantly in Fe I-XVII or so. In a previous LEG observation the line was
double-peaked, at ~6.4 keV and ~6.9 keV (H-like Fe). Such a wide range in
ionization state of Fe is not ruled out by the HEG data and an earlier ASCA
observation, and is suggestive of a complex structure for the line-emitter.


title:
SINFONI in the Galactic Center: young stars and IR flares in the central
  light month

abstract:
  We report 75 milli-arcsec resolution, near-IR imaging spectroscopy within the
central 30 light days of the Galactic Center [...]. To a limiting magnitude of
K~16, 9 of 10 stars in the central 0.4 arcsec, and 13 of 17 stars out to 0.7
arcsec from the central black hole have spectral properties of B0-B9, main
sequence stars. [...] all brighter early type stars have normal rotation
velocities, similar to solar neighborhood stars. We [...] derive improved 3d
stellar orbits for six of these S-stars in the central 0.5 arcsec. Their
orientations in space appear random. Their orbital planes are not co-aligned
with those of the two disks of massive young stars 1-10 arcsec from SgrA*. We
can thus exclude [...] that the S-stars as a group inhabit the inner regions of
these disks. They also cannot have been located/formed in these disks [...].
[...] we conclude that the S-stars were most likely brought into the central
light month by strong individual scattering events. The updated estimate of
distance to the Galactic center from the S2 orbit fit is Ro = 7.62 +/- 0.32
kpc, resulting in a central mass value of 3.61 +/- 0.32 x 10^6 Msun. We
happened to catch two smaller flaring events from SgrA* [...]. The 1.7-2.45 mum
spectral energy distributions of these flares are fit by a featureless, red
power law [...]. The observed spectral slope is in good agreement with
synchrotron models in which the infrared emission comes from [...] radiative
inefficient accretion flow in the central R~10 Rs region.


title:
Quiescent Cores and the Efficiency of Turbulence-Accelerated,
  Magnetically Regulated Star Formation

abstract:
  The efficiency of star formation, defined as the ratio of the stellar to
total (gas and stellar) mass, is observed to vary from a few percent in regions
of dispersed star formation to about a third in cluster-forming cores. This
difference may reflect the relative importance of magnetic fields and
turbulence in controlling star formation. We investigate the interplay between
supersonic turbulence and magnetic fields using numerical simulations, in a
sheet-like geometry. We demonstrate that star formation with an efficiency of a
few percent can occur over several gravitational collapse times in moderately
magnetically subcritical clouds that are supersonically turbulent. The
turbulence accelerates star formation by reducing the time for dense core
formation. The dense cores produced are predominantly quiescent, with subsonic
internal motions. These cores tend to be moderately supercritical. They have
lifetimes long compared with their local gravitational collapse time. Some of
the cores collapse to form stars, while others disperse away without star
formation. In turbulent clouds that are marginally magnetically supercritical,
the star formation efficiency is higher, but can still be consistent with the
values inferred for nearby embedded clusters. If not regulated by magnetic
fields at all, star formation in a multi-Jeans mass cloud endowed with a strong
initial turbulence proceeds rapidly, with the majority of cloud mass converted
into stars in a gravitational collapse time. The efficiency is formally higher
than the values inferred for nearby cluster-forming cores, indicating that
magnetic fields are dynamically important even for cluster formation.


title: AB Aurigae Resolved: Evidence for Spiral Structure

abstract:
  We obtained high angular resolution (~2") images of the 13CO(J=1-0) line and
2.7 millimeter continuum emission, and slightly lower resolution images of
12CO(J=1-0) and C18O(J=1-0) line emission toward the Herbig Ae star AB Aurigae.
We resolve a circumstellar disk of diameter 780 AU (FWHM) with a velocity
pattern consistent with a purely rotational disk at inclination 21.5 degrees
and position angle 58.6 degrees. Using Keplerian disk models, we find a central
source dynamical mass of 2.8+-0.1 Msun and a cutoff radius of 615 AU for the
13CO emission. Inclination, mass, and radius determined from 12CO and C18O
observations agree with those values, given optical depth and abundance
effects. As a result of the high angular resolution of our observations, we
confirm the existence of spiral structure suggested by near-IR scattered light
images and show that the spiral arms represent density contrasts in the disk.


title:
Galactic modulation of extragalactic cosmic rays: Possible origin of the
  knee in the cosmic ray spectrum

abstract:
  The existence of the spectral break around $\sim 3 \times 10^{15}$ eV in the
cosmic ray spectrum (referred to as the `knee') is one of the biggest questions
in cosmic ray astrophysics. At the same time, the origin of cosmic rays above
the knee energies (between 10$^{15}$ and 10$^{18}$ eV) is also still unsettled.
In this paper, we investigate how the hypothetical extragalactic CRs after
modulated by the galactic wind contribute to the knee in the CR spectrum. We
numerically calculate the modulated energy spectrum of the hypothetical cosmic
rays coming into the galaxy from just outside of the ``galactic sphere'' where
the galactic wind terminates. We show that the observed knee structure is
reproduced well by a superposition of the modulated component and the galactic
cosmic rays originating in supernova remnants.


title:
On the evolution of rapidly rotating massive white dwarfs towards
  supernovae or collapses

abstract:
  A recent study by Yoon & Langer (2004a) indicated that the inner cores of
rapidly accreting (Mdot > 10^{-7} M_sun/yr) CO white dwarfs may rotate
differentially, with a shear rate near the threshold value for the onset of the
dynamical shear instability. Such differentially rotating white dwarfs obtain
critical masses for thermonuclear explosion or electron-capture induced
collapse which significantly exceed the canonical Chandrasekhar limit. Here, we
construct two-dimensional differentially rotating white dwarf models with
rotation laws resembling those of the one-dimensional models of Yoon & Langer
(2004a). We derive analytic relations between the white dwarf mass, its angular
momentum, and its rotational-, gravitational- and binding energy. We show that
these relations are applicable for a wide range of angular velocity profiles,
including solid body rotation. We demonstrate that pre-explosion and
pre-collapse conditions of both, rigidly and differentially rotating white
dwarfs are well established by the present work, which may facilitate future
multi-dimensional simulations of Type Ia supernova explosions and studies of
the formation of millisecond pulsars and gamma-ray bursts from collapsing white
dwarfs.Our results lead us to suggest various possible evolutionary scenarios
for progenitors of Type Ia supernovae, leading to a new paradigm of a variable
mass of exploding white dwarfs, at values well above the classical
Chandrasekhar mass. Based on our 2D-models, we argue for the supernova peak
brightness being proportional to the white dwarf mass, which could explain
various aspects of the diversity of Type Ia supernovae, such as their variation
in brightness, the dependence of their mean luminosity on the host galaxy type,
and the weak correlation between ejecta velocity and peak brightness.


title: Cool Versus Ultracool White Dwarfs

abstract:
  A preliminary $BVRIJHK$ analysis of the white dwarfs SSSPM J2231$-$7514 and
SSSPM J2231$-$7515 is presented. Although both stars were reported to have
$T_{\rm eff}<4000$ K, the analysis here indicates $T_{\rm eff}\approx4250$ K
for both SSSPM J2231$-$7514 and SSSPM J2231$-$7515. Given substantial
scientific interest in the coolest extant degenerate stars, it is necessary to
distinguish sub 4000 K objects from the bulk of cool white dwarfs. This
analysis reiterates the importance of near infrared observations in
constraining the spectral energy distributions and effective temperatures of
the coolest white dwarfs and briefly discusses their possible origins.


title: Numerical Modelling of Dusty Debris Disks

abstract:
  Infrared and submillimetre observations of nearby Vega-like stars have
revealed a number of clumpy, asymmetric dust debris disks. Previous studies
using semi-analytical and numerical methods have suggested planetary companions
of various mass as the likely cause of most examples of disk asymmetry. In this
paper, we modify an N-body symplectic gravitational integrator to include
radiation terms and conduct medium-resolution parameter searches to identify
likely planetary candidates in observed Vega-like systems. We also present high
resolution models of Vega and epsilon Eridani, comparing our results to those
of previous authors, and a new model for Fomalhaut.


title: Primordial Power Spectrum Reconstruction

abstract:
  In order to reconstruct the initial conditions of the universe it is
important to devise a method that can efficiently constrain the shape of the
power spectrum of primordial matter density fluctuations in a model-independent
way from data. In an earlier paper we proposed a method based on the wavelet
expansion of the primordial power spectrum. The advantage of this method is
that the orthogonality and multiresolution properties of wavelet basis
functions enable information regarding the shape of $P_{\rm in}(k)$ to be
encoded in a small number of non-zero coefficients. Any deviation from
scale-invariance can then be easily picked out. Here we apply this method to
simulated data to demonstrate that it can accurately reconstruct an input
$P_{\rm in}(k)$, and present a prescription for how this method should be used
on future data.


title: The dust obscuration bias in Damped Lyman alpha systems

abstract:
  We present a new study of the effects of quasar obscuration on the statistics
of Damped Ly alpha (DLA) systems. We show that the extinction of any Galactic
or extragalactic HI region increases with the column density of zinc with a
turning point above which background sources are suddenly obscured. We derive a
relation between the extinction of a DLA system and its HI column density, N,
metallicity, Z, fraction of iron in dust, f_Fe(Z), and redshift, z. From this
relation we estimate the fraction of DLA systems missed as a consequence of
their own extinction in magnitude-limited surveys. We derive a method for
recovering the true frequency distributions of N and Z in DLAs, f_N and f_Z,
using the biased distributions measured in the redshift range where the
observations have sufficient statistics (1.8 </= z </= 3). By applying our
method we find that the well-known empirical thresholds of DLA column
densities, N(ZnII) </~ 10^13.1 cm^-2 and N(HI) </~ 10^22 cm^-2 can be
successfully explained in terms of the obscuration effect without tuning of the
local dust parameters. The obscuration has a modest effect on the distribution
of quasar apparent magnitudes, but plays an important role in shaping the
statistical distributions of DLAs. The exact estimate of the bias is still
limited by the paucity of the data (~40 zinc measurements at 1.8 </~ z </~ 3).
We find that the fraction of DLAs missed as a consequence of obscuration is
\~30% to 50%, consistent with the results of surveys of radio-selected quasars.
By modelling the metallicity distribution with a Schechter function we find
that the mean metallicity can be ~5 to 6 times higher than the value commonly
reported for DLAs at z~2.3.


title:
Spectrum and amplitudes of internal gravity waves excited by penetrative
  convection in solar-type stars

abstract:
  The excitation of internal gravity waves by penetrative convective plumes is
investigated using 2-D direct simulations of compressible convection. The wave
generation is quantitatively studied from the linear response of the radiative
zone to the plumes penetration, using projections onto the g-modes solutions of
the associated linear eigenvalue problem for the perturbations. This allows an
accurate determination of both the spectrum and amplitudes of the
stochastically excited modes. Using time-frequency diagrams of the mode
amplitudes, we then show that the lifetime of a mode is around twice its period
and that during times of significant excitation up to 40% of the total kinetic
energy may be contained into g-modes.


title: Cosmology and Astrophysics

abstract:
  In these lectures I review the present status of the so-called Standard
Cosmological Model, based on the hot Big Bang Theory and the Inflationary
Paradigm. I will make special emphasis on the recent developments in
observational cosmology, mainly the acceleration of the universe, the precise
measurements of the microwave background anisotropies, and the formation of
structure like galaxies and clusters of galaxies from tiny primodial
fluctuations generated during inflation.


title: Spin-up of the hyperon-softened accreting neutron stars

abstract:
  We study the spin-up of the accreting neutron stars with a realistic
hyperon-softened equation of state. Using precise 2-D calculations we study the
evolutionary tracks of accreting neutron stars in the angular-momentum -
frequency plane. In contrast to the case of spinning-down solitary
radio-pulsars, where a strong back-bending behavior has been observed, we do
not see back-bending phenomenon in the accretion-powered spinning-up case. We
conclude that in the case of accretion-driven spin-up the back-bending is
strongly suppressed by the mass-increase effect accompanying the
angular-momentum increase.


title: Interacting Phantom Energy and Avoidance of the Big Rip Singularity

abstract:
  Models of the universe with arbitrary (non gravitational) interaction between
the components of the cosmic fluid: the phantom energy and the background, are
investigated. A general form of the interaction that is inspired in
scalar-tensor theories of gravity is considered. No specific model for the
phantom fluid is assumed. We concentrate our investigation on solutions that
are free of the coincidence problem. We found a wide region in the parameter
space where the solutions are free of the big rip singularity also. Physical
arguments, together with arguments based on the analysis of the observational
evidence, suggest that phantom models without big rip singularity might be
preferred by Nature.


title: ROMA: a map-making algorithm for polarised CMB data sets

abstract:
  We present ROMA, a parallel code to produce joint optimal temperature and
polarisation maps out of multidetector CMB observations. ROMA is a fast,
accurate and robust implementation of the iterative generalised least squares
approach to map-making. We benchmark ROMA on realistic simulated data from the
last, polarisation sensitive, flight of BOOMERanG.


title: Intermediate-mass Black Hole and stellar orbits in the Galactic Center

abstract:
  Many young stars reside within the central half-parsec from SgrA*, the
supermassive black hole in the Galactic Center. The origin of these stars
remains a puzzle. Recently, Hansen and Milosavljevic (2003, HM) have argued
that an Intermediate-Mass Black Hole (IMBH) could have delivered the young
stars to the immediate vicinity of SgrA*. Here we focus on the final stages of
the HM scenario. Namely, we integrate numerically the orbits of stars which are
initially bound to the IMBH, but are stripped from it by the tidal field of
SgrA*. Our numerical algorithm is a symplectic integrator designed specifically
for the problem at hand; however, we have checked our results with SYMBA, a
version of the widely available SWIFT code. We find that the distribution of
the post-inspiral orbital parameters is sensitive to the eccentricity of the
inspiraling IMBH. If the IMBH is on a circular orbit, then the inclinations of
numerically computed orbits relative to the inspiral plane are almost always
smaller than 10 degrees, and therefore (a) the simulations are in good
agreement with the observed motions of stars in a clockwise-moving stellar
disc, (b) the simulations never reproduce the orbits of stars outside this
disc, which include those in the second thick ring of stars and the randomly
oriented unrelaxed orbits of some of the S-stars. If the IMBH's orbital
eccentricity is e=0.6, then approximately half of the stars end up with orbital
inclinations below 10 degrees, and another half have inclinations anywhere
between 0 and 180 degrees; this is somewhat closer to what's observed. We also
show that if IRS13 cluster is bound by an IMBH, as has been argued by Maillard
et. al. 2004, then the same IMBH could not have delivered all of the young
stars to their present location.


title:
Spitzer Observations of Optically "Invisible" Radio and X-Ray Sources:
  High Redshift AGN

abstract:
  We have combined a survey at 24 microns to 0.3 mJy with the Multiband Imaging
Photometer (MIPS) on the Spitzer Space Telescope, a 20 cm A-array VLA survey
covering 0.5 deg^2, and an existing 172 ks Chandra X-Ray Observatory exposure
to investigate the nature of optically faint radio and X-ray sources in the
NOAO Deep Wide-Field Survey (NDWFS) in Bootes. We find little overlap between
the radio and infrared selected populations: only 9% of the infrared sources
are detected in the radio and only 33% of the radio sources are detected in the
infrared. Thirty-six (10%) of the 377 compact radio sources lack optical
counterparts in the NDWFS Bw, R, & I images. We refer to these objects as
optically invisible radio sources (OIRS). Only four of the thirty-one OIRSs
observed with MIPS are detected at 24 microns. Comparisons of the radio and
infrared properties of the OIRSs with various galaxy spectral energy
distributions demonstrate that most of these sources are powered by AGN rather
than starbursts. Similarly, eleven X-ray sources observed by both MIPS and the
VLA are classified as optically invisible X-ray sources (OIXS). None are
detected at 24 microns or 20 cm. All seven OIXSs detected in Chandra's 0.5-2
keV band have infrared to X-ray flux ratios consistent with their luminosity
being dominated by an unobscured AGN. From these results we conclude that both
the optically invisible radio and X-ray source populations are primarily AGN,
relatively unaffected by dust and most likely at z > 1. No OIRSs are detected
in X-ray emission and no OIXSs are detected at 20 cm. However, given the wide
range in radio and X-ray properties of known AGN and the size of our samples,
this lack of overlap does not necessarily imply AGN source populations.


title:
Feedback from quasars in star-forming galaxies and the triggering of
  massive galactic winds

abstract:
  The shining of quasars is a likely trigger of massive galatic winds, able to
remove most ISM from a star-forming spheroid. However, the mechanism
responsible for the deposition of energy into the ISM is still unclear.
Starting from a model for feedback in galaxy formation with a two-phase medium
(Monaco 2004a), we propose that the perturbation induced by radiative heating
from a quasar on the ISM triggers a critical change of feedback regime. In the
feedback model, SNRs expanding in the hot and pressurized phase of a
star-forming spheroid tipically become pressure-confined before the hot
interior gas is able to cool. Whenever the evaporation flow due to radiative
heating of the quasar is significant with respect to the star-formation rate,
the SNRs reach the point where their interior gas cools before being confined,
forming a thick cold shell. We show that in this conditions the shells
percolate into a super-shell of cold gas that sweeps the whole galaxy.
Radiation pressure then pushes the shell out of the galaxy. This self-limiting
mechanism leads to a correlation between black hole and bulge masses. The
insertion of a motivated wind trigger criterion in a hierarchical galaxy
formation model shows however that winds are not necessary to obtain a good
black hole--bulge correlation. In absence of winds, good results are obtained
if the mechanism responsible for the creation of a reservoir of low-angular
momentum gas (able to accrete onto the black hole) deposits mass at a rate
proportional to the star-formation rate. Using a novel galaxy formation model,
we show under which conditions black hole masses are self-limited by the wind
mechanism described above, and outline the possible observational consequences
of this self-limitation. [Abridged]


title: MHD Simulations of Relic Radio Bubbles in Clusters

abstract:
  In order to better understand the origin and evolution of relic radio bubbles
in clusters of galaxies, we report on an extensive set of 2D MHD simulations of
hot buoyant bubbles evolving in a realistic intracluster medium. Our bubbles
are inflated near the base of the ICM over a finite time interval from a region
whose magnetic field is isolated from the ICM. We confirm both the early
conjecture from linear analysis and the later results based on preformed MHD
bubbles; namely, that very modest ICM magnetic fields can stabilize the rising
bubbles against disruption by Rayleigh-Taylor and Kelvin-Helmholtz
instabilities. We find in addition that amplification of the ambient fields as
they stretch around the bubbles can be sufficient to protect the bubbles or
their initial fragments even if the fields are initially much too weak to play
a significant role early in the evolution of the bubbles. Indeed, even with
initial fields less than a micro-Gauss and values of $\beta = P_g/P_b$
approaching $10^5$, magnetic stresses in our simulations eventually became
large enough to influence the bubble evolution. Magnetic field influence also
depends significantly on the geometry of the ICM field and on the topology of
the field at the bubble/ICM interface. For example, reconnection of
anti-parallel fields across the bubble top greatly reduced the ability of the
magnetic field to inhibit disruptive instabilities. Our results confirm earlier
estimates of $10^8$ yr for relic radio bubble lifetimes and show that magnetic
fields can account for the long term stability of these objects against
disruption by surface instabilities. In addition these calculations show that
lifting and mixing of the ambient ICM may be a critical function of field
geometries in both the ICM and in the bubble interior.


title: An asteroseismic test of diffusion theory in white dwarfs

abstract:
  The helium-atmosphere (DB) white dwarfs are commonly thought to be the
descendants of the hotter PG1159 stars, which initially have uniform He/C/O
atmospheres. In this evolutionary scenario, diffusion builds a pure He surface
layer which gradually thickens as the star cools. In the temperature range of
the pulsating DB white dwarfs (T_eff ~ 25,000 K) this transformation is still
taking place, allowing asteroseismic tests of the theory. We have obtained
dual-site observations of the pulsating DB star CBS114, to complement existing
observations of the slightly cooler star GD358. We recover the 7 independent
pulsation modes that were previously known, and we discover 4 new ones to
provide additional constraints on the models. We perform objective global
fitting of our updated double-layered envelope models to both sets of
observations, leading to determinations of the envelope masses and pure He
surface layers that qualitatively agree with the expectations of diffusion
theory. These results provide new asteroseismic evidence supporting one of the
central assumptions of spectral evolution theory, linking the DB white dwarfs
to PG1159 stars.


title: The distances of short-hard GRBs and the SGR connection

abstract:
  We present a search for nearby (D<100 Mpc) galaxies in the error boxes of six
well-localized short-hard gamma-ray bursts (GRBs). None of the six error boxes
reveals the presence of a plausible nearby host galaxy. This allows us to set
lower limits on the distances and, hence, the isotropic-equivalent energy of
these GRBs. Our lower limits are around $1 \times 10^{49}$ erg (at $2\sigma$
confidence level); as a consequence, some of the short-hard GRBs we examine
would have been detected by BATSE out to distances greater than 1 Gpc and
therefore constitute a bona fide cosmological population. Our search is
partially motivated by the December 27, 2004 hypergiant flare from SGR 1806-20,
and the intriguing possibility that short-hard GRBs are extragalactic events of
a similar nature. Such events would be detectable with BATSE to a distance of
\~50 Mpc, and their detection rate should be comparable to the actual BATSE
detection rate of short-hard GRBs. The failure of our search, by contrast,
suggests that such flares constitute less than 15% of the short-hard GRBs (<40%
at 95% confidence). We discuss possible resolutions of this discrepancy.


title:
RFI Identification and Mitigation Using Simultaneous Dual Station
  Observations

abstract:
  RFI mitigation is a critically important issue in radio astronomy using
existing instruments as well as in the development of next-generation radio
telescopes, such as the Square Kilometer Array (SKA). Most designs for the SKA
involve multiple stations with spacings of up to a few thousands of kilometers
and thus can exploit the drastically different RFI environments at different
stations. As demonstrator observations and analysis for SKA-like instruments,
and to develop RFI mitigation schemes that will be useful in the near term, we
recently conducted simultaneous observations with Arecibo Observatory and the
Green Bank Telescope (GBT). The observations were aimed at diagnosing RFI and
using the mostly uncorrelated RFI between the two sites to excise RFI from
several generic kinds of measurements such as giant pulses from Crab-like
pulsars and weak HI emission from galaxies in bands heavily contaminated by
RFI. This paper presents observations, analysis, and RFI identification and
excision procedures that are effective for both time series and spectroscopy
applications using multi-station data.


title:
The Concordance Cosmic Star Formation Rate: Implications from and for
  the Supernova Neutrino and Gamma Ray Backgrounds

abstract:
  We constrain the Cosmic Star Formation Rate (CSFR) by requiring that massive
stars produce the observed UV, optical, and IR light while at the same time not
overproduce the Diffuse Supernova Neutrino Background as bounded by
Super-Kamiokande. With the massive star component so constrained we then show
that a reasonable choice of stellar Initial Mass Function and other parameters
results in SNIa rates and iron yields in good agreement with data. In this way
we define a `concordance' CSFR that predicts the optical SNII rate and the SNIa
contribution to the MeV Cosmic Gamma-Ray Background. The CSFR constrained to
reproduce these and other proxies of intermediate and massive star formation is
more clearly delineated than if it were measured by any one technique and has
the following testable consequences: (1) SNIa contribute only a small fraction
of the MeV Cosmic Gamma-Ray Background, (2) massive star core-collapse is
nearly always accompanied by a successful optical SNII, and (3) the Diffuse
Supernova Neutrino Background is tantalizingly close to detectability.


title: Cyclotron Maser Emission from Blazar Jets?

abstract:
  We consider the production of electron cyclotron maser emission by
low-density, highly magnetized plasmas in relativistic jets. The population
inversion required to drive cyclotron maser instability could occur in
localized, transient sites where hydromagnetic instabilities, shocks, and/or
turbulence lead to magnetic mirroring along current-carrying flux tubes. The
maser is pumped as electrons are accelerated by the parallel electric field
that develops as a result of the mirror. We estimate the maximum brightness
temperatures that can be obtained in a single maser site and in an array of
many masers operating simultaneously, under conditions likely to apply in
blazar jets. Synchrotron absorption, by relativistic electrons within the jet,
presents the largest obstacle to the escape of the maser radiation, and may
render most of it invisible. However, we argue that a high brightness
temperature could be produced in a thin boundary layer outside the synchrotron
photosphere, perhaps in the shear layer along the wall of the jet. Induced
Compton scattering provides additional constraints on the maximum brightness
temperature of a masing jet. We suggest that recent observations of diffractive
scintillation in the blazar J1819+3845, indicating intrinsic brightness
temperatures greater than 10^{14} K at 5 GHz, may be explained in terms of
cyclotron maser emission. High brightness temperature maser emission from
blazar jets may extend to frequencies as high as ~100 GHz, with the maximum
possible T_B scaling roughly as 1/frequency. Less massive relativistic jet
sources, such as microquasars, are even better candidates for producing
cyclotron maser emission, primarily in the infrared and optical bands.


title: Formation of Carbon Dwarfs

abstract:
  We consider the formation of dwarf carbon stars via accretion from a carbon
AGB companion in light of the new 107 object sample of Downes et al. (2004).
This sample is now large enough to allow good mass determination via comparison
of a composite spectrum to theoretical atmospheric models. Carbon dwarfs of
spectral type M are indeed main sequence M dwarfs with enhanced metallicity and
carbon abundance. We also calculate the predicted abundance of both M and of
F/G carbon dwarfs, and show that the latter should be falsifiable in the near
future.


title:
Measuring the Three-Dimensional Structure of Galaxy Clusters. I.
  Application to a Sample of 25 Clusters

abstract:
  We discuss a method to constrain the intrinsic three-dimensionale shapes of
galaxy clusters by combining X-Ray and Sunyaev-Zeldovich observations. The
method is applied to a sample of 25 X-Ray selected clusters, with measured
Sunyaev-Zeldovich temperature decrements. The sample turns out to be slightly
biased, with strongly elongated clusters preferentially aligned along the line
of sight. This result demonstrates that X-Ray selected cluster samples may be
affected by morphological and orientation effects even if a relatively high
threshold signal-to-noise ratio is used to select the sample. A large majority
of the clusters in our sample exhibit a marked triaxial structure, with
prolate-like shapes being slightly more likely than oblate-like ones; the
spherical hypothesis is strongly rejected for most sample members. Cooling flow
clusters do not show preferentially regular morphologies.


title: Infrared Spectroscopy of U Equulei's Warm Circumstellar Gas

abstract:
  Medium and high resolution spectroscopy of U Equulei from 1 to 4 microns
during 1997-2003 has revealed information about its unusual circumstellar
envelope, observed previously at optical and radio wavelengths. Strong
absorption bands of H2O and of CO dominate the 1-4um spectrum. The gas has a
mean temperature of 600 K and 12C/13C =< 10. The CO 2-0 line profiles and
velocities imply no net ejection or infall and indicate either rapid radial gas
motions being seen along a narrow continuum beam, or absorption by orbiting gas
that is nearly coincident with a highly extended continuum source. The gas
could be located in a disk-like structure. The observed high column densities
of warm CO and H2 normally would be associated with sufficient dust to
completely obscure the star at optical wavelengths. The observations thus
indicate either a highly abnormal gas-to-dust ratio, consistent with the
earlier optical observation of abundant refractory metal oxides in the
circumstellar gas, or peculiar geometry and/or illumination.


title:
The T Tauri Phase Down to Nearly Planetary Masses: Echelle Spectra of 82
  Very Low Mass Stars and Brown Dwarfs

abstract:
  Using the largest high-resolution spectroscopic sample to date of young, very
low mass stars (VLMS) and brown dwarfs (BDs), we investigate disk accretion in
objects ranging from just above the hydrogen-burning limit all the way to
nearly planetary masses. Our 82 targets span spectral types from M5 to M9.5, or
masses from 0.15 Msun down to ~15 Jupiters. They are confirmed members of the
rho Oph, Taurus, Cha I, IC 348, R CrA, Upper Sco and TW Hydrae regions, with
ages <1 to ~10 Myr. The sample contains 41 BDs (spectral types >= M6.5). We
find that: (1) classical T Tauri-like disk-accretion persists in the BD domain
down to nearly the deuterium-burning limit; (2) in addition to H-alpha,
permitted emission lines of CaII, OI and HeI are also good accretion
indicators, as in CTTs; (3) the CaII 8662A flux is an excellent quantitative
measure of the accretion rate (Mdot) in VLMS and BDs(as in CTTs); (4) Mdot
diminishes as M^2 -- our measurements support previous findings of this
correlation, and extend it to the entire range of sub-stellar masses; (5) the
accretor fraction among VLMS and BDs decreases substantially with age, as in
higher-mass stars; (6) at any given age, the VLMS and BD accretor fraction is
comparable to that in higher-mass stars; and (7) a number of sources with IR
disk excesses do not evince measurable accretion, with the incidence of such a
mismatch increasing with age: this implies that disks in the low mass regime
can persist beyond the main accretion phase, and parallels the transition from
the classical to post-T Tauri stage in more massive stars. These strong
similarities at young ages, between higher-mass stars and low-mass bodies close
to and below the hydrogen-burning limit, are consistent with a common formation
mechanism in the two mass regimes. (abridged)


title:
Gamma-Ray Burst Prompt Emission: Implications from Shock Acceleration
  Theory

abstract:
  The principal paradigm for gamma-ray bursts suggest that the prompt transient
gamma-ray signal arises from multiple shocks internal to the relativistic
expansion. This paper illustrates some properties of diffusive acceleration at
relativistic shocks that pertain to GRB models, providing interpretation of the
BATSE/EGRET data. Using a standard Monte Carlo simulation, computations of the
spectral shape, and the range of spectral indices are presented, as functions
of the shock speed, magnetic field obliquity and the type of particle
scattering. It is clear that while quasi-parallel, relativistic shocks with
fields approximately normal to the shock plane can efficiently accelerate
particles, highly oblique and perpendicular ones cannot unless the particle
diffusion is almost isotropic, i.e. extremely close to the Bohm limit.
Accordingly, an array of distribution indices should be present in the burst
population, as is exhibited by the EGRET data, and even mildly-relativistic
internal shocks require strong field turbulence in order to model the >100 MeV
observations. In addition, recent spectral fitting to burst data in the BATSE
band is discussed, providing probes of the efficiency of injection of
non-thermal electrons.


title:
A Photometric Redshift Galaxy Catalog from the Red-Sequence Cluster
  Survey

abstract:
  The Red-Sequence Cluster Survey (RCS) provides a large and deep photometric
catalog of galaxies in the $z'$ and $R_c$ bands for ~90 square degrees of sky,
and supplemental $V$ and $B$ data have been obtained for 33.6 deg$^{2}$. We
compile a photometric redshift catalog from these 4-band data by utilizing the
empirical quadratic polynomial photometric redshift fitting technique in
combination with CNOC2 and GOODS/HDF-N redshift data. The training set includes
4924 spectral redshifts. The resulting catalog contains more than one million
galaxies with photometric redshifts $< 1.5$ and $R_c < 24$, giving an rms
scatter $\sigma(\Delta{z}) < 0.06$ within the redshift range $0.2 < z < 0.5$
and $\sigma(\Delta{z}) < 0.11$ for galaxies at $0.0 < z < 1.5$. We describe the
empirical quadratic polynomial photometric redshift fitting technique which we
use to determine the relation between redshift and photometry. A kd-tree
algorithm is used to divide up our sample to improve the accuracy of our
catalog. We also present a method for estimating the photometric redshift error
for individual galaxies. We show that the redshift distribution of our sample
is in excellent agreement with smaller and much deeper photometric and
spectroscopic redshift surveys.


title:
Using the ROSAT Bright Source Catalogue to find Counterparts for
  IBIS/ISGRI Survey Sources

abstract:
  The IBIS/ISGRI first year galactic plane survey has produced a catalogue
containing 123 hard X-ray sources visible down to a flux limit of a few
milliCrabs. The point source location accuracy of typically 1-3 arcminutes has
allowed the counterparts for 95 of these sources to be found at other
wavelengths. In order to identify the remaining 28 objects, we have
cross-correlated the ISGRI catalogue with the ROSAT All Sky Survey Bright
Source Catalogue. In this way, for ISGRI sources which have a counterpart in
soft X-rays, we can use the, much smaller, ROSAT error box to search for
identifications. As expected, we find a strong correlation between the two
catalogues and calculate that there are 75 associations with the number
expected by chance to be almost zero. Of these 75 sources, ten are in the list
of unidentified objects. Using the ROSAT error boxes we provide tentative
associations for 8 of these.


title: Extra galactic sources of high energy neutrinos

abstract:
  The main goal of the construction of large volume, high energy neutrino
telescopes is the detection of extra-Galactic neutrino sources. The existence
of such sources is implied by observations of ultra-high energy, >10^{19} eV,
cosmic-rays (UHECRs), the origin of which is a mystery. The observed UHECR flux
sets an upper bound to the extra-Galactic high energy neutrino intensity, which
implies that the detector size required to detect the signal in the energy
range of 1 TeV to 1 PeV is >=1 giga-ton, and much larger at higher energy.
Optical Cerenkov neutrino detectors, currently being constructed under ice and
water, are expected to achieve 1 giga-ton effective volume for 1 TeV to 1 PeV
neutrinos. Coherent radio Cerenkov detectors (and possibly large air-shower
detectors) will provide the >> 1 giga-ton effective volume required for
detection at ~10^{19} eV. Detection of high energy neutrinos associated with
electromagnetically identified sources will allow to identify the sources of
UHECRs, will provide a unique probe of the sources, which may allow to resolve
open questions related to the underlying physics of models describing these
powerful accelerators, and will provide information on fundamental neutrino
properties.


title: Optical Studies of Isolated Neutron Stars and Their Environments

abstract:
  The results of optical studies of Isolated Neutron Stars (INSs), their
Pulsar-Wind Nebulae (PWNe) and Pulsar Bow Shocks are reviewed and discussed.


title:
Exploring the relativistic regime with Newtonian hydrodynamics: An
  improved effective gravitational potential for supernova simulations

abstract:
  We investigate the possibility to approximate relativistic effects in
hydrodynamical simulations of stellar core collapse and post-bounce evolution
by using a modified gravitational potential in an otherwise standard Newtonian
hydrodynamic code. Different modifications of the effective relativistic
potential introduced by Rampp & Janka (2002) are discussed. Corresponding
hydrostatic solutions are compared with solutions of the TOV equations, and
hydrodynamic simulations with two different codes are compared with fully
relativistic results. One code is applied for one- and two-dimensional
calculations with a simple equation of state, and employs either the modified
effective relativistic potential in a Newtonian framework or solves the general
relativistic field equations under the assumption of the conformal flatness
condition (CFC) for the three-metric. The second code allows for full-scale
supernova runs including a microphysical equation of state and neutrino
transport based on the solution of the Boltzmann equation and its moments
equations. We present prescriptions for the effective relativistic potential
for self-gravitating fluids to be used in Newtonian codes, which produce
excellent agreement with fully relativistic solutions in spherical symmetry,
leading to significant improvements compared to previously published
approximations. Moreover, they also approximate qualitatively well relativistic
solutions for models with rotation.


title: The stability of buoyant bubbles in the atmospheres of galaxy clusters

abstract:
  The buoyant rise of hot plasma bubbles inflated by AGN outflows in galaxy
clusters can heat the cluster gas and thereby compensate radiative energy
losses of this material. Numerical simulations of this effect often show the
complete disruption of the bubbles followed by the mixing of the bubble
material with the surrounding cluster gas due to fluid instabilities on the
bubble surface. This prediction is inconsistent with the observations of
apparently coherent bubble structures in clusters. We derive a general
description in the linear regime of the growth of instabilities on the surface
between two fluids under the influence of a gravitational field, viscosity,
surface tension provided by a magnetic field and relative motion of the two
fluids with respect to each other. We demonstrate that Kelvin-Helmholtz
instabilities are always suppressed, if the fluids are viscous. They are also
suppressed in the inviscid case for fluids of very different mass densities. We
show that the effects of shear viscosity as well as a magnetic fields in the
cluster gas can prevent the growth of Rayleigh-Taylor instabilities on relevant
scale lengths. R-T instabilities on pc-scales are suppressed even if the
kinematic viscosity of the cluster gas is reduced by two orders of magnitude
compared to the value given by Spitzer for a fully ionised, unmagnetised gas.
Similarly, magnetic fields exceeding a few microG result in an effective
surface tension preventing the disruption of bubbles. For more massive
clusters, instabilities on the bubble surface grow faster. This may explain the
absence of thermal gas in the north-west bubble observed in the Perseus cluster
compared to the apparently more disrupted bubbles in the Virgo cluster.


title: On the determination of the deceleration parameter from Supernovae data

abstract:
  Supernovae searches have shown that a simple matter-dominated and
decelerating universe should be ruled out. However a determination of the
present deceleration parameter $q_0$ through a simple kinematical description
is not exempt of possible drawbacks. We show that, with a time dependent
equation of state for the dark energy, a bias is present for $q_0$ : models
which are very far from the so-called Concordance Model can be accommodated by
the data and a simple kinematical analysis can lead to wrong conclusions. We
present a quantitative treatment of this bias and we present our conclusions
when a possible dynamical dark energy is taken into account.


title:
Particle Swarm Optimization: An efficient method for tracing periodic
  orbits in 3D galactic potentials

abstract:
  We propose the Particle Swarm Optimization (PSO) as an alternative method for
locating periodic orbits in a three--dimensional (3D) model of barred galaxies.
We develop an appropriate scheme that transforms the problem of finding
periodic orbits into the problem of detecting global minimizers of a function,
which is defined on the Poincar\'{e} Surface of Section (PSS) of the
Hamiltonian system. By combining the PSO method with deflection techniques, we
succeeded in tracing systematically several periodic orbits of the system. The
method succeeded in tracing the initial conditions of periodic orbits in cases
where Newton iterative techniques had difficulties. In particular, we found
families of 2D and 3D periodic orbits associated with the inner 8:1 to 12:1
resonances, between the radial 4:1 and corotation resonances of our 3D Ferrers
bar model. The main advantages of the proposed algorithm is its simplicity, its
ability to work using function values solely, as well as its ability to locate
many periodic orbits per run at a given Jacobian constant.


title:
Mutual information between geomagnetic indices and the solar wind as
  seen by WIND - implications for propagation time estimates

abstract:
  The determination of delay times of solar wind conditions at the sunward
libration point to effects on Earth is investigated using mutual information.
This measures the amount of information shared between two timeseries. We
consider the mutual information content of solar wind observations, from WIND,
and the geomagnetic indices. The success of five commonly used schemes for
estimating interplanetary propagation times is examined. Propagation assuming a
fixed plane normal at 45 degrees to the GSE x-axis (i.e. the Parker Spiral
estimate) is found to give optimal mutual information. The mutual information
depends on the point in space chosen as the target for the propagation
estimate, and we find that it is maximized by choosing a point in the nightside
rather than dayside magnetosphere. In addition, we employ recurrence plot
analysis to visualize contributions to the mutual information, this suggests
that it appears on timescales of hours rather than minutes.


title:
The Cusp/Core Problem in Galactic Halos: Long-Slit Spectra for a Large
  Dwarf Galaxy Sample

abstract:
  We derive inner dark matter halo density profiles for a sample of 165
low-mass galaxies using rotation curves obtained from high-quality, long-slit
optical spectra assuming minimal disks and spherical symmetry. For $\rho(r)
\sim r^{-\alpha}$ near the galaxy center we measure median inner slopes ranging
from $\alpha_m = 0.22 \pm 0.08$ to $0.28 \pm 0.06$ for various subsamples of
the data. This is similar to values found by other authors, and in stark
contrast to the intrinsic cusps ($\alpha_{int}\sim1$) predicted by simulations
of halo assembly in cold dark matter (CDM) cosmologies. To elucidate the
relationship between $\alpha_m$ and $\alpha_{int}$ in our data, we simulate
long-slit observations of model galaxies with halo shapes broadly consistent
with the CDM paradigm. Simulations with $\alpha_{int}=1/2$ and 1 recover both
the observed distribution of $\alpha_m$ and correlations between $\alpha_m$ and
primary observational parameters such as distance and disk inclination, whereas
those with $\alpha_{int}=5/4$ are marginally consistent with the data.
Conversely, the hypothesis that low-mass galaxies have $\alpha_{int}=3/2$ is
rejected. While the simulations do not imply that the data favor intrinsic
cusps over cores, they demonstrate that the discrepancy between $\alpha_m$ and
$\alpha_{int}\sim1$ for our sample does not necessarily imply a genuine
conflict between our results and CDM predictions: rather, the apparent
cusp/core problem may be reconciled by considering the impact of observing and
data processing techniques on rotation curves derived from long-slit spectra.


title:
The Solar Neighborhood XIII: Parallax Results from the CTIOPI 0.9-m
  Program -- Stars with mu >= 1"/year (MOTION Sample)

abstract:
  We present the first set of definitive trigonometric parallaxes and proper
motions from the Cerro Tololo Inter-American Observatory Parallax Investigation
(CTIOPI). Full astrometric reductions for the program are discussed, including
methods of reference stars selection, differential color refraction
corrections, and conversion of relative to absolute parallax. Using data
acquired at the 0.9-m at CTIO, full astrometric solutions and $VRIJHK_s$
photometry are presented for 36 red and white dwarf stellar systems with proper
motions faster than 1\farcs0/yr. Of these, thirty three systems have the first
ever trigonometric parallaxes, which comprise 41% of MOTION systems (those with
proper motions greater than 1\farcs0/yr) south of $\delta$ $=$ 0 that have no
parallaxes. Four of the systems are new members of the RECONS 10 pc sample for
which the first accurate trigonometric parallaxes are published here: DENIS
J1048-3956 (4.04 $\pm$ 0.03 pc), GJ 1128 (LHS 271, 6.53 $\pm$ 0.10 pc), GJ 1068
(LHS 22, 6.97 $\pm$ 0.09 pc), and GJ 1123 (LHS 263, 9.02 $\pm$ 0.16 pc). In
addition, two red subdwarf-white dwarf pairs, LHS 193AB and LHS 300AB, are
identified. The white dwarf secondaries fall in a previously uncharted region
of the HR diagram.


title:
A fresh look at the unstable simulations of Bondi-Hoyle-Lyttleton
  accretion

abstract:
  The instability of Bondi-Hoyle-Lyttleton accretion, observed in numerical
simulations, is analyzed through known physical mechanisms and possible
numerical artefacts. The mechanisms of the longitudinal and transverse
instabilities, established within the accretion line model, are clarified. They
cannot account for the instability of BHL accretion at moderate Mach number
when the pressure forces within the shock cone are taken into account. The
advective-acoustic instability is considered in the context of BHL accretion
when the shock is detached from the accretor. This mechanism naturally explains
the stability of the flow when the shock is weak, and the instability when the
accretor is small. In particular, it is a robust proof of the instability of 3D
accretion when gamma=5/3 if the accretor is small enough, even for moderate
shock strength (M sim 3). The numerical artefacts that may be present in
existing numerical simulations are reviewed, with particular attention paid to
the advection of entropy/vorticity perturbations and the artificial acoustic
feedback from the accretor boundary condition. Several numerical tests are
proposed to test these mechanisms.


title: Henry Kandrup's Ideas About Relaxation of Stellar Systems

abstract:
  Henry Kandrup wrote prolifically on the problem of relaxation of stellar
systems. His picture of relaxation was significantly more refined than the
standard description in terms of phase mixing and violent relaxation. In this
article, I summarize Henry's work in this and related areas.


title: HST/WFPC2 morphologies and bar structures of field galaxies at 0.4<z<1

abstract:
  To address how the galaxy Hubble sequence is established and what physical
processes are involved, we studied morphological properties and internal
structures of field galaxies in the past (0.4<z<1). In addition to structural
parameters derived from bulge+disk decomposition, Zheng et al. (2004)
introduced color maps in recognizing galaxies and properly classified
morphologies of 36 luminous infrared galaxies (LIRGs, Lir(8-1000um)>=10^11
L_sun). Here we presented morphological classification of a parallel 75
non-LIRG sample. Our examination revealed that a significant fraction of the
galaxies shows remarkable morphological evolution, most likely related to the
present-day spiral galaxies. Comparison of the morphological properties between
LIRGs and non-LIRGs shows that the LIRGs contain a higher fraction of ongoing
major mergers and systems with signs of merging/interaction. This suggests that
the merging process is one of the major mechanisms to trigger star formation.
We found that spiral LIRGs probably host much fewer bars than spiral non-LIRGs,
suggesting that a bar is not efficient in triggering violent star formation.
Differing from Abraham et al. (1999), no dramatic change of the bar frequency
is detected up to redshift ~0.8. The bar frequency of the distant spirals is
similar to (and may be higher than) the present-day spirals in the rest-frame
$B$ band. We conclude that bar-driven secular evolution is not a major
mechanism to drive morphological evolution of field galaxies, especially their
bulge formation, which is more likely related to multiple intense star
formation episodes during which the galaxies appear as LIRGs (Hammer et al.
2005).


title:
Analysis of Strong Outbursts in Selected Blazars from the Metsahovi and
  UMRAO Monitoring Databases

abstract:
  Frequency-dependent time lags for strong outbursts in four gamma-blazars are
determined. The time lags for two adjacent outbursts in 2230+114 are correlated
with the outburst amplitudes. There is evidence that bright outbursts in
2230+114 appear with a quasi-period of (8.0 +- 0.3) yr.


title:
Discovery of a candidate protoplanetary disk around the embedded source
  IRc9 in Orion

abstract:
  We report the detection of spatially-extended mid-infrared emission around
the luminous embedded star IRc9 in OMC-1, as seen in 8.8, 11.7, and 18.3 micron
images obtained with T-ReCS on Gemini South. The extended emission is
asymmetric, and the morphology is reminiscent of warm dust disks around other
young stars. The putative disk has a radius of roughly 1.5 arcsec (700 AU), and
a likely dust mass of almost 10 Earth masses. The infrared spectral energy
distribution of IRc9 indicates a total luminosity of about 100 Lsun, implying
that it shall become an early A-type star when it reaches the main sequence.
Thus, the candidate disk around IRc9 may be a young analog of the planetary
debris disks around Vega-like stars and the disks of Herbig Ae stars, and may
provide a laboratory in which to study the earliest phases of planet formation.
A disk around IRc9 may also add weight to the hypothesis that an enhanced T
Tauri-like wind from this star has influenced the molecular outflow from the
OMC-1 core.


title: Multi-frequency Polarization Imaging of Blazars with Cyclic Activity

abstract:
  Results of multi-frequency VLBA polarization imaging for sources showing
evidence of quasi-periodic variations in their total flux density are
discussed. Possible origins of the observed behavior are proposed.


title:
Limits on the Polarization of the Cosmic Microwave Background Radiation
  at Multipoles up to l~2000

abstract:
  We report upper limits on the polarization of the CMBR as measured with the
Cosmic Background Imager, a 13 element interferometer that operates in the
26-36 GHz band and is sited on Llano de Chajnantor in northern Chile. The array
consists of 90-cm Cassegrain antennas mounted on a steerable platform that can
be rotated about the optical axis to facilitate polarization observations. The
CBI employs single-mode circularly polarized receivers and it samples
multipoles from l~400 to l~3500. The polarization data were calibrated on 3C279
and Tau A. The polarization observations consist of 278 hours of data on two
fields taken in 2000, during the first CBI observing season. A joint likelihood
analysis of the two fields yields three upper limits (95% c.l.) for
\mathcal{C}_l^{EE} = C^{EE}l(l+1)/(2pi) under the assumption that
\mathcal{C}_l^{BB}=0: 49.0 microK^2 (l=603); 164 microK^2 (l=1144); and 630
microK^2 (l=2048).


title: The velocity field of baryonic gas in the universe

abstract:
  The dynamic evolution of the baryonic intergalactic medium (IGM) caused by
the underlying dark matter gravity is governed by the Navier-Stokes equations
in which many cooling and heating processes are involved. However, it has long
been recognized that the growth mode dynamics of cosmic matter clustering can
be sketched by a random force driven Burgers' equation if cooling and heating
are ignored. Just how well the dynamics of the IGM can be described as a
Burgers fluid has not been fully investigated probably because cooling and
heating are essential for a detailed understanding of the IGM. Using IGM
samples produced by a cosmological hydrodynamic simulation in which heating and
cooling processes are properly accounted for, we show that the IGM velocity
field in the nonlinear regime shows the features of a Burgers fluid, that is,
when the Reynolds number is high, the velocity field consists of an ensemble of
shocks. Consequently, (1) the IGM velocity $v$ is generally smaller than that
of dark matter; (2) for the smoothed field, the IGM velocity shows tight
correlation with dark matter given by $v \simeq s v_{dm}$, with $s<1$, such
that the lower the redshift, the smaller $s$; (3) the velocity PDFs are
asymmetric between acceleration and deceleration events; (4) the PDF of
velocity difference $\Delta v=v(x+r)-v(x)$ satisfies the scaling relation for a
Burgers fluid, i.e., $P(\Delta v)=(1 r^y)F(\Delta v/r^y)$. We find the scaling
function and parameters for the IGM which are applicable to the entire scale
range of the samples (0.26 - 8 h$^{-1}$ Mpc). These properties show that the
similarity mapping between the IGM and dark matter is violated on scales much
larger than the Jeans length of the IGM.


title: SiO Maser Sources toward Globular Clusters

abstract:
  We report on the detection of SiO masers in Asymptotic Giant Branch variables
toward bulge/disk globular clusters. In five out of six cases, the radial
velocities are compatible with the optically measured radial velocities of
globular clusters in the assessed uncertainty. Two sources, toward Terzan~5 and
Terzan~12, lie very close to the cluster centers. The objects toward Pal~6 and
Terzan~12 have luminosities appropriate to the AGB tip in globular clusters,
while those toward NGC 6171, Pal~10, and Terzan~5 are brighter than expected.
It is suggested that the latter three may have evolved from merged binaries,
offering a test for binary-evolution scenarios in globular clusters, if the
membership is approved.


title: Observational Gamma-ray Cosmology

abstract:
  We discuss how measurements of the absorption of gamma-rays from GeV to TeV
energies via pair production on the extragalactic background light (EBL) can
probe important issues in galaxy formation. Semi-analytic models (SAMs) of
galaxy formation, based on the flat LCDM hierarchical structure formation
scenario, are used to make predictions of the EBL from 0.1 to 1000 microns.
SAMs incorporate simplified physical treatments of the key processes of galaxy
formation -- including gravitational collapse and merging of dark matter halos,
gas cooling and dissipation, star formation, supernova feedback and metal
production. We will summarize SAM successes and failures in accounting for
observations at low and high redshift. New ground- and space-based gamma ray
telescopes will help to determine the EBL, and also help to explain its origin
by constraining some of the most uncertain features of galaxy formation theory,
including the stellar initial mass function, the history of star formation, and
the reprocessing of light by dust. On a separate topic concerning gamma ray
cosmology, we discuss a new theoretical insight into the distribution of dark
matter at the center of the Milky Way, and its implications concerning the high
energy gamma rays observed from the Galactic center.


title: The baryon content of the Universe

abstract:
  The large discrepancy between the amount of baryons that were synthesized in
Big-Bang and that we detect at $z=0$ locked in stars inside galaxies and in
hot/cold gas in galaxies. goup and clusters, is a well known crucial issue for
present day cosmology. It is also thought that this riddle is at the backbone
of how the ordinary matter has formed, inside dark potential wells, the
structures we see today. Then, it is useful to reprint, by means of this
archive, the first (pre- astro-ph era) published work in which the amount of
"luminous" baryons was actually and suitably computed and the disagreement with
the BBN predictions strongly claimed. This because 12 years after the method
and the results are still up-to-date, and above all, people are occasionally
found to know only later works (appeared on astro-ph) that were meant to be
just (ours or other's) follow ups of the present paper.


title: Normal Gas-Rich Galaxies in the Far-Infrared: The Legacy of ISOPHOT

abstract:
  Following on from IRAS, the ISOPHOT instrument on board the Infrared Space
Observatory (ISO) has provided a huge advancement in our knowledge of the
phenomenology of the far-infrared (FIR) emission of normal galaxies and the
underlying physical processes. Highlights include: the discovery of an extended
cold dust emission component, present in all types of gas-rich galaxies and
carrying the bulk of the dust luminosity; the definitive characterisation of
the spectral energy distribution in the FIR, revealing the channels through
which stars power the FIR light; the derivation of realistic geometries for
stars and dust from ISOPHOT imaging and the discovery of cold dust associated
with HI extending beyond the optical body of galaxies.


title: HST/WFPC2 Color-Magnitude Diagrams for Globular Clusters in M31

abstract:
  We report new HST/WFPC2 photometry for 10 globular clusters (GC) in M31
observed in F5555W(V) and F814W(I). Additionally we have reanalyzed HST
archival data of comparable quality for 2 more GCs. Extraordinary care is taken
to account for the effects of blended stellar images and required field
subtraction. We thus reach 1 mag fainter than the horizontal branch (HB) even
in unfavorable cases. We present the color-magnitude diagrams (CMDs) and
discuss their main features also in comparison with the properties of the
Galactic GCs. This analysis is augmented with CMDs previously obtained and
discussed by Fusi Pecci et al. (1996) on 8 other M31 clusters. We report the
following significant results: 1. The locus of the red giant branches give
reliable metallicity determinations which compare generally very well with
ground-based integrated spectroscopic and photometric measures, as well as
giving good reddening estimates. 2. The HB morphologies show the same behavior
with metallicity as the Galactic GCs, with indications that the 2nd-parameter
effect can be present in some GCs of our sample. However, at [Fe/H] ~ -1.7 we
observe a number of GCs with red HB morphology such that the HB type versus
[Fe/H] relation is offset from the MW and resembles that of the Fornax dwarf
spheroidal galaxy. One explanation for the offset is that they are younger than
their MW counterparts by 1-2 Gyr. 3. The Mv(HB)-[Fe/H] relationship has been
determined and the slope (~0.20) is very similar to the values derived from RR
Lyrae stars in the MW and the LMC. The zero-point of this relation based on the
assumed distance modulus (m-M)o(M31)=24.47+/-0.03 is consistent with
(m-M)o(LMC)=18.55.


title: Aldebaran's angular diameter: how well do we know it?

abstract:
  The bright, well-known K5 giant Aldebaran, alpha Tau, is probably the star
with the largest number of direct angular diameter determinations, achieved
over a long time by several authors using various techniques. In spite of this
wealth of data, or perhaps as a direct result of it, there is not a very good
agreement on a single angular diameter value. This is particularly unsettling
if one considers that Aldebaran is also used as a primary calibrator for some
angular resolution methods, notably for optical and infrared long baseline
interferometry. Directly connected to Aldebaran's angular diameter and its
uncertainties is its effective temperature, which also has been used for
several empirical calibrations. Among the proposed explanations for the
elusiveness of an accurate determination of the angular diameter of Aldebaran
are the possibility of temporal variations as well as a possible dependence of
the angular diameter on the wavelength. We present here a few, very accurate
new determinations obtained by means of lunar occultations and long baseline
interferometry. We derive an average value of 19.96+-0.03 milliarcseconds for
the uniform disk diameter. The corresponding limb-darkened value is 20.58+-0.03
milliarcseconds, or 44.2+-0.9 R(sun). We discuss this result, in connection
with previous determinations and with possible problems that may affect such
measurements.


title: End-point of the rp process and periodic gravitational wave emission

abstract:
  The general end-point of the rp process in rapidly accreting neutron stars is
believed to be a surface distribution of matter whose nuclear composition may
depend on position. Its evolution during compression beyond the neutron-drip
threshold density is determined by the presence of nuclear formation enthalpy
minima at the proton closed shells. At threshold, a sequence of weak
interactions with capture or emission of neutron pairs rapidly transform nuclei
to the most accessible proton closed shell. Therefore, angular asymmetries in
nuclear composition present in accreted matter at neutron drip are preserved
during further compression to higher densities provided transition rates
between closed shells are negligible. Although it has been confirmed that this
condition is satisfied for predicted internal temperatures and for the
formation enthalpy distribution used in this work, it would not be so if the
true enthalpy differences between maxima and minima in the distribution were a
factor of two smaller. For this reason, it does not appear possible to assert
with any confidence that position-dependent surface composition can lead to
significant angle-dependence of the equation of state and to potentially
observable gravitational radiation. The effect of non-radial internal
temperature gradients on angle-dependency of the equation of state is also not
quantifiable.


title: Chandra and XMM-Newton Observations of NGC 6251

abstract:
  We present new X-ray observations of the nucleus, jet and extended emission
of the nearby radio galaxy NGC 6251 using the Chandra/ACIS-S camera, together
with a reanalysis of archival Chandra/ACIS-I and XMM-Newton/EPIC data. We find
that the nuclear X-ray spectrum is well-fitted with an absorbed power-law, and
that there is tentative, but not highly significant, evidence for Fe K$\alpha$
emission. We argue that the observed nuclear X-ray emission is likely to
originate in a relativistic jet, based on the double-peaked nature, and our
synchrotron self-Compton modelling, of the radio-to-X-ray spectral energy
distribution. However, we cannot rule out a contribution from an accretion
flow. We resolve X-ray jet emission in three distinct regions, and argue in
favour of a synchrotron origin for all three; inverse-Compton emission models
are possible but require extreme parameters. We detect thermal emission on both
galaxy and group scales, and demonstrate that hot gas can confine the jet,
particularly if relativistic beaming is important. We show evidence that the
radio lobe has evacuated a cavity in the X-ray-emitting gas, and suggest that
the lobe is close to the plane of the sky, with the jet entering the lobe close
to the surface nearest to the observer.


title:
Radial velocity-acceleration curve analysis of the spectroscopic binary
  stars by the nonlinear regression

abstract:
  We will introduce a new method to derive the orbital elements of the
spectroscopic binary stars. Fitting the adopted radial velocity curves on the
measured experimental data, the corresponding radial acceleration data are
obtained. The orbital parameters are estimated by the nonlinear least squares
of the radial velocity-acceleration curves. This method is implemented for the
three double line spectroscopic binary systems RZ CAS, CC Cas and V1130 Tau.
Numerical calculations show that the result are in good agreement with the
those obtained by others using the method of Lehmann-Filh\'{e}s.


title:
Energetics - Spectral correlations vs the BATSE Gamma-Ray Bursts
  population

abstract:
  Recently proposed correlations between the energetics of Gamma-Ray Bursts
(GRB) and their spectral properties, namely the peak energy of their prompt
emission, are found to account for the observed fluence distribution of all
`bright' BATSE GRB. Furthermore for an intrinsic GRB peak energy distribution
extending toward lower energies with respect to that characterizing bright GRB,
such correlations allow to reproduce the fluence distribution of the whole
BATSE long GRB population. We discuss the constraints that such analysis
imposes on the shape of the peak energy distribution, the opening angle
distribution and the tightness of such correlations.


title:
Probing the existence of the E_peak-E_iso correlation in long Gamma Ray
  Bursts

abstract:
  We probe the existence of the E_peak-E_iso correlation in long GRBs using a
sample of 442 BATSE bursts with known E_peak and with redshift estimated
through the lag-luminosity correlation. This sample confirms that the rest
frame peak energy is correlated with the isotropic equivalent energy. The
distribution of the scatter of the points around the best fitting line is
similar to that obtained with the 27 bursts with spectroscopic redshifts. We
interpret the scatter in the E_peak-E_iso plane as due to the opening angle
distribution of GRB jets. By assuming that the collimation corrected energy
correlates with E_peak we can derive the observed distribution of the jet
opening angles, which turns out to be log-normal with a peak value of ~6.5
degrees.


title: EUSO In September 2004

abstract:
  After a short comparison of cosmic ray observation from ground versus space,
EUSO detector and its capabilities are described. The political situation is
sketched.


title: Systematic Effects in CMB Polarization Measurements

abstract:
  The cosmic microwave background polarization is rich of cosmological
information complementary to those from temperature anisotropies. Linear
polarization can be decomposed uniquely in two components of opposite parities,
called E and B. While E mode allows measurement of cosmological parameters in a
way independent from temperature, B mode allows to detect the primordial
gravitational waves produced during inflation, and thus to determine its energy
scale. However, measuring CMB polarization is complicated by foregrounds, whose
polarization is poorly known, and by systematic effects, which mainly affects B
mode measurement because of its low level. As an example, we show here the
effect of beams uncertainty on polarization measurement in the case of the
Planck HFI instrument, and how we can correct for it.


title: The Substellar Mass Function: A Bayesian Approach

abstract:
  We report our efforts to constrain the form of the low-mass star and brown
dwarf mass function via Bayesian inference. Recent surveys of M, L, and T
dwarfs in the local solar neighborhood are an essential component of our study.
Uncertainties in the age distribution of local field stars make reliable
inference complicated. We adopt a wide range of plausible assumptions about the
rate of galactic star formation and show that their deviations from a uniform
rate produce little effect on the resulting luminosity function for a given
mass function. We use a Bayesian statistical formalism to evaluate the
probability of commonly used mass functions in light of recent discoveries. We
consider three functional forms of the mass function, include a two-segment
power law, a single power law with a low-mass cutoff, and a log-normal
distribution. Our results show that, at a 60% confidence level, the power-law
index, $\alpha$, for the low-mass arm of a two-segment power law has a value
between -0.5 and 0.5 for objects with masses between $0.04 M_{\odot}$ and $0.10
M_{\odot}$. The best-fit index is $\alpha = 0.3\pm0.6$ at the 60% confidence
level for a single-segment mass function. Current data require this function
extend to at least $0.05 M_{\odot}$ with no restrictions placed on a lower mass
cutoff. Inferences of the parameter values for a log-normal mass function are
virtually unaffected by recent estimates of the local space density of L and T
dwarfs. We find no preference among these three forms using this method. We
discuss current and future capabilities that may eventually discriminate
between mass-function models and refine estimates of their associated parameter
values.


title: On the local birth place of Geminga

abstract:
  Using estimates of the distance and proper motion of Geminga and the
constraints on its radial velocity posed by the shape of its bow shock, we
investigate its birth place by tracing its space motion backwards in time. Our
results exclude the lambda Ori association as the origin site because of the
large distance between both objects at any time. Our simulations place the
birth region at approximately 90-240 pc from the Sun, between 197 degrees and
199 degrees in Galactic longitude and -16 degrees and -8 degrees in latitude,
most probably inside the Cas-Tau OB association or the Ori OB1a association. We
discard the possibility of the progenitor being a massive field star. The
association of Geminga with either stellar association implies an upper limit
of M = 15 Msun for the mass of its progenitor. We also propose new members for
the Cas-Tau and Ori OB1 associations.


title:
A possible new interpretation of the results of $\Delta\alpha/\alpha$
  from QSO absorption lines

abstract:
  The measurement of $\Delta\alpha/\alpha$ from the QSO absorption lines of
Fe_II taken at two different redshifts (Quast et al, Levshakov et al) is
compared with the result based on the 23 data points also obtained from
VLT/UVES (Chand et al), to demonstrate that the apparent oscillatory
time-dependence fitting the latter taken at face value is reinforced by the
former claimed to be of much better accuracy.


title: Discovery of a stellar system in the background of 47 Tucanae

abstract:
  We report on the discovery of a stellar system in the background of the
Galactic globular cluster 47 Tucanae (NGC 104), located 14.8' North-West of the
cluster center. The object, whose apparent diameter is D~30'', is partially
resolved into stars on the available CCD images, reaching a limiting magnitude
of V~22.5, and is detected as a significant (more than 5 sigma) overdensity of
blue stars (B-V<0.7). The color magnitude diagram of the system, its
characteristic projected size and its position in the sky suggest that it is an
intermediate-old age cluster belonging to the Small Magellanic Cloud, whose
outskirts lie in the background of 47 Tuc. Although less likely, the
possibility that the object is an unknown dwarf galaxy in the outskirts of the
Local Group cannot completely be ruled out by the present data.


title: Pulsations induced by deuterium-burning in young brown dwarfs

abstract:
  Very low-mass stars and brown dwarfs can undergo pulsational instability
excited by central deuterium burning during the initial phases of their
evolution. We present the results of evolutionary and nonadiabatic linear
stability models that show the presence of unstable fundamental modes. The
pulsation periods vary bewteen ~5 hr for a 0.1 Msun star and ~1 hr for a 0.02
M$_\odot$ brown dwarf. The results are rather insensitive to variations in the
input physics of the models. We show the location of the instability strip in
the HR and c-m diagrams and discuss the observational searches for young
pulsators in nearby star forming regions.


title: Third Order Effect of Rotation on Stellar Oscillations of a B Star

abstract:
  The present paper aims at investigating the effect of rotation up to third
order in the angular velocity of a star on p and g modes, based on the
formalism developed by Soufi et al. (1998). Our ultimate goal is the study of
oscillations of $\beta$ Cephei stars which are often rapidly rotating stars.
Our study shows that the third-order perturbation formalism presented by Soufi
et al. (1998) must be corrected for some missing terms and some misprints in
the equations. As a first step in our study of $\beta$ Cephei stars, we
quantify by numerical calculations the effect of rotation on the oscillation
frequencies of a uniformly rotating zero-age main-sequence star with
12~$M_\odot$. For an equatorial velocity of 100~$\rm km \, s^{-1}$, it is found
that the second- and third-order corrections for $(l,m)=(2,2)$, for instance,
are of order of 0.01$\%$ of the frequency for radial order $n=6$ and reaches up
to 0.5$\%$ for $n=14$.


title: Helium self--enrichment and the second parameter problem in M3 and M13

abstract:
  Inspection of the CM diagrams of globular clusters having similar heavy
element content shows that the luminosity of the red giant bump relative to the
turnoff (Delta V_{TO}^{bump}) differs by more than 0.1 mag between clusters
with different horizontal branch morphology. Unfortunately, careful
consideration of the data leaves us with only one pair (M3 and M13) of clusters
good for a quantitative discussion. For this pair we consider differences in
age and helium content as possible causes for the difference in Delta
V_{TO}^{bump}, and find more convincing support for the latter. A larger helium
content in M13 stars (Y~0.28 vs. Y~0.24) accounts for various CM diagram
features, such as the difference in the luminosity level of RR Lyr variables
and of the red giant bump with respect to the turnoff luminosity, and the
horizontal branch morphology. This enhanced helium can be tentatively
understood in the framework of self--enrichment by massive asymptotic giant
branch stars in the first ~100 Myr of the cluster life. A modest
self--enrichment can be present also in M3 and can be the reason for the still
unexplained presence of a not negligible number of luminous, Oosterhoff II type
RR Lyr variables. The hypothesis that a larger helium content is the second
parameter for clusters with very blue horizontal branch morphology could be
checked by an accurate set of data for more clusters giving turnoff, RR Lyrs
and bump magnitudes within a unique photometry.


title: New constraints on SN Ia progenitor models

abstract:
  We use the StarTrack population synthesis code to discuss potential
progenitor models of SN Ia: single degenerate scenario, semi-detached double
white dwarf binary and double degenerate scenario. Using the most recent
calculations of accretion onto white dwarfs, we consider SN Ia explosions of
various white dwarfs in binary systems. We calculate the evolutionary delay
times from the zero age main sequence to the explosion, and verify which
scenarios can satisfy the constraints found by Strolger et al. (2004), i.e. a
delay time of 2-4 Gyrs. It is found that the semi-detached double white dwarf
binary model is inconsistent with observations. Only SN Ia progenitors in the
double degenerate scenario are compatible with observations in all tested
evolutionary models, with a characteristic delay time of about 3 Gyrs. If
double degenerate mergers are excluded as SN Ia progenitors, we find that the
single degenerate scenario may explain the observed delay times for models with
low common envelope efficiency. It is also noted that the delay time
distributions within the various tested SN Ia scenarios vary significantly and
potentially can be used as an additional constraint on progenitor models.


title:
Exploring the Structure of Galaxy Clusters: XMM-Newton observations of
  the REFLEX-DXL clusters at z~0.3

abstract:
  The precise determination of global properties of galaxy clusters, and their
scaling relations, is a task of prime importance for the use of clusters as
cosmological probes. We performed a detailed XMM-Newton study of 14 X-ray
luminous REFLEX Survey clusters at z~0.3. We found that the properties of the
galaxy clusters show a self-similar behavior at r>0.1r_{vir}. This helps to
establish tighter scaling relations. Peculiarities in the individual clusters
are important to understand the scatter from the self-similar frame in the
cluster central parts.


title: Evolution of Binary Supermassive Black Holes via Chain Regularization

abstract:
  A chain regularization method is combined with special purpose computer
hardware to study the evolution of massive black hole binaries at the centers
of galaxies. Preliminary results with up to N=260,000 particles are presented.
The decay rate of the binary is shown to decrease with increasing N, as
expected on the basis of theoretical arguments. The eccentricity of the binary
remains small.


title:
Energy input from quasars regulates the growth and activity of black
  holes and their host galaxies

abstract:
  In the early Universe, while galaxies were still forming, black holes as
massive as a billion solar masses powered quasars. Supermassive black holes are
found at the centers of most galaxies today, where their masses are related to
the velocity dispersions of stars in their host galaxies and hence to the mass
of the central bulge of the galaxy. This suggests a link between the growth of
the black holes and the host galaxies, which has indeed been assumed for a
number of years. But the origin of the observed relation between black hole
mass and stellar velocity dispersion, and its connection with the evolution of
galaxies have remained unclear. Here we report simulations that simultaneously
follow star formation and the growth of black holes during galaxy-galaxy
collisions. We find that in addition to generating a burst of star formation, a
merger leads to strong inflows that feed gas to the supermassive black hole and
thereby power the quasar. The energy released by the quasar expels enough gas
to quench both star formation and further black hole growth. This determines
the lifetime of the quasar phase (approaching 100 million years) and explains
the relationship between the black hole mass and the stellar velocity
dispersion.


title: A Direct Method for Measuring Heat Conductivity in Intracluster Medium

abstract:
  The inverse Compton scattering of the cosmic microwave background (CMB)
radiation with electrons in the intracluster medium which has a temperature
gradient, was examined by the third-order perturbation theory of the Compton
scattering. A new type of the spectrum distortion of the CMB was found and
named as gradient T Sunyaev-Zel'dovich effect (gradT SZE). The spectrum has an
universal shape. The spectrum crosses over zero at 326GHz. The sign of the
spectrum depends on the relative direction of the line-of-sight to the
direction of the temperature gradient. This unique spectrum shape can be used
to detect the gradT SZE signal by broad-band or multi-frequency observations of
the SZE. The amplitude of the spectrum distortion does not depend on the
electron density and is proportional to the heat conductivity. Therefore, the
gradT SZE provides an unique opportunity to measure thermally nonequilibrium
electron momentum distribution function when the ICM has a temperature gradient
and the heat conductivity in the ICM. However, the expected amplitude of the
signal is very small. The modifications to the thermal SZE spectrum due to
variety of known effects, such as relativistic correction etc., can become
problematic when using multi-frequency separation techniques to detect the
gradT SZE signal.


title:
Bulk Comptonization of the Cosmic Microwave Background by Extragalactic
  Jets as a Probe of their Matter Content

abstract:
  We propose a method for estimating the composition, i.e. the relative amounts
of leptons and protons, of extragalactic jets which exhibit X-ray bright knots
in their kpc scale jets. The method relies on measuring, or setting upper
limits on, the component of the Cosmic Microwave Background (CMB) radiation
that is bulk-Comptonized by cold electrons in the relativistically flowing jet.
These measurements, along with modeling of the broadband knot emission that
constrain the bulk Lorentz factor of the jets, can yield estimates of the jet
power carried by protons and leptons. We provide an explicit calculation of the
spectrum of the bulk-Comptonized (BC) CMB component and apply these results to
PKS 0637--752 and 3C 273, two superluminal quasars with Chandra-detected large
scale jets. What makes these sources particularly suited for such a procedure
is the absence of significant non-thermal jet emission in the `bridge', the
region between the core and the first bright jet knot, which guarantees that
most of the electrons are cold there, leaving the BC scattered CMB radiation as
the only significant source of photons in this region. At lambda=3.6-8.0
microns the most likely band to observe the BC scattered CMB emission, the
Spitzer angular resolution (~ 1''-3) is considerably smaller than the `bridges'
of these jets (~10''), making it possible to both measure and resolve this
emission.


title:
Metal Abundances of KISS Galaxies. IV. Galaxian Luminosity-Metallicity
  Relations in the Optical and Near-IR

abstract:
  We explore the galaxian luminosity-metallicity (L-Z) relationship in both the
optical and the near-IR using a combination of optical photometric and
spectroscopic observations from the KPNO International Spectroscopic Survey
(KISS) and near-infrared photometry from the Two-micron All Sky Survey (2MASS).
We supplement the 2MASS data with our own NIR photometry for a small number of
lower-luminosity ELGs that are under-represented in the 2MASS database. Our
B-band L-Z relationship includes 765 star-forming KISS galaxies with coarse
abundance estimates from our follow-up spectra, while the correlation with KISS
and 2MASS yields a total of 420 galaxies in our J-band L-Z relationship. We
explore the effect that changing the correlation between the strong-line
abundance diagnostic R_23 and metallicity has on the derived L-Z relation. We
find that the slope of the L-Z relationship decreases as the wavelength of the
luminosity bandpass increases. We interpret this as being, at least in part, an
effect of internal absorption in the host galaxy. Furthermore, the dispersion
in the L-Z relation decreases for the NIR bands, suggesting that variations in
internal absorption contribute significantly to the observed scatter. We
propose that our NIR L-Z relations are more fundamental than the B-band
relation, since they are largely free of absorption effects and the NIR
luminosities are more directly related to the stellar mass of the galaxy than
are the optical luminosities.


title: A Search for Giant Pulses from Millisecond Pulsars

abstract:
  We have searched for microsecond-timescale broadband emission from a sample
of eighteen millisecond pulsars. Our study places strong limits on such
emission from several millisecond pulsars and shows that it is only present in
a small subset of millisecond pulsars. Giant pulses of up to 64 times the mean
pulse energy were detected from PSR J1823-3021A in the globular cluster NGC
6624. In contrast to the giant pulses of PSR B1937+21, nearly all of the giant
pulses from PSR J1823-3021A were distributed within the trailing half of the
main-pulse component of the integrated pulse profile. The fact that no giant
pulses were observed on the leading side of the main-pulse component suggests
that giant pulses are preferentially emitted closer to the last open field line
than ordinary emission. The correlation between giant pulse emissivity and
spin-down luminosity in millisecond pulsars suggests that the high period
derivative of PSR J1823-3021A is intrinsic and is not just an artifact of its
acceleration in the gravitational potential of NGC 6624.


title:
The Mass Assembly Histories of Galaxies of Various Morphologies in the
  GOODS Fields

abstract:
  We present an analysis of the growth of stellar mass with cosmic time
partitioned according to galaxy morphology. Using a well-defined catalog of
2150 galaxies based, in part, on archival data in the GOODS fields, we assign
morphological types in three broad classes (Ellipticals, Spirals,
Peculiar/Irregulars) to a limit of z_AB=22.5 and make the resulting catalog
publicly available. We combine redshift information, optical photometry from
the GOODS catalog and deep K-band imaging to assign stellar masses. We find
little evolution in the form of the galaxy stellar mass function from z~1 to
z=0, especially at the high mass end where our results are most robust.
Although the population of massive galaxies is relatively well established at
z~1, its morphological mix continues to change, with an increasing proportion
of early-type galaxies at later times. By constructing type-dependent stellar
mass functions, we show that in each of three redshift intervals, E/S0's
dominate the higher mass population, while spirals are favored at lower masses.
This transition occurs at a stellar mass of 2--3 times 10^{10} Msun at z~0.3
(similar to local studies) but there is evidence that the relevant mass scale
moves to higher mass at earlier epochs. Such evolution may represent the
morphological extension of the ``downsizing'' phenomenon, in which the most
massive galaxies stop forming stars first, with lower mass galaxies becoming
quiescent later. We infer that more massive galaxies evolve into spheroidal
systems at earlier times, and that this morphological transformation may only
be completed 1--2 Gyr after the galaxies emerge from their active star forming
phase. We discuss several lines of evidence suggesting that merging may play a
key role in generating this pattern of evolution.


title:
The Effect of Spiral Structure on the Stellar Velocity Distribution in
  the Solar Neighborhood

abstract:
  Clumps in the solar neighborhood's stellar velocity distribution could be
caused by spiral density waves. In the solar neighborhood, stellar velocities
corresponding to orbits that are nearly closed in the frame rotating with a
spiral pattern represent likely regions for stellar concentrations. Via
particle integration, we show that orbits can intersect the solar neighborhood
when they are excited by Lindblad resonances with a spiral pattern. We find
that a two-armed spiral density wave with pattern speed placing the Sun near
the 4:1 Inner Lindblad Resonance (ILR) can cause two families of nearly closed
orbits in the solar neighborhood. One family corresponds to square shaped
orbits aligned so their peaks lie on top of, and support, the two dominant
stellar arms. The second family correspond to orbits 45 degrees out of phase
with the other family. Such a spiral density pattern could account for two
major clumps in the solar neighborhood's velocity distribution. The
Pleiades/Hyades moving group corresponds to the first family of orbits and the
Coma Berenices moving group corresponds to the second family. This model
requires a spiral pattern speed of approximately 0.66 +- 0.03 times the angular
rotation rate of the Sun or 18.1 +- 0.8 km/s/kpc.


title: Plasma Diffuser Sorts Light Atoms to Solar Surface

abstract:
  The Sun operates like a giant plasma diffuser that sorts lighter isotopes and
elements to the solar surface. Measurements indicate that the interior of the
Sun consists mostly of the same seven, even-numbered elements as ordinary
meteorites: Iron, oxygen, nickel, silicon, sulfur, magnesium, and calcium.
These ordinary elements compose clothing on the central neutron star that was
produced at the core of the supernova that exploded here 5 billion years ago.
Neutron emission generates most solar energy. Neutron-decay near the core
produces Hydrogen ions that are accelerated upward by deep-seated magnetic
fields. This is the carrier gas that maintains mass separation in the Sun. Like
smoke, Hydrogen is a by-product from the solar furnace that powers the Sun. As
smoke passes over catalytic converters in the flue of a high-efficiency
furnace, most Hydrogen is fused into Helium during its upward journey. H-fusion
makes less than 38 percent of solar energy. Each year 50 trillion tons of
Hydrogen reach the solar surface and are flung off in the solar wind, with
isotopes of other trace elements carefully sorted by mass. Hydrogen is smoke
from the solar furnace, rather than its primary fuel.


title: SDSS J1553+0056: A BALQSO mimicking a Lyman-break galaxy

abstract:
  Using the UVES echelle spectrograph at the ESO VLT we obtained
high-resolution (R = 40 000) spectra of the object SDSS J1553+0056, which has
been identified in the literature alternatively as a high-redshift quasar or as
a Lyman-break galaxy (LBG). Although low-resolution spectra of SDSS J1553+0056
closely resemble those of LBGs, our high-resolution spectra allow us to
identify this object unambiguously as a LoBAL quasar, probably belonging to the
rare FeLoBALQSO class. Based on our spectrum we discuss how misidentifications
of such objects from low-resolution spectra can be avoided.


title:
Weak lensing in the second post-Newtonian approximation: Gravitomagnetic
  potentials and the integrated Sachs-Wolfe effect

abstract:
  Dark matter currents in the large-scale structure give rise to
gravitomagnetic terms in the metric, which affect the light propagation.
Corrections to the weak lensing power spectrum due to these gravitomagnetic
potentials are evaluated by perturbation theory. A connection between
gravitomagnetic lensing and the integrated Sachs-Wolfe (iSW) effect is drawn,
which can be described by a line-of-sight integration over the divergence of
the gravitomagnetic vector potential. This allows the power spectrum of the
iSW-effect to be derived within the framework of the same formalism as derived
for gravitomagnetic lensing and reduces the iSW-effect to a second order
lensing phenomenon. The three-dimensional power spectra are projected by means
of a generalised Limber-equation to yield the angular power spectra. While
gravitomagnetic corrections to the weak lensing spectrum are negligible at
observationally accessible scales, the angular power spectrum of the iSW-effect
should be detectable as a correction to the CMB spectrum up to multipoles of l
\~ 100 with the PLANCK-satellite.