title:
An Upper Limit on the Albedo of HD 209458b: Direct Imaging Photometry
  with the MOST Satellite

abstract:
  We present space-based photometry of the transiting exoplanetary system HD
209458 obtained with the MOST (Microvariablity and Oscillations of STars)
satellite, spanning 14 days and covering 4 transits and 4 secondary eclipses.
The HD 209458 photometry was obtained in MOST's lower-precision Direct Imaging
mode, which is used for targets in the brightness range $6.5 < V < 13$. We
describe the photometric reduction techniques for this mode of observing, in
particular the corrections for stray Earthshine. We do not detect the secondary
eclipse in the MOST data, to a limit in depth of 0.053 mmag (1 \sigma). We set
a 1 \sigma upper limit on the planet-star flux ratio of 4.88 x 10^-5
corresponding to a geometric albedo upper limit in the MOST bandpass (400 to
700 nm) of 0.25. The corresponding numbers at the 3 \sigma level are 1.34 x
10^-4 and 0.68 respectively. HD 209458b is half as bright as Jupiter in the
MOST bandpass. This low geometric albedo value is an important constraint for
theoretical models of the HD209458b atmosphere, in particular ruling out the
presence of reflective clouds. A second MOST campaign on HD 209458 is expected
to be sensitive to an exoplanet albedo as low as 0.13 (1 sigma), if the star
does not become more intrinsically variable in the meantime.


title: Relativistic Electrodynamics of Spinning Compact Objects

abstract:
  A theoretical study of some electrodynamic features of a region close to a
{\it slowly-rotating} magnetized relativistic star is performed. To be a little
more specific, based on the solution-generating method given by Wald, the
magnetic fields around both uncharged and (slightly) charged relativistic stars
have been obtained. Particularly for a charged relativistic star, again
following the argument by Wald, the star was shown to gradually accrete charge
until it reached an equilibrium value $\tilde{Q}=2B_{0}J$. This value of the
equilibrium charge seems to be generic as a rotating black hole is known to
accrete exactly the same amount. Although these results are equally relevant to
all species of slowly-rotating relativistic stars, we particularly have the
rotating neutron star in mind. As such, it would be of some interest to attempt
to make contact with a real pulsar case. Thus, we discuss how many of the
theoretical results obtained in the present work can be carried over to a
realistic, general relativistic description of a pulsar's magnetosphere.


title: The GOODS-North Radio Galaxies: On the Origin of the Radio Emission

abstract:
  We report on a preliminary study concerning the origin of radio emission
within radio galaxies at L(1.4GHz)>1E24 W/Hz in the GOODS-N field. In the local
universe, Condon et al. (2002) and Yun et al. (2001) have shown that in
galaxies with radio luminosities greater than 1E23 W/Hz the majority of the
radio emission originates from a `monster' i.e., an AGN. Using the Chandra
2Msec X-ray image centered on the GOODS-N field and a reprocessed VLA HDF
A-array data plus newly acquired VLA B-array data (rms=5.3microJy), we find
that radio galaxies (with spectroscopic redshifts; all have z>1) with
L(1.4GHz)>1E24 W/Hz typically have an X-ray detection rate of 72% (60% emit
hard X-rays suggesting an AGN origin for the radio emission) in contrast to 25%
for radio galaxies with L < 1E23 W/Hz. The ACS images of these L(1.4 GHz) >
1E24 W/Hz galaxies typically show compact rather than extended galaxy
morphology which is generally found for the less luminous radio emitting
galaxies but a few appear to be ongoing galaxy mergers. We also present SED
fitting for these luminous radio galaxies including Spitzer IRAC & MIPS 24um
photometry and 60% show distinct power-law SED indicative of an AGN. Initial
results tell us that the X-ray emitting radio galaxy population are generally
not submm sources but the few (~10%) that are SCUBA sources appear to be the
small AGN population found by Pope et al. and others.


title:
Multi-object spectroscopy of the field surrounding PKS 2126-158:
  Discovery of a z=0.66 galaxy group

abstract:
  The high-redshift radio-loud quasar PKS 2126-158 is found to have a large
number of red galaxies in close apparent proximity. We use the Gemini
Multi-Object Spectrograph (GMOS) on Gemini South to obtain optical spectra for
a large fraction of these sources. We show that there is a group of galaxies at
$z\sim0.66$, coincident with a metal-line absorption system seen in the
quasar's optical spectrum. The multiplexing capabilities of GMOS also allow us
to measure redshifts of many foreground galaxies in the field surrounding the
quasar.
  The galaxy group has five confirmed members, and a further four fainter
galaxies are possibly associated. All confirmed members exhibit early-type
galaxy spectra, a rare situation for a Mg II absorbing system. We discuss the
relationship of this group to the absorbing gas, and the possibility of
gravitational lensing of the quasar due to the intervening galaxies.


title: Possible Molecular Spiral Arms in the Protoplanetary Disk of AB Aur

abstract:
  The circumstellar dust disk of the Herbig Ae star AB Aur has been found to
exhibit complex spiral-like structures in the near-IR image obtained with the
Subaru Telescope. We present maps of the disk in both 12CO (3-2) and dust
continuum at 345 GHz with the SMA at an angular resolution of 1.0"x0.7" (144AU
x 100AU). The continuum emission traces a dust disk with a central depression
and a maximum overall dimension of 450AU (FWHM). This dust disk exhibits
several distinct peaks that appear to coincide with bright features in the
near-IR image, in particular the brightest inner spiral arm. The CO emission
traces a rotating gas disk of size 530AU x 330AU with a deprojected maximum
velocity of 2.8km/s at 450AU. In contrast to the dust disk, the gas disk
exhibits an intensity peak at the stellar position. Furthermore, the CO
emission in several velocity channels traces the innermost spiral arm seen in
the near-IR. We compare the observed spatial-kinematic structure of the CO
emission to a simple model of a disk in Keplerian rotation, and find that only
the emission tracing the main spiral arm clearly lies outside the confines of
our model. This emission has a net outward radial motion compared with the
radial velocity predicted by the model at the location of the main spiral arms.
The disk of AB Aur is therefore quite different from the Keplerian disks seen
around many Herbig Ae stars. The spiral-like structures of the disk with
non-Keplerian motions we revealed in 12CO (3-2), together with the central
depression of the dust disk, may be explained to be driven by the possible
existence of a giant planet forming in the disk.


title:
Rotational velocities of the giants in symbiotic stars: II. Are S-type
  symbiotics synchronized?

abstract:
  We have measured the projected rotational velocities (v sin i) of the mass
donors for 29 S-type symbiotic stars using high resolution spectroscopic
observations and the cross-correlation function (CCF) method.
  The results of the CCF have been controlled with synthetic spectra. The
typical rotational velocity of the K and M giants in S-type symbiotics appeared
to be 4.5 < vsini < 11.7 km/s. In a sub-sample of 16 S--type symbiotic stars
(with known orbital periods and well measured vsini) 15 have deviations from
synchronization less then the 3-sigma level. This means that we did not find
evidence for a statistically significant deviation from the synchronization for
any of these 15 objects. The deviation from synchronization is statistically
significant (at confidence level >99%) only for the recurrent nova RS Oph.
  For 22 S-type symbiotics we give clues as to what their orbital periods could
be.


title:
Broad-band photometric colors and effective temperature calibrations for
  late-type giants. II. Z<0.02

abstract:
  (Abridged) We investigate the effects of metallicity on the broad-band
photometric colors of late-type giants, and make a comparison of synthetic
colors with observed photometric properties of late-type giants over a wide
range of effective temperatures (T_eff=3500-4800 K) and gravities (log
g=0.0-2.5), at [M/H]=-1.0 and -2.0. The influence of metallicity on the
synthetic photometric colors is generally small at effective temperatures above
\~3800 K, but the effects grow larger at lower T_eff, due to the changing
efficiency of molecule formation which reduces molecular opacities at lower
[M/H]. To make a detailed comparison of the synthetic and observed photometric
colors of late type giants in the T_eff--color and color--color planes, we
derive a set of new T_eff--log g--color relations based on synthetic
photometric colors, at [M/H]=-0.5, -1.0, -1.5, and -2.0. While differences
between the new T_eff--color relations and those available from the literature
are typically well within ~100 K, effective temperatures predicted by the
scales based on synthetic colors tend to be slightly higher than those
resulting from the T_eff--color relations based on observations, with the
offsets up to ~100 K. This is clearly seen both at [M/H]=-1.0 and -2.0,
especially in the T_eff--(B-V) and T_eff--(V-K) planes. The consistency between
T_eff--log g--color scales based on synthetic colors calculated with different
stellar atmosphere codes is very good, with typical differences being well
within \Delta T_eff~70 K at [M/H]=-1.0 and \Delta T_eff~40 K at [M/H]=-2.0.


title: Magnetic field confinement by meridional flow and the solar tachocline

abstract:
  We show that the MHD theory that explains the solar tachocline by an effect
of the magnetic field can work with the decay modes of a fossil field in the
solar interior if the meridional flow of the convection zone penetrates
slightly the radiative zone beneath. An equatorward flow of about 10 m/s
penetrating to a maximum depth of 1000 km below the convection zone is able to
generate almost horizontal field lines in the tachocline region so that the
internal field is almost totally confined to the radiative zone. The theory of
differential solar rotation indeed provides meridional flows of about 10 m/s
and a penetration depth of < 1000 km for viscosity values that are
characteristic of a stable tachocline.


title: Magnetic fields and UV-line variability in $\beta$ Cephei

abstract:
  We present results of numerical simulations of wind variability in the
magnetic B1 IVe star $\beta$ Cephei. 2D-MHD simulations are used to determine
the structure of the wind. From these wind models we calculate line profiles
for different aspect angles to simulate rotation. The results are compared with
the observed UV wind line profiles.


title:
An estimate of the time variation of the abundance gradient from
  planetary nebulae III. O, S, Ar, and Ne: A comparison of PN samples

abstract:
  The time behaviour of the radial abundance gradients in the galactic disk is
investigated on the basis of four different samples of planetary nebulae,
comprising both smaller, homogeneous sets of data, and larger, albeit
non-homogeneous samples. Four different chemical elements are considered,
namely, oxygen, sulphur, argon and neon. Our analysis support our earlier
conclusions that, on the average, the radial abundance gradients have flattened
out in the last 6 to 8 Gyr.


title: The Narrow Line Region of the Seyfert 2 galaxy Mrk 78. An infrared view

abstract:
  We report near-infrared spectroscopic data for the Seyfert 2 galaxy Mrk 78,
taken with the LIRIS near-infrared camera/spectrometer at the William Herschel
Telescope (WHT). The long-slit spectra clearly show extended emission. The
resolution and depth of the near-infrared spectra allows the examination of its
morphology and ionization regions, and a direct comparison with similarly deep
visible spectra. The emission-line ratios obtained are used to derive the
extinction towards the nucleus. The detection of strong features such as [Fe
II], H$_{2}$, hydrogen recombination lines and the coronal [Si
VI]$\lambda$1.962 line is used to study the kinematics and excitation
mechanisms occurring in Mrk 78, revealing that despite of the strong radio-jet
interaction present in this object, photoionization from the active nucleus
dominates the narrow line region emission, while UV fluorescence is the source
of the H$_{2}$ emission. Lines with extended emission yield velocity
distributions with an amplitude of about 600 km/s, the consequence of an
eastern lobe moving away from us plus a western lobe with the opposite
contribution. We used the photoionization code CLOUDY to recreate a typical
narrow line region region, to derive the ionization parameter, and to compare
our spectral data with diagnostic diagrams.


title:
The OLS-lens survey: The discovery of five new galaxy-galaxy strong
  lenses from the SDSS

abstract:
  Bright galaxy-galaxy strong lenses are much more powerful than lensed quasars
for measuring the mass profiles of galaxies, but until this year only a handful
have been known. Here we present five new examples, identified via the optimal
line-of-sight gravitational lens search strategy applied to luminous red
galaxies in the Sloan Digital Sky Survey (SDSS). Our survey largely complements
a similar survey by Bolton et al., who recently presented several new lenses.
The lensed background galaxies are selected from the SDSS spectra via the
presence of narrow emission line signatures, including the [OII] 3726,3729, Hb
and [OIII] 4960,5008 lines, superposed on the spectra of the bright,
intervening, deflector galaxies. Our five confirmed new systems include
deflector galaxies with redshifts z=0.17-0.28 and lensed galaxies with
redshifts z=0.47-1.18. Simulations of moderately deep (few orbits) HST-ACS
imaging of systems such as these, where the lensed source is brighter than
r~23, are presented. These demonstrate the feasibility of measuring accurately
the inner slope of the dark matter halo to within an uncertainty
sigma(gamma)~0.1, the dark matter fraction within the Einstein radius, and the
mass-to-light ratio of the stars alone, independently of dynamical
measurements. The high success rate of our search so far, >60%, and the
relatively modest observational resources necessary to confirm the
gravitational lens nature of the candidates, demonstrate that compilation of a
sample of ~100 galaxy-galaxy lenses from the SDSS is readily achievable,
opening up a rich new field in dark matter studies.


title:
The Planetary Nebula population of the Sagittarius Dwarf Spheroidal
  Galaxy

abstract:
  The identification of two new Planetary Nebulae in the Sagittarius Dwarf
Spheroidal Galaxy (Sgr) is presented. This brings the total number to four.
  The first, StWr 2-21, belongs to the main body of Sgr. The second, the halo
PN BoBn 1, has a location, distance and velocity in agreement with the leading
tidal tail of Sgr. We estimate that 10 per cent of the Galactic halo consists
of Sgr debris. The specific frequency of PNe indicates a total luminosity of
Sgr, including its tidal tails, of M_V=-14.1. StWr 2-21 shows a high abundance
of [O/H]=-0.23, which confirms the high-metallicity population in Sgr uncovered
by Bonaficio et al. (2004). The steep metallicity--age gradient in Sgr is due
to ISM removal during the Galactic plane passages, ISM reformation due to
stellar mass loss, and possibly accretion of metal-enriched gas from our
Galaxy. The ISM re-formation rate of Sgr, from stellar mass loss, is 5 X 10^-4
M_sun yr^-1, amounting to ~10^6 M_sun per orbital period. HST images reveal
well-developed bipolar morphologies, and provide clear detections of the
central stars. All three stars with deep spectra show WR-lines, suggesting that
the progenitor mass and metallicity determines whether a PN central star
develops a WR spectrum. One Sgr PN belongs to the class of IR-[WC] stars.
Expansion velocities are determined for three nebulae. Comparison with
hydrodynamical models indicates an initial density profile of rho ~ r^-3. This
is evidence for increasing mass-loss rates on the AGB. Peak mass-loss rates are
indicated of ~ 10^-4 M_sun yr^-1. The IR-[WC] PN, He 2-436, provides the sole
direct detection of dust in a dwarf spheroidal galaxy, to date.


title: [CII] emission and star formation in the spiral arms of M31

abstract:
  The CII 158 microns line is the most important coolant of the interstellar
medium in galaxies but substantial variations are seen from object to object.
The main source of the emission at a galactic scale is still poorly understood.
Previous studies of the CII emission in galaxies have a resolution of several
kpc or more so the observed emission is an average of different ISM components.
The aim of this work is to study, for the first time, the CII emission at the
scale of a spiral arm. We want to investigate the origin of this line and its
use as a tracer of star formation. We present CII and OI observations of a
segment of a spiral arm of M~31 using the Infrared Space Observatory. The CII
emission is compared with tracers of neutral gas (CO, HI) and star formation
(H\alpha, Spitzer 24 mu.) The similarity of the CII emission with the Ha and 24
mu images is striking when smoothed to the same resolution, whereas the
correlation with the neutral gas is much weaker. The CII cooling rate per H
atom increases dramatically from ~2.7e-26 ergs/s/atom in the border of the map
to ~ 1.4e-25 ergs/s/atom in the regions of star formation. The CII/FIR(42-122)
ratio is almost constant at 2%, a factor 3 higher than typically quoted.
However, we do not believe that M~31 is unusual. Rather, the whole-galaxy
fluxes used for the comparisons include the central regions where the CII/FIR
ratio is known to be lower and the resolved observations neither isolate a
spiral arm nor include data as far out in the galactic disk as the observations
presented here. A fit to published PDR models yields a plausible average
solution of G_0~100 and n~3000 for the PDR emission in the regions of star
formation in the arm of M31.


title:
The Thermal Structure of Gas in Pre-Stellar Cores: A Case Study of
  Barnard 68

abstract:
  We present a direct comparison of a chemical/physical model to
multitransitional observations of C18O and 13CO towards the Barnard 68
pre-stellar core. These observations provide a sensitive test for models of low
UV field photodissociation regions and offer the best constraint on the gas
temperature of a pre-stellar core. We find that the gas temperature of this
object is surprisingly low (~7-8 K), and significantly below the dust
temperature, in the outer layers (Av < 5 mag) that are traced by C18O and 13CO
emission. As shown previously, the inner layers (Av > 5 mag) exhibit
significant freeze-out of CO onto grain surfaces. Because the dust and gas are
not fully coupled, depletion of key coolants in the densest layers raises the
core (gas) temperature, but only by ~1 K. The gas temperature in layers not
traced by C18O and 13CO emission can be probed by NH3 emission, with a
previously estimated temperature of ~10-11 K. To reach these temperatures in
the inner core requires an order of magnitude reduction in the gas to dust
coupling rate. This potentially argues for a lack of small grains in the
densest gas, presumably due to grain coagulation.


title:
The impacts of dark matter particle annihilation on recombination and
  the anisotropies of the cosmic microwave background

abstract:
  The recombination history of the Universe provides a useful tool for
constraining the annihilation of dark matter particles. Even a small fraction
of dark matter particles annihilated during the cosmic dark age can provide
sufficient energy to affect the ionization state of the baryonic gas. Although
this effect is too small for neutralinos, lighter dark matter particle
candidates, e.g. with mass of 1-100 MeV, which was proposed recently to explain
the observed excess of positrons in the Galactic Center, may generate
observable differences in the cosmic microwave background (CMB) temperature and
polarization anisotropies. The annihilations at the era of recombination
affects mainly the CMB anisotropy at small angular scales (large $\ell$), and
is distinctively different from the effect of early reionization. We perform a
multi-parameter analysis of the CMB data, including the both the WMAP first
year and three year data, and the ACBAR, Boomerang, CBI, and VSA data. Assuming
that the observed excess of $e^+e^-$ pairs in the galactic center region is
produced by dark matter annihilation, and that a sizable fraction of the energy
produced in the annihilation is deposited in the baryonic gas during
recombination, we obtain a %95 dark matter mass limit of $M<8 \MeV$ with the
current data set.


title:
Swift Observations of GRB 050603: An afterglow with a steep late time
  decay slope

abstract:
  We report the results of Swift observations of the Gamma Ray Burst GRB
050603. With a V magnitude V=18.2 about 10 hours after the burst the optical
afterglow was the brightest so far detected by Swift and one of the brightest
optical afterglows ever seen. The Burst Alert Telescope (BAT) light curves show
three fast-rise-exponential-decay spikes with $T_{90}$=12s and a fluence of
7.6$\times 10^{-6}$ ergs cm$^{-2}$ in the 15-150 keV band. With an $E_{\rm
\gamma, iso} = 1.26 \times 10^{54}$ ergs it was also one of the most energetic
bursts of all times. The Swift spacecraft began observing of the afterglow with
the narrow-field instruments about 10 hours after the detection of the burst.
The burst was bright enough to be detected by the Swift UV/Optical telescope
(UVOT) for almost 3 days and by the X-ray Telescope (XRT) for a week after the
burst. The X-ray light curve shows a rapidly fading afterglow with a decay
index $\alpha$=1.76$^{+0.15}_{-0.07}$. The X-ray energy spectral index was
$\beta_{\rm X}$=0.71\plm0.10 with the column density in agreement with the
Galactic value. The spectral analysis does not show an obvious change in the
X-ray spectral slope over time. The optical UVOT light curve decays with a
slope of $\alpha$=1.8\plm0.2.
  The steepness and the similarity of the optical and X-ray decay rates suggest
that the afterglow was observed after the jet break. We estimate a jet opening
angle of about 1-2$^{\circ}$


title: The upstream magnetic field of GRB shocks

abstract:
  Gamma-ray burst (GRB) afterglow emission is believed to be produced by
synchrotron emission of electrons accelerated to high energy by a relativistic
collisionless shock propagating into a weakly magnetized plasma. Afterglow
observations have been used to constrain the post-shock magnetic field and
structure, as well as the accelerated electron energy distribution. Here we
show that X-ray afterglow observations on day time scale constrain the
pre-shock magnetic field to satisfy B>0.2[n/(1/cc)]^{5/8} mG, where n is the
pre-shock density. This suggests that either the shock propagates into a highly
magnetized fast, v~10^3 km/s, wind, or that the pre-shock magnetic field is
strongly amplified, most likely by the streaming of high energy shock
accelerated particles. More stringent constraints may be obtained by afterglow
observations at high photon energy at late, >1 d, times.


title:
The Remarkable Mid-Infrared Jet of Massive Young Stellar Object
  G35.20-0.74

abstract:
  The young massive stellar object G35.20-0.74 was observed in the mid-infrared
using T-ReCS on Gemini South. Previous observations have shown that the near
infrared emission has a fan-like morphology that is consistent with emission
from the northern lobe of a bipolar radio jet known to be associated with this
source. Mid-infrared observations presented in this paper show a monopolar
jet-like morphology as well, and it is argued that the mid-infrared emission
observed is dominated by thermal continuum emission from dust. The mid-infrared
emission nearest the central stellar source is believed to be directly heated
dust on the walls of the outflow cavity. The hydroxyl, water, and methanol
masers associated with G35.20-0.74 are spatially located along these
mid-infrared cavity walls. Narrow jet or outflow cavities such as this may also
be the locations of the linear distribution of methanol masers that are found
associated with massive young stellar objects. The fact that G35.20-0.74 has
mid-infrared emission that is dominated by the outflow, rather than disk
emission, is a caution to those that consider mid-infrared emission from young
stellar objects as only coming from circumstellar disks.


title: Supersoft X-ray Sources. Parameters of Stellar Atmospheres

abstract:
  ROSAT spectra of 11 supersoft X-ray sources (RX J0439.8-6809, RX
J0513.9-6951, RX J0527.8-6954, CAL 87, CAL 83, 1E 0035.4-7230, RX J0048.4-7332,
1E 0056.8-7154, RX J0019.8 +2156, RX J0925.7-4758, AG Draconis) are
approximated with theoretical spectra obtained in LTE models for the
atmospheres of hot white dwarfs with line blanketing. The confidence intervals
of parameters derived from these approximations $ T_{\rm eff}$, $\log g$,
$N_H$, and $R^2/d^2$ are determined. The results are compared with predictions
for a model with stable/recurrent thermonuclear burning on the white-dwarf
surface.


title: Supersoft X-ray Sources. Basic Parameters

abstract:
  The parameters of ten supersoft X-ray sources (RX J0439.8-6809, RX
J0513.9-6951, RX J0527.8-6954, CAL 87, CAL 83, 1E 0035.4-7230, RX J0048.4-7332,
1E 0056.8-7154, RX J0019.8 +2156, RX J0925.7-4758) observed by ROSAT obtained
using blanketing LTE model atmospheres are analyzed. The consistency of the
resulting parameters with a model with stable/recurrent burning on the surface
of the white dwarf is studied. The luminosity and sizes of seven of the sources
are in good agreement with this model. The masses of the white dwarfs in these
sources are estimated. A formula that can be used to estimate the masses of
white dwarfs in classical supersoft sources based on their effective
temperatures is presented.


title: The Gamma-ray burst 050904 : evidence for a termination shock ?

abstract:
  We analyze optical and X-ray observations of GRB 050904 obtained with TAROT
and SWIFT. We perform temporal and spectral analysis of the X-ray and optical
data. We find significant absorption in the early phase of the X-ray light
curve, with some evidence (3 sigma level) of variability. We interpret this as
a progressive photo-ionization. We investigate the environment of the burst and
constrain its density profile. We find that the overall behavior of the
afterglow is compatible with a fireball expanding in a wind environment during
the first 2000 seconds after the burst (observer frame). On the other hand, the
late (after 0.5 days, observer frame) afterglow is consistent with an
interstellar medium, suggesting the possible presence of a termination shock.
We estimate the termination shock position to be R_t ~ 1.8 x 10^{-2} pc, and
the wind density parameter to be A_* ~ 1.8. We try to explain the simultaneous
flares observed in optical and X-ray bands in light of different models :
delayed external shock from a thick shell, inverse Compton emission from
reverse shock, inverse Compton emission from late internal shocks or a very
long internal shock activity. Among these models, those based on a single
emission mechanism, are unable to account for the broad-band observations.
Models invoking late internal shocks, with the inclusion of IC emission, or a
properly tuned very long internal shock activity, offer possible explanations.


title:
Progenitors of Type Ia Supernovae: Circumstellar Interaction, Rotation,
  and Steady Hydrogen Burning

abstract:
  Among the important issues in identifying the progenitor system of Type Ia
supernovae (SNe Ia), we focus mostly on circumstellar interaction in SN 2002ic,
and give brief discussion on the controversial issues of the effects of
rotation in merging double degenerates and steady hydrogen shell burning in
accreting white dwarfs.
  SN 2002ic is a unique supernova which shows the typical spectral features of
SNe Ia near maximum light, but also apparent hydrogen features that have been
absent in SNe Ia. Based on the hydrodynamical models of circumstellar
interaction in SN Ia, we suggest that circumstellar medium is aspherical (or
highly clumpy) and contains ~1.3 Msun. Possible progenitor systems of SN 2002ic
are discussed.


title:
Yields of Population III Supernovae and the Abundance Patterns of
  Extremely Metal-Poor Stars

abstract:
  The abundance patterns of extremely metal-poor (EMP) stars provide us with
important information on nucleosynthesis in supernovae (SNe) formed in a Pop
III or EMP environment, and thus on the nature of the first stars in the
Universe. We review nucleosynthesis yields of various types of those SNe,
focusing on core-collapse (black-hole-forming) SNe with various progenitor
masses, explosion energies (including Hypernovae), and asphericity. We discuss
the implications of the observed trends in the abundance ratios among iron-peak
elements, and the large C/Fe ratio observed in certain EMP stars with
particular attention to recently discovered hyper metal-poor (HMP) stars. We
show that the abundance pattern of the HMP stars with [Fe/H] < -5 and other EMP
stars are in good accord with those of black-hole-forming supernovae, but not
pair-instability supernovae. This suggests that black-hole-forming supernovae
made important contributions to the early Galactic (and cosmic) chemical
evolution. Finally we discuss the nature of First (Pop III) Stars.


title: The Polar Regions of Cassiopeia A: The Aftermath of a Gamma Ray Burst?

abstract:
  Probably not, but it is interesting nevertheless to investigate just how
close Cas A might have come to generating such an event. Focusing on the
northeast jet filaments, we analyze the polar regions of the recently acquired
very deep 1 Ms Chandra X-ray observation. We infer that the so-called "jet"
regions are indeed due to jets emanating from the explosion center, and not due
to polar cavities in the circumstellar medium at the time of explosion. We
place limits on the equivalent isotropic explosion energy in the polar regions
(around 2.3 x 10^52 ergs), and the opening angle of the x-ray emitting ejecta
(around 7 degrees), which give a total energy in the NE jet of order 10^50
ergs; an order of magnitude or more lower than inferred for "typical" GRBs.
While the Cas A progenitor and explosion exhibit many of the features
associated with GRB hosts, e.g. extensive presupernova mass loss and rotation,
and jets associated with the explosion, we speculate that the recoil of the
compact central object, with velocity 330 km/s, may have rendered the jet
unstable. In such cases the jet rapidly becomes baryon loaded, if not truncated
altogether. Although unlikely to have produced a gamma ray burst, the jets in
Cas A suggest that such outflows may be common features of core-collapse SNe.


title: The Cavity of Cygnus A

abstract:
  In this paper, we focus on the limb-brightened, prolate spheroidal cavity of
the radio galaxy Cygnus A, as revealed by the Chandra X-ray Observatory. We use
the shock heated, thermal intracluster medium around the expanding cavity to
infer the properties of the radio synchrotron-emitting gas inside the cavity.
The gas along the N and S edges of the cavity is found to have an average
temperature of 6.0 keV, which is hotter than the temperature (4.6 keV) of the
adjacent intracluster gas. It is proposed that this hotter gas is intracluster
gas shocked by the expanding cavity. The shock is thus inferred to be weak
(Mach number 1.3, a value also inferred from the density jump at the cavity
edge) and its velocity 1,460 km/s. The total kinetic power of the expansion is
found to be 1.2 x 10^{46} erg/s, which is larger than both the total radio
power and the power emitted by the entire intracluster medium in the 2 -- 10
keV band. It appears that most of the power of the jets in Cygnus A is
currently going into heating the intracluster medium. From the derived pressure
inside the cavity, there is no conclusive evidence for a component contributing
pressure additional to the magnetic fields and relativistic particles
responsible for the synchrotron radio emission. Further, the ratio of energy
densities in positive to negative cosmic rays in Cygnus A is between 1 and 100
(the value in our Galaxy).


title:
Signature of Temporary Burning Front Stalling from a Non-Photospheric
  Radius Expansion Double-peaked Burst

abstract:
  Non-photospheric-radius-expansion (non-PRE) double-peaked bursts may be
explained in terms of spreading (and temporary stalling) of thermonuclear
flames on the neutron star surface, as we argued in a previous study of a burst
assuming polar ignition. Here we analyze Rossi X-ray Timing Explorer (RXTE)
Proportional Counter Array (PCA) data of such a burst (but with a considerably
different intensity profile from the previous one) from the low mass X-ray
binary (LMXB) system 4U 1636-536, and show that this model can qualitatively
explain the observed burst profile and spectral evolution, if we assume an
off-polar, but high-latitude ignition, and burning front stalling at a higher
latitude compared to that for the previous burst. The off-polar ignition can
account for the millisecond period brightness oscillations detected from this
burst. This is the first time oscillations have been seen from such a burst.
Our model can qualitatively explain the oscillation amplitude measured during
the first (weaker) peak, and the absence of oscillations during the second
peak. The higher latitude front stalling facilitates the first clear detection
of a signature of this stalling, which is the primary result of this work, and
may be useful for understanding thermonuclear flame spreading on neutron stars.


title: The properties of extragalactic radio sources selected at 20 GHz

abstract:
  We present some first results on the variability, polarization and general
properties of radio sources selected in a blind survey at 20 GHz, the highest
frequency at which a sensitive radio survey has been carried out over a large
area of sky. Sources with flux densities above 100 mJy in the AT20G Pilot
Survey at declination -60 to -70 were observed at up to three epochs during
2002-4, including near-simultaneous measurements at 5, 8 and 18 GHz in 2003. Of
the 173 sources detected, 65% are candidate QSOs, BL Lac objects or blazars,
20% galaxies and 15% faint (b > 22 mag) optical objects or blank fields.
  On a 1-2 year timescale, the general level of variability at 20 GHz appears
to be low. For the 108 sources with good-quality measurements in both 2003 and
2004, the median variability index at 20 GHz was 6.9% and only five sources
varied by more than 30% in flux density.
  Most sources in our sample show low levels of linear polarization (typically
1-5%), with a median fractional polarization of 2.3% at 20 GHz. There is a
trend for fainter sources to show higher fractional polarization.
  At least 40% of sources selected at 20GHz have strong spectral curvature over
the frequency range 1-20 GHz. We use a radio `two-colour diagram' to
characterize the radio spectra of our sample, and confirm that the radio-source
population at 20 GHz (which is also the foreground point-source population for
CMB anisotropy experiments like WMAP and Planck) cannot be reliably predicted
by extrapolating the results of surveys at lower frequencies. As a result,
direct selection at 20 GHz appears to be a more efficient way of identifying 90
GHz phase calibrators for ALMA than the currently-proposed technique of
extrapolation from all-sky surveys at 1-5 GHz.


title: Source Mergers and Bubble Growth During Reionization

abstract:
  The recently introduced models of reionization bubbles based on extended
Press-Schechter theory (Furlanetto, Zaldarriaga & Hernquist 2004) are
generalized to include mergers of ionization sources. Sources with a recent
major merger are taken to have enhanced photon production due to star
formation, and accretion onto a central black hole if a black hole is present.
This produces a scatter in the number of ionized photons corresponding to a
halo of a given mass and a change in photon production over time for any given
halo mass. Photon production histories, bubble distributions, and ionization
histories are computed for several different parameter and recombination
assumptions; the resulting distributions interpolate between previously
calculated limiting cases.


title:
Mass Deficits, Stalling Radii, and the Merger Histories of Elliptical
  Galaxies

abstract:
  A binary supermassive black hole leaves an imprint on a galactic nucleus in
the form of a "mass deficit," a decrease in the mass of the nucleus due to
ejection of stars by the binary. The magnitude of the mass deficit is in
principle related to the galaxy's merger history, but the relation has never
been quantified. Here, high-accuracy N-body simulations are used to calibrate
this relation. Mass deficits are shown to be approximately 0.5M_{12}, with
M_{12} the total mass of the binary; the coefficient in this relation depends
only weakly on the binary mass ratio or on the galaxy's pre-existing density
profile. Hence, after N mergers, the mass deficit is ~0.5 N M_h with M_h the
final (current) black hole mass. When compared with observed mass deficits,
this result implies between 1 and 3 mergers for most galaxies, in accord with
hierarchical galaxy formation models. Implications for binary stalling radii,
the origin of hyper-velocity stars, and the distribution of dark matter at the
centers of galaxies are discussed.


title:
The redshift distribution of short gamma-ray bursts from dynamically
  formed neutron star binaries

abstract:
  Short-hard gamma-ray bursts (SHBs) may arise from gravitational wave (GW)
driven mergers of double neutron star (DNS) systems. DNSs may be "primordial"
or can form dynamically by binary exchange interactions in globular clusters
during core-collapse. For primordial binaries, the time delay between formation
and merger is expected to be short, tau~0.1 Gyr, implying that the redshift
distribution of merger events should follow that of star-formation. We point
out here that for dynamically formed DNSs, the time delay between
star-formation and merger is dominated by the cluster core-collapse time,
rather than by the GW inspiral time, yielding delays comparable to the Hubble
time. We derive the redshift distribution of merger events of dynamically
formed DNSs, and find it to differ significantly from that typically expected
for primordial binaries. The observed redshift distribution of SHBs favors
dynamical formation, although a primordial origin cannot be ruled out due to
possible detection biases. Future red-shift observations of SHBs may allow to
determine whether they are dominated by primordial or dynamically formed DNSs.


title:
Detection Rate Estimates of Gravity-waves Emitted During Parabolic
  Encounters of Stellar Black Holes in Globular Clusters

abstract:
  The rapid advance of gravitational-wave (GW) detector facilities makes it
very important to estimate the event rates of possible detection candidates. We
consider an additional possibility of GW bursts produced during parabolic
encounters (PEs) of stellar mass compact objects. We estimate the rate of
successful detections for specific detectors: the initial Laser Interferometric
Gravitational-Wave Observatory (InLIGO), the French-Italian gravitational-wave
antenna VIRGO, the near-future Advanced-LIGO (AdLIGO), the space-based Laser
Interferometric Space Antenna (LISA), and the Next Generation LISA (NGLISA).
Simple GC models are constructed to account for the compact object mass
function, mass segregation, number density distribution, and velocity
distribution. We calculate encounters both classically and account for general
relativistic corrections by extrapolating the results for infinite mass ratios.
We also include the cosmological redshift of waveforms and event rates. We find
that typical PEs with masses m_1=m_2=40 Msun are detectable with matched
filtering over a signal to noise ratio of 5 within a distance d_L~200Mpc for
InLIGO and VIRGO, z=1 for AdLIGO, 0.4Mpc for LISA, and 1Gpc for NGLISA. We
estimate single datastream total detection rates of 5.5 x 10^{-5} for InLIGO,
7.2 x 10^{-5} for VIRGO, 0.063 for AdLIGO, 2.9 x 10^{-6} for LISA, and 1.0 for
NGLISA per year, for reasonably conservative assumptions. These estimates are
subject to uncertainties in the GC parameters, most importantly the total
number and mass-distribution of black holes (BHs) in the cluster core. In
reasonably optimistic cases, we get >~1 detections for AdLIGO per year. The
regular detection of GWs during PEs would provide a unique observational probe
for constraining the stellar BH mass function of dense clusters. (abridged)


title:
Infrared SEDs of Seyfert Galaxies: Starbursts and the Nature of the
  Obscuring Medium

abstract:
  We present the results of IRS low-resolution spectroscopy of 51 Seyfert
galaxies, part of a large Spitzer observing program to determine the mid-to-far
infrared spectral energy distributions of a well-defined sample of 87 nearby,
12 micron-selected Seyferts. We find that the spectra clearly divide into
groups based on their continuum shapes and spectral features. The infrared
spectral types appear to be related to the Seyfert types. Some features are
clearly related to a starburst contribution to the IR spectrum, while the
observed power-law continuum shapes, attributed to the AGN, may be dust or
non-thermal emission. Principal component analysis results suggest that the
relative contribution of starburst emission is the dominant cause of variance
in the spectra. We find that the Sy 2's show on average stronger starburst
contributions than the Sy 1's.


title:
Spitzer IRS Spectra of Luminous 8 micron Sources in the Large Magellanic
  Cloud

abstract:
  We have produced an atlas of Spitzer Infrared Spectrograph (IRS) spectra of
mass-losing, evolved stars in the Large Magellanic Cloud. These stars were
selected to have high mass-loss rates and so contribute significantly to the
return of processed materials to the ISM. Our high-quality spectra enable the
determination of the chemistry of the circumstellar envelope from the mid-IR
spectral features and continuum. We have classified the spectral types of the
stars and show that the spectral types separate clearly in infrared color-color
diagrams constructed from 2MASS data and synthetic IRAC/MIPS fluxes derived
from our IRS spectra. We present diagnostics to identify and classify evolved
stars in nearby galaxies with high confidence levels using Spitzer and 2MASS
photometry. Comparison of the spectral classes determined using IRS data with
the IR types assigned based on NIR colors also revealed a significant number of
misclassifications and enabled us to refine the NIR color criteria resulting in
more accurate NIR color classifications of dust-enshrouded objects.


title: The Jeans mass and the origin of the knee in the IMF

abstract:
  We use numerical simulations of the fragmentation of a 1000 solar mass
molecular cloud and the formation of a stellar cluster to study how the initial
conditions for star formation affect the resulting initial mass function (IMF).
In particular, we are interested in the relation between the thermal Jeans mass
in a cloud and the knee of the initial mass function, i.e. the mass separating
the region with a flat IMF slope from that typified by a steeper,
Salpeter-like, slope. In three isothermal simulations with M_J=1 solar mass,
M_J=2 solar masses and M_J=5 solar masses, the number of stars formed, at
comparable dynamical times, scales roughly with the number of initial Jeans
masses in the cloud. The mean stellar mass also increases (though less than
linearly) with the initial Jeans mass in the cloud. It is found that the IMF in
each case displays a prominent knee, located roughly at the mass scale of the
initial Jeans mass. Thus clouds with higher initial Jeans masses produce IMFs
which are shallow to higher masses. This implies that a universal IMF requires
a physical mechanism that sets the Jeans mass to be near 1 solar mass.
Simulations including a barotropic equation of state as suggested by Larson,
with cooling at low densities followed by gentle heating at higher densities,
are able to produce realistic IMFs with the knee located at approximately 1
solar mass, even with an initial M_J=5 solar masses. We therefore suggest that
the observed universality of the IMF in the local Universe does not require any
fine tuning of the initial conditions in star forming clouds but is instead
imprinted by details of the cooling physics of the collapsing gas.


title:
Three Gravitational Lenses for the Price of One: Enhanced Strong Lensing
  through Galaxy Clustering

abstract:
  We report the serendipitous discovery of two strong gravitational lens
candidates (ACS J160919+6532 and ACS J160910+6532) in deep images obtained with
the Advanced Camera for Surveys on the Hubble Space Telescope, each less than
40 arcsec from the previously known gravitational lens system CLASS B1608+656.
The redshifts of both lens galaxies have been measured with Keck and Gemini:
one is a member of a small galaxy group at z~0.63, which also includes the
lensing galaxy in the B1608+656 system, and the second is a member of a
foreground group at z~0.43. By measuring the effective radii and surface
brightnesses of the two lens galaxies, we infer their velocity dispersions
based on the passively evolving Fundamental Plane (FP) relation. Elliptical
isothermal lens mass models are able to explain their image configurations
within the lens hypothesis, with a velocity dispersion compatible with that
estimated from the FP for a reasonable source-redshift range. Based on the
large number of massive early-type galaxies in the field and the number-density
of faint blue galaxies, the presence of two additional lens systems around
CLASS B1608+656 is not unlikely in hindsight. Gravitational lens galaxies are
predominantly early-type galaxies, which are clustered, and the lensed quasar
host galaxies are also clustered. Therefore, obtaining deep high-resolution
images of the fields around known strong lens systems is an excellent method of
enhancing the probability of finding additional strong gravitational lens
systems.


title: Orientation Angles of a Pulsar's Polarization Vector

abstract:
  A statistical model of the polarization of pulsar radio emission is used to
derive the general statistics of a polarization vector's orientation angles.
The theoretical distributions are compared with orientation angle histograms
computed from single-pulse, polarization observations of PSR B2020+28. The
favorable agreement between the theoretical and measured distributions lends
support to the underlying assumptions of the statistical model, and
demonstrates, like recent work on other pulsars, that the handedness of
circular polarization is associated with the radiation's orthogonally polarized
modes. Comprehensive directional statistics of the vector's orientation angles
are also derived, and are shown to follow the Watson bipolar and Fisher
distributions in its limiting forms.


title: The Origin of the Initial Mass Function

abstract:
  We review recent advances in our understanding of the origin of the initial
mass function (IMF). We emphasize the use of numerical simulations to
investigate how each physical process involved in star formation affects the
resulting IMF. We stress that it is insufficient to just reproduce the IMF, but
that any successful model needs to account for the many observed properties of
star forming regions including clustering, mass segregation and binarity.
Fragmentation involving the interplay of gravity, turbulence, and thermal
effects is probably responsible for setting the characteristic stellar mass.
Low-mass stars and brown dwarfs can form through the fragmentation of dense
filaments and disks, possibly followed by early ejection from these dense
environments which truncates their growth in mass. Higher-mass stars and the
Salpeter-like slope of the IMF are most likely formed through continued
accretion in a clustered environment. The effects of feedback and magnetic
fields on the origin of the IMF are still largely unclear. Lastly, we discuss a
number of outstanding problems that need to be addressed in order to develop a
complete theory for the origin of the IMF.


title:
The Gravitational Lens -- Galaxy Group Connection. II. Groups Associated
  with B2319+051 and B1600+434

abstract:
  We report on the results of a spectroscopic survey of the environments of the
gravitational lens systems CLASS B1600+434 (z_l = 0.41, z_s = 1.59) and CLASS
B2319+051 (z_l = 0.62). The B1600+434 system has a time delay measured for it,
and we find the system to lie in a group with a velocity dispersion of 100 km/s
and at least six members. B2319+051 has a large group in its immediate
foreground with at least 10 members and a velocity dispersion of 460 km/s and
another in the background of the lens with a velocity dispersion of 190 km/s.
There are several other small groups in the fields of these lens systems, and
we describe the properties of these moderate redshift groups. Furthermore, we
quantify the effects of these group structures on the gravitational lenses and
find a ~5% correction to the derived value of H_0 for B1600+434.


title:
Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results:
  Implications for Cosmology

abstract:
  A simple cosmological model with only six parameters (matter density, Omega_m
h^2, baryon density, Omega_b h^2, Hubble Constant, H_0, amplitude of
fluctuations, sigma_8, optical depth, tau, and a slope for the scalar
perturbation spectrum, n_s) fits not only the three year WMAP temperature and
polarization data, but also small scale CMB data, light element abundances,
large-scale structure observations, and the supernova luminosity/distance
relationship. Using WMAP data only, the best fit values for cosmological
parameters for the power-law flat LCDM model are (Omega_m h^2, Omega_b h^2, h,
n_s, tau, sigma_8) = 0.1277+0.0080-0.0079, 0.02229+-0.00073, 0.732+0.031-0.032,
0.958+-0.016, 0.089+-0.030, 0.761+0.049-0.048). The three year data
dramatically shrink the allowed volume in this six dimensional parameter space.
Assuming that the primordial fluctuations are adiabatic with a power law
spectrum, the WMAP data_alone_ require dark matter, and favor a spectral index
that is significantly less than the Harrison-Zel'dovich-Peebles scale-invariant
spectrum (n_s=1, r=0). Models that suppress large-scale power through a running
spectral index or a large-scale cut-off in the power spectrum are a better fit
to the WMAP and small scale CMB data than the power-law LCDM model; however,
the improvement in the fit to the WMAP data is only Delta chi^2 = 3 for 1 extra
degree of freedom. The combination of WMAP and other astronomical data yields
significant constraints on the geometry of the universe, the equation of state
of the dark energy, the gravitational wave energy density, and neutrino
properties. Consistent with the predictions of simple inflationary theories, we
detect no significant deviations from Gaussianity in the CMB maps.


title:
Three Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations:
  Polarization Analysis

abstract:
  The Wilkinson Microwave Anisotropy Probe WMAP has mapped the entire sky in
five frequency bands between 23 and 94 GHz with polarization sensitive
radiometers. We present three-year full-sky maps of the polarization and
analyze them for foreground emission and cosmological implications. These
observations open up a new window for understanding the universe. WMAP observes
significant levels of polarized foreground emission due to both Galactic
synchrotron radiation and thermal dust emission. The least contaminated channel
is at 61 GHz. Informed by a model of the Galactic foreground emission, we
subtract the foreground emission from the maps. In the foreground corrected
maps, for l=2-6, we detect l(l+1) C_l^{EE} / (2 pi) = 0.086 +-0.029
microkelvin^2. This is interpreted as the result of rescattering of the CMB by
free electrons released during reionization and corresponds to an optical depth
of tau = 0.10 +- 0.03. We see no evidence for B-modes, limiting them to l(l+1)
C_l^{BB} / (2 pi) = -0.04 +- 0.03 microkelvin^2. We find that the limit from
the polarization signals alone is r<2.2 (95% CL) corresponding to a limit on
the cosmic density of gravitational waves of Omega_{GW}h^2 < 5 times 10^{-12}.
  From the full WMAP analysis, we find r<0.55 (95% CL) corresponding to a limit
of Omega_{GW}h^2 < 10^{-12} (95% CL).


title:
Three-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations:
  Temperature Analysis

abstract:
  We present new full-sky temperature maps in five frequency bands from 23 to
94 GHz, based on the first three years of the WMAP sky survey. The new maps,
which are consistent with the first-year maps and more sensitive, incorporate
improvements in data processing made possible by the additional years of data
and by a more complete analysis of the polarization signal. These include
refinements in the gain calibration and beam response models. We employ two
forms of multi-frequency analysis to separate astrophysical foreground signals
from the CMB, each of which improves on our first-year analyses. First, we form
an improved 'Internal Linear Combination' map, based solely on WMAP data, by
adding a bias correction step and by quantifying residual uncertainties in the
resulting map. Second, we fit and subtract new spatial templates that trace
Galactic emission; in particular, we now use low-frequency WMAP data to trace
synchrotron emission. The WMAP point source catalog is updated to include 115
new sources. We derive the angular power spectrum of the temperature anisotropy
using a hybrid approach that combines a maximum likelihood estimate at low l
(large angular scales) with a quadratic cross-power estimate for l>30. Our best
estimate of the CMB power spectrum is derived by averaging cross-power spectra
from 153 statistically independent channel pairs. The combined spectrum is
cosmic variance limited to l=400, and the signal-to-noise ratio per l-mode
exceeds unity up to l=850. The first two acoustic peaks are seen at l=220.8 +-
0.7 and l=530.9 +- 3.8, respectively, while the first two troughs are seen at
l=412.4 +- 1.9 and l=675.1 +- 11.1, respectively. The rise to the third peak is
unambiguous; when the WMAP data are combined with higher resolution CMB
measurements, the existence of a third acoustic peak is well established.


title:
Three-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations:
  Beam Profiles, Data Processing, Radiometer Characterization and Systematic
  Error Limits

abstract:
  The WMAP satellite has completed 3 years of observations of the cosmic
microwave background radiation. The 3-year data products include several sets
of full sky maps of the Stokes I, Q and U parameters in 5 frequency bands,
spanning 23 to 94 GHz, and supporting items, such as beam window functions and
noise covariance matrices. The processing used to produce the current sky maps
and supporting products represents a significant advancement over the first
year analysis, and is described herein. Improvements to the pointing
reconstruction, radiometer gain modeling, window function determination and
radiometer spectral noise parametrization are presented. A detailed description
of the updated data processing that produces maximum likelihood sky map
estimates is presented, along with the methods used to produce reduced
resolution maps and corresponding noise covariance matrices. Finally two
methods used to evaluate the noise of the full resolution sky maps are
presented along with several representative year-to-year null tests,
demonstrating that sky maps produced from data from different observational
epochs are consistent.


title:
Morphology of Spitzer 24um-Detected Galaxies in the UDF: the Links
  between the Star Formation and Galaxy Morphology

abstract:
  We have studied the morphologies of luminous infrared galaxies (LIRGs;
L_IR(8-1000um)>10^11 Lsun) at 0.3< z<1.4 in the HST Ultradeep Field (UDF) by
calculating concentration and asymmetry indices and comparing the results with
similar calculations for: (1) galaxies at similar redshift that are less
infrared-active; and (2) local LIRGs. We find that the high-redshift samples
are dominated by galaxies with concentrations similar to local late-type disk
galaxies; however, they are significantly more asymmetric than most local
galaxies but are similar in both regards to local LIRGs. On average, the
high-redshift infrared-active galaxies are slightly more asymmetric than the
less-active ones, although they do include a significantly higher portion of
highly asymmetric (merging?) systems and a lower portion of more concentrated,
symmetric ones. The morphological similarity of infrared-active and typical
infrared-inactive galaxies at high-redshift suggests that they may be from the
same parent population, but are in different stages of an episodic star
formation process. The similarity between high-redshift and local LIRGs
suggests that a certain level of asymmetry is generally associated with
LIRG-level activity.


title: Spatially Resolved X-ray Spectroscopy of Vela Shrapnel A

abstract:
  We present the detailed X-ray spectroscopy of Vela shrapnel A with the
XMM-Newton satellite. Vela shrapnel A is one of several protrusions identified
as bullets from Vela supernova explosion. The XMM-Newton image shows that
shrapnel A consists of a bright knot and a faint trailing wake. We extracted
spectra from various regions, finding a prominent Si Ly$_\alpha$ emission line
in all the spectra. All the spectra are well represented by the non-equilibrium
ionization (NEI) model. The abundances are estimated to be O$\sim$0.3,
Ne$\sim$0.9, Mg$\sim$0.8, Si$\sim$3, Fe$\sim$0.8 times their solar values. The
non-solar abundance ratio between O and Si indicates that shrapnel A originates
from a deep layer of a progenitor star. We found that the relative abundances
between heavy elements are almost uniform in shrapnel A, which suggests that
the ejecta from supernova explosion are well mixed with swept-up interstellar
medium.


title: Central Star Formation in Pseudobulges and Classical Bulges

abstract:
  I use Spitzer 3.6-8.0 \mu m color profiles to compare the radial structure of
star formation in pseudobulges and classical bulges. Pseudobulges are
``bulges'' which form through secular evolution, rather than mergers. In this
study, pseudobulges are identified using the presence of disk-like structure in
the center of the galaxy (nuclear spiral, nuclear bar, and/or high ellipticity
in bulge); classical bulges are those galaxy bulges with smooth isophotes which
are round compared to the outer disk, and show no disky structure in their
bulge. I show that galaxies structurally identified as having pseudobulges have
higher central star formation rates than those of classical bulges. Further, I
also show that galaxies identified as having classical bulges have remarkably
regular star formation profiles. The color profiles of galaxies with classical
bulges show a star forming outer disk with a sharp change, consistent with a
decline in star formation rates, toward the center of the galaxy. Classical
bulges have a nearly constant inner profile (r < 1.5 kpc) that is similar to
elliptical galaxies. Pseudobulges in general show no such transition in star
formation properties from the outer disk to the central pseudobulge. Thus I
conclude that pseudobulges and classical bulges do in fact form their stars via
different mechanisms. Further, this adds to the evidence that classical bulges
form most of their stars in fast episodic bursts, in a similar fashion to
elliptical galaxies; whereas, pseudobulges form stars from longer lasting
secular processes.


title:
Second Core Formation and High Speed Jets: Resistive MHD Nested Grid
  Simulations

abstract:
  The stellar core formation and high speed jets driven by the formed core are
studied by using three-dimensional resistive MHD nested grid simulations.
Starting with a Bonnor-Ebert isothermal cloud rotating in a uniform magnetic
field, we calculate the cloud evolution from the molecular cloud core (n = 10^6
cm^-3, r_c = 4.6 times 10^4 AU) to the stellar core (n \simeq 10^23 cm^-3, r_c
\simeq 1 solar radius). We resolve cloud structure over 7 orders of magnitude
in spatial extent and over 17 orders of magnitude in density contrast. For
comparison, we calculate two models: resistive and ideal MHD models. Both
models have the same initial condition, but the former includes dissipation
process of magnetic field while the latter does not. The magnetic fluxes in
resistive MHD model are extracted from the first core during 10^12 cm^-3 < n <
10^16 cm^-3 by Ohmic dissipation. Magnetic flux density of the formed stellar
core (n \simeq 10^20 cm^-3) in resistive MHD model is two orders of magnitude
smaller than that in ideal MHD model. Since magnetic braking is less effective
in resistive MHD model, rapidly rotating stellar core (the second core) is
formed. After stellar core formation, the magnetic field of the core is largely
amplified both by magneto-rotational instability and the shearing motion
between the stellar core and ambient medium. As a consequence, high speed
(simeq 45 km,s^-1) jets are driven by the second core, which results in strong
mass ejection. A cocoon-like structure around the second core also forms with
clear bow shocks.


title:
Stellar halos and thick disks around edge-on spiral galaxies IC2233,
  IC5052, NGC4631 and NGC5023

abstract:
  Aims. The extraplanar stellar populations of highly-inclined disk galaxies IC
2233, IC 5052, NGC 4631 and NGC 5023 are analyzed with the goal to quantify
their vertical extent and structure.
  Methods. Based on the single-star photometry, we separate different stellar
populations and analyze their spatial distribution. Results. On archival images
obtained with the Hubble Space Telescope ACS/WFC the surroundings of these
galaxies are well resolved into stars with the red giant population (RGB)
identified far above the galaxy mid-planes. We find that there are a profound
change in slope of the number density profile of the evolved RGB stars at
extraplanar height of 4-8 kpc, that possibly reflects a truncation of the thick
disk and reaching the 2-3 times more extended oblate stellar component (``the
halo''). This structure is consistent with our previous studies of both edge-on
and face-on disk galaxies in the Local Universe and allow us to improve the
spatial model of the stellar components of a typical spiral galaxy. In NGC4631,
the revealed asymmetry of its stellar thick disk and halo, is likely caused by
the neighbor dwarf galaxy NGC4627. Based on the tip of the red giant branch
method (TRGB) we estimated a distance of 10.42+/-0.38 Mpc for IC2233,
5.62+/-0.20 Mpc for IC5052, 7.11+/-0.13 Mpc for NGC4631 (6.70+/-0.15 for its
satellite NGC4627) and 6.14+/-0.15 Mpc for NGC5023. We confirm the presence of
slight extraplanar metallicity gradient of evolved stars at NGC5023 and IC5052,
based on the systematic changes of the colour distribution of red giant stars.


title: UV Upturn in Elliptical Galaxies: Theory

abstract:
  The UV upturn is the rising flux with decreasing wavelength between the Lyman
limit and 2500\AA found virtually in all bright spheroidal galaxies. It has
been a mystery ever since it was first detected by the OAO-2 space telescope
(Code & Welch 1979) because such old metal-rich populations were not expected
to contain any substantial number of hot stars. It was confirmed by following
space missions, ANS (de Boer 1982), IUE (Bertola et al. 1982) and HUT (Brown et
al. 1997). The positive correlation between the UV-to-optical colour (i.e., the
strength of the UV upturn) and the Mg2 line strength found by Burstein et al.
(1987) through IUE observations has urged theorists to construct novel
scenarios in which metal-rich ($\gtrsim Z_{\odot}$) old ($\gtrsim$ a few Gyr)
stars become UV bright (Greggio & Renzini 1990; Horch et al. 1992). Also
interesting was to find using HUT that, regardless of the UV strength, the UV
spectral slopes at 1000--2000\AA in the six UV bright galaxies were nearly
identical suggesting a very small range of temperatures of the UV sources in
these galaxies (Brown et al. 1997), which corresponds to $T_{\rm eff} \approx
20,000 \pm 3,000$ K. This, together with other evidence, effectively ruled out
young stars as the main driver of the UV upturn. A good review on the
observational side of the story is given in the next article by Tom Brown, as
well as in the recent articles of Greggio & Renzini (1999) and O'Connell
(1999).


title: Search for high column density systems with gamma ray bursts

abstract:
  We investigate the possibility to search for metal-poor high column density
(> 10^{23} cm^{-2}) clouds at high redshift (z) by using gamma ray burst (GRB)
afterglows. Such clouds could be related to primeval galaxies which may cause a
burst of star formation. We show that a large part of hydrogen is in molecular
form in such a high column density environment. Therefore, hydrogen molecules
(H2) rather than hydrogen atoms should be searched for. Then we show that
infrared H2 lines are detectable for metal-poor (< 0.01 solar metallicity) high
column density (log NH [cm^{-2}] > 23.5) systems at high-z without suffering
dust extinction. Optical properties of dust in infrared could also be
constrained by observations of high column density systems. Some possible
scenarios of producing high column density systems are finally discussed in the
context of galaxy evolution.


title:
Systematic Effects in Measurement of Black Hole Masses by Emission-Line
  Reverberation of Active Galactic Nuclei: Eddington Ratio and Inclination

abstract:
  We try to identify the sources and systematics of the uncertainty of the
masses of the central black holes in active galactic nuclei (AGNs) which have
been obtained by reverberation-mapping methods. We characterize the broad
H$\beta$ emission-line profiles by the ratio of their full-width at half
maximum (FWHM) to their line dispersion, i.e., the second moment of the line
profile. We use this parameter to separate the reverberation-mapped AGNs into
two populations, the first with narrower H$\beta$ lines with relatively
extended wings, and the second with broader lines that are relatively
flat-topped. The first population is characterized by higher Eddington ratios
than the second. Within each population, we calibrate the black-hole mass scale
by comparison of the reverberation-based mass with that predicted by the bulge
velocity dispersion. We also use the distribution of ratios of the
reverberation-based mass to the velocity-dispersion mass prediction in a
comparison with a ``generalized thick disk'' model in order to see if
inclination can plausibly account for the observed distribution. We find that
the line dispersion is a less biased parameter in general than FWHM for black
hole mass estimation, although we show that it is possible to empirically
correct for the bias introduced by using FWHM to characterize the emission-line
width. We also argue that inclination effects are apparent in a small subset of
objects with the narrowest emission lines. Our principal conclusion is that the
H$\beta$ profile is sensitive primarily to Eddington ratio, but that
inclination effects play a role in some cases. (abridged)


title:
Turbulence and particle acceleration in collisionless supernovae remnant
  shocks: I-Anisotropic spectra solutions

abstract:
  This paper investigates the nature of the MHD turbulence excited by the
streaming of accelerated cosmic rays in a shock wave precursor. The two
recognised regimes (non-resonant and resonant) of the streaming instability are
taken into account. We show that the non-resonant instability is very efficient
and saturates through a balance between its growth and non-linear transfer. The
cosmic-ray resonant instability then takes over and is quenched by advection
through the shock. The level of turbulence is determined by the non-resonant
regime if the shock velocity $V_{\rm sh}$ is larger than a few times $\xi_{\rm
CR} c$, where $\xi_{\rm CR}$ is the ratio of the cosmic-ray pressure to the
shock kinetic energy. The instability determines the dependence of the spectrum
with respect to $k_\parallel$ (wavenumbers along the shock normal). The
transverse cascade of Alfv\'en waves simultaneously determines the dependence
in $k_{\perp}$. We also study the redistribution of turbulent energy between
forward and backward waves, which occurs through the interaction of two
Alfv\'en and one slow magneto-sonic wave. Eventually the spectra at the longest
wavelengths are found almost proportional to $k_{\parallel}^{-1}$. Downstream,
anisotropy is further enhanced through the compression at shock crossing.


title:
Turbulence and particle acceleration in collisionless supernovae remnant
  shocks: II- Cosmic-ray transport

abstract:
  Supernovae remnant shock waves could be at the origin of cosmic rays up to
energies in excess of the knee ($E\simeq3\cdot 10^{15} $eV) if the magnetic
field is efficiently amplified by the streaming of accelerated particles in the
shock precursor. This paper follows up on a previous paper \citep{pell05} which
derived the properties of the MHD turbulence so generated, in particular its
anisotropic character, its amplitude and its spectrum. In the present paper, we
calculate the diffusion coefficients, also accounting for compression through
the shock, and show that the predicted three-dimensional turbulence spectrum
$k_\perp S_{3\rm d}(k_\parallel,k_\perp)\propto
k_\parallel^{-1}k_\perp^{-\alpha}$ (with $k_\parallel$ and $k_\perp$ the
wavenumber components along and perpendicular to the shock normal) generally
leads to Bohm diffusion in the parallel direction. However, if the anisotropy
is constrained by a relation of the form $k_\parallel \propto k_\perp^{2/3}$,
which arises when the turbulent energy cascade occurs at a constant rate
independent of scale, then the diffusion coefficient loses its Bohm scaling and
scales as in isotropic Kolmogorov turbulence. We show that these diffusion
coefficients allow to account for X-ray observations of supernova remnants.
This paper also calculates the modification of the Fermi cycle due to the
energy lost by cosmic rays in generating upstream turbulence and the
concomittant steepening of the energy spectrum. Finally we confirm that cosmic
rays can produced an amplified turbulence in young SNr during their free
expansion phase such that the maximal energy is close to the knee and the
spectral index is close to 2.3 in the warm phase of the interstellar medium


title: Ray-tracing for complex astrophysical high-opacity structures

abstract:
  We present a ray-tracing technique for radiative transfer modeling of complex
three-dimensional (3D) structures which include dense regions of high optical
depth like in dense molecular clouds, circumstellar disks, envelopes of evolved
stars, and dust tori around active galactic nuclei. The corresponding continuum
radiative transfer problem is described and the numerical requirements for
inverse 3D density and temperature modeling are defined. We introduce a
relative intensity and transform the radiative transfer equation along the rays
to solve machine precision problems and to relax strong gradients in the source
term. For the optically thick regions where common ray-tracers are forced to
perform small trace steps, we give two criteria for making use of a simple
approximative solver crossing the optically thick region quickly. Using an
example of a density structure with optical depth changes of 6 orders of
magnitude and sharp temperature variations, we demonstrate the accuracy of the
proposed scheme using a common 5th-order Runge-Kutta ray-tracer with adaptive
step size control. In our test case, the gain in computational speed is about a
factor of 870. The method is applied to calculate the temperature distribution
within a massive molecular cloud core for different boundary conditions for the
radiation field.


title: Quark matter imprint on Gravitational Waves from oscillating stars

abstract:
  We discuss the possibility that the detection of gravitational waves emitted
by compact stars may allow to constrain the MIT bag model of quark matter
equation of state. Our results show that the combined knowledge of the
frequency of the emitted gravitational wave and of the mass, or the radiation
radius, of the source allows one to discriminate between strange stars and
neutron stars and set stringent bounds on the bag constants.


title: Galactic polarization surveys

abstract:
  Following the detection of polarized diffuse Galactic emission in 1962 a
number of surveys were undertaken at low frequencies in the following years
resulting in important insights on the local magnetic field, polarization of
the giant radio loops and other Galactic structures, as well as on the
properties of the diffuse magnetized interstellar medium. This field of
research experienced a revival in the eighties and nineties by a number of high
resolution observations at low and high frequencies, which showed a large
variety of polarization structures having no corresponding signature in the
total intensity images. 'Canals' and 'Faraday screens' were reported, which
clearly indicate that Faraday rotation in the magneto-ionic medium may largely
vary on small scales. These findings called for a systematic approach and a
number of new unbiased polarization surveys were started. Also new attempts for
absolute calibration are under way, which is a critical issue when interpreting
polarization structures. This paper reviews polarization survey projects and
also summarizes recent results and interpretations of this rather active field
of research.


title:
Highly-magnified, Multiply-imaged radio counterparts of the Sub-mm
  Starburst Emission in the Cluster-Lens MS0451.6-0305

abstract:
  Previous authors have reported the detection of intrinsically faint sub-mm
emission lensed by the cluster MS0451.6-0305. They suggest that this emission
arises from a merging system composed of a Ly-break galaxy and a pair of
extremely red objects which are multiply-imaged in the optical/NIR
observations. Since the submm emission presents an unusually large angular
extent (~1 arcmin), the possible radio emission asociatted with that system can
help to identify optical/NIR counterparts due to the higher spatial resolution
and astrometric accuracy of the radio observations. Archive VLA data (BnA
configuration at 1.4 GHz) was reduced and analysed. A simple lens model was
constructed to aid the interpretation of the radio and pre-existing sub-mm and
optical/NIR data. We present a 1.4 GHz map of the central region of
MS0451.6-0305 and report the detection of gravitationally lensed radio
emission, coincident with the previously discovered sub-mm lensed emission. The
overall morphology and scale of the radio and sub-mm emission are strikingly
similar, extending ~1 arcmin across the sky. This observation strongly suggests
that the radio and sub-mm emission arise from the same sources. Preliminary
estimates of the total S_850 microns/S_1.4 GHz flux density ratio appear to be
consistent with that expected from distant star forming galaxies. The radio
emission is resolved into 7 distinct components, and the overall structure can
be explained, using a simple lens model, with three multiply-imaged radio
sources at z~2.9. One of these sources is predicted to lie in the middle of the
previously mentioned system in the source plane, suggesting that it is related
to the intense star formation generated during the merging process.


title:
Discovery of luminous pulsed hard X-ray emission from anomalous X-ray
  pulsars 1RXS J1708-4009, 4U 0142+61 and 1E 2259+586 by INTEGRAL and RXTE

abstract:
  We report on the discovery of hard spectral tails for energies above 10 keV
in the total and pulsed spectra of anomalous X-ray pulsars 1RXS J1708-4009, 4U
0142+61 and 1E 2259+586 using RXTE PCA (2-60 keV) and HEXTE (15-250 keV) data
and INTEGRAL IBIS ISGRI (20-300 keV) data. Improved spectral information on 1E
1841-045 is presented. The pulsed and total spectra measured above 10 keV have
power-law shapes and there is so far no significant evidence for spectral
breaks or bends up to ~150 keV. The pulsed spectra are exceptionally hard with
indices measured for 4 AXPs approximately in the range -1.0 -- 1.0. We also
reanalyzed archival CGRO COMPTEL (0.75-30 MeV) data to search for signatures
from our set of AXPs. No detections can be claimed, but the obtained
upper-limits in the MeV band indicate that for 1RXS J1708-4009, 4U 0142+61 and
1E 1841-045 strong breaks must occur somewhere between 150 and 750 keV.


title: Is PSR B0943+10 a low-mass quark star?

abstract:
  A recent X-ray observation has shown that the radio pulsar PSR B0943+10, with
clear drifting subpulses, has a much smaller polar cap area than that of
conventional pulsars with mass of $\sim\msun$ and radius of $\sim10$ km. Zhang
et al. (2005) addressed then that this new result conflicts with the standard
vacuum gap model. Nonetheless, the discrepancy could be explained if PSR
B0943+10 is actually a low-mass quark star. It is found that the potential drop
in the open-field-line region of oblique pulsars (i.e., inclination angle
$\alpha\neq 0$) might be $\sim 10^2$ times that of aligned pulsars, and that
PSR B0943+10 with $\alpha = 12.4^{\rm o}$ could be well above the deathline. We
thus conclude that the Ruderman-Sutherland-type vacuum gap model still works
well for this pulsar if it is a bare quark star with a mass of $\sim
0.02M_\odot$ and a radius of $\sim 2.6$ km.


title:
On the role of galactic magnetic halo in the ultra high energy cosmic
  rays propagation

abstract:
  The study of propagation of Ultra High Energy Cosmic Rays (UHECR) is a key
step in order to unveil the secret of their origin. Up to now it was considered
only the influence of the galactic and the extragalactic magnetic fields. In
this article we focus our analysis on the influence of the magnetic field of
the galaxies standing between possible UHECR sources and us. Our main approach
is to start from the well known galaxy distribution up to 120 Mpc. We use the
most complete galaxy catalog: the LEDA catalog. Inside a sphere of 120 Mpc
around us, we extract 60130 galaxies with known position. In our simulations we
assign a Halo Dipole magnetic Field (HDF) to each galaxy. The code developed is
able to retro-propagate a charged particle from the arrival points of UHECR
data across our galaxies sample. We present simulations in case of Virgo
cluster and show that there is a non negligible deviation in the case of
protons of $7 \times 10^{19}$ eV, even if the $B$ value is conservative. Then
special attention is devoted to the AGASA triplet where we find that NGC3998
and NGC3992 could be possible candidates as sources.


title: Dust-cooling--induced Fragmentation of Low-metallicity Clouds

abstract:
  Dynamical collapse and fragmentation of low-metallicity cloud cores is
studied using three-dimensional hydrodynamical calculations, with particular
attention devoted whether the cores fragment in the dust-cooling phase or not.
The cores become elongated in this phase, being unstable to non-spherical
perturbation due to the sudden temperature decrease. In the metallicity range
of 10^{-6}-10^{-5}Z_sun, cores with an initial axis ratio >2 reach a critical
value of the axis ratio (>30) and fragment into multiple small clumps. This
provides a possible mechanism to produce low-mass stars in ultra-metal-poor
environments.


title:
Alignment between Luminous Red Galaxies and surrounding structures at
  $z\sim ~0.5$

abstract:
  We analyse a high redshift sample ($0.4<z<0.5$) of LRG's extracted from the
Sloan Digital Sky Survey Data Release 4 and their surrounding structures to
explore the presence of alignment effects of these bright galaxies with
neighbor objects. In order to avoid projection effects we compute photometric
redshifts for galaxies within $3~\mpc$ in projection of LRGs and calculate the
relative angle between the LRG major axis and the direction to neighbors within
1000 km/s. We find a clear signal of alignment between LRG orientations and the
distribution of galaxies within $1.5\mpc$. The alignment effects are present
only for the red population of tracers, LRG orientation is uncorrelated to the
blue population of neighbor galaxies. These results add evidence to the
alignment effects between primaries and satellites detected at low redshifts.
We conclude that such alignments were already present at $z\sim 0.5$


title:
Photometry of Magellanic Cloud clusters with the Advanced Camera for
  Surveys - II. The unique LMC cluster ESO 121-SC03

abstract:
  We present the results of photometric measurements from images of the LMC
cluster ESO 121-SC03 taken with HST/ACS. Our resulting CMD reaches 3 magnitudes
below the main-sequence turn-off, representing the deepest observation of this
cluster to date. We also present similar photometry from ACS imaging of the
accreted Sagittarius dSph cluster Pal. 12, used in this work as a comparison
cluster. From analysis of its CMD, we obtain estimates for the metallicity and
reddening of ESO 121-SC03: [Fe/H] = -0.97 +/- 0.10 and E(V-I) = 0.04 +/- 0.02,
in excellent agreement with previous studies. The observed horizontal branch
level in ESO 121-SC03 suggests this cluster may lie 20 per cent closer to us
than does the centre of the LMC. ESO 121-SC03 also possesses a significant
population of blue stragglers, which we briefly discuss. Our new photometry
allows us to undertake a detailed study of the age of ESO 121-SC03 relative to
Pal. 12 and the Galactic globular cluster 47 Tuc. Our main result is that ESO
121-SC03 is 73 +/- 4 per cent the age of 47 Tuc, and 91 +/- 5 per cent the age
of Pal. 12. Pal. 12 is 79 +/- 6 per cent as old as 47 Tuc, consistent with
previous work. Our result corresponds to an absolute age for ESO 121-SC03 in
the range 8.3-9.8 Gyr depending on the age assumed for 47 Tuc, therefore
confirming ESO 121-SC03 as the only known cluster to lie squarely within the
LMC age gap. We briefly discuss a suggestion from earlier work that ESO
121-SC03 may have been accreted into the LMC system.


title: Observations of magnetic fields in regular and irregular clusters

abstract:
  The existence of magnetic fields associated with the intracluster medium in
clusters of galaxies is now well established through different methods of
analysis. The most detailed evidence for the presence of cluster magnetic
fields comes from radio observations. Magnetic fields can be investigated
through the synchrotron emission of cluster-wide diffuse sources and from
studies of the rotation measure of polarized radio galaxies. I will review
efforts to measure magnetic field strengths and power spectra and the main
issues that have led to our knowledge on magnetic fields in regular and
irregular clusters of galaxies.


title:
An Observational Perspective of Low Mass Dense Cores II: Evolution
  towards the Initial Mass Function

abstract:
  We review the properties of low mass dense molecular cloud cores, including
starless, prestellar, and Class 0 protostellar cores, as derived from
observations. In particular we discuss them in the context of the current
debate surrounding the formation and evolution of cores. There exist several
families of model scenarios to explain this evolution (with many variations of
each) that can be thought of as a continuum of models lying between two extreme
paradigms for the star and core formation process. At one extreme there is the
dynamic, turbulent picture, while at the other extreme there is a slow,
quasi-static vision of core evolution. In the latter view the magnetic field
plays a dominant role, and it may also play some role in the former picture.
Polarization and Zeeman measurements indicate that some, if not all, cores
contain a significant magnetic field. Wide-field surveys constrain the
timescales of the core formation and evolution processes, as well as the
statistical distribution of core masses. The former indicates that prestellar
cores typically live for 2--5 free-fall times, while the latter seems to
determine the stellar initial mass function. In addition, multiple surveys
allow one to compare core properties in different regions. From this it appears
that aspects of different models may be relevant to different star-forming
regions, depending on the environment. Prestellar cores in cluster-forming
regions are smaller in radius and have higher column densities, by up to an
order of magnitude, than isolated prestellar cores. This is probably due to the
fact that in cluster-forming regions the prestellar cores are formed by
fragmentation of larger, more turbulent cluster-forming cores, which in turn
form as a result of strong external compression.


title: The X-ray afterglow of the short gamma ray burst 050724

abstract:
  Short duration (<2 s) Gamma-ray bursts (GRBs) have been a mystery since their
discovery. Until May 2005 very little was known about short GRBs, but this
situation has changed rapidly in the last few months since the Swift and HETE-2
satellites have made it possible to discover X-ray and optical counterparts to
these sources. Positional associations indicate that short GRBs arise in
close-by galaxies (z<0.7). Here we report on a detailed study of the short GRB
050724 X-ray afterglow. This burst shows strong flaring variability in the
X-ray band. It clearly confirms early suggestions of X-ray activity in the
50-100 s time interval following the GRB onset seen with BATSE. Late flare
activity is also observed. These observations support the idea that flares are
related to the inner engine for short GRBs, as well as long GRBs.


title:
Gravitational waves from stochastic relativistic sources: primordial
  turbulence and magnetic fields

abstract:
  The power spectrum of a homogeneous and isotropic stochastic variable,
characterized by a finite correlation length, does in general not vanish on
scales larger than the correlation scale. If the variable is a divergence free
vector field, we demonstrate that its power spectrum is blue on large scales.
Accounting for this fact, we compute the gravitational waves induced by an
incompressible turbulent fluid and by a causal magnetic field present in the
early universe. The gravitational wave power spectra show common features: they
are both blue on large scales, and peak at the correlation scale. However, the
magnetic field can be treated as a coherent source and it is active for a long
time. This results in a very effective conversion of magnetic energy in
gravitational wave energy at horizon crossing. Turbulence instead acts as a
source for gravitational waves over a time interval much shorter than a Hubble
time, and the conversion into gravitational wave energy is much less effective.
We also derive a strong constraint on the amplitude of a primordial magnetic
field when the correlation length is much smaller than the horizon.


title: A Simple Model For Mid-Infrared Emission from Normal Galaxies

abstract:
  We have combined up-to-date stellar population synthesis models, a simple
radiative transfer approach, and a fully comprehensive dust model with the aim
of developing a simple but quantitative way of interpreting the mid-infrared
spectra of galaxies. We apply these models to the observed correlations of
mid-infrared luminosities (at 8 and 24 micron) with the star-formation rate of
normal galaxies and find that the observations are naturally reproduced by our
models. We further find that the observed 24 micron correlation places a weak
constraint on relative distribution of dust and stars.


title: Observations of Mkn 421 with the MAGIC Telescope

abstract:
  The MAGIC telescope took data of very high energy gamma-ray emission from the
blazar Markarian 421 (Mkn 421) between November 2004 and April 2005. We present
a combined analysis of data samples recorded under different observational
conditions, down to gamma-ray energies of 100 GeV. The flux was found to vary
between 0.5 -- 2 Crab units (integrated above 200 GeV), considered a low state
when compared to known data. Although the flux varied on a day-by-day basis, no
short-term variability was observed, although there is some indication that not
all nights are in an equally quiescent state. The results at higher energies
were found to be consistent with previous observations. A clear correlation is
observed between gamma-rays and X-rays fluxes, whereas no significant
correlation between gamma-rays and optical data is seen. The spectral energy
distribution between 100 GeV and 3 TeV shows a clear deviation from a power
law, more clearly and at lower flux than previous observations at higher
energies. The deviation persists after correcting for the effect of attenuation
by the extragalactic background light, and most likely is source-inherent.
There is a rather clear indication of an inverse Compton peak around 100 GeV.
The spectral energy distribution of Mkn 421 can be fitted by a one-zone
synchrotron self-compton model suggesting once again a leptonic origin of the
very high energy gamma-ray emission from this blazar.


title: Stellar Population Diagnostics of Elliptical Galaxy Formation

abstract:
  Major progress has been achieved in recent years in mapping the properties of
passively-evolving, early-type galaxies (ETG) from the local universe all the
way to redshift ~2. Here, age and metallicity estimates for local cluster and
field ETGs are reviewed as based on color-magnitude, color-sigma, and
fundamental plane relations, as well as on spectral-line indices diagnostics.
The results of applying the same tools at high redshifts are then discussed,
and their consistency with the low-redshift results is assessed. Most low- as
well as high-redshift (z~1) observations consistently indicate 1) a formation
redshift z>~3 for the bulk of stars in cluster ETGs, with their counterparts in
low-density environments being on average ~1-2 Gyr younger, i.e., formed at
z>~1.5-2, 2) the duration of the major star formation phase anticorrelates with
galaxy mass, and the oldest stellar populations are found in the most massive
galaxies. With increasing redshift there is evidence for a decrease in the
number density of ETGs, especially of the less massive ones, whereas existing
data appear to suggest that most of the most-massive ETGs were already fully
assembled at z~1. Beyond this redshift, the space density of ETGs starts
dropping significantly, and as ETGs disappear, a population of massive,
strongly clustered, starburst galaxies progressively becomes more and more
prominent, which makes them the likely progenitors to ETGs.


title: Magnetic fields in M dwarfs: rapid magnetic field variability in EV Lac

abstract:
  We report here our spectropolarimetric observations obtained using the
Espadons/CFHT high resolution spectrograph of two M dwarf stars which standard
models suggest are fully convective: EV Lac (M3.5) and HH And (M5.5). The
difference in their rotational velocity makes them good targets to study the
dependence of the magnetic field topology in M dwarfs on rotation. Our results
reveal some aspects of the field topology in EV Lac and HH And. We measured
mean longitudinal magnetic field strengths (Bz) in EV Lac ranging from 18+-3 G
to -40+-3 G. The Bz variations are seen to occur in a timescale of less than 50
minutes, significantly shorter than the rotation period, and are not due to a
flaring event. We discuss some formation scenarios of the Zeeman signatures
found in EV Lac. For HH And we could not detect circular polarization and thus
we place an upper limit to Bz of 5 G.


title:
Local Kelvin-Helmholtz instability and synchrotron modulation in Pulsar
  Wind Nebulae

abstract:
  We present here a series of numerical simulations of the development of
Kelvin-Helmholtz instability in a relativistically hot plasma. The physical
parameters in the unperturbed state are chosen to be representative of local
conditions encountered in Pulsar Wind Nebulae (PWNe), with a main magnetic
field perpendicular to a mildly relativistic shear layers. By using a numerical
code for Relativistic MHD, we investigate the effect of an additional magnetic
field component aligned with the shear velocity, and we follow the evolution of
the instability to the saturation and turbulent regimes. Based on the resulting
flow structure, we then compute synchrotron maps in order to evaluate the
signature of Kelvin-Helmholtz instability on the emission and we investigate
how the time scale and the amplitude of the synchrotron modulations depend on
shear velocity and magnetic field. Finally we compare our results to the
observed variable features in the Crab Nebula. We show that the
Kelvin-Helmholtz instability cannot account for the wisps variability, but it
might be responsible for the time dependent filamentary structure observed in
the main torus.


title:
Electron impact excitation of Helium-like ions up to n=4 levels
  including radiation damping

abstract:
  Helium-like ions provide the most important X-ray spectral diagnostics in
high temperature fusion and astrophysical plasmas. We previously presented
computed collision strengths for O~VII including relativistic fine structure,
levels up to the $n=4$ complex and radiation damping of autoionizing
resonances. We have extended this work to other He-like ions (N, Ne, Mg, Al,
Si, S, Ca). The calculations are carried out using the Breit-Pauli R-matrix
(BPRM) method with a 31-level eigenfunction expansion. Collision strengths for
the principal lines important in X-ray plasma diagnostics, w, x, y and z,
corresponding to the 4 transitions to the ground level 1s^2(^1S_0) <-
1s2p(^1P^o_1), 1s2p(^3P^o_2), 1s2p(^3P^o_1), 1s2s(^3S_1), are explicitly shown.
We find the effect of radiation damping to be significant for the forbidden
transitions in heavier He-like ions, which should affect the diagnostic line
ratios. We extrapolated the collision strengths to their values at infinite
energy using the Burgess-Tully extrapolation technique. This is required to
calculate the Maxwellian average collision strengths at high temperature. We
show that the coupling between dipole allowed and inter-combination transitions
affects increasingly the effective collision strengths for the n ^1S_0 - n'
^3P_1 transition as the charge of the ion increases. This clearly affects the
treatment of the extrapolation toward the infinite energy point of the
collision strength. This work is carried out as part of the Iron Project-RmaX
Network.


title:
Detecting shock waves in cosmological smoothed particle hydrodynamics
  simulations

abstract:
  We develop a formalism for the identification and accurate estimation of the
strength of structure formation shocks during cosmological smoothed particle
hydrodynamics simulations. Shocks not only play a decisive role for the
thermalization of gas in virialising structures but also for the acceleration
of relativistic cosmic rays (CRs) through diffusive shock acceleration. Our
formalism is applicable both to ordinary non-relativistic thermal gas, and to
plasmas composed of CRs and thermal gas. To this end, we derive an analytical
solution to the one-dimensional Riemann shock tube problem for a composite
plasma of CRs and thermal gas. We apply our methods to study the properties of
structure formation shocks in high-resolution hydrodynamic simulations of the
LCDM model. We find that most of the energy is dissipated in weak internal
shocks with Mach numbers M~2 which are predominantly central flow shocks or
merger shock waves traversing halo centres. Collapsed cosmological structures
are surrounded by external shocks with much higher Mach numbers up to M~1000,
but they play only a minor role in the energy balance of thermalization. We
show that after the epoch of cosmic reionisation the Mach number distribution
is significantly modified by an efficient suppression of strong external shock
waves due to the associated increase of the sound speed of the diffuse gas.
Invoking a model for CR acceleration in shock waves, we find that the average
strength of shock waves responsible for CR energy injection is higher than that
for shocks that dominate the thermalization of the gas. When combined with
radiative dissipation and star formation, our formalism can also be used to
study CR injection by supernova shocks, or to construct models for
shock-induced star formation in the interstellar medium. (abridged)


title: Cosmic ray physics in calculations of cosmological structure formation

abstract:
  Cosmic rays (CRs) play a decisive role within our own Galaxy. They provide
partial pressure support against gravity, they trace past energetic events such
as supernovae, and they reveal the underlying structure of the baryonic matter
distribution through their interactions. To study the impact of CRs on galaxy
and cosmic structure formation and evolution, we develop an approximative
framework for treating dynamical and radiative effects of CRs in cosmological
simulations. Our guiding principle is to try to find a balance between
capturing as many physical properties of CR populations as possible while at
the same time requiring as little extra computational resources as possible. We
approximate the CR spectrum of each fluid element by a single power-law, with
spatially and temporally varying normalisation, low-energy cut-off, and
spectral index. Principles of conservation of particle number, energy, and
pressure are then used to derive evolution equations for the basic variables
describing the CR spectrum, both due to adiabatic and non-adiabatic processes.
The processes considered include compression and rarefaction, CR injection via
shocks in supernova remnants, injection in structure formation shock waves,
in-situ re-acceleration of CRs, CR spatial diffusion, CR energy losses due to
Coulomb interactions, ionisation losses, Bremsstrahlung losses, and, finally,
hadronic interactions with the background gas, including the associated
gamma-ray and radio emission due to subsequent pion decay. We show that the
formalism reproduces CR energy densities, pressure, and cooling rates with an
accuracy of ~10% in steady state conditions where CR injection balances
cooling. Our framework is therefore well suited to be included into numerical
simulation schemes of galaxy and structure formation. (abridged)