title: Chandra and Hubble Study of a New Transient X-ray Source in M31

abstract:
  We present X-ray and optical observations of a new transient X-ray source in
M31 first detected 23-May-2004 at R.A.=00:43:09.940 +/- 0.65'',
Dec.=41:23:32.49 +/- 0.66''. The X-ray lightcurve shows two peaks separated by
several months, reminiscent of many Galactic X-ray novae. The location and
X-ray spectrum of the source suggest it is a low mass X-ray binary (LMXB).
Follow-up HST ACS observations of the location both during and after the
outburst provide a high-confidence detection of variability for one star within
the X-ray position error ellipse. This star has $\Delta$B ~ 1 mag, and there is
only a ~1% chance of finding such a variable in the error ellipse. We consider
this star a good candidate for the optical counterpart of the X-ray source. The
luminosity of this candidate provides a prediction for the orbital period of
the system of 2.3$^{+3.7}_{-1.2}$ days.


title:
Enhancement of the $\bar\nu_e$ flux from astrophysical sources by two
  photon annihilation interactions

abstract:
  The ratio of anti-electron to total neutrino flux,
$\Phi_{\bar{\nu}_e}:\Phi_\nu$, expected from $p\gamma$ interactions in
astrophysical sources is $\le1:15$. We point out that this ratio is enhanced by
the decay of $\mu^+\mu^-$ pairs, created by the annihilation of secondary high
energy photons from the decay of the neutral pions produced in $p\gamma$
interactions. We show that, under certain conditions, the
$\Phi_{\bar{\nu}_e}:\Phi_\nu$ ratio may be significantly enhanced in gamma-ray
burst (GRB) fireballs, and that detection at the Glashow resonance of
$\bar{\nu}_e$ in kilometer scale neutrino detectors may constrain GRB fireball
model parameters, such as the magnetic field and energy dissipation radius.


title: Characterizing a cosmic string with the statistics of string lensing

abstract:
  The deep imaging of the field of an observed lensing event by a cosmic string
reveals many additional lensing events. We study the statistics of such string
lensing. We derive explicit expressions for the distributions of image
separations of lensing by a cosmic string and point out that they are quite
sensitive to parameters which characterize the cosmic string, such as the
redshift and tension of the cosmic string. Thus the statistics of string
lensing events add new important information on the cosmic string which cannot
be obtained from the detailed investigation of one lensing event.


title:
Excess Infrared Radiation from a Massive DAZ White Dwarf: GD362 - a
  Debris Disk?

abstract:
  We report the discovery of excess K-band radiation from a massive DAZ white
dwarf star, GD362. Combining infrared photometric and spectroscopic
observations, we show that the excess radiation cannot be explained by a
stellar or substellar companion, and is likely to be caused by a debris disk.
This would be only the second such system known, discovered 18 years after
G29-38, the only single white dwarf currently known to be orbited by
circumstellar dust. Both of these systems favor a model with accretion from a
surrounding debris disk to explain the metal abundances observed in DAZ white
dwarfs. Nevertheless, observations of more DAZs in the mid-infrared are
required to test if this model can explain all DAZs.


title: Broad-Band Imaging of a Large Sample of Irregular Galaxies

abstract:
  We present the results of UBV imaging of a large sample of irregular
galaxies: 94 Im systems, 24 Blue Compact Dwarfs (BCDs), and 18 Sm galaxies. We
also include JHK imaging of 41 of these galaxies. The sample spans a large
range in galactic parameters. Ellipse fit axial ratios, inclinations, and
position angles are derived, integrated photometry and azimuthally-averaged
surface photometry profiles are determined, and exponential fits give the
central surface brightnesses, scale lengths, and isophotal and half-power
radii. These data are used to address the shapes of Im galaxies, look for clues
to past interactions in large-scale peculiarities, examine the nature and
consequences of bars, study color gradients and large-scale color variations,
and compare the exponential disk profiles of the young and old stellar
components. For example, color gradients exhibit a great variety and not all
passbands are correlated. Bars are associated with higher star formation rates.
Many irregulars show a double exponential radial light profile that is steeper
in the outer parts, and these are reproduced by a new model of star formation
that is discussed in a companion paper. Some galaxies, primarily BCDs, have
double exponentials that are steeper (and bluer) in the inner parts, presumably
from centralized star formation. Im-types have thicker, less-prominent dust
layers than spiral galaxies because of their lower average surface densities
and midplane extinctions.


title:
Radial Profiles of Star Formation in the Far Outer Regions of Galaxy
  Disks

abstract:
  Star formation in galaxies is triggered by a combination of processes,
including gravitational instabilities, spiral wave shocks, stellar compression,
and turbulence compression. Some of these persist in the far outer regions
where the column density is far below the threshold for instabilities, making
the outer disk cutoff somewhat gradual. We show that in a galaxy with a single
exponential gas profile the star formation rate can have a double exponential
with a shallow one in the inner part and a steep one in the outer part. Such
double exponentials have been observed recently in the broad-band intensity
profiles of spiral and dwarf Irregular galaxies. The break radius in our model
occurs slightly outside the threshold for instabilities provided the Mach
number for compressive motions remains of order unity to large radii. The ratio
of the break radius to the inner exponential scale length increases for higher
surface brightness disks because the unstable part extends further out. This is
also in agreement with observations. Galaxies with extended outer gas disks
that fall more slowly than a single exponential, such as 1/R, can have their
star formation rate scale approximately as a single exponential with radius,
even out to 10 disk scale lengths. Halpha profiles should drop much faster than
the star formation rate as a result of the rapidly decreasing ambient density.


title: Deeper Chandra Follow-up of Cygnus TeV Source Perpetuates Mystery

abstract:
  A 50 ksec Chandra observation of the unidentified TeV source in Cygnus
reported by the HEGRA collaboration reveals no obvious diffuse X-ray
counterpart. However, 240 Pointlike X-ray sources are detected within or nearby
the extended TeV J2032+4130 source region, of which at least 36 are massive
stars and 2 may be radio emitters. That the HEGRA source is a composite, having
as counterpart the multiple point-like X-ray sources we observe, cannot be
ruled out. Indeed, the distribution of point-like X-ray sources appears
non-uniform and concentrated broadly within the extent of the TeV source
region. We offer a hypothesis for the origin of the very high energy gamma-ray
emission in Cyg OB2 based on the local acceleration of TeV range cosmic rays
and the differential distribution of OB vs. less massive stars in this
association.


title: Fitting Formula for Flux Scintillation of Compact Radio Sources

abstract:
  We present a fitting function to describe the statistics of flux modulations
caused by interstellar scintillation. The function models a very general
quantity: the cross-correlation of the flux observed from a compact radio
source of finite angular size observed at two frequencies and at two positions
or times. The formula will be useful for fitting data from sources such as
intra-day variables and gamma-ray burst afterglows. These sources are often
observed at relatively high frequencies (several gigahertz) where interstellar
scattering is neither very strong nor very weak, so that asymptotic formulae
are inapplicable.


title:
A Dusty Disk Around GD 362, a White Dwarf With a Uniquely High
  Photospheric Metal Abundance

abstract:
  Eighteen years after an infrared excess was discovered associated with the
white dwarf G29-38, we report ground-based measurements (JHKL'N') with
mJy-level sensitivity of GD 362 that show it to be a second single white dwarf
with an infrared excess. As a first approximation, the excess around GD 362,
which amounts to about 3% of the total stellar luminosity, can be explained by
emission from a passive, flat, opaque dust disk that lies within the Roche
radius of the white dwarf. The dust may have been produced by the tidal
disruption of a large parent body such as an asteroid. Accretion from this
circumstellar disk could account for the remarkably high abundance of metals in
the star's photosphere.


title:
Estimation and reduction of the uncertainties in chemical models:
  Application to hot core chemistry

abstract:
  It is not common to consider the role of uncertainties in the rate
coefficients used in interstellar gas-phase chemical models. In this paper, we
report a new method to determine both the uncertainties in calculated molecular
abundances and their sensitivities to underlying uncertainties in the kinetic
data utilized. The method is used in hot core models to determine if previous
analyses of the age and the applicable cosmic-ray ionization rate are valid. We
conclude that for young hot cores ($\le 10^4$ yr), the modeling uncertainties
related to rate coefficients are reasonable so that comparisons with
observations make sense. On the contrary, the modeling of older hot cores is
characterized by strong uncertainties for some of the important species. In
both cases, it is crucial to take into account these uncertainties to draw
conclusions from the comparison of observations with chemical models.


title:
Gemini Spectroscopy of Supernovae from SNLS: Improving High Redshift SN
  Selection and Classification

abstract:
  We present new techiques for improving the efficiency of supernova (SN)
classification at high redshift using 64 candidates observed at Gemini North
and South during the first year of the Supernova Legacy Survey (SNLS). The SNLS
is an ongoing five year project with the goal of measuring the equation of
state of Dark Energy by discovering and following over 700 high-redshift SNe Ia
using data from the Canada-France-Hawaii Telescope Legacy Survey. We achieve an
improvement in the SN Ia spectroscopic confirmation rate: at Gemini 71% of
candidates are now confirmed as SNe Ia, compared to 54% using the methods of
previous surveys. This is despite the comparatively high redshift of this
sample, where the median SN Ia redshift is z=0.81 (0.155 <= z <= 1.01). These
improvements were realized because we use the unprecedented color coverage and
lightcurve sampling of the SNLS to predict whether a candidate is an SN Ia and
estimate its redshift, before obtaining a spectrum, using a new technique
called the "SN photo-z." In addition, we have improved techniques for galaxy
subtraction and SN template chi^2 fitting, allowing us to identify candidates
even when they are only 15% as bright as the host galaxy. The largest
impediment to SN identification is found to be host galaxy contamination of the
spectrum -- when the SN was at least as bright as the underlying host galaxy
the target was identified more than 90% of the time. However, even SNe on
bright host galaxies can be easily identified in good seeing conditions. When
the image quality was better than 0.55 arcsec the candidate was identified 88%
of the time. Over the five-year course of the survey, using the selection
techniques presented here we will be able to add approximately 170 more
confirmed SNe Ia than would be possible using previous methods.


title: Dark Matter in Many Forms

abstract:
  Since ordinary matter constitutes about 4% of the closure density of the
Universe while dark matter constitutes about six times as much, it is urged
that searches for dark matter consider that it may exist in several forms.
Implications for detection and hadron and $e^+ e^-$ colliders are discussed.


title:
Specific star formation rates to redshift 5 from the FORS Deep Field and
  the GOODS-S Field

abstract:
  We explore the build-up of stellar mass in galaxies over a wide redshift
range 0.4 < z < 5.0 by studying the evolution of the specific star formation
rate (SSFR), defined as the star formation rate per unit stellar mass, as a
function of stellar mass and age. Our work is based on a combined sample of ~
9000 galaxies from the FORS Deep Field and the GOODS-S field, providing high
statistical accuracy and relative insensitivity against cosmic variance. As at
lower redshifts, we find that lower-mass galaxies show higher SSFRs than higher
mass galaxies, although highly obscured galaxies remain undetected in our
sample. Furthermore, the highest mass galaxies contain the oldest stellar
populations at all redshifts, in principle agreement with the existence of
evolved, massive galaxies at 1 < z < 3. It is remarkable, however, that this
trend continues to very high redshifts of z ~ 4. We also show that with
increasing redshift the SSFR for massive galaxies increases by a factor of ~
10, reaching the era of their formation at z ~ 2 and beyond. These findings can
be interpreted as evidence for an early epoch of star formation in the most
massive galaxies, and ongoing star-formation activity in lower mass galaxies.


title: The Radio Quiescence of Active Galaxies with High Accretion Rates

abstract:
  We present 6 cm Very Large Array observations of the Greene & Ho (2004)
sample of 19 low-mass active galaxies with high accretion rates. This is one of
the only studies of a uniform sample of narrow-line Seyfert 1 (NLS1) galaxies
with such high sensitivity and resolution. Although we detect only one source,
the entire sample is very radio-quiet down to strong limits. GH10 was found to
have a radio power of 8.5 x 10^21 W/Hz, and a ratio R = f(6 cm)/f(4400 A) of
2.8. The 3 sigma upper limits for the remaining nondetections correspond to
radio powers from 3 x 10^20 to 8 x 10^21 W/Hz and 0.47 < R <9.9. Stacking all
nondetections yields an even stronger upper limit of R < 0.27. An assessment of
existing observations in the literature confirms our finding that NLS1s are
consistently radio-quiet, with a radio-loud fraction of 0%-6%, which is
significantly lower than the 10%-20% observed in the general quasar population.
By analogy with stellar-mass black holes, we argue that AGNs undergo a state
transition at L_bol/L_Edd~0.01. Below this value a radiatively inefficient
accretion flow effectively drives an outflow, which disappears when the flow
turns into an optically thick, geometrically thin disk, or a radiation
pressure-dominated slim disk at still higher L_bol/L_Edd.


title:
Frequency of Debris Disks around Solar-Type Stars: First Results from a
  Spitzer/MIPS Survey

abstract:
  We have searched for infrared excesses around a well defined sample of 69 FGK
main-sequence field stars. These stars were selected without regard to their
age, metallicity, or any previous detection of IR excess; they have a median
age of ~4 Gyr. We have detected 70 um excesses around 7 stars at the 3-sigma
confidence level. This extra emission is produced by cool material (< 100 K)
located beyond 10 AU, well outside the ``habitable zones'' of these systems and
consistent with the presence of Kuiper Belt analogs with ~100 times more
emitting surface area than in our own planetary system. Only one star, HD
69830, shows excess emission at 24 um, corresponding to dust with temperatures
> 300 K located inside of 1 AU. While debris disks with Ld/L* > 10^-3 are rare
around old FGK stars, we find that the disk frequency increases from 2+-2% for
Ld/L* > 10^-4 to 12+-5% for Ld/L* > 10^-5. This trend in the disk luminosity
distribution is consistent with the estimated dust in our solar system being
within an order of magnitude, greater or less, than the typical level around
similar nearby stars.


title:
Is the Broad-Line Region Clumped or Smooth? Constraints from the H alpha
  Profile in NGC 4395, the Least Luminous Seyfert 1 Galaxy

abstract:
  The origin and configuration of the gas which emits broad lines in Type I
active galactic nuclei is not established yet. The lack of small-scale
structure in the broad emission-line profiles is consistent with a smooth gas
flow, or a clumped flow with many small clouds. An attractive possibility for
the origin of many small clouds is the atmospheres of bloated stars, an origin
which also provides a natural mechanism for the cloud confinement. Earlier
studies of the broad-line profiles have already put strong lower limits on the
minimum number of such stars, but these limits are sensitive to the assumed
width of the lines produced by each cloud. Here we revisit this problem using
high-resolution Keck spectra of the H alpha line in NGC 4395, which has the
smallest known broad-line region (~10^14 cm). Only a handful of the required
bloated stars (each having r~10^14 cm) could fit into the broad-line region of
NGC 4395, yet the observed smoothness of the H alpha line implies a lower limit
of ~10^4-10^5 on the number of discrete clouds. This rules out conclusively the
bloated-stars scenario, regardless of any plausible line-broadening mechanisms.
The upper limit on the size of the clouds is ~10^12 cm, which is comparable to
the size implied by photoionization models. This strongly suggests that gas in
the broad-line region is structured as a smooth rather than a clumped flow,
most likely in a rotationally dominated thick disk-like configuration. However,
it remains to be clarified why such a smooth, gravity-dominated flow generates
double-peaked emission lines only in a small fraction of active galactic
nuclei.


title: Dynamical decay of a massive multiple system in Orion KL?

abstract:
  We present absolute astrometry of 35 radio sources in the Orion Trapezium and
Becklin-Neugebauer/Kleinman-Low regions, obtained from Very Large Array
archival observations collected over a period of 15 years. By averaging the
results for all the sources, we estimate the mean absolute proper motion of
Orion to be --in Galactic coordinates-- $\mu_\ell \cos b$ = +2.1 $\pm$ 0.2 mas
yr$^{-1}$; $\mu_b$ = $-$0.1 $\pm$ 0.2 mas yr$^{-1}$. These values agree
remarkably well with those expected from the differential rotation of the Milky
Way. Subtraction of this mean motion from the individual measurements allows us
to register all proper motions to the rest frame of the Orion nebula, and
identify radio sources with large residual velocities. In the KL region, we
find three sources in this situation: the BN object, the radio source I, and
the radio counterpart of the infrared source n. All three objects appear to be
moving away from a common point where they must all have been located about 500
years ago. This suggests that all three sources were originally part of a
multiple massive stellar system that recently disintegrated as a result of a
close dynamical


title:
The Multiwavelength Survey by Yale-Chile (MUSYC): Survey Design and Deep
  Public UBVRIz' Images and Catalogs of the Extended Hubble Deep Field South

abstract:
  We present UBVRIz' optical images of the 0.32 square degree Extended Hubble
Deep Field South. This is one of four fields comprising the MUSYC survey, which
is optimized for the study of galaxies at z=3, AGN demographics, and Galactic
structure. We calculate corrected aperture photometry and its uncertainties and
find through tests that these provide a significant improvement upon standard
techniques. Our photometric catalog of 62968 objects is complete to a total
magnitude of R_AB=25. We select z=3 Lyman break galaxy (LBG) candidates from
their UVR colors and find a sky surface density of 1.4/sq. arcmin and an
angular correlation function w(theta) = 2.3+-1.0 theta^{-0.8}. (Abridged)


title: Implications of the Cosmic Background Imager Polarization Data

abstract:
  We present new measurements of the power spectra of the E-mode of CMB
polarization, the temperature T, the cross-correlation of E and T, and upper
limits on the B-mode from 2.5 years of dedicated Cosmic Background Imager (CBI)
observations. Both raw maps and optimal signal images in the uv-plane and real
space show strong detections of the E-mode (11.7 sigma for the EE power
spectrum overall) and no detection of the B-mode. The power spectra are used to
constrain parameters of the flat tilted adiabatic Lambda-CDM models: those
determined from EE and TE bandpowers agree with those from TT, a powerful
consistency check. There is little tolerance for shifting polarization peaks
from the TT-forecast locations, as measured by the angular sound crossing scale
theta = 100 ell_s = 1.03 +/- 0.02 from EE and TE cf. 1.044 +/- 0.005 with the
TT data included. The scope for extra out-of-phase peaks from subdominant
isocurvature modes is also curtailed. The EE and TE measurements of CBI, DASI
and BOOMERANG are mutually consistent, and, taken together rather than singly,
give enhanced leverage for these tests.


title: Phase Lags in the Optical-Infrared Light Curves of AGB Stars

abstract:
  To search for phase lags in the optical-infrared light curves of asymptotic
giant branch stars, we have compared infrared data from the COBE DIRBE
satellite with optical light curves from the AAVSO and other sources. We found
17 examples of phase lags in the time of maximum in the infrared vs. that in
the optical, and 4 stars with no observed lags. There is a clear difference
between the Mira variables and the semi-regulars in the sample, with the
maximum in the optical preceding that in the near-infrared in the Miras, while
in most of the semi-regulars no lags are observed. Comparison to published
theoretical models indicates that the phase lags in the Miras are due to strong
titanium oxide absorption in the visual at stellar maximum, and suggests that
Miras pulsate in the fundamental mode, while at least some semi-regulars are
first overtone pulsators. There is a clear optical-near-infrared phase lag in
the carbon-rich Mira V CrB; this is likely due to C2 and CN absorption
variations in the optical.


title: The Knotty Question of the Jet of PKS B1421-490

abstract:
  We report the discovery of unusually strong optical and X-ray emission
associated with a knot in the radio jet of PKS B1421-490. The knot is the
brightest feature observed beyond the radio band, with knot/core flux ratios
\~300 and 3.7 at optical and X-ray frequencies. We interpret the extreme
optical output of the knot as synchrotron emission. The nature of the X-ray
emission is unclear. We consider a second synchrotron component, inverse
Compton emission from a relativistic, decelerating jet, and the possibility
that this feature is a chance superposition of an unusual BL Lac object.


title:
HE1327-2326, an unevolved star with [Fe/H]<-5.0. I. A Comprehensive
  Abundance Analysis

abstract:
  We present the elemental abundances of HE1327-2326, the most iron-deficient
star known, determined from a comprehensive analysis of spectra obtained with
the Subaru Telescope High Dispersion Spectrograph.


title:
Total masses of the Local Group and M 81 group derived from the local
  Hubble flow

abstract:
  Based on accurate measurements of distances to nearby galaxies made with
Hubble Space Telescope, we determined the radii of the zero-velocity surface:
R_0 = 0.96+-0.03 Mpc for the Local Group and R_0 = 0.89+-0.05 Mpc for the group
of galaxies around M81/M82. This yields the total masses of the groups to be
M_T = (1.29+-0.14) 10^{12} M_sun and M_T = (1.03+-0.17) 10^{12} M_sun,
respectively.
  The R_0-method allowed us to determine the mass ratio of the brightest two
members in the considered groups. Based on the minimum scatter of galaxies with
respect to the Hubble regression, we derived a mass ratio of 0.8 : 1.0 for the
Milky Way and Andromeda, and 0.54 : 1.00 for M82 and M81, which is quite close
to the ratio of luminosities of these galaxies.


title: First AMBER/VLTI observations of hot massive stars

abstract:
  AMBER is the first near infrared focal instrument of the VLTI. It combines
three telescopes and produces spectrally resolved interferometric measures.
This paper discusses some preliminary results of the first scientific
observations of AMBER with three Unit Telescopes at medium (1500) and high
(12000) spectral resolution. We derive a first set of constraints on the
structure of the circumstellar material around the Wolf Rayet Gamma2 Velorum
and the LBV Eta Carinae.


title: Squeezing the window on isocurvature modes with the Lyman-alpha forest

abstract:
  Various recent studies proved that cosmological models with a significant
contribution from cold dark matter isocurvature perturbations are still
compatible with most recent data on cosmic microwave background anisotropies
and on the shape of the galaxy power spectrum, provided that one allows for a
very blue spectrum of primordial entropy fluctuations (n_iso > 2). However,
such models predict an excess of matter fluctuations on small scales, typically
below 40 Mpc/h. We show that the proper inclusion of high-resolution high
signal-to-noise Lyman-alpha forest data excludes most of these models. The
upper bound on the isocurvature fraction alpha=f_iso^2/(1+f_iso^2), defined at
the pivot scale k_0=0.05/Mpc, is pushed down to alpha<0.4, while n_iso=1.9+-1.0
(95% confidence limits). We also study the bounds on curvaton models
characterized by maximal correlation between curvature and isocurvature modes,
and a unique spectral tilt for both. We find that f_iso<0.05 (95% c.l.) in that
case. For double inflation models with two massive inflatons coupled only
gravitationally, the mass ratio should obey R < 3 (95% c.l.).


title:
Lunar Satellite Detection of Ultra-High Energy Neutrinos with the Use of
  Radio Methods

abstract:
  Neutrinos interact with matter only through weak processes with low
cross-section. To detect cosmic neutrinos most efforts have relied on the
detection of visible Vavilov-Cerenkov light in detectors embedded in the target
volumes. To access the decreasing flux of ultra-high energy neutrinos, far
above 1 PeV, ideas on how to increase the detection volume by observing
coherent radio frequency emission caused by the Askaryan effect have been put
forward. Here we describe how a satellite in lunar orbit equipped with an
electromagnetic vector sensor could detect Askaryan pulses induced by neutrinos
interacting with the moon. The threshold neutrino energy is found to be 50 EeV
for this setup, and the sensitivity is determined from simulations. A model
dependent event rate of 2.2 events per year is calculated.


title:
The HARPS search for southern extra-solar planets. VI. A Neptune-mass
  planet around the nearby M dwarf Gl 581

abstract:
  We report the discovery of a Neptune-mass planet around Gl 581 (M3V, M = 0.31
Msol), based on precise Doppler measurements with the HARPS spectrograph at La
Silla Observatory. The radial velocities reveal a circular orbit of period P =
5.366 days and semi-amplitude K1 = 13.2 m/s. The resulting minimum mass of the
planet (m2 sin i) is only 0.052 Mjup = 0.97 Mnep = 16.6 Mearth making Gl 581b
one of the lightest extra-solar planet known to date. The Gl 581 planetary
system is only the third centered on an M dwarf, joining the Gl 876
three-planet system and the lone planet around Gl 436. Its discovery reinforces
the emerging tendency of such planets to be of low mass, and found at short
orbital periods. The statistical properties of the planets orbiting M dwarfs do
not seem to match a simple mass scaling of their counterparts around solar-type
stars.


title: Age of High Redshift Objects - a Litmus Test for the Dark Energy Models

abstract:
  The discovery of the quasar, the APM 08279+5255 at z = 3.91 whose age is 2-3
Gyr has once again led to ``age crisis''. The noticeable fact about this object
is that it cannot be accommodated in a universe with $\Omega_m = 0.27$,
currently accepted value of matter density parameter and $\omega =
\mathrm{constant}$. In this work, we explore the concordance of various dark
energy parameterizations ($w(z)$ models) with the age estimates of the old high
redshift objects. It is alarming to note that the quasar cannot be accommodated
in any dark energy model even for $\Omega_m = 0.23$, which corresponds to $1
\sigma$ deviation below the best fit value provided by WMAP. There is a need to
look for alternative cosmologies or some other dark energy parameterizations
which allow the existence of the high redshift objects.


title: Search for Correlated High Energy Cosmic Ray Events with CHICOS

abstract:
  We present the results of a search for time correlations in high energy
cosmic ray data (primary E > 10^14 eV) collected by the California HIgh school
Cosmic ray ObServatory (CHICOS) array. Data from 69 detector sites spread over
an area of 400 km^2 were studied for evidence of isolated events separated by
more than 1 km with coincidence times ranging from 1 microseconds up to 1
second. We report upper limits for the coincidence probability as a function of
coincidence time.


title: High-energy neutrino emission from X-ray binaries

abstract:
  We show that high-energy neutrinos can be efficiently produced in X-ray
binaries with relativistic jets and high-mass primary stars. We consider a
system where the star presents a dense equatorial wind and the jet has a small
content of relativistic protons. In this scenario, neutrinos and correlated
gamma-rays result from pp interactions and the subsequent pion decays. As a
particular example we consider the microquasar LS I +61 303. Above 1 TeV, we
obtain a mean-orbital neutrino muon induced luminosity of 5 10^34 erg/s which
can be related to an event rate of 4-5 muon-type neutrinos per
kilometer-squared per year after considering the signal attenuation due to
maximal neutrino oscillations. The maximal neutrino energies here considered
will range between 20 and 85 TeV along the orbit. The local infrared
photon-field is responsible for opacity effects on the associated gamma
radiation at high energies, but below 50 GeV the source could be detected by
MAGIC telescope. GLAST observations at photon energies E>100 MeV should also
reveal a strong source.


title:
High-significance Sunyaev-Zel'dovich measurement: Abell 1914 seen with
  the Arcminute Microkelvin Imager

abstract:
  We report the first detection of a Sunyaev-Zel'dovich (S-Z) decrement with
the Arcminute Microkelvin Imager (AMI). We have made commissioning observations
towards the cluster A1914 and have measured an integrated flux density of -8.61
mJy in a uv-tapered map with noise level 0.19 mJy/beam. We find that the
spectrum of the decrement, measured in the six channels between 13.5-18GHz, is
consistent with that expected for a S-Z effect. The sensitivity of the
telescope is consistent with the figures used in our simulations of cluster
surveys with AMI.


title: Cosmology with Weak Lensing Surveys

abstract:
  Weak gravitational lensing surveys measure the distortion of the image of
distant sources due to the deflections of light rays by the fluctuations of the
gravitational potential along the line of sight. Since they probe the
non-linear matter power spectrum itself at medium redshift such surveys are
complimentary to both galaxy surveys (which follow stellar light) and cosmic
microwave background observations (which probe the linear regime at high
redshift). Ongoing CMB experiments such as WMAP and the future Planck satellite
mission will measure the standard cosmological parameters with unprecedented
accuracy. The focus of attention will then shift to understanding the nature of
dark matter and vacuum energy: several recent studies suggest that lensing is
the best method for constraining the dark energy equation of state. During the
next 5 year period ongoing and future weak lensing surveys such as the Joint
Dark Energy Mission (JDEM, e.g. SNAP) or the Large-aperture Synoptic Survey
Telescope (LSST) will play a major role in advancing our understanding of the
universe in this direction. In this review article we describe various aspects
of weak lensing surveys and how they can help us in understanding our universe.


title: Parametrization of the Galactic Structure by two exponentials

abstract:
  We parametrized the total structure of the Galaxy in cylindrical coordinates
by radial and vertical exponentials up to z=10 kpc, covering thin disc, thick
disc, and the inner spheroid. However, we let the scaleheight and scalelength
to be a continuous function of distance from the Galactic plane. The standard
deviations for the differences between the space densities estimated by means
of the newly defined scaleheight and scalelength and the observed space
densities for three absolute magnitude intervals, 5<M(g)<=6, 6<M(g)<=7, and
7<M(g)<=8, for the fields SA 114, ELAIS, and #0952+5245 are rather small. The
uncertainties for the scaleheight are also small, indicating that this
parameter is very sensitive to the distance from the Galactic plane, whereas
those for the scalelength are larger.


title: Evolution of 1612 MHz Maser Emission in Expanding Circumstellar Shells

abstract:
  Observations show that 1612 MHz masers of OH/IR stars can fade on a timescale
of a decade. This fading is probably associated with the switch from rapid mass
loss, which is ultimately linked with an internal He-shell flash, to the much
slower mass loss supported by more quiescent conditions. We study the observed
maser decay with a composite computational model, comprising a time-dependent
chemical model of the envelope, and a radiation transfer model which provides
the maser pumping. Our combined model is able to reproduce the rapid decay of
maser intensity, following a sudden drop in the stellar mass-loss rate. The
explanation for the rapid fall in maser emission is not a fall in the OH number
density, or the kinetic temperature in the inverted layers, but the loss of a
radiative pump route which carries population from level 1 to level 4 via
levels 16, 15 and 11. The loss of these pump routes is a result, in turn, of a
greatly reduced energy density of 53 micron radiation.


title:
Plasma Diagnostics of Active Region Evolution and Implications for
  Coronal Heating

abstract:
  A detailed study is presented of the decaying solar active region NOAA 10103
observed with the Coronal Diagnostic Spectrometer (CDS), the Michelson Doppler
Imager (MDI) and the Extreme-ultraviolet Imaging Telescope (EIT) onboard the
Solar and Heliospheric Observatory (SOHO). Electron density maps formed using
Si X (356.03A/347.41A) show that the density varies from ~10^10 cm^-3 in the
active region core, to ~7x10^8 cm^-3 at the region boundaries. Over the five
days of observations, the average electron density fell by ~30%. Temperature
maps formed using Fe XVI(335.41A)/Fe XIV(334.18A) show electron temperatures of
\~2.34x10^6 K in the active region core, and ~2.10x10^6 K at the region
boundaries. Similarly to the electron density, there was a small decrease in
the average electron temperature over the five day period. The radiative,
conductive, and mass flow losses were calculated and used to determine the
resultant heating rate (P_H). Radiative losses were found to dominate the
active region cooling process. As the region decayed, the heating rate
decreased by almost a factor of five between the first and last day of
observations. The heating rate was then compared to the total unsigned magnetic
flux (Phi_tot), yielding a power-law of the form P_H ~ Phi_tot^(0.81 +/- 0.32).
This result suggests that waves rather than nanoflares may be the dominant
heating mechanism in this active region.


title:
Nonlinear Evolution of Cosmic Magnetic Fields and Cosmic Microwave
  Background Anisotropies

abstract:
  In this work we investigate the effects of the primordial magnetic fields on
cosmic microwave background anisotropies (CMB). Based on cosmological
magnetohydrodynamic (MHD) simulations we calculate the CMB anisotropy spectra
and polarization induced by fluid fluctuations (Alfv\'en modes) generated by
primordial magnetic fields. The strongest effect on the CMB spectra comes from
the transition epoch from a turbulent regime to a viscous regime. The balance
between magnetic and kinetic energy until the onset of the viscous regime
provides a one to one relation between the comoving coherence length $L$ and
the comoving magnetic field strength $B$, such as $L \sim 30 (B/10^{-9}{\rm
G})^3 \rm pc$. The resulting CMB temperature and polarization anisotropies are
somewhat different from the ones previously obtained by using linear
perturbation theory. Our calculation gives a constraint on the magnetic field
strength in the intermediate scale of CMB observations. Upper limits are set by
WMAP and BOOMERANG results for comoving magnetic field strength of $B < 28 \rm
nG$ with a comoving coherence length of $L > 0.7 \rm Mpc$ for the most extreme
case, or $B < 30 \rm nG$ and $L> 0.8 \rm Mpc$ for the most conservative case.


title:
Modelling the energy dependencies of X-ray quasi-periodic oscillations
  in accreting compact objects

abstract:
  We have constructed models of quasi-periodic variability of X-ray emission
from accreting compact objects. Assuming a general scenario of a propagation
model of variability, with inverse Compton upscatering as the emission
mechanism, we have considered a number of cases for the periodic modulation:
modulation of the plasma heating rate, cooling rate by external soft photons,
and the amplitude of the reprocessed component. We have computed various
observational characteristics which can be compared to good quality data.These
include Fourier-frequency resolved spectra and results of cross-correlation
analysis between light-curves at different energies. Each model of modulation
predicts specific observational signatures, which help in identifying the
physical processes driving QPO emission in accreting sources.


title: On the Electrodynamics of Cosmic repulsion

abstract:
  Applying the known physics of plasmas, the 40 plus year old "Strong" Magnetic
Field (SMF) model has been extended from explaining the nature of the
AGN/quasar central engine, the evolution of galaxies, quasars and jets, the
origin of large-scale magnetic fields and large-scale structure of galaxies in
our Big Bang Universe, to explaining cosmic repulsion and why it overcame the
influence of Gravity only about five billion years ago. Well-known facts about
Einstein's general relativity equations, together with the SMF model, are used
to explain the astronomical observations that forced us to deduce a present
acceleration of the expansion of the Universe.
  Two groups of astronomical observers, one headed by Saul Perlmutter and the
other by Robert Kirshner, recently found an amazing transition, from the
expected slowing of the expansion of the Universe due to Gravity, to the
expansion of the Universe beginning to be accelerated, at about an age of the
Universe of nine billion years in our Big Bang Universe. Profound questions
that arise are: what is this "dark energy" causing this result, and why has it
started to overcome attractive gravity only in the last five billion years of
our 14 billion year old Universe.


title: On the Electrodynamics of the Big Bang Universe

abstract:
  Applying the known physics of plasmas to the evolution of galaxies and
quasars in the Early Universe, a unique "Strong" Magnetic Field Modsl (SMF) was
created that explains the origin of a very large-scale primordial magnetic
field in each Supercluster and the observed large-scale structure of galaxies.
This physical model, involving both gravitation and cosmical magnetism,
explains the existence of significant magnetic fields in galaxies. An intense
highly relativistic gravitationally bound current loop (Storage Ring) is formed
by gravitational collapse explaining the nature of the AGN/Quasar Central
Engine, galactic structure and radio, optical and X-ray jets.


title:
Timing an Accreting Millisecond Pulsar: Measuring the Accretion Torque
  in IGR J00291+5934

abstract:
  We present here a timing analysis of the fastest accreting millisecond pulsar
IGR J00291+5934 using RXTE data taken during the outburst of December 2004. We
corrected the arrival times of all the events for the orbital (Doppler) effects
and performed a timing analysis of the resulting phase delays. In this way we
find a clear parabolic trend of the pulse phase delays showing that the pulsar
is spinning up as a consequence of accretion torques during the X-ray outburst.
The accretion torque gives us for the first time an independent estimate of the
mass accretion rate onto the neutron star, which can be compared with the
observed X-ray luminosity. We also report a revised value of the spin period of
the pulsar.


title:
Imaging Fabry-Perot Spectroscopy of NGC 5775: Kinematics of the Diffuse
  Ionized Gas Halo

abstract:
  We present imaging Fabry-Perot observations of Halpha emission in the nearly
edge-on spiral galaxy NGC 5775. We have derived a rotation curve and a radial
density profile along the major axis by examining position-velocity (PV)
diagrams from the Fabry-Perot data cube as well as a CO 2-1 data cube from the
literature. PV diagrams constructed parallel to the major axis are used to
examine changes in azimuthal velocity as a function of height above the
midplane. The results of this analysis reveal the presence of a vertical
gradient in azimuthal velocity. The magnitude of this gradient is approximately
1 km/s/arcsec, or about 8 km/s/kpc, though a higher value of the gradient may
be appropriate in localized regions of the halo. The evidence for an azimuthal
velocity gradient is much stronger for the approaching half of the galaxy,
although earlier slit spectra are consistent with a gradient on both sides.
There is evidence for an outward radial redistribution of gas in the halo. The
form of the rotation curve may also change with height, but this is not
certain. We compare these results with those of an entirely ballistic model of
a disk-halo flow. The model predicts a vertical gradient in azimuthal velocity
which is shallower than the observed gradient, indicating that an additional
mechanism is required to further slow the rotation speeds in the halo.


title: Studying Galaxy Formation in Loose Galaxy Groups

abstract:
  We present the results of our HI survey of six loose groups of galaxies
analogous to the Local Group. The survey was conducted using the Parkes
telescope and the Australia Telescope Compact Array to produce a census of all
the gas-rich galaxies and analogs to the high-velocity clouds (HVCs) within
these groups down to M(HI) < 10^7 M(sun) as a test of models of galaxy
formation. We present the HI mass function and halo mass function of the loose
groups and show that they are consistent with those of the Local Group. We
discuss the possible role of HVCs in solving the ``missing satellite'' problem
and discuss the implications of our observations for models of galaxy
formation.


title: Radial velocities in the globular cluster omega Centauri

abstract:
  We have used the ARGUS multi-object spectrometer at the CTIO 4m Blanco
telescope to obtain 2756 radial velocity measurements for 1966 individual stars
in the globular cluster omega Centauri brighter than blue photographic
magnitude of about 16.5. Of these, 1589 stars are cluster members. A comparison
with two independent radial velocity studies, carried out by Suntzeff & Kraft
and by Mayor et al., demonstrates that the median error of our measurements is
below 2 km/s for the stars brighter than B-magnitude 15, which constitute the
bulk of the sample. The observed velocity dispersion decreases from about 15
km/s in the inner few arcmin to about 6 km/s at a radius of 25 arcmin. The
cluster shows significant rotation, with a maximum amplitude of about 6 km/s in
the radial zone between 6 and 10 arcmin. In a companion paper by van de Ven et
al., we correct these radial velocities for the perspective rotation caused by
the space motion of the cluster, and combine them with the internal proper
motions of nearly 8000 cluster members measured by van Leeuwen et al., to
construct a detailed dynamical model of omega Centauri and to measure its
distance.


title:
The dynamical distance and intrinsic structure of the globular cluster
  omega Centauri

abstract:
  We determine the dynamical distance D, inclination i, mass-to-light ratio M/L
and the intrinsic orbital structure of the globular cluster omega Cen, by
fitting axisymmetric dynamical models to the ground-based proper motions of van
Leeuwen et al. and line-of-sight velocities from four independent data-sets. We
correct the observed velocities for perspective rotation caused by the space
motion of the cluster, and show that the residual solid-body rotation component
in the proper motions can be taken out without any modelling other than
assuming axisymmetry. This also provides a tight constraint on D tan i.
Application of our axisymmetric implementation of Schwarzschild's orbit
superposition method to omega Cen reveals no dynamical evidence for a
significant radial dependence of M/L. The best-fit dynamical model has a
stellar V-band mass-to-light ratio M/L_V = 2.5 +/- 0.1 M_sun/L_sun and an
inclination i = 50 +/- 4 degrees, which corresponds to an average intrinsic
axial ratio of 0.78 +/- 0.03. The best-fit dynamical distance D = 4.8 +/- 0.3
kpc (distance modulus 13.75 +/- 0.13 mag) is significantly larger than obtained
by means of simple spherical or constant-anisotropy axisymmetric dynamical
models, and is consistent with the canonical value 5.0 +/- 0.2 kpc obtained by
photometric methods. The total mass of the cluster is (2.5 +/- 0.3) x 10^6
M_sun. The best-fit model is close to isotropic inside a radius of about 10
arcmin and becomes increasingly tangentially anisotropic in the outer region,
which displays significant mean rotation. This phase-space structure may well
be caused by the effects of the tidal field of the Milky Way. The cluster
contains a separate disk-like component in the radial range between 1 and 3
arcmin, contributing about 4% to the total mass.


title:
Possible Detection of Lyman-alpha Fluorescence from a Damped Lyman Alpha
  system at Redshift z=2.8

abstract:
  We have detected Lyman-alpha emission from a damped Lyman-alpha system (DLA)
that lies near the bright quasar HS1549+1919. The DLA has the same redshift as
HS1549+1919 and was discovered in the spectrum of a faint QSO that lies 49"
away (380 proper kpc). The emission line's luminosity, double-peaked profile,
and small spatial separation from the DLA suggest that it may be fluorescent
Lyman-alpha emission from gas that is absorbing the nearby QSO's radiation. If
this is the case, our observations show that the DLA has a size of at least
1.5" and that the QSO's luminosity one million years ago was similar to its
luminosity today. A survey for similar systems within 1' of bright QSOs would
put interesting limits on the mean quasar lifetime.


title: Tommy Gold Revisited: Why Does Not The Universe Rotate?

abstract:
  Understanding gravitational collapse requires understanding how $\sim
10^{58}$ nucleons can be destroyed in $\sim 10^{-5}$ seconds. The recent
proposal that the endpoint of gravitational collapse can be a "dark energy
star" implies that the mass-energy of the nucleons undergoing gravitational
collapse can be converted to vacuum energy when one gets near to conditions
where classical general relativity predicts that a trapped surface would form.
The negative pressure associated with a large vacuum energy prevents an event
horizon from forming, thus resolving the long-standing puzzle as to why
gravitational collapse always leads to an explosion. An indirect consequence is
that the reverse process - creation of matter from vacuum energy - should also
be possible. Indeed this process may be responsible for the "big bang". In this
new cosmology the observable universe began as a fluctuation in an overall
steady state universe. The fluctuations in the CMB in this picture are the
result of quantum turbulence associated with vorticity. This explanation for
the CMB fluctuations is superior to inflationary scenarios because there is a
natural explanation for both the level of CMB fluctuations and the deviation
from a scale invariant spectrum at large scales.


title: The Colliding Winds of WR146: Seeing the Works

abstract:
  WR146 is a WC6+O8 colliding-wind binary (CWB) system with thermal emission
from the stellar winds of the two stars, and bright non-thermal emission from
the wind-collision region (WCR) where the winds collide. We present high
resolution radio observations from 1.4 to 43 GHz that give one of the best
quality radio spectra of any CWB to date. Observations at 22 GHz now span 8
years, and reveal the proper motion of the system, allowing comparison of
multi-epoch data. VLBI observations show the location of the WCR relative to
the stellar components, from which the wind momentum ratio can be shown to be
0.06+/-0.15. The radio spectrum and the spatial distribution of emission are
modelled, and we determine the contribution of both stellar winds and the WCR
to the observed emission. We show that our current models fail to account for
the high frequency spectrum of WR146, and also produce too much emission far
from the stagnation point of the wind collision.


title: Photospheric signatures imprinted on the gamma-ray burst spectra

abstract:
  A solution is presented for the spectrum of high-energy gamma-ray burst
photons confined to a quasi-thermal baryonic photosphere. The solution is valid
in the steady-state limit assuming the region under consideration is optically
thick to the continuously injected photons. It is shown that for a high
luminosity photosphere, the non-thermal electrons resulting from gamma-ray
Compton cooling lose their energy by upscattering the soft thermalised
radiation. The resulting spectral modifications offer the possibility of
diagnosing not only the burst comoving luminosity but also the baryon load of
the ejecta. This model leads to a simple physical interpretation of X-ray rich
bursts and anomalous low-energy slopes.


title: The diffuse supernova neutrino flux, supernova rate and SN1987A

abstract:
  I calculate the diffuse flux of electron antineutrinos from all supernovae
using the information on the neutrino spectrum from SN987A and the information
on the rate of supernovae from direct supernova observations. The interval of
flux allowed at 99 % confidence level is 0.05 - 0.35 cm^-2 s ^-1 above the
SuperKamiokande (SK) energy cut of 19.3 MeV. This result is at least a factor
of 4 smaller than the current SK upper limit of 1.2 cm^-2 s ^-1, thus
motivating the experimental efforts to lower the detection energy threshold or
to upgrade to higher volumes. A Megaton water Cherenkov detector with 90 %
efficiency would record 2 - 44 inverse beta decay events a year depending on
the energy cut.


title: UBVRI Light Curves of 44 Type Ia Supernovae

abstract:
  We present UBVRI photometry of 44 type-Ia supernovae (SN Ia) observed from
1997 to 2001 as part of a continuing monitoring campaign at the Fred Lawrence
Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics. The
data set comprises 2190 observations and is the largest homogeneously observed
and reduced sample of SN Ia to date, nearly doubling the number of
well-observed, nearby SN Ia with published multicolor CCD light curves. The
large sample of U-band photometry is a unique addition, with important
connections to SN Ia observed at high redshift. The decline rate of SN Ia
U-band light curves correlates well with the decline rate in other bands, as
does the U-B color at maximum light. However, the U-band peak magnitudes show
an increased dispersion relative to other bands even after accounting for
extinction and decline rate, amounting to an additional ~40% intrinsic scatter
compared to B-band.


title: Nonlinear shock acceleration beyond the Bohm limit

abstract:
  We suggest a physical mechanism whereby the acceleration time of cosmic rays
by shock waves can be significantly reduced. This creates the possibility of
particle acceleration beyond the knee energy at ~10^15eV. The acceleration
results from a nonlinear modification of the flow ahead of the shock supported
by particles already accelerated to the knee momentum at p ~ p_*. The particles
gain energy by bouncing off converging magnetic irregularities frozen into the
flow in the shock precursor and not so much by re-crossing the shock itself.
The acceleration rate is thus determined by the gradient of the flow velocity
and turns out to be formally independent of the particle mean free path
(m.f.p.). The velocity gradient is, in turn, set by the knee-particles at p ~
p_* as having the dominant contribution to the CR pressure. Since it is
independent of the m.f.p., the acceleration rate of particles above the knee
does not decrease with energy, unlike in the linear acceleration regime. The
reason for the knee formation at p ~ p_* is that particles with $p > p_*$ are
effectively confined to the shock precursor only while they are within limited
domains in the momentum space, while other particles fall into
``loss-islands'', similar to the ``loss-cone'' of magnetic traps. This
structure of the momentum space is due to the character of the scattering
magnetic irregularities. They are formed by a train of shock waves that
naturally emerge from unstably growing and steepening magnetosonic waves or as
a result of acoustic instability of the CR precursor. These losses steepen the
spectrum above the knee, which also prevents the shock width from increasing
with the maximum particle energy.


title:
Resolving the Effects of Rotation in Altair with Long-Baseline
  Interferometry

abstract:
  We report successful fitting of a Roche model, with a surface temperature
gradient following the von Zeipel gravity darkening law, to observations of
Altair made with the Navy Prototype Optical Interferometer. We confirm the
claim by Ohishi, Nordgren, & Hutter that Altair displays an asymmetric
intensity distribution due to rotation, the first such detection in an isolated
star. Instrumental effects due to the high visible flux of this first magnitude
star appear to be the limiting factor in the accuracy of this fit, which
nevertheless indicates that Altair is rotating at 0.90+/-0.02 of its breakup
(angular) velocity. Our results are consistent with the apparent oblateness
found by van Belle et al. and show that the true oblateness is significantly
larger owing to an inclination of the rotational axis of ~64 degrees to the
line of sight. Of particular interest, we conclude that instead of being
substantially evolved as indicated by its classification, A7 VI-V, Altair is
only barely off the ZAMS and represents a good example of the difficulties
rotation can introduce in the interpretation of this part of the HR diagram.


title:
Imaging Optically-Thin Hot Spots Near the Black Hole Horizon of Sgr A*
  at Radio and Near-Infrared Wavelengths

abstract:
  Sub milli-arcsecond astrometry and imaging of the black hole Sgr A* at the
Galactic centre may become possible in the near future at infrared and
sub-millimetre wavelengths. Motivated by observations of short-term infrared
and X-ray variability of Sgr A*, in a previous paper we computed the expected
images and light curves, including polarization, associated with an compact
emission region orbiting the central black hole. We extend this work, using a
more realistic hot-spot model and including the effects of opacity in the
underlying accretion flow. We find that at infrared wavelengths the qualitative
features identified by our earlier work are present, namely it is possible to
extract the black hole mass and spin from spot images and light curves of the
observed flux and polarization. At radio wavelengths, disk opacity produces
significant departures from the infrared behaviour, but there are still generic
signatures of the black hole properties. Detailed comparison of these results
with future data can be used to test general relativity and to improve existing
models for the accretion flow in the immediate vicinity of the black hole.


title:
Observing muon decays in water Cherenkov detectors at the Pierre Auger
  Observatory

abstract:
  Muons decaying in the water volume of a Cherenkov detector of the Pierre
Auger Observatory provide a useful calibration point at low energy. Using the
digitized waveform continuously recorded by the electronics of each tank, we
have devised a simple method to extract the charge spectrum of the Michel
electrons, whose typical signal is about 1/8 of a crossing vertical muon. This
procedure, moreover, allows continuous monitoring of the detector operation and
of its water level. We have checked the procedure with high statistics on a
test tank at the Observatory base and applied with success on the whole array.


title:
Non-LTE Line-Formation and Abundances of Sulfur and Zinc in F, G, and K
  Stars

abstract:
  Extensive statistical-equilibrium calculations on neutral sulfur and zinc
were carried out, in order to investigate how the non-LTE effect plays a role
in the determination of S and Zn abundances in F, G, and K stars. Having
checked on the spectra of representative F-type stars (Polaris, Procyon, and
alpha Per) and the Sun that our non-LTE corrections yield a reasonable
consistency between the abundances derived from different lines, we tried an
extensive non-LTE reanalysis of published equivalent-width data of S I and Zn I
lines for metal-poor halo/disk stars. According to our calculations, S I
9212/9228/9237 lines suffer significant negative non-LTE corrections amounting
to <~ 0.2--0.3 dex, while LTE is practically valid for S I 8683/8694 lines.
Embarrassingly, as far as the very metal-poor regime is concerned, a marked
discordance is observed between the [S/Fe] values from these two abundance
indicators, in the sense that the former attains a nearly flat plateau (or even
a slight downward bending) while the latter shows an ever-increasing trend with
a further lowering of metallicity. The reason for this discrepancy is yet to be
clarified. Regarding Zn, we almost confirmed the characteristic tendencies of
[Zn/Fe] reported from recent LTE studies (i.e., an evident/slight increase of
[Zn/Fe] with a decrease of [Fe/H] for very metal-poor/disk stars), since the
non-LTE corrections for the Zn I 4722/4810 and 6362 lines (tending to be
positive and gradually increasing towards lower [Fe/H]) are quantitatively of
less significance (<~ 0.1 dex).


title:
Testing LMC Microlensing Scenarios: The Discrimination Power of the
  SuperMACHO Microlensing Survey

abstract:
  Characterizing the nature and spatial distribution of the lensing objects
that produce the previously measured microlensing optical depth toward the
Large Magellanic Cloud (LMC) remains an open problem. We present an appraisal
of the ability of the SuperMACHO Project, a next-generation microlensing survey
directed toward the LMC, to discriminate between various proposed lensing
populations. We consider two scenarios: lensing by a uniform foreground screen
of objects and self-lensing by LMC stars. We have carried out extensive
simulations, based upon data obtained during the first year of the project, to
assess the SuperMACHO survey's ability to discriminate between these two
scenarios. We find that the event rate itself shows significant sensitivity to
the choice of the LMC luminosity function, limiting the conclusions which can
be drawn from the absolute rate. If instead we determine the differential event
rate across the LMC, we will decrease the impact of these systematic biases and
render our conclusions more robust. With this approach the SuperMACHO Project
should be able to distinguish between the two categories of lens populations.
This will provide important constraints on the nature of the lensing objects
and their contributions to the Galactic dark matter halo.


title: Chemical Homogeneity in the Hyades

abstract:
  We present an abundance analysis of the heavy elements Zr, Ba, La, Ce, and Nd
for Hyades cluster F-K dwarfs based on high resolution, high S/N ratio spectra
from Keck/HIRES. The derived abundances show the stellar members to be highly
uniform, although some elements show a small residual trend with temperature.
The rms scatter for each element for the cluster members is as follows; Zr =
0.055 dex, Ba = 0.049 dex, Ce = 0.025 dex, La = 0.025 dex, Nd = 0.032 dex. This
is consistent with the measurement errors, and implies that there is little or
no intrinsic scatter among the Hyades members. Several stars thought to be
non-members of the cluster based on their kinematics are found to deviate from
the cluster mean abundances by about 2sigma. Establishing chemical homogeneity
in open clusters is the primary requirement for the viability of chemically
tagging Galactic disk stars to common formation sites, in order to unravel the
dissipative history of early disk formation.


title:
Envelope Expansion with Core Collapse II. Quasi-Spherical Self-Similar
  Solutions for an Isothermal Magnetofluid

abstract:
  We investigate self-similar magnetohydrodynamic (MHD) processes in an
isothermal self-gravitating fluid with a quasi-spherical symmetry and extend
the envelope expansion with core collapse (EECC) solutions of Lou & Shen by
incorporating a random magnetic field. Stagnation surfaces of EECC solutions
that seperate core collapse and envelope expansion propagate at constant speeds
either sub-magnetosonically or super-magnetosonically. Crossing the
magnetosonic line twice analytically, there exists an infinite number of
discrete magnetized EECC and ECCC solutions. In addition to the EECC shock
solution which could change the central accretion rate, the magnetic field can
also affect the core accretion rate. As the magnetic parameter $\lambda$
increases, the core accretion rate appropriate for the MHD EWCS becomes larger.
Under the frozen-in approximation, magnetic fields in the envelope expansion
portion would scale as $B\propto r^{-1}$, while in the core collapse portion
they would scale as $B\propto r^{-1/2}$. We discuss several astrophysical
applications of EECC similarity solutions to the formation process of
proto-planetary nebulae connecting the AGB phase and the planetary nebula, to
supernova remnants, collapse of magnetized molecular cloud, to $\textrm{H}\
{\textrm{\small{II}}}$ clouds surrounding massive OB stars and to a certain
evolution phase of galaxy clusters.


title: The distribution of Quiet Sun magnetic field strengths from 0 to 1800 G

abstract:
  The quiet Sun photospheric plasma has a variety of magnetic field strengths
going from zero to 1800 G. The empirical characterization of these field
strengths requires a probability density function (PDF), i.e., a function P(B)
describing the fraction of quiet Sun occupied by each field strength B. We show
how to combine magnetic field strength measurements based on the Zeeman effect
and the Hanle effect to estimate an unbiased P(B). The application of the
method to real observations renders a set of possible PDFs, which outline the
general characteristics of the quiet Sun magnetic fields. Their most probable
field strength differs from zero. The magnetic energy density is a significant
fraction of the kinetic energy of the granular motions at the base of the
photosphere (larger than 15% or larger than 2 10^{3} erg cm^{-3}). The unsigned
flux density (or mean magnetic field strength) has to be between 130 G and 190
G. A significant part of the unsigned flux (between 10% and 50%) and of the
magnetic energy (between 45% and 85%) are provided by the field strengths
larger than 500 G which, however, occupy only a small fraction of the surface
(between 1% and 10%). The fraction of kG fields in the quiet Sun is even
smaller, but they are important for a number of reasons. The kG fields still
trace a significant fraction of the total magnetic energy, they reach the high
photosphere, and they appear in unpolarized light images. The quiet Sun
photosphere has far more unsigned magnetic flux and magnetic energy than the
active regions and the network all together.


title:
The HELLAS2XMM survey. IX. Spectroscopic identification of super-EROs
  hosting AGNs

abstract:
  We present VLT near-IR spectroscopic observations of three X-ray sources
characterized by extremely high X-ray-to-optical ratios (X/O>40), extremely red
colors (6.3<R-K<7.4, i.e. EROs) and bright infrared magnitudes (17.6<K<18.3).
These objects are very faint in the optical, making their spectroscopic
identification extremely challenging. Instead, our near-IR spectroscopic
observations have been successful in identifying the redshift of two of them
(z=2.08 and z=1.35), and tentatively even of the third one (z=2.13). When
combined with the X-ray properties, our results clearly indicate that all these
objects host obscured QSOs (4e44 < L(2-10keV) < 1.5e45 erg/s, 2e22 < N_H < 4e23
cm-2) at high redshift. The only object with unresolved morphology in the K
band shows broad Halpha emission, but not broad Hbeta, implying a type 1.9 AGN
classification. The other two objects are resolved and dominated by the host
galaxy light in the K band, and appear relatively quiescent: one of them has a
LINER-like emission line spectrum and the other presents only a single, weak
emission line which we tentatively identify with Halpha. The galaxy
luminosities for the latter two objects are an order of magnitude brighter than
typical local L* galaxies and the derived stellar masses are well in excess of
10^11 Msun. For these objects we estimate black hole masses higher than 10^9
Msun and we infer that they are radiating at Eddington ratios L/L_Edd < 0.1. We
discuss the implications of these findings for the coevolution of galaxies and
black hole growth. Our results provide further support that X-ray sources with
high X/O ratios and very red colors tend to host obscured QSO in very massive
galaxies at high redshift.


title:
Do the low PN velocity dispersions around elliptical galaxies imply that
  these lack dark matter?

abstract:
  While kinematical modelling of the low PN velocity dispersions observed in
the outer regions of elliptical galaxies suggest a lack of dark matter around
these galaxies, we report on an analysis of a suite of $N$-body simulations
(with gas) of major mergers of spiral galaxies embedded in dark matter halos,
and find that the outer velocity dispersions are as low as observed for the
PNe. The inconsistency between our dynamical modelling and previous kinematical
modelling is caused by very radial stellar orbits and projection effects when
viewing face-on oblate ellipticals. Our simulations (weakly) suggest the youth
of PNe around ellipticals, and we propose that the universality of the PN
luminosity function may be explained if the bright PNe in ellipticals are
formed after the regular accretion of very low mass gas-rich galaxies.


title:
Spectral index of the H2O-maser emitting planetary nebula IRAS
  17347-3139

abstract:
  We present radio continuum observations of the planetary nebula (PN) IRAS
17347-3139 (one of the only two known to harbour water maser emission), made to
derive its spectral index and the turnover frequency of the emission. The
spectrum of the source rises in the whole frequency range sampled, from 2.4 to
24.9 GHz, although the spectral index seems to decrease at the highest
frequencies (0.79+-0.04 between 4.3 and 8.9 GHz, and 0.64+-0.06 between 16.1
and 24.9 GHz). This suggests a turnover frequency around 20 GHz (which is
unusual among PNe, whose radio emission usually becomes optically thin at
frequencies < 10 GHz), and a relatively high emission measure (1.5 x 10^9
cm^{-6} pc). The radio continuum emission has increased by a factor of ~1.26 at
8.4 GHz in 13 years, which can be explained as expansion of the ionized region
by a factor of ~1.12 in radius with a dynamical age of ~120 yr and at an
expansion velocity of ~5-40 km/s. These radio continuum characteristics,
together with the presence of water maser emission and a strong optical
extinction suggest that IRAS 17347-3139 is one of the youngest PNe known, with
a relatively massive progenitor star.


title: 6^Li in the atmosphere of GJ 117

abstract:
  We present high resolution VLT UVES observations of the active K dwarf GJ
117. 6^Li enhancement has been shown for energetic solar events, one
chromospherically active binary, and several dwarf halo stars. Our analysis
reveals the detection of 6^Li on this source with 6^Li/7^Li = 0.030+/-0.010. We
found no significant contribution from other lines, including Ti I, in the Li
profile of GJ 117 and a template star of similar spectral type and metallicity.
We discuss the possibility for 6^Li production by spallation and find it to be
consistent with the activity levels of the object.


title:
Simple Model of the Outflow from Starburst Galaxies: Application to
  Radio Observations

abstract:
  We present an analytical model for the hydrodynamic outflow from the disk of
a starburst galaxy. The model is used to calculate the cosmic ray propagation
and the radio intensity distribution in the nuclear starbust region of NGC 253.
We find that the cosmic ray energy production rate of the central 600 pc of NGC
253 is about $3\cdot 10^{41}$ erg s$^{-1}$, that is about 15 percent of the
total mechanical supernova power.
  For this inner region we estimate a terminal outflow velocity of 900 km
s$^{-1}$ and a mass loss rate of $\dot{M}=2\div 4M_\odot$ per year.


title:
Young Star Cluster Complexes in NGC 4038/39: Integral field spectroscopy
  using VIMOS-VLT

abstract:
  We present the first results of a survey to obtain Integral Field
Spectroscopy of merging galaxies along the Toomre Sequence. In the present
work, we concentrate on the star cluster complexes in the Antennae galaxies
(NGC 4038/39) in the overlap region as well as the nuclear region of NGC 4038.
Using optical spectroscopy we derive the extinction age, metallicity, velocity,
velocity dispersion of the gas and star formation rate for each of the eight
complexes detected. We supplement this study with archival HST-WFPC2 U, B, V,
H$\alpha$, and I band imaging. Correcting the observed colours of the star
clusters within the complexes for extinction, measured through our optical
spectra, we compare the clusters with simple stellar population models, with
which we find an excellent agreement. In five of the complexes we detect strong
Wolf-Rayet emission features, indicating young ages (3-5 Myr). The ionized gas
surrounding the complexes is expanding at speeds of 20-40 km/s. This slow
expansion can be understood as a bubble, caused by the stellar winds and
supernovae within the complexes, expanding into the remnant of the progenitor
giant molecular cloud. We also find that the complexes themselves are grouped,
at about the largest scale of which young star clusters are correlated,
representing the largest coherent star forming region. We show that the area
normalized star formation rates of these complexes clearly place them in the
regime of star forming regions in starburst galaxies, thereby justifying the
label of localized starbursts. Finally, we estimate the stability of the
complexes, and find that they will probably loose a large fraction of their
mass to the surrounding environment, although the central regions may merge
into a single large star cluster.


title:
Friedmann cosmology with a generalized equation of state and bulk
  viscosity

abstract:
  The universe media is considered as a non-perfect fluid with bulk viscosity
and described by a more general equation of state. We assume the bulk viscosity
is a linear combination of the two terms: one is constant, and the other is
proportional to the scalar expansion $\theta=3\dot{a}/a$. The equation of state
is described as $p=(\gamma-1)\rho+p_0$, where $p_0$ is a parameter. This model
can be used to explain the dark energy dominated universe. Different choices of
the parameters may lead to three kinds of fates of the cosmological evolution:
no future singularity, big rip, or Type III singularity of Ref. [S. Nojiri,
S.D. Odintsov, and S. Tsujikawa, Phys. Rev. D \textbf{71}, 063004 (2005)].


title: Phenomena in Gravitational Clustering

abstract:
  This thesis examines some of the applications of scaling relations in
understanding non linear structure formation.


title: Weak Gravitational Lensing

abstract:
  This review forms the Weak Lensing part of the Saas-Fee Advanced Course on
Gravitational Lensing. It describes the basicsm applications and results of
weak lensing. Contents: (1) Introduction (2) The principles of weak
gravitational lensing (3) Observational issues and challenges (4) Clusters of
galaxies: Introduction, and strong lensing (5) Mass reconstructions from weak
lensing (6) Cosmic shear -- lensing by the LSS (7) Large-scale structure
lensing: results (8) The mass of, and associated with galaxies (9) Additional
issues in cosmic shear (10) Concluding remarks.


title: Galactic cosmic rays and the knee - Results from the KASCADE experiment

abstract:
  Results from the KASCADE air shower experiment investigating the origin of
cosmic rays in the energy region from 10^13 to 10^17 eV are presented.
Attention is drawn on the investigation of interactions in the atmosphere and
the energy spectrum and mass composition of cosmic rays.


title:
Cosmos++: Relativistic Magnetohydrodynamics on Unstructured Grids with
  Local Adaptive Refinement

abstract:
  A new code and methodology are introduced for solving the general
relativistic magnetohydrodynamic (GRMHD) equations in fixed background
spacetimes using time-explicit, finite-volume discretization. The code has
options for solving the GRMHD equations using traditional artificial-viscosity
(AV) or non-oscillatory central difference (NOCD) methods, or a new extended AV
(eAV) scheme using artificial-viscosity together with a dual
energy-flux-conserving formulation. The dual energy approach allows for
accurate modeling of highly relativistic flows at boost factors well beyond
what has been achieved to date by standard artificial viscosity methods. It
provides the benefit of Godunov methods in capturing high Lorentz boosted flows
but without complicated Riemann solvers, and the advantages of traditional
artificial viscosity methods in their speed and flexibility. Additionally, the
GRMHD equations are solved on an unstructured grid that supports local adaptive
mesh refinement using a fully threaded oct-tree (in three dimensions) network
to traverse the grid hierarchy across levels and immediate neighbors. A number
of tests are presented to demonstrate robustness of the numerical algorithms
and adaptive mesh framework over a wide spectrum of problems, boosts, and
astrophysical applications, including relativistic shock tubes, shock
collisions, magnetosonic shocks, Alfven wave propagation, blast waves,
magnetized Bondi flow, and the magneto-rotational instability in Kerr black
hole spacetimes.


title: New brown dwarf companions to dM(e) stars

abstract:
  We present new astrometric and spectroscopic data to confirm two new M/L
dwarf systems, G124-62 and LHS5166, and discuss the nature of a third system
(LP261-75). Age and thus mass determinations of the L dwarf companions are
discussed based on various activity-age relationships of the M dwarf primaries.
This publication will update the list of widely separated substellar companions
to nearby stars.


title: Studies of Air Showers above 10^18 eV with the CHICOS Array

abstract:
  CHICOS (California HIgh school Cosmic ray ObServatory) is presently an array
of more than 140 detectors distributed over a large area (~400 km^2) of
southern California, and will consist of 180 detectors at 90 locations in the
near future. These sites, located at area schools, are equipped with
computerized data acquisition and automatic nightly data transfer (via
internet) to our Caltech lab. The installed sites make up the largest currently
operating ground array for ultra-high energy cosmic ray research in the
northern hemisphere. The goal of CHICOS is to provide data related to the flux
and distribution of arrival directions for ultra-high energy cosmic rays.
  We have performed detailed Monte-Carlo calculations to determine the density
and arrival-time distribution of charged particles in extensive air showers for
the CHICOS array. Calculations were performed for proton primaries with
energies 10^18 to 10^21 eV and zenith angles out to 50 degrees. We have
developed novel parameterizations for both distributions as functions of
distance from the shower axis, primary energy, and incident zenith angle. These
parameterizations are used in aperture calculations and reconstruction of
shower data, enabling preliminary analysis of ultra-high energy shower data
from CHICOS.


title: Hyperstars - Main Origin of Short Gamma Ray Bursts?

abstract:
  The first well-localized short-duration gamma ray bursts (GRBs), GRB 050509b,
GRB 050709 and GRB 050724, could have been the narrowly beamed initial spike of
a burst/hyper flare of soft gamma ray repeaters (SGRs) in host galaxies at
cosmological distances. Such bursts are expected if SGRs are young hyperstars,
i.e. neutron stars where a considerable fraction of their neutrons have
converted to hyperons and/or strange quark matter.


title:
The Anisotropic Distribution of M 31 Satellite Galaxies: A Polar Great
  Plane of Early-Type Companions

abstract:
  The highly anisotropic distribution and apparent alignment of the Galactic
satellites in polar great planes begs the question how common such
distributions are. The satellite system of M31 is the only nearby system for
which we currently have sufficiently accurate distances to study the
three-dimensional satellite distribution. We present the spatial distribution
of the 15 presently known M31 companions in a coordinate system centered on M31
and aligned with its disk. Through a detailed statistical analysis we show that
the full satellite sample describes a plane that is inclined by -56 deg with
respect to the poles of M31 and that has an r.m.s. height of 100 kpc. With 88%
the statistical significance of this plane is low and it is unlikely to have a
physical meaning. The great stellar stream found near Andromeda is inclined to
this plane by 7 deg. There is little evidence for a Holmberg effect. If we
confine our analysis to early-type dwarfs, we find a best-fit polar plane
within 5 deg to 7 deg from the pole of M31. This polar great plane has a
statistical significance of 99.3% and includes all dSphs (except for And II),
M32, NGC 147, and PegDIG. The r.m.s. distance of these galaxies from the polar
plane is 16 kpc. The nearby spiral M33 has a distance of only about 3 kpc from
this plane, which points toward the M81 group. We discuss the anisotropic
distribution of M31's early-type companions in the framework of three
scenarios, namely as remnants of the break-up of a larger progenitor, as tracer
of a prolate dark matter halo, and as tracer of collapse along large-scale
filaments. (Abridged)


title:
Limits on spin-independent WIMP-nucleon interactions from the two-tower
  run of the Cryogenic Dark Matter Search

abstract:
  We report new results from the Cryogenic Dark Matter Search (CDMS II) at the
Soudan Underground Laboratory. Two towers, each consisting of six detectors,
were operated for 74.5 live days, giving spectrum-weighted exposures of 34 kg-d
for germanium and 12 kg-d for silicon targets after cuts, averaged over recoil
energies 10-100 keV for a WIMP mass of 60 GeV. A blind analysis was conducted,
incorporating improved techniques for rejecting surface events. No WIMP signal
exceeding expected backgrounds was observed. When combined with our previous
results from Soudan, the 90% C.L. upper limit on the spin-independent
WIMP-nucleon cross section is 1.6 x 10^{-43} cm^2 from Ge, and 3 x 10^{-42}
cm^2 from Si, for a WIMP mass of 60 GeV. The combined limit from Ge (Si) is a
factor of 2.5 (10) lower than our previous results, and constrains predictions
of supersymmetric models.


title:
Baryon Oscillations and Consistency Tests for Photometrically-Determined
  Redshifts of Very Faint Galaxies

abstract:
  Weak lensing surveys that can potentially place strong constraints on dark
energy parameters can only do so if the source redshift means and error
distributions are very well known. We investigate prospects for controlling
errors in these quantities by exploiting their influence on the power spectra
of the galaxies. Although, from the galaxy power spectra alone, sufficiently
precise and simultaneous determination of redshift biases and variances is not
possible, a strong consistency test is. Given the redshift error rms, galaxy
power spectra can be used to determine the mean redshift of a group of galaxies
to subpercent accuracy. Although galaxy power spectra cannot be used to
determine the redshift error rms, they can be used to determine this rms
divided by the Hubble parameter, a quantity that may be even more valuable for
interpretation of cosmic shear data than the rms itself. We also show that
galaxy power spectra, due to the baryonic acoustic oscillations, can
potentially lead to constraints on dark energy that are competitive with those
due to the cosmic shear power spectra from the same survey.


title: Fate of clumps in damped Ly$\alpha$ systems

abstract:
  Recent observations have revealed that damped Ly$\alpha$ clouds (DLAs) host
star formation activity. In order to examine if such star formation activity
can be triggered by ionization fronts, we perform high-resolution hydrodynamics
and radiative transfer simulations of the effect of radiative feedback from
propagating ionization fronts on high-density clumps. We examine two sources of
ultraviolet (UV) radiation field to which high-redshift (z ~ 3) galaxies could
be exposed: one corresponding to the UV radiation originating from stars within
the DLA, itself, and the other corresponding to the UV background radiation. We
find that, for larger clouds, the propagating I-fronts created by local stellar
sources can trigger cooling instability and collapse of significant part, up to
85%, of the cloud, creating conditions for star formation in a timescale of a
few Myr. The passage of the I-front also triggers collapse of smaller clumps
(with radii below ~4 pc), but in these cases the resulting cold and dense gas
does not reach conditions conducive to star formation. Assuming that 85% of the
gas initially in the clump is converted into stars, we obtain a star formation
rate of $\sim 0.25 M_\odot {yr}^{-1} {kpc}^{-2}$. This is somewhat higher than
the value derived from recent observations. On the other hand, the background
UV radiation which has harder spectrum fails to trigger cooling and collapse.
Instead, the hard photons which have long mean-free-path heat the dense clumps,
which as a result expand and essentially dissolve in the ambient medium.
Therefore, the star formation activity in DLAs is strongly regulated by the
radiative feedback, both from the external UV background and internal stellar
sources and we predict quiescent evolution of DLAs (not starburst-like
evolution).


title: Expansion and Collapse in the Cosmic Web

abstract:
  We study the kinematics of the gaseous cosmic web at high redshift with Lyman
alpha forest absorption in multiple QSO sightlines. Using a simple analytic
model and a cosmological hydrodynamic simulation we constrain the underlying
three-dimensional distribution of velocities from the observed line-of-sight
distribution of velocity shear across the plane of the sky. The distribution is
found to be in good agreement with the intergalactic medium (IGM) undergoing
large scale motions dominated by the Hubble flow. Modeling the Lyman alpha
clouds analytically and with a hydrodynamics simulation, the average expansion
velocity of the gaseous structures causing the Lyman alpha forest in the lower
redshift (z = 2) sample appears about 20 percent lower than the local Hubble
expansion velocity. We interpret this as tentative evidence for some clouds
undergoing gravitational collapse. However, the distribution of velocities is
highly skewed, and the majority of clouds at redshifts from 2 to 3.8 expand
typically about 5 - 20 percent faster than the Hubble flow. This behavior is
explained if most absorbers in the column density range typically detectable
are expanding filaments that stretch and drain into more massive nodes. We find
no evidence for the observed distribution of velocity shear being significantly
influenced by processes other than Hubble expansion and gravitational
instability, like galactic winds. To avoid overly disturbing the IGM, winds may
be old and/or limp by the time we observe them in the Lyman alpha forest, or
they may occupy only an insignificant volume fraction of the IGM. (abridged)


title:
Cosmological Simulations of Galaxy Formation I: Star Formation,
  Feedback, Resolution and Matching the Tully--Fisher Relation (among other
  things)

abstract:
  We used fully cosmological, high resolution N-body+SPH simulations to follow
the formation of disk galaxies with a rotational velocity between 140 and 280
Km/sec in a Lambda CDM universe. The simulations include gas cooling, star
formation (SF), the effects of a uniform UV background and a physically
motivated description of feedback from supernovae (SN). Feedback parameters
have been chosen to match the star formation rate and interstellar medium (ISM)
properties of local galaxies. In cosmological simulations galaxies formed
rotationally supported disks with realistic exponential scale lengths and fall
on the I-band and baryonic Tully Fisher relations. The combination of UV
background and SN feedback drastically reduced the number of visible satellites
orbiting inside a Milky Way sized halo, bringing it in fair agreement with
observations. Feedback delays SF in small galaxies and more massive ones
contain older stellar populations. Here we focus on the SF and feedback
implementations. We also briefly discuss how high mass and force resolution and
a realistic description of SF and feedback are important ingredients to match
the observed properties of galaxies.


title: The Radial Velocity Distribution of Class I and Flat-Spectrum Protostars

abstract:
  We analyze radial velocities for a sample of 31 Class I and flat spectrum
protostars in Taurus-Auriga, rho Ophiuchi and Serpens for evidence of the
global dynamical state of extremely young stellar populations buried within
parental molecular clouds. Comparing the radial velocity of each protostar to
that of the local CO gas, we are able to constrain the one dimensional radial
velocity dispersion of Class I and flat spectrum objects to ~ 2.5 km/sec or
below. This upper limit to the protostellar velocity dispersion is consistent
with the velocity dispersions of surrounding CO gas which we measure to be ~
1.4 km/sec, suggesting that the motions of protostars and local CO gas are
dynamically linked and dominated by the gravitational potential of the
molecular cloud. However, the upper limit on the protostellar velocity
dispersion could still allow for slightly inflated motions of protostars
relative to the local molecular gas. Four of the protostars analyzed appear to
have velocities more than 3 sigma (7.5 km/sec) away from the central local CO
gas velocity while showing spectroscopic indicators of youth and accretion such
as H_2 emission, HI Br Gamma emission, or K band continuum veiling. These
radial velocity outliers may represent protostellar spectroscopic binaries or
ejected cluster members.


title:
Nonthermal THz to TeV Emission from Stellar Wind Shocks in the Galactic
  Center

abstract:
  The central parsec of the Galaxy contains dozens of massive stars with a
cumulative mass loss rate of ~ 10^{-3} solar masses per year. Shocks among
these stellar winds produce the hot plasma that pervades the central part of
the galaxy. We argue that these stellar wind shocks also efficiently accelerate
electrons and protons to relativistic energies. The relativistic electrons
inverse Compton scatter the ambient ultraviolet and far infrared radiation
field, producing high energy gamma-rays with a roughly constant luminosity from
\~ GeV to ~ 10 TeV. This can account for the TeV source seen by HESS in the
Galactic Center. Our model predicts a GLAST counterpart to the HESS source with
a luminosity of ~ 10^{35} ergs/s and cooling break at ~ 4 GeV. Synchrotron
radiation from the same relativistic electrons should produce detectable
emission at lower energies, with a surface brightness ~ 10^{32} B^2_{-3}
ergs/s/arcsec^2 from ~ THz to ~ keV, where B_{-3} is the magnetic field
strength in units of mG. The observed level of diffuse thermal X-ray emission
in the central parsec requires B < 300 micro-G in our models. Future detection
of the diffuse synchrotron background in the central parsec can directly
constrain the magnetic field strength, providing an important boundary
condition for models of accretion onto Sgr A*.


title: Nonlinear Stability of Thin, Radially-Stratified Disks

abstract:
  We perform local numerical experiments to investigate the nonlinear stability
of thin, radially-stratified disks. We demonstrate the presence of radial
convective instability when the disk is nearly in uniform rotation, and show
that the net angular momentum transport is slightly inwards, consistent with
previous investigations of vertical convection. We then show that a
convectively-unstable equilibrium is stabilized by differential rotation.
Convective instability is determined by the Richardson number Ri =
N_r^2/(q\Omega)^2, where N_r is the radial Brunt-Vaisala frequency and q\Omega
is the shear rate. Classical convective instability in a nonshearing medium (Ri
-> -infinity) is suppressed when Ri > -1, i.e. when the shear rate becomes
greater than the growth rate. Disks with a nearly-Keplerian rotation profile
and radial gradients on the order of the disk radius have Ri > -0.01 and are
therefore stable to local nonaxisymmetric disturbances. One implication of our
results is that the ``baroclinic'' instability recently claimed by Klahr &
Bodenheimer is either global or nonexistent. We estimate that our simulations
would detect any genuine growth rate > 0.0025\Omega.


title:
A Comparison of the Chemical Evolutionary Histories of the Galactic Thin
  Disk and Thick Disk Stellar Populations

abstract:
  We have studied 23 long-lived G dwarfs that belong to the thin disk and thick
disk stellar populations. Abundances have been derived for 24 elements: O, Na,
Mg, Al, Si, Ca, Ti, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Zr, Ba, La, Ce,
Nd, and Eu. We find that the behavior of [alpha/Fe] and [Eu/Fe] vs. [Fe/H] are
quite different for the two populations. As has long been known, the thin disk
O, Mg, Si, Ca, and Ti ratios are enhanced relative to iron at the lowest
metallicities, and decline toward solar values as [Fe/H] rises above -1.0. For
the thick disk, the decline in [alpha/Fe] and [Eu/Fe] does not begin at [Fe/H]
= -1.0, but at -0.4. Other elements share this behavior, including Sc, Co, and
Zn, suggesting that at least in the chemical enrichment history of the thick
disk, these elements were manufactured in similar-mass stars. Combining our
results for the oldest and longest-lived stars with prior work, we find clear
signs for an independent origin for the Galactic thick disk. (Abridged)


title: The Long-Term Future of Space Travel

abstract:
  The fact that we apparently live in an accelerating universe places
limitations on where humans might visit. If the current energy density of the
universe is dominated by a cosmological constant, a rocket could reach a galaxy
observed today at a redshift of 1.7 on a one-way journey or merely 0.65 on a
round trip. Unfortunately these maximal trips are impractical as they require
an infinite proper time to traverse. However, calculating the rocket trajectory
in detail shows that a rocketeer could nearly reach such galaxies within a
lifetime (a long lifetime admittedly -- about 100 years). For less negative
values of $w$ the maximal redshift increases becoming infinite for $w\geq
-1/3$.


title:
Limits on spin-dependent WIMP-nucleon interactions from the Cryogenic
  Dark Matter Search

abstract:
  The Cryogenic Dark Matter Search (CDMS) is an experiment to detect weakly
interacting massive particles (WIMPs) based on their interactions with Ge and
Si nuclei. We report the results of an analysis of data from the first two runs
of CDMS at the Soudan Underground Laboratory in terms of spin-dependent
WIMP-nucleon interactions on 73Ge and 29Si. These data exclude new regions of
spin-dependent WIMP-nucleon interaction parameter space, including regions
relevant to spin-dependent interpretations of the annual modulation signal
reported by the DAMA/NaI experiment.


title:
High-Resolution Spectroscopy of the Planetary Host HD 13189:
  Highly-Evolved and Metal-Poor

abstract:
  We report on the abundances of 13 elements in the planetary host HD 13189, a
massive giant star. Abundances are found to be sub-solar, with [Fe/H] = -0.58
+/- 0.04$; HD 13189 is one of the most metal-poor planetary hosts yet
discovered. Abundance ratios relative to Fe show no peculiarities with respect
to random field stars. A census of metallicities of the seven currently known
planet-harboring giants results in a distribution that is more metal-poor than
the well-known metal-rich distribution of main sequence (MS) planetary hosts.
This finding is discussed in terms of accretion of H-depleted material, one of
the possible mechanisms responsible for the high-metallicity distribution of MS
stars with planets. We estimate the mass of the HD 13189 progenitor to be 3.5
M_sun but cannot constrain this value to better than 2-6 M_sun. A stellar mass
of 3.5 M_sun implies a planetary mass of m sin i = 14.0 +/- 0.8 M_J, placing
the companion at the planet/brown dwarf boundary. Given its physical
characteristics, the HD 13189 system is potentially unique among planetary
systems, and its continued investigation should provide invaluable data to
extrasolar planetary research.


title:
Oxygen from the Lambda 7774 High-Excitation Triplet in Open Cluster
  Dwarfs: Hyades

abstract:
  Oxygen abundances have been derived from the near-IR, high-excitation Lambda
7774 O I triplet in high-resolution, high signal-to-noise spectra of 45 Hyades
dwarfs using standard one dimensional, plane-parallel LTE models. Effective
temperatures of the stellar sample range from 4319-6301 K, and the derived
relative O abundances as a function of T_eff evince a trichotomous morphology.
At T_eff > 6100 K, there is evidence of an increase in the O abundances with
increasing T_eff, consistent with non-LTE (NLTE) predictions. At intermediate
T_eff (5450 < T_eff < 6100 K), the O abundances are flat, and star-to-star
values are in good agreement, having a mean value of [O/H] = +0.25 +/- 0.02;
however, systematic errors at the ~0.10 dex level might exist. The O abundances
for stars with T_eff < 5450 K show a striking increase with decreasing T_eff,
in stark contrast to expectations and canonical NLTE calculations. The cool
Hyades triplet results are compared to those recently reported for dwarfs in
the Pleiades cluster and the UMa moving group; qualitative differences between
the trends observed in these stellar aggregates point to a possible age-related
diminution of triplet abundance trends in cool open cluster dwarfs.
Correlations with age-related phenomena, i.e., chromospheric activity and
photospheric spots, faculae, and/or plages, are investigated. No correlation
with Ca II H+K chromospheric activity indicators is observed. Multi-component
LTE ``toy'' models have been constructed in order to simulate photospheric
temperature inhomogeneities that could arise from the presence of starspots,
and we demonstrate that photospheric spots are a plausible source of the
triplet trends among the cool dwarfs.


title: Supernova Constraints on Models of Neutrino Dark Energy

abstract:
  In this paper we use the recently released Type Ia Supernova (SNIa) data to
constrain the interactions between the neutrinos and the dark energy scalar
fields. In the analysis we take the dark energy scalars to be either
Quintessence-like or Phantom-like. Our results show the data mildly favor a
model where the neutrinos couple to a phantom-like dark energy scalar, which
implies the equation of state of the coupled system behaves like Quintom
scenario in the sense of parameter degeneracy. We find future observations like
SNAP are potentially promising to measure the couplings between neutrino and
dark energy.


title:
Very Early Optical Afterglows of Gamma-Ray Bursts: Evidence for Relative
  Paucity of Detection

abstract:
  Very early observations with the Swift satellite of gamma-ray burst (GRB)
afterglows reveal that the optical component is not detected in a large number
of cases. This is in contrast to the bright optical flashes previously
discovered in some GRBs (e.g. GRB 990123 and GRB 021211). Comparisons of the
X-ray afterglow flux to the optical afterglow flux and prompt gamma-ray fluence
is used to quantify the seemingly deficient optical, and in some cases X-ray,
light at these early epochs. This comparison reveals that some of these bursts
appear to have higher than normal gamma-ray efficiencies. We discuss possible
mechanisms and their feasibility for explaining the apparent lack of early
optical emission. The mechanisms considered include: foreground extinction,
circumburst absorption, Ly-alpha blanketing and absorption due to high
redshift, low density environments, rapid temporal decay, and intrinsic
weakness of the reverse shock. Of these, foreground extinction, circumburst
absorption, and high redshift provide the best explanations for most of the
non-detections in our sample. There is tentative evidence of suppression of the
strong reverse shock emission. This could be because of a
Poynting-flux-dominated flow or a pure non-relativistic hydrodynamical reverse
shock.