title:
Organic Molecules in the Galactic Center. Hot Core Chemistry without Hot
  Cores

abstract:
  We study the origin of large abundances of complex organic molecules in the
Galactic center (GC). We carried out a systematic study of the complex organic
molecules CH3OH, C2H5OH, (CH3)2O, HCOOCH3, HCOOH, CH3COOH, H2CO, and CS toward
40 GC molecular clouds. Using the LTE approximation, we derived the physical
properties of GC molecular clouds and the abundances of the complex
molecules.The CH3OH abundance between clouds varies by nearly two orders of
magnitude from 2.4x10^{-8} to 1.1x10^{-6}. The abundance of the other complex
organic molecules relative to that of CH3OH is basically independent of the
CH3OH abundance, with variations of only a factor 4-8. The abundances of
complex organic molecules in the GC are compared with those measured in hot
cores and hot corinos, in which these complex molecules are also abundant. We
find that both the abundance and the abundance ratios of the complex molecules
relative to CH3OH in hot cores are similar to those found in the GC clouds.
However, hot corinos show different abundance ratios than observed in hot cores
and in GC clouds. The rather constant abundance of all the complex molecules
relative to CH3OH suggests that all complex molecules are ejected from grain
mantles by shocks. Frequent (similar 10^{5}years) shocks with velocities >6km/s
are required to explain the high abundances in gas phase of complex organic
molecules in the GC molecular clouds. The rather uniform abundance ratios in
the GC clouds and in Galactic hot cores indicate a similar average composition
of grain mantles in both kinds of regions. The Sickle and the Thermal Radio
Arches, affected by UV radiation, show different relative abundances in the
complex organic molecules due to the differentially photodissociation of these
molecules.


title: Lyman Limit Systems in Cosmological Simulations

abstract:
  We used cosmological simulation with self-consistent radiative transfer to
investigate the physical nature of Lyman Limit systems at z=4. In agreement
with previous studies, we find that most of Lyman Limit systems are ionized by
the cosmological background, while higher column density systems seem to be
illuminated by the local sources of radiation. In addition, we find that most
of Lyman limit systems in our simulations are located within the virial radii
of galaxies with a wide range of masses, and are physically associated with
them (``bits and pieces'' of galaxy formation). While the finite resolution of
our simulations cannot exclude an existence of a second population of
self-shielded, neutral gas clouds located in low mass dark matter halos
(``minihalos''), our simulations are not consistent with ``minihalos''
dominating the total abundance of Lyman limit systems.


title: The Sulfur Abundance Anomaly in Planetary Nebulae

abstract:
  The failure of S and O abundances in most planetary nebulae to display the
same strong direct correlation that is observed in extragalactic H II regions
represents one of the most perplexing problems in the area of PN abundances
today. Galactic chemical evolution models as well as large amounts of
observational evidence from H II region studies support the contention that
cosmic abundances of alpha elements such as O, Ne, S, Cl, and Ar increase
together in lockstep. Yet abundance results from the Henry, Kwitter, & Balick
(2004) database show a strong tendency for most PNe to have S abundances that
are significantly less than expected from the observed level of O. One
reasonable hypothesis for the sulfur anomaly is the past failure to properly
measure the abundances of unseen ionization stages above S^+2. Future
observations with Spitzer will allow us to test this hypothesis.


title:
Parameter estimation of binary compact objects with LISA: Effects of
  time-delay interferometry, Doppler modulation, and frequency evolution

abstract:
  We study the limits on how accurately LISA will be able to estimate the
parameters of low-mass compact binaries, comprising white dwarfs (WDs), neutron
stars (NSs) or black holes (BHs), while battling the amplitude, frequency, and
phase modulations of their signals. We show that Doppler-phase modulation aids
sky-position resolution in every direction, improving it especially for sources
near the poles of the ecliptic coordinate system. However, it increases the
frequency estimation error by a factor of over 1.5 at any sky position, and at
f=3 mHz. Since accounting for Doppler-phase modulation is absolutely essential
at all LISA frequencies and for all chirp masses in order to avoid a fractional
loss of signal-to-noise ratio (SNR) of more than 30%, LISA science will be
simultaneously aided and limited by it. For a source with f > 2.5mHz, searching
for its frequency evolution for 1 year worsens the error in the frequency
estimation by a factor of over 3.5 relative to that of sources with f < 1mHz.
Increasing the integration time to 2 years reduces this relative error factor
to about 2, which still adversely affects the resolvability of the galactic
binary confusion noise. Thus, unless the mission lifetime is increased several
folds, the only other recourse available for reducing the errors is to exclude
the chirp parameter from ones search templates. Doing so improves the
SNR-normalized parameter estimates. This works for the lightest binaries since
their SNR itself does not suffer from that exclusion. However, for binaries
involving a neutron star, a black hole, or both, the SNR and, therefore, the
parameter estimation, can take a significant hit, thus, severely affecting the
ability to resolve such members in LISA's confusion noise.


title: The Role of Pressure in GMC Formation II: The H_2 - Pressure Relation

abstract:
  We show that the ratio of molecular to atomic gas in galaxies is determined
by hydrostatic pressure and that the relation between the two is nearly linear.
The pressure relation is shown to be good over three orders of magnitude for 14
galaxies including dwarfs, HI-rich, and H_2-rich galaxies as well as the Milky
Way. The sample spans a factor of five in mean metallicity. The rms scatter of
individual points of the relation is only about a factor of two for all the
galaxies, though some show much more scatter than others. Using these results,
we propose a modified star formation prescription based on pressure determining
the degree to which the ISM is molecular. The formulation is different in high
and low pressure regimes defined by whether the gas is primarily atomic or
primarily molecular. This formulation can be implemented in simulations and
provides a more appropriate treatment of the outer regions of spiral galaxies
and molecule-poor systems such as dwarf irregulars and damped Lyman-alpha
systems.


title:
On Extending the Mass-Metallicity Relation of Galaxies by 2.5 Decades in
  Stellar Mass

abstract:
  We report 4.5 micron luminosities for 27 nearby (D < 5 Mpc) dwarf irregular
galaxies measured with the Spitzer Infrared Array Camera. We have constructed
the 4.5 micron luminosity-metallicity (L-Z) relation for 25 dwarf galaxies with
secure distance and interstellar medium oxygen abundance measurements. The 4.5
micron L-Z relation is 12+log(O/H) = (5.78 +/- 0.21) + (-0.122 +/- 0.012)
M_[4.5], where M_[4.5] is the absolute magnitude at 4.5 micron. The dispersion
in the near-infrared L-Z relation is smaller than the corresponding dispersion
in the optical L-Z relation. The subsequently derived stellar mass-metallicity
M-Z relation is 12+log(O/H) = (5.65 +/- 0.23) + (0.298 +/- 0.030) log Mstar.
and extends the SDSS M-Z relation to lower mass by about 2.5 dex. We find that
the dispersion in the M-Z relation is similar over five orders of magnitude in
stellar mass, and that the relationship between stellar mass and interstellar
medium metallicity is similarly tight from high-mass to low-mass systems. We
find a larger scatter at low mass in the relation between effective yield and
total baryonic mass. In fact, there are a few dwarf galaxies with large yields,
which is difficult to explain if galactic winds are ubiquitous in dwarf
galaxies. The low scatter in the L-Z and M-Z relationships are difficult to
understand if galactic superwinds or blowout are responsible for the low
metallicities at low mass or luminosity. Naively, one would expect an ever
increasing scatter at lower masses, which is not observed.


title:
SDSS J1534+1615AB: A Novel T Dwarf Binary Found with Keck Laser Guide
  Star Adaptive Optics and the Potential Role of Binarity in the L/T Transition

abstract:
  We have resolved the newly discovered T dwarf SDSS J1534+1615 into a 0.11''
binary using the Keck sodium laser guide star adaptive optics system. With an
integrated-light spectral type of T3.5, this binary provides a new benchmark
for studying the distinctive J-band brightening previously noted among early
and mid-T dwarfs, using two brown dwarfs with different spectral types but
having a common metallicity and age and very similar surface gravities. We
estimate spectral types of T1.5+/-0.5 and T5.5+/-0.5 for the two components
based on their near-IR colors, consistent with modeling the integrated-light
spectrum as the blend of two components. The observed near-IR flux ratios are
unique compared to all previously known substellar binaries: the component that
is fainter at H and K' is brighter at J. This inversion of the near-IR fluxes
is a manifestation of the J-band brightening within this individual binary
system. Therefore, SDSS 1534+1615 demonstrates that the brightening can be
intrinsic to ultracool photospheres (e.g., arising from cloud disruption and/or
rapid increase in cloud sedimentation) and does not necessarily result from
physical variations among the observed ensemble of T dwarfs (e.g., a range in
masses, ages and/or metallicities). We suggest that the apparently large
amplitude of the J-band brightening may be due to a high incidence of
unresolved binaries and that the true amplitude of the phenomenon could be more
modest. This scenario would imply that truly single objects in these spectral
subclasses are relatively rare, in agreement with the small effective
temperature range inferred for the L/T transition.


title: The Mass of the Central Black Hole in the Seyfert Galaxy NGC 4151

abstract:
  In order to improve the reverberation-mapping based estimate of the mass of
the central supermassive black hole in the Seyfert 1 galaxy NGC 4151, we have
reanalyzed archival ultraviolet monitoring spectra from two campaigns
undertaken with the International Ultraviolet Explorer. We measure
emission-line time delays for four lines, C IV 1549, He II 1640, C III] 1909,
and Mg II 2798, from both campaigns. We combine these measurements with the
dispersion of the variable part of each respective emission line to obtain the
mass of the central object. Despite the problematic nature of some of the data,
we are able to measure a mass of 41.1 (+/- 7.3) million solar masses, although
this, like all reverberation-based masses, is probably systematically uncertain
by a factor of 3-4.


title: BLAST Autonomous Daytime Star Cameras

abstract:
  We have developed two redundant daytime star cameras to provide the fine
pointing solution for the balloon-borne submillimeter telescope, BLAST. The
cameras are capable of providing a reconstructed pointing solution with an
absolute accuracy < 5 arcseconds. They are sensitive to stars down to
magnitudes ~ 9 in daytime float conditions. Each camera combines a 1 megapixel
CCD with a 200 mm f/2 lens to image a 2 degree x 2.5 degree field of the sky.
The instruments are autonomous. An internal computer controls the temperature,
adjusts the focus, and determines a real-time pointing solution at 1 Hz. The
mechanical details and flight performance of these instruments are presented.


title: Gallery of Planetary Nebula Spectra

abstract:
  We present the Gallery of Planetary Nebula Spectra now available at
http://oit.williams.edu/nebulae The website offers high-quality, moderate
resolution (~7-10 A FWHM) spectra of 128 Galactic planetary nebulae from
3600-9600 A, obtained by Kwitter, Henry, and colleagues with the Goldcam
spectrograph at the KPNO 2.1-m or with the RC spectrograph at the CTIO 1.5-m.
The master PN table contains atlas data and an image link. A selected object's
spectrum is displayed in a zoomable window; line identification templates are
provided. In addition to the spectra themselves, the website also contains a
brief discussion of PNe as astronomical objects and as contributors to our
understanding of stellar evolution. We envision that this website, which
concentrates a large amount of data in one place, will be of interest to a
variety of users: researchers might need to check the spectrum of a particular
object of interest; the non-specialist astronomer might simply be interested in
perusing such a collection of spectra; and finally, teachers of introductory
astronomy can use this database to illustrate basic principles of atomic
physics and radiation. To particularly encourage this last use, we have
developed two paper-and-pencil exercises to introduce beginning astronomy
students to the wealth of information that PN spectra contain.


title:
Outer irregular satellites of the planets and their relationship with
  asteroids, comets and Kuiper Belt objects

abstract:
  Outer satellites of the planets have distant, eccentric orbits that can be
highly inclined or even retrograde relative to the equatorial planes of their
planets. These irregular orbits cannot have formed by circumplanetary accretion
and are likely products of early capture from heliocentric orbit. The irregular
satellites may be the only small bodies remaining which are still relatively
near their formation locations within the giant planet region. The study of the
irregular satellites provides a unique window on processes operating in the
young solar system and allows us to probe possible planet formation mechanisms
and the composition of the solar nebula between the rocky objects in the main
asteroid belt and the very volatile rich objects in the Kuiper Belt. The gas
and ice giant planets all appear to have very similar irregular satellite
systems irrespective of their mass or formation timescales and mechanisms.
Water ice has been detected on some of the outer satellites of Saturn and
Neptune whereas none has been observed on Jupiter's outer satellites.


title: How accurate are the time delay estimates in gravitational lensing?

abstract:
  We present a novel approach to estimate the time delay between light curves
of multiple images in a gravitationally lensed system, based on Kernel methods
in the context of machine learning. We perform various experiments with
artificially generated irregularly-sampled data sets to study the effect of the
various levels of noise and the presence of gaps of various size in the
monitoring data. We compare the performance of our method with various other
popular methods of estimating the time delay and conclude, from experiments
with artificial data, that our method is least vulnerable to missing data and
irregular sampling, within reasonable bounds of Gaussian noise. Thereafter, we
use our method to determine the time delays between the two images of quasar
Q0957+561 from radio monitoring data at 4 cm and 6 cm, and conclude that if
only the observations at epochs common to both wavelengths are used, the time
delay gives consistent estimates, which can be combined to yield 408\pm 12
days. The full 6 cm dataset, which covers a longer monitoring period, yields a
value which is 10% larger, but this can be attributed to differences in
sampling and missing data.


title:
Infalling Faint [OII] Emitters in Abell 851. I. Spectroscopic
  Confirmation of Narrowband-Selected Objects

abstract:
  We report on a spectroscopic confirmation of narrowband-selected [OII]
emitters in Abell 851 catalogued by Martin et al. (2000). The optical spectra
obtained from the Keck I Low Resolution Imaging Spectrometer (LRIS) and Keck II
Deep Imaging Multi-Object Spectrograph (DEIMOS) have confirmed [OII]3727
emission in narrowband-selected cluster [OII] candidates at a 85% success rate
for faint (i <~ 25) blue (g-i < 1) galaxies. The rate for the successful
detection of [OII] emission is a strong function of galaxy color, generally
proving the efficacy of narrowband [OII] search supplemented with broadband
colors in selecting faint cluster galaxies with recent star formation. Balmer
decrement-derived reddening measurements show a high degree of reddening
[E(B-V) >~ 0.5] in a significant fraction of this population. Even after
correcting for dust extinction, the [OII]/Ha line flux ratio for the
high-E(B-V) galaxies remains generally lower by a factor of ~2 than the mean
[OII]/Ha ratios reported by the studies of nearby galaxies. The strength of
[OII] equivalent width shows a negative trend with galaxy luminosity while the
Ha equivalent width does not appear to depend as strongly on luminosity. This
in part is due to the high amount of reddening observed in luminous galaxies.
Furthermore, emission line ratio diagnostics show that AGN-like galaxies are
abundant in the high luminosity end of the cluster [OII]-emitting sample, with
only moderately strong [OII] equivalent widths, consistent with a scenario of
galaxy evolution connecting AGNs and suppression of star-forming activity in
massive galaxies.


title:
Infalling Faint [OII] Emitters in Abell 851. II. Environment,
  Kinematics, and Star Formation History

abstract:
  We report on the environments, kinematics, and SFH of [OII]-selected objects
in the z=0.4 galaxy cluster A851, using Keck optical spectra. A large fraction
(~55%) of cluster [OII] emitters show strong Balmer absorptions (>4A in
equivalent width at Hd). These e(a) spectra have been attributed to dusty
starburst galaxies, an interpretation supported by our reddening measurements,
which show a high frequency of very reddened [EBV>0.5] [OII] emitters. Our
spectral modeling requires starburst ages >1Gyr, shorter than the cluster
crossing timescale. We argue that this starburst phase occurs during cluster
infall based on the radial velocity distribution of the cluster [OII] emitters,
which present a deficit of systems near the cluster systemic velocity. The
spatial segregation of some redshifted and blueshifted groups strongly
indicates that the accretion was recent. Throughout the cluster, the fraction
in [OII] emitters is a strong function of the local galaxy density. Our
analysis supports previous suggestions that dusty starburst galaxies arise at
the expense of gas-rich spiral galaxies. In addition, we describe a fainter
[OII]-emitting population, comprised largely of dwarf galaxies and find an even
stronger suppression of [OII] emission in high density environments among this
subsample, indicative of more effective destruction by harassment and/or
gas-stripping. Comparison to previous morphological studies, limited to the
core of A851, suggests that galaxy-galaxy interactions may trigger the
starbursts. The high e(a) galaxy fraction in A851 compared to that in the
field, however, suggests that some cluster-specific mechanism, likely related
to the dynamical assembly of the cluster, also contributes to the high number
of starbursts. (abridged)


title: Natural Downsizing in Hierarchical Galaxy Formation

abstract:
  Stellar-population analyses of today's galaxies show "downsizing", where the
stars in more massive galaxies tend to have formed earlier and over a shorter
time span. We show that this phenomenon is not necessarily "anti-hierarchical"
but rather has its natural roots in the bottom-up clustering process of
dark-matter haloes. While the main progenitor does indeed show an opposite
effect, the integrated mass in all the progenitors down to a given minimum mass
shows a robust downsizing that is qualitatively similar to what has been
observed. These results are derived analytically from the standard extended
Press Schechter (EPS) theory, and are confirmed by merger trees based on EPS or
drawn from N-body simulations. The downsizing is valid for any minimum mass, as
long as it is the same for all haloes at any given time, but the effect is
weaker for smaller minimum mass. If efficient star formation is triggered by
atomic cooling, then a minimum halo mass arises naturally from the minimum
virial temperature for cooling, T~10^4 K, though for such a small minimum mass
the effect is weaker than observed. Baryonic feedback effects, which are
expected to stretch the duration of star formation in small galaxies and shut
it down in massive haloes at late epochs, are likely to play a subsequent role
in shaping up the final downsizing behaviour. Other appearances of downsizing,
such as the decline with time of the typical mass of star-forming galaxies, may
not be attributed to the gravitational clustering process but rather arise from
the gas processes.


title: On the viability of holistic cosmic-ray source models

abstract:
  We consider the energy spectrum of cosmic-rays (CRs) from a purely
phenomenological point of view and investigate the possibility that they all be
produced by the same type of sources with a single power-law spectrum, in
E^{-x}, from thermal to ultra-high energies. We show that the relative fluxes
of the Galactic (GCR) and extra-galactic (EGCR) components are compatible with
such a holistic model, provided that the index of the source spectrum be x
\simeq 2.23\pm 0.07. This is compatible with the best-fit indices for both GCRs
and EGCRs, assuming that their source composition is the same, which is indeed
the case in a holistic model. It is also compatible with theoretical
expectations for particle acceleration at relativistic shocks.


title:
The Blue Straggler Population of the Globular Cluster M5: Comparison
  with M3

abstract:
  We have surveyed the blue straggler star population of the Galactic globular
cluster M5 using high-resolution images of the core along with wide-field
ground-based images reaching to more than 19 core radii. To gauge M5's relative
efficiency of producing stragglers, we compared our sample to five studies of
other globular clusters (mainly Ferraro et al. 1997b; Ferraro et al 2003; and
Piotto et al. 2004). Using a "bright" sample selected in the same way as
Ferraro et al. 1997b, we found a bimodal radial distribution similar to those
found in three other luminous clusters. When the radial distributions for
different clusters are scaled using the core radius, there is good
cluster-to-cluster agreement in the size of the core straggler sample and the
center of the "zone of avoidance". However, M5 has the smallest fraction of
stragglers in the zone of avoidance of any of the clusters measured to date,
and its zone of avoidance appears to be wider (in r / r_c) than that of M3,
which has a very similar surface brightness profile. Both of these facts
indicate that M5's straggler population has dynamically evolved to a larger
extent than M3. Using an ultraviolet sample from Hubble Space Telescope
selected in the same way as Ferraro et al. 2003 and Ferraro et al. 2004, we
find that the frequency of blue stragglers in M5 is lower than all but two of
the clusters examined. We also identified seven bright blue stragglers that
were previously misidentified as HB stars by Sandquist et al. (2004). These
bright stragglers are most likely the result of stellar collisions involving
binary stars.


title:
Dynamical Formation of Close Binaries in Globular Clusters II:
  Cataclysmic Variables

abstract:
  We answer the long-standing question of which production mechanism is
responsible for the cataclysmic variables (CVs) in globular clusters. Arguments
have been given that range from mostly primordial presence to a significant
contribution of later dynamical formation in close stellar encounters. We
conclude, based on a thorough analysis of a homogeneous {\it Chandra} data set,
that the majority of CVs in globulars has a dynamical origin.


title:
X-rays from the Globular Cluster G1: Intermediate Mass Black Hole or Low
  Mass X-ray Binary?

abstract:
  The globular cluster G1 (Mayall II) in M31 is the most massive (~10^7 M_sun)
stellar cluster in the Local Group, and it has the highest central velocity
dispersion (~28 km/s). It has been claimed to host a central ~20,000 M_sun
black hole, but these claims have been controversial. We report here the
XMM-Newton detection of X-ray emission from G1 at a level of Lx ~ 2x10^{36}
erg/s. This emission could be the result of Bondi-Hoyle accretion of ionized
cluster gas by a central black hole, or it could be produced by a conventional
low-mass X-ray binary. A precise localization of the X-ray emission, which is
not possible with the current XMM data, could distinguish between these
possibilities. While such a measurement may be difficult, it is of sufficient
potential importance to pursue.


title: GLAST Tracker

abstract:
  The Large Area Telescope (LAT) on board the Gamma-ray Large-Area Space
Telescope (GLAST) is a pair-conversion gamma-ray detector designed to explore
the gamma-ray universe in the 20 MeV-300 GeV energy band. The Tracker subsystem
of the LAT will perform tracking of electron and positrons to determine the
origin of the gamma-ray. The design and performance of the GLAST LAT Tracker
are described in this paper.


title:
Spitzer Reveals Infrared Optically-Thin Synchrotron Emission from the
  Compact Jet of the Neutron Star X-Ray Binary 4U 0614+091

abstract:
  Spitzer observations of the neutron star (ultra-compact) X-ray binary (XRB)
4U 0614+091 with the Infrared Array Camera reveal emission of non-thermal
origin in the range 3.5-8 um. The mid-infrared spectrum is well fit by a power
law with spectral index of alpha=-0.57+/-0.04 (where the flux density is F_nu
\propto nu^(alpha)). Given the ultra-compact nature of the binary system, we
exclude the possibility that either the companion star or the accretion disk
can be the origin of the observed emission. These observations represent the
first spectral evidence for a compact jet in a low-luminosity neutron star XRB
and furthermore of the presence, already observed in two black hole (BH) XRBs,
of a `break' in the synchrotron spectrum of such compact jets. We can derive a
firm upper limit on the break frequency of the spectrum of nu_thin=3.7x10^(13)
Hz, which is lower than that observed in BH XRBs by at least a factor of 10.
Assuming a high-energy cooling cutoff at ~1 keV, we estimate a total
(integrated up to X-rays) jet power to X-ray bolometric luminosity ratio of
\~5%, much lower than that inferred in BHs.


title:
Formation and evolution of early-type galaxies. II. Models with
  quasi-cosmological initial conditions

abstract:
  In this study, with the aid of N-Body simulations based on quasi-cosmological
initial conditions, we have followed the formation and evolution of two models
of early-type galaxies, from their separation from global expansion of the
Universe to their collapse to virialized structures, the formation of stars and
subsequent nearly passive evolution. The cosmological background we have
considered is the Standard CDM. The models have significantly different nitial
total mass. Particular care has been paid to the star formation process,
heating and cooling of gas, and chemical enrichment. In both models star
formation is completed within the first Gyrs of evolution. The structural
properties of the present-day models are in good agreement with current
observations. The chemical properties, mean metallicity and metallicity
gradients also agree with available observational data. Finally, conspicuous
galactic winds are found to occur. The models conform to the so-called revised
monolithic scheme, because mergers of substructures have occurred very early in
the galaxy life. Our results agree with those obtained in other similar recent
studies, thus strengthening the idea that the revised monolithic scheme is the
right trail to follow in the forest of galaxy formation and evolution.


title:
Accurate laboratory ultraviolet wavelengths for quasar absorption-line
  constraints on varying fundamental constants

abstract:
  The most precise method of investigating possible space-time variations of
the fine-structure constant, using high-redshift quasar absorption lines, is
the many-multiplet (MM) method. For reliable results this method requires very
accurate relative laboratory wavelengths for a number of UV resonance
transitions from several different ionic species. For this purpose laboratory
wavelengths and wavenumbers of 23 UV lines from MgI, MgII, TiII, CrII, MnII,
FeII and ZnII have been measured using high-resolution Fourier Transform (FT)
spectrometry. The spectra of the different ions (except for one FeII line, one
MgI line and the TiII lines) are all measured simultaneously in the same FT
spectrometry recording by using a composite hollow cathode as a light source.
This decreases the relative uncertainties of all the wavelengths. In addition
to any measurement uncertainty, the wavelength uncertainty is determined by
that of the ArII calibration lines, by possible pressure shifts and by
illumination effects. The absolute wavenumbers have uncertainties of typically
0.001 to 0.002 cm^(-1) (0.06 to 0.1 mAA at 2500 AA), while the relative
wavenumbers for strong, symmetric lines in the same spectral recording have
uncertainties of 0.0005 cm^(-1) (0.03 mAA at 2500 AA) or better, depending
mostly on uncertainties in the line fitting procedure. This high relative
precision greatly reduces the potential for systematic effects in the MM
method, while the new TiII measurements now allow these transitions to be used
in MM analyses.


title: Algorithmic regularization with velocity-dependent forces

abstract:
  Algorithmic regularization uses a transformation of the equations of motion
such that the leapfrog algorithm produces exact trajectories for two-body
motion as well as regular results in numerical integration of the motion of
strongly interacting few-body systems. That algorithm alone is not sufficiently
accurate and one must use the extrapolation method for improved precision. This
requires that the basic leapfrog algorithm be time-symmetric, which is not
directly possible in the case of velocity-dependent forces, but is usually
obtained with the help of the implicit midpoint method. Here we suggest an
alternative explicit algorithmic regularization algorithm which can handle
velocity-dependent forces. This is done with the help of a generalized midpoint
method to obtain the required time symmetry, thus eliminating the need for the
implicit midpoint method and allowing the use of extrapolation.


title:
Chandra Observation of the Persistent Emission from the Dipping Source
  XB 1916-053

abstract:
  We present the results of a 50 ks long Chandra observation of the dipping
source XB 1916-053. During the observation two X-ray bursts occurred and the
dips were not present at each orbital period. From the zero-order image we
estimate the precise X-ray coordinates of the source with a 90% uncertainty of
0.6''. In this work we focus on the spectral study of discrete absorption
features, during the persistent emission, using the High Energy Transmission
Grating Spectrometer on board the Chandra satellite. We detect, for the first
time in the 1st-order spectra of XB 1916-053, absorption lines associated to Ne
X, Mg XII, Si XIV, and S XVI, and confirm the presence of the Fe XXV and Fe
XXVI absorption lines with a larger accuracy with respect to the previous XMM
EPIC pn observation. Assuming that the line widths are due to a bulk motion or
a turbulence associated to the coronal activity, we estimate that the lines are
produced in a photoionized absorber distant from the neutron star 4 x 10^{10}
cm, near the disk edge.


title:
First stars IX -Mixing in extremely metal-poor giants. Variation of the
  12C/13C, [Na/Mg] and [Al/Mg] ratios

abstract:
  Extremely metal-poor (EMP) stars preserve a fossil record of the composition
of the ISM when the Galaxy formed. It is crucial, however, to verify whether
internal mixing has modified their surface. We aim to understand the CNO
abundance variations found in some, but not all EMP field giants analysed
earlier. Mixing beyond the first dredge-up of standard models is required, and
its origin needs clarification.The 12C/13C ratio is the most robust diagnostic
of deep mixing, because it is insensitive to the adopted stellar parameters and
should be uniformly high in near-primordial gas. We have measured 12C and 13C
abundances in 35 EMP giants from high-quality VLT/UVES spectra. Correlations
with other abundance data are used to study the depth of mixing.The 12C/13C
ratio is found to correlate with [C/Fe] (and Li/H), and clearly anti-correlate
with [N/Fe]. Evidence for such deep mixing is observed in giants above log
L/Lsolar = 2.6, brighter than in less metal-poor stars, but matching the bump
in the luminosity function in both cases. Three of the mixed stars are also
Na-and Al-rich, another signature of deep mixing, but signatures of the ON
cycle are not clearly seen in these stars. Extra mixing processes clearly occur
in luminous RGB stars. The Na-and Al-rich giants could be AGB stars themselves,
but an inhomogeneous early ISM or pollution from a binary companion remain
possible alternatives (abridged).


title: Probing the Environment with Galaxy Dynamics

abstract:
  I present various projects to study the halo dynamics of elliptical galaxies.
This allows one to study the outer mass and orbital distributions of
ellipticals in different environments, and the inner distributions of groups
and clusters themselves.


title:
The GRB 060218/SN 2006aj event in the context of other Gamma-Ray Burst
  Supernovae

abstract:
  The supernova SN 2006aj associated with GRB 060218 is the second-closest
GRB-SN observed to date (z=0.033). We present Very Large Telescope, Liverpool
Telescope, and Katzman Automatic Imaging Telescope multi-color photometry of SN
2006aj. This supernova is found to be subluminous and rapidly evolving. Its
early light curve includes an additional wavelength-dependent component, which
can be interpreted as shock break-out. We compare the photometric evolution of
multi-band light curves with the corresponding properties of the present sample
of more than 10 GRB-SNe with precisely known redshifts. Using host-galaxy
extinction measurements, we derive extinction-corrected GRB-SN luminosities and
place SN 2006aj in the context of this GRB-selected supernova sample as well as
in the context of local stripped-envelope supernovae.


title: The Abundances of Light Neutron-Capture Elements in Planetary Nebulae

abstract:
  We present preliminary results from a large-scale survey of the
neutron(n)-capture elements Se and Kr in Galactic planetary nebulae (PNe).
These elements may be produced in PN progenitors by s-process nucleosynthesis,
and brought to the stellar envelope by third dredge-up (TDU). We have searched
for [Kr III] 2.199 and [Se IV] 2.287 $\mu$m in 120 PNe, and detected one or
both lines in 79 objects, for a detection rate of 66%. In order to determine
abundances of Se and Kr, we have added these elements to the atomic database of
the photoionization code CLOUDY, and constructed a large grid of models to
derive corrections for unobserved ionization stages. Se and Kr are enriched in
73% of the PNe in which they have been detected, and exhibit a wide range of
abundances, from roughly solar to enriched by a factor of 10 or more. These
enrichments are interpreted as evidence for the operation of the s-process and
TDU in the progenitor stars. In line with theoretical expectations, Kr is more
strongly enhanced than Se, and the abundances of both elements are correlated
with the carbon abundance. Kr and Se are strongly enhanced in Type I PNe, which
may be evidence for the operation of the $^{22}$Ne neutron source in
intermediate-mass AGB stars. These results constitute the first broad
characterization of s-process enrichments in PNe as a population, and reveal
the impact of low- and intermediate-mass stars on the chemical evolution of
trans-iron elements in the Galaxy.


title:
Star Formation History of the Hubble Ultra Deep Field: Comparison with
  the HDFN

abstract:
  We use the NICMOS Treasury and ACS HUDF images to measure the extinction
corrected star formation history for 4681 galaxies in the region common to both
images utilizing the star formation rate distribution function and other
techniques similar to those employed with the NICMOS and WFPC2 images in the
HDFN. Unlike the HDFN the NICMOS region of the HUDF appears to lack highly
luminous and high star formation rate galaxies at redshifts beyond 3. The HUDF
provides a region that is completely uncorrelated to the HDFN and therefore
provides and independent measure of the star formation history of the universe.
The combined HUDF and HDFN star formation rates show an average star formation
rate of 0.2 solar masses per yer per cubic megaparsec. The average SFR of the
combined fields at z = 1-3 is 0.29 solar masses per year per cubic megaparsec
while the average at z = 4-6 is 1.2 solar masses per year per cubic megaparsec.
The SFRs at all redshifts are within 3 sigma of the average over all redshifts.


title: Rapid Formation of Super-Earths around M Dwarf Stars

abstract:
  While the recent microlensing discoveries of super-Earths orbiting two M
dwarf stars have been taken as support for the core accretion mechanism of
giant planet formation, we show here that these planets could also have been
formed by the competing mechanism of disk instability, coupled with
photoevaporative loss of their gaseous envelopes by a strong external source of
UV radiation, i.e., an O star. M dwarfs that form in regions of future
high-mass star formation would then be expected to have super-Earths orbiting
at distances of several AU and beyond, while those that form in regions of
low-mass star formation would be expected to have gas giants at those
distances. Given that most stars are born in the former rather than in the
latter regions, M dwarfs should have significantly more super-Earths than gas
giants, as seems to be indicated by the microlensing surveys.


title: MHD Turbulent Mixing Layers: Equilibrium Cooling Models

abstract:
  We present models of turbulent mixing at the boundaries between hot
(T~10^{6-7} K) and warm material (T~10^4 K) in the interstellar medium, using a
three-dimensional magnetohydrodynamical code, with radiative cooling. The
source of turbulence in our simulations is a Kelvin-Helmholtz instability,
produced by shear between the two media. We found, that because the growth rate
of the large scale modes in the instability is rather slow, it takes a
significant amount of time (~1 Myr) for turbulence to produce effective mixing.
We find that the total column densities of the highly ionized species (C IV, N
V, and O VI) per interface (assuming ionization equilibrium) are similar to
previous steady-state non-equilibrium ionization models, but grow slowly from
log N ~10^{11} to a few 10^{12} cm^{-2} as the interface evolves. However, the
column density ratios can differ significantly from previous estimates, with an
order of magnitude variation in N(C IV)/N(O VI) as the mixing develops.


title: Planetary Nebulae as Probes of Stellar Populations

abstract:
  Planetary nebulae (PNe) have the potential to revolutionize our understanding
of extragalactic stellar populations. Indeed, in many systems, bright PNe are
the only individual objects identifiable from the ground, and, even more often,
they are the only stars that are amenable to spectroscopy. We review the ways
in which ensembles of PNe can be used to probe the metallicity, age, and
history of a stellar population. In particular, we discuss three cases: the
weak line spectroscopic regime, where one has knowledge of the line-strengths
of faint forbidden lines such as [O III] 4363, a bright-line regime, where only
the strongest emission lines are visible, and the photometric regime, where the
only information available is the [O III] 5007 luminosity function. We show
that each of these cases, when properly calibrated, can provide unique insights
into the objects that make up a stellar population.


title:
Globular Clusters at the Centre of the Fornax Cluster: Tracing
  Interactions Between Galaxies

abstract:
  We present the combined results of two investigations: a large-scale study of
the globular cluster system (GCS) around NGC 1399, the central galaxy of the
Fornax cluster, and a study of the GCSs around NGC 1374, NGC 1379 and NGC 1387,
three low-luminosity early-type galaxies located close to the centre of the
same cluster. In both cases, the data consist of images from the wide-field
MOSAIC Imager of the CTIO 4-m telescope, obtained with Washington C and
Kron-Cousins R filters, which provide good metallicity resolution. The colour
distributions and radial projected densities of the GCSs are analyzed. We focus
on the properties of the GCSs that trace possible interaction processes between
the galaxies, such as tidal stripping of globular clusters. For the blue
globular clusters, we find tails between NGC 1399 and neighbouring galaxies in
the azimuthal projected distribution, and the three low-luminosity galaxies
show low specific frequencies and a low proportion of blue GCs.


title:
Legacy data and cosmological constraints from the angular-size/redshift
  relation for ultra-compact radio sources

abstract:
  We have re-examined an ancient VLBI survey of ultra-comact radio sources at
2.29 GHz, which gave fringe amplitudes for 917 such objects with total flux
density >0.5 Jy approximately. A number of cosmological investigations based
upon this survey have been published in recent years. We have updated the
sample with respect to both redshift and radio information, and now have full
data for 613 objects, significantly larger than the number (337) used in
earlier investigations. The corresponding angular-size/redshift diagram gives
Omega_m=0.25+0.04/-0.03, Omega_\Lambda=0.97+0.09/-0.13 and K=0.22+0.07/-0.10.
In combination with supernova data, and a simple-minded approach to CMB data
based upon the angular size of the acoustic horizon, our best figures are
Omega_m=0.298+0.025/-0.024, Omega_\Lambda=0.702+0.035/-0.036 and K=
0.000+0.021/-0.019. We have examined simple models of dynamical vacuum energy;
the first, based upon a scalar potential V(phi)=omega_C^2 phi^2/2, gives
w(0)=-1.00+0.06/-0.00, (dw/dz)_0=+0.00/-0.08; in this case conditions at z=0
require particular attention, to preclude behaviour in which phi becomes
singular as z -->infinity. For fixed w limits are w=-1.20+0.15/-0.14. The above
error bars are 68% confidence limits.


title: Galactic Abundance Patterns via Peimbert Types I & II Planetary Nebulae

abstract:
  Planetary Nebulae (PNe) abundance patterns have long been used to note
signatures of nuclear processing and to trace the distribution of metals
throughout galaxies. We present abundance gradients and heavy element ratios
based upon newly acquired spectrophotometry of a sample of >120 Galactic PNe.
This new data set is extracted from spectra that extend from 3600 - 9600 A,
allowing the use of [S III] features at 9069 and 9532 A. Since a significant
portion of S in PNe resides in S+2 and higher ionization stages, including
these strong features should improve the extrapolation from observed ion
abundances to total element abundance. S is believed to be precluded from
enhancement and depletion across the range of PNe progenitor masses, making it
an alternate metallicity tracer to the canonical oxygen. If S can be reliably
determined in PNe, its stability in intermediate mass stars makes it a valuable
tool to probe the natal conditions as well as the evolution of PNe progenitors.
This is a continuation of our Type II PNe work, the impetus being to compile a
relatively large set of line strengths and abundances with internally
consistent observation, reduction, measurement, and abundance determination,
minimizing systematic effects that come from compiling various data sets. This
research is supported by the AAS Small Research Grants program, the Franklin &
Marshall Committee on Grants, and NSF grant AST- 0307118.


title: Sensitivity and pointing accuracy of the NEMO km$^3$ telescope

abstract:
  n this paper we present the results of Monte Carlo simulation studies on the
capability of the proposed NEMO km3 telescope to detect high energy neutrinos.
We calculated the detector sensitivity to muon neutrinos coming from a generic
point-like source. We also simulated the lack of atmospheric muons in
correspondence to the Moon disk in order to determine the detector angular
resolution and to check the absolute pointing capability.


title: Effects of architectural issues on a km3 scale detector

abstract:
  Simulation results showing the comparison between the performance of
different km3 detector geometries are reported. Effective neutrino areas and
angular resolutions are reported for three different geometries based on
NEMO-towers and strings. The results show that the NEMO-tower based detector
has the best performance concerning both the effective area and the angular
resolution isotropy


title: A New Look at the Binary Characteristics of Massive Stars

abstract:
  We constrain the properties of massive binaries by comparing radial velocity
data of Cygnus OB2 with Monte Carlo models. Our comparisons test several
popular prescriptions for massive binary parameters. We explore a range of true
binary fraction, F, a range of power-law slopes, \alpha, describing the
distribution of companion masses, and a range of power-law slopes, \beta,
describing the distribution of orbital separations. We also consider
distributions of secondary masses described by a Miller-Scalo type initial mass
function and by a two-component IMF that includes a substantial ``twin''
population with M_2 ~ M_1. We show that binary fractions F<0.7 are considerably
less probable than F>0.8. Thus, the true binary fraction is high. For F=1.0 and
a distribution of orbital separations near the canonical Opik's Law
distribution (i.e., flat; \beta=0), the power law slope of the mass ratio
distribution is \alpha= -0.6 - 0.0. For F~0.8, \alpha is somewhat larger, in
the range -0.4 - 1.0. In any case, the secondary star mass function is
inconsistent with a Miller-Scalo -like IMF unless the lower end is truncated
below ~ 2--4 solar masses. In other words, massive stars preferentially have
massive companions. The best fitting models are described by a Salpeter or
Miller-Scalo IMF for 60% of secondary star masses with the other 40% of
secondaries having M_2 ~ M_1, i.e., ``twins''. These best-fitting model
parameters simultaneously predict the fraction of type Ib/c supernovae to be
30-40% of all core-collapse supernovae, in agreement with recent observational
estimates.


title: Dynamics of galaxy cores and supermassive black holes

abstract:
  Recent work on the dynamical evolution of galactic nuclei containing
supermassive black holes is reviewed. Topics include galaxy structural
properties; collisionless and collisional equilibria; loss-cone dynamics; and
dynamics of binary and multiple supermassive black holes.


title:
The Spin-Resolved Atomic Velocity Distribution and 21-cm Line Profile of
  Dark-Age Gas

abstract:
  The 21-cm hyperfine line of atomic hydrogen (HI) is a promising probe of the
cosmic dark ages. In past treatments of 21-cm radiation it was assumed the
hyperfine level populations of HI could be characterized by a
velocity-independent ``spin temperature'' T_s determined by a competition
between 21-cm radiative transitions, spin-changing collisions, and (at lower
redshifts) Lyman-alpha scattering. However we show here that, if the
collisional time is comparable to the radiative time, the spin temperature will
depend on atomic velocity, T_s=T_s(v), and one must replace the usual hyperfine
level rate equations with a Boltzmann equation describing the spin and velocity
dependence of the HI distribution function. We construct here the Boltzmann
equation relevant to the cosmic dark ages and solve it using a basis-function
method. Accounting for the actual spin-resolved atomic velocity distribution
results in up to a 2 per cent suppression of the 21-cm emissivity, and a
redshift and angular-projection dependent suppression or enhancement of the
linear power spectrum of 21-cm fluctuations of up to 5 per cent. The effect on
the 21-cm line profile is more dramatic -- its full-width at half maximum
(FWHM) can be enhanced by up to 60 per cent relative to the
velocity-independent calculation. We discuss the implications for 21-cm
tomography of the dark ages.


title: The dynamical evolution of young clusters and galactic implications

abstract:
  Star clusters are observed to form in a highly compact state and with low
star-formation efficiencies. If the residual gas is expelled on a dynamical
time the clusters disrupt thereby (i) feeding a hot kinematical stellar
component into their host-galaxy's field population, and (ii) if the
gas-evacuation time-scale depends on cluster mass, then a power-law
embedded-cluster mass function transforms within ten to a few dozen Myr to a
mass function with a turnover near 10^5 M_sun, thereby possibly explaining this
universal empirical feature.


title:
Discovery of a tight correlation among the prompt emission properties of
  long Gamma Ray Bursts

abstract:
  We report the discovery of a correlation among three prompt emission
properties of GRBs. These are the isotropic peak luminosity L_iso, the peak
energy of the time-integrated prompt emission spectrum E_pk, and the ``high
signal" timescale T_0.45, previously used to characterize the variability
behavior of bursts. In the rest frame of the source the found correlation reads
L_iso\propto E_pk^1.62 T_0.45^-0.49. We find other strong correlations, but at
the cost of increasing the number of variables, involving the variability and
the isotropic energy of the prompt emission. With respect to the previous tight
correlations found in GRBs the newly found correlation does not require any
information from the afterglow phase of the bursts, nor any model-dependent
assumption. In the popular scenario in which we are receiving beamed radiation
originating in a fireball pointing at us, the found correlation preserves its
form in the comoving frame. This helps to explain the small scatter of the
correlation, and underlines the role of the local brightness (i.e. the
brightness of the visible fraction of the fireball surface). This correlation
has been found for 19 objects, and it is hard to establish if any selection
bias affects it. Its connection with the prompt local brightness is promising,
but a solid physical understanding is still to be found. Despite all that, we
find that some properties of the correlation, which we discuss, support its
true existence, and this has important implications for the GRB physics.
Furthermore, it is possible to use such correlation as an accurate redshift
estimator, and its tightness will allow us to use it as a tool to constrain the
cosmological parameters (abridged)


title:
New results on the time variation of the radial abundance gradients from
  planetary nebulae

abstract:
  New results on the time variation of the radial abundance gradients in the
galactic disk are presented on the basis of four different samples of planetary
nebulae. These comprise both smaller, homogeneous sets of data, and larger but
non-homogeneous samples. Four different chemical elements are considered,
namely, O, S, Ar, and Ne. Other objects such as open clusters, cepheids and HII
regions are also taken into account. Our analysis support our earlier
conclusions in the sense that, on the average, the radial abundance gradients
have flattened out during the last 6 to 8 Gyr, with important consequences for
models of the chemical evolution of the Galaxy.


title: On the Incidence of Strong MgII Absorbers Along GRB Sightlines

abstract:
  We report on a survey for strong (rest equivalent width W_r >= 1A),
intervening MgII systems along the sightlines to long-duration gamma-ray bursts
(GRBs). The GRB spectra which comprise the survey have a heterogeneous mix of
resolution and wavelength coverage, but we implement a strict, uniform set of
search criteria to derive a well-defined statistical sample. We identify 15
strong MgII absorbers along 14 GRB sightlines (nearly every sightline exhibits
at least one absorber) with spectra covering a total pathlength Delta z = 15.5
at a mean redshift <z> = 1.1. In contrast, the predicted incidence of such
absorber systems along the same path length to quasar sightlines is only 3.8.
The roughly four times higher incidence along GRB sightlines is inconsistent
with a statistical fluctuation at greater than 99.9% c.l. Several effects could
explain the result: (i) dust within the MgII absorbers obscures faint quasars
giving a lower observed incidence along quasar sightlines; (ii) the gas is
intrinsic to the GRB event; (iii) the GRB are gravitationally lensed by these
absorbers. We present strong arguments against the first two effects and also
consider lensing to be an unlikely explanation. The results suggest that at
least one of our fundamental beliefs on absorption line research is flawed.


title:
Multiwavelength Observations of the Extreme X-Ray Selected BL Lac Object
  PG 1553+11 (1ES 1553+113)

abstract:
  PG 1553+11 was the target of a coordinated three week multiwavelength
campaign during 2003 April and May. A significant X-ray flare was observed
during the second half of this campaign. Although no optical flare was recorded
during the X-ray campaign, optical observations obtained immediately prior to
the campaign displayed a higher flux than that recorded during the campaign. An
optical flare was observed a few days after the end of the X-ray campaign and
may be related to the X-ray flare. Radio observations were made at three
frequencies, with no significant changes in flux detected near the times of the
optical and X-ray flares. The spectral energy distributions and flux ratios in
different wavebands observed for this object are compared to other X-ray
selected blazars to demonstrate how PG 1553+11 is an extreme member of this
group.


title: Radio and millimeter observations of z~2 luminous QSOs

abstract:
  We present Very Large Array observations at 1.4 and 5 GHz of a sample of 16
quasi-stellar objects (QSOs) at z = 1.78 to 2.71. Half of the chosen quasars
are bright at mm wavelengths (250 or 350 GHz) while the other half were not
detected at mm wavelengths; the former QSOs were detected at 1.4 GHz, in most
cases at high significance (S/N > ~7), but only three of the latter sources
were detected at radio frequencies, and only at lower significance (S/N ~ 3).
The data are consistent with a correlation between the mm and radio fluxes
indicating a physical connection between the mechanisms responsible for the
radio and mm emission. However, this conclusion is based on data which includes
many upper limits, and deeper observations are clearly needed to verify this
correlation.
  All eight mm detected QSOs are detected in the radio continuum, with radio
flux densities consistent with the radio-to-FIR correlation for low z star
forming galaxies. However, four of these have flatter spectral indices than is
typical for star forming galaxies (i.e. greater than -0.5) suggesting that
radiation from the central AGN dominates the observed radio emission. All the
sources detected at 1.4 GHz are spatially unresolved, with the size limits
typically < 1'' = 6 kpc. High star formation rate galaxies at low redshift are
typically nuclear starbursts, with sizes < 1 kpc. Hence, the current radio size
limits are insufficient to constrain the emission model (AGN or starburst).


title:
The Kinematic and Plasma Properties of X-ray Knots in Cassiopeia A from
  the Chandra HETGS

abstract:
  We present high-resolution X-ray spectra from the young supernova remnant Cas
A using a 70-ks observation taken by the Chandra High Energy Transmission
Grating Spectrometer (HETGS). Line emission, dominated by Si and S ions, is
used for high-resolution spectral analysis of many bright, narrow regions of
Cas A to examine their kinematics and plasma state. These data allow a 3D
reconstruction using the unprecedented X-ray kinematic results: we derive
unambiguous Doppler shifts for these selected regions, with values ranging
between -2500 and +4000 km/s. Plasma diagnostics of these regions, derived from
line ratios of resolved He-like triplet lines and H-like lines of Si, indicate
temperatures largely around 1 keV, which we model as O-rich reverse-shocked
ejecta. The ionization age also does not vary considerably over these regions
of the remnant. The gratings analysis was complemented by the non-dispersed
spectra from the same dataset, which provided information on emission measure
and elemental abundances for the selected Cas A regions. The derived electron
density of X-ray emitting ejecta varies from 20 to 200 cm^{-3}. The measured
abundances of Mg, Si, S and Ca are consistent with O being the dominant element
in the Cas A plasma. With a diameter of 5 arcmin, Cas A is the largest source
observed with the HETGS to date. We, therefore, describe the technique we use
and some of the challenges we face in the HETGS data reduction from such an
extended, complex object.


title: Near Infrared Adaptive Optics Imaging of QSO Host Galaxies

abstract:
  We report near-infrared (primarily H-band) adaptive optics (AO) imaging with
the Gemini-N and Subaru Telescopes, of a representative sample of 32 nearby
(z<0.3) QSOs selected from the Palomar-Green (PG) Bright Quasar Survey (BQS),
in order to investigate the properties of the host galaxies. 2D modeling and
visual inspection of the images shows that ~36% of the hosts are ellipticals,
\~39% contain a prominent disk component, and ~25% are of undetermined type.
30% show obvious signs of disturbance. The mean M_H(host) = -24.82 (2.1L_H*),
with a range -23.5 to -26.5 (~0.63 to 10 L_H*). At <L_H*, all hosts have a
dominant disk component, while at >2 L_H* most are ellipticals. "Disturbed"
hosts are found at all M_H(host), while "strongly disturbed" hosts appear to
favor the more luminous hosts. Hosts with prominent disks have less luminous
QSOs, while the most luminous QSOs are almost exclusively in ellipticals or in
mergers (which presumably shortly will be ellipticals). At z<0.13, where our
sample is complete at B-band, we find no clear correlation between M_B(QSO) and
M_H(host). However, at z>0.15, the more luminous QSOs (M_B<-24.7), and 4/5 of
the radio-loud QSOs, have the most luminous H-band hosts (>7L_H*), most of
which are ellipticals. Finally, we find a strong correlation between the
"infrared-excess", L_IR/L_BB, of QSOs with host type and degree of disturbance.
Disturbed and strongly disturbed hosts and hosts with dominant disks have
L_IR/L_BB twice that of non-disturbed and elliptical hosts, respectively. QSOs
with "disturbed" and "strongly-disturbed" hosts are also found to have
morphologies and mid/far-infrared colors that are similar to what is found for
"warm" ultraluminous infrared galaxies, providing further evidence for a
possible evolutionary connection between both classes of objects.


title: Populating the Galaxy with low-mass X-ray binaries

abstract:
  We perform binary population synthesis calculations to investigate the
incidence of low-mass X-ray binaries and their birth rate in the Galaxy. We use
a binary evolution algorithm that models all the relevant processes including
tidal circularization and synchronization. Parameters in the evolution
algorithm that are uncertain and may affect X-ray binary formation are allowed
to vary during the investigation. We agree with previous studies that under
standard assumptions of binary evolution the formation rate and number of
black-hole low-mass X-ray binaries predicted by the model are more than an
order of magnitude less than what is indicated by observations. We find that
the common-envelope process cannot be manipulated to produce significant
numbers of black-hole low-mass X-ray binaries. However, by simply reducing the
mass-loss rate from helium stars adopted in the standard model, to a rate that
agrees with the latest data, we produce a good match to the observations.
Including low-mass X-ray binaries that evolve from intermediate-mass systems
also leads to favourable results. We stress that constraints on the X-ray
binary population provided by observations are used here merely as a guide as
surveys suffer from incompleteness and much uncertainty is involved in the
interpretation of results.


title: Medium-resolution spectroscopy of galaxies with redshifts 2.3 < z < 3.5

abstract:
  Using FORS2 at the ESO VLT we obtained medium resolution (R ~ 2000) spectra
of 12 galaxies with 2.37 < z < 3.40 in the FORS Deep Field. Two individual
spectra with good S/N and a composite of all 12 spectra were used to derive
properties of the stellar and interstellar absorption lines of galaxies in this
redshift range. Systematic differences between the individual spectra were
found for the strength and profiles of the intrinsic interstellar lines. For
eight spectra with sufficient S/N we measured the `1370' and `1425' metallicity
indices. From these indices we find for our sample that galaxies at z > 3 have
lower mean metallicity than galaxies at 2.5 < z < 3. However there remain
uncertainties concerning the absolute calibration of the metallicity tracers in
use for high-redshift galaxies. Additional modeling will be needed to resolve
these uncertainties.


title: Optical recombination lines as probes of conditions in planetary nebulae

abstract:
  Since the last IAU symposium on planetary nebulae (PNe), several deep
spectroscopic surveys of the relatively faint optical recombination lines
(ORLs) emitted by heavy element ions in PNe and H II regions have been
completed. New diagnostic tools have been developed thanks to progress in the
calculations of basic atomic data. Together, they have led to a better
understanding of the physical conditions under which the various types of
emission lines arise. The studies have strengthened the previous conjecture
that nebulae contain another component of cold, high metallicity gas, which is
too cool to excite any significant optical or UV CELs and is thus invisible via
such lines. The existence of such a plasma component in PNe and possibly also
in H II regions provides a natural solution to the long-standing problem in
nebular astrophysics, i.e. the dichotomy of nebular plasma diagnostics and
abundance determinations using ORLs and continua on the one hand and
collisionally excited lines (CELs) on the other.


title: New Planerary Nebulae towards the Galactic bulge

abstract:
  New Planetary Nebulae (PNe) were discovered through an [O III] 5007 A
emission line survey in the Galactic bulge region with l>0 deg. We detected 240
objects, including 44 new PNe. Deep Halpha+[N II] CCD images as well as low
resolution spectra were obtained for the new PNe in order to study them in
detail. Preliminary photo-ionization models of the new PNe with Cloudy resulted
in first estimates of the physical parameters and abundances. They are compared
to the abundances of Galactic PNe.


title:
The ring statistics - how to separate E- and B-modes of cosmic shear
  correlation functions on a finite interval

abstract:
  Aims. One of the main probes for systematic errors in the cosmic shear signal
are the division of the shear field into E- and B-mode shear, where
gravitational lensing only produces the former. As shown in a recent note, all
currently used E-/B-mode separation methods for the shear correlation functions
xi_pm require them to be measured to arbitrarily small and/or large separations
which is of course not feasible in practice.
  Methods. We derive second-order shear statistics which provide a clean
separation into E- and B-modes from measurements of xi_pm(theta) over a finite
interval only. We call these new statistics the circle and ring statistics,
respectively; the latter is obtained by an integral over the former. The
mathematical properties of these new shear statistics are obtained, as well as
specific expressions for applying them to observed data.
  Results. It is shown that an E-/B-mode separation can be performed on
measurements of xi_pm over a finite interval in angular separation, using the
ring statistics. We furthermore generalize this result to derive the most
general class of second-order shear statistics which provide a separation of E-
and B-mode shear on a given angular interval theta_min <= theta <= theta_max.
Our results will be of practical use particularly for future cosmic shear
surveys where highly precise measurements of the shear will become available
and where control of systematics will be mandatory.


title: Isolated galaxies: residual of primordial building blocks?

abstract:
  CONTEXT.The mass assembly is believed to be the dominant process of early
galaxy formation. This mechanism of galaxy building can proceed either by
repeated major mergers with other systems, or by means of accretion of matter
from the surrounding regions. AIMS.In this paper we compare the properties of
local disk galaxies that appear isolated, i.e. not tidally affected by other
galaxies during the last few Gyr within the volume given by cz<= 5000 km/s,
with those galaxies at z values from 0.25 to 5.
  METHODS.Effective radii for 203 isolated galaxies and 1645 galaxies from the
RC3 have been collected and the two samples have been analyzed statistically. A
similar comparison has been made with half light radii studied at high z from
the literature.
  RESULTS.We found that isolated galaxies are in general smaller than other
present epoch galaxies from the RC3. We notice the lack of systems larger than
7 kpc among them. Their size distribution appears to be similar to that of
galaxies at 1.4 <= z <= 2. The models of the merging history also indicate that
the isolated galaxies did stop their merging process at about that redshift,
evolving passively since then. The galaxy density seems to have remained
unchanged since that epoch.
  CONCLUSIONS.Isolated galaxies appears to be the end products of the merging
process as proposed in the hierarchical accretion scenario at around z=1.4. For
this class of galaxies this was the last significant merging event in their
lives and have evolved passively since then. This is confirmed by the
analytical estimate of the merging fraction with z and by the comparison with
sizes of distant galaxies.


title: Giant Pulses in Pulsar PSR J1752+2359

abstract:
  We report the detection of Giant Pulses (GPs) in the pulsar PSR J1752+2359.
The energy of the strongest GP exceeds the energy of the average pulse by a
factor of 200, in which it stands out from all known pulsars with GPs. PSR
J1752+2359 as well as the previously detected PSR B0031-07 and PSR B1112+50,
belongs to the first group of pulsars found to have GPs without a high magnetic
field at the light cylinder.


title: Probing the Pulsar Wind Nebula of PSR B0355+54

abstract:
  We present XMM-Newton and Chandra X-ray observations of the middle-aged radio
pulsar PSR B0355+54. Our X-ray observations reveal emission not only from the
pulsar itself, but also from a compact diffuse component extending ~50'' in the
opposite direction to the pulsar's proper motion. There is also evidence for
the presence of fainter diffuse emission extending ~5' from the point source.
The compact diffuse feature is well-fitted with a power-law, the index of which
is consistent with the values found for other pulsar wind nebulae. The
morphology of the diffuse component is similar to the ram-pressure confined
pulsar wind nebulae detected for other sources. The X-ray emission from the
pulsar itself is described well by a thermal plus power-law fit, with the
thermal emission most likely originating in a hot polar cap.


title: The Turbulent Interstellar Medium

abstract:
  An overview is presented of the main properties of the interstellar medium.
Evidence is summarized that the interstellar medium is highly turbulent, driven
on different length scales by various energetic processes. Large-scale
turbulence determines the formation of structures like filaments and shells in
the diffuse interstellar medium. It also regulates the formation of dense, cold
molecular clouds. Molecular clouds are now believed to be transient objects
that form on timescales of order 1e7 yrs in regions where HI gas is compressed
and cools. Supersonic turbulence in the compressed HI slab is generated by a
combination of hydrodynamical instabilities, coupled with cooling. Turbulent
dissipation is compensated by the kinetic energy input of the inflow. Molecular
hydrogen eventually forms when the surface density in the slab reaches a
threshold value of 1e21 cm^-2 at which point further cooling triggers the onset
of star formation by gravitational collapse. A few Myrs later, the newly formed
stars and resulting supernovae will disperse their molecular surrounding and
generate new expanding shells that drive again turbulence in the diffuse gas
and trigger the formation of a next generation of cold clouds. Although a
consistent scenario of interstellar medium dynamics and star formation is
emerging many details are still unclear and require more detailed work on
microphysical processes as well as a better understanding of supersonic,
compressible turbulence.


title:
Comments on the paper "The Mexican Hat Wavelet Family. Application to
  point source detection in CMB maps" by J. Gonzalez-Nuevo et al.
  (astro-ph/0604376)

abstract:
  The arguments presented by Gonzalez-Nuevo et. al (2006) in favour of the
Mexican Hat Wavelet Family (MHWF) are critically discussed here. These authors
allege the optimal properties of this new class of filters in the detection of
point sources embedded in a noise background but their claim is not based upon
a solid mathematical foundation and proof.


title: Unravelling the mystery of the M31 bar

abstract:
  The inclination of M31 is too close to edge-on for a bar component to be
easily recognised and is not sufficiently edge-on for a boxy/peanut bulge to
protrude clearly out of the equatorial plane. Nevertheless, a sufficient number
of clues allow us to argue that this galaxy is barred. We use fully
self-consistent N-body simulations of barred galaxies and compare them with
both photometric and kinematic observational data for M31. In particular, we
rely on the near infrared photometry presented in a companion paper. We compare
isodensity contours to isophotal contours and the light profile along cuts
parallel to the galaxy major axis and offset towards the North, or the South,
to mass profiles along similar cuts on the model. All these comparisons, as
well as position velocity diagrams for the gaseous component, give us strong
arguments that M31 is barred. We compare four fiducial N-body models to the
data and thus set constraints on the parameters of the M31 bar, as its
strength, length and orientation. Our `best' models, although not meant to be
exact models of M31, reproduce in a very satisfactory way the main relevant
observations. We present arguments that M31 has both a classical and a
boxy/peanut bulge. Its pseudo-ring-like structure at roughly 50' is near the
outer Lindblad resonance of the bar and could thus be an outer ring, as often
observed in barred galaxies. The shape of the isophotes also argues that the
vertically thin part of the M31 bar extends considerably further out than its
boxy bulge, i.e. that the boxy bulge is only part of the bar, thus confirming
predictions from orbital structure studies and from previous N-body
simulations.


title:
Tagging single muons and other long-flying relativistic charged
  particles by ultra-fast timing in air Cherenkov telescopes

abstract:
  Atmospheric air Cherenkov telescopes are successfully used for ground-based,
very high-energy (VHE) gamma ray astronomy. Triggers from the so-called single
muon and other long-flying relativistic charged particle events are an unwanted
background for the Cherenkov telescope. Because of low rate at TeV energies the
muon background is unimportant. It is much more intense for telescopes with
high photon sensitivity and low energy threshold. Below a few hundred GeV
energy, the so-called muon background becomes so intense, that it can
deteriorate the sensitivity of telescopes (the so-called muon-wall problem).
  From general considerations it can be anticipated that the signature of these
particles should be a light pulse with a narrow time structure. In fact,
simulations show that the pulses from muons have a very narrow time profile
that is well below the time resolutions of nearly all currently operating
telescopes. In this report we elaborate on the time profile of Cherenkov light
from the so-called single muons and show that a telescope with ultra-fast time
response can open a new dimension allowing one to tag and to reject those
events.


title: A magnetically collimated jet from the evolved star W43A

abstract:
  We present the first direct measurements of the magnetic field strength and
direction in a collimated jet from an evolved star on its way to become a
planetary nebula. Very Long Baseline Array (VLBA) observations of the linear
and circular polarization of the water masers in the collimated jet of W43A
reveal a strong toroidal magnetic field, indicating that the jet is
magnetically collimated. The magnetic field strength in the jet extrapolated
back to the stellar surface yields a surface field of several Gauss, consistent
with the measurements of maser polarization in a large sample of evolved stars.
The origin of the magnetic field is yet unknown, although the jet precession
might point to the existence of a heavy planet or stellar companion. This is
the first direct observational evidence for magnetic collimation in the jets,
that likely play an important role in shaping planetary nebulae.


title:
Toroidal LNRF-velocity profiles in thick accretion discs orbiting
  rapidly rotating Kerr black holes

abstract:
  We show that in the equatorial plane of marginally stable thick discs (with
uniformly distributed specific angular momentum the orbital velocity relative
to the locally non-rotating frames (LNRF) has a positive radial gradient in the
vicinity of black holes with spin a>0.99979. The change of sign of the velocity
gradient occurs just above the center of the thick toroidal discs, in the
region where stable circular geodesics of the Kerr spacetime are allowed. The
global character of the phenomenon is given in terms of topology changes of the
von Zeipel surfaces (equivalent to the equivelocity surfaces in the tori with
constant specific angular momentum distribution). Toroidal von Zeipel surfaces
exist around the circle corresponding to the minimum of the equatorial LNRF
velocity profile, indicating a possibility of development of some vertical
instabilities in those parts of marginally stable tori with positive gradient
of the LNRF velocity. Eventual oscillatory frequencies connected with the
phenomenon are given in a coordinate-independent form.


title: Basic properties of toroidal structures in Kerr--de Sitter backgrounds

abstract:
  Perfect fluid tori with uniform distribution of the specific angular momentum
orbiting the Kerr-de Sitter black holes or naked singularities are studied.
Closed equipotential surfaces corresponding to stationary toroidal discs are
allowed only in the spacetimes admitting stable circular geodesics. The last
closed surface crosses itself in the cusp(s) enabling outflow(s) of matter from
the torus due to the violation of hydrostatic equilibrium. The repulsive
cosmological constant, $\Lambda >0$, implies the existence of the outer cusp
(with a stabilizing effect on the tori because of "excretion", i.e., outflow of
matter from the torus into the outer space) and the strong collimation of open
equipotential surfaces along the rotational axis. Both the effects take place
nearby the so-called static radius where the gravitational attraction is just
balanced by the cosmic repulsion. The plus-family discs (which are always
corotating in the black-hole backgrounds but can be counterrotating, even with
negative energy of the fluid elements, in some naked singularity backgrounds)
are thicker and more extended than the minus-family ones (which are always
counterrotating in all backgrounds). If the parameters of naked-singularity
spacetimes are very close to the parameters of extreme black-hole spacetimes,
the family of possible disc-like configurations includes members with two
isolated discs where the inner one is always a counterrotating accretion disc.
Mass estimates for tori with nonrelativistic adiabatic equation of state give
limits on their central mass-density, for which the approximation of test fluid
is adequate.


title:
HST/STIS Spectroscopy of Five Super Star Clusters in the Starburst
  Galaxy M82

abstract:
  We present optical spectroscopy obtained with the Space Telescope Imaging
Spectrograph (STIS) of five young massive star clusters in the starburst galaxy
M82. A detailed analysis is performed for one cluster `M82-A1' and its
immediate environment in the starburst core. From HST archive images, we find
that it is elliptical with an effective radius of 3.0+/-0.5 pc and is
surrounded by a compact (r=4.5+/-0.5 pc) H II region. We determine the age and
reddening of M82-A1 using synthetic spectra from population synthesis models by
fitting both the continuum energy distribution and the depth of the Balmer
jump. We find an age of 6.4+/-0.5 Myr and a photometric mass estimate of M=7-13
x 10^5 solar masses. We associate its formation with the most recent starburst
event 4-6 Myr ago. We find that the oxygen abundance of the H II region
surrounding M82-A1 is solar or slightly higher. The H II region has a high
pressure P/k = 1-2 x 10^7 cm^-3 K. The diffuse gas in region A has a slightly
lower pressure, which together with the broad H alpha emission line width,
suggests that both the thermal and turbulent pressures in the M82 starburst
core are unusually high. We discuss how this environment has affected the
evolution of the cluster wind for M82-A1. We find that the high pressure may
have caused the pressure-driven bubble to stall. We also obtain spectroscopic
ages for clusters B1-2 and B2-1 in the `fossil' starburst region and for the
intermediate age clusters F and L. These are consistent with earlier studies
and demonstrate that star formation activity, sufficiently intense to produce
super star clusters, has been going on in M82 during the past Gyr, perhaps in
discrete and localized episodes.


title:
X-ray and IR Point Source Identification and Characteristics In the
  Embedded, Massive Star-Forming Region RCW 38

abstract:
  We report on results of a 96.7 ks Chandra observation of one of the youngest,
most embedded and massive young stellar clusters studied in X-rays - RCW 38. We
detect 460 sources in the field of which 360 are confirmed to be associated
with the RCW~38 cluster. The cluster members range in luminosity from ~10^30
ergs s^-1 to 10^33.5 ergs s^-1. Over ten percent of the cluster members with
over 100 counts exhibit flares while about 15% of cluster members with over 30
counts are variable. Of the sources identified as cluster members, 160 have
near-infrared (NIR) counterparts either in the 2MASS database or detected via
VLT observations. Of these about 20% appear to have optically thick disks. An
additional 353 members are identified through NIR observations of which at
least 50% possess optically thick disks. We fit over 100 X-ray sources as
absorbed Raymond-Smith type plasmas and find the column to the cluster members
varies from 10^21.5 to 10^23 per sq cm. We compare the gas to dust absorption
signatures in these stars and find Nh= A_v x 2 x 10^21 cm^-2. We find that the
cluster contains 31 candidate OB stars and is centered about 10" (0.1 pc) west
of the primary source of the ionization, the O5 star IRS 2. The cluster has a
peak central density of about 400 X-ray sources pc^-2. We estimate that the
total cluster membership exceeds 2000 stars.


abstract:
  Mass loss on the Asymptotic Giant Branch provides the origin of planetary
nebulae. This paper reviews several relevant aspects of AGB evolution:
pulsation properties, mass loss formalisms and time variable mass loss,
evidence for asymmetries on the AGB, binarity, ISM interaction, and mass loss
at low metallicity. There is growing evidence that mass loss on the AGB is
already asymmetric, but with spherically symmetric velocity fields. The origin
of the rings may be in pulsational instabilities causing mass-loss variations
on time scales of centuries.


title:
Exploring Halo Substructure with Giant Stars XI: The Tidal Tails of the
  Carina Dwarf Spheroidal and the Discovery of Magellanic Cloud Stars in the
  Carina Foreground

abstract:
  A new large-area Washington M,T_2+DDO51 filter survey of more than 10 deg^2
around the Carina dSph galaxy reveals a spectroscopically confirmed power law
radial density "break" population of Carina giant stars extending several
degrees beyond the central King profile. Magellan telescope MIKE spectroscopy
establishes the existence of Carina stars to at least 4.5 times its central
King limiting radius, r_lim and primarily along Carina's major axis. To keep
these stars bound to the dSph would require a global Carina mass-to-light ratio
of M/L > 6,300 M/L_sun. The MIKE velocities, supplemented with ~950 additional
Carina field velocities from archived VLT+GIRAFFE spectra with r<=r_lim,
demonstrate a nearly constant Carina velocity dispersion to just beyond r =
r_lim, and both a rising velocity dispersion and a velocity shear at still
larger radii. Together, the observational evidence suggests that the discovered
extended Carina population represents tidal debris from the dSph. Of 65 giant
candidates at large angular radii from the Carina center for which MIKE spectra
have been obtained 94% are associated either with Carina or a second, newly
discovered diffuse, but strongly radial velocity-coherent (velocity dispersion
of 9.8 km s^-1), foreground halo system. The fifteen stars in this second,
retrograde velocity population have (1) a mean metallicity ~1 dex higher than
that of Carina, and (2) colors and magnitudes consistent with the red clump of
the Large Magellanic Cloud (LMC). Additional spectroscopy of giant star
candidates in fields linking Carina and the LMC shows a smooth velocity
gradient between the LMC and the retrograde Carina moving group. We conclude
that we have found Magellanic stars almost twice as far (22 deg) from the LMC
center than previously known.


title: ELSA: An Integrated, Semi-Automated Nebular Abundance Package

abstract:
  We present ELSA, a new modular software package, written in C, to analyze and
manage spectroscopic data from emission-line objects. In addition to
calculating plasma diagnostics and abundances from nebular emission lines, the
software provides a number of convenient features including the ability to
ingest logs produced by IRAF's splot task, to semi-automatically merge spectra
in different wavelength ranges, and to automatically generate various data
tables in machine-readable or LaTeX format. ELSA features a highly
sophisticated interstellar reddening correction scheme that takes into account
temperature and density effects as well as He II contamination of the hydrogen
Balmer lines. Abundance calculations are performed using a 5-level atom
approximation with recent atomic data, based on R. Henry's ABUN program.
Improvements planned in the near future include use of a three-region
ionization model, similar to IRAF's nebular package, error propagation, and the
addition of ultraviolet and infrared line analysis capability. Detailed
documentation for all aspects of ELSA are available at
http://www.williams.edu/Astronomy/research/PN .


title: The Massive Star Population in the Giant HII Region Tol89 in NGC5398

abstract:
  We present new high spectral resolution VLT/UVES spectroscopy and archival
HST/STIS imaging and spectroscopy of the giant HII region Tol89 in NGC5398.
  From optical and UV HST images, we find that the star-forming complex as a
whole contains at least seven young compact massive clusters. We resolve the
two brightest optical knots, A and B, into five individual young massive
clusters along our slit, A1-4 and B1 respectively. From Starburst99 (Leitherer
et al.) UV spectral modelling, and nebular H beta equivalent widths in the
optical, we derive ages that are consistent with the formation of two separate
burst events, of ~4+/-1 Myr and <3 Myr for knots A (A1-4) and B (B1). An LMC
metallicity is measured for both knots, while nebular HeII 4686 is observed in
knot B and perhaps in knot A. We detect underlying broad wings on the strongest
nebular emission lines indicating velocities up to 600 km/s. We estimate that
there are ~95 early WN stars and ~35 early WC stars in Tol89-A, using empirical
template spectra of LMC WR stars from Crowther and Hadfield. Remarkably, we
also detect ~ three mid WNs in the smallest (mass) cluster in Tol89-A, A4. From
the strength of nebular H beta, we obtain N(O) ~690 and 2800 for knots A and B.
We also employ a complementary approach using Starburst99 models, in which the
O star content is inferred from the stellar continuum, and the WR population is
obtained from spectral synthesis of optical WR features using the grids from
Smith et al. We find reasonable agreement between the two methods for the O
star content and the N(WR)/N(O) ratio but find that the WR subtype distribution
is in error in the Starburst99 models, with far too few WN stars being
predicted. We attribute this failure to the neglect of rotational mixing in
evolutionary models. [abridged]


title:
A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy: Variation of the
  Metallicity Distribution Function Along the Sagittarius Stream

abstract:
  We present reliable measurements of the metallicity distribution function
(MDF) at different points along the tidal stream of the Sagittarius (Sgr) dwarf
spheroidal (dSph) galaxy, based on high resolution, echelle spectroscopy of
candidate M giant members of the Sgr system. The Sgr MDF is found to evolve
significantly from a median [Fe/H] ~-0.4 in the core to ~-1.1 dex over a Sgr
leading arm length representing ~2.5-3.0 Gyr of dynamical (i.e. tidal
stripping) age. This is direct evidence that there can be significant chemical
differences between current dSph satellites and the bulk of the stars they have
contributed to the halo. Our results suggest that Sgr experienced a significant
change in binding energy over the past several Gyr, which has substantially
decreased its tidal boundary across a radial range over which there must have
been a significant metallicity gradient in the progenitor galaxy. By accounting
for MDF variation along the debris arms, we approximate the MDF Sgr would have
had several Gyr ago. We also analyze the MDF of a moving group of M giants we
previously discovered towards the North Galactic Cap having opposite radial
velocities to the infalling Sgr leading arm stars there and propose that most
of these represent Sgr trailing arm stars overlapping the Sgr leading arm in
this part of the sky. If so, these trailing arm stars further demonstrate the
strong MDF evolution within the Sgr stream.


title: Deceleration without dark matter

abstract:
  In homogeneous isotropic cosmological models the angular size theta of a
standard measuring rod changes with redshift z in a manner that depends upon
the parameters of the model. It has been argued that as a population
ultracompact (milliarcsecond) radio sources measured by very long-baseline
interferometry (VLBI) do not evolve with cosmic epoch, and thus comprise a set
of standard objects, at least in a statistical sense. Here we examine the
angular-size/redshift relation for 256 ultracompact sources with z in the range
0.5 to 3.8 for cosmological models with two degrees of freedom (Omega_0 and
Lambda_0). The canonical inflationary cold dark matter model(Omega_0=1,
Lambda_0=0) appears to be ruled out by the observed relationship, whereas
low-density models with a cosmological constant of either sign are favoured.


title: AMANDA Observations Constrain the Ultra-High Energy Neutrino Flux

abstract:
  A number of experimental techniques are currently being deployed in an effort
to make the first detection of ultra-high energy cosmic neutrinos. To
accomplish this goal, techniques using radio and acoustic detectors are being
developed, which are optimally designed for studying neutrinos with energies in
the PeV-EeV range and above. Data from the AMANDA experiment, in contrast, has
been used to place limits on the cosmic neutrino flux at less extreme energies
(up to ~10 PeV). In this letter, we show that by adopting a different analysis
strategy, optimized for much higher energy neutrinos, the same AMANDA data can
be used to place a limit competitive with radio techniques at EeV energies. We
also discuss the sensitivity of the IceCube experiment, in various stages of
deployment, to ultra-high energy neutrinos.


title:
Comparing Pattern Recognition Feature Sets for Sorting Triples in the
  FIRST Database

abstract:
  Pattern recognition techniques have been used with increasing success for
coping with the tremendous amounts of data being generated by automated
surveys. Usually this process involves construction of training sets, the
typical examples of data with known classifications. Given a feature set, along
with the training set, statistical methods can be employed to generate a
classifier. The classifier is then applied to process the remaining data.
Feature set selection, however, is still an issue. This report presents
techniques developed for accommodating data for which a substantive portion of
the training set cannot be classified unambiguously, a typical case for low
resolution data. Significance tests on the sort-ordered, sample-size normalized
vote distribution of an ensemble of decision trees is introduced as a method of
evaluating relative quality of feature sets. The technique is applied to
comparing feature sets for sorting a particular radio galaxy morphology,
bent-doubles, from the Faint Images of the Radio Sky at Twenty Centimeters
(FIRST) database. Also examined are alternative functional forms for feature
sets. Associated standard deviations provide the means to evaluate the effect
of the number of folds, the number of classifiers per fold, and the sample size
on the resulting classifications.


title: Galaxy orbits and the intracluster gas temperature in clusters

abstract:
  In this paper we examine how well galaxies and intra-cluster gas trace the
gravitational potential of clusters. Utilizing mass profiles derived from
gravitational lensing and X-ray observations, coupled with measured galaxy
velocities, we solve for the velocity anisotropy parameter using the
anisotropic Jeans equation. This is done for five clusters, three at low
redshift: A2199, A496 and A576 and two at high redshifts: A2390 and MS1358.
With X-ray temperature profiles obtained from Chandra and ASCA/ROSAT data, we
estimate the ratio of energy in the galaxies compared to the X-ray gas. We find
that none of these clusters is strictly in hydro-static equilibrium. We compare
the properties of our sample with clusters that form in high-resolution
cosmological N-body simulations that include baryonic physics. Simulations and
data show considerable scatter both these profiles. We demonstrate the future
feasibility and potential for directly comparing the orbital structure of
clusters inferred from multi-wavelength observations with high resolution
simulated clusters.


title: EXO 0748-676 Rules out Soft Equations of State for Neutron Star Matter

abstract:
  The interiors of neutron stars contain matter at very high densities, in a
state that differs greatly from those found in the early universe or achieved
at terrestrial experiments. Matter in these conditions can only be probed
through astrophysical observations that measure the mass and radius of neutron
stars with sufficient precision. Here I report for the first time a unique
determination of the mass and radius of the neutron star EXO 0748-676, which
appears to rule out all the soft equations of state of neutron star matter. If
this object is typical, then condensates and unconfined quarks do not exist in
the centers of neutron stars.


title: XTE J1118+480: A Metal-Rich Black Hole Binary in the Galactic Halo

abstract:
  We present medium-resolution optical spectra of the secondary star in the
high Galactic latitude black hole X-ray binary XTE J1118+480 and determine the
abundance of Mg, Al, Ca, Fe, and Ni in its atmosphere. For all the elements
investigated we find supersolar abundances; thus, we reject the hypothesis that
the black hole came from the direct collapse of an ancient massive halo star.
The compact primary most likely formed in a supernova event of a massive star
whose nucleosynthetic products polluted the secondary star. The observed
element abundances and their ratios can be explained using a variety of
supernova models with a wide range of metallicities. While an explosive origin
in the Galactic halo or thick disk cannot be discarded, a metal-rich progenitor
is clearly favored by the observed abundance pattern. This suggests that the
black hole was produced in the Galactic thin disk with a violent natal kick,
propelling the X-ray binary to its current location and orbit.


title: Observations of Early Optical Afterglows

abstract:
  The Swift Ultra-Violet/Optical Telescope (UVOT) has performed extensive
follow-up on 71 Swift Burst Alert Telescope triggered gamma-ray bursts (GRBs)
in its first ten months of operations. In this paper, we discuss some of the UV
and optical properties of UVOT detected afterglows such as XRF 050406, the
bright GRB 050525A, the high redshift GRB 050730, the early flaring GRB 050801,
and others. We also discuss some of the implications of why 75% of GRB
afterglows observed by UVOT in less than one hour are "dark."


title:
Metal-Rich Globular Clusters: an Unaccounted Factor Responsible for
  Their Formation?

abstract:
  Presently unaccounted but quite probable "chemical factor" may be responsible
for the formation of old metal-rich globular clusters (MRGCs) in spheroids, as
well as of their conterparts, young (intermediate-age) massive star clusters
(MSCs) in irregulars. Their formation presumably occurs at the same stage of
the host galaxies' chemical evolution and is related to the essentially
increased SF activity in the hosts around the same metallicity, Zsol/3
([Fe/H]~-0.5). It is achieved very soon in massive spheroids, later in
lower-mass spheroids, and (much) more later in irregulars.


title:
Analytical protostellar disk models 1: the effect of internal
  dissipation and surface irradiation on the structure of disks and the
  location of the snow line around Sun-like stars

abstract:
  We construct a new set of self-consistent analytical disk models by taking
into account both viscous and radiative sources of thermal energy. We analyze
the non-isothermal structure of the disk across the mid-plane for optically
thick disks, and use the standard two-temperature model in the case of
optically thin disks. We deduce a set of general formula for the relationship
between the mass accretion rate and the surface density profile. Our results
recover those of Chiang & Goldreich in the optically thin regions, but extend
their work for the opaque regions of the disk.
  For the purpose of illustration, we apply our theory in this paper to
determine the structure of protostellar disks around T Tauri stars under a
state of steady accretion and derive the corresponding radial distribution
function of various disk properties such as surface density and temperature
near the mid-plane. We calculate the position of the snow line around a
sun-like T Tauri star, and deduce that it can evolve from well outside 10 AU
during FU Orionis outbursts, to about 4 AU during passive accretion phase, to
the present-day orbital radius of Venus and finally re-expand to over 2.2 AU
during the protostellar- to-debris disk transition. This non-monotonous
evolution of the snow line may provide some novel and deterministic explanation
for the total water content and its isotopic composition of both Venus and the
Earth. In the optically thin, outermost regions of the disk we find that the
surface density profile of the dust varies roughly as 1/r, which is consistent
with mm observations of spatially resolved disk of Mundy et al. (2000).


title: Swift observations of GRB050712

abstract:
  We present the results of X-ray and optical observations of GRB050712
performed by Swift. The X-ray lightcurve of this burst exhibits episodes of
flares in the first 1000s, the same epoch at which the UVOT detected an optical
counterpart. A shallow X-ray decay, with a decay slope of -0.73, followed and
lasted ~70ks. This behaviour can be explained in terms of activity of GRB
'inner engine', with the possibility of that the last flare is caused by the
interaction of the ejecta with the surrounding medium. We also find interesting
spectral parameters for the X-ray emission. In particular, data suggest the
presence of an intrinsic absorption in the first 1000s, which can be explained
if circumbust medium clouds lie along the line of sight.


title: Post-Swift Gamma-ray Burst Science and Capabilities Needed to EXIST

abstract:
  The exhilerating results from Swift in its first year of operations have
opened a new era of exploration of the high energy universe. The surge to
higher redshifts of the Gamma-ray bursts now imaged with increased sensitivity
establishes them as viable cosmic probes of the early universe. Wide-field
coded aperture imaging with solid-state pixel detectors (Cd-Zn-Te) has been
also established as the optimum approach for GRB discovery and location as well
as to conduct sensitive full-sky hard X-ray sky surveys. I outline the current
and future major science questions likely to dominate the post-Swift era for
GRBs and several related disciplines and the mission requirements to tackle
these. The EXIST mission, under study for NASA's Black Hole Finder Probe (BHFP)
in the Beyond Einstein Program, could achieve these objectives as the Next
Generation GRB Mission with `ultimate' sensitivity and wide-field survey
capability. Analysis tools for processing Swift/BAT slew data are under
development at CfA and will both test EXIST scanning imaging and provide new
data on GRBs and transients.