2,046 research outputs found
The Mass Assembly History of Spheroidal Galaxies: Did Newly-Formed Systems Arise Via Major Mergers?
We examine the properties of a morphologically-selected sample of 0.4<z<1.0
spheroidal galaxies in the GOODS fields in order to ascertain whether their
increase in abundance with time arises primarily from mergers. To address this
question we determine scaling relations between the dynamical mass determined
from stellar velocity dispersions, and the stellar mass determined from optical
and infrared photometry. We exploit these relations across the larger sample
for which we have stellar masses in order to construct the first statistically
robust estimate of the evolving dynamical mass function over 0<z<1. The trends
observed match those seen in the stellar mass functions of Bundy et al. 2005
regarding the top-down growth in the abundance of spheroidal galaxies. By
referencing our dynamical masses to the halo virial mass we compare the growth
rate in the abundance of spheroidals to that predicted by the assembly of dark
matter halos. Our comparisons demonstrate that major mergers do not fully
account for the appearance of new spheroidals since z~1 and that additional
mechanisms, such as morphological transformations, are required to drive the
observed evolution.Comment: Accepted to ApJL; New version corrects the Millennium merger
predictions--further details at
http://www.astro.utoronto.ca/~bundy/millennium
The Dynamical Distinction between Elliptical and Lenticular Galaxies in Distant Clusters: Further Evidence for the Recent Origin of S0 Galaxies
We examine resolved spectroscopic data obtained with the Keck II telescope
for 44 spheroidal galaxies in the fields of two rich clusters, Cl0024+16
(z=0.40) and MS0451-03 (z=0.54), and contrast this with similar data for 23
galaxies within the redshift interval 0.3<z<0.65 in the GOODS northern field.
For each galaxy we examine the case for systemic rotation, derive central
stellar velocity dispersions sigma and photometric ellipticities, epsilon.
Using morphological classifications obtained via Hubble Space Telescope imaging
as the basis, we explore the utility of our kinematic quantities in
distinguishing between pressure-supported ellipticals and
rotationally-supported lenticulars (S0s). We demonstrate the reliability of
using the v/(1-epsilon) vs sigma and v/sigma vs epsilon distributions as
discriminators, finding that the two criteria correctly identify 63%+-3% and
80%+-2% of S0s at z~0.5, respectively, along with 76%+8-3% and 79%+-2% of
ellipticals. We test these diagnostics using equivalent local data in the Coma
cluster, and find that the diagnostics are similarly accurate at z=0. Our
measured accuracies are comparable to the accuracy of visual classification of
morphologies, but avoid the band-shifting and surface brightness effects that
hinder visual classification at high redshifts. As an example application of
our kinematic discriminators, we then examine the morphology-density relation
for elliptical and S0 galaxies separately at z~0.5. We confirm, from kinematic
data alone, the recent growth of rotationally-supported spheroidals. We discuss
the feasibility of extending the method to a more comprehensive study of
cluster and field galaxies to z~1, in order to verify in detail the recent
density-dependent growth of S0 galaxies.Comment: 7 pages, 4 figures, updated with version accepted to Ap
A Proof Strategy Language and Proof Script Generation for Isabelle/HOL
We introduce a language, PSL, designed to capture high level proof strategies
in Isabelle/HOL. Given a strategy and a proof obligation, PSL's runtime system
generates and combines various tactics to explore a large search space with low
memory usage. Upon success, PSL generates an efficient proof script, which
bypasses a large part of the proof search. We also present PSL's monadic
interpreter to show that the underlying idea of PSL is transferable to other
ITPs.Comment: This paper has been submitted to CADE2
Guide to some minerals and rocks in Indiana
Indiana Geological Survey Circular 4The study of minerals and rocks is an important part of the science of geology, which treats of the history of the earth and its life, especially as recorded in the rocks. Surprisingly many of us accept as commonplace many of nature's creations because they are so familiar. Actually, we can find the earth we live on a fascinating world if only we open our eyes to see it.
Geologically, Indiana is an interesting state. It has many fascinating geologic and scenic prospects in its more rugged regions., and even its flat areas possess much interesting geologic phenomenan.
At one time or another everyone probably has been curious about some particular rock or other object originating in the earth. But most of us who have been curious about these rocks or objects could not identify them, and thus our curiosity remained unsatisfied because we could find no explanation for their existence. This circular was prepared with the hope that it may satisfy, at least in part, the curiosity aroused by finding rocks or minerals. It is hoped that those who have discovered rocks and minerals will be encouraged to become further acquainted with their finds by using this guide.
It is impossible to cover fully in this brief report all the characteristics and variations of each kind of rock and mineral found in Indiana. For detailed information regarding Indiana geology, the reader should consult the more detailed reports of the Geological Survey and its predecessors.Indiana Department of Conservatio
Epidemiology of single and multiple species of helminth infections among school children in Busia District, Kenya
Objective: To describe the patterns of single and multiple helminth infection in school children from Busia District, Kenya.Design: A cross-sectional school survey using a randomly selected sample, forming part of an evaluation study of an ongoing deworming project.Setting: Budalangi and Funyula divisions of Busia District, Western Province, Kenya.Subjects: One thousand seven hundred and thirty eight school children aged 8-20 years randomly selected from those enrolled in standards 3-8 in 25 randomly selected primary schools.Results: Overall, 91.7% of children were infected with either hookworm, Ascaris lumbricoides, Trichuris trichiura or Schistosoma mansoni. Infection prevalence of each species varied considerably among schools, being most marked for S. mansoni, where prevalence was highest in lakeshore schools. Children were typically infected with two or more species of helminth. Infection intensity of each geohelminth species was higher in school children infected with multiple species than in school children with single species infections, and intensity increased with the number of concurrent infections.Conclusion: Helminth infections are exceptionally common among school children in Busia district, thus confirming the good sense of the school-based approach adopted by the control programme. The study also shows that there is an association between concurrent infectionand the intensity of infection, which may have consequences for nutritional and educational status
AEGIS: Extinction and Star Formation Tracers from Line Emission
Strong nebular emission lines are a sensitive probe of star formation and
extinction in galaxies, and the [O II] line detects star forming populations
out to z>1. However, star formation rates from emission lines depend on
calibration of extinction and the [O II]/H-alpha line ratio, and separating
star formation from AGN emission. We use calibrated line luminosities from the
DEEP2 survey and Palomar K magnitudes to show that the behavior of emission
line ratios depends on galaxy magnitude and color. For galaxies on the blue
side of the color bimodality, the vast majority show emission signatures of
star formation, and there are strong correlations of extinction and [O
II]/H-alpha with restframe H magnitude. The conversion of [O II] to
extinction-corrected H-alpha and thus to star formation rate has a significant
slope with M_H, 0.23 dex/mag. Red galaxies with emission lines have a much
higher scatter in their line ratios, and more than half show AGN signatures. We
use 24 micron fluxes from Spitzer/MIPS to demonstrate the differing populations
probed by nebular emission and by mid-IR luminosity. Although extinction is
correlated with luminosity, 98% of IR-luminous galaxies at z~1 are still
detected in the [O II] line. Mid-IR detected galaxies are mostly bright and
intermediate color, while fainter, bluer galaxies with high [O II] luminosity
are rarely detected at 24 microns.Comment: 4 pages, 3 figures. Accepted for publication in ApJ Letters AEGIS
special editio
Measuring Three-Dimensional Temperature Distributions in Steel-Concrete Composite Slabs Subjected to Fire using Distributed Fiber Optic Sensors
Detailed information about temperature distribution can be important to understand structural behavior in fire. This study develops a method to image three-dimensional temperature distributions in steel–concrete composite slabs using distributed fiber optic sensors. The feasibility of the method is explored using six 1.2 m × 0.9 m steel–concrete composite slabs instrumented with distributed sensors and thermocouples subjected to fire for over 3 h. Dense point clouds of temperature in the slabs were measured using the distributed sensors. The results show that the distributed sensors operated at material temperatures up to 960◦C with acceptable accuracy for many structural fire applications. The measured non-uniform temperature distributions indicate a spatially distributed thermal response in steel–concrete composite slabs, which can only be adequately captured using approaches that provide a high density of through-depth data points
The development and validation of an age-structured model for the evaluation of disease control strategies for intestinal helminths
Epidemiological modelling can be a useful tool for the evaluation of parasite control strategies. An age-structured epidemiological model of intestinal helminth dynamics is developed. This model includes the explicit representation of changing worm distributions between hosts as a result of treatment, and estimates the morbidity due to heavy infections. The model is used to evaluate the effectiveness of different programmes of age-targeted community chemotherapy in reducing the amount of morbidity due to helminth infection. The magnitude of age-related heterogeneities is found to be very important in determining the results of age-targeted treatment programmes. The model was verified using field data from control programmes for Ascaris lumbricoides and Trichuris trichiura, and was found to provide accurate predictions of prevalence and mean intensities of infection during and following different control regime
The Sloan Lens ACS Survey. IX. Colors, Lensing and Stellar Masses of Early-type Galaxies
We present the current photometric dataset for the Sloan Lens ACS (SLACS)
Survey, including HST photometry from ACS, WFPC2, and NICMOS. These data have
enabled the confirmation of an additional 15 grade `A' (certain) lens systems,
bringing the number of SLACS grade `A' lenses to 85; including 13 grade `B'
(likely) systems, SLACS has identified nearly 100 lenses and lens candidates.
Approximately 80% of the grade `A' systems have elliptical morphologies while
~10% show spiral structure; the remaining lenses have lenticular morphologies.
Spectroscopic redshifts for the lens and source are available for every system,
making SLACS the largest homogeneous dataset of galaxy-scale lenses to date. We
have developed a novel Bayesian stellar population analysis code to determine
robust stellar masses with accurate error estimates. We apply this code to
deep, high-resolution HST imaging and determine stellar masses with typical
statistical errors of 0.1 dex; we find that these stellar masses are unbiased
compared to estimates obtained using SDSS photometry, provided that informative
priors are used. The stellar masses range from 10^10.5 to 10^11.8 M and
the typical stellar mass fraction within the Einstein radius is 0.4, assuming a
Chabrier IMF. The ensemble properties of the SLACS lens galaxies, e.g. stellar
masses and projected ellipticities, appear to be indistinguishable from other
SDSS galaxies with similar stellar velocity dispersions. This further supports
that SLACS lenses are representative of the overall population of massive
early-type galaxies with M* >~ 10^11 M, and are therefore an ideal
dataset to investigate the kpc-scale distribution of luminous and dark matter
in galaxies out to z ~ 0.5.Comment: 20 pages, 18 figures, 5 tables, published in Ap
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