144 research outputs found
Galaxy-Scale Strong Lensing Tests of Gravity and Geometric Cosmology: Constraints and Systematic Limitations
Galaxy-scale strong gravitational lenses with measured stellar velocity
dispersions allow a test of the weak-field metric on kiloparsec scales and a
geometric measurement of the cosmological distance-redshift relation, provided
that the mass-dynamical structure of the lensing galaxies can be independently
constrained to a sufficient degree. We combine data on 53 galaxy-scale strong
lenses from the Sloan Lens ACS Survey with a well-motivated fiducial set of
lens-galaxy parameters to find (1) a constraint on the post-Newtonian parameter
gamma = 1.01 +/- 0.05 and (2) a determination of Omega_Lambda = 0.75 +/- 0.17
under the assumption of a flat universe. These constraints assume that the
underlying observations and priors are free of systematic error. We evaluate
the sensitivity of these results to systematic uncertainties in (1) total
mass-profile shape, (2) velocity anisotropy, (3) light-profile shape, and (4)
stellar velocity dispersion. Based on these sensitivities, we conclude that
while such strong-lens samples can in principle provide an important tool for
testing general relativity and cosmology, they are unlikely to yield precision
measurements of gamma and Omega_Lambda unless the properties of the lensing
galaxies are independently constrained with substantially greater accuracy than
at present.Comment: 8 pages, 5 figures; Accepted to Ap
MQ-8B Fire Scout UAV Manning Cost Benefit Analysis
EMBA Project ReportEXECUTIVE SUMMARY:
At the request of the Intelligence, Surveillance, and Reconnaissance Task Force, the Naval Air Systems Command‘s program office for Multi-Mission Tactical Unmanned Aerial Systems (UAS)—also known as PMA-266, began MQ-8B flight operations in Afghanistan. Due to the importance and short notice of this request, the initial manning and support measures for the Fire Scout detachment has relied heavily on contractors.
In an effort to refine and redirect the future manning of Fire Scout detachments, PMA-266 asked the Washington DC Naval Postgraduate School Consulting Group to evaluate three different courses of action (COAs) detailing manning options for deployment of the MQ-8B Fire Scout for the next year. The three COAs were:
1) Manning with a military component
2) Manning with NGC contract services
3) Manning through a third party contractor.
This report recommends that PMA-266 use the military component COA to the maximum extent possible. In addition to annual cost savings of over $10M, a military component provides greater mission-focus and flexibility inherent in a military chain of command as compared to a contract manning structure. The Navy would also benefit by obtaining operational UAS experience as it looks to develop an unmanned aviation community. The experience gained could be used to develop Navy instructors for operator and maintenance training instead of continuing to rely on contract support for these requirements.For Capt Patrick Smith
Director PMA-266http://archive.org/details/mqbfirescoutuavm10945707
Well-Sampled Far-Infrared Spectral Energy Distributions of z ~ 2 Galaxies: Evidence for Scaled up Cool Galaxies
We present an analysis of the far-infrared (FIR) spectral energy
distributions (SEDs) of two massive K-selected galaxies at z = 2.122 and z =
2.024 detected at 24um, 70um, 160um by Spitzer, 250um, 350um, 500um by BLAST,
and 870um by APEX. The large wavelength range of these observations and the
availability of spectroscopic redshifts allow us to unambiguously identify the
peak of the redshifted thermal emission from dust at ~ 300um. The SEDs of both
galaxies are reasonably well fit by synthetic templates of local galaxies with
L_IR ~ 10^{11} L_{sun} -- 10^{12} L_{sun} yet both galaxies have L_{IR} ~
10^{13} L_{sun}. This suggests that these galaxies are not high redshift
analogues of the Hyper-LIRGs/ULIRGs used in local templates, but are instead
"scaled up" versions of local ULIRGs/LIRGs. For both galaxies the star
formation rate determined from the best-fit FIR SEDs (SFR(L_{IR})) agrees with
the SFR determined from the dust corrected H-alpha luminosity (SFR(H-alpha)) to
within a factor of ~ 2; however, when the SFR of these galaxies is estimated
using only the observed 24um flux and the standard luminosity-dependent
template method (SFR(24um)), it systematically overestimates the SFR by as much
as a factor of 6. A larger sample of 24 K-selected galaxies at z ~ 2.3 drawn
from the Kriek et al. (2008) GNIRS sample shows the same trend between
SFR(24um) and SFR(H-alpha). Using that sample we show that SFR(24um) and
SFR(H-alpha) are in better agreement when SFR(24um) is estimated using the log
average of local templates rather than selecting a single luminosity-dependent
template, because this incorporates lower luminosity templates. The better
agreement between SFRs from lower luminosity templates suggests that the FIR
SEDs of the BLAST-detected galaxies may be typical for massive galaxies at z ~
2, and that the majority are scaled up versions of lower luminosity local
galaxies.Comment: 8 pages, 3 figures, revised version, accepted by Ap
Two-dimensional kinematics of SLACS lenses: III. Mass structure and dynamics of early-type lens galaxies beyond z ~ 0.1
We combine in a self-consistent way the constraints from both gravitational
lensing and stellar kinematics to perform a detailed investigation of the
internal mass distribution, amount of dark matter, and dynamical structure of
the 16 early-type lens galaxies from the SLACS Survey, at z = 0.08 - 0.33, for
which both HST/ACS and NICMOS high-resolution imaging and VLT VIMOS IFU
spectroscopy are available. Based on this data set, we analyze the inner
regions of the galaxies, i.e. typically within one (3D) effective radius r_e,
under the assumption of axial symmetry and by constructing dynamical models
supported by two-integral stellar DFs. For all systems, the total mass density
distribution is found to be well approximated by a simple power-law: this
profile is on average slightly super-isothermal, with a logarithmic slope
= 2.074^{+0.043}_{-0.041} (68% CL) and an intrinsic scatter
0.144^{+0.055}_{-0.014}, and is fairly round, with an average axial ratio =
0.77+/-0.04. The lower limit for the dark matter fraction (fDM) inside r_e
ranges, in individual systems, from nearly zero to almost a half, with a median
value of 12%. By including stellar masses derived from SPS models with a
Salpeter IMF, we obtain an average fDM = 31%. The fDM rises to 61% if, instead,
a Chabrier IMF is assumed. For both IMFs, the dark matter fraction increases
with the total mass of the galaxy (3-sigma correlation). Based on the intrinsic
angular momentum parameter calculated from our models, we find that the
galaxies can be divided into two dynamically distinct groups, which are shown
to correspond to the usual classes of the slow and fast rotators. Overall, the
SLACS systems are structurally and dynamically very similar to their nearby
counterparts, indicating that the inner regions of early-type galaxies have
undergone little, if any, evolution since redshift z ~ 0.35. (Abridged)Comment: 27 pages, 34 figures. MNRAS, in pres
Cosmological distance indicators
We review three distance measurement techniques beyond the local universe:
(1) gravitational lens time delays, (2) baryon acoustic oscillation (BAO), and
(3) HI intensity mapping. We describe the principles and theory behind each
method, the ingredients needed for measuring such distances, the current
observational results, and future prospects. Time delays from strongly lensed
quasars currently provide constraints on with < 4% uncertainty, and with
1% within reach from ongoing surveys and efforts. Recent exciting discoveries
of strongly lensed supernovae hold great promise for time-delay cosmography.
BAO features have been detected in redshift surveys up to z <~ 0.8 with
galaxies and z ~ 2 with Ly- forest, providing precise distance
measurements and with < 2% uncertainty in flat CDM. Future BAO
surveys will probe the distance scale with percent-level precision. HI
intensity mapping has great potential to map BAO distances at z ~ 0.8 and
beyond with precisions of a few percent. The next years ahead will be exciting
as various cosmological probes reach 1% uncertainty in determining , to
assess the current tension in measurements that could indicate new
physics.Comment: Review article accepted for publication in Space Science Reviews
(Springer), 45 pages, 10 figures. Chapter of a special collection resulting
from the May 2016 ISSI-BJ workshop on Astronomical Distance Determination in
the Space Ag
The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe
The preponderance of matter over antimatter in the early Universe, the
dynamics of the supernova bursts that produced the heavy elements necessary for
life and whether protons eventually decay --- these mysteries at the forefront
of particle physics and astrophysics are key to understanding the early
evolution of our Universe, its current state and its eventual fate. The
Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed
plan for a world-class experiment dedicated to addressing these questions. LBNE
is conceived around three central components: (1) a new, high-intensity
neutrino source generated from a megawatt-class proton accelerator at Fermi
National Accelerator Laboratory, (2) a near neutrino detector just downstream
of the source, and (3) a massive liquid argon time-projection chamber deployed
as a far detector deep underground at the Sanford Underground Research
Facility. This facility, located at the site of the former Homestake Mine in
Lead, South Dakota, is approximately 1,300 km from the neutrino source at
Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino
charge-parity symmetry violation and mass ordering effects. This ambitious yet
cost-effective design incorporates scalability and flexibility and can
accommodate a variety of upgrades and contributions. With its exceptional
combination of experimental configuration, technical capabilities, and
potential for transformative discoveries, LBNE promises to be a vital facility
for the field of particle physics worldwide, providing physicists from around
the globe with opportunities to collaborate in a twenty to thirty year program
of exciting science. In this document we provide a comprehensive overview of
LBNE's scientific objectives, its place in the landscape of neutrino physics
worldwide, the technologies it will incorporate and the capabilities it will
possess.Comment: Major update of previous version. This is the reference document for
LBNE science program and current status. Chapters 1, 3, and 9 provide a
comprehensive overview of LBNE's scientific objectives, its place in the
landscape of neutrino physics worldwide, the technologies it will incorporate
and the capabilities it will possess. 288 pages, 116 figure
Comparative Analysis of Dengue and Zika Outbreaks Reveals Differences by Setting and Virus.
The pacific islands of Micronesia have experienced several outbreaks of mosquito-borne diseases over the past decade. In outbreaks on small islands, the susceptible population is usually well defined, and there is no co-circulation of pathogens. Because of this, analysing such outbreaks can be useful for understanding the transmission dynamics of the pathogens involved, and particularly so for yet understudied pathogens such as Zika virus. Here, we compared three outbreaks of dengue and Zika virus in two different island settings in Micronesia, the Yap Main Islands and Fais, using a mathematical model of transmission dynamics and making full use of commonalities in disease and setting between the outbreaks. We found that the estimated reproduction numbers for Zika and dengue were similar when considered in the same setting, but that, conversely, reproduction number for the same disease can vary considerably by setting. On the Yap Main Islands, we estimated a reproduction number of 8.0-16 (95% Credible Interval (CI)) for the dengue outbreak and 4.8-14 (95% CI) for the Zika outbreak, whereas for the dengue outbreak on Fais our estimate was 28-102 (95% CI). We further found that the proportion of cases of Zika reported was smaller (95% CI 1.4%-1.9%) than that of dengue (95% CI: 47%-61%). We confirmed these results in extensive sensitivity analysis. They suggest that models for dengue transmission can be useful for estimating the predicted dynamics of Zika transmission, but care must be taken when extrapolating findings from one setting to another
Self-reported dental hygiene, obesity, and systemic inflammation in a pediatric rural community cohort
Background
A growing body of epidemiologic evidence links oral health, obesity, and cardiovascular health, though few studies have reported on these relationships in children. While underlying mechanisms are unclear, adult studies have suggested sub-acute systemic inflammation, also implicated in the etiology of both obesity and cardiovascular disease. This study investigated associations between self-reported dental hygiene, obesity, and systemic inflammation in children. Methods
128 children \u3c 19 years of age from rural counties in West Virginia participated in a community-based health screening that included anthropometric assessments, blood collection, and a questionnaire about dental hygiene and self-assessed oral health. Results
Participants ranged from 3.0-18.7 years. Univariate analysis demonstrated an association between parent-reported dental hygiene, including frequency of preventive dental care and parent-assessed overall dental health, and markers of systemic inflammation but not obesity. In multivariable regression, parent-assessed overall dental health and obesity were independent predictors of systemic inflammation, after adjustment for age, gender, and parent education. Conclusions
This is the first known study of the association between dental hygiene, obesity, and systemic inflammation in children. These results highlight the importance of preventive dental care in overall, systemic health in children and are consistent with previous reports in adults
Exploring Reionization-era Quasars. III. Discovery of 16 Quasars at 6.4 ≲ z ≲ 6.9 with DESI Legacy Imaging Surveys and the UKIRT Hemisphere Survey and Quasar Luminosity Function at z ∼ 6.7
This is the third paper in a series aimed at finding reionization-era quasars with the combination of DESI Legacy imaging Surveys (DELS), the Pan-STARRS1 (PS1) Survey, and near-infrared imaging surveys, such as the UKIRT Hemisphere Survey (UHS), as well as the Wide-field Infrared Survey Explorer (WISE) mid-infrared survey. In this paper, we describe the updated quasar candidate selection procedure, report the discovery of 16 quasars at 6.4 z 6.9 from an area of ~13,020 deg2, and present the quasar luminosity function (QLF) at z ~ 6.7. The measured QLF follows in the magnitude range −27.6 5 that was found by previous works continues to z > 6, at a rate significantly faster than the average decline rate between z ~ 3 and 5. We measured quasar comoving emissivity at z ~ 6.7, which indicates that high-redshift quasars are highly unlikely to make a significant contribution to hydrogen reionization. The broad absorption line quasar fraction at z 6.5 is measured to be 22%. In addition, we also report the discovery of six additional quasars at z ~ 6 in the Appendix
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