A key goal of the Stage IV dark energy experiments Euclid, LSST, and WFIRST is to measure the growth of structure with cosmic time from weak lensing analysis over large regions of the sky. Weak ...lensing cosmology will be challenging: in addition to highly accurate galaxy shape measurements, statistically robust and accurate photometric redshift (photo-z) estimates for billions of faint galaxies will be needed in order to reconstruct the three-dimensional matter distribution. Here we present an overview of and initial results from the Complete Calibration of the Color-Redshift Relation (C3R2) survey, which is designed specifically to calibrate the empirical galaxy color-redshift relation to the Euclid depth. These redshifts will also be important for the calibrations of LSST and WFIRST. The C3R2 survey is obtaining multiplexed observations with Keck (DEIMOS, LRIS, and MOSFIRE), the Gran Telescopio Canarias (GTC; OSIRIS), and the Very Large Telescope (VLT; FORS2 and KMOS) of a targeted sample of galaxies that are most important for the redshift calibration. We focus spectroscopic efforts on undersampled regions of galaxy color space identified in previous work in order to minimize the number of spectroscopic redshifts needed to map the color-redshift relation to the required accuracy. We present the C3R2 survey strategy and initial results, including the 1283 high-confidence redshifts obtained in the 2016A semester and released as Data Release 1.
ABSTRACT Calibrating the photometric redshifts of 109 galaxies for upcoming weak lensing cosmology experiments is a major challenge for the astrophysics community. The path to obtaining the required ...spectroscopic redshifts for training and calibration is daunting, given the anticipated depths of the surveys and the difficulty in obtaining secure redshifts for some faint galaxy populations. Here we present an analysis of the problem based on the self-organizing map, a method of mapping the distribution of data in a high-dimensional space and projecting it onto a lower-dimensional representation. We apply this method to existing photometric data from the COSMOS survey selected to approximate the anticipated Euclid weak lensing sample, enabling us to robustly map the empirical distribution of galaxies in the multidimensional color space defined by the expected Euclid filters. Mapping this multicolor distribution lets us determine where-in galaxy color space-redshifts from current spectroscopic surveys exist and where they are systematically missing. Crucially, the method lets us determine whether a spectroscopic training sample is representative of the full photometric space occupied by the galaxies in a survey. We explore optimal sampling techniques and estimate the additional spectroscopy needed to map out the color-redshift relation, finding that sampling the galaxy distribution in color space in a systematic way can efficiently meet the calibration requirements. While the analysis presented here focuses on the Euclid survey, similar analysis can be applied to other surveys facing the same calibration challenge, such as DES, LSST, and WFIRST.
The Complete Calibration of the Color-Redshift Relation (C3R2) survey is a multi-institution, multi-instrument survey that aims to map the empirical relation of galaxy color to redshift to i ∼ 24.5 ...(AB), thereby providing a firm foundation for weak lensing cosmology with the Stage IV dark energy missions Euclid and WFIRST. Here we present 3171 new spectroscopic redshifts obtained in the 2016B and 2017A semesters with a combination of DEIMOS, LRIS, and MOSFIRE on the Keck telescopes.13 The observations come from all of the Keck partners: Caltech, NASA, the University of Hawaii, and the University of California. Combined with the 1283 redshifts published in DR1, the C3R2 survey has now obtained and published 4454 high-quality galaxy redshifts. We discuss updates to the survey design and provide a catalog of photometric and spectroscopic data. Initial tests of the calibration method performance are given, indicating that the sample, once completed and combined with extensive data collected by other spectroscopic surveys, should allow us to meet the cosmology requirements for Euclid, and make significant headway toward solving the problem for WFIRST. We use the full spectroscopic sample to demonstrate that galaxy brightness is weakly correlated with redshift once a galaxy is localized in the Euclid or WFIRST color space, with potentially important implications for the spectroscopy needed to calibrate redshifts for faint WFIRST and LSST sources.
Abstract
We study the probability distribution function (PDF) of relative velocity between two different dark matter halos (i.e., pairwise velocity) with high-resolution cosmological
N
-body ...simulations. We revisit a non-Gaussian framework to predict pairwise velocity statistics developed in Tinker. We investigate the pairwise velocity PDFs over a wide range of halo masses of 10
12.5
≲
M
h
−1
M
⊙
≲ 10
15
and redshifts of 0 <
z
< 1. At a given set of masses, redshift, and separation length between two halos, our model requires three parameters to set the pairwise velocity PDF, whereas previous non-Gaussian models in the literature assumed four or more free parameters. At length scales of 5 <
r
h
−1
Mpc < 40, our model predicts the mean and dispersion of the pairwise velocity for dark matter halos with masses of 10
12.5
≲
M
h
−1
M
⊙
≲ 10
13.5
at 0.3 <
z
< 1 with a 5%-level precision. We demonstrate that our model of the pairwise velocity PDF provides an accurate mapping of the two-point clustering of massive-galaxy-sized halos at scales of
O
(10)
h
−1
Mpc between redshift and real space for a given real-space correlation function. For a mass-limited halo sample with masses greater than 10
13.5
h
−1
M
⊙
at
z
= 0.55, our model can explain the monopole and quadrupole moments of the redshift-space two-point correlations with a precision better than 5% at the scales of 5−40 and 10–30
h
−1
Mpc, respectively. Our model of the pairwise velocity PDF will give a detailed explanation of the statistics of massive galaxies at intermediate scales in redshift surveys.
Economic hardship is a major threat to children's health, implying that pediatric out-of-hospital cardiac arrest (pOHCA) might be promoted by lower incomes and child poverty. To target resources, it ...is helpful to identify geographical hotspots. Rhode Island is the smallest state by area in the United States of America. It has one million inhabitants and is comparable to many larger cities worldwide. We aimed to investigate the possible associations of pOHCA with economic factors and the coronavirus 2019 (COVID-19) pandemic. Our goal was to identify high-risk areas and evaluate whether the COVID-19 pandemic had an influence on delays in prehospital care.
We analyzed all pOHCA cases (patients <18 years of age) in Rhode Island between March 1, 2018-February 28, 2022. We performed Poisson regression with pOHCA as dependent and economic risk factors (median household income MHI and child poverty rate from the US Census Bureau) as well as the COVID-19 pandemic as independent variables. Hotspots were identified using local indicators of spatial association (LISA) statistics. We used linear regression to assess the association of emergency nedical services-related times with economic risk factors and COVID-19.
A total of 51 cases met our inclusion criteria. Lower MHIs (incidence-rate ratio IRR) 0.99 per $1,000 MHI; P=0.01) and higher child poverty rates (IRR 1.02 per percent; P=0.02) were significantly associated with higher numbers of ambulance calls due to pOHCA. The pandemic did not have a significant influence (IRR 1.1; P=0.7). LISA identified 12 census tracts as hotspots (P<0.01). The pandemic was not associated with delays in prehospital care.
Lower median household income and higher child poverty rate are associated with higher numbers of pediatric out-of-hospital cardiac arrest.
The End of Galaxy Surveys Rhodes, Jason D.; Huff, Eric; Masters, Daniel ...
The Astronomical journal,
12/2020, Volume:
160, Issue:
6
Journal Article
Peer reviewed
Open access
For nearly a century, imaging and spectroscopic surveys of galaxies have given us information about the contents of the universe. We attempt to define the logical end point of such surveys by ...defining not the next galaxy survey but rather the final galaxy survey at near-infrared wavelengths; this would be the galaxy survey that exhausts the information content useful for addressing extant questions. Such a survey would require incredible advances in a number of technologies, and the survey details will depend on the as yet poorly constrained properties of the earliest galaxies. Using an exposure time calculator, we define nominal surveys for extracting the useful information for three science cases: dark energy cosmology, galaxy evolution, and supernovae (SN). We define scaling relations that trade off sky background, telescope aperture, and focal plane size to allow for a survey of a given depth over a given area. For optimistic assumptions, a 280 m telescope with a marginally resolved focal plane of 20 deg2 operating at L2 could potentially exhaust the cosmological information content of galaxies in a 10 yr survey. For galaxy evolution (making use of gravitational lensing to magnify the earliest galaxies) and SN, the same telescope would suffice. We discuss the technological advances needed to complete the last galaxy survey. While the final galaxy survey remains well outside of our technical reach today, we present scaling relations that show how we can progress toward the goal of exhausting the information content encoded in the shapes, positions, and colors of galaxies.
The first half of this paper explores the origin of systematic biases in the measurement of weak gravitational lensing. Compared to previous work, we expand the investigation of point spread function ...instability and fold in for the first time the effects of non-idealities in electronic imaging detectors and imperfect galaxy shape measurement algorithms. Together, these now explain the additive
and multiplicative
systematics typically reported in current lensing measurements. We find that overall performance is driven by a product of a telescope/camera's absolute performance, and our knowledge about its performance.
The second half of this paper propagates any residual shear measurement biases through to their effect on cosmological parameter constraints. Fully exploiting the statistical power of Stage IV weak lensing surveys will require additive biases
and multiplicative biases
. These can be allocated between individual budgets in hardware, calibration data and software, using results from the first half of the paper.
If instrumentation is stable and well calibrated, we find extant shear measurement software from Gravitational Lensing Accuracy Testing 2010 (GREAT10) already meet requirements on galaxies detected at signal-to-noise ratio = 40. Averaging over a population of galaxies with a realistic distribution of sizes, it also meets requirements for a 2D cosmic shear analysis from space. If used on fainter galaxies or for 3D cosmic shear tomography, existing algorithms would need calibration on simulations to avoid introducing bias at a level similar to the statistical error. Requirements on hardware and calibration data are discussed in more detail in a companion paper. Our analysis is intentionally general, but is specifically being used to drive the hardware and ground segment performance budget for the design of the European Space Agency's recently selected Euclid mission.
Abstract
The Superpressure Balloon-borne Imaging Telescope (
SuperBIT
) is a diffraction-limited, wide-field, 0.5 m, near-infrared to near-ultraviolet observatory designed to exploit the ...stratosphere’s space-like conditions.
SuperBIT
’s 2023 science flight will deliver deep, blue imaging of galaxy clusters for gravitational lensing analysis. In preparation, we have developed a weak-lensing measurement pipeline with modern algorithms for PSF characterization, shape measurement, and shear calibration. We validate our pipeline and forecast
SuperBIT
survey properties with simulated galaxy cluster observations in
SuperBIT
’s near-UV and blue bandpasses. We predict imaging depth, galaxy number (source) density, and redshift distribution for observations in
SuperBIT
’s three bluest filters; the effect of lensing sample selections is also considered. We find that, in three hours of on-sky integration,
SuperBIT
can attain a depth of
b
= 26 mag and a total source density exceeding 40 galaxies per square arcminute. Even with the application of lensing-analysis catalog selections, we find
b
-band source densities between 25 and 30 galaxies per square arcminute with a median redshift of
z
= 1.1. Our analysis confirms
SuperBIT
’s capability for weak gravitational lensing measurements in the blue.
BACKGROUND:Orientation abnormalities of the acetabulum and femur have been implicated in early-onset coxarthrosis. The purpose of this study was to identify clinical examination findings predictive ...of such hip morphologies.
METHODS:A consecutive cohort of 221 patients (442 hips) undergoing hip arthroscopy was included. Demographic characteristics including age, diagnosis, sex, height, weight, body mass index (BMI), and physical activity level were recorded. Passive range of motion was measured for all hips. Preoperative computed tomography scans were utilized to measure femoral torsion and central acetabular version, and a combined femoral torsion-acetabular version (COTAV) index was defined as their sum.
RESULTS:The study cohort comprised 221 patients (sixty-four males, 157 females) with a mean age of 32.5 years and mean BMI of 24.2 kg/m. Overall, hips with femoral antetorsion and acetabular anteversion exhibited the greatest internal rotation range of motion at a neutral hip position (mean, 44.2°), whereas hips with femoral retrotorsion and acetabular retroversion demonstrated the lowest corresponding value (20.1°; p < 0.001). Femoral torsion was significantly associated with female sex (p < 0.001), BMI (p < 0.001), and presence of pathology corresponding to cam-type femoroacetabular impingement (FAI) (p = 0.044). Central acetabular version was significantly associated with age (p = 0.021), female sex (p < 0.001), and absence of mixed-type FAI pathology (p = 0.025). Increasing age and internal rotation range of motion at a neutral hip position were the most significant predictors of an increased COTAV index.
CONCLUSIONS:This study confirmed that passive hip range of motion significantly predicts combined femoral torsion and central acetabular version. Accurate clinical assessment of the COTAV index may inform surgical decision-making in hip preservation surgery.
The primary purpose of this analysis was to compare supracondylar humerus fracture (SCHF) treatment patterns at a single quaternary pediatric hospital relative to the American Academy of Orthopedic ...Surgeons (AAOS) appropriate use treatment recommendation(s).
Among all fractures included in the cohort (n=571), the observed treatment approach was evaluated relative to the AAOS "Appropriate" treatment recommendation(s). The proportion, and corresponding 95% confidence interval, of cases that agreed with the "Appropriate" treatment recommendation was estimated. Demographics and clinical characteristics among cases that were managed in accordance with the "Appropriate," "May be Appropriate," or "Rarely Appropriate" were compared.
All fractures were treated according to the "Appropriate," "May be Appropriate," or "Rarely Appropriate" AAOS treatment guidelines. The observed treatment among fractures included in the cohort agreed with AAOS "Appropriate" recommendations in 92.1% 95% confidence interval (CI): 89.6%-94.2% of the cases. Fracture type differed significantly between patients treated according to AAOS "Appropriate" recommendations compared to those treated according to "May be Appropriate," or "Rarely Appropriate" recommendation.
The treatment approach implemented at a single level 1 trauma center was in concordance with the appropriate use criteria treatment recommendations in a significant majority of cases. Fractures not treated according to "Appopriate" recommendations were primarily type IIA injuries, and were treated with closed reduction and casting instead of the recommended closed reduction and percutaneous pinning.
Level III.
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