Abstract
We present analysis using a citizen science campaign to improve the cosmological measures from the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX). The goal of HETDEX is to measure ...the Hubble expansion rate,
H
(
z
), and angular diameter distance,
D
A
(
z
), at
z
= 2.4, each to percent-level accuracy. This accuracy is determined primarily from the total number of detected Ly
α
emitters (LAEs), the false positive rate due to noise, and the contamination due to O
ii
emitting galaxies. This paper presents the citizen science project, Dark Energy Explorers (
https://www.zooniverse.org/projects/erinmc/dark-energy-explorers
), with the goal of increasing the number of LAEs and decreasing the number of false positives due to noise and the O
ii
galaxies. Initial analysis shows that citizen science is an efficient and effective tool for classification most accurately done by the human eye, especially in combination with unsupervised machine learning. Three aspects from the citizen science campaign that have the most impact are (1) identifying individual problems with detections, (2) providing a clean sample with 100% visual identification above a signal-to-noise cut, and (3) providing labels for machine-learning efforts. Since the end of 2022, Dark Energy Explorers has collected over three and a half million classifications by 11,000 volunteers in over 85 different countries around the world. By incorporating the results of the Dark Energy Explorers, we expect to improve the accuracy on the
D
A
(
z
) and
H
(
z
) parameters at
z
= 2.″4 by 10%–30%. While the primary goal is to improve on HETDEX, Dark Energy Explorers has already proven to be a uniquely powerful tool for science advancement and increasing accessibility to science worldwide.
Absorption Troughs of Lyα Emitters in HETDEX Weiss, Laurel H.; Davis, Dustin; Gebhardt, Karl ...
Astrophysical journal/The Astrophysical journal,
02/2024, Volume:
962, Issue:
2
Journal Article
Peer reviewed
Open access
Abstract The Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) is designed to detect and measure the redshifts of more than 1 million Ly α emitting galaxies (LAEs) 1.88 < z < 3.52. In addition ...to its cosmological measurements, these data enable studies of Ly α spectral profiles and the underlying radiative transfer. Using the roughly half a million LAEs in the HETDEX Data Release 3, we stack various subsets to obtain the typical Ly α profile for the z ∼ 2–3 epoch and to understand their physical properties. We find clear absorption wings around Ly α emission, which extend ∼2000 km s −1 both redward and blueward of the central line. Using far-UV spectra of nearby (0.002 < z < 0.182) LAEs in the COS Legacy Archive Spectroscopic Survey treasury and optical/near-IR spectra of 2.8 < z < 6.7 LAEs in the Multi Unit Spectroscopic-Wide survey, we observe absorption profiles in both redshift regimes. Dividing the sample by volume density shows that the troughs increase in higher-density regions. This trend suggests that the depth of the absorption is dependent on the local density of objects near the LAE, a geometry that is similar to damped Ly α systems. Simple simulations of Ly α radiative transfer can produce similar troughs due to absorption of light from background sources by H i gas surrounding the LAEs.
Abstract
We describe the ensemble properties of the 1.9 <
z
< 3.5 Lyman alpha emitters (LAEs) found in the HETDEX survey’s first public data release, HETDEX Public Source Catalog 1. Stacking the ...low-resolution (
R
∼ 800) spectra greatly increases the signal-to-noise ratio (S/N), revealing spectral features otherwise hidden by noise, and we show that the stacked spectrum is representative of an average member of the set. The flux-limited, Ly
α
S/N restricted stack of 50,000 HETDEX LAEs shows the ensemble biweight
average
z
∼ 2.6 LAE to be a blue (UV continuum slope ∼ −2.4 and
E(B – V)
< 0.1), moderately bright (
M
UV
∼ −19.7) star-forming galaxy with strong Ly
α
emission (log
L
Ly
α
∼ 42.8 and
W
λ
(Ly
α
) ∼ 114 Å), and potentially significant leakage of ionizing radiation. The rest-frame UV light is dominated by a young, metal-poor stellar population with an average age of 5–15 Myr and metallicity of 0.2–0.3
Z
⊙
.
Abstract
The Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) is an untargeted spectroscopic survey that aims to measure the expansion rate of the universe at
z
∼ 2.4 to 1% precision for both
H
...(
z
) and
D
A
(
z
). HETDEX is in the process of mapping in excess of one million Ly
α
emitting (LAE) galaxies and a similar number of lower-
z
galaxies as a tracer of the large-scale structure. The success of the measurement is predicated on the post-observation separation of galaxies with Ly
α
emission from the lower-
z
interloping galaxies, primarily O
ii
, with low contamination and high recovery rates. The Emission Line eXplorer (ELiXer) is the principal classification tool for HETDEX, providing a tunable balance between contamination and completeness as dictated by science needs. By combining multiple selection criteria, ELiXer improves upon the 20 Å rest-frame equivalent width cut commonly used to distinguish LAEs from lower-
z
O
ii
emitting galaxies. Despite a spectral resolving power,
R
∼ 800, that cannot resolve the O
ii
doublet, we demonstrate the ability to distinguish LAEs from foreground galaxies with 98.1% accuracy. We estimate a contamination rate of Ly
α
by O
ii
of 1.2% and a Ly
α
recovery rate of 99.1% using the default ELiXer configuration. These rates meet the HETDEX science requirements.
Abstract
We present the first publicly released catalog of sources obtained from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). HETDEX is an integral field spectroscopic survey designed ...to measure the Hubble expansion parameter and angular diameter distance at 1.88 <
z
< 3.52 by using the spatial distribution of more than a million Ly
α
-emitting galaxies over a total target area of 540 deg
2
. The catalog comes from contiguous fiber spectra coverage of 25 deg
2
of sky from 2017 January through 2020 June, where object detection is performed through two complementary detection methods: one designed to search for line emission and the other a search for continuum emission. The HETDEX public release catalog is dominated by emission-line galaxies and includes 51,863 Ly
α
-emitting galaxy (LAE) identifications and 123,891 O
ii
-emitting galaxies at
z
< 0.5. Also included in the catalog are 37,916 stars, 5274 low-redshift (
z
< 0.5) galaxies without emission lines, and 4976 active galactic nuclei. The catalog provides sky coordinates, redshifts, line identifications, classification information, line fluxes, O
ii
and Ly
α
line luminosities where applicable, and spectra for all identified sources processed by the HETDEX detection pipeline. Extensive testing demonstrates that HETDEX redshifts agree to within Δ
z
< 0.02, 96.1% of the time to those in external spectroscopic catalogs. We measure the photometric counterpart fraction in deep ancillary Hyper Suprime-Cam imaging and find that only 55.5% of the LAE sample has an
r
-band continuum counterpart down to a limiting magnitude of
r
∼ 26.2 mag (AB) indicating that an LAE search of similar sensitivity to HETDEX with photometric preselection would miss nearly half of the HETDEX LAE catalog sample. Data access and details about the catalog can be found online at
http://hetdex.org/
. A copy of the catalogs presented in this work (Version 3.2) is available to download at Zenodo doi:
10.5281/zenodo.7448504
.
Regular vascular access blood flow (Qa) surveillance is recommended to detect graft stenosis; however, there is little evidence that monitoring and correcting with angioplasty improves graft ...survival. This blinded, randomized, controlled trial of 112 patients studied time to graft thrombosis and graft loss, comparing monthly Qa plus standard surveillance (dynamic venous pressure and physical examination) (treatment group) to standard surveillance alone (control group). Only the treatment group was referred for angiogram if Qa <650 ml/min or a 20% decrease in Qa from baseline. Percutaneous angioplasty was performed for stenosis >50%. The rate of graft thrombosis per patient-year at risk was 0.41 and 0.51 in the control and treatment groups, respectively. Fifty-one interventions (0.93/patient-years at risk) were performed in the treatment group versus 31 interventions (0.61/patient-years at risk) in the control group. There was no difference in time to graft loss (P = 0.890). In a multivariate analysis, aspirin (ASA) therapy at baseline was associated with an 84% reduction in risk of graft thrombosis (odds ratio OR, 0.14; P = 0.002). Higher baseline Qa (OR, 0.84; P = 0.05) and longer interval since graft insertion (OR, 0.97; P = 0.07) were associated with a decrease in graft thrombosis. Results reveal that graft surveillance that uses Qa increases the detection of stenosis, compared with standard surveillance; however, intervention with angioplasty does not improve the time to graft thrombosis or time to graft loss.
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