56 research outputs found
Bostonia: 1998-1999, no. 1, 3-4
Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs
Using Dark Energy Explorers and Machine Learning to Enhance the Hobby-Eberly Telescope Dark Energy Experiment
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, ,
and angular diameter distance, , at 2.4, each to percent-level
accuracy. This accuracy is determined primarily from the total number of
detected Lyman- 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, with the goal of increasing the
number of LAEs, 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 and
parameters at 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.Comment: 14 pages, 6 figures, accepted for publication in The Astrophysical
Journa
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The Active Galactic Nuclei in the Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX). III. A Red Quasar with Extremely High Equivalent Widths Showing Powerful Outflows
We report an active galactic nucleus (AGN) with an extremely high equivalent width (EW), EWLyα+N V,rest ≳921 Å, in the rest frame, at z ∼ 2.24 in the Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX), as a representative case of the high-EW AGN population. The continuum level is a nondetection in the HETDEX spectrum; thus the measured EW is a lower limit. The source is detected with significant emission lines (>7σ) at Lyα + N v λ1241, C iv λ1549, and a moderate emission line (∼4σ) at He ii λ1640 within the wavelength coverage of HETDEX (3500-5500 Å). The r-band magnitude is 24.57 from the Hyper Suprime-Cam-HETDEX joint survey with a detection limit of r = 25.12 at 5σ. The Lyα emission line spans a clearly resolved region of ∼10″ (85 kpc) in diameter. The Lyα line profile is strongly double peaked. The spectral decomposed blue gas and red gas Lyα emission are separated by ∼1.″2 (10.1 kpc) with a line-of-sight velocity offset of ∼1100 km s−1. This source is probably an obscured AGN with powerful winds
Association of early childhood abdominal circumference and weight gain with blood pressure at 36 months of age: secondary analysis of data from a prospective cohort study
To assess whether changes in measures of fat distribution and body size during early life are associated with blood pressure at 36 months of age
The HETDEX Survey: Emission Line Exploration and Source Classification
The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) is an untargeted
spectroscopic survey that aims to measure the expansion rate of the Universe at
to 1% precision for both and . HETDEX is in the
process of mapping in excess of one million Lyman Alpha 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 emission from the lower- interloping
galaxies, primarily [OII], 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 Angstrom rest-frame equivalent width cut commonly used to
distinguish LAEs from lower- [OII] emitting galaxies. Despite a spectral
resolving power, R , that cannot resolve the [OII] doublet, we
demonstrate the ability to distinguish LAEs from foreground galaxies with 98.1%
accuracy. We estimate a contamination rate of Ly by [OII] of 1.2% and a
Ly recovery rate of 99.1% using the default ELiXer configuration. These
rates meet the HETDEX science requirements.Comment: 38 pages, 11 figure
Absorption Troughs of Lyα Emitters in HETDEX
The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) is designed to detect and measure the redshifts of more than 1 million Lyα emitting galaxies (LAEs) 1.88 < z < 3.52. In addition to its cosmological measurements, these data enable studies of Lyα 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 Lyα profile for the z ∼ 2-3 epoch and to understand their physical properties. We find clear absorption wings around Lyα 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 Lyα systems. Simple simulations of Lyα radiative transfer can produce similar troughs due to absorption of light from background sources by H i gas surrounding the LAEs
HETDEX Public Source Catalog 1 -- Stacking 50K Lyman Alpha Emitters
We describe the ensemble properties of the Lyman Alpha
Emitters (LAEs) found in the HETDEX survey's first public data release, HETDEX
Public Source Catalog 1 (Mentuch Cooper et al. 2023). Stacking the
low-resolution ( 800) spectra greatly increases the signal-to-noise
ratio, 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 signal-to-noise ratio restricted stack of 50K HETDEX
LAEs shows the ensemble biweight ``average" LAE to be a blue (UV
continuum slope and E(B-V) ), moderately bright
(M) star forming galaxy with strong Ly
emission (log 42.8 and (Ly)
114\AA), and potentially significant leakage of ionizing radiation. The
restframe UV light is dominated by a young, metal poor stellar population with
an average age 5-15 Myr and metallicity of 0.2-0.3 Z.Comment: 17 pages, 11 figures, 2 data files (ApJ Accepted
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