103 research outputs found
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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, H(z), and angular diameter distance, D [subscript A](z), at z = 2.4, each to percent-level accuracy. This accuracy is determined primarily from the total number of detected Lyα 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 [subscript 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.Astronom
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
The end of the beginning? Taking forward local democratic renewal in the post-referendum North East.
This article draws upon the author’s commissioned research on the nature of regional governance following the 2004 Referendum in the North East on elected regional assemblies. The article aimed to both capture these views and to assess how the ‘No vote in the referendum has impacted on subsequent developments in sub-national governance. The article provides both an empirical overview of recent developments and engages with the wider conceptual debates on democratic renewal. The arguments covered in this output are aimed at both academic and practitioner audiences, and have been also disseminated at regional and national conferences
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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
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 Lyman Alpha Emitters in HETDEX
The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) is designed to
detect and measure the redshifts of more than one million Ly emitting
galaxies (LAEs) between . In addition to its cosmological
measurements, these data enable studies of Ly 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 profile for the epoch and to understand their physical
properties. We find clear absorption wings around Ly emission, which
extend km both redward and blueward of the
central line. Using far-UV spectra of nearby () LAEs in the
CLASSY treasury and optical/near-IR spectra of LAEs in the
MUSE-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 Lyman- systems. Simple simulations of Ly
radiative transfer can produce similar troughs due to absorption of light from
background sources by HI gas surrounding the LAEs.Comment: 15 pages, 10 figures, accepted for publication in The Astrophysical
Journa
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
The Pre-explosion Environments and The Progenitor of SN 2023ixf from the Hobby Eberly Telescope Dark Energy Experiment (HETDEX)
Supernova (SN) 2023ixf was discovered on May 19th, 2023. The host galaxy,
M101, was observed by the Hobby Eberly Telescope Dark Energy Experiment
(HETDEX) collaboration over the period April 30, 2020 -- July 10, 2020, using
the Visible Integral-field Replicable Unit Spectrograph (VIRUS;
\r{A}) on the 10-m Hobby-Eberly Telescope
(HET). The fiber filling factor within 30 arcsec of SN 2023ixf is 80%
with a spatial resolution of 1 arcsec. The r<5.5 arcsec surroundings are 100%
covered. This allows us to analyze the spatially resolved pre-explosion local
environments of SN 2023ixf with nebular emission lines. The 2-dimensional (2D)
maps of the extinction and the star-formation rate (SFR) surface density
() show weak increasing trends in the radial distributions
within the r<5.5 arcsec regions, suggesting lower values of extinction and SFR
in the vicinity of the progenitor of SN 2023ixf. The median extinction and that
of the surface density of SFR within r<3 arcsec are , and
. There is no significant change in extinction before and after the
explosion. The gas metallicity does not change significantly with the
separation from SN 2023ixf. The metal-rich branch of the calculations
indicates that the gas metallicity around SN 2023ixf is similar to the solar
metallicity (). The archival deep images from the
Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) show a clear detection of
the progenitor of SN 2023ixf in the -band at mag, but
non-detections in the remaining four bands of CFHTLS (). The results
suggest a massive progenitor of 22 .Comment: 11 pages, 5 figures, Accepted by ApJ
The Preexplosion Environments and the Progenitor of SN 2023ixf from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX)
Supernova (SN) 2023ixf was discovered on 2023 May 19. The host galaxy, M101, was observed by the Hobby-Eberly Telescope Dark Energy Experiment collaboration over the period 2020 April 30-2020 July 10, using the Visible Integral-field Replicable Unit Spectrograph (3470 ≲ λ ≲ 5540 Å) on the 10 m Hobby-Eberly Telescope. The fiber filling factor within ±30″ of SN 2023ixf is 80% with a spatial resolution of 1″. The r < 5.″5 surroundings are 100% covered. This allows us to analyze the spatially resolved preexplosion local environments of SN 2023ixf with nebular emission lines. The two-dimensional maps of the extinction and the star formation rate (SFR) surface density (ΣSFR) show weak increasing trends in the radial distributions within the r < 5.″5 regions, suggesting lower values of extinction and SFR in the vicinity of the progenitor of SN 2023ixf. The median extinction and that of the surface density of SFR within r < 3″ are E(B − V) = 0.06 ± 0.14, and Σ SFR = 10 − 5.44 ± 0.66 M ☉ yr − 1 arcsec − 2 . There is no significant change in extinction before and after the explosion. The gas metallicity does not change significantly with the separation from SN 2023ixf. The metal-rich branch of the R 23 calculations indicates that the gas metallicity around SN 2023ixf is similar to the solar metallicity (∼Z ☉). The archival deep images from the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) show a clear detection of the progenitor of SN 2023ixf in the z band at 22.778 ± 0.063 mag, but nondetections in the remaining four bands of CFHTLS (u, g, r, i). The results suggest a massive progenitor of ≈22 M
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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