Detection of Lyman Continuum from 3.0 &lt; z &lt; 3.5 Galaxies in the HETDEX Survey

Davis, Dustin; Gebhardt, Karl; Cooper, Erin Mentuch; Chisholm, John; Ciardullo, Robin; Farrow, Daniel J.; Finkelstein, Steven L.; Grönwall, C.; Gawiser, Eric; Hill, Gary J.; Hopp, U.; Jeong, Donghui; Landriau, Martin; Liu, Chenxu; Niemeyer, Maja Lujan; Schneider, Donald P.; Snigula, J.; Tuttle, Sarah

doi:10.3847/1538-4357/ac1598

Cited by 15 publications

(30 citation statements)

References 61 publications

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“…The neutral IGM precludes direct LyC detections at z > 4 in a statistical sense (Inoue et al 2014;Becker et al 2021), outside of rare ionized regions (Endsley et al 2021;Endsley & Stark 2022). However, f esc,LyC can be directly measured at z < 4 (Bergvall et al 2006;Leitet et al 2011;Borthakur et al 2014;Izotov et al 2016a,b;Vanzella et al 2016;Leitherer et al 2016;Shapley et al 2016;Izotov et al 2018a,b;Steidel et al 2018;Fletcher et al 2019;Wang et al 2019;Rivera-Thorsen et al 2019;Ji et al 2020;Izotov et al 2021;Davis et al 2021;Marques-Chaves et al 2021;Xu et al 2022). To overcome the neutral high-redshift IGM, recent work has correlated indirect observables with f esc,LyC at these low redshifts.…”

Section: Introductionmentioning

confidence: 99%

The Far-Ultraviolet Continuum Slope as a Lyman Continuum Escape Estimator at High-redshift

Chisholm¹,

Saldana-Lopez²,

Flury³

et al. 2022

Preprint

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Most of the hydrogen in the intergalactic medium (IGM) was rapidly ionized at high-redshifts. While observations have established that reionization occurred, observational constraints on the emissivity of ionizing photons at high-redshift remains elusive. Here, we present a new analysis of the Low-redshift Lyman Continuum Survey (LzLCS) and archival observations, a combined sample of 89 star-forming galaxies at redshifts near 0.3 with Hubble Space Telescope observations of their ionizing continua (or Lyman Continuum, LyC). We find a strong (6σ significant) inverse correlation between the continuum slope at 1550 Å (defined as F λ ∝ λ β 1550 obs ) and both the LyC escape fraction ( f esc,LyC ) and f esc,LyC times the ionizing photon production efficiency (ξ ion ). On average, galaxies with redder continuum slopes have smaller f esc,LyC than galaxies with bluer slopes due to the higher dust attenuation in redder galaxies. More than 5% (20%) of the LyC emission escapes galaxies with β 1550 obs < −2.1 (-2.6). We find strong correlations between β 1550 obs and the gas-phase ionization ([O iii]/[O ii] flux ratio; at 7.5σ significance), galaxy stellar mass (at 5.9σ), the gas-phase metallicity (at 4.6σ), and the observed FUV absolute magnitude (at 3.4σ). Using previous observations of β 1550 obs at high-redshift, we estimate the evolution of f esc,LyC with both redshift and galaxy magnitude. The LzLCS observations suggest that fainter and lower mass galaxies dominate the ionizing photon budget at higher redshift, possibly due to their rapidly evolving metal and dust content. Finally, we use our correlation between β 1550 obs and f esc,LyC × ξ ion to predict the ionizing emissivity of galaxies during the epoch of reionization. Our estimated emissivities match IGM observations, and suggest that star-forming galaxies emit sufficient LyC photons into the IGM to exceed recombinations near redshifts of 7-8.

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Section: Introductionmentioning

confidence: 99%

The Far-Ultraviolet Continuum Slope as a Lyman Continuum Escape Estimator at High-redshift

Chisholm¹,

Saldana-Lopez²,

Flury³

et al. 2022

Preprint

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“…With the focus on P(Ly𝛼) as the primary classification metric and with its flexible threshold selection, what constitutes "good" agreement is somewhat subjective but is also highly adaptable to the specific scientific needs. For example, the stacking of spectra to measure Lyman Continuum in Davis et al (2021) is very sensitive to contamination but does not specifically require a highly complete sample and so utilizes a P(Ly𝛼) selection of 0.8 and greater. On the other hand, the 𝐻 (𝑧) and 𝐷 𝐴 (𝑧) precision goals for the primary HETDEX science is less sensitive to contamination but needs to be largely complete (Gebhardt et al 2021;Farrow et al 2021) and a P(Ly𝛼) threshold of 0.5, or even lower, is more appro-priate.…”

Section: Calibrationmentioning

confidence: 99%

The HETDEX Survey: Emission Line Exploration and Source Classification

Davis¹,

Gebhardt²,

Cooper³

et al. 2023

Preprint

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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 Lyman-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 postobservation separation of galaxies with Ly𝛼 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 ] doublet, we demonstrate the ability to distinguish LAEs from foreground galaxies with 98.1% accuracy. We estimate a contamination rate of Ly𝛼 by [O II] of 1.2% and a Ly𝛼 recovery rate of 99.1% using the default ELiXer configuration. These rates meet the HETDEX science requirements.

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“…The vast majority of detections consist of just a single emission line, which is likely to be either Lyα or [O II]. To classify these lines, HETDEX then employs multiple analyses that use all fiber spectra, along with other information such as bandpass continuum estimates, physical size estimates, overlapping neighbor PSFs, etc., from imaging and multiwavelength photometry when available (Leung et al 2017;Davis et al 2021;Farrow et al 2021). The imaging utilized by the HETDEX emission-line-finding code involves a suite of imaging surveys: Hyper Suprime Cam -Dark Energy Experiment (HSC-DEX; HETDEX Specific Survey; m 25.5 lim ~for a 2″ aperture), the Dark Energy Camera Legacy Survey (DECaLS; m g 24.0 lim ~and m r 23.4 24.0 lim -~for a 2″ aperture), and the HETDEX-Imaging Mosaic taken with the Kitt Peak National Observatory (KPNO) Mayall four-meter telescope in the g-band (m g lim 23.4 for a 2″ aperture; observations taken in 2011, 2012, and 2015).…”

Section: Hetdexmentioning

confidence: 99%

“…This more powerful, comprehensive method was the utilization of HETDEXʼs Emission Line eXplorer (ELiXer; Davis et al 2021) software, which extracts spectra from the HETDEX HDR2 database. ELiXer is a data visualization, search, and diagnostic tool that combines HETDEX observational data and multiple photometric catalogs to provide a compact, user-friendly representation of emission-line detections to assist the researcher in identifying line-emitting objects and their properties.…”

Section: Extracting Spectramentioning

confidence: 99%

“…In addition to the added fiber coverage, ELiXer executes its own diagnostics to flag detections that may be spurious or nonastrophysical (bad pixels, meteors, cosmic rays, scattered light, etc.) and returns line identification probabilities based on an aggregate weighting of various information sources (ratios of likelihoods based on equivalent widths, position and flux ratios from other possible emission lines, physical size with assumed redshifts, and more; see Leung et al 2017;Davis et al 2021;Farrow et al 2021;Gebhardt et al 2021 for more details). The ELiXer success rate in identifying Lyα is ∼98% (Davis et al 2021;Gebhardt et al 2021), though as we discuss in the following section, we only use these probabilities when considering potential lensed sources >2″ from the lens galaxy (such that the lens continuum does not bias the classification).…”

Section: Extracting Spectramentioning

confidence: 99%

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A Search for Lensed Lyα Emitters within the Early HETDEX Data Set

Laseter

Finkelstein

Bagley

et al. 2022

ApJ

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The Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) is a large-volume spectroscopic survey without preselection of sources, searching ∼540 deg2 for Lyα emitting galaxies (LAEs) at 1.9 < z < 3.5. Taking advantage of such a wide-volume survey, we perform a pilot study using early HETDEX data to search for lensed Lyα emitters (LAEs). After performing a proof of concept using a previously known lensed LAE covered by HETDEX, we perform a search for previously unknown lensed LAEs in the HETDEX spectroscopic sample. We present a catalog of 26 potential LAEs lensed by foreground, red, non-star-forming galaxies at z ∼ 0.4–0.7. We estimate the magnification for each candidate system, finding 12 candidates to be within the strong lensing regime (magnification μ > 2). Follow-up observations of these potential lensed LAEs have the potential to confirm their lensed nature and explore these distant galaxies in more detail.

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Detection of Lyman Continuum from 3.0 < z < 3.5 Galaxies in the HETDEX Survey

Cited by 15 publications

References 61 publications

The Far-Ultraviolet Continuum Slope as a Lyman Continuum Escape Estimator at High-redshift

The Far-Ultraviolet Continuum Slope as a Lyman Continuum Escape Estimator at High-redshift

The HETDEX Survey: Emission Line Exploration and Source Classification

A Search for Lensed Lyα Emitters within the Early HETDEX Data Set

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