J/ApJ/920/122 Candidate Lyα-emitting galaxies spectra (Davis+, 2021)
Detection of Lyman Continuum from 3.0<z<3.5 galaxies in the HETDEX survey.
Davis D., Gebhardt K., Mentuch Cooper E., Chisholm J., Ciardullo R.,
Farrow D.J., Finkelstein S.L., Gronwall C., Gawiser E., Hill G.J.,
Hopp U., Jeong D., Landriau M., Liu C., Lujan Niemeyer M., Schneider D.P.,
Snigula J., Tuttle S.
<Astrophys. J., 920, 122 (2021)>
=2021ApJ...920..122D 2021ApJ...920..122D
ADC_Keywords: Galaxies; Spectra, ultraviolet; Redshifts
Keywords: Reionization ; Lyman-alpha galaxies
Abstract:
Questions as to what drove the bulk reionization of the universe, how
that reionization proceeded, and how the hard ionizing radiation
reached the intergalactic medium remain open and debated. Observations
probing that epoch are severely hampered by the increasing amounts of
neutral gas with increasing redshift, so a small, but growing, number
of experiments are targeting star-forming galaxies (z∼3) as proxies.
However, these studies, while providing fantastic detail, are time
intensive, contain relatively few targets, and can suffer from
selection biases. As a complementary alternative, we investigate
whether stacking the already vast (and growing) numbers of low-
resolution (Δλ/λ=800) Lyα-emitting (LAE)
galaxy spectra from the Hobby-Eberly Telescope Dark Energy Experiment
(HETDEX) can be used to measure ionizing photons (rest-frame
880-910Å) escaping their galaxy hosts. As a blind survey, HETDEX
avoids the biases from continuum-selected galaxies, and its planned
540deg2 coverage promotes the statistical power of large numbers. In
this paper, we confirm the feasibility of Lyman continuum detection by
carefully selecting a sample of 214 high-redshift (z∼3) LAEs from a
subset of HETDEX observations, stacking their spectra and measuring a
≳3σ detection of 0.10µJy rest-frame Lyman continuum
emission, uncorrected for attenuation in the intergalactic medium,
over the full sample stack (3.0<z<3.5 and -22.0≲MUV≲-19.0).
Description:
The point-spread function (PSF) weighted, extracted spectra and
astrometric solutions from HETDEX are taken as the initial, primary
inputs to this work. Briefly, each HETDEX observation consists of
three 360s exposures with VIRUS, offset in a triangular dither pattern
to fill in the spatial gaps in the fiber layout of the (up to) 74
integral field unit (IFU) spectrographs. Each VIRUS IFU covers a
50x50arcsec2 area with 448, 1.5" diameter fibers arranged in a
hexagonal grid pattern with 1/3 fill factor on the IFU. Each IFU feeds
light from the prime focus of the 10m Hobby-Eberly telescope to a pair
of spectrographs covering ∼3500-5500Å with R=800. The IFUs are
arranged in a square grid on 100" centers. Thus, each exposure
contains more than 3x104 low-resolution spectra, and an observation of
three dithered exposures covers more than 50 arcmin2 sky area spread
over an 18' diameter field of view with a 1:4.6 fill factor.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 73 214 Candidate LAE galaxies for this work
table2.dat 97 123 Sub-sample Stacked Spectra
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See also:
J/ApJ/612/L93 : Candidates of z∼5.5-7 galaxies in the HST-UDF (Yan+, 2004)
J/ApJ/667/79 : Lyα emission-line galaxies at z=3.1 (Gronwall+, 2007)
J/ApJS/192/5 : Emission-line galaxies from HETDEX pilot survey (Adams+, 2011)
J/ApJ/803/34 : z∼4-10 galaxies from HST legacy fields (Bouwens+, 2015)
J/ApJ/810/71 : UV mag of candidate galaxies at 3~<z~<8.5 (Finkelstein+, 2015)
J/ApJ/869/123 : Keck Lyman continuum spectroscopic survey (Steidel+, 2018)
J/A+A/641/A118 : Mean rest-UV spectra of Lya emitters at z>3 (Feltre+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 I10 --- ID Detection ID
12- 37 A26 --- Name HETDEX Detection Name, JHHMMSS.ss+DDMMSS.s
39- 46 F8.4 deg RAdeg [165/230] Right Ascension (ICRS)
48- 54 F7.4 deg DEdeg [48/57] Declination, decimal degrees (ICRS)
56- 61 F6.4 --- zspec [2.99/3.5] Spectroscopic redshift
63- 67 F5.2 mag rmag [23.5/26.5] r-band magnitude
69- 73 F5.3 mag e_rmag [0.04/2]?=0.000 Uncertainty in rmag (1)
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Note (1): Entries with no result are fainter than the imaging
magnitude limit of 26.5.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 F7.2 0.1nm lambda1 [780/1378] Full sample, wavelength
9- 15 F7.4 10-17mW/m2 flux1 [-8.6/60]? Full sample, flux (1)
17- 22 F6.4 10-17mW/m2 e_flux1 [0.4/8]? Full sample, flux uncertainty (1)
24- 30 F7.2 0.1nm lambda2 [782/1379]? Brightest 1/3, wavelength
32- 39 F8.4 10-17mW/m2 flux2 [-12/68]? Brightest 1/3, flux (1)
41- 47 F7.4 10-17mW/m2 e_flux2 [0.7/13]? Brightest 1/3, flux uncertainty
(1)
49- 55 F7.2 0.1nm lambda3 [780/1378] Faintest 2/3, wavelength
57- 64 F8.4 10-17mW/m2 flux3 [-39/56]? Faintest 2/3, flux (1)
66- 72 F7.4 10-17mW/m2 e_flux3 [0.4/13]? Faintest 2/3, flux uncertainty
(1)
74- 80 F7.2 0.1nm lambda4 [779/1378]? Faintest 1/3, wavelength
82- 89 F8.4 10-17mW/m2 flux4 [-18/54]? Faintest 1/3, flux (1)
91- 97 F7.4 10-17mW/m2 e_flux4 [0.6/21]? Faintest 1/3 flux uncertainty (1)
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Note (1): Null entries for the flux# and e_flux# are present only for alignment
across the four samples.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 13-Feb-2024