Inferences on the timeline of reionization at z ∼ 8 from the KMOS Lens-Amplified Spectroscopic Survey
By C. Mason, A. Fontana, T. Treu, K. Schmidt, A. Hoag, L. Abramson, R. Amorín, M. Bradač, L. Guaita, T. Jones and 5 more. Monthly notices of the Royal Astronomical Society, 2019
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Detections and non-detections of Lyman alpha (Lyα) emission from z > 6 galaxies (<1 Gyr after the big bang) can be used to measure the timeline of cosmic reionization. Of key interest to measuring reionization’s mid-stages, but also increasing observational challenge, are observations at z > 7, where Lyα redshifts to near infra-red wavelengths. Here we present a search for z > 7.2 Lyα emission in 53 intrinsically faint Lyman Break Galaxy candidates, gravitationally lensed by massive galaxy clusters, in the KMOS Lens-Amplified Spectroscopic Survey (KLASS). With integration times of ∼7–10 h, we detect no Lyα emission with signal-to-noise ratio (S/N) > 5 in our sample. We determine our observations to be 80 per cent complete for 5σ spatially and spectrally unresolved emission lines with integrated line flux >5.7 × 10−18 erg s−1 cm−2. We define a photometrically selected sub-sample of 29 targets at z = 7.9 ± 0.6, with a median 5σ Lyα EW limit of 58 Å. We perform a Bayesian inference of the average intergalactic medium (IGM) neutral hydrogen fraction using their spectra. Our inference accounts for the wavelength sensitivity and incomplete redshift coverage of our observations, and the photometric redshift probability distribution of each target. These observations, combined with samples from the literature, enable us to place a lower limit on the average IGM neutral hydrogen fraction of $\gt 0.76 \,\, (68{{\ \rm per\ cent}}), \,\, \gt 0.46 \,\, (95{{\ \rm per\ cent}})$ at z ∼ 8, providing further evidence of rapid reionization at z ∼ 6–8. We show that this is consistent with reionization history models extending the galaxy luminosity function to $M_ \rm {\small UV}\lesssim -12$, with low ionizing photon escape fractions, $f_\textrm{esc} \lesssim 15{{\ \rm per\ cent}}$.
Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/9a9e31715658c320d2ca76637156e82393c33c73
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Citations in the corpus
- Rapid Reionization by the Oligarchs: The Case for Massive, UV-bright, Star-forming Galaxies with High Escape Fractions (2019, methodology): “3. z∼7−8 Lyα Equivalent Width (EW) Distributions: = - +x 0.59H 0.15 0.11 I¯ at z∼7, = -+x 0.88H 0.100.05I¯ at z∼7.5, and >x 0.76H I¯ at z∼8 (Mason et al. 2018, 2019a; Hoag et al. 2019).”
- RELICS: Reionization Lensing Cluster Survey (2019, background): “…have proven increasingly difficult beyond z > 6 (Stark et al. 2010; Bradač et al. 2012; Schenker et al. 2014; Schmidt et al. 2016; Hoag et al. 2019; Mason et al. 2019), likely due primarily to absorption by patchy neutral hydrogen before reionization was complete (Treu et al. 2013; Tilvi et al.…”
- Pōniuā‘ena: A Luminous z = 7.5 Quasar Hosting a 1.5 Billion Solar Mass Black Hole (2020, background): “Studies of the Lyα emission from z > 6 galaxies have suggested neutral fractions of 〈xHI〉 = 0.59+0.11−0.15 at z ∼ 7 and 〈xHI〉 > 0.76 at z ∼ 8 (Mason et al. 2018, 2019).”
- The GLASS-JWST Early Release Science Program. I. Survey Design and Release Plans (2022, background): “Multiple lines of evidence indicate that the universe was reionized at z 6 (e.g., Planck Collaboration et al. 2020; Mason et al. 2018a, 2019a; Hoag et al. 2019a; Davies et al. 2018; Greig et al. 2019; Morales et al. 2021; Qin et al. 2021).”