Lyα EMISSION FROM A LUMINOUS z = 8.68 GALAXY: IMPLICATIONS FOR GALAXIES AS TRACERS OF COSMIC REIONIZATION

By A. Zitrin, I. Labbé, S. Belli, R. Bouwens, Richard S. Ellis, G. Roberts-Borsani, D. Stark, P. Oesch, R. Smit. 2015

142 citations recorded by the source corpus.

We report the discovery of Lyman-alpha emission (Lyα) in the bright galaxy EGSY-2008532660 (hereafter EGSY8p7) using the Multi-Object Spectrometer For Infra-Red Exploration spectrograph at the Keck Observatory. First reported by Roberts-Borsani et al., this galaxy was selected for spectroscopic observations because of its photometric redshift ( z phot = 8.57 − 0.43 + 0.22 ?> ), apparent brightness (H 160 = 25.26 ± 0.09 ?> ), and red Spitzer/IRAC [3.6]–[4.5] color indicative of contamination by strong oxygen emission in the [4.5] band. With a total integration of ∼4.3 hr, our data reveal an emission line at ≃11776 Å that we argue is likely Lyα at a redshift of z spec = 8.683 − 0.004 + 0.001 ?> , in good agreement with the photometric estimate. The line was detected independently on two nights using different slit orientations and its detection significance is ∼ 7.5 &sgr; ?> . An overlapping skyline contributes significantly to the uncertainty on the total line flux, although the significance of the detected line is robust to a variety of skyline-masking procedures. By direct addition and a Gaussian fit, we estimate a 95% confidence range of 1.0–2.5 × 10−17 erg s−1 cm−2, corresponding to a rest-frame equivalent width of 17–42 Å. EGSY8p7 is the most distant spectroscopically confirmed galaxy to date, and the third luminous source in the EGS field beyond z phot ≳ 7.5 ?> with detectable Lyα emission, viewed at a time when the intergalactic medium is believed to be fairly neutral. Although the reionization process was probably patchy, we discuss whether luminous sources with prominent IRAC color excesses may harbor harder ionizing spectra than the dominant fainter population, thereby creating earlier ionized bubbles. Further spectroscopic follow-up of such bright sources promises important insights into the early formation of galaxies.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/9dd5bc03689ed0eb68d948f48dcfd4bea0233ec8

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In Astronomy and Astrophysics

1. Richard S. Ellis
2. R. Bouwens
3. P. Oesch
4. P. V. van Dokkum
5. M. Franx
6. G. Illingworth
7. I. Labbé
8. M. Ouchi

In Instrumentation

1. Richard S. Ellis
2. M. Franx
3. P. V. van Dokkum
4. R. Bouwens
5. I. Labbé
6. P. Oesch
7. G. Illingworth
8. J. Dunlop

Citations in the corpus

• A REMARKABLY LUMINOUS GALAXY AT Z = 11.1 MEASURED WITH HUBBLE SPACE TELESCOPE GRISM SPECTROSCOPY (2016, background): “…the large number of candidates from HST imaging, only a handful of galaxies in the epoch of reionization have confirmed redshifts to date (Vanzella et al. 2011; Ono et al. 2012; Shibuya et al. 2012; Finkelstein et al. 2013; Oesch et al. 2015b; Roberts-Borsani et al. 2015; Zitrin et al. 2015).”
• Lyα and C iii] emission in z = 7–9 Galaxies: accelerated reionization around luminous star-forming systems? (2016, background): “One possibility, suggested in Zitrin et al. (2015), is that the identification of the four most luminous z > 7 galaxies in the CANDELS fields picks out overdense regions which have the largest ionized bubbles at any given redshift.”
• Systematic Identification of LAEs for Visible Exploration and Reionization Research Using Subaru HSC (SILVERRUSH). I. Program strategy and clustering properties of ∼2000 Lyα emitters at z = 6–7 over the 0.3–0.5 Gpc2 survey area (2017, background): “Recent deep spectroscopy also detected strong Lyα emission of ∼10 LAEs at z = 7.0–8.7, pushing the redshift frontier of LAEs to-date (e.g., Pentericci et al. 2011; Ono et al. 2012; Shibuya et al. 2012; Finkelstein et al. 2013; Schenker et al. 2014; Oesch et al. 2015; Zitrin et al. 2015).”
• SILVERRUSH. IV. Lyα luminosity functions at z = 5.7 and 6.6 studied with ∼1300 Lyα emitters on the 14–21 deg2 sky (2017, background): “…et al. 2010; Shibuya et al. 2012; Yamada et al. 2012; Konno et al. 2014) and spectroscopic observations (e.g., Deharveng et al. 2008; Adams et al. 2011; Finkelstein et al. 2013; Schenker et al. 2014; Cassata et al. 2015; Oesch et al. 2015; Zitrin et al. 2015; Song et al. 2016; Stark et al. 2017).”
• The Universe Is Reionizing at z ∼ 7: Bayesian Inference of the IGM Neutral Fraction Using Lyα Emission from Galaxies (2017, background): “…7.5 with strong Spitzer/IRAC excesses have recently been observed with Lyα (Finkelstein et al. 2013; Roberts-Borsani et al. 2016; Oesch et al. 2015; Zitrin et al. 2015; Stark et al. 2017), at a redshift when the IGM is expected to be significantly neutral (Planck Collaboration et al. 2016; Greig…”
• CONTRASTING GALAXY FORMATION FROM QUANTUM WAVE DARK MATTER, ψDM, WITH ΛCDM, USING PLANCK AND HUBBLE DATA (2015, background): “Exceptions have been found with strong Lyα emission at ~z 7.7 (Oesch et al. 2015), and also the currently highest redshift galaxy established by spectroscopy at ~z 8.7 (Zitrin et al. 2015).”
• Inferences on the timeline of reionization at z ∼ 8 from the KMOS Lens-Amplified Spectroscopic Survey (2019, methodology): “However, Lyα has been observed in a handful of UV bright galaxies at z∼> 7.5 (Zitrin et al. 2015; Oesch et al. 2015; Roberts-Borsani et al. 2016; Stark et al. 2017).”
• An extreme [O III] emitter at z = 3.2: a low metallicity Lyman continuum source (2015, background): “From the very large EW([O iii]λλ4959, 5007+Hβ) observed at high-redshift (Oesch et al. 2015; Zitrin et al. 2015; Roberts-Borsani et al. 2015; Smit et al. 2015), we can speculate that these galaxies have a leakage of ionizing photons.”
• Big Three Dragons: A z = 7.15 Lyman-break galaxy detected in [O iii] 88 μm, [C ii] 158 μm, and dust continuum with ALMA (2018, background): “More recently, Stark et al. (2017) have demonstrated a striking LAE fraction of 100% in the sample of most luminous LBGs (Oesch et al. 2015; Zitrin et al. 2015; Roberts-Borsani et al. 2016).”
• Detection of the Far-infrared [O iii] and Dust Emission in a Galaxy at Redshift 8.312: Early Metal Enrichment in the Heart of the Reionization Era (2018, background): “…8–10 m telescope time have been invested in Lyα searches for z>8 candidates, but so far this resulted in only a few detections (z=8.683, 8.38, 9.11, Zitrin et al. 2015b; Laporte et al. 2017; Hashimoto et al. 2018c, respectively), likely indicating that the Lyα signal is substantially attenuated…”
• Planck intermediate results. XLVI. Reduction of large-scale systematic effects in HFI polarization maps and estimation of the reionization optical depth (2016, unknown): “…of full reionization provided by Lyman-α absorption in the spec- ∗Corresponding author: J. L. Puget, jean-loup.puget@ias.u-psud.fr tra of high redshift objects (see Dijkstra 2014; Mashian et al. 2016; Robertson et al. 2015; Bouwens et al. 2015; Zitrin et al. 2015, for recent results and reviews).”