Spectroscopic detection of C iv λ1548 in a galaxy at z = 7.045: implications for the ionizing spectra of reionization-era galaxies

By D. Stark, G. Walth, S. Charlot, B. Clément, A. Feltre, Julia Gutkin, J. Richard, R. Mainali, Brant Robertson, B. Siana and 2 more. 2015

175 citations recorded by the source corpus.

We present Keck/MOSFIRE observations of UV metal lines in four bright gravitationally-lensed z~6-8 galaxies behind the cluster Abell 1703. The spectrum of A1703-zd6, a highly-magnified star forming galaxy with a Lyman-alpha redshift of z=7.045, reveals a confident detection of the nebular CIV emission line (unresolved with FWHM 7, it would indicate that reionization-era galaxies are more efficient ionizing agents than previously thought. Alternatively, we suggest that the small sample of Lyman-alpha emitters at z>7 may trace a rare population with intense radiation fields capable of ionizing their surrounding hydrogen distribution. Additional constraints on high ionization emission lines in galaxies with and without Lyman-alpha detections will help clarify whether hard ionizing spectra are common in the reionization era.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/0ac9f67af166b015bd3698c6127ba31bae3c2297

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In Astronomy and Astrophysics

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

Citations in the corpus

• Conditions for Reionizing the Universe with a Low Galaxy Ionizing Photon Escape Fraction (2019, background): “Stark et al. (2015b, 2016) measured ξion via ionized carbon emission, finding ξion= - +25.68 0.19 0.27 erg−1 Hz in a lensed galaxy at z=7.045 with an intrinsic MUV=−19.3 and ξion=25.6 for three luminous (MUV=−22) galaxies at z=7.15, 7.48, and 7.73.”
• Evolution of the AGN UV luminosity function from redshift 7.5 (2018, background): “…may also be consistent with the shallow bright-end slopes of the z ∼ 7 UV luminosity function of galaxies relative to a Schechter function (Bowler et al. 2012, 2014; Bradley et al. 2014; Bowler et al. 2015) and the hard spectra of these galaxies (Stark et al. 2015a,b, 2017; Laporte et al. 2017).”
• 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): “Because LAEs are low stellar mass galaxies with strong Lyα indicative of a starburst with young massive stars producing a large amount of ionizing photons (Ouchi et al. 2013; Sobral et al. 2015; Stark et al. 2015), LAEs are used as probes of young galaxies.”
• Lyα and C iii] emission in z = 7–9 Galaxies: accelerated reionization around luminous star-forming systems? (2016, methodology): “Yet owing to the lack of strong nebular lines in reionization-era galaxies, there are currently only a handful of ∆vLyα measurements at z > 6 (Willott et al. 2015; Stark et al. 2015a).”
• The Universe Is Reionizing at z ∼ 7: Bayesian Inference of the IGM Neutral Fraction Using Lyα Emission from Galaxies (2017, background): “…from the literature (Erb et al. 2014; Steidel et al. 2014; Bradač et al. 2017; Inoue et al. 2016; Mainali et al. 2017; Pentericci et al. 2016; Stark et al. 2015, 2017; Willott et al. 2015) in Figure 2 (left) where it is clear the high redshift galaxies have lower ∆v at given Muv compared…”
• 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): “These lines, in addition to the restframe optical oxygen and nitrogen lines, are also useful for characterizing the metal enrichment of the interstellar medium (ISM) and stellar components of the galaxies (e.g., Stark et al. 2015a, 2015b, 2017; Mainali et al. 2018).”
• Modelling the nebular emission from primeval to present-day star-forming galaxies (2016, methodology): “…to the epoch of cosmic reionization, rapid progress is being accomplished in the observation of fainter emission lines in the rest-frame ultraviolet spectra of galaxies in this redshift range (e.g., Shapley et al. 2003; Erb et al. 2010; Stark et al. 2014, 2015a,b, 2016; Sobral et al. 2015).”
• Nuclear activity versus star formation: emission-line diagnostics at ultraviolet and optical wavelengths (2015, methodology): “Thus, emission lines associated with ion species requiring ionization energies greater than 50 eV should be the most promising indicators of the presence of an AGN, as we shall see in the following sections (see also Steidel et al. 2014; Stark et al. 2015b).”
• Inferences on the timeline of reionization at z ∼ 8 from the KMOS Lens-Amplified Spectroscopic Survey (2019, background): “These upper limits are comparable to, and in one case below, the Civ detection presented by Stark et al. (2015) in a Muv ∼ −19 galaxy (with EWciv ≈ 38 Å), and so suggest that the proposed anticorrelation between UV luminosity and Civ EW may not be so simple.”
• The HDUV Survey: A Revised Assessment of the Relationship between UV Slope and Dust Attenuation for High-redshift Galaxies (2017, background): “Thus, such models predict a ξion that is elevated by a factor of ≈ 2 relative to those assumed in standard calibrations between Hα/UV luminosity and SFR (e.g., see also Nakajima et al. 2016; Bouwens et al. 2016a; Stark et al. 2015; Reddy et al. 2016b).”
• 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): “1-1145 [Cii] 6.77 20+140 −40 −20.8 + 2.5 log(µ) b 26± 4 7.0+1.0 −1.5/µ b 5.0± 0.3 B17 NTTDF6345 [Cii] 6.70 110 −21.6 15 17.7 - P16 UDS16291 [Cii] 6.64 110 −21.0 6 7.15 - P16 COSMOS24108 [Cii] 6.62 240 −21.7 27 10.0 - P16 CR7 (full) [Cii] 6.60 167± 22 −22.2 211± 20 21.7± 3.6c - S15, Mat17 Himiko (Tot”