Spectroscopic detection of C IV λ1548 in a galaxy at z = 7.045: implications for the ionizing spectra of reionization-era galaxies - Archive ouverte HAL Access content directly
Journal Articles Monthly Notices of the Royal Astronomical Society Year : 2015

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

, , (1) , (2) , (1) , (1) , (2) , , , , ,
1
2
Daniel P. Stark
  • Function : Author
Gregory Walth
Stéphane Charlot
Anna Feltre
Ramesh Mainali
  • Function : Author
Brant Robertson
  • Function : Author
Brian Siana
  • Function : Author
Mengtao Tang
Matthew Schenker
  • Function : Author

Abstract

We present Keck/MOSFIRE observations of UV metal emission lines in four bright (H = 23.9-25.4) gravitationally lensed z ≃ 6-8 galaxies behind the cluster Abell 1703. The spectrum of A1703-zd6, a highly magnified star-forming galaxy with a Lyα redshift of z = 7.045, reveals a confident detection of the nebular C IV λ1548 emission line (unresolved with full width at half-maximum<125 km s-1). UV metal emission lines are not detected in the three other galaxies. At z ≃ 2-3, nebular C IV emission is observed in just 1 per cent of UV-selected galaxies. The presence of strong C IV emission in one of the small sample of galaxies targeted in this paper may indicate that hard ionizing spectra are more common at z ≃ 7. The total estimated rest-frame equivalent width of the C IV doublet and C IV/Lyα flux ratio are comparable to measurements of narrow-lined AGNs. Photoionization models show that the nebular C IV line can also be reproduced by a young stellar population, with very hot metal-poor stars dominating the photon flux responsible for triply ionizing carbon. Regardless of the origin of the C IV, we show that the ionizing spectrum of A1703-zd6 is different from that of typical galaxies at z ≃ 2, producing more H ionizing photons per unit 1500 Å luminosity (log(ξion/erg- 1 Hz) = 25.68) and a larger flux density at 30-50 eV. If such extreme radiation fields are typical in UV-selected systems at z ≳ 7, it would indicate that reionization-era galaxies are more efficient ionizing agents than previously thought. Alternatively, we suggest that the small sample of Lyα 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 Lyα detections will help clarify whether hard ionizing spectra are common in the reionization era.
Fichier principal
Vignette du fichier
stv1907.pdf (1.27 Mo) Télécharger le fichier
Origin : Publisher files allowed on an open archive

Dates and versions

insu-03644674 , version 1 (25-04-2022)

Identifiers

Cite

Daniel P. Stark, Gregory Walth, Stéphane Charlot, Benjamin Clément, Anna Feltre, et al.. Spectroscopic detection of C IV λ1548 in a galaxy at z = 7.045: implications for the ionizing spectra of reionization-era galaxies. Monthly Notices of the Royal Astronomical Society, 2015, 454, pp.1393-1403. ⟨10.1093/mnras/stv1907⟩. ⟨insu-03644674⟩
10 View
7 Download

Altmetric

Share

Gmail Facebook Twitter LinkedIn More