UCL Discovery
UCL home » Library Services » Electronic resources » UCL Discovery

Spectroscopy of an extreme [OIII] emitting active galactic nucleus at z = 3.212: implications for the reionisation era

Tang, M; Stark, DP; Ellis, RS; Charlot, S; Feltre, A; Shapley, AE; Endsley, R; (2022) Spectroscopy of an extreme [OIII] emitting active galactic nucleus at z = 3.212: implications for the reionisation era. Monthly Notices of the Royal Astronomical Society , 509 (2) pp. 3102-3112. 10.1093/mnras/stab3279. Green open access

[thumbnail of Ellis_stab3279.pdf]
Preview
Text
Ellis_stab3279.pdf - Published Version

Download (2MB) | Preview

Abstract

Reionization-era galaxies often display intense nebular emission lines, both in rest-frame optical ([O III] + H β) and ultraviolet (UV; C III], C IV). How such strong nebular emission is powered remains unclear, with both active galactic nuclei (AGNs) and hot stars considered equally viable. The UV continuum slopes of these early systems tend to be very blue (β < −2), reflecting minimal dust obscuration, young ages, and low metallicities. This contrasts with narrow-lined AGNs at z ∼ 2−3, whose UV slopes are significantly redder (β > −1) than typical star-forming systems in the reionization era. To investigate the properties of AGNs in the reionization era, we have conducted a search for potential examples of rare analogues with blue continua at intermediate redshift (⁠z ∼ 2−3). Our goals are to determine whether AGNs with intense line emission and blue continua exist and thereby to establish the range of rest-frame UV and optical line ratios in this population. In this paper, we report the detection of an X-ray luminous AGN at z = 3.21 (UDS-24561) with extreme [O III] + H β line emission (equivalent width = 1300 Å) and a blue UV continuum slope (β = −2.34). MMT/Binospec and Keck/MOSFIRE spectra indicate rest-frame UV line ratios consistent with AGN photoionization models and rest-frame optical lines with both a narrow component [full width at half-maximum (FWHM) =154kms−1] and extended broad wings (FWHM =977kms−1⁠), consistent with outflowing gas. We describe how such objects can be identified in future James Webb Space Telescope emission line surveys in the reionization era, thereby providing a valuable census of AGN activity at z > 6 and understanding their contribution to cosmic reionization.

Type: Article
Title: Spectroscopy of an extreme [OIII] emitting active galactic nucleus at z = 3.212: implications for the reionisation era
Open access status: An open access version is available from UCL Discovery
DOI: 10.1093/mnras/stab3279
Publisher version: https://doi.org/10.1093/mnras/stab3279
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher's terms and conditions.
Keywords: galaxies: active, galaxies: evolution, galaxies: formation, galaxies: high-redshift, cosmology: observations
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/10137973
Downloads since deposit
5Downloads
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item