Publication details for Professor Ian SmailSobral, David, Matthee, Jorryt, Darvish, Behnam, Smail, Ian, Best, Philip N., Alegre, Lara, Röttgering, Huub, Mobasher, Bahram, Paulino-Afonso, Ana, Stroe, Andra & Oteo, Iván (2018). The nature of luminous Ly α emitters at z ∼ 2–3: maximal dust-poor starbursts and highly ionizing AGN. Monthly Notices of the Royal Astronomical Society 477(2): 2817-2840.
- Publication type: Journal Article
- ISSN/ISBN: 0035-8711 (print), 1365-2966 (electronic)
- DOI: 10.1093/mnras/sty782
- Further publication details on publisher web site
- Durham Research Online (DRO) - may include full text
Author(s) from Durham
Deep narrow-band surveys have revealed a large population of faint Ly α emitters (LAEs) in the distant Universe, but relatively little is known about the most luminous sources (
). Here we present the spectroscopic follow-up of 21 luminous LAEs at z ∼ 2–3 found with panoramic narrow-band surveys over five independent extragalactic fields (≈4 × 106 Mpc3 surveyed at z ∼ 2.2 and z ∼ 3.1). We use WHT/ISIS, Keck/DEIMOS, and VLT/X-SHOOTER to study these sources using high ionization UV lines. Luminous LAEs at z ∼ 2–3 have blue UV slopes (
) and high Ly α escape fractions (
per cent) and span five orders of magnitude in UV luminosity (MUV ≈ −19 to −24). Many (70 per cent) show at least one high ionization rest-frame UV line such as C IV, N V, C III], He II or O III], typically blue-shifted by ≈100–200 km s−1 relative to Ly α. Their Ly α profiles reveal a wide variety of shapes, including significant blue-shifted components and widths from 200 to 4000 km s−1. Overall, 60 ± 11 per cent appear to be active galactic nucleus (AGN) dominated, and at LLyα > 1043.3 erg s−1 and/or MUV < −21.5 virtually all LAEs are AGNs with high ionization parameters (log U = 0.6 ± 0.5) and with metallicities of ≈0.5 − 1 Z⊙. Those lacking signatures of AGNs (40 ± 11 per cent) have lower ionization parameters (
and log ξion = 25.4 ± 0.2) and are apparently metal-poor sources likely powered by young, dust-poor ‘maximal’ starbursts. Our results show that luminous LAEs at z ∼ 2–3 are a diverse population and that
mark a sharp transition in the nature of LAEs, from star formation dominated to AGN dominated.