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  • 1802.10102v1

    Rights statement: This is a pre-copy-editing, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The definitive publisher-authenticated version David Sobral, Jorryt Matthee, Behnam Darvish, Ian Smail, Philip N Best, Lara Alegre, Huub Röttgering, Bahram Mobasher, Ana Paulino-Afonso, Andra Stroe, Iván Oteo; 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, Volume 477, Issue 2, 21 June 2018, Pages 2817–2840, https://doi.org/10.1093/mnras/sty782 is available online at: https://academic.oup.com/mnras/article/477/2/2817/4953429

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The nature of luminous Lyman-alpha emitters at z~2-3: maximal dust-poor starbursts and highly ionising AGN

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  • David Sobral
  • Jorryt Matthee
  • Behnam Darvish
  • Ian Smail
  • Philip N. Best
  • Lara Alegre
  • Huub Röttgering
  • Bahram Mobasher
  • Ana Paulino-Afonso
  • Andra Stroe
  • Iván Oteo
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<mark>Journal publication date</mark>21/06/2018
<mark>Journal</mark>Monthly Notices of the Royal Astronomical Society
Issue number2
Volume477
Number of pages24
Pages (from-to)2817–2840
Publication statusPublished
Early online date24/03/18
Original languageEnglish

Abstract

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 (⁠LLyα≳1042.7LLyα≳1042.7 erg s−1; LLyα≳L∗LyαLLyα≳LLyα∗⁠). 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 (⁠β=−2.0+0.3−0.1β=−2.0−0.1+0.3⁠) and high Ly α escape fractions (⁠50+20−1550−15+20 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 (⁠logU=−3.0+1.6−0.9log⁡U=−3.0−0.9+1.6and 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 2×L∗Lyα2×LLyα∗ and 2×M∗UV2×MUV∗ mark a sharp transition in the nature of LAEs, from star formation dominated to AGN dominated.

Bibliographic note

This is a pre-copy-editing, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The definitive publisher-authenticated version David Sobral, Jorryt Matthee, Behnam Darvish, Ian Smail, Philip N Best, Lara Alegre, Huub Röttgering, Bahram Mobasher, Ana Paulino-Afonso, Andra Stroe, Iván Oteo; 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, Volume 477, Issue 2, 21 June 2018, Pages 2817–2840, https://doi.org/10.1093/mnras/sty782 is available online at: https://academic.oup.com/mnras/article/477/2/2817/4953429