2018MNRAS.477.2817S -
Mon. Not. R. Astron. Soc., 477, 2817-2840 (2018/June-3)
The nature of luminous Ly α emitters at z ∼ 2-3: maximal dust-poor starbursts and highly ionizing AGN.
SOBRAL D., MATTHEE J., DARVISH B., SMAIL I., BEST P.N., ALEGRE L., ROTTGERING H., MOBASHER B., PAULINO-AFONSO A., STROE A. and OTEO I.
Abstract (from CDS):
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 ( L_ Lyα_ ≳1042.7 erg s–1; L_ Lyα_≳L^*_ Lyα_). 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 x 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+0.3–0.1) and high Ly α escape fractions (50+20–15 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+1.6–0.9 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 2×L^*_ Lyα_ and 2×M_ UV_^* mark a sharp transition in the nature of LAEs, from star formation dominated to AGN dominated.
Abstract Copyright:
© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
Journal keyword(s):
galaxies: active - galaxies: evolution - galaxies: high-redshift - galaxies: ISM - galaxies: starburst - cosmology: observations
VizieR on-line data:
<Available at CDS (J/MNRAS/477/2817): table2.dat sp/*>
Nomenclature:
Table 2: [SMD2018b] SSA22-NB5-NN (Nos 10, 14, 18), [SMD2018b] GN-NB5-NNNN (Nos 3378, 5878, 6712).
Simbad objects:
42
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