D. Sobral
The most luminous H α emitters at z ∼ 0.8–2.23 from HiZELS: evolution of AGN and star-forming galaxies
Sobral, D.; Kohn, S.A.; Best, P.N.; Smail, I.; Harrison, C.M.; Stott, J.; Calhau, J.; Matthee, J.
Authors
S.A. Kohn
P.N. Best
Professor Ian Smail ian.smail@durham.ac.uk
Emeritus Professor
C.M. Harrison
J. Stott
J. Calhau
J. Matthee
Abstract
We use new near-infrared spectroscopic observations to investigate the nature and evolution of the most luminous Hα emitters at z ∼ 0.8–2.23, which evolve strongly in number density over this period, and compare them to more typical Hα emitters. We study 59 luminous Hα emitters with LHα > L ∗ Hα LHα∗ , roughly equally split per redshift slice at z ∼ 0.8, 1.47 and 2.23 from the HiZELS and CF-HiZELS surveys. We find that, overall, 30 ± 8 per cent are active galactic nuclei [AGNs; 80 ± 30 per cent of these AGNs are broad-line AGNs, BL-AGNs], and we find little to no evolution in the AGN fraction with redshift, within the errors. However, the AGN fraction increases strongly with Hα luminosity and correlates best with LHα/L ∗ Hα (z) LHα∗(z) . While LHα ≤ L ∗ Hα (z) LHα∗(z) Hα emitters are largely dominated by star-forming galaxies (>80 per cent), the most luminous Hα emitters (L Hα >10L ∗ Hα (z) LHα>10LHα∗(z) ) at any cosmic time are essentially all BL-AGN. Using our AGN-decontaminated sample of luminous star-forming galaxies, and integrating down to a fixed Hα luminosity, we find a factor of ∼1300 evolution in the star formation rate density from z = 0 to 2.23. This is much stronger than the evolution from typical Hα star-forming galaxies and in line with the evolution seen for constant luminosity cuts used to select ‘ultraluminous’ infrared galaxies and/or sub-millimetre galaxies. By taking into account the evolution in the typical Hα luminosity, we show that the most strongly star-forming Hα-selected galaxies at any epoch (L Hα >L ∗ Hα (z) LHα>LHα∗(z) ) contribute the same fractional amount of ≈15 per cent to the total star formation rate density, at least up to z = 2.23.
Citation
Sobral, D., Kohn, S., Best, P., Smail, I., Harrison, C., Stott, J., …Matthee, J. (2016). The most luminous H α emitters at z ∼ 0.8–2.23 from HiZELS: evolution of AGN and star-forming galaxies. Monthly Notices of the Royal Astronomical Society, 457(2), 1739-1752. https://doi.org/10.1093/mnras/stw022
Journal Article Type | Article |
---|---|
Acceptance Date | Jan 4, 2016 |
Online Publication Date | Feb 4, 2016 |
Publication Date | Apr 1, 2016 |
Deposit Date | Feb 16, 2016 |
Publicly Available Date | Feb 22, 2016 |
Journal | Monthly Notices of the Royal Astronomical Society |
Print ISSN | 0035-8711 |
Electronic ISSN | 1365-2966 |
Publisher | Royal Astronomical Society |
Peer Reviewed | Peer Reviewed |
Volume | 457 |
Issue | 2 |
Pages | 1739-1752 |
DOI | https://doi.org/10.1093/mnras/stw022 |
Keywords | Galaxies: evolution, Galaxies: high-redshift, Cosmology: observations. |
Related Public URLs | http://adsabs.harvard.edu/abs/2016MNRAS.457.1739S |
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Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society ©: 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
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