The brightest Ly alpha emitter:Pop III or black hole?

Pallottini, A. and Ferrara, A. and Pacucci, F. and Gallerani, S. and Salvadori, S. and Schneider, R. and Schaerer, D. and Sobral, D. and Matthee, J. (2015) The brightest Ly alpha emitter:Pop III or black hole? Monthly Notices of the Royal Astronomical Society, 453 (3). pp. 2465-2470. ISSN 0035-8711

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CR7 is the brightest z = 6.6 Ly alpha emitter (LAE) known to date, and spectroscopic follow-up by Sobral et al. suggests that CR7 might host Population (Pop) III stars. We examine this interpretation using cosmological hydrodynamical simulations. Several simulated galaxies show the same 'Pop III wave' pattern observed in CR7. However, to reproduce the extreme CR7 Ly alpha/He II1640 line luminosities (L-alpha/He II) a top-heavy initial mass function and a massive (greater than or similar to 10(7)M(circle dot)) Pop III burst with age less than or similar to 2 Myr are required. Assuming that the observed properties of Ly alpha and He II emission are typical for Pop III, we predict that in the COSMOS/UDS/SA22 fields, 14 out of the 30 LAEs at z = 6.6 with L-alpha > 10(43.3) erg s(-1) should also host Pop III stars producing an observable L-He II greater than or similar to 10(42.7) erg s(-1). As an alternate explanation, we explore the possibility that CR7 is instead powered by accretion on to a direct collapse black hole. Our model predicts L-alpha, L-He II, and X-ray luminosities that are in agreement with the observations. In any case, the observed properties of CR7 indicate that this galaxy is most likely powered by sources formed from pristine gas. We propose that further X-ray observations can distinguish between the two above scenarios.

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Journal Article
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Monthly Notices of the Royal Astronomical Society
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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 A. Pallottini, A. Ferrara, F. Pacucci, S. Gallerani, S. Salvadori, R. Schneider, D. Schaerer, D. Sobral, and J. Matthee The brightest Ly α emitter: Pop III or black hole? MNRAS 2015 453: 2465-2470 is available online at:
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20 Jan 2016 12:00
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02 May 2022 00:54