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

Pallottini, A. ; Ferrara, A. ; Pacucci, F. ; Gallerani, S. ; Salvadori, S. ; Schneider, R. ; Schaerer, D. ; Sobral, D. ; Matthee, J.

In: Monthly Notices of the Royal Astronomical Society, 2015, vol. 453, no. 3, p. 2465-2470

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    Titre
    • The brightest Ly α emitter: Pop III or black hole?
    Auteur
    • Pallottini, A.. Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy
    • Ferrara, A.. Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy
    • Pacucci, F.. Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy
    • Gallerani, S.. Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy
    • Salvadori, S.. Kapteyn Astronomical Institute, Landleven 12, NL-9747 AD Groningen, the Netherlands
    • Schneider, R.. INAF, Osservatorio Astronomico di Roma, Via Frascati 33, I-00040 Monteporzio Catone, Italy
    • Schaerer, D.. Observatoire de Genève, Departement d'Astronomie, Université de Genève, 51 Ch. des Maillettes, CH-1290 Versoix, Switzerland
    • Sobral, D.. Instituto de Astrofísica e Ciências do Espaço, Universidade de Lisboa, OAL, Tapada da Ajuda, P-1349-018 Lisboa, Portugal
    • Matthee, J.. Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, the Netherlands
    Type de document
    • Postprint
    Langue
    • Anglais
    Publié dans
    • Monthly Notices of the Royal Astronomical Society, 2015, vol. 453, no. 3, p. 2465-2470. Oxford University Press
    Autre version électronique
    Identifiant OAI-PMH
    • oai:doc.rero.ch:296447
    Summary
    CR7 is the brightest z=6.6 Ly α emitter (LAE) known to date, and spectroscopic follow-up by Sobral etal. 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 α/He ii1640 line luminosities ($L_{\rm \alpha /He\,\small {II}}$) a top-heavy initial mass function and a massive ( ≳ 107 M⊙) Pop III burst with age ≲ 2Myr are required. Assuming that the observed properties of Ly α 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 Lα>1043.3 erg s−1 should also host Pop III stars producing an observable $L_{\rm He\,\small {II}}\gtrsim 10^{42.7}\,{\rm erg}\,{\rm s}^{-1}$. 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 Lα, $L_{\rm He\,\small {II}}$, 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