Séminaire Doctorants / Seminar PhD students |
| « Exploring the nature of the Lyman-alpha emitter CR7 » |
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Tilman Hartwig |
| CR7 is the brightest Lyman-alpha emitter observed at z>6, which shows very strong Lyman-alpha and HeII1640A line luminosities, but no metal line emission. Previous studies suggest that CR7 hosts either young primordial stars with a total stellar mass of ~10^7 M_sun or a black hole of ~10^6 M_sun. Here, we explore different formation scenarios for CR7 with a semianalytical model, based on the random sampling of dark matter merger trees. We find that primordial stars cannot account for the observed line luminosities because of their short lifetimes and because of early metal enrichment. Black holes that are the remnants of the first stars are either not massive enough, or reside in metal-polluted haloes, ruling out this possible explanation of CR7. Our models instead suggest that direct collapse black holes, which form in metal-free haloes exposed to large Lyman-Werner fluxes, are more likely the origin of CR7. However, this result is derived under optimistic assumptions and future observations are necessary to further constrain the nature of CR7. |
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jeudi 17 décembre 2015 - 17:00 Salle Entresol Daniel Chalonge, Institut d'Astrophysique |
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