Séminaire Doctoral / Seminar PhD |
| « Supermassive black holes are rather hot OR The thermodynamics of black hole seed formation » |
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Tilman Hartwig |
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The highest redshift quasars at z>6 have mass estimates of about a billion solar masses. One of the most promising pathways to their formation includes direct collapse of gas, forming a supermassive star, precursor of the black hole seed. In contrast to the widely know Habouzit-Theorem (“supermassive black holes are super cool!”), I will show that this statement is not entirely true for the formation process, because the gas has to remain hot throughout the collapse.
In this talk, I will present the main processes leading to the formation of supermassive black hole seeds and a new method for the determination of H2 self-shielding in 3D simulations. This new method captures the gas geometry and velocity field, enabling us to properly determine the direction-dependent self-shielding factor of H2 against the photodissociating background radiation. We find that the use of this new method yields a more than ten times higher probability to form black hole seeds by direct collapse. This may translate into a similar enhancement in the predicted number density of supermassive black holes and hence explain current observations. |
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mercredi 13 mai 2015 - 17:00 Salle Entresol Daniel Chalonge, Institut d'Astrophysique |
| Page web du séminaire / Seminar's webpage |