03 February 2022Séminaire – Tiago Costa (MPA Garching)

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Quasar feedback and the origin of extended Lyα glow in z > 6 quasars

Abstract
The detection of quasars out to z ≈ 7.5 shows that supermassive black holes with masses of ≈109
M☉ have already assembled by the time the Universe was only ≈ 680 Myr old. These observations
strenuously test theoretical models of galaxy evolution, which have to explain how such rapid black
hole growth comes about. I will start by reviewing results from state-of-the-art cosmological
simulations that show that black hole growth to ≈109 M☉ can be accommodated by galaxy evolution
models. These black holes, however, must evolve inside rare, massive dark matter haloes tracing
extreme overdensities. Zooming-in on the quasar host galaxies, I will argue that the required rapid
black hole growth is expected to ignite powerful quasar feedback in the form of large-scale
outflows. I will illustrate how these outflows, which are characterized by a multi-phase structure
resembling that of the interstellar medium, affect quasar environments in a myriad of ways. I will
then demonstrate how the same cosmological simulations that succeed in reproducing ≈109 M☉
black holes also account for recent observations of bright, extended Lyα nebulae around z > 6
quasars. I will make the case that the uncanny match between theoretical models and observations is
only possible if quasar feedback already operates efficiently in z > 6 quasars. I will conclude my
talk by highlighting new theoretical insights into the nature of Lyα nebulae at z = 6, explaining their
detailed observational properties, their dominant physical mechanism, and the potential to detect
them at z = 7.5.