Séminaire/Seminar Galaxies |
| « The lack of growth of the most massive black holes since z=4 » |
|
Paloma Guetzoyan |
|
The formation and growth of Supermassive Black Holes (BHs) of mass MBH = 10^(6 - 10) Msun, have always challenged our understanding of modern astronomy. Indeed, some of these objects were already in place at very early cosmic times, which makes us wonder how
they assembled so quickly, and what happens once they reach such high masses that early in the history of the Universe. The focus of this talk is the BH - galaxy assembly in the most massive galaxies. We chose to explore the Boötes field, making use of multi-wavelength data to target efficiently both Active Galactic Nuclei (AGN) in the X-ray with Chandra, and the host galaxy with optical/IR photometry to build their Spectral Energy Distribution (SED). By doing so, we assess how often massive galaxies host a growing BH, and how growth is governed in these extreme objects. Is it still on-going ? If so, how many of these objects are still growing and at which rate ? What are the properties of the galaxies hosting these extreme active BHs ? We found that, while AGN seem preferentially located in moderately massive galaxies of log(Mstar) > 10 Msol, we do not find a strong stellar mass dependence in AGN fraction or accretion rate distribution above this mass threshold. Our BH-galaxy growth tracks reveal that while most BH mass has been accumulated since z=4 for lower mass BHs, the assembly of the most massive BHs is more complex, with little to no mass gain since this epoch, and that the bulk of their mass was already in place very early on. This implies that we cannot account for most of BH growth through accretion between z=0-4, and that rapid and intense growth episodes over the first billion year of the Universe, were necessary to form these massive BHs. |
|
jeudi 20 mars 2025 - 11:30 Salle Entresol Daniel Chalonge Institut d'Astrophysique de Paris |
| Page web du séminaire / Seminar's webpage |