Albert Sneppen
Salle Entresol Daniel Chalonge, Institut d'Astrophysique de Paris
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| « The origin of the spectra of Little Red Dots » |
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Albert Sneppen |
| JWST has discovered a population of puzzling objects predominantly in the first two billion years of the universe; the inscrutable `little red dots’ (LRDs), compact galaxies with v-shaped spectral energy distributions and often broadened emission lines from hydrogen and helium, strongly suggestive of supermassive black hole activity. It has been proposed that LRDs are the outcome of direct collapse black holes, quasi-stars, indicators of primordial black holes, supermassive stars, and tidal disruption events. We assemble a sample of LRD-like objects at z>3 and use self-consistent radiative-transfer calculations to show that a supermassive black hole accreting from a dense gas cocoon accurately reproduces the detailed spectra. We show that the cocoons must be non-spherical, with comparable amounts of inflowing and outflowing material. And we predict correlations between Balmer break strength, Balmer line-absorption and scattering line width, which we confirm in our observed sample. We reproduce all LRD-like properties without requiring star-like atmospheres and we determine the typical black hole in our sample to be of order a million solar masses, with ionized cocoon masses of tens of solar masses potentially supplied from a much larger cold-gas reservoir. |
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jeudi 26 mars 2026 - 11:00 Salle Entresol Daniel Chalonge, Institut d'Astrophysique de Paris |
| Page web du séminaire / Seminar's webpage |