Little red dots as young supermassive black holes in dense ionized cocoons
NatureTL;DR
Imagine you see a blurry, red light in a thick fog. You might guess it's a giant bonfire. But what if it's actually a much smaller, intensely bright spotlight, and the fog is just scattering its light, making it look bigger and fuzzier? Scientists using the James Webb Space Telescope found these 'little red dots' in the early universe. At first, they looked like evidence for already-massive black holes. This study proposes they are actually smaller, 'toddler' black holes furiously eating gas inside a super-dense cocoon of cosmic fog. This fog not only makes their light look 'blurry' but also hides them from X-ray and radio telescopes, explaining why they've been so hard to find until now.
The James Webb Space Telescope (JWST) has uncovered many compact galaxies at high redshift with broad hydrogen and helium lines, including the enigmatic population of little red dots (LRDs). These galaxies are linked to supermassive black holes (SMBHs) or intense star formation. Unusual properties for SMBHs, like overmassive black holes and weak X-ray and radio emission, are observed. The study finds that electron scattering broadens the lines, with the data requiring high electron column densities and compact sizes. Reprocessed nebular emission from a dense cocoon explains LRD spectral characteristics, suggesting a population of young SMBHs accreting close to the Eddington limit.
- 1Electron scattering broadens the lines, not Doppler motions.
- 2High electron column densities and compact sizes are observed.
- 3The data implies black hole masses lower than previously estimated.
- 4Suggests a population of young supermassive black holes accreting close to the Eddington limit.
- 5Dense cocoon of ionized gas explains weak X-ray and radio emission.
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