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ABSTRACT The brightest steady sources of radiation in the universe, active galactic nuclei (AGNs), are powered by gas accretion on to a central supermassive black hole (SMBH). The large sizes and accretion rates implicated in AGN accretion discs are expected to lead to gravitational instability and fragmentation, effectively cutting off mass inflow to the SMBH. Radiative feedback from disc-embedded stars has been invoked to yield marginally stable, steady-state solutions in the outer discs. Here, we examine the consequences of this star formation with a semi-analytical model in which stellar-mass black hole (sBH) remnants in the disc provide an additional source of stabilizing radiative feedback. Assuming star formation seeds the embedded sBH population, we model the time-evolving feedback from both stars and the growing population of accreting sBHs. We find that in the outer disc, the luminosity of the sBHs quickly dominates that of their parent stars. However, because sBHs consume less gas than stars to stabilize the disc, the presence of the sBHs enhances the mass flux to the inner disc. As a result, star formation persists over the lifetime of the AGN, damped in the outer disc, but amplified in a narrow ring in the inner disc. Heating from the embedded sBHs significantly modifies the disc’s temperature profile and hardens its spectral energy distribution, and direct emission from the sBHs adds a new hard X-ray component.
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Constraining intermediate-mass black holes from the stellar disc of SgrA*
ABSTRACT Stars evolving around a supermassive black hole see their orbital orientations diffuse efficiently, a process called ‘vector resonant relaxation’. In particular, stars within the same disc, i.e. neighbours in orientations, will slowly diffuse away from one another through this stochastic process. We use jointly (i) detailed kinetic predictions for the efficiency of this dilution and (ii) the recent observation of a stellar disc around SgrA*, the supermassive black hole at the centre of the Milky Way, to constrain SgrA*’s unobserved stellar cluster. Notably, we investigate quantitatively the impact of a population of intermediate-mass black holes on the survivability of the stellar disc.
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- Award ID(s):
- 2207594
- PAR ID:
- 10466025
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 526
- Issue:
- 1
- ISSN:
- 0035-8711
- Format(s):
- Medium: X Size: p. 1471-1481
- Size(s):
- p. 1471-1481
- Sponsoring Org:
- National Science Foundation
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