Aligning Retrograde Nuclear Cluster Orbits with an Active Galactic Nucleus Accretion Disc
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Stars and stellar remnants orbiting a supermassive black hole (SMBH) can interact with an active galactic nucleus (AGN) disc. Over time, prograde orbiters (inclination i < 90◦) decrease inclination, as well as semimajor axis (a) and eccentricity (e) until orbital alignment with the gas disc ('disc capture'). Captured stellar-origin black holes (sBH) add to the embedded AGN population that drives sBH-sBH mergers detectable in gravitational waves using LIGO-Virgo-KAGRA or sBH-SMBH mergers detectable with Laser Interferometer Space Antenna. Captured stars can be tidally disrupted by sBH or the SMBH or rapidly grow into massive 'immortal' stars. Here, we investigate the behaviour of polar and retrograde orbiters (i ≥ 90◦) interacting with the disc. We show that retrograde stars are captured faster than prograde stars, flip to prograde orientation (i < 90◦) during capture, and decrease a dramatically towards the SMBH. For sBH, we find a critical angle iret ∼ 113◦, below which retrograde sBH decay towards embedded prograde orbits (i → 0◦), while for io > iret sBH decay towards embedded retrograde orbits (i → 180◦). sBH near polar orbits (i ∼ 90◦) and stars on nearly embedded retrograde orbits (i ∼ 180◦) show the greatest decreases in a. Whether a star is captured by the disc within an AGN lifetime depends primarily on disc density, and secondarily on stellar type and initial a. For sBH, disc capture time is longest for polar orbits, low-mass sBH, and lower density discs. Larger mass sBH should typically spend more time in AGN discs, with implications for the spin distribution of embedded sBH.
| Originalsprog | Engelsk |
|---|---|
| Tidsskrift | Monthly Notices of the Royal Astronomical Society |
| Vol/bind | 522 |
| Udgave nummer | 4 |
| Sider (fra-til) | 5393-5401 |
| Antal sider | 9 |
| ISSN | 0035-8711 |
| DOI | |
| Status | Udgivet - 1 jul. 2023 |
Bibliografisk note
Funding Information:
SSN was supported by NSF PHY-2011334, and thanks Mordecai-Mark Mac Low for computational resources. GF was supported by ERC starting grant no. # 1218171001 and thanks Johan Samsing for insightful discussions. AS was supported by the National Science Foundation Graduate Research Fellowship Program under grant no. # DGE1656466. KESF and BM were supported by NSF AST-1831415 and Simons Foundation grant 533845. JMB was supported by NSF award AST-2107764. NWCL gratefully acknowledges the generous support of a Fondecyt Iniciación grant 11180005, as well as support from Millenium Nucleus NCN19-058 (TITANs) and funding via the BASAL Centro de Excelencia en Astrofisica y Tecnologias Afines (CATA) grant PFB-06/2007. He also thanks support from ANID BASAL projects ACE210002 and FB210003.
Funding Information:
SSN was supported by NSF PHY-2011334, and thanks Mordecai-Mark Mac Low for computational resources. GF was supported by ERC starting grant no. # 1218171001 and thanks Johan Samsing for insightful discussions. AS was supported by the National Science Foundation Graduate Research Fellowship Program under grant no. # DGE1656466. KESF and BM were supported by NSF AST-1831415 and Simons Foundation grant 533845. JMB was supported by NSF award AST-2107764. NWCL gratefully acknowledges the generous support of a Fondecyt Iniciación grant 11180005, as well as support from Millenium Nucleus NCN19-058 (TITANs) and funding via the BASAL Centro de Excelencia en Astrofisica y Tecnologias Afines (CATA) grant PFB-06/2007. He also thanks support from ANID BASAL projects ACE210002 and FB210003.
Publisher Copyright:
© 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
ID: 360681225