TY - JOUR

T1 - Aligning Retrograde Nuclear Cluster Orbits with an Active Galactic Nucleus Accretion Disc

AU - Nasim, Syeda S.

AU - Fabj, Gaia

AU - Caban, Freddy

AU - Secunda, Amy

AU - Ford, K. E.Saavik

AU - McKernan, Barry

AU - Bellovary, Jillian M.

AU - Leigh, Nathan W.C.

AU - Lyra, Wladimir

N1 - Publisher Copyright: © 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.

PY - 2023/7/1

Y1 - 2023/7/1

N2 - 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.

AB - 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.

KW - accretion

KW - accretion discs

KW - galaxies: active

KW - galaxies: nuclei

KW - gravitational waves

KW - stars: black holes

KW - stars: kinematics and dynamics

U2 - 10.1093/mnras/stad1295

DO - 10.1093/mnras/stad1295

M3 - Journal article

AN - SCOPUS:85161561282

VL - 522

SP - 5393

EP - 5401

JO - Royal Astronomical Society. Monthly Notices

JF - Royal Astronomical Society. Monthly Notices

SN - 0035-8711

IS - 4

ER -