Given radio, X-ray, and IR upper limits on OC's IMBH, compute the Bondi accretion rate and determine which radiative modes (ADAF, jet-dominated, thin disc) survive current observational constraints.
| Mode | Valid when | Predicted LX (W) | vs. X-ray limit | Predicted LR (W/Hz) | vs. radio limit |
|---|---|---|---|---|---|
| ADAF | — | — | — | — | — |
| Jet-dominated | — | — | — | — | — |
| Thin disc | — | — | — | — | — |
The Bondi–Hoyle–Lyttleton rate ṁ_B = 4π (GM)² ρ / c_s³ gives the maximum rate at which a black hole accretes from a uniform gas medium at rest. In OC's core, gas density is uncertain but estimated ~0.1–10 cm⁻³ at temperatures of ~8,000–25,000 K (c_s ~ 10–15 km/s). F_Bondi ≈ 0.03 is a commonly used fraction (Xie & Yuan 2012) accounting for winds and outflows that prevent all Bondi material from reaching the horizon.
ADAF (advection-dominated accretion flow, Narayan & Yi 1994): at λ ≪ 0.01, the accretion flow is radiatively very inefficient. L_X ≈ 10⁻³ × λ² × L_Edd (from ADAF cooling function scaling). Radio emission from the ADAF corona follows the fundamental plane (Merloni et al. 2003).
Jet-dominated: low-power jet with mechanical efficiency η_jet ≈ 10⁻⁵. Radio luminosity L_R = η_jet × ṁ_acc × c²; X-ray from the jet base ≈ 10× L_R.
Thin disc (Shakura–Sunyaev): valid at λ > 0.01. Radiative efficiency η = 0.1. L_bol = η × ṁ_acc × c². X-ray = 20% of bolometric; radio much weaker.
Mahida et al. 2025 (ApJ 996:122, arXiv:2512.09649): ATCA 7.25 GHz observations of OC's IMBH candidate. No radio counterpart detected. Headline constraint: accretion efficiency ε ≲ 4×10⁻³ (3σ). (Note: González Prieto is the lead author of a separate N-body growth paper also in measurements.js; the two should not be conflated.)
Mahida et al. 2025 (ApJ 996:122, arXiv:2512.09649) · Bondi 1952 (MNRAS 112:195) · Narayan & Yi 1994 (ApJ 428:L13) · Merloni et al. 2003 (MNRAS 345:1057) · Xie & Yuan 2012 (MNRAS 427:1580)