Chen et al. (2025) report no detectable accretion signature from the candidate Omega Centauri IMBH. That non-detection becomes a mass upper limit only after assumptions about Bondi accretion and ADAF radiative efficiency. This tool exposes those assumptions.
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Read the description instead →Plots the predicted bolometric accretion luminosity of a Bondi-fed IMBH as a function of mass, overlaid against the JWST non-detection sensitivity floor. Where the curve crosses the floor sets the inferred mass upper limit. The three sliders expose the model's principal uncertainties.
Bondi accretion: a non-rotating mass M accretes ambient gas of density ρ_∞ and sound speed c_s at a rate Ṁ = 4π G² M² ρ_∞ / c_s³. This rises as M².
Radiative efficiency: a fraction ε of Ṁ c² escapes as electromagnetic emission. For radiatively inefficient accretion flows (ADAFs) at very low Eddington ratios, ε ≪ 0.1 — most of the energy is advected into the hole rather than radiated. Plausible range is 10⁻⁵ to 10⁻². See Yuan & Narayan (2014, ARA&A 52:529).
Predicted luminosity: L = ε · Ṁ · c². Since Ṁ ∝ M², L ∝ M². Doubling M quadruples L.
Inversion: at the JWST sensitivity floor L_lim, the corresponding mass is M = √(L_lim · c_s³ / (ε · 4π G² ρ_∞ · c²)) — what the tool plots as the crossover point.
The mass scales as √(1/ε) and √(1/ρ_∞). Dialing ε from 10⁻³ to 10⁻⁵ moves the limit by a factor of 10. Dialing ρ_∞ from 10⁻²¹ to 10⁻²⁴ moves it by another factor of ~32. Together the limit can shift by three orders of magnitude across the plausible parameter space — which is why the Chen et al. constraint, taken on its own, does not close out the IMBH hypothesis.
Chen et al. (2025) performed PSF-fitting photometry on JWST NIRCam (F200W and F444W bands) and MIRI (F770W and F1500W bands) of the central region of Omega Centauri around the Häberle 2024 candidate IMBH position. They constructed UV-to-IR SEDs for each detected source, including HST photometry from the oMEGACat program, and compared each SED to model SEDs for IMBHs accreting at low Eddington ratios via ADAF emission. No source's SED matched. The paper reports that JWST limits become more restrictive than existing radio (VLA) limits for IMBH masses below roughly 20,000 M☉.
A companion analysis (Madhuri et al. 2026, ApJ 996:122) combined JWST and radio non-detections to derive concrete efficiency bounds. Assuming the actual accretion rate is 3% of the Bondi rate (F = 0.03, a typical value for radiatively inefficient flows), they report 99% upper limits on the radiative efficiency of ε ≲ 8×10⁻⁵ for adiabatic gas and ε ≲ 9×10⁻⁷ for isothermal gas at the Bañares-mass scale. The presets in the slider above will jump to these published values.
The same calculation drives the JWST marker in the IMBH Constraint Stacker. The sliders here are local to this tool, but the math is identical. To see all current constraints together, including the JWST one, use the Stacker.
🔬 Bondi accretion and ADAF radiative efficiency are established physics. The JWST photometry itself is a clean measurement. ⚠ The translation from non-detection to mass upper limit depends on (a) which accretion model is correct (adiabatic vs. isothermal, the choice changes the inferred ε bound by a factor of ~100), and (b) the ambient gas density in the OC core, which is not directly measured in the relevant region.
JWST's NIRCam (0.6–5 μm) and MIRI (5–28 μm) photometric sensitivities reach AB magnitudes of ~29–30 in deep observations, corresponding to bolometric luminosities of ~10²⁹ to 10³¹ erg/s at OC's distance of 5.4 kpc. The Chen et al. 2025 paper used F200W, F444W, F770W, and F1500W bands, which together span the SED region where ADAF accretion would peak. JWST has also enabled deep IMBH searches in nearby dwarf galaxies (Reines et al. 2025, ApJ), pushing the low-mass end of the BH occupation fraction debate.
Before JWST, the tightest accretion-based limits came from radio: Tremou et al. 2018 (ApJ 862:16) used the VLA at 6 GHz to set L_radio < 10²⁷ erg/s for OC's center, equivalent to M_BH < 10⁴ M☉ under standard accretion assumptions. Tudor et al. 2018 (MNRAS 476:3585) used MeerKAT 1.3 GHz commissioning data to push slightly tighter. The 2025 JWST limits supersede these for IMBH masses ≲ 20,000 M☉ because of the band-coverage advantage (JWST sees the SED peak; radio only sees the optically-thin tail).
Radiatively inefficient accretion flow (RIAF/ADAF) models have been studied since Narayan & Yi 1994. The Yuan & Narayan 2014 review (ARA&A 52:529) gives ε in the range 10⁻⁵ to 10⁻² depending on Ṁ relative to Eddington, with the adiabatic limit (ε ~ 10⁻⁴) appropriate when Ṁ/Ṁ_Edd < 10⁻⁴ and the isothermal limit (ε ~ 10⁻⁷) for the very lowest accretion rates. Madhuri et al. 2026 derived ε ≲ 8×10⁻⁵ (adiabatic) and ε ≲ 9×10⁻⁷ (isothermal) for OC by combining JWST and radio non-detections at the Bañares mass.