The Intermediate-mass Black Hole in Omega Centauri: Constraints on Accretion from JWST

Abstract We analyze JWST observations of the central region of the globular cluster ω Centauri (NGC 5139), around the position of the candidate intermediate-mass black hole (IMBH) inferred by M. Häberle et al. from the motion of fast-moving stars in multiepoch Hubble Space Telescope (HST) observations. We performed point-spread-function-fitting photometry for sources in NIRCam (F200W and F444W) and MIRI (F770W and F1500W) and constructed ultraviolet-to-infrared spectral energy distributions (SEDs) for sources within the central region of the cluster, by using HST photometry from oMEGACat. None of the SEDs of the reliably measured sources within this region resemble the SEDs computed from the model of D. W. Pesce et al. for IMBHs accreting from the intracluster medium at low rates. Our JWST limits place constraints on combinations of the IMBH mass and accretion rate, either due to the amount of material available to be accreted or due to the fraction of accreting matter that actually falls into the IMBH. Our nondetection then does not necessarily contradict the mass range of the IMBH inferred from the fast-moving stars. We discuss these constraints in the context of the model of D. W. Pesce et al. We find that the JWST limits are more restrictive than the existing radio limits for IMBH masses ≲6000 M ⊙ . It is also possible that the faint IMBH emission is dominated by the light of a nearby star. Tighter limits on the accretion onto the candidate IMBH can be placed with deeper observations, a more precise localization of the IMBH, and better measurements of the local intracluster medium density and temperature at the center of the cluster.