2019ApJ...886...80D

Luminous spheroids (M_V <= -21.50 ± 0.75 mag) contain partially depleted cores with sizes (R_b) typically 0.02-0.5 kpc. However, galaxies with R_b > 0.5 kpc are rare and poorly understood. Here, we perform detailed decompositions of the composite surface brightness profiles, extracted from archival Hubble Space Telescope and ground-based images, of 12 extremely luminous "large-core" galaxies that have R_b > 0.5 kpc and M_V <= -23.50 ± 0.10 mag, fitting a core-Sersic model to the galaxy spheroids. Using 28 "normal-core" (i.e., R_b < 0.5 kpc) galaxies and one "large-core" (i.e., R_b > 0.5 kpc) galaxy from the literature, we constructed a final sample of 41 core-Sersic galaxies. We find that large-core spheroids (with stellar masses M_* >= 10¹²M_☉) are not simple high-mass extensions of the less luminous normal-core spheroids having M_* ∼ 8 x 10¹⁰-10¹²M_☉. While the two types follow the same strong relations between the spheroid luminosity L_V and R_b (R_b∝L_V^1.38±0.13^), and the spheroid half-light radius R_e (R_e∝L_V^1.08±0.09^, for ellipticals plus Brightest Cluster Galaxies), we discover a break in the core-Sersic σ-L_V relation occurring at M_V ∼ -23.50 ± 0.10 mag. Furthermore, we find a strong log-linear R_b-M_BH relation for the 11 galaxies in the sample with directly determined supermassive black hole (SMBH) masses M_BH-3/11 galaxies are large-core galaxies-such that R_b∝M_BH^0.83±0.10^. However, for the large-core galaxies the SMBH masses estimated from the M_BH-σ and core-Sersic M_BH-L relations are undermassive, by up to a factor of 40, relative to expectations from their large R_b values, confirming earlier results. Our findings suggest that large-core galaxies harbor overmassive SMBHs (M_BH >= 10¹⁰M_☉), considerably (∼3.7-15.6σ and ∼0.6-1.7σ) larger than expectations from the spheroid σ and L, respectively. We suggest that the R_b-M_BH relation can be used to estimate SMBH masses in the most massive galaxies.