The Most Massive Galaxies with Large Depleted Cores: Structural Parameter Relations and Black Hole Masses

• Published in: The Astrophysical journal 2019-12, Vol.886 (2), p.80
• Main Author: Dullo, Bililign T.
• Format: Article
• Language: English
• Subjects: Astrophysics; Black holes; cD galaxies; Cores; Elliptical galaxies; Galaxies; Galaxy nuclei; Galaxy photometry; Galaxy structure; Lenticular galaxies; Space telescopes; Spheroids; Stars & galaxies; Supermassive black holes
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ab4d4f

Luminous spheroids (MV −21.50 0.75 mag) contain partially depleted cores with sizes (Rb) typically 0.02-0.5 kpc. However, galaxies with Rb > 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 Rb > 0.5 kpc and MV −23.50 0.10 mag, fitting a core-Sérsic model to the galaxy spheroids. Using 28 "normal-core" (i.e., Rb < 0.5 kpc) galaxies and one "large-core" (i.e., Rb > 0.5 kpc) galaxy from the literature, we constructed a final sample of 41 core-Sérsic 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 × 1010-1012M☉. While the two types follow the same strong relations between the spheroid luminosity LV and Rb ( ), and the spheroid half-light radius Re ( , for ellipticals plus Brightest Cluster Galaxies), we discover a break in the core-Sérsic -LV relation occurring at MV ∼ −23.50 0.10 mag. Furthermore, we find a strong log-linear Rb-MBH relation for the 11 galaxies in the sample with directly determined supermassive black hole (SMBH) masses MBH-3/11 galaxies are large-core galaxies-such that . However, for the large-core galaxies the SMBH masses estimated from the MBH- and core-Sérsic MBH-L relations are undermassive, by up to a factor of 40, relative to expectations from their large Rb values, confirming earlier results. Our findings suggest that large-core galaxies harbor overmassive SMBHs (MBH 1010M☉), considerably (∼3.7-15.6 and ∼0.6-1.7 ) larger than expectations from the spheroid and L, respectively. We suggest that the Rb-MBH relation can be used to estimate SMBH masses in the most massive galaxies.