Splitting the lentils: Clues to galaxy/black hole coevolution from the discovery of offset relations for non-dusty versus dusty (wet-merger-built) lenticular galaxies in theMbh–M*,spheroid andMbh–M*,galaxy diagrams

Abstract

This work advances the (galaxy morphology)-dependent (black hole mass, Mbh)-(spheroid/galaxy stellar mass, M*) scaling relations by introducing ‘dust bins’ for lenticular (S0) galaxies. Doing so has led to the discovery of Mbh-M*, sph and Mbh-M*, gal relations for dusty S0 galaxies—built by major wet mergers and comprising half the S0 sample—offset from the distribution of dust-poor S0 galaxies. The situation is reminiscent of how major dry mergers of massive S0 galaxies have created an offset population of ellicular and elliptical galaxies. For a given Mbh, the dust-rich S0 galaxies have 3–4 times higher M*, sph than the dust-poor S0 galaxies, and the steep distributions of both populations in the Mbh-M*, sph diagram bracket the $M_{\rm bh} \propto M_{\rm *,sph}^{2.27+/-0.48}$ relation defined by the spiral galaxies, themselves renovated through minor mergers. The new relations offer refined means to estimate Mbh in other galaxies and should aid with: (i) constructing (galaxy morphology)-dependent black hole mass functions; (ii) estimating the masses of black holes associated with tidal disruption events; (iii) better quantifying evolution in the scaling relations via improved comparisons with high-z data by alleviating the pickle of apples versus oranges; (iv) mergers and long-wavelength gravitational wave science; (v) simulations of galaxy/black hole coevolution and semi-analytic works involving galaxy speciation; plus (vi) facilitating improved extrapolations into the intermediate-mass black hole landscape. The role of the galaxy’s environment is also discussed, and many potential projects that can further explore the morphological divisions are mentioned.

Discovery of a Planar Black Hole Mass Scaling Relation for Spiral Galaxies

“…Although late-type galaxies may be complex, early-type galaxies are complicated; the distinction being that complexity implies many understandable components and complication implying less components, but more chaos and disorder. This can be understood by tracking the impact of merger histories and the genesis of morphologically dependent black hole mass scaling relations (Graham 2023a(Graham , 2023bGraham & Sahu 2023a, 2023b. As such, the unique merger history of a galaxy can effectively muddle the ordered rotationally supported disk galaxies by transforming them into dispersion-supported elliptical galaxies.…”

“…Black hole mass scaling relations (i.e., relations with central black hole mass as the dependent variable and some physical property of its host galaxy as the independent variable) have evolved and proliferated over the past quarter-century, beginning with the identification of a correlation between black hole mass (M • ) and the stellar mass of its host galaxy's bulge (Magorrian et al 1998). The most reliable of these scaling relations are those that are built and calibrated upon samples of galaxies with dynamically measured black hole masses (e.g., Graham & Scott 2013;Savorgnan et al 2013Savorgnan et al , 2016Savorgnan 2016aSavorgnan , 2016bDavis et al 2017Davis et al , 2018Davis et al , 2019aDavis et al , 2019bDavis et al , 2019cSahu et al 2019aSahu et al , 2019bSahu et al , 2020Sahu et al , 2022aSahu et al , 2022bSahu 2021Sahu , 2022Graham 2023aGraham , 2023bGraham & Sahu 2023a, 2023b; Z. Jin & B. L. Davis 2023, in preparation). 1 To date, only about 150 such supermassive black holes (SMBHs) with M •  10 6 M e have been directly measured in just the nearest and most massive galaxies.…”