Classical bulges, supermassive black holes, and agn feedback: Extension to low-mass galaxies

Abstract

The empirical model of Lu et al. for the relation between star formation rate and halo mass growth is adopted to predict the classical bulge mass (Mcb)-total stellar mass (M∗) relation for central galaxies. The assumption that the supermassive black hole (SMBH) mass (MBH) is directly proportional to the classical bulge mass, with the proportionality given by that for massive galaxies, predicts a MBH-M∗relation that matches well the observed relation for different types of galaxies. In particular, the model reproduces the strong transition at M∗= 1010.5-1011 Me⊙, below which MBH drops rapidly with decreasing M∗. Our model predicts a new sequence at M∗< 1010.5 M⊙, where MBH ∝ M∗but the amplitude is a factor of ∼50 lower than the amplitude of the sequence at M∗> 1011 M⊙. If all SMBHs grow through similar quasar modes with a feedback efficiency of a few percent, then the energy produced in low-mass galaxies at redshift z ≳ 2 can heat the circumgalactic medium up to a specific entropy level that is required to prevent excessive star formation in low-mass dark matter halos.