The M_bh-sigma diagram, and the offset nature of barred active galaxies

TL;DR

This study investigates how the presence of bars in galaxies affects the supermassive black hole mass versus velocity dispersion relation, revealing that barred galaxies tend to deviate from the standard relation, which impacts understanding of galaxy evolution.

Contribution

It introduces the first analysis of active galaxies in the M_bh-sigma diagram, demonstrating the offset behavior of barred galaxies and deriving a new relation for non-barred galaxies.

Findings

Barred galaxies are offset from the M_bh-sigma relation by up to ~1 dex.

Active barred galaxies show similar offset behavior as inactive ones.

A new non-barred M_bh-sigma relation is established.

Abstract

From a sample of 50 predominantly inactive galaxies with direct supermassive black hole mass measurements, it has recently been established that barred galaxies tend to reside rightward of the M_bh-sigma relation defined by non-barred galaxies. Either black holes in barred galaxies tend to be anaemic or the central velocity dispersions in these galaxies have a tendency to be elevated by the presence of the bar. The latter option is in accord with studies connecting larger velocity dispersions in galaxies with old bars, while the former scenario is at odds with the observation that barred galaxies do not deviate from the M_bh-luminosity relation. Using a sample of 88 galaxies with active galactic nuclei, whose supermassive black hole masses have been estimated from their associated emission lines, we reveal for the first time that they also display this same general behavior in the M_bh-sigma diagram depending on the presence of a bar or not. A new symmetrical and non-symmetrical "barless" M_bh-sigma relation is derived using 82 non-barred galaxies. The barred galaxies are shown to reside on or up to ~1 dex below this relation. This may explain why narrow-line Seyfert 1 galaxies appear offset from the "barless" M_bh-sigma relation, and has far reaching implications given that over half of the disk galaxy population are barred.