The effect of bars on the M•-σe relation: offset, scatter and residuals correlations

Abstract

We analyse a set of collisionless disc galaxy simulations to study the consequences of bar formation and evolution on the M • −σ e relation of supermassive black holes (SMBHs). The redistribution of angular momentum driven by bars leads to a mass increase within the central region, raising the velocity dispersion of the bulge, σ e , on average by ∼12 per cent and as much as ∼20 per cent. If a disc galaxy with an SMBH satisfying the M • −σ e relation forms a bar, and the SMBH does not grow in the process, then the increase in σ e moves the galaxy off the M • −σ e relation. We explore various effects that can affect this result including contamination from the disc and anisotropy. The displacement from the M • −σ e relation for individual model barred galaxies correlates with both the bulge-to-total stellar mass ratio, M(B)/M(B + D), and the 2D anisotropy, β φ (B + D), both measured within the effective radius of the bulge. Overall, this process leads to an M • −σ e for barred galaxies offset from that of unbarred galaxies, as well as an increase in its scatter. We assemble samples of observed unbarred and barred galaxies with classical bulges and find tentative hints of an offset between the two consistent with the predicted. Including all barred galaxies, rather than just those with a classical bulge, leads to a significantly larger offset, which is mostly driven by the significantly larger offset of pseudo bulges.

Revealing Hidden Substructures in the MBH–σ Diagram, and Refining the Bend in the L–σ Relation

“…Our previous image analysis improved upon this situation, and in our current larger sample we also have new galaxies with bars. Given that bars are known to elevate the velocity dispersion (Hartmann et al 2014), this result begs further investigation, possibly folding in disc inclination, bar orientation to our line-of-sight, and rotational velocity.…”

Galaxy Bulges and Their Massive Black Holes: A Review

“…Graham (2008a) similarly considered the offset galaxies to have undermassive black holes, due to secular evolution over-developing the bulge, or to have elevated velocity dispersions due to the dynamics of the bar. The choice appears answered because Hartmann et al (2014) have shown that bars are indeed capable of increasing the velocity dispersion in galaxies, and by exactly the average offset observed in the M bh -σ diagram (see also Debattista et al 2013 andMonari et al 2014). Furthermore, Figure 2 shows that pseudobulges and classical bulges (and clump bulges) follow the same broad distribution in the M bh -M sph diagram; at low spheroid masses they both reside systematically below the near-linear relation defined by the massive core-Sérsic spheroids.…”

Recalibration of the MBH–σ⋆ Relation for AGN

“…Contamination by dynamically distinct substructure is usually unavoidable, and rotational broadening due to disk contamination can strongly affect σ measurements from single-aperture spectra (e.g. Graham et al 2011;Hartmann et al 2014;Bellovary et al 2014, W13). In addition, Batiste et al (2017) (hereafter B17) showed that slit orientation relative to substructure, such as bars, can strongly affect the measured σ .…”