What drives galaxy quenching? A deep connection between galaxy kinematics and quenching in the local Universe

TL;DR

This study reveals that galaxy quenching in the local Universe is most strongly linked to the velocity dispersion, indicating a connection to bulge properties and AGN feedback, rather than disc kinematics.

Contribution

It introduces a 2D inclined rotating disc model and uses machine learning to identify key kinematic factors associated with galaxy quenching, emphasizing the role of velocity dispersion.

Findings

Velocity dispersion is the primary predictor of galaxy quenching.

Disc kinematic parameters are weakly related to quenching at fixed velocity dispersion.

Quenching correlates with black hole mass and AGN feedback mechanisms.

Abstract

We develop a 2D inclined rotating disc model, which we apply to the stellar velocity maps of 1862 galaxies taken from the MaNGA survey (SDSS public Data Release 15). We use a random forest classifier to identify the kinematic parameters that are most connected to galaxy quenching. We find that kinematic parameters that relate predominantly to the disc (such as the mean rotational velocity) and parameters that characterise whether a galaxy is rotation- or dispersion-dominated (such as the ratio of rotational velocity to velocity dispersion) are not fundamentally linked to the quenching of star formation. Instead, we find overwhelmingly that it is the absolute level of velocity dispersion (a property that relates primarily to a galaxy's bulge/spheroidal component) that is most important for separating star forming and quenched galaxies. Furthermore, a partial correlation analysis shows that many commonly discussed correlations between galaxy properties and quenching are spurious, and that the fundamental correlation is between quenching and velocity dispersion. In particular, we find that at fixed velocity dispersion, there is only a very weak dependence of quenching on the disc properties, whereby more discy galaxies are slightly more likely to be forming stars. By invoking the tight relationship between black hole mass and velocity dispersion, and noting that black hole mass traces the total energy released by AGN, we argue that these data support a scenario in which quenching occurs by preventive feedback from AGN. The kinematic measurements from this work are publicly available.