SDSS IV MaNGA -- Gas Rotation Velocity lags in the Final Sample of MaNGA Galaxies

TL;DR

This study analyzes the gas rotation velocity lags in a large sample of edge-on galaxies from the MaNGA survey, revealing correlations with galaxy mass and structure, and suggesting accretion processes influence extraplanar gas kinematics.

Contribution

It introduces the concept of stop altitude for gas rotation and links lag properties to galaxy mass, structure, and accretion history, providing new insights into extraplanar gas dynamics.

Findings

300 galaxies exhibit negative vertical gas rotation gradients

Low mass, low Sersic index galaxies have wider influence zones

Accretion events are linked to negative radial lag gradients

Abstract

We consider the largest sample of 561 edge-on galaxies observed with integral field units by the MaNGA survey and find 300 galaxies where the ionised gas shows a negative vertical gradient (lag) in its rotational speed. We introduce the stop altitude as the distance to the galactic midplane at which the gas rotation should stop in the linear approximation. We find correlations between the lags, stop altitude and galactic mass, stellar velocity dispersion and overall Sersic index. We do not find any correlation of the lags or stop altitude with the star formation activity in the galaxies. We conclude that low mass galaxies (log(M*/Mo) < 10) with low Sersic index and with low stellar velocity dispersion posses a wider "zone of influence" in the extragalactic gas surrounding them with respect to higher mass galaxies that have a significant spherical component. We estimated the trend of the vertical rotational gradient with radius and find it flat for most of the galaxies in our sample. A small subsample of galaxies with negative radial gradients of lag has an enhanced fraction of objects with aged low surface brightness structures around them (e.g. faint shells), which indicates that noticeable accretion events in the past affected the extraplanar gas kinematics and might have contributed to negative radial lag gradients. We conclude that an isotropic accretion of gas from the circumgalactic medium plays a significant role in the formation of rotation velocity lags.