Kinematical Signatures of Disc Instabilities and Secular Evolution in the MUSE TIMER Survey

TL;DR

This study uses high-resolution integral-field spectroscopy from the MUSE TIMER Survey to analyze stellar kinematics in the central regions of 21 nearby massive disc galaxies, confirming theoretical predictions about bar-driven secular evolution and identifying kinematic signatures of box/peanuts and inner discs.

Contribution

It provides the first detailed kinematic evidence of bar-driven secular evolution and inner disc formation in a large sample of nearby galaxies, linking kinematic features with galaxy evolution.

Findings

Inner discs are common and consistent with bar-driven secular evolution.

Kinematic signatures of box/peanuts are identified in various galaxy inclinations.

Inner discs have higher rotational support than the main disc.

Abstract

The MUSE TIMER Survey has obtained high signal and high spatial resolution integral-field spectroscopy data of the inner $\sim6\times6$ kpc of 21 nearby massive disc galaxies. This allows studies of the stellar kinematics of the central regions of massive disc galaxies that are unprecedented in spatial resolution. We confirm previous predictions from numerical and hydrodynamical simulations of the effects of bars and inner bars on stellar and gaseous kinematics, and also identify box/peanuts via kinematical signatures in mildly and moderately inclined galaxies, including a box/peanut in a face-on inner bar. In 20/21 galaxies we find inner discs and show that their properties are fully consistent with the bar-driven secular evolution picture for their formation. In addition, we show that these inner discs have, in the region where they dominate, larger rotational support than the main galaxy disc, and discuss how their stellar population properties can be used to estimate when in cosmic history the main bar formed. Our results are compared with photometric studies in the context of the nature of galaxy bulges and we show that inner discs are identified in image decompositions as photometric bulges with exponential profiles (i.e., S\'ersic indices near unity).