IFU spectroscopy of 10 early-type galactic nuclei - IV. Properties of the circumnuclear stellar kinematics

TL;DR

This study investigates the stellar kinematic properties of the central regions of 10 early-type galaxies using IFU spectroscopy, revealing rotation patterns, decoupled cores, and complex velocity structures that inform galaxy formation theories.

Contribution

It provides new detailed measurements of circumnuclear stellar kinematics in early-type galaxies, highlighting features like rotation, decoupled cores, and potential non-axisymmetric potentials.

Findings

Detection of rotation patterns in 7 galaxies.

Identification of a kinematic decoupled core in NGC 1404.

Observation of a sigma-drop possibly linked to counterrotation or star formation.

Abstract

The study of stellar kinematic properties may provide hints on the formation and evolution of elliptical and lenticular galaxies. Although most previous studies have focused on the large scale of these galaxies, their central regions (scales of $\sim$ 100 pc) may contain important clues about their structure, such as kinematically decoupled cores. This is the fourth paper on a sample of 10 massive ($\sigma$ $>$ 200 km s$^{-1}$) and nearby ($d$ $<$ 31 Mpc) early-type galaxies, observed with the integral field unit of the Gemini South Multi Object Spectrograph. Here, we analyse the properties of the stellar kinematics in the circumnuclear region. We fitted the line-of-sight velocity distribution with a Gauss-Hermite function. In seven galaxies of the sample, we detected a rotation pattern in their radial velocity maps that are anti-correlated with $h_3$. We interpret this as stellar structures in rotation embedded in the bulges of the objects. Comparing the stellar kinematic results with the PCA Tomography results and also with the gas kinematic results of IC 5181, it seems that this object may have a non-axisymmetric potential at its centre. The velocity dispersion maps of four objects have a nuclear peak, which must correspond, in part, to unresolved stellar rotation. In NGC 1404, we detected a kinematic decoupled core with an extension of $\sim$ 200 pc. This galaxy also has a $\sigma$-drop in the centre, which may be related to both stellar components in counterrotation or with a kinematically cold star-forming region.