SDSS-IV MaNGA: Internal mass distributions and orbital structures of early-type galaxies and their dependence on environment

TL;DR

This study applies Schwarzschild dynamical modeling to MaNGA early-type galaxies, revealing how their internal mass distributions, shapes, and orbital structures depend on galaxy mass and environment.

Contribution

It extends previous simulation-based analysis to real observational data, providing new insights into the mass and orbital structures of early-type galaxies from MaNGA.

Findings

Low-mass ETGs are more oblate and rotation-dominated with lower dark matter fractions.

High-mass ETGs are more prolate, rotation about their major axis, and have higher dark matter fractions.

Prolate-like and hot-orbit-rich ETGs are more likely to have close neighbors.

Abstract

In our earlier 2019 paper, we evaluated the reliability of Schwarzschild's orbit-superposition dynamical modelling method in estimating the internal mass distribution, intrinsic stellar shapes and orbit distributions of early-type galaxies (ETGs) taken from the Illustris cosmological simulation. We now apply the same techniques to galaxies taken from the integral-field survey Mapping Nearby Galaxies with APO (MaNGA), using a sample of 149 ETGs in the mass range of $10^{9.90}\sim10^{11.80} M_{\odot}$ and made up of 105 central and 44 satellite galaxies. We find that low-mass ETGs with $\log(M_*/M_{\odot})<11.1$ have an average dark matter fraction of $\sim0.2$ within one effective radius $R_{\rm e}$, tend to be oblate-like, and are dominated by rotation about their minor axis. High-mass ETGs with $\log(M_*/M_{\odot})>11.1$ have an average dark matter fraction of $\sim0.4$ within one effective radius $R_{\rm e}$, tend to be prolate-like, and are dominated by rotation about their major axis and by centrophilic orbits. The changes of internal structures within one $R_{\rm e}$ are dominated by the total stellar mass of the individual galaxies. We find no differences of internal structures between central and satellite ETGs for the same stellar masses. However, for similar stellar mass and colour distributions, we find that ETGs more prolate-like, or with more hot orbits, tend to have higher close neighbour counts at $r_p\sim40$ kpc.