The EDGE-CALIFA survey: validating stellar dynamical mass models with CO kinematics

TL;DR

This study compares stellar and CO gas kinematics in 54 galaxies to validate three dynamical models, finding they all reliably estimate galaxy mass at one effective radius within 10-20% accuracy.

Contribution

It provides a homogeneous validation of three common dynamical models using combined stellar and CO kinematic data across diverse galaxy types.

Findings

All three models recover Mdyn at 1Re within 10% accuracy.

Inner regions show increased scatter up to 20%, indicating model limitations.

Models perform reliably at larger radii despite inner region complexities.

Abstract

Deriving circular velocities of galaxies from stellar kinematics can provide an estimate of their total dynamical mass, provided a contribution from the velocity dispersion of the stars is taken into account. Molecular gas (e.g., CO) on the other hand, is a dynamically cold tracer and hence acts as an independent circular velocity estimate without needing such a correction. In this paper we test the underlying assumptions of three commonly used dynamical models, deriving circular velocities from stellar kinematics of 54 galaxies (S0-Sd) that have observations of both stellar kinematics from the CALIFA survey, and CO kinematics from the EDGE survey. We test the Asymmetric Drift Correction (ADC) method, as well as Jeans, and Schwarzschild models. The three methods each reproduce the CO circular velocity at 1Re to within 10%. All three methods show larger scatter (up to 20%) in the inner regions (R < 0.4Re) which may be due to an increasingly spherical mass distribution (which is not captured by the thin disk assumption in ADC), or non-constant stellar M/L ratios (for both the JAM and Schwarzschild models). This homogeneous analysis of stellar and gaseous kinematics validates that all three models can recover Mdyn at 1Re to better than 20%, but users should be mindful of scatter in the inner regions where some assumptions may break down.