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

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 1R e to within 10%. All three methods show larger scatter (up to 20%) in the inner regions (R < 0.4R e ) 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 M dyn at 1R e to better than 20%, but users should be mindful of scatter in the inner regions where some assumptions may break down.velocity, Vc, defined as V 2 c (R) ≡ −R(∂Φ/∂R), is an optimal tracer of a galaxy's potential. The mass profile of galaxies provides insight into, for example, understanding how baryons and dark matter co-habitate in galaxies, how the galaxies assemble, and how galaxy evolution proceeds across the Hubble sequence in a variety of environments (e.g. see re-

First Gaia dynamical model of the Milky Way disc with six phase space coordinates: a test for galaxy dynamics

“…, is consistent with observations of external galaxies, where such deviations are widespread, but models can still capture the average kinematic properties (Cappellari et al 2013) and recover circular velocity profiles to 10% accuracy (Leung et al 2018), even from data of much inferior quality.…”

“…The JAM cyl method was applied to model the integralfield stellar kinematics of large numbers of external galaxies (see review in Cappellari 2016) and has been extensively tested against N-body simulations (Lablanche et al 2012;Li et al 2016) and in real galaxies against CO circular velocities (Leung et al 2018), including many barred galaxies like the Milky Way. It was found to recover unbiased density profiles, even more accurately than the more general Schwarzschild (Schwarzschild 1979) approach (see Fig.…”

Survival of molecular gas in a stellar feedback-driven outflow witnessed with the MUSE TIMER project and ALMA

“…6 we show a decomposition of the Hα velocity dispersion into gravitational and non-gravitational (turbulent) components. As described in § 2.4, this is possible by comparing the Hα rotation curve to the "true" circular velocity -as traced independently by the dynamically cold CO rotation curve (and confirmed by dynamical modeling of the stellar kinematics; e.g., Leung et al 2018). The ionised gas in Fig.…”

“…In the latter case we have derived the circular velocity from the stellar kinematics using Jeans Axisymmetric Models (JAM) Cappellari 2008). The stellar dynamical model for NGC 3351 was constructed identical to the descriptions in Leung et al (2018), and we refer readers to that study for a detailed description. As shown in Leung et al (2018), the circular velocities derived from JAM agree well with that derived using CO.…”

Efficient solution of the anisotropic spherically aligned axisymmetric Jeans equations of stellar hydrodynamics for galactic dynamics

“…However, the JAM cyl method was found to provide smaller errors, especially at large radii where the gas velocities are better-determined ( fig. 8 of Leung et al 2018).…”