Disk mass and disk heating in the spiral galaxy NGC 3223

TL;DR

This study measures stellar and gaseous kinematics in NGC 3223 to understand disk heating and estimate the stellar M/L ratio, but the weak constraints limit dark matter distribution determination.

Contribution

It provides detailed kinematic measurements and explores the vertical-to-radial velocity dispersion ratio in NGC 3223, highlighting challenges in constraining the stellar M/L ratio.

Findings

Vertical-to-radial velocity dispersion ratio of 1.21±0.14

Weakly constrained stellar M/L ratio between 0.5 and 1.7

Difficulty in determining dark matter distribution from current data

Abstract

We present the stellar and gaseous kinematics of an Sb galaxy, NGC 3223, with the aim of determining the vertical and radial stellar velocity dispersion as a function of radius, which can help to constrain disk heating theories. Together with the observed NIR photometry, the vertical velocity dispersion is also used to determine the stellar mass-to-light (M/L) ratio, typically one of the largest uncertainties when deriving the dark matter distribution from the observed rotation curve. We find a vertical-to-radial velocity dispersion ratio of sigma_z/sigma_R=1.21+-0.14, significantly higher than expectations from known correlations, and a weakly-constrained Ks-band stellar M/L ratio in the range 0.5-1.7, at the high end of (but consistent with) the predictions of stellar population synthesis models. Such a weak constraint on the stellar M/L ratio, however, does not allow us to securely determine the dark matter density distribution. To achieve this, either a statistical approach or additional data (e.g. integral-field unit) are needed.