Cluster kinematics and stellar rotation in NGC 419 with MUSE and adaptive optics

TL;DR

This study uses adaptive optics-assisted MUSE spectroscopy to analyze the dynamics and rotation of stars in the intermediate-age cluster NGC 419, revealing significant rotation and differences between stellar populations.

Contribution

It demonstrates the effectiveness of AO-fed MUSE observations in studying cluster kinematics and uncovers rotation differences among stellar populations in NGC 419.

Findings

Dynamical mass of NGC 419 is approximately 1.4x10^5 solar masses.

Red MSTO stars rotate faster than blue MSTO stars.

Average V sin i for blue MSTO stars is 87 km/s, and for red MSTO stars is 130 km/s.

Abstract

We present adaptive optics (AO) assisted integral-field spectroscopy of the intermediate-age star cluster NGC 419 in the Small Magellanic Cloud. By investigating the cluster dynamics and the rotation properties of main sequence turn-off stars (MSTO), we demonstrate the power of AO-fed MUSE observations for this class of objects. Based on 1 049 radial velocity measurements, we determine a dynamical cluster mass of 1.4+/-0.2x10^5 M_sun and a dynamical mass-to-light ratio of 0.67+/-0.08, marginally higher than simple stellar population predictions for a Kroupa initial mass function. A stacking analysis of spectra at both sides of the extended MSTO reveals significant rotational broadening. Our analysis further provides tentative evidence that red MSTO stars rotate faster than their blue counterparts. We find average V sin i values of 87+/-16 km/s and 130+/-22 km/s for blue and red MSTO stars, respectively. Potential systematic effects due to the low spectral resolution of MUSE can reach 30 km/s but the difference in V sin i between the populations is unlikely to be affected.