Cluster Glimpses with Raven: AO Corrected Near and Mid-Infrared Images of Glimpse C01 and Glimpse C02

TL;DR

This study used the RAVEN adaptive optics system on Subaru to capture near and mid-infrared images of star clusters GC01 and GC02, revealing detailed stellar populations and properties, including distances and ages.

Contribution

First demonstration of open loop AO with RAVEN delivering diffraction-limited images in near-infrared for star clusters, enabling detailed analysis of their stellar content.

Findings

GC01's Red Clump identified, distance modulus 13.6

GC01's age estimated > 1 Gyr from K luminosity function

GC02 shows a flat K luminosity function, suggesting a different age or distance

Abstract

We discuss images of the star clusters GLIMPSE C01 (GC01) and GLIMPSE C02 (GC02) that were recorded with the Subaru IRCS. Distortions in the wavefront were corrected with the RAVEN adaptive optics (AO) science demonstrator, allowing individual stars in the central regions of both clusters -- where the fractional contamination from non-cluster objects is lowest -- to be imaged. In addition to J, H, and K' images, both clusters were observed through a narrow-band filter centered near 3.05um; GC01 was also observed through two other narrow-band filters that sample longer wavelengths. Stars in the narrow-band images have a FWHM that is close to the telescope diffraction limit, demonstrating that open loop AO systems like RAVEN can deliver exceptional image quality. The near-infrared color magnitude diagram of GC01 is smeared by non-uniform extinction with a dispersion +/- 0.13 magnitudes in A_K. The Red Clump is identified in the K luminosity function (LF) of GC01, and a distance modulus of 13.6 is found. The K LF of GC01 is consistent with a system that is dominated by stars with an age > 1 Gyr. As for GC02, the K LF is flat for K > 16, and the absence of a sub-giant branch argues against an old age if the cluster is at a distance of ~ 7 kpc. Archival SPITZER [3.6] and [4.5] images of the clusters are also examined, and the red giant branch-tip is identified.