Deep Near‐Infrared Imaging of a Field in the Outer Disk of M82 with the Altair Adaptive Optics System on Gemini‐North

Abstract

ABSTRACTDeep H and K′ images recorded with the Altair adaptive optics system and Near‐Infrared Imager on Gemini‐North are used to probe the red stellar content in a field with a projected distance of 1 kpc above the disk plane of the starburst galaxy M82. The data have an angular resolution of 008 FWHM, and individual asymptotic giant branch (AGB) and red giant branch (RGB) stars are resolved. The AGB extends to at least 1.7 mag in K above the RGB tip, which occurs at K = 21.7. The relative numbers of bright AGB stars and RGB stars are consistent with stellar evolution models, and one of the brightest AGB stars has an H−K color and K brightness that is consistent with it being a C star. The brightnesses of the AGB stars suggest that they formed during intermediate epochs, possibly after the last major interaction with M81. Therefore, star formation in M82 during intermediate epochs may not have been restricted to the plane of the disk.