Raven and the Center of Maffei 1: Multi-Object Adaptive Optics Observations of the Center of a Nearby Elliptical Galaxy and the Detection of an Intermediate Age Population

TL;DR

This study uses high-resolution near-infrared spectra obtained with adaptive optics to analyze the stellar populations in Maffei 1's center, revealing an intermediate age population and the presence of carbon stars.

Contribution

First application of multi-object adaptive optics to study the stellar content of a nearby elliptical galaxy's core, detecting intermediate age stars and carbon star features.

Findings

Detection of C_2 absorption band indicating carbon stars.

Evidence for an intermediate age stellar population dominates the core.

Red stars are well-mixed within 15 arcseconds of the galaxy center.

Abstract

Near-infrared (NIR) spectra that have an angular resolution of ~ 0.15 arcsec are used to examine the stellar content of the central regions of the nearby elliptical galaxy Maffei 1. The spectra were recorded at the Subaru Telescope, with wavefront distortions corrected by the RAVEN Multi-Object Adaptive Optics science demonstrator. The Ballick-Ramsey C_2 absorption bandhead near 1.76 microns is detected, and models in which 10 - 20% of the light near 1.8 microns originates from stars of spectral type C5 reproduce this feature. Archival NIR and mid-infrared images are also used to probe the structural and photometric properties of the galaxy. Comparisons with models suggest that an intermediate age population dominates the spectral energy distribution between 1 and 5 microns near the galaxy center. This is consistent not only with the presence of C stars, but also with the large HBeta index that has been measured previously for Maffei 1. The J-K color is more-or-less constant within 15 arcsec of the galaxy center, suggesting that the brightest red stars are well-mixed in this area.