Program: GN-2012A-Q-22

The near-infrared (NIR) region (1-2.4 micron) contains signatures of AGN, molecular gas, ionization mechanisms, stellar evolution phases and dust. Moreover, the NIR range offers significantly lower dust obscuration, high spatial resolution with adaptive optics, and will be the standard spectral regime for future studies using JWST. Despite its enormous information content and importance, the NIR is largely unexplored in galaxies, and remarkably little is known about how NIR diagnostics contrast with optical tracers. We propose to undertake crucial groundwork in characterizing the NIR spectral energy distribution of nearby galaxies, drawing from the Atlas3D sample of early-type galaxies (ETGs). The sample has excellent supporting data, including optical integral-field spectroscopy, interferometric CO maps, UV to mid-IR photometry, making these the best understood ETGs available. In this pilot program, we focus on stellar populations, and propose a GNIRS cross-dispersed 'snapshot' survey of 26 galaxies from Atlas3D spanning mean ages of 1-14 Gyr, at similar velocity dispersion and metallicity. This will provide a conclusive view on the debated importance of TP-AGB stars in the young stellar populations of galaxies. We will simultaneously investigate the interactions of putative AGN and molecular gas - a mechanism for 'feedback' quenching star formation, often quoted but little understood.