Chronicling the Histories of Galaxies at Distances of 1 to 20 Mpc: Simulated Performance of 30-m, 50-m, and 100-m Telescopes

K. Olsen¹, B. Ellerbroek², S. Strom^3
1 Cerro Tololo Inter-American Observatory, Casilla 603, La Serena, Chile
² TMT Project Office, California Institute of Technology, Pasadena, CA 91126
³ National Optical Astronomy Observatory, 950 N. Cherry Ave., Tucson, AZ 85719
A key science driver for future ELTs is to chronicle the complete formation and evolutionary histories of a meaningful number of nearby galaxies through their resolved stars. The goal will be to measure the entire star formation and chemical enrichment histories of a sample of galaxies that includes all Hubble types and covers all of their components, demanding photometry of stars in regions with high surface brightness at distances of up to ~ 20 Mpc. We present simulations that compare the abilities of 30-m, 50-m, and 100-m telescopes to recover the correct stellar population mix represented in field star color-magnitude diagrams observed with I, J, H, and K filters. As input, our simulations use scenes containing stars drawn from a mix of model isochrones with differing ages and metallicities, with surface densities set to match that found in typical spiral bulges and disks and out to a few effective radii in giant elliptical galaxies. We convolve these scenes with PSFs corresponding to the projected performance of MCAO systems containing two deformable mirrors, including the effect of realistic variations in the atmospheric turbulence profile over the span of the observations. From PSF-fitting photometry of the simulated images, we derive the best-fit stellar population mixes through an automated maximum likelihood analysis. These simulations provide a way to evaluate the scientific advances enabled by ELTs of differing apertures in the area of extragalactic stellar populations.

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