The Onset of Star-Formation Quenching in Massive Galaxies in the Early Universe

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The rate of star formation peaked when the Universe was 3 billion years old. Curiously, when you look back even further in time, when the Universe was only 1-2 billion years old, some galaxies have seemingly already completed their growth, becoming very massive, with little ongoing star formation. Finkelstein and his team will use data from the Spitzer/Hobby-Eberly Telescope Dark Energy Experiment Exploratory Large Area (SHELA) survey to discover and catalog 5000-10,000 massive galaxies and quantify how many are quiescent. To investigate why these galaxies had such a short and effective growth spurt the team will make a detailed comparison to simulations, deciphering which combination of physical processes reproduce the observations. A cohort of undergraduate students will be paired with graduate students to form the first Vertically Integrated Project Team at UT Austin. Secondary school teachers will attend a residential workshop at McDonald Observatory, resulting in ~4,500 students learning about this research through classroom activities during this 3-year project. The 23 square degree SHELA survey consists of optical imaging from the Cerro Tololo Inter-American Observatory/Dark Energy Camera (5-sigma depths of ugriz=25-26.5 AB mag; Y=22), near-infrared imaging from the Kitt Peak National Observatory Mayall 4 m Telescope/National Optical-Infrared Astronomy Research Laboratory’s Extremely Wide-Field Infrared Imager (K=23) and the Visible and Infrared Survey Telescope for Astronomy (J=21.3, K=20.9), mid-infrared imaging from Spitzer/Infrared Array Camera ([3.6], [4.5]= 22.3 mag), as well as coverage in the X-rays from the Chandra X-ray Observatory and sub-millimeter from the Herschel Space Observatory. Finkelstein and his team will leverage this order of magnitude increase in sample size to i) publish a multi-wavelength photometric catalog of massive (log M/Msol 11) galaxies at 3z5, robust against both Poisson and cosmic variance; ii) measure the quiescent fraction as a function of stellar mass and redshift; iii) perform a critical analysis of contamination rates in the quiescent galaxy sample using spectroscopic observations with the Atacama Large Millimeter/submillimeter Array and the Keck/Multi-Object Spectrometer For Infra-Red Exploration, and iv) compare the data to multiple theoretical simulations to explore which simulation best matches the observations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.