ZFOURGE: Using Composite Spectral Energy Distributions to Characterize Galaxy Populations at 1 < z < 4
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2018. The American Astronomical Society. All rights reserved. We investigate the properties of galaxies as they shut off star formation over the 4 billion years surrounding peak cosmic star formation. To do this, we categorize 7000 galaxies from 1 < z < 4 into 90 groups based on the shape of their spectral energy distributions (SEDs) and build composite SEDs with R 50 resolution. These composite SEDs show a variety of spectral shapes and also show trends in parameters such as color, mass, star formation rate, and emission-line equivalent width. Using emission-line equivalent widths and strength of the 4000 break, , we categorize the composite SEDs into five classes: extreme emission line, star-forming, transitioning, post-starburst, and quiescent galaxies. The transitioning population of galaxies shows modest H emission (EWREST 40 ) compared to more typical star-forming composite SEDs at log10(M/M o) 10.5 (EWREST 80 ). Together with their smaller sizes (3 kpc vs. 4 kpc) and higher Srsic indices (2.7 vs. 1.5), this indicates that morphological changes initiate before the cessation of star formation. The transitional group shows a strong increase of over 1 dex in number density from z 3 to z 1, similar to the growth in the quiescent population, while post-starburst galaxies become rarer at z 1.5. We calculate average quenching timescales of 1.6 Gyr at z 1.5 and 0.9 Gyr at z 2.5 and conclude that a fast-quenching mechanism producing post-starbursts dominated the quenching of galaxies at early times, while a slower process has become more common since z 2.
Forrest, B., Tran, K., Broussard, A., Cohn, J. H., Kennicutt, R., Papovich, C., ... Straatman, C.
complete list of authors
Forrest, Ben||Tran, Kim-Vy H||Broussard, Adam||Cohn, Jonathan H||Kennicutt, Robert C Jr||Papovich, Casey||Allen, Rebecca||Cowley, Michael||Glazebrook, Karl||Kacprzak, Glenn G||Kawinwanichakij, Lalitwadee||Nanayakkara, Themiya||Salmon, Brett||Spitler, Lee R||Straatman, Caroline MS