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ZFOURGE: Using Composite Spectral Energy Distributions to Characterize Galaxy Populations at 1 z 4

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posted on 2024-08-06, 11:41 authored by Ben Forrest, Kim Vy H. Tran, Adam Broussard, Jonathan H. Cohn, Robert C. Kennicutt, Casey Papovich, Rebecca AllenRebecca Allen, Michael Cowley, Karl GlazebrookKarl Glazebrook, Glenn KacprzakGlenn Kacprzak, Lalitwadee Kawinwanichakij, Themiya NanayakkaraThemiya Nanayakkara, Brett Salmon, Lee R. Spitler, Caroline M.S. Straatman
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 Å 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 Hα emission (EWREST ∼ 40 Å) compared to more typical star-forming composite SEDs at log10(M/M o) ∼ 10.5 (EWREST ∼ 80 Å). Together with their smaller sizes (3 kpc vs. 4 kpc) and higher Sérsic 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.

Funding

Simulating galaxy ecosystems

Australian Research Council

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PDF (Published version)

ISSN

1538-4357

Journal title

Astrophysical Journal

Volume

863

Issue

2

Article number

article no. 131

Pagination

1 p

Publisher

Institute of Physics Publishing

Copyright statement

Copyright © 2018 The American Astronomical Society. All rights reserved. The published version is reproduced in accordance with the copyright policy of the publisher.

Language

eng

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