The size evolution of star-forming galaxies since z ∼ 7 using ZFOURGE

Rebecca J. Allen, Glenn G. Kacprzak, Karl Glazebrook, Ivo Labbé, Kim-Vy H Tran, Lee R. Spitler, Michael Cowley, Themiya Nanayakkara, Casey Papovich, Ryan Quadri, Caroline M S Straatman, Vithal Tilvi, Pieter Van Dokkum

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    For the first time, we present the size evolution of a mass-complete (log(M /M o) > 10) sample of star-forming galaxies over redshifts z = 1-7, selected from the FourStar Galaxy Evolution Survey. Observed H-band sizes are measured from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) Hubble Space Telescope (HST)/F160W imaging. Distributions of individual galaxy masses and sizes illustrate that a clear mass-size relation exists up to z ∼ 7. At z ∼ 7, we find that the average galaxy size from the mass-size relation is more compact at a fixed mass of log(M /M o) = 10.1, with kpc, than at lower redshifts. This is consistent with our results from stacking the same CANDELS HST/F160W imaging, when we correct for galaxy position angle alignment. We find that the size evolution of star-forming galaxies is well fit by a power law of the form kpc, which is consistent with previous works for normal star-formers at 1 < z < 4. In order to compare our slope with those derived Lyman break galaxy studies, we correct for different IMFs and methodology and find a slope of -0.97 ± 0.02, which is shallower than that reported for the evolution of Lyman break galaxies (LBGs) at z > 4 (). Therefore, we conclude the LBGs likely represent a subset of highly star-forming galaxies that exhibit rapid size growth at z > 4.

    Original languageEnglish
    Article numberL11
    Pages (from-to)1-7
    Number of pages7
    JournalAstrophysical Journal Letters
    Issue number2
    Publication statusPublished - 10 Jan 2017

    Bibliographical note

    Copyright 2017 The American Astronomical Society. First published in Astrophysical Journal Letters, 834(2), L11. The original publication is available at, published by IOP Publishing. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.


    • galaxies: evolution
    • galaxies: high-redshift
    • galaxies: structure


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