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Unbiased Differential Size Evolution and the Inside-Out Growth of Galaxies in the Deep CANDELS GOODS Fields at 1≤z≤7

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Original languageEnglish
Number of pages16
JournalAstrophysical Journal
Issue number2
Publication statusPublished - 16 Dec 2019



We present a size analysis of a sample of 49,000 galaxies from the CANDELS GOODS North and South fields using redshift-independent relative surface brightness metrics to determine an unbiased measure of the differential size evolution of galaxies at 1 z 7. We introduce a novel method of removing foreground objects from distant galaxy (z > 3) images that makes use of the Lyman-break at 912A, in what we call `2-D Lyman-Break Imaging'. The images used are in the rest-frame optical at z < 3 and progressively bluer bands at z > 3. They are therefore subject to K-correction and cosmological dimming effects which are tested and corrected for. We separately consider a mass-selected sample (with masses in the range 109MM1010:5M) and a number density selected sample (using a constant number density of n = 1 10&#x100000;4Mpc&#x100000;3). Instead of utilising the commonly used, but potentially biased, effective radii for size measurements, we measure the redshift-independent Petrosian radius, defined by the parameter , for each galaxy for three values of and use this as a proxy for size. The evolution of the measured radii can be described by a power-law of the form RPetr = (1 + z) kpc where < 0. We nd that the outer radius increases more rapidly, suggesting that as a galaxy grows mass is added to its outer regions via an inside-out growth. This growth is stronger for the number density selected sample, with a growth rate of nearly three in the outer radii compared to the inner. We test and confirm these results using a series of image simulations.

    Research areas

  • astro-ph.GA

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