Abstract
We present the results of a study investigating the sizes and
morphologies of redshift 4 <z <8 galaxies in the CANDELS (Cosmic
Assembly Near-infrared Deep Extragalactic Legacy Survey) GOODS-S (Great
Observatories Origins Deep Survey southern field), HUDF (Hubble
Ultra-Deep Field) and HUDF parallel fields. Based on non-parametric
measurements and incorporating a careful treatment of measurement
biases, we quantify the typical size of galaxies at each redshift as the
peak of the lognormal size distribution, rather than the arithmetic mean
size. Parametrizing the evolution of galaxy half-light radius as
r50 ∝ (1 + z)n, we find n = -0.20 ±
0.26 at bright UV-luminosities (0.3L*(z = 3) <L <
L*) and n = -0.47 ± 0.62 at faint luminosities
(0.12L* <L <0.3L*). Furthermore,
simulations based on artificially redshifting our z ˜ 4 galaxy
sample show that we cannot reject the null hypothesis of no size
evolution. We show that this result is caused by a combination of the
size-dependent completeness of high-redshift galaxy samples and the
underestimation of the sizes of the largest galaxies at a given epoch.
To explore the evolution of galaxy morphology we first compare asymmetry
measurements to those from a large sample of simulated single
Sérsic profiles, in order to robustly categorize galaxies as
either `smooth' or `disturbed'. Comparing the disturbed fraction amongst
bright (M1500 ≤ -20) galaxies at each redshift to that
obtained by artificially redshifting our z ˜ 4 galaxy sample,
while carefully matching the size and UV-luminosity distributions, we
find no clear evidence for evolution in galaxy morphology over the
redshift interval 4 <z <8. Therefore, based on our results, a
bright (M1500 ≤ -20) galaxy at z ˜ 6 is no more
likely to be measured as `disturbed' than a comparable galaxy at z
˜ 4, given the current observational constraints.
Original language | English |
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Pages (from-to) | 440-464 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 457 |
Issue number | 1 |
DOIs | |
Publication status | Published - 1 Mar 2016 |
Keywords
- galaxies: evolution
- galaxies: high-redshift
- galaxies: star formation
- galaxies: structure
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Ross McLure
- School of Physics and Astronomy - Personal Chair in Extragalactic Astrophysics
Person: Academic: Research Active