http://arxiv.org/abs/1409.1832
We present the results of a study investigating the sizes and morphologies of redshift 4<z<8 galaxies in the CANDELS GOODS-S, HUDF 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 log-normal size distribution, rather than the arithmetic mean size. Parameterizing the evolution of galaxy half-light radius as r50\propto(1+z)^n, we find n=-0.34\pm0.29 at bright UV-luminosities (0.3L*(z=3)<L<L*) and n=-0.57\pm0.76 at faint luminosities (0.12L*<L<0.3L*). In a given luminosity range, these measurements are consistent with no evolution in typical galaxy size with redshift. Moreover, simulations based on artificially redshifting our z~4 galaxy sample also confirm that we cannot reject the null hypothesis of no size evolution. This result is caused by the systematic under-estimation of the largest galaxy sizes, such that the build-up in the tail of the log-normal size distribution seen at z~4-5 cannot be distinguished from a scenario where the large, low surface-brightness, galaxies at higher redshifts have their sizes systematically underestimated. To explore the evolution of galaxy morphology we first compare asymmetry measurements to those from a large sample of simulated single Sersic profiles, in order to robustly categorise galaxies as either `smooth’ or `disturbed’. Comparing the disturbed fraction amongst bright (MUV<-20) galaxies at each redshift to that obtained by artificially redshifting our z~4 galaxy sample, we find no clear evidence for evolution in galaxy morphology over the redshift interval 4<z<8. Therefore, based on our results, a bright (MUV<-20) galaxy at z~6 is no more likely to be measured as `disturbed’ than a comparable galaxy at z~4. (abr.)
E. Curtis-Lake, R. McLure, J. Dunlop, et. al.
Mon, 8 Sep 14
33/69
Comments: 19 pages, 12 figures, 3 tables, submitted to MNRAS
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