Galaxy And Mass Assembly (GAMA): mass–size relations of z < 0.1 galaxies subdivided by Sérsic index, colour and morphology

Abstract

We use data from the Galaxy And Mass Assembly (GAMA) survey in the redshift range 0.01<z<0.1 (8399 galaxies in g to K s bands) to derive the stellar mass -halflight radius relations for various divisions of 'early' and 'late'-type samples. We find the choice of division between early and late (i.e., colour, shape, morphology) is not particularly critical, however, the adopted mass limits and sample selections (i.e., the careful rejection of outliers and use of robust fitting methods) are important. In particular we note that for samples extending to low stellar mass limits (< 10 10 M ) the Sérsic index bimodality, evident for high mass systems, becomes less distinct and no-longer acts as a reliable separator of early-and late-type systems. The final set of stellar mass -half-light radius relations are reported for a variety of galaxy population subsets in 10 bands (ugrizZY JHK s ) and are intended to provide a comprehensive low-z benchmark for the many ongoing high-z studies. Exploring the variation of the stellar mass -half-light radius relations with wavelength we confirm earlier findings that galaxies appear more compact at longer wavelengths albeit at a smaller level than previously noted: at 10 10 M both spiral systems and ellipticals show a decrease in size of 13% from g to K s (which is near linear in log wavelength). Finally we note that the sizes used in this work are derived from 2D Sérsic light profile fitting (using GALFIT3), i.e., elliptical semi-major half light radii, improving on earlier low-z benchmarks based on circular apertures.

Galaxy And Mass Assembly (GAMA): $\mathcal {M_\star }\text{--}R_{\rm e}$ relations ofz= 0 bulges, discs and spheroids

“…We adopt a simple power law, following Shen et al (2003) and Lange et al (2015), to fit the M − Re relation:…”

“…This is most obvious in the Sérsic index -colour plane where the single component Sd and elliptical galaxies occupy distinct peaks with composite galaxies (S0abc) scattered between and around these peaks (see e.g., Driver et al 2006;Cameron et al 2009;Kelvin et al 2012;Lange et al 2015). These components have very different characteristics with spheroids typically having a featureless appearance and being pressure supported.…”

Sizes, colour gradients and resolved stellar mass distributions for the massive cluster galaxies in XMMUJ2235-2557 atz= 1.39

“…Nevertheless, different authors disagree on the extent of the reduction in sizes in various datasets. For example, in a recent study Lange et al (2015) revisited the GAMA sample with deeper NIR imaging data and found a smaller size decrease, ∼ 13% from g to K s band.…”

“…We also attempt to divide the sample in mass bins as in Lange et al (2015) to investigate the size change with wavelength for different masses. Lange et al (2015) showed that the size reduction decreases from ∼ 13% for local passive galaxies with log(M * /M ) = 10.0 to ∼ 11% for those with log(M * /M ) = 11.0.…”

The size evolution of star-forming and quenched galaxies in the IllustrisTNG simulation

“…Galaxy size is a basic observational property that is found to significantly vary with galaxy mass, color or star-formation activity, and redshift (Shen et al 2003;Ferguson et al 2004;Trujillo et al 2006;Elmegreen et al 2007;Williams et al 2010;Mosleh et al 2012;Ono et al 2013;van der Wel et al 2014;Lange et al 2015). These dependencies encode important information on the formation processes of galaxies of different types.…”