A new view of the size-mass distribution of galaxies : using r20 and r80 Instead of r50

Ondertitel:A new view of the size-mass distribution of galaxies : using r(20) and r(80) Instead of r(50)

When investigating the sizes of galaxies it is standard practice to use the half-light radius, r(50). Here we explore the effects of the size definition on the distribution of galaxies in the size-stellar mass plane. Specifically, we consider r(20) and r(80), the radii that contain 20% and 80% of a galaxy's total luminosity, as determined from a Sersic profile fit, for galaxies in the 3D-HST/CANDELS and COSMOS-DASH surveys. These radii are calculated from size catalogs based on a simple calculation assuming a Sersic profile. We find that the size-mass distributions for r(20) and r(80) are markedly different from each other and also from the canonical r(50) distribution. The most striking difference is in the relative sizes of star-forming and quiescent galaxies at fixed stellar mass. Whereas quiescent galaxies are smaller than star-forming galaxies in r(50), this difference nearly vanishes for r(80). By contrast, the distance between the two populations increases for r(20). Considering all galaxies in a given stellar mass and redshift bin we detect a significant bimodality in the distribution of r(20), with one peak corresponding to star-forming galaxies and the other to quiescent galaxies. We suggest that different measures of the size are tracing different physical processes within galaxies; r(20) is closely related to processes controlling the star formation rate of galaxies and r(80) may be sensitive to accretion processes and the relation of galaxies with their halos.

Jaar van publicatie:2019

BOF-keylabel:ja

IOF-keylabel:ja

BOF-publication weight:2

CSS-citation score:2

Auteurs:International

Authors from:Higher Education

Toegankelijkheid:Open