Centro de Astrofísica U.Porto

The structural and size evolution of star-forming galaxies over the last 11 Gyr

A. Paulino-Afonso, D. Sobral, F. Buitrago, J. Afonso

Abstract
We present new results on the evolution of rest-frame blue/UV sizes and Sersic indices of H $α$ -selected star-forming galaxies over the last 11 Gyrs. We investigate how the perceived evolution can be affected by a range of biases and systematics such as cosmological dimming and resolution effects. We use GALFIT and an artificial redshifting technique, which includes the luminosity evolution of H $α$ -selected galaxies, to quantify the change on the measured structural parameters with redshift. We find typical sizes of 2 to 3 kpc and Sersic indices of n~1.2, close to pure exponential disks all the way from z=2.23 to z=0.4. At z=0 we find typical sizes of 4-5 kpc. Our results show that, when using GALFIT, cosmological dimming has a negligible impact on the derived effective radius for galaxies with 〈10 kpc, but we find a ~20% bias on the estimate of the median Sersic indices, rendering galaxies more disk-like. Star-forming galaxies have grown on average by a factor of 2-3 in the last 11 Gyrs with $r_{e} \propto (1 + z)^{- 0.75}$ . By exploring the evolution of the stellar mass-size relation we find evidence for a stronger size evolution of the most massive star-forming galaxies since z~2, as they grow faster towards z~0 when compared to the lower stellar mass counterparts. As we are tracing the rest-frame blue/UV, we are likely witnessing the growth of disks where star formation is ongoing in galaxies while their profiles remain close to exponential disks, n〈1.5, across the same period.

Keywords
galaxies: evolution – galaxies: star formation – galaxies: structure.

Monthly Notices of the Royal Astronomical Society
Volume 465, Page 2717
November 2016

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Institute of Astrophysics and Space Sciences