http://arxiv.org/abs/1409.1583
From mock Hubble Space Telescope images, we quantify non-parametric statistics of galaxy morphology, thereby predicting the emergence of relationships among stellar mass, star formation, and observed rest-frame optical structure at 1 < z < 3. We measure these diagnostics of galaxy morphology from cosmological simulations of the formation of 22 central galaxies with 9.3 < log_10 M_*/M_sun < 10.7. These high-spatial-resolution zoom-in calculations enable accurate modeling of the rest-frame UV and optical morphology. This could depend strongly on dust radiative transfer, which we model using the Sunrise code. Even with small numbers of galaxies, we find that structural evolution is neither universal nor monotonic: galaxy interactions may trigger either bulge or disc formation, and optically bulge-dominated galaxies at this mass may not remain so forever. Simulated galaxies with M_* > 10^10 M_sun contain relatively more disc-dominated light profiles than those with lower mass, reflecting significant disc brightening in some haloes at 1 < z < 2. By this epoch, simulated galaxies with specific star formation rates below 10^-9.7 yr^-1 are more likely than normal star-formers to have a broader mix of structural types, especially at M_* > 10^10 M_sun. We analyze a cosmological major merger at z~1.5 and find that the newly proposed MID morphology diagnostics trace later stages while G-M20 trace earlier ones. MID is sensitive also to clumpy star-forming discs. The observability time of typical MID-enhanced events in our simulation sample is less than 100 Myr. A larger sample of cosmological assembly histories may be required to calibrate such diagnostics in the face of their sensitivity to viewing angle, segmentation algorithm, and various phenomena such as clumpy star formation and minor mergers.
G. Snyder, J. Lotz, C. Moody, et. al.
Mon, 8 Sep 14
60/69
Comments: 20 pages, 13 figures, submitted to MNRAS