Diverse Structural Evolution at z > 1 in Cosmologically Simulated Galaxies

Abstract

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 automated diagnostics of galaxy morphology in cosmological simulations of the formation of 22 central galaxies with 9.3 < log10 M_*/M_sun < 10.7. These high-spatial-resolution zoom-in calculations enable accurate modeling of the rest-frame UV and optical morphology. Even with small numbers of galaxies, we find that structural evolution is neither universal nor monotonic: galaxy interactions can 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 merger 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.

23 pages, 16 figures, MNRAS accepted version

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Cited by in corpus (10)

• Compaction and Quenching of High-z Galaxies in Cosmological Simulations: Blue and Red Nuggets
• The Formation of Massive, Compact Galaxies at z=2 in the Illustris Simulation
• The role of mergers and halo spin in shaping galaxy morphology
• Morphology and star formation in IllustrisTNG: the build-up of spheroids and discs
• z~2: An Epoch of Disk Assembly
• The imprint of clump formation at high redshift. I. A disc alpha-abundance dichotomy
• Massive Close Pairs Measure Rapid Galaxy Assembly in Mergers at High Redshift
• Distinguishing Mergers and Disks in High Redshift Observations of Galaxy Kinematics
• Finding the Needles in the Haystacks: High-Fidelity Models of the Modern and Archean Solar System for Simulating Exoplanet Observations
• The Global Star-Formation Law by Supernova Feedback