INSIDE OUT AND UPSIDE DOWN: TRACING THE ASSEMBLY OF A SIMULATED DISK GALAXY USING MONO-AGE STELLAR POPULATIONS
- Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States)
- Institute for Astronomy, ETH Zuerich, Wolgang-Pauli-Strasse 27, CH-8093 Zuerich (Switzerland)
- Anthropology Institute and Museum, University of Zuerich, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland)
- Institute for Theoretical Physics, University of Zuerich, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland)
- Department of Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)
We analyze the present day structure and assembly history of a high-resolution hydrodynamic simulation of the formation of a Milky-Way-(MW)-like disk galaxy, from the ''Eris'' simulation suite, dissecting it into cohorts of stars formed at different epochs of cosmic history. At z = 0, stars with t{sub form} < 2 Gyr mainly occupy the stellar spheroid, with the oldest (earliest forming) stars having more centrally concentrated profiles. The younger age cohorts populate disks of progressively longer radial scale lengths and shorter vertical scale heights. At a given radius, the vertical density profiles and velocity dispersions of stars vary smoothly as a function of age, and the superposition of old, vertically extended and young, vertically compact cohorts gives rise to a double-exponential profile like that observed in the MW. Turning to formation history, we find that the trends of spatial structure and kinematics with stellar age are largely imprinted at birth, or immediately thereafter. Stars that form during the active merger phase at z > 3 are quickly scattered into rounded, kinematically hot configurations. The oldest disk cohorts form in structures that are radially compact and relatively thick, while subsequent cohorts form in progressively larger, thinner, colder configurations from gas with increasing levels of rotational support. The disk thus forms ''inside out'' in a radial sense and ''upside down'' in a vertical sense. Secular heating and radial migration influence the final state of each age cohort, but the changes they produce are small compared to the trends established at formation. The predicted correlations of stellar age with spatial and kinematic structure are in good qualitative agreement with the correlations observed for mono-abundance stellar populations in the MW.
- OSTI ID:
- 22140257
- Journal Information:
- Astrophysical Journal, Vol. 773, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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