期刊
ASTROPHYSICAL JOURNAL
卷 773, 期 1, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/773/1/43
关键词
galaxies: evolution; galaxies: spiral; Galaxy: evolution; Galaxy: formation; Galaxy: kinematics and dynamics; Galaxy: structure
资金
- Vanderbilt Office of the Provost through the Vanderbilt Initiative in Data-intensive Astrophysics (VIDA)
- Ohio State University
- Center for Cosmology and Astro-Particle Physics at The Ohio State University
- Marie Curie Actions for People COFUND Program through the ETH Zurich Postdoctoral Fellowship
- NSF [AST-0908910, AST-1009505, AST-1211853, OIA-1124453]
- NASA [NNX12AF87G]
- Distinguished University Fellowship
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [1009505, 1211853] Funding Source: National Science Foundation
- Office of Integrative Activities
- Office Of The Director [1124453] Funding Source: National Science Foundation
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(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.
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