THE DUAL ORIGIN OF STELLAR HALOS
- Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States)
- Haverford College, Department of Astronomy, 370 Lancaster Avenue, Haverford, PA 19041 (United States)
- California Institute of Technology, M/C 350-17, Pasadena, CA 91125 (United States)
- Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States)
- Jeremiah Horrocks Institute, University of Central Lancashire, Preston, PR1 2HE (United Kingdom)
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, L8S4M1 (Canada)
We investigate the formation of the stellar halos of four simulated disk galaxies using high-resolution, cosmological SPH + N-body simulations. These simulations include a self-consistent treatment of all the major physical processes involved in galaxy formation. The simulated galaxies presented here each have a total mass of {approx}10{sup 12} M{sub sun}, but span a range of merger histories. These simulations allow us to study the competing importance of in situ star formation (stars formed in the primary galaxy) and accretion of stars from subhalos in the building of stellar halos in a {lambda}CDM universe. All four simulated galaxies are surrounded by a stellar halo, whose inner regions (r < 20 kpc) contain both accreted stars, and an in situ stellar population. The outer regions of the galaxies' halos were assembled through pure accretion and disruption of satellites. Most of the in situ halo stars formed at high redshift out of smoothly accreted cold gas in the inner 1 kpc of the galaxies' potential wells, possibly as part of their primordial disks. These stars were displaced from their central locations into the halos through a succession of major mergers. We find that the two galaxies with recently quiescent merger histories have a higher fraction of in situ stars ({approx}20%-50%) in their inner halos than the two galaxies with many recent mergers ({approx}5%-10% in situ fraction). Observational studies concentrating on stellar populations in the inner halo of the Milky Way will be the most affected by the presence of in situ stars with halo kinematics, as we find that their existence in the inner few tens of kpc is a generic feature of galaxy formation.
- OSTI ID:
- 21336045
- Journal Information:
- Astrophysical Journal, Vol. 702, Issue 2; Other Information: DOI: 10.1088/0004-637X/702/2/1058; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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