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Cited by 343Galaxies: Formation, Evolution, PhenomenaStellar, planetary, and galactic studiesAstrophysics and Star Formation Studies

THE DUAL ORIGIN OF STELLAR HALOS

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Zolotov, Adi, Willman, Beth, Brooks, Alyson M., Governato, Fabio, Brook, Chris B., Hogg, David W., Quinn, Tom, Stinson, Greg·2009·The Astrophysical Journal
DOI 10.1088/0004-637x/702/2/1058
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Abstract

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 ∼10 12 M ☉ , 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 ΛCDM 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 (∼20%–50%) in their inner halos than the two galaxies with many recent mergers (∼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.

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Crossref · 10.1088/0004-637x/702/2/1058

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  • What Norris called the contracted halo is actually largely heated proto-thick disk, formed mostly in situ but in a disk that was heavily dynamically perturbed during a merger.

    “We now know from the Gaia DR2 data that what Norris (1994) called the contracted halo is actually largely heated (proto-)thick disk.So it was indeed formed mostly in situ; however, the stars did not form during a collapse but in a disk that was heavily dynamically perturbed during a merger, as in the simulations of Zolotov et al. (2009) and Tissera et al. (2013).”

    From Streams, Substructures, and the Early History of the Milky Way (2020) · cites this paper as Zolotov et al. 2009

    Section 3.1 (page unavailable) says in situ stars formed in gas that also formed the disk and were displaced into the halo by mergers, supporting the proposed disk-and-merger mechanism. But it also describes their formation as involving a rapid inflow and collapse of gas, so the source does not support the sentence’s unqualified contrast with collapse. The paper’s simulations do not establish the Gaia-based identification of Norris’s contracted halo. (LLM, conf=0.86)

    Experimental — accuracy not yet measured

  • Mergers can lead to the formation of a bulge, thickening of the disk, and formation of a halo of stars from the original disk and the destroyed satellite.

    “Depending on the mass ratio, such an event could lead to the formation of a bulge (Barnes 1992), or merely to the thickening of the disk (Quinn et al. 1993), and possibly also to the formation of a halo of stars from the original disk and the destroyed satellite (Zolotov et al. 2009, Purcell et al. 2010), as seems to have happened for the Milky Way (see Section 4.2 for details).”

    From Streams, Substructures, and the Early History of the Milky Way (2020) · cites this paper as Zolotov et al. 2009

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Research works printed but not linked: 3

  1. Governato, F., et al. 2009, MNRAS, in press
  2. Guhathakurta, P., Ostheimer, J. C., Gilbert, K. M., Rich, R. M., Majewski, S. R., Kalirai, J. S., Reitzel, D. B., & Patterson, R. J. 2005, arXiv:0502366
  3. Smith, M. C., et al. 2009, in press

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Authors
Zolotov, A., Willman, B., Brooks, A. M., Governato, F., Brook, C. B., Hogg, D. W., Quinn, T., & Stinson, G.
Affiliations
  • Haverford College (US)
  • California Institute of Technology (US)
  • University of Washington (US)
  • University of Lancashire (GB)
  • New York University (US)
  • McMaster University (CA)
ORCID
Venue
The Astrophysical Journal
Publisher
American Astronomical Society
Published
2009-08-18
Volume
702
Issue
2
Pages
1058-1067
ISSN
  • 0004-637X (ISSN-L)
  • 1538-4357
DOI
10.1088/0004-637x/702/2/1058
OpenAlex
W2085130064
Cited by
342
References
54
Citations by year
2026: 5 · 2025: 14 · 2024: 20 · 2023: 15 · 2022: 15 · 2021: 8 · 2020: 30 · 2019: 32 · 2018: 18 · 2017: 18 · 2016: 29 · 2015: 18 · 2014: 17 · 2013: 19 · 2012: 27
FWCI
13.95
Type
journal article
Language
en
Open access
Locations
  • The Astrophysical Journal (publishedVersion)
  • arXiv (Cornell University) (acceptedVersion)
  • Rutgers University Community Repository (Rutgers University) (submittedVersion)
  • CaltechAUTHORS (California Institute of Technology) (submittedVersion)
  • arXiv (Cornell University)
  • PhDT
Funders
  • National Science Foundation (0205413, 0607819)
  • Smithsonian Institution
  • National Aeronautics and Space Administration (NNX08AJ48G, ATP NNX08AG84G, NNX08AG84G)
  • Haverford College
  • York University
  • Ames Research Center
  • Smithsonian Astrophysical Observatory
  • Science and Technology Facilities Council (ST/F002432/1)
Topics
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Galaxies: Formation, Evolution, Phenomena
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Stellar, planetary, and galactic studies
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astrophysics and Star Formation Studies
Keywords
stellar halo, in situ star formation, halo accretion, major mergers, disk galaxy evolution, satellite disruption, halo kinematics, Galactic halo

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