期刊
ASTROPHYSICAL JOURNAL
卷 833, 期 2, 页码 -出版社
IOP Publishing Ltd
DOI: 10.3847/1538-4357/833/2/158
关键词
galaxies: elliptical and lenticular, CD; galaxies: evolution; galaxies: halos; galaxies: stellar content
资金
- NSF Graduate Research Fellowship Program [DGE-1144152]
- NASA grant [NNX15AK14G, NNX12AC67G]
- NSF grant [AST-1313280, AST-1312095]
- Packard Foundation
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [1312095] Funding Source: National Science Foundation
- NASA [807612, NNX12AC67G, 52414, NNX15AK14G] Funding Source: Federal RePORTER
Long dynamical timescales in the outskirts of galaxies preserve the information content of their accretion histories, for example in the form of stellar population gradients. We present a detailed analysis of the stellar halo properties of a statistically representative sample of early-type galaxies from the Illustris simulation, and show that stellar population gradients at large radii can indeed be used to infer basic properties of galactic accretion histories. We measure metallicity, age, and surface-brightness profiles in quiescent Illustris galaxies ranging from M star = 10(10) - 2 x 10(12) M-circle dot and show that they are in reasonable agreement with observations. At fixed mass, galaxies that accreted little of their stellar halo material tend to have steeper metallicity and surface-brightness profiles, between 2-4 effective radii (R-e), than those with larger accreted fractions. Profiles of metallicity and surface-brightness in the stellar halo typically flatten from z = 1 to the present. This suggests that the accretion of stars into the stellar halo tends to flatten metallicity and surface-brightness profiles, a picture which is supported by the tight correlation between the two gradients in the stellar halo. We find no statistical evidence of additional information content related to accretion histories in stellar halo metallicity profiles, beyond what is contained in surface-brightness profiles. Age gradients in the stellar halo do not appear to be sensitive to galactic accretion histories, and none of the stellar population gradients studied are strongly correlated with the mean merger mass-ratio. Our findings relate specifically to regions of the stellar halo within 4 R-e, but suggest that future observations that reach large radii outside galaxies (including to 10 R-e and beyond) will have the best potential to constrain galactic accretion histories.
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