期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 466, 期 2, 页码 1491-1512出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stw2992
关键词
galaxies: evolution; galaxies: general; galaxies: haloes; galaxies: individual: NGC 253, NGC 891, NGC 3031, NGC 4565; NGC 4945, NGC 7814; galaxies: stellar content
资金
- NSF [AST 1008342]
- HST by NASA through a grant from the Space Telescope Science Institute [GO-11613, GO-12213]
- NASA [NAS5-26555]
- NASA Office of Space Science [NNX09AF08G]
- IACs IT Division
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [1514835] Funding Source: National Science Foundation
We have examined the resolved stellar populations at large galactocentric distances along the minor axis (from 10 kpc up to between 40 and 75 kpc), with limited major axis coverage, of six nearby highly inclined MilkyWay(MW) mass disc galaxies using Hubble Space Telescope data from the Galaxy haloes, Outer discs, Substructure, Thick discs, and Star clusters (GHOSTS) survey. We select red giant branch stars to derive stellar halo density profiles. The projected minor axis density profiles can be approximated by power laws with projected slopes of -2 to -3.7 and a diversity of stellar halo masses of 1-6 x 10(9) M-circle dot, or 2-14 per cent of the total galaxy stellar masses. The typical intrinsic scatter around a smooth power-law fit is 0.05-0.1 dex owing to substructure. By comparing the minor and major axis profiles, we infer projected axis ratios c/a at similar to 25 kpc between 0.4and0.75. The GHOSTS stellar haloes are diverse, lying between the extremes charted out by the (rather atypical) haloes of the MW and M31. We find a strong correlation between the stellar halo metallicities and the stellar halo masses. We compare our results with cosmological models, finding good agreement between our observations and accretion-only models where the stellar haloes are formed by the disruption of dwarf satellites. In particular, the strong observed correlation between stellar halo metallicity and mass is naturally reproduced. Low-resolution hydrodynamical models have unrealistically high stellar halo masses. Current high-resolution hydrodynamical models appear to predict stellar halo masses somewhat higher than observed but with reasonable metallicities, metallicity gradients, and density profiles.
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