Unmixing the Galactic Halo with RR Lyrae tagging
Monthly Notices of the Royal Astronomical Society
Oxford University Press
MetadataShow full item record
Belokurov, V., Deason, A., Koposov, S., Catelan, M., Erkal, D., Drake, A., & Evans, W. (2018). Unmixing the Galactic Halo with RR Lyrae tagging. Monthly Notices of the Royal Astronomical Society, 477 (2), 1472-1483. https://doi.org/10.1093/mnras/sty615
We show that tagging RR Lyrae stars according to their location in the period-amplitude diagram can be used to shed light on the genesis of the Galactic stellar halo. The mixture of RR Lyrae of ab type, separated into classes along the lines suggested by Oosterhoff, displays a strong and coherent evolution with Galactocentric radius. The change in the RR Lyrae composition appears to coincide with the break in the halo's radial density profile at ~25 kpc. Using simple models of the stellar halo, we establish that at least three different types of accretion events are necessary to explain the observed RRab behavior. Given that there exists a correlation between the RRab class fraction and the total stellar content of a dwarf satellite, we hypothesize that the field halo RRab composition is controlled by the mass of the progenitor contributing the bulk of the stellar debris at the given radius. This idea is tested against a suite of cosmological zoom-in simulations of Milky Way-like stellar halo formation. Finally, we study some of the most prominent stellar streams in the Milky Way halo and demonstrate that their RRab class fractions follow the trends established previously.
Milky Way, galaxies: dwarf, galaxies: structure, Local Group, stars: variables: RR Lyrae
The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 308024. A.D. is supported by a Royal Society University Research Fellowship. A.D. also acknowledges support from the STFC grant ST/P000451/1. NWE thanks the Center for Computational Astrophysics for hospitality during a working visit. The authors gratefully acknowledge support by CONICYT/RCUK’s PCI program through grant DPI20140066 (“Newton Funds”). M.C. is additionally supported by the Ministry for the Economy, Development, and Tourism’s Millennium Science Initiative through grant IC 120009, awarded to the Millennium Institute of Astrophysics (MAS); by Proyecto Basal PFB-06/2007; and by FONDECYT grant #1171273.
SCIENCE & TECHNOLOGY FACILITIES COUNCIL (ST/N000927/1)
European Research Council (308024)
Embargo Lift Date
External DOI: https://doi.org/10.1093/mnras/sty615
This record's URL: https://www.repository.cam.ac.uk/handle/1810/276832