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Published September 20, 2019 | Submitted + Published
Journal Article Open

Under the Firelight: Stellar Tracers of the Local Dark Matter Velocity Distribution in the Milky Way

Abstract

The Gaia era opens new possibilities for discovering the remnants of disrupted satellite galaxies in the solar neighborhood. If the population of local accreted stars is correlated with the dark matter sourced by the same mergers, one can then map the dark matter distribution directly. Using two cosmological zoom-in hydrodynamic simulations of Milky-Way-mass galaxies from the Latte suite of the FIRE-2 simulations, we find a strong correlation between the velocity distribution of stars and dark matter at the solar circle that were accreted from luminous satellites. This correspondence holds for dark matter that is either relaxed or in a kinematic substructure called debris flow, and is consistent between two simulated hosts with different merger histories. The correspondence is more problematic for streams because of possible spatial offsets between the dark matter and stars. We demonstrate how to reconstruct the dark matter velocity distribution from the observed properties of the accreted stellar population by properly accounting for the ratio of stars to dark matter contributed by individual mergers. This procedure does not account for the dark matter that originates from nonluminous satellites, which may constitute a nontrivial fraction of the local contribution. After validating this method using the FIRE-2 simulations, we apply it to the Milky Way and use it to recover the dark matter velocity distribution associated with the recently discovered stellar debris field in the solar neighborhood. Based on results from Gaia, we estimate that 42^(+26)_(-22)% of the local dark matter that is accreted from luminous mergers is in debris flow.

Additional Information

© 2019 The American Astronomical Society. Received 2019 February 15; revised 2019 August 9; accepted 2019 August 12; published 2019 September 18. We thank V. Belokurov, E. Kirby, A. Peter, and D. Spergel for useful conversations. L.N. is supported by the DOE under award number DESC0011632, and the Sherman Fairchild fellowship. M.L. is supported by the DOE under award number DESC0007968 and the Cottrell Scholar Program through the Research Corporation for Science Advancement. Support for S.G.K. was provided by NASA through Einstein Postdoctoral Fellowship grant No. PF5-160136 awarded by the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical Observatory for NASA under contract NAS8-03060. A.W. was supported by NASA through ATP grant 80NSSC18K1097 and grants HST-GO-14734 and HST-AR-15057 from STScI. C.A.F.G. was supported by NSF through grants AST-1517491, AST-1715216, and CAREER award AST-1652522, by NASA through grants NNX15AB22G and 17-ATP17-0067, and by a Cottrell Scholar Award from the Research Corporation for Science Advancement. Support for P.F.H., S.G.K., and R.E.S. was provided by an Alfred P. Sloan Research Fellowship, NSF Collaborative Research Grant #1715847 and CAREER grant #1455342, and NASA grants NNX15AT06G, JPL 1589742, and 17-ATP17-0214. Numerical calculations were run on the Caltech compute cluster "Wheeler," allocations from XSEDE TG-AST130039 and PRAC NSF.1713353 supported by the NSF, and NASA HEC SMD-16-7592. D.K. was supported by NSF grant AST-1715101 and the Cottrell Scholar Award from the Research Corporation for Science Advancement. This work was performed in part at the Aspen Center for Physics, which is supported by National Science Foundation grant PHY-1607611. We used computational resources from the Extreme Science and Engineering Discovery Environment (XSEDE), supported by NSF. Software: Astropy (Astropy Collaboration et al. 2013), IPython (Pérez & Granger 2007), GIZMO (Hopkins 2015), GADGET-3 (Springel 2005), STARBURST99 v7.0 (Leitherer et al. 1999, 2014), Rockstar (Behroozi et al. 2013b).

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Published - Necib_2019_ApJ_883_27.pdf

Submitted - 1810.12301.pdf

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Additional details

Created:
August 19, 2023
Modified:
October 20, 2023