Professor Alis Deason alis.j.deason@durham.ac.uk
Professor
We measure the total stellar halo luminosity using red giant branch (RGB) stars selected from Gaia data release 2. Using slices in magnitude, colour, and location on the sky, we decompose RGB stars belonging to the disc and halo by fitting two-dimensional Gaussians to the Galactic proper motion distributions. The number counts of RGB stars are converted to total stellar halo luminosity using a suite of isochrones weighted by age and metallicity, and by applying a volume correction based on the stellar halo density profile. Our method is tested and calibrated using Galaxia and N-body models. We find a total luminosity (out to 100 kpc) of Lhalo = 7.9 ± 2.0 × 108 L excluding Sgr, and Lhalo = 9.4 ± 2.4 × 108 L including Sgr. These values are appropriate for our adopted stellar halo density profile and metallicity distribution, but additional systematics related to these assumptions are quantified and discussed. Assuming a stellar mass-to-light ratio appropriate for a Kroupa initial mass function (M/L = 1.5), we estimate a stellar halo mass of M halo = 1.4 ± 0.4 × 109 M. This mass is larger than previous estimates in the literature, but is in good agreement with the emerging picture that the (inner) stellar halo is dominated by one massive dwarf progenitor. Finally, we argue that the combination of a ∼109 M mass and an average metallicity of [Fe/H]∼−1.5 for the Galactic halo points to an ancient (∼10 Gyr) merger event.
Deason, A. J., Belokurov, V., & Sanders, J. L. (2019). The total stellar halo mass of the Milky Way. Monthly Notices of the Royal Astronomical Society, 490(3), 3426-3439. https://doi.org/10.1093/mnras/stz2793
Journal Article Type | Article |
---|---|
Acceptance Date | Oct 1, 2019 |
Online Publication Date | Oct 7, 2019 |
Publication Date | Dec 31, 2019 |
Deposit Date | Jan 9, 2020 |
Publicly Available Date | Jan 1, 2020 |
Journal | Monthly Notices of the Royal Astronomical Society |
Print ISSN | 0035-8711 |
Electronic ISSN | 1365-2966 |
Publisher | Royal Astronomical Society |
Peer Reviewed | Peer Reviewed |
Volume | 490 |
Issue | 3 |
Pages | 3426-3439 |
DOI | https://doi.org/10.1093/mnras/stz2793 |
Public URL | https://durham-repository.worktribe.com/output/1279634 |
Published Journal Article
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Copyright Statement
This article has been accepted for publication in the Monthly notices of the Royal Astronomical Society ©: 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
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