Casagrande, Luca2022-07-142022-07-140004-637Xhttp://hdl.handle.net/1885/268844The Gaia H-R diagram shows the presence of apparently young stars at high tangential velocities. Using a simple analytical model, I show that these stars are likely to be blue stragglers. Once normalized to red giant stars, the fraction of nearby halo blue stragglers is of order 20%, and remarkably close to that measured in dwarf galaxies. Motivated by this similarity, I apply to field blue stragglers scaling relations inferred from blue stragglers in dwarf galaxies. Doing this for the Milky Way halo returns an average stellar density of $(3.4\pm 0.7)\times {10}^{-5}{M}_{\odot }\,{\mathrm{pc}}^{-3}$ and a dark matter density of $\simeq {0.006}_{-0.003}^{+0.005}\,{M}_{\odot }\,{\mathrm{pc}}^{-3}\simeq {0.22}_{-0.10}^{+0.20}\,\mathrm{GeV}\,{\mathrm{cm}}^{-3}$ within 2 kpc from the Sun. These values compare favorably to other determinations available in the literature but are based on an independent set of assumptions. A few considerations of this methodology are discussed, most notably that the correlation between the dark matter halo core density and stellar mass seems to hold from dwarf galaxies to the nearby Milky Way halo.Funding for this work has been provided by the ARC Future Fellowship FT160100402. Parts of this research were conducted by the ARC Centre of Excellence ASTRO 3D, through project No. CE170100013. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www. cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa. int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.application/pdfen-AU© 2020. The American Astronomical SocietyBaryon densityDark matter densityBlue straggler starsGalaxy stellar halosDwarf galaxies202010.3847/1538-4357/ab929f2021-08-01