How Lumpy Is the Milky Way’s Dark Matter Halo?

By K. Johnston, David N. Spergel, Christian Haydn. 2001

183 citations recorded by the source corpus.

Cold dark matter (CDM) simulations predict that there are hundreds of lumps with masses greater than 107 M☉ in the Milky Way halo. However, we know of only a dozen dwarf satellites close to this mass. Are these lumps simply lacking in stars, or is there a fundamental flaw in our most popular cosmology? By studying the tidal debris of known satellites, we can potentially address this question. In this paper, we quantify the effects of the dark matter lumps on tidal tails. The lumps scatter stars in the tidal tails from their original orbits, producing a distinctive signature. We simulate debris evolution in smooth and lumpy halo potentials, and use our simulations to motivate and test a statistical measure of the degree of scattering apparent in the angular position and radial velocity measurement of debris stars—the "scattering index." We find that the scattering index can in general distinguish between the levels of substructure predicted by CDM cosmologies and smooth Milky Way models, but the sensitivity of the debris depends on the orientation of the parent satellite's orbit relative to the largest lumps' orbits. We apply our results to the carbon star stream associated with the Sagittarius dwarf galaxy (Sgr), and find that these stars appear to be more scattered than we expect for debris orbiting in a smooth halo. However, the degree of scattering is entirely consistent with that expected because of the influence of the Large Magellanic Cloud, which is on an orbit that intersects Sgr's own. We conclude that the current data are unable to constrain CDM models. Nevertheless, our study suggests that future data sets of debris stars associated with other Milky Way satellites could provide strong constraints on CDM models.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/a889cbd51525dc777eb9f0ab27955aebcc30fa7a

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Citations in the corpus

Dark matter cores all the way down (2015, methodology): “…subhalos are actually destroyed this will affect methods like lensing (e.g. Metcalf & Zhao 2002; Bacon et al. 2010) or ‘satellite stream bumps’ (e.g. Johnston et al. 2002) that gravitationally probe the ex- 8 Arraki et al. (2014) point out that ram pressure stripping of gas can also lower the…”
A Two Micron All Sky Survey View of the Sagittarius Dwarf Galaxy. II. Swope Telescope Spectroscopy of M Giant Stars in the Dynamically Cold Sagittarius Tidal Stream (2004, methodology): “The variables d and in equations (1) and (2) of Johnston et al. (2002) correspond to and for Sgr debris in Paper I.”
Halo Substructure and the Power Spectrum (2002, background): “…to detect substructure via gravitational lensing (e.g., DK01; Keeton 2003; Keeton, Gaudi, & Petters 2002; Moustakas & Metcalf 2003) or by probes within our own Galaxy (e.g., Johnston et al. 2002; Ibata et al. 2002a, 2002b; Mayer et al. 2002; Font et al. 2001) offer useful avenues for doing so.”
Not so lumpy after all: modelling the depletion of dark matter subhaloes by Milky Way-like galaxies (2017, background): “…for detecting dark substructure are through gaps or kinematic distortions in dynamically cold stellar streams formed from disrupting globular clusters, such as Palomar-5 and GD-1 (e.g. Johnston et al. 2002; Koposov et al. 2010; Carlberg et al. 2012; Ngan et al. 2015, and references therein).”
Wide-Field InfrarRed Survey Telescope-Astrophysics Focused Telescope Assets WFIRST-AFTA 2015 Report (2015, background): “If the dark matter is not cold, but warm as suggested in some theories, these massive subhalos will not exist, and the stellar streams will be smooth and unperturbed (Johnston et al. 2002).”
Luminosity function and radial distribution of Milky Way satellites in a ΛCDM Universe (2009, background): “…detect the presence of a significant dark population of subhaloes in the MW halo could come from the signatures of the interaction of such a population with the thin stellar streams in the MW halo ( e.g. Odenkirchen et al. 2001, Ibata et al. 2002, Johnston et al. 2002, Grillmair & Dionatos 2006).”
The stellar halo of the Galaxy (2008, background): “Galaxies are essentially collisionless systems (Binney & Tremaine 1987), and the effect of dark matter substructure on the coherence of tidal streams has been shown to be very small (Johnston et al. 2002).”
CLUMPY STREAMS FROM CLUMPY HALOS: DETECTING MISSING SATELLITES WITH COLD STELLAR STRUCTURES (2010, background): “For the streams of larger satellites like the Sagittarius dwarf galaxy (hereafter Sgr), Johnston et al. (2002) found that although stars in the debris are scattered by encounters with dark matter subhalos, the thickness of the current Sgr stream could be explained as being due to the Large…”
A Two Micron All Sky Survey View of the Sagittarius Dwarf Galaxy. I. Morphology of the Sagittarius Core and Tidal Arms (2003, background): “The degree of coherence of tidal debris streams provide a powerful constraint on the lumpiness of the Galactic halo potential (Font et al. 2001; Johnston et al. 2002b; Ibata et al. 2001b;Mayer et al. 2001).”
A Two Micron All-Sky Survey View of the Sagittarius Dwarf Galaxy. IV. Modeling the Sagittarius Tidal Tails (2004, background): “Earlier work (Johnston et al. 2002) has found that significant heating of a Sgr-like debris stream can occur in a simulation using a live halo, even in a halomodel realizedwith 106 particles.”