The Observed Properties of Dark Matter on Small Spatial Scales

By R. Wyse, G. Gilmore. Proceedings of the International Astronomical Union, 2007

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We present a synthesis of recent photometric and kinematic data for several of the most dark matter dominated galaxies, the dwarf spheroidal Galactic satellites, and compare them to star clusters. There is a bimodal distribution in half-light radii, with stable star clusters always being smaller than ~30 pc, while stable galaxies are always larger than ~120 pc. We extend the previously known observational relationships and interpret them in terms of a more fundamental pair of intrinsic properties of dark matter itself: dark matter forms cored mass distributions, with a core scale length of greater than about 100 pc, and always has a maximum central mass density within a narrow range. The dark matter in dSph galaxies appears to be clustered such that there is a mean volume mass density within the stellar distribution which has the very low value of less than about 0.1 M☉ pc-3 (about 5 GeV/c2 cm-3). All dSph's have velocity dispersions at the edge of their light distributions equivalent to circular velocities of ~15 km s-1. The maximum central dark matter density derived is model dependent but is likely to have a characteristic value (averaged over a volume of radius 10 pc) of ~0.1 M☉ pc-3 for the favored cored dark mass distributions (where it is similar to the mean value), or ~60 M ☉ pc-3 (about 2 TeV/c2 cm-3) if the dark matter density distribution is cusped. Galaxies are embedded in dark matter halos with these properties; smaller systems containing dark matter are not observed. These values provide new information about the nature of the dominant form of dark matter.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/b2296bc8729deaf14031274ee9ba83bbda506774

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Citations in the corpus

A MegaCam Survey of Outer Halo Satellites. III. Photometric and Structural Parameters (2018, background): “We note that, as has been argued in the past, King model parameters do not have obvious physical interpretation for darkmatter dominated systems (e.g., Koch et al. 2006; Gilmore et al. 2007).”
The Orbital Poles of Milky Way Satellite Galaxies: A Rotationally Supported Disk of Satellites (2008, background): “Recent observational constraints question the validity of the CDM model in these systems and imply that perhaps the warm dark matter model may need to be considered as a viable alternative (Gilmore et al. 2007).”
THE RELATIONSHIPS AMONG COMPACT STELLAR SYSTEMS: A FRESH VIEW OF ULTRACOMPACT DWARFS (2011, background): “There is then an apparent gap between galaxies and star clusters, which is now seen to be a diagonal region rather than a simple size gap (cf the “Shapley line” of van den Bergh 2008; and also Gilmore et al. 2007; Forbes et al. 2008; Tolstoy et al. 2009; Misgeld & Hilker 2011).”
Redefining the Missing Satellites Problem (2007, background): “It is possible to fit all of the dSphs at present with a constant density cores with scale-lengths ∼ 100 pc (Strigari et al. 2006; Gilmore et al. 2007), although the data by no means demand such a situation.”
THE NUCLEUS OF THE SAGITTARIUS DSPH GALAXY AND M54: A WINDOW ON THE PROCESS OF GALAXY NUCLEATION (2008, background): “In particular, as already noted, mass - follows -light models are incompatible with the observed velocity dispersion profile of Sgr,N (Gilmore et al. 2007).”
The properties of warm dark matter haloes (2013, background): “…(Macciò et al. 2012; Shao et al. 2013; Macciò et al. 2013) has shown that the resulting cores are astrophysically uninteresting being, in particular, significantly smaller than the cores claimed to be present in dwarf satellites of the Milky Way (e.g. Gilmore et al. 2007; de Vega & Sanchez 2010).”
A Comprehensive Maximum Likelihood Analysis of the Structural Properties of Faint Milky Way Satellites (2008, background): “As previously noted by Belokurov et al. (2007) and Gilmore et al. (2007), the clear size difference that existed before between globular clusters, with sizes smaller than ∼ 20 pc and dwarf galaxies ∼ > 100 pc becomes blurred at low luminosities.”
Dark matter cores and cusps: the case of multiple stellar populations in dwarf spheroidals (2011, background): “For example, Gilmore et al. (2007) provided a succinct summary of the then available observational evidence.”
Accurate masses for dispersion-supported galaxies (2009, background): “…galaxies (Romanowsky et al. 2003; Dekel et al. 2005), to measure the mass profile of the Milky Way from stellar halo kinematics (Battaglia et al. 2005; Dehnen et al. 2006), and to in- fer accurate mass distributions in dwarf spheroidal galaxies (dSphs) (Gilmore et al. 2007; Strigari et al. 2007b).”
Luminosity function and radial distribution of Milky Way satellites in a ΛCDM Universe (2009, background): “As a result the number of known dwarf spheroidals has doubled in the recent past (e.g Willman et al. 2005, Zucker et al. 2006; Belokurov et al. 2007; Irwin et al. 2007, Gilmore et al. 2007).”
A NEW FAINT MILKY WAY SATELLITE DISCOVERED IN THE PAN-STARRS1 3π SURVEY (2015, background): “…have provided us with greater observational constraints in our backyard, especially to understand the faint end of galaxy formation in the preferred cosmological paradigm of ΛCDM (Belokurov 2013), they have also led to debates about the nature of the faintest satellites (Gilmore et al. 2007).”
Axion Cosmology (2015, background): “• The cusp-core problem [270]: many observed low-mass systems contain flat central density profiles, not NFW cusps.”
CONFIRMATION OF FAINT DWARF GALAXIES IN THE M81 GROUP (2013, methodology): “The smallest object in our sample, dSph d0944+69, was originally measured in our MegaCam data to have a size of 90 pc, which falls within the 40-100 pc size gap between most dwarf galaxies and globular clusters (Gilmore et al. 2007).”
ACCURATE STELLAR KINEMATICS AT FAINT MAGNITUDES: APPLICATION TO THE BOÖTES I DWARF SPHEROIDAL GALAXY (2011, background): “…have typical half-light radii greater than 100pc, low surface brightnesses (∼ 25-30 mag/sq. arcsec), and central velocity dispersions of several km/s, implying that the luminous component is embedded in a dominant extended dark matter halo (M/LV ∼ 10 − 100M/LV,⊙; (Mateo 1998; Gilmore et al. 2007)).”
Local-Group tests of dark-matter concordance cosmology - Towards a new paradigm for structure formation (2010, result): “Their results confirm the earlier suggestion by Mateo et al. (1993), Mateo (1998), Gilmore et al. (2007), and Peñarrubia et al. (2008) that the satellites share a common DM mass scale of about 107 M⊙, “and conclusively establish” (S08) this common mass scale.”
The Role of Sterile Neutrinos in Cosmology and Astrophysics (2008, background): “[108, 109]); – direct measurements of DM density profiles in dSphs seem to favor cored profiles [110–112, 108]; – there may be indications towards the existence of the smallest scale at which the DM is observed [108, 113].”