Dark matter in dwarf spheroidals – II. Observations and modelling of Draco

By J. Kleyna, M. Wilkinson, N. Evans II, G. Gilmore, C. Frayn. 2001

161 citations recorded by the source corpus.

We present stellar radial velocity data for the Draco dwarf spheroidal (dSph) galaxy obtained using the AF2/WYFFOS instrument combination on the William Herschel Telescope. Our data set consists of 186 member stars, 159 of which have good quality velocities, extending to a magnitude V 19.5 with a mean velocity precision of 2 km s - 1 . As this survey is based on a high-precision photometric target list, it contains many more Draco members at large radii. For the first time, this allows a robust determination of the radial behaviour of the velocity dispersion in a dSph. We find statistically strong evidence of a rising velocity dispersion consistent with a dark matter halo that has a gently rising rotation curve. There is a <2σ signature of rotation about the long axis, inconsistent with tidal disruption as the source of the rising dispersion. By comparing our data set with earlier velocities, we find that Draco probably has a binary distribution and fraction comparable to those in the solar neighbourhood. We apply a novel maximum likelihood algorithm and fit the velocity data to a two parameter spherical model with an adjustable dark matter content and velocity anisotropy. Draco is best fit by a weakly tangentially anisotropic distribution of stellar orbits in a dark matter halo with a very slowly rising rotation law (v c i r c oc r 0 . 1 7 ). We are able to rule out both a mass-follows-light distribution and an extended halo with a harmonic core at the 2.5 to 3σ significance level, depending on the details of our assumptions about Draco's stellar binary population. Our modelling lends support to the idea that the dark matter in dwarf spheroidals is distributed in the form of massive, nearly isothermal haloes.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/0efb8ba69e22b093e3062e7794f79fb371098f08

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Citations in the corpus

VLT/UVES Abundances in Four Nearby Dwarf Spheroidal Galaxies. II. Implications for Understanding Galaxy Evolution (2002, background): “If dwarfs have a more extended dark matter halo than currently thought (e.g., Kleyna et al. 2002), these metal-rich bubbles will be smaller and more likely to collapse back into the central potential.”
Dark matter cores and cusps: the case of multiple stellar populations in dwarf spheroidals (2011, background): “…of the most luminous dSphs are available, the only clear conclusion is that the methods of stellar dynamics have so far been unable to prove whether the central regions of such haloes are cored or cusped (e.g., Kleyna et al. 2002; Koch et al. 2007; Walker et al. 2009; Amorisco & Evans 2011).”
A MegaCam Survey of Outer Halo Satellites. III. Photometric and Structural Parameters (2018, methodology): “Using the radial velocity data of Kleyna et al. (2002), Muñoz et al. (2005) reanalyzed Draco’s velocity dispersion profile.”
Galactic Searches for Dark Matter (2012, background): “Early studies of classical dSphs indicated that this binary contamination was ∼ 1 − 2 km/s, so it is a small systematic to classical satellite mass measurements (Kleyna et al., 2002).”
STELLAR VELOCITIES IN THE CARINA, FORNAX, SCULPTOR, AND SEXTANS dSph GALAXIES: DATA FROM THE MAGELLAN/MMFS SURVEY (2008, background): “With samples reaching hundreds of stars per dSph, velocity dispersion profiles are now available for all of the brighter MW dSphs (Kleyna et al. 2002, 2004; Wilkinson et al. 2004; Muñoz et al. 2005, 2006; Sohn et al. 2007; Walker et al. 2006a, 2006b, 2007b; Battaglia et al. 2006; Mateo et al.…”
A UNIVERSAL MASS PROFILE FOR DWARF SPHEROIDAL GALAXIES? (2009, background): “However, whereas most previously published velocity dispersion profiles are quite flat7 (e.g., Kleyna et al. 2002; Koch et al. 2007b,a; Walker et al. 2007b), we now detect gently decreasing dispersion in the outer regions of Fornax (Figure 1).”
BARYONS MATTER: WHY LUMINOUS SATELLITE GALAXIES HAVE REDUCED CENTRAL MASSES (2012, background): “…Spano et al. 2008; Trachternach et al. 2008; de Blok et al. 2008; Donato et al. 2009; Oh et al. 2011; Del Popolo 2012), and observed in satellites (Kleyna et al. 2002, 2003; Mashchenko et al. 2005; Goerdt et al. 2006; Strigari et al. 2006; Gilmore et al. 2007; Walker et al. 2009; Strigari et al.…”
A Dynamical Fossil in the Ursa Minor Dwarf Spheroidal Galaxy (2003, methodology): “Using the mass of Draco as a reference (Kleyna et al. 2001), we normalized the enclosed mass of the model to inside , where corresponds to 600 pc,75 # 10 M r p 1 r p 1, approximately the maximum extent of the stellar distribution.”
The Luminosity Function of the Milky Way Satellites (2007, methodology): “The spatial distribution of stars in the simulated objects is chosen to follow a Plummer law, which is a reasonable fit to most of the Milky Way dwarf spheroidals (see e.g. Irwin & Hatzidimitriou 1995; Kleyna et al. 2002).”
Velocity Dispersion Profiles of Seven Dwarf Spheroidal Galaxies (2007, background): “Recent velocity measurements for several hundred stars per dSph (Kleyna et al. 2002, 2003, 2004; Muñoz et al. 2005, 2006; Walker et al. 2006a,b; Simon & Geha 2007) demonstrate that dSph velocity dispersions remain approximately flat with radius.”
A Two Micron All Sky Survey View of the Sagittarius Dwarf Galaxy. I. Morphology of the Sagittarius Core and Tidal Arms (2003, result): “While a comparably high M/L has recently been claimed for the Draco dSph on the basis of internal velocity dispersion measures (Kleyna et al. 2002), it is hard to understand how Sgr could be so obviously losing mass into long tidal tails under these conditions (whereas, in contrast, several studies…”
ACCURATE STELLAR KINEMATICS AT FAINT MAGNITUDES: APPLICATION TO THE BOÖTES I DWARF SPHEROIDAL GALAXY (2011, background): “As a result, any estimation of a dSph’s total mass must contend with the fundamental degeneracy between mass and anisotropy in the velocity distribution (e.g., Wilkinson et al 2002; Kleyna et al. 2002).”
Internal Kinematics of the Fornax Dwarf Spheroidal Galaxy (2005, unknown): “Estimates of mass-tolight ratios (M/L) based on the equilibrium assumption have yieldedM/L ∼ 5− 500 in solar units for various Milky Way dSphs (Mateo 1998 and references therein; Kleyna et al. 2001; Odenkirchen et al. 2001; Kleyna et al. 2005).”
Simultaneous ram pressure and tidal stripping; how dwarf spheroidals lost their gas (2005, background): “Journal compilation C© 2006 RAS Downloaded from https://academic.oup.com/mnras/article-abstract/369/3/1021/1225729 by guest on 29 July 2018 Kleyna et al. 2002; Kazantzidis et al. 2004; Wilkinson et al. 2004) for supernovae winds to remove most of the baryons (Mori, Ferrara & Madau 2002; Mayer &…”
A Comprehensive Maximum Likelihood Analysis of the Structural Properties of Faint Milky Way Satellites (2008, background): “9 In Draco, Kleyna et al. (2002) have shown that there is mild evidence of a lower binary fraction than the solar neighborhood value used here.”