The Kinematic Status and Mass Content of the Sculptor Dwarf Spheroidal Galaxy

By G. Battaglia, A. Helmi, E. Tolstoy, M. Irwin, V. Hill, P. Jablonka. 2008

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We present VLT FLAMES spectroscopic observations (R ∼ 6500) in the Ca II triplet region for 470 probable kinematic members of the Sculptor (Scl) dwarf spheroidal galaxy. The accurate velocities (±2 km s−1) and large area coverage of Scl allow us to measure a velocity gradient of 7.6+ 3.0−2.2 km s−1 deg−1 along the projected major axis of Scl, likely a signature of intrinsic rotation. We also use our kinematic data to measure the mass distribution within this system. By considering independently the kinematics of the two distinct stellar components known to be present in Scl, we are able to relieve known degeneracies and find that the observed velocity dispersion profiles are best fitted by a cored dark matter halo with core radius rc = 0.5 kpc and mass enclosed within the last measured point M(<1.8 kpc) = (3.4 ± 0.7) × 108 M☉, assuming an increasingly radially anisotropic velocity ellipsoid. This results in a mass-to-light ratio of 158 ± 33 (M/L)☉ inside 1.8 kpc. An NFW profile with concentration c = 20 and mass M(<1.8 kpc) = 2.2+ 1.0−0.7 × 108 M☉ is also statistically consistent with the observations, but it tends to yield poorer fits for the metal-rich stars.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/4e7fc5490bef72bb29c4a982f4685f4dfbd3c640

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Citations in the corpus

Dark matter and fundamental physics with the Cherenkov Telescope Array (2012, background): “A systematic study has been done for Sculptor, to estimate the effect of the profile shape and velocity anisotropy assumptions [68].”
Bar formation and evolution in disc galaxies with gas and a triaxial halo: morphology, bar strength and halo properties (2012, background): “…observations (e.g. de Blok et al. 2001, 2008; de Blok & Bosma 2002; de Blok, Bosma & McGaugh 2003; Simon et al. 2003; Kuzio de Naray et al. 2006; Battaglia et al. 2008; Kuzio de Naray, McGaugh & de Blok 2008; Oh et al. 2008; de Blok 2010; Walker & Peñarrubia 2011; Amorisco & Evans 2012;…”
Dark matter cores all the way down (2015, background): “The situation for the gas-poor dSphs is more murky, with claims of cores (e.g. Battaglia et al. 2008; Walker & Peñarrubia 2011; Amorisco & Evans 2011; Agnello & Evans 2012); cusps (Richardson & Fairbairn 2014; Strigari et al. 2014, e.g.); and everything in between (e.g. Breddels & Helmi 2014;…”
A constant dark matter halo surface density in galaxies (2009, methodology): “Cusped models can also reproduce the dispersion velocity data in most dSphs (Gilmore et al. 2007; Koch et al. 2007; Battaglia et al. 2008), modulus an appropriate run with radius of the anisotropy parameter.”
Galactic Searches for Dark Matter (2012, background): “The half-light radius for metal rich component is ∼ 230 kpc, and the half-light radius for the metal-poor population is 350 kpc (Battaglia et al., 2008).”
The local dark matter density (2014, background): “This is perhaps surprising given claims from the spherical Jeans modelling community of the power of population splitting (e.g. Battaglia et al., 2008; Walker & Peñarrubia, 2011).”
One Law to Rule Them All: The Radial Acceleration Relation of Galaxies (2016, background): “…late-type galaxies (LTGs) like spirals and irregulars (e.g., Rubin et al. 1985; van Albada & Sancisi 1986; Persic & Salucci 1991; van der Kruit & Freeman 2011), and dwarf spheroidals (dSphs) in the Local Group (e.g., Mateo 1998; Battaglia et al. 2008; Strigari et al. 2008; Walker et al. 2009b).”
MULTI-ELEMENT ABUNDANCE MEASUREMENTS FROM MEDIUM-RESOLUTION SPECTRA. III. METALLICITY DISTRIBUTIONS OF MILKY WAY DWARF SATELLITE GALAXIES (2010, background): “Since then, the Dwarf Abundances and Radial Velocities Team (DART) have measured MDFs for Carina and Sextans in addition to Fornax and Sculptor (Tolstoy et al. 2004; Helmi et al. 2006; Battaglia et al. 2006, 2008b, 2010).”
The star formation and chemical evolution history of the Fornax dwarf spheroidal galaxy (2012, methodology): “Reference isochrones have been overlaid on the CMDs, representative of the metallicity of the old, intermediate and young populations present in Fornax (Battaglia et al. 2008; Starkenburg et al. 2010; Letarte et al. 2010).”
Dark matter cores and cusps: the case of multiple stellar populations in dwarf spheroidals (2011, methodology): “Completely analogous results have been obtained when the original kinematic profiles taken from Battaglia et al. (2008) have been replaced with kinematic profiles derived directly from the radial velocity dataset using slightly different metallicity cuts (within 0.1 [Fe/H]) or membership criteria…”
Dark matter annihilation and decay in dwarf spheroidal galaxies: the classical and ultrafaint dSphs (2015, background): “…favour dark matter cores over the cusps predicted by pure cold dark matter cosmological simulations (e.g. Kleyna et al. 2003; Goerdt et al. 2006; Battaglia et al. 2008; Walker & Peñarrubia 2011; Cole et al. 2012; Agnello & Evans 2012; Amorisco, Agnello & Evans 2013), though this has been…”
Galaxy Masses: A Review (2013, methodology): “An example of this method is shown in Figure 18 for the Sculptor dwarf spheroidal galaxy, studied in detail by Battaglia et al. (2008), who fit the PPS assuming Gaussian LOS velocity distributions (adding a component for contamination by our Milky Way).”
STELLAR VELOCITIES IN THE CARINA, FORNAX, SCULPTOR, AND SEXTANS dSph GALAXIES: DATA FROM THE MAGELLAN/MMFS SURVEY (2008, methodology): “…more than doubles the number of velocity measurements for dSph stars, dating from Aaronson’s (1983) initial kinematic study to the most recent published data from surveys using Keck and the VLT (Muñoz et al. 2006; Koch et al. 2006, 2007b, 2007a; Battaglia et al. 2006; Battaglia et al. 2008).”
A METHOD FOR MEASURING (SLOPES OF) THE MASS PROFILES OF DWARF SPHEROIDAL GALAXIES (2011, methodology): “Indeed, Battaglia et al. (2008a) find that the metal-rich subcomponent of the Sculptor dSph has a falling velocity dispersion profile (see their Figure 3).”
Cusp-core transformations in dwarf galaxies: observational predictions (2012, background): “It is interesting to note, however, that the very latest dynamical models for Sculptor appear to favour a cored rather than cusped mass distribution (Battaglia et al. 2008; Walker & Peñarrubia 2011; Amorisco & Evans 2012).”