Implications for dwarf spheroidal mass content from interloper removal

¹ Dipartimento di Fisica Generale “Amedeo Avogadro”Università degli studi di Torino, via P. Giuria 1, 10125 Turin, Italy
e-mail: serra@ph.unito.it; angus@ph.unito.it; diaferio@ph.unito.it
² Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Torino, Turin, Italy

Received: 9 June 2010
Accepted: 20 August 2010

Abstract

Using the caustic method, we identify the member stars of five dwarf spheroidal (dSph) galaxies of the Milky Way, the smallest dark matter (DM) dominated systems in the Universe. After our interloper rejection, we compute line-of-sight velocity dispersion profiles that are substantially smoother than previous results. Moreover, two dSphs have line-of-sight velocity dispersions 20% smaller than previous calculations suggested. Our Jeans modelling confirms that the DM content interior to 300 pc is roughly constant with satellite luminosity. Finally, if we assume that MOND provides the true law of gravity, our identification of interlopers implies that four dSphs have mass-to-light ratios in agreement with stellar population synthesis models, whereas Carina still has a mass-to-light ratio a factor of two too large and remains a problem for MOND.