Research Note

Isolated and non-isolated dwarfs in terms of modified Newtonian dynamics

G. Gentile¹, G. W. Angus², B. Famaey^3,4, S.-H. Oh^5,6 and W. J. G. de Blok⁷

¹ Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281-S9, 9000 Gent, Belgium
e-mail: gianfranco.gentile@ugent.be
² Astrophysics, Cosmology & Gravity Centre, University of Cape Town, Private Bag X3, Rondebosch, 7700, South Africa
³ Observatoire Astronomique, Université de Strasbourg, CNRS UMR 7550, 67000 Strasbourg, France
⁴ AIfA, Universtät Bonn, 53121 Bonn, Germany
⁵ International Centre for Radio Astronomy Research (ICRAR), Univ. of Western Australia, 35 Stirling Highway, Perth, WA 6009, Australia
⁶ ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), 44-70 Rosehill Street, Redfern NSW 2016, Sydney, Australia
⁷ ASTRON, the Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA, Dwingeloo, The Netherlands

Received: 9 February 2012
Accepted: 4 May 2012

Abstract

Within the framework of modified Newtonian dynamics (MOND), we investigate the kinematics of two dwarf spiral galaxies belonging to very different environments, namely KK 246 in the Local Void and Holmberg II in the M 81 group. A mass model of the rotation curve of KK 246 is presented for the first time, and we show that its observed kinematics are consistent with MOND. We re-derive the outer rotation curve of Holmberg II, by modelling its HI data cube, and find that its inclination should be closer to face-on than previously derived. This implies that Holmberg II has a higher rotation velocity in its outer parts, which, although not very precisely constrained, is consistent with the MOND prediction.