Journal Article

The distribution of mass in the Orion dwarf Galaxy

N. Frusciante, P. Salucci, D. Vernieri, J. M. Cannon and E. C. Elson

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 426, issue 1, pages 751-757
Published in print October 2012 | ISSN: 0035-8711
Published online October 2012 | e-ISSN: 1365-2966 | DOI:
The distribution of mass in the Orion dwarf Galaxy

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Dwarf galaxies are good candidates to investigate the nature of dark matter (DM), because their kinematics are dominated by this component down to small galactocentric radii. We present here the results of detailed kinematic analysis and mass modelling of the Orion dwarf galaxy, for which we derive a high-quality and high-resolution rotation curve that contains negligible non-circular motions and we correct it for the asymmetric drift. Moreover, we leverage the proximity (D = 5.4 kpc) and convenient inclination (47°) to produce reliable mass models of this system. We find that the universal rotation curve mass model (Freeman disc + Burkert halo + gas disc) fits the observational data accurately. In contrast, the NFW halo + Freeman disc + gas disc mass model is unable to reproduce the observed rotation curve, a common outcome in dwarf galaxies. Finally, we attempt to fit the data with a modified Newtonian dynamics (MOND) prescription. With the present data and with the present assumptions on distance, stellar mass, constant inclination and reliability of the gaseous mass, the MOND ‘amplification’ of the baryonic component appears to be too small to mimic the required ‘dark component’. The Orion dwarf reveals a cored DM density distribution and a possible tension between observations and the canonical MOND formalism.

Keywords: galaxies: dwarf; galaxies: kinematics and dynamics; dark matter

Journal Article.  4280 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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