Asymmetric mass models of disk galaxies - I. Messier 99

L. Chemin 1 J.-M. Huré 2 C. Soubiran 1 Stefano, Zibetti Stephane, Charlot 3 Daisuke, Kawata
1 M2A 2016
LAB - Laboratoire d'Astrophysique de Bordeaux [Pessac]
2 ECLIPSE 2016
LAB - Laboratoire d'Astrophysique de Bordeaux [Pessac]
Abstract : Mass models of galactic disks traditionnally rely on axisymmetric density and rotation curves, paradoxically acting as if their most remarkable asymmetric features, like e.g. lopsidedness or spiral arms, were not important. In this article, we relax the axisymmetry approximation and introduce a methodology that derives 3D gravitational potentials of disk-like objects and robustly estimates the impacts of asymmetries on circular velocities in the disk mid-plane. Mass distribution models can then be directly fitted to asymmetric line-of-sight velocity fields. Applied to the grand-design spiral M99, the new strategy shows that circular velocities are highly non-uniform, particularly in the inner disk of the galaxy, as a natural response to the perturbed gravitational potential of luminous matter. A cuspy inner density profile of dark matter is found in M99, in the usual case where luminous and dark matter share the same centre. The impact of the velocity non-uniformity is to make the inner profile less steep, though the density remains cuspy. On another hand, a model where the halo is core-dominated and shifted by 2.2-2.5 kpc from the luminous mass centre is more appropriate to account for most of the kinematical lopsidedness evidenced in the velocity field of M99. However, the gravitational potential of luminous baryons is not asymmetric enough to explain the kinematical lopsidedness of the innermost regions, irrespective of the density shape of dark matter. This discrepancy points out the necessity of an additional dynamical process in these regions, maybe a lopsided distribution of dark matter.
Type de document :
Article dans une revue
Astronomy and Astrophysics - A&A, EDP Sciences, 2016, 588, 〈10.1051/0004-6361/201527730〉
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Soumis le : lundi 11 janvier 2016 - 08:27:09
Dernière modification le : lundi 10 décembre 2018 - 01:24:01

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L. Chemin, J.-M. Huré, C. Soubiran, Stefano, Zibetti, Stephane, Charlot, et al.. Asymmetric mass models of disk galaxies - I. Messier 99. Astronomy and Astrophysics - A&A, EDP Sciences, 2016, 588, 〈10.1051/0004-6361/201527730〉. 〈hal-01253551〉



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