Dearth of dark matter or massive dark halo Mass-shape-anisotropy degeneracies revealed by NMAGIC dynamical models of the elliptical galaxy NGC 3379 - AstrophysicsReportar como inadecuado




Dearth of dark matter or massive dark halo Mass-shape-anisotropy degeneracies revealed by NMAGIC dynamical models of the elliptical galaxy NGC 3379 - Astrophysics - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Abstract: Recent results from the Planetary Nebula Spectrograph PN.S survey haverevealed a rapidly falling velocity dispersion profile in the nearby ellipticalgalaxy NGC 3379, casting doubts on whether this intermediate-luminosity galaxyhas the kind of dark matter halo expected in LambdaCDM cosmology. We present adetailed dynamical study of this galaxy, combining long-slit spectroscopy,SAURON integral-field data, and PN.S velocities, reaching to more than seveneffective radii R e. We construct spherical and axisymmetric dynamical modelsfor these data with the flexible made-to-measure NMAGIC code, in a sequence ofgravitational potentials with varying dark halo mass. We find that the data areconsistent both with near-isotropic spherical systems dominated by the stellarmass, and with models in massive halos with strongly radially anisotropic outerparts beta >~ 0.8 at 7R e. Formal likelihood limits would exclude at 1sigma the model with stars only, as well as halo models with v circ7R e >~250 km-s. A sequence of more realistic axisymmetric models of differentinclinations and a small number of triaxial tests confirm the sphericalresults. All valid models fitting all the data are dynamically stable overGyrs, including the most anisotropic ones. NGC 3379 may well have a dark matterhalo as predicted by recent merger models within LambdaCDM cosmology, providedits outer envelope is strongly radially anisotropic. abridged



Autor: F. De Lorenzi, O. Gerhard, L. Coccato, M. Arnaboldi, M. Capaccioli, N. G. Douglas, K. C. Freeman, K. Kuijken, M. R. Merrifield, N

Fuente: https://arxiv.org/







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