Journal Article

Mapping the galactic gravitational potential with peculiar acceleration

C. Quercellini, L. Amendola and A. Balbi

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 391, issue 3, pages 1308-1314
Published in print December 2008 | ISSN: 0035-8711
Published online November 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13968.x
Mapping the galactic gravitational potential with peculiar acceleration

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It has been suggested recently that the change in cosmological redshift (the Sandage test of expansion) could be observed in the next generation of large telescopes and ultra-stable spectrographs. In a recent paper, we estimated the change of peculiar velocity, that is the peculiar acceleration, in nearby galaxies and clusters and shown it to be of the same order of magnitude as the typical cosmological signal. Mapping the acceleration field allows for a reconstruction of the galactic gravitational potential without assuming virialization. In this paper, we focus on the peculiar acceleration in our own Galaxy, modelled as a Kuzmin disc and a dark matter spherical halo. We estimate the peculiar acceleration for all known Galactic globular clusters and find some cases with an expected velocity shift in excess of 20 cm s−1 for observations 15 yr apart, well above the typical cosmological acceleration. We then compare the predicted signal for a modified Newtonian dynamics (MOND) model in which the spherical dark matter halo is absent. We find that the signal pattern is qualitatively different, showing that the peculiar acceleration field could be employed to test competing theories of gravity. However, the difference seems too small to be detectable in the near future.

Keywords: gravitation; galaxies: kinematics and dynamics

Journal Article.  4089 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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