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MOND and IMF variations in early-type galaxies from ATLAS3D


Tortora, C; Romanowsky, A J; Cardone, V F; Napolitano, N R; Jetzer, P (2014). MOND and IMF variations in early-type galaxies from ATLAS3D. Monthly Notices of the Royal Astronomical Society. Letters, 438(1):46-50.

Abstract

MOdified Newtonian dynamics (MOND) represents a phenomenological alternative to dark matter (DM) for the missing mass problem in galaxies and clusters of galaxies. We analyze the central regions of a local sample of ∼220 early-type galaxies from the ATLAS3D survey, to see if the data can be reproduced without recourse to DM. We estimate dynamical masses in the MOND context through Jeans analysis, and compare to ATLAS3D stellar masses from stellar population synthesis. We find that the observed stellar mass--velocity dispersion relation is steeper than expected assuming MOND with a fixed stellar initial mass function (IMF) and a standard value for the acceleration parameter a0. Turning from the space of observables to model space, a) fixing the IMF, a universal value for a0 cannot be fitted, while, b) fixing a0 and leaving the IMF free to vary, we find that it is "lighter" (Chabrier-like) for low-dispersion galaxies, and "heavier" (Salpeter-like) for high dispersions. This MOND-based trend matches inferences from Newtonian dynamics with DM, and from detailed analysis of spectral absorption lines, adding to the converging lines of evidence for a systematically-varying IMF.

Abstract

MOdified Newtonian dynamics (MOND) represents a phenomenological alternative to dark matter (DM) for the missing mass problem in galaxies and clusters of galaxies. We analyze the central regions of a local sample of ∼220 early-type galaxies from the ATLAS3D survey, to see if the data can be reproduced without recourse to DM. We estimate dynamical masses in the MOND context through Jeans analysis, and compare to ATLAS3D stellar masses from stellar population synthesis. We find that the observed stellar mass--velocity dispersion relation is steeper than expected assuming MOND with a fixed stellar initial mass function (IMF) and a standard value for the acceleration parameter a0. Turning from the space of observables to model space, a) fixing the IMF, a universal value for a0 cannot be fitted, while, b) fixing a0 and leaving the IMF free to vary, we find that it is "lighter" (Chabrier-like) for low-dispersion galaxies, and "heavier" (Salpeter-like) for high dispersions. This MOND-based trend matches inferences from Newtonian dynamics with DM, and from detailed analysis of spectral absorption lines, adding to the converging lines of evidence for a systematically-varying IMF.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Physics Institute
Dewey Decimal Classification:530 Physics
Language:English
Date:2014
Deposited On:24 Feb 2015 09:39
Last Modified:05 Apr 2016 19:03
Publisher:Oxford University Press
ISSN:1745-3933
Additional Information:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society: Letters ©: 2014 Published by Oxford University Press on behalf of The Royal Astronomical Society. All rights reserved.
Publisher DOI:https://doi.org/10.1093/mnrasl/slt155

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