MOND and IMF variations in early-type galaxies from ATLAS

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. DOI: https://doi.org/10.1093/mnrasl/slt155 Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-108193 Accepted Version Originally published at: 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. DOI: https://doi.org/10.1093/mnrasl/slt155 ar X iv :1 31 0. 76 06 v2 [ as tr oph .C O ] 1 8 N ov 2 01 3 Mon. Not. R. Astron. Soc. 000, 1–?? (xxxx) Printed 19 November 2013 (MN LTEX style file v2.2) MOND and IMF variations in early-type galaxies from ATLAS C. Tortora, A.J. Romanowsky, V.F. Cardone, N.R. Napolitano, Ph. Jetzer 1 Universität Zürich, Institut für Theoretische Physik, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland 2 Department of Physics and Astronomy, San José State University, San Jose, CA 95192, USA 3 University of California Observatories, 1156 High Street, Santa Cruz, CA 95064, USA 4 INAF – Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monte Porzio Catone, Roma, Italy 5 INAF – Osservatorio Astronomico di Capodimonte, Salita Moiariello, 16, 80131 Napoli, Italy