The relation between stellar mass and weak lensing signal around galaxies: implications for modified Newtonian dynamics |
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| Authors: | Lanlan Tian Henk Hoekstra † Hongsheng Zhao |
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| Institution: | Department of Physics and Astronomy, University of Victoria, Victoria, BC V8W 2Y2, Canada;SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, KY16 9SS |
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| Abstract: | We study the amplitude of the weak gravitational lensing signal as a function of stellar mass around a sample of relatively isolated galaxies. This selection of lenses simplifies the interpretation of the observations, which consist of data from the Red-Sequence Cluster Survey and the Sloan Digital Sky Survey. We find that the amplitude of the lensing signal as a function of stellar mass is well described by a power law with a best-fitting slope α= 0.74 ± 0.08 . This result is inconsistent with modified Newtonian dynamics (MOND), which predicts α= 0.5 (we find α > 0.5 with 99.7 per cent confidence). As a related test, we determine the MOND mass-to-light ratio as a function of luminosity. Our results require dark matter for the most luminous galaxies ( L ? 1011 L⊙). We rule out an extended halo of gas or active neutrinos as a way of reconciling our findings with MOND. Although we focus on a single alternative gravity model, we note that our results provide an important test for any alternative theory of gravity. |
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| Keywords: | gravitation gravitational lensing galaxies: halos dark matter |
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