http://arxiv.org/abs/1607.01800
We use the mass discrepancy-acceleration relation (the correlation between the ratio of dark-to-visible mass and acceleration in galaxies; MDAR) to test the galaxy-halo connection. We analyse the MDAR using a set of 14 statistics which quantify its four most important features: its shape, its scatter, the presence of a “characteristic acceleration scale,” and the correlation of its residuals with other galaxy properties. We construct an empirical framework for the galaxy-halo connection in $\Lambda$CDM to generate predictions for these statistics, starting with conventional correlations (halo abundance matching; AM) and introducing more where required. Comparing to the SPARC data (Lelli, McGaugh & Schombert 2016), we find: 1) The approximate shape of the MDAR is readily reproduced by AM, and there is no evidence that the acceleration at which dark matter becomes negligible has less spread in the data than in AM mocks; 2) Even under conservative assumptions, AM significantly overpredicts the scatter in the relation and its normalisation at low acceleration, and furthermore positions dark matter too close to galaxies’ centres on average; 3) The MDAR affords $2 \sigma$ evidence for a correlation of surface brightness with halo mass or concentration. Our analysis lays the groundwork for a bottom-up determination of the galaxy-halo connection from relations such as the MDAR, provides concrete statistical tests for specific galaxy formation models, and brings into sharper focus the relative evidence accorded by galaxy kinematics to $\Lambda$CDM and modified gravity alternatives.
H. Desmond
Fri, 8 Jul 16
1/56
Comments: 20 pages, 7 figures, MNRAS submitted. Comments welcome
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