Dynamical Confirmation of Sloan Digital Sky Survey Weak-lensing Scaling Laws

Galaxy masses can be estimated by a variety of methods; each applicable indifferent circumstances, and each suffering from different systematicuncertainties. Confirmation of results obtained by one technique with analysisby another is particularly important. Recent SDSS weak lensing measurements ofthe projected-mass correlation function reveal a linear relation between galaxyluminosities and the depth of their dark matter halos (measured on 260 \hinvkpc scales). In this work we use an entirely independent dynamical method toconfirm these results. We begin by assembling a sample of 618 relativelyisolated host galaxies, surrounded by a total of 1225 substantially faintersatellites. We observe the mean dynamical effect of these hosts on the motionsof their satellites by assembling velocity difference histograms. Dividing thesample by host properties, we find significant variations in satellite velocitydispersion with host luminosity. We quantify these variations using a simpledynamical model, measuring \mtsd a dynamical mass within 260 \hinv kpc. Theappropriateness of this mass reconstruction is checked by conducting a similaranalysis within an N-body simulation. Comparison between the dynamical andlensing mass-to-light scalings shows reasonable agreement, providing somequantitative confirmation for the lensing results.Comment: 7 pages, 3 figures, accepted for publication in ApJ Letter