The masses of satellites in GAMA galaxy groups from 100 square degrees of KiDS weak lensing data

We use the first 100 sq. deg. of overlap between the Kilo-Degree Survey (KiDS) and the Galaxy And Mass Assembly (GAMA) survey to determine the galaxy halo mass of ~10,000 spectroscopically-confirmed satellite galaxies in massive ($M>{10}^{13}{h}^{-1}{\mathrm{M}}_{\odot }$) galaxy groups. Separating the sample as a function of projected distance to the group centre, we jointly model the satellites and their host groups with Navarro-Frenk-White (NFW) density profiles, fully accounting for the data covariance. The probed satellite galaxies in these groups have total masses $\log M_{\rm sub} /(h^{-1}{\rm M}\odot) \approx 11.7 - 12.2$ consistent across group-centric distance within the errorbars. Given their typical stellar masses, $\log M{\rm \star,sat}/(h^{-2}{\rm M}\odot) \sim 10.5$, such total masses imply stellar mass fractions of $M_{\star ,\mathrm{s}\mathrm{a}\mathrm{t}}\mathrm{/}{M}_{\mathrm{s}\mathrm{u}\mathrm{b}}\approx 0.04h^{-1}$ . The average subhalo hosting these satellite galaxies has a mass $M{\rm sub} \sim 0.015M_{\rm host}$ independent of host halo mass, in broad agreement with the expectations of structure formation in a $\mathrm{\Lambda }$CDM universe.