Galactic scaling relations out to hundreds of kpc from weak lensing
The dynamical properties of galaxies exhibit strong regularities such as the Baryonic Tully-Fisher Relation and the Radial Acceleration Relation (RAR). The RAR relates the baryonic Newtonian acceleration $g_”bar”$ and the observed total acceleration $g_”obs”$ which includes the effects of dark matter. Recently, it was shown that weak-lensing observations allow to probe the RAR of isolated galaxies down to extremely small accelerations $g_”bar”$, corresponding to many hundreds of $”kpc”$. I will introduce this weak-lensing RAR and discuss its most recent iteration which features improved stellar masses, a stricter isolation criterion, and a novel deprojection method. The lensing RAR smoothly continues the kinematic RAR by about 2.5 dex in $g_”bar”$, implying flat rotation curves out to hundreds of $”kpc”$. I will discuss how this relation constrains models of dark matter and modified gravity.