Testing screened modified gravity with SDSS-IV-MaNGA

Fifth forces are ubiquitous in modified gravity theories, and must be screened to evade stringent local tests. This can introduce unusual behaviour in galaxy phenomenology by affecting galaxies' components differently. Here we use the SDSS-IV-MaNGA dataset to search for a systematic excess of gas circular velocity over stellar circular velocity, expected in thin-shell-screened theories in the partially screened regime. Accounting for asymmetric drift and calibrating our model on screened subsamples, we find no significant evidence for a screened fifth force. We bound the fifth-force strength to $\Delta G/G_\text{N} < 0.1$ for all astrophysical ranges, strengthening to $\sim$0.01 at Compton wavelength of 3 Mpc for the Hu-Sawicki model, for instance. This implies a stringent constraint on scalar-tensor theories, for example $f_{\mathcal{R}0} \lesssim 10^{-8}$ in Hu-Sawicki $f(\mathcal{R})$ gravity.