2020MNRAS.493L..33S

We present new observations of two z = 0.12 strong-lensing elliptical galaxies, originally discovered from the SDSS-IV MaNGA survey, using the new FOCAS IFU spectrograph on the Subaru Telescope. For J1436+4943, our observations confirm the identification of this system as a multiple-image lens, in a cusp configuration, with an Einstein radius θEin = 2.0 arcsec. For J1701+3722, the improved data confirm earlier hints of a complex source plane, with different configurations evident in different emission lines. The new observations reveal a previously unseen inner counter-image to the [O III] arc found from MaNGA, leading to a smaller revised Einstein radius of θEin = 1.6 arcsec. The inferred projected masses within the Einstein apertures (3.7-4.7 kpc) are consistent with being dominated by stars with an initial mass function (IMF) similar to that of the Milky Way, and a dark matter contribution of ∼35 per cent as supported from cosmological simulations. These results are consistent with `pure lensing' analyses of lower redshift lenses, but contrast with claims for heavier IMFs from combined lensing and dynamical studies of more distant early-type galaxies.