S19B0097abst
S19B0097
Low-redshift strong lenses yield uniquely-robust measurements of the stellar masses of galaxies, and hence offer a sensitive probe of possible variation in the stellar IMF as a function of galaxy properties. We have developed a novel method to discover such lenses, using IFUs to search for multiply-imaged line emission behind massive low-z elliptical galaxies. We have successfully applied this technique to data from SINFONI and MUSE at the VLT, discovering four systems so far, which are the only z<0.1 strong-lensing ellipticals known to date. All yield stellar mass measurements which are compatible with a Milky-Way-like IMF, and exclude the very heavy IMFs suggested for similarly massive galaxies from spectroscopic analysis (e.g. Conroy & van Dokkum 2012). However, with the current very small sample, we cannot exclude modestly heavy IMFs, nor assess galaxy-to-galaxy variations or correlations: more nearby lenses are urgently required. In S19A we will begin observations with the new FOCAS IFU, to search for low-redshift lenses in the northern hemisphere. Here we request two nights to continue this programme in S19B.
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