The day opened with a conversation with Guangtun Zhu (formerly JHU) who has been doing great things with the eBOSS and MaNGA spectra from SDSS-IV. On the former, he has made a composite (average) spectrum and can see many things that haven't been seen before in galaxies like these. He can see fluorescence from the outer ISM (or maybe IGM) and he can see the effects of other extremely weak emission and absorption lines. He can also see that the emission lines are due to outflows, but in great detail: Different lines with different relative amounts of absorption and emission have different profiles and he has a consistent story for all of these.
I ended the day by working on the text in the paper on image modeling (image differencing) by Dun Wang (NYU) and in the paper on data-driven galaxy SED models by Boris Leistedt (NYU).