In this figure, we label the most important emission lines used in our studies, in particular, the strong Balmer hydrogen recombination lines and
collisionally excited emission lines, such as [O II] [lambda][lambda]3726,3729, [O III] [lambda]4363, [O III] [lambda]5007, [S II] [lambda][lambda]6717,6731, and [N II] [lambda]6584, which have been used for the determination of physical conditions (e.g., electron temperature and density) and chemical abundances (e.g., oxygen, nitrogen, etc.).
He relates a theory that hundreds of bodies larger than Ceres, perhaps as large as Mars, may have existed in the early asteroid belt, without pointing out that presumably all of these bodies were ejected, intact, from the solar system (they're too big to have been
collisionally fragmented into smaller pieces).