absorption lines

Brice Ménard (CITA) came by for the day, and Schiminovich came down in the afternoon and we all discussed weak but measurable correlations in quasar spectra and imaging. For example, Ménard has measured relationships between quasar images and absorbers (to show that there is extended star formation associated with absorbers), between emission lines and absorption lines in absorbers (same conclusion), and between quasar colors and angular separation to nearby galaxies (to show that there is dust correlated with galaxies). These projects are all describable as stacking projects, because they involve measuring very weak signals that are only detectable in large ensembles of objects that can be, in some sense, aligned. However, they are also all describable as correlation function projects, because they are measurements of excess in one signal that is keyed by the presence of a somehow neighboring signal. Either way, they are projects that are only possible with large uniform data sets; Ménard is the world's expert in finding signals like these. Schiminovich and I committed to giving Ménard some GALEX data for extension of these projects into the ultraviolet.

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