Redshifted broad absorption line quasars found via machine-learned spectral similarity

Itamar Reis*, Dovi Poznanski, Patrick B. Hall

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


We report the discovery of 31 new redshifted broad absorption line quasars (RSBALs) from the Sloan Digital Sky Survey (SDSS). The number of previously known such objects is 19. The identification of the new objects was enabled by calculating similarities between quasar spectra in the SDSS. Using these similarities we look for the objects that are similar to the ones in the original sample, visually inspecting only hundreds, out of over 160 000 spectra considered. We compare the performance of several similarity measures, as well as different methods of employing them, in finding the RSBALs. We find that decision tree based similarities recover the most objects, and that an ensemble of methods performs better than any single one. As the similarities are not tailored for the specific problem of finding RSBALs, they could be used for searching for other types of quasars. The similarities and the code for their calculation are available online.

Original languageEnglish
Pages (from-to)3889-3897
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - 1 Nov 2018


FundersFunder number
National Aeronautics and Space Administration
Alfred P. Sloan Foundation
Yale University
Vanderbilt University
New York University
Ohio State University
University of Colorado Boulder
University of Utah
Johns Hopkins University
University of Arizona
University of Notre Dame
Pennsylvania State University
University of Portsmouth
New Mexico State University
Natural Sciences and Engineering Research Council of Canada
University of Oxford
University of Tokyo


    • Methods: data analysis
    • Quasars: absorption lines
    • Quasars: general
    • Techniques: spectroscopic


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