A Study of Quasar Selection in the Dark Energy Survey Supernova fields
Abstract
We present a study of quasar selection using the DES supernova fields. We used a quasar catalog from an overlapping portion of the SDSS Stripe 82 region to quantify the completeness and efficiency of selection methods involving color, probabilistic modeling, variability, and combinations of color/probabilistic modeling with variability. We only considered objects that appear as point sources in the DES images. We examine color selection methods based on the WISE mid-IR W1-W2 color, a mixture of WISE and DES colors (g-i and i-W1) and a mixture of VHS and DES colors (g-i and i-K). For probabilistic quasar selection, we used XDQSOz, an algorithm that employs an empirical multi-wavelength flux model of quasars to assign quasar probabilities. Our variability selection uses the multi-band chi2-probability that sources are constant in the DES Year 1 griz-band light curves. The completeness and efficiency are calculated relative to an underlying sample of point sources that are detected in the required selection bands and pass our data quality and photometric error cuts. We conduct our analyses at two magnitude limits, i<19.8 mag and i<22 mag. For sources with W1 and W2 detections, the W1-W2 color or XDQSOz method combined with variability gives the highest completenesses of >85% for both i-band magnitude limits and efficiencies of >80% to the bright limit and >60% to the faint limit; however, the giW1 and giW1+variability methods give the highest quasar surface densities. The XDQSOz method and combinations of W1W2/giW1/XDQSOz with variability are among the better selection methods when both high completeness and high efficiency are desired. We also present the OzDES Quasar Catalog of 1,263 spectroscopically-confirmed quasars taken by the OzDES survey. The catalog includes quasars with redshifts up to z~4 and brighter than i=22 mag, although the catalog is not complete up this magnitude limit.
Keywords
Cite
@article{arxiv.1611.05456,
title = {A Study of Quasar Selection in the Dark Energy Survey Supernova fields},
author = {S. S. Tie and P. Martini and D. Mudd and F. Ostrovski and S. L. Reed and C. Lidman and C. Kochanek and T. M. Davis and R. Sharp and S. Uddin and A. King and W. Wester and B. E. Tucker and D. L. Tucker and E. Buckley-Geer and D. Carollo and M. Childress and K. Glazebrook and S. R. Hinton and G. Lewis and E. Macaulay and C. R. O'Neill and T. M. C. Abbott and F. B. Abdalla and J. Annis and A. Benoit-L'evy and E. Bertin and D. Brooks and A. Carnero Rosell and M. Carrasco Kind and J. Carretero and C. E. Cunha and L. N. da Costa and D. L. DePoy and S. Desai and P. Doel and T. F. Eifler and A. E. Evrard and D. A. Finley and B. Flaugher and P. Fosalba and J. Frieman and J. Garcia-Bellido and E. Gaztanaga and D. W. Gerdes and D. A. Goldstein and D. Gruen and R. A. Gruendl and G. Gutierrez and K. Honscheid and D. J. James and K. Kuehn and N. Kuropatkin and M. Lima and M. A. G. Maia and J. L. Marshall and F. Menanteau and C. J. Miller and R. Miquel and R. C. Nichol and B. Nord and R. Ogando and A. A. Plazas and A. K. Romer and E. Sanchez and B. Santiago and V. Scarpine and M. Schubnell and I. Sevilla-Noarbe and R. C. Smith and M. Soares-Santos and F. Sobreira and E. Suchyta and M. E. C. Swanson and G. Tarle and D. Thomas and A. R. Walker and The DES Collaboration},
journal= {arXiv preprint arXiv:1611.05456},
year = {2017}
}
Comments
16 pages, 12 figures, 3 tables; Submitted to ApJ. The OzDES Quasar Catalog can be downloaded at http://bit.ly/2fWsK9t . For a video summary of the paper, please see https://www.youtube.com/watch?v=JeQNdUATze0