Finding new high-redshift quasars by asking the neighbours
Abstract
Quasars with a high redshift (z) are important to understand the evolution processes of galaxies in the early Universe. However, only a few of these distant objects are known to this date. The costs of building and operating a 10-m class telescope limit the number of facilities and, thus, the available observation time. Therefore, an efficient selection of candidates is mandatory. This paper presents a new approach to select quasar candidates with high redshift (z > 4.8) based on photometric catalogues. We have chosen to use the z > 4.8 limit for our approach because the dominant Lyman α emission line of a quasar can only be found in the Sloan i- and z-band filters. As part of the candidate selection approach, a photometric redshift estimator is presented, too. Three of the 120 000 generated candidates have been spectroscopically analysed in follow-up observations and a new z = 5.0 quasar was found. This result is consistent with the estimated detection ratio of about 50 per cent and we expect 60 000 high-redshift quasars to be part of our candidate sample. The created candidates are available for download at MNRAS or at http://www.astro.rub.de/polsterer/quasar-candidates.csv.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- January 2013
- DOI:
- 10.1093/mnras/sts017
- arXiv:
- arXiv:1210.7071
- Bibcode:
- 2013MNRAS.428..226P
- Keywords:
-
- methods: statistical;
- techniques: photometric;
- catalogues;
- surveys;
- galaxies: distances and redshifts;
- quasars: general;
- Astrophysics - Instrumentation and Methods for Astrophysics;
- Astrophysics - Cosmology and Extragalactic Astrophysics
- E-Print:
- 10 pages, 9 figures, accepted (MNRAS)