Discovery of 16 new z ∼ 5.5 quasars: filling in the redshift gap of quasar color selection

Yang, Jinyi; Fan, Xiaohui; Wu, Xue-Bing; Wang, Feige; Bian, Fuyan; Yang, Qian; McGreer, Ian D.; Yi, Weimin; Jiang, Linhua; Green, Richard; Yue, Minghao; Wang, Shu; Li, Zefeng; Ding, Jiani; Dye, Simon; Lawrence, Andy

Abstract

We present initial results from the first systematic survey of luminous z ∼ 5.5 quasars. Quasars at z ∼ 5.5, the post-reionization epoch, are crucial tools to explore the evolution of intergalactic medium, quasar evolution, and the early super-massive black hole growth. However, it has been very challenging to select quasars at redshifts 5.3 ≤ z ≤ 5.7 using conventional color selections, due to their similar optical colors to late-type stars, especially M dwarfs, resulting in a glaring redshift gap in quasar redshift distributions. We develop a new selection technique for z ∼ 5.5 quasars based on optical, near-IR, and mid-IR photometric data from Sloan Digital Sky Survey (SDSS), UKIRT InfraRed Deep Sky Surveys—Large Area Survey (ULAS), VISTA Hemisphere Survey (VHS), and Wide Field Infrared Survey Explorer. From our pilot observations in the SDSS-ULAS/VHS area, we have discovered 15 new quasars at 5.3 ≤ z ≤ 5.7 and 6 new lower redshift quasars, with SDSS z band magnitude brighter than 20.5. Including other two z ∼ 5.5 quasars already published in our previous work, we now construct a uniform quasar sample at 5.3 ≤ z ≤ 5.7, with 17 quasars in a ∼4800 square degree survey area. For further application in a larger survey area, we apply our selection pipeline to do a test selection by using the new wide field J-band photometric data from a preliminary version of the UKIRT Hemisphere Survey (UHS). We successfully discover the first UHS selected z ∼ 5.5 quasar.

Citation

Yang, J., Fan, X., Wu, X.-B., Wang, F., Bian, F., Yang, Q., McGreer, I. D., Yi, W., Jiang, L., Green, R., Yue, M., Wang, S., Li, Z., Ding, J., Dye, S., & Lawrence, A. (2017). Discovery of 16 new z ∼ 5.5 quasars: filling in the redshift gap of quasar color selection. Astronomical Journal, 153(4), 184. https://doi.org/10.3847/1538-3881/aa6577

• Journal Article Type: Article
• Acceptance Date: Mar 6, 2017
• Online Publication Date: Mar 30, 2017
• Publication Date: Mar 30, 2017
• Deposit Date: Apr 27, 2017
• Publicly Available Date: Apr 27, 2017
• Journal: Astronomical Journal
• Print ISSN: 0004-6256
• Electronic ISSN: 1538-3881
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 153
• Issue: 4
• Pages: 184
• DOI: https://doi.org/10.3847/1538-3881/aa6577
• Keywords: Galaxies: active; Galaxies: high-redshift; Quasars: emission lines; Quasars: general
• Public URL: https://nottingham-repository.worktribe.com/output/853494
• Publisher URL: http://iopscience.iop.org/article/10.3847/1538-3881/aa6577/meta
• Additional Information: Journal title: The Astronomical Journal; Article type: paper; Article title: Discovery of 16 Newz∼ 5.5 Quasars: Filling in the Redshift Gap of Quasar Color Selection; Copyright information: © 2017. The American Astronomical Society. All rights reserved.; Date received: 2016-10-23; Date accepted: 2017-03-06; Online publication date: 2017-03-30
• Contract Date: Apr 27, 2017