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

Yang, Jinyi and Fan, Xiaohui and Wu, Xue-Bing and Wang, Feige and Bian, Fuyan and Yang, Qian and McGreer, Ian D. and Yi, Weimin and Jiang, Linhua and Green, Richard and Yue, Minghao and Wang, Shu and Li, Zefeng and Ding, Jiani and Dye, S. and Lawrence, Andy (2017) Discovery of 16 new z ∼ 5.5 quasars: filling in the redshift gap of quasar color selection. Astronomical Journal, 153 (4). p. 184. ISSN 1538-3881

PDF - Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader
Download (1MB) | Preview


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.

Item Type: Article
Keywords: Galaxies: active; Galaxies: high-redshift; Quasars: emission lines; Quasars: general
Schools/Departments: University of Nottingham, UK > Faculty of Science > School of Physics and Astronomy
Identification Number: 10.3847/1538-3881/aa6577
Depositing User: Eprints, Support
Date Deposited: 27 Apr 2017 08:08
Last Modified: 27 Apr 2017 08:17

Actions (Archive Staff Only)

Edit View Edit View