DISCOVERY OF EIGHT z ~ 6 QUASARS IN THE SLOAN DIGITAL SKY SURVEY OVERLAP REGIONS

Date

2015

Authors

Jiang, Linhua
McGreer, Ian
Fan, Xiaohui
Bian, Fuyan
Clément, Benjamin
Wang, Ran
Fan, Zhou

Journal Title

Journal ISSN

Volume Title

Publisher

University of Chicago Press

Abstract

We present the discovery of eight quasars at z ∼ 6 identified in the Sloan Digital Sky Survey (SDSS) overlap regions. Individual SDSS imaging runs have some overlap with each other, leading to repeat observations over an area spanning >4000 deg2 (more than one-fourth of the total footprint). These overlap regions provide a unique data set that allows us to select high-redshift quasars more than 0.5 mag fainter in the z band than those found with the SDSS single-epoch data. Our quasar candidates were first selected as i-band dropout objects in the SDSS imaging database. We then carried out a series of follow-up observations in the optical and near-IR to improve photometry, remove contaminants, and identify quasars. The eight quasars reported here were discovered in a pilot study utilizing the overlap regions at high galactic latitude (|b| > 30°). These quasars span a redshift range of 5.86 < z < 6.06 and a flux range of 19.3 < z<inf>AB</inf> < 20.6 mag. Five of them are fainter than z<inf>AB</inf> = 20 mag, the typical magnitude limit of z ∼ 6 quasars used for the SDSS single-epoch images. In addition, we recover eight previously known quasars at z ∼ 6 that are located in the overlap regions. These results validate our procedure for selecting quasar candidates from the overlap regions and confirming them with follow-up observations, and they provide guidance to a future systematic survey over all SDSS imaging regions with repeat observations.

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Citation

Source

Astronomical Journal

Type

Journal article

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Access Statement

Open Access

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DOI

10.1088/0004-6256/149/6/188

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