13
IRUS TotalDownloads
Altmetric
A complete search for redshift z>6.5 quasars in the VIKING survey
File | Description | Size | Format | |
---|---|---|---|---|
barnett_etal_2020.pdf | Accepted version | 1.63 MB | Adobe PDF | View/Open |
Title: | A complete search for redshift z>6.5 quasars in the VIKING survey |
Authors: | Barnett, R Warren, SJ Cross, NJG Mortlock, DJ Fan, X Wang, F Hewett, PC |
Item Type: | Journal Article |
Abstract: | We present the results of a new, deeper, and complete search for high-redshift $6.5<z<9.3$ quasars over 977deg$^2$ of the VISTA Kilo-Degree Infrared Galaxy (VIKING) survey. This exploits a new list-driven dataset providing photometry in all bands ZYJHKs, for all sources detected by VIKING in $J$. We use the Bayesian model comparison (BMC) selection method of Mortlock et al., producing a ranked list of just 21 candidates. The sources ranked 1, 2, 3 and 5 are the four known $z>6.5$ quasars in this field. Additional observations of the other 17 candidates, primarily DESI Legacy Survey photometry and ESO FORS2 spectroscopy, confirm that none is a quasar. This is the first complete sample from the VIKING survey, and we provide the computed selection function. We include a detailed comparison of the BMC method against two other selection methods: colour cuts and minimum-$\chi^2$ SED fitting. We find that: i) BMC produces eight times fewer false positives than colour cuts, while also reaching 0.3 mag. deeper, ii) the minimum-$\chi^2$ SED fitting method is extremely efficient but reaches 0.7 mag. less deep than the BMC method, and selects only one of the four known quasars. We show that BMC candidates, rejected because their photometric SEDs have high $\chi^2$ values, include bright examples of galaxies with very strong [OIII]$\lambda\lambda$4959,5007 emission in the $Y$ band, identified in fainter surveys by Matsuoka et al. This is a potential contaminant population in Euclid searches for faint $z>7$ quasars, not previously accounted for, and that requires better characterisation. |
Issue Date: | 10-Dec-2020 |
Date of Acceptance: | 4-Dec-2020 |
URI: | http://hdl.handle.net/10044/1/85221 |
DOI: | 10.1093/mnras/staa3808 |
ISSN: | 0035-8711 |
Publisher: | Royal Astronomical Society |
Start Page: | 1663 |
End Page: | 1676 |
Journal / Book Title: | Monthly Notices of the Royal Astronomical Society |
Volume: | 501 |
Issue: | 2 |
Copyright Statement: | © 2020 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model). This is a pre-copy-editing, author-produced version of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The definitive publisher-authenticated version R Barnett, S J Warren, N J G Cross, D J Mortlock, X Fan, F Wang, P C Hewett, A complete search for redshift z ≳ 6.5 quasars in the VIKING survey, Monthly Notices of the Royal Astronomical Society, Volume 501, Issue 2, February 2021, Pages 1663–1676 is available online at: https://doi.org/10.1093/mnras/staa3808 |
Sponsor/Funder: | Science and Technology Facilities Council Science and Technology Facilities Council (STFC) Science and Technology Facilities Council (STFC) |
Funder's Grant Number: | ST-N000838 ST/N000838/1 ST/S000372/1 |
Keywords: | astro-ph.GA astro-ph.GA astro-ph.CO astro-ph.GA astro-ph.GA astro-ph.CO Astronomy & Astrophysics 0201 Astronomical and Space Sciences |
Notes: | Accepted for MNRAS |
Publication Status: | Published |
Online Publication Date: | 2020-12-10 |
Appears in Collections: | Physics Astrophysics |