Photometric redshifts for the next generation of deep radio continuum surveys - II. Gaussian processes and hybrid estimates

Journal article

Building on the first paper in this series (Duncan et al. 2018), we present a study investigating the performance of Gaussian process photometric redshift (photo-z) estimates for galaxies and active galactic nuclei detected in deep radio continuum surveys. A Gaussian process redshift code is used to produce photo-z estimates targeting specific subsets of both the AGN population - infrared, X-ray and optically selected AGN - and the general galaxy population. The new estimates for the AGN population are found to perform significantly better at z > 1 than the template-based photo-z estimates presented in our previous study. Our new photo-z estimates are then combined with template estimates through hierarchical Bayesian combination to produce a hybrid consensus estimate that outperforms both of the individual methods across all source types. Photo-z estimates for radio sources that are X-ray sources or optical/IR AGN are significantly improved in comparison to previous template-only estimates - with outlier fractions and robust scatter reduced by up to a factor of ∼4. The ability of our method to combine the strengths of the two input photo-z techniques and the large improvements we observe illustrate its potential for enabling future exploitation of deep radio continuum surveys for both the study of galaxy and black hole co-evolution and for cosmological studies.

Authors: Duncan, K; Jarvis, M; Brown, M; Röttgering, H

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Oxford University Press
• Journal: Monthly Notices of the Royal Astronomical Society
• Volume: 477
• Issue: 4
• Pages: 5177–5190
• Publication date: 2018-04-18
• Acceptance date: 2018-04-11
• DOI: 10.1093/mnras/sty940
• EISSN: 1365-29661
• ISSN: 0035-8711
• Keywords: radio continuum: galaxies; galaxies: active; galaxies: distances and redshifts