A Caltech Library Service

Improved photometric redshifts with colour-constrained galaxy templates for future wide-area surveys

Lee, Bomee and Chary, Ranga-Ram (2020) Improved photometric redshifts with colour-constrained galaxy templates for future wide-area surveys. Monthly Notices of the Royal Astronomical Society, 497 (2). pp. 1935-1945. ISSN 0035-8711. doi:10.1093/mnras/staa2100.

PDF - Published Version
See Usage Policy.

[img] PDF - Submitted Version
See Usage Policy.


Use this Persistent URL to link to this item:


Cosmology and galaxy evolution studies with LSST, Euclid, and Roman, will require accurate redshifts for the detected galaxies. In this study, we present improved photometric redshift estimates for galaxies using a template library that populates three-colour space and is constrained by HST/CANDELS photometry. For the training sample, we use a sample of galaxies having photometric redshifts that allows us to train on a large, unbiased galaxy sample having deep, unconfused photometry at optical-to-mid infrared wavelengths. Galaxies in the training sample are assigned to cubes in 3D colour space, V − H, I − J, and z − H. We then derive the best-fitting spectral energy distributions of the training sample at the fixed CANDELS median photometric redshifts to construct the new template library for each individual colour cube (i.e. colour-cube-based template library). We derive photometric redshifts (photo-z) of our target galaxies using our new colour-cube-based template library and with photometry in only a limited set of bands, as expected for the aforementioned surveys. As a result, our method yields σ_(NMAD) of 0.026 and an outlier fraction of 6 per cent using only photometry in the LSST and Euclid/Roman bands. This is an improvement of ∼10 per cent on σ_(NMAD) and a reduction in outlier fraction of ∼13 per cent compared to other techniques. In particular, we improve the photo-z precision by about 30 per cent at 2 < z < 3. We also assess photo-z improvements by including K or mid-infrared bands to the ugrizYJH photometry. Our colour-cube-based template library is a powerful tool to constrain photometric redshifts for future large surveys.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Lee, Bomee0000-0003-1954-5046
Chary, Ranga-Ram0000-0001-7583-0621
Alternate Title:Improved photometric redshifts with color-constrained galaxy templates for future wide-area surveys
Additional Information:© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2020 July 8. Received 2020 June 20; in original form 2019 October 22. Published: 17 July 2020. This work is funded by NASA/Euclid grant 1484822 and Joint Survey Processing (JSP) effort at Infrared Processing and Analysis Centre (IPAC), which has been provided by NASA grant 80NM0018F0803. The data used in this work are based on observations taken by the CANDELS MultiCycle Treasury Program with the NASA/ESA HST, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. The authors thank Andreas Faisst for thoughtful comments that improved this manuscript and Gabe Brammer for helpful ideas that improved our analysis. We also thank the anonymous referee for very useful comments that helped to improve the presentation of the paper. Data Availability: The CANDELS multiwavelength catalogues and photometric redshifts catalogues used in this study are publicly available on the Mikulski Archive for Space Telescopes: The photometric redshift estimations underlying this article will be shared on reasonable request to the corresponding author.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Subject Keywords:methods: statistical – techniques: photometric – galaxies: photometry
Issue or Number:2
Record Number:CaltechAUTHORS:20200406-101835276
Persistent URL:
Official Citation:Bomee Lee, Ranga-Ram Chary, Improved photometric redshifts with colour-constrained galaxy templates for future wide-area surveys, Monthly Notices of the Royal Astronomical Society, Volume 497, Issue 2, September 2020, Pages 1935–1945,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:102346
Deposited By: Tony Diaz
Deposited On:06 Apr 2020 18:31
Last Modified:16 Nov 2021 18:11

Repository Staff Only: item control page