The miniJPAS survey: Maximising the photo-z accuracy from multi-survey datasets with probability conflation

¹ Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Unidad Asociada al CSIC, Plaza San Juan, 1, 44001 Teruel, Spain
e-mail: ahernan@cefca.es
² Tartu Observatory, University of Tartu, Observatooriumi 1, 61602 Tõravere, Estonia
³ Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Plaza San Juan, 1, 44001 Teruel, Spain
⁴ Department of Physics, University of Helsinki, Gustaf H allstr omin katu 2, 00014 Helsinki, Finland
⁵ Institut de Física d’Altes Energies, The Barcelona Institute of Science and Technology, Campus UAB, 08193 Bellaterra (Barcelona), Spain
⁶ Instituto de Física de Cantabria (Consejo Superior de Investi-gaciones Científicas – Universidad de Cantabria), Avda. de los Castros, 39005, Santander, Spain
⁷ Unidad Asociada “Grupo de astrofísica extragaláctica y cos-mología” (IFCA – Universitat de València), Parc Científic UV, 46980, Paterna, Spain
⁸ Instituto de Astrofísica de Andalucía (CSIC), PO Box 3004, 18080 Granada, Spain
⁹ Departamento de Astrofísica, Universidad de La Laguna, 38206, La Laguna, Tenerife, Spain
¹⁰ Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
¹¹ Universidade de São Paulo, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Rua do Matão 1226, 05508-090 São Paulo, Brazil
¹² Observatório Nacional, Ministério da Ciência, Tecnologia, Inovação e Comunicações, Rua General José Cristino, 77, São Cristóvão, 20921-400 Rio de Janeiro, Brazil
¹³ Observatório do Valongo, Universidade Federal do Rio de Janeiro, Ladeira do Pedro Antônio 43, Rio de Janeiro, RJ 20080-090, Brazil
¹⁴ Núcleo de Astrofísica e Cosmologia & Departamento de Física, Universidade Federal do Espírito Santo, 29075-910, Vitória, ES, Brazil
¹⁵ INAF – Osservatorio Astronomico di Trieste, via Tiepolo 11, 34131 Trieste, Italy
¹⁶ IFPU – Institute for Fundamental Physics of the Universe, via Beirut 2, 34151 Trieste, Italy
¹⁷ Instituto de Física, Universidade de São Paulo, Rua do Matão 1371, CEP 05508-090, São Paulo, Brazil
¹⁸ Donostia International Physics Centre, Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastian, Spain
¹⁹ Ikerbasque, Basque Foundation for Science, 48013 Bilbao, Spain
²⁰ Instituto de Física, Universidade Federal da Bahia, 40210-340, Salvador, BA, Brazil
²¹ Department of Astronomy, University of Michigan, 311 West Hall, 1085 South University Ave., Ann Arbor, USA
²² Department of Physics and Astronomy, University of Alabama, Box 870324, Tuscaloosa, AL, USA
²³ Departamento de Astronomia, Instituto de Astronomia, Geofísica e Ciências Atmosféricas da USP, Cidade Universitária, 05508-900, São Paulo, SP, Brazil
²⁴ Instruments4, 4121 Pembury Place, La Cañada-Flintridge, CA 91011, USA

Received: 6 November 2023
Accepted: 29 January 2024

Abstract

We present a new method for obtaining photometric redshifts (photo-z) for sources observed by multiple photometric surveys using a combination (conflation) of the redshift probability distributions (PDZs) obtained independently from each survey. The conflation of the PDZs has several advantages over the usual method of modelling all the photometry together, including the modularity, speed, and accuracy of the results. Using a sample of galaxies with narrow-band photometry in 56 bands from J-PAS and deeper grίzy photometry from the Hyper-SuprimeCam Subaru Strategic program (HSC-SSP), we show that PDZ conflation significantly improves photo-z accuracy compared to fitting all the photometry or using a weighted average of point estimates. The improvement over J-PAS alone is particularly strong for i≳22 sources, which have low signal-to-noise ratios in the J-PAS bands. For the entire i<22.5 sample, we obtain a 64% (45%) increase in the number of sources with redshift errors |Δz|<0.003, a factor of 3.3 (1.9) decrease in the normalised median absolute deviation of the errors (σ_NMAD), and a factor of 3.2 (1.3) decrease in the outlier rate (η) compared to J-PAS (HSC-SSP) alone. The photo-z accuracy gains from combining the PDZs of J-PAS with a deeper broad-band survey such as HSC-SSP are equivalent to increasing the depth of J-PAS observations by ~ 1.2–1.5 mag. These results demonstrate the potential of PDZ conflation and highlight the importance of including the full PDZs in photo-z catalogues.