J-NEP: 60-band photometry and photometric redshifts for the James Webb Space Telescope North Ecliptic Pole Time-Domain Field

¹ Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Plaza San Juan, 1, 44001 Teruel, Spain
e-mail: ahernan@cefca.es
² Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA
³ Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Unidad Asociada al CSIC, Plaza San Juan, 1, 44001 Teruel, Spain
⁴ Donostia International Physics Centre, Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastian, Spain
⁵ Ikerbasque, Basque Foundation for Science, Plaza Euskadi 5, 48013 Bilbao, Spain
⁶ Observatório Nacional, Ministério da Ciência, Tecnologia, Inovação e Comunicações, Rua General José Cristino, 77, São Cristóvão, 20921-400, Rio de Janeiro, Brazil
⁷ Department of Astronomy, University of Michigan, 311 West Hall, 1085 South University Ave., Ann Arbor, USA
⁸ Department of Physics and Astronomy, University of Alabama, Box 870324, Tuscaloosa, AL, USA
⁹ Department of Physics, University of Hong Kong, 852-2219 4924, Hong Kong
¹⁰ Tartu Observatory, University of Tartu, Observatooriumi 1, 61602 Tõravere, Estonia
¹¹ Departamento de Astrofísica, Universidad de La Laguna, Avda. Astrofísico Francisco Sánchez s/n, 38206, La Laguna, Tenerife, Spain
¹² Instituto de Astrofísica de Canarias, c Vía Láctea s/n, 38200 La Laguna, Tenerife, Spain
¹³ Instituto de Física de Cantabria (Consejo Superior de Investigaciones Científicas – Universidad de Cantabria). Avda. de los Castros, 39005, Santander, Spain
¹⁴ Unidad Asociada “Grupo de astrofísica extragaláctica y cosmología” (IFCA – Universitat de València). Parc Científic UV, 46980, Paterna, Spain
¹⁵ Instituto de Astrofísica de Andalucía (CSIC), PO Box 3004, 18080 Granada, Spain
¹⁶ Instituto de Física, Universidade de São Paulo, Rua do Matão 1371, CEP 05508-090, São Paulo, Brazil
¹⁷ Departamento de Astronomia, Instituto de Física, Universidade Federal do Rio Grande do Sul (UFRGS), Av. Bento Gonçalves 9500, Porto Alegre, RS, Brazil
¹⁸ Instituto de Física, Universidade Federal da Bahia, Campus Universitário de Ondina, 40210-340, Salvador, BA, Brazil
¹⁹ Departamento de Astronomia, Instituto de Astronomia, Geofísica e Ciências Atmosféricas da USP, Cidade Universitária, 05508-900, São Paulo, SP, Brazil
²⁰ Instruments4, 4121 Pembury Place, La Cañada-Flintridge, CA 91011, USA

Received: 17 August 2022
Accepted: 23 January 2023

Abstract

The Javalambre-Physics of the Accelerating Universe Astrophysical Survey (J-PAS) will observe approximately one-third of the northern sky with a set of 56 narrow-band filters using the dedicated 2.55 m Javalambre Survey Telescope (JST) at the Javalambre Astrophysical Observatory. Prior to the installation of the main camera, in order to demonstrate the scientific potential of J-PAS, two small surveys were performed with the single-CCD Pathfinder camera: miniJPAS (~1 deg² along the Extended Groth Strip), and J-NEP (~0.3 deg² around the JWST North Ecliptic Pole Time Domain Field), including all 56 J-PAS filters as well as u, g, r, and i. J-NEP is ~0.5–1.0 mag deeper than miniJPAS, providing photometry for 24,618 r-band-detected sources and photometric redshifts (photo-z) for the 6662 sources with r < 23. In this paper, we describe the photometry and photo-z of J-NEP and demonstrate a new method for the removal of systematic offsets in the photometry based on the median colours of galaxies, which we call ‘galaxy locus recalibration’. This method does not require spectroscopic observations except in a few reference pointings and, unlike previous methods, is directly applicable to the whole J-PAS survey. We use a spectroscopic sample of 787 galaxies to test the photo-z performance for J-NEP and in comparison to miniJPAS. We find that the deeper J-NEP observations result in a factor ~1.5–2 decrease in σ_NMAD (a robust estimate of the standard deviation of the photo-z error) and η (the outlier rate) relative to miniJPAS for r > 21.5 sources, but no improvement in brighter ones, which is probably because of systematic uncertainties. We find the same relation between σ_NMAD and odds in J-NEP and miniJPAS, which suggests that we will be able to predict the σ_NMAD of any set of J-PAS sources from their odds distribution alone, with no need for additional spectroscopy to calibrate the relation. We explore the causes of photo-z outliers and find that colour-space degeneracy at low S/N, photometry artefacts, source blending, and exotic spectra are the most important factors.