The miniJPAS survey: Photometric redshift catalogue

MiniJPAS is a ∼1 deg2 imaging survey of the AEGIS field in 60 bands, performed to demonstrate the scientific potential of the upcoming Javalambre-Physics of the Accelerating Universe Astrophysical Survey (J-PAS). Full coverage of the 3800–9100 A range with 54 narrow-band filters, in combination with 6 optical broad-band filters, allows for extremely accurate photometric redshifts (photo-z ), which, applied over areas of thousands of square degrees, will enable new applications of the photo-z technique, such as measurement of baryonic acoustic oscillations. In this paper we describe the method we used to obtain the photo-z that is included in the publicly available miniJPAS catalogue, and characterise the photo-z performance. We built photo-spectra with 100 A resolution based on forced-aperture photometry corrected for point spread function. Systematic offsets in the photometry were corrected by applying magnitude shifts obtained through iterative fitting with stellar population synthesis models. We computed photo-z with a customised version of LEPHARE, using a set of templates that is optimised for the J-PAS filter-set. We analysed the accuracy of miniJPAS photo-z and their dependence on multiple quantities using a subsample of 5266 galaxies with spectroscopic redshifts from SDSS and DEEP, which we find to be representative of the whole r uncertainties for the photo-z that are calculated with the Δχ 2 method underestimate the actual redshift errors. The o d d s parameter has a stronger correlation with |Δz | and accurately reproduces the probability of a redshift outlier (|Δz | > 0.03), regardless of the magnitude, redshift, or spectral type of the sources. We show that the two main summary statistics characterising the photo-z accuracy for a population of galaxies (σ NMAD and η ) can be predicted by the distribution of o d d s in this population, and we use this to estimate the statistics for the whole miniJPAS sample. At r with valid photo-z estimates, ∼4200 of which are expected to have |Δz | NMAD = 0.013 with an outlier rate η = 0.39. The target photo-z accuracy σ NMAD = 0.003 is achieved for o d d s > 0.82 with η = 0.05, at the cost of decreasing the density of selected galaxies to n ∼ 5200 deg−2 (∼2600 of which have |Δz | < 0.003).