Photometric redshifts for active galactic nuclei with LePHARE for the Vera C. Rubin Observatory
Year: 2026
Type: article
Abstract: Context . Active galactic nuclei (AGNs) play a crucial role in galaxy evolution, but they are a minority of extragalactic sources with diverse spectral energy distributions (SEDs), which depend on their means of selection. Upcoming large-scale surveys such as LSST will identify many AGNs, but analysis tools are not optimized for them. The limited number of photometric bands in these surveys impacts the calculation of photometric redshifts for AGNs, which are essential for scientific advancement. Aims . We use LePHARE to demonstrate the impact that a limited number of bands and erroneous assumptions have on the determination of the photometric redshifts of AGNs. We conducted tests on six AGN samples selected using X-ray, radio, infrared, variability, color, and spectroscopic criteria in the COSMOS field, using photometry from HSC-CLAUDS, which is closest in depth and wavelength coverage to LSST. Methods . We present the LSST pipeline for LePHARE within the redshift assessment infrastructure layers (RAIL), facilitating comparison between SED fitting and machine-learning algorithms. Results . AGNs that appear as point-like sources in optical data are assigned highly unreliable photometric redshifts if they are processed using galaxy templates. Additionally, shallow all-sky surveys (such as eROSITA, WISE, and ZTF) miss many AGNs. As a result, these “hidden” AGNs are often misidentified as galaxies in public survey data, leading to incorrect photometric redshifts. Conclusions . We provide the configurations that are suggested for each type of AGN alongside measures of expected performance as a function of redshift, magnitude, and selection. To facilitate studies with a panchromatic view of AGNs, we also released photometric redshifts and posterior distributions for all AGN sources identified in the COSMOS field using the six criteria, based on 28-band photometry.
Source: Astronomy and Astrophysics
Authors: R. Shirley, M. Salvato, J. Cohen-Tanugi, O. Ilbert, S. Arnouts, R. Ansari, R. Assef, M. Banerji, A. Bongiorno, W. N. Brandt, J. Buchner, J. Comparat, D. Ilić, A. Kovačević, J. Kubica, B. Laloux, O. Lynn, A. Malz, L. Marchetti, C. Mazzucchelli, T. Mkrtchyan, K. Nandra, D. Oldag, C. Ricci, W. Roster, E. Saremi, S. Satheesh-Sheeba, T. Tasnim. Ananna, M. J. Temple, M. Vaccari, A. Viitanen, C. Wolf, Z. Yu, T. Zhang
Institutions: Max Planck Institute for Extraterrestrial Physics, Excellence Cluster Origins, Centre National de la Recherche Scientifique, Université Clermont Auvergne, Laboratoire de Physique de Clermont Auvergne, Aix-Marseille Université, Université Paris Cité, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Université Paris-Saclay, Universidad Diego Portales, University of Southampton, Astronomical Observatory of Rome, National Institute for Astrophysics, Pennsylvania State University, Pôle de recherche et d'enseignement supérieur Université de Grenoble, Université Grenoble Alpes, University of Belgrade, Carnegie Mellon University, Astronomical Observatory of Capodimonte, University of Cape Town, Istituto di Radioastronomia di Bologna, Inter-university Institute for Data Intensive Astronomy, University of Washington, University of Geneva, Universidad Andrés Bello, Wayne State University, Durham University, University of Helsinki, Australian National University, University of Pittsburgh
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
Award: G1559578688
OpenAlex ID: W7204953044