Multimodality for improved CNN photometric redshifts

¹ Aix Marseille Univ., CNRS, CNES, LAM, 13388 Marseille, France
e-mail: reda.ait-ouahmed@lam.fr
² AMIS – Université Paul-Valéry – Montpellier 3, 34000 Montpellier, France
³ UMR TETIS – INRAE, AgroParisTech, Cirad, CNRS, 34000 Montpellier, France
⁴ Sorbonne Université, CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98 bis bd Arago, 75014 Paris, France

Received: 7 July 2023
Accepted: 12 September 2023

Abstract

Photometric redshift estimation plays a crucial role in modern cosmological surveys for studying the universe’s large-scale structures and the evolution of galaxies. Deep learning has emerged as a powerful method to produce accurate photometric redshift estimates from multiband images of galaxies. Here, we introduce a multimodal approach consisting of the parallel processing of several subsets of prior image bands, the outputs of which are then merged for further processing through a convolutional neural network (CNN). We evaluate the performance of our method using three surveys: the Sloan Digital Sky Survey (SDSS), the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS), and the Hyper Suprime-Cam (HSC). By improving the model’s ability to capture information embedded in the correlation between different bands, our technique surpasses state-of-the-art photometric redshift precision. We find that the positive gain does not depend on the specific architecture of the CNN and that it increases with the number of photometric filters available.