Photometric Redshifts in JWST Deep Fields: A Pixel-Based Alternative with DeepDISC

TL;DR

This paper evaluates DeepDISC, a deep learning method that estimates photometric redshifts directly from JWST NIRCam images, showing it can match or outperform traditional template fitting in accuracy and efficiency.

Contribution

The study introduces DeepDISC as a pixel-based deep learning approach for photo-z estimation on high-redshift JWST data, demonstrating its effectiveness without relying on measured photometry.

Findings

DeepDISC produces reliable photo-zs comparable to template fitting.

DeepDISC outperforms template fitting with matched photometric filters.

It can generate 94,000 photo-z estimates in about 4 minutes.

Abstract

Photo-z algorithms that utilize SED template fitting have matured, and are widely adopted for use on high-redshift near-infrared data that provides a unique window into the early universe. Alternative photo-z methods have been developed, largely within the context of low-redshift optical surveys. Machine learning based approaches have gained footing in this regime, including those that utilize raw pixel information instead of aperture photometry. However, the efficacy of image-based algorithms on high-redshift, near-infrared data remains underexplored. Here, we test the performance of Detection, Instance Segmentation and Classification with Deep Learning (DeepDISC) on photometric redshift estimation with NIRCam images from the JWST Advanced Deep Extragalactic Survey (JADES) program. DeepDISC is designed to produce probabilistic photometric redshift estimates directly from images, after detecting and deblending sources in a scene. Using NIRCam-only images and a compiled catalog of spectroscopic redshifts, we show that DeepDISC produces reliable photo-zs and uncertainties comparable to those estimated from template fitting using HST+JWST filters; DeepDISC even outperforms template fitting (lower scatter/fewer outliers) when the input photometric filters are matched. Compared with template fitting, DeepDISC does not require measured photometry from images, and can produce a catalog of 94000 photo-zs in ~4 minutes on a single NVIDIA A40 GPU. While current spectroscopic training samples are small and incomplete in color-magnitude space, this work demonstrates the potential of DeepDISC for increasingly larger image volumes and spectroscopic samples from ongoing and future programs. We discuss the impact of the training data on applications to broader samples and produce a catalog of photo-zs for all JADES DR2 photometric sources in the GOOD-S field, with quality flags indicating caveats.