ULTIMATE deblending I. A 50-band UV-to-MIR photometric catalog combining space- and ground-based data in the JWST/PRIMER survey

Abstract

Our understanding of the early Universe has long been limited by biased galaxy samples selected through various color criteria. With deep JWST infrared imaging, mass-complete galaxy samples can now be studied up to $z \sim 8$ for the first time. However, recent work has revealed systematic uncertainties in measuring physical properties of galaxies based solely on JWST/NIRCam and HST photometry, due to their limited wavelength coverage. This highlights the need for supplementary data, particularly in the rest-frame UV and near-infrared. Here we present the ULTIMATE-deblending project, which will eventually deliver self-consistent UV-to-Radio photometry for galaxies detected in deep JWST surveys, including both NIRCam and MIRI data. In this first paper, we release a 50-band photometric catalog spanning CFHT/U to JWST/MIRI F1800W, covering a total of 627.1 arcmin$^2$ across two JWST/PRIMER fields. We detail the reduction of JWST imaging data, the photometric procedures, and the SED-fitting methodology used to derive galaxy properties. Compared with photometry including only HST and JWST bands, the inclusion of deblended low-resolution photometry from ground-based telescopes improves the accuracy of photometric redshifts by $\sim$40%, while reducing the outlier fraction by $\sim$60%. This galaxy sample can serve as a key reference for statistical studies of galaxy formation and evolution in the early universe. All catalogs and JWST mosaics from the ULTIMATE-deblending project will be made publicly available.

Figures (11)

• Figure 1: The coverage of the key surveys within PRIMER-COSMOS (left panel) and PRIMER-UDS (right panel). The background grayscale image presents the 3$\sigma$ limiting depth (in 0.2" diameter apertures) for point sources of the stacked JWST/NIRCam image, which is used for source detection. The blue, orange, and red lines show the coverage of the HST data from the CANDELS survey Galametz2013Nayyeri2017, the Magellan/Fourstar medium-bands data from the ZFOURGE survey Straatman2016, and the JWST/MIRI data taken with the PRIMER survey. The boundary of our mosaics in PRIMER-COSMOS is determined by the coverage of the JWST/MIRI data from PRIMER Dunlop2021 and the deep SCUBA-2 data from STUDIES WangWH2017GaoZK2024.
• Figure 2: The 3 $\sigma$ depth and wavelength range of the multi-band data used by PRIMER-COSMOS (upper panel) and PRIMER-UDS (lower panel). All depths of point sources are measured using empty circular apertures and have been corrected to consider the aperture losses. We use the apertures with the highest sensitivity (among 0.2", 0.5", and Kron apertures) for JWST and HST data, and apertures with $d = 3.5 \times {\rm{FWH}}{{\rm{M}}_{{\rm{PSF}}}}$ for the other low-resolution data.
• Figure 3: Validation of our astrometric alignment. The left panel shows the astrometric difference between our detection image and gaia DR3 Gaia2018, while the right panels shows the astrometric difference between different NIRCam bands. Sources from both PRIMER-COSMOS and PRIMER-UDS are included in this figure. Outliers in the right panel include galaxies with different morphologies at different bands.
• Figure 4: Source number counts and detection completeness. The red line in the upper panel presents the source number count density as a function of F444W magnitude. The blue line shows the number count density from the JADES survey Eisenstein2023. The lower panel shows the ratio between the number count density of our work and JADES, which presents the detection completeness of our catalog.
• Figure 5: Example of the TPHOT deblending photometry. The upper panels show the images in the center of the Bigfoot protocluster in PRIMER-UDS Sun2025, with locations of the three massive member galaxies in Bigfoot marked as crosses. The first image is the high-resolution image from JWST/NIRCam F200W, which is used to provide high-resolution priors for K-band photometry. The second image is the low-resolution image from UKIRT/K, which is the measurement band in this example. The third and fourth images are the best-fit models and residuals after the deblending photometry. The lower panels show the best-fit SEDs (combining both high-resolution and low-resolution data) of three member galaxies in Bigfoot from Bagpipes.