Deblending the MIGHTEE-COSMOS survey with XID+: The resolved radio source counts to $S_{1.4}\approx 5\mu$Jy

TL;DR

This paper develops a probabilistic deblending framework using XID+ and multi-wavelength priors to produce accurate radio source catalogs from confused MIGHTEE data, enabling detailed source counts and background resolution.

Contribution

It introduces a high-purity prior strategy combined with masking to improve deblending accuracy and provides a comprehensive catalog and source counts in the MIGHTEE-COSMOS field.

Findings

High-purity priors improve flux recovery accuracy.

The method resolves the radio background down to ~4.8 μJy.

The catalog contains 89,562 sources with reliable flux measurements.

Abstract

Deep radio continuum surveys provide fundamental constraints on galaxy evolution, but source confusion limits sensitivity to the faintest sources. We present a complete framework for producing high-fidelity deblended radio catalogs from the confused MIGHTEE maps using the probabilistic deblending framework XID+ and prior positions from deep multi-wavelength data in the COSMOS field. To assess performance, we construct MIGHTEE-like simulations based on the Tiered Radio Extragalactic Continuum Simulation (T-RECS) radio source population, ensuring a realistic distribution of star-forming galaxies and active galactic nuclei (AGN) for validation. Through these simulations, we show that prior catalog purity is the dominant factor controlling deblending accuracy: a high-purity prior, containing only sources with a high likelihood of radio detection, recovers accurate flux densities and reproduces input source counts down to $\sim 3\sigma$ (where $\sigma = $ thermal noise). On the other hand, a complete prior overestimates the source counts due to spurious detections. Our optimal strategy combines the high-purity prior with a mask that removes sources detected above $50~\mu$Jy. Applied to the $\sim$1.3\,deg$^2$ area of the MIGHTEE-COSMOS field defined by overlapping multi-wavelength data, this procedure yields a deblended catalog of 89,562 sources. The derived 1.4\,GHz source counts agree with independent P(D) analyses and indicate that we resolve the radio background to $\sim 4.8\,\mu$Jy. We also define a recommended high-fidelity sample of 20,757 sources, based on detection significance, flux density, and goodness-of-fit, which provides reliable flux densities for individual sources in the confusion-limited regime.