"Super-deblended" Dust Emission in Galaxies: II. Far-IR to (sub)millimeter photometry and high redshift galaxy candidates in the full COSMOS field

TL;DR

This paper introduces a comprehensive 'super-deblended' far-infrared to (sub)millimeter photometric catalog for the COSMOS field, enabling the detection of high-redshift galaxy candidates and advancing methods for accurate flux measurement in crowded fields.

Contribution

It develops an improved deblending technique combining PSF fitting, spectral energy distribution fitting, and uncertainty modeling, validated against ALMA data, and provides a large catalog of high-redshift galaxy candidates.

Findings

Detected 11,220 galaxies in the FIR/(sub)mm range up to z~7.

Identified 85 high-redshift galaxy candidates with secure detections.

Validated the deblending method with ALMA photometry.

Abstract

We present a "super-deblended" far-infrared to (sub)millimeter photometric catalog in the Cosmic Evolution Survey (COSMOS), prepared with the method recently developed by Liu et al. 2018, with key adaptations. We obtain point spread function (PSF) fitting photometry at fixed prior positions including 88,008 galaxies detected in either VLA 1.4~GHz, 3~GHz and/or MIPS 24~$\mu$m images. By adding a specifically carved mass-selected sample (with an evolving stellar mass limit), a highly complete prior sample of 194,428 galaxies is achieved for deblending FIR/(sub)mm images. We performed ``active' removal of non relevant priors at FIR/(sub)mm bands using spectral energy distribution (SED) fitting and redshift information. In order to cope with the shallower COSMOS data we subtract from the maps the flux of faint non-fitted priors and explicitly account for the uncertainty of this step. The resulting photometry (including data from Spitzer, Herschel, SCUBA2, AzTEC, MAMBO and NSF's Karl G. Jansky Very Large Array at 3~GHz and 1.4~GHz) displays well behaved quasi-Gaussian uncertainties, calibrated from Monte Carlo simulations and tailored to observables (crowding, residual maps). Comparison to ALMA photometry for hundreds of sources provide a remarkable validation of the technique. We detect 11,220 galaxies over the 100--1200~$\mu$m range, extending to $z_{\rm phot}\sim7$. We conservatively selected a sample of 85 $z>4$ high redshift candidates, significantly detected in the FIR/(sub)mm, often with secure radio and/or Spitzer/IRAC counterparts. This provides a chance to investigate the first generation of vigorous starburst galaxies (SFRs$\sim1000\mathrm{M}_\odot$~yr$^{-1}$). The photometric and value added catalogs are publicly released.