The ALMA Frontier Fields Survey. VI. Lensing-corrected 1.1mm number counts in Abell 2744, MACSJ0416.1-2403, MACSJ1149.5+2223, Abell 370 and Abell S1063

Abstract

Context. Probing the faint end of the number counts at mm wavelengths is important to identify the origin of the extragalactic background light in this regime. Aided by strong gravitational lensing, ALMA observations towards massive galaxy clusters have opened a window to disentangle this origin, allowing to resolve sub-mJy dusty star-forming galaxies. Aims. We aim to derive number counts at 1.1 mm down to flux densities fainter than 0.1 mJy, based on ALMA observations towards five Hubble Frontier Fields (FF) galaxy clusters, following a statistical approach to correct for lensing effects. Methods. We created a source catalog that includes ALMA 1.1 mm continuum detections around two new FF galaxy clusters, together with the sources previously detected around three FF galaxy clusters, making a total of 29 detected sources down to a 4.5σ significance. ALMA 1.1mm mosaics used for our source extraction covered the inner ≈ 2 × 2 FF regions, reached rms depths of ≈ 55 − 71 µJy beam −1 , and had synthesized beam sizes between ≈ 0 . 5 − 1 . 5 (natural weighting). We derived source intrinsic flux densities using public lensing models. We folded the uncertainties in both magnifications and source redshifts into the number counts through Monte Carlo simulations. Results. Using the combination of all cluster fields, we derive cumulative number counts over two orders of magnitude down to ≈ 0.01 mJy after correction for lensing effects. Cosmic variance estimates are all exceeded by uncertainties in our median combined cumulative counts that come from both our Monte Carlo simulations and Poisson statistics. Our number counts agree at a 1σ level with our previous estimates using ALMA observations of the first three FFs, exhibiting a similar flattening at faint flux densities. They are also consistent to 1σ with most of recent ALMA estimates and galaxy evolution models. However, below ≈ 0.1 mJy, our cumulative number counts are lower by ≈ 0.4 dex compared to all deep ALMA studies but the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field Large Program (ASPECS-LP). Importantly, the flattening found for our cumulative counts extends further to ≈ 0.01 mJy, i.e., ≈ 0.4 dex fainter than ASPECS-LP, and remains in agreement with extrapolations of their number counts down to this flux limit. We find a median contribution to the extragalactic background light (EBL) of 14 +12 −8 Jy deg −2 resolved in our demagnified sources down to ≈ 0.01 mJy, representing 75 − 86% of Planck-derived extragalactic EBL estimates at 1.1 mm. Conclusions. We estimate cumulative 1.1 mm number counts down to ≈ 0.01 mJy, along the line of sight of five galaxy clusters that benefit from having rich deep multiwavelength data. They bring further support in line of the flattening of the number counts reported previously by us and ASPECS-LP, which has been interpreted by a recent galaxy evolution model as a measurement of the "knee" of the infrared luminosity function at high redshift. Our estimates of the contribution to the EBL associated with 1.1 mm galaxies i...

2 mm Observations and the Search for High-redshift Dusty Star-forming Galaxies

“…Ultradeep galaxy number counts, which nearly fully resolve the EBL, have now been obtained at 850 μm or 870 μm (e.g., Hsu et al 2016;Béthermin et al 2020;Chen et al 2023) and at 1.1 mm or 1.2 mm (e.g., Fujimoto et al 2016;Muñoz Arancibia et al 2018;González-López et al 2020;Muñoz Arancibia et al 2022). Here we make comparisons with Hsu et al (2016) by converting their differential number counts, which take the form of a broken power law…”

The Disk Population in a Distant Massive Protocluster

“…To examine the level of possible contaminants from extragalactic sources, we take the deep 1.2 mm ALMA survey of submillimeter galaxies in González-López et al (2020) as a reference (see also Aravena et al 2016;Fujimoto et al 2016;Muñoz Arancibia et al 2022). In this work the number density of submillimeter galaxies is 19,300 4400 4700 -+ per square degree for a flux density above 0.1 mJy.…”