GOODS-ALMA: Using IRAC and VLA to probe fainter millimeter galaxies

Abstract

In this paper, we extend the source detection in the GOODS-ALMA field (69 arcmin², 1σ ≃ 0.18 mJy beam⁻¹) to deeper levels than presented in our previous work. Using positional information at 3.6 and 4.5 μm (from Spitzer-IRAC) as well as the Very Large Array (VLA) at 3 GHz, we explore the presence of galaxies detected at 1.1 mm with ALMA below our original blind detection limit of 4.8-σ, at which the number of spurious sources starts to dominate over that of real sources. In order to ensure the most reliable counterpart association possible, we have investigated the astrometry differences between different instruments in the GOODS–South field. In addition to a global offset between the Atacama Large Millimeter/submillimeter Array (ALMA) and the Hubble Space Telescope (HST) already discussed in previous studies, we have highlighted a local offset between ALMA and the HST that was artificially introduced in the process of building the mosaic of the GOODS–South image. We created a distortion map that can be used to correct for these astrometric issues. In this Supplementary Catalog, we find a total of 16 galaxies, including two galaxies with no counterpart in HST images (also known as optically dark galaxies), down to a 5σ limiting depth of H = 28.2 AB (HST/WFC3 F160W). This brings the total sample of GOODS-ALMA 1.1 mm sources to 35 galaxies. Galaxies in the new sample cover a wider dynamic range in redshift (z = 0.65−4.73), are on average twice as large (1.3 vs 0.65 kpc), and have lower stellar masses (M⋆^(SC) = 7.6 × 10¹⁰ M_⊙ vs M⋆^(MC) = 1.2 × 10¹¹ M_⊙). Although exhibiting larger physical sizes, these galaxies still have far-infrared sizes that are significantly more compact than inferred from their optical emission.