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

M. Franco, D. Elbaz, L. Zhou, B. Magnelli, C. Schreiber, L. Ciesla, M. Dickinson, N. Nagar, G. Magdis, D. M. Alexander, M. Béthermin, R. Demarco, E. Daddi, T. Wang, J. Mullaney, H. Inami, X. Shu, F. Bournaud, R. Chary, R. T. CooganH. Ferguson, S. L. Finkelstein, M. Giavalisco, C. Gómez-Guijarro, D. Iono, S. Juneau, G. Lagache, L. Lin, K. Motohara, K. Okumura, M. Pannella, C. Papovich, A. Pope, W. Rujopakarn, J. Silverman, M. Xiao

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In this paper, we extend the source detection in the GOODS-ALMA field (69 arcmin$^2$, rms sensitivity $\sigma$ $\simeq$ 0.18 mJy.beam$^{-1}$), to deeper levels than presented in Franco et al. (2018). Using positional information at 3.6 and 4.5 $\mu$m (from Spitzer-IRAC), we explore the presence of galaxies detected at 1.1 mm with ALMA below our original blind detection limit of 4.8-$\sigma$ at which the number of spurious sources starts to dominate over that of real sources. In this Supplementary Catalog, we find a total of 16 galaxies, including 2 galaxies with no counterpart in HST images (also known as optically-dark galaxies) down to a 5$\sigma$ 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 and have lower stellar mass (M$_{\star}^{\rm SC}$ = 7.6$\times$10$^{10}$M$_\odot$ vs M$_{\star}^{\rm MC}$ = 1.2$\times$10$^{11}$M$_\odot$). Although exhibiting larger physical sizes, these galaxies have still far-infrared sizes significantly more compact than inferred from their optical emission. We show that the astrometry of the HST image does not only suffer from a global astrometric shift, as already discussed in previous papers, but also from local shifts. These distortions were artificially introduced in the process of building the mosaic of the GOODS-South HST image. By comparing the positions of almost 400 galaxies detected by HST, Pan-STARRS and ALMA, we create a distortion map which can be used to correct for these astrometric issues.
Original languageEnglish
Article numberA53
Number of pages17
JournalAstronomy & Astrophysics
Publication statusPublished - 2 Nov 2020


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