PUGLISI, ANNAGRAZIAANNAGRAZIAPUGLISIDaddi, E.E.DaddiLiu, D.D.LiuBournaud, F.F.BournaudSilverman, J. D.J. D.SilvermanCircosta, C.C.CircostaCalabrò, A.A.CalabròAravena, M.M.AravenaCibinel, A.A.CibinelDannerbauer, H.H.DannerbauerDELVECCHIO, IVANIVANDELVECCHIOElbaz, D.D.ElbazGao, Y.Y.GaoGobat, R.R.GobatJin, S.S.JinFloc’h, E. LeE. LeFloc’hMagdis, G. E.G. E.MagdisMancini, C.C.ManciniRiechers, D. A.D. A.RiechersRodighiero, G.G.RodighieroSargent, M.M.SargentValentino, F.F.ValentinoZanisi, L.L.Zanisi2021-02-102021-02-1020192041-8205http://hdl.handle.net/20.500.12386/30277Atacama Large Millimeter/submillimeter Array (ALMA) measurements for 93 Herschel-selected galaxies at 1.1 ≤ z ≤ 1.7 in COSMOS reveal a sizable (>29%) population with compact star formation (SF) sizes, lying on average >×3.6 below the optical stellar mass (M ⋆)-size relation of disks. This sample widely spans the star-forming main sequence (MS), having 108 ≤ M ⋆ ≤ 1011.5 M ☉ and 20 ≤ star formation rate (SFR) ≤ 680 M ☉ yr-1. The 32 size measurements and 61 upper limits are measured on ALMA images that combine observations of CO(5-4), CO(4-3), CO(2-1), and λ obs ∼ 1.1-1.3 mm continuum, all tracing the star-forming molecular gas. These compact galaxies have instead normally extended K band sizes, suggesting strong specific SFR gradients. Compact galaxies comprise the 50 ± 18% of MS galaxies at M ⋆ > 1011 M ☉. This is not expected in standard bimodal scenarios, where MS galaxies are mostly steadily growing extended disks. We suggest that compact MS objects are early post-starburst galaxies in which the merger-driven boost of SF has subsided. They retain their compact SF size until either further gas accretion restores premerger galaxy-wide SF, or until becoming quenched. The fraction of merger-affected SF inside the MS seems thus larger than anticipated and might reach ∼50% at the highest M ⋆. The presence of large galaxies above the MS demonstrates an overall poor correlation between galaxy SF size and specific SFR.STAMPAenArticle10.3847/2041-8213/ab1f922-s2.0-85069964571000469811200003https://iopscience.iop.org/article/10.3847/2041-8213/ab1f922019ApJ...877L..23PFIS/05 - ASTRONOMIA E ASTROFISICA