Journal
ASTROPHYSICAL JOURNAL LETTERS
Volume 877, Issue 2, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.3847/2041-8213/ab1f92
Keywords
galaxies: evolution; galaxies: high-redshift; galaxies: interactions; galaxies: ISM; galaxies: star formation
Categories
Funding
- INAF PRIN-SKA [2017 1.05.01.88.04]
- Chinese Academy of Sciences President's International Fellowship Initiative [2018VMA0014]
- Villum Fonden grant [13160]
- Cosmic Dawn Center of Excellence by the Danish National Research Foundation
- ERC [648179]
- National Science Foundation [AST-1614213]
- Spanish Ministry of Economy and Competitiveness [MINECO RYC-2014-15686]
- National Key R&D Program of China [2017YFA0402704]
- CAS Key Research Program of Frontier Sciences
- NSFC [11420101002]
- ALMA Japan Research Grant of NAOJ Chile Observatory [NAOJ-ALMA-0127]
- JSPS KAKENHI [JP18H04346]
- World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan
- Region Ile-de-France
- Incoming CEA fellowship from the CEA-Enhanced Eurotalents program
- FP7 Marie-Sklodowska-Curie COFUND program [600382]
- European Union [788679]
- Marie Curie Actions (MSCA) [788679] Funding Source: Marie Curie Actions (MSCA)
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Atacama 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 > x 3.6 below the optical stellar mass (M-*)-size relation of disks. This sample widely spans the star-forming main sequence (MS), having 10(8) <= M-* <= 10(11.5 )M(circle dot) and 20 star formation rate (SFR) <= 680 M-circle dot 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 lambda(obs )similar to 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-* > 10(11) M-circle dot. 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 similar to 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.
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