Journal article · Preprint article
The Main Sequence at z similar to 1.3 Contains a Sizable Fraction of Galaxies with Compact Star Formation Sizes: A New Population of Early Post-starbursts?
Université Paris-Saclay1
Nanjing University2
National Space Institute, Technical University of Denmark3
National Institute for Astrophysics4
Max Planck Institute for Astronomy5
The University of Tokyo6
European Southern Observatory7
Universidad Diego Portales8
University of Sussex9
Instituto de Astrofísica de Canarias10
Chinese Academy of Sciences11
Pontificia Universidad Católica de Valparaíso12
...and 2 moreAtacama 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 sstarf)–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.
Language: | English |
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Year: | 2019 |
Pages: | 7 |
ISSN: | 20418213 and 20418205 |
Types: | Journal article and Preprint article |
DOI: | 10.3847/2041-8213/ab1f92 |
ORCIDs: | Magdis, G. E. and 0000-0001-6477-4011 |