The ALMA REBELS Survey: Average [CII] 158μm Sizes of Star-forming Galaxies from z~7 to z~4

Y. Fudamoto, R. Smit, R. A.A. Bowler, P. A. Oesch, R. Bouwens, M. Stefanon, H. Inami, R. Endsley, V. Gonzalez, S. Schouws, D. Stark, H. S.B. Algera, M. Aravena, L. Barrufet, E. Da Cunha, P. Dayal, A. Ferrara, L. Graziani, J. A. Hodge, A. P.S. HygateA. K. Inoue, T. Nanayakkara, A. Pallottini, E. Pizzati, R. Schneider, L. Sommovigo, Y. Sugahara, M. Topping, P. Van Der Werf, M. Bethermin, P. Cassata, M. Dessauges-Zavadsky, E. Ibar, A. L. Faisst, S. Fujimoto, M. Ginolfi, N. Hathi, G. C. Jones, F. Pozzi, D. Schaerer

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


We present the average [C II] 158 μm emission line sizes of UV-bright star-forming galaxies at z ~ 7. Our results are derived from a stacking analysis of [C II] 158 μm emission lines and dust continua observed by the Atacama Large Millimeter/submillimeter Array (ALMA), taking advantage of the large program Reionization Era Bright Emission Line Survey. We find that the average [C II] emission at z ~ 7 has an effective radius re of 2.2 ± 0.2 kpc. It is ≥2× larger than the dust continuum and the rest-frame UV emission, in agreement with recently reported measurements for z ≤ 6 galaxies. Additionally, we compared the average [C II] size with 4 < z < 6 galaxies observed by the ALMA Large Program to INvestigate [C II] at Early times (ALPINE). By analyzing [C II] sizes of 4 < z < 6 galaxies in two redshift bins, we find an average [C II] size of re = 2.2 ± 0.2 kpc and re = 2.5 ± 0.2 kpc for z ~ 5.5 and z ~ 4.5 galaxies, respectively. These measurements show that star-forming galaxies, on average, show no evolution in the size of the [C II] 158 μm emitting regions at redshift between z ~ 7 and z ~ 4. This finding suggests that the star-forming galaxies could be morphologically dominated by gas over a wide redshift range.

Original languageEnglish (US)
Article number144
JournalAstrophysical Journal
Issue number2
StatePublished - Aug 1 2022

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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