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.
The ALMA REBELS Survey: Average [CII] 158μm Sizes of Star-forming Galaxies from z~7 to z~4 / Fudamoto Y.; Smit R.; Bowler R.A.A.; Oesch P.A.; Bouwens R.; Stefanon M.; Inami H.; Endsley R.; Gonzalez V.; Schouws S.; Stark D.; Algera H.S.B.; Aravena M.; Barrufet L.; Da Cunha E.; Dayal P.; Ferrara A.; Graziani L.; Hodge J.A.; Hygate A.P.S.; Inoue A.K.; Nanayakkara T.; Pallottini A.; Pizzati E.; Schneider R.; Sommovigo L.; Sugahara Y.; Topping M.; Van Der Werf P.; Bethermin M.; Cassata P.; Dessauges-Zavadsky M.; Ibar E.; Faisst A.L.; Fujimoto S.; Ginolfi M.; Hathi N.; Jones G.C.; Pozzi F.; Schaerer D.. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - ELETTRONICO. - 934:(2022), pp. 144.0-144.0. [10.3847/1538-4357/ac7a47]
The ALMA REBELS Survey: Average [CII] 158μm Sizes of Star-forming Galaxies from z~7 to z~4
Ginolfi M.;
2022
Abstract
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.
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