The ALPINE–ALMA [C ii] Survey: Size of Individual Star-forming Galaxies at z = 4–6 and Their Extended Halo Structure
Seiji Fujimoto, J. D. Silverman, M. Béthermin, M. Ginolfi, Gareth C. Jones, O. Le Fèvre, M. Dessauges‐Zavadsky, W. Rujopakarn, Andreas L. Faisst, Yoshinobu Fudamoto, P. Cassata, L. Morselli, R. Maiolino, D. Schaerer, P. Capak, Lin Yan, L. Vallini, Sune Toft, F. Loiacono, Zamorani, Gianni, M. Talia, Desika Narayanan, Nimish P. Hathi, B. C. Lemaux, M. Boquien, R. Amorín, Ibar, Edo, Anton M. Koekemoer, Hugo Méndez-Hernàndez, S. Bardelli, D. Vergani, E. Zucca, Michael Romano, A. Cimatti
Abstract
We present the physical extent of [C ii] 158 μm line-emitting gas from 46 star-forming galaxies at z = 4–6 from the ALMA Large Program to INvestigate C ii at Early Times (ALPINE). Using exponential profile fits, we measure the effective radius of the [C ii] line ( ) for individual galaxies and compare them with the rest-frame ultraviolet (UV) continuum ( ) from Hubble Space Telescope images. The effective radius exceeds by factors of ∼2–3, and the ratio of increases as a function of Mstar. We do not find strong evidence that the [C ii] line, rest-frame UV, and far-infrared (FIR) continuum are always displaced over ≃1 kpc scale from each other. We identify 30% of isolated ALPINE sources as having an extended [C ii] component over 10 kpc scales detected at 4.1σ–10.9σ beyond the size of rest-frame UV and FIR continuum. One object has tentative rotating features up to ∼10 kpc, where the 3D model fit shows the rotating [C ii]-gas disk spread over 4 times larger than the rest-frame UV-emitting region. Galaxies with the extended [C ii] line structure have high star formation rate, high stellar mass (Mstar), low Lyα equivalent width, and more blueshifted (redshifted) rest-frame UV metal absorption (Lyα line), as compared to galaxies without such extended [C ii] structures. Although we cannot rule out the possibility that a selection bias toward luminous objects may be responsible for such trends, the star-formation-driven outflow also explains all these trends. Deeper observations are essential to test whether the extended [C ii] line structures are ubiquitous to high-z star-forming galaxies.