The ALPINE-ALMA [C II] Survey: Size of Individual Star-forming Galaxies at z = 4-6 and Their Extended Halo Structure
Hathi, Nimish P.; Koekemoer, Anton M.; Maiolino, Roberto; Jones, Gareth C.; Fujimoto, Seiji; Vallini, Livia; Schaerer, Daniel; Boquien, Médéric; Capak, Peter; Le Fèvre, Olivier; Toft, Sune; Narayanan, Desika; Loiacono, Federica; Amorin, Ricardo; Fudamoto, Yoshinobu; Rujopakarn, Wiphu; Silverman, John D.; Cimatti, Andrea; Faisst, Andreas L.; Lemaux, Brian C.; Yan, Lin; Talia, Margherita; Ibar, Edo; Bethermin, Matthieu; Ginolfi, Michele; Dessauges-Zavadsky, Miroslava; Cassata, Paolo; Morselli, Laura; Zamorani, Gianni; Méndez-Hernández, Hugo; Bardelli, Sandro; Vergani, Daniela; Zucca, Elena; Romano, Michael
Denmark, Japan, France, Switzerland, United Kingdom, Thailand, United States, Italy, Netherlands, Chile
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 (${r}_{{\rm{e}},[{\rm{C}}{\rm\small{II}}]}$) for individual galaxies and compare them with the rest-frame ultraviolet (UV) continuum (${r}_{{\rm{e}},\mathrm{UV}}$) from Hubble Space Telescope images. The effective radius ${r}_{{\rm{e}},[{\rm{C}}{\rm\small{II}}]}$ exceeds ${r}_{{\rm{e}},\mathrm{UV}}$ by factors of ∼2-3, and the ratio of ${r}_{{\rm{e}},[{\rm{C}}{\rm\small{II}}]}/{r}_{{\rm{e}},\mathrm{UV}}$ 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.