The Extended [C II] under Construction? Observation of the Brightest High-z Lensed Star-forming Galaxy at z = 6.2
Ravindranath, Swara; Mahler, Guillaume; Henry, Alaina; Bradač, Maruša; Strait, Victoria; Fujimoto, Seiji; Inoue, Akio K.; Hashimoto, Takuya; Sugahara, Yuma; Tamura, Yoichi; Xu, Xinfeng; Florian, Michael; Acebron, Ana; Zitrin, Adi; Coe, Dan; Frye, Brenda; Sharon, Keren; Trenti, Michele; Oesch, Pascal A.; Windhorst, Rogier A.; Bauer, Franz E.; Bradley, Larry D.; Fudamoto, Yoshinobu; Zackrisson, Erik; Vanzella, Eros; Welch, Brian; Diego, Jose M.; Mandelker, Nir; Ricotti, Massimo; Rigby, Jane
Japan, United States, Italy, Israel, Chile, Slovenia, Spain, United Kingdom, Switzerland, Denmark, Australia, Sweden
Abstract
We present results of [C II] 158 μm emission line observations, and report the spectroscopic redshift confirmation of a strongly lensed (μ ~ 20) star-forming galaxy, MACS0308-zD1 at z = 6.2078 ± 0.0002. The [C II] emission line is detected with a signal-to-noise ratio >6 within the rest-frame UV-bright clump of the lensed galaxy (zD1.1) and exhibits multiple velocity components; the narrow [C II] has a velocity full width half maximum (FWHM) of 110 ± 20 km s-1, while broader [C II] is seen with an FWHM of 230 ± 50 km s-1. The broader [C II] component is blueshifted (-80 ± 20 km s-1) with respect to the narrow [C II] component, and has a morphology that extends beyond the UV-bright clump. We find that, while the narrow [C II] emission is most likely associated with zD1.1, the broader component is possibly associated with a physically distinct gas component from zD1.1 (e.g., outflowing or inflowing gas). Based on the nondetection of λ 158μm dust continuum, we find that MACS0308-zD1's star formation activity occurs in a dust-free environment indicated by a strong upper limit of infrared luminosity ≲9 × 108 L ⊙. Targeting this strongly lensed faint galaxy for follow-up Atacama Large Millimeter/submillimeter Array and JWST observations will be crucial to characterize the details of typical galaxy growth in the early Universe.