Oral Presentation

REBELS survey: [CII] 158um emission line observations and average [CII] size of star-forming galaxies at z~7

Author(s): Y. Fudamoto(Waseda University, NAOJ), R. Smit (John Moores University), A. K. Inoue(Waseda University, NAOJ), Y. Sugahara (Waseda University, NAOJ), H. Inami (Hiroshima University, NAOJ), H. Algera (Hiroshima University, NAOJ), and REBELS collaboration

Presenter: Yoshinobu Fudamoto (Waseda University, NAOJ)

Thanks to deep galaxy surveys with the Hubble Space Telescope and large ground-based telescopes, it is now widely established that high-redshift galaxies (from z~11 to z~4) have been rapidly forming stars at an accelerating rate (e.g., Madau&Dickinson 2014), supported by their high gas fractions. However, the gas fueling mechanisms at high-redshift is still poorly understood as detailed observations of interstellar medium (ISM) have been limited. In this talk, we present results based on the on-going ALMA large program, Reionization Era Bright Emission Line Survey (REBELS: Bouwens+21). In REBELS, we scanned [CII] 158um or [OIII] 88um of 40 star-forming galaxies at z~7. So far, we successfully detected ~25 [CII] emission lines (as of ~85% completion of the survey). To investigate geometries between ISM and star-formation activity, we measured the average size of [CII] emission line at z~7, which shows an average effective radius of ~2.2kpc. The [CII] size is significantly larger than the dust continuum, in agreement with recently reported measurements for z<6 galaxies. Also, combing z=4-6 galaxy observations, the average [CII] sizes suggest that there is no or little evolution of [CII] emission sizes across z~4 to z~7, which might be in contrast to the observed UV size evolution (e.g., Shibuya+15).