Studying [CII] Emission in Low-mass Galaxies at z   7

We report on a [CII]_158μm search using the Atacama Large Millimeter/submillimeter Array (ALMA) on three lensed, confirmed emitting galaxies at z ∼ 7. Our targets are ultra-violet (UV) faint systems with stellar masses on the order of M_*∼ 10^9 M_⊙. We detect a single [CII] line emission (4σ) from the brightest (L ∼ 2.4 × 10^10L_⊙) galaxy in our sample, MACS0454-1251. We determine a systemic redshift (z_[CII] = 6.3151 ± 0.0005) for MACS0454-1251 and measure a velocity offset of Δ v ≈ 300 ± 70 km s^-1. The remaining two galaxies we detect no but provide 3 σ upper limits on their line luminosities which we use to investigate the L_[CII] - SFR relation. Overall our single detection shows agreement with the relation for dwarf and local starburst galaxies. Our [CII] deficient galaxies could potentially be exhibiting low metallicities (Z更多