ALMA Reveals Strong Emission in a Galaxy Embedded in a Giant Lyα Blob at z = 3.1

Abstract

We report the result from observations conducted with the Atacama Large Millimeter/submillimeter Array (ALMA) to detect [ C ii ] 158 μ m fine structure line emission from galaxies embedded in one of the most spectacular Ly α blobs (LABs) at z = 3.1, SSA22-LAB1. Of three dusty star-forming galaxies previously discovered by ALMA 860 μ m dust continuum survey toward SSA22-LAB1, we detected the [ C ii ] line from one, LAB1-ALMA3 at z = 3.0993 ± 0.0004. No line emission was detected, associated with the other ALMA continuum sources or from three rest-frame UV/optical selected z spec  ≃ 3.1 galaxies within the field of view. For LAB1-ALMA3, we find relatively bright [ C ii ] emission compared to the infrared luminosity ( L [ C ii ] / L IR  ≈ 0.01) and an extremely high [ C ii ] 158 μ m and [ N ii ] 205 μ m emission line ratio ( L [ C ii ] / L [N ii]  > 55). The relatively strong [ C ii ] emission may be caused by abundant photodissociation regions and sub-solar metallicity, or by shock heating. The origin of the unusually strong [ C ii ] emission could be causally related to the location within the giant LAB, although the relationship between extended Ly α emission and interstellar medium conditions of associated galaxies is yet to be understand.