S22A0100
S22A0100
During the course of HSC Hα survey of NGC 6822, we found very diffuse Hα emitting regions which are likely to be associated with north-west HI cloud, a potentially-accreting building block of galaxy formation in action. As they accompany strong UV sources, they would be active star-forming regions. These Hα emitting regions allow us to probe the metal abundance of HI cloud which is the long-awaited missing parameter to address the nature of this intriguing system. We propose to carry out a FOCAS IFU spectroscopy for these newly discovered Hα emitting regions to probe their metal abundance. By utilizing the area coverage of IFU, this proposed 2-nights observation will derive the metallicity indicator [NII]/Hα with an accuracy of <0.2 dex down to [NII]/Hα = 0.01, which corresponds to the metallicity of 12+log(O/H) ∼ 8.0, and allow us to conclude whether the infalling HI cloud is metal deficit or enriched. It can even identify a potential primordial abundance through negative [NII] detections, with respect to the detected Hα. If confirmed, this will be the first clear case for genuinely young galaxies with primordial abundance in the local universe.
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