Oral Presentation

Spatially-resolved [CI] study in Arp 220

Author(s): Junko Ueda (NAOJ)

Presenter: Junko Ueda (NAOJ)

While CO has been widely used as a molecular gas tracer, recent observations demonstrate that [CI] is a good indicator of total molecular gas mass. Most of these results are, however, global characteristics averaged across whole galaxies. We thus investigate the spatially-resolved relation between [CI] (1-0) and CO (1-0) emission at 100pc scales in Arp 220 using ALMA archival data. We conduct pixel-by-pixel comparison between [CI] and CO, and find that the [CI] luminosity correlates roughly with the CO. However, the correlation is different between the two progenitors of Arp 220. This could be caused by the differences in the opacity, abundance ratio, excitation condition, and AGN feedback. We also find that the diffuse gas traced by [CI] is associated with the outflows in the western nucleus. The molecular gas mass estimated using the [CI]-to-H2 conversion factor is several times larger than the previous measurement using CO observations. These results suggest that the relation between [CI] and CO varies at 100 pc scales in at least extreme environment.