Kavli Affiliate: Sarah Church
| Summary:
We report observations of the ground state transitions of $^12$CO, $^13$CO C$^18$O, HCN, and HCO$^+$ at 88-115 GHz in the inner region of the nearby galaxy IC 342. These data were obtained with the 16-pixel spectroscopic focal plane array Argus on the 100-m Robert C. Byrd Green Bank Telescope (GBT) at 6-9$^primeprime$ resolution. In the nuclear bar region, the intensity distributions of $^12$CO(1-0) and $^13$CO(1-0) emission trace moderate densities, and differ from the dense gas distributions sampled in C$^18$O(1-0), HCN(1-0), and HCO$^+$(1-0). We observe a constant HCN(1-0)-to-HCO$^+$(1-0) ratio of 1.2$pm$0.1 across the whole $sim$1 kpc bar. This indicates that HCN(1-0) and HCO$^+$(1-0) lines have intermediate optical depth, and that the corresponding $n_textrmH_2$ of the gas producing the emission is of 10$^4.5-6$ cm$^-3$. We show that HCO$^+$(1-0) is thermalized and HCN(1-0) is close to thermalization. The very tight correlation between HCN(1-0) and HCO$^+$(1-0) intensities across the 1~kpc bar suggests that this ratio is more sensitive to the relative abundance of the two species than to the gas density. We confirm the angular offset ($sim$10$^primeprime$) between the spatial distribution of molecular gas and the star formation sites. Finally, we find a breakdown of the $L_textrmIR$-$L_textrmHCN$ correlation at high spatial resolution due to the effect of incomplete sampling of star-forming regions by HCN emission in IC 342. The scatter of the $L_textrmIR$-$L_textrmHCN$ relation decreases as the spatial scale increases from 10$^primeprime$~to 30$^primeprime$ (170-510~pc), and is comparable to the scatter of the global relation at the scale of 340 pc.
| Search Query: arXiv Query: search_query=au:”Church Sarah”&id_list=&start=0&max_results=10
Read More