부산대학교 도서관

We used the Atacama Large Millimeter/submillimeter Array (ALMA) to map$^{12}$CO($J$ = 1-0), $^{12}$CO($J$ = 2-1), $^{12}$CO($J$ = 3-2), $^{13}$CO($J$= 2-1), and [CI]($^3P_1$-$^3P_0$) emission lines around the type 1 activegalactic nucleus (AGN) of NGC 7469 ($z = 0.0164$) at $\sim 100$ pc resolutions.The CO lines are bright both in the circumnuclear disk (central $\sim 300$ pc)and the surrounding starburst (SB) ring ($\sim 1$ kpc diameter), with twobright peaks on either side of the AGN. By contrast, the [CI]($^3P_1$-$^3P_0$)line is strongly peaked on the AGN. Consequently, the brightness temperatureratio of [CI]($^3P_1$-$^3P_0$) to $^{13}$CO(2-1) is $\sim 20$ at the AGN, ascompared to $\sim 2$ in the SB ring. Our local thermodynamic equilibrium (LTE)and non-LTE models indicate that the enhanced line ratios (or CI enhancement)are due to an elevated C$^0$/CO abundance ratio ($\sim 3-10$) and temperature($\sim 100-500$ K) around the AGN as compared to the SB ring (abundance ratio$\sim 1$, temperature $\lesssim 100$ K), which accords with the picture of theX-ray-dominated Region (XDR). Based on dynamical modelings, we also provideCO(1-0)-to- and [CI]($^3P_1$-$^3P_0$)-to-molecular mass conversion factors atthe central $\sim 100$ pc of this AGN as $\alpha_{\rm CO} = 4.1$ and$\alpha_{\rm CI} = 4.4~M_\odot$ (K km s$^{-1}$ pc$^2$)$^{-1}$, respectively.Our results suggest that the CI enhancement is potentially a good marker ofAGNs that could be used in a new submillimeter diagnostic method toward dustyenvironments.