Poster Presentation
Mm/submm Energy Diagnostics & Non-LTE Modeling of the AGN-Starburst Composite Galaxy NGC 7469 with ALMA
Presenter: Suzuka Nakano (NAOJ/SOKENDAI)
Identifying energy sources of galaxies at mm/submm (least affected by dust extinction) can be an excellent way to uncover dust-obscured AGNs, which are elusive at optical. In Izumi et al. (2020), the AGN in NGC 7469 was found to have a [CI](1-0)/13CO(2-1) emission line ratio nearly 10 times higher than that in starburst (SB) regions. It is important to evaluate quantitatively that (1) very high gas excitation (temperature) and (2) dissociation of CO molecules occurred by XDR are taking place in AGN.
In this poster, we present the details of the results of non-local thermal equilibrium (non-LTE) analysis and compare them with the chemical model. We modeled the emission of [C I](1–0), 13CO(2–1) and 12CO(1–0), (2–1), and (3–2) lines under non-LTE analysis by using RADEX code (van der Tak et al. 2007) toward the AGN and SB regions in NGC 7469.
We searched for the optimal values of kinematic temperature (Tkin), [C0]/[CO] abundance ratio and CO column density (N_CO) to minimize the reduced χ2 by comparing the observed line ratios with modeled ones (under fixed H2 volume density n(H2), for simplicity). We found Tkin and [C0]/[CO] are higher and N_CO is lower in AGN than those in SB, that is following the trends from the XDR models (Meijerink & Spaans 2005).
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