Distributions of the Density and Kinetic Temperature of the Molecular Gas in the Central Region of NGC 613 using Hierarchical Bayesian Inference
Abstract
We present position-position-velocity (PPV) cubes of the physical and chemical properties of the molecular medium in the central 1.2 kpc region of the active galaxy NGC 613 at a PPV resolution of 0.8×0.8×10 km s-1 (0.8 = 68 pc). We used eight molecular lines obtained with ALMA. Non-LTE calculation with hierarchical Bayesian inference was used to construct PPV cubes of the gas kinetic temperature (Tkin), molecular hydrogen volume density (nH2), column densities (NH2), and fractional abundances of four molecules (12C18O, HCN, HCO+, and CS). The derived nH2, NH2, and Tkin ranged 103.21-3.85 cm-3, 1020.8-22.1 cm-2, and 102.33-2.64 K, respectively. Our first application of the non-LTE method with the hierarchical Bayesian inference to external galaxies yielded compatible results compared with the previous studies of this galaxy, demonstrating the efficacy of this method for application to other galaxies. We examined the correlation between gas surface density H2 (converted from NH2) and the star formation rate SFR obtained from the 110 GHz continuum flux map and found two distinct sequences in the H2-SFR diagram; the southwestern subregion of the star-forming ring exhibited a 0.5 dex higher star formation efficiency (SFE; SFR/H2) than the eastern subregion. However, they exhibited no systematic difference in nH2, which is often argued as a driver of SFE variation. We suggest that the deficiency of molecular gas in the southwestern subregion, where no significant gas supply is evident along the offset ridges in the bar, is responsible for the elevated SFE.
Turn this paper into a lesson
ArcXiv compiles a structured reading guide from this paper's metadata: plain-English importance, contributions, prerequisite concepts, which sections to read first, flashcards, and a quiz. Grounded in the abstract, never invented.