ALMA obs. of HCN and HCO+ for 12 (U)LIRGs

After matching beam sizes of all molecular line data to the same values in all (U)LIRGs, we derive molecular line flux ratios by extracting spectra in the central 0.5, 1, and 2kpc circular regions and in 0.5-1 and 1-2kpc annular regions.

Based on non-local thermal equilibrium model calculations, we quantitatively confirm that the innermost (<~0.5kpc) molecular gas is very dense (>~10^5^cm^-3^) and warm ({>~300K) in ULIRGs, and that in one LIRG, it is also modestly dense (10^4-5^cm^-3^) and warm (~100K). We then investigate the spatial variation of the HCN-to-HCO^+^ flux ratios and high-J to low-J flux ratios of HCN and HCO+. A subtle sign of a decreasing trend in these ratios from the innermost (<~0.5kpc) to the outer nuclear (0.5-2kpc) region is discernible in a significant fraction of the observed ULIRGs.