Left: modeling results and observations of the ¹²CO emission for the best-fitting physical gas model for J1604-2130 for the inner 30 AU cavity comparing δ_gas2 (gas density drop inside the 30 AU dust cavity). δ_gas2 is varied as 10⁰, 10^-1, ..., 10^-6 as blue, light blue, cyan, green, yellow, orange, and red (δ_gas is taken as 1). The observations are plotted in black. The panel shows the intensity cuts through the major (bottom) and minor (top) axis of the ¹²CO zero-moment map. Right: comparison between the density profile derived in this study and the profile used in Zhang et al. (2014).