2019ApJ...881..108J

We search a large parameter space of the LkCa 15's disk density profile to fit its observed radial intensity profile of ¹²CO (J = 3-2) obtained from Atacama Large Millimeter/submillimeter Array. The best-fit model within the parameter space has a disk mass of 0.1 M_☉ (using an abundance ratio of ¹²CO/H₂ = 1.4 x 10^–4 in mass), an inner cavity of 45 au in radius, an outer edge at ∼600 au, and a disk surface density profile that follows a power law of the form ρ_r ∝ r^–4. For the disk density profiles that can lead to a small reduced χ² of the goodness-of-fit, we find that there is a clear linear correlation between the disk mass and the power-law index, γ, in the equation of the disk density profile. This suggests that the ¹²CO disk of LkCa 15 is optically thick, and we can fit its ¹²CO radial intensity profile using either a lower disk mass with a smaller γ or a higher disk mass with a bigger γ. By comparing the ¹²CO channel maps of the best-fit model with disk models with higher or lower masses, we find that a disk mass of ∼0.1 M_☉ can best reproduce the observed morphology of the ¹²CO channel maps. The dust continuum map at 0.87 mm of the LkCa 15 disk shows an inner cavity of the similar size of the best-fit gas model, but its outer edge is at ∼200 au, which is much smaller than the fitted gas disk. Such a discrepancy between the outer edges of the gas and dust disks is consistent with dust drifting and trapping models.