tokens: ), and it has a mass accretion rate of about 10 −9 M ⊙ yr −1 (Hartmann et al. 1998 ). The outer edge of the dust disk inferred from continuum emission is at ∼150 au (Piétu et al. 2007 ; Isella et al. 2012 ). The dust mass estimated from 1.3 mm continuum observation is about 5 × 10 −4 M ⊙ (Isella et al. 2012 ). Recent images of scattered light suggest a warped inner disk component inside the inner gap, providing clear picture details of the inner gap region of the LkCa 15 disk (Thalmann et al. 2015 , 2016 ; Oh et al. 2016 ). As a young star, LkCa 15 is a luminous source of X-ray and extreme ultraviolet (EUV) emission (Skinner Güdel 2013 ), indicating that the LkCa 15 disk could still be undergoing the active evolution phase of disk physics and chemistry. Consequently, the protoplanetary disk of LkCa 15 has been found to be especially chemically rich and has been detected in several molecular transitions (Thi et al. 2004 ; Piétu et al. 2007 ; Chapillon et al. 2008 ; Öberg et al. 2010 ; Punzi et al. 2015 ). Molecular line emission shows that the gas disk around LkCa 15 is the size of ∼900 au (Piétu et al. 2007 ; Isella et al. 2012 ). It is highly optically thick in the emission of 12 CO but is optically thin in 13 CO emission (Punzi et al. 2015 ; van der Marel et al. 2015 ). The discrepancy between the outer disk radii shown in the dust continuum and molecular line emissions (∼150 au versus 900 au) suggests that the mm-size dust is depleted in the outer part of the LkCa 15 disk, which is consistent with dust drifting and trapping models (Birnstiel et al. 2010 ; Pinilla et al. 2012 ). Being a protoplanetary disk that may have a young planet candidate, the LkCa 15 system serves as a unique laboratory to study the dust evolution models under planet–disk interaction (Zhu et al. 2011 ; Pinilla et al. 2012 ). The distribution of dust and gas in the LkCa 15 disk provides an important constraint on theoretic models. Here, we fit the gas and dust surface density profiles based on the high-resolution dust continuum image and CO 3–2 line maps obtained from the ALMA. We study how the goodness-of-fit changes along with different key parameters used in the disk density profile, which is related with different physics. Our disk model and the parameter grid is described in Section 3 . In Section 4 , we show the best-fit model with respect to the observed 12 CO image. We discuss the dependence of the parameters in Section 5 . 2. Observation The LkCa 15 was observed on 2014 August 17 and 29 with ALMA Band 7 (345 GHz, 880 μ m) in ALMA program 2012.1.00870.S (PI Pérez, L. M.). The 12 CO, 13 CO, and C 18 O 3–2 line maps and 0.87 mm dust continuum image were taken with two different tunings. The 12 CO 3–2 data were obtained with a spectral window centered on 345.796 GHz with 1885 channels of 122.06 kHz (0.106 km s −1 ) channel width. The angular resolution of the 12 CO image is 036 × 023 (50 au × 32 au). The 13 CO 3–2 data were centered on 330.588 GHz, with 1967
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