2014ApJ...789...95K

We present Submillimeter Array interferometric observations of the ¹²CO (J = 2-1), ¹³CO (J = 2-1), and C¹⁸O (J = 2-1) lines and 225 GHz continuum emission and Submillimeter Telescope single-dish observations of C¹⁸O (J = 2-1) toward L43, a protostellar object in transition from Class I to II. The 225 GHz continuum emission shows a weak (∼23.6 mJy), compact (<1000 AU) component associated with the central protostar. Our simulated observations show that it can be explained by dust thermal emission arising from an envelope which has a hole or a constant intensity region within a few hundred AU of the protostar. This suggests the disappearance or a lower concentration distribution of the envelope on a small scale. The ¹²CO and ¹³CO emission exhibit molecular outflows to the south and north. The C¹⁸O emission shows two molecular blobs, which correspond to the reflection nebulosity seen in near-infrared images, while there is no C¹⁸O emission associated with the protostar. The near-infrared features are likely due to the scattering at the positions of the blobs. The visible scattering features should result from the optical thinness of the envelope material, which is consistent with the less-concentrated distribution in the continuum emission. From single-dish observations, we found that the mass of the envelope (∼1.5 M_☉) + protostar (∼0.5 M_☉) is comparable with the virial mass of M_vir= 1.0 M_☉ within 40''. This suggests that the envelope is likely gravitationally bound. We suggest that the protostellar envelope of L43 has been disappearing by consumption through accretion, at least in the close vicinity of the protostar.