Half-power primary beams of the four fields observed with the SMA (circles) superposed on the integrated CO (1–0) emission in grayscale and the SiO (2–1) emission as white contours (from Gueth et al. 1998). The cross indicates the position of the protostar L1157-mm, α = 20^h39^m06.19^s, (J2000.0) given by Gueth et al. (1997). The bottom-right corner shows the HPBW of the Gueth et al. (1998) observations. Yellow and green ellipses indicate the location of the two cavities proposed by Gueth et al. (1997).