Integrated intensity of C¹⁸O (1–2) (top) and DCO⁺ (3–2) (bottom) toward IRAS 15398. The white contour levels are 10, 20, and 30 times of mean rms value for the DCO⁺ line and 40, 50, and 60 times of mean rms value for the C¹⁸O (2–1) line. The beam size is shown in the bottom left corner. The yellow contours in both images show H₂ column density (levels:[1.0, 1.5, 2.0] 10²² cm⁻²). The black star gives the position of the protostar.