Streamer and disk of IRS 63 as probed by p-H₂CO 3(0, 3)−2(0, 2), HDCO 4(1, 4)−3(1, 3), and o-D₂CO 4(0, 4)−3(0, 3). From left to right: Panels A and B show the moment 0 and moment 1 maps of the H₂CO emission. Panels C, D, and E show a zoom-in of H₂CO, HDCO, and D₂CO integrated intensity on the blueshifted velocity range [+2.0, +2.6] km s⁻¹, which probes the terminal portion of the streamer impacting onto the disk. The map of HDCO covers a larger velocity range [+1.4, +2.6] km s⁻¹ due to the larger channel width of the line cube (1.19 km s⁻¹). The first contours and steps correspond to 3σ (0.5 mJy beam⁻¹ km s⁻¹).