Velocity integrated SO₂(11_1,11 – 10_0,10) together with sample spectra of SO₂, SO, and H₂CO at positions a to d. Left and right: Beam averaged spectra at positions a to d. Each color represents the spectrum of a molecule: blue corresponds to H₂CO, green to SO and red to SO₂. The dotted vertical line marks the central velocity of the protostar V_LSR = 7.5 km s⁻¹. The dashed horizontal line represents the 0 K level. If a molecule does not appear at a panel, its because emission from that molecule has a S/N < 5. Middle: Velocity integrated image of the SO₂(11_1,11 – 10_0,10) molecular transition. The crosses represent the places where each spectrum was extracted, labeled from a to d. The white contours represent the three and five times the rms of the integrated map contours of H₂CO (0.25 K km s⁻¹). The white ellipse in the bottom left corner represents the beam size. The blue star marks the position of Per-emb-50.