AFGL 2591 integrated intensity, , maps of rotational transition lines spanning a range of energy levels. The upper state energy level is indicated in the top right-hand corner and the beam size in the bottom left-hand corner. The source VLA 3 is noted by a white or black ‘x’. CH₃CCH, in the first column, c-C₃H₂, in the second, H₂CO, in the third, have contour levels of 10, 20, 30, and 40 times the noise level of the respective frequency range. CH₃OH, in the fourth column, has contour levels of 10, 20, 40, 80, and 120 times the noise level of the respective frequency range.