Arp 220: the ellipse in the bottom left corner of each map represents the synthesized beam size. Top row: ¹²CO J = 1 − 0, J = 2 − 1 and HN¹³C J = 1 − 0 with contours corresponding to [4, 6, 8, 10] × 0.45 Jy beam^-1 km s^-1, [4, 8, 12, 16, 20, 24] × 0.5 Jy beam^-1 km s^-1 and [3, 4, 5, 6] × 0.135 Jy beam^-1 km s^-1, respectively. (2nd row) HNCO J_k,k′ = 5_0,4 − 4_0,4, SiO J = 2 − 1 and C₂H N = 1 − 0 with contours corresponding to [4, 6, 8,10] × 0.36 Jy beam^-1 km s^-1, [4, 6, 8, 10, 15, 20, 25, 30] × 0.135 Jy beam^-1 km s^-1 and [5, 10, 15, 20, 25] × 0.135 Jy beam^-1 km s^-1, respectively. (3rd row) CS J = 2 − 1, J = 4 − 3 (ALMA) and J = 5 − 4 with contours corresponding to [4, 8, 12, 16, 20, 24] × 0.5, 1.2 and 0.29 Jy beam^-1 km s^-1, respectively. (4th row) HCN J = 1 − 0 and HCO⁺J = 1 − 0 with contours corresponding to [5, 10, 15, 20, 25] × 0.52 and 0.15 Jy beam^-1 km s^-1, respectively. Bottom row: CH₃CN(6−5) and (10−9) with contours corresponding to [4, 6, 8, 10] and [6, 12, 18, 24, 30, 40, 50] × 0.33 Jy beam^-1 km s^-1, respectively.