Panels a and b: maps of the eigenvalues of the tidal tensor λ_max and λ_min (refer to Sect. 3.4) toward G53. The solid black ellipses represent C1, C3, C2, and C4 from left to right. The dashed black circles represent regions 4 and 3 from left to right. Panel c: Herschel H₂ column density. Thee color and direction of the arrows indicate the magnitude and direction of the gravitational field. Panel d: same as panel c but with two opposing arrows in one direction indicating that the gas in this pixel is collapsing along the corresponding directions, while two arrows pointing away from each other indicate the gas in this pixel is expanding along the corresponding directions.