a, The fraction of SDSS quiescent galaxies as a function of the orientation based on the worst-fitting functional form (de Vaucouleurs versus exponential) according to the SDSS photometric pipeline. The stability of the signal demonstrates that our results are robust against the photometric fitting procedure. Error bars represent the best-fitting standard deviation, as described in the Methods. b, Coloured curves indicate the best-fitting solution for SDSS data obtained while randomly perturbating the PA of the central galaxy by ΔPA. For reference, black symbols and curves are the same as in Fig. 2. A clear modulation in the fraction of quiescent galaxies is observed even for ΔPA ≈ 30, which is an order of magnitude larger than the expected error on the individual PAs. c, d, The SDSS g-band images of galaxies best-fitted by a de Vaucouleurs (top row) and an exponential profile (bottom row), with the PA uncertainty indicated by the white-shaded area. The adopted PA is indicated in the top left corner of each image.