3D intrinsic shapes of quiescent galaxies in observations and simulations

We study the intrinsic 3D shapes of quiescent galaxies over the last half of cosmic history based on their axial ratio distribution. To this end, we construct a sample of unprecedented size, exploiting multi-wavelength \(u\)-to-\(K_s\) photometry from the deep wide area surveys KiDS+VIKING paired with high-quality \(i\)-band imaging from HSC-SSP. Dependencies of the shapes on mass, redshift, photometric bulge prominence and environment are considered. For comparison, the intrinsic shapes of quenched galaxies in the IllustrisTNG simulations are analyzed and contrasted to their formation history. We find that over the full \(0