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We study the shapes and intrinsic alignments of disks and elliptical galaxiesin the MassiveBlack-II (MBII) and Illustris cosmological hydrodynamicsimulations, with volumes of $(100h^{-1}Mpc)^{3}$ and $(75h^{-1}Mpc)^{3}$respectively. We find that simulated disk galaxies are more oblate in shape andmore misaligned with the shape of their host dark matter subhalo when comparedwith ellipticals. The disk major axis is found to be oriented towards thelocation of nearby elliptical galaxies. We also find that the disks are thinnerin MBII and misalignments with dark matter halo orientations are smaller inboth disks and ellipticals when compared with Illustris. As a result, theintrinsic alignment correlation functions at fixed mass have a higher amplitudein MBII than in Illustris. Finally, at scales above $\sim 0.1$\hmpc, theintrinsic alignment two-point correlation functions for disk galaxies in bothsimulations are consistent with a null detection, unlike those for ellipticals.Despite significant differences in the treatments of hydrodynamics and baryonicphysics in the simulations, we find that the $w_{\delta +}$ correlationfunction scales similarly with transverse separation. However, the less massivegalaxies show different scale dependence in the ED correlation. This resultindicates that, while hydrodynamic simulations are a promising tool to studyintrinsic alignments, further study is needed to understand the impact ofdifferences in the implementations of hydrodynamics and baryonic feedback.

Intrinsic alignments of disk and elliptical galaxies in the MassiveBlack-II and Illustris simulations