HJPDOC contains references to the papers, data files and links to the Internet resources related to measurements and calculations of the optical constants in the wavelength interval from X-rays to radio domain. This publicly-available resource gives access to all the data produced in the context of the IllustrisTNG simulations, a suite of large volume, cosmological, gravo-magnetohydrodynamical simulations for the physics of galaxies, run with the moving-mesh code AREPO.