A giant central red disk galaxy at redshift $z=0.76$: challenge to
  theories of galaxy formation
  We report a giant red central disk galaxy in the XMM-LSS north region. The
region is covered with a rich variety of multiband photometric and
spectroscopic observations. Using the photometric data of the
Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) and spectroscopic
observation of the Baryon Oscillation Spectroscopic Survey (BOSS), we find that
the galaxy has a stellar mass of $\sim 10^{11.6}$ times of the solar mass
$M_\odot$. The galaxy has a red color and has an old stellar population, and
thus its star formation has stopped. With the photometric image data of Hyper
Suprime-Cam (HSC) Subaru Strategic Program, we demonstrate that its luminosity
profile is perfectly described by a S\'ersic form with $n=1.22$ indicating disk
morphology. We also analyze its environment based on the VIMOS Public
Extragalactic Redshift Survey (VIPERS) photometric catalog, and find that its
close neighbors are all less massive, indicating that our observed galaxy is
sitting at the center of its host halo. Existence of the giant red central disk
galaxy seriously challenges the current standard paradigm of galaxy formation,
as there is no known physical mechanism to explain the quenching of its star
formation. This conclusion is supported by state-of-the-art hydrodynamical
simulations of galaxy formation.
