Zeldovich pancakes in observational data are cold
  The present day universe consists of galaxies, galaxy clusters,
one-dimensional filaments and two-dimensional sheets or pancakes, all of which
combine to form the cosmic web. The so called "Zeldovich pancakes", are very
difficult to observe, because their overdensity is only slightly greater than
the average density of the universe.
  Falco et al (2014) presented a method to identify Zeldovich pancakes in
observational data, and these were used as a tool for estimating the mass of
galaxy clusters. Here we expand and refine that observational detection method.
We study two pancakes on scales of 10 Mpc, identified from spectroscopically
observed galaxies near the Coma cluster, and compare with twenty numerical
pancakes.
  We find that the observed structures have velocity dispersion about 100
km/sec, which is relatively low compared to typical groups and filaments. These
velocity dispersions are consistent with those found for the numerical
pancakes. We also confirm that the identified structures are in fact
two-dimensional structures. Finally, we estimate the stellar to total mass of
the observational pancakes to be $2 \times 10^{-4}$, within one order of
magnitude, which is smaller than that of clusters of galaxies.
