Gravitational Redshift of Galaxies in Clusters from the Sloan Digital
  Sky Survey and the Baryon Oscillation Spectroscopic Survey
  The gravitational redshift effect allows one to directly probe the
gravitational potential in clusters of galaxies. Following up on Wojtak et al.
[Nature (London) 477, 567 (2011)], we present a new measurement. We take
advantage of new data from the tenth data release of the Sloan Digital Sky
Survey and the Baryon Oscillation Spectroscopic Survey. We compare the
spectroscopic redshift of the brightest cluster galaxies (BCGs) with that of
galaxies at the outskirts of clusters, using a sample with an average cluster
mass of $10^{14} M_{\odot}$. We find that these galaxies have an average
relative redshift of -11 km/s compared with that of BCGs, with a standard
deviation of +7 and -5 km/s. Our measurement is consistent with that of Wojtak
et al. However, our derived standard deviation is larger, as we take into
account various systematic effects, beyond the size of the dataset. The result
is in good agreement with the predictions from general relativity.
