Cross-correlating 2MRS galaxies with UHECR flux from Pierre Auger
  Observatory
  We apply a recently proposed cross-correlation power spectrum technique to
study relationship between the ultra-high energy cosmic ray (UHERC) flux from
the Pierre Auger Observatory and galaxies from the 2MASS Redshift Survey. Using
a simple linear bias model relative to the galaxy auto power spectrum, we are
able to constrain the value of bias to be less than 1% for UHECR with energies
4 EeV - 8 EeV, less than 2.3% for UHECR with energies above 8 EeV and less than
21% for UHECR with energies above 52 EeV (all 95% confidence limit). We study
energy dependence of the bias, but the small sample size does not allow us to
reach any statistically significant conclusions. For the cosmic ray events
above 52 EeV we discover a curious excess cross-correlation at $\sim 1^\circ$
degree scales. Given similar cross-correlation is not visible at larger angular
scales, statistical fluctuation seems like the most plausible explanation.
