Relativistic distortions in the largescale clustering of SDSSIII BOSS CMASS galaxies
Abstract
General relativistic effects have long been predicted to subtly influence the observed largescale structure of the universe. The current generation of galaxy redshift surveys has reached a size where detection of such effects is becoming feasible. In this paper, we report the first detection of the redshift asymmetry from the crosscorrelation function of two galaxy populations that is consistent with relativistic effects. The data set is taken from the Sloan Digital Sky Survey Data Release 12 CMASS galaxy sample, and we detect the asymmetry at the 2.7σ level by applying a shellaveraged estimator to the crosscorrelation function. Our measurement dominates at scales around 10 h^{1} Mpc, larger than those over which the gravitational redshift profile has been recently measured in galaxy clusters, but smaller than scales for which linear perturbation theory is likely to be accurate. The detection significance varies by 0.5σ with the details of our measurement and tests for systematic effects. We have also devised two null tests to check for various survey systematics and show that both results are consistent with the null hypothesis. We measure the dipole moment of the crosscorrelation function, and from this the asymmetry is also detected, at the 2.8σ level. The amplitude and scale dependence of the clustering asymmetries are approximately consistent with the expectations of general relativity and a biased galaxy population, within large uncertainties. We explore theoretical predictions using numerical simulations in a companion paper.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 September 2017
 DOI:
 10.1093/mnras/stx1421
 arXiv:
 arXiv:1709.07855
 Bibcode:
 2017MNRAS.470.2822A
 Keywords:

 gravitation;
 galaxies: statistics;
 cosmological parameters;
 largescale structure of Universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 Astrophysics  Astrophysics of Galaxies;
 General Relativity and Quantum Cosmology;
 Physics  Popular Physics
 EPrint:
 13 pages, 10 figures, published in MNRAS, see link for a combined video summary of this and three other related papers posted today: https://youtu.be/nESs6jsXBCs . An elementary introduction to gravitational redshift is here: https://youtu.be/6tbCk_4Tk10