Tomographic constraints on gravity from angular redshift fluctuations in the late Universe

Fluctuations in sky maps of galaxy redshifts, dubbed angular redshift fluctuations (ARF), contain precise information about the growth rate of structures and the nature of gravity in the Universe. Specifically, ARFs constrain the combination of cosmological parameters H / H-0 f sigma(8)(z), while being an intrinsically tomographic probe and largely insensitive to many observational systematic errors, all without requiring the assumption of any redshift-to-distance relation under a given fiducial cosmology. We present the first cosmological constraints derived from ARF by using Baryon Oscillation Spectroscopic Survey (BOSS) LOWZ(Low redshift(Z))+CMASS(Constant MASS) DR12(Data Release 12) galaxy samples, obtaining 7 per cent accurate constraints on H/H(0)f sigma(8)(z) at more than 20 redshifts over the range z is an element of [0.26, 0.72]. Our best-fitting value is 10 per cent larger, but compatible at the 1.4 sigma level, than the Lambda CDM expectation set by Planck observations of cosmic microwave background (CMB) radiation. Our tomographic measurements, combined with these CMB data, provide one of the strongest constraints on the gravity index gamma, gamma = 0.44(-0.07)(+0.09) which lies within 2 sigma of the prediction of General Relativity (gamma(GR) similar or equal to 0.55).

Automated summary

Fluctuations in sky maps of galaxy redshifts, known as angular redshift fluctuations (ARF), provide precise information about the growth rate of structures and the nature of gravity in the Universe. Utilizing the BOSS LOWZ+CMASS DR12 galaxy samples, we obtained 7% accurate constraints on H/H(0)f sigma(8)(z) and found the gravity index gamma to be 0.44, within 2 sigma of the prediction of General Relativity.