Prospects for high-resolution probes of galaxy dynamics tracing background cosmology in MaNGA

Abstract

Large-$N$ galaxy surveys offer unprecedented opportunities to probe weak gravitation in galaxy dynamics that may contain correlations tracing background cosmology. Of particular interest is the potential of finite sensitivities to the background de Sitter scale of acceleration $a_{dS}=cH$, where $H$ is the Hubble parameter and $c$ is the velocity of light. At sufficiently large $N$, this is possibly probed by ensemble-averaged (“stacked”) rotation curves (RCs) at resolutions on par with present estimates of the Hubble parameter $H_0$. Here, we consider the prospect for these studies using the large $N$ Mapping Nearby Galaxies at Apache Point Observatory MaNGA at APO survey. In a first and preliminary step, we consider unbiased control of sub-sample size by consistency in the three Position Angles, $\theta$ , from photometry and velocity fields of gas and stars by spectroscopy within 30°. In sub-samples of size $N=N_i\left(\theta \right)$, the scatter in-the-mean $\sigma /\sqrt{N}$ is found to reach one percent levels, differentiated over inclination angle $i$ and $\theta$. In regular propagation of uncertainties, this scatter contributes $\kappa \sigma /\sqrt{N}$ to the standard error in-the-mean to the observable, where $\kappa$ is determined by the choice of observables. As a lower bound to scatter in stacked RCs, MaNGA hereby appears promising for high-resolution analysis of sensitivity to RCs to background cosmology, notably across a sharp $C^0$-transition (van Putten, 2018) of Newtonian to anomalous dynamics across $a_{dS}$ and, further out, the baryonic Tully–Fisher relation. In turn, these markers provide a novel measurement of cosmological parameters including $H_0$.