Distance to M87 as the Mode of the Modulus Distribution

Abstract

de Grijs and Bono (ApJS 2020, 246, 3) compiled a list of distances to M87 from the literature published in the last 100 years. They reported the arithmetic mean of the three most stable tracers (Cepheids, tip of the red giant branch, and surface brightness fluctuations). The arithmetic mean is one of the measures of central tendency of a distribution; others are the median and mode. The three do not align for asymmetric distributions, which is the case for the distance moduli μ0 to M87. I construct a kernel density distribution of the set of μ0 and estimate the recommended distance to M87 as its mode, obtaining μ0=31.06±0.001(statistical)−0.06+0.04(systematic) mag, corresponding to D=16.29−0.45+0.30 Mpc, which yields uncertainties smaller than those associated with the mean and median.

Keywords

• distance scale
• distances and redshifts
• data analysis
• statistical methods