Astrophysical Distance Scale IV. Preliminary Zero-Point Calibration of the JAGB Method in the HST/WFC3-IR Broad J-Band (F110W) Filter

Abstract

We present an absolute calibration of the J-region Asymptotic Giant Branch (JAGB) method using published photometry of resolved stars in 20 nearby galaxies observed with HST using the WFC3-IR camera and the F110W (Broad J-Band) filter. True distance moduli for each of the galaxies are based on the Tip of the Red Giant Branch (TRGB) method as uniformly determined by Dalcanton et al. (2012). From a composite color-magnitude diagram composed of over 6 million stars, leading to a sample of 453 JAGB stars in these galaxies, we find M JAGB F 110W = −5.77 ± 0.02 mag (statistical error on the mean). The external scatter seen in a comparison of the individual TRGB and the JAGB moduli is ±0.081 mag (or 4% in distance). Some of this scatter can be attributed to small-number statistics arising from the sparse JAGB populations found in the generally low-luminosity galaxies that comprise the particular sample studied here. However, if this inter-method scatter is shared equitably between the JAGB and TRGB methods that implies that each are good to ±0.06 mag, or better than 3% in distance.

Emergence of smooth distance and apparent magnitude in a lumpy Universe

“…where F DF is called the reference flux or the zero-point of the filter [45][46][47]. The observed flux density at both distances obeys the inverse square law with the luminosity distance:…”

Consequences of using a smooth cosmic distance in a lumpy universe: I

“…where F D F is called the reference flux or the zero-point of the filter [44][45][46]. The observed flux density at both distances obey the inverse square law with the luminosity distance, d L :…”