http://arxiv.org/abs/2305.02453
The J-region Asymptotic Giant Branch (JAGB) method is a standard candle based on the intrinsic luminosities of carbon stars in the near infrared. For the first time, we directly constrain the impact of metallicity, age, and reddening on the JAGB method. We assess how the mode, skew, and scatter of the JAGB star luminosity function change throughout diverse stellar environments in M31’s NE disk from 13<d<18 kpc using data from the Panchromatic Hubble Andromeda Treasury (PHAT). As expected, the mode is found to be fainter in higher-reddening regions. To cross-check this result, we also measure a fiducial J-band ground-based JAGB distance using data from the UKIRT/WFCam in M31’s outermost disk (18<d<40 kpc) where internal reddening is minimal. We find that this J-band distance modulus agrees well with the F110W distance moduli measured in the lowest reddening regions of the PHAT data, demonstrating the JAGB method is most accurate if measured in the low-reddening outer disks of galaxies. On the other hand, the mode of the JAGB star luminosity function appears empirically to show no dependence on metallicity and age, disputing theoretical predictions that the average luminosity of metal-rich carbon stars is brighter than for metal-poor carbon stars. In conclusion, the JAGB method proves to be a robust standard candle capable of calibrating the luminosities of type Ia supernovae and therefore providing a high-accuracy, high-precision measurement of the Hubble constant.
A. Lee
Fri, 5 May 23
38/67
Comments: 15 pages, 9 figures 1 tables, submitted to AAS Journals