Precise JAGB distances to M83 and Centaurus A not obtained

Determine precise distances to M83 (NGC 5236) and Centaurus A (NGC 5128) using the J-region Asymptotic Giant Branch (JAGB) method applied to Magellan/FourStar near-infrared J-band photometry, overcoming the absence of a clearly defined modal peak in the JAGB luminosity function that prevented distance measurements in the present analysis.

Background

The paper measures JAGB and near-infrared TRGB distances to a homogeneous sample of nearby galaxies using Magellan/FourStar JHK photometry. For 11 galaxies, JAGB distances were successfully derived via the modal magnitude of the GLOESS-smoothed luminosity function of color-selected carbon-rich AGB stars.

However, for two galaxies—M83 and Centaurus A—the JAGB luminosity functions lacked a clearly defined peak, precluding a precise JAGB distance. The authors note that M83 is the farthest galaxy in their sample and speculate that the ground-based JAGB method may be approaching its practical distance limit, while for Centaurus A the complex star formation history and large photometric scatter may contribute to the difficulty. They verified that their photometry is consistent with published long-period variable star photometry in Centaurus A, indicating the issue is not due to obvious photometric errors.