Astrophysical Distance Scale The JAGB Method: I. Calibration and a First Application

TL;DR

This paper calibrates the luminosity of JAGB stars as a reliable distance indicator using LMC and SMC data, and applies it to measure the distance to NGC 253, demonstrating its potential for extragalactic distance measurements.

Contribution

The study provides the first calibration of JAGB stars' absolute magnitude and demonstrates its application to measure galaxy distances, offering a new tool for the cosmic distance scale.

Findings

JAGB stars have a consistent absolute magnitude of about -6.20 mag in J-band.

The calibrated JAGB method yields a distance to NGC 253 of 3.40 Mpc.

The JAGB distance agrees well with the TRGB distance, validating its accuracy.

Abstract

J-Branch Asymptotic Giant Branch (JAGB) stars are a photometrically well-defined population of extremely red, intermediate-age AGB stars that are found to have tightly-constrained luminosities in the near-infrared. Based on JK photometry of some 3,300 JAGB stars in the bar of the Large Magellanic Cloud (LMC) we find that these very red AGB stars have a constant absolute magnitude of <M_J> = -6.22 mag, adopting the Detached Eclipsing Binary (DEB) distance to the LMC of 18.477 +/- 0.004 (stat) +/- 0.026 (sys). Undertaking a second, independent calibration in the SMC, which also has a DEB geometric distance, we find <M_J> = -6.18 +/- $ 0.01 (stat) +/- 0.05~(sys) mag. The scatter is +/-0.27 mag for single-epoch observations, (falling to +/-0.15~mag for multiple observations averaged over a window of more than one year). We provisionally adopt <M_J> = -6.20 mag +/- 0.01 (stat) +/- 0.04 (sys) mag for the mean absolute magnitude of JAGB stars. Applying this calibration to JAGB stars recently observed in the galaxy NGC 253, we determine a distance modulus of 27.66 +/- 0.01(stat) +/- 0.04 mag (sys), corresponding to a distance of 3.40 +/- 0.06 Mpc (stat). This is in excellent agreement with the averaged TRGB distance modulus of 27.68 +/- 0.05 mag, assuming M_I = -4.05 mag for the TRGB zero point.