The Tip of the Red Giant Branch Distance to the Large Magellanic Cloud

摘要

We present the I-band luminosity function of the red giant branch stars in the Large Magellanic Cloud (LMC) using the data from the Magellanic Clouds Photometric Survey (MCPS). By selecting stars in uncrowded, low-extinction regions, we observe a discontinuity in the luminosity function at I0 = 14.54 mag. Identifying this feature with the tip of the red giant branch (TRGB) and adopting an absolute TRGB magnitude of -4.05 ± 0.04 based on the calibration of Lee, Freedman, & Madore, we obtain a distance modulus of 18.59 ± 0.09 (random) ± 0.16 (systematic) mag. If the theoretical TRGB calibration provided by Cassisi & Salaris is adopted instead, the derived distance would be 4% greater. The LMC distance modulus reported here, 18.59 ± 0.09, is larger by 0.09 mag (1 σ) than the value that is most commonly used in the extragalactic distance scale calibrated by the period-luminosity relation of the Cepheid variable stars. Our TRGB distance modulus agrees with several RR Lyrae distances to the LMC based on Hipparcos parallaxes. Finally, we note that, by using the same MCPS data, we obtain a distance modulus of 18.29 ± 0.03 mag using the red clump method, which yields a distance shorter by 0.3 mag compared with the TRGB estimate.