The Tip of the Red Giant Branch Distance to the Perfect Spiral Galaxy M74 Hosting Three Core-collapse Supernovae

Abstract

M74 (NGC 628) is a famous face-on spiral galaxy, hosting three core-collapse supernovae (SNe): SN Ic 2002ap, SN II-P 2003gd, and SN II-P 2013ej. However, its distance is not well known. We present a distance estimation for this galaxy based on the Tip of the Red Giant Branch (TRGB) method. We obtain photometry of the resolved stars in the arm-free region of M74 from F555W and F814W images in the Hubble Space Telescope archive. The color-magnitude diagram of the resolved stars shows a dominant red giant branch (RGB) as well as blue main sequence stars, red helium burning stars, and asymptotic giant branch stars. The I-band luminosity function of the RGB stars shows the TRGB to be at I _TRGB = 26.13 ± 0.03 mag, and T _RGB = 25.97 ± 0.03. From this, we derive the distance modulus to M74 to be 30.04 ± 0.04 (random) ± 0.12 (systematic) (corresponding to a linear distance of 10.19 ± 0.14 ± 0.56 Mpc). With this distance estimate, we calibrate the standardized candle method for SNe II-P. From the absolute magnitudes of SN 2003gd, we derive a value of the Hubble constant, H ₀ = 72 ± 6 (random) ± 7 (systematic) km s^-1 Mpc^-1. It is similar to recent estimates based on the luminosity calibration of Type Ia supernovae.