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

TL;DR

This paper determines the distance to the galaxy M74 using the TRGB method and calibrates the Hubble constant with its supernovae, providing a precise cosmic distance measurement.

Contribution

It presents a new distance estimate for M74 using HST data and applies this to calibrate the Hubble constant via Type II-P supernovae.

Findings

Distance to M74 is 10.19 Mpc with small uncertainties.

Calibrated Hubble constant as 72 km s^-1 Mpc^-1.

Confirmed consistency with recent supernova-based Hubble estimates.

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 pm 0.03 mag, and T_RGB = 25.97 pm 0.03. From this we derive the distance modulus to M74 to be 30.04 pm 0.04 (random) pm 0.12 (systematic) (corresponding to a linear distance, 10.19 pm 0.14 pm 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 pm 6 (random) pm 7 (systematic) km s^-1 Mpc^-1. It is similar to recent estimates based on the luminosity calibration of Type Ia supernovae.