2017ApJ...841...23L

There is a well-known discrepancy in the distance estimation of M60, a giant elliptical galaxy in Virgo; the planetary nebula luminosity function (PNLF) distance moduli for this galaxy are, on average, 0.4 mag smaller than the values based on the surface brightness fluctuation (SBF) in the literature. We present photometry of the resolved stars in an outer field of M60 based on deep F775W and F850LP images in the Hubble Space Telescope obtained as part of the Pure Parallel Program in the archive. Detected stars are mostly old red giants in the halo of M60. With this photometry, we determine a distance to M60 using the tip of the red giant branch (TRGB). A TRGB is detected at F850LP_TRGB=26.70±0.06 mag, in the luminosity function of the red giants. This value corresponds to F814W_0,TRGB=27.13±0.06 mag and QT_TRGB=27.04±0.07 mag, where QT is a color-corrected F814W magnitude. From this we derive a distance modulus, (m-M)₀=31.05±0.07(ran) ±0.06(sys) (d=16.23±0.50(ran)±0.42(sys) Mpc). This value is 0.3 mag larger than the PNLF distances and 0.1 mag smaller than the SBF distances in the previous studies, which indicates that the PNLF distances to M60 reported in the literature have larger uncertainties than the suggested values.