Isochrone Fitting of Galactic Globular Clusters – VII. NGC1904 (M79), NGC4372, and revision of NGC288, NGC362, NGC5904 (M5), NGC6205 (M13), and NGC6218 (M12)

Abstract We estimate key parameters for the Galactic globular clusters NGC1904 (M79) and NGC4372. Additionally, we update the parameters for NGC288, NGC362, NGC5904 (M5), NGC6205 (M13), and NGC6218 (M12), which were analysed in our previous papers, to incorporate significant advancements in data sets and isochrones in recent years. We fit various colour–magnitude diagrams (CMDs) of the clusters using isochrones from the Dartmouth Stellar Evolution Database and the Bag of Stellar Tracks and Isochrones, adopting an α –enrichment value of α /Fe = +0.4. The CMDs are constructed fromdata sets provided by the Hubble Space Telescope , Gaia , SkyMapper Southern Sky Survey Data Release 4, a large compilation of ground-based observations by Stetson, and other sources, using multiple filters for each cluster. Our cross-identification of almost all the data sets with those from Gaia or Hubble Space Telescope allows us to use their astrometry to precisely select cluster members in all the data sets. We obtain the following estimates, along with their total uncertainties, for NGC288, NGC362, NGC1904, NGC4372, NGC5904, NGC6205 and NGC6218, respectively: metallicities Fe/H= –1.28 ± 0.08, –1.26 ± 0.07, –1.64 ± 0.09, –2.28 ± 0.09, –1.33 ± 0.10, –1.56 ± 0.09, and –1.27 ± 0.10 dex; ages 12.94±0.76, 10.33±0.75, 13.16±0.76, 12.81±0.81, 11.53±0.76, 12.75±0.76, and 13.03±0.81 Gyr; distances 8.83±0.21, 9.00±0.21, 12.66±0.36, 5.17±0.15, 7.24±0.16, 7.39±0.08, and 4.92±0.13 kpc; reddenings E ( B – V ) = 0.022±0.024, 0.029±0.025, 0.031±0.018, 0.545±0.032, 0.045±0.027, 0.024±0.021, and 0.210±0.028mag; extinctions A V = 0.09±0.06, 0.09±0.06, 0.11±0.06, 1.58±0.06, 0.13±0.06, 0.09±0.06, and 0.67±0.06mag; and extinction-to-reddening ratio R V = 3.9±0.7, 3.0±0.5, 3.8±0.5, 2.9±0.4, 2.9±0.2, 3.6 ± 0.7, and 3.2 ± 0.1. The R V estimates are fairly accurate, as the cross-identification of data sets enables us to calculate extinction across all ultraviolet, optical, and infrared filters used, thereby allowing us to derive an empirical extinction law for each combination of cluster, data set, and model. We confirm that the differences in horizontal branch morphology among the 16 Galactic globular clusters analysed in our studies can be explained by variations in their metallicity, age, mass-loss efficiency, and the loss of low-mass members during cluster evolution. Accordingly, most clusters indicate a relatively high mass-loss efficiency, consistent with the Reimers mass-loss law with η > 0.3.