GOTHAM survey: GlObular clusTer Homogeneous Abundances Measurements

New metallicity scale for 152 clusters

Source papers

Dias et al. 2015, A&A, 573, 13

Dias et al. 2016a, A&A, 590, 9

Metallicity compilation
for 152 clusters

Click to see text table

Average metallicities from different homogeneous studies as done by Harris (1996, 2010 edition; H10), Carretta et al. (2009; C09), and by us (Dias et al. 2016; D16).

(a) C09 vs. H10: H10 adopted the C09 scale for 95 clusters and gave a triple weight to these metallicities to take the average with other sources. Therefore in the range [Fe/H] < -1.0 the values averaged by H10 using spectroscopic and photometric indicators are in good agreement with the average taken by C09. For clusters more metal-rich than that, C09 present higher values than those of H10. In fact, Carretta et al. said in their source paper that "problems might arise at the high metallicity extreme" because they did not observe clusters with [Fe/H] > -0.4.

(b) C09 vs. D16: our metallicity scale is based on the homogeneous set of [Fe/H] of 51 globular clusters covering the full range of metallicities -2.4 < [Fe/H] < 0.0. Therefore our average (D16) of previous homogeneous metallicities in our scale is valid for the full range of metallicities. Consistently to what we found in Dias et al. (2016a, in press), C09 present higher metallicities for clusters with [Fe/H] > -0.4.

(c) D16 vs. H10: finally, our compilation of metallicities naturally agrees with the averages adopted by H10 for the full range of metallicities. We also have included newer references with respect to C09 and increased the number of clusters with homogeneous metallicities from 95 to 111. We call the attention that H10 took an average of different sources, including photometric metallicities in some cases, and our scale agrees well with this average. It seems that we are converging to a complete homogeneous scale of globular cluster metallicities!