10.7.4 Completeness

We compare the completeness in different globular clusters with the expected HST completeness, after removing the duplicated sources. No other filtering was applied to the data. The HST magnitudes were converted to the G magnitudes using the relations of Jordi et al. (2010). The zero point of this transformation was adjusted for each cluster using a subset of bright stars in common, in order to avoid variations due to metallicity and interstellar extinction

Figures 10.50, 10.51, and 10.52 present the luminosity function (in HST and Gaia data) for three globulars at different level of crowding. In NGC 6656 the completeness is better than 80% down to G =17 and then drops to 0 at G =18; in NGC 6366 the completeness is around 90% even at 20.5. For NGC 5139 it is about 100% at G =14; 80% near G =15, drops around G =16, down to 0 at G =17.

Figure 10.50: Completeness for NGC 6656.
Figure 10.51: Same as Figure 10.50, for NGC 5139.
Figure 10.52: Same as Figure 10.50, for NGC 6366.

We computed the ratio of number of sources in different magnitude bins, in the inner (inside 0.5 arcmin) and outer (0.5 to 2.2 arcmin) regions of each GC. An example is shown for NGC 6121 (M4) in Figure 10.53. The result for all GCs is presented in Table 10.6. The content of this Table is also presented Figure 10.54, where the double dependence on magnitude and local density can be clearly seen. The completeness of the Gaia DR2 Catalogue is, overall, higher than it was in Gaia DR1.

Figure 10.53: Completeness level with respect to HST data in the inner (within 0.5 arcmin) and outer region of the cluster (from Arenou et al. 2018).
Figure 10.54: Completeness levels in different regions of 26 globular clusters with different local density, showing the influence of crowding on the completeness (from Arenou et al. 2018).
Table 10.6: Completeness level (in percentage with respect to HST fields) in various magnitude ranges, in the inner and outer regions of 26 globular clusters (inner: within 0.5 arcmin; outer: 0.5 to 2.2 arcmin)
name region G
11 – 13 12 – 14 13 – 15 14 – 16 15 – 17 16 – 18 17 – 19 18 – 20 19 – 21 20 – 22
LYN07 inner – – – – – 56 33 18 5 1
LYN07 outer – – – – 54 50 35 24 9 2
NGC0104 inner 23 2 0 0 0 0 0 0 0 0
NGC0104 outer 85 55 43 21 7 1 0 0 0 0
NGC0288 inner – – – – – – 60 40 15 1
NGC0288 outer – – – 100 85 79 70 54 28 6
NGC1261 inner – – – 77 55 37 10 1 0 0
NGC1261 outer – – – 100 96 89 62 30 11 2
NGC1851 inner – – 40 29 14 3 0 0 0 0
NGC1851 outer – – – 100 86 61 34 14 5 1
NGC2298 inner – – – – 86 67 30 10 3 0
NGC2298 outer – – – – 97 90 83 62 36 10
NGC4147 inner – – – – – 52 29 12 3 1
NGC4147 outer – – – – – 94 78 63 27 7
NGC5053 inner – – – – – – – 78 44 13
NGC5053 outer – – – – – 100 94 82 46 13
NGC5139 inner – – 1 1 0 0 0 0 0 0
NGC5139 outer 43 11 5 2 1 0 0 0 0 0
NGC5272 inner – – 69 44 27 6 0 0 0 0
NGC5272 outer – 100 99 86 75 45 17 6 1 0
NGC5286 inner – – 52 33 13 4 0 0 0 0
NGC5286 outer – – 86 83 69 51 25 6 1 0
NGC5466 inner – – – – – – – 69 31 7
NGC5466 outer – – – – 100 99 100 86 48 12
NGC5927 inner – – – 52 37 24 2 0 0 0
NGC5927 outer – – 81 75 75 60 28 6 1 0
NGC5986 inner – – – 59 34 14 2 0 0 0
NGC5986 outer – – 90 88 81 61 34 10 2 0
NGC6121 inner – – – 66 54 38 20 5 0 0
NGC6121 outer – 95 92 85 79 66 48 25 7 0
NGC6205 inner – – 68 42 15 1 0 0 0 0
NGC6205 outer 89 92 92 80 56 25 7 2 0 0
NGC6366 inner – – – – – – 69 55 32 9
NGC6366 outer – – – 91 90 81 79 69 42 11
NGC6397 inner – – 62 49 28 11 2 0 0 0
NGC6397 outer – 95 89 82 72 56 33 12 2 0
NGC6656 inner – – 53 38 11 1 0 0 0 0
NGC6656 outer 75 75 69 61 41 10 1 0 0 0
NGC6752 inner – 62 37 18 6 1 0 0 0 0
NGC6752 outer – 98 94 78 57 32 13 3 0 0
NGC6779 inner – – – – 63 43 16 2 0 0
NGC6779 outer – – 94 87 82 76 56 30 13 2
NGC6809 inner – – – – – 48 20 4 0 0
NGC6809 outer – – 100 96 84 66 37 11 1 0
NGC6838 inner – – – – – 67 54 31 8 1
NGC6838 outer – – 91 89 72 80 74 56 28 5
NGC7099 inner – – – 47 34 11 2 0 0 0
NGC7099 outer – – – 94 80 66 38 17 5 1
PAL01 inner – – – – – – – – 73 39
PAL01 outer – – – – – – – – 67 21
PAL02 inner – – – – – – 84 62 24 7
PAL02 outer – – – – – – 92 89 47 14