Table 2
Photometric and morphometric selection criteria adopted.
| Quantity | Band | NGC 3115 | NGC 1399 |
|---|---|---|---|
| ΔX6−12 | g/i | ± 0.15 | ± 0.15 |
| CLASS_STAR | g | ≥0.4 | ≥0.4 |
| CLASS_STAR | i | ≥0.7 | ≥0.2 |
| PSF FWHM | g | ≥3.5, ≤7.5 | ≥4.5, ≤8.5 |
| PSF FWHM | i | ≥3.5, ≤7.5 | ≥4.5, ≤8.5 |
| Flux radius | g | ≤4.5 | ≤4.5 |
| Flux radius | i | ≤4.0 | ≤4.5 |
| Kron radius | g/i | ≤5 | ≤5 |
| Petro. radius | i | ≥3.5, ≤7.5 | ≥3.5, ≤7.5 |
| Elongation a/b | g/i | ≤1.5 | ≤1.5 |
| (u − i) | ≥1.25, ≤3.75 | ≥1.25, ≤3.75 | |
| (g − i) | ≥0.4, ≤1.4 | ≥0.4, ≤1.4 | |
| Δ(u − i) | ≤0.3 | ≤0.3 | |
| Δ(g − i) | ≤0.2 | ≤0.2 | |
| Δ mag | g/i | ≤0.2 | ≤0.2 |
| mbright | g | 19.5 | 20.2 |
| mbright | i | 18.5 | 19.2 |
| Color–color | ∣(g − i) − [0.380(u − i) − 0.005]∣ ≤ 0.2 | ∣(g − i) − [0.362(u − i) − 0.0205]∣ ≤ 0.2 | |
Notes. Explanation of listed parameters. ΔX6−12: interval adopted for the magnitude concentration index in g- and i-band. SExtractor output parameters: CLASS_STAR: Neural-Network-based star/galaxy classifier; PSF FWHM: point spread function full width at half maximum; Flux Radius: half light radius; Kron Radius: defined from the automatic aperture photometry, intended to give a precise estimate of total magnitude, inspired to Kron (1980) first moments algorithm; Petro. Radius: the radius at which the surface brightness of the isophote is η times the average surface brightness within the isophote; Elongation: semi-major over semi-minor axis ratio (see Bertin & Arnouts 1996, and references therein for more details). Other selection parameters. (u − i) and (g − i): colour intervals adopted from the comparison with empirical data and stellar population models; Δ(g − i) and Δ(u − i): maximum allowed error on colors; Δ mag: maximum error on magnitude; mbright : bright cut magnitude, at ~3 × σ brighter than the turn-over magnitude of the GCLF; color–color: equation of color–color region used for selecting GC candidates.
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