Table 2.
Steps of data selection and size of VIPERS and SDSS samples after each selection step.
| Selection | VIPERS | SDSS |
|---|---|---|
| Spectroscopic sample | 88 340 | 927 552 |
| Sample with properties | 39 204 | 601 082 |
| Hα (S/N> 15) | – | 299 070 |
| Hβ (S/N> 3) | 20 545 | 296 027 |
| Redshift | – | 279 851 |
| Redshift flag | 20 545 | – |
| E(B−V) < 0.8 | 20 545 | 267 922 |
| Line flags | 9290 | – |
| BPT diagram | 6251 | 158 416 |
| Upper branch | 6116 | 157 404 |
| Metallicity calibration (Z > 8.4) | 6018 | 157 223 |
| Error on metallicity (σZ < 0.3) | 5776 | 151 345 |
| sSFR (> 5th percentile) | 5487 | 143 774 |
Notes. Selection on S/N on Hα was applied only for the SDSS as this line is not visible in the VIPERS spectra. The redshift range of the VIPERS sample (0.48 < z < 0.8) is a natural consequence of the requirement of having the lines Hβ, [O II]λ3727, [O III]λ4959, and [O III]λ5007 in the spectral range. In the SDSS, we do not use the redshift or the line flags, but the spectral quality is assured by the high S/N of Hα and we limit the redshift at z ≥ 0.027 to include [O II] doublet in the spectra.
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