Abstract

To precisely measure the redshifts of non-ELGs (ELGs: emission-line galaxies), weaker-ELGs and galaxies with only one emission line that is clearly visible in the optical band, a fast automatic redshift determination algorithm (FRA) is proposed, which is different from the widely used cross-correlation method. The algorithm has higher speed because it determines the redshift by extracting and recognizing two pairs of prominent absorption lines in the blue band of a spectrum, G-band |$\lambda$|4306 and H|${\gamma}$||$\lambda$|4342 (vacuum wavelength), H|${\beta}$||$\lambda$|4863 and Mg |$\lambda$|5177, rather than through matching an observational galaxy spectrum with the complete galaxy templates. Moreover, a wide range of redshift measurements from 0 to 0.65 and relatively high success rates can be reached by FRA. For spectra with a relatively wide wavelength range and with a resolution above |$R$||$=$| 1000, FRA is an efficient automatic algorithm that can be used in spectra redshift surveys with large amounts of data.

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