[A New Redshift Measuring Method for Low-Quality Galaxy Spectra Based on Multi Resolution Fusion Distance]

The redshift measurement of galaxy spectrum is a key issue in large astronomical spectral survey. Its goal is to extract the redshift from spectrum, which is caused the Doppler Effect. With the development of the extragalactic sky survey project, the distance (redshift) of the observed targets is becoming further. As a result, the magnitude of the observed objects becomes darker and the spectral quality becomes poorer. Therefore, how to effectively and accurately measure the redshift from these low quality spectra is becoming an important problem in the extragalactic survey. Considering the spectral features and the data character, a new definition of multi-resolution fusion distance for low quality spectra is proposed. In this paper, we put forward a redshift measuring method for low quality galaxy spectra. This method combines the spectral features with different resolutions. The template spectrum and the spectrum to measure are reduced to the resolution and then a distance is computed by combining the offset of the above two spectra in different wavelengths. Then, a fusion distance is weighted averaged from the distances with different resolutions. In this paper, the effect of signal-to-noise ratio (SNR) on the measuring accuracy of the proposed method is discussed. The measuring accuracy is larger than 90% when the SNR is larger than 5. A large number of experiments show that the method proposed in this paper is very efficient in measuring the redshift of the low-quality galaxy spectra and the measuring error has nothing to do with the redshift value. The proposed method can be applied in redshift measurement of galaxies for the large-scale survey data.