Measurement of radial velocities and velocity dispersions using MEGARA data

Cross-correlation techniques have been applied since 1974 (see Simkin) in order to calculate objects’ redshift and velocity dispersions from the center and the width of the cross-correlation peak respectively. In 1979, Tonry and Davis detailed a correlation analysis based in the Fourier Method. It provides a determination of cross correlation function operationally straightforward and with an internal error measure of the correlation peak. In this work, we have adapted this method to implement it to very high spectral resolution data in red wavelengths and have developed a python package that can be used to calculate it automatically. We present an example of the correlation function using observations from MEGARA instrument at the 10.4-m GTC. We have used HR-I setup (VPH863-HR grating) that cover a wavelength range between 8380 and 8882 A and provide a velocity dispersion limit around 14.6 km/s (FWHM).The algorithms developed in this work will be published soon and will be available in the standard Python distribution channels.