| Abstract | The first installment of a H I redshift survey in the region of the Hercules Supercluster, defined as 14^h^<=α<=17^h^,0^deg^<=δ<=+38^deg^, is presented. Two hundred ninety-eight new spectra of UGC galaxies, most of them in that area, are given; the measured parameters from those spectra and the computed H I properties are listed. Of the 1063 UGC galaxies in that region, 426 now have H I parameters available. The three-dimensional distribution of the sample deviates markedly from that expected for a randomly distributed sample. The survey volume contains an underdense region in front of the supercluster and a possible foreground cluster. The application of the Tully-Fisher relation for the detection of large-scale deviations from the Hubble flow is discussed. A method of detecting such streaming motion in a sample of galaxies that is seriously affected by Malmquist bias is given. An attempt to improve the Tully-Fisher relation by introducing additional observational parameters is shown to be unsuccessful. The application of this method allows a preliminary estimate of an upper limit to the expansion velocity of the void in front of the supercluster of 400 km s^-1^. The inaccuracies in the available magnitudes and in the estimates of the inclinations of the galaxies are identified as the main sources of the uncertainty of the estimated upper limit of the peculiar velocity. |
