From the poor cluster catalog of White et al. (1996), we define a sample of 71 optically-selected poor galaxy clusters. The surface-density enhancement we require for our clusters falls between that of the loose associations of Turner & Gott [AJ, 91,204(1976)] and the Hickson compact groups [Hickson, ApJ, 255, 382(1982)]. We review the selection biases and determine the statistical completeness of the sample. For this sample, we report new velocity measurements made with the ARC 3.5-m Dual-Imaging spectrograph and the 2.3-m Steward Observatory MX fiber spectrograph. Combining our own measurements with those from the literature, we examine the velocity distributions, velocity dispersions, and ID velocity substructure for our poor cluster sample, and compare our results to other poor cluster samples. We find that approximately half of the sample may have significant ID velocity substructure. The optical morphology, large-scale environment, and velocity field of many of these clusters are indicative of young, dynamically evolving systems. In future papers, we will use this sample to derive the poor cluster x-ray luminosity function and gas mass function, and will examine the optical/x-ray properties of the clusters in more detail.
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Ledlow et al. (1996) studied this question.