New Reference Galaxy Standards for HI Emission Observations

Abstract

We have taken advantage of the improved baselines and higher sensitivity available with the upgraded Arecibo 305m telescope to create a new HI spectral line catalog of disk galaxies which can be used as a reference catalog for anyone interested in 21-cm spectral line work. In all 108 galaxies were observed, covering 24h of the sky at declinations between 0 < delta < 36 degrees and velocities between 0 - 25,000 km s-1. The majority of the galaxies were observed at least two times on different nights to avoid problems with RFI, baselines fluctuations, etc. Comparing our measured values with all those available in the literature show that while large individual variations may exist, the average differences between the measurements to be zero. In all we have considerable confidence in our measurements, and the resultant catalog should be extremely useful as a well defined reference catalog for anyone interested in 21-cm spectral line work.