For over half a century, the 21cm line of neutral hydrogen (HI) has been one of the main observational tools for galactic studies and cosmology. It has been used with ever-increasing sensitivity and resolution to investigate the structure of our own Galaxy and of other disk systems, their interactions with other galaxies, the large-scale structure of the Universe, and the physical conditions of high redshift systems. The recent evolution of 21 cm detectors, spectrometers and multi-feed systems has dramatically expanded both the accessible volume of parameter space and our ability to sample it quickly. The new seven-feed array for the Arecibo telescope enables it to study the HI Universe to unprecedented volumes and low mass levels.
The first part of this research will explore the faint end of the HI mass function, and act as a pilot for the second part, which will carry out, develop the necessary analysis tools for, and process and make publicly accessible the products of, (a) a fast survey of the Arecibo HI sky, (b) a medium-deep survey of the Virgo cluster of galaxies, and (c) a deep extragalactic HI survey in the Zone of Avoidance, all using the Arecibo feed array system. All three surveys lend themselves to synergistic coordination with several different projects, not just the present ones, including studies of Milky Way structure and high velocity clouds, a pulsar search, and the detection of radio continuum transients.
The software tools and data products will be made available to the community, and the research work will provide fertile ground for the training of a new generation of US-based single-dish radio astronomers.
