Neutral Hydrogen in Individual Galaxies



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Neutral Hydrogen in Individual Galaxies

The new 1.4 GHz receivers already provide impressively low system temperatures, so an important part of the 1.4 GHz upgrade has already been accomplished. The new correlator and the E configuration will also allow progress in studying H I emission from normal galaxies. To allow imaging of an entire, rapidly rotating, large spiral the correlator should cover a velocity range of at least 1000 km/s to allow for good continuum subtraction. Channel sizes should be adjustable by factors of two, with a channel of approximately 2.5 km/s and 1.25 km/s available to resolve the smallest anticipated width of the H I line (currently in the range 5 to 10 km/s) in most systems. The new correlator would allow detailed studies of the ISM in galaxies out to the distance of Virgo and spiral structure studies somewhat farther. The variety of environments observable out to Virgo should exhibit a wide variety in ISM structure, including the possibility of testing proposals that H I is formed primarily from dissociation of molecular hydrogen. The E configuration will allow more sensitive searches for faint outer parts of galaxies to determine where spiral disks end, for bridges between neighbors to set limits on interaction in normal systems (e.g., the Milky Way and M31), and for extended streamers in interacting systems.



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