The Integrated Neutral Hydrogen Properties of Nearby Galaxies

Abstract
The H I emission from 17 nearby spiral and irregular galaxies has been studied with the MK II radio telescope (beamwidth 31′ × 33′) to provide integrated H I flux densities to an accuracy of 10 per cent or better. Observations were made at a grid of points extending to the limits of each galaxy. These were used to derive the integrated spectrum, the extent and position angle of the line of isovelocity centroids and the systemic velocity for each galaxy. An indicative total mass, MT, was estimated directly from the H I observations which agreed well with the value derived by other observers from rotation curves. This provides a simple H I technique for measuring MT for any spiral or irregular galaxy. These new results gave value of MH/L, MH/MT and MT/L which showed less scatter within each morphological type as compared with previous investigations.

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