NEUTRAL HYDROGEN IN GALACTIC-CENTER REGION .1. OBSERVATIONS

A survey of the 21-cm line of neutral hydrogen has been made at Jodrell Bank with the Mark II radio telescope (beamwidth 31′×35′) and the Mark IA radio telescope (beamwidth 13′×13′), covering the region 355°≤ l ≤10°-5° ≤ b ≤5°, and the velocity range - 530 km s-1 to + 530 km s-1. The velocity resolution was 7·3 km s-1, and the rms noise level typically 0·1 K. The data are presented in the form of contour maps of antenna temperature as a function of galactic latitude and velocity, and also as a function of galactic longitude and velocity. Six new high-velocity emission features have been detected, all lying out of the galactic plane. The present paper describes in detail all the high-velocity features seen in the survey. An interpretation of the features will appear separately in Paper II of the series. © 1975 Royal Astronomical Society.