Molecular clouds in the Carina arm - Large-scale properties of molecular gas and comparison with H I

Abstract

The authors report results from the first large-scale survey in the CO (J = 1→0) line of the Vela-Carina-Centaurus region of the southern Milky Way. The observations, made with the Columbia University 1.2 m telescope at Cerro Tololo, were spaced every beamwidth (0°.125) in the range 270° ≤ l ≤ 300° and -1° ≤ b ≤ 1°, with latitude extensions to cover all Carina arm (l &gt; 280°) emission beyond |b| = 1°. The Carina arm is the dominant feature in the data. Its abrupt tangent at l ≈ 280° and characteristic loop in the (l, v)-diagram are unmistakable evidence for CO spiral structure. Comparison of the CO and H I data shows close agreement in a segment of the arm lying outside the solar circle (R<SUB>0</SUB> = 10 kpc); within R<SUB>0</SUB> the arm is more difficult to trace in H I than in CO.