Publication Abstracts

Grabelsky et al. 1987

Grabelsky, D.A., R.S. Cohen, L. Bronfman, P. Thaddeus, and J. May, 1987: Molecular clouds in the Carina Arm: Large-scale properties of molecular gas and comparison with H I. Astrophys. J., 315, 122-141, doi:10.1086/165118.

We 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 millimeterwave telescope at Cerro Tololo, were spaced every beamwidth (0.125°) in the range 270° ≤ l ≤ 300° and -l° < b < l°, with latitude extensions to cover all Carina arm (1 > 280°) emission beyond |b| = l°. In a concurrent survey made with the same telescope, every half-degree in latitude and longitude was sampled in the range 270° ≤ l ≤ 300° and -5° ≤ b ≤ 5° at a spatial resolution of 0.5°. Both surveys had a spectral coverage of 333 km/s with a resolution of 1.3 km/s.

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. When the emission is integrated over velocity and latitude, the height of the step seen in the tangent direction indicates that the arm-interarm contrast is at least 13:l. Spatial maps of the arm exhibit a projected narrowing in latitude of the CO layer with increasing kinematic distance, lending support to the kinematically implied picture of the arm. Comparison of the CO and H I data shows close agreement in a segment of the arm lying outside the solar circle (R0 = 10 kpc); within R0 the arm is more difficult to trace in H I than in CO.

The distribution of the molecular layer about the Galactic plane in the outer Galaxy is determined on the basis of the assumption of axial symmetry with respect to the Galactic center. Between R = 10.5 and 12.5 kpc, the average CO midplane dips from z = -48 to - 167 pc below the b = 0° plane, following a well-known similar warping of the H I layer. In the same range of radii, the half-thickness of the CO layer increases from 112 to 182 pc, mimicking the long-recognized flaring of the H I layer in the outer Galaxy.

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BibTeX Citation

@article{gr07800y,
  author={Grabelsky, D. A. and Cohen, R. S. and Bronfman, L. and Thaddeus, P. and May, J.},
  title={Molecular clouds in the Carina Arm: Large-scale properties of molecular gas and comparison with H I},
  year={1987},
  journal={Astrophys. J.},
  volume={315},
  pages={122--141},
  doi={10.1086/165118},
}

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RIS Citation

TY  - JOUR
ID  - gr07800y
AU  - Grabelsky, D. A.
AU  - Cohen, R. S.
AU  - Bronfman, L.
AU  - Thaddeus, P.
AU  - May, J.
PY  - 1987
TI  - Molecular clouds in the Carina Arm: Large-scale properties of molecular gas and comparison with H I
JA  - Astrophys. J.
VL  - 315
SP  - 122
EP  - 141
DO  - 10.1086/165118
ER  -

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