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Astron. Astrophys. 347, 37-46 (1999)

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5. Conclusion

We studied the inner molecular disk of the barred spiral galaxy NGC 1530 by means of millimeter interferometry. The main conclusions of this paper are:
- The 12CO(2-1) intensity map obtained with a [FORMULA] resolution is very similar to the 12CO(1-0) distribution, with a nuclear ring, and around it, two bright curved arcs.
- The 13CO(1-0) intensity map synthesized with a [FORMULA] beam is rather similar to the 12CO(1-0) map, with weaker curved arcs.
- The average ratios are [FORMULA] and [FORMULA], comparable to other spiral galaxies. [FORMULA] shows a general decrease from the central ring ([FORMULA]) to the curved arcs([FORMULA]). [FORMULA] shows no such systematic trend. The ratio is highest ([FORMULA]) in a region close to the dynamical center.
- The VLA cm maps show a ring very similar to the 12CO ring, but little or no emission in the curved arcs.
- An escape probability analysis reproduces well the line ratios in five regions of the disk. We could derive the kinetic temperature and the density of the gas, together with filling factor. The gas density seems higher in the nuclear ring than in the curved arcs, except for an isolated region in the south-western arc.
- The conversion factor deduced from this model is
[FORMULA] [FORMULA] (K [FORMULA] pc2)-1, three times lower than the standard galactic value of 4.8 [FORMULA] (K [FORMULA] pc2)-1.
- The star formation rate as calculated from the 20 cm flux and the mass of dense gas deduced from the HCN flux are spatially correlated.

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© European Southern Observatory (ESO) 1999

Online publication: June 18, 1999