Nobeyama CO atlas of nearby spiral galaxies

Abstract

The results of a CO(1–0) mapping survey of 40 nearby spiral galaxies performed with the Nobeyama 45-m telescope are presented. The maps of CO cover most of the optical disk of the galaxies. We investigated the influence of bar on distribution of molecular gas in spiral galaxies using these data. We confirmed that the degree of central concentration is higher in barred spirals than in non-barred spirals as shown by previous works. Furthermore, we show that bars are efficient in driving molecular gas that lies within their radial scales toward the center, while the role in the accumulation from the larger spatial scales on the disks is small. The transported gas accounts for about half of molecular gas within the central region in barred spiral galaxies. We found a correlation between the degree of central concentration and bar strength. Galaxies with stronger bars tend to have higher central concentration. The correlation implies that stronger bars accumulate molecular gas toward the center more efficiently. These results are consistent with long-lived bars.