110–111 H2CO and H110α observations towards the giant HII region in cloud complex W43

The 1 10 -1 11 formaldehyde (H 2 CO) absorption line and H 110α radio recom bination line (H RRL) are observed towards the giant HII region in cloud complex W43. The observations are obtained using the Nanshan 25 m single dish operated by Urumqi Observatory, National Astronomical Observatories of China. A region about 30'×30' is observed, which covers the whole HII region in W43. Except for the central 10' region, all the other seven points are first observed with the H 2 CO 1 10 - 1 11 absorption. The column density of the H 2 CO is calculated, and the H 2 CO density contours show some differences with the infrared image. Multiple features appear in the H 2 CO and H RRL which indicate complex structure. The intensities of the H 2 CO and the velocities of the H 110α seem to present a linear correlation, which illustrates that the sphere of influence of the central WR/OB cluster may be much more extended than presently known, since the size is nearly 50 pc.

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