Exploring morphological correlations among H2CO, 12CO, MSX and continuum mappings |
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| Authors: | Chuan Peng Zhang Jarken Esimbek Jian Jun Zhou Gang Wu Zhi Mao Du |
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| Institution: | (1) Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi, 830011, China;(2) Graduate University of the Chinese Academy of Sciences, Beijing, 100080, China;(3) Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Urumqi, 830011, China |
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| Abstract: | There are relatively few H2CO mappings of large-area giant molecular cloud (GMCs). H2CO absorption lines are good tracers for low-temperature molecular clouds towards star formation regions. Thus, the aim of
the study was to identify H2CO distributions in ambient molecular clouds. We investigated morphologic relations among 6-cm continuum brightness temperature
(CBT) data and H2CO (111−110; Nanshan 25-m radio telescope), 12CO (1–0; 1.2-m CfA telescope) and midcourse space experiment (MSX) data, and considered the impact of background components
on foreground clouds. We report simultaneous 6-cm H2CO absorption lines and H110α radio recombination line observations and give several large-area mappings at 4.8 GHz toward W49 (50′×50′), W3 (70′×90′),
DR21/W75 (60′×90′) and NGC2024/NGC2023 (50′×100′) GMCs. By superimposing H2CO and 12CO contours onto the MSX color map, we can compare correlations. The resolution for H2CO, 12CO and MSX data was ∼10′, ∼8′ and ∼18.3″, respectively. Comparison of H2CO and 12CO contours, 8.28-μm MSX colorscale and CBT data revealed great morphological correlation in the large area, although there
are some discrepancies between 12CO and H2CO peaks in small areas. The NGC2024/NGC2023 GMC is a large area of HII regions with a high CBT, but a H2CO cloud to the north is possible against the cosmic microwave background. A statistical diagram shows that 85.21% of H2CO absorption lines are distributed in the intensity range from −1.0 to 0 Jy and the ΔV range from 1.206 to 5 km s−1. |
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