The relation of H2CO, 12CO, and 13CO in molecular clouds⋆
1 Xinjiang Astronomical Observatory, Chinese Academy of Sciences, 830011 Urumqi, PR China
2 Graduate University of the Chinese Academy of Sciences, 100080 Beijing, PR China
3 Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, 830011 Urumqi, PR China
4 Physics & Astronomy Department, University of Nigeria, 410001 Nsukka, Nigeria
Received: 13 June 2012
Accepted: 15 January 2013
Aims. We seek to understand how the 4.8 GHz formaldehyde absorption line is distributed in the MON R2, S156, DR17/L906, and M17/M18 regions. More specifically, we look for the relationship among the H2CO, 12CO, and 13CO spectral lines.
Methods. The four regions of MON R2 (60′ × 90′), S156 (50′ × 70′), DR17/L906 (40′ × 60′), and M17/M18 (70′ × 80′) were observed for H2CO (beam 10′), H110α recombination (beam 10′), 6 cm continuum (beam 10′), 12CO (beam 1′), and 13CO (beam 1′). We compared the H2CO, 12CO, 13CO, and continuum distributions, and also the spectra line parameters of H2CO, 12CO, and 13CO. Column densities of H2CO, 13CO, and H2 were also estimated.
Results. We found out that the H2CO distribution is similar to the 12CO and the 13CO distributions on a large scale. The correlation between the 13CO and the H2CO distributions is better than between the 12CO and H2CO distributions. The H2CO and the 13CO tracers systematically provide consistent views of the dense regions. Their maps have similar shapes, sizes, peak positions, and molecular spectra and present similar central velocities and line widths. Such good agreement indicates that the H2CO and the 13CO arise from similar regions.
Key words: ISM: clouds / ISM: molecules / stars: formation
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© ESO, 2013