Astronomy and Astrophysics, volume 609A, 16-16 (2018/1-1)
Kinetic temperature of massive star-forming molecular clumps measured with formaldehyde. III. The Orion molecular cloud 1.
TANG X.D., HENKEL C., MENTEN K.M., WYROWSKI F., BRINKMANN N., ZHENG X.W., GONG Y., LIN Y.X., ESIMBEK J., ZHOU J.J., YUAN Y., LI D.L. and HE Y.X.
Abstract (from CDS):
We mapped the kinetic temperature structure of the Orion molecular cloud 1 (OMC-1) with para-H2CO (JKaKc=303-202, 322-221, and 321-220) using the APEX 12 m telescope. This is compared with the temperatures derived from the ratio of the NH3 (2,2)/(1,1) inversion lines and the dust emission. Using the RADEX non-LTE model, we derive the gas kinetic temperature modeling the measured averaged line ratios of para-H2CO 322-221/303-202 and 321-220/303-202. The gas kinetic temperatures derived from the para-H2CO line ratios are warm, ranging from 30 to >200K with an average of 62±2K at a spatial density of 105cm–3. These temperatures are higher than those obtained from NH3 (2,2)/(1,1) and CH3CCH (6-5) in the OMC-1 region. The gas kinetic temperatures derived from para-H2CO agree with those obtained from warm dust components measured in the mid infrared (MIR), which indicates that the para-H2CO (3-2) ratios trace dense and warm gas. The cold dust components measured in the far infrared (FIR) are consistent with those measured with NH3 (2,2)/(1,1) and the CH3CCH (6-5) line series. With dust at MIR wavelengths and para-H2CO (3-2) on one side, and dust at FIR wavelengths, NH3 (2,2)/(1,1), and CH3CCH (6-5) on the other, dust and gas temperatures appear to be equivalent in the dense gas (n(H2)≥104cm–3) of the OMC-1 region, but provide a bimodal distribution, one more directly related to star formation than the other. The non-thermal velocity dispersions of para-H2CO are positively correlated with the gas kinetic temperatures in regions of strong non-thermal motion (Mach number ≥2.5) of the OMC-1, implying that the higher temperature traced by para-H2CO is related to turbulence on a ∼0.06pc scale. Combining the temperature measurements with para-H2CO and NH3 (2,2)/(1,1) line ratios, we find direct evidence for the dense gas along the northern part of the OMC-1 10km/s filament heated by radiation from the central Orion nebula.
© ESO, 2017
stars: formation - stars: massive - ISM: clouds - ISM: molecules - radio lines: ISM
VizieR on-line data:
<Available at CDS (J/A+A/609/A16): list.dat fits/*>
View the reference in ADS
To bookmark this query, right click on this link: simbad:2018A&A...609A..16T and select 'bookmark this link' or equivalent in the popup menu