Infrared detection of gas phase formaldehyde towards the high mass protostar W33A

Abstract

We report the detection of numerous absorption lines of the ν 1 band of gaseous formaldehyde (H 2 CO) near 3.6 µm towards the high-mass protostar W33A. This is the first infrared detection of gaseous H 2 CO in an interstellar cloud. An upper limit toward RAFGL 7009S is also reported. The column density of H 2 CO detected at 3.6 µm toward W33A is much higher than that measured in large beam millimeter wave observations toward the same source, suggesting that it is concentrated close to the infrared continuum source. The mean temperature of the H 2 CO, derived from LTE spectral modelling, is ∼100 K, which is close to the values found for most other gas phase species observed in absorption and is the expected temperature of the cloud at the dust mantle sublimation interface, implying a large jump in the abundance of gaseous H 2 CO from the surrounding cold cloud to the warm gas. The ratio of gaseous and solid H 2 CO column densities is about 0.03 for W33A and less than 0.02 for RAFGL 7009S. We discuss this detection in the context of the two most likely mechanisms for H 2 CO formation: grain mantle evaporation, and gas phase reactions between species produced by photodissociation of grain mantle evaporants.

Constraining the ortho-to-para ratio of H2 with anomalous H2CO absorption

“…Complex radial motions have been observed in this source, but their amplitude is also small (<0.05 km s −1 , . As a result, we are currently unable to distinguish between gas phase and grain surface chemistry for the H 2 CO formation, which has long been enigmatic in a variety of objects (e.g., Roueff et al 2006). Future studies will address this important issue further.…”

FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45 m telescope (FUGIN): Molecular clouds toward W 33; possible evidence for a cloud–cloud collision triggering O star formation

“…The Submillimeter Array (SMA) high-resolution observations showed that W33 Main harbors multiple ultra-compact H II regions and three high density clumps (W33 Main-A, W33 Main-B1, W33 Main-B2) embedded in a dense gas envelope detected in C2H (Jiang et al 2015). W33 A has been studied based on the observations in various wavelengths (Gibb et al 2000;Roueff et al 2006;Davies et al 2010;de Wit et al 2007de Wit et al , 2010. Galván-Madrid et al (2010) detected high-velocity gas associated with an outflow in the CO J = 2-1 transition by SMA 230 GHz band observations in W33 A.…”

Uniform Supersonic Chemical Reactors: 30 Years of Astrochemical History and Future Challenges

“…[165] Following this idea, amino acids were produced in the laboratory by UV irradiation of interstellar ice analogues composed of H 2 O, CH 3 OH, NH 3 ,a nd HCN; [166] H 2 O, CH 3 OH, NH 3 ,C O, and CO 2 ; [167] and H 2 O, CH 3 OH, and NH 3 . [169] However,s ome of the chemical precursors of amino acids,s uch as glycolaldehyde (HOCH 2 CHO), [170] formamide (HC(O)NH 2 ), [171] and formaldehyde (CH 2 O) [172] have been identified in different objects of the ISM. [169]).…”

“…No other amino acid has been observed up to now. [169] However,s ome of the chemical precursors of amino acids,s uch as glycolaldehyde (HOCH 2 CHO), [170] formamide (HC(O)NH 2 ), [171] and formaldehyde (CH 2 O) [172] have been identified in different objects of the ISM.…”