===== On the Formyl Radical, HCO, in the ISM =====

HCO is frequently discussed in conjunction with PDRs (photo dissiciation regions). L. E. Snyder, J. M. Hollis, and B. L. Ulich, reported on the\\
**[[https://ui.adsabs.harvard.edu/abs/1976ApJ...208L..91S|Radio Detection of the Interstellar Formyl Radical]]**\\
//Astrophys. J.// **208**, L91–L94 (1976).\\
The NRAO 11 M dish was used to detect the strongest HFS components (//J// = 1.5 – 0.5, //F// = 2 – 1) of the 1<sub>01</sub> – 0<sub>00</sub> transition near 86.671 GHz in emission toward sources showing carbon recombination lines: W3, W51, NGC 2024C, and K3-50. Please note that the NGC 2024 position was stated more precisely in the follwing paragraph.

J. M. Hollis and E. Churchwell\\
looked at the\\
**[[https://ui.adsabs.harvard.edu/abs/1983ApJ...271..170H|Comparison of C<sup>+</sup> Distributions with new Interstellar Sources of HCO Emission]]**\\
//Astrophys. J.// **271**, 170–744 (1983).\\
The same HFS component was observed with the same instruments as above. New detections were made at a position close to Sgr B2(OH) and in DR21C.

L. E. Snyder, M. S. Schenewerk, and J. M. Hollis,\\
reported on the\\
**[[https://ui.adsabs.harvard.edu/abs/1985ApJ...298..360S|Observations of Several new Transitions of Interstellar HCO]]**\\
//Astrophys. J.// **298**, 360–368 (1985).\\
Observations of the 2<sub>02</sub> – 1<sub>01</sub> and 3<sub>03</sub> – 2<sub>01</sub> transitions were made. In addition,\\
Å Hjalmarson, M. S. Schenewerk, and L. E. Snyder,\\
reported on\\
**[[https://ui.adsabs.harvard.edu/abs/1985ApJ...298..360S|Interstellar HCO – Detection of the Missing 3 Millimeter Quartet]]**\\
//Astrophys. J.// **298**, L71–L74 (1986).

H. S. Liszt, J. Pety, M. Gerin, and R. Lucas,\\
detected with the IRAM 30 m telescope\\
**[[https://doi.org/10.1051/0004-6361/201323320|HCO, //c//-C<sub>3</sub>H and CF<sup>+</sup>: three new molecules in diffuse, translucent and “spiral-arm” clouds]]**\\
//Astron. Astrophys.// **564**, Art. No. A64 (2014).

The formyl radical is also found quite commonly toward certain types of dark clouds, as found, e.g., by\\
M. Agúndez, J. Cernicharo, and M. Guélin\\
in the report on the\\
**[[https://doi.org/10.1051/0004-6361/201526317|Discovery of Interstellar Ketenyl (HCCO), a Surprisingly Abundant Radical]]**\\
//Astron. Astrophys.// **577**, Art. No. L5 (2015).


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Contributor(s): H. S. P. Müller; 05, 2015

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