Show pageOld revisionsBacklinksBack to top This page is read only. You can view the source, but not change it. Ask your administrator if you think this is wrong. ===== SiO in Space ===== Silicon monoxide, SiO, is very widespread in space. It is generally viewed as an indicator of shocks. It was among the first molecules detected in space by means of radio astronomy.\\ R. W. Wilson, A. A. Penzias, K. B. Jefferts, M. Kutner, and P. Thaddeus\\ reported on the\\ **[[https://ui.adsabs.harvard.edu/abs/1971ApJ...167L..97W|Discovery of Interstellar Silicon Monoxide]]**\\ //Astrophys. J.// **167**, L97–L100 (1971).\\ The //J// = 3 – 2 transition of SiO near 130.2 GHz was detected in emission with the 11 m Kitt Peak telescope toward Sgr B2(OH).\\ D. F. Dickinson\\ reported on the\\ **[[https://ui.adsabs.harvard.edu/abs/1972ApJ...175L..43D|Detection of Silicon Monoxide at 87 GHz]]**\\ //Astrophys. J.// **175**, L43–L100 (1972).\\ The 11 m Kitt Peak telescope was used to detect the line toward Sgr B2(OH) and Orion A.\\ \\ P. Schilke, G. Pineau des Forêts, C. M. Walmsley, and J. Martín-Pintado\\ performed\\ **[[https://doi.org/10.1051/0004-6361:20010470|Observations of SiO towards Photon Dominated Regions]]**\\ //Astron. Astrophys.// **372**, 291–301 (2001).\\ The IRAM 30 m telecope was used to detect several SiO transitions toward the Orion Bar and S 140.\\ \\ S. Yamamoto, H. Mikami, S. Saito, N. Kaifu, M. Ohishi, and K. Kawaguchi\\ detected\\ **[[https://ui.adsabs.harvard.edu/abs/1992PASJ...44..459Y|SiO in Barnard 1]]**\\ //Publs. Astron. Soc. Japan// **167**, L97–L100 (1971),\\ a low-mass star-forming region.\\ \\ The molecule is conspicuously absent in cold, quiescent molecular clouds, as reported by\\ L. M. Ziurys, P. Friberg, and W. M. Irvine,\\ **[[https://ui.adsabs.harvard.edu/abs/1989ApJ...343..201Z|Interstellar SiO as a Tracer of High-temperature Chemistry]]**\\ //Astrophys. J.// **343**, 201–207 (1989).\\ The absence of SiO was reported for TMC-1, L134N (aka L183) and for B335 (aka L663). Hence,\\ J. Martin-Pintado, R. Bachiller, and A. Fuente\\ view\\ **[[https://ui.adsabs.harvard.edu/abs/1992A%26A...254..315M|SiO Emission as a Tracer of Shocked Gas in Molecular Outflows]]**\\ //Astron. Astrophys.// **254**, 315–326 (1992).\\ \\ L. E. Snyder and D. Buhl\\ proposed the\\ **[[https://doi.org/10.1093/10.1086/181457|Detection of Possible Maser Emission Near 3.48 Millimeters from an Unidentified Molecular Species in Orion]]**\\ //Astrophys. J.// **189**, L31–L33 (1974).\\ Orion A was observed with the 11 m Kitt Peak telescope. The frequency coincidence with the //J// = 2 – 1 transition of SiO in its first excited vibrational state was noted.\\ Confirmation came from\\ J. H. Davis, G. N. Blair, H. van Till, and P. Thaddeus,\\ who studied\\ **[[https://doi.org/10.1093/10.1086/181520|Vibrationally Excited Silicon Monoxide in the Orion Nebula]]**\\ //Astrophys. J.// **190**, L117–L119 (1974).\\ They observed the //J// = 3 – 2 transition of SiO.\\ \\ D. Buhl, L. E. Snyder, F. J. Lovas, and D. R. Johnson\\ reported subsequently on\\ **[[https://ui.adsabs.harvard.edu/abs/1974ApJ...192L..97B|Silicon Monoxide: Detection of Maser Emission from the Second Vibrationally Excited State]]**\\ //Astrophys. J.// **192**, L97–L100 (1974).\\ Half of the authors are laboratory spectroscopists, thus highlighting the crucial importance for radio astronomical observations.\\ \\ T. Kaminski, C. A. Gottlieb, K. H. Young, K. M. Menten, and N. A. Patel\\ performed\\ **[[https://doi.org/10.1088/0067-0049/209/2/38|An Interferometric Spectral Line and Imaging Survey of VY Canis Majoris in the 345 GHz Band]]**\\ //Astrophys. J. Suppl. Ser.// **209**, Art. No. 38 (2013),\\ and detected a //v// = 5 SiO maser.\\ \\ B. Pimpanuwat, S. Etoka, M. D. Gray, A. M. S. Richards, A. Baudry, F. Herpin, T. Danilovich, L. Decin, M. O. Lewis, I. El Mellah, C. A. Gottlieb, Y. Mori, H. S. P. Müller, R. Sahai, K. T. Wong, J. A. Yates, and A. Zijlstra\\ published on\\ **[[https://doi.org/10.1093/mnras/stag888|ATOMIUM: Inner Circumstellar Envelopes of Oxygen-Rich AGB Stars as Revealed by Highly Excited SiO Lines]]**\\ //Mon. Not. R. Astron. Soc.// **549**, Art. No. stag888 (2026).\\ SiO //v// = 8 //J// = 6 − 5 was detected possibly (meaning 3.0 ≲ S/N ≲ 5.0) in emission toward R Hya and in absorption toward S Pav and R Aql.\\ \\ ---- Employing the NRAO 11 m dish,\\ F.J. Lovas, D.R. Johnson, D. Buhl, and L.E. Snyder\\ identified\\ **[[https://doi.org/10.1086/154774|Millimeter emission lines in Orion A]]**\\ //Astrophys. J.// **209**, 770–777 (1976).\\ Among them was the //J// = 2 − 1 transition of <sup>29</sup>SiO. The <sup>28</sup>Si/<sup>29</sup>Si ratio is 17.5 ± 5, consistent with the terrestrial ratio of 19.6.\\ \\ F.O. Clark and F.J. Lovas\\ detected similarly\\ **[[https://doi.org/10.1086/182536|<sup>30</sup>SiO in the interstellar medium]]**\\ //Astrophys. J.// **217**, L47–L48 (1977).\\ The isotopolog was detected toward Orion A and Sgr B2. The <sup>28</sup>Si/<sup>30</sup>Si ratio is 32 ± 8, concordant with the terrestrial ratio of 29.8. The line of the SiO main species displayed a double peak, suggestive of opacity or foreground absorption, preventing an isotopic ratio to be determined.\\ \\ E. Gonzalez-Alfonso, J. Alcolea, and J. Cernicharo\\ reported on the\\ **[[https://ui.adsabs.harvard.edu/abs/1996A%26A...313L..13G|Detection of <sup>29</sup>SiO //v// = 3 //J// = 8 → 7 Maser Emission: a new IR SiO Overlap]]**\\ //Astron. Astrophys.// **313**, L13–L16 (1996).\\ \\ S.-H. Cho, H.-G. Kim, Y.-S. Park, C.-H. Choi, and N. Ukita\\ reported on the\\ **[[https://doi.org/10.1086/426585|First Detection of <sup>28</sup>Si<sup>18</sup>O Maser and Thermal Emission from Orion KL]]**\\ //Astrophys. J.// **622**, 390–392 (2005).\\ \\ L. Decin, J. Cernicharo, M. J. Barlow, et al.\\ investigated\\ **[[https://doi.org/10.1051/0004-6361/201014562|Silicon in the Dust Formation Zone of IRC +10216]]**\\ //Astron. Astrophys.// **518**, Art. No. L143 (2010).\\ Using the PACS low-resolution spectrometer on board of the //Herschel// satellite, they identified unblended SiO rotational transitions beyond 3 THz.\\ \\ The observation of <sup>28</sup>Si<sup>17</sup>O was reported by\\ L. Velilla Prieto, C. Sánchez Contreras, J. Cernicharo, M. Agúndez, G. Quintana-Lacaci, V. Bujarrabal, J. Alcolea, C. Balança, F. Herpin, K. M. Menten, and F. Wyrowski\\ in the course of\\ **[[https://doi.org/10.1051/0004-6361/201628776|The Millimeter IRAM-30m Line Survey toward IK Tauri]]**\\ //Astron. Astrophys.// **597**, Art. No. A25 (2017).\\ \\ L. Decin, A. M. S. Richards, T. Danilovich, W. Homan, and J. A. Nuth\\ reported on an\\ **[[https://doi.org/10.1051/0004-6361/201732216|ALMA Spectral Line and Imaging Survey of a Low and a High Mass-loss Rate AGB Star between 335 and 362 GHz]]**\\ //Astron. Astrophys.// **615**, Art. No. A28 (2018).\\ The low mass-loss star was R Dor, the high mass-loss star was IK Tau. The very sensitive data permitted detection of <sup>29</sup>Si<sup>18</sup>O and <sup>30</sup>Si<sup>18</sup>O.\\ \\ B. Pimpanuwat et al. (see above)\\ also report detections of <sup>30</sup>SiO //v// = 4 and 5 //J// = 6 − 5 toward R Hya and one or possibly toward three further sources, as well as possibly <sup>29</sup>SiO //v// = 6 //J// = 6 − 5 toward R Hya.\\ **[[https://doi.org/10.1093/mnras/stag888|ATOMIUM: Inner Circumstellar Envelopes of Oxygen-Rich AGB Stars as Revealed by Highly Excited SiO Lines]]**\\ //Mon. Not. R. Astron. Soc.// **549**, Art. No. stag888 (2026).\\ \\ ---- Contributor(s): H. S. P. Müller; 12, 2014; 10, 2018; 07, 2026 ---- molecules/ism/sio.txt Last modified: 2026/08/25 10:17by mueller