The first detection of SiC 2 in the interstellar medium

• Published in: Astronomy and astrophysics (Berlin) Vol. 678; p. A45
• Main Authors: Massalkhi, S., Jiménez-Serra, I., Martín-Pintado, J., Rivilla, V. M., Colzi, L., Zeng, S., Martín, S., Tercero, B., de Vicente, P., Requena-Torres, M. A.
• Format: Journal Article
• Language: English
• Published: 01.10.2023
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361/202346822

We report the first detection of SiC 2 in the interstellar medium. The molecule was identified through six rotational transitions toward G +0.693-0.027, a molecular cloud located in the Galactic center. The detection is based on a line survey carried out with the GBT, the Yebes 40m, and the IRAM 30m telescopes covering a range of frequencies from 12 to 276 GHz. We fit the observed spectra assuming local thermodynamic equilibrium and derive a column density of (1.02 ± 0.04) × 10 13 cm −2 , which gives a fractional abundance of 7.5 × 10 −11 with respect to H 2 , and an excitation temperature of 5.9 ± 0.2 K. We conclude that SiC 2 can be formed in the shocked gas by a reaction between the sputtered atomic silicon and C 2 H 2 , or it can be released directly from the dust grains due to disruption. We also search for other Si-bearing molecules and detect eight rotational transitions of SiS and four transitions of Si 18 O. The derived fractional abundances are 3.9 × 10 −10 and 2.1 × 10 −11 , respectively. All Si-bearing species toward G+0.693−0.027 show fractional abundances well below what is typically found in late-type evolved stars.