We report the first detection of SiC2 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)×1013 cm−2, which gives a
fractional abundance of 7.5×10−11 with respect to H2, and an
excitation temperature of 5.9±0.2 K. We conclude that SiC2 can be formed
in the shocked gas by a reaction between the sputtered atomic silicon and
C2H2, 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 Si18O. 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.Comment: 8 pages, 5 figure
