| #2 – BREAKTHROUGHS in CARBON CHEMISTRY in COLD DARK CLOUDS (TMC-1) |
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| Theoretical goals Identification of novel molecules and study of the chemical routes in the production of complex molecules, in particular, polycyclic aromatic hydrocarbons (PAHs) and their derivatives. |
| Experimental goals Improvement of the sensitivity of previous / state-of-the-art line surveys by a factor of 40 (0.5 mK at 5 sigma detection) |
| Innovative observing methodology The Nanocosmos new mm broad band receivers and backends, installed at the Yebes 40m radio telescope, allow an instantaneous band coverage of the Q band (31 – 50 GHz) with a spectral resolution of 38 KHz. Thus they provide a huge sensitivity leading the new generation of line surveys at the millikelvin level of sensitivity. |
| Results First unambiguous detection of a pure PAH in space (indene, c-C9H8) together with two other organic compounds, the ethynyl cyclopropenylidene (c-C3HCCH), and cyclopentadiene (c-C5H6). |
| Conclusions The derived abundance of ethynyl cyclopropenylidene (c-C3HCCH) can be accounted for through the reaction between CCH and c-C3H2, given that both reactants are quite abundant in TMC-1. However, the high derived abundances of cyclopentadiene and indene need to be explained through non-obvious chemical formation routes to elucidate which plausible bottom-up mechanisms of the formation of such complex aromatic hydrocarbons can be at work in cold dense clouds. |
| Breakthroughs 1) Our ultra high sensitivity line survey observations of cold molecular clouds (TMC-1) has proved a valuable tool to discover many new molecular species. In particular, QUIJOTE (Q-band Ultrasensitive Inspection Journey to the Obscure TMC-1 Environment) has reported 25 detections until May 2021. 2) First robust detection of a PAH in space (indene). Theoretical plausible scenario: PAHs in the interstellar medium could be formed in situ and from less complex molecules. They may not be dragged from other environments (e.g. on the surface of dust grains in circumstellar envelopes), but could be formed according to what is called a bottom-up formation mechanism from smaller molecules. |
| Outstanding publications – Pure hydrocarbon cycles in TMC-1: Discovery of ethynyl cyclopropenylidene, cyclopentadiene, and indene (J. Cernicharo et al., Astronomy & Astrophysics 649, L15, 2021). DOI link. – A new golden age era for Astrochemistry: Discovering PAHs with millikelvin sensitive radio astronomical molecular line surveys (J. Cernicharo, on behalf of the Nanocosmos ERC team, AstroPAH: A Newsletter on Astronomical PAHs, Leiden University, the Netherlands, issue 78, May 21, 2021). Other oustanding NANOCOSMOS related publications: – Learning mid-IR emission spectra of polycyclic aromatic hydrocarbon populations from observations (S. Foschino, O. Berné and C. Joblin, Astronomy & Astrophysics 632, 2019). DOI link. – Detection of buckminsterfullerene emission in the diffuse interstellar medium (O. Berné, N. L. J. Cox, G. Mulas and C. Joblin, Astronomy & Astrophysics 605, L1, 2017). DOI link. – PAH and H2 emission in the Ring Nebula (N. L. J. Cox, P. Pilleri, O. Berné, J. Cernicharo and C. Joblin, Journal of Physics: Conference Series, Volume 728, Issue 3, 2016). Link. |
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