Search for corannulene (C20H10) in the Red Rectangle

Abstract

Polycyclic Aromatic Hydrocarbons (PAHs) are widely accepted as the carriers of the Aromatic Infrared Bands (AIBs), but an unambiguous identification of any specific interstellar PAH is still missing. For polar PAHs, pure rotational transitions can be used as fingerprints for identification. Combining dedicated experiments, detailed simulations and observations, we explored the mm domain to search for specific rotational transitions of corannulene (C20H10). We performed high-resolution spectroscopic measurements and a simulation of the emission spectrum of UV-excited C20H10 in the environment of the Red Rectangle, calculating its synthetic rotational spectrum. Based on these results, we conducted a first observational campaign at the IRAM 30m telescope towards this source to search for several high-J rotational transitions of (C20H10). The laboratory detection of the J = 112 <- 111 transition of corannulene showed that no centrifugal splitting is present up to this line. Observations with the IRAM 30m telescope towards the Red Rectangle do not show any corannulene emission at any of the observed frequencies, down to a rms noise level of Tmb = 8 mK for the J =135 -> 134 transition at 137.615 GHz. Comparing the noise level with the synthetic spectrum, we are able to estimate an upper limit to the fraction of carbon locked in corannulene of about 1.0x10(-5) relative to the total abundance of carbon in PAHs. The sensitivity achieved shows that radio spectroscopy can be a powerful tool to search for polar PAHs. We compare this upper limit with models for the PAH size distribution, emphasising that small PAHs are much less abundant than predicted. We show that this cannot be explained by destruction but is more likely related to the chemistry of their formation in the environment of the Red Rectangle.

8 pages, 7 figures, 2 tables, accepted for publication in MNRAS

References in corpus (6)

• On-line database of the spectral properties of polycyclic aromatic hydrocarbons
• The role of the charge state of PAHs in ultraviolet extinction
• A general model for the identification of specific PAHs in the far-IR
• Carriers of the mid-IR emission bands in PNe reanalysed. Evidence of a link between circumstellar and interstellar aromatic dust
• Diagnostics for specific PAHs in the far-IR: searching neutral naphthalene and anthracene in the Red Rectangle
• The optical spectrum of a large isolated polycyclic aromatic hydrocarbon: hexa-peri-hexabenzocoronene, C42H18

Cited by in corpus (19)

• Detection of the Aromatic Molecule Benzonitrile ($c$-C${}_6$H${}_5$CN) in the Interstellar Medium
• Evolution of PAHs in photodissociation regions: Hydrogenation and charge states
• Top-down formation of fullerenes in the interstellar medium
• Spinning dust emission: the effect of rotation around a non-principal axis
• Aromatics and Cyclic Molecules in Molecular Clouds: A New Dimension of Interstellar Organic Chemistry
• Can neutral and ionized PAHs be carriers of the UV extinction bump and the diffuse interstellar bands?
• H2 formation on PAHs in photodissociation regions: a high-temperature pathway to molecular hydrogen
• Laboratory photo-chemistry of covalently bonded fluorene clusters: observation of an interesting PAH bowl-forming mechanism
• Excitation of the aromatic infrared emission bands: Chemical energy in hydrogenated amorphous carbon particles?
• Random mixtures of polycyclic aromatic hydrocarbon spectra match interstellar infrared emission
• Positron Annihilation on Polycyclic Aromatic Hydrocarbon molecules in the Interstellar Medium
• The 217.5 nm band, infrared absorption and infrared emission features in hydrogenated amorphous carbon nanoparticles
• Rotational spectroscopy of interstellar PAHs
• Rotational spectra of interstellar N- and CN-PAHs: pyrene and coronene
• Intermediate-size fullerenes as degradation products of interstellar PAHs
• Search for PAHs in the Perseus molecular cloud with the Green Bank Telescope
• DFT study of five-membered ring PAHs
• Photofragmentation of Corannulene (C20H10) and Sumanene (C21H12) cations in gas phase and its Astrophysical implications
• Searching for Corannulene with ALMA: Observations of the Red Rectangle Nebula