title: Probing non polar interstellar molecules through their protonated form: Detection of protonated cyanogen (NCCNH+).
abstract: Cyanogen (NCCN) is the simplest member of the series of dicyanopolyynes. It has been hypothesized that this family of molecules can be important constituents of interstellar and circumstellar media, although the lack of a permanent electric dipole moment prevents its detection through radioastronomical techniques. Here we present the first solid evidence of the presence of cyanogen in interstellar clouds through the detection of its protonated form toward the cold dark clouds TMC-1 and L483. Protonated cyanogen (NCCNH+) has been identified through theJ= 5 - 4 andJ= 10 - 9 rotational transitions using the 40m radiotelescope of Yebes and the IRAM 30m telescope. We derive beam averaged column densities for NCCNH+of (8.6 ± 4.4) × 1010cm-2in TMC-1 and (3.9 ± 1.8) × 1010cm-2in L483, which translate to fairly low fractional abundances relative to H2, in the range (1-10) × 10-12. The chemistry of protonated molecules in dark clouds is discussed, and it is found that, in general terms, the abundance ratio between the protonated and non protonated forms of a molecule increases with increasing proton affinity. Our chemical model predicts an abundance ratio NCCNH+/NCCN of ~ 10-4, which implies that the abundance of cyanogen in dark clouds could be as high as (1-10) × 10-8relative to H2, i.e., comparable to that of other abundant nitriles such as HCN, HNC, and HC3N.
authors.affiliation: Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Agúndez
authors.affiliation: Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Cernicharo
authors.affiliation: Centro Nacional de Tecnologías Radioastronómicas y Aplicaciones Geoespaciales(CNTRAG), Observatorio de Yebes (IGN), Spain.
authors.forename: P
authors.initials: P
authors.lastname: de Vicente
authors.affiliation: INAF, Istituto di Radioastronomia, via P. Gobetti 101, 40129 Bologna, Italy.
authors.forename: N
authors.initials: N
authors.lastname: Marcelino
authors.affiliation: LERMA, Observatoire de Paris, PSL Research University, CNRS, UMR8112, Place Janssen, 92190 Meudon Cedex, France.
authors.forename: E
authors.initials: E
authors.lastname: Roueff
authors.affiliation: Observatorio Astronómico Nacional (OAN), Calle Alfonso XII, No 3, 28014 Madrid, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Fuente
authors.affiliation: LERMA, Observatoire de Paris, École Normale Supérieure, PSL Research University, CNRS, UMR8112, F-75014, Paris, France.
authors.forename: M
authors.initials: M
authors.lastname: Gerin
authors.affiliation: Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 St. Martin d'Héres, France.
authors.forename: M
authors.initials: M
authors.lastname: Guélin
authors.affiliation: Centro Nacional de Tecnologías Radioastronómicas y Aplicaciones Geoespaciales(CNTRAG), Observatorio de Yebes (IGN), Spain.
authors.forename: C
authors.initials: C
authors.lastname: Albo
authors.affiliation: Centro Nacional de Tecnologías Radioastronómicas y Aplicaciones Geoespaciales(CNTRAG), Observatorio de Yebes (IGN), Spain.
authors.forename: A
authors.initials: A
authors.lastname: Barcia
authors.affiliation: Centro Nacional de Tecnologías Radioastronómicas y Aplicaciones Geoespaciales(CNTRAG), Observatorio de Yebes (IGN), Spain.
authors.forename: L
authors.initials: L
authors.lastname: Barbas
authors.affiliation: Centro Nacional de Tecnologías Radioastronómicas y Aplicaciones Geoespaciales(CNTRAG), Observatorio de Yebes (IGN), Spain.
authors.forename: R
authors.initials: R
authors.lastname: Bolaño
authors.affiliation: Centro Nacional de Tecnologías Radioastronómicas y Aplicaciones Geoespaciales(CNTRAG), Observatorio de Yebes (IGN), Spain.
authors.forename: F
authors.initials: F
authors.lastname: Colomer
authors.affiliation: Centro Nacional de Tecnologías Radioastronómicas y Aplicaciones Geoespaciales(CNTRAG), Observatorio de Yebes (IGN), Spain.
authors.forename: M C
authors.initials: MC
authors.lastname: Diez
authors.affiliation: Centro Nacional de Tecnologías Radioastronómicas y Aplicaciones Geoespaciales(CNTRAG), Observatorio de Yebes (IGN), Spain.
authors.forename: J D
authors.initials: JD
authors.lastname: Gallego
authors.affiliation: Centro Nacional de Tecnologías Radioastronómicas y Aplicaciones Geoespaciales(CNTRAG), Observatorio de Yebes (IGN), Spain.
authors.forename: J
authors.initials: J
authors.lastname: Gómez-González
authors.affiliation: Centro Nacional de Tecnologías Radioastronómicas y Aplicaciones Geoespaciales(CNTRAG), Observatorio de Yebes (IGN), Spain.
authors.forename: I
authors.initials: I
authors.lastname: López-Fernández
authors.affiliation: Centro Nacional de Tecnologías Radioastronómicas y Aplicaciones Geoespaciales(CNTRAG), Observatorio de Yebes (IGN), Spain.
authors.forename: J A
authors.initials: JA
authors.lastname: López-Fernández
authors.affiliation: Centro Nacional de Tecnologías Radioastronómicas y Aplicaciones Geoespaciales(CNTRAG), Observatorio de Yebes (IGN), Spain.
authors.forename: J A
authors.initials: JA
authors.lastname: López-Pérez
authors.affiliation: Centro Nacional de Tecnologías Radioastronómicas y Aplicaciones Geoespaciales(CNTRAG), Observatorio de Yebes (IGN), Spain.
authors.forename: I
authors.initials: I
authors.lastname: Malo
authors.affiliation: Centro Nacional de Tecnologías Radioastronómicas y Aplicaciones Geoespaciales(CNTRAG), Observatorio de Yebes (IGN), Spain.
authors.forename: J M
authors.initials: JM
authors.lastname: Serna
authors.affiliation: Centro Nacional de Tecnologías Radioastronómicas y Aplicaciones Geoespaciales(CNTRAG), Observatorio de Yebes (IGN), Spain.
authors.forename: F
authors.initials: F
authors.lastname: Tercero
keywords: ISM: clouds; ISM: molecules; astrochemistry; line: identification; radio lines: ISM