J/A+A/681/L19ivo://CDS.VizieR/J/A+A/681/L19doi:10.26093/cds/vizier.36819019CDSBop T.C.Agundez M.Cernicharo J.Lefloch B.Lique F.2024-11-28T20:06:01Z2024-01-23T12:50:06ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.fratomic-physicsThe protonated form of hydrogen cyanide, HCNH^+^, holds significant importance in astrochemistry, serving as an intermediate species in ion-neutral reactions occurring in the cold molecular clouds. Although it plays a crucial role in the chemistry of HCN and HNC, the excitation rate coefficients of this molecular cation by the dominant interstellar colliders have not been thoroughly investigated, leading to limitations in radiative transfer models use to derive its abundance. We present here the first hyperfine-resolved excitation rate coefficients for HCNH^+^ induced by collisions with both He and H_2_ at low temperatures, addressing a crucial requirement for precise modeling of HCNH^+^ abundance in typical cold dense molecular clouds. Using non-local thermodynamic equilibrium (LTE) radiative transfer calculations, we reproduce fairly well the 1-->0 and 2-->1 observational spectra of HCNH^+^ and derive updated molecular column densities. For the TMC-1 molecular cloud, the new HCNH^+^ abundance is twice larger than suggested by previous LTE modeling, whereas the column density of this molecular cation is improved only by 10% in the case of the L483 proto-star. The factor of 2 in the case of TMC-1 most likely arises from an error in the early analysis of observational spectra rather than an effect of the LTE assumption, given that the HCNH^+^ lines are predominantly thermalized at densities higher than 2x10^4^cm^-3^. For multiline studies of clouds of moderate density, we strongly recommend to use the collisional rate coefficients reported in this work.2024A&A...681L..19Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/681/L19CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/681/L19https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/681/L19http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/681/L19https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/681/L19https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/681/L19http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/681/L19GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/A+A/681/L19/hcnhp-elRotational energy levels of HCNH+recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintLevel[1/25] Level identification numbermeta.id;meta.mainintEEnergyphys.energy;phys.atmol.leveldoubleWeithWeightstat.weight;phys.atmolfloatJ-FJ and F transition (J_F)meta.codecharJ/A+A/681/L19/hcnhp-h2HFS rates due to collision with H2recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTransTrasnsition identification numbermeta.idintUp[1/25] Upper level numbermeta.idintLow[1/25] Lower level numbermeta.idintRCT5First hyperfine resolved rate coefficient for T=5.0Kcm**-3.s**-1arith.rate;phys.atmol.collisionaldoubleRCT10First hyperfine resolved rate coefficient for T=10.0Kcm**-3.s**-1arith.rate;phys.atmol.collisionaldoubleRCT15First hyperfine resolved rate coefficient for T=15.0Kcm**-3.s**-1arith.rate;phys.atmol.collisionaldoubleRCT20First hyperfine resolved rate coefficient for T=20.0Kcm**-3.s**-1arith.rate;phys.atmol.collisionaldoubleRCT25First hyperfine resolved rate coefficient for T=25.0Kcm**-3.s**-1arith.rate;phys.atmol.collisionaldoubleRCT30First hyperfine resolved rate coefficient for T=30.0Kcm**-3.s**-1arith.rate;phys.atmol.collisionaldoubleJ/A+A/681/L19/hcnhp-heHFS rates due to collision with HerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTransTrasnsition identification numbermeta.idintUp[1/25] Upper level numbermeta.idintLow[1/25] Lower level numbermeta.idintRCT5First hyperfine resolved rate coefficient for T=5.0Kcm**-3.s**-1arith.rate;phys.atmol.collisionaldoubleRCT10First hyperfine resolved rate coefficient for T=10.0Kcm**-3.s**-1arith.rate;phys.atmol.collisionaldoubleRCT15First hyperfine resolved rate coefficient for T=15.0Kcm**-3.s**-1arith.rate;phys.atmol.collisionaldoubleRCT20First hyperfine resolved rate coefficient for T=20.0Kcm**-3.s**-1arith.rate;phys.atmol.collisionaldoubleRCT25First hyperfine resolved rate coefficient for T=25.0Kcm**-3.s**-1arith.rate;phys.atmol.collisionaldoubleRCT30First hyperfine resolved rate coefficient for T=30.0Kcm**-3.s**-1arith.rate;phys.atmol.collisionaldouble