HCN/HNC chemistry in shocks: a study of L1157-B1 with ASAI

Autor(es):Mostrar menos -

Lefloch, B. ^[1] ; Busquet, G. ^{[1, 2, 3]} ; Viti, S. ^{[4, 5]} ; Vastel, C. ^[6] ; Mendoza, E. ^[7] ; Benedettini, M. ^[8] ; Codella, C. ^{[1, 9]} ; Podio, L. ^[9] ; Schutzer, A. ^[1] ; Rivera-Ortiz, P. R. ^[1] ; Lepine, J. R. D. ^[7] ; Bachiller, R. ^[10]

Afiliação do(s) autor(es)

^[1] Univ Grenoble Alpes, IPAG, CNRS, F-38000 Grenoble - France

^[2] CSIC, Inst Ciencies Espai ICE, Can Magrans S-N, E-08193 Cerdanyola Del Valles, Catalonia - Spain

^[3] Inst Estudis Espacials Catalunya IEEC, E-08034 Barcelona, Catalonia - Spain

^[4] UCL, Dept Phys & Astron, Gower St, London WC1E 6BT - England

^[5] Leiden Univ, Leiden Observ, POB 9513, NL-2300 RA Leiden - Netherlands

^[6] Univ Toulouse, CNES, UPS, CNRS, IRAP, F-31400 Toulouse - France

^[7] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, BR-05508090 Sao Paulo, SP - Brazil

^[8] Ist Astrofis & Planetol Spaziali, INAF, Via Fosso del Cavaliere 100, I-00133 Rome - Italy

^[9] Osserv Astrofis Arcetri, INAF, Largo Enrico Fermi 5, I-50125 Florence - Italy

^[10] Observatorio Astron Nacl, IGN, Calle Alfonso XII, 3, E-28004 Madrid - Spain

• Tipo de documento: Artigo Científico
• Fonte: Monthly Notices of the Royal Astronomical Society; v. 507, n. 1, p. 1034-1046, OCT 2021.
• Citações Web of Science: 0

Resumo

Hydrogen cyanide (HCN) and its isomer hydrogen isocyanide (HNC) play an important role in molecular cloud chemistry and the formation of more complex molecules. We investigate here the impact of protostellar shocks on the HCN and HNC abundances from high-sensitivity LRAM 30m observations of the prototypical shock region L1157-B1 and the envelope of the associated Class 0 protostar, as a proxy for the pre-shock gas. The isotopologues (HCN)-C-12, (HNC)-C-12, (HCN)-C-13, (HNC)-C-13, (HCN)-N-15, (HNC)-N-15, DCN, and DNC were all detected towards both regions. Abundances and excitation conditions were obtained from radiative transfer analysis of molecular line emission under the assumption of local thermodynamical equilibrium. In the pre-shock gas, the abundances of the HCN and HNC isotopologues are similar to those encountered in dark clouds, with an HCN/HNC abundance ratio approximate to 1 for all isotopologues. A strong D-enrichment (D/H approximate to 0.06) is measured in the pre-shock gas. There is no evidence of N-15 fractionation neither in the quiescent nor in the shocked gas. At the passage of the shock, the HCN and HNC abundances increase in the gas phase in different manners so that the HCN/HNC relative abundance ratio increases by a factor 20. The gas-grain chemical and shock model UCLCHEM allows us to reproduce the observed trends for a C-type shock with pre-shock density n(H) = 10(5) cm(-3) and shock velocity V-s = 40 km s(-1). We conclude that the HCN/HNC variations across the shock are mainly caused by the sputtering of the grain mantle material in relation with the history of the grain ices. (AU)

• Processo FAPESP: 14/22095-6 - ACHEMOS: astroquímica da nossa origem, um estudo abrangente da química prebiótica em regiões pré-estelares
• Beneficiário: Edgar Fabián Mendoza Rodríguez
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 15/22254-0 - Preparação para o LLAMA: astroquímica de regiões de formação estelar I. sobre a origem de cadeias carbônicas e deuteração em protoestrelas
• Beneficiário: Edgar Fabián Mendoza Rodríguez
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Pós-Doutorado