ATTENZIONE! IL REPOSITORY E’ APERTO ESCLUSIVAMENTE ALL’IMMISSIONE DEI RAPPORTI TECNICI (COLLEZIONE 4.01). NON E’ POSSIBILE INSERIRE PRODOTTI IN TUTTE LE ALTRE COLLEZIONI, A CAUSA DI PROBLEMI TECNICI. THE REPOSITORY IS OPEN EXCLUSIVELY FOR THE SUBMISSION OF TECHNICAL REPORTS (COLLECTION 4.01). SUBMISSIONS TO ALL OTHER COLLECTIONS ARE TEMPORARILY UNAVAILABLE, DUE TO TECHNICAL ISSUES.
 

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

Journal
Date Issued
2021
Author(s)
Lefloch, B.
•
Busquet, G.
•
Viti, S.
•
Vastel, C.
•
Mendoza, E.
•
•
•
•
Schutzer, A.
•
Rivera-Ortiz, P. R.
•
Lépine, J. R. D.
•
Bachiller, R.
DOI
Abstract
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 IRAM 30 m 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 H12CN, HN12C, H13CN, HN13C, HC15N, H15NC, 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 ≍1 for all isotopologues. A strong D-enrichment (D/H ≍ 0.06) is measured in the pre-shock gas. There is no evidence of 15N 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) = $10^5\hbox{cm$^{-3}$}$ and shock velocity $V_\mathrm{ s}= 40\hbox{kms$^{-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.
Volume
507
Issue
1
Start page
1034
Uri
Url
Issn Identifier
0035-8711
Ads BibCode
2021MNRAS.507.1034L
Rights
open.access
File(s)
Loading...
Thumbnail Image
Name

lefloch_2021.pdf

Description
Pdf editoriale
Size

1.88 MB

Format

Adobe PDF

Checksum (MD5)

ade048cd23c53f4f55e9ca4ffb774f04