2024/03/20 by Tian-Yu Tu, Yang Chen, Tu, Tian-Yu +5
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Astrophysics of Galaxies (astro-ph.GA) #Dark Matter and Cosmic Phenomena #FOS: Physical sciences #Gamma-ray bursts and supernovae #High Energy Astrophysical Phenomena (astro-ph.HE)
paper · pdf · doi:10.48550/arxiv.2403.13305
openalex publication_date 2024/03/20 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Supernova remnants (SNRs) exert strong influence on the physics and chemistry of the nearby molecular clouds (MCs) through shock waves and the cosmic rays (CRs) they accelerate. To investigate the SNR-cloud interaction in the prototype interacting SNR W28 (G6.4-0.1), we present new observations of \rm HCO+, HCN and HNC J=1--0 lines, supplemented by archival data of CO isotopes, \rm N2H+ and \rm H13CO+. We compare the spatial distribution and spectral line profiles of different molecular species. Using local thermodynatic equilibrium (LTE) assumption, we obtain an abundance ratio N(\rm HCO+)/N(\rm CO)∼10-4 in the northeastern shocked cloud, which is higher by an order of magnitude than the values in unshocked clouds. This can be accounted for by the chemistry jointly induced by shock and CRs, with the physical parameters previously obtained from observations: preshock density n\rm H∼ 2× 105\rm cm-3, CR ionization rate ζ=2.5× 10-15 \rm s-1 and shock velocity V\rm s=15--20\rm km s-1. Towards a point outside the northeastern boundary of W28 with known high CR ionization rate, we estimate the abundance ratio N(\rm HCO+)/N(\rm N2H+) ≈ 0.6--3.3, which can be reproduced by a chemical simulation if a high density n\rm H∼ 2× 105 \rm cm-3 is adopted.