2017MNRAS.472.4444P -
Mon. Not. R. Astron. Soc., 472, 4444-4455 (2017/December-3)
Modelling the ArH+ emission from the Crab nebula.
PRIESTLEY F.D., BARLOW M.J. and VITI S.
Abstract (from CDS):
We have performed combined photoionization and photodissociation region (PDR) modelling of a Crab nebula filament subjected to the synchrotron radiation from the central pulsar wind nebula, and to a high flux of charged particles; a greatly enhanced cosmic-ray ionization rate over the standard interstellar value, ζ0, is required to account for the lack of detected [C I] emission in published Herschel SPIRE FTS observations of the Crab nebula. The observed line surface brightness ratios of the OH+ and ArH+ transitions seen in the SPIRE FTS frequency range can only be explained with both a high cosmic-ray ionization rate and a reduced ArH+ dissociative recombination rate compared to that used by previous authors, although consistent with experimental upper limits. We find that the ArH+/OH+ line strengths and the observed H2 vibration-rotation emission can be reproduced by model filaments with nH = 2 x 104 cm–3, ζ = 107ζ0 and visual extinctions within the range found for dusty globules in the Crab nebula, although far-infrared emission from [O I] and [C II] is higher than the observational constraints. Models with nH = 1900 cm–3 underpredict the H2 surface brightness, but agree with the ArH+ and OH+ surface brightnesses and predict [O I] and [C II] line ratios consistent with observations. These models predict HeH+ rotational emission above detection thresholds, but consideration of the formation time-scale suggests that the abundance of this molecule in the Crab nebula should be lower than the equilibrium values obtained in our analysis.
Abstract Copyright:
© 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
Journal keyword(s):
astrochemistry - ISM: individual objects: (Crab nebula) - ISM: molecules - ISM: supernova remnants - ISM: supernova remnants
Errata:
erratum vol. 488, p.5437 (2019)
Simbad objects:
1
Full paper
View the references in ADS
To bookmark this query, right click on this link: simbad:2017MNRAS.472.4444P and select 'bookmark this link' or equivalent in the popup menu