Determine the abundance of PO relative to PO⁺ in SNR shocks

Determine whether PO is present in the W44 and IC443 shock regions and establish the relative abundances of PO and PO⁺ to distinguish chemical redistribution of phosphorus-bearing species from an overall enhancement of gas-phase phosphorus.

Background

The observations covered PO⁺ and PN but did not include suitable PO transition lines. Consequently, the measured PO⁺ abundance cannot by itself reveal whether PO⁺ is produced by ionisation of pre-existing PO or whether the shock has increased the total gas-phase phosphorus inventory.

Observations of PO and PO⁺ at higher sensitivity and angular resolution would provide the abundance ratios needed to test the proposed ion-molecule chemistry in the highly ionised environments of W44 and IC443.

References

Since PO is not covered in our frequency bandwidth, additional observations are needed to establish the relative abundance between PO and PO$+$ and whether the obtained PO$+$ abundances are due to a chemical re-distribution of P-bearing species or an enhancement of Phosphorous in the gas-phase.

— Chemical complexity in feedback from supernova remnants: first detection of PO+ in IC443 and W44  (2610.01211 - Cosentino et al., 1 Oct 2026) in Section 4, Discussion