Mapping the high ionization rate of the GC starburst Sgr B2 through low HCO+ /N2H+ J=1-0 intensity ratiosMiriam G. Santa-Maria and Javier R. GoicoecheaEPJ Web of Conferences, 265 (2022) 00017DOI: https://doi.org/10.1051/epjconf/202226500017