New calibrations for estimating the N/O ratio in H II regions Florido Navio, Estrella Zurita Muñoz, Almudena Pérez Montero, Enrique ISM: abundances (ISM:) H II regions Galaxies: abundances Galaxies: ISM Galaxies: spiral We thank the anonymous referee for his/her constructive report that improved the clarity of the manuscript. This work is supported by the Spanish 'Ministerio de Ciencia e Innovacion' and from the European Regional Development Fund (FEDER) via grants PID2020114414GB-I00 and PID2020-113689GB-I00, and from the 'Junta de Andalucia' (Spain) local government through the FQM108 and AFQM-510-UGR20 projects. EPM acknowledges financial support from the State Agency for Research of the Spanish 'Ministerio de Ciencia, Innovacon y Universidades' through the 'Center of Excellence Severo Ochoa' award to the Instituto de Astrofisica de Andalucia (SEV-2017-0709) and to projects 'Estallidos7' PID2019107408GB-C44 (Spanish 'Ministerio de Ciencia e Innovacion'), and from the 'Junta de Andalucia' Excellence project EXC/2011 FQM7058, and also the assistance from his guide dog Rocko without whose daily help this work would have been much more difficult. We use a sample of 536 H II regions located in nearby spirals, with a homogeneous determination of their T e -based abundances, to obtain new empirical calibrations of the N2O2, N2S2, O3N2, and N2 strong-line indices to estimate the nitrogen-to-oxygen abundance ratio when auroral lines are not detected. All indices are strongly correlated with the T e -based log (N/O) for our H II re gion sample, ev en more strongly than with 12 + log (O/H). N2O2 is the most strongly correlated index, and the best fit to the log (N/O)–N2O2 relation is obtained with a second-order polynomial. The derived relation has a low dispersion (rms < 0.09 dex), being valid in the range −1.74 < N2O2 < 0.62 (or −1.81 < log (N/O) < −0.13). We have compared our calibration with previous ones and have discussed the differences between them in terms of the nature of the objects used as calibrators. 2022-06-02T10:59:10Z 2022-06-02T10:59:10Z 2022-04-07 info:eu-repo/semantics/article Estrella Florido, Almudena Zurita, Enrique Pérez-Montero, New calibrations for estimating the N/O ratio in H II regions, Monthly Notices of the Royal Astronomical Society, Volume 513, Issue 2, June 2022, Pages 2006–2018, [https://doi.org/10.1093/mnras/stac919] http://hdl.handle.net/10481/75202 10.1093/mnras/stac919 eng http://creativecommons.org/licenses/by-nc-nd/3.0/es/ info:eu-repo/semantics/openAccess Atribución-NoComercial-SinDerivadas 3.0 España Oxford University Press