@article{2023A&A...669A..88P,
 abstract = {\ Aims: We explore the so-called softness diagram - whose
main function is to provide the hardness of the ionizing
radiation in star-forming regions - in order to check whether
hot and old low-mass evolved stars (HOLMES) are significant
contributors to the ionization within star-forming regions, as
suggested by previous MaNGA data analyses. \
Methods: We used the code HCM-TEFF to derive both the ionization
parameter and the equivalent effective temperature (T$_*$),
adopting models of massive stars and planetary nebulae (PNe),
and exploring different sets of emission lines in the softness
diagram to figure out the main causes of the observed
differences in the softness parameter in the MaNGA and CHAOS
star-forming region samples. \ Results: We find
that the fraction of regions with a resulting T$_*$ > 60 kK,
which are supposedly ionised by sources harder than massive
stars, is considerably larger in the MaNGA (66%) than in the
CHAOS (20%) sample when the [S II]
\ensuremathłambda\ensuremathłambda 6716,6731 ̊A
emission lines are used in the softness diagram. However, the
respective fractions of regions in this regime for both samples
are considerably reduced (20% in MaNGA and 10% in CHAOS) when
the [N II] emission line at \ensuremathłambda 6584 \Å
is used instead. This may indicate that diffuse ionised gas
(DIG) contamination in the lower resolution MaNGA data is
responsible for artificially increasing the measured T$_*$ as
opposed to there being a predominant role of HOLMES in the H II
regions.},
 adsnote = {Provided by the SAO/NASA Astrophysics Data System},
 adsurl = {https://ui.adsabs.harvard.edu/abs/2023A&A...669A..88P},
 archiveprefix = {arXiv},
 author = {Pérez-Montero, E. and Zinchenko, I.~A. and Vı́lchez, J.~M. and Zurita, A. and Florido, E. and Pérez-D\áz, B.},
 doi = {10.1051/0004-6361/202244591},
 eid = {A88},
 eprint = {2212.03216},
 journal = {åp},
 keywords = {galaxies: abundances, galaxies: stellar content, galaxies: star formation, Astrophysics - Astrophysics of Galaxies},
 month = {January},
 pages = {A88},
 primaryclass = {astro-ph.GA},
 title = {The softness diagram for MaNGA star-forming regions: diffuse ionized gas contamination or local HOLMES predominance?},
 volume = {669},
 year = {2023}
}