The softness diagram for MaNGA star-forming regions: diffuse ionized gas contamination or local HOLMES predominance?
A&A 669, A88 (2023) 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-fo...
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Main Authors | , , , , , |
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Format | Journal Article |
Language | English |
Published |
06.12.2022
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Subjects | |
Online Access | Get full text |
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Summary: | A&A 669, A88 (2023) 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. 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. 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 [SII] $\lambda\lambda$ 6716,6731 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 [NII] emission line at $\lambda$ 6584 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 HII regions. |
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DOI: | 10.48550/arxiv.2212.03216 |