Spatially resolved direct method metallicity in a high-redshift analogue local galaxy: temperature structure impact on metallicity gradients
Abstract We investigate how H ii region temperature structure assumptions affect “direct-method” spatially-resolved metallicity observations using multispecies auroral lines in a galaxy from the SAMI Galaxy Survey. SAMI609396B, at redshift z = 0.018, is a low-mass galaxy in a minor merger with inten...
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croxfordunivpr:10.1093/mnras/staa3757 2024-02-11T10:08:23+01:00 Spatially resolved direct method metallicity in a high-redshift analogue local galaxy: temperature structure impact on metallicity gradients Cameron, Alex J Yuan, Tiantian Trenti, Michele Nicholls, David C Kewley, Lisa J 2020 http://dx.doi.org/10.1093/mnras/staa3757 http://academic.oup.com/mnras/advance-article-pdf/doi/10.1093/mnras/staa3757/34802394/staa3757.pdf en eng Oxford University Press (OUP) https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model Monthly Notices of the Royal Astronomical Society ISSN 0035-8711 1365-2966 Space and Planetary Science Astronomy and Astrophysics journal-article 2020 croxfordunivpr https://doi.org/10.1093/mnras/staa3757 2024-01-12T09:47:19Z Abstract We investigate how H ii region temperature structure assumptions affect “direct-method” spatially-resolved metallicity observations using multispecies auroral lines in a galaxy from the SAMI Galaxy Survey. SAMI609396B, at redshift z = 0.018, is a low-mass galaxy in a minor merger with intense star formation, analogous to conditions at high redshifts. We use three methods to derive direct metallicities and compare with strong-line diagnostics. The spatial metallicity trends show significant differences among the three direct methods. Our first method is based on the commonly used electron temperature Te([O iii]) from the [O iii]λ4363 auroral line and a traditional Te([O ii]) – Te([O iii]) calibration. The second method applies a recent empirical correction to the O+ abundance from the [O iii]/[O ii] strong-line ratio. The third method infers the Te([O ii]) from the [S ii]λλ4069,76 auroral lines. The first method favours a positive metallicity gradient along SAMI609396B, whereas the second and third methods yield flattened gradients. Strong-line diagnostics produce mostly flat gradients, albeit with unquantified contamination from shocked regions. We conclude that overlooked assumptions about the internal temperature structure of H ii regions in the direct method can lead to large discrepancies in metallicity gradient studies. Our detailed analysis of SAMI609396B underlines that high-accuracy metallicity gradient measurements require a wide array of emission lines and improved spatial resolutions in order to properly constrain excitation sources, physical conditions, and temperature structures of the emitting gas. Integral-field spectroscopic studies with future facilities such as JWST/NIRSpec and ground-based ELTs will be crucial in minimising systematic effects on measured gradients in distant galaxies. Article in Journal/Newspaper sami Oxford University Press Monthly Notices of the Royal Astronomical Society |
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Oxford University Press |
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English |
topic |
Space and Planetary Science Astronomy and Astrophysics |
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Space and Planetary Science Astronomy and Astrophysics Cameron, Alex J Yuan, Tiantian Trenti, Michele Nicholls, David C Kewley, Lisa J Spatially resolved direct method metallicity in a high-redshift analogue local galaxy: temperature structure impact on metallicity gradients |
topic_facet |
Space and Planetary Science Astronomy and Astrophysics |
description |
Abstract We investigate how H ii region temperature structure assumptions affect “direct-method” spatially-resolved metallicity observations using multispecies auroral lines in a galaxy from the SAMI Galaxy Survey. SAMI609396B, at redshift z = 0.018, is a low-mass galaxy in a minor merger with intense star formation, analogous to conditions at high redshifts. We use three methods to derive direct metallicities and compare with strong-line diagnostics. The spatial metallicity trends show significant differences among the three direct methods. Our first method is based on the commonly used electron temperature Te([O iii]) from the [O iii]λ4363 auroral line and a traditional Te([O ii]) – Te([O iii]) calibration. The second method applies a recent empirical correction to the O+ abundance from the [O iii]/[O ii] strong-line ratio. The third method infers the Te([O ii]) from the [S ii]λλ4069,76 auroral lines. The first method favours a positive metallicity gradient along SAMI609396B, whereas the second and third methods yield flattened gradients. Strong-line diagnostics produce mostly flat gradients, albeit with unquantified contamination from shocked regions. We conclude that overlooked assumptions about the internal temperature structure of H ii regions in the direct method can lead to large discrepancies in metallicity gradient studies. Our detailed analysis of SAMI609396B underlines that high-accuracy metallicity gradient measurements require a wide array of emission lines and improved spatial resolutions in order to properly constrain excitation sources, physical conditions, and temperature structures of the emitting gas. Integral-field spectroscopic studies with future facilities such as JWST/NIRSpec and ground-based ELTs will be crucial in minimising systematic effects on measured gradients in distant galaxies. |
format |
Article in Journal/Newspaper |
author |
Cameron, Alex J Yuan, Tiantian Trenti, Michele Nicholls, David C Kewley, Lisa J |
author_facet |
Cameron, Alex J Yuan, Tiantian Trenti, Michele Nicholls, David C Kewley, Lisa J |
author_sort |
Cameron, Alex J |
title |
Spatially resolved direct method metallicity in a high-redshift analogue local galaxy: temperature structure impact on metallicity gradients |
title_short |
Spatially resolved direct method metallicity in a high-redshift analogue local galaxy: temperature structure impact on metallicity gradients |
title_full |
Spatially resolved direct method metallicity in a high-redshift analogue local galaxy: temperature structure impact on metallicity gradients |
title_fullStr |
Spatially resolved direct method metallicity in a high-redshift analogue local galaxy: temperature structure impact on metallicity gradients |
title_full_unstemmed |
Spatially resolved direct method metallicity in a high-redshift analogue local galaxy: temperature structure impact on metallicity gradients |
title_sort |
spatially resolved direct method metallicity in a high-redshift analogue local galaxy: temperature structure impact on metallicity gradients |
publisher |
Oxford University Press (OUP) |
publishDate |
2020 |
url |
http://dx.doi.org/10.1093/mnras/staa3757 http://academic.oup.com/mnras/advance-article-pdf/doi/10.1093/mnras/staa3757/34802394/staa3757.pdf |
genre |
sami |
genre_facet |
sami |
op_source |
Monthly Notices of the Royal Astronomical Society ISSN 0035-8711 1365-2966 |
op_rights |
https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model |
op_doi |
https://doi.org/10.1093/mnras/staa3757 |
container_title |
Monthly Notices of the Royal Astronomical Society |
_version_ |
1790607557938642944 |