Spatially resolved direct method metallicity in a high-redshift analogue local galaxy: Temperature structure impact on metallicity gradients
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 inte...
Published in: | Monthly Notices of the Royal Astronomical Society |
---|---|
Main Authors: | , , , , |
Other Authors: | |
Format: | Article in Journal/Newspaper |
Language: | unknown |
Published: |
Oxford University Press (OUP)
2020
|
Subjects: | |
Online Access: | http://hdl.handle.net/1959.3/459890 https://doi.org/10.1093/mnras/staa3757 |
id |
ftswinburne:tle:62d96b8b-27cc-47f9-8274-d7421c706660:28f49f06-0da8-44be-9edc-ad1dd0a9c582:1 |
---|---|
record_format |
openpolar |
spelling |
ftswinburne:tle:62d96b8b-27cc-47f9-8274-d7421c706660:28f49f06-0da8-44be-9edc-ad1dd0a9c582:1 2023-05-15T18:13:11+02:00 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. Swinburne University of Technology 2020 http://hdl.handle.net/1959.3/459890 https://doi.org/10.1093/mnras/staa3757 unknown Oxford University Press (OUP) http://hdl.handle.net/1959.3/459890 https://doi.org/10.1093/mnras/staa3757 Copyright © 2020. Monthly Notices of the Royal Astronomical Society, Vol. 501, no. 3 (Dec 2020), pp. 3695-3714 Journal article 2020 ftswinburne https://doi.org/10.1093/mnras/staa3757 2021-02-15T23:25:45Z 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 minimizing systematic effects on measured gradients in distant galaxies. Article in Journal/Newspaper sami Swinburne University of Technology: Swinburne Research Bank Monthly Notices of the Royal Astronomical Society |
institution |
Open Polar |
collection |
Swinburne University of Technology: Swinburne Research Bank |
op_collection_id |
ftswinburne |
language |
unknown |
description |
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 minimizing systematic effects on measured gradients in distant galaxies. |
author2 |
Swinburne University of Technology |
format |
Article in Journal/Newspaper |
author |
Cameron, Alex J. Yuan, Tiantian Trenti, Michele Nicholls, David C. Kewley, Lisa J. |
spellingShingle |
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 |
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://hdl.handle.net/1959.3/459890 https://doi.org/10.1093/mnras/staa3757 |
genre |
sami |
genre_facet |
sami |
op_source |
Monthly Notices of the Royal Astronomical Society, Vol. 501, no. 3 (Dec 2020), pp. 3695-3714 |
op_relation |
http://hdl.handle.net/1959.3/459890 https://doi.org/10.1093/mnras/staa3757 |
op_rights |
Copyright © 2020. |
op_doi |
https://doi.org/10.1093/mnras/staa3757 |
container_title |
Monthly Notices of the Royal Astronomical Society |
_version_ |
1766185680368566272 |