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Exploring chemical homogeneity in dwarf galaxies: a VLT-MUSE study of JKB 18

James, Bethan L. and Kumari, Nimisha and Emerick, Andrew and Koposov, Sergey E. and McQuinn, Kristen B. W. and Stark, Daniel P. and Belokurov, Vasily and Maiolino, Roberto (2020) Exploring chemical homogeneity in dwarf galaxies: a VLT-MUSE study of JKB 18. Monthly Notices of the Royal Astronomical Society, 495 (3). pp. 2564-2581. ISSN 0035-8711. doi:10.1093/mnras/staa1280.

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Deciphering the distribution of metals throughout galaxies is fundamental in our understanding of galaxy evolution. Nearby, low-metallicity, star-forming dwarf galaxies, in particular, can offer detailed insight into the metal-dependent processes that may have occurred within galaxies in the early Universe. Here, we present VLT/MUSE observations of one such system, JKB 18, a blue diffuse dwarf galaxy with a metallicity of only 12 + log(O/H)=7.6 ± 0.2 (∼0.08 Z⊙). Using high spatial resolution integral-field spectroscopy of the entire system, we calculate chemical abundances for individual H II regions using the direct method and derive oxygen abundance maps using strong-line metallicity diagnostics. With large-scale dispersions in O/H, N/H, and N/O of ∼0.5–0.6 dex and regions harbouring chemical abundances outside this 1σ distribution, we deem JKB 18 to be chemically inhomogeneous. We explore this finding in the context of other chemically inhomogeneous dwarf galaxies and conclude that neither the accretion of metal-poor gas, short mixing time-scales or self-enrichment from Wolf–Rayet stars are accountable. Using a galaxy-scale, multiphase, hydrodynamical simulation of a low-mass dwarf galaxy, we find that chemical inhomogeneities of this level may be attributable to the removal of gas via supernovae and the specific timing of the observations with respect to star formation activity. This study not only draws attention to the fact that dwarf galaxies can be chemically inhomogeneous, but also that the methods used in the assessment of this characteristic can be subject to bias.

Item Type:Article
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URLURL TypeDescription Paper
James, Bethan L.0000-0003-4372-2006
Kumari, Nimisha0000-0002-5320-2568
Emerick, Andrew0000-0003-2807-328X
Koposov, Sergey E.0000-0003-2644-135X
Belokurov, Vasily0000-0002-0038-9584
Additional Information:© 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2020 May 4. Received 2020 April 1; in original form 2019 November 8. Published: 08 May 2020. This study is based on observations collected at the European Organisation for Astronomical Research in the Southern hemisphere under ESO programme(s) 096.B-0212(A). We are grateful to the European Southern Observatory time assignment committee, who awarded time to this programme and to the staff astronomers at Paranal, who conducted the observations. We thank Peter Zeidler for his invaluable assistance in the MUSE data reduction and for allowing us access to MUSEPACK during its development phase, and Roger Wesson for his advice on optimizing ALFA for our line-fitting needs. We are sincerely grateful to Evan Skillman for discussions concerning chemical inhomogeneities, to Danielle Berg for the assessment of anomalously low metallicity measurements, and Matthew Auger for his assistance with several of the figures presented here. The authors would also like thank the anonymous referee, whose insightful comments helped greatly improve this manuscript. BLJ thanks support from the European Space Agency (ESA). NK thanks the Schlumberger Foundation for the fellowship supporting her postdoctoral work at the University of Cambridge. SK is partially supported by NSF grants AST-1813881, AST-1909584 and Heising-Simon’s foundation grant 2018-1030.
Funding AgencyGrant Number
European Space AgencyUNSPECIFIED
Schlumberger FoundationUNSPECIFIED
Heising-Simons Foundation2018-1030
Subject Keywords:galaxies: abundances – galaxies: dwarf – galaxies: evolution – galaxies: irregular – galaxies: star formation
Issue or Number:3
Record Number:CaltechAUTHORS:20200717-101425177
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Official Citation:Bethan L James, Nimisha Kumari, Andrew Emerick, Sergey E Koposov, Kristen B W McQuinn, Daniel P Stark, Vasily Belokurov, Roberto Maiolino, Exploring chemical homogeneity in dwarf galaxies: a VLT-MUSE study of JKB 18, Monthly Notices of the Royal Astronomical Society, Volume 495, Issue 3, July 2020, Pages 2564–2581,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104424
Deposited By: Tony Diaz
Deposited On:17 Jul 2020 17:34
Last Modified:16 Nov 2021 18:31

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