Oxygen Abundance Throughout the Dwarf Starburst Galaxy IC 10

Creators: Cosens, Maren¹; Wright, Shelley A.²; Sandstrom, Karin²; Armus, Lee³; Murray, Norman⁴; Runco, Jordan N.⁵; Sabhlok, Sanchit²; Wiley, James²

1. Carnegie Observatories
2. University of California, San Diego
3. California Institute of Technology
4. Canadian Institute for Theoretical Astrophysics
5. University of California, Los Angeles

Abstract

Measurements of oxygen abundance throughout galaxies provide insight to the formation histories and ongoing processes. Here we present a study of the gas-phase oxygen abundance in the H ii regions and diffuse gas of the nearby starburst dwarf galaxy, IC 10. Using the Keck Cosmic Web Imager at W. M. Keck Observatory, we map the central region of IC 10 from 3500 to 5500 Å. The auroral [O III] 4363 Å line is detected with a high signal-to-noise ratio in 12 of 46 H II regions observed, allowing for direct measurement of the oxygen abundance, yielding a median and standard deviation of 12 + log ( O / H ) = 8.37 ± 0.25 . We investigate trends between these directly measured oxygen abundances and other H II region properties, finding weak negative correlations with the radius, velocity dispersion, and luminosity. We also find weak negative correlations between the oxygen abundance and the derived quantities of turbulent pressure and ionized gas mass, and a moderate correlation with the derived dynamical mass. Strong line, R₂₃ abundance estimates are used in the remainder of the H II regions and on a resolved spaxel-by-spaxel basis. There is a large offset between the abundances measured with R₂₃ and the auroral line method. We find that the R 23 method is unable to capture the large range of abundances observed via the auroral line measurements. The extent of this variation in the measured abundances further indicates a poorly mixed interstellar medium in IC 10, which is not typical of dwarf galaxies and may be partly due to the ongoing starburst, accretion of pristine gas, or a late stage merger.

Copyright and License

Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Acknowledgement

M.C. is supported by a Brinson Prize Fellowship at Carnegie Observatories. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. We also thank the anonymous referee for their time reviewing this paper and providing helpful feedback.

Facilities

Keck:II - KECK II Telescope (KCWI).

Software References

astrodendro (R. Thomas et al. 2013), Astropy (Astropy Collaboration et al. 2013; A. M. Price-Whelan et al. 2018), IPython (F. Perez & B. E. Granger 2007), Matplotlib (J. D. Hunter 2007), NumPy (C. R. Harris et al. 2020), pandas (W. McKinney 2010; The Pandas Development Team 2016), photutils (L. Bradley et al. 2019), and reproject (T. Robitaille et al. 2020).

Data Availability

All the HST data used in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST) at the Space Telescope Science Institute. The specific observations analyzed can be accessed via 10.17909/7shz-n457.

Files

Cosens_2024_AJ_168_250.pdf

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