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The Smith Cloud: A Dust Bowl Barrelling through Our Galactic Halo
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AAS
Date
2024
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Abstract
Around our Milky Way, there is no shortage of gas being ejected and accreted into our Galaxy. Among these high-velocity clouds (HVCs) is the Smith Cloud: a particular HVC that has been studied in-depth for over 60 years. Recent studies have explored the chemistry of the Smith Cloud, finding elemental abundances of [[N II]/Hα] = -0.49 ± 0.07 in the main body and an average UV-based sulfur abundance of [S/H] = -0.28 ± 0.14 in the tail. With the discrepancy in chemical abundances as well as a potential gradient of metallicity and trajectory of the Smith Cloud, there have been countless questions as to its origin. To probe the question of origin, we explored further aspects of the chemistry of the Smith Cloud using HI-21cm emission-line spectra from the Green Bank Telescope and UV absorption-line spectra from the Cosmic Origins Spectrograph on the Hubble Space Telescope. We utilized these observations to provide the first detection of dust within the Smith Cloud ([Si/S] = -1.04 ± 0.10 ± 0.07) and two new metallicity measurements of ([S/H] = -0.09 ± 0.18; [N/H] = -1.06 ± 0.18). We also provide the first detection of a UV nitrogen abundance. This could mean that nitrogen is under-abundant in the Smith Cloud. These results could indicate an even higher metallicity in the main body of the Smith Cloud. Our first measurement of the dust content of the Smith Cloud shows that the Smith Cloud very likely came from our Milky Way galaxy.
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Vazquez.pdf
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Physics and Astronomy