The Metallicity Distribution of the Ultra-Faint Dwarf Galaxy Segue 1
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| Autores principales: | , , , , , , , , |
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| Formato: | Preprint |
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2026
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| author | Bissonette, Daisy Ji, Alexander P. Simon, Joshua D. Bland-Hawthorn, Joss Chiti, Anirudh Geha, Marla Li, Ting S. Frebel, Anna Luna, Alice M. |
| author_facet | Bissonette, Daisy Ji, Alexander P. Simon, Joshua D. Bland-Hawthorn, Joss Chiti, Anirudh Geha, Marla Li, Ting S. Frebel, Anna Luna, Alice M. |
| contents | Ultra-faint dwarf galaxies (UFDs, $M_* < 10^5 M_\odot$) offer unique insights into early chemical evolution in low-mass systems. However, interpreting their metallicity distribution functions (MDFs) has been challenging due to limited spectroscopic samples, especially beyond the red giant branch. We present metallicities from the Ca II K absorption feature, measured from low-resolution ($R \sim 1000$) Keck/LRIS spectroscopy of 40 stars in the UFD Segue 1 ($M_* \approx 500 M_\odot$), including both red giant branch and main-sequence turnoff stars, resulting in a metallicity sample more than six times larger than previously published data for Segue 1. The resulting MDF has an average [Fe/H] $= -2.52 \pm 0.10$ dex and a dispersion of $σ= 0.59 \pm 0.06$ dex, with no evidence for distinct subpopulations. This is consistent with a continuous, short-duration ($\lesssim 1$ Gyr) episode of star formation and chemical enrichment prior to reionization. The nonzero metallicity spread reaffirms its classification as a galaxy. Segue 1 highlights the rich chemical enrichment histories present even in the least massive galaxies, and underscores the importance of deep spectroscopic follow-up to fully characterize these ancient stellar systems. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_12810 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | The Metallicity Distribution of the Ultra-Faint Dwarf Galaxy Segue 1 Bissonette, Daisy Ji, Alexander P. Simon, Joshua D. Bland-Hawthorn, Joss Chiti, Anirudh Geha, Marla Li, Ting S. Frebel, Anna Luna, Alice M. Astrophysics of Galaxies Ultra-faint dwarf galaxies (UFDs, $M_* < 10^5 M_\odot$) offer unique insights into early chemical evolution in low-mass systems. However, interpreting their metallicity distribution functions (MDFs) has been challenging due to limited spectroscopic samples, especially beyond the red giant branch. We present metallicities from the Ca II K absorption feature, measured from low-resolution ($R \sim 1000$) Keck/LRIS spectroscopy of 40 stars in the UFD Segue 1 ($M_* \approx 500 M_\odot$), including both red giant branch and main-sequence turnoff stars, resulting in a metallicity sample more than six times larger than previously published data for Segue 1. The resulting MDF has an average [Fe/H] $= -2.52 \pm 0.10$ dex and a dispersion of $σ= 0.59 \pm 0.06$ dex, with no evidence for distinct subpopulations. This is consistent with a continuous, short-duration ($\lesssim 1$ Gyr) episode of star formation and chemical enrichment prior to reionization. The nonzero metallicity spread reaffirms its classification as a galaxy. Segue 1 highlights the rich chemical enrichment histories present even in the least massive galaxies, and underscores the importance of deep spectroscopic follow-up to fully characterize these ancient stellar systems. |
| title | The Metallicity Distribution of the Ultra-Faint Dwarf Galaxy Segue 1 |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2605.12810 |