FAST Discovery of a Gas-rich and Ultrafaint Dwarf Galaxy: KK153
Based on a high-sensitivity H i survey using the Five-hundred-meter Aperture Spherical radio Telescope, we identified an isolated H i cloud with a system velocity of ∼127.0 km s ^−1 , which is associated with an optical galaxy KK153 in space. The H i gas of KK153 shows a typical disk-galaxy structu...
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| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal Letters |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/2041-8213/adbe7e |
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| Summary: | Based on a high-sensitivity H i survey using the Five-hundred-meter Aperture Spherical radio Telescope, we identified an isolated H i cloud with a system velocity of ∼127.0 km s ^−1 , which is associated with an optical galaxy KK153 in space. The H i gas of KK153 shows a typical disk-galaxy structure. Using the baryonic Tully–Fisher relation, we obtained that the distance to KK153 is 2.0 ${}_{-0.8}^{+1.7}$ Mpc. Adopting this distance, we derived a stellar mass of 4.1 ${}_{-2.6}^{+10.0}\times 1{0}^{5}$ M _⊙ and a neutral gas fraction of 0.63, implying that KK153 is a gas-rich ultrafaint dwarf galaxy in the Local Group or its outskirts. KK153 shows a cool (∼200 K) and warm (∼7400 K) two-phase neutral medium. The g − r color distribution of KK153 suggests that new stars are mostly forming in its inner disk. The dynamical mass of KK153 is 6.9 ${}_{-3.0}^{+5.5}\times 1{0}^{7}$ M _⊙ , which is about 60 times larger than its baryonic matter. Detection of such a low-mass and gas-rich halo poses a challenge to the theory of cosmic reionization. |
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| ISSN: | 2041-8205 |