The MUSE-Faint survey V. The binary fraction of Leo T
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| Autori principali: | , , , , , |
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| Natura: | Preprint |
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2026
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| author | Vaz, Daniel Brinchmann, Jarle Kamann, Sebastian Saracino, Sara Cunha, P. A. C. Júlio, Mariana P. |
| author_facet | Vaz, Daniel Brinchmann, Jarle Kamann, Sebastian Saracino, Sara Cunha, P. A. C. Júlio, Mariana P. |
| contents | The Leo T dwarf galaxy, the faintest and least massive galaxy known to have recent star formation ($\leq 1~Gyr$), exhibits a high dynamical mass-to-light ratio based on its stellar velocity dispersion ($7.07^{+1.29}_{-1.12}~\mathrm{km\ s^{-1}}$), indicating extreme dark matter dominance. We present the first measurement of the binary fraction of Leo T using MUSE-Faint multi-epoch spectroscopy. We also determine the binary fraction for both young and old stellar populations separately and gain insights into binary properties in more metal-poor environments than the Milky Way or Magellanic Clouds. Finally, we investigate the potential impact of binaries on the inferred stellar velocity dispersion. We employed a forward model methodology combining empirical scaling relations to predict stellar velocity variations and a constrained binary distribution from the literature. To estimate the close binary fraction, we limited the maximum semi-major axis ($a < 10~\mathrm{au}$) and repeated the analysis with a semi-amplitude threshold ($\geq~10~ \mathrm{km\ s^{-1}}$) to check the impact on the inferred stellar velocity dispersion.} The overall binary fraction of Leo T is estimated to be $55^{+40}_{-9} \%$, consistent with similar systems. The close binary fraction ($a < 10~\mathrm{au}$) is $30^{+34}_{-9} \%$, which is aligned with low-metallicity environments. We found a lower binary fraction for the older stellar population ($15^{+43}_{-15} \%$) when compared to the younger population ($35^{+40}_{-6} \%$). Finally, we found no significant inflation of the velocity dispersion estimate due to binary motions when compared to the dispersion inferred from the co-added spectra. This suggests that the co-added spectra effectively provide period-averaged velocities of the stars, thus mitigating the impact of binaries on the overall velocity dispersion measurement. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2603_02643 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | The MUSE-Faint survey V. The binary fraction of Leo T Vaz, Daniel Brinchmann, Jarle Kamann, Sebastian Saracino, Sara Cunha, P. A. C. Júlio, Mariana P. Astrophysics of Galaxies The Leo T dwarf galaxy, the faintest and least massive galaxy known to have recent star formation ($\leq 1~Gyr$), exhibits a high dynamical mass-to-light ratio based on its stellar velocity dispersion ($7.07^{+1.29}_{-1.12}~\mathrm{km\ s^{-1}}$), indicating extreme dark matter dominance. We present the first measurement of the binary fraction of Leo T using MUSE-Faint multi-epoch spectroscopy. We also determine the binary fraction for both young and old stellar populations separately and gain insights into binary properties in more metal-poor environments than the Milky Way or Magellanic Clouds. Finally, we investigate the potential impact of binaries on the inferred stellar velocity dispersion. We employed a forward model methodology combining empirical scaling relations to predict stellar velocity variations and a constrained binary distribution from the literature. To estimate the close binary fraction, we limited the maximum semi-major axis ($a < 10~\mathrm{au}$) and repeated the analysis with a semi-amplitude threshold ($\geq~10~ \mathrm{km\ s^{-1}}$) to check the impact on the inferred stellar velocity dispersion.} The overall binary fraction of Leo T is estimated to be $55^{+40}_{-9} \%$, consistent with similar systems. The close binary fraction ($a < 10~\mathrm{au}$) is $30^{+34}_{-9} \%$, which is aligned with low-metallicity environments. We found a lower binary fraction for the older stellar population ($15^{+43}_{-15} \%$) when compared to the younger population ($35^{+40}_{-6} \%$). Finally, we found no significant inflation of the velocity dispersion estimate due to binary motions when compared to the dispersion inferred from the co-added spectra. This suggests that the co-added spectra effectively provide period-averaged velocities of the stars, thus mitigating the impact of binaries on the overall velocity dispersion measurement. |
| title | The MUSE-Faint survey V. The binary fraction of Leo T |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2603.02643 |