Ly-alpha emission reveals two satellite halos around massive groups at z ~ 3: the puzzling case of a quiescent central galaxy
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2025
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| author | Guo, Sicen Daddi, Emanuele Gobat, Raphael Sillassen, Nikolaj B. D'Eugenio, Chiara Rich, R. Michael Elias, Guillaume Aravena, Manuel Bruckmann, Franziska Correa, Camila Delvecchio, Ivan Elbaz, David Gallego, Sofia G. Gentile, Fabrizio Jin, Shuowen Kalita, Boris S. Neill, James D. Solimano, Manuel Valentino, Francesco Wang, Tao |
| author_facet | Guo, Sicen Daddi, Emanuele Gobat, Raphael Sillassen, Nikolaj B. D'Eugenio, Chiara Rich, R. Michael Elias, Guillaume Aravena, Manuel Bruckmann, Franziska Correa, Camila Delvecchio, Ivan Elbaz, David Gallego, Sofia G. Gentile, Fabrizio Jin, Shuowen Kalita, Boris S. Neill, James D. Solimano, Manuel Valentino, Francesco Wang, Tao |
| contents | We present the discovery and characterisation of two Ly$α$ nebulae (LANs), RO-1001-Sat and RO-0959-Sat, as satellite structures of two giant LANs at $z=2.920$ and 3.092. They are found neighbouring two out of four known giant LANs at $z\sim3$ in our MUSE follow-up observations, reinforcing the idea that Ly$α$ emission can be used to trace massive dark matter halos at high-$z$. This high occurrence of massive satellite halos agrees with simulations. With sizes of $\simeq80\times160$ and $80\times100~\mathrm{pkpc}^2$, the two nebulae are both $\sim$300pkpc from the main LANs. The Ly$α$ emission is only shifted by $\simeq100-300$ km s$^{-1}$ between each of the two pairs, suggesting connections via large-scale structure. RO-1001-Sat and RO-0959-Sat are estimated to have log$(M_\mathrm{h}/M_\odot)\simeq13.2\pm0.3$ and $12.8\pm0.3$, putting them potentially close to the regime of cold-mode accretion. The central brightest galaxies in the two halos are morphologically distinct despite having similar stellar mass $\sim10^{11}M_\odot$, one being an elliptical quiescent galaxy in RO-1001-Sat and the other being a dusty star-forming spiral in RO-0959-Sat. Intriguingly, the quiescent galaxy aligns well with the peak of the LAN as well as the potential well of the host halo, making it the first clear-cut case where the cold gas ought to be accreting onto the galaxy but with no observable star formation, either due to morphological quenching or, more likely, radio-mode feedback from an active galactic nucleus. Finally, we show a tentative detection of a Ly$α$ filament connecting RO-1001 and RO-1001-Sat. This work shows how panoramic MUSE (and in the future, BlueMUSE) observations of massive halo seeds can be used to efficiently search for additional halos, unveiling their large-scale structure and enabling the study of Ly$α$-selected galaxy groups. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2510_01421 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Ly-alpha emission reveals two satellite halos around massive groups at z ~ 3: the puzzling case of a quiescent central galaxy Guo, Sicen Daddi, Emanuele Gobat, Raphael Sillassen, Nikolaj B. D'Eugenio, Chiara Rich, R. Michael Elias, Guillaume Aravena, Manuel Bruckmann, Franziska Correa, Camila Delvecchio, Ivan Elbaz, David Gallego, Sofia G. Gentile, Fabrizio Jin, Shuowen Kalita, Boris S. Neill, James D. Solimano, Manuel Valentino, Francesco Wang, Tao Astrophysics of Galaxies We present the discovery and characterisation of two Ly$α$ nebulae (LANs), RO-1001-Sat and RO-0959-Sat, as satellite structures of two giant LANs at $z=2.920$ and 3.092. They are found neighbouring two out of four known giant LANs at $z\sim3$ in our MUSE follow-up observations, reinforcing the idea that Ly$α$ emission can be used to trace massive dark matter halos at high-$z$. This high occurrence of massive satellite halos agrees with simulations. With sizes of $\simeq80\times160$ and $80\times100~\mathrm{pkpc}^2$, the two nebulae are both $\sim$300pkpc from the main LANs. The Ly$α$ emission is only shifted by $\simeq100-300$ km s$^{-1}$ between each of the two pairs, suggesting connections via large-scale structure. RO-1001-Sat and RO-0959-Sat are estimated to have log$(M_\mathrm{h}/M_\odot)\simeq13.2\pm0.3$ and $12.8\pm0.3$, putting them potentially close to the regime of cold-mode accretion. The central brightest galaxies in the two halos are morphologically distinct despite having similar stellar mass $\sim10^{11}M_\odot$, one being an elliptical quiescent galaxy in RO-1001-Sat and the other being a dusty star-forming spiral in RO-0959-Sat. Intriguingly, the quiescent galaxy aligns well with the peak of the LAN as well as the potential well of the host halo, making it the first clear-cut case where the cold gas ought to be accreting onto the galaxy but with no observable star formation, either due to morphological quenching or, more likely, radio-mode feedback from an active galactic nucleus. Finally, we show a tentative detection of a Ly$α$ filament connecting RO-1001 and RO-1001-Sat. This work shows how panoramic MUSE (and in the future, BlueMUSE) observations of massive halo seeds can be used to efficiently search for additional halos, unveiling their large-scale structure and enabling the study of Ly$α$-selected galaxy groups. |
| title | Ly-alpha emission reveals two satellite halos around massive groups at z ~ 3: the puzzling case of a quiescent central galaxy |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2510.01421 |