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| Main Authors: | , , , , , , , , , , , , , , , , |
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| Format: | Preprint |
| Published: |
2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2508.06607 |
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| _version_ | 1866915436866568192 |
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| author | Akins, Hollis B. Casey, Caitlin M. Champagne, Jaclyn B. Cooper, Olivia Franco, Maximilien Fujimoto, Seiji Knudsen, Kirsten K. Koekemoer, Anton M. Long, Arianna S. Man, Allison Manning, Sinclaire M. McKinney, Jed Zavala, Jorge Haro, Pablo Arrabal Dickinson, Mark Kokorev, Vasily Taylor, Anthony J. |
| author_facet | Akins, Hollis B. Casey, Caitlin M. Champagne, Jaclyn B. Cooper, Olivia Franco, Maximilien Fujimoto, Seiji Knudsen, Kirsten K. Koekemoer, Anton M. Long, Arianna S. Man, Allison Manning, Sinclaire M. McKinney, Jed Zavala, Jorge Haro, Pablo Arrabal Dickinson, Mark Kokorev, Vasily Taylor, Anthony J. |
| contents | We present high-resolution ALMA [CII] 158 micron observations and JWST/NIRCam+MIRI imaging of MAMBO-9, a pair of optically-dark, dusty star-forming galaxies at $z=5.85$. MAMBO-9 is among the most massive, gas-rich, and actively star-forming galaxies at this epoch, when the Universe was less than 1 Gyr old. The new, 400 pc-resolution [CII] observations reveal velocity gradients in both objects; we estimate dynamical masses and find a relative mass ratio of 1:5. The kinematics of both objects suggest both rotation and strong tidal interaction, suggesting that the pair has already experienced a close encounter. Indeed, the new JWST imaging reveals a continuous bridge of moderately dust-obscured material between the two. We perform spatially-resolved SED fitting using the high-resolution ALMA+JWST imaging, finding that the majority of recent star-formation is concentrated in extremely obscured ($A_V > 10$) clouds, while the majority of rest-optical light (stellar continuum and H$α$ emission) is emergent from moderate-to-highly obscured ($A_V\sim 1$-$5$) regions on the outskirts. Combining our new stellar and dynamical mass measurements with previous CO observations, we find that the mass budget of MAMBO-9 requires a CO-to-H$_2$ conversion factor ($α_{\rm CO}$) of roughly unity, indicative of a highly metal-enriched ISM. Finally, we show that MAMBO-9 resides in a large overdensity spanning the PRIMER-COSMOS field, with 39 galaxies spectroscopically confirmed within $\sim 25$ cMpc. With a total baryonic mass $\sim 10^{11}\,M_\odot$, MAMBO-9 can be considered a prototype of massive galaxy formation and likely progenitor of the brightest cluster galaxies (BCGs) in the lower-redshift Universe. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2508_06607 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | JWST+ALMA reveal the ISM kinematics and stellar structure of MAMBO-9, a merging pair of DSFGs in an overdense environment at $z=5.85$ Akins, Hollis B. Casey, Caitlin M. Champagne, Jaclyn B. Cooper, Olivia Franco, Maximilien Fujimoto, Seiji Knudsen, Kirsten K. Koekemoer, Anton M. Long, Arianna S. Man, Allison Manning, Sinclaire M. McKinney, Jed Zavala, Jorge Haro, Pablo Arrabal Dickinson, Mark Kokorev, Vasily Taylor, Anthony J. Astrophysics of Galaxies We present high-resolution ALMA [CII] 158 micron observations and JWST/NIRCam+MIRI imaging of MAMBO-9, a pair of optically-dark, dusty star-forming galaxies at $z=5.85$. MAMBO-9 is among the most massive, gas-rich, and actively star-forming galaxies at this epoch, when the Universe was less than 1 Gyr old. The new, 400 pc-resolution [CII] observations reveal velocity gradients in both objects; we estimate dynamical masses and find a relative mass ratio of 1:5. The kinematics of both objects suggest both rotation and strong tidal interaction, suggesting that the pair has already experienced a close encounter. Indeed, the new JWST imaging reveals a continuous bridge of moderately dust-obscured material between the two. We perform spatially-resolved SED fitting using the high-resolution ALMA+JWST imaging, finding that the majority of recent star-formation is concentrated in extremely obscured ($A_V > 10$) clouds, while the majority of rest-optical light (stellar continuum and H$α$ emission) is emergent from moderate-to-highly obscured ($A_V\sim 1$-$5$) regions on the outskirts. Combining our new stellar and dynamical mass measurements with previous CO observations, we find that the mass budget of MAMBO-9 requires a CO-to-H$_2$ conversion factor ($α_{\rm CO}$) of roughly unity, indicative of a highly metal-enriched ISM. Finally, we show that MAMBO-9 resides in a large overdensity spanning the PRIMER-COSMOS field, with 39 galaxies spectroscopically confirmed within $\sim 25$ cMpc. With a total baryonic mass $\sim 10^{11}\,M_\odot$, MAMBO-9 can be considered a prototype of massive galaxy formation and likely progenitor of the brightest cluster galaxies (BCGs) in the lower-redshift Universe. |
| title | JWST+ALMA reveal the ISM kinematics and stellar structure of MAMBO-9, a merging pair of DSFGs in an overdense environment at $z=5.85$ |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2508.06607 |