JWST observes the assembly of a massive galaxy at z~4

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Main Authors: Saxena, Aayush, Overzier, Roderik A., Aydar, Catarina, Lyu, Jianwei, Rieke, George H., Reynaldi, Victoria, Villar-Martín, Montserrat, Gabányi, Krisztina Éva, Duncan, Kenneth J., Frey, Sándor, Humphrey, Andrew, Miley, George, Pentericci, Laura, Perger, Krisztina, Röttgering, Huub, Best, Philip, Bosman, Sarah E. I., Mező, Gyorgy, Onoue, Masafusa, Paragi, Zsolt, Venemans, Bram
Format: Preprint
Published: 2025
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author Saxena, Aayush
Overzier, Roderik A.
Aydar, Catarina
Lyu, Jianwei
Rieke, George H.
Reynaldi, Victoria
Villar-Martín, Montserrat
Gabányi, Krisztina Éva
Duncan, Kenneth J.
Frey, Sándor
Humphrey, Andrew
Miley, George
Pentericci, Laura
Perger, Krisztina
Röttgering, Huub
Best, Philip
Bosman, Sarah E. I.
Mező, Gyorgy
Onoue, Masafusa
Paragi, Zsolt
Venemans, Bram
author_facet Saxena, Aayush
Overzier, Roderik A.
Aydar, Catarina
Lyu, Jianwei
Rieke, George H.
Reynaldi, Victoria
Villar-Martín, Montserrat
Gabányi, Krisztina Éva
Duncan, Kenneth J.
Frey, Sándor
Humphrey, Andrew
Miley, George
Pentericci, Laura
Perger, Krisztina
Röttgering, Huub
Best, Philip
Bosman, Sarah E. I.
Mező, Gyorgy
Onoue, Masafusa
Paragi, Zsolt
Venemans, Bram
contents We present JWST observations of the radio galaxy TGSSJ1530+1049, spectroscopically confirmed at $z=4.0$. NIRCam images and NIRSpec/IFU spectroscopy (R=2700) show that TGSSJ1530+1049 is part of one of the densest-known structures of continuum and line-emitting objects found at these redshifts. NIRCam images show a number of distinct continuum objects and evidence of interactions traced by diffuse emission, and the NIRSpec IFU cube reveals further strong line emitting regions. We identify six continuum and four additional strong H$α$ emitting sources with weaker or no underlying continuum within the 3x3 arcsec IFU field. From spatial alignment with high-resolution radio data and emission line profiles, the radio AGN host galaxy is clearly identified. The bright H$α$ emission (but not the optical components) is distributed remarkably linearly along the radio axis, suggestive of a biconical illumination zone by a central obscured AGN. The emission line kinematics indicate jet-gas interactions on scales of a few kpc. However, due to large relative velocities and presence of underlying continuum, the alignment with the radio structure appears to be, at least partly, caused by a particular configuration of interacting galaxies. At least four objects within a 10x10 (projected) kpc$^2$ area which includes the radio source have high stellar masses ($\log(M_\star/M_\odot)>10.3$) and star formation rates in the range $70-163\,M_\odot$ yr$^{-1}$. Using a stellar mass-based analysis, we predict a total dark matter halo mass of $\approx10^{13} M_\odot$. Based on the physical separations and velocity differences between the galaxies, it is expected that these galaxies will merge to form a massive galaxy within a few Gyr. The system qualitatively resembles the forming brightest cluster galaxies in cosmological simulations that form early through a rapid succession of mergers.
format Preprint
id arxiv_https___arxiv_org_abs_2511_13650
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle JWST observes the assembly of a massive galaxy at z~4
Saxena, Aayush
Overzier, Roderik A.
Aydar, Catarina
Lyu, Jianwei
Rieke, George H.
Reynaldi, Victoria
Villar-Martín, Montserrat
Gabányi, Krisztina Éva
Duncan, Kenneth J.
Frey, Sándor
Humphrey, Andrew
Miley, George
Pentericci, Laura
Perger, Krisztina
Röttgering, Huub
Best, Philip
Bosman, Sarah E. I.
Mező, Gyorgy
Onoue, Masafusa
Paragi, Zsolt
Venemans, Bram
Astrophysics of Galaxies
We present JWST observations of the radio galaxy TGSSJ1530+1049, spectroscopically confirmed at $z=4.0$. NIRCam images and NIRSpec/IFU spectroscopy (R=2700) show that TGSSJ1530+1049 is part of one of the densest-known structures of continuum and line-emitting objects found at these redshifts. NIRCam images show a number of distinct continuum objects and evidence of interactions traced by diffuse emission, and the NIRSpec IFU cube reveals further strong line emitting regions. We identify six continuum and four additional strong H$α$ emitting sources with weaker or no underlying continuum within the 3x3 arcsec IFU field. From spatial alignment with high-resolution radio data and emission line profiles, the radio AGN host galaxy is clearly identified. The bright H$α$ emission (but not the optical components) is distributed remarkably linearly along the radio axis, suggestive of a biconical illumination zone by a central obscured AGN. The emission line kinematics indicate jet-gas interactions on scales of a few kpc. However, due to large relative velocities and presence of underlying continuum, the alignment with the radio structure appears to be, at least partly, caused by a particular configuration of interacting galaxies. At least four objects within a 10x10 (projected) kpc$^2$ area which includes the radio source have high stellar masses ($\log(M_\star/M_\odot)>10.3$) and star formation rates in the range $70-163\,M_\odot$ yr$^{-1}$. Using a stellar mass-based analysis, we predict a total dark matter halo mass of $\approx10^{13} M_\odot$. Based on the physical separations and velocity differences between the galaxies, it is expected that these galaxies will merge to form a massive galaxy within a few Gyr. The system qualitatively resembles the forming brightest cluster galaxies in cosmological simulations that form early through a rapid succession of mergers.
title JWST observes the assembly of a massive galaxy at z~4
topic Astrophysics of Galaxies
url https://arxiv.org/abs/2511.13650