Gas outflows in two recently quenched galaxies at z = 4 and 7
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2025
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| author | Valentino, F. Heintz, K. E. Brammer, G. Ito, K. Kokorev, V. Whitaker, K. E. Gallazzi, A. de Graaff, A. Weibel, A. Frye, B. L. Kamieneski, P. S. Jin, S. Ceverino, D. Faisst, A. Farcy, M. Fujimoto, S. Gillman, S. Gottumukkala, R. Hamadouche, M. Harrington, K. C. Hirschmann, M. Jespersen, C. K. Kakimoto, T. Kubo, M. Lagos, C. d. P. Lee, M. Magdis, G. E. Man, A. W. S. Onodera, M. Rizzo, F. Shimakawa, R. Setton, D. J. Tanaka, M. Toft, S. Wu, P. -F. Zhu, P. |
| author_facet | Valentino, F. Heintz, K. E. Brammer, G. Ito, K. Kokorev, V. Whitaker, K. E. Gallazzi, A. de Graaff, A. Weibel, A. Frye, B. L. Kamieneski, P. S. Jin, S. Ceverino, D. Faisst, A. Farcy, M. Fujimoto, S. Gillman, S. Gottumukkala, R. Hamadouche, M. Harrington, K. C. Hirschmann, M. Jespersen, C. K. Kakimoto, T. Kubo, M. Lagos, C. d. P. Lee, M. Magdis, G. E. Man, A. W. S. Onodera, M. Rizzo, F. Shimakawa, R. Setton, D. J. Tanaka, M. Toft, S. Wu, P. -F. Zhu, P. |
| contents | Outflows are a key element in the baryon cycle of galaxies, and their properties provide a fundamental test for our models of how star formation quenches in galaxies. Here we report the detection of outflowing gas in two recently quenched, massive ($M_\star\sim10^{10.2}M_\odot$) galaxies at z=4.106 (NS_274) and z=7.276 (RUBIES-UDS-QG-z7) observed with JWST/NIRSpec. The outflows are traced by blue-shifted MgII absorption lines, and in the case of the z=4.1 system, also by FeII and NaI features. The spectra of the two sources are similar to those of local post-starburst galaxies, showing deep Balmer features and minimal star formation on 10 Myr timescales as traced by the lack of bright emission lines, also suggesting the absence of a strong and radiatively efficient AGN. The galaxies' SFHs are consistent with an abrupt quenching of star formation, which continued at rates of $\sim15\,M_\odot$/yr averaged over 100 Myr timescales. Dedicated millimeter observations of NS_274 constrain its dust obscured SFR to $<12\,M_\odot$/yr. Under simple geometrical assumptions, we derive mass loading factors $\lesssim1$ and $>10$ for the z=4.1 and z=7.3 systems, respectively, and similarly different energies carried by the outflows. Supernova feedback can account for the mass and energy of the outflow in NS_274. However, the low mass loading factor and average gas velocity suggest that the observed outflow is likely not the primary factor behind its quenching. SF-related processes seem to be insufficient to explain the extreme mass outflow rate of RUBIES-UDS-QG-z7, which would require an additional ejective mechanism such as an undetected AGN. Finally, the average outflow velocities per unit $M_\star$, SFR, or its surface area are consistent with those of lower-redshift post-starburst galaxies, suggesting that outflows in rapidly quenched galaxies might occur similarly across cosmic time. [Abridged] |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2503_01990 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Gas outflows in two recently quenched galaxies at z = 4 and 7 Valentino, F. Heintz, K. E. Brammer, G. Ito, K. Kokorev, V. Whitaker, K. E. Gallazzi, A. de Graaff, A. Weibel, A. Frye, B. L. Kamieneski, P. S. Jin, S. Ceverino, D. Faisst, A. Farcy, M. Fujimoto, S. Gillman, S. Gottumukkala, R. Hamadouche, M. Harrington, K. C. Hirschmann, M. Jespersen, C. K. Kakimoto, T. Kubo, M. Lagos, C. d. P. Lee, M. Magdis, G. E. Man, A. W. S. Onodera, M. Rizzo, F. Shimakawa, R. Setton, D. J. Tanaka, M. Toft, S. Wu, P. -F. Zhu, P. Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics Outflows are a key element in the baryon cycle of galaxies, and their properties provide a fundamental test for our models of how star formation quenches in galaxies. Here we report the detection of outflowing gas in two recently quenched, massive ($M_\star\sim10^{10.2}M_\odot$) galaxies at z=4.106 (NS_274) and z=7.276 (RUBIES-UDS-QG-z7) observed with JWST/NIRSpec. The outflows are traced by blue-shifted MgII absorption lines, and in the case of the z=4.1 system, also by FeII and NaI features. The spectra of the two sources are similar to those of local post-starburst galaxies, showing deep Balmer features and minimal star formation on 10 Myr timescales as traced by the lack of bright emission lines, also suggesting the absence of a strong and radiatively efficient AGN. The galaxies' SFHs are consistent with an abrupt quenching of star formation, which continued at rates of $\sim15\,M_\odot$/yr averaged over 100 Myr timescales. Dedicated millimeter observations of NS_274 constrain its dust obscured SFR to $<12\,M_\odot$/yr. Under simple geometrical assumptions, we derive mass loading factors $\lesssim1$ and $>10$ for the z=4.1 and z=7.3 systems, respectively, and similarly different energies carried by the outflows. Supernova feedback can account for the mass and energy of the outflow in NS_274. However, the low mass loading factor and average gas velocity suggest that the observed outflow is likely not the primary factor behind its quenching. SF-related processes seem to be insufficient to explain the extreme mass outflow rate of RUBIES-UDS-QG-z7, which would require an additional ejective mechanism such as an undetected AGN. Finally, the average outflow velocities per unit $M_\star$, SFR, or its surface area are consistent with those of lower-redshift post-starburst galaxies, suggesting that outflows in rapidly quenched galaxies might occur similarly across cosmic time. [Abridged] |
| title | Gas outflows in two recently quenched galaxies at z = 4 and 7 |
| topic | Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2503.01990 |