Gas outflows in two recently quenched galaxies at z = 4 and 7

2025/03/03 by F. Valentino, Valentino, F., K. E. Heintz +69 · 1 voice · 8 citations
Physics and Astronomy · #Astrophysics of Galaxies (astro-ph.GA) #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #astro-ph.CO #astro-ph.GA

paper · pdf · doi:10.48550/arxiv.2503.01990

arxiv published 2025/03/03 · arxiv updated 2025/07/03

Abstract

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_⋆∼10^10.2M_\odot) galaxies at z=4.106 (NS₂74) 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 ∼15 M_\odot/yr averaged over 100 Myr timescales. Dedicated millimeter observations of NS₂74 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 NS₂74. 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_⋆, 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]

Cited by

• First Statistical Detection of MgII-traced Cool Gas Outflows with JWST Towards Cosmic Dawn
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• A Fleeting GLIMPSE of N/O Enrichment at Cosmic Dawn: Evidence for Wolf Rayet N Stars in a z = 6.1 Galaxy
• Feeding the dead: neutral gas inflow with suppressed star formation in a long-quenched ancient massive galaxy at z~2.7 observed with JWST/NIRSpec
• A GLIMPSE of Intermediate Mass Black holes in the epoch of reionization: Witnessing the Descendants of Direct Collapse?
• The JWST EXCELS survey: Insights into the nature of quenching at cosmic noon
• SQuIGGLE: Buried star formation cannot explain the rapidly fading CO(2-1) luminosity in massive, z∼0.7 post-starburst galaxies
• There and back again? Neutral outflows in z~3.5 quiescent galaxies

Discussions

• The PRIMORDIAL team has two papers on ArXiv today! 🥳 The first one, led by Francesco Valentino, reports the detection of neutral gas outflows in two galaxies at z=4 and 7: arxiv.org/abs/2503.01990 [bsky, 2 points, 1 comments]

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