In a paper published in the journal Nature Astronomy, researchers presented James Webb space telescope's near-infrared spectrograph (JWST/NIRSpec), a massive quiescent galaxy at redshift z = 3.064. They measured its stellar mass and detected gas outflows driven by supermassive black hole (SMBH) feedback, with outflow rates exceeding the current star-formation rate. The study provided evidence of ejective SMBH feedback, demonstrating how this process quenched star formation without disrupting the galaxy's stellar disk.
Study: A fast-rotator post-starburst galaxy quenched by supermassive black-hole feedback at z = 3. Image Credit: Vladi333/Shutterstock.com
Quiescent Galaxy Dynamics
The present state of the universe reveals local, massive, quiescent galaxies as remnants of their once-glorious star-formation histories, now lacking the cold gas necessary for ongoing star formation. The JWST has allowed astronomers to observe these monumental galaxies from when they flourished.
Specifically, at redshift z = 1.5–2, massive quiescent galaxies exhibited minimal cold gas, raising questions about whether this fuel was consumed through starbursts or expelled by feedback from SMBHs. This study focuses on GS-10578, a massive quiescent galaxy observed at redshift z = 3.064. Identified as a "blue nugget," GS-10578 is currently in an advanced stage of quenching and merging with several low-mass satellites, undergoing significant ejective feedback from its SMBH.
The near-infrared observations using JWST's NIRSpec reveal complex morphological features, with extended nebular emissions indicating satellite interactions and potential gas outflows. The galaxy's stellar mass density and star formation history were assessed through detailed spectral energy distribution modeling, showing that most stars formed approximately 0.5 billion years before the observation, followed by a rapid decline in the star formation rate (SFR).
The current SFR is significantly below the expected levels for star-forming galaxies at that redshift, aligning with its classification as a quenched galaxy. Additionally, high ratios and the detection of X-ray emissions suggest active galactic nucleus (AGN) activity, which contributes to the galaxy's overall dynamics and quenching processes.
The spatially resolved emission-line kinematics of the massive quiescent galaxy GS-10578, observed at redshift z = 3.064, show significant line broadening exceeding 500 km/s, with a blueshifted central region and a diffuse emission at larger radii, suggesting an outflow normal to the disk.
Most nebular flux is concentrated in the central area, which exhibits a velocity offset of −400 km/s, while the surrounding regions display velocities of ±100 km/s. The high interpercentile line widths indicate a potential merger origin, although the kinematics also support a fast-rotator classification. Deep absorption features, including prominent hydrogen and Na lines, point to neutral-gas outflows with cone-like geometry, capable of depleting star-forming fuel and potentially halting star formation.
The dynamics imply that AGN feedback drives the outflows, with a mass outflow rate significantly higher than the star formation rate. GS-10578 represents a unique case in studying the mechanisms by which massive galaxies transition to quiescence, highlighting the role of neutral-phase outflows in this process.
The present state of the universe reveals local, massive, quiescent galaxies as remnants of their once-glorious star-formation histories, now lacking the cold gas necessary for ongoing star formation. The JWST has allowed astronomers to observe these monumental galaxies from when they flourished. Specifically, at redshift z = 1.5–2, massive quiescent galaxies exhibited minimal cold gas, raising questions about whether this fuel was consumed through starbursts or expelled by feedback from SMBHs.
This study focuses on GS-10578, a massive quiescent galaxy observed at redshift z = 3.064. Identified as a "blue nugget," GS-10578 is currently in an advanced stage of quenching and merging with several low-mass satellites, undergoing significant ejective feedback from its SMBH.
The near-infrared observations using JWST's NIRSpec reveal complex morphological features, with extended nebular emissions indicating satellite interactions and potential gas outflows. The galaxy's stellar mass density and star formation history were assessed through detailed spectral energy distribution modeling, showing that most stars formed approximately 0.5 billion years before the observation, followed by a rapid decline in the star formation rate (SFR).
The current SFR is significantly below the expected levels for star-forming galaxies at that redshift, aligning with its classification as a quenched galaxy. Additionally, high ratios and the detection of X-ray emissions suggest AGN activity, which contributes to the galaxy's overall dynamics and quenching processes.
NIRSpec Analysis of GS-10578
The study utilized NIRSpec observations from the GA-NIFS survey to analyze the galaxy GS-10578, employing various disperser and filter combinations for spectral data collection. Data reduction followed the JWST pipeline, including additional noise and flux calibration corrections using standard stars and other datasets. The point spread function (PSF) was determined through three independent methods, revealing an elongated shape aligned with instrument slices.
Redshift was assessed using a Monte Carlo approach, yielding a systemic redshift of zsys = 3.06404, while ultraviolet-visible near-infrared (UVJ) color analysis placed GS-10578 in the quiescent region of the diagram. Stellar population properties were modeled using spaxel-by-spaxel analysis, incorporating a range of parameters and constructing stellar mass and age maps.
Conclusion
To sum up, the study provided direct evidence for ejective feedback from the central SMBH in the massive, recently quenched galaxy GS-10578. The observed outflows, with rates exceeding the current star-formation rate, indicated that SMBH feedback effectively interrupted star formation.
Additionally, the stellar kinematics suggested that the galaxy remained rotation-supported despite the quenching process. These findings advanced the understanding of how SMBHs influence their host galaxies.
Journal Reference
G., P., Maiolino, R., et al. (2024). A fast-rotator post-starburst galaxy quenched by supermassive black-hole feedback at z = 3. Nature Astronomy, 1-14.DOI: 10.1038/s41550-024-02345-1, https://www.nature.com/articles/s41550-024-02345-1
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