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 universe today is home to massive, quiescent galaxies—the remnants of their once-active star-forming pasts. These galaxies, now devoid of the cold gas needed for star formation, have become dormant. With the James Webb Space Telescope (JWST), astronomers can look back in time to observe these galaxies in their prime, when they were still actively forming stars.
At redshift z = 1.5–2, many massive quiescent galaxies showed minimal cold gas, prompting questions about whether this fuel was consumed in starbursts or expelled by supermassive black hole (SMBH) feedback. This study examines GS-10578, a massive quiescent galaxy observed at redshift z = 3.064. Identified as a "blue nugget," GS-10578 is in an advanced stage of quenching, merging with several low-mass satellites, and undergoing significant ejective feedback from its SMBH.
Near-infrared observations using JWST’s NIRSpec reveal complex morphological features, including extended nebular emissions, which suggest interactions with satellites and potential gas outflows. Detailed spectral energy distribution (SED) modeling shows that most of GS-10578's stars formed roughly 0.5 billion years before the observation, followed by a rapid decline in its star formation rate (SFR).
The current SFR is much lower than expected for star-forming galaxies at this redshift, consistent with its quenched galaxy status. Furthermore, high ratios of emission lines and the detection of X-ray emissions point to active AGN activity, contributing to the galaxy's quenching processes.
Spatially resolved emission-line kinematics of GS-10578 show significant line broadening exceeding 500 km/second, with a blueshifted central region and diffuse emission at larger radii, suggesting an outflow normal to the disk. The majority of the nebular flux is concentrated in the center, which shows a velocity offset of −400 km/second, while outer regions display velocities of ±100 km/second. The high interpercentile line widths indicate a potential merger origin, though the dynamics also support a fast-rotator classification.
Notably, deep absorption features, such as prominent hydrogen and Na lines, indicate neutral-gas outflows with a cone-like geometry, which may be responsible for depleting the star-forming fuel and halting star formation. The dynamics suggest that AGN feedback drives these outflows, with the mass outflow rate exceeding the current SFR.
GS-10578 provides a unique case for studying how massive galaxies transition to quiescence, emphasizing the role of neutral-phase outflows in this process. Observations of this galaxy and others at high redshifts, facilitated by JWST, help illuminate the mechanisms behind the quenching of massive galaxies.
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. The data reduction process followed the standard JWST pipeline, with additional corrections for noise and flux calibration, using standard stars and other datasets for accuracy. The point spread function (PSF) was determined through three independent methods, revealing an elongated shape aligned with the instrument’s slices.
The galaxy’s redshift was calculated using a Monte Carlo approach, resulting in a systemic redshift of zsys = 3.06404. Ultraviolet-visible near-infrared (UVJ) color analysis placed GS-10578 firmly in the quiescent region of the UVJ diagram. To further explore its properties, spaxel-by-spaxel analysis was used to model the galaxy’s stellar population, accounting for various parameters and producing detailed 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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Article Revisions
- Sep 24 2024 - Revised sentence structure, word choice, punctuation, and clarity to improve readability and coherence.