In the vast expanse of the cosmos, a team of researchers led by Elizabeth Taylor from the University of Edinburgh, along with collaborators from various institutions, has been peering into the distant universe using the James Webb Space Telescope (JWST). Their focus? Understanding the behavior of ancient galaxies and the forces that shape their evolution.
The team, including members from the University of Edinburgh, University of Nottingham, University of Cambridge, and others, has been investigating the presence and origin of neutral gas outflows and inflows in post-starburst (PSB) and quiescent galaxies. These galaxies, located at redshifts between 1.8 and 4.6, are observed as they were billions of years ago, providing a window into the early universe.
Using JWST’s NIRSpec spectroscopy from the EXCELS survey, the researchers analyzed the sodium D-line (NaD) absorption profiles of 13 galaxies. They found that three of these galaxies exhibited blueshifted absorption indicative of outflows, while two others showed signs of inflowing gas. The outflow velocities ranged from approximately 300 to 1200 kilometers per second. Notably, these gas flows were detected exclusively in galaxies that had stopped forming stars less than 600 million years ago.
The mass outflow rates observed were significantly higher than the current levels of star formation in these galaxies, suggesting that the winds are unlikely to be driven by supernovae. Instead, the researchers propose that these outflows are likely relics of previous, more luminous active galactic nucleus (AGN) activity that has since faded. This conclusion is supported by the fact that the majority of the outflow sample exhibited anomalously high energy and momentum outflow rates compared to those predicted for current levels of star formation or AGN activity.
To further explore this phenomenon, the team compared their observations with the EAGLE simulation. They found that their observations are consistent with a model in which galaxies at redshifts around 3 undergo short periods of AGN activity strong enough to drive outflows. These periods last approximately 5 million years and occur every 40 million years on average. The outflows driven by this AGN activity can persist for up to 10 million years after the AGN fades, followed by a 20 million-year lull, and a subsequent short inflow, which eventually re-ignites AGN activity, and the cycle repeats.
This research, published in the journal Nature Astronomy, sheds light on the complex interplay between AGN activity and galaxy evolution. Understanding these processes is crucial for developing accurate models of galaxy formation and evolution, which in turn can inform our understanding of the universe’s energy dynamics and the role of AGN in shaping the cosmos.
For the energy sector, this research highlights the importance of understanding the life cycles of galaxies and the role of AGN in driving outflows. These outflows can have significant impacts on the interstellar medium and the overall evolution of galaxies, potentially influencing the distribution and availability of resources for future generations of stars and planets. By studying these processes, we can gain insights into the fundamental mechanisms that govern the universe’s energy dynamics and the potential for harnessing these processes for practical applications.
This article is based on research available at arXiv.