Probing the role of AGN and star-formation gas outflows in galaxy evolution with the new generation of spectroscopic surveys

• Applicant: Dr. Guilherme Couto
• Subject Area: Astrophysics and Astronomy
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 549842652

In the standard scenario of galaxy formation, the baryonic matter falls inside the potential wells created by dark matter halos. This infalling material cools and forms stars. However, both low- and high-mass halos have a significantly lower than predicted value of stellar masses. To reconcile these problems, it has been proposed that supernovae and starbursts provide thermal energy injection and cause large amounts of mass to flow out of the galaxy as galactic superwinds. The star formation is suppressed as the galaxies lose a significant portion of their baryons due to this negative mass feedback. This picture can provide an explanation for the low-mass halos, but for the high-mass halos, gravity becomes strong and the supernovae are not sufficient to drive the gas out. In order to resolve the discrepancy at the high-mass end, it has been argued that the active galactic nucleus (AGN) outflows may sweep away the baryons and suppress the star formation in high-mass galaxies. These two feedback processes are believed to explain the shape of the galaxy's stellar mass function at both the low- and high-mass ends. However, as galactic outflows are computationally infeasible to fully model due to its complex physics, simulations usually scale feedback parameters with observable host galaxy properties, thus making it fundamental to fully understand how outflows correlate with galaxy properties. Furthermore, feedback properties have historically been based on uncertain assumptions and measurements. In this project, my main goal is to characterize gas outflows to compare and test galaxy evolution models that infer this to be the main mechanism for suppressing the mass growth in both low- and high-mass galaxies. In order to do this, I will use both fiber integrated and integral field spectroscopy data from upcoming large surveys 4MOST and WEAVE, which will provide large galaxy samples across cosmic time. With these spectroscopic surveys, which improves both the sample size and spectral resolution when compared to previous galaxy surveys, I will be able to study the ionization of the gas emission, as well as obtaining gas and stellar metallicities, gas kinematics, and much more information that the expected rich dataset will unveil, allowing to understand how outflows shape galaxies. Once we have characterized the behavior of outflows, both in star-forming and AGN host galaxies, and retrieved its physical properties such as mass outflow rate and kinetic power, these informations will be used to probe simulations on galaxy evolution, constraining the outcome of galaxy properties in the future. As a member of both 4MOST and WEAVE collaborations, and actively involved in the data quality and galaxy spectra fitting pipelines, I already participate intensively in these collaborations. This puts me in an ideal position to conduct the proposed project efficiently, as I have the knowledge of the data format and these surveys capabilities and data handling.

• DFG Programme: Research Grants
• International Connection: Australia, France, Spain
• Cooperation Partners: Dr. Anelise Audibert; Professor Dr. Simon Driver; Dr. Jesus Falcón Barroso; Professor Dr. Jens-Kristian Krogager