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Welcome to CLEVeR
CLuster and group
Environment as
Viewed by
eROSITA

CLEVeR is an ERC-funded project dedicated to understanding how Active Galactic Nuclei (AGN) and stellar feedback shape the distribution of baryons in the universe. Using eROSITA’s deep X-ray surveys, along with optical and radio observations, CLEVeR aims to:

  • Measure the hot gas content in galaxy groups down to Milky Way-sized halos.

  • Examine the interplay of cooling and feedback in galaxy clusters and groups.

  • Identify AGN-driven outflows and feedback mechanisms across cosmic time.

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Our Research Focus

CLEVeR: Unveiling the Hidden Universe of Galaxy Groups

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Galaxy groups are the missing link in our understanding of galaxy evolution and large-scale structure formation. These systems, with halo masses between 10¹² - 10¹⁴ M☉, are the most common environments for galaxies, serving as the building blocks of larger clusters. However, they remain poorly understood, as their hot gas content is faint and difficult to detect in X-rays.

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Despite their observational challenges, galaxy groups are key to testing AGN feedback models, which strongly influence their X-ray appearance and baryon distribution. CLEVeR leverages multi-wavelength observations to answer fundamental questions about how feedback processes shape these systems:

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  • How does AGN feedback regulate the hot gas content in galaxy groups?

    • Theoretical models predict dramatically different X-ray brightness and gas content in galaxy groups, ranging from gas-rich halos to systems completely devoid of hot gas. CLEVeR will use eROSITA’s deep X-ray survey to refine the LX-Mh scaling relation and constrain feedback processes at these crucial mass scales.

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  • How do central galaxies influence the CGM in groups?

    • Unlike massive clusters, where feedback is limited to the core region, AGN-driven energy in groups can impact the entire halo volume, influencing gas cooling and star formation. CLEVeR will test the precipitation framework by mapping CGM conditions using X-ray (eROSITA), radio (LOFAR, ALMA), and optical/IR spectroscopy (MUSE, JWST, 4MOST).

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  • How are satellite galaxies transformed in group environments?

    • As satellites fall into groups, they experience strangulation, ram-pressure stripping, and tidal interactions, which progressively remove their gas and quench star formation. CLEVeR will study thousands of satellite galaxies across different halo masses, using X-ray, HI, and spectroscopic surveys to track how these quenching mechanisms evolve.

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  • How well do simulations predict the X-ray appearance of galaxy groups?

    • Current feedback models struggle to match observed baryon distributions in groups. CLEVeR will generate synthetic eROSITA observations from IllustrisTNG, Magneticum, and BahamasXL light-cone simulations, enabling a direct comparison between predicted and real X-ray data to refine feedback prescriptions.

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By focusing on the most common yet least understood galactic environments, CLEVeR bridges the gap between observations and simulations, providing a high-precision benchmark for refining cosmological models of feedback, galaxy transformation, and baryon redistribution.

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