Euclid-ARRAKIHS ISSI project

Euclid-ARRAKIHS ISSI project

Euclid and ARRAKIHS join forces to explore the extremely low surface brightness Universe

A series of three ISSI (International Space Science Institute) meetings between experts from ESA’s Euclid and ARRAKIHS space missions aims to address shared technical challenges, develop advanced image processing techniques, and evaluate the synergy between the two missions in exploring the low surface brightness Universe.

The Universe contains galaxies so faint they merge with the darkness of space, making them difficult to detect. These low surface brightness galaxies (LSBGs) and the stellar streams surrounding them offer crucial insights into galaxy formation and dark matter. Addressing this challenge, the ARRAKIHS mission is partnering with the European Space Agency’s Euclid mission, combining specialized observational approaches to uncover these elusive cosmic structures.

Euclid focuses on mapping the large-scale structure of the universe, observing galaxies with high precision across multiple filters to measure cosmic geometry and distribution. ARRAKIHS, meanwhile, is designed to detect faint, low surface brightness features like stellar streams and galactic halos around Milky Way-type galaxies. Both missions use different but complementary strategies to explore the outskirts and finer structures of galaxies.

In astronomy, simulations play a critical role. They allow scientists to refine techniques and test theories before real data is available. For this project, ARRAKIHS and Euclid will generate simulated observations using their respective instruments and filters. Euclid will observe using VIS, Y, and J bands, while ARRAKIHS will focus on VIS1, VIS2, NIR1, and NIR2. The simulations will incorporate complex elements, including noise, stray light, and realistic galaxy features, providing a robust framework for comparison. Using identical galaxy models ensures that differences between the missions reflect their distinct designs and capabilities.

The collaboration seeks answers to fundamental questions: how effectively can Euclid and ARRAKIHS detect faint streams and satellite galaxies? What proportion of detections will be genuine structures rather than artifacts? Most importantly, can combining data from both missions reveal details that might be missed by observing with just one? These insights will help refine detection algorithms and improve future observational strategies.

By working together, ARRAKIHS and Euclid are setting a new standard for collaborative astronomy. Their joint analysis will culminate in a white paper and a peer-reviewed publication by 2025, demonstrating the complementary nature of their instruments and the transformative potential of working together. This effort not only advances our understanding of LSBGs and galactic outskirts but also paves the way for future missions to push even further into the universe’s most hidden corners.