## What is NECO?

NECO is a France - Japan International Research Network dedicated to the development of collaborations and cross-formation in extragalactic Astrophysics and in Cosmology. It started on the 1st of January 2020 for 5 years.

## Why France and Japan?

One of the main challenges is to keep and improve the role and position of the French and Japanese researchers in the international astrophysical competition. NECo also wants to build a communication link between France and Japan in Astrophysics and therefore put strong efforts on the educational front. Japan and France have many scientific and instrumental projects in common. However, by comparing the French and Japanese contributions in the fields of Cosmology and extragalactic Astrophysics to those of the rest of the international community (already established or in the development phase), we are aware that there is room for improvement. We know intellectually that we need the knowledge of others to deal with scientific questions. However, it is not easy to initiate collaborations and we sometimes lack the motivation to collaborate. Collaboration is a way of working that attracts and involves people outside of formal control, organization and expertise to achieve common goals. Understanding what collaboration is not is crucial to improving it. In addition, we need to identify the tasks that are suitable for collaborations.

## Why do we need to increase the communication between Japan and France?

We cannot collaborate on everything. The first, mandatory step is therefore 1) to know what the other is doing and knows better what we do. Then, we will 2) be able to define and achieve common scientific objectives. Learning to collaborate is a learning process. A good collaboration is limited by ignorance of what the other party is doing and mistrust of the ability to meet your expectations. Our knowledge of the other partner is already relatively developed thanks to the established collaborations. NECo will go even further, for the benefit of both parties. In addition to the development of new collaborations, researchers working together must meet (virtually and physically) to follow the evolution of expertise. Collaborating means that we will attract and involve people from outside our usual community, who do not normally call on our expertise to achieve common goals. We need to get to know and share knowledge and the development of expertise so that both parties can benefit from it and make the most of it. Most of today's cosmological and astrophysical issues are so complex and multifaceted that a single team can hardly tackle them. NECo is designed to be a structure that will help French / Japanese to develop current collaborations and create new ones with people in the other country.
Added value also lies in the development of student exchanges and more generally of young researchers. This will be done through the development of collaborative works and visits and summer schools. We also plan to organize awareness actions for even younger students to encourage their participation in extragalactic Astrophysics and Cosmology. Another important point for the NECo is to try to achieve a better gender balance by offering equal visibility and presence of both genders in our activities. As can be seen from the list of people involved, we have to seriously work on this issue in Japan but even in France.