Understanding the formation and evolution of the first galaxies is a key priority for many current and upcoming observatories, such as ALMA, ELT, Euclid, JWST and Roman. It has also been the focus of theoretical modelling; the multitude of complex processes during this nascent period of galaxy evolution necessitates the use of detailed numerical simulations. Notably, this is also a regime where the models have not been rigorously tested, as the accumulation of multi-wavelength data has only started in recent years. Current JWST results have revealed unprecedented details on this previously poorly understood epoch, and are already challenging existing models. However, these data by themselves are not enough. Understanding them and providing strong constraints on the physics of the high-redshift Universe require them to be interpreted in the context of theoretical models or simulations. Yet, there is a disconnect in how comparisons are made between models and observations, for example, order magnitude differences in stellar mass and metallicity estimates, and evolved stellar populations at high-z due to different modelling assumptions as well as in identification of structures in models and observations. This session aims to bring together theoreticians and observers in the high-redshift community to discuss the challenges and strategies for assessing the best parameter spaces to compare the two. To frame our discussion, we will tackle the following key questions:

• Is what simulator's model consistent with the model assumptions of observer's; or are we comparing apples to oranges?
• Are current observations of high-redshift galaxies consistent with state-of-the-art theoretical models?
• What aspect of our models, both theoretical and observational, require refinement and enhancement?

Programme

Block 1: Consistency between models used by observers and simulators
The aim here is to focus on how differently the two regimes model galaxy properties (e.g. how SED fitting inferred properties differ from physical properties of galaxies in simulations). Are we comparing apples to oranges? A review and invited talk in this session with 2 contributed talks and short poster presentations.

Block 2: Comparing high-redshift galaxy observations with theoretical models
The aim of this session is to understand if current observations of high-redshift galaxies are consistent with state-of-the-art theoretical models. A review and invited talk in this session with 3 contributed talks

Block 3: Discussion
3 contributed talks in this session. Rest of the time will be allocated for discussion on talking points from the session talks.

Invited speakers

• Andrea Pallottini (Scuola Normale Superiore, Italy)
• Anna de Graaff (MPIA, Germany)
• Michaela Hirschmann (EPFL, Switzerland)
• Tereza Jerabkova (ESO, Germany)

Scientific organisers

Aswin P Vijayan (Chair, University of Sussex, UK & Cosmic Dawn Center, Denmark)
Anne Hutter (Cosmic Dawn Center, Denmark)
Christopher Lovell (University of Portsmouth, UK)
Maxime Trebitsch (University of Groningen, The Netherlands)

Contact

eas2024.apples.to.oranges @ gmail.com