The dwarf galaxies of the Local Group, due to their proximity, have allowed us to study their internal chemo-dynamics, star formation histories and orbital properties in an exquisite way. They have led us to a better understanding of the hierarchical formation mechanisms of larger galaxies, and to probe the cosmological model at the smallest mass scales. Over the years, a number of tensions have arisen at the scale of dwarf galaxies between observations and predictions inferred from cosmological simulations, also known as small-scale problems. Efforts to solve them have led to significant advances in both directions. In particular, observations not only have become more extensive and accurate, thanks to all-sky surveys (e.g., SDSS, DES, PANSTARRS, Gaia), but have also started to explore galaxy groups outside the Local Group. Several surveys (e.g., SAGA, MATLAS, PISCeS, ELVES, LIGHTS, DGSAT) are substantially increasing the number of known dwarf satellites around hosts up to a distance of 40 Mpc. It is now possible to compare the satellite luminosity function of the Milky Way and M31 with several other hosts, to study how much the Local Group differs from other associations, and to investigate if small-scale problems persist in other environments. In addition, the advent of new instruments such as the Vera Rubin Observatory, E-ELT, SKA, EUCLID and JWST, will soon enable us to study the dwarf regime, in unprecedented detail, out to cosmological distances (at least out to intermediate redshift). On the other hand, state-of-the-art cosmological simulations, which have tens-of-parsec scale resolution (or better) are now able to predict statistical samples of realistic dwarf populations. These can be used to make testable predictions for the formation pathways and physical properties of dwarf galaxies and their black holes. The comparison of these simulations to existing and forthcoming datasets will enable us to quantify the place of dwarf galaxies in our broader understanding of how galaxies evolve over time.

The aim of this Special Session is to bring together observers and theorists to explore the key open questions in the dwarf galaxy regime. Our wish is to provide an overview of the current situation, while waiting for upcoming advances in observing capabilities and computational tools that will continue to revolutionize this field.

Programme

Topics to be discussed include:

• Observational surveys and the status of small-scale problems in the Local Universe
• The impact of the environment on the evolution of satellite galaxy systems
• The role of AGN in dwarf-galaxy evolution
• The search for the first stars in dwarf galaxies
• Ultra-diffuse galaxies as seen from simulations
• Results from constrained cosmological simulations
• What to expect from future facilities/surveys? What theoretical advances are expected in this field?

Invited speakers

• Francine Marleau (University of Innsbruck)
• Till Sawala (University of Helsinki)
• Vivienne Baldassare (Washington State University)

Scientific organisers

Ryan Jackson (co-Chair, Yonsei University, South Korea)
Salvatore Taibi (co-Chair, Leibniz-Institut fur Astrophysik Potsdam, Germany)
Denija Crnojevic (University of Tampa, USA)
Arianna Di Cintio (Universidad de La Laguna, Spain)
Azadeh Fattahi (University of Durham, UK)
Sugata Kaviraj (University of Hertfordshire, UK)
Andrea Valerio Macciò (NYU Abu Dhabi, United Arab Emirates)
Garreth Martin (Korea Astronomy and Space Science Institute, South Korea)
Mar Mezcua (Institute of Space Sciences, Spain)
Marcel Pawlowski (Leibniz-Institut fur Astrophysik Potsdam, Germany)
Marina Rejkuba (European Southern Observatory, Germany)
Laura Sales (University of California - Riverside, USA)
Stefania Salvadori (University of Florence, Italy)
Ignacio Trujillo (Instituto de Astrofísica de Canarias, Spain)

Contact

r.jackson9 @ herts.ac.uk; staibi @ aip.de

Cover credits: Dwarf satellite galaxies from the SAGA Survey (sagasurvey.org)
© 2021 Yao-Yuan Mao, with images from Legacy Surveys / D. Lang