ENGLISH: The pre-publication version of my invited article “Fordern galaktische Zwerge die Kosmologie heraus” (“Do galactic dwarfs challenge cosmology”) has been published online now. It will appear in print in early 2024 in the German magazine “Physik in unserer Zeit” (Physics in our times), which targets an audience with broader physics (e.g. physicists, engineers, teachers) in contrast to a specialist audience. So it is a good opportunity for all those interested in learning a bit more about my research without having to go through primary research articles of reviews. The article is open access, too!

GERMAN: Die Vorabversion meines eingeladenen Artikels “Fordern galaktische Zwerge die Kosmologie heraus” ist jetzt online veröffentlicht worden. Er wird in gedruckter Form Anfang 2024 in der Zeitschrift “Physik in unserer Zeit” erscheinen, die sich nicht an ein Fachpublikum, sondern an ein breiteres Publikum mit Physik-Vorbildung richtet (z.B. Physiker, Ingenieure, Lehrer). Der Text ist also eine gute Gelegenheit für alle, die etwas mehr über meine Forschung erfahren möchten, ohne sich durch primäre Forschungsartikel oder Reviews arbeiten zu müssen. Der Artikel ist außerdem frei zugänglich!

With my collaborators around Francois Hammer (GEPI, Paris Observatory) we have published a new series of papers on the dwarf galaxies surrounding the Milky Way:

1. “The accretion history of the Milky Way – I. How it shapes globular clusters and dwarf galaxies“, Hammer, F., Li, H., Mamon, G. A., Pawlowski, M. S., Bonifacio, P., Jiao, Y., Wang, H., Wang, J., Yang, Y. (2023), MNRAS, 519, 5059.
2. “The accretion history of the Milky Way. II. Internal kinematics of globular clusters and of dwarf galaxies“, Hammer, F., Wang, J., Mamon, G. A., Pawlowski, M. S., Yang, Y., Jiao, Y., Li, H., Bonifacio, P., Caffau, E., Wang, H. (2023), MNRAS, 527, 2718.
3. “The Accretion History of the Milky Way: III. Hydrodynamical Simulations of Galactic Dwarf Galaxies at First Infall“, Wang, J., Hammer, F., Yang, Y., Pawlowski, M. S., Mamon, G. A., Wang, H. (2023), arXiv: 2311.05687

The results indicate that many of them might have been accreted only recently, which in turn does not give them much time to be transformed from the gas-rich, rotating dwarfs found at larger distances from the Milky Way, to the gas-free pressure-supported dwarf spheroidals in the vicinity of our Galaxy. We propose that gas-dominated, dark matter free dwarfs might fit the bill, as they are both transformed quickly and also undergo “ram-pressure breaking” which slows them down. Upon being stripped of their gas by the hot halo of the Milky Way, their stellar distribution expands (see this video). Interestingly, this can explain why for many observed dwarfs stars are now found at very large distances. Ultimately, the dwarfs end up out of equilibrium, which means that common estimates of their dark matter content that must assume equilibrium might be unreliable. 

If you want to know a bit more without reading the papers in full: press releases on the topic were just published by both the Leibniz Institute for Astrophysics and the Paris Observatory.