Low-surface brightness galaxies
The nature of very low surface brightness galaxies with large effective radii (recently been dubbed “Ultra Diffuse Galaxies” or “UDGs”) has been intensely debated in past years. This debate has focused on the possible differences between UDGs and the general galaxy population with the same luminosity (i.e. dwarf galaxies) and, in particular, on the amount of dark matter these galaxies may possess. While the vast majority of works point to UDGs having the properties of dwarf galaxies, some UDGs do not fit nicely into the categories of “normal” dwarf galaxies, as their dark matter content has been suggested to be very high or very low. In my current research, I study the dark matter content and formation of these objects by means of ground-based and space-based observations.
(Image credit: T. Saifollahi, NASA/HST)
Ultra-compact dwarf galaxies
Ultra-compact dwarfs or UCDs resemble globular clusters (GCs) but they are larger, brighter and more massive than any Milky Way GCs. UCDs resemble globular clusters (GCs) but are more luminous and more massive. They are expected to have various origins including the nuclear star cluster of stripped dwarf galaxies and massive GCs. Currently I am searching for UCDs in the Fornax cluster to learn more about various astrophysical processes that can give birth to such massive stellar systems in galaxy clusters.
(Image credit: X-ray: NASA/CXC/MSU/J.Strader et al, Optical: NASA/STScI)
Ultra-compact dwarfs beyond the centre of the Fornax galaxy cluster: hints of UCD formation in low-density environments (ADS), Teymoor Saifollahi, Joachim Janz, Reynier F Peletier, Michele Cantiello, Michael Hilker, Steffen Mieske, Edwin A Valentijn, Aku Venhola, Gijs Verdoes Kleijn, Monthly Notices of the Royal Astronomical Society, 2021 (in the media: phys.org)
The number of globular clusters around the iconic UDG DF44 is as expected for dwarf galaxies (ADS), Teymoor Saifollahi, Ignacio Trujillo, Michael A Beasley, Reynier F Peletier, Johan H Knapen, Monthly Notices of the Royal Astronomical Society, 2021 (in the media: space.com, Youtube)