Current Research

Ultra-diffuse galaxies and their Globular Clusters

Ultra-diffuse galaxies (UDGs), a term that was introduced by Peter van Dokkum and collaborators in 2015, refers to galaxies with very low-surface brightness and large effective radius (comparable to the Milky Way). This objects are found to be surprising in different aspects and in the last 5 years, many work have been done on UDGs, observations and simulations. While it seems that the majority of these objects are normal dwarfs that are expanded (for example due to internal stellar feedback or external tidal interactions), a few extreme cases have been attracted more attention. In my current research, I study the dark matter content and formation of these objects through their globular clusters.

Formation of Ultra-compact dwarfs

Ultra-compact dwarfs or UCDs resemble globular clusters (GCs) but they are larger, brighter and more massive than any Milky Way GCs. While the majority of them are expected to originate from GCs (whether massive GCs or the result of merged GCs), some of them are the stripped nuclei of dwarf galaxies (and carry a supermassive black hole in their center). However, all the knowledge that we have comes from observations around galaxies and in the center of galaxy clusters (high-density environments). Therefore, we do not know much about the UCDs that may be found/formed in low-density environments. Currently, I’m searching for such objects.

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Search for the weirdest galaxies in the universe

Most of the major astronomical discoveries are unplanned. For example, of the 10 greatest discoveries made by the Hubble Space Telescope, only one was listed in its key science goals. However, because of the large volume and complexity of the data from astronomical surveys, these discoveries are unlikely to be found by chance. Therefore, novel techniques in data mining are required to detect anomalies in the data and discover the unexpected.

Main Publications

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,

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Quasar Candidates behind the Milky Way Disk and M31 (ADS)

Kovács, Tímea Orsolya; Loukaidou, Georgia; Pennock, Clara; Saifollahi, Teymoor; Umbriaco, Gabriele; Ivanov, Valentin D.; Nedialkov, Petko; Korhonen, Heidi; Pizzella, Alessandro; Costantin, Luca; Berton, Marco; Tóth, L. Viktor

Research Notes of the American Astronomical Society

BSc/MSc projects


Lorraine Putman (MSc Astronomy), Globular clusters around the low-surface brightness galaxies in the Fornax galaxy cluster


Job Formsma (MSc Astronomy), In search of the weirdest galaxies in the universe (

Jarvin Mutatiina (MSc Computer Science), Classification and Feature Relevance Determination of Imbalanced Astronomical Data (

Sander Verdult (BSc Astronomy), Unsupervised feature selection in Astronomical surveys (