Photo credits:
Danish Saroee

Martin Sahlén

Natural Sciences Fellow, SCAS.
Researcher and Docent/Associate Professor of Astronomy with specialization in Astrophysics,
Uppsala University

Martin Sahlén received his PhD in Astronomy from the University of Sussex in 2009. He has
held postdoctoral fellowships at the Wellcome Sanger Institute, Stockholm University, and the
University of Oxford. He was a Fulbright Fellow at Johns Hopkins University in 2016. He par-
ticipates in the Euclid satellite project, the telescopes 4MOST and the Square Kilometre Array.

Sahlén’s main field of research concerns the physical processes involved in the formation and
evolution of large-scale structure in the Universe. He has shown that statistical samples of
clusters and voids in the galaxy distribution of the late-time Universe are powerful tools for
measuring the properties of dark energy, dark matter and neutrinos, and for testing whether
General Relativity holds on cosmological scales (Phys. Rev. Lett. 2013, Phys. Rev. D 2018,
2019). He produced the first-ever measurements of cosmological model parameters based on
voids, showing that the existence of the largest known cluster and void is sufficient to infer
the existence of dark energy (Astrop. J. Lett. 2016). In the early Universe, large-scale structure
is tightly linked to the emergence of the first galaxies. This epoch is a unique testbed for primordial
galaxy formation and possible non-standard dark matter and dark energy. Sahlén is developing the
advanced state-of-the-art software GalaxyMC to model and analyse galaxy samples in the early

Sahlén also works on machine learning and inference methods, as well as the philosophy of cosmo-
logy. He has argued that explanations of the geometrical flatness of the Universe or the expected
value for the cosmological constant based on the standard paradigm of cosmic inflation, or multi-
verse scenarios, are empirically untestable. Therefore, he proposed a generalization of Bayesian
probability that extends inference to meta-empirical domains (in The Philosophy of Cosmology,
Cambridge University Press 2017; selected in The Best Writing on Mathematics 2018, M. Pitici [Ed].,
Princeton University Press 2019).

During his time as a Fellow, Sahlén will focus on a project investigating which environments in
galaxies are the best habitats for life on exoplanets and on how common such environments are.

This information is accurate as of the academic year 2020-21.