Recent Advances in Gravitational Lensing and Galactic Dynamics

Dear Colleagues,

About a century after the prediction of the gravitational lensing effect and about four decades after its first observation, gravitational lensing still constitutes an extremely important tool in astrophysics and cosmology, and most of its potential is still hidden. Gravitational lensing was adopted to study the distribution of the stellar component in the Milky Way and other galaxies to study dark matter and dark energy on very large scales. It is now a standard technique that has allowed the discovery of about three hundred exoplanets.

Gravitational lensing manifests on different scales: when the lens images appear separated, we are in the regime called strong (or macro) lensing, which also includes distorted galaxy images including Einstein rings and arcs. If, instead, the distortions induced by the gravitational fields on background objects are much smaller, then we have the weak lensing effect. On the other hand, if one considers the phenomenology of star-on-star lensing, then the resulting angular distance between the images is generally not separable using telescopes, and we are in the microlensing regime. In all of these regimes, the gravitational field can be treated as a weak field approximation. Another scale to which gravitational lensing applies is that involving black holes. In particular, when light rays come very close to the event horizon, they are subject to strong gravitational field effects, and, therefore, the deflection angles are large. This effect is called retrolensing. The current observational facilities (JWST, Euclid, EHT, etc.) and those that are forthcoming open up new avenues for the observation of gravitational lensing effects.

Galactic dynamics deals with the dynamical structure and evolution of galaxies and other stellar systems and provides important information about the dark matter content of many types of astrophysical systems and the existence of massive black holes at the center of galaxies.

Dr. Francesco De Paolis
Prof. Dr. Alexander F. Zakharov
Prof. Dr. Luka Č. Popović
Guest Editors

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• gravitational lensing
• weak lensing
• astrophysics of black holes and neutron stars
• gravitational waves
• astrophysical tests of general relativity
• relativistic astrophysics
• galactic dynamics
• JWST, EHT, and Euclid observations
• exoplanets