Galaxies as High-resolution Telescopes

Abstract

Recent observations show a population of active galaxies with milliarcseconds offsets between optical and radio emission. Such offsets can be an indication of extreme phenomena associated with supermassive black holes including relativistic jets, binary supermassive black holes, or even recoiling supermassive black holes. However, the multi-wavelength structure of active galaxies at a few milliarcseconds cannot be resolved with direct observations. We propose using strong gravitational lensing to elucidate the multi-wavelength structure of sources. When sources are located close to the caustic of lensing galaxy, even small offset in the position of the sources results in a drastic difference in the position and magnification of mirage images. We show that the angular offset in the position of the sources can be amplified more than 50 times in the observed position of mirage images. We find that at least 8% of the observed gravitationally lensed quasars will be in the caustic configuration. The synergy between SKA and Euclid will provide an ideal set of observations for thousands of gravitationally lensed sources in the caustic configuration, which will allow us to resolve the multiwavelength structure for a large ensemble of sources, and study the physical origin of radio emissions, their connection to supermassive black holes, and their cosmic evolution.

Constraining VLBI−optical offsets in high redshift galaxies using strong gravitational lensing

“…Selected systems, CLASS B0712+472 and CLASS B1608+656, are both quadruply-imaged in fold configuration. Therefore, they are ideal to use their properties as lensed systems for spatially locating the multi-wavelength emission (Barnacka 2017). Below, we provide an overview of the properties of these two systems.…”

“…As the caustics in a gravitational potential of lensing galaxies act as non-linear amplifiers, the created multiple lensed images provide strong constraints on the model of the lens (e.g. Barnacka 2017Barnacka , 2018. A precise lens model is critical for reconstructing the position of the source with high accuracy.…”

“…Magnification and positions of lensed images change rapidly depending on the distance from the source to the caustics. Such non-linear amplification in the position of lensed images and magnifications can be used to improve spatial resolution by orders of magnitude as proposed by Barnacka (2017Barnacka ( , 2018 (we refer to Congdon & Keeton 2018 for an in-depth description of critical and caustic curves). The combination of gravitational lensing with high angular resolution observations can give access to the pc and sub-pc scales of distant galaxies, and can be used to reveal offset-AGN even at high redshift (e.g.…”

Gravitational lenses as high-resolution telescopes

“…Resolving complex multi-wavelength emission of distant sources is still precluded by the limited resolution and astrometry of current and future instruments. To overcome these technological limitations, Barnacka (2017) demonstrated that caustics of lensing galaxies can act as non-linear amplifiers and can be used to enhance the performance of telescopes by orders of magnitude using only relative positions of lensed images.…”

“…Resolving the multi-wavelength emission of the inner regions of active galaxies requires angular resolution and astrometric accuracy below 1 mas, which is challenging to achieve with current and future facilities. Barnacka (2017) proposed using caustics of lensing galaxies to study the multi-wavelength structure of sources. The caustic of the lensing galaxy is a place where lensed images merge or separate.…”