Featured Image: Modeling a Cosmic Horseshoe


These beautiful images reveal the Cosmic Horseshoe, a gravitational lens system, in a 20-square-arcsecond field in five different Hubble filter bands. The lovely arc — a nearly complete Einstein ring — is created by the strong gravitational lensing of a background source (or sources) by a foreground object. In this case, the foreground object is a luminous red galaxy, visible as the bright source in the center of the ring. But what is the background, lensed source? Complex modeling of the lens system is necessary to disentangle the observations and reconstruct the source. A study led by Jun Cheng (Purdue University) uses a new method to fit different lens models to Hubble images of the Cosmic Horseshoe. While past models have focused on a scenario in which a single star-forming galaxy is lensed to form the Einstein ring, Cheng and collaborators show that there may be at least two background sources contributing to the total Einstein-ring flux of the Cosmic Horseshoe. For more information, check out the article below!


“Adaptive Grid Lens Modeling of the Cosmic Horseshoe Using Hubble Space Telescope Imaging,” Jun Cheng et al 2019 ApJ 872 185. doi:10.3847/1538-4357/ab0029