X-ray study of the double source plane gravitational lens system Eye of Horus observed with XMM–Newton

ABSTRACT A double source plane (DSP) system is a precious probe for the density profile of distant galaxies and cosmological parameters. However, these measurements could be affected by the surrounding environment of the lens galaxy. Thus, it is important to evaluate the cluster-scale mass for detailed mass modelling. We observed the Eye of Horus, a DSP system discovered by the Hyper Suprime-Cam Subaru Strategic Survey (HSC–SSP), with XMM–Newton. We detected two X-ray extended emissions, originating from two clusters, one centred at the Eye of Horus, and the other located ∼100 arcsec north-east to the Eye of Horus. We determined the dynamical mass assuming hydrostatic equilibrium, and evaluated their contributions to the lens mass interior of the Einstein radius. The contribution of the former cluster is $1.1^{+1.2}_{-0.5}\times 10^{12}\, \mathrm{M}_{\odot }$, which is $21\!-\!76{{\ \rm per\ cent}}$ of the total mass within the Einstein radius. The discrepancy is likely due to the complex gravitational structure along the line of sight. On the other hand, the contribution of the latter cluster is only $\sim 2{{\ \rm per\ cent}}$ on the Eye of Horus. Therefore, the influence associated with this cluster can be ignored.

Stylized and photographic eye images do not increase charitable donations in a field experiment

The effects of watching eyes upon prosocial behavior have been explored in various contexts, for example, in relation to charitable donations, honor-system payments and littering. Whilst studies have explored the effects of both photographic and stylized eyes upon prosocial behavior, no study, to our knowledge, has compared stylized eyes to photographic eyes. Here we explored the effects of stylized and photographic eye images upon prosocial behavior assessed via charitable donations in a ‘free cakes’ field experiment. Charitable giving was assessed under six eye image conditions, three stylized eye images (evil eye, eye of Horus, all-seeing eye), one photographic eye image (human eye image) and two control images (geometric shape control and blank control). No difference in the amount of money donated was found between any of the eye image conditions. These results suggest that watching eyes, whether stylized or photographic, are not effective at eliciting prosocial behavior via charitable giving. However, further study contrasting single and paired eye imagery, and exploration of the effects of stylized eye imagery in deterring littering and crime, would be beneficial.