Constraining the Size of the Narrow‐Line Region in Distant Quasars

We propose a proper method to measure the size of the narrow line region(NLR) in distant quasars. The apparent angular size of the NLR is, in general,too small to resolve technically. However, it is possible to map the NLR ifwith gravitational lensing. In our method, we directly compare the observedimage of the NLR with the expected lensed images of the NLR for various sourcesizes and lens models. Seeking the best fit image via the comparisonprocedures, we can obtain the best-fit size and the best-fit lens model. Weapply this method to the two-dimensional spectroscopic data of a famous lensedquasar, Q2237+0305. If the lens galaxy resembles the applied lens model, anupper limit to the NLR size can be set 750 pc. Further, we examine how thefitting results will be improved by future observations, taking into accountthe realistic observational effects, such as seeing. Future observations willprovide us more stringent constraints on the size of the NLR and on the densityprofile of the lens galaxy.Comment: 17 pages including 4 figures, accepted to Ap