VIBI Observations of Two Quasars at 1.3cm

The quasars, 0748+126 and 2251+158 (3C 454.3), have been observed at 1.3cm by using aglobal VLBI network.We have obtained the images of the quasarswith a resolution higher than 0.001.The brightness distribution is revealed in the nuclear region of the quasars.The radio emission FWHM from 0748+126 is 0.61×0.27 mas.2251+158 shows a nucleus-jet structure, and the nuclear region is elongated in the direction PA =-130°, The quasar can be fitted with 4 Gaussian components.The most west and east components are separated by 0.8mas (3pc).The integrated flux density in the nuclear region is 6.138Jy.The most east component shows the highest brightness, and its flux is～4.11Jy (in 67% of the total detected flux), concent rated in the area of 0.16×0.01 mas.This causes the brightness temperature up to 2.6×10¹²K.