LINDITA HAMOLLI , ESMERALDA GULIQANI , MIMOZA HAFIZI
KEYWORDS : quasar, galaxy, strong lensing, time delay
ABSTRACT :
Measurement of lensed quasar time delays depends on the quality of the light curves obtained in each split image. These delays are created because the light rays of images follow different paths through the gravitational field of the galaxy and can be measured when the source is time-variable. Generally, the source of variability has a finite size, and when it is widely distributed (>100 pc as a whole), variabilities between split images may not show a good correlation. In these cases, multiple different delays can be measured. We investigate this phenomenon in the case of the double lensed quasars that are expected to be observed by the Roman Space Telescope. Using Monte Carlo simulations, we generate quasar-galaxy systems based on the mass-luminosity function of galaxies and the redshift distribution of both galaxies and quasars taken from observations. Relying on the capabilities of the Roman Telescope, we define the lensed quasars, the time delays between images, and time delay differences for the variability source size in the range of 10 to 1000 pc. We find values of time delay differences exceeding 30 days, and these do not depend on the mass distribution of the lens galaxy. We also conclude that in 30% of double lensed quasars, the light curves will not be correlated, and multiple time delays can be measured.