Answer Happy

2. Two lensing galaxies of different masses are observed to lens identical background QSOs. a) A type 1 SN (known to be a standard candle) is found in both lensing galaxies, in the first we detect a SN flux of 2.5x 10-15 W/m² and in the second we detect a SN flux of 5x10-15 W/m². What are the distances to the two lensing galaxies in units of Mpc? [2] b) The two background QSOs have measured redshifts of 1.4 and 2.6. Given that the angular radius of the Einstein ring we observe is twice as big for the first lensing galaxy as the second, what is the ratio of the lens masses? (assume Ho=70 km/s/Mpe) Hint: first obtain the velocities of

the QSOs and use Hubble's Law [6] c) An astronomer makes an observational error and measures the distance to the redshift 1.4 QSO to be 4Gpc. What would they determine H, to be (2)? How much older would they subsequently determine the Universe to be compared to someone obtaining the age from Ho = 70km/s/Mpc? [2]