Time Delay of QSO 0957+561 and Cosmological Implications

Oscoz, Alejandro; Mediavilla, E.; Goicoechea, Luis Julian; Serra-Ricart, Miquel; Buitrago, J.
Bibliographical reference

Astrophysical Journal Letters v.479, p.L89

Advertised on:
4
1997
Number of authors
5
IAC number of authors
2
Citations
37
Refereed citations
34
Description
We obtain the time delay between the arrival time of the A and B images of the QSO 0957+561. The results of applying two different methods (the discrete cross-correlation function and the dispersion estimation technique) to the observed light curves of the A and B images are presented. The adopted value (time delay) is of Delta tau BA = 424 +/- 3 days (1 sigma ). We have used this time delay as well as a recent measurement of the one-dimensional velocity dispersion of the main lensing galaxy ( sigma gal) to estimate H0. Two H0 = H0( Delta tau BA, sigma gal) relations based on different pictures of the lens galaxy, lead to H0 = 64 ^{+14}_{-15} km s-1 Mpc-1 (2 sigma ) (softened power-law sphere) and H0 = 66 ^{+15}_{-14} km s-1 Mpc-1 (2 sigma ) (King profile plus a point-mass at the center).