WFI J2026-4536 and WFI J2033-4723: Two New Quadruple Gravitational Lenses

Abstract

We report the discovery of two new gravitationally lensed quasars, WFI J2026-4536 and WFI J2033-4723, at respective source redshifts of z=2.23 and z=1.66. Both systems are quadruply imaged and have similar PG 1115-like image configurations. WFI J2026-4536 has a maximum image separation of 1.4", a total brightness of g=16.5, and a relatively simple lensing environment, while WFI J2033-4723 has a maximum image separation of 2.5", an estimated total brightness of g~17.9, and a more complicated environment of at least six galaxies within 20". The primary lensing galaxies are detected for both systems after point-spread function subtraction. Several of the broadband flux ratios in these systems show a strong (0.1-0.4 mag) trend with wavelength, suggesting either microlensing or differential extinction through the lensing galaxy. For WFI J2026-4536, the total quasar flux has dimmed by 0.1 mag in the blue but only half as much in the red over 3 months, suggestive of microlensing-induced variations. For WFI J2033-4723, resolved spectra of some of the quasar components reveal emission-line flux ratios that agree better with the macromodel predictions than either the broadband or continuum ratios, also indicative of microlensing. The predicted differential time delays for WFI J2026-4536 are short, ranging from 1 to 2 weeks for the long delay, but are longer for WFI J2033-4723, ranging from 1 to 2 months. Both systems hold promise for future monitoring campaigns aimed at microlensing or time delay studies.

Based on observations obtained with the MPG/ESO 2.2 m telescope, the CTIO 1.5 m telescope, and the Clay and Baade 6.5 m telescopes at the Las Campanas Magellan Observatories. Also based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Rsearch in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with HST program 9744.