The Time Delays of Gravitational Lens HE 0435-1223: An Early-Type Galaxy with a Rising Rotation Curve

Abstract

We present Hubble Space Telescope images and 2 years of optical photometry of the quadruple quasar HE 0435-1223. The time delays between the intrinsic quasar variations are Δt_AD=-14.37^+0.75_-0.85, Δt_AB=-8.00^+0.73_-0.82, and Δt_AC=-2.10^+0.78_-0.71 days. We also observed nonintrinsic variations of ~0.1 mag yr^-1 that we attribute to microlensing. Instead of the traditional approach of assuming a rotation curve for the lens galaxy and then deriving the Hubble constant (H₀), we assume H₀=(72+/-7) km s^-1 Mpc^-1 and derive constraints on the rotation curve. On the scale over which the lensed images occur (1.2"=5 h^-1 kpc~=1.5R_e), the lens galaxy must have a rising rotation curve, and it cannot have a constant mass-to-light ratio. These results add to the evidence that the structures of early-type galaxies are heterogeneous.

Based on observations obtained with the 1.3 m telescope of the Small and Moderate Aperture Research Telescope System (SMARTS), which is operated by the SMARTS Consortium; the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium; and the NASA/ESA Hubble Space Telescope as part of program HST-GO-9744 of the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.