The Gravitational Lens B1608+656: I. V, I, and H-band HST Imaging

Abstract

We present a multi-wavelength analysis of high-resolution observations of the quadruple lens B1608+656 from the HST archive, acquired with WFPC2 through filters F606W (V-band) and F814W (I-band), and with NIC1 in filter F160W (H-band). In the three bands, the observations show extended emission from the four images of the source in a ring-like configuration that surrounds the two, resolved, lensing galaxies. B1608+656 was discovered as a double-lobed radio source, and later identified as a post-starburst galaxy in the optical. Based on photometry and optical spectroscopy we estimate that the stellar population of the source has an age of $\sim$ 500 Myr. This provides a model for the spectrum of the source that extends over spectral regions where no observations are available, and is used to generate Tiny Tim PSFs for the filters. Deconvolutions performed with the Lucy-Richardson method are presented, and the limitations of these restorations is discussed. V$-$I and I$-$H color maps show evidence of extinction by dust associated with one of the lensing galaxies, a late type galaxy presumably disrupted after its close encounter with the other lens, an elliptical galaxy. The extinction affects the two lens galaxies and two of the four multiple images. The diagnostic of wavelength-dependent effects in the images shows that corrections for contamination with light from the lenses, extinction, and PSF convolution need to be applied before using the extended structure in the images as a constraint on lens models. We will present the restoration of the images in a subsequent paper.