PG-1700- ADAPTIVE-OPTICS IMAGING AND A REVISED STARBURST AGE FOR THE COMPANION(518 REVISITED )

We present the results of adaptive-optics imaging of the z = 0.2923 QS O PG 1700+518 in the J and H bands. The extension to the north of the QSO is clearly seen to be a discrete companion with a well-defined tid al tail, rather than a feature associated with the host galaxy of PG 1 700+518 itself. On the other hand, an extension to the southwest of th e QSO (seen best in deeper, but lower resolution, optical images) does likely comprise tidal material from the host galaxy. The spectral ene rgy distribution (SED) derived from images in J, H, and two nonstandar d optical bands indicates the presence of dust intermixed with the ste llar component. We use our previously reported Keck spectrum of the co mpanion, the SED found from the imaging data, and updated spectral syn thesis models to constrain the stellar populations in the companion an d to redetermine the age of the starburst. While our best-fit age of 0 .085 Gyr is nearly the same as our earlier determination, the fit of t he new models is considerably better. This age is found to be remarkab ly robust with respect to different assumptions about the nature of th e older stellar component and the effects of dust.