PG 1700+518 revisited: Adaptive-optics imaging and a revised starburst age for the companion

Alan Stockton, Gabriela Canalizo, Laird M. Close

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28 Scopus citations


We present the results of adaptive-optics imaging of the z = 0.2923 QSO 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 tidal tail, rather than a feature associated with the host galaxy of PG 1700+518 itself. On the other hand, an extension to the southwest of the QSO (seen best in deeper, but lower resolution, optical images) does likely comprise tidal material from the host galaxy. The spectral energy distribution (SED) derived from images in J, H, and two nonstandard optical bands indicates the presence of dust intermixed with the stellar component. We use our previously reported Keck spectrum of the companion, the SED found from the imaging data, and updated spectral synthesis models to constrain the stellar populations in the companion and 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 the new models is considerably better. This age is found to be remarkably robust with respect to different assumptions about the nature of the older stellar component and the effects of dust.

Original languageEnglish (US)
Pages (from-to)L121-L127
JournalAstrophysical Journal
Issue number2 PART II
StatePublished - 1998


  • Galaxies: interactions

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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