PAH emission and star formation in the host of the z ∼ 2 . 56 Cloverleaf QSO

We report the first detection of the 6.2μm and 7.7μm infrared ‘PAH’ emission features in the spectrum of a high redshift QSO, from the Spitzer-IRS spectrum of the Cloverleaf lensed QSO (H1413+117, z∼2.56). The ratio of PAH features and rest frame far-infrared emission is the same as in lower luminosity star forming ultraluminous infrared galaxies and in local PG QSOs, supporting Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany [email protected], [email protected], [email protected], [email protected], [email protected] School of Physics and Astronomy and the Wise Observatory, The Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel [email protected] INAF, Osservatorio Astronomico di Roma, via di Frascati 13, 00040 Monte Porzio Catone, Italy [email protected] ESO, Karl-Schwarzschildstraße 2, 85748 Garching, Germany [email protected] Department of Astronomy and Astrophysics, 525 Davey Laboratory, Pennsylvania State University, University Park, PA 16802, USA [email protected] Department of Astronomy, University of Maryland, College Park, MD 20742-2421, USA [email protected]