ULASJ1234+0907: the reddest type 1 quasar at z = 2.5 revealed in the X-ray and far-infrared

Abstract

We present Herschel and XMM-Newton observations of ULASJ1234+0907 (z = 2.503), the reddest broad-line type 1 quasar currently known with (i - K)AB > 7.1. Herschel observations indicate that the quasar host is a hyperluminous infrared galaxy with a total infrared luminosity of log10(LIR/L⊙) = 13.90 ± 0.02. A greybody fit gives a dust temperature of Td = 60 ± 3 K assuming an emissivity index of β = 1.5, considerably higher than in submillimeter bright galaxies observed at similar redshifts. The star formation rate is estimated to be >2000 M⊙ yr-1 even accounting for a significant contribution from an active galactic nucleus (AGN) component to the total infrared luminosity or requiring that only the far-infrared luminosity is powered by a starburst. XMM-Newton observations constrain the hard X-ray luminosity to be L2-10 keV = 1.3 × 1045 erg s-1, putting ULASJ1234+0907 among the brightest X-ray quasars known. Through very deep optical and near-infrared imaging of the field at subarcsecond seeing, we demonstrate that despite its extreme luminosity, it is highly unlikely that ULASJ1234+0907 is being lensed. We measure a neutral hydrogen column density of NH = 9.0 × 1021 cm-2 corresponding to AV ∼ 6. The observed properties of ULASJ1234+0907 - high luminosity and Eddington ratio, broad lines, moderate column densities and significant infrared emission from reprocessed dust - are similar to those predicted by galaxy formation simulations for the AGN blowout phase. The high Eddington ratio, combined with the presence of significant amounts of dust, is expected to drive strong outflows due to the effects of radiation pressure on dust.

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ORCID for Manda Banerji: orcid.org/0000-0002-0639-5141

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