On the discovery of fast molecular gas in the UFO/BAL quasar APM 08279+5255 at z = 3.912 ^⋆,⋆⋆

¹ INAF Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, 34143 Trieste, Italy
e-mail: feruglio@oats.inaf.it
² Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
³ INAF Osservatorio Astronomico di Roma, via Frascati 33, 00078 Monteporzio Catone, Italy
⁴ Universitá degli Studi di Roma “Tor Vergata”, via Orazio Raimondo 18, 00173 Roma, Italy
⁵ Cavendish Laboratory, University of Cambridge, 19 J.J. Thomson Ave., Cambridge CB3 0HE, UK
⁶ IRAM – Institut de RadioAstronomie Millimétrique, 300 rue de la Piscine, 38406 Saint Martin d’ Hères, France
⁷ Université Grenoble Alpes, IPAG, 38000 Grenoble, France
⁸ INAF Osservatorio Astronomico di Brera, via Brera 28, 20121 Milan, Italy
⁹ Kavli Insitute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
¹⁰ Dipartimento di Fisica e Astronomia, Universitá degli Studi di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy

Received: 14 June 2017
Accepted: 20 September 2017

Abstract

We have performed a high sensitivity observation of the UFO/BAL quasar APM 08279+5255 at z = 3.912 with NOEMA at 3.2 mm, aimed at detecting fast moving molecular gas. We report the detection of blueshifted CO(4−3) with maximum velocity (v95%) of −1340 km s^-1, with respect to the systemic peak emission, and a luminosity of L′ = 9.9 × 10⁹μ^-1 K km s^-1 pc^-2, where μ is the lensing magnification factor. We discuss various scenarios for the nature of this emission and conclude that this is the first detection of fast molecular gas at redshift > 3. We derived a mass flow rate of molecular gas in the range Ṁ = 3−7.4 × 10³M_⊙/yr and momentum boost Ṗ_OF/Ṗ_AGN ~ 2−6, which is therefore consistent with a momentum conserving flow. For the largest Ṗ_OF the scaling is also consistent with an energy conserving flow with an efficiency of ~10−20%. The present data can hardly discriminate between the two expansion modes. The mass loading factor of the molecular outflow η = Ṁ_OF/SFR is ≫ 1. We also detected a molecular emission line at a frequency of 94.83 GHz corresponding to a rest-frame frequency of 465.8 GHz; we tentatively identified this frequency with the cation molecule N₂H⁺(5−4), which would be the first detection of this species at high redshift. We discuss the alternative possibility that this emission is due to a CO emission line from the, so far undetected, lens galaxy. Further observations of additional transitions of the same species with NOEMA can discriminate between the two scenarios.