Letter to the Editor
Yet another UFO in the X-ray spectrum of a high-z lensed QSO
INAF/OAS, Osservatorio di Astrofisica e Scienza dello Spazio di Bologna,
via Gobetti 93/3,
2 Dipartimento di Fisica e Astronomia dell’Universitá degli Studi di Bologna, via P. Gobetti 93/2, 40129 Bologna, Italy
3 Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
4 Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Bartycka 18, 00-716 Warsaw, Poland
5 Department of Physics and Astronomy of the College of Charleston, Charleston, SC 29424, USA
6 SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
Accepted: 18 January 2018
Aim. Ultra-fast outflows (UFO) appear to be common in local active galactic nuclei (AGN) and may be powerful enough (Ėkin ≥ 1% of Lbol) to effectively quench the star formation in their host galaxies. To test feedback models based on AGN outflows, it is mandatory to investigate UFOs near the peak of AGN activity, that is, at high-z where only a few studies are available to date.
Methods. UFOs produce Fe resonant absorption lines measured above ≈7 keV. The most critical problem in detecting such features in distant objects is the difficulty in obtaining X-ray data with sufficient signal-to-noise. We therefore selected a distant QSO that gravitational lensing made bright enough for these purposes, the z = 2.64 QSO MG J0414+0534, and observed it with XMM-Newton for ≈78 ks.
Results. The X-ray spectrum of MG J0414+0534 is complex and shows signatures of cold absorption (NH ≈ 4 × 1022 cm−2) and of the presence of an iron emission line (E ≈ 6.4 keV, EW = 95 ± 53 eV) consistent with it originating in the cold absorber. Our main result, however, is the robust detection (more than 5σ) of an absorption line at Eint ≈ 9.2 keV (Eobs ≈ 2.5 keV observer frame). If interpreted as due to FeXXVI, it implies gas outflowing at vout ≈ 0.3c. To our knowledge, this is the first detection of an UFO in a radio-loud quasar at z ≥ 1.5. We estimated that the UFO mechanical output is Ėkin ≈ 2.5Lbol with ṗout∕ṗrad ≈ 17 indicating that it is capable of installing significant feedback between the super-massive black hole and the bulge of the host galaxy. We argue that this also suggests a magnetic driving origin of the UFO.
Key words: galaxies: high-redshift / quasars: individual: MG J0414+0534 / X-rays: individuals: MG J0414+0534
© ESO 2018