AGN feedback in action: a new powerful wind in 1SXPS J050819.8+172149?^⋆

¹ Osservatorio Astronomico di Brera (INAF), via Brera 28, 20121 Milano, Italy
e-mail: lucia.ballo@brera.inaf.it
² Osservatorio Astronomico di Brera (INAF), via E. Bianchi 46, 23807 Merate, LC, Italy
³ Department of Physics, University of Maryland, Baltimore County, Baltimore, MD 21250, USA
⁴ Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy
⁵ Osservatorio Astronomico di Bologna (INAF), via Ranzani 1, 40127 Bologna, Italy

Received: 21 May 2015
Accepted: 29 June 2015

Abstract

Context. Galaxy merging is widely accepted to be a driving factor in galaxy formation and evolution, while the feedback from actively accreting nuclei is thought to regulate the black hole-bulge coevolution and the star formation process.

Aims. In this context, we focused on 1SXPS J050819.8+172149, a local (z = 0.0175) Seyfert 1.9 galaxy (L _bol ~ 4 × 10⁴³ erg s^-1). The source belongs to an infrared-luminous interacting pair of galaxies, characterized by a luminosity for the whole system (due to the combination of star formation and accretion) of log (L _IR/L_⊙) = 11.2. We present here the first detailed description of the 0.3–10 keV spectrum of 1SXPS J050819.8+172149, monitored by Swift with nine pointings performed in less than one month.

Methods. The X-ray emission of 1SXPS J050819.8+172149 is analysed by combining all the Swift pointings, for a total of ~72 ks XRT net exposure. The averaged Swift-BAT spectrum from the 70-month survey is also analysed.

Results. The slope of the continuum is Γ ~ 1.8, with an intrinsic column density of ~2.4 × 10²²cm^-2, and a de-absorbed luminosity of ~4 × 10⁴² erg s^-1 in the 2–10 keV band. Our observations provide a tentative (2.1σ) detection of a blueshifted Fe xxvi absorption line (rest-frame E ~ 7.8 keV), thus suggesting the discovery of a new candidate powerful wind in 1SXPS J050819.8+172149. The physical properties of the outflow cannot be firmly assessed owing to the low statistics of the spectrum and to the observed energy of the line, too close to the higher boundary of the Swift-XRT bandpass. However, our analysis suggests that, if the detection is confirmed, the line could be associated with a high-velocity (v _out ~ 0.1c) outflow most likely launched within 80 r _S. To our knowledge this is the first detection of a previously unknown ultrafast wind with Swift. The high column density suggested by the observed equivalent width of the line (EW ~ −230 eV, although with large uncertainties) would imply a kinetic output strong enough to be comparable to the AGN bolometric luminosity.