Abstract
Abstract Simultaneous XMM-Newton, NuSTAR, and HST observations, performed in 2017 March, of the nearby (z = 0.184) luminous quasar PDS 456 are presented. PDS 456 had a low X-ray flux compared to past observations, where the first of the two new XMM-Newton observations occurred during a pronounced dip in the X-ray light curve. The broadband X-ray spectrum is highly absorbed, attenuated by a soft X-ray absorber of column density N H = 6 × 1022 cm−2. An increase in obscuration occurs during the dip, which may be due to an X-ray eclipse. In addition, the persistent, fast Fe K outflow is present, with velocity components of −0.25c and −0.4c. The soft absorber is less ionized ( ) compared to the iron K outflow ( ) and is outflowing with a velocity of approximately −0.2c. A soft X-ray excess is present below 1 keV against the highly absorbed continuum and can be attributed to the re-emission from a wide-angle wind. The complex X-ray absorption present in PDS 456 suggests that the wind is inhomogeneous, whereby the soft X-ray absorber originates from denser clumps or filaments that may form farther out along the outflow. In contrast to the X-ray observations, the simultaneous UV spectrum of PDS 456 is largely unabsorbed, where only a very weak broad absorption trough is present blueward of Lyα, compared to a past observation in 2000 when the trough was significantly stronger. The relative weakness of the UV absorption may be due to the soft X-ray absorber being too highly ionized and almost transparent in the UV band.
Highlights
Since their initial detection more than a decade ago (Chartas et al 2002, 2003; Pounds et al 2003; Reeves et al 2003), the presence of ultrafast outflows has been found to be increasingly common in active galactic nuclei (AGNs)
AGN winds could have provided the mechanical feedback that controlled both the formation of stellar bulges and simultaneously self-regulated supermassive black hole growth, leading to the observed M–σ relation for galaxies (Ferrarese & Merritt 2000; Gebhardt 2000). Evidence for the latter process has come from the discovery of massive, large scale molecular outflows (Feruglio et al 2010; Veilleux et al 2013; Cicone et al 2014), which might be driven by the ultrafast outflows launched near the black hole (Feruglio et al 2015, 2017; Tombesi et al 2015; Fiore et al 2017)
We presented simultaneous XMM-Newton, NuSTAR, and Hubble Space Telescope (HST) observations of PDS 456, observed in 2017 March
Summary
Since their initial detection more than a decade ago (Chartas et al 2002, 2003; Pounds et al 2003; Reeves et al 2003), the presence of ultrafast outflows has been found to be increasingly common in active galactic nuclei (AGNs). The fast wind in PDS 456 was first discovered in an XMM-Newton observation in 2001 (Reeves et al 2003), through the detection of deep blueshifted absorption troughs, both above 7 keV in the iron K band and above 1 keV in the iron L-shell band Since this initial detection, the persistence of the ultrafast outflow in PDS 456 has become established through over a decade’s worth of X-ray observations (Reeves et al 2009; Behar et al 2010; Gofford et al 2014; Reeves et al 2014; Hagino et al 2015; Nardini et al 2015; Matzeu et al 2016, 2017; Parker et al 2018).
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