A broad-band X-ray view of the warm absorber in radio-quiet quasar MR 2251−178

Abstract

We present the analysis of a new broad-band X-ray spectrum (0.6-180.0 keV) of the radioquiet quasar MR 2251−178 which uses both Suzaku and Swift/Burst Alert Telescope data. In accordance with previous observations, we find that the general continuum can be well described by a power law with = 1.6 and an apparent soft excess below 1 keV. Warm absorption is clearly present, and absorption lines due to the Fe unresolved transition array, Fe L (Fe XXIII-XXIV), S XV and S XVI are detected below 3 keV. At higher energies, Fe K absorption from Fe XXV-XXVI is detected and a relatively weak (EW = 25 +12 −8 eV) narrow Fe Kα emission line is observed (E = 6.44 ± 0.04 keV) which is well modelled by the presence of a mildly ionized (ξ 30) reflection component with a low reflection fraction (R < 0.2). At least five ionized absorption components with 10 20 N H 10 23 cm −2 and 0 log ξ /erg cm s −1 4 are required to achieve an adequate spectral fit. Alternatively, we show that the continuum can also be fit if a ∼ 2.0 power law is absorbed by a column of N H ∼ 10 23 cm −2 which covers ∼30 per cent of the source flux. Independent of which continuum model is adopted, the Fe L and Fe XXV Heα lines are well fit by a single absorber outflowing with v out ∼ 0.14c. Such an outflow/disc-wind is likely to be substantially clumped (b ∼ 10 −3 ) in order to not vastly exceed the likely accretion rate of the source.

What drives the growth of black holes?

“…High-velocity winds are also commonly observed using X-ray spectroscopy, which can trace atomic transitions in ionized gas. The presence of highly blueshifted absorption and emission lines in a number of quasars and Seyferts (e.g., PDS 456, PG 1211+143, NGC 4051, 3C 455, MR2251-178) indicate outflows of v ≈ 0.1-0.3c (Pounds et al, 2003;Reeves et al, 2003;Tombesi et al, 2010;Lobban et al, 2011;Gofford et al, 2011), as expected for models of momentum-driven winds, as discussed below. A lower velocity outflow (∼500 km s −1 ) is observed in the local Seyfert 2 galaxy NGC 1068 (although it is confined to the nuclear regions rather than extending on host galaxy scales).…”

Models of the compact jet in GRS 1915+105

“…The AGN feature that possesses the majority of the characteristics of the jet model of GRS 1915+105 are the near‐relativistic outflows that are seen in X‐ray absorption. A few radio quiet quasars have been observed to have out‐flowing, X‐ray absorbing winds with velocities between 0.1 c and 0.6 c (Chartas, Brandt & Gallagher 2003; Pounds et al 2003; Saez, Chartas & Brandt 2009; Gofford et al 2011). The outflow in APM08279+5255 is the most energetic with a mass flux similar to the accretion mass flux and a kinetic luminosity comparable to the thermal luminosity of the accretion flow as in GRS 1915+105 (Saez et al 2009).…”

Accretion disk winds in active galactic nuclei: X‐ray observations, models, and feedback

“…The advent of the higher energy resolution grating spectrometers onboard Chandra and XMM-Newton provided a revolution in these studies, showing that the absorption is be composed of a number of lines and edges from different elements at different ionization states (e.g., Kaspi et al 2002). Importantly, the energies of these lines are found to be systematically blue-shifted compared to the expected values, indicating that the material is likely a wind outflowing from the central regions of these galaxies with velocities in the range of v out ∼ 100-1000 km s −1 (e.g., Kaastra et al 2000;McKernan etal 2007;Gofford et al 2011;Lobban et al 2011;Detmers et al 2011;. Overall, such warm absorbers (WAs) are detected in more than half of local Seyfert galaxies and have ionization and column densities in the range log ξ ∼ 1-3 erg s −1 cm and N H ∼ 10 20 -10 22 cm −2 , respectively (e.g., Crenshaw & Kraemer 2012).…”