Simultaneous X-ray and UV spectroscopy of the Seyfert galaxy NGC 5548 - II. Physical conditions in the X-ray absorber

By K. Steenbrugge, J. Kaastra, D. Crenshaw, S. Kraemer, N. Arav, I. George, D. Liedahl, R. Meer, F. Paerels, T. J. Turner and 1 more. 2005

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We present the results from a 500 ks Chandra observation of the Seyfert 1 galaxy NGC 5548. We detect broadened (full width half maximum = 8000 km s −1 ) emission lines of O  and C  in the spectra, similar to those observed in the optical and UV bands. The source was continuously variable, with a 30% increase in luminosity in the second half of the observation. The gradual increase in luminosity occurred over a timescale of ∼300 ks. No variability in the warm absorber was detected between the spectra from the first 170 ks and the second part of the observation. The longer wavelength range of the LETGS resulted in the detection of absorption lines from a broad range of ions, in particular of C, N, O, Ne, Mg, Si, S and Fe. The velocity structure of the X-ray absorber is consistent with the velocity structure measured simultaneously in the ultraviolet spectra. We find that the highest velocity outflow component, at −1040 km s −1 , becomes increasingly important for higher ionization parameters. This velocity component spans at least three orders of magnitude in ionization parameter, producing both highly ionized X-ray absorption lines (Mg  ,S i) as well as UV absorption lines. A similar conclusion is very probable for the other four velocity components. Based upon our observations, we argue that the warm absorber probably does not manifest itself in the form of photoionized clumps in pressure equilibrium with a surrounding wind. Instead, a model with a continuous distribution of column density versus ionization parameter gives an excellent fit to our data. From the shape of this distribution and the assumption that the mass loss through the wind should be smaller than the accretion rate onto the black hole, we derive upper limits to the solid angle as small as 10 −4 sr. From this we argue that the outflow occurs in density-stratified streamers. The density stratification across the stream then produces the wide range of ionization parameter observed in this source. We determine an upper limit of 0.3 Myr −1 for the mass loss from the galaxy due to the observed outflows.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/c492ee78c56a08c8afe6ba11017f747b403927cc

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Citations in the corpus

The Compact, Conical, Accretion-Disk Warm Absorber of the Seyfert 1 Galaxy NGC 4051 and Its Implications for IGM-Galaxy Feedback Processes (2007, background): “…of the warm absorbers in our line of sight is that of a continuous range of ionization structures spanning a large radial region (of the order of pc) in the nuclear environment, and spanning more than two orders of magnitude in ionization parameter (e.g. Ogle et al. 2004, Steenbrugge et al. 2005).”
Quasar outflows and AGN feedback in the extreme UV: HST/COS observations of HE 0238−1904 (2013, background): “X-ray observations of Seyfert outflows, the so-called “warm absorbers”, routinely show the need for two or more ionization phases (e.g., Netzer et al. 2003; Steenbrugge et al. 2005; Holczer et al. 2007).”
On the origin of soft X-rays in obscured AGN: answers from high-resolution spectroscopy with XMM–Newton (2006, result): “Interestingly enough, these values are in good agreement with the column densities measured in “warm absorbers” observed along the lines of sight to unobscured AGN (Blustin et al. 2003; Steenbrugge et al. 2005; Blustin et al. 2005).”
A semi-analytic model for the co-evolution of galaxies, black holes and active galactic nuclei (2008, background): “However, their impact on the host galaxy remains unclear, as the mass outflow rates of these winds are difficult to constrain (though see Steenbrugge et al. 2005; Chartas et al. 2007; Krongold et al. 2007).”
Stellar and Quasar Feedback in Concert: Effects on AGN Accretion, Obscuration, and Outflows (2015, background): “These manifest themselves observationally as the broad emission line regions and broad absorption line quasars (e.g. Weymann et al. 1981; de Kool et al. 2001; Gabel et al. 2006; Ganguly et al. 2007), more moderate velocity outflows (v ∼ 102− 103 kms−1) associated with the narrow line region and the ”
Quasar feedback: more bang for your buck (2009, background): “…from the central engine of a quasar is sufficient to unbind the cold gas in the host (see e.g. Baum & McCarthy 2000; de Kool et al. 2001, 2002; Steenbrugge et al. 2005; Gabel, Arav & Kim 2006; Holt et al. 2006; Batcheldor et al. 2007; Ganguly et al. 2007; Krongold et al. 2007; McKernan,…”