English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

An extended XMM-Newton observation of the Seyfert 1 galaxy NGC 4051 in 2009revealed an unusually rich absorption spectrum with outflow velocities, in bothRGS and EPIC spectra, up to ~ 9000 km/s (Pounds and Vaughan 2011). Evidence wasagain seen for a fast ionised wind with velocity ~ 0.12c (Tombesi 2010, Poundsand Vaughan 2012). Detailed modelling with the XSTAR photoionisation code nowconfirms the general correlation of velocity and ionisation predicted by massconservation in a Compton-cooled shocked wind (King 2010). We attribute thestrong column density gradient in the model to the addition of strong two-bodycooling in the later stages of the flow, causing the ionisation (and velocity)to fall more quickly, and confining the lower ionisation gas to a narrowerregion. The column density and recombination timescale of the highly ionisedflow component, seen mainly in Fe K lines, determine the primary shellthickness which, when compared with the theoretical Compton cooling length,determines a shock radius of ~ 10^17 cm. Variable radiative recombinationcontinua (RRC) provide a key to scaling the lower ionisation gas, with the RRCflux then allowing a consistency check on the overall flow geometry. Weconclude that the 2009 observation of NGC 4051 gives strong support to the ideathat a fast, highly ionised wind, launched from the vicinity of thesupermassive black hole, will lose much of its mechanical energy after shockingagainst the ISM at a sufficiently small radius for strong Compton cooling.However, the total flow momentum will be conserved, retaining the potential fora powerful AGN wind to support momentum-driven feedback (King 2003; 2005). Wespeculate that the `warm absorber' components often seen in AGN spectra resultfrom accumulation of shocked wind and ejected ISM.

The shocked outflow in NGC 4051 - momentum-driven feedback, UFO's and warm absorbers