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TOPIC: NGC 4051

Blobrana

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Posts: 131433

Date: Jan 24 11:30 2017

RE: NGC 4051	Permalink

Title: Nature of the Warm Absorber Outflow in NGC 4051 Author: Misaki Mizumoto, Ken Ebisawa The Narrow-line Seyfert 1 galaxy NGC 4051 is known to exhibit significant X-ray spectral/flux variations and have a number of emission/absorption features. X-ray observations have revealed that these absorption features are blueshifted, which indicates that NGC 4051 has warm absorber outflow. In order to constrain physical parameters of the warm absorber outflow, we analyze the archival data with the longest exposure taken by XMM-Newton in 2009. We calculate the root-mean-square (RMS) spectra with the grating spectral resolution for the first time. The RMS spectra have a sharp peak and several dips, which can be explained by variable absorption features and non-variable emission lines; a lower-ionized warm absorber (WA1: log xi=1.5,v=-650kms^-1) shows large variability, whereas higher-ionized warm absorbers (WA2: log xi=2.5,v=-4100kms^-1, WA3: log xi=3.4,v=-6100kms^-1) show little variability. WA1 shows the maximum variability at a timescale of ~10^4~s, suggesting that the absorber locates at ~10^3 times of the Schwarzschild radius. The depth of the absorption features due to WA1 and the observed soft X-ray flux are anti-correlated in several observational sequences, which can be explained by variation of partial covering fraction of the double-layer blobs that are composed of the Compton-thick core and the ionized layer (=WA1). WA2 and WA3 show little variability and presumably extend uniformly in the line of sight. The present result shows that NGC 4051 has two types of the warm absorber outflows; the static, high-ionized and extended line-driven disk winds, and the variable, low-ionized and clumpy double-layer blobs. Read more (2319kb, PDF) __________________

Blobrana

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Posts: 131433

Date: Jan 24 11:24 2017

PGC 38068	Permalink

NGC 4051 (also known as IRAS 12005 +4448, MCG 8-22-59, UGC 7030 and PGC 38068) is a magnitude +10.8 inclined barred spiral Seyfert galaxy located about 55 million light-years away in the constellation Ursa Major. The nucleus of the galaxy contains a supermassive black hole with a mass of about 1.9 million solar masses. The galaxy has hosted supernova 1983I, supernova 2003ie and supernova 2010br. The galaxy was discovered by German-British astronomer William Herschel using a 47.5 cm (18.7 inch) f/13 speculum reflector at Windsor Road, Slough, on the 6th February 1788 Right Ascension 12h 03m 9.6s, Declination +44° 31' 55" __________________

Blobrana

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Posts: 131433

Date: May 13 01:12 2013

NGC 4051	Permalink

Title: The shocked outflow in NGC 4051 - momentum-driven feedback, UFO's and warm absorbers Authors: Ken Pounds, Andrew King An extended XMM-Newton observation of the Seyfert 1 galaxy NGC 4051 in 2009 revealed an unusually rich absorption spectrum with outflow velocities, in both RGS and EPIC spectra, up to ~ 9000 km/s (Pounds and Vaughan 2011). Evidence was again seen for a fast ionised wind with velocity ~ 0.12c (Tombesi 2010, Pounds and Vaughan 2012). Detailed modelling with the XSTAR photoionisation code now confirms the general correlation of velocity and ionisation predicted by mass conservation in a Compton-cooled shocked wind (King 2010). We attribute the strong column density gradient in the model to the addition of strong two-body cooling in the later stages of the flow, causing the ionisation (and velocity) to fall more quickly, and confining the lower ionisation gas to a narrower region. The column density and recombination timescale of the highly ionised flow component, seen mainly in Fe K lines, determine the primary shell thickness which, when compared with the theoretical Compton cooling length, determines a shock radius of ~ 10^17 cm. Variable radiative recombination continua (RRC) provide a key to scaling the lower ionisation gas, with the RRC flux then allowing a consistency check on the overall flow geometry. We conclude that the 2009 observation of NGC 4051 gives strong support to the idea that a fast, highly ionised wind, launched from the vicinity of the supermassive black hole, will lose much of its mechanical energy after shocking against the ISM at a sufficiently small radius for strong Compton cooling. However, the total flow momentum will be conserved, retaining the potential for a powerful AGN wind to support momentum-driven feedback (King 2003; 2005). We speculate that the 'warm absorber' components often seen in AGN spectra result from accumulation of shocked wind and ejected ISM. Read more (1191kb, PDF) __________________

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