X-ray imaging of the ionisation cones in NGC 5252

Dadina, M.; Guainazzi, M.; Cappi, M.; Bianchi, S.; Vignali, C.; Malaguti, G.; Comastri, A.

doi:10.1051/0004-6361/200913727

Cited by 33 publications

(37 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The FWHM of the ionized gas inside the cone is around 200–300 km s −1 . The density is <10 3 cm −3 , without a radial trend, in contrast to the results found by Dadina et al (2010) in NGC 5252. These authors derived a r −2 relation from the constant [O iii ]/(0.5–2 keV) flux ratio, which suggests a radial independence of the ionization parameter.…”

Section: Ionization Conecontrasting

confidence: 88%

The origin of gas in extended narrow-line regions of nearby Seyfert galaxies - I. NGC 7212

Cracco¹,

Ciroi²,

Mille³

et al. 2011

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

The extended narrow‐line region (ENLR) of an active galactic nucleus (AGN) is a region of highly ionized gas with a size of a few up to 15–20 kpc. When it shows a conical or biconical shape with the apexes pointing towards the active nucleus, this region is also called an ionization cone. Ionization cones are evidence of the unified model, which predicts an anisotropic escape of ionizing photons from a nucleus confined to a cone by a dusty torus. Many details about the complex structure of the ENLR still remain to be unveiled, such as for example the origin of the ionized gas. Here we present new results of a study of the physical and kinematic properties of the circumnuclear gas in the nearby Seyfert 2 galaxy NGC 7212. Medium‐ and high‐resolution integral‐field spectra and broad‐band photometric data were collected and analysed in the frame of an observational campaign of nearby Seyfert galaxies, with the aim of handling the complicated issue of the origin of gas in the ENLR. This work is based on (i) the analysis of gas physical properties (density, temperature and metallicity), (ii) the analysis of emission‐line ratios and (iii) the study of kinematics of gas and stars. By reconstructing the [O iii]/Hβ ionization map, we point out for the first time the presence of an ionization cone extended up to about 6 kpc, made of a large amount of low‐metallicity gas, kinematically disturbed and decoupled from stars, a highly ionized component of which shows radial motions at multiple velocities, as proved by the complex profiles of the spectral lines. Since NGC 7212 is a strongly interacting triple galaxy system, gravitational effects are likely to be at the origin of the ENLR in this Seyfert galaxy.

show abstract

Section: Ionization Conecontrasting

confidence: 88%

The origin of gas in extended narrow-line regions of nearby Seyfert galaxies - I. NGC 7212

Cracco¹,

Ciroi²,

Mille³

et al. 2011

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…At the adopted 5-σ confidence level, a broadened relativistic line is detected in only two sources. In both cases, this detection has been reported A131, page 4 of 13 Beckmann et al 2004), and NGC 5252 (Dadina et al 2010). The detection fraction in GREDOS ( 15%) is nominally smaller than for unobscured AGN.…”

Section: Spectral Resultsmentioning

confidence: 53%

On the driver of relativistic effect strength in Seyfert galaxies

Guainazzi¹,

Bianchi²,

Pérez³

et al. 2011

A&A

Self Cite

View full text Add to dashboard Cite

Context. Spectroscopy of X-ray emission lines emitted from accretion discs around supermassive black holes is one of the most powerful probes of the accretion flow physics and geometry, while also providing in principle observational constraints on the black hole spin. Previous studies have suggested that relativistically broadened line profiles are fairly common in nearby unobscured Seyfert galaxies. Their strength, as parametrised by the equivalent width (EW) against the total underlying continuum, spans a range of almost two orders of magnitude. Aims. We attempt to determine the ultimate physical driver of the strength of this relativistic reprocessing feature. Methods. We first extend the hard X-ray flux-limited sample of Seyfert galaxies studied so far in the framework of the FERO (Finding Extreme Relativistic Objects) project to obscured objects up to a column density N H = 6 × 10 23 cm −2 . We verify that none of the line properties depends on the AGN optical classification, as expected from the Seyfert unification scenarios. There is also no correlation between the accretion disc inclination, as derived from formal fits of the line profiles, and the optical type or host galaxy aspect angle, suggesting that the innermost regions of the accretion disc and the host galaxy plane are not aligned. We use this extended sample to study the dependence of the EW on various observables, and compare it with the predictions of Monte Carlo accretion-disc reprocessing simulation. Results. The behaviour of the EW as a function of disc inclination, shape of the intrinsic power-law nuclear continuum, or iron abundance does not agree with the simulation predictions. Our observational data are not sensitive enough to the detailed ionisation state of the line-emitting disc. However, the lack of dependence of the line EW on either the luminosity or the rest-frame centroid energy rules out disc ionisation playing an important role on the EW dynamical range in Seyferts.Conclusions. The dynamical range of the relativistically broadened K α iron line EW in nearby Seyferts appears to be mainly determined by the properties of the innermost accretion flow. We discuss several mechanisms (disc ionisation, disc truncation, and aberration due to a mildly relativistic outflowing corona) that can explain this. We stress that the above results represent neither a falsification or proof of the relativistically blurring scenario. Observational data still do not contradict scenarios invoking different mechanisms for the spectral complexity around the iron line, most notably the "partial covering" absorption scenario.

show abstract

“…The emission‐line structures can be large and well resolved, offering a way to measure the opening angle over which ionizing radiation escapes. Some previous studies have also noted that these emission‐line clouds provide a view to the immediate past of the AGN, via light travel time to the cloud and then towards us (Dadina et al 2010).…”

Section: Introductionmentioning

confidence: 85%

The Galaxy Zoo survey for giant AGN-ionized clouds: past and present black hole accretion events

Keel¹,

Chojnowski²,

Bennert³

et al. 2011

Monthly Notices of the Royal Astronomical Society

151

195

View full text Add to dashboard Cite

Some active galactic nuclei (AGN) are surrounded by extended emission‐line regions (EELRs), which trace both the illumination pattern of escaping radiation and its history over the light travel time from the AGN to the gas. From a new set of such EELRs, we present evidence that the AGN in many Seyfert galaxies undergo luminous episodes 0.2–2 years in duration. Motivated by the discovery of the spectacular nebula known as Hanny’s Voorwerp, ionized by a powerful AGN which has apparently faded dramatically within years, Galaxy Zoo volunteers have carried out both targeted and serendipitous searches for similar emission‐line clouds around low‐redshift galaxies. We present the resulting list of candidates and describe spectroscopy identifying 19 galaxies with AGN‐ionized regions at projected radii kpc. This search recovered known EELRs (such as Mrk 78, Mrk 266 and NGC 5252) and identified additional previously unknown cases, one with detected emission to kpc. One new Sy 2 was identified. At least 14/19 are in interacting or merging systems, suggesting that tidal tails are a prime source of distant gas out of the galaxy plane to be ionized by an AGN. We see a mix of one‐ and two‐sided structures, with observed cone angles from 23 to 112. We consider the energy balance in the ionized clouds, with lower and upper bounds on ionizing luminosity from recombination and ionization‐parameter arguments, and estimate the luminosity of the core from the far‐infrared data. The implied ratio of ionizing radiation seen by the clouds to that emitted by the nucleus, on the assumption of a non‐variable nuclear source, ranges from 0.02 to ; 7/19 exceed unity. Small values fit well with a heavily obscured AGN in which only a small fraction of the ionizing output escapes to be traced by surrounding gas. However, large values may require that the AGN has faded over tens of thousands of years, giving us several examples of systems in which such dramatic long‐period variation has occurred; this is the only current technique for addressing these time‐scales in AGN history. The relative numbers of faded and non‐faded objects we infer, and the projected extents of the ionized regions, give our estimate (0.2–2 years) for the length of individual bright phases.

show abstract

X-ray imaging of the ionisation cones in NGC 5252

Cited by 33 publications

References 48 publications

The origin of gas in extended narrow-line regions of nearby Seyfert galaxies - I. NGC 7212

The origin of gas in extended narrow-line regions of nearby Seyfert galaxies - I. NGC 7212

On the driver of relativistic effect strength in Seyfert galaxies

The Galaxy Zoo survey for giant AGN-ionized clouds: past and present black hole accretion events

Contact Info

Product

Resources

About