Iron Is Not Depleted in High-Ionization Nuclear Emission-Line Regions of Active Galactic Nuclei

Nagao, Tohru; Murayama, Takashi; Shioya, Yasuhiro; Taniguchi, Yoshiaki

doi:10.1086/368248

Cited by 23 publications

(18 citation statements)

References 73 publications

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“…These results suggest that the Civλ1549, Heiiλ1640 and Ciii]λ1909 emitting regions in NLRs are dust-free. This is consistent with previous works in that gas clouds in the high-ionization part of NLRs are dust-free (e.g., Marconi et al 1994;Ferguson et al 1997;Nagao et al 2003). We verified that the effects of changing the grain composition (see Ferland 1997 for details) are less than 30% for the line flux ratios.…”

Section: Dust Grainssupporting

confidence: 93%

Gas metallicity in the narrow-line regions of high-redshift active galactic nuclei

Nagao

Maiolino

Marconi

2006

A&A

142

216

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We analyze optical (UV rest-frame) spectra of X-ray selected narrow-line QSOs at redshift 1.5 < ∼ z < ∼ 3.7 found in the Chandra Deep Field South and of narrow-line radio galaxies at redshift 1.2 < ∼ z < ∼ 3.8 to investigate the gas metallicity of the narrow-line regions and their evolution in this redshift range. Such spectra are also compared with UV spectra of local Seyfert 2 galaxies. The observational data are inconsistent with the predictions of shock models, suggesting that the narrow-line regions are mainly photoionized. The photoionization models with dust grains predict line flux ratios which are also in disagreement with most of the observed values, suggesting that the high-ionization part of the narrowline regions (which is sampled by the available spectra) is dust-free. The photoionization dust-free models provide two possible scenarios which are consistent with the observed data: low-density gas clouds (n H < ∼ 10 3 cm −3 ) with a sub-solar metallicity (0.2 < ∼ Z gas /Z < ∼ 1.0), or high-density gas clouds (n H ∼ 10 5 cm −3 ) with a wide range of gas metallicity (0.2 < ∼ Z gas /Z < ∼ 5.0). Regardless of the specific interpretation, the observational data do not show any evidence for a significant evolution of the gas metallicity in the narrow-line regions within the redshift range 1.2 < ∼ z < ∼ 3.8. Instead, we find a trend for more luminous active galactic nuclei to have more metal-rich gas clouds (luminosity-metallicity relation), which is in agreement with the same finding in the studies of the broad-line regions. The lack of evolution for the gas metallicity of the narrow-line regions implies that the major epoch of star formation in the host galaxies of these active galactic nuclei is at z > ∼ 4.

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Section: Dust Grainssupporting

confidence: 93%

Gas metallicity in the narrow-line regions of high-redshift active galactic nuclei

Nagao

Maiolino

Marconi

2006

A&A

142

216

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“…Two key types of models might explain the CLs and their properties: either photoionization by the central continuum source (e.g. Korista & Ferland 1989; Oliva et al 1994; Binette et al 1997; Ferguson et al 1997a; Nagao et al 2003; Mullaney et al 2009), or shock ionization or other processes directly or indirectly linked to the presence of radio jets (e.g. Tadhunter et al 1988; Viegas‐Aldrovandi & Contini 1989; Morse, Raymond & Wilson 1996; Axon et al 1998).…”

Section: Demystifying the Coronal‐line Region Of Active Galactic Numentioning

confidence: 99%

“…On one hand, authors have attempted to match CL strengths in samples of Seyfert galaxies, with an eye on the highest observed line ratios of CLs relative to low‐ionization lines (e.g. Erkens et al 1997; Komossa & Schulz 1997; Binette 1998; Rodríguez‐Ardila et al 2002; Nagao et al 2003; Rodrígue‐Ardila et al 2006). On the other hand, attention has focused on individual well‐studied Seyfert galaxies which have spatially resolved NLRs, and photoionization models have been presented which successfully reproduce the emission‐line ratios (with focus on low‐ionization lines, but including [Ne v ] and [Fe vii ]) of individual clouds.…”

Section: Demystifying the Coronal‐line Region Of Active Galactic Numentioning

confidence: 99%

Demystifying the coronal-line region of active galactic nuclei: spatially resolved spectroscopy with theHubble Space Telescope

Mazzalay¹,

Rodríguez-Ardila²,

Komossa³

2010

Monthly Notices of the Royal Astronomical Society

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We present an analysis of Space Telescope Imaging Spectrograph (STIS)/Hubble Space Telescope optical spectra of a sample of 10 Seyfert galaxies aimed at studying the structure and physical properties of the coronal-line region (CLR). The high spatial resolution provided by STIS allowed us to resolve the CLR and obtain key information about the kinematics of the CL gas, measure directly its spatial scale, and study the mechanisms that drive the high-ionization lines. We find CLRs extending from just a few parsecs (∼10 pc) up to 230 pc in radius, consistent with the bulk of the coronal lines (CLs) originating between the broad-line region and narrow-line region (NLR), and extending into the NLR in the case of [Fe VII] and [Ne V] lines. The CL profiles strongly vary with the distance to the nucleus. We observed line splitting in the core of some of the galaxies. Line peak shifts, both redshift and blueshift, typically reached 500 km s −1 , and even higher velocities (1000 km s −1 ) in some of the galaxies. In general, CLs follow the same pattern of rotation curves as low-ionization lines like [O III]. From a direct comparison between the radio and the CL emission we find that neither the strength nor the kinematics of the CLs scales in any obvious and strong way with the radio jets. Moreover, the similarity of the flux distributions and kinematics of the CLs and low-ionization lines, the low temperatures derived for the gas, and the success of photoionization models to reproduce, within a factor of a few, the observed line ratios, point towards photoionization as the main driving mechanism of CLs.

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“…This was so that the cloudy results were not affected by the depletion of iron due to condensation on to dust grains. Nagao et al (2003) have demonstrated for a large sample of AGNs that the observed FHIL ratios 7 cannot be reproduced in cloudy models that contain grains, but can be successfully reproduced with models not containing grains.…”

Section: Discussionmentioning

confidence: 99%

The forbidden high-ionization-line region of the type 2 quasar SDSS J11311.05+162739.5: a clear view of the inner face of the torus?

Rose¹,

Tadhunter²,

Holt³

et al. 2011

Monthly Notices of the Royal Astronomical Society

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We present spectroscopic observations of the type 2 quasar SDSS J11311.05+162739.5 (z = 0.1732), which has the richest spectrum of forbidden high-ionization lines (FHILs, e.g. [Fe VII], [Fe X], [Fe XI] and [Ne V]) yet reported for an active galactic nucleus (AGN), as well as unusually strong [O III] λ4363 emission. The study of this object provides a rare opportunity to investigate the physical conditions and kinematics of the region(s) emitting the FHILs. By comparison with photoionization model results, we find that the FHIL region has high densities (10 5.5 < n H < 10 8.0 cm −3 ) and ionization parameters (−1.5 < log [U] < 0), yet its kinematics are similar to those of the low-ionization emission-line region detected in the same object (full width at half-maximum ∼360 ± 30 km s −1 ), with no evidence for a significant shift between the velocity centroid of the FHILs and the rest frame of the host galaxy. The deduced physical conditions lie between those of the broad-line (n H > 10 9 cm −3 ) and narrow-line regions (n H < 10 6 cm −3 ) of AGNs, and we demonstrate that the FHIL regions must be situated relatively close to the illuminating AGN (0.32 < r FHIL < 50 pc). We suggest that the inner torus wall is the most likely location for the FHIL region, and that the unusual strength of the FHILs in this object is due to a specific viewing angle of the far wall of the torus, coupled with a lack of dust on larger scales that might otherwise obscure our view of the torus.

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Iron Is Not Depleted in High-Ionization Nuclear Emission-Line Regions of Active Galactic Nuclei

Cited by 23 publications

References 73 publications

Gas metallicity in the narrow-line regions of high-redshift active galactic nuclei

Gas metallicity in the narrow-line regions of high-redshift active galactic nuclei

Demystifying the coronal-line region of active galactic nuclei: spatially resolved spectroscopy with theHubble Space Telescope

The forbidden high-ionization-line region of the type 2 quasar SDSS J11311.05+162739.5: a clear view of the inner face of the torus?

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