An unsolved problem in the spectrum of quasars: the FeII emission lines

Joly, M.

doi:10.1051/anphys:01993001803024100

Cited by 13 publications

(25 citation statements)

References 104 publications

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“…This result is also important because it challenges some models proposed for the production of the strong Fe II characteristic of NLS1s, as has been noted previously. The large Fe II to Hb ratio is generally difficult to understand because both emission lines are predicted to be produced under the same conditions in photoionization models and those models generically underestimate Fe II (for a review, see Joly 1993). It has been proposed that strong Fe II emission would be produced if the X-ray spectrum is Ñat because hard X-ray photons can penetrate deeper into emission line clouds producing heating and leading to strong Fe II emission.…”

Section: Fig 8èresults Of Correlation Analysismentioning

confidence: 99%

A Comprehensive Spectral and Variability Study of Narrow‐Line Seyfert 1 Galaxies Observed by ASCA . II. Spectral Analysis and Correlations

Leighly

1999

ASTROPHYS J SUPPL S

315

197

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I present a comprehensive and uniform analysis of 25 ASCA observations from 23 narrow-line Seyfert 1 galaxies (NLS1s). The spectral analysis and correlations are presented in this paper ; the reduction and time series analysis are presented in the companion paper. A maximum likelihood analysis conÐrms that the hard X-ray photon index is signiÐcantly steeper at more than 90% conÐdence in this sample of NLS1s compared with a random sample of Seyfert galaxies with broad optical lines. Soft excess emission was detected in 17 of the 19 objects that had no signiÐcant absorption, a result that demonstrates that soft excesses appear considerably more frequently in NLS1s than in Seyfert 1 galaxies with broad optical lines. The strength of the soft excess, parameterized using a Ñux ratio obtained from the blackbody plus power-law model, has a wide range of values in these objects (a factor of 50). The photon index was found to be correlated with the Hb FWHM, despite the small range of the latter parameter ; however, neither parameter is correlated with the strength of the soft excess or ROSAT slope. Therefore, assuming that an excess of soft photons causes the steep photon index and narrow Hb FWHM, that excess may lie primarily in the unobservable EUV. The strength of the soft excess is correlated with the variability parameters, so that objects with strong soft excesses show higher amplitude variability ; this potentially important result is not easily explained. While a range of 2 orders of magnitude in luminosity is represented, the temperature of the soft excess is approximately consistent throughout the sample, in contrast with expectations of simple accretion disk models. The presence of ionized absorption was sought using a two-edge model. It was found that this component appears to be typically less common in NLS1s and some evidence was found that the typical ionization state is lower compared with broad-line Seyfert galaxies. This fact, plus evidence for a correlation between the presence of the warm absorber and signiÐcant optical polarization, may imply that the inner warm absorber is missing or is too highly ionized to be detected, and only the outer, dusty, less ionized warm absorber is present in many cases. The iron line equivalent width appears to be similar among narrow and broad-line Seyfert galaxies. This could mean that reprocessing occurs with similar geometry in both classes of objects ; however, the detection of ionized iron lines in a few objects, implying possibly altered Ñuorescence yields, and poor statistics, makes this conclusion tentative. Constraints on physical processes and models based on extreme values of orientation and accretion rate for NLS1s are examined in light of the observational results.

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Section: Fig 8èresults Of Correlation Analysismentioning

confidence: 99%

A Comprehensive Spectral and Variability Study of Narrow‐Line Seyfert 1 Galaxies Observed by ASCA . II. Spectral Analysis and Correlations

Leighly

1999

ASTROPHYS J SUPPL S

315

197

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“…However, it should be noted that the most extreme Fe ii emitters are RQ quasars, while Fe ii is not detected in many RL AGN. Nuclear SB where violent SF processes occur in high metallicity/pressure environments (Terlevich & Melnick 1988). Collisional ionization process (Joly 1987, 1989, 1993; Veron et al 2006), which could be related mainly to shocks, in OF events.…”

Section: The Fe II Problem and The Fe Ii Correlationsmentioning

confidence: 99%

“…Collisional ionization process (Joly 1987, 1989, 1993; Veron et al 2006), which could be related mainly to shocks, in OF events.…”

Section: The Fe II Problem and The Fe Ii Correlationsmentioning

confidence: 99%

Evolutionary unification in composite active galactic nuclei

Lípari

Terlevich

2006

Monthly Notices of the Royal Astronomical Society

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In this paper, we present an evolutionary unification scenario, involving supermassive black holes (SMBHs) and starbursts (SBs) with outflow (OF), that seems capable of explaining most of the observational properties (of at least part) of active galactic nuclei (AGN).The scenario includes a nuclear/circumnuclear SB closely associated with the AGN where the narrow-line region (NLR), broad-line region (BLR) and broad absorption line (BAL) region are produced in part by the OF process with shells and in compact supernova remnants (cSNRs).The OF process in BAL quasi-stellar objects (QSOs) with extreme infrared (IR) and Fe II emission is studied. In addition, the Fe II problem regarding the BLR of AGN is analysed. The correlations between the BAL, IR emission, Fe II intensity and the intrinsic properties of the AGN are not clearly understood. We suggest here that the behaviour of the BAL, IR and Fe II emission in AGN can be understood within an evolutionary and composite model for AGN.In our model, strong BAL systems and Fe II emission are present (and intense) in young IR objects. Parameters like the BALs, IR emission, Fe II/Hβ intensity ratio, Fe II equivalent width (EW), broad-line width, [O III] λ5007-Å intensity and width, NLR size, X-ray spectral slope in radio quiet (RQ) AGN plus lobe separation, and lobe to core intensity ratio in radio loud (RL) AGN are proposed to be fundamentally time-dependent variables inside time-scales of the order of 10 8 yr. Orientation/obscuration effects take the role of a second parameter providing the segregation between Seyfert 1/Seyfert 2 galaxies (Sy1/Sy2) and broad-/narrow-line radio galaxies (BLRG/NLRG).

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“…Finally, two bands centered at 1160 and 1115 sample the Ñux below Lya. The twelfth A band, centered at 2500 where there are several strong Fe A , II multiplets (Joly 1993), was selected to gauge Fe II strength.…”

Section: Computation Of Continuum Fluxesmentioning

confidence: 99%

“…Two are the residuals at 2500 and 2660 Recall A A . that the 2500 window is centered on a strong Fe II multi-A plet (Joly 1993), and the 2660 one is the only other A window of the four between 2000 and 4000 within which A luminosities could be directly measured for a signiÐcant part of the sample. Another measure is the luminosity of the excess relative to the continuum between 2200 and 3023 A ,…”

Section: Uv T Urnovermentioning

confidence: 99%

Untitled

2001

ASTROPHYS J SUPPL S

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For 15 bright (V \ 17.5), high-redshift (z [ 3) quasars, we have obtained infrared spectra and photometry, and optical spectrophotometry and photometry, which we use to construct their spectral energy distributions (SEDs) from High-resolution spectroscopy for seven enable measurej rest D 1285È5100 A . ments of their continua shortward of Lya, and L @ detections of four of these extend their SEDs redward toWe examine the optical/UV continuum shapes and compare these to those of a set of j rest D 7500 A . 27 well-studied low-redshift (z D 0.1) quasars which are matched to the high-redshift ones in evolved luminosity. Single power-law Ðts to the average Ñuxes within a set of narrow, line-free, windows between 1285 and 5100 but excluding the 2000È4000 region of the Fe II]BaC "" small bump,ÏÏ are adequate A , A for most of the objects. For both the high-and low-redshift samples, the distributions of spectral indices, span a wide range, with The cause of such diversity is investigated, and our. analysis is consistent with the conclusion of Rowan-Robinson : that it arises from di †erences in both the emitted continua themselves and in the amounts of intrinsic extinction undergone. The mean (median) optical/UV spectral indices for the high-and low-redshift samples are [0.32 ([0.29) and [0.38 ([0.40), respectively. A StudentÏs t-test indicates that these do not di †er signiÐcantly, and a K-S test shows likewise for the distributions. Assuming the optical/UV continuum derives from accretion, the similarity of the spectral indices at high and low redshift is inconsistent with models which interpret the statistical evolution as resulting from a single generation of slowly dimming quasars and instead favors those involving multiple generations of short-lived quasars formed at successively lower luminosities. A clear di †erence between the high-and low-redshift samples occurs in the region of "" small bump.ÏÏ The powerlaw Ðt residuals for the low-redshift sample show a systematic excess from D2200 to 3000 but this A ; feature is weak or absent in the high-redshift sample. Further study is needed to determine what is responsible for this contrast, but it could reÑect di †erences in iron abundance or Fe II energy source, or alternatively, an intrinsic turnover in the continuum itself which is present at low but not at high redshift.

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An unsolved problem in the spectrum of quasars: the FeII emission lines

Cited by 13 publications

References 104 publications

A Comprehensive Spectral and Variability Study of Narrow‐Line Seyfert 1 Galaxies Observed by ASCA . II. Spectral Analysis and Correlations

A Comprehensive Spectral and Variability Study of Narrow‐Line Seyfert 1 Galaxies Observed by ASCA . II. Spectral Analysis and Correlations

Evolutionary unification in composite active galactic nuclei

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