Spectroscopic study of the [O iii]λ5007 profile in Seyfert 1 galaxies

Astronomy & Astrophysics, 2001

We have compiled a list of 83 objects classified as Narrow-Line Seyfert 1 galaxies (NLS1s) or known to have a broad Balmer component narrower than 2 000 km s −1. Of these, 19 turned out to have been spectroscopically misidentified in previous studies; only 64 of the selected objects are genuine NLS1s. We have spectroscopically observed 59 of them and tried to characterize their Narrow and Broad-Line Regions (NLR and BLR) by fitting the emission-lines with Gaussian and/or Lorentzian profiles. In most cases, the broad Balmer components are well fitted by a single Lorentzian profile, confirming previous claims that Lorentzian rather than Gaussian profiles are better suited to reproduce the shape of the NLS1s broad emission lines. This has consequences concerning their FWHMs and line ratios: when the broad Balmer components are fitted with a Lorentzian, most narrow line regions have line ratios typical of Seyfert 2s while, when a Gaussian profile is used for fitting the broad Balmer components, the line ratios are widely scattered in the usual diagnostic diagrams (Veilleux & Osterbrock 1987); moreover, the FWHM of the best fitting Lorentzian is systematically smaller than the FWHM of the Gaussian. We find that, in general, the [O III] lines have a relatively narrow Gaussian profile (∼200-500 km s −1 FWHM) with often, in addition, a second broad (∼500-1 800 km s −1 FWHM), blueshifted Gaussian component. We do not confirm that the [O III] lines are weak in NLS1s. As previously suggested, there is a continuous transition of all properties between NLS1s and classical Broad-Line Seyfert 1 Galaxies (BLS1s) and the limit of 2000 km s −1 used to separate the two species is arbitrary; R4570, the ratio of the Fe II to the Hβ fluxes, could be a physically more meaningful parameter to distinguish them.

Astronomy & Astrophysics - ASTRON ASTROPHYS, 2000

The main goal of this work is to further investigate the classification of emission-line galaxies from the ``Spectrophotometric Catalogue of H II galaxies'' by Terlevich et al. (1991) in a homogeneous and objective way, using the three line-ratio diagrams, called diagnostic diagrams, of Veilleux & Osterbrock (1987). On the basis of the resulting catalogue, we critically discuss the classification methods in the optical range. In particular we compare our classification scheme to the one done by Rola et al. (1997) which is efficient for the classification of redshifted galaxies. We also propose a new diagnostic diagram involving the known intensity ratio R23=([O II],l 3727+[O III] l 4959+{[O III] l 5007)/Hb which appears to be a very good criterion allowing to discriminate the Seyfert 2 from H ii galaxies. The revised catalogue including 314 narrow-emission-line galaxies contains H II galaxies, Seyfert 2 galaxies, Low Ionization Nuclear Emission-Line Regions (hereafter LINE...

Astronomy & Astrophysics, 2017

We present the analysis of the emission line galaxies members of 46 low-redshift (0.04 < z < 0.07) clusters observed by WINGS (WIde-field Nearby Galaxy cluster Survey). Emission line galaxies were identified following criteria that are meant to minimize biases against non-star-forming galaxies and classified employing diagnostic diagrams. We examined the emission line properties and frequencies of star-forming galaxies, transition objects, and active galactic nuclei (AGNs: LINERs and Seyferts), unclassified galaxies with emission lines, and quiescent galaxies with no detectable line emission. A deficit of emission line galaxies in the cluster environment is indicated by both a lower frequency, and a systematically lower Balmer emission line equivalent width and luminosity with respect to control samples; this implies a lower amount of ionized gas per unit mass and a lower star formation rate if the source is classified as Hii region. A sizable population of transition objects and of low-luminosity LINERs (≈10−20% of all emission line galaxies) are detected among WINGS cluster galaxies. These sources are a factor of ≈1.5 more frequent, or at least as frequent, as in control samples with respect to Hii sources. Transition objects and LINERs in clusters are most affected in terms of line equivalent width by the environment and appear predominantly consistent with so-called retired galaxies. Shock heating can be a possible gas excitation mechanism that is able to account for observed line ratios. Specific to the cluster environment, we suggest interaction between atomic and molecular gas and the intracluster medium as a possible physical cause of line-emitting shocks.

2008

In the unification scheme of Seyfert galaxies, a dusty torus blocks the continuum source and broad line region in Seyfert 2 galaxies. However it is not clear whether or not and to what extent the torus affects the narrow line spectra. In this paper, we show that Seyfert 1 and Seyfert 2 galaxies have different distributions on the [O III]/H β vs [N II]/H α diagram (BPT diagram) for narrow lines. Seyfert 2 galaxies display a clear left boundary on the BPT diagram and only 7.3% of them lie on the left. By contrast, Seyfert 1 galaxies do not show such a cutoff and 33.0% of them stand on the left side of the boundary. Among Seyfert 1 galaxies, the distribution varies with the extinction to broad lines. As the extinction increases, the distribution on BPT diagram moves to larger [N II]/H α value. We interpret this as an evidence for the obscuration of inner dense narrow line region by the dusty torus. We also demonstrate that the [O III] and broad line luminosity correlation depends on the extinction of broad lines in the way that high extinction objects have lower uncorrected [O III] luminosities, suggesting that [O III] is partially obscured in these objects. Therefore, using [O III] as an indicator for the nuclear luminosity will systematically under-estimate the nuclear luminosity of Seyfert 2 galaxies.

Arxiv preprint arXiv: …, 2007

The Astrophysical Journal Supplement Series, 2003

We present a Hubble Space Telescope (HST) survey of extended [OIII] emission for a sample of 60 Seyfert galaxies (22 Seyfert 1's and 38 Seyfert 2's), selected based on their far infrared properties. The observations for 42 of these galaxies were done in a snapshot survey with WFPC2. The remaining 18 were obtained from the HST archive, most of which were observed with the same configuration. These observations cover 68% of the objects in the sample defined by Kinney et al. (2000), and create a valuable dataset for the study of the Narrow Line Region (NLR) properties of Seyfert galaxies. In this paper, we present the details of the observations, reductions, and measurements. We also discuss the extended structure of individual sources, and the relation of this emission to the radio and host galaxy morphology. We also address how representative the subsample of [O III]-imaged galaxies is of the entire sample, and possible selection effects that may affect this comparison of the properties of Seyfert 1 and Seyfert 2 galaxies.

2008

El resumen será traducido al español por los editores. We present the first optical photometric study of the active galaxy SBS 0748+499. First, we present B, V, R and I photometric data: total magnitudes and B −V, B −R, B −I colors; surface brightness, color and geometric profiles, with emphasis on the morphology and its relation to the global photometric properties of this galaxy. Then, from our surface photometry study we derive the bulge–to–disk luminosity ratio B/D in the four bands. We find that the host galaxy shows a bar (a ∼ 8 kpc) and a low– brightness spiral structure. The morphological classification for the host galaxy of this AGN is SBab. Additionally, we present new optical spectrophotometric observations that clearly show that the object can be classified as Sy 1.9 galaxy. Finally, we estimate the black hole mass (MBH) associated with the nucleus of SBS 0748+499 using the absolute R–band bulge magnitude–MBH relation, and the FWHM [OIII]5007 – σ ⋆ relation. We find tha...

The Astrophysical Journal, 2004

We present the intrinsic spectral energy distribution (SED) of the Narrow-Line Seyfert 1 galaxy (NLS1) Ark 564, constructed with contemporaneous data obtained during a multi-wavelength, multi-satellite observing campaign in 2000 and 2001. We compare this SED with that of the NLS1 Ton S180 and with those obtained for Broad-Line Seyfert 1s to infer how the relative accretion rates vary among the Seyfert 1 population. Although the peak of the SED is not well constrained, in our parameterization most of the energy of this object is emitted in the 10-100 eV regime, constituting roughly half of the emitted energy in the optical/X-ray ranges. This is consistent with a primary spectral component peaking in the extreme UV/soft X-ray band, and with disk-corona models, hence high accretion rates. Indeed, we estimate thatṁ ≈ 1. We also address the issue of the energy budget in this source by examining the emission lines observed in its spectrum, and we constrain the physical properties of the line-emitting gas through photoionization modeling. The available data suggest that the line-emitting gas is characterized by log n ≈ 11 and logU ≈ 0, and is stratified around logU ≈ 0. Our estimate of the radius of the Hβ-emitting region R Hβ BLR ≈ 10 ± 2 lt-days is consistent with the R Hβ BLR-luminosity relationships found for Sy1 galaxies, which indicates that the narrowness of the emission lines in this NLS1 is not due to the Broad-Line Region being relatively further away from the central mass than in BLS1s of comparable luminosity. We also find evidence for super-solar metallicity in this NLS1. We show that the emission lines are not good diagnostics for the underlying SEDs and that the absorption line studies offer a far more powerful tool to determine the ionizing continuum of AGNs, especially if comparing the lower-and higher-ionization lines.

The Spitzer IRS high resolution spectra of about 90 Seyfert galaxies from the 12um Galaxy Sample are presented and discussed. These represent about 70% of the total complete sample of local Seyfert galaxies. The presence of starburst components in these galaxies can be quantified by powerful mid-IR diagnostics tools (i.e. 11.25um PAH feature equivalent width and the H_2 emission line intensity) as well as the AGN dominance can be measured by specific fine structure line ratios (e.g. [NeV]/[NeII], [NeV]/[SiII], etc.). The observed line ratios are compared to the results of semianalytical models, which can be used to compute the AGN and starburst contributions to the total luminosity of the galaxies. The results are also discussed in the light of unification and evolution models.

Monthly Notices of the Royal Astronomical Society

We present oxygen abundances relative to hydrogen (O/H) in the narrow line regions (NLRs) gas phases of Seyferts 1 (Sy 1s) and Seyferts 2 (Sy 2s) active galactic nuclei (AGNs). We used fluxes of the optical narrow emission line intensities [$3\, 500\lt \lambda ($Å$)\lt 7\, 000$] of 561 Seyfert nuclei in the local Universe ( z ≲ 0.31) from the second catalogue and data release (DR2) of the BAT AGN Spectroscopic Survey, which focuses on the Swift-BAT hard X-ray (≳ 10 keV) detected AGNs. We derived O/H from relative intensities of the emission lines via the strong-line methods. We find that the AGN O/H abundances are related to their hosts stellar masses and that they follow a downward redshift evolution. The derived O/H together with the hard X-ray luminosity (LX) were used to study the X-ray luminosity–metallicity (LX–ZNLR) relation for the first time in Seyfert galaxies. In contrast to the broad-line focused (LX–ZBLR) studies, we find that the LX–ZNLR exhibit significant anticorrela...