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Note from the editor: This article is a re-print of the original, which appeared in Astron. Nachr. 319 (1/2), 7 (1998). In the original version the figure was ruined in the process of paper production and the scientific content of the paper considerably degraded. Instead of printing only the correct figure, thus loosing the scientific context, we decided to re-print the whole article. We describe how recent X-ray surveys have led to advances in the understanding of ultrasoft narrow-line Seyfert 1 galaxies. The number of known ultrasoft narrow-line Seyfert 1s has increased greatly in recent years due to X-ray surveys, and it is now possible to obtian high quality 0.1–10 keV spectral and variability measurements for a large number of these galaxies. We generalize some of the correlations between X-ray properties and optical emission line properties,focusing on how the ROSAT band spectral slope appears to be directly connected to the Boroson & Green (1992) primary eigenvector. We discuss how ultrasoft narrow-line Seyfert 1s may well have extremal values of a primary physical parameter, and we describe new projects that should further improve our understanding of these extreme representatives of Seyfert activity. 相似文献
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Stellar velocity dispersion in narrow-line Seyfert 1 galaxies 总被引：1，自引：0，他引：1
V. Botte † S. Ciroi † F. Di Mille P. Rafanelli A. Romano 《Monthly notices of the Royal Astronomical Society》2005,356(2):789-793
Several authors have recently explored, for narrow-line Seyfert 1 galaxies (NLS1s), the relationship between black hole mass ( M BH ) and stellar velocity dispersion (σ* ). Their results are more or less in agreement and seem to indicate that NLS1s fill the region below the fit obtained by Tremaine et al., showing a range of σ* similar to that of Seyfert 1 galaxies, and a lower M BH . Until now, the [O iii ] width has been used in place of the stellar velocity dispersion, but some indications have begun to arise against the effectiveness of the gaseous kinematics in representing the bulge potential, at least in NLS1s. Bian & Zhao have stressed the urgency of producing true σ* measurements. Here, we present new stellar velocity dispersions obtained through direct measurements of the Ca ii absorption triplet (∼8550 Å) in the nuclei of eight NLS1 galaxies. The resulting σ* values and a comparison with σ[O III] confirm our suspicion that [O iii ] typically overestimates the stellar velocity dispersion. We demonstrate that NLS1s follow the M BH –σ* relation as Seyfert 1, quasars and non-active galaxies. 相似文献
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Black hole masses in narrow-line Seyfert 1 galaxies 总被引：1，自引：0，他引：1
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S. Vaughan J. Reeves R. Warwick R. Edelson 《Monthly notices of the Royal Astronomical Society》1999,309(1):113-124
We present a systematic analysis of the X-ray spectral properties of a sample of 22 'narrow-line' Seyfert 1 galaxies for which data are available from the ASCA public archive. Many of these sources, which were selected on the basis of their relatively narrow H β linewidth (FWHM ≤2000 km s−1 ), show significant spectral complexity in the X-ray band. Their measured hard power-law continua have photon indices spanning the range 1.6–2.5 with a mean of 2.1, which is only slightly steeper than the norm for 'broad-line' Seyfert 1s. All but four of the sources exhibit a soft excess, which can be modelled as blackbody emission ( T bb ≈100–300 eV) superposed on the underlying power law. This soft component is often so strong that, even in the relatively hard bandpass of ASCA , it contains a significant fraction, if not the bulk, of the X-ray luminosity, apparently ruling out models in which the soft excess is produced entirely through reprocessing of the hard continuum.
Most notably, six of the 22 objects show evidence for a broad absorption feature centred in the energy range 1.1–1.4 keV , which could be the signature of resonance absorption in highly ionized material. A further three sources exhibit 'warm absorption' edges in the 0.7–0.9 keV bandpass. Remarkably, all nine 'absorbed' sources have H β linewidths below 1000 km s−1 , which is less than the median value for the sample taken as a whole. This tendency for very narrow linewidths to correlate with the presence of ionized absorption features in the soft X-ray spectra of NLS1s, if confirmed in larger samples, may provide a further clue in the puzzle of active galactic nuclei. 相似文献
Most notably, six of the 22 objects show evidence for a broad absorption feature centred in the energy range 1.1–1.4 keV , which could be the signature of resonance absorption in highly ionized material. A further three sources exhibit 'warm absorption' edges in the 0.7–0.9 keV bandpass. Remarkably, all nine 'absorbed' sources have H β linewidths below 1000 km s
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S. Vaughan K. A. Pounds J. Reeves R. Warwick R. Edelson 《Monthly notices of the Royal Astronomical Society》1999,308(4):L34-L38
We present simultaneous ASCA and RXTE observations of Ark 564, the brightest known 'narrow-line' Seyfert 1 in the 2–10 keV band. The measured X-ray spectrum is dominated by a steep (Γ≈2.7) power-law continuum extending to at least 20 keV, with imprinted Fe K-line and edge features and an additional 'soft excess' below ∼1.5 keV. The energy of the iron K-edge indicates the presence of highly ionized material, which we identify in terms of reflection from a strongly irradiated accretion disc. The high reflectivity of this putative disc, together with its strong intrinsic O viii Ly α and O viii recombination emission, can also explain much of the observed soft excess flux. Furthermore, the same spectral model also provides a reasonable match to the very steep 0.1–2 keV spectrum deduced from ROSAT data. The source is much more rapidly variable than 'normal' Seyfert 1s of comparable luminosity, increasing by a factor of ∼50 per cent in 1.6 h, with no measurable lag between the 0.5–2 keV and 3–12 keV bands, consistent with much of the soft excess flux arising from reprocessing of the primary power-law component in the inner region of the accretion disc. We note, finally, that if the unusually steep power-law component is a result of Compton cooling of a disc corona by an intense soft photon flux, then the implication is that the bulk of these soft photons lie in the unobserved extreme ultraviolet. 相似文献
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We present results from spectral analysis of ASCA data on the strong Fe ii narrow-line Seyfert 1 galaxy Mrk 507. This galaxy was found to have an exceptionally flat ROSAT spectrum among the narrow-line Seyfert 1 galaxies (NLS1s) studied by Boller, Brandt & Fink. The ASCA spectrum, however, shows a clear absorption feature in the energy band below 2 keV, which partly accounts for the flat spectrum observed with the ROSAT Position Sensitive Proportional Counter (PSPC). Such absorption is rarely observed in other NLS1s. The absorption is mainly the result of cold (neutral or slightly ionized) gas with a column density of (2–3) × 1021 cm−2 . A reanalysis of the PSPC data shows that an extrapolation of the best-fitting model for the ASCA spectrum underpredicts the X-ray emission observed with the PSPC below 0.4 keV if the absorber is neutral (which indicates that the absorber is slightly ionized), covers only part of the central source, or there is extra soft thermal emission from an extended region. There is also evidence that the X-ray absorption is complex; an additional edge feature marginally detected at 0.84 keV suggests the presence of an additional high-ionization absorber, which imposes a strong O viii edge on the spectrum. After correction for the absorption, the photon index of the intrinsic continuum, Γ ≃ 1.8, obtained from the ASCA data is quite similar to that of ordinary Seyfert 1 galaxies. Mrk 507 still has one of the flattest continuum slopes among the NLS1s, but is no longer exceptional. The strong optical Fe ii emission remains unusual in the light of the correlation between Fe ii strengths and steepness of soft X-ray slope. 相似文献
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Chris Simpson 《Monthly notices of the Royal Astronomical Society》1998,297(2):L39-L43
We undertake a quantitative investigation, using Monte Carlo simulations, of the amount by which quasars are expected to exceed radio galaxies in optical luminosity in the context of the 'receding torus' model. We compare these simulations with the known behaviour of the [O III ] λ5007 and [O II ] λ3727 emission lines and conclude that [O III ] is the better indicator of the strength of the underlying non-stellar continuum. 相似文献
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P.T. O'Brien K. Page J.N. Reeves K. Pounds M.J.L. Turner E.M. Puchnarewicz 《Monthly notices of the Royal Astronomical Society》2001,327(4):L37-L41
We present XMM-Newton observations of Mrk 359, the first narrow-line Seyfert 1 galaxy (NLS1) discovered. Even among NLS1s, Mrk 359 is an extreme case with extraordinarily narrow optical emission lines. The XMM-Newton data show that Mrk 359 has a significant soft X-ray excess which displays only weak absorption and emission features. The continuum, including reflection, is flatter than that of the typical NLS1, with . A strong emission line of equivalent width ≈200 eV is also observed, centred near 6.4 keV. We fit this emission with two line components of approximately equal strength: a broad iron line from an accretion disc and a narrow, unresolved core. The unresolved line core has an equivalent width of ≈120 eV and is consistent with fluorescence from neutral iron in distant reprocessing gas, possibly in the form of a 'molecular torus'. Comparison of the narrow-line strengths in Mrk 359 and other low–moderate luminosity Seyfert 1 galaxies with those in QSOs suggests that the solid angle subtended by the distant reprocessing gas decreases with increasing active galactic nucleus luminosity. 相似文献
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