Results 1 - 10 of 2001
Results 1 - 10 of 2001. Search took: 0.024 seconds
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[en] The different observational properties used, up to now, to discriminate between Seyfert 1 and seyfert 2 are reviewed: emission lines widths, Fe II lines, intensity ratio [OIII= 500.7 nm/Hβ, radio, infrared, visible, UV and X emission. Most of these parameters exhibit a more or less continuous distribution from the less powerful Seyfert 2 up to the Seyfert 1 nuclei (exept in the radio range)
[fr]Les differents criteres observationnels que l'on peut utiliser pour differencier Seyfert 1 et Seyfert 2 sont passes en revue: largeur des raies d'emission, raies de FeII, rapport d'intensite [OIII] 500.7 nm/Hβ rayonnements radio, infra-rouge, visible, UV et X. La plupart de ces parametres indiquent, en fait, une sequence continue entre ces objets, les Seyfert 1 apparaissant presque toujours comme des emetteurs plus puissants (radio excepte)
[en] Photographic photometry of the Seyfert galaxy nuclei NGC 1068, 3227, 4051, 4151, 5548, and 7469 in two colours has been carried out on available observational material obtained at the Byurakan observatory on a 20-21 Schmidt camera and covering the period from 1963 to 1969. The photometry results are given in tables. Part of the observations overlaps in time those of other authors, but they basically refer to a period when practically no other observations have been made
[en] We present a catalogue of 183 extended ionized nebulosities detected around active galactic nuclei (AGN) of all activity levels from LINERs (Low Ionization Nuclear Emitting Regions), Seyfert 2s, Seyfert 1s to quasars, with extensions ranging between one and several hundred kpc
[en] We present new measurements of stellar velocity dispersions, using spectra obtained with the Keck Echellette Spectrograph and Imager (ESI) and the Magellan Echellette (MagE), for 76 Seyfert 1 galaxies from the recent catalog of Greene and Ho. These objects were selected from the Sloan Digital Sky Survey (SDSS) to have estimated black hole (BH) masses below 2 x 106 Msun. Combining our results with previous ESI observations of similar objects, we obtain an expanded sample of 93 galaxies and examine the relation between BH mass and velocity dispersion (the MBH-σ* relation) for active galaxies with low BH masses. The low-mass active galaxies tend to follow the extrapolation of the MBH-σ* relation of inactive galaxies. Including results for active galaxies of higher BH mass from the literature, we find a zero point α = 7.68 ± 0.08 and slope of β = 3.32 ± 0.22 for the MBH-σ* relation (in the form log MBH = α + βlog (σ*/200 km s-1)), with intrinsic scatter of 0.46 ± 0.03 dex. This result is consistent, within the uncertainties, with the slope of the MBH-σ* relation for reverberation-mapped active galaxies with BH masses from 106 to 109 Msun. For the subset of our sample having morphological information from Hubble Space Telescope images, we examine the slope of the MBH-σ* relation separately for subsamples of barred and unbarred host galaxies, and find no significant evidence for a difference in slope. We do find a mild offset between low-inclination and high-inclination disk galaxies, such that more highly inclined galaxies tend to have larger σ* at a given value of BH mass, presumably due to the contribution of disk rotation within the spectroscopic aperture. We also find that the velocity dispersion of the ionized gas, measured from narrow emission lines including [N II] λ6583, [S II] λλ6716, 6731, and the core of [O III] λ5007 (with the blueshifted wing removed), trace the stellar velocity dispersion well for this large sample of low-mass Seyfert 1 galaxies.
[en] Detailed photographic UBV photometry of the double UV-excess galaxy Kazarian 163 performed on 2.6-m Biurakan telescope plates yields integrated magnitudes and colors for the object as a whole, the two main components, and their nuclei. The two-color diagram demonstrates that the blueness of the galaxy is dictated by the bright S-component nucleus, whose colors U - B = -0.63 mag, B - V = +0.42 mag are typical of active Seyfert nuclei. Having very different photometric parameters, the N component resembles a normal E galaxy. 8 references
[en] We present a study of the core of the Fe Kα emission line at ∼6.4 keV in a sample of type II Seyfert galaxies observed by the Chandra high-energy grating. The sample consists of 29 observations of 10 unique sources. We present measurements of the Fe Kα line parameters with the highest spectral resolution currently available. In particular, we derive the most robust intrinsic line widths for some of the sources in the sample to date. We obtained a weighted mean full width at half-maximum (FWHM) of 2000 ± 160 km s-1 for 8 out of 10 sources (the remaining sources had insufficient signal to noise). From a comparison with the optical emission-line widths obtained from spectropolarimetric observations, we found that the location of Fe Kα line-emitting material is a factor of ∼0.7-11 times the size of the optical broad-line region. Furthermore, compared to 13 type I active galactic nuclei (AGNs) for which the best Fe Kα line FWHM constraints were obtained, we found no difference in the FWHM distribution or the mean FWHM, and this conclusion is independent of the central black hole mass. This result suggests that the bulk of the Fe Kα line emission may originate from a universal region at the same radius with respect to the gravitational radius, ∼3 x 104 rg on average. By examining the correlation between the Fe Kα luminosity and the [O IV] line luminosity, we found a marginal difference in the Fe Kα line flux between type I and type II AGNs, but the spread in the ratio of LFe to L[OIV] is about two orders of magnitude. Our results confirm the theoretical expectation that the Fe Kα emission-line luminosity cannot trivially be used as a proxy of the intrinsic AGN luminosity, unless a detailed comparison of the data with proper models is applied.