Philippe Veron

A catalogue of quasars and active nuclei: 12th edition

Aims. This catalogue is aimed at presenting a compilation of all known AGN in a compact and convenient form and we hope that it will be useful to all workers in this field. Methods. Like the eleventh edition, it includes position and redshift as well as photometry ( U , B , V ) andxa06xa0cm flux densities when available. We now givexa020xa0cm rather than 11 cm flux densities. Results. The present version contains 85u2009221xa0quasars, 1122xa0BLxa0Lac objects andxa021u2009737 active galaxies (includingxa09628xa0Seyfertxa01s), almost doubling the number listed in thexa011thxa0edition. We also give a list of all known lensed and double quasars.

A spectrophotometric atlas of Narrow-Line Seyfert 1 galaxies

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 2000 km/s. Out 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. 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 isused for fitting the broad Balmer components, the line ratios are widely scattered in the usual diagnostic diagrams (Veilleux & Osterbrock 1987). We find that, in general, the [O III] lines have a relatively narrow Gaussian profile (~ 200-500 km/s FWHM) with often, in addition, a second broad (~ 500-1800 km/s 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 used to separate the two species is arbitrary; R_4570, the ratio of the Fe II to the H_beta fluxes, could be a physically more meaningful parameter to distinguish them. (abridged abstract)

The Unusual emission line spectrum of IZw1

Most Seyfert 1 galaxies show strong Fe II lines in their spectrum having the velocity and width of the broad emission lines. To remove the Fe II contribution in these objects, an accurate template is necessary. We used very high signal-to-noise, medium resolution archive optical spectra of I Zw 1 to build such a template. I Zw 1 is a bright narrow-line Seyfert 1 galaxy. As such it is well suited for a detailed analysis of its emission line spectrum. Furthermore it is known to have a very peculiar spectrum with, in addition to the usual broad and narrow line regions, two emission regions emitting broad and blue shifted (O III) lines making it a peculiarly interesting object. While analysing the spectra, we found that the narrow-line region is, unlike the NLR of most Seyfert 1 galaxies, a very low excitation region dominated by both permitted and forbidden Fe II lines. It is very similar to the emission spectrum of a blob in η Carinae which is a low temperature (Te ∼ 6500 K), relatively high density (Ne = 10 6 cm −3 ) cloud. The Fe II lines in this cloud are mainly due to pumping via the stellar continuum radiation field (Verner et al. 2002). We did not succeed in modelling the spectrum of the broad-line region, and we suggest that a non radiative heating mechanism increases the temperature in the excited H I region, thus providing the necessary additional excitation of the Fe II lines. For the low-excitation narrow-line region, we are able to apply boundaries to the physical conditions accounting for the forbidden and permitted Fe II lines (10 6 < Ne < 10 7 cm −3 ;1 0 −6 < U < 10 −5 ).

Reverse engineering of architectural buildings based on a hybrid modeling approach

This article presents a set of theoretical reflections and technical demonstrations that constitute a new methodological base for the architectural surveying and representation using computer graphics techniques. The problem we treated relates to three distinct concerns: the surveying of architectural objects, the construction and the semantic enrichment of their geometrical models, and their handling for the extraction of dimensional information. A hybrid approach to 3D reconstruction is described. This new approach combines range-based modeling and image-based modeling techniques; it integrates the concept of architectural feature-based modeling. To develop this concept set up a first process of extraction and formalization of architectural knowledge based on the analysis of architectural treaties is carried on. Then, the identified features are used to produce a template shape library. Finally the problem of the overall model structure and organization is addressed.

A generic formalism for the semantic modeling and representation of architectural elements

This article presents a methodological approach to the semantic description of architectural elements based both on theoretical reflections and research experiences. To develop this approach, a first process of extraction and formalization of architectural knowledge on the basis of the analysis of architectural treaties is proposed. Then, the identified features are used to produce a template shape library dedicated to buildings surveying. Finally, the problem of the overall model structuring and organization using semantic information is addressed for user handling purposes.

Static polyhedron simplification using error measurements

Abstract Polyhedral models of objects represent an efficient issue for reverse engineering applications and visualization purposes. Because digitizing devices can produce large amounts of points, the polyhedral representation of objects may require a treatment of simplification to preserve the efficiency of subsequent processes for machining or visualization. Here, a new approach is introduced to reduce the number of nodes of a polyhedral model in accordance to an error criterion which can be easily understood by the user. This criterion uses error zones assigned to each node of the initial polyhedron and guarantees that the simplified polyhedron intersects each of the error zones. This behaviour is equivalent to constraining the simplified polyhedron to be included into the geometric envelope defined by all the error zones attached to the initial polyhedron. The iterative treatments involved in the simplification process incorporate an inheritance mechanism to transfer the error zones from one iteration to the next one. Thus, an intuitive manner to monitor the simplification process is set up. A node selection criterion based on curvature approximation has been included to sort the nodes according to their probability of removal. A specific remeshing scheme has also been included to increase the robustness of the treatment when face arrangements around a node generate distorted polygon shapes. Examples highlight the predictable behaviour of the algorithm.

AGNs with composite spectra - II. Additional data

In a previous paper (Veron et al. 1997) we presented medium resolution (3.4xa0Axa0FWHM ) spectroscopic observations of 15 transition objects”, selected for having an ambiguous location in the Veilleux & Osterbrock (1987) diagnostic diagrams, and showed that most of them were in fact composite”, this being due to the simultaneous presence on the slit of both a Seyfert or Liner nucleus and a HIIu2000region. Here, we report new spectroscopic observations of 53 emission-line galaxies with a transition” spectrum, bringing up to 61 the total number of observed objects in an unbiased sample of 88 transition objects”. Almost all of the observed galaxies have a composite nature, confirming the finding that true transition” spectra may not exist at all. By eliminating composite objects” from the diagnostic diagrams, a clear separation between the different classes of nuclear emission-line regions (Seyfert 2s, Liners and HIIu2000regions) becomes apparent; by restricting the volume occupied by the different line-emitting regions in the 3-dimensional diagnostic diagrams, we are also restricting the range of possible physical parameters in these regions. There seems to be no continuity between Seyfert 2s and Liners, the two classes occupying distinct volumes in the 3-dimensional space defined by , , and .

Shape preserving polyhedral simplification with bounded error

Abstract A new approach is introduced to reduce the number of nodes of a polyhedral model according to several conditions which allow to produce high quality simplified geometries. The simplified polyhedron must satisfy everywhere a geometric restoration criterion based on an error zone assigned to each node of its initial model. These error zones can be specified by the user or automatically set up using the accuracy characteristics of the digitizing device. Moreover, specific criteria are used to preserve the shape of the object during the simplification process both from geometric and topologic points of view. Indeed, the uses of such polyhedra require a good geometric quality without topologic and geometric singularities. The simplification process is based on a node removal method. A new strategy is developed to produce the simplified polyhedron using front propagations and multiple remeshing schemes which take into account the discrete curvature characteristics of the object. Such an approach allows to increase the node reduction of the initial polyhedron and produces a smoothing effect on the simplified geometry. The front propagation technique also leads to a better preservation of the shape of the object. Examples illustrate the behaviour of the simplification algorithm in terms of data reduction, quality of the simplified geometry and shape preservation of objects.

The emission spectrum of the strong fe II emitter bal seyfert 1 galaxy iras 07598+6508

The narrow-line Seyfert 1 galaxy IRASu200907598+6508 is known to be axa0stong Feu2009IIxa0emitter. The analysis of several high S/N xa0ratio spectra shows that its spectrum is dominated by axa0relatively narrow “broad line” region (1780xa0kmu2009s -1 FWHM ) emitting not only Feu2009II, but also Tiu2009II and Cru2009IIxa0lines. Although we were unable to find axa0completely satisfactory physical model, we got the best agreement with the observations with collisional rather than radiative models, with axa0high density (

Are all radio galaxies genuine ellipticals

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