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Infrared Imaging and Optical Imaging and Spectroscopy of (mostly) Type I Planetary Nebulae. I.
Optical spectra, images in the main optical emission lines and IR imagesdirected towards the detection of molecular hydrogen, were obtained for14 planetary nebulae (PNe). It was found that nine of these comply withthe two criteria defining a type I PNe (He-rich with a large N/O ratio).All of these objects are bipolar and, with the exception of Sh 2-71,show shocked molecular hydrogen. The chemical composition of JnEr 1indicates it was produced by a massive progenitor, and it can betentatively classified as a type I PN. A 26 is a helium rich ellipticalPN with a low N/O abundance ratio, probably without H2.Shocked H2 was found in K 3-92, an elliptical type IIb PN,which implies that this object is probably young. The chemicalcomposition of K 3-72, K 4-55, M 1-75, and Sh 2-71 indicate that thirddredge-up episodes occurred in their progenitor star. The temperaturesand spectral properties of BV 5-1, K 4-55, M 1-41, M 1-75, and Sh 2-71suggest the presence of shock waves in their ionized component.

Nearby Optical Galaxies: Selection of the Sample and Identification of Groups
In this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation ``friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales.

Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies
We present a catalogue of aperture photometry of galaxies, in UBVRI,assembled from three different origins: (i) an update of the catalogueof Buta et al. (1995) (ii) published photometric profiles and (iii)aperture photometry performed on CCD images. We explored different setsof growth curves to fit these data: (i) The Sersic law, (ii) The net ofgrowth curves used for the preparation of the RC3 and (iii) A linearinterpolation between the de Vaucouleurs (r(1/4) ) and exponential laws.Finally we adopted the latter solution. Fitting these growth curves, wederive (1) the total magnitude, (2) the effective radius, (3) the colourindices and (4) gradients and (5) the photometric type of 5169 galaxies.The photometric type is defined to statistically match the revisedmorphologic type and parametrizes the shape of the growth curve. It iscoded from -9, for very concentrated galaxies, to +10, for diffusegalaxies. Based in part on observations collected at the Haute-ProvenceObservatory.

Excitation class of nebulae - an evolution criterion?
A principally new quantitative system of the classification of thespectra of planetary nebulae is proposed. Spectral class of excitationclass of the nebula p is determined according to the relativeintensities of forbidden mission lines (N1 + N2) O III/4686 He II and(N1 + N2) O III/H-beta. The excitation classes are obtained for 142planetary nebulae of all classes - low (p = 1-3), middle (p = 4-8), andhigh (p = 9-12/+/). An empirical relationship between excitation classp, as an independent parameter, admit an evolutionary interpretation. Itis shown that after reaching the highest class of excitation p = 12(+)the nebulae decrease their class of excitation with the furtherincreases of sizes.

Galaxy alignments
Large areas of the sky around the brightest apparent magnitude galaxieshave been examined. In almost every case where they are not crowded byother right galaxies, clearly marked lines of higher red shift galaxieshave been going through, or originating from, the positions of thesebright apparent magnitude galaxies. It is shown that galaxies of about3000 to 5000 km/s red shift define narrow filaments of from 10 to 50 degin length. It is found that galaxies of very bright apparent magnitudetend to occur at the center or ends of these alignments. The 20brightest galaxies in apparent magnitude north of delta = 0 deg areinvestigated here. Of the 14 which are uncrowded by nearby brightgalaxies, a total of 13 have well marked-lines and concentrations offainter, higher red shift galaxies.

The environment and the origin of twisting in early-type galaxies
The effects of random collisions in groups or clusters on thedevelopment of isophotal twisting (IT) in early-type galaxies areinvestigated. The maximum ellipticity and IT in each galaxy is estimatedon the basis of published observational data and correlated with thegalaxy number density. The proportions of S0 and elliptical (E) galaxieswith IT are found to be independent of local environmental density. CCDobservations of six isolated nonhierarchical pairs containing early-typegalaxies, obtained at the Cassegrain focus of the 1.82-m telescope atAsiago Observatory, are then used to study tidal interactions ingalaxies with normal morphology; the data are presented in tables andgraphs and examined in detail. It is shown that mutual tidalperturbations alone cannot explain the IT phenomena: S0 galaxies areless twisted than Es in all density regimes, and the proportion oftwisted Es in E+E pairs is similar to that in the overall sample.

Morphology of bipolar planetary nebulae. II - The three-dimensional structures
Isophotal maps of bipolar planetary nebulae (BPN) are used here to studythe BPN morphology and to produce maps of their normalized densitydistribution. Shell models are calculated, and the theoretical isophotesare compared with CCD contours. It is shown that a simple large-scalesmooth structure can be derived and that a unique prolate model with twoor three adjustable parameters seems suitable for most BPN. The BPNNGC6720, NGC7293, and He2-66 are shown to be morphologically identical.

Deep-sky wonders.
Not Available

Radio and infrared structures of type I post-main sequence nebulae
High-resolution VLA radio mapping at 1.46, 4.84, and 15.0 GHz ispresented together with NIR J,H,K,L, and M mapping and photometry of abroad range of type I postmain-sequence nebulae. Many of these sourceshave extremely compact infrared and radio cores ranging from 0.1 to 0.01pc in size; in some cases they contain up to 96 percent of the totalradio flux. A detailed investigation of the IRAS photometry for type Inebulae was undertaken; a typical interior grain temperature isestimated to be 200 K while outer shell temperatures are estimated to beless than 50 K.

Two senile nearby planetary nebulae and the local PN population
Two newly found, exceptionally large, nearby planetary nebulae (PN) arereported. Both are PN at a very late evolutionary state, with H-alphasurface brightnesses over 25.1 mag/sq arcsec, linear radii over 0.56 pc,and electron densities less than 10/cu cm. The expansion velocities areless than 8 km/s in forbidden O III and the absolute magnitudes of thecentral stars are very small. The local PN population was investigated,and high projected surface densities and space densities were obtained.The PN birthrate is about 0.008/cu kpc/yr, much larger than the whitedwarf birthrate.

Lokale Planetarische Nebel - eine Revision
Not Available

Statistical evolutionary properties of planetary nebulae Thicknesses of the nebulae and temperatures of the stars
A comparative study of Zanstra temperatures of the central stars ofplanetary nebulae indicates that when present the discrepancies betweenTZ H I and TZ He II can be mainly ascribed to the variation of theoptical thickness of a nebulae of hydrogen and helium ionized by a starwhich emits as a black-body. Different evolutionary trends of TZ H I andTZ He II are obtained for planetary nebulae of the subclasses B and C ofGreig (1971, 1972): B nebulae spend most of their life in a thickstatus, whereas C nebulae start as thick objects but they quickly becomeoptically thin. These results give further support to the suggestion bySabbadin (1984) that planetary nebulae of the subclass B have stellarmasses and/or nebular masses which are statistically larger than thoseof planetary nebulae belonging to the subclass C.

Ultraviolet spectra of the central stars of large planetary nebulae
The ultraviolet spectra of 32 planetary nebula nuclei have been examinedwith the IUE. Ultraviolet and UV-to-optical flux ratios are derived,from which color temperatures are derived. The distribution of thelatter ranges from rough agreement with the Zanstra temperatures upwardto infinite values. The high-luminosity stars have generally lower,determinable color temperatures; the infinite or indeterminable colortemperatures are contained by the set of lower luminosity stars. Abouthalf the stars exhibit a mixture of line features, most commonly He II1640 A and C IV 1550 A in emission or absorption. Three display clear PCygni lines, while a fourth appears to display a remarkably broad C IV1550 A P Cygni profile. The other half of the stars have no perceptibleline features.

Type I planetary nebulae
The general properties of PN of Type I are reviewed. A list of 29 PN ofType I is presented, most of them are bipolar. Their bipolar naturemight be a direct consequence of the large masses and angular momenta oftheir progenitor stars. PN of Type I are He and N rich, their observedchemical abundances are compared with theoretical predictions. A groupof Type I PN candidates is presented.

The evolution of large planetary nebulae and their central stars
A description is presented of results obtained in wide aperturespectrophotometry studies of large planetary nebulae, taking intoaccount the interpretation of the data in terms of location on the logL-log T plane, abundances, and morphology. The criterion forconsideration is that the nebular radius be larger than 0.175 pc, wherethe distance and radius are based upon the distance scale used by Cahnand Kaler (1971), the measured H-beta flux, and extinction, and thelargest angular radius given by Perek and Kohoutek (1967). Attention isgiven to the photometry provided by the Prairie Observatory, publishedphotometry, the calibration of photographic fluxes, a comparison withradio fluxes, the coordinates of the nebulae, central star magnitudes,angular radii and geometric filling factors, distances and radii,Zanstra temperatures and luminosities, the choice of temperature andluminosity, nitrogen-to-oxygen ratios, the distribution of core masses,time scales, and questions of evolution and stellar mass.

Corrections to the Reference Catalogue of Bright Galaxies
Not Available

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Observation and Astrometry data

Right ascension:07h58m00.40s
Aparent dimensions:0.813′ × 0.759′

Catalogs and designations:
Proper Names   (Edit)
NGC 2000.0NGC 2475

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