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J/A+A/475/217       Classification of planetary nebulae      (Quireza+, 2007)

Bayesian posterior classification of planetary nebulae according to the Peimbert types. Quireza C., Rocha-Pinto H.J., Maciel W.J. <Astron. Astrophys. 475, 217 (2007)> =2007A&A...475..217Q
ADC_Keywords: Planetary nebulae ; Abundances Keywords: ISM: planetary nebulae: general - Galaxy: abundances - Galaxy: kinematics and dynamics - Galaxy: bulge - Galaxy: halo - Galaxy: disk Abstract: In this paper we present a re-analysis of the criteria used to characterize the Peimbert classes I, IIa, IIb, III and IV, through a statistical study of a large sample of planetary nebulae previously classified according to these groups. In the original classification, it is usual to find planetary nebulae that cannot be associated with a single type; these most likely have dubious classifications into two or three types. Statistical methods can greatly contribute in providing a better characterization of planetary nebulae groups. We use the Bayes Theorem to calculate the posterior probabilities for an object to be member of each of the types I, IIa, IIb, III and IV. This calculation is particularly important for planetary nebulae that are ambiguously classified in the traditional method. The posterior probabilities are defined from the probability density function of classificatory parameters of a well-defined sample, composed only by planetary nebulae unambiguously fitted into the Peimbert types. Because the probabilities depend on the available observational data, they are conditional probabilities, and, as new observational data are added to the sample, the classification of the nebula can be improved, to take into account this new information. This method differs from the original classificatory scheme, because it provides a quantitative result of the representativity of the object within its group. Also, through the use of marginal distributions it is possible to extend the Peimbert classification even to those objects for which only a few classificatory parameters are known. Description: Table 1 lists chemical composition, spatial and kinematic properties for a sample of 476 planetary nebulae. Nebular properties have been compiled from selected sources from the literature. Table 6 lists the probability of each planetary nebula to be member of a given Peimbert type. And the final classification of each planetary nebulae according to the Peimbert types (prior and after the statistical analysis). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 198 476 Parameters and pre-classification refs.dat 140 88 References table6.dat 74 476 Posterior probabilities for the planetary nebulae to belong to Peimbert classes
See also: V/84 : Strasbourg-ESO Catalogue of Galactic Planetary Nebulae (Acker+, 1992) V/127 : MASH Catalog of Planetary Nebulae (Parker+ 2006) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 14 A14 --- Name Planetary nebula main designation (Common name) 16- 26 A11 --- PNG Designation of the Galactic Planetary Nebula 28- 32 F5.3 --- He/H ? Helium over hydrogen abundance ratio by number 33 A1 --- n_He/H [:] Note about the He/H abundance ratio (1) 35- 53 A19 --- r_He/H Reference of the He/H abundance ratio 55- 58 F4.2 --- lg(O/H)+12 ? Oxygen over hydrogen abundance ratio by number 60- 81 A22 --- r_lg(O/H)+12 Reference of the O/H abundance ratio 83- 86 F4.2 --- lg(N/H)+12 ? Nitrogen over hydrogen abundance ratio by number 88-106 A19 --- r_lg(N/H)+12 Reference of the N/H abundance ratio 108-112 F5.2 --- lg(N/O) ? Nitrogen over oxygen abundance ratio by number 114-117 F4.1 kpc dhel ? Heliocentric distance 119-120 I2 --- r_dhel ?=- Reference of the heliocentric distance 122-125 F4.1 kpc RGal ? Galactocentric distance 127-132 F6.3 kpc abs(Z) ? Absolute value of the height in relation to the Galactic plane 134-139 F6.1 km/s VLSR ? Radial velocity relative to the Local Sandard of Rest (2) 143-147 F5.1 km/s abs(DV) ? Absolute value of the peculiar velocity 149-154 F6.1 arcsec Theta ? Angular diameter of the planetary nebula 156-163 A8 --- r_Theta Reference of the angular diameter 165-170 F6.1 mJy S5GHz ? 5GHz (6cm) radio flux density 172-174 I3 --- r_S5GHz ?=- Reference of the 5 GHz flux density 176-198 A23 --- Type Classification according to the Peimbert's types
Note (1): ":" in the He/H abundance ratio, denotes sources with He/H<0.06 (probable low-excitation sources); sources that have simultaneously very high He/H (generally He/H>0.180) and very low N/O abundance ratios; or outliers in the trend of increasing N/O versus He/H (He2-152 and M1-11). Note (2): Radial velocities from the catalog of Durand et al. (1998, Cat. J/A+AS/132/13) Exceptions are DdDm1 and NGC 2242, whose velocity were adopted from Howard et al. (1997MNRAS.284..465H). For every object, the heliocentric radial velocities have been converted to the Local Standard of Rest radial velocities (see text).
Byte-by-byte Description of file: refs.dat
Bytes Format Units Label Explanations
1- 3 I3 --- Ref Reference number 5- 23 A19 --- BibCode BibCode 25- 50 A26 --- Aut Author's name 52-140 A89 --- Com Comments
Byte-by-byte Description of file: table6.dat
Bytes Format Units Label Explanations
1- 14 A14 --- Name Planetary nebula main designation (Common name) 16- 19 F4.2 --- p(typeI) Posterior probability for the membership of each object to the type I group 22- 25 F4.2 --- p(typeIIa) Posterior probability for the membership of each object to the type IIa group 28- 31 F4.2 --- p(typeIIb) Posterior probability for the membership of each object to the type IIb group 34- 37 F4.2 --- p(typeIII) Posterior probability for the membership of each object to the type III group 40- 43 F4.2 --- p(typeIV) Posterior probability for the membership of each object to the type IV group 45- 66 A22 --- Pre-class Previous classification (as in column "Type" of Table 1) 68- 74 A7 --- Post-class Posterior classification
Acknowledgements: Cintia Quireza, quireza(at)on.br
(End) Cintia Quireza [Obs. Nacional (MCT), Brazil], P. Vannier [CDS] 22-Oct-2007
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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