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 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:
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FileName Lrecl Records Explanations
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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
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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
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Bytes Format Units Label Explanations
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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
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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 1997MNRAS.284..465H). For every
object, the heliocentric radial velocities have been converted to the
Local Standard of Rest radial velocities (see text).
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Ref Reference number
5- 23 A19 --- BibCode BibCode
25- 50 A26 --- Aut Author's name
52-140 A89 --- Com Comments
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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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
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Acknowledgements:
Cintia Quireza, quireza(at)on.br
(End) Cintia Quireza [Obs. Nacional (MCT), Brazil], P. Vannier [CDS] 22-Oct-2007