J/MNRAS/274/1107 Morphological classifications of APM galaxies (Naim+ 1995)
A comparative study of morphological classifications of APM galaxies
Naim A., Lahav O., Buta R.J., Corwin H.G.Jr., De Vaucouleurs G.,
Dressler A., Huchra J.P., Van Den Bergh S., Raychaudhury S., Sodre L.Jr,
Storrie-Lombardi M.C.
<Mon. Not. R. Astron. Soc. 274, 1107 (1995)>
=1995MNRAS.274.1107N 1995MNRAS.274.1107N
ADC_Keywords: Galaxy catalogs ; Morphology
Keywords: methods: data analysis - galaxies: general - galaxies: structure
Abstract:
We investigate the consistency of visual morphological classifications
of galaxies by comparing classifications for 831 galaxies from six
independent observers. The galaxies were classified on laser print
copy images or on computer screen using scans made with the Automated
Plate Measuring (APM) machine. Classifications are compared using the
Revised Hubble numerical type index T. We find that individual
observers agree with one another with rms combined dispersions of
between 1.3 and 2.3 type units, typically about 1.8 units. The
dispersions tend to decrease slightly with increasing angular diameter
and, in some cases, with increasing axial ratio (b/a). The agreement
between independent observers is reasonably good but the scatter is
non-negligible. In spite of the scatter, the Revised Hubble T system
can be used to train an automated galaxy classifier, e.g. an
artificial neural network, to handle the large number of galaxy images
that are being compiled in the APM and other surveys.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
experts.dat 99 835 Unified table of T-type classifications and mean types
gdevauc.dat 27 833 G. de Vaucouleurs full classification
hcorwin.dat 38 833 H. Corwin full classification
svdbergh.dat 52 833 S. van den Bergh full classification
jhuchra.dat 53 835 J. Huchra full classification
rbuta.dat 72 835 R. Buta full classification
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See also:
VII/155 : Third Reference Cat. of Bright Galaxies (RC3) (de Vaucouleurs+ 1991)
Byte-by-byte Description of file: experts.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- GalID Galaxy identification
11- 12 I2 h RAh Right ascension (1950)
14- 15 I2 min RAm Right ascension (1950)
17- 20 F4.1 s RAs Right ascension (1950)
22 A1 --- DE- Declination sign
23- 24 I2 deg DEd Declination (1950)
26- 27 I2 arcmin DEm Declination (1950)
29- 32 F4.1 arcsec DEs Declination (1950)
34- 38 F5.2 arcmin Diam Diameter
41- 45 F5.1 --- RC3 ?=999 RC3 (Cat. VII/155) T-type
classification (1)
47- 49 I3 --- RB ?=999 R. Buta classification (1)
51- 53 I3 --- HC ?=999 H. Corwin classification (1)
55- 59 F5.1 --- GV ?=999 G. de Vaucouleurs classification (1)
61- 63 I3 --- AD ?=999 A. Dressler classification (1)
65- 67 I3 --- JH ?=999 J. Huchra classification (1)
69- 71 I3 --- vdB ?=999 ? S. van den Bergh classification (1)
73- 78 F6.2 --- Ts ?=999 Straight-mean type (1)
80- 85 F6.2 --- Tw ?=999 Weighted-mean type (1)
87-101 A15 --- Names Other Ids
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Note (1): Numerical types outside the range [-6,11] have the following
interpretations:
66: duplicate image
77: not a galaxy (plate faults, etc.)
88: merger
90: type I0
99: peculiar
999: no classification given
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Byte-by-byte Description of file: gdevauc.dat hcorwin.dat svdbergh.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- GalID Galaxy identification
11- 52 A42 --- Class Full classification
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Byte-by-byte Description of file: jhuchra.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- GalID Galaxy identification
10- 13 I4 --- NGC ? NGC number of the galaxy
15- 53 A39 --- Class Full classification
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Byte-by-byte Description of file: rbuta.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Gal Galaxy identification
12- 24 A13 --- Class Full classification
25- 27 I3 --- Type T-type classification
28- 29 A2 --- u_Type [: ?] Uncertainty flag on Type
30- 72 A43 --- Com Comments
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(End) Patricia Bauer [CDS] 27-Feb-1998