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J/A+A/525/A157 SDSS automated morphology classification (Huertas-Company+, 2011)

Revisiting the Hubble sequence in the SDSS DR7 spectroscopic sample: a publicly available Bayesian automated classification. Huertas-Company M., Aguerri J.A.L., Bernardi M., Mei S., Sanchez Almeida J. <Astron. Astrophys. 525, A157 (2011)> =2011A&A...525A.157H
ADC_Keywords: Surveys ; Galaxies, spectra ; Morphology Keywords: catalogs - astronomical databases: miscellaneous - Galaxy: fundamental parameters - galaxies: evolution - Galaxy: formation Abstract: We present an automated morphological classification in 4 types (E, S0, Sab, Scd) of ∼700 000 galaxies from the SDSS DR7 spectroscopic sample based on support vector machines. The main new property of the classification is that we associate a probability to each galaxy of being in the four morphological classes instead of assigning a single class. The classification is therefore better adapted to nature where we expect a continuous transition between different morphological types. The algorithm is trained with a visual classification and then compared to several independent visual classifications including the Galaxy Zoo first-release catalog. We find a very good correlation between the automated classification and classical visual ones. Description: We used all the SDSS DR7 spectroscopic sample as the starting base. Then, the selection of objects was based on Sanchez Almeida et al. (2010ApJ...714..487A) who performed an unsupervised automated classification of all the SDSS spectra. Basically, we chose galaxies with redshift below 0.25, and with good photometric data and clean spectra, meaning objects not too close to the edges, not saturated, or not properly deblended. The final catalog contains 698420 objects for which we estimate the morphology (also available at http://gepicom04.obspm.fr/sdss_morphology/Morphology_2010.html ). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file catalog.dat 163 698420 Automated probabilistic morphological classification of SDSS DR7 catalog classes.dat 62 28 Main properties of the ASK classes (from Sanchez Alemida et al., 2010ApJ...714..487A) catalog.fit 2880 21345 FITS file of the catalog
See also: http://www.sdss.org : SDSS Home Page Byte-by-byte Description of file: catalog.dat
Bytes Format Units Label Explanations
1- 6 I6 --- ID [1,699684] Sequential number 10- 27 A18 --- SpecObjID SDSS SpecObjID 29- 39 F11.7 deg RAdeg Right ascension in decimal degrees (J2000) 41- 51 E11.7 deg DEdeg Declination in decimal degrees (J2000) 53- 62 E10.7 --- z Redshift (from SDSS-DR7) 64- 72 E9.7 --- pE/S0 Probability of being early-type (E or S0) 74- 94 E21.19 --- pE Probability of being elliptical 96-116 E21.19 --- pS0 Probability of being S0 type 118-138 F21.19 --- pSab Probability of being Sa or Sb 140-160 F21.19 --- pScd Probability of being Sc or Sd 162-163 I2 --- ASK [0/27] Spectral class from Sanchez Alemida et al. (2010ApJ...714..487A) in classes.dat file
Byte-by-byte Description of file: classes.dat
Bytes Format Units Label Explanations
1- 2 I2 --- ASK [0/27] ASK Class 3 A1 --- n_ASK [*] Major class (1) 5- 10 I6 --- N Number of members in SDSS DR7 12- 15 F4.2 mag u-g SDSS u-g computed colour index (2) 17- 21 F5.2 mag g-r SDSS g-r computed colour index(2) 23- 27 F5.2 mag r-i SDSS r-i computed colour index(2) 29- 33 F5.1 0.1nm EWHb Equivalent width of Hbeta (3) 35- 39 F5.1 0.1nm EW[OIII] Equivalent width of [OIII] lambda5007 (3) 41- 45 F5.1 0.1nm EWHa Equivalent width of Halpha (3) 47- 50 F4.1 0.1nm EW[NII] Equivalent width of [N II] lambda6583 (3) 52- 54 I3 % Em Percentage of galaxies in the class with Hbeta in emission according to the SDSS/DR7 catalog 56- 62 A7 --- Clust Clustering (Good, Neutral)
Note (1): The asterisks denote major classes, i.e., those that altogether include 99% of the galaxies. Note (2): The colors have been computed from the template spectra using the appropriate SDSS bandpasses. Note (3): Equivalent width in the template spectra given in Aring. Negative implies line in absorption.
Acknowledgements: Marc Huertas-Company, marc.huertas(at)obspm.fr
(End) Patricia Vannier [CDS] 10-Dec-2010
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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