MORFOMETRYKA-A NEW WAY OF ESTABLISHING MORPHOLOGICAL CLASSIFICATION OF GALAXIES

Author(s)

Ferrari, F. ^[1] ; de Carvalho, R. R. ^[2] ; Trevisan, M. ^{[2, 3]}

Affiliation

^[1] IMEF FURG, Rio Grande, RS - Brazil

^[2] INPE MCT, Div Astrofis, Sao Jose Dos Campos - Brazil

^[3] Inst Astrophys Paris, F-75014 Paris - France

• Document type: Journal article
• Source: ASTROPHYSICAL JOURNAL; v. 814, n. 1 NOV 20 2015.
• Web of Science Citations: 8

Abstract

We present an extended morphometric system to automatically classify galaxies from astronomical images. The new system includes the original and modified versions of the CASGM coefficients (Concentration C-1, Asymmetry A(3), and Smoothness S-3), and the new parameters entropy, H, and spirality sigma(psi). The new parameters A(3), S-3, and H are better to discriminate galaxy classes than A(1), S-1, and G, respectively. The new parameter sigma(psi) the amount of non-radial pattern on the image and is almost linearly dependent on T-type. Using a sample of spiral and elliptical galaxies from the Galaxy Zoo project as a training set, we employed the Linear Discriminant Analysis (LDA) technique to classify EFIGI (Baillard et al. 4458 galaxies), Nair \& Abraham (14,123 galaxies), and SDSS Legacy (779,235 galaxies) samples. The cross-validation test shows that we can achieve an accuracy of more than 90% with our classification scheme. Therefore, we are able to define a plane in the morphometric parameter space that separates the elliptical and spiral classes with a mismatch between classes smaller than 10%. We use the distance to this plane as a morphometric index (M-i) and we show that it follows the human based T-type index very closely. We calculate morphometric index Mi for similar to 780k galaxies from SDSS Legacy Survey DR7. We discuss how Mi correlates with stellar population parameters obtained using the spectra available from SDSS DR7. (AU)

• FAPESP's process: 12/05142-5 - Assembling Baryons to Dark Halos: Stellar Content and the Star Formation History of Early-­type Galaxies
• Grantee: Marina Trevisan
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 14/11156-4 - What drives the stellar mass growth of Early-Type galaxies? Born or made: the saga continues
• Grantee: Reinaldo Ramos de Carvalho
• Support Opportunities: Research Projects - Thematic Grants