Towards a new classification of galaxies: principal component analysis of CALIFA circular velocity curves

DOI: 
10.1093/mnras/stx901
Publication date: 
01/08/2017
Main author: 
Kalinova, V.
IAA authors: 
García-Benito, R.;González Delgado, R.;Sánchez-Menguiano, L.
Authors: 
Kalinova, V.;Colombo, D.;Rosolowsky, E.;Kannan, R.;Galbany, L.;García-Benito, R.;González Delgado, R.;Sánchez, S. F.;Ruiz-Lara, T.;Méndez-Abreu, J.;Catalán-Torrecilla, C.;Sánchez-Menguiano, L.;de Lorenzo-Cáceres, A.;Costantin, L.;Florido, E.;Kodaira, K.;Marino, R. A.;Läsker, R.;Bland-Hawthorn, J.
Journal: 
Monthly Notices of the Royal Astronomical Society
Refereed: 
Yes
Publication type: 
Article
Volume: 
469
Pages: 
2539-2594
Abstract: 

We present a galaxy classification system for 238 (E1-Sdm) CALIFA (Calar Alto Legacy Integral Field Area) galaxies based on the shapes and amplitudes of their circular velocity curves (CVCs). We infer the CVCs from the de-projected surface brightness of the galaxies, after scaling by a constant mass-to-light ratio based on stellar dynamics - solving axisymmetric Jeans equations via fitting the second velocity moment V_{rms}=√{V^2+σ ^2} of the stellar kinematics. We use principal component analysis (PCA) applied to the CVC shapes to find characteristic features and use a k-means classifier to separate circular curves into classes. This objective classification method identifies four different classes, which we name slow-rising (SR), flat (FL), round-peaked (RP) and sharp-peaked (SP) circular curves. SR are typical for low-mass, late-type (Sb-Sdm), young, faint, metal-poor and disc-dominated galaxies. SP are typical for high-mass, early-type (E1-E7), old, bright, metal-rich and bulge-dominated galaxies. FL and RP appear presented by galaxies with intermediate mass, age, luminosity, metallicity, bulge-to-disc ratio and morphologies (E4-S0a, Sa-Sbc). The discrepancy mass factor, f<SUB>d</SUB> = 1 - M<SUB>*</SUB>/M<SUB>dyn</SUB>, have the largest value for SR and SP classes (̃ 74 per cent and ̃ 71 per cent, respectively) in contrast to the FL and RP classes (with ̃ 59 per cent and ̃ 61 per cent, respectively). Circular curve classification presents an alternative to typical morphological classification and appears more tightly linked to galaxy evolution.

Database: 
ADS
SCOPUS
URL: 
https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020264270&doi=10.1093%2fmnras%2fstx901&partnerID=40&md5=d1ec8d06238a53836431fc447ec109b7
ADS Bibcode: 
2017MNRAS.469.2539K
Keywords: 
methods: data analysis;methods: statistical;galaxies: evolution;galaxies: kinematics and dynamics;galaxies: structure