Independent Component Analysis for the objective classification of globular clusters of the galaxy NGC 5128

  • Authors:
  • Asis Kumar Chattopadhyay;Saptarshi Mondal;Tanuka Chattopadhyay

  • Affiliations:
  • Department of Statistics, Calcutta University, Kolkata/ 35, Ballygunge Circular Road, Kolkata - 700019, India;Department of Statistics, Calcutta University, Kolkata/ 35, Ballygunge Circular Road, Kolkata - 700019, India;Department of Applied Mathematics, Calcutta University, Kolkata/ 92 A.P.C. Road, Kolkata - 700009, India

  • Venue:
  • Computational Statistics & Data Analysis
  • Year:
  • 2013

Quantified Score

Hi-index 0.03

Visualization

Abstract

Independent Component Analysis (ICA) is closely related to Principal Component Analysis (PCA) and factor analysis. Whereas ICA finds a set of source data that are mutually independent, PCA finds a set of data that are mutually uncorrelated. The assumption that data from different physical processes are uncorrelated does not always imply the reverse case that uncorrelated data are coming from different physical processes. This is because lack of correlation is a weaker property than independence. In the present case an objective classification of the globular clusters (GCs) of NGC 5128 has been carried out. Components responsible for significant variation have been obtained through both Principal Component Analysis (PCA) and Independent Component Analysis (ICA) and the classification has been done by K-means clustering. The set of observable parameters includes structural parameters, spectroscopically determined Lick indices and radial velocities from the literature. We propose that GCs of NGC 5128 consist of two groups. One group originated in the original cluster formation event that coincided with the formation of the elliptical galaxy and the other group emerged from an accreted spiral galaxy. This is unlike the previous result (Chattopadhyay et al., 2009) which accounts for a third group originating from the accretion of tidally stripped dwarf galaxies.