%0 Journal Article
%T A Principle Component Analysis of Galaxy Properties from a Large, Gas-Selected Sample
%A Yu-Yen Chang
%A Rikon Chao
%A Wei-Hao Wang
%A Pisin Chen
%J Advances in Astronomy
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/208901
%X Disney et al. (2008) have found a striking correlation among global parameters of HI-selected galaxies and concluded that this is in conflict with the CDM model. Considering the importance of the issue, we reinvestigate the problem using the principal component analysis on a fivefold larger sample and additional near-infrared data. We use databases from the Arecibo Legacy Fast Arecibo -band Feed Array Survey for the gas properties, the Sloan Digital Sky Survey for the optical properties, and the Two Micron All Sky Survey for the near-infrared properties. We confirm that the parameters are indeed correlated where a single physical parameter can explain 83% of the variations. When color ( ) is included, the first component still dominates but it develops a second principal component. In addition, the near-infrared color ( ) shows an obvious second principal component that might provide evidence of the complex old star formation. Based on our data, we suggest that it is premature to pronounce the failure of the CDM model and it motivates more theoretical work. 1. Introduction One way to understand our universe is to gain insights into the structure of galaxies. For one thing, it helps to reveal the role of dark matter in their formation and dynamics. The cosmological model that consists of a cosmological constant and the cold dark matter in addition to the ordinary baryon matter and radiation ( CDM) has been able to successfully explain the evolution of the cosmic structures especially at large scales. By measuring CMB fluctuations COBE [4, 5], WMAP [6¨C9], Type Ia supernovae [10], and gravitational lensing [11], this model of cosmology has by now been established as the standard model of cosmology. Among its various implications, it suggests a hierarchical, bottom-up history of structure formation that evolves from small fluctuations to galaxies, clusters, and eventually superclusters. On the other side, the success of CDM has not been as clearcut at small scales. There still exist several inconsistencies between CDM and the observations at small scales. For example, the simulations based on CDM have revealed more number of galactic satellites [12¨C15] and less number of disk galaxies [16] than what have been observed. Besides, the degree of emptiness in the voids is also inconsistent between theory and observation [17]. While the CDM can explain the galaxy rotational curves at large radii [18], the relatively higher density at the galactic core than that predicted by the CDM, that is, the so-called cusp-core problem, is still unresolved [19]. The
%U http://www.hindawi.com/journals/aa/2012/208901/