2006/10/31 by Christopher J. Conselice · 6 citations
Environmental Science · Physics and Astronomy · #Astronomy #Astrophysics #Brightest cluster galaxy #Elliptical galaxy #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy formation and evolution #Galaxy merger #Interacting galaxy #Lenticular galaxy #Luminous infrared galaxy #Peculiar galaxy #Physics #Remote Sensing in Agriculture #Star formation #Stellar mass #Stellar, planetary, and galactic studies #Surface brightness fluctuation #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2006.11114.x
published as Mon.Not.Roy.Astron.Soc.373:1389-1408,2006 · MNRAS in press, 22 pages (some references and typos fixed)
arxiv created 2006/11/04 · openalex publication_date 2006/11/17 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present in this paper a new three-dimensional galaxy classification system designed to account for the diversity of galaxy properties in the nearby universe. To construct this system we statistically analyse a sample of >22 000 galaxies at v < 15 000 km s−1 (z < 0.05) with Spearman rank and principal-component analyses (PCAs). Fourteen major galaxy properties are considered, including: Hubble type, size, colour, surface brightness, magnitude, stellar mass, internal velocities, H i gas content and an index that measures dynamical disturbances. We find, to a high degree, that most galaxy properties are correlated, with in particular Hubble type, colour and stellar mass all strongly related. We argue that this tight three-way correlation is a result of evolutionary processes that depend on galaxy mass, as we show that the relation between colour and mass is independent of Hubble type. Various PCAs reveal that most of the variation in nearby galaxy properties can be accounted for by eigenvectors dominated by (i) the scale of a galaxy, such as its stellar mass, (ii) the spectral type and (iii) the degree of dynamical disturbances. We suggest that these three properties: mass, star formation and interactions/mergers are the major features that determine a galaxy's physical state, and should be used to classify galaxies. As shown by Conselice et al., these properties are measurable within the CAS (concentration, asymmetry, clumpiness) structural system, thus providing an efficient mechanism for classifying galaxies in optical light within a physical meaningful framework. We furthermore discuss the fraction and number density of galaxies in the nearby universe as a function of Hubble type, for comparison with higher redshift populations.