The Millennium Galaxy Catalogue: on the natural subdivision of galaxies

S. C. Ellis, S. P. Driver, P. D. Allen, J. Liske, J. Bland-Hawthorn, R. De Propris

Research output: Contribution to journalArticleResearchpeer-review

Abstract

The distribution of global photometric, spectroscopic, structural and morphological parameters for a well-defined sample of 350 nearby galaxies has been examined. The usual trends were recovered demonstrating that E/SO galaxies are redder, more quiescent, more centrally concentrated and possess larger Sérsic indices than late-type galaxies. Multivariate statistical analyses were performed to examine the distribution of all parameters simultaneously. The main result of these analyses was the existence of only two classes of galaxies, corresponding closely to early and late types. Linear discriminant analysis (LDA) was able to reproduce the classifications of early- and late-type galaxies with high success, but further refinement of galaxy types was not reproduced in the distribution of observed galaxy properties. A principal components analysis (PCA) showed that the major variance of the parameter set corresponded to a distinction between early and late types, highlighting the importance of the distinction. A hierarchical clustering analysis (HCA) revealed only two clear natural classes within the parameter set, closely corresponding to early and late types. Early and late types are clearly distinct and the distinction is of fundamental importance. In contrast, late types from Sa to Irr are smoothly distributed throughout the parameter space. A population of galaxies classified by eye as elliptical/lenticular, and exhibiting concentration indices similar to early types were found to have a significant star formation activity. These galaxies are preferentially faint, suggesting they are low-mass systems.

LanguageEnglish
Pages1257-1271
Number of pages15
JournalMonthly Notices of the Royal Astronomical Society
Volume363
Issue number4
DOIs
Publication statusPublished - 11 Nov 2005
Externally publishedYes

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subdivisions
catalogs
galaxies
discriminant analysis
principal component analysis
parameter
principal components analysis
star formation
distribution
trends

Cite this

Ellis, S. C. ; Driver, S. P. ; Allen, P. D. ; Liske, J. ; Bland-Hawthorn, J. ; De Propris, R. / The Millennium Galaxy Catalogue : on the natural subdivision of galaxies. In: Monthly Notices of the Royal Astronomical Society. 2005 ; Vol. 363, No. 4. pp. 1257-1271.
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The Millennium Galaxy Catalogue : on the natural subdivision of galaxies. / Ellis, S. C.; Driver, S. P.; Allen, P. D.; Liske, J.; Bland-Hawthorn, J.; De Propris, R.

In: Monthly Notices of the Royal Astronomical Society, Vol. 363, No. 4, 11.11.2005, p. 1257-1271.

Research output: Contribution to journalArticleResearchpeer-review

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