The nature of the Sloan Digital Sky Survey galaxies in various classes based on morphology, colour and spectral features - I. Optical properties

Abstract

We present a comprehensive study of the nature of the Sloan Digital Sky Survey (SDSS) galaxies divided into various classes based on their morphology, colour and spectral features. The SDSS galaxies are classified into early-type and late-type; red and blue; passive, H II, Seyfert and LINER, returning a total of 16 fine classes of galaxies. We examine the luminosity dependence of seven physical parameters of galaxies in each class. We find that more than half of red early-type galaxies (REGs) have star formation or active galactic nuclei activity, and that these active REGs have smaller axis ratio and bluer outside compared to the passive REGs. Blue early-type galaxies (BEGs) show structural features similar to those of REGs, but their centres are bluer than REGs. H II BEGs are found to have bluer centres than passive BEGs, but H II REGs have bluer outside than passive REGs. Bulge-dominated late-type galaxies have red colours. Passive red late-types are similar to REGs in several aspects. Most blue late-type galaxies (BLGs) have forming stars, but a small fraction of BLGs do not show evidence for current star formation activity. Differences of other physical parameters among different classes are inspected, and their implication on galaxy evolution is discussed.

Korea Institute for Advanced Study Value-Added Galaxy Catalog

“…Morphology information given by this scheme has been used in many studies on relation between galaxy properties and the environment (Choi et al 2007;Park et al 2007; Lee et al 2008 Han et al 2010) and on the topology of large scale structure Zhang, Springel, & Yang 2010). Reliability and completeness of this classification reaches about 90% (Park & Choi 2005).…”

The nature of the Sloan Digital Sky Survey galaxies in various classes based on morphology, colour and spectral features - III. Environments

“…For example, several unusual classes of galaxies such as blue early‐type galaxies (BEGs) (Ferreras et al 2005; Lee, Lee & Hwang 2006) and passive spiral galaxies (Yamauchi & Goto 2004; Ishigaki, Goto & Matsuhara 2007), or the fundamental parameter difference between finely divided classes in the same morphology class (Lee et al 2007; Choi, Goto & Yoon 2009a) are difficult to investigate using simple classification schemes. Recently, Lee et al (2008, 2010, hereafter Paper I and Paper II, respectively) presented studies on the optical and multiwavelength properties of the Sloan Digital Sky Survey (SDSS; York et al 2000) galaxies divided into fine classes based on their morphology, colour and spectral features. Those finely classified SDSS galaxies show distinguishable differences from each other in their photometric (both optical and multiwavelength) and structural properties, which are hardly found in the studies using simple classification schemes.…”

Spectral classification and composites of galaxies in LAMOST DR4

“…1981, Kewley et al 2001, Kauffmann et al 2003a, Brinchmann et al 2004, Kewley et al 2006, Stasinska et al 2006, Cid Fernandes et al 2010. Some researchers also use more than one criterion, for example, in the work of Lee et al (2008), galaxies were classified into 16 classes by morphology, color and spectral features, and Dobos et al (2012) presented a refined classification using both color and spectral features for galaxies. For the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey, we use spectral features in galaxy classification in this paper .…”

“…In Lee et al (2008), passive galaxies were selected as galaxies with no or insufficient signal of Hα emission. In Dobos et al (2012), passive galaxies were divided into two further classes: completely passive with no detectable emission lines and passive with weak Hα emission.…”