The fundamental properties of galaxies and a new galaxy classification system

By Christopher J. Conselice. 2006

159 citations recorded by the source corpus.

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.

Subfields: Astronomy and Astrophysics, Ecology

View Paper: https://www.semanticscholar.org/paper/bf9792911a39680f0a324fa0e1cc6ff8de6bc508

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Citations in the corpus

Galaxy Zoo: Disentangling the Environmental Dependence of Morphology and Colour ⋆ (2008, methodology): “Automated methods for classifying galaxies using more structural information have also been recently developed (e.g., Conselice 2006, Park et al. 2007).”
The structures of distant galaxies – III. The merger history of over 20 000 massive galaxies at z < 1.2 (2008, methodology): “As shown in Conselice (2006) there are phases of a merger which will not be picked up by the CAS technique.”
Introducing the Illustris Project: simulating the coevolution of dark and visible matter in the Universe (2014, methodology): “24, where we compare our findings to the observations of Conselice (2006) and to the predictions of the semi-analytic model of Guo et al. (2011) (based on the MS-II).”
Minor Galaxy Interactions: Star Formation Rates and Galaxy Properties (2007, background): “Galaxy colors are well correlated with gas content, star formation rates, and other galaxy properties (e.g., Sandage & Visvanathan 1978; Baldry et al. 2004; Bernardi et al. 2003; Conselice 2006).”
Erratum: From dwarf spheroidals to cD galaxies: simulating the galaxy population in a ΛCDM cosmology (2010, background): “4 are observational results from Conselice (2006).”
Galaxy Zoo 1: data release of morphological classifications for nearly 900 000 galaxies (2010, background): “concentration index, spectral features, surface brightness profile, structural features, spectral energy distribution (Kinney et al. 1996) or some combination of these as a proxy for morphology (e.g. Abraham, van den Bergh & Nair 2003; Conselice 2006).”
Galactic accretion and the outer structure of galaxies in the CDM model (2013, result): “This is in good agreement with observations (e.g. Conselice 2006, see figure 4 of G11) and a similar transition scale has been found in other semi-analytic models (De Lucia et al. 2011).”
The evolution of massive black holes and their spins in their galactic hosts (2012, background): “The symbols are actual dat from Conselice (2006) (squares: ellipticals, circles: spirals, stars: irregulars), while the predictions of our model are shown withthick lines (heavy seeds) and thin lines (light seeds).”
STELLAR MASSES AND STAR FORMATION RATES FOR 1 M GALAXIES FROM SDSS+WISE (2015, background): “However, as most recently shown by Taylor et al. (2015), many galaxies in this region are reddened because of dust (also see, e.g., Conselice 2006) and not primarily due to a reduced level of SF.”
A CATALOG OF BULGE+DISK DECOMPOSITIONS AND UPDATED PHOTOMETRY FOR 1.12 MILLION GALAXIES IN THE SLOAN DIGITAL SKY SURVEY (2011, background): “…properties have made significant progress over the last few years (Peng et al. 2002; Simard et al. 2002; de Souza et al. 2004; Lotz et al. 2004; Conselice 2006; Pignatelli et al. 2006) and now provide an important framework for 1 National Research Council of Canada, Herzberg Institute of…”
The structures of distant galaxies – I. Galaxy structures and the merger rate to z∼ 3 in the Hubble Ultra-Deep Field (2007, methodology): “As explained in detail in Conselice (2006), there are majormergers with AB 0.35, and thus we are not complete in finding mergers by using this definition.”
Galaxy Zoo: Passive Red Spirals . (2009, unknown): “For example Mignoli et al. (2009) argued that 85% of galaxies to z∼1 are either red, bulgedominated galaxies or blue, disk dominated galaxies; while Conselice (2006) showed a similar result for 22000 low redshift galaxies (both using automated methods for morphological classification).”
Galaxy Zoo: the dependence of morphology and colour on environment (2008, background): “This corresponds with the finding of Conselice (2006) that the correlation betweengalaxy colour and stellar mass does not strongly depend on morphology.”
The Evolution of Galaxy Structure Over Cosmic Time (2014, methodology): “This quantitatively expands into other physical parameters as well (e.g., Roberts 1963; Roberts & Haynes 1994; Conselice 2006a; Allen et al. 2006).”
The ATLAS3D project – I. A volume-limited sample of 260 nearby early-type galaxies: science goals and selection criteria (2010, background): “(5) As found by previous authors there is little scatter in the relation at the high-mass end, while at the lower mass-end some galaxies appear to be still in transition between the blue and red sequence (Strateva et al. 2001; Conselice 2006; van den Bergh 2007; Bernardi et al. 2010).”
The Horizon-AGN Simulation: Morphological Diversity of Galaxies ,Promoted by AGN Feedback (2016, background): “Observations of galaxies establish that a wide variety of morphological types is witnessed at all times in the Universe, from discs to ellipticals and irregular galaxies, although morphologies strongly depend on the galaxy mass (e.g. Conselice 2006; Ilbert et al. 2010; Bundy et al. 2010).”
Structure and Kinematics of Early-Type Galaxies from Integral Field Spectroscopy (2016, background): “In fact applying different selection criteria for ETGs leads to quite different sets of galaxies (Strateva et al. 2001; Conselice 2006; van den Bergh 2007; Bernardi et al. 2010).”
Galaxy Zoo: morphologies derived from visual inspection of galaxies from the Sloan Digital Sky Survey (2008, methodology): “…based on galaxy properties such as colour, concentration index, spectral features, surface brightness profile, structural parameters or some combination of these are used (e.g. Strateva et al. 2001; Abraham, van den Bergh & Nair 2003; Kauffmann et al. 2004; Conselice 2006; Scarlata et al. 2007).”