The ATLAS3D project - VII. A new look at the morphology of nearby galaxies: the kinematic morphology-density relation

By M. Cappellari, Eric Emsellem, D. Krajnovi'c, R. McDermid, P. Serra, K. Alatalo, L. Blitz, M. Bois, Frédéric Bournaud, M. Bureau and 13 more. 2011

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In Paper I of this series we introduced a volume-limited parent sample of 871 galaxies from which we extracted the ATLAS(3D) sample of 260 early-type galaxies (ETGs). In Papers II and III we classified the ETGs using their stellar kinematics, in a way that is nearly insensitive to the projection effects, and we separated them into fast and slow rotators. Here we look at galaxy morphology and note that the edge-on fast rotators generally are lenticular galaxies. They appear like spiral galaxies with the gas and dust removed, and in some cases are flat ellipticals (E5 or flatter) with discy isophotes. Fast rotators are often barred and span the same full range of bulge fractions as spiral galaxies. The slow rotators are rounder (E4 or rounder, except for counter-rotating discs) and are generally consistent with being genuine, namely spheroidal-like, elliptical galaxies. We propose a revision to the tuning-fork diagram by Hubble as it gives a misleading description of ETGs by ignoring the large variation in the bulge sizes of fast rotators. Motivated by the fact that only one third (34 per cent) of the ellipticals in our sample are slow rotators, we study for the first time the kinematic morphology-density T-Sigma relation using fast and slow rotators to replace lenticulars and ellipticals. We find that our relation is cleaner than using classic morphology. Slow rotators are nearly absent at the lowest density environments [f(SR) less than or similar to 2 per cent] and generally constitute a small fraction [f (SR) approximate to 4 per cent] of the total galaxy population in the relatively low-density environments explored by our survey, with the exception of the densest core of the Virgo cluster [f(SR) approximate to 20 per cent]. This contrasts with the classic studies that invariably find significant fractions of (misclassified) ellipticals down to the lowest environmental densities. We find a clean log-linear relation between the fraction f(Sp) of spiral galaxies and the local galaxy surface density Sigma(3), within a cylinder enclosing the three nearest galaxies. This holds for nearly four orders of magnitude in the surface density down to Sigma(3) approximate to 0.01 Mpc(-2), with f(Sp) decreasing by 10 per cent per dex in Sigma(3), while f(FR) correspondingly increases. The existence of a smooth kinematic T-Sigma relation in the field excludes processes related to the cluster environment, like e.g. ram-pressure stripping, as main contributors to the apparent conversion of spirals into fast rotators in low-density environments. It shows that the segregation is driven by local effects at the small-group scale. This is supported by the relation becoming shallower when using a surface density estimator Sigma(10) with a cluster scale. Only at the largest densities in the Virgo core does the f(Sp) relation break down and steepen sharply, while the fraction of slow rotators starts to significantly increase. This suggests that a different mechanism is at work there, possibly related to the stripping of the gas from spirals by the hot intergalactic medium in the cluster core and the corresponding lack of cold accretion.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

Galaxy morphology and star formation in the Illustris Simulation at z = 0 (2015, methodology): “As in real nearby galaxies, Illustris galaxies appear to have structures implying that meaningful intrinsic classification is more like a “comb” than a “tuning fork” (e.g., Figure 1 by Cappellari et al. 2011b).”
The ATLAS3D project – XX. Mass–size and mass–σ distributions of early-type galaxies: bulge fraction drives kinematics, mass-to-light ratio, molecular gas fraction and stellar initial mass function (2012, background): “The volume-limited ATLAS3D sample of nearby early-type galaxies (ETGs; Cappellari et al. 2011a, hereafter Paper I) constitute an ideal benchmark for studying scaling relations and the distribution of galaxy properties, given the availability of a highquality multiwavelength data set.”
A REVISED PARALLEL-SEQUENCE MORPHOLOGICAL CLASSIFICATION OF GALAXIES: STRUCTURE AND FORMATION OF S0 AND SPHEROIDAL GALAXIES (2011, methodology): “…good agreement between the above dichotomy and the results of the SAURON and ATLAS3D surveys (e. g., de Zeeuw et al. 2002; Emsellem et al. 2004, 2007, 2011; Cappellari et al. 2007, 2011a, b; Krajnović et al. 2008, 2011; McDermid et al. 2006): 3 PARALLEL-SEQUENCE GALAXY CLASSIFICATION Vol. 00 A –”
The ATLAS3D project XV: benchmark for early-type galaxies scaling relations from 260 dynamical models: mass-to-light ratio, dark matter, fundamental plane and mass plane (2012, background): “Our volume-limited sample of ETGs is dominated by fast rotators (Paper II; Paper III), characterized by the presence of discs (Krajnović et al. 2013, hereafter Paper XVII) and closely linked to spiral galaxies (Cappellari et al. 2011b, hereafter Paper VII; Paper XX).”
ANGULAR MOMENTUM AND GALAXY FORMATION REVISITED (2012, methodology): “For ATLAS3D, we adopt the power-law relations provided by Cappellari et al. (2011a), after adapting them to the parameters that we plot for our sample.”
Galaxy Zoo 2: detailed morphological classifications for 304,122 galaxies from the Sloan Digital Sky Survey (2013, result): “This is consistent with the “parallel-sequence” model of van den Bergh (1976) and later revised by several groups (including Cappellari et al. 2011; Laurikainen et al. 2011; Kormendy & Bender 2012).”
Galaxy And Mass Assembly (GAMA): mass–size relations of z < 0.1 galaxies subdivided by Sérsic index, colour and morphology (2014, background): “Due to the similarity between the morphology-dependent mass– size relation and the fundamental mass–spin–morphology relation (Cappellari et al. 2011; Romanowsky & Fall 2012; Obreschkow & Glazebrook 2014), this work lays the foundations for approximate studies of angular momentum scalings in a large…”
THE DATA REDUCTION PIPELINE FOR THE SDSS-IV MaNGA IFU GALAXY SURVEY (2016, background): “…(Bershady et al. 2010) have indicated that late-type galaxies tend to have sub-maximal disks (Bershady et al. 2011), while Atlas-3D observations (Cappellari et al. 2011a) showed that early-type galaxies frequently have rapidly-rotating components (especially in low density environments;…”
The ATLAS3D project - X. On the origin of the molecular and ionized gas in early-type galaxies (2011, background): “…our local the luminosity surface density estimator, based on a redshift cylinder with a depth of 600 km s−1, and an angular size adapted to include the 3rd nearest neighbor, as presented in Cappellari et al. (2011b) (Paper VII; Table 2, Column 7 and available online athttp://www.purl.org/atlas3d).”
Structure and Kinematics of Early-Type Galaxies from Integral Field Spectroscopy (2016, methodology): “Instead, the ratio is nearly constant outside clusters, while inside clusters it becomes a strong function of the local galaxy number density (Cappellari et al. 2011b; Houghton et al. 2013; D’Eugenio et al. 2013; Fogarty et al. 2014).”
The ATLAS3D Project – XXVIII. Dynamically driven star formation suppression in early-type galaxies (2014, background): “…for stellar luminosity, the offsets aboveand below the line defined in Equation 1 for the CO non-detected sample do not correlate with stellar kinematic quantities (Krajnović et al. 2011; Emsellem et al. 2011), ionised-gas quantities,or measures of galaxy environment (Cappellari et al. 2011b).”
THE NEXT GENERATION VIRGO CLUSTER SURVEY (NGVS). I. INTRODUCTION TO THE SURVEY (2012, background): “…rotationally flattened lenticulars versus quiescent, or dynamically hot ellipticals (a notable counterexample is the ATLAS3D survey, which analyzed earlytype galaxies selected largely independently of morphology; Cappellari et al. 2011a, 2011b; Emsellem et al. 2011; FalcónBarroso et al. 2011).”
The Sydney-AAO Multi-object Integral field spectrograph (2011, methodology): “A great success of the SAURON and ATLAS-3D projects (Bacon et al. 2001; Cappellari et al. 2011a) has been the discovery that most early type galaxies have significant rotation, with only ≃ 14 percent (predominantly at high mass) being slow rotators.”
The ATLAS3D project - XIII. Mass and morphology of H I in early-type galaxies as a function of environment (2011, background): “These results are placed on a firm statistical ground by ATLAS3D, a multi-wavelength study of a volume-limited sample of 260 morphologically selected ETGs (Cappellari et al. 2011a, hereafter Paper I).”
The ATLAS3D project - XXIX. The new look of early-type galaxies and surrounding fields disclosed by extremely deep optical images (2014, methodology): “For a consistent comparison, they were not multiplied by the factor of 1.35 used to reconcile the MGE value with the original one in Cappellari et al. (2011). c© 0000 RAS, MNRAS 000, 000–000 and kinematical properties probed by the ATLAS3D survey. g and r band images are available for all galaxies…”
The ATLAS3D Project – XXX. Star formation histories and stellar population scaling relations of early-type galaxies (2015, methodology): “Further details of the ATLAS3D SAURON observations are given in Cappellari et al. (2011a).”
Theoretical Challenges in Galaxy Formation (2016, background): “Recent integral field studies have significantly improved our understanding of the complex kinematics of galaxies (Bundy et al. 2015, Cappellari et al. 2011, de Zeeuw et al. 2002, Fogarty et al. 2014, Sánchez et al. 2012).”
A CLASSICAL MORPHOLOGICAL ANALYSIS OF GALAXIES IN THE SPITZER SURVEY OF STELLAR STRUCTURE IN GALAXIES (S4G) (2015, background): “Kormendy (2012) reviews the evidence that dE and dS0 galaxies are environmentally-modified, bulgeless extreme late-type galaxies whose existence favors reconsideration of the old van den Bergh (1976) “parallel sequence” idea (see also Laurikainen et al. 2011; Cappellari et al. 2011).”