The SAURON project – XII. Kinematic substructures in early-type galaxies: evidence for discs in fast rotators

By D. Krajnovi'c, R. Bacon, M. Cappellari, Roger Davies, P. de Zeeuw, Eric Emsellem, J. Falc'on-Barroso, H. Kuntschner, R. McDermid, Reynier Peletier and 3 more. 2008

160 citations recorded by the source corpus.

We analysed two-dimensional maps of 48 early-type galaxies obtained with the SAURON and OASIS integral-field spectrographs using kinemetry, a gene ralisation of surface photometry to the higher order moments of the line-of-sight velocity distribution (LOSVD). The maps analysed include: reconstructed image, mean velocity, velocity dispersion, h3 and h4 GaussHermite moments. Kinemetry is a good method to recognise structures otherwise missed by using surface photometry, such as embedded disks and kinematic sub-components. In the SAURON sample, we find that 31% of early-type galaxies are sin gle component systems. 91% of the multi-components systems have two kinematic subcomponents, the rest having three. In addition, 29% of galaxies have kinematically decoupled components, nuclear components with significant kinematic twists. We differentiate betwee n slow and fast rotators using velocity maps only and find that fast rotating galaxies contain disks with a large range in mass fractions to the main body. Specifically, we find that the velo city maps of fast rotators closely resemble those of inclined disks, except in the transition r egions between kinematic subcomponents. This deviation is measured with the kinemetric k5/k1 ratio, which is large and noisy in slow rotators and about 2% in fast rotators. In terms of E/S0 classification, this means that 74% of Es and 92% of S0s have components with disk-like kinematics. We suggest that differences in k5/k1 values for the fast and slow rotators arise from their differ ent intrinsic structure which is reflected on the velocity maps. For the majority of fa st rotators, the kinematic axial ratios are equal to or less than their photometric axial rati os, contrary to what is predicted with isotropic Jeans models viewed at different inclinations. T he position angles of fast rotators are constant, while they vary abruptly in slow rotators. Velocity dispersion maps of face-on galaxies have shapes similar to the distribution of light. Veloci ty dispersion maps of the edge-on fast rotators and all slow rotators show differences which can only be partially explained with isotropic models and, in the case of fast rotators, often req uire additional cold components. We constructed local (bin-by-bin) h3 V/σ and h4 V/σ diagrams from SAURON observations. We confirm the classical anti-correlation of h3 and V/σ, but we also find that h3 is almost zero in some objects or even weakly correlated with V/σ. The distribution of h4 for fast and slow rotators is mildly positive on average. In general, fast rot ators contain flattened components characterised by a disk-like rotation. The difference betw een slow and fast rotators is traceable throughout all moments of the LOSVD, with evidence for different intrinsic shapes and orbital contents and, hence, likely different evolutionary paths.

Subfields: Astronomy and Astrophysics, Instrumentation

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In Astronomy and Astrophysics

1. M. Cappellari
2. T. Naab
3. P. Hopkins
4. L. Hernquist
5. J. Kormendy
6. M. Sarzi
7. Frédéric Bournaud
8. A. Dekel

In Instrumentation

1. M. Cappellari
2. T. Naab
3. P. Hopkins
4. J. Kormendy
5. M. Sarzi
6. Frédéric Bournaud
7. L. Hernquist
8. Eric Emsellem

Citations in the corpus

• Idealized models for galactic disc formation and evolution in ‘realistic’ ΛCDM haloes (2012, background): “Misaligned components are common in observed galaxies in the form of warps (Sancisi 1976), polar rings (Whitmore et al. 1990), polar bulges (Corsini et al. 2012) or counter-rotating components in early-type galaxies (Krajnović et al. 2008).”
• Structure and Kinematics of Early-Type Galaxies from Integral Field Spectroscopy (2016, methodology): “Krajnović et al. (2006, 2008) discovered that the velocity field of ETGs along the best-fitting ellipse, is approximated by a cosine law V (ψ) = V0 +B1 cos(ψ) with better than 2% accuracy.”
• STRUCTURE AND FORMATION OF ELLIPTICAL AND SPHEROIDAL GALAXIES (2008, background): “Similarly, in NGC 4387, Halliday et al. (2001) suggest that a central decrease inσ implies a rotationally supported subsystem that is confirmed by Emsellem et al. (2004) and Krajnovíc et al. (2008).”
• Kinematic properties of early-type galaxy haloes using planetary nebulae (2008, unknown): “This proxy angular momentum can be simplified to a one-dimensional problem by adopting the approximation that the rotation is aligned with the photometric major axis, and its azimuthal dependence is related to the major-axis velocity by V(φ) = Vmax cos(φ) (cf. Krajnović et al. 2008).”
• MORPHOLOGICAL QUENCHING OF STAR FORMATION: MAKING EARLY-TYPE GALAXIES RED (2009, background): “The galaxy therefore remains elliptical-like, with only a low-mass disk component, as in many real elliptical galaxies (see Krajnović et al. 2008).”
• Physical properties and environments of nearby galaxies (2009, methodology): “The recent analysis of SAURON data has greatly increased our understanding of the variety and incidence of kinematic substructures and other features (e.g., Krajnović et al. 2008).”
• Simulations of binary galaxy mergers and the link with fast rotators, slow rotators, and kinematically distinct cores (2011, methodology): “As emphasized in E+07, Cappellari et al. (2007) and Krajnović et al. (2008), fast and slow rotators exhibit qualitatively and quantitatively different stellar kinematic properties.”
• The ATLAS3D project – I. A volume-limited sample of 260 nearby early-type galaxies: science goals and selection criteria (2010, methodology): “In addition, when galaxies are barred, theSAURON survey has shown that the kinematics are generally still aligned with the position angle of the galaxy photometry at large radiiPAphot (Krajnović et al. 2008), which de- c© 2011 RAS, MNRAS000, 1–27”
• The ATLAS3D project – III. A census of the stellar angular momentum within the effective radius of early‐type galaxies: unveiling the distribution of fast and slow rotators (2011, background): “…misalignment between the kinematic and photometric axes (excluding the few systems consistent with having no apparent rotation at all), or complex/irregular stellar velocity maps with twists and strong misalignment with respect to the photometry (Emsellem et al. 2004; Krajnović et al. 2008).”
• THE NGC 404 NUCLEUS: STAR CLUSTER AND POSSIBLE INTERMEDIATE-MASS BLACK HOLE (2010, background): “Kinematically, both NSCs and extra-light can be disky and rotating (Krajnović et al. 2008; Seth et al. 2008b; Trippe et al. 2008) and in early-type galaxies, the stellar populations of many NSCs are not significantly different from their underlying galaxy (Côté et al. 2006; Rossa et al. 2006).”
• The ATLAS3D project - X. On the origin of the molecular and ionized gas in early-type galaxies (2011, background): “Krajnović et al. (2008) have shown that many ETGs have kinematically distinct stellar substructures, that may cause confusion in long-slit spectroscopic data.”
• The ATLAS3D project - XIII. Mass and morphology of H I in early-type galaxies as a function of environment (2011, background): “These show that most ETGs host a rotating, kinematically cold component (Krajnović et al. 2008) whose stars are usually younger and more metal-rich than those in the bulge (Kuntschner et al. 2010).”
• WIDE-FIELD PRECISION KINEMATICS OF THE M87 GLOBULAR CLUSTER SYSTEM (2011, methodology): “…next begin to put the kinematics information into a simplified quantifiable format using the general approach of “kinemetry”, which extends the standard techniques used in ellipse-based galaxy surface photometry to quantify spatial variations of the kinematics (Krajnović et al. 2006, 2008).”
• ANGULAR MOMENTUM AND GALAXY FORMATION REVISITED (2012, unknown): “There is also a connection here to the “kinemetric” methods of modeling data from integral-field spectrographs, where the two-dimensional kinematics are expanded in a Fourier series (Krajnović et al. 2006; Krajnović et al. 2008).”
• Towards a more realistic population of bright spiral galaxies in cosmological simulations (2013, background): “These processes are of interest in the context of the formation of counter-rotating components and 2σ signatures found in several elliptical galaxies (Krajnović et al. 2008).”
• A REVISED PARALLEL-SEQUENCE MORPHOLOGICAL CLASSIFICATION OF GALAXIES: STRUCTURE AND FORMATION OF S0 AND SPHEROIDAL GALAXIES (2011, result): “…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 –”