The SAURON project – IX. A kinematic classification for early‐type galaxies

By Eric Emsellem, M. Cappellari, D. Krajnovi'c, Glenn van de Ven, R. Bacon, M. Bureau, Roger Davies, P. de Zeeuw, J. Falc'on-Barroso, H. Kuntschner and 12 more. 2007

586 citations recorded by the source corpus.

Two-dimensional stellar kinematics of 48 representative elliptical (E) and lenticular (S0) galaxies obtained with the SAURON integral-field spectrograph reveal that early-type galaxies appear in two broad flavours, depending on whether they exhibit clear large-scale rotation or not. We define a new parameter lambda(R) equivalent to / , which involves luminosity-weighted averages over the full two-dimensional kinematic field as a proxy to quantify the observed projected stellar angular momentum per unit mass. We use it as a basis for a new kinematic classification: early-type galaxies are separated into slow and fast rotators, depending on whether they have lambda(R) values within their effective radius R(e) below or above 0.1, respectively. Slow and fast rotators are shown to be physically distinct classes of galaxies, a result which cannot simply be the consequence of a biased viewing angle. Fast rotators tend to be relatively low-luminosity galaxies with M(B) greater than or similar to-20.5. Slow rotators tend to be brighter and more massive galaxies, but are still spread over a wide range of absolute magnitude. Three slow rotators of our sample, among the most massive ones, are consistent with zero rotation. Remarkably, all other slow rotators (besides the atypical case of NGC 4550) contain a large kpc-scale kinematically decoupled core (KDC). All fast rotators (except one galaxy with well-known irregular shells) show well-aligned photometric and kinemetric axes, and small velocity twists, in contrast with most slow rotators which exhibit significant misalignments and velocity twists. These results are supported by a supplement of 18 additional early-type galaxies observed with SAURON. In a companion paper (Paper X), we also show that fast and slow rotators are distinct classes in terms of their orbital distribution. We suggest that gas is a key ingredient in the formation and evolution of fast rotators, and that the slowest rotators are the extreme evolutionary end point reached deep in gravitational potential wells where dissipationless mergers had a major role in the evolution, and for which most of the baryonic angular momentum was expelled outwards. Detailed numerical simulations in a cosmological context are required to understand how to form large-scale KDCs within slow rotators, and more generally to explain the distribution of lambda(R) values within early-type galaxies and the distinction between fast and slow rotators.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/11a491cb2b23a4feea7d88729879bbae2715359e

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Citations in the corpus

Coevolution (Or Not) of Supermassive Black Holes and Host Galaxies (2013, methodology): “Figure 11 Comparison of our adopted σe (Tables 2 and 3) to (left) the central velocity dispersion as tabulated in HyperLeda and to (right) the σe value tabulated by the SAURON/ATLAS3D teams (Emsellem et al. 2007; Cappellari et al. 2013).”
HOW DO DISKS SURVIVE MERGERS? (2008, background): “…and they form a continuous sequence with most S0 galaxies, known to have prominent stellar (and even gaseous) disks (Kormendy 1985; Bender et al. 1992; Ferrarese et al. 1994; Kormendy et al. 1994; Lauer et al. 1995; Faber et al. 1997; Kormendy 1999; Ferrarese et al. 2006; Emsellem et al. 2007).”
High luminosity, slow ejecta and persistent carbon lines: SN 2009dc challenges thermonuclear explosion scenarios (2010, background): “Although lenticular galaxies are by no means dead stellar systems (e.g. Emsellem et al. 2007; Kawabata et al. 2010), such a host galaxy might still be considered as an indication for a predominantly old stellar population.”
Physical properties and environments of nearby galaxies (2009, background): “Figure 14 shows the distribution of λR from Emsellem et al. (2007), for the SAURON sample of Es and S0s.”
An updated MILES stellar library and stellar population models (2011, unknown): “…to be an often used, well calibrated stellar library that has been extensively used for a wide range of different applications (Davis et al. 2007; Emsellem et al. 2007; Shields et al. 2007; Martins & Coelho 2007; Cenarro et al. 2008; Scelsi et al. 2008; Zuckerman et al. 2008; Cid Fernandes &…”
Structure and Kinematics of Early-Type Galaxies from Integral Field Spectroscopy (2016, methodology): “…like the Vrms ≡ √ V 2 + σ2, which is proportional to mass, according to the scalar virial theorem (Binney & Tremaine 2008), one obtains the parameter (Emsellem et al. 2007) λR ≡ 〈R|V |〉〈R √ V 2 + σ2〉 = ∑N n=1 FnRn|Vn|∑N n=1 FnRn √ V 2n + σ2n , (17) where the Fn are the fluxes within the N…”
Kinematic properties of early-type galaxy haloes using planetary nebulae (2008, unknown): “…of rotation as a function of radius and is related to the angular momentum per unit of mass within R: λR = ∑ RiFi |Vi |∑ RiFi √ V 2i + σ 2i , (13) where the sum includes data points within R. Based on the λR profile within ∼ 1Re, galaxies can be divided into two main groups (Emsellem et al. 2007).”
THE HERSCHEL REFERENCE SURVEY: DUST IN EARLY-TYPE GALAXIES AND ACROSS THE HUBBLE SEQUENCE (2011, methodology): “This parameter is suggested by the ATLAS3D team as appropriate to separate out the slow and fast rotators since it is a good measure of the projected stellar angular momentum per unit mass (Emsellem et al. 2007).”
STRUCTURE AND FORMATION OF ELLIPTICAL AND SPHEROIDAL GALAXIES (2008, unknown): “…et al. (1991); Kormendy et al. (1994, 1996a); Lauer et al. (1995); Kormendy & Bender (1996); Tremblay & Merritt (1996); Gebhardt et al. (1996); Faber et al. (1997); Rest et al. (2001), Ravindranath et al. (2001); Lauer et al. (2005, 2007b); Emsellem et al. (2007), and Cappellari et al. (2007).”
The ATLAS3D project - VII. A new look at the morphology of nearby galaxies: the kinematic morphology-density relation (2011, background): “This exquisite level of detail allows us to properly classify the ETGs into genuinely spheroidal systems, the slow rotators, and lenticular-like galaxies, the fast rotators, in a robust way that is nearly insensitiveto projection effects (Cappellari et al. 2007; Emsellem et al. 2007).”
Galaxy Masses: A Review (2013, background): “is meant as a modern revision of, early treatises on the masses and mass-to-light ratios of galaxies by Burbidge & Burbidge (1975) and Faber & Gallagher (1979), respectively.”
The ATLAS3D project – I. A volume-limited sample of 260 nearby early-type galaxies: science goals and selection criteria (2010, unknown): “…be used to kinematically classify these galaxies in a way that is more r bust than the(V/σ, ε) diagram, is nearly insensitive to projection effects (Emsellem et al. 2007; Cappellari et al. 2007).λR relates directly to their formation, and is precisely reproducible in current cosmological…”
THE SINFONI BLACK HOLE SURVEY: THE BLACK HOLE FUNDAMENTAL PLANE REVISITED AND THE PATHS OF (CO)EVOLUTION OF SUPERMASSIVE BLACK HOLES AND BULGES (2016, background): “Core ellipticals are also slow rotators and mildly triaxial (Nieto & Bender 1989; Kormendy & Bender 1996; Faber et al. 1997; Emsellem et al. 2007; Lauer 2012), a further clue to their dry merger origin.”
The Sydney-AAO Multi-object Integral field spectrograph (2011, methodology): “Integral field spectroscopy also enables studies of stellar kinematics that describe the observed projected stellar angular momentum per unit mass of galaxies, not possible with other techniques (Emsellem et al. 2007, 2011; Brough et al. 2011).”
Galaxy morphology and star formation in the Illustris Simulation at z = 0 (2015, background): “In Figure 7, the low-redshift Illustris galaxies occupy a sequence very similar to the one put forth by observational studies (e.g., Emsellem et al. 2007; Cappellari et al. 2007, 2011b): quenched bulge-dominated galaxies with very little rotation are rare and occupy the bottom left tip of the locus…”
Multiple minor mergers: formation of elliptical galaxies and constraints for the growth of spiral disks (2007, background): “…more detailed parameters, like the h3 of the projected velocity distribution (González-Garćıa, Balcells & Olshevsky 2006), the λR parameter defined by Emsellem et al. (2007) which couples the resolved kinematics to the density profile and revealed different families of early-type galaxies, or…”
Measuring the inclination and mass-to-light ratio of axisymmetric galaxies via anisotropic Jeans models of stellar kinematics (2008, methodology): “More useful may be to use the fitted galaxy inclination to deprojected theobservedgalaxy stellar angular momentum per unit mass (Emsellem et al. 2007).”