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

被引:643
作者
Emsellem, Eric [1 ]
Cappellari, Michele
Krajnovic, Davor
van de Ven, Glenn
Bacon, R.
Bureau, M.
Davies, Roger L.
de Zeeuw, P. T.
Falcon-Barroso, Jesus
Kuntschner, Harald
McDermid, Richard
Peletier, Reynier F.
Sarzi, Marc
机构
[1] Univ Lyon, F-69007 Lyon, France
[2] Observ Lyon, CRAL, F-69230 St Genis Laval, France
[3] Univ Lyon 1, F-69007 Lyon, France
[4] ENS Lyon, Lyon, France
[5] CNRS, UMR 5574, Lyon, France
[6] Leiden Univ, Sterrewacht Leiden, NL-2333 CA Leiden, Netherlands
[7] Univ Oxford, Sub Dept Astrophys, Oxford OX1 3RH, England
[8] Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA
[9] Inst Adv Study, Princeton, NJ 08540 USA
[10] European Space Technol Ctr, NL-2200 AG Noordwijk, Netherlands
[11] European So Observ, Space Telescope European Coordinating Facil, D-85748 Garching, Germany
[12] Univ Groningen, Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands
[13] Univ Hertfordshire, Ctr Astrophys Res, Hatfield AL10 9AB, Herts, England
关键词
galaxies : elliptical and lenticular; cD; galaxies : evolution; galaxies : formation; galaxies : kinematics and dynamics; galaxies : structure; SIGHT VELOCITY DISTRIBUTIONS; INTEGRAL-FIELD SPECTROGRAPH; HUBBLE-SPACE-TELESCOPE; VIRGO-CLUSTER SURVEY; POLAR RING GALAXIES; ELLIPTIC GALAXIES; ANGULAR-MOMENTUM; S0; GALAXIES; LENTICULAR GALAXIES; SURFACE PHOTOMETRY;
D O I
10.1111/j.1365-2966.2007.11752.x
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
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 < R vertical bar V vertical bar >/< R root V(2)+sigma(2)>, 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.
引用
收藏
页码:401 / 417
页数:17
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