IJAA  Vol.6 No.2 , June 2016
Kinematic Decoupled Core Paradigm: Counterrotation or Just Warping
Abstract: Several mechanisms have been proposed in recent years to explain kinematic decoupled cores (KDCs) in early type galaxies as well as the large differences in angular momentum between KDCs and host galaxy. Most of the proposed scenarios involve large fractions of merging events, high speed interactions with dwarf spheroidal galaxies, cusp effect of the dark matter density profiles, etc. We here argue that counterrotation as well as fast and slow rotation of disks or spheroids at the center of galaxies can also be explained by a misalignment of the central spheroid equatorial plane with regard to that defined by the observed external stellar rotation. Contrary to what happens at the outer region of disk galaxies, once instability has led to the inner warped core, the perturbed orbits can maintain a common orientation due to the rigid body like rotation at the central region of the galaxy. The spatial configuration that furnishes the smallest angular momentum difference between the KDC and the host galaxy is completely defined by observed parameters in the plane of the sky, namely, the inclination of the inner and outer disks and the angle between the two lines of nodes. As an example we modeled the paradigmatic and extreme case of the 2D radial velocity field of NGC 4382 nucleus. Tilt angles of the KDC not larger than 30 degrees also allow explaining fast and low rotators of the called “Sauron paradigm” in a unified scenario. The maximum for the three parameters, namely, velocity of the inner rotator, difference of position angle and difference with the outer rotation velocity of the whole Sauron sample, are consistently correlated in agreement with the proposed scenario. These quantities do not correlate with the galaxies magnitude, mass (since large and dwarf spheroidals show apparent counterrotation as well) or environment, also suggesting that an internal phenomenon like the central spheroid warping, that we are here proposing, may be at work.
Cite this paper: Díaz, R. , Dottori, H. (2016) Kinematic Decoupled Core Paradigm: Counterrotation or Just Warping. International Journal of Astronomy and Astrophysics, 6, 198-205. doi: 10.4236/ijaa.2016.62016.

[1]   Efstathiou, G., Ellis, R. and Carter, D. (1982) Further Observations of the Elliptical Galaxy NGC 5813A. Monthly Notices of the Royal Astronomical Society (MNRAS), 201, 975-990.

[2]   Franx, M. and Illingworth, G. (1988) A Counter Rotating Core in IC 1459. Astrophysical Journal, 327, L55-L59.

[3]   Bender, R. (1988) Rotating and Counter-Rotating Cores in Elliptical Galaxies. A&A, 202, L5-L8.

[4]   Franx, M., Illingworth, G. and Heckman, T. (1989) Major and Minor Axis Kinematics of 22 Ellipticals. Astrophysical Journal, 344, 613-636.

[5]   Binney, J. (1985) Testing for Triaxiality with Kinematic Data. Monthly Notices of the Royal Astronomical Society (MNRAS), 212, 767-781.

[6]   Balcells, M. and Quinn, P.J. (1990) The Formation of Couter Rotating Cores in Elliptical Galaxies. Astrophysical Journal, 361, 381-393.

[7]   Forbes, D., Franx, M. and Illingworth, G. (1995) Ellipticals with Kinematically Distinct Cores: WFPC1 Imaging of nearby Ellipticals. Astronomical Journal, 109, 1988-1995.

[8]   Bak, J. (2000) Retrograde Minor Mergers and Couter Rotating Cores. Ph. D. Thesis, DAI-B 61/06, Ohio University, Athens.

[9]   De Rijcke, S., Dejonghe, H., Zeilinger, W. and Hau, G. (2004) Dwarf Elliptical Galaxies with Kinematically Decoupled Cores. Astronomy & Astrophysics (A&A), 426, 56-63.

[10]   Geha, M., Guhathakurta, P. and van der Marel, R. (2005) NGC 770: A Counterrotating Core in a Dwarf Elliptical Galaxy. Astronomical Journal, 129, 2617-2627.

[11]   Emsellem, E., Cappellari, M., Peletier, R., McDermid, R.M., Bacon, R., et al. (2004) The SAURON Project—III: Integral-Field Absorption-Lines Kinematics of 48 Elliptical and Lenticular Galaxies. Monthly Notices of the Royal Astronomical Society (MNRAS), 352, 721-743.

[12]   Thomas, D., Brimioulle, F., Bender, R., Hopp, U., Greggio, L., Maraston, C. and Saglia, R.P. (2006) A Counter-Ro-tating Core in the Dwarf Elliptical VCC 510. Astronomy & Astrophysics (A&A), 445, L19-L22.

[13]   Carollo, C., Danziger, J., Rich, R.M. and Chen, X. (1997) Nuclear Properties of Kinematically Distinct Cores. Astrophysical Journal, 491, 545-560.

[14]   Davies, R., Kuntschner, H., Emsellem, E., Bacon, R., Bureau, M., Carollo, C.M., et al. (2001) Galaxy Mapping with the SAURON Integral-Field Spectrograph: The Star Formation History of NGC 4365. Astrophysical Journal, 548, L33-L36.

[15]   Rogstad, D., Lockhart, I. and Wright, M. (1974) Aperture-Synthesis Observations of HI in the Galaxy M83. Astrophysical Journal, 193, 309-319.

[16]   Rogstad, D., Lockhart, I. and Wright, M. (1976) Aperture-Synthesis Observations of HI in the Galaxy M33. Astrophysical Journal, 204, 703-711.

[17]   Rogstad, D., Crutcher, R. and Chu, K. (1979) Aperture-Synthesis Observations of HI in NGC 300. Astrophysical Journal, 229, 509-513.

[18]   Binney, J. and Tremaine, S. (1991) Galactic Dynamics. Princeton Univ. Press, Princeton, 539-548.

[19]   Binney, J. (1985) Testing for Triaxiality with Kinematic Data. Monthly Notices of the Royal Astronomical Society (MNRAS), 212, 767-781.

[20]   De Zeeuw, P.T., Bureau, M., Emsellem, E., Bacon, R., Carollo, C., Copin, Y., Davies, R., Kuntschner, H., Miller, B., Monnet, G., Peletier, R. and Verolme, E. (2002) The SAURON Project—II: Sample and Early Results. Monthly Notices of the Royal Astronomical Society (MNRAS), 329, 513-530.

[21]   Bacon, R., Copin, Y., Monnet, G., Miller, B., Allington-Smith, J., Bureau, M., Carollo, C., Davies, R., Emsellem, E., Kuntschner, H., Peletier, R., Verolme, E. and de Zeeuw, P.T. (2001) The Sauron Project—I. The Panoramic Integral Field spectrograph. Monthly Notices of the Royal Astronomical Society (MNRAS), 326, 23-35.

[22]   McDermid, R., Emsellem, E., Capellari, M., et al. (2004) OASIS High-Resolution Integral field Spectroscopy of the SAURON Ellipticals and Lenticulars. Astronomische Nachrichten, 325, 100-103.

[23]   Copin, Y., Cretton, N. and Emsellem, E. (2004) Axisymmetric dynamical models for SAURON and OASIS Observations of NGC3377. Astronomy & Astrophysics (A&A), 415, 889-903.

[24]   Wernli, F., Emsellem, E. and Copin, Y. (2002) A 60 pc Counter-Rotating Core in NGC 4621. Astronomy & Astrophysics (A&A), 396, 73-81.

[25]   Shields, J., Rix, H., McIntosh, D., Ho, L., Rudnick, G., Filippenko, A., Sargent, W. and Sarzi, M. (2000) Evidence for a Black Hole and Accretion Disk in the LINER NGC 4203. Astrophysical Journal, 534, L27-L30.