Astrophys. J., 835, 104-104 (2017/January-3)
The SAMI Galaxy Survey: revisiting Galaxy classification through high-order stellar kinematics.
VAN DE SANDE J., BLAND-HAWTHORN J., FOGARTY L.M.R., CORTESE L., D'EUGENIO F., CROOM S.M., SCOTT N., ALLEN J.T., BROUGH S., BRYANT J.J., CECIL G., COLLESS M., COUCH W.J., DAVIES R., ELAHI P.J., FOSTER C., GOLDSTEIN G., GOODWIN M., GROVES B., HO I.-T., JEONG H., JONES D.H., KONSTANTOPOULOS I.S., LAWRENCE J.S., LESLIE S.K., LOPEZ-SANCHEZ A.R., McDERMID R.M., McELROY R., MEDLING A.M., OH S., OWERS M.S., RICHARDS S.N., SCHAEFER A.L., SHARP R., SWEET S.M., TARANU D., TONINI C., WALCHER C.J. and YI S.K.
Abstract (from CDS):
Recent cosmological hydrodynamical simulations suggest that integral field spectroscopy can connect the high-order stellar kinematic moments h3 (∼skewness) and h4 (∼kurtosis) in galaxies to their cosmological assembly history. Here, we assess these results by measuring the stellar kinematics on a sample of 315 galaxies, without a morphological selection, using two-dimensional integral field data from the SAMI Galaxy Survey. Proxies for the spin parameter (λRe_) and ellipticity (εe) are used to separate fast and slow rotators; there exists a good correspondence to regular and non-regular rotators, respectively, as also seen in earlier studies. We confirm that regular rotators show a strong h3 versus V/σanti-correlation, whereas quasi-regular and non-regular rotators show a more vertical relation in h3 and V/σ. Motivated by recent cosmological simulations, we develop an alternative approach to kinematically classify galaxies from their individual h3 versus V/σsignatures. Within the SAMI Galaxy Survey, we identify five classes of high-order stellar kinematic signatures using Gaussian mixture models. Class 1 corresponds to slow rotators, whereas Classes 2-5 correspond to fast rotators. We find that galaxies with similar λRe–εe_ values can show distinctly different h3–V/σsignatures. Class 5 objects are previously unidentified fast rotators that show a weak h3 versus V/σanti-correlation. From simulations, these objects are predicted to be disk-less galaxies formed by gas-poor mergers. From morphological examination, however, there is evidence for large stellar disks. Instead, Class 5 objects are more likely disturbed galaxies, have counter-rotating bulges, or bars in edge-on galaxies. Finally, we interpret the strong anti-correlation in h3 versus V/σas evidence for disks in most fast rotators, suggesting a dearth of gas-poor mergers among fast rotators.
© 2017. The American Astronomical Society. All rights reserved.
cosmology: observations - galaxies: evolution - galaxies: formation - galaxies: kinematics and dynamics - galaxies: stellar content - galaxies: structure - galaxies: structure
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<Available at CDS (J/ApJ/835/104): table2.dat table3.dat>
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