The SAMI Galaxy Survey: Revisiting galaxy classification through high-order stellar kinematics

Sande, JVD; Bland-Hawthorn, J; Fogarty, LMR; Cortese, L; d’Eugenio, F; Croom, SM; Scott, N; Allen, JT; Brough, S; Bryant, JJ; Cecil, G; Colless, M; Couch, WJ; Davies, R; Elahi, PJ; Foster, C; Goldstein, G; Goodwin, M; Groves, B; Ho, I-T; Jeong, H; Jones, DH; Konstantopoulos, IS; Lawrence, JS; Leslie, SK; López-Sánchez, ÁR; McDermid, RM; McElroy, R; Medling, AM; Oh, S; Owers, MS; Richards, SN; Schaefer, AL; Sharp, R; Sweet, SM; Taranu, D; Tonini, C; Walcher, CJ; Yi, SK

Journal article

The SAMI Galaxy Survey: Revisiting galaxy classification through high-order stellar kinematics

Abstract:: 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 (∈e) 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 h3versus V/σ anti-correlation, whereas quasi-regular and non-regular rotators show a more vertical relation in h3and V/σ. Motivated by recent cosmological simulations, we develop an alternative approach to kinematically classify galaxies from their individual h3versus V/σ signatures. 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- ∈evalues can show distinctly different h3- V/σ signatures. Class 5 objects are previously unidentified fast rotators that show a weak h3versus V/σ anti-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 h3versus V/σ as evidence for disks in most fast rotators, suggesting a dearth of gas-poor mergers among fast rotators.

Publication status:: Published

Peer review status:: Peer reviewed

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APA Style

Sande, J. V. D., 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., … Yi, S. K. (2017). The SAMI Galaxy Survey: Revisiting galaxy classification through high-order stellar kinematics. Astrophysical Journal, 835(1), 104–104.

MLA Style

Sande, J. VD, et al. “The SAMI Galaxy Survey: Revisiting Galaxy Classification through High-Order Stellar Kinematics.” Astrophysical Journal, vol. 835, no. 1, Institute of Physics, 2017, pp. 104–04.

Chicago Style

Sande, JVD, J Bland-Hawthorn, LMR Fogarty, L Cortese, F d’Eugenio, SM Croom, N Scott, et al. 2017. “The SAMI Galaxy Survey: Revisiting Galaxy Classification through High-Order Stellar Kinematics.” Astrophysical Journal 835 (1): 104–.
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