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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 742392.0, MPI für Astronomie / Publikationen_mpia
The SAMI Galaxy Survey: Revisiting galaxy classification throughhigh-order stellar kinematics
Authors: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.; López-Sánchez, Á. 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.; Yi, S. K.
Date of Publication (YYYY-MM-DD):2017
Title of Journal:The Astrophysical Journal
Issue / Number:1
Start Page:id. 104 (35 pp)
Audience:Not Specified
Abstract / Description:Recent cosmological hydrodynamical simulations suggest that integral field spectroscopy can connect the high-order stellar kinematic moments h 3 (∼skewness) and h 4 (∼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 ({λ }{R{{e}}}) and ellipticity ({ε }{{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 h 3 versus V/σ anti-correlation, whereas quasi-regular and non-regular rotators show a more vertical relation in h 3 and V/σ . Motivated by recent cosmological simulations, we develop an alternative approach to kinematically classify galaxies from their individual h 3 versus 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 {λ }{R{{e}}}{--}{ε }{{e}} values can show distinctly different {h}3{--}V/σ signatures. Class 5 objects are previously unidentified fast rotators that show a weak h 3 versus 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 h 3 versus V/σ as evidence for disks in most fast rotators, suggesting a dearth of gas-poor mergers among fast rotators.
Free Keywords:cosmology: observations; galaxies: evolution; galaxies: formation; galaxies: kinematics and dynamics; galaxies: stellar content; galaxies: structure
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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