- Title
- The Sami Galaxy Survey: revisiting galaxy classification through high-order stellar kinematics
- Creator
- van De Sande, Jesse; Bland-Hawthorn, Joss; Cecil, Gerard; Colless, Matthew; Couch, Warrick J.; Davies, Roger; Elahi, Pascal J.; Foster, Caroline; Goldstein, Gregory; Goodwin, Michael; Groves, Brent; Ho, I.-Ting; Fogarty, Lisa M. R.; Jeong, Hunjin; Jones, D. Heath; Cortese, Luca; D'Eugenio, Francesco; Croom, Scott M.; Scott, Nicholas; Allen, James T.; Brough, Sarah; Bryant, Julia J.
- Relation
- Astrophysical Journal Vol. 835, Issue 1
- Publisher Link
- http://dx.doi.org/10.3847/1538-4357/835/1/104
- Publisher
- Institute of Physics Publishing
- Resource Type
- journal article
- Date
- 2017
- Description
- 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/σ anti-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/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 - ϵₑ values can show distinctly different h₃ - V/σ signatures. Class 5 objects are previously unidentified fast rotators that show a weak h₃ 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 h₃ versus V/σ as evidence for disks in most fast rotators, suggesting a dearth of gas-poor mergers among fast rotators.
- Subject
- cosmology; galaxies; galaxy evolution; galaxy formation; kinematics; stellar content; galaxy structure
- Identifier
- http://hdl.handle.net/1959.13/1399011
- Identifier
- uon:34514
- Identifier
- ISSN:0004-637X
- Language
- eng
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