The SAMI Galaxy Survey:revisiting galaxy classification through high-order stellar kinematics
ecent 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 s...
Published in: | The Astrophysical Journal |
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Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
2017
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Subjects: | |
Online Access: | https://researchers.mq.edu.au/en/publications/fd646d49-b6c4-4c6e-8b81-7413e258292d https://doi.org/10.3847/1538-4357/835/1/104 https://research-management.mq.edu.au/ws/files/86293933/Publisher_version_open_access_.pdf http://purl.org/au-research/grants/arc/FT140100255 http://purl.org/au-research/grants/arc/CE110001020 http://www.scopus.com/inward/record.url?scp=85011279106&partnerID=8YFLogxK |
Summary: | ecent 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 ( ∈ 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 - ∈ 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. |
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