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The SAMI Galaxy Survey: Revisiting Galaxy Classification through High-order Stellar Kinematics

van de Sande, Jesse and Medling, Anne M. (2017) The SAMI Galaxy Survey: Revisiting Galaxy Classification through High-order Stellar Kinematics. Astrophysical Journal, 835 (1). Art. No. 104. ISSN 0004-637X.

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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.

Item Type:Article
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URLURL TypeDescription Paper
van de Sande, Jesse0000-0003-2552-0021
Medling, Anne M.0000-0001-7421-2944
Additional Information:© 2017 The American Astronomical Society. Received 2016 September 30; revised 2016 November 15; accepted 2016 November 16; published 2017 January 20. We thank the anonymous referee for the constructive comments which improved the quality of the paper. We also thank Michele Cappellari and Thorsten Naab for useful comments and discussions. The SAMI Galaxy Survey is based on observations made at the Anglo-Australian Telescope. The Sydney-AAO Multi-object Integral-field spectrograph (SAMI) was developed jointly by the University of Sydney and the Australian Astronomical Observatory, and funded by ARC grants FF0776384 (Bland-Hawthorn) and LE130100198. J.vdS. is funded under Bland-Hawthorn's ARC Laureate Fellowship (FL140100278). J.T.A. acknowledges the award of a SIEF John Stocker Fellowship. M.S.O. acknowledges the funding support from the Australian Research Council through a Future Fellowship Fellowship (FT140100255). S.B. acknowledges the funding support from the Australian Research Council through a Future Fellowship (FT140101166). S.M.C. acknowledges the support of an Australian Research Council Future Fellowship (FT100100457). S.K.Y. acknowledges support from the Korean National Research Foundation (NRF-2014R1A2A1A01003730) and the Yonsei University Future-leading Research Initiative (RMS2 2015-22-0064). The SAMI input catalog is based on data taken from the Sloan Digital Sky Survey, the GAMA Survey and the VST ATLAS Survey. The SAMI Galaxy Survey is funded by the Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO), through project number CE110001020, and other participating institutions. The SAMI Galaxy Survey website is GAMA is a joint European-Australasian project based around a spectroscopic campaign using the Anglo-Australian Telescope. The GAMA input catalog is based on data taken from the Sloan Digital Sky Survey and the UKIRT Infrared Deep Sky Survey. Complementary imaging of the GAMA regions is being obtained by a number of independent survey programs including GALEX MIS, VST KiDS, VISTA VIKING, WISE, Herschel-ATLAS, GMRT and ASKAP providing UV to radio coverage. GAMA is funded by the STFC (UK), the ARC (Australia), the AAO, and the participating institutions. The GAMA website is: Based on data products (VST/ATLAS) from observations made with ESO Telescopes at the La Silla Paranal Observatory under program ID 177.A-3011(A, B, C). This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III web site is
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Australian Research CouncilFF0776384
Australian Research CouncilLE130100198
Australian Research CouncilFL140100278
SIEF John Stocker FellowshipUNSPECIFIED
Australian Research CouncilFT140100255
Australian Research CouncilFT140101166
Australian Research CouncilFT100100457
National Research Foundation of KoreaNRF-2014R1A2A1A01003730
Yonsei UniversityRMS2 2015-22-0064
Australian Research CouncilCE110001020
Science and Technology Facilities Council (STFC)UNSPECIFIED
Australian Astronomical Observatory (AAO)UNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
Subject Keywords:cosmology: observations – galaxies: evolution – galaxies: formation – galaxies: kinematics and dynamics – galaxies: stellar content – galaxies: structure
Issue or Number:1
Record Number:CaltechAUTHORS:20170127-091339895
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Official Citation:Jesse van de Sande et al 2017 ApJ 835 104
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:73771
Deposited By: Tony Diaz
Deposited On:27 Jan 2017 19:06
Last Modified:09 Mar 2020 13:19

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