Dynamical models are crucial for uncovering the internal dynamics of galaxies; however, most of the results to date assume axisymmetry, which is not representative of a significant fraction of massive galaxies. Here, we build triaxial Schwarzschild orbit-superposition models of galaxies taken from the SAMI Galaxy Survey, in order to reconstruct their inner orbital structure and mass distribution. The sample consists of 161 passive galaxies with total stellar masses in the range 109.5-1012 M ⊙. We find that the changes in internal structures within 1R e are correlated with the total stellar mass of the individual galaxies. The majority of the galaxies in the sample (73% ± 3%) are oblate, while 19% ± 3% are mildly triaxial and 8% ± 2% have triaxial/prolate shape. Galaxies with logM∗/M⊙>10.50 are more likely to be non-oblate. We find a mean dark matter fraction of f DM = 0.28 ± 0.20, within 1R e. Galaxies with higher intrinsic ellipticity (flatter) are found to have more negative velocity anisotropy β r (tangential anisotropy). β r also shows an anticorrelation with the edge-on spin parameter λRe,EO, so that β r decreases with increasing λRe,EO, reflecting the contribution from disk-like orbits in flat, fast-rotating galaxies. We see evidence of an increasing fraction of hot orbits with increasing stellar mass, while warm and cold orbits show a decreasing trend. We also find that galaxies with different (V/σ - h 3) kinematic signatures have distinct combinations of orbits. These results are in agreement with a formation scenario in which slow- and fast-rotating galaxies form through two main channels.
|Publication status||Published - 2022 May 1|
Bibliographical noteFunding Information:
We thank the anonymous referee for their comments that helped to improve this manuscript. We thank the DYNAMITE team for their invaluable support with the code and optimization and Michele Cappellari for useful discussions. The SAMI Galaxy Survey is based on observations made at the Anglo-Australian Telescope. SAMI was developed jointly by the University of Sydney and the Australian Astronomical Observatory. The SAMI input catalog is based on data taken from SDSS, the GAMA Survey, and the VST ATLAS Survey. The SAMI Galaxy Survey is supported by the Australian Research Council center of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013, the Australian Research Council center of Excellence for All-sky Astrophysics (CAASTRO), through project number CE110001020, and other participating institutions. The SAMI Galaxy Survey website is located at http://sami-survey.org/ .
This research is supported by an Australian Government Research Training Program (RTP) Scholarship. S.B. acknowledges funding support from the Australian Research Council through a Future Fellowship (FT140101166). J.v.d.S. acknowledges support of an Australian Research Council Discovery Early Career Research Award (project number DE200100461) funded by the Australian Government. R.M.c.D. acknowledges funding support via an Australian Research Council Future Fellowship (project No. FT150100333). G.v.d.V. acknowledges funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program under grant agreement No. 724857 (Consolidator Grant ArcheoDyn). L.Z. acknowledges the support from National Natural Science Foundation of China under grant No. Y945271001. F.D.E. acknowledges funding through the ERC Advanced grant 695671 “QUENCH”, the H2020 ERC Consolidator Grant 683184 and support by the Science and Technology Facilities Council (STFC). J.B.H. is supported by an ARC Laureate Fellowship FL140100278. The SAMI instrument was funded by Bland-Hawthorn’s former Federation Fellowship FF0776384, an ARC LIEF grant LE130100198 (PI Bland-Hawthorn) and funding from the Anglo-Australian Observatory. J.J.B. acknowledges support of an Australian Research Council Future Fellowship (FT180100231). M.S.O. acknowledges the funding support from the Australian Research Council through a Future Fellowship (FT140100255). S.K.Y. acknowledges support from the Korean National Research Foundation (NRF-2020R1A2C3003769).
© 2022. The Author(s). Published by the American Astronomical Society.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science