The SAMI Galaxy Survey: The Internal Orbital Structure and Mass Distribution of Passive Galaxies from Triaxial Orbit-superposition Schwarzschild Models

Author(s): Giulia Santucci, Sarah Brough, Jesse van de Sande, Richard M. McDermid, Glenn van de Ven, Ling Zhu, Francesco D'Eugenio, Joss Bland-Hawthorn, Stefania Barsanti, Julia J. Bryant, Scott M. Croom, Roger L. Davies, Andrew W. Green, Jon S. Lawrence, Nuria P. F. Lorente, Matt S. Owers, Adriano Poci, Samuel N. Richards, Sabine Thater, Sukyoung Yi
Abstract: 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 10^9.5-10¹² 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 $\mathrm{log}{M}_{\star }/{M}_{\odot }\gt 10.50$ 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 ${\lambda }_{\mathrm{Re},\mathrm{EO}}$ , so that β r decreases with increasing ${\lambda }_{\mathrm{Re},\mathrm{EO}}$ , 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.
Organisation(s): Department of Astrophysics
External organisation(s): University of New South Wales, ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), The University of Sydney, Macquarie University, Chinese Academy of Sciences (CAS), University of Cambridge, Ghent University , Australian National University, University of Oxford, Durham University, Yonsei University
Journal: The Astrophysical Journal
Volume: 930
No. of pages: 32
ISSN: 0004-637X
DOI: https://doi.org/10.3847/1538-4357/ac5bd5
Publication date: 05-2022
Peer reviewed: Yes
Austrian Fields of Science 2012: 103003 Astronomy, 103004 Astrophysics
Keywords
ASJC Scopus subject areas: Astronomy and Astrophysics, Space and Planetary Science
Portal url: https://ucrisportal.univie.ac.at/en/publications/b2556b29-c77c-495b-bc39-2d7739ccc940

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