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

Santucci, Giulia; Brough, Sarah; van de Sande, Jesse; McDermid, Richard M.; van de Ven, Glenn; Zhu, Ling; D’Eugenio, Francesco; Bland-Hawthorn, Joss; Barsanti, Stefania; Bryant, Julia J.; M. Croom, Scott; Davies, Roger L.; Green, Andrew W.; Lawrence, Jon S.; Lorente, Nuria P.F.; Owers, Matt S.; Poci, Adriano; Richards, Samuel N.; Thater, Sabine; Yi, Sukyoung

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


Authors

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

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 109.5–1012M⊙. We find that the changes in internal structures within 1Re 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 fDM = 0.28 ± 0.20, within 1Re. Galaxies with higher intrinsic ellipticity (flatter) are found to have more negative velocity anisotropy βr (tangential anisotropy). βr also shows an anticorrelation with the edge-on spin parameter ${\lambda }_{\mathrm{Re},\mathrm{EO}}$, so that βr 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 – h3) 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.

Citation

Santucci, G., Brough, S., van de Sande, J., McDermid, R. M., van de Ven, G., Zhu, L., …Yi, S. (2022). The SAMI Galaxy Survey: The Internal Orbital Structure and Mass Distribution of Passive Galaxies from Triaxial Orbit-superposition Schwarzschild Models. Astrophysical Journal, 930(2), Article 153. https://doi.org/10.3847/1538-4357/ac5bd5

Journal Article Type Article
Acceptance Date Mar 6, 2022
Online Publication Date May 13, 2022
Publication Date May 10, 2022
Deposit Date Jul 14, 2022
Publicly Available Date Jul 14, 2022
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 930
Issue 2
Article Number 153
DOI https://doi.org/10.3847/1538-4357/ac5bd5

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Publisher Licence URL
http://creativecommons.org/licenses/by/4.0/

Copyright Statement
Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.





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