The SAMI Galaxy Survey: The Internal Orbital Structure and Mass Distribution of Passive Galaxies from Triaxial Orbit-superposition Schwarzschild Models
Authors
Green, AW
Lawrence, JS
Lorente, NPF
Richards, SN
Publication Date
2022Journal Title
Astrophysical Journal
ISSN
0004-637X
Publisher
American Astronomical Society
Volume
930
Issue
2
Language
en
Type
Article
This Version
VoR
Metadata
Show full item recordCitation
Santucci, G., Brough, S., Van De Sande, J., McDermid, R., Van De Ven, G., Zhu, L., D'Eugenio, F., et al. (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) https://doi.org/10.3847/1538-4357/ac5bd5
Abstract
<jats:title>Abstract</jats:title>
<jats:p>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<jats:sup>9.5</jats:sup>–10<jats:sup>12</jats:sup>
<jats:italic>M</jats:italic>
<jats:sub>⊙</jats:sub>. We find that the changes in internal structures within 1<jats:italic>R</jats:italic>
<jats:sub>e</jats:sub> 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 <jats:inline-formula>
<jats:tex-math>
<?CDATA $\mathrm{log}{M}_{\star }/{M}_{\odot }\gt 10.50$?>
</jats:tex-math>
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mi>log</mml:mi>
<mml:msub>
<mml:mrow>
<mml:mi>M</mml:mi>
</mml:mrow>
<mml:mrow>
<mml:mo>⋆</mml:mo>
</mml:mrow>
</mml:msub>
<mml:mrow>
<mml:mo stretchy="true">/</mml:mo>
</mml:mrow>
<mml:msub>
<mml:mrow>
<mml:mi>M</mml:mi>
</mml:mrow>
<mml:mrow>
<mml:mo>⊙</mml:mo>
</mml:mrow>
</mml:msub>
<mml:mo>></mml:mo>
<mml:mn>10.50</mml:mn>
</mml:math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5bd5ieqn1.gif" xlink:type="simple" />
</jats:inline-formula> are more likely to be non-oblate. We find a mean dark matter fraction of <jats:italic>f</jats:italic>
<jats:sub>DM</jats:sub> = 0.28 ± 0.20, within 1<jats:italic>R</jats:italic>
<jats:sub>e</jats:sub>. Galaxies with higher intrinsic ellipticity (flatter) are found to have more negative velocity anisotropy <jats:italic>β</jats:italic>
<jats:sub>
<jats:italic>r</jats:italic>
</jats:sub> (tangential anisotropy). <jats:italic>β</jats:italic>
<jats:sub>
<jats:italic>r</jats:italic>
</jats:sub> also shows an anticorrelation with the edge-on spin parameter <jats:inline-formula>
<jats:tex-math>
<?CDATA ${\lambda }_{\mathrm{Re},\mathrm{EO}}$?>
</jats:tex-math>
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:msub>
<mml:mrow>
<mml:mi>λ</mml:mi>
</mml:mrow>
<mml:mrow>
<mml:mi>Re</mml:mi>
<mml:mo>,</mml:mo>
<mml:mi>EO</mml:mi>
</mml:mrow>
</mml:msub>
</mml:math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5bd5ieqn2.gif" xlink:type="simple" />
</jats:inline-formula>, so that <jats:italic>β</jats:italic>
<jats:sub>
<jats:italic>r</jats:italic>
</jats:sub> decreases with increasing <jats:inline-formula>
<jats:tex-math>
<?CDATA ${\lambda }_{\mathrm{Re},\mathrm{EO}}$?>
</jats:tex-math>
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:msub>
<mml:mrow>
<mml:mi>λ</mml:mi>
</mml:mrow>
<mml:mrow>
<mml:mi>Re</mml:mi>
<mml:mo>,</mml:mo>
<mml:mi>EO</mml:mi>
</mml:mrow>
</mml:msub>
</mml:math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5bd5ieqn3.gif" xlink:type="simple" />
</jats:inline-formula>, 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 (<jats:italic>V</jats:italic>/<jats:italic>σ</jats:italic> – <jats:italic>h</jats:italic>
<jats:sub>3</jats:sub>) 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.</jats:p>
Keywords
310, Galaxies and Cosmology
Sponsorship
European Research Council (695671)
Identifiers
apjac5bd5, ac5bd5, aas35564
External DOI: https://doi.org/10.3847/1538-4357/ac5bd5
This record's URL: https://www.repository.cam.ac.uk/handle/1810/337137
Rights
Licence:
http://creativecommons.org/licenses/by/4.0/
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