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Comparing lensing and stellar orbital models of a nearby massive strong-lens galaxy

Poci, Adriano; Smith, Russell J

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Exploiting the relative proximity of the nearby strong-lens galaxy SNL-1, we present a critical comparison of the mass estimates derived from independent modelling techniques. We fit triaxial orbit-superposition dynamical models to spatially resolved stellar kinematics, and compare to the constraints derived from lens modelling of high-resolution photometry. From the dynamical model, we measure the total (dynamical) mass enclosed within a projected aperture of radius the Einstein radius to be log10(MEin/M) = 11.00 ± 0.02, which agrees with previous measurements from lens modelling to within 5 per cent. We then explore the intrinsic (de-projected) properties of the best-fitting dynamical model. We find that SNL-1 has approximately constant, intermediate triaxiality at all radii. It is oblate like in the inner regions (around the Einstein radius) and tends towards spherical at larger radii. The stellar velocity ellipsoid gradually transforms from isotropic in the very central regions to radially biased in the outskirts. We find that SNL-1 is dynamically consistent with the broader galaxy population, as measured by the relative fraction of orbit ‘temperatures’ compared to the CALIFA survey. On the mass–size plane, SNL-1 occupies the most-compact edge given its mass, compared to both the MaNGA and SAMI surveys. Finally, we explore how the observed lensing configuration is affected by the orientation of the lens galaxy. We discuss the implications of such detailed models on future combined lensing and dynamical analyses.


Poci, A., & Smith, R. J. (2022). Comparing lensing and stellar orbital models of a nearby massive strong-lens galaxy. Monthly Notices of the Royal Astronomical Society, 512(4), 5298-5310.

Journal Article Type Article
Acceptance Date Mar 17, 2022
Online Publication Date Mar 22, 2022
Publication Date 2022-06
Deposit Date Jun 28, 2022
Publicly Available Date Jun 28, 2022
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 512
Issue 4
Pages 5298-5310


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Copyright Statement
© The Author(s) 2022. Published by Oxford University Press on behalf of Royal Astronomical Society.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.

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