Issue |
A&A
Volume 683, March 2024
|
|
---|---|---|
Article Number | A254 | |
Number of page(s) | 11 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/202348313 | |
Published online | 22 March 2024 |
Dissipationless collapse and the dynamical mass–ellipticity relation of elliptical galaxies in Newtonian gravity and MOND
1
National Council of Research – Institute of Complex Systems (CNR-ISC), Via Madonna del piano 10, 50019 Sesto Fiorentino, Italy
e-mail: pierfrancesco.dicintio@cnr.it
2
National Institute of Nuclear Physics (INFN) – Florence unit, Via G. Sansone 1, 50019 Sesto Fiorentino, Italy
3
Department of Physics and Astronomy, University of Florence, Piazzale E. Fermi 2, 50125 Firenze, Italy
4
National Institute of Astrophysics – Arcetri Astrophysical Observatory (INAF-OAA), Piazzale E. Fermi 5, 50125 Firenze, Italy
Received:
18
October
2023
Accepted:
5
February
2024
Context. Recent observational studies proposed an empirical relation between the dark-to-total mass ratio and ellipticity in elliptical galaxies based on their observed total dynamical mass-to-light ratio data M/L = (14.1 ± 5.4)ϵ. In other words, the larger the content of dark matter in the galaxy, the more the stellar component will be flattened. If true, this observation appears to be in stark contrast with the commonly accepted galaxy formation scenario, whereby this process takes place inside dark halos with reasonably spherical symmetry.
Aims. Comparing the processes of dissipationless galaxy formation in different theories of gravity and the emergence of the galaxy scaling relations therein provides an important framework within which, in principle, one can discriminate between these processes.
Methods. By means of collisionless N-body simulations in modified Newtonian dynamics (MOND) and Newtonian gravity with and without active dark matter halos, with both spherical and clumpy initial structure, I study the trends of intrinsic and projected ellipticities, Sérsic index, and anisotropy with the total dynamical-to-stellar mass ratio.
Results. I show that the end products of both cold spherical collapses and mergers of smaller clumps show an increasing departure from spherical symmetry for increasing values of the total dynamical-to-stellar mass ratio, at least in a range of halo masses. The equivalent Newtonian systems of the end products of MOND collapses show a similar behaviour. However, the M/L relation obtained from the numerical experiments in both gravities is rather different from that reported by Deur and coauthors.
Key words: gravitation / methods: numerical / galaxies: evolution / galaxies: formation
© The Authors 2024
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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