Issue |
A&A
Volume 664, August 2022
|
|
---|---|---|
Article Number | L6 | |
Number of page(s) | 8 | |
Section | Letters to the Editor | |
DOI | https://doi.org/10.1051/0004-6361/202243646 | |
Published online | 10 August 2022 |
Letter to the Editor
Intervelocity of galaxy pairs in ΛCDM
Observed velocity peak at ∼130 km s−1 not unique to modified Newtonian dynamics
Leibniz-Institute for Astrophysics, An der Sternwarte 16, 14482 Potsdam, Germany
e-mail: mpawlowski@aip.de
Received:
26
March
2022
Accepted:
16
July
2022
Context. Observational studies of pairs of galaxies have uncovered that their differential line-of-sight velocities indicate the presence of a peak in their three-dimensional (3D) intervelocity distribution at 130−150 km s−1. It had been argued that galaxy pairs in the standard model of cosmology, ΛCDM, should not exhibit such an intervelocity peak, while modified Newtonian dynamics (MOND) predicts such a preferred intervelocity for paired galaxies. However, no direct comparison with ΛCDM applying the same selection criteria and methodology as the observational studies has been performed at present, placing the comparison on uncertain footing.
Aims. To rectify this situation, we investigate this potential challenge to ΛCDM by determining whether an analog of the observed intervelocity peak is present in galaxy pairs within the IllustrisTNG-300 cosmological simulation.
Methods. We identified galaxy pairs following the observational study’s selection criteria, measured their projected velocity difference, and analyzed both the de-projected and the full velocity difference for this galaxy pair sample in the simulation.
Results. We recovered a deprojected intervelocity peak at ∼130 km s−1 for galaxy pairs selected from the simulation. The full 3D velocity information available for the pairs in the simulation also reveals a clear preference for this intervelocity.
Conclusions. The intervelocity peak among galaxy pairs does not appear to be a feature unique to MOND, as it is also present in ΛCDM. Thus, it cannot be claimed to be a unique success characteristic of either theory over the other. Developing the galaxy pair intervelocity into a test of gravity in the low-acceleration regime will require more detailed studies to identify measurable differences among the models.
Key words: galaxies: groups: general / galaxies: interactions / galaxies: kinematics and dynamics / galaxies: statistics / dark matter
© M. S. Pawlowski et al. 2022
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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