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Constraining SIDM with halo shapes: revisited predictions from realistic simulations of early-type galaxies
Cosmology and Nongalactic Astrophysics · Submitted 26 Apr 2022
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim Contrary to previous claims at the scale of elliptical galaxies, we conclude that both CDM and our SIDM model can still explain observed shapes once we include baryons in the simulations.
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The abstract, sentence by sentence
We study the effect of self-interacting dark matter (SIDM) and baryons on the shape of early-type galaxies (ETGs) and their dark matter haloes, comparing them to the predictions of the cold dark matter (CDM) scenario. We use five hydrodynamical zoom-in simulations of haloes hosting ETGs ($M_{\rm vir}\sim 10^{13}M_{\odot}$ and $M_{*}\sim10^{11}M_{\odot}$), simulated in CDM and a SIDM model with constant cross-section of $\sigma_T/m_\chi = 1\ \mathrm{cm}^2 \mathrm{g}^{-1}$. We measure the three-dimensional and projected shapes of the dark matter haloes and their baryonic content using the inertia tensor and compare our measurements to the results of three $HST$ samples of gravitational lenses and $Chandra$ and $XMM-Newton$ X-ray observations. We find that the inclusion of baryons greatly reduces the differences between CDM and a SIDM, together with the ability to draw constraints based on shapes. Lensing measurements reject the predictions of CDM dark-matter-only simulations and prefer one of the hydro scenarios. When we consider the total sample of lenses, observational data prefer the CDM hydro scenario. The shapes of the X-ray emitting gas are compatible with observational results in both hydro runs, with CDM predicting higher elongations only in the very centre. Contrary to previous claims at the scale of elliptical galaxies, we conclude that both CDM and our SIDM model can still explain observed shapes once we include baryons in the simulations. Our results demonstrate that this is essential to derive realistic constraints and that new simulations are needed to confirm and extend our findings.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We study the effect of self-interacting dark matter (SIDM) and baryons on the shape of early-type galaxies (ETGs) and their dark matter haloes, comparing them to the predictions of the cold dark matter (CDM) scenario. | contribution 0.98 | 0.90 | 0.04 | asserted 0.58 |
| s1 | We use five hydrodynamical zoom-in simulations of haloes hosting ETGs ($M_{\rm vir}\sim 10^{13}M_{\odot}$ and $M_{*}\sim10^{11}M_{\odot}$), simulated in CDM and a SIDM model with constant cross-section of $\sigma_T/m_\chi = 1\ \mathrm{cm}^2 \mathrm{g}^{-1}$. | method 0.99 | 0.91 | 0.02 | asserted 0.97 |
| s2 | We measure the three-dimensional and projected shapes of the dark matter haloes and their baryonic content using the inertia tensor and compare our measurements to the results of three $HST$ samples of gravitational lenses and $Chandra$ and $XMM-Newton$ X-ray observations. | method 1.00 | 0.95 | 0.03 | asserted 0.99 |
| s3 | We find that the inclusion of baryons greatly reduces the differences between CDM and a SIDM, together with the ability to draw constraints based on shapes. | result 0.95 | 0.96 | 0.40 | asserted 1.00 |
| s4 | Lensing measurements reject the predictions of CDM dark-matter-only simulations and prefer one of the hydro scenarios. | result 0.95 | 0.83 | 0.11 | asserted 1.00 |
| s5 | When we consider the total sample of lenses, observational data prefer the CDM hydro scenario. | result 0.98 | 0.86 | 0.16 | asserted 0.94 |
| s6 | The shapes of the X-ray emitting gas are compatible with observational results in both hydro runs, with CDM predicting higher elongations only in the very centre. | result 1.00 | 0.89 | 0.06 | asserted 0.80 |
| s7 | Contrary to previous claims at the scale of elliptical galaxies, we conclude that both CDM and our SIDM model can still explain observed shapes once we include baryons in the simulations. | result 0.54 | 0.90 | 0.77 | asserted 0.98 |
| s8 | Our results demonstrate that this is essential to derive realistic constraints and that new simulations are needed to confirm and extend our findings. | future work 0.87 | 0.58 | 0.16 | asserted 1.00 |
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The paper
Original abstract
We study the effect of self-interacting dark matter (SIDM) and baryons on the shape of early-type galaxies (ETGs) and their dark matter haloes, comparing them to the predictions of the cold dark matter (CDM) scenario. We use five hydrodynamical zoom-in simulations of haloes hosting ETGs ($M_{\rm vir}\sim 10^{13}M_{\odot}$ and $M_{*}\sim10^{11}M_{\odot}$), simulated in CDM and a SIDM model with constant cross-section of $\sigma_T/m_\chi = 1\ \mathrm{cm}^2 \mathrm{g}^{-1}$. We measure the three-dimensional and projected shapes of the dark matter haloes and their baryonic content using the inertia tensor and compare our measurements to the results of three $HST$ samples of gravitational lenses and $Chandra$ and $XMM-Newton$ X-ray observations. We find that the inclusion of baryons greatly reduces the differences between CDM and a SIDM, together with the ability to draw constraints based on shapes. Lensing measurements reject the predictions of CDM dark-matter-only simulations and prefer one of the hydro scenarios. When we consider the total sample of lenses, observational data prefer the CDM hydro scenario. The shapes of the X-ray emitting gas are compatible with observational results in both hydro runs, with CDM predicting higher elongations only in the very centre. Contrary to previous claims at the scale of elliptical galaxies, we conclude that both CDM and our SIDM model can still explain observed shapes once we include baryons in the simulations. Our results demonstrate that this is essential to derive realistic constraints and that new simulations are needed to confirm and extend our findings.
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References
How the literature uses it
1 arXiv paper cite this in 4 sentences
Papers citing it · 3 sentences without a confident label
Uses its data or values 1 paper
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In particular, we take the approximate constraint on the cross section in massive ellipticals set in [ref] and more recently in [ref] of $<σ_max> ≤1 cm^2g^-1$ at halo mass $M_0 = 10^13M_⊙$.
Gravothermal collapse of Self-Interacting Dark Matter halos as the Origin of Intermediate Mass Black Holes in Milky Way satellites · IMBHs in the ultra-faint galaxies · 0.99
What it cites · 2 sentences without a confident label
Uses the method or tool of 1 paper
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Each galaxy was re-simulated both in the standard CDM scenario and in a SIDM model with a constant cross-section of $σ_T/m_χ= 1 cm^2g^-1$, using an extended version of the AREPO code that includes both elastic and multi-state inelastic SIDM [ref] .
Evaporating the Milky Way halo and its satellites with inelastic self-interacting dark matter · Simulations · 0.99
Compares with 1 paper
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In CDM-h, our results are compatible with those from previous works [ref] and in SIDM-h we find an even more pronounced central sphericity, due to the combined effect of baryons and self-interactions [ref] .
X-ray morphology of cluster-mass haloes in self-interacting dark matter · Triaxial shapes in 3D · 0.91
Cites as background 2 papers
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Recent works have started to explore the interplay between SIDM and baryons, using hydrodynamical simulations at galaxy [ref] and galaxy cluster [ref] scales.
X-ray morphology of cluster-mass haloes in self-interacting dark matter · INTRODUCTION · 0.85
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Other recent works focus instead on similar constraints at the scale of galaxy clusters [ref] or on the intrinsic alignments of galaxy shapes [ref] .
Constraints on dark matter self-interaction from the internal density profiles of X-COP galaxy clusters · INTRODUCTION · 0.98
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