More Like this

1. Central densities of dark matter haloes in fire-2 simulations of low-mass galaxies with cold dark matter and self-interacting dark matter

   https://doi.org/10.1093/mnras/staf1539  

   Straight, Maria C; Boylan-Kolchin, Michael; Bullock, James S; Hopkins, Philip F; Shen, Xuejian; Necib, Lina; Lazar, Alexandres; Graus, Andrew S; Samuel, Jenna (October 2025, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We investigate the central density structure of dark matter haloes in cold dark matter (CDM) and self-interacting dark matter (SIDM) models using simulations that are part of the Feedback In Realistic Environments (fire) project. For simulated haloes of dwarf galaxy scale ($$M_{\rm halo}(z=0)\approx 10^{10}\, \mathrm{ M}_\odot$$), we study the central structure in both dissipationless simulations and simulations with full fire-2 galaxy formation physics. As has been demonstrated extensively in recent years, both baryonic feedback and self-interactions can convert central cusps into cores, with the former process doing so in a manner that depends sensitively on stellar mass at fixed $$M_{\rm halo}$$. Whether the two processes (baryonic feedback and self-interactions) are distinguishable, however, remains an open question. Here we demonstrate that, compared to feedback-induced cores, SIDM-induced cores transition more quickly from the central region of constant density to the falling density at larger radial scales. This result holds true even when including identical galaxy formation modelling in SIDM simulations as is used in CDM simulations, since self-interactions dominate over galaxy formation physics in establishing the central structure of SIDM haloes in this mass regime. The change in density profile slope as a function of radius therefore holds the potential to discriminate between self-interactions and galaxy formation physics as the driver of core formation in dwarf galaxies. 

   more » « less
2. The central densities of Milky Way-mass galaxies in cold and self-interacting dark matter models

   https://doi.org/10.1093/mnras/stab2173  

   Sameie, Omid; Boylan-Kolchin, Michael; Sanderson, Robyn; Vargya, Drona; Hopkins, Philip F; Wetzel, Andrew; Bullock, James; Graus, Andrew; Robles, Victor H (August 2021, Monthly Notices of the Royal Astronomical Society)

   null (Ed.)

   ABSTRACT We present a suite of baryonic cosmological zoom-in simulations of self-interacting dark matter (SIDM) haloes within the ‘Feedback In Realistic Environment’ (FIRE) project. The three simulated haloes have virial masses of $$\sim 10^{12}\, \text{M}_\odot$$ at z = 0, and we study velocity-independent self-interaction cross sections of 1 and 10 $${\rm cm^2 \, g^{-1}}$$. We study star formation rates and the shape of dark matter density profiles of the parent haloes in both cold dark matter (CDM) and SIDM models. Galaxies formed in the SIDM haloes have higher star formation rates at z ≤ 1, resulting in more massive galaxies compared to the CDM simulations. While both CDM and SIDM simulations show diverse shape of the dark matter density profiles, the SIDM haloes can reach higher and more steep central densities within few kpcs compared to the CDM haloes. We identify a correlation between the build-up of the stars within the half-mass radii of the galaxies and the growth in the central dark matter densities. The thermalization process in the SIDM haloes is enhanced in the presence of a dense stellar component. Hence, SIDM haloes with highly concentrated baryonic profiles are predicted to have higher central dark matter densities than the CDM haloes. Overall, the SIDM haloes are more responsive to the presence of a massive baryonic distribution than their CDM counterparts. 

   more » « less
3. Unravelling the interplay between SIDM and baryons in MW haloes: defining where baryons dictate heat transfer

   https://doi.org/10.1093/mnras/stac3634  

   Rose, Jonah C; Torrey, Paul; Vogelsberger, Mark; O’Neil, Stephanie (January 2023, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We present a new set of cosmological zoom-in simulations of a Milky Way (MW)-like galaxy that for the first time include elastic velocity-dependent self-interacting dark matter (SIDM) and IllustrisTNG physics. With these simulations, we investigate the interaction between SIDM and baryons and its effects on the galaxy evolution process. We also introduce a novel set of modified dark matter-only simulations that can reasonably replicate the effects of fully realized hydrodynamics on the DM halo while simplifying the analysis and lowering the computational cost. We find that baryons change the thermal structure of the central region of the halo to a greater extent than the SIDM scatterings for MW-like galaxies. Additionally, we find that the new thermal structure of the MW-like halo causes SIDM to create cuspier central densities rather than cores because the SIDM scatterings remove the thermal support by transferring heat away from the centre of the galaxy. We find that this effect, caused by baryon contraction, begins to affect galaxies with a stellar mass of 108 M⊙ and increases in strength to the MW-mass scale. 

   more » « less
4. A semi-analytic study of self-interacting dark-matter haloes with baryons

   https://doi.org/10.1093/mnras/stad705  

   Jiang, Fangzhou; Benson, Andrew; Hopkins, Philip F; Slone, Oren; Lisanti, Mariangela; Kaplinghat, Manoj; Peter, Annika H; Zeng, Zhichao Carton; Du, Xiaolong; Yang, Shengqi; et al (March 2023, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We combine the isothermal Jeans model and the model of adiabatic halo contraction into a semi-analytic procedure for computing the density profile of self-interacting dark-matter (SIDM) haloes with the gravitational influence from the inhabitant galaxies. The model agrees well with cosmological SIDM simulations over the entire core-forming stage up to the onset of gravothermal core-collapse. Using this model, we show that the halo response to baryons is more diverse in SIDM than in CDM and depends sensitively on galaxy size, a desirable feature in the context of the structural diversity of bright dwarfs. The fast speed of the method facilitates analyses that would be challenging for numerical simulations – notably, we quantify the SIDM halo response as functions of the baryonic properties, on a fine mesh grid spanned by the baryon-to-total-mass ratio, Mb/Mvir, and galaxy compactness, r1/2/Rvir; we show with high statistical precision that for typical Milky-Way-like systems, the SIDM profiles are similar to their CDM counterparts; and we delineate the regime of core-collapse in the Mb/Mvir − r1/2/Rvir space, for a given cross section and concentration. Finally, we compare the isothermal Jeans model with the more sophisticated gravothermal fluid model, and show that the former yields faster core formation and agrees better with cosmological simulations. We attribute the difference to whether the target CDM halo is used as a boundary condition or as the initial condition for the gravothermal evolution, and thus comment on possible improvements of the fluid model. We have made our model publicly available at https://github.com/JiangFangzhou/SIDM. 

   more » « less
5. Real and counterfeit cores: how feedback expands haloes and disrupts tracers of inner gravitational potential in dwarf galaxies

   https://doi.org/10.1093/mnras/stad109  

   Jahn, Ethan D; Sales, Laura V; Marinacci, Federico; Vogelsberger, Mark; Torrey, Paul; Qi, Jia; Smith, Aaron; Li, Hui; Kannan, Rahul; Burger, Jan D; et al (January 2023, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT The tension between the diverging density profiles in Lambda cold dark matter simulations and the constant-density inner regions of observed galaxies is a long-standing challenge known as the ‘core–cusp’ problem. We demonstrate that the SMUGGLE galaxy formation model implemented in the arepo moving mesh code forms constant-density cores in idealized dwarf galaxies of M⋆ ≈ 8 × 107 Msun with initially cuspy dark matter (DM) haloes of M200 ≈ 1010 Msun. Identical initial conditions run with an effective equation of state interstellar medium model preserve cuspiness. Literature on the subject has pointed to the low density threshold for star formation, ρth, in such effective models as an obstacle to baryon-induced core formation. Using a SMUGGLE run with equal ρth, we demonstrate that core formation can proceed at low density thresholds, indicating that ρth is insufficient on its own to determine whether a galaxy develops a core. We reaffirm that the ability to resolve a multiphase interstellar medium at sufficiently high densities is a more reliable indicator of core formation than any individual model parameter. In SMUGGLE, core formation is accompanied by large degrees of non-circular motion, with gas rotational velocity profiles that consistently fall below the circular velocity $$v_\text{circ} = \sqrt{GM/R}$$ out to ∼2 kpc. Asymmetric drift corrections help recover the average underlying DM potential for some of our less efficient feedback runs, but time-variations in the instantaneous azimuthal gas velocity component are substantial, highlighting the need for careful modelling in the inner regions of dwarfs to infer the true distribution of DM. 

   more » « less