An official website of the United States government
ABSTRACT We analyse strongly lensed images in eight galaxy clusters to measure their dark matter density profiles in the radial region between 10 kpc and 150 kpc, and use this to constrain the self-interaction cross-section of dark matter (DM) particles. We infer the mass profiles of the central DM haloes, bright central galaxies, key member galaxies, and DM subhaloes for the member galaxies for all eight clusters using the qlens code. The inferred DM halo surface densities are fit to a self-interacting dark matter model, which allows us to constrain the self-interaction cross-section over mass σ/m. When our full method is applied to mock data generated from two clusters in the Illustris-TNG simulation, we find results consistent with no dark matter self-interactions as expected. For the eight observed clusters with average relative velocities of $$1458_{-81}^{+80}$$ km s−1, we infer $$\sigma /m = 0.082_{-0.021}^{+0.027} \rm cm^2\, g^{ -1}$$ and $$\sigma /m \lt 0.13~ \rm cm^2\, g^{ -1}$$ at the 95 per cent confidence level.
more »
« less
Warm dark matter chills out: constraints on the halo mass function and the free-streaming length of dark matter with eight quadruple-image strong gravitational lenses
ABSTRACT The free-streaming length of dark matter depends on fundamental dark matter physics, and determines the abundance and concentration of dark matter haloes on sub-galactic scales. Using the image positions and flux ratios from eight quadruply imaged quasars, we constrain the free-streaming length of dark matter and the amplitude of the subhalo mass function (SHMF). We model both main deflector subhaloes and haloes along the line of sight, and account for warm dark matter free-streaming effects on the mass function and mass–concentration relation. By calibrating the scaling of the SHMF with host halo mass and redshift using a suite of simulated haloes, we infer a global normalization for the SHMF. We account for finite-size background sources, and marginalize over the mass profile of the main deflector. Parametrizing dark matter free-streaming through the half-mode mass mhm, we constrain the thermal relic particle mass mDM corresponding to mhm. At $$95 \, {\rm per\, cent}$$ CI: mhm < 107.8 M⊙ ($$m_{\rm {DM}} \gt 5.2 \ \rm {keV}$$). We disfavour $$m_{\rm {DM}} = 4.0 \,\rm {keV}$$ and $$m_{\rm {DM}} = 3.0 \,\rm {keV}$$ with likelihood ratios of 7:1 and 30:1, respectively, relative to the peak of the posterior distribution. Assuming cold dark matter, we constrain the projected mass in substructure between 106 and 109 M⊙ near lensed images. At $$68 \, {\rm per\, cent}$$ CI, we infer $$2.0{-}6.1 \times 10^{7}\, {{\rm M}_{\odot }}\,\rm {kpc^{-2}}$$, corresponding to mean projected mass fraction $$\bar{f}_{\rm {sub}} = 0.035_{-0.017}^{+0.021}$$. At $$95 \, {\rm per\, cent}$$ CI, we obtain a lower bound on the projected mass of $$0.6 \times 10^{7} \,{{\rm M}_{\odot }}\,\rm {kpc^{-2}}$$, corresponding to $$\bar{f}_{\rm {sub}} \gt 0.005$$. These results agree with the predictions of cold dark matter.
more »
« less
- Award ID(s):
- 1714953
- PAR ID:
- 10175463
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 491
- Issue:
- 4
- ISSN:
- 0035-8711
- Page Range / eLocation ID:
- 6077 to 6101
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
ABSTRACT We analyse the cold dark matter density profiles of 54 galaxy haloes simulated with Feedback In Realistic Environments (FIRE)-2 galaxy formation physics, each resolved within $$0.5{{\ \rm per\ cent}}$$ of the halo virial radius. These haloes contain galaxies with masses that range from ultrafaint dwarfs ($$M_\star \simeq 10^{4.5}\, \mathrm{M}_{\odot }$$) to the largest spirals ($$M_\star \simeq 10^{11}\, \mathrm{M}_{\odot }$$) and have density profiles that are both cored and cuspy. We characterize our results using a new, analytic density profile that extends the standard two-parameter Einasto form to allow for a pronounced constant density core in the resolved innermost radius. With one additional core-radius parameter, rc, this three-parameter core-Einasto profile is able to characterize our feedback-impacted dark matter haloes more accurately than other three-parameter profiles proposed in the literature. To enable comparisons with observations, we provide fitting functions for rc and other profile parameters as a function of both M⋆ and M⋆/Mhalo. In agreement with past studies, we find that dark matter core formation is most efficient at the characteristic stellar-to-halo mass ratio M⋆/Mhalo ≃ 5 × 10−3, or $$M_{\star } \sim 10^9 \, \mathrm{M}_{\odot }$$, with cores that are roughly the size of the galaxy half-light radius, rc ≃ 1−5 kpc. Furthermore, we find no evidence for core formation at radii $$\gtrsim 100\ \rm pc$$ in galaxies with M⋆/Mhalo < 5 × 10−4 or $$M_\star \lesssim 10^6 \, \mathrm{M}_{\odot }$$. For Milky Way-size galaxies, baryonic contraction often makes haloes significantly more concentrated and dense at the stellar half-light radius than DMO runs. However, even at the Milky Way scale, FIRE-2 galaxy formation still produces small dark matter cores of ≃ 0.5−2 kpc in size. Recent evidence for a ∼2 kpc core in the Milky Way’s dark matter halo is consistent with this expectation.more » « less
-
ABSTRACT We study the formation of ultradiffuse galaxies (UDGs) using the cosmological hydrodynamical simulation TNG50 of the Illustris-TNG suite. We define UDGs as dwarf galaxies in the stellar mass range $$\rm {7.5 \le log (M_{\star } / {\rm M}_{\odot }) \le 9 }$$ that are in the 5 per cent most extended tail of the simulated mass–size relation. This results in a sample of UDGs with half-mass radii $$\rm {r_{h \star } \gtrsim 2 \ kpc}$$ and surface brightness between $$\rm {24.5}$$ and $$\rm {28 \ mag \ arcsec^{-2}}$$, similar to definitions of UDGs in observations. The large cosmological volume in TNG50 allows for a comparison of UDGs properties in different environments, from the field to galaxy clusters with virial mass $$\rm {M_{200} \sim 2 \times 10^{14} ~ {\rm M}_{\odot }}$$. All UDGs in our sample have dwarf-mass haloes ($$\rm {M_{200}\sim 10^{11} ~ {\rm M}_{\odot } }$$) and show the same environmental trends as normal dwarfs: field UDGs are star-forming and blue while satellite UDGs are typically quiescent and red. The TNG50 simulation predicts UDGs that populate preferentially higher spin haloes and more massive haloes at fixed $$\rm {M_{\star }}$$ compared to non-UDG dwarfs. This applies also to most satellite UDGs, which are actually ‘born’ UDGs in the field and infall into groups and clusters without significant changes to their size. We find, however, a small subset of satellite UDGs ($$\lesssim 10~{{\ \rm per\ cent}}$$) with present-day stellar size a factor ≥1.5 larger than at infall, confirming that tidal effects, particularly in the lower mass dwarfs, are also a viable formation mechanism for some of these dwarfs, although sub-dominant in this simulation.more » « less
-
ABSTRACT We quantify the impact of galaxy formation on dark matter halo shapes using cosmological simulations at redshift z = 0. Using magnetohydrodynamic simulations from the IllustrisTNG project, we focus on haloes of mass $$10^{10\!-\!14} \, \rm M_{\odot }$$ from the 50 Mpc (TNG50) and 100 Mpc (TNG100) boxes and compare them to dark matter-only (DMO) analogues and other simulations, e.g. Numerical Investigation of a Hundred Astrophysical Objects (NIHAO) and Evolution and Assembly of GaLaxies and their Environments (EAGLE). We further quantify the prediction uncertainty by varying the feedback models using smaller 25 $${\rm Mpc}\, h^{-1}$$ boxes. We find that (i) galaxy formation results in rounder haloes compared to DMO simulations, in qualitative agreement with past results. Haloes of mass $${\approx }2\times 10^{12} \, \rm M_{\odot }$$ are most spherical, with an average minor-to-major axial ratio of $$\langle s \rangle$$ ≈ 0.75 in the inner halo, an increase of 40 per cent compared to their DMO counterparts. No significant difference is present for low-mass $$10^{10} \, \rm M_{\odot }$$ haloes; (ii) stronger feedback, e.g. increasing galactic wind speed, reduces the impact of baryons; (iii) the inner halo shape correlates with the stellar mass fraction, explaining the dependence of halo shapes on feedback models; and (iv) the fiducial and weaker feedback models are most consistent with observational estimates of the Milky Way halo shape. At fixed halo mass, very diverse and possibly unrealistic feedback models all predict inner shapes closer to one another than to the DMO results. Because of the large halo-to-halo variation in halo shape, a larger observational sample is required to statistically distinguish different baryonic prescriptions.more » « less
-
ABSTRACT The dark matter (DM) distribution in dwarf galaxies provides crucial insights into both structure formation and the particle nature of DM. GraphNPE (Graph Neural Posterior Estimator), first introduced in Nguyen et al. (2023), is a novel simulation-based inference framework that combines graph neural networks and normalizing flows to infer the DM density profile from line-of-sight stellar velocities. Here, we apply GraphNPE to satellite dwarf galaxies in the FIRE-2 Latte simulation suite of Milky Way-mass haloes, testing it against both Cold and Self-Interacting DM scenarios. Our method demonstrates superior precision compared to conventional Jeans-based approaches, recovering DM density profiles to within the 95 per cent confidence level even in systems with as few as 30 tracers. Moreover, we present the first evaluation of mass modelling methods in constraining two key parameters from realistic simulations: the peak circular velocity, $$V_\mathrm{max}$$, and the peak virial mass, $$M_\mathrm{200m}^\mathrm{peak}$$. Using only line-of-sight velocities, GraphNPE can reliably recover both $$V_\mathrm{max}$$ and $$M_\mathrm{200m}^\mathrm{peak}$$ within our quoted uncertainties, including those experiencing tidal effects ($$\gtrsim 63~{{\rm per\ cent}}$$ of systems are recovered within our 68 per cent confidence intervals and $$\gtrsim 92~{{\rm per\ cent}}$$ within our 95 per cent confidence intervals). The method achieves $$10-20~{{\rm per\ cent}}$$ accuracy in $$V_\mathrm{max}$$ recovery, while $$M_\mathrm{200m}^\mathrm{peak}$$ is recovered to $$0.1-0.4 \, \mathrm{dex}$$ accuracy. This work establishes GraphNPE as a robust tool for inferring DM density profiles in dwarf galaxies, offering promising avenues for constraining DM models. The framework’s potential extends beyond this study, as it can be adapted to non-spherical and disequilibrium models, showcasing the broader utility of simulation-based inference and graph-based learning in astrophysics.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/mnras/stz3480
