Alternatives to the cold, collisionless dark matter (DM) paradigm in which DM behaves as a collisional fluid generically suppress small-scale structure. Herein we use the observed population of Milky ...Way (MW) satellite galaxies to constrain the collisional nature of DM, focusing on DM-baryon scattering. We first derive conservative analytic upper limits on the velocity-independent DM-baryon scattering cross section by translating the upper bound on the lowest mass of halos inferred to host satellites into a characteristic cutoff scale in the linear matter power spectrum. We then confirm and improve these results through a detailed probabilistic inference of the MW satellite population that marginalizes over relevant astrophysical uncertainties. This yields 95% confidence upper limits on the DM-baryon scattering cross section of 6 × 10−30 cm2 (10−27 cm2) for DM particle masses mχ of 10 keV (10 GeV); these limits scale as mχ1/4 for mχ < 1 GeV and mχ for mχ > 1 GeV. This analysis improves upon cosmological bounds derived from cosmic-microwave-background anisotropy measurements by more than three orders of magnitude over a wide range of DM masses, excluding regions of parameter space previously unexplored by other methods, including direct-detection experiments. Our work reveals a mapping between DM-baryon scattering and other alternative DM models, and we discuss the implications of our results for warm and fuzzy DM scenarios.
Abstract
As cosmic microwave background (CMB) photons traverse the universe, anisotropies can be induced via Thomson scattering (proportional to the electron density; optical depth) and inverse ...Compton scattering (proportional to the electron pressure; thermal Sunyaev–Zel’dovich effect). Measurements of anisotropy in optical depth
τ
and Compton
y
parameters are imprinted by the galaxies and galaxy clusters and are thus sensitive to the thermodynamic properties of the circumgalactic medium and intergalactic medium. We use an analytic halo model to predict the power spectrum of the optical depth (
τ
τ
), the cross-correlation between the optical depth and the Compton
y
parameter (
τ
y
), and the cross-correlation between the optical depth and galaxy clustering (
τ
g
), and compare this model to cosmological simulations. We constrain the optical depths of halos at
z
≲ 3 using a technique originally devised to constrain patchy reionization at a higher redshift range. The forecasted signal-to-noise ratio is 2.6, 8.5, and 13, respectively, for a CMB-S4-like experiment and a Vera C. Rubin Observatory–like optical survey. We show that a joint analysis of these probes can constrain the amplitude of the density profiles of halos to 6.5% and the pressure profiles to 13%. These constraints translate to astrophysical parameters, such as the gas mass fraction,
f
g
, which can be constrained to 5.3% uncertainty at
z
∼ 0. The cross-correlations presented here are complementary to other CMB and galaxy cross-correlations since they do not require spectroscopic galaxy redshifts and are another example of how such correlations are a powerful probe of the astrophysics of galaxy evolution.
Abstract
Sterile neutrinos only interact with the standard model through the neutrino sector, and thus represent a simple dark matter (DM) candidate with many potential astrophysical and cosmological ...signatures. Recently, sterile neutrinos produced through self-interactions of active neutrinos have received attention as a particle candidate that can yield the entire observed DM relic abundance without violating the most stringent constraints from X-ray observations. We examine consistency of this production mechanism with the abundance of small-scale structure in the universe, as captured by the population of ultrafaint dwarf galaxies orbiting the Milky Way, and derive a lower bound on the sterile-neutrino particle mass of 37 keV. Combining these results with previous collider and X-ray limits excludes 100% sterile-neutrino DM produced by strong neutrino self-coupling, mediated by a heavy (≳1 GeV) scalar; however, data permits sterile-neutrino DM production via a light mediator.
We explore an interacting dark matter (IDM) model that allows for a fraction of dark matter (DM) to undergo velocity-independent scattering with baryons. In this scenario, structure on small scales ...is suppressed relative to the cold DM scenario. Using the effective field theory of large-scale structure, we perform the first systematic analysis of BOSS full-shape galaxy clustering data for the IDM scenario, and we find that this model ameliorates the S8 tension between large-scale structure and Planck data. Adding the S8 prior from the Dark Energy Survey (DES) to our analysis further leads to a mild ∼3σ preference for a nonvanishing DM–baryon scattering cross section, assuming ∼10% of DM is interacting and has a particle mass of 1 MeV. This result produces a modest ∼20% suppression of the linear power at k ≲ 1 h Mpc−1, consistent with other small-scale structure observations. Similar scale-dependent power suppression was previously shown to have the potential to resolve S8 tension between cosmological data sets. The validity of the specific IDM model explored here will be critically tested with upcoming galaxy surveys at the interaction level needed to alleviate the S8 tension.
Abstract The abundance of faint dwarf galaxies is determined by the underlying population of low-mass dark matter (DM) halos and the efficiency of galaxy formation in these systems. Here, we quantify ...potential galaxy formation and DM constraints from future dwarf satellite galaxy surveys. We generate satellite populations using a suite of Milky Way (MW)–mass cosmological zoom-in simulations and an empirical galaxy–halo connection model, and assess sensitivity to galaxy formation and DM signals when marginalizing over galaxy–halo connection uncertainties. We find that a survey of all satellites around one MW-mass host can constrain a galaxy formation cutoff at peak virial masses of M 50 = 10 8 M ⊙ at the 1 σ level; however, a tail toward low M 50 prevents a 2 σ measurement. In this scenario, combining hosts with differing bright satellite abundances significantly reduces uncertainties on M 50 at the 1 σ level, but the 2 σ tail toward low M 50 persists. We project that observations of one (two) complete satellite populations can constrain warm DM models with m WDM ≈ 10 keV (20 keV). Subhalo mass function (SHMF) suppression can be constrained to ≈70%, 60%, and 50% that in cold dark matter (CDM) at peak virial masses of 10 8 , 10 9 , and 10 10 M ⊙ , respectively; SHMF enhancement constraints are weaker (≈20, 4, and 2 times that in CDM, respectively) due to galaxy–halo connection degeneracies. These results motivate searches for faint dwarf galaxies beyond the MW and indicate that ongoing missions like Euclid and upcoming facilities including the Vera C. Rubin Observatory and Nancy Grace Roman Space Telescope will probe new galaxy formation and DM physics.
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