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 ultra-faint 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 limits from particle physics and astrophysics excludes \(100\%\) sterile neutrino DM produced by strong neutrino self-coupling, mediated by a heavy (\(\gtrsim 1~\mathrm{GeV}\)) scalar particle; however, data permits sterile-neutrino DM production via a light mediator.
ApJL 954, L8 (2023) 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 alleviates the $S_8$ tension between
large-scale structure and Planck data. Adding the $S_8$ prior from DES to our
analysis further leads to a mild $\sim3\sigma$ preference for a non-vanishing
DM-baryon scattering cross-section, assuming $\sim 10\%$ of DM is interacting
and has a particle mass of 1 MeV. This result produces a modest $\sim 20$%
suppression of the linear power at $k\lesssim 1~h$/Mpc, consistent with other
small-scale structure observations. Similar scale-dependent power suppression
was previously shown to have the potential to resolve $S_8$ 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 $S_8$ tension.
We present the first cosmological constraint on dark matter scattering with protons in the early Universe for the entire range of dark matter masses between 1 keV and 1 TeV. This constraint is ...derived from the Planck measurements of the cosmic microwave background (CMB) temperature and polarization anisotropy, and the CMB lensing anisotropy. It improves upon previous CMB constraints by many orders of magnitude, where limits are available, and closes the gap in coverage for low-mass dark matter candidates. We focus on two canonical interaction scenarios: spin-independent and spin-dependent scattering with no velocity dependence. Our results exclude (with 95% confidence) spin-independent interactions with cross sections greater than \(5.3 \times 10^{-27}\) cm\(^2\) for 1 keV, \(3.0 \times 10^{-26}\) cm\(^2\) for 1 MeV, \(1.7 \times 10^{-25}\) cm\(^2\) for 1 GeV, and \(1.6 \times 10^{-23}\) cm\(^2\) for 1 TeV dark matter mass. Finally, we discuss the implications of this study for dark matter physics and future observations.
Modelling the growth histories of specific galaxies often involves generating the entire population of objects that arise in a given cosmology and selecting systems with appropriate properties. This ...approach is highly inefficient when targeting rare systems such as the extremely luminous high-redshift galaxy candidates detected by JWST. Here, we present a novel framework for generating merger trees with branches that are guaranteed to achieve a desired halo mass at a chosen redshift. This method augments extended Press Schechter theory solutions with constrained random processes known as Brownian bridges and is implemented in the open-source semi-analytic model \(\texttt{Galacticus}\). We generate ensembles of constrained merger trees to predict the growth histories of seven high-redshift JWST galaxy candidates, finding that these systems most likely merge \(\approx 2~\mathrm{Gyr}\) after the observation epoch and occupy haloes of mass \(\gtrsim 10^{14}~M_{\mathrm{\odot}}\) today. These calculations are thousands of times more efficient than existing methods, are analytically controlled, and provide physical insights into the evolution of haloes with rapid early growth. Our constrained merger tree implementation is publicly available at http://github.com/galacticusorg/galacticus.
We obtain the first cosmological constraints on interactions between dark matter and protons within the formalism of nonrelativistic effective field theory developed for direct detection. For each ...interaction operator in the effective theory, parameterized by different powers of the relative velocity of the incoming particles, we use the Planck 2015 cosmic microwave background (CMB) temperature, polarization, and lensing anisotropy to set upper limits on the scattering cross section for all dark matter masses above 15 keV. We find that for interactions associated with a stronger dependence on velocity, dark matter and baryons stay thermally coupled for longer, but the interaction strengths are suppressed at the low temperatures relevant for Planck observations and are thus less constrained. At the same time, cross sections with stronger velocity dependencies are more constrained in the limit of small dark matter mass. In all cases, the effect of dark matter-proton scattering is most prominent on small scales in the CMB power spectra and in the matter power spectrum, and we thus expect substantial improvement over the current limits with data from ground-based CMB experiments and galaxy surveys.
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 \(M_{50}=10^8~M_{\mathrm{\odot}}\) at the \(1\sigma\) level; however, a tail toward low \(M_{50}\) prevents a \(2\sigma\) measurement. In this scenario, combining hosts with differing bright satellite abundances significantly reduces uncertainties on \(M_{50}\) at the \(1\sigma\) level, but the \(2\sigma\) tail toward low \(M_{50}\) persists. We project that observations of one (two) complete satellite populations can constrain warm DM models with \(m_{\mathrm{WDM}}\approx 10~\mathrm{keV}\) (\(20~\mathrm{keV}\)). Subhalo mass function (SHMF) suppression can be constrained to \(\approx 70\%\), \(60\%\), and \(50\%\) that in cold dark matter (CDM) at peak virial masses of \(10^8\), \(10^9\), and \(10^{10}~M_{\mathrm{\odot}}\), respectively; SHMF enhancement constraints are weaker (\(\approx 20\), \(4\), 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.
The presence of light thermally coupled dark matter affects early expansion history and production of light elements during the Big Bang Nucleosynthesis. Specifically, dark matter that annihilates ...into Standard Model particles can modify the effective number of light species in the universe \(N_\mathrm{eff}\), as well as the abundance of light elements created buring BBN. These quantities in turn affect the cosmic microwave background (CMB) anisotropy. We present the first joint analysis of small-scale temperature and polarization CMB anisotropy from Atacama Cosmology Telescope (ACT) and South Pole Telescope (SPT), together with Planck data and the recent primordial abundance measurements of helium and deuterium to place comprehensive bounds on the mass of light thermal-relic dark matter. We consider a range of models, including dark matter that couples to photons and Standard-Model neutrinos. We find that the combination of ACT, SPT, and Planck generally leads to the most stringent mass constraint for dark matter that couples to neutrinos, improving the lower limit by 40%-80%, with respect to previous Planck analyses. On the other hand, the addition of ACT and SPT leads to a slightly weaker bound on electromagnetically coupled particles, due to a shift in the preferred values of \(Y_\mathrm{p}\) and \(N_\mathrm{eff}\) driven by the ground based experiments. Combining all CMB measurements with primordial abundance measurements, we rule out masses below \(\sim\)4 MeV at 95% confidence, for all models. We show that allowing for new relativistic species can weaken the mass bounds for dark matter that couples to photons by up to an order of magnitude or more. Finally, we discuss the reach of the next generation of the CMB experiments in terms of probing the mass of the thermal relic dark matter.
The nature of dark matter remains unknown, but upcoming measurements probing the high-redshift Universe may provide invaluable insight. In the presence of dark matter-baryon scattering, the ...suppression in the matter power spectrum and the colder mean gas temperature are expected to modify the evolution of cosmic dawn and reionization. However, the contributions from such interactions to the baryon and dark matter temperature perturbations have been neglected thus far. In this work, we derive these contributions, evolve the cosmological perturbations until the end of the dark ages and show that they may have a significant impact in the beginning of cosmic dawn. In particular, we find that the amplitude of the temperature power spectrum at large scales can change by up to 1--2 orders of magnitude and that the matter power spectrum is further suppressed with respect to \(\Lambda\)CDM by \(5\)-\(10\%\) at \(k\sim 200\, {\rm Mpc^{-1}}\) compared to the computation ignoring these contributions for scattering cross sections at current CMB limits. As a case example, we also compute the HI power spectrum from the dark ages, finding significant differences due to the changes in the temperature and ionization fraction power spectra. We argue that these new contributions must be included in studies of this dark matter model relying on cosmic dawn and reionization observables.
We use the latest measurements of the Milky Way satellite population from the Dark Energy Survey and Pan-STARRS1 to infer the most stringent astrophysical bound to date on velocity-dependent ...interactions between dark matter particles and protons. We model the momentum-transfer cross section as a power law of the relative particle velocity \(v\) with a free normalizing amplitude, \(\sigma_\text{MT}=\sigma_0 v^n\), to broadly capture the interactions arising within the non-relativistic effective theory of dark matter-proton scattering. The scattering leads to a momentum and heat transfer between the baryon and dark matter fluids in the early Universe, ultimately erasing structure on small physical scales and reducing the abundance of low-mass halos that host dwarf galaxies today. From the consistency of observations with the cold collisionless dark matter paradigm, using a new method that relies on the most robust predictions of the linear perturbation theory, we infer an upper limit on \(\sigma_0\) of \(1.4\times10^{-23}\), \(2.1\times10^{-19}\), and \(1.0\times10^{-12}\ \mathrm{cm}^2\), for interaction models with \(n=2,4,6\), respectively, for a dark matter particle mass of \(10\ \mathrm{MeV}\). These results improve observational limits on dark matter--proton scattering by orders of magnitude and thus provide an important guide for viable sub-GeV dark matter candidates.
As cosmic microwave background (CMB) photons traverse the Universe, anisotropies can be induced via Thomson scattering (proportional to the integrated electron density; optical depth) and inverse ...Compton scattering (proportional to the integrated electron pressure; thermal Sunyaev-Zel'dovich effect). Measurements of anisotropy in optical depth \(\tau\) and Compton \(y\) parameter are imprinted by the galaxies and galaxy clusters and are thus sensitive to the thermodynamic properties of circumgalactic medium and intergalactic medium. We use an analytic halo model to predict the power spectrum of the optical depth (\(\tau\tau\)), the cross-correlation between the optical depth and the Compton \(y\) parameter (\(\tau y\)), as well as the cross-correlation between the optical depth and galaxy clustering (\(\tau g\)), and compare this model to cosmological simulations. We constrain the optical depths of halos at \(z\lesssim 3\) using a technique originally devised to constrain patchy reionization at a much 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 VRO-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 profile to 13%, marginalizing over the outer slope of the pressure profile. These constraints translate to astrophysical parameters related to the physics of galaxy evolution, such as the gas mass fraction, \(f_{\rm g}\), which can be constrained to 5.3% uncertainty at \(z\sim 0\), assuming an underlying model for the shape of the density profile. 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.
