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1. Forecasts for Galaxy Formation and Dark Matter Constraints from Dwarf Galaxy Surveys

   https://doi.org/10.3847/1538-4357/ad3bb1  

   Nadler, Ethan_O; Gluscevic, Vera; Driskell, Trey; Wechsler, Risa_H; Moustakas, Leonidas_A; Benson, Andrew; Mao, Yao-Yuan (May 2024, The Astrophysical Journal)

   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 ${\mathcal{M}}_{50}={10}^8{M}_{\odot }$at the 1σlevel; however, a tail toward low ${\mathcal{M}}_{50}$prevents a 2σmeasurement. In this scenario, combining hosts with differing bright satellite abundances significantly reduces uncertainties on ${\mathcal{M}}_{50}$at the 1σlevel, but the 2σtail toward low ${\mathcal{M}}_{50}$persists. We project that observations of one (two) complete satellite populations can constrain warm DM models withm_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 10⁸, 10⁹, and 10¹⁰M_⊙, 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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2. 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

   https://doi.org/10.1093/mnras/stz3480  

   Gilman, Daniel; Birrer, Simon; Nierenberg, Anna; Treu, Tommaso; Du, Xiaolong; Benson, Andrew (February 2020, Monthly Notices of the Royal Astronomical Society)

   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. 

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3. Milky Way Satellite Census. IV. Constraints on Decaying Dark Matter from Observations of Milky Way Satellite Galaxies

   https://doi.org/10.3847/1538-4357/ac6e65  

   Mau, S.; Nadler, E. O.; Wechsler, R. H.; Drlica-Wagner, A.; Bechtol, K.; Green, G.; Huterer, D.; Li, T. S.; Mao, Y. -Y.; Martínez-Vázquez, C. E.; et al (June 2022, The Astrophysical Journal)

   Abstract We use a recent census of the Milky Way (MW) satellite galaxy population to constrain the lifetime of particle dark matter (DM). We consider two-body decaying dark matter (DDM) in which a heavy DM particle decays with lifetimeτcomparable to the age of the universe to a lighter DM particle (with mass splittingϵ) and to a dark radiation species. These decays impart a characteristic “kick velocity,”V_kick=ϵc, on the DM daughter particles, significantly depleting the DM content of low-mass subhalos and making them more susceptible to tidal disruption. We fit the suppression of the present-day DDM subhalo mass function (SHMF) as a function ofτandV_kickusing a suite of high-resolution zoom-in simulations of MW-mass halos, and we validate this model on new DDM simulations of systems specifically chosen to resemble the MW. We implement our DDM SHMF predictions in a forward model that incorporates inhomogeneities in the spatial distribution and detectability of MW satellites and uncertainties in the mapping between galaxies and DM halos, the properties of the MW system, and the disruption of subhalos by the MW disk using an empirical model for the galaxy–halo connection. By comparing to the observed MW satellite population, we conservatively exclude DDM models withτ< 18 Gyr (29 Gyr) forV_kick= 20 kms⁻¹(40 kms⁻¹) at 95% confidence. These constraints are among the most stringent and robust small-scale structure limits on the DM particle lifetime and strongly disfavor DDM models that have been proposed to alleviate the Hubble andS₈tensions. 

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4. Structure, Kinematics, and Observability of the Large Magellanic Cloud’s Dynamical Friction Wake in Cold versus Fuzzy Dark Matter

   https://doi.org/10.3847/1538-4357/ace533  

   Foote, Hayden R.; Besla, Gurtina; Mocz, Philip; Garavito-Camargo, Nicolás; Lancaster, Lachlan; Sparre, Martin; Cunningham, Emily C.; Vogelsberger, Mark; Gómez, Facundo A.; Laporte, Chervin F. P. (September 2023, The Astrophysical Journal)

   Abstract The Large Magellanic Cloud (LMC) will induce a dynamical friction (DF) wake on infall to the Milky Way (MW). The MW’s stellar halo will respond to the gravity of the LMC and the dark matter (DM) wake, forming a stellar counterpart to the DM wake. This provides a novel opportunity to constrain the properties of the DM particle. We present a suite of high-resolution, windtunnel-style simulations of the LMC's DF wake that compare the structure, kinematics, and stellar tracer response of the DM wake in cold DM (CDM), with and without self-gravity, versus fuzzy DM (FDM) withm_a= 10⁻²³eV. We conclude that the self-gravity of the DM wake cannot be ignored. Its inclusion raises the wake’s density by ∼10%, and holds the wake together over larger distances (∼50 kpc) than if self-gravity is ignored. The DM wake’s mass is comparable to the LMC’s infall mass, meaning the DM wake is a significant perturber to the dynamics of MW halo tracers. An FDM wake is more granular in structure and is ∼20% dynamically colder than a CDM wake, but with comparable density. The granularity of an FDM wake increases the stars’ kinematic response at the percent level compared to CDM, providing a possible avenue of distinguishing a CDM versus FDM wake. This underscores the need for kinematic measurements of stars in the stellar halo at distances of 70–100 kpc. 

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5. S8 Tension in the Context of Dark Matter–Baryon Scattering

   https://doi.org/10.3847/2041-8213/acdb63  

   He, Adam; Ivanov, Mikhail M.; An, Rui; Gluscevic, Vera (August 2023, The Astrophysical Journal Letters)

   Abstract 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 theS₈tension between large-scale structure and Planck data. Adding theS₈prior from the Dark Energy Survey (DES) to our analysis further leads to a mild ∼3σpreference 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 atk≲ 1hMpc⁻¹, consistent with other small-scale structure observations. Similar scale-dependent power suppression was previously shown to have the potential to resolveS₈tension 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 theS₈tension. 

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