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Constraints on the epoch of dark matter formation from Milky Way satellites

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dc.contributor.author Das, Subinoy
dc.contributor.author Nadler, E. O
dc.date.accessioned 2021-02-24T11:29:17Z
dc.date.available 2021-02-24T11:29:17Z
dc.date.issued 2021-02-15
dc.identifier.citation Physical Review D (Particles, Fields, Gravitation, and Cosmology), Vol. 103, No. 4, 043517 en_US
dc.identifier.issn 2470-0029
dc.identifier.uri http://hdl.handle.net/2248/7670
dc.description © American Physical Society https://doi.org/10.1103/PhysRevD.103.043517 en_US
dc.description.abstract A small fraction of thermalized dark radiation that transitions into cold dark matter (CDM) between big bang nucleosynthesis and matter-radiation equality can account for the entire dark matter relic density. Because of its transition from dark radiation, “late-forming dark matter” (LFDM) suppresses the growth of linear matter perturbations and imprints the oscillatory signatures of dark radiation perturbations on small scales. The cutoff scale in the linear matter power spectrum is set by the redshift z T of the phase transition; tracers of small-scale structure can therefore be used to infer the LFDM formation epoch. Here, we use a forward model of the Milky Way (MW) satellite galaxy population to address the question: How late can dark matter form? For dark radiation with strong self-interactions, which arises in theories of neutrinolike LFDM, we report z T > 5.5 × 10 6 at 95% confidence based on the abundance of known MW satellite galaxies. This limit rigorously accounts for observational incompleteness corrections, marginalizes over uncertainties in the connection between dwarf galaxies and dark matter halos, and improves upon galaxy clustering and Lyman- α forest constraints by nearly an order of magnitude. We show that this limit can also be interpreted as a lower bound on z T for LFDM that free-streams prior to its phase transition, although dedicated simulations will be needed to analyze this case in detail. Thus, dark matter created by a transition from dark radiation must form no later than one week after the big bang en_US
dc.language.iso en en_US
dc.publisher The American Physical Society en_US
dc.title Constraints on the epoch of dark matter formation from Milky Way satellites en_US
dc.type Article en_US

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