14 research outputs found
Ultra-cold WIMPs: relics of non-standard pre-BBN cosmologies
Weakly interacting massive particles (WIMPs) are one of very few probes of
cosmology before Big Bang nucleosynthesis (BBN). We point out that in scenarios
in which the Universe evolves in a non-standard manner during and after WIMP
kinetic decoupling, the horizon mass scale at decoupling can be smaller and the
dark matter WIMPs can be colder than in standard cosmology. This would lead to
much smaller first objects in hierarchical structure formation. In low
reheating temperature scenarios the effect may be large enough as to noticeably
enhance indirect detection signals in GLAST and other detectors, by up to two
orders of magnitude.Comment: Six pages, one figure- Extensive additions and rewriting with respect
to v1. Figure change
Non-universality of halo profiles and implications for dark matter experiments
We explore the cosmological halo-to-halo scatter of the distribution of mass
within dark matter halos utilizing a well-resolved statistical sample of
clusters from the cosmological Millennium simulation. We find that at any
radius, the spherically-averaged dark matter density of a halo (corresponding
to the "smooth-component") and its logarithmic slope are well-described by a
Gaussian probability distribution. At small radii (within the scale radius),
the density distribution is fully determined by the measured Gaussian
distribution in halo concentrations. The variance in the radial distribution of
mass in dark matter halos is important for the interpretation of direct and
indirect dark matter detection efforts. The scatter in mass profiles imparts
approximately a 25 percent cosmological uncertainty in the dark matter density
at the Solar neighborhood and a factor of ~3 uncertainty in the expected
Galactic dark matter annihilation flux. The aggregate effect of halo-to-halo
profile scatter leads to a small (few percent) enhancement in dark matter
annihilation background if the Gaussian concentration distribution holds for
all halo masses versus a 10 percent enhancement under the assumption of a
log-normal concentration distribution. The Gaussian nature of the cluster
profile scatter implies that the technique of "stacking" halos to improve
signal to noise should not suffer from bias.Comment: replaced with accepted mnras versio
Electromagnetic probes of primordial black holes as dark matter
The LIGO discoveries have rekindled suggestions that primordial black holes (BHs) may constitute part to all of the dark matter (DM) in the Universe. Such suggestions came from 1) the observed merger rate of the BHs, 2) their unusual masses, 3) their low/zero spins, and 4) also from the independently uncovered cosmic infrared background (CIB) fluctuations signal of high amplitude and coherence with unresolved cosmic X-ray background (CXB). Here we summarize the prospects to resolve this important issue with electromagnetic observations using the instruments and tools expected in the 2020's. These prospects appear promising to make significant, and potentially critical, advances. We demonstrate that in the next decade, new space- and ground-borne electromagnetic instruments, combined with concurrent theoretical efforts, should shed critical light on the long-considered link between primordial BHs and DM. Specifically the new data and methodologies under this program will involve: I) Probing with high precision the spatial spectrum of source-subtracted CIB with Euclid and WFIRST, and its coherence with unresolved cosmic X-ray background using eROSITA and Athena, II) Advanced searches for microlensing of Galactic stars by the intervening Galactic Halo BHs with OGLE, Gaia, LSST and WFIRST, III) Supernovae (SNe) lensing in the upcoming surveys with WFIRST, LSST and also potentially with Euclid and JWST, IV) Advanced theoretical work to understand the details of PBH accretion and evolution and their influence on cosmic microwave background (CMB) anisotropies in light of the next generation CMB experiments, V) Better new samples and theoretical understanding involving stability and properties of ultra faint dwarf galaxies, pulsar timing, and cosmological quasar lensing
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Dark Matter Science in the Era of LSST
Astrophysical observations currently provide the only robust, empirical
measurements of dark matter. In the coming decade, astrophysical observations
will guide other experimental efforts, while simultaneously probing unique
regions of dark matter parameter space. This white paper summarizes
astrophysical observations that can constrain the fundamental physics of dark
matter in the era of LSST. We describe how astrophysical observations will
inform our understanding of the fundamental properties of dark matter, such as
particle mass, self-interaction strength, non-gravitational interactions with
the Standard Model, and compact object abundances. Additionally, we highlight
theoretical work and experimental/observational facilities that will complement
LSST to strengthen our understanding of the fundamental characteristics of dark
matter
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Primordial Non-Gaussianity
Our current understanding of the Universe is established through the pristine
measurements of structure in the cosmic microwave background (CMB) and the
distribution and shapes of galaxies tracing the large scale structure (LSS) of
the Universe. One key ingredient that underlies cosmological observables is
that the field that sources the observed structure is assumed to be initially
Gaussian with high precision. Nevertheless, a minimal deviation from
Gaussianityis perhaps the most robust theoretical prediction of models that
explain the observed Universe; itis necessarily present even in the simplest
scenarios. In addition, most inflationary models produce far higher levels of
non-Gaussianity. Since non-Gaussianity directly probes the dynamics in the
early Universe, a detection would present a monumental discovery in cosmology,
providing clues about physics at energy scales as high as the GUT scale
Dark Matter Science in the Era of LSST
Astrophysical observations currently provide the only robust, empirical measurements of dark matter. In the coming decade, astrophysical observations will guide other experimental efforts, while simultaneously probing unique regions of dark matter parameter space. This white paper summarizes astrophysical observations that can constrain the fundamental physics of dark matter in the era of LSST. We describe how astrophysical observations will inform our understanding of the fundamental properties of dark matter, such as particle mass, self-interaction strength, non-gravitational interactions with the Standard Model, and compact object abundances. Additionally, we highlight theoretical work and experimental/observational facilities that will complement LSST to strengthen our understanding of the fundamental characteristics of dark matter