649 research outputs found
Dark Matter Decay and the Abundance of Ultracompact Minihalos
Ultracompact minihalos would be formed if there are larger density
perturbations () in the earlier epoch. The
density profile of them is steeper than the standard dark matter halos. If the
dark matter can annihilate or decay into the standard particles, e.g., photons,
these objects would be the potential astrophysical sources. In order to be
consistent with the observations, such as , the abundance of
ultracompact minihalos must be constrained. On the other hand, the formation of
these objects has very tight relation with the primordial curvature
perturbations on smaller scale, so the fraction of ultracompact minihalos is
very important for modern cosmology. In previous works, the studies are focused
on the dark matter annihilation for these objects. But if the dark matter is
not annihilated, the dark matter decay is another important possible case. On
the other hand, the abundance of ultracompact minihalos is related to many
other parameters, such as the mass of dark matter, the decay channels and the
density profile of dark matter halo. One of the important aspects of this work
is that we investigate the -ray signals from nearby ultracompact
minihalos due to dark matter decay and another important aspect is to study in
detail how the different decay channels and density profiles affect the
constraints on the abundance of ultracompact minihalos.Comment: 11 pages, 4 figures, 1 table. Comments Welcome!! Some presentations
are improved and added, figures are replotted according to the referees'
suggestion. The constraints on the primordial curvature perturbations are
also given. Accepted for publication in EP
The impact of primordial black holes on the 21-cm angular-power spectrum in the dark ages
We investigate the impact of radiation from primordial black holes (PBHs), in
the mass range of and
, on the 21-cm
angular-power spectrum in the dark ages. PBHs in the former mass range effect
the 21-cm angular-power spectrum through the evaporation known as Hawking
radiation, while the radiation from the accretion process in the latter mass
range. In the dark ages, radiation from PBHs can increase the ionization
fraction and temperature of the intergalactic medium, change the global 21-cm
differential brightness temperature and then effect the 21-cm angular-power
spectrum. Taking into account the effects of PBHs, we find that in the dark
ages, , the amplitude of the 21-cm angular-power
spectrum is decreased depending on the mass and mass fraction of PBHs. We also
investigate the potential constraints on the mass fraction of PBHs in the form
of dark matter for the future radio telescope in lunar obit or on the farside
surface of the Moon.Comment: 6 pages, 5 figures. Comments are welcom
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