Man Ho Chan

Heating of the intergalactic medium by the radiative decay of neutrinos

Assuming that there exists a species of heavy sterile neutrinos (mν > 1 keV) and that their decays can serve as a heating source for the hot gas in galaxy clusters, we study how the observational constraints on cooling flow limit the masses of these sterile neutrinos. We predict a relation among the luminosity, the total mass, and the redshift of a cluster, and we compare this relation with data from 12 clusters to obtain an estimate of the decay rate of sterile neutrinos.

Decaying sterile neutrinos as a heating source in the Milky Way centre

Recent Chandra and XMM–Newton observations indicate that there are two-temperature components (T ∼ 8 keV, 0.8 keV) of the diffuse X-rays emitted from deep inside the centre of Milky Way. We show that this can be explained by the existence of sterile neutrinos, which decay to emit photons that can be bound-free absorbed by the isothermal hot-gas particles in the centre of Milky Way. The model can account for a stable configuration of the two-temperature components hot gas naturally as well as the energy needed to maintain the ∼8 keV temperature in the hot gas. The predicted sterile neutrino mass is between 16–18 keV.

Revisiting the constraints on annihilating dark matter by the radio observational data of M31

Recent gamma-ray observations and radio observations put strong constraints on the parameters of dark matter annihilation. In this article, we derive new constraints for six standard model annihilation channels by using the recent radio data of M31 galaxy. The new constraints are generally tighter than the constraints obtained from 6 years of Fermi Large Area Telescope gamma-ray observations of the Milky Way dwarf spheroidal satellite galaxies. The conservative lower limits of dark matter mass annihilating via

Observational Evidence for Dark Matter Interacting through a Yukawa Potential

b\bar{b}

Reconciliation of modified Newtonian dynamics and dark matter theory

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OBSERVATIONAL EVIDENCES FOR THE EXISTENCE OF 17.4 keV DECAYING DEGENERATE STERILE NEUTRINOS NEAR THE GALACTIC CENTER

\mu^+\mu^-

Ruling out dark matter interpretation of the galactic GeV excess by gamma-ray data of galaxy clusters

and

A tight scaling relation of dark matter in galaxy clusters

\tau^+\tau^-

THE EXISTENCE OF STERILE NEUTRINO HALOS IN GALACTIC CENTERS AS AN EXPLANATION OF THE BLACK HOLE MASS-VELOCITY DISPERSION RELATION

channels are 90 GeV, 90 GeV and 80 GeV respectively with the canonical thermal relic cross section and the Burkert profile being the dark matter density profile. Hence, our results do not favor the most popular models of the dark matter interpretation of the Milky Way GeV gamma-ray excess.

A predicted relation between the temperature and density profile of cluster hot gas

Recent observations in galaxies and clusters indicate that dark matter density profiles exhibit core-like structures which contradict the numerical simulation results of collisionless cold dark matter (CDM). On the other hand, it has been shown that CDM particles interacting through a Yukawa potential could naturally explain the cores in dwarf galaxies. In this Letter, I use the Yukawa potential interacting dark matter model to derive two simple scaling relations on the galactic and cluster scales, respectively, which give excellent agreements with observations. Also, in our model, the masses of the force carrier and dark matter particle can be constrained by the observational data.Recent observations in galaxies and clusters indicate dark matter density profiles exhibit core-like structures which contradict to the numerical simulation results of collisionless cold dark matter. On the other hand, it has been shown that cold dark matter particles interacting through a Yukawa potential could naturally explain the cores in dwarf galaxies. In this article, I use the Yukawa Potential interacting dark matter model to derive two simple scaling relations on the galactic and cluster scales respectively, which give excellent agreements with observations. Also, in our model, the masses of the force carrier and dark matter particle can be constrained by the observational data. Subject headings: dark matter, galaxies, clusters