A DARK MATTER HALO AS SOURCE OF GAMMA-RAYS?

Image: Illustration of a dark matter halo around the Milky Way. Credit: ESO/L. Calçada.

The gamma-ray source 3FGL J2212.5+0703 shows evidence of being spatially extended.

In a recent paper (Bertoni et al. 2016) the authors use a large sample of active galactic nuclei and other known gamma-rays sources as a control group, confirming, as expected, that statistically significant extension is rare among such objects.

They argue that the most likely (non-dark matter) explanation for this apparent extension is a pair of bright gamma-ray sources that serendipitously lie very close to each other, and estimate that there is a chance probability of ~2% that such a pair would exist somewhere on the sky.

If a gamma-ray source without detectable emission at other wavelengths were unambiguously determined to be spatially extended, it could not be explained by known astrophysics, and would constitute a smoking gun for dark matter particles annihilating in a nearby subhalo.

The authors assess that if 3FGL J2212.5+0703 is a dark matter subhalo, it would imply that dark matter particles have a mass of ∼18^-33 GeV and an annihilation cross section on the order of σv ∼ 10⁻²⁶ cm³/s, similar to the values required to generate the Galactic Center gamma-ray excess.

Although the information available does not allow to determine the mass of or distance to this subhalo, simulations suggest that the first gamma-ray detected subhalos could plausibly be on the scale of an ultra-faint dwarf galaxy located at a distance of ~10 kpc, or a much smaller clump of dark matter residing within a few tens of parsecs of the Solar System.

Bertoni et al. 2016 - Is The Gamma-Ray Source 3FGL J2212.5+0703 A Dark Matter Subhalo? (arXiv)

Comments

A METHOD TO TEST THE EXISTENCE OF REGULAR BLACK HOLES

Illustration of a black hole. Image Credit & Copyright: Alain Riazuelo The existence of the singularity is an intrinsic problem of the General Relativity (GR). At the fundamentally level, the resolution of the problem of the singularity lies with the expectation that under situations where quantum effects become strong, the behavior of gravity could possibly greatly deviate from that predicted by the classical theory of GR. Regular black hole solution are proposed with the same spacetime geometry outside the horizon as the traditional black hole, but bears no singularity inside. Whether or not black hole singularities should exist, they would be covered by the black hole horizon. The black hole horizon serves as an information curtain hindering outside observers from directly observing the interior structure of the black hole, and determining that whether or not the black hole singularity does really exist. A method is needed to check the correctness of the new constructions ...

Dark Neutron Stars

Illustration of a neutron star. Credit: NASA/Dana Berry There is good evidence that electron-positron pair formation is not present in that section of the pulsar open magnetosphere which is the source of coherent radio emission, but the possibility of two-photon pair creation in an outer gap remains. Calculation of transition rates for this process based on measured whole-surface temperatures, combined with a survey of gamma-ray, X-ray and optical luminosities, expressed per primary beam lepton, shows that few Fermi LAT pulsars have significant outer-gap pair creation. For radio-loud pulsars with positive polar-cap corotational charge density and an ion-proton plasma there must be an outward flow of electrons from some other part of the magnetosphere to maintain a constant net charge on the star. In the absence of pair creation, it is likely that this current is the source of GeV gamma-emission observed by the Fermi LAT and its origin is in the region of the outer gap. With n...

SUPERNOVAE FROM WD-WD DIRECT COLLISIONS

Image: Supernova remnant N 63A. Credit: NASA/ESA/HEIC and The Hubble Heritage Team (STScI/AURA) Models for supernovae (SNe) related to thermonuclear explosions of white dwarfs (WDs) have been extensively studied over the last few decades, mostly focusing on single degenerate (accretion of material of a WD) and double degenerate (WD-WD merger) scenarios.

SpaceTime

Search This Blog