Is the gamma-ray source 3FGL J2212.5+0703 a dark matter subhalo?

Abstract

Abstract. In a previous paper, we pointed out that the gamma-ray source 3FGL J2212.5+0703shows evidence of being spatially extended. 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. With this prospect in mind, we scrutinize the gamma-ray emission from this source, finding that it prefers a spatially extended profile over that of a single point-like source with 5.1σ statistical significance. We also 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. We 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. In the case of 3FGL J2212.5+0703, a model with a second gamma-ray point source at the location of a known BZCAT/CRATES radio source yields fits that are comparable in quality to those obtained for a single extended source. 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 cm 3 /s (for the representative case of annihilations to bb), similar to the values required to generate the Galactic Center gamma-ray excess.arXiv:1602.07303v1 [astro-ph.HE]

Testing the dark matter subhalo hypothesis of the gamma-ray source 3FGL J2212.5+0703

“…For such a purpose, in this work we re-analyze the spatial, temporal and spectral characters of 3FGL J2212.5+0703. The difference between this work and [48,56] are the following: (1) In order to effectively suppress the possible contamination from two nearby extremelybright blazars (3FGL J2254.0+1608 and 3FGL J2232.5+1143), we just take into account the front-converting gammarays that have angular resolutions better than the back-converting photons; (2) We have extended the spectrum analysis down to the energy ∼ 100 MeV and special attention has been given to the possible improvement in the fit by introducing a phenomenological shape in comparison to the bb model. Note that if significant improvement is found, the astrophysical origin will be favored; (3) The variability of the emission in the past 8 years rather than just the first four years has been thoroughly examined to better test the stability.…”

“…As argued in [56], an unambiguously spatially extended source without multi-wavelength associations could be a nearby DM subhalo. In the left pannel of Fig.1, some residuals remain near 3FGL J2212.5+0703 when we model it with a point source template.…”

“…In astrophysical scenarios it is rather hard to give rise to a spatially-extended steady source without any association in other wavelength. Therefore 3FGL J2212.5+0703 is an interesting DM subhalo candidate, as stressed in [56].…”

“…Dedicated efforts have been made to search for such objects [46][47][48][49][50][51][52][53][54][55][56][57][58]. For instance, by fitting spectral energy distribution (SED) with DM spectra, bright high latitude point sources are investigated in [46][47][48][49]56]. Candidates are selected from the spectrally hard sources and their multi-wavelength counterparts are examined in [51,54].…”

“…Machine learning algorithms are also used to classify un-associated sources, and outliers, which are probably DM subhalos, are selected [50,53,57]. One very attractive finding is the identification of a spatially-extended source, 3FGL J2212.5+0703, among the unidentified sources [48,56] in the Fermi-LAT third source catalog (3FGL). In astrophysical scenarios it is rather hard to give rise to a spatially-extended steady source without any association in other wavelength.…”