I Further Evidence of a 3.5 keV line in Galactic X-Ray Spectra

[MrRobotoToo]

That pesky 3.5 keV line just won't go away. The authors note that it's compatible with dark matter composed of 7.02 keV sterile neutrinos. If such is the case, the Majorana mass scale of the seesaw mechanism needn't coincide with the GUT scale (if such a scale even exists).

Searching[/PLAIN] for the 3.5 keV Line in the Deep Fields with Chandra: the 10 Ms observations

Nico Cappelluti, Esra Bulbul, Adam Foster, Priyamvada Natarajan, Megan C. Urry, Mark W. Bautz, Francesca Civano, Eric Miller, Randall K. Smith

(Submitted on 27 Jan 2017)
In this paper we report a 3σ detection of an emission line at ∼3.5 keV in the spectrum of the Cosmic X-ray Background using a total of ∼10 Ms Chandra observations towards the COSMOS Legacy and CDFS survey fields. The line is detected with an intensity is 8.8±2.9×10−7 ph cm−2s−1. Based on our knowledge of Chandra, and the reported detection of the line by other instruments, we can rule out an instrumental origin for the line. We cannot though rule out a background fluctuation, in that case, with the current data, we place a 3σ upper limit at 10−6 ph cm−2s−1. We discuss the interpretation of this observed line in terms of the iron line background, S XVI charge exchange, as well as arising from sterile neutrino decay. We note that our detection is consistent with previous measurements of this line toward the Galactic center, and can be modeled as the result of sterile neutrino decay from the Milky Way when the dark matter distribution is modeled with an NFW profile. In this event, we estimate a mass ms∼7.02 keV and a mixing angle sin2(2θ)= 0.69-2.29 ×10−10. These derived values of the neutrino mass are in agreement with independent measurements toward galaxy clusters, the Galactic center and M31.

 

[mfb]

If something simply stays, instead of getting a larger significance with more detailed observations, it is probably not real.

 

[Conundrum1885]

Intriguing.
I often wonder if the reason we haven't yet detected DM is that (like gravitational waves) our detectors simply weren't able to detect the particles being screened out by the Earth's atmosphere, or not sensitive enough at specific wavelengths for whatever reason.
Ironically one of the early Russian Mars probes might have seen this, had bad ICs not doomed it to a lonely demise in deep space.

 

[mfb]

Gravitational wave detectors were not expected to see anything before aLIGO. There was some hope to have violent events close enough, but the non-observation was totally within expectations. This has nothing to do with any screening effect, it is just the sensitivity limit. LIGO and aLIGO look in the wavelength range where the strongest gravitational waves are expected thanks to black hole mergers.

Dark matter cannot interact with Earth strong enough for any screening effect (otherwise it would not be dark!). The experiments cover the whole relevant mass range, so the coupling strength is the open question. If the coupling is very weak, we need better detectors.

 

[Jimojo]

My 6th sense is Ecstatic ! I'd been coming up to speed on sterile neutrino (`Sterino') physics in 2015, only to read that it was DOA in the total absence of evidence. Now the incredible possibility is that if a Sterino triplet exists, not only is it trivially incorporatible into the SM, but it's the basis for models in which the Higgs field is the driver of inflation. Boyarsky et.al., the original discoverers of the 3.5 Kev line, saw their result picked apart & pretty much discarded.
Now it returns stronger than ever, with the added bonus of a viable 7 Kev DM candidate.
I expect confidence in this new result to grow, not wither & fade.