Celine Bœhm | Searcharxiv

arXiv2020

Is it Mixed dark matter or neutrino masses?

In this paper, we explore a scenario where the dark matter is a mixture of interacting and non interacting species. Assuming dark matter-photon interactions for the interacting species, we find that the suppression of the matter power spectrum in this scenario can mimic that expected in the case of massive neutrinos. Our numerical studies include present limits from Planck Cosmic Microwave Background data, which render the strength of the dark matter photon interaction unconstrained when the fraction of interacting dark matter is small. Despite the large entangling between mixed dark matter and neutrino masses, we show that future measurements from the Dark Energy Instrument (DESI) could help in establishing the dark matter and the neutrino properties simultaneously, provided that the interaction rate is very close to its current limits and the fraction of interacting dark matter is at least of $\mathcal{O}\left(10\%\right)$. However, for that region of parameter space where a small fraction of interacting DM coincides with a comparatively large interaction rate, our analysis highlights a considerable degeneracy between the mixed dark matter parameters and the neutrino mass scale.

astro-ph.CO↗

arXiv2017

Discovery of a new extragalactic source population of energetic particles

We report the discovery of a statistically significant hardening in the Fermi-LAT $γ$-ray spectrum of Centaurus A's core, with the spectral index hardening from $Γ_{1}=2.73 \pm 0.02$ to $Γ_{1}=2.29 \pm 0.07$ at a break energy of ($2.6 \pm 0.3$) GeV. Using a likelihood analysis, we find no evidence for flux variability in Cen A's core lightcurve above or below the spectral break when considering the entire 8 year period. Interestingly, however, the first $\sim3.5$ years of the low energy lightcurve shows evidence of flux variability at the $\sim3.5 σ$ confidence level. To understand the origin of this spectral break, we assume that the low energy component below the break feature originates from leptons in Centaurus A's radio jet and we investigate the possibility that the high energy component above the spectral break is due to an additional source of very high energy particles near the core of Cen A. We show for the first time that the observed $γ$-ray spectrum of an Active Galactic Nucleus is compatible with either a very large localized enhancement (referred to as a spike) in the dark matter halo profile or a population of millisecond pulsars. Our work constitutes the first robust indication that new $γ$-ray production mechanisms can explain the emission from active galaxies and could provide tantalizing first evidence for the clustering of heavy dark matter particles around black holes.

astro-ph.HE↗