Hints of the existence of Axion-Like-Particles from the gamma-ray spectra of cosmological sources

By M. Sánchez-Conde, D. Paneque, E. Bloom, Francisco Prada, A. D. IAA-CSIC, Kipacslac National Accelerator Center, Visiting student at Kipacslac National Accelerator Center, U. Sevilla, Visiting research physicist at Scipp, U. Cruz. 2009

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Axionlike particles (ALPs) are predicted to couple with photons in the presence of magnetic fields. This effect may lead to a significant change in the observed spectra of gamma-ray sources such as active galactic nuclei (AGNs). Here we carry out a detailed study that for the first time simultaneously considers in the same framework both the photon/axion mixing that takes place in the gamma-ray source and that one expected to occur in the intergalactic magnetic fields. An efficient photon/axion mixing in the source always means an attenuation in the photon flux, whereas the mixing in the intergalactic medium may result in a decrement and/or enhancement of the photon flux, depending on the distance of the source and the energy considered. Interestingly, we find that decreasing the value of the intergalactic magnetic field strength, which decreases the probability for photon/axion mixing, could result in an increase of the expected photon flux at Earth if the source is far enough. We also find a 30% attenuation in the intensity spectrum of distant sources, which occurs at an energy that only depends on the properties of the ALPs and the intensity of the intergalactic magnetic field, and thus independent of the AGN sourcemore » being observed. Moreover, we show that this mechanism can easily explain recent puzzles in the spectra of distant gamma-ray sources, like the possible detection of TeV photons from 3C 66A (a source located at z=0.444) by MAGIC and VERITAS, which should not happen according to conventional models of photon propagation over cosmological distances. Another puzzle is the recent published lower limit to the extragalactic background light intensity at 3.6 {mu}m (which is almost twice larger as the previous one), which implies very hard spectra for some detected TeV gamma-ray sources located at z=0.1-0.2. The consequences that come from this work are testable with the current generation of gamma-ray instruments, namely Fermi (formerly known as GLAST) and imaging atmospheric Cherenkov telescopes like CANGAROO, HESS, MAGIC, and VERITAS.« less

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/5802da1a93f2ec24c9ec7d46362376802f875f87

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Citations in the corpus

Modelling the coincident observation of a high-energy neutrino and a bright blazar flare (2018, background): “After correction for this absorption, the spectra of blazars suggest the existence an additional radiation component in addition to that expected with leptonic models (19), which may indicate for the existence of new elementary particles such as axions (20) or blazars emitting a very powerful stream”
3FHL: The Third Catalog of Hard Fermi-LAT Sources (2017, background): “These photons permit testing EBL models and evaluating potential changes in the optical depth due to other more exotic scenarios (e.g., de Angelis et al. 2007; Sánchez-Conde et al. 2009; Essey & Kusenko 2010; Domínguez et al. 2011b; Horns & Meyer 2012).”
The type IIB string axiverse and its low-energy phenomenology (2012, background): “tantalising astrophysical hints, which together point to a light ALP with couplings and mass [7–12]:”
A lower-limit flux for the extragalactic background light (2010, background): “Particles, like Axions (Sanchez-Conde et al. 2009) or hidden photons (Zechlin, Horns & Redondo 2008), can prevent high energy gamma-ray photons frm being absorbed.”
Exploring the Role of Axions and Other WISPs in the Dark Universe (2012, unknown): “10 −9 eV, ALP, which couples to two photons with strength [63, 64, 65, 66], giγ ∼ 10 GeV ⇒ fai/Ciγ ∼ 10(8) GeV.”
Revisiting the SN1987A gamma-ray limit on ultralight axion-like particles (2014, background): “Hence, the SN1987A limit has been questioned in the recent literature (especially its ALP-mass dependence) and occasionally even objected [22, 23, 49–51].”
Dark matter and fundamental physics with the Cherenkov Telescope Array (2012, methodology): “ively. This diagram collects the main physical scenarios that we might identify inside our formalism. Each of them are schematically represented by a line that goes from the source to the Earth. From [143]. The probability of a photonof energy Eγto be convertedinto an ALP (and vice versa) can be wri”
The extragalactic background light and the gamma-ray opacity of the universe (2012, background): “Other explanations avoid substantial EBL absorption by introducing axion-like particles that couple with photons in intergalactic magnetic fields thus reducing the γ−ray opacity of the universe substantially (Sánchez-Conde et al., 2009).”