The first measurement of the diffuse background spectrum at 0.8-1.7 $μ\rm{m}$ from the CIBER experiment has revealed a significant excess of the cosmic infrared background (CIB) radiation compared to the theoretically expected spectrum. We revisit the hypothesis that decays of axionlike particle (ALP) can explain this excess, extending previous analyses to the case of a warm relic population. We show that such a scenario is not excluded by anisotropy measurements nor by stellar cooling arguments. Moreover, we find that the increased extragalactic background light (EBL) does not contradict observations of blazar spectra. Furthermore, the increased EBL attenuates the diffuse TeV gamma-ray flux and alleviates the tension between the detected neutrino and gamma ray fluxes.
Observations with the Imaging Atmospheric Cherenkov Telescopes H.E.S.S., MAGIC, CANGAROO III and VERITAS have shown that the Universe is more transparent than expected to gamma rays above 100GeV. As a natural explanation, the DARMA scenario has previously been proposed, wherein photons can oscillate into a new very light axionlike particle and vice-versa in the presence of cosmic magnetic fields. Here we demonstrate that the most recent observations further support the DARMA scenario, thereby making the existence of a very light axion-like particle more likely.
We propose a multi-messenger probe of QCD axion Dark Matter based on observations of black hole-neutron star binary inspirals. It is suggested that a dense Dark Matter spike may grow around intermediate mass black holes ($10^{3}-10^{5} \mathrm{\,M_{\odot}}$). The presence of such a spike produces two unique effects: a distinct phase shift in the gravitational wave strain during the inspiral and an enhancement of the radio emission due to the resonant axion-photon conversion occurring in the neutron star magnetosphere throughout the inspiral and merger. Remarkably, the observation of the gravit…
Blazar Constraints on Axions through New Spectral Modulation Searches in 1ES 1959+650 & B2 1811+31
Università di Bologna（博洛尼亚大学）；INFN, Sezione di Bologna（意大利国家核物理研究所博洛尼部分所）；University of California, Berkeley（加州大学伯克利分校）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）
Axions are increasingly favoured as a candidate particle for the dark matter in galaxies, since they satisfy the observational requirements for cold dark matter and are theoretically well motivated. Fluctuations in the axion field give rise to stable localised overdensities known as axion stars, which, for the most massive, compact cases, are potential neutron star mimickers. In principle, there are no fundamental arguments against the multi-messenger observations of GW170817/GRB170817A/AT2017gfo arising from the merger of a neutron star with a neutron star mimicker, rather than from a binary …
We propose that the interaction between the axionlike particles (ALPs) and photons can be a possible origin of optical circular polarization (CP) in blazars. Given that there is no definite detection of optical CP at $\sim0.1\%$ level, a rough limit on ALP-photon coupling can be obtained, specifically $g_{aγ}\cdot B_\mathrm{T0}\lesssim7.9\times10^{-12}~\mathrm{G\cdot GeV}^{-1}$ for $m_{a}\lesssim 10^{-13}~\mathrm{eV}$, depending on the magnetic field configuration of the blazar jet. Obviously, for the blazar models with a larger magnetic field strength, such as hadronic radiation models, this …
The oscillation of photons and axion-like particles (ALPs) in the astrophysical magnetic fields could modify the measured very high energy (VHE; $\mathcal{E}\gtrsim 100\, \rm GeV$) $γ$-ray spectra of the blazar sources. In this paper, we use the VHE $γ$-ray observations of the blazar Markarian 421 (Mrk 421) measured by MAGIC and Fermi-LAT in 2017 with four phases to constrain the ALP. We give the spectral energy distributions (SEDs) of these phases under the null and ALP hypotheses. We also test the effects of the $γ$-ray blazar intrinsic spectra models on the ALP constraints. No significant r…
Probing Extragalactic Ultralight Axion Dark Matter with Decade-long Blazar Optical Polarimetry of 1ES 1959+650
Purple Mountain Observatory, Chinese Academy of Sciences（中国科学院紫金山天文台）；School of Astronomy and Space Sciences, University of Science and Technology of China（中国科学技术大学天文与空间科学学院）
Multi-messenger signal from QCD-Axion Ultracompact Minihalos
Institut de Fìsica d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology（高能物理研究所，巴塞罗那科技研究院）；Facultad de Ingeniería, Universidad San Sebastián（圣塞巴斯蒂安大学工程学院）；Departamento de Ciencias Físicas, Universidad Andrés Bello（安德斯贝略大学物理科学系）
Axion-like particles (ALPs) are a broad class of pseudo-scalar bosons that generically arise from broken symmetries in extensions of the standard model. In many scenarios, ALPs can mix with photons in regions with high magnetic fields. Photons from distant sources can mix with ALPs, which then travel unattenuated through the Universe, before they mix back to photons in the Milky Way galactic magnetic field. Thus, photons can traverse regions where their signals would normally be blocked or attenuated. In this paper, we study TeV $γ$-ray observations from distant blazars, utilizing the signific…
Very high energy (VHE) gamma-rays undergo pair production with low energy photons of background radiation fields. This leads to an attenuation of the primary gamma-ray flux of extragalactic sources in the interaction with the extragalactic background light (EBL) which stretches from ultraviolet to far-infrared wavelengths. In the presence of magnetic fields, gamma-rays could oscillate into hypothetical axion-like particles (ALPs). This might lead to a reduced opacity of the Universe for VHE gamma-rays, as ALPs circumvent pair production. Here, the impact of photon-ALP conversions on the spectr…
Decaying axion-like particles (ALP) with masses in the eV range which might occupy dark matter halos of the Milky Way and other galaxies produce a characteristic "bump" feature in the spectrum of extragalactic background light (EBL). This feature leaves an imprint on the gamma-ray spectra of distant extragalactic sources. We derive constraints on the ALP coupling to photons based on analysis of spectra of very-high-energy gamma-ray loud blazars. We combine gamma-ray spectral measurements by Fermi/LAT and Cherenkov telescopes and fit a model in which the intrinsic source spectrum is modified by…
We investigate a scenario where the dark matter of the Universe is made from very light hidden photons transforming under a $Z_{2}$-symmetry. In contrast to the usual situation, kinetic mixing is forbidden by the symmetry and the dark photon interacts with the Standard Model photon only via an axion-like particle acting as a "messenger". Focusing on signatures involving the ordinary photon, our survey of the phenomenology includes limits from cosmological stability, CMB distortions, astrophysical energy loss, light-shining-through-walls experiments, helioscopes and solar X-ray observations.
We explore the axion-like particle (ALP)-photon oscillation effect in the $γ$-ray spectra of the blazars Markarian 421 (Mrk 421) and PG 1553+113, which are measured by the Major Atmospheric Gamma Imaging Cherenkov Telescopes (MAGIC) and Fermi Large Area Telescope (Fermi-LAT) with high precision. We investigate the constraints on the ALP parameter space using the Mrk 421 and PG 1553+113 observations of 15 and 5 phases, respectively. We find that the combined analysis with all the 15 phases improves the limits from the Mrk 421 observations. The combined limit set by the Mrk 421 observations has …
Axion-like particle limits from multi-messenger sources
The University of Chicago（芝加哥大学）；Virginia Tech（弗吉尼亚理工大学）；Massachusetts Institute of Technology（麻省理工学院）；Harvard University（哈佛大学）；CNRS（法国国家科学研究中心）；New York University Abu Dhabi（纽约大学阿布扎比分校）
We consider the largest observed sample including all intermediate-frequency peaked (IBL) and high-frequency peaked (HBL) flaring blazars above 100 GeV up to redshift $z = 0.6$. We show that the best-fit regression line of the emitted spectral indices $Γ_{\rm em} (z)$ is a concave parabola decreasing as $z$ increases, thereby implying a statistical correlation between the $\{Γ_{\rm em} (z) \}$ distribution and $z$. This result contradicts our expectation that such a distribution should be $z$-independent. We argue that the above correlation does not arise from any selection bias. We show that …
The idea that photons can convert into axion-like particles (ALPs) $γ\to a$ in or around an AGN and reconvert back into photons $a \to γ$ in the Milky Way magnetic field has been put forward in 2008 and has recently attracted growing interest. Yet, so far nobody has estimated the conversion probability $γ\to a$ as carefully as allowed by present-day knowledge. Our aim is to fill this gap. We first remark that AGN that can be detected above 100 GeV are blazars, namely AGN with jets, with one of them pointing towards us. Moreover, blazars fall into two well defined classes: BL Lac objects (BL La…
Axion-Like Particles (ALPs), if exist in nature, are expected to mix with photons in the presence of an external magnetic field. The energy range of photons which undergo strong mixing with ALPs depends on the ALP mass, on its coupling with photons as well as on the external magnetic field and particle density configurations. Recent observations of blazars by the Fermi Gamma-Ray Space Telescope in the 0.1-300 GeV energy range show a break in their spectra in the 1-10 GeV range. We have modeled this spectral feature for the flat-spectrum radio quasar 3C454.3 during its November 2010 outburst, a…
One of the targets of future Cosmic Microwave Background and Baryon Acoustic Oscillation measurements is to improve the current accuracy in the neutrino sector and reach a much better sensitivity on extra dark radiation in the Early Universe. In this paper we study how these improvements can be translated into constraining power for well motivated extensions of the Standard Model of elementary particles that involve axions thermalized before the quantum chromodynamics (QCD) phase transition by scatterings with gluons. Assuming a fiducial $Λ$CDM cosmological model, we simulate future data for S…
D. Wouters and P. Brun in Phys. Rev. D 86, 043005 (2012) claim that an observable effect in the spectra of distant very-high-energy blazars arises as a consequence of oscillations of photons into axion-like particles (ALPs) in the presence of turbulent extra-galactic magnetic fields. The main objective of this comment is to demonstrate that such a result is physically incorrect. We also show that a physically correct treatment of the same issue leads to a much less relevant conclusion, which makes the effect pointed out by WB likely unobservable with the present capabilities.
Starburst galaxies, which are known as "reservoirs" of high-energy cosmic-rays, can represent an important high-energy neutrino "factory" contributing to the diffuse neutrino flux observed by IceCube. In this paper, we revisit the constraints affecting the neutrino and gamma-ray hadronuclear emissions from this class of astrophysical objects. In particular, we go beyond the standard prototype-based approach leading to a simple power-law neutrino flux, and investigate a more realistic model based on a data-driven blending of spectral indexes, thereby capturing the observed changes in the proper…
The search at hadron colliders for new massive resonances of a few 100 GeVs that couple effectively to colored states is an extremely challenging issue, due principally to the presence of large QCD multijet backgrounds at this energy, rendering the searches at the LHC particularly difficult. Recently, it was realized that these large backgrounds could be overcome by demanding one high-$p_T$ jet from initial-state radiation (ISR) and by means of novel jet-reconstruction techniques through which the resulting hadronized products of the massive resonances are reconstructed as a fat-jet, a unique …
Axion-like particles (ALPs) are attracting increasing interest since, among other things, they are a prediction of many extensions of the standard model of elementary particles physics and in particular of superstrings and superbranes. Remarkably, depending on the set of their parameter space, they strongly increase the photon transparency in the very-high energy band. The recent discovery of photon dispersion on the CMB requires a substantial modification of the previous picture: this is indeed the goal of the present paper. We compute the photon survival probability from a blazar to us exact…
Several extensions of the Standard Model predict the existence of Axion-Like Particles (ALPs), very light spin-zero bosons with a two-photon coupling. ALPs can give rise to observable effects in very-high-energy astrophysics. Above roughly 100 GeV the horizon of the observable Universe progressively shrinks as the energy increases, due to scattering of beam photons off background photons in the optical and infrared bands, which produces e+e- pairs. In the presence of large-scale magnetic fields photons emitted by a blazar can oscillate into ALPs on the way to us and back into photons before re…
We consider implications of high-energy neutrino emission from blazar flares, including the recent event IceCube-170922A and the 2014-2015 neutrino flare that could originate from TXS 0506+056. First, we discuss their contribution to the diffuse neutrino intensity taking into account various observational constraints. Blazars are likely to be subdominant in the diffuse neutrino intensity at sub-PeV energies, and we show that blazar flares like those of TXS 0506+056 could make <1-10 percent of the total neutrino intensity. We also argue that the neutrino output of blazars can be dominated by th…
Many extensions of the Standard Model predict the existence of ALPs, which are very light spin-zero bosons with a two-photon coupling. Photon-ALP oscillations occur in the presence of an external magnetic field, and ALPs can lead to observable effects on the measured photon spectrum of astrophysical sources. An intriguing situation arises when blazars are observed with the Cherenkov Telescopes H.E.S.S., MAGIC, CANGAROO III and VERITAS. The extragalactic background light (EBL) produced by galaxies during cosmic evolution gives rise to a source dimming which becomes important in the VHE band. Th…
A mechanism for leptogenesis at the electroweak scale was investigated in a model of dark energy and dark matter proposed by one of us (PQH). This model involves an asymptotically free gauge group SU(2)Z and an axion-like particle with an SU(2)Z-instanton-induced potential which yields a scenario for the dark energy. Furthermore, the extended particle content of this SU(2)Z model contains a possible candidate for the cold dark matter, namely, the SU(2)Z "shadow" fermion, which couples with the Standard Model lepton through a scalar "messenger field" carrying both SU(2)Z and electroweak quantum…
Gamma rays from TeV blazars have been detected by ground-based experiments for more than two decades. We have collected the most extensive set of archival spectra from these sources in order to constrain the processes affecting gamma-ray propagation on cosmological distances. We discuss our results on the diffuse photon field that populates universe, called the extragalactic background light, on the expansion rate of the Universe, and on fundamental physics in the form of axion-like particles and Lorentz-invariance violation. Specifically, we present a spectrum of the extragalactic background …
Photons may convert into axion like particles and back in the magnetic field of various astrophysical objects, including active galaxies, clusters of galaxies, intergalactic space and the Milky Way. This is a potential explanation for the candidate neutral ultra-high-energy (E>10^18 eV) particles from distant BL Lac type objects which have been observed by the High Resolution Fly's Eye experiment. Axions of the same mass and coupling may explain also TeV photons detected from distant blazars.
We revisit the sgoldstino interpretation of the diphoton excess in the context of gauge mediation. While the bound on the gluino mass might seem to make the sgoldstino contribution to the diphoton excess unobservable, we show that the interpretation is viable in a thin, near critical region of the parameter space. This regime gives rise to drastic departures from the standard gauge mediation picture. While the fermion messengers lie in the (10-100) TeV range, some scalar messengers are significantly lighter and are responsible for the sgoldstino production and decay. Their effective coupling t…
Flat spectrum radio quasars (FSRQs) are a particular class of blazars rich of optical/ultraviolet photons inside the broad line region (BLR), necessarily implying a huge optical depth for $γ$ rays above 20 GeV. As a consequence, photons with energy above such a threshold should not be emitted. However, photons in the energy range 70 - 400 GeV have been observed by MAGIC from the FSRQ PKS 1222+216. Several astrophysical explanations exist in the literature, but they are all ad hoc, namely devised only for that specific purpose. We show that such a surprising discovery can be explained within st…
Recent observations by H.E.S.S. and MAGIC strongly suggest that the Universe is more transparent to very-high-energy gamma rays than previously thought. We show that this fact can be reconciled with standard blazar emission models provided that photon oscillations into a very light Axion-Like Particle occur in extragalactic magnetic fields. A quantitative estimate of this effect indeed explains the observed data and in particular the spectrum of blazar 3C279.
Resonant photon-axion conversion driven by axion dark matter oscillations
Hangzhou Institute for Advanced Study, UCAS（杭州高等研究院）；University of Chinese Academy of Sciences（中国科学院大学）；State Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences（高能物理研究所粒子天体物理国家重点实验室）；Institute of Theoretical Physics, Chinese Academy of Sciences（理论物理研究所）
The IceCube collaboration reported a $\sim 3.5σ$ excess of $13\pm5$ neutrino events in the direction of the blazar TXS 0506+56 during a $\sim$6 month period in 2014-2015, as well as the ($\sim3σ$) detection of a high-energy muon neutrino during an electromagnetic flare in 2017. We explore the possibility that the 2014-2015 neutrino excess and the 2017 multi-messenger flare are both explained in a common physical framework that relies on the emergence of a relativistic neutral beam in the blazar jet due to interactions of accelerated cosmic rays (CRs) with photons. We demonstrate that the neutr…
Recent detection of blazar 3C279 by MAGIC has confirmed previous indications by H.E.S.S. that the Universe is more transparent to very-high-energy gamma rays than currently thought. This circumstance can be reconciled with observations of nearby blazars provided that photon oscillations into a very light Axion-Like Particle occur in extragalactic magnetic fields. The emerging "DARMA scenario" can be tested in the near future by the satellite-borne Fermi LAT detector as well as by the ground-based Imaging Atmospheric Cherenkov Telescopes H.E.S.S., MAGIC, CANGAROO III, VERITAS and by the Extensi…
Early indications by H.E.S.S. and the subsequent detection of blazar 3C279 by MAGIC show that the Universe is more transparent to very-high-energy gamma rays than previously thought. We demonstrate that this circumstance can be reconciled with standard blazar emission models provided that photon oscillations into a very light Axion-Like Particle occur in extragalactic magnetic fields. A quantitative estimate of this effect indeed explains the observed spectrum of 3C279. Our prediction can be tested by the satellite-borne Fermi/LAT detector as well as by the ground-based Imaging Atmospheric Che…
We present the dissection in space, time, and energy of the region around the IceCube-170922A neutrino alert. This study is motivated by: (1) the first association between a neutrino alert and a blazar in a flaring state, TXS 0506+056; (2) the evidence of a neutrino flaring activity during 2014 - 2015 from the same direction; (3) the lack of an accompanying simultaneous $γ$-ray enhancement from the same counterpart; (4) the contrasting flaring activity of a neighbouring bright $γ$-ray source, the blazar PKS 0502+049, during 2014 - 2015. Our study makes use of multi-wavelength archival data acc…
Axion-like particles (ALPs), which are very light neutral spin zero elusive particles primarily interacting with two photons and predicted by superstring and superbrane theories, have come to help by solving two distinct problems about blazars (a type of active galactic nuclei), thus providing two hints at the existence of ALPs themselves. In the presence of an external magnetic field, ALPs produce: (i) photon-ALP oscillations, (ii) the change of the polarization state of photons. The former effect has many consequences in the astrophysical contest, such as the modification of the transparency…
Background radiation fields pervade the Universe, and above a certain energy any $γ$-ray flux emitted by an extragalactic source should be attenuated due to $e^+e^-$ pair production. The opacity could be alleviated if photons oscillated into hypothetical axion-like particles (ALPs) in ambient magnetic fields, leading to a $γ$-ray excess especially at high optical depths that could be detected with imaging air Cherenkov telescopes (IACTs). Here, we introduce a method to search for such a signal in $γ$-ray data and to estimate sensitivities for future observations. Different magnetic fields clos…
Photons may convert to axion-like particles (ALPs) in external magnetic fields. Under certain conditions, this effect should result in irregular features in observed spectra of astrophysical sources. Lack of such irregularities in particular spectra was used to constrain ALP parameters, with two most popular sources being the radio galaxy NGC 1275 and the blazar PKS 2155-304. The effect and, consequently, the constraints, depend on the magnetic fields through which the light from the source is propagated. Here, we revisit ALP constraints from gamma-ray observations of NGC 1275 taking into acco…
Prompted by the increasing interest of axion-like particles (ALPs) for very-high-energy (VHE) astrophysics, we have considered a full scenario for the propagation of a VHE photon/ALP beam emitted by a BL Lac and reaching us in the light of the most up-to-date astrophysical information and for energies up to above $100 \, \rm TeV$. During its trip, the beam -- generated in a small region of a BL Lac jet -- crosses a variety of magnetic structures in very different astronomical environments: the BL Lac jet, the host elliptical galaxy, the extragalactic space and the Milky Way. We have taken an e…
The surprising discovery by MAGIC of an intense, rapidly varying emission in the energy range 70 - 400 GeV from the flat spectrum radio quasar PKS 1222+216 represents a challenge for all interpretative scenarios. Indeed, in order to avoid absorption of γrays in the dense ultraviolet radiation field of the broad line region (BLR), one is forced to invoke some unconventional astrophysical picture, like for instance the existence of a very compact (r\sim 10^{14} cm) emitting blob at a large distance (R \sim10^{18} cm) from the jet base. We offer the investigation of a scenario based on the standa…
