Cosmological magnetic field correlators from blazar induced cascade

Tashiro, Hiroyuki; Vachaspati, Tanmay

doi:10.1103/physrevd.87.123527

Cited by 38 publications

(52 citation statements)

References 62 publications

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“…[38,39,41]) with satisfactory results. In this work we have, for the first time, introduced the S-statistics, which is a direct measure of the handedness of a pattern with respect to the line of sight.…”

Section: Discussion and Outlookmentioning

confidence: 62%

“…[38][39][40]. The key elements here are the observed energies and the arrival directions of gamma rays at Earth.…”

Section: Computing the Q-factorsmentioning

confidence: 99%

“…[38][39][40], the calculation of the parity-odd statistics, or Q-statistics, should enable us, depending on the sign and general shape of the Qfactors for different values of E 1 , E 2 , E 3 , and R, to draw conclusions about the helicity of the intervening helical magnetic field.…”

Section: Computing the Q-factorsmentioning

confidence: 99%

“…More recently, it has been proposed that helicity can leave characteristic parity-odd imprints on the arrival directions of gamma rays that are the result of gamma-rayinduced electromagnetic cascades [32,[38][39][40][41]. In particular, Long & Vachaspati [41] have carried out a thorough analysis of the morphology of the arrival directions of gamma rays using a semi-analytical approach, but without including the stochasticity of the magnetic field or the cascade process.…”

Section: Introductionmentioning

confidence: 99%

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Probing intergalactic magnetic fields with simulations of electromagnetic cascades

et al. 2016

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We determine the effect of intergalactic magnetic fields on the distribution of high energy gamma rays by performing three-dimensional Monte Carlo simulations of the development of gamma-rayinduced electromagnetic cascades in the magnetized intergalactic medium. We employ the so-called "Large Sphere Observer" method to efficiently simulate blazar gamma ray halos. We study magnetic fields with a Batchelor spectrum and with maximal left-and right-handed helicities. We also consider the case of sources whose jets are tilted with respect to the line of sight. We verify the formation of extended gamma ray halos around the source direction, and observe spiral-like patterns if the magnetic field is helical. We apply the Q-statistics to the simulated halos to extract their spiral nature and also propose an alternative method, the S-statistics. Both methods provide a quantative way to infer the helicity of the intervening magnetic fields from the morphology of individual blazar halos for magnetic field strengths B 10 −15 G and magnetic coherence lengths Lc 100 Mpc. We show that the S-statistics has a better performance than the Q-statistics when assessing magnetic helicity from the simulated halos.

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Section: Discussion and Outlookmentioning

confidence: 62%

“…[38][39][40]. The key elements here are the observed energies and the arrival directions of gamma rays at Earth.…”

Section: Computing the Q-factorsmentioning

confidence: 99%

Section: Computing the Q-factorsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Probing intergalactic magnetic fields with simulations of electromagnetic cascades

et al. 2016

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“…To get the estimate above, we followed the discussion in A. Neronov and D. V. Semikoz [20] (see also [23]), where z γγ is the redshift of pair production, d γ and d s are the commoving mean free path for pair production and the commoving distance to the source, respectively [21]. Given the finite Fermi PSF, it is quite unlikely to detect the extended emission from high-redshift sources.…”

Section: Data Preparation and Selection Criteria For Stacking Sourcesmentioning

confidence: 99%

Search for GeVγ-Ray Pair Halos Around Low Redshift Blazars

2015

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We report on the results of a search for γ-ray pair halos with a stacking analysis of low-redshift blazars using data from the Fermi Large Area Telescope. For this analysis we used a number of a-priori selection criteria, including the spatial and spectral properties of the Fermi sources. The angular distribution of ∼ 1GeV photons around 24 stacked isolated high-synchrotron-peaked BL Lacs with redshift z < 0.5 shows an excess over that of point-like sources. A statistical analysis yields a Bayes factor of log 10 B10 > 2, providing evidence in favor of extended emission against the point-source hypothesis, consistent with expectations for pair halos produced in the IGMF with strength BIGMF ∼ 10 −17 − 10 −15 G. PACS numbers: 95.85.Pw, 98.58.Ay, 98.54.Cm, INTRODUCTIONThe magnetic fields that are observed in galaxies and galaxy clusters are believed to result from the dynamo amplification of weak magnetic field seeds, whose origin remains a mystery. Intergalactic magnetic fields (IGMFs), deep in the voids between galaxies, provide the most accurate image of the weak primordial seed fields and could be linked to the early stages in the evolution of the universe (see e.g.[1] for a recent review). Among the several methods used to study cosmological magnetic fields (see e.g. [2] for a recent review), the observation (or nondetection) of cascade emission from blazars can potentially measure very weak IGMFs. A number of blazars have been observed to emit both very-high-energy (VHE, > 100 GeV) γ-rays with ground-based γ-ray instruments and high-energy (HE, MeV/GeV) γ-rays with the Fermi Gamma-ray Space Telescope [3,4]. Most of the detected TeV γ-rays are from the nearest sources since such high energy γ-rays cannot propagate over long distances in intergalactic space due to interactions with the extragalactic background light (EBL). Of course, some higherredshift sources still have detectable TeV emission (e.g. blazar PKS1424+240, which has redshift lower limit of z > 0.6 [5]), but with highly absorbed spectra consistent with theoretical calculations of the attenuation by the EBL. [6][7][8][9][10]. These interactions of TeV γ-rays with the EBL produce electron-positron pairs that subsequently are cooled by inverse Compton (IC) interactions with the Cosmic Microwave Background (CMB), ultimately leading to GeV γ-ray emission from these pair cascades. Since magnetic fields deflect the electron-positron pairs changing the angular distribution of cascade emission, searches for extended GeV emission around blazars can provide an avenue for constraining the IGMF.Due to the low GeV γ-ray flux from extragalactic sources, it is difficult to examine the angular extent of the photon events from a single blazar or even to assess the joint likelihood for detailed fits to a set of individual sources where individual source parameters are taken to be completely independent. To overcome this limitation, stacking sources has been used to make such statistical analysis feasible. Despite early hints at a signal in the stacking analysis of 1...

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Wash-in leptogenesis after axion inflation

Domcke

Kamada

Mukaida

et al. 2023

J. High Energ. Phys.

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CP violation and the violation of baryon-minus-lepton number B−L do not necessarily have to occur simultaneously in order to accomplish successful leptogenesis. Instead, it suffices if new CP-violating interactions at high energies result in primordial charge asymmetries, which are then reprocessed into a nonvanishing B−L asymmetry by right-handed neutrinos (RHNs) at lower energies. In this paper, we study this novel mechanism known as wash-in leptogenesis, utilizing axion inflation as the source of high-scale CP violation. We specifically consider axion inflation coupled to the Standard Model hypercharge sector, which results in the dual production of hypermagnetic helicity and fermionic charge asymmetries. Although the survival of these charges is endangered by sphaleron processes, magnetic diffusion, and the chiral plasma instability, we find a large range of viable scenarios. We consistently account for RHN flavor effects and coherence among the Standard Model lepton flavors across a wide range of RHN masses. We find a lower bound of 105···9 GeV on the mass of the lightest RHN involved in wash-in leptogenesis, depending on the onset of turbulence in the chiral plasma and the Hubble scale of inflation. Our model is representative of a broader class of new leptogenesis scenarios and suggests interesting observational signatures with regard to intergalactic magnetic fields, primordial black holes, and gravitational waves.

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Cosmological magnetic field correlators from blazar induced cascade

Cited by 38 publications

References 62 publications

Probing intergalactic magnetic fields with simulations of electromagnetic cascades

Probing intergalactic magnetic fields with simulations of electromagnetic cascades

Search for GeVγ-Ray Pair Halos Around Low Redshift Blazars

Wash-in leptogenesis after axion inflation

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