Observational Links Between Fermi-LAT Pulsars and Their Nebulae

Wilhelmi, E. de Oña

doi:10.1007/978-3-319-63031-1_4

Cited by 3 publications

(4 citation statements)

References 68 publications

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“…The blast waves of supernova remnants (SNRs) are the most likely sources of Galactic CRs (Neronov 2017; for extensive reviews, see Reynolds 2008;Marcowith et al 2016). There are other potential sources that might contribute, including shocks associated with young star forming regions (Yang et al 2017), high-energy processes at the Galactic center (HESS Collaboration et al 2016), or shocks associated with a large-scale Galactic wind that are driven by thermal or CR pressure gradients (Sarkar et al 2015;Pfrommer et al 2017b).…”

Section: Introductionmentioning

confidence: 99%

The effect of cosmic ray acceleration on supernova blast wave dynamics

Pais

Pfrommer

Ehlert

et al. 2018

Monthly Notices of the Royal Astronomical Society

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Non-relativistic shocks accelerate ions to highly relativistic energies provided that the orientation of the magnetic field is closely aligned with the shock normal (quasiparallel shock configuration). In contrast, quasi-perpendicular shocks do not efficiently accelerate ions. We model this obliquity-dependent acceleration process in a spherically expanding blast wave setup with the moving-mesh code arepo for different magnetic field morphologies, ranging from homogeneous to turbulent configurations. A Sedov-Taylor explosion in a homogeneous magnetic field generates an oblate ellipsoidal shock surface due to the slower propagating blast wave in the direction of the magnetic field. This is because of the efficient cosmic ray (CR) production in the quasi-parallel polar cap regions, which softens the equation of state and increases the compressibility of the post-shock gas. We find that the solution remains self-similar because the ellipticity of the propagating blast wave stays constant in time. This enables us to derive an effective ratio of specific heats for a composite of thermal gas and CRs as a function of the maximum acceleration efficiency. We finally discuss the behavior of supernova remnants expanding into a turbulent magnetic field with varying coherence lengths. For a maximum CR acceleration efficiency of about 15 per cent at quasi-parallel shocks (as suggested by kinetic plasma simulations), we find an average efficiency of about 5 per cent, independent of the assumed magnetic coherence length.

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Section: Introductionmentioning

confidence: 99%

The effect of cosmic ray acceleration on supernova blast wave dynamics

Pais

Pfrommer

Ehlert

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…It also does not exhibit any X-rays that are spatially coincident with the TeV source. Additionally, diffuse GeV gamma-ray emission has been detected with Fermi-LAT towards Westerlund 2 (Yang et al 2017). The authors have argued for a hadronic origin based on its 200 pc extension of the 1 to 250 GeV emission.…”

Section: Hess J1026-583mentioning

confidence: 99%

Connecting the ISM to TeV PWNe and PWN candidates

Voisin

Rowell

Burton

et al. 2019

Publ. Astron. Soc. Aust.

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We investigate the interstellar medium (ISM) towards seven TeV gamma-ray sources thought to be pulsar wind nebulae (PWNe) using Mopra molecular line observations at 7mm [CS(1-0), SiO(1-0,v=0)], Nanten CO(1-0) data and the SGPS/GASS Hi survey. We have discovered several dense molecular clouds co-located to these TeV gamma-ray sources, which allows us to search for cosmic-rays (CRs) coming from progenitor SNRs or, potentially, from PWNe. We notably found SiO(1-0,v=0) emission towards HESS J1809−193, highlighting possible interaction between the adjacent supernova remnant SNR G011.0−0.0 and the molecular cloud at d ∼ 3.7 kpc. Using morphological features, and comparative studies of our column densities with those obtained from X-ray measurements, we claim a distance d ∼ 8.6 − 9.7 kpc for SNR G292.2−00.5, d ∼ 3.5 − 5.6 kpc for PSR J1418−6058 and d ∼ 1.5 kpc for the new SNR candidate found towards HESS J1303−631. From our mass and density estimates of selected molecular clouds, we discuss signatures of hadronic/leptonic components from PWNe and their progenitor SNRs. Interestingly, the molecular gas, which overlaps HESS J1026−582 at d ∼5 kpc, may support a hadronic origin. We find however that this scenario requires an undetected cosmic-ray accelerator to be located at d < 10 pc from the molecular cloud. For HESS J1809−193, the cosmic-rays which have escaped SNR G011.0−0.0 could contribute to the TeV gamma-ray emission. Finally, from the hypothesis that at most 20% the pulsar spin down power could be converted into CRs, we find that, among the studied PWNe, only those from PSR J1809−1917 could potentially contribute to the TeV emission.

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“…(b) Extended sources with γ-ray emission correlated with the HI density: In this case, the standard IEM should carefully be refined and such extended γ-ray sources should be extracted from the IEM template for modelling 5 . This class includes Galactic objects, such as Gould Belt MCs and HI gas shells (e.g., Yang et al 2014;Mizuno et al 2016), and extragalactic objects, such as the gaseous disc of the Andromeda galaxy (Abdo et al 2010a). To refine the standard IEM model for objects of this class, one needs to redo a decomposition of γ-ray emission into the linear combination of templates for various components of the Galactic diffuse emission (Ackermann et al 2012b) or to adopt a background model from other regions using the standard IEM.…”

Section: Model Preparationmentioning

confidence: 99%

“…Therefore, one needs to take both the diffuse Galactic γ-ray emission gradient and the hard spectral contribution from the Fermi bubble into account. Yang et al (2014) explains the observed spectral hardness of the ρ Oph MC by the fact that point γ-ray sources contribute to the total γ-ray signal and therefore one needs to consider how to incorporate the point sources in the model in order to alleviate this problem. Below we list the improvements over the previous work based on the background extraction method.…”

Section: ρ Ophiuchi Molecular Cloudmentioning

confidence: 99%

Testing spatial uniformity of the CR spectrum in the local ISM with γ-ray observations

Prokhorov

Colafrancesco

2018

Monthly Notices of the Royal Astronomical Society

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Gamma-ray observations of nearby radio-line-emitting gas structures in the interstellar medium allow us to probe the spectrum of cosmic rays (CRs). In this paper, we analysed Fermi Large Area Telescope (LAT) γ-ray observations of three such structures located near each other to check if their CR spectra are compatible with that of the CR background or might provide evidence for a population of "fresh" CRs. We found that the shape of the γ-ray spectrum in the Aquarius HI shell is consistent with the previously published stacked γ-ray spectrum of the Gould Belt molecular clouds. We also found that assumptions on the diffuse Galactic γ-ray background affect the spectral shapes of CRs derived in the R Coronae Australis and ρ Ophiuchi molecular clouds in which spectral deviations had previously been suggested. These two facts provide evidence to support the hypothesis of uniformity of the shapes of cosmic ray spectra in the local Galaxy environment.

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Observational Links Between Fermi-LAT Pulsars and Their Nebulae

Cited by 3 publications

References 68 publications

The effect of cosmic ray acceleration on supernova blast wave dynamics

The effect of cosmic ray acceleration on supernova blast wave dynamics

Connecting the ISM to TeV PWNe and PWN candidates

Testing spatial uniformity of the CR spectrum in the local ISM with γ-ray observations

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