On the Continuum Radio Spectrum of Cas A: Possible Evidence of Nonlinear Particle Acceleration

Onić, D.; Urošević, D.

doi:10.1088/0004-637x/805/2/119

Cited by 19 publications

(17 citation statements)

References 28 publications

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“…Also, modelled spectra of G1.9+0.3 reveals concave-up curvature at millimetre and sub-millimetre wavelengths. This is expected and indeed observed by the Planck 11 telescope in the radio continuum of another young SNR Cas A (Onić & Urošević 2015). After investigating alternative explanations of the ob-served curvature, Onić & Urošević (2015) agree that nonlinear effects of particle acceleration are mainly responsible for high-frequency curvature in the radio spectrum.…”

Section: Figuresupporting

confidence: 58%

Hydrodynamical and radio evolution of young supernova remnant G1.9+0.3 based on the model of diffusive shock acceleration

Pavlović¹

2017

Monthly Notices of the Royal Astronomical Society

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The radio evolution of, so far the youngest known, Galactic supernova remnant (SNR) G1.9+0.3 is investigated by using three-dimensional (3D) hydrodynamic modelling and non-linear kinetic theory of cosmic ray (CR) acceleration in SNRs. We include consistent numerical treatment of magnetic field amplification (MFA) due to resonant streaming instability. Under the assumption that SNR G1.9+0.3 is the result of a Type Ia supernova explosion located near the Galactic Centre, using widely accepted values for explosion energy 10 51 erg and ejecta mass 1.4 M ⊙ , the non-thermal continuum radio emission is calculated. The main purpose of this paper is to explain radio flux brightening measured over recent decades and also predict its future temporal evolution. We estimate that the SNR is now ∼ 120 yr old, expanding in an ambient density of 0.02 cm −3 , and explain its steep radio spectral index only by means of efficient non-linear diffusive shock acceleration (NLDSA). We also make comparison between simulations and observations of this young SNR, in order to test the models and assumptions suggested. Our model prediction of a radio flux density increase of ∼ 1.8 per cent yr −1 during the past two decades agrees well with the measured values. We synthesize the synchrotron spectrum from radio to X-ray and it fits well the Very Large Array, Molonglo Observatory Synthesis Telescope, Effelsberg, Chandra and NuSTAR measurements. We also propose a simplified evolutionary model of the SNR in gamma rays and suggest it may be a promising target for gamma-ray observations at TeV energies with the future generation of instruments like Cherenkov Telescope Array. SNR G1.9+0.3 is the only known Galactic SNR with the increasing flux density and we present here the prediction that the flux density will start to decrease approximately 500 yr from now. We conclude that this is a general property of SNRs in free expansion phase.

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Section: Figuresupporting

confidence: 58%

Hydrodynamical and radio evolution of young supernova remnant G1.9+0.3 based on the model of diffusive shock acceleration

Pavlović¹

2017

Monthly Notices of the Royal Astronomical Society

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“…A spectral index of α=-0.644 is also somewhat shallower compared to the values used in several other studies of Cas A: α = -0.69 (Hines et al 2004), α = -0.70 (Barlow et al 2010), α = -0.71 (Rho et al 2003(Rho et al , 2008Arendt et al 1999), which were based on spectral index measurements at lower frequencies. A flattening of the synchrotron spectrum was suggested by Onić & Urošević (2015) and attributed to non-linear particle acceleration. The best fitting synchrotron spectrum including spectral curvature (Sν =S1GHz ν −α+a log ν e −τ 0 ν −2.1 with α=0.760, a=0.020, τ0=8.559×10 −5 , see green dotted curve in Figure 4) reported by Onić & Urošević (2015) (where the scaling relations of Vinyaikin 2014 were used to account for secular fading) is however consistent with the best-fitting synchrotron spectrum derived for Cas A based on Planck data in this work.…”

Section: Modelling the Synchrotron Componentmentioning

confidence: 94%

“…The red dashed lines indicate the upper and lower limits to the synchrotron spectrum, determined from the uncertainties on the spectral index fitting. The green dashed curve shows an extrapolation of the synchrotron spectrum with spectral curvature from Onić & Urošević (2015) which greatly overestimates the IRAC 3.6 µm flux. maps which allows a more accurate background subtraction.…”

Section: Flux Comparisonsmentioning

confidence: 99%

The dust mass in Cassiopeia A from a spatially resolvedHerschelanalysis

Looze¹,

Barlow²,

Swinyard³

et al. 2016

Mon. Not. R. Astron. Soc.

154

152

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Theoretical models predict that core-collapse supernovae (CCSNe) can be efficient dust producers (0.1-1.0 M ), potentially accounting for most of the dust production in the early Universe. Observational evidence for this dust production efficiency is however currently limited to only a few CCSN remnants (e.g., SN 1987A, Crab Nebula). In this paper, we revisit the dust mass produced in Cassiopeia A (Cas A), a ∼330-year old Orich Galactic supernova remnant (SNR) embedded in a dense interstellar foreground and background. We present the first spatially resolved analysis of Cas A based on Spitzer and Herschel infrared and submillimetre data at a common resolution of ∼0.6 for this 5 diameter remnant following a careful removal of contaminating line emission and synchrotron radiation. We fit the dust continuum from 17 to 500 µm with a fourcomponent interstellar medium (ISM) and supernova (SN) dust model. We find a concentration of cold dust in the unshocked ejecta of Cas A and derive a mass of 0.3-0.5 M of silicate grains freshly produced in the SNR, with a lower limit of ≥0.1-0.2 M . For a mixture of 50% of silicate-type grains and 50% of carbonaceous grains, we derive a total SN dust mass between 0.4 M and 0.6 M . These dust mass estimates are higher than from most previous studies of Cas A and support the scenario of supernova dominated dust production at high redshifts. We furthermore derive an interstellar extinction map for the field around Cas A which towards Cas A gives average values of A V = 6-8 mag, up to a maximum of A V = 15 mag.

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“…Both are dense knots of gas heated by relatively slow shock waves. The X-ray and radio show synchrotron emission, and the Xrays also show thermal emission from shocked ejecta and circumstellar gas (Vink & Laming 2003;DeLaney et al 2010;Hwang & Laming 2012;Onić & Urošević 2015).…”

Section: Introductionmentioning

confidence: 99%

The Temperature and Ionization of Unshocked Ejecta in Cas A

Raymond

Koo

Lee

et al. 2018

ApJ

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The supernova remnant Cassiopeia A (Cas A) is one of the few remnants in which it is possible to observe unshocked ejecta. A deep 1.64 µm image of Cas A shows a patch of diffuse emission from unshocked ejecta, as well as brighter emission from Fast-Moving Knots and Quasi-Stationary Flocculi. Emission at 1.64 µm is usually interpreted as [Fe II] emission, and spectra of the bright knots confirm this by showing the expected emission in other [Fe II] lines. We performed NIR spectroscopy on the diffuse emission region and found that the unshocked ejecta emission does not show those lines, but rather the [Si I] 1.607 µm line. This means that the 1.64 µm line from the unshocked ejecta may be the [Si I] 1.645 line from the same upper level, rather than [Fe II]. We find that the [Si I] line is formed by recombination, and we use the [Si I] to [Si II] ratio to infer a temperature about 100 K, close to the value assumed for analysis of low frequency radio absorption and that inferred from emission by cool dust. Our results constrain estimates of Cas A's total mass of unshocked ejecta that are extremely sensitive to temperature assumptions, but they do not resolve the ambiguity due to clumping.

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On the Continuum Radio Spectrum of Cas A: Possible Evidence of Nonlinear Particle Acceleration

Cited by 19 publications

References 28 publications

Hydrodynamical and radio evolution of young supernova remnant G1.9+0.3 based on the model of diffusive shock acceleration

Hydrodynamical and radio evolution of young supernova remnant G1.9+0.3 based on the model of diffusive shock acceleration

The dust mass in Cassiopeia A from a spatially resolvedHerschelanalysis

The Temperature and Ionization of Unshocked Ejecta in Cas A

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