A study of Kepler supernova remnant: angular power spectrum estimation from radio frequency data

Saha, Pinku; Bharadwaj, Somnath; Roy, Nirupam; Choudhuri, Samir; Chattopadhyay, Debatri

doi:10.1093/mnras/stz2528

Cited by 12 publications

(15 citation statements)

References 39 publications

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“…Interestingly, they have found another break in the power spectrum at even smaller scales less than the shell thickness. As concluded in Saha et al (2019), this might be due to the dominant contribution from the Galactic or extra-galactic foregrounds.…”

Section: Introductionmentioning

confidence: 73%

“…They also observed a break in the measured power spectrum for the shell-type SNR Cas A due to transition from three-dimensional (3D) to two-dimensional (2D) turbulence at scale corresponds to the shell thickness of Cas A. Recently, Saha et al (2019) have extended this work and studied the power spectrum of the Kepler SNR. They also have found a break due to the shell thickness of the Kepler SNR.…”

Section: Introductionmentioning

confidence: 89%

“…The inferred power spectrum of the intensity fluctuations from observations of SNRs (radio synchrotron emission, but also at other wavelengths) might change due to various effects. As shown in Roy et al (2009) and Saha et al (2019), the intrinsic slope of the SNR power spectrum is changed due to the shell thickness of a shell-type SNR. The projection of a 3D structure in a 2D observational plane can modify the shape of the intrinsic power spectrum generated by the actual magnetohydrodynamic turbulence.…”

Section: Introductionmentioning

confidence: 99%

“…For example, Stafford et al (2019) found that larger (older) SNRs are more elliptical/elongated as SNR shells become more asymmetric as they sweep up the ISM. On the other hand, the small-scale structures of the SNR are expected to reveal the nature of the turbulence in the remnant plasma (Roy et al 2009;Saha et al 2019).…”

Section: Introductionmentioning

confidence: 99%

“…This work presents the details of a systematic forward modelling approach that can be adopted to infer the intrinsic power spectra from the measured power spectra. An application of this method for the specific case of the radio synchrotron emission from Kepler SNR has been reported in Saha et al (2019). Further implementation for radio and X-ray power spectra, as well as cross power spectra, will be presented in future work (Saha et al, in preparation).…”

Section: Introductionmentioning

confidence: 99%

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Angular power spectrum of supernova remnants: effects of structure, geometry and diffuse foreground

Choudhuri

Saha

Roy

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The study of the intensity fluctuation power spectrum of individual supernova remnants (SNRs) can reveal the structures present at sub-pc scales, and also constrain the physical process that generates those structures. There are various effects, such as the remnant shell thickness, projection of a three-dimensional structure onto a two-dimensional observational plane, and the presence of diffuse “foreground” emission, which causes the observed power spectrum to deviate from the intrinsic power spectrum of the fluctuations. Here, we report results from a systematic study of these effects, using direct numerical simulations, in the measured power spectrum. For an input power-law power spectrum, independent of the power-law index, we see a break in the observed power law at a scale which depends on the shell thickness of a shell-type SNR, and the three-dimensional turbulence changes to two-dimensional turbulence beyond that scale. We also report how the estimated power spectrum is expected to deviate from the intrinsic SNR power spectrum in the presence of additional diffuse Galactic synchrotron emission (DGSE) around the remnant shell. For a reasonable choice of the parameters, if the intrinsic SNR power spectrum is shallower than the DGSE power spectrum, the SNR contribution dominates at small angular scales of the estimated power spectra. On the other hand, if the SNR power spectrum is relatively steeper, the original power spectra is recovered only over a small window of angular scales. This study shows how detailed modeling may be used to infer the true power spectrum from the observed SNR intensity fluctuations power spectrum, which in turn can be used to constrain the nature of the turbulence that gives rise to these small scale structures.

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Section: Introductionmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Angular power spectrum of supernova remnants: effects of structure, geometry and diffuse foreground

Choudhuri

Saha

Roy

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The Tracking Tapered Gridded Estimator for the 21-cm power spectrum from MWA drift scan observations I: Validation and preliminary results

Chatterjee,

Elahi,

Bharadwaj

et al. 2024

Publ. Astron. Soc. Aust.

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Drift scan observations provide the broad sky coverage and instrumental stability needed to measure the Epoch of Reionization (EoR) 21-cm signal. In such observations, the telescope’s pointing centre (PC) moves continuously on the sky. The Tracking Tapered Gridded Estimator (TTGE) combines observations from different PC to estimate $P(k_{\perp}, k_{\parallel})$ the 21-cm power spectrum, centred on a tracking centre (TC) which remains fixed on the sky. The tapering further restricts the sky response to a small angular region around TC, thereby mitigating wide-field foregrounds. Here we consider $154.2\,\mathrm{MHz}$ ( $z = 8.2$ ) Murchison Widefield Array (MWA) drift scan observations. The periodic pattern of flagged channels, present in MWA data, is known to introduce artefacts which pose a challenge for estimating $P(k_{\perp}, k_{\parallel})$ . Here we have validated the TTGE using simulated MWA drift scan observations which incorporate the flagged channels same as the data. We demonstrate that the TTGE is able to recover $P(k_{\perp}, k_{\parallel})$ without any artefacts and estimate $P(k)$ within $5 \%$ accuracy over a large $k$ -range. We also present preliminary results for a single PC, combining 9 nights of observation $(17 \, \mathrm{min}$ total). We find that $P(k_{\perp}, k_{\parallel})$ exhibits streaks at a fixed interval of $k_{\parallel}=0.29 \, \mathrm{Mpc}^{-1}$ , which matches $\Delta \nu_\mathrm{per}=1.28 \, \mathrm{MHz}$ that is the period of the flagged channels. Since the simulations demonstrate that the TTGE is impervious to the flagged channels, the streaks seen for the actual data are possibly caused by some systematic that has the same period as the flagged channels. These streaks are more than 3–4 orders of magnitude smaller than the peak foreground power $\mid P(k_{\perp}, k_{\parallel}) \mid \approx 10^{16} \, \mathrm{mK^2}\, \mathrm{Mpc^3}$ at $k_{\parallel}=0$ . The streaks are not as pronounced at larger $k_{\parallel}$ , and in some cases they do not appear to extend across the entire $k_{\perp}$ range. The rectangular region $0.05 \leq k_{\perp} \leq 0.16 \, \mathrm{Mpc^{-1}}$ and $0.9 \leq k_{\parallel}\leq 4.6 \, \mathrm{Mpc^{-1}}$ is found to be relatively free of foreground contamination and artefacts, and we have used this to place the $2\unicode{x03C3}$ upper limit $\Delta^2(k) < (1.85\times10^4)^2\, \mathrm{mK^2}$ on the EoR 21-cm mean squared brightness temperature fluctuations at $k=1 \,\mathrm{Mpc}^{-1}$ .

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Feedback of Efficient Shock Acceleration on Magnetic-field Structure Inside Young Type Ia Supernova Remnants

Shen,

Bao,

Zhang

2024

Res. Astron. Astrophys.

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Using an effective adiabatic index $\gamma_{\mathrm{eff}}$ to mimic the feedback of efficient shock acceleration, we simulate the temporal evolution of a young type Ia supernova remnant (SNR) with two different background magnetic field (BMF) topologies: a uniform and a turbulent BMF. The density distribution and magnetic-field characteristics of our benchmark SNR are studied with two-dimensional cylindrical magnetohydrodynamic (MHD) simulations. When $\gamma_{\mathrm{eff}}$ is considered, we find that: (1) the two-shock structure shrinks and the downstream magnetic-field orientation is dominated by the Rayleigh-Taylor instability structures; (2) \del{for the uniform case, }there exists more quasi-radial magnetic fields inside the shocked region.\del{ While for the turbulent case, owing to the turbulence in BMF, the downstream magnetic-field orientation is time-dependent}; and (3) inside the intershock region, both the quasi-radial magnetic energy density and the total magnetic energy density are enhanced: in radial direction, with $\gamma_{\mathrm{eff}}=$1.1, they are amplified \add{about 10-26 times more than} those with $\gamma_{\mathrm{eff}}=$5/3. While in angular direction, the total magnetic energy densities could be amplified \add{about 350 times more than} those with $\gamma_{\mathrm{eff}}=$5/3, \add{and there are more grid cells within the intershock region where the magnetic energy density is amplified by a factor greater than 100.(3) inside the intershock region, both the quasi-radial magnetic energy density and the total magnetic energy density are enhanced: in radial direction, with $\gamma_{\mathrm{eff}}=$1.1, they are amplified about 6-9 times those with $\gamma_{\mathrm{eff}}=$5/3. While in angular direction, the total magnetic energy densities could be amplified more than 125 times those with $\gamma_{\mathrm{eff}}=$5/3. More grid cells within the intershock region manifest magnetic energy densities surpassing the background magnetic energy density by a factor $>$ 100.

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A study of Kepler supernova remnant: angular power spectrum estimation from radio frequency data

Cited by 12 publications

References 39 publications

Angular power spectrum of supernova remnants: effects of structure, geometry and diffuse foreground

Angular power spectrum of supernova remnants: effects of structure, geometry and diffuse foreground

The Tracking Tapered Gridded Estimator for the 21-cm power spectrum from MWA drift scan observations I: Validation and preliminary results

Feedback of Efficient Shock Acceleration on Magnetic-field Structure Inside Young Type Ia Supernova Remnants

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