Mapping Cassiopeia A’s silicon/sulfur Doppler velocities with XRISM/Resolve

Abstract Young supernova remnants (SNRs) provide crucial insights into explosive nucleosynthesis products and their velocity distribution soon after the explosion. However, these velocities are influenced by the dynamics of the circumstellar medium (CSM), which in young core-collapse SNRs originates from the progenitor’s late-phase mass loss. Cassiopeia A (Cas A), the youngest known Galactic core-collapse SNR, was studied to analyze the spatial distribution of silicon and sulfur radial velocities using two high-spectral-resolution observations from the XRISM/Resolve imaging spectrometer. Resolve’s capabilities enabled the detailed characterization of Si xiii, Si xiv, S xv, and S xvi lines, whose line shapes can be resolved and modeled using Gaussian radial velocity components. The radial velocities measured generally align with previous CCD-based results, confirming that they were not artifacts caused by blended lines or ionization variations. Modeling line profiles with two-component Gaussians improved fits in some regions, revealing distinct redshifted (back side) and blueshifted (front side) components only in a few specific areas. In most regions, however, both components were either both redshifted (north-west) or both blueshifted (south-east), consistent with the patchy ejecta shell morphology seen in optically emitting fast-moving knots. The individual line components revealed line broadening ranging from $\sigma _v \approx 200$ to $\sigma _v \approx 2000$ ${\rm km\, s^{-1}}$. Components with $1000 \lesssim \sigma _v \lesssim 2000$ ${\rm km\, s^{-1}}$ are consistent with previously determined reverse-shock velocities, suggesting non-equilibrated or partially equilibrated ion temperatures. Narrow components with small radial velocities found near Cas A’s projected center likely originate from shocked CSM plasma. But the low radial velocity and small $\sigma _v$ poses a challenge to identify these components with either the front side or back side of the SNR, or a blend of both sides.

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Publication Details

Journal
Publications of the Astronomical Society of Japan
Published
2025-06-06
DOI
https://doi.org/10.1093/pasj/psaf053
Citations
8
Primary Topic
Gamma-ray bursts and supernovae
Type
article
Field-Weighted Citation Impact
9.24

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article

Mapping Cassiopeia A’s silicon/sulfur Doppler velocities with XRISM/Resolve

Lía Corrales, Ehud Behar, Paul P. Plucinsky, Kai Matsunaga et al.
8 citations
Publications of the Astronomical Society of Japan
Gamma-ray bursts and supernovae
9.24
article

Mapping Cassiopeia A’s silicon/sulfur Doppler velocities with XRISM/Resolve

Lía Corrales, Ehud Behar, Paul P. Plucinsky, Kai Matsunaga, Y. Terada, Jacco Vink, Aya Bamba, Hiroyuki Uchida, Hironori Matsumoto, Masahiro Ichihashi, Adam Foster, Liyi Gu, Hidetaka Sonoda, Satoru Katsuda, Tsunefumi Mizuno, Manan Agarwal, Shin-ichiro Fujimoto, Makoto Sawada, Dai Tateishi, Toshiki Sato, Shunsuke Suzuki, Koji Mori, Hiroshi Murakami, Hiroshi Nakajima, Kazuhiro Ichikawa
article en
8 citations

Abstract

Abstract Young supernova remnants (SNRs) provide crucial insights into explosive nucleosynthesis products and their velocity distribution soon after the explosion. However, these velocities are influenced by the dynamics of the circumstellar medium (CSM), which in young core-collapse SNRs originates from the progenitor’s late-phase mass loss. Cassiopeia A (Cas A), the youngest known Galactic core-collapse SNR, was studied to analyze the spatial distribution of silicon and sulfur radial velocities using two high-spectral-resolution observations from the XRISM/Resolve imaging spectrometer. Resolve’s capabilities enabled the detailed characterization of Si xiii, Si xiv, S xv, and S xvi lines, whose line shapes can be resolved and modeled using Gaussian radial velocity components. The radial velocities measured generally align with previous CCD-based results, confirming that they were not artifacts caused by blended lines or ionization variations. Modeling line profiles with two-component Gaussians improved fits in some regions, revealing distinct redshifted (back side) and blueshifted (front side) components only in a few specific areas. In most regions, however, both components were either both redshifted (north-west) or both blueshifted (south-east), consistent with the patchy ejecta shell morphology seen in optically emitting fast-moving knots. The individual line components revealed line broadening ranging from $\sigma _v \approx 200$ to $\sigma _v \approx 2000$ ${\rm km\, s^{-1}}$. Components with $1000 \lesssim \sigma _v \lesssim 2000$ ${\rm km\, s^{-1}}$ are consistent with previously determined reverse-shock velocities, suggesting non-equilibrated or partially equilibrated ion temperatures. Narrow components with small radial velocities found near Cas A’s projected center likely originate from shocked CSM plasma. But the low radial velocity and small $\sigma _v$ poses a challenge to identify these components with either the front side or back side of the SNR, or a blend of both sides.

Publications of the Astronomical Society of JapanVol. 77(Supplement_1)
Hiroshima University (JP), University of Miyazaki (JP), Aoyama Gakuin University (JP), Rikkyo University (JP), Meiji University (JP), Technion – Israel Institute of Technology (IL), Kanto Gakuin University (JP), Kyoto University (JP), University of Michigan (US), National Institute of Technology, Kumamoto College (JP), Tohoku Gakuin University (JP), National Sagamihara Hospital (JP), Center for Astrophysics Harvard & Smithsonian (US), Astronomical Institute of the Slovak Academy of Sciences (SK), Space Research Organisation Netherlands (NL), Saitama University (JP), The University of Tokyo (JP), University of Amsterdam (NL), The University of Osaka (JP)
Astronomical Society of Japan, Universiteit van Amsterdam, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, Japan Society for the Promotion of Science
Openalex Percentile: Top 2%
Gamma-ray bursts and supernovae
9.24
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