Attributing the point symmetric structure of core-collapse supernova remnant N132D to the jittering jets explosion mechanism

TL;DR

The paper analyzes SNR N132D to test the jittering jets explosion mechanism by identifying a point-symmetric morphology. By combining X-ray Fe K alpha mapping with 3D oxygen torus reconstructions, it shows two perpendicular jet axes linking inner and outer structures. It discusses prior work and jet-driven interpretation, noting Runaway Knot as a silicon-rich jet and torus breaks aligning with jet axes. The findings challenge the neutrino-driven mechanism as the primary CCSN driver and position JJEM as a robust explanation for point-symmetric CCSNR morphologies.

Abstract

I identified a point-symmetric morphology in the core-collapse supernova (CCSN) remnant (CCSNR) N132D, composed of two symmetry axes: the short symmetry axis extending from the northwest ear and through the center of the iron-rich emission on the other side, and the second along the long dimension of N132D and coincides with the extension of the central oxygen-rich gas to the northeast. Namely, the point-symmetry of the outer zones of CCSNR N132D correlates with that of the oxygen-rich gas near the center. The surrounding gas cannot shape the inner oxygen-rich material, implying that the point-symmetric morphology is a property of the explosion mechanism, as predicted by the jittering jets explosion mechanism (JJEM). The oxygen-rich material is known to be in a torus. According to the JJEM, an energetic pair of opposite jets, more or less perpendicular to the plane of the torus, has shaped the torus; this pair is along the short symmetry axis. Another energetic pair, perpendicular to the first one, shaped the elongated, large-scale structure of CCSNR N132D. I discuss how the JJEM accounts for two perpendicular pairs of jets and the unequal jets in each pair. CCSNR N132D is the fifteenth CCSNR with an identified point-symmetric morphology attributed to the JJEM. Because the neutrino-driven mechanism cannot explain such morphologies, this study further strengthens the claim that the JJEM is the primary explosion mechanism of CCSNe.

Figures (4)

• Figure 1: (a) An X-ray image of SNR N132D adapted from Fosteretal2025. Colored $2.^{\prime \prime}5 \times 2.^{\prime \prime}5$ squares show the count image in Fe K$\alpha$ line in the energy range of $6.50-7.05 ~\rm{keV}$, with continuum emission subtracted. The contours are Chandra images in the energy band $0.5-8.0 ~\rm{keV}$. I visually added a line connecting the tip of the northwest ear (protrusion) and the center of the iron distribution. I identify this line as the short-symmetry axis of SNR N132D. (b) An X-ray image adapted from the Chandra site (credit: NASA/CXC/NCSU/K.J.Borkowski et al.; https://chandra.si.edu/photo/2008/n132d/): red for low energy, green intermediate energy, and blue for high energy emission. I added a double-sided arrow from the tip of the NW ear to the other side at the same location as the dashed, pale blue line in panel (a). The dashed-orange double-sided arrow is perpendicular to the short-symmetry axis arrow and of the same length; they intersect at their centers. I added the two red lines to connect opposite dents. (c) An image of oxygen emission adapted from Banovetzetal2023, who mark their determination of the center of the proper motion expansion (CoE: yellow plus), and the centers that Morseetal1995 found by fitting an ellipse to the diffuse outer rim (blue cross) and the O-rich geometric center (red cross); see Section \ref{['subsec:Morse1995']}. I added the intersection points of the red lines from panel (b) (red dot) and of the two perpendicular double-ended arrows (orange dot). (d) A Chandra $0.3-7.0 ~\rm{keV}$ X-ray image of SNR N132D adapted from Borkowskietal2007. The size of the image is $120^{\prime \prime} \times 115^{\prime \prime}$, and the scale is $\times 1.25$ that of panels (a) and (b). The four closed green lines near the center of the remnant mark the location of optically emitting O-rich ejecta; these and the ellipse are from the original figure. I copied the two red lines and the two double-sided arrows from panel (b) (increased by a factor of 1.25), as well as the three different SNR centers from panel (c). I added an alternative long-symmetry axis (dotted orange double-sided arrow), which touches the tip of a small ear in the southwest. The intersection of the three double-sided arrows is at the center of each of them. The two solid-orange arrows indicate the possibility that the two opposite jets that shaped the elongation of SNR N132D were at $171^\circ$ to each other (see text).
• Figure 2: Two panels adapted from Morseetal1995 and emphasize the oxygen-rich ejecta. (a) The velocity map by [O iii]$\lambda$5007 of fast oxygen-rich filaments in SNR N132D on a gray scale of low-velocity [O iii] emission as presented by Morseetal1995: B2 and B3 are highly blueshifted, B1 and B4 are close to the mean velocity, and R1 and R2 are highly redshifted (Section \ref{['subsec:3D']}). The "+" marks the center of the remnant as Morseetal1995 determined by fitting an ellipse to the diffuse rim, while the "$\times$" marks the center of the high-velocity oxygen-rich ejecta by the four lines that Morseetal1995 mark on panel (b). (b) Contours of the oxygen-rich filaments in N132D (panel a). Morseetal1995 drew the four pale-blue lines by connecting regions which show a symmetric distribution about a common center (the "$\times$" symbol on panel a). I discuss the runaway knot in Section \ref{['subsec:3D']}. I added the two double-sided arrows from panel (b) of Figure \ref{['Fig:SNRN132Dfigure4P']}; the arrows are not to scale in length, but only show the directions.
• Figure 3: Panels presenting the oxygen-rich torus/ring. To both panels I added the three axes from panel (d) of Figure \ref{['Fig:SNRN132Dfigure4P']}. (a) A multiwavelength three-color image of SNR N132D adapted from Rhoetal2023: Herschel $350 \mu$m (blue), Spitzer $24 \mu$m (red), and Chandra X-rays (green). They added the high-velocity blue- and redshifted optical ejecta from Morseetal1995 as contours of blue and red, respectively. (b) An image adapted from Lawetal2020, presenting a Chandra image of counts per pixel in the $0.35-8.0 ~\rm{keV}$ band (orange zones), with oxygen-rich optical ejecta overlaid in gray. The inset shows the $5^{\prime \prime} \simeq 1.2 ~\rm{pc}$ offset between the X-ray bright spot and the runaway knot (marked RK on the lower left).
• Figure 4: Panels adapted from Lawetal2020 presenting the optically-emitting oxygen-rich material they analyzed (the gray zones in panel (b) of Figure \ref{['Fig:SNRN132DfigureDynamic']}). My additions are the marks in red. (a) The 3D Doppler reconstructed torus-like structure from different directions. The colors indicate the Doppler shift velocity according to the color bar (from $-3000 ~\rm{km} ~\rm{s}^{-1}$ in blue to $2300 ~\rm{km} ~\rm{s}^{-1}$ in red). The translucent sphere serves as a visual aid to help distinguish between front and back materials. Lawetal2020 identified a break in the torus. I identify a counter break that is opposite to the break and narrower in opening. On two panels, I added the double-sided red arrow to connect the break with the counter break. (b) Regions with oxygen-rich knots emission, where colors indicate Doppler shift velocity from $-2900 ~\rm{km} ~\rm{s}^{-1}$ in blue to $2500 ~\rm{km} ~\rm{s}^{-1}$ in red. Lawetal2020 indicated major knots and the two centers from Morseetal1995, and the runaway knot (RK). I added the perpendicular axis from Figure \ref{['Fig:SNRN132Dfigure4P']}, but shifted to go through the center that Morseetal1995 identified. (c) Projections in the plane of the line of sight and the east-west direction of the oxygen-rich material that Lawetal2020 analyzed. The axes are the expansion velocity in $~\rm{km} ~\rm{s}^{-1}$. In the three panels, I marked the same blue-shifted fast knot with a red circle.