Three-Dimensional Velocity Diagnostics to Constrain the Type Ia Origin of Tycho's Supernova Remnant

While various methods have been proposed to disentangle the progenitor system for Type Ia supernovae, their origin is still unclear. Circumstellar environment is a key to distinguishing between the double-degenerate (DD) and single-degenerate (SD) scenarios since a dense wind cavity is expected only in the case of the SD system. We perform spatially resolved X-ray spectroscopy of Tycho's supernova remnant (SNR) with XMM-Newton and reveal the three-dimensional velocity structure of the expanding shock-heated ejecta measured from Doppler-broadened lines of intermediate-mass elements. Obtained velocity profiles are fairly consistent with those expected from a uniformly expanding ejecta model near the center, whereas we discover a rapid deceleration ($\sim4000$ km s$^{-1}$ to $\sim1000$ km s$^{-1}$) near the edge of the remnant in almost every direction. The result strongly supports the presence of a dense wall entirely surrounding the remnant, which is confirmed also by our hydrodynamical simulation. We thus conclude that Tycho's SNR is likely of the SD origin. Our new method will be useful for understanding progenitor systems of Type Ia SNRs in the era of high-angular/energy resolution X-ray astronomy with microcalorimeters.