Resolved shock structure of the Balmer-dominated filaments in Tycho's supernova remnant: Cosmic-ray precursor?

TL;DR

This study uses Hubble Space Telescope imaging to analyze the shock structure and precursor emission in Tycho's supernova remnant, providing insights into cosmic-ray acceleration effects.

Contribution

It presents the first detailed imaging of the shock precursor in Tycho's SNR and links the precursor emission to cosmic-ray acceleration.

Findings

Detection of a thin shock precursor (~1") ahead of the shock

Significant Hα emission from the precursor affects temperature estimates

Precursor likely caused by cosmic rays, indicating efficient cosmic-ray acceleration

Abstract

We report on the results from H{\alpha} imaging observations of the eastern limb of Tycho's supernova remnant (SN1572) using the Wide Field Planetary Camera 2 on the Hubble Space Telescope. We resolve the detailed structure of the fast, collisionless shock wave into a delicate structure of nearly edge-on filaments. We find a gradual increase of H{\alpha} intensity just ahead of the shock front, which we interpret as emission from the thin (~1") shock precursor. We find that a significant amount of the H{\alpha} emission comes from the precursor and that this could affect the amount of temperature equilibration derived from the observed flux ratio of the broad and narrow H{\alpha} components. The observed H{\alpha} emission profiles are fit using simple precursor models, and we discuss the relevant parameters. We suggest that the precursor is likely due to cosmic rays and discuss the efficiency of cosmic-ray acceleration at this position.