Journal Article

JCMT 12CO J = 3–2 Observations of Tycho’s Supernova Remnant: Constraints on the Environmental Gas Properties

Zhou, Ping, Sano, Hidetoshi, Safi-Harb, Samar, Huang, Yu, Tu, Tian-Yu, Chen, Yang, Bo, Sen-Di, Zhang, Zhi-Yu

2026

Overview

Recent observations suggest that Tycho’s supernova remnant (SNR; SN 1572) is expanding into a cavity wall of molecular clouds (MCs), which decelerate the SNR and influence its multiwavelength morphology. To constrain the physical properties of environmental MCs and search for heated gas, we perform a James Clerk Maxwell Telescope 12CO J = 3–2 observation and compare with previous 12CO J = 2–1, 12CO J = 1–0 and 13CO J = 1–0 data. We present the 12CO J = 3–2 map toward Tycho and show that the 12CO J = 3–2 spatial distribution and line profiles are similar to those of the lower-J CO lines. By comparing the multiple transitions of CO and the RADEX models, we constrain the physical properties of molecular gas surrounding Tycho: the northern cloud has a molecular column density of N(H2) = 0.5–4.5 × 1022 cm−2, while other regions have N(H2) = 0.2–3.9 × 1021 cm−2; the kinetic temperatures Tk of these clouds are in the range of 9–22 K, and the volume densities n(H2) are 20–700 cm−3. We also discuss the difficulty in finding hot molecular gas shocked by such a young SNR. We estimate that the shocked molecular layer can be as thin as 0.003 pc, corresponding to 0 .″ 2 at the distance of 2.5 kpc, which is 2 orders of magnitude smaller than the angular resolution of current CO observations. Therefore, our molecular observations are largely insensitive to the thin shocked gas layer; instead, they detect the environmental gas.

• Publisher: IOP Publishing
• Subject: Angular resolution / Molecular clouds / Molecular gases / Physical properties / Spatial distribution / Supernova / Supernova remnants