Discovery of Shocked Molecular Clouds Associated with the Shell-type Supernova Remnant RX J0046.5−7308 in the Small Magellanic Cloud

Abstract

RX J0046.5−7308 is a shell-type supernova remnant (SNR) in the Small Magellanic Cloud (SMC). We carried out new 12 CO(J = 1-0, 3-2) observations toward the SNR using Mopra and the Atacama Submillimeter Telescope Experiment. We found eight molecular clouds (A-H) along the X-ray shell of the SNR. The typical cloud size and mass are ∼10-15 pc and ∼1000-3000 M ⊙ , respectively. The X-ray shell is slightly deformed and has the brightest peak in the southwestern shell where two molecular clouds A and B are located. The four molecular clouds A, B, F, and G have high intensity ratios of 12 CO(J = 3-2) / 12 CO(J = 1-0) > 1.2, which are not attributable to any identified internal infrared sources or high-mass stars. The Hi cavity and its expanding motion are found toward the SNR, which are likely created by strong stellar winds from a massive progenitor. We suggest that the molecular clouds A-D, F, and G, and Hi clouds within the wind-blown cavity at V LSR = 117.1-122.5 km s −1 are associated with the SNR. The X-ray spectroscopy reveals the dynamical age of 26000 +1000 −2000yr and the progenitor mass of 30 M ⊙ , which is also consistent with the proposed scenario. We determine physical conditions of the giant molecular cloud LIRS 36A using the large velocity gradient analysis with archival datasets of the Atacama Large Millimeter/submillimeter Array; the kinematic temperature is 72 +50 −37 K and the number density of molecular hydrogen is 1500 +600 −300 cm −3 . The next generation of γ-ray observations will allow us to study the pion-decay γ-rays from the molecular clouds in the SMC SNR.

ALMA CO Observations of the Mixed-Morphology Supernova Remnant W49B: Efficient Production of Recombining Plasma and Hadronic Gamma-rays via Shock-Cloud Interactions

“…In the present study, an expanding velocity ∆V is derived to be ∼6 km s −1 for the 10 km s −1 cloud; and ∼3 km s −1 for the 40 km s −1 cloud. These values are roughly consistent with other Galactic/Magellanic SNRs (e.g., Koo et al 1990;Koo & Heiles 1991;Sano et al 2017bSano et al , 2019cKuriki et al 2018).…”

Origin of the gamma-ray emission from supernova remnant HB9

“…In general, the expanding shell is thought to be formed by strong stellar winds from the progenitor of the SNR and the SNR shock is now likely interacting with the wind-wall (e.g. Sano et al 2017Sano et al , 2019b, which are walls of the stellar wind bubble formed in the ISM by swept up cold and warm gas, in neutral and ionised state (R. Boomsma, 2007). Therefore, accelerated CRs by the shock fronts of HB9 are mainly interacting with the inner wall of the stellar wind bubble.…”

Discovery of a Wind-Blown Bubble Associated with the Supernova Remnant G346.6-0.2: A Hint for the Origin of Recombining Plasma

“…It is noteworthy that the size of such a wind-blown bubble is expected to be consistent with that of the SNR shell because the shock propagation time inside the bubble is very short due to a much-lower density (e.g., Weaver et al 1977). Moreover, the expansion velocities of wind-blown bubbles were observationally derived to be ∼ 3-13 km s −1 in the several Galactic and Magellanic SNRs (e.g., Landecker et al 1989;Fukui et al 2012;Zhou et al 2016;Sano et al 2017Sano et al , 2018Sano et al , 2019Kuriki et al 2018). In the case of G346.6−0.2, the wind-blown bubble shows the expanding velocity of ∼ 10 km s −1 and the size of which is roughly consistent with that of the radio continuum shell (see Figure 3).…”