New Insights on 30 Dor B Revealed by High-Quality Multi-wavelength Observations

TL;DR

This study uses multi-wavelength observations to reveal the complex structure, multiple supernova events, and varied interstellar environments of the supernova remnant 30 Dor B, providing new insights into its evolution.

Contribution

It presents high-resolution multi-wavelength data that uncover the distinct zones and multiple supernova events in 30 Dor B, advancing understanding of its complex interstellar environment.

Findings

30 Dor B contains three zones with different X-ray brightness and kinematics.

The X-ray shell expansion velocity is estimated at ~4000 km/s, indicating recent supernova activity.

The faint diffuse X-ray halo may be from older supernova remnants.

Abstract

The supernova remnant (SNR) 30 Dor B is associated with the \ion{H}{2} region ionized by the OB association LH99. The complex interstellar environment has made it difficult to study the physical structure of this SNR. We have used Hubble Space Telescope H$\alpha$ images to identify SNR shocks and deep Chandra X-ray observations to detect faint diffuse emission. We find that 30 Dor B hosts three zones with very different X-ray surface brightnesses and nebular kinematics that are characteristic of SNRs in different interstellar environments and/or evolutionary stages. The ASKAP 888 MHz map of 30 Dor B shows counterparts to all X-ray emission features except the faint halo. The ASKAP 888 MHz and 1420 MHz observations are used to produce a spectral index map, but its interpretation is complicated by the background thermal emission and the pulsar PSR J0537$-$6910's flat spectral index. The stellar population in the vicinity of 30 Dor B indicates a continuous star formation in the past 8--10 Myr. The observed very massive stars in LH99 cannot be coeval with the progenitor of 30 Dor B's pulsar. Adopting the pulsar's spin-down timescale, 5000 yr, as the age of the SNR, the X-ray shell would be expanding at $\sim$4000 km\,s$^{-1}$ and the post-shock temperature would be 1--2 orders of magnitude higher than that indicated by the X-ray spectra. Thus, the bright central region of 30 Dor B and the X-ray shell requires two separate SN events, and the faint diffuse X-ray halo perhaps other older SN events.