Spitzer observations of the N157B supernova remnant and its surroundings

TL;DR

This study uses multiwavelength infrared, X-ray, optical, and radio data to analyze the environment of the N157B supernova remnant in the LMC, finding minimal impact of the SNR on surrounding molecular clouds and dust.

Contribution

It provides new infrared observations and spatially resolved spectroscopy to clarify the interaction between the supernova remnant and its environment.

Findings

The SNR has no infrared counterpart.

Infrared emission is dominated by a blister-type HII region.

The SNR does not currently affect the surrounding molecular cloud.

Abstract

(Aims): We study the LMC interstellar medium in the field of the nebula N157B, which contains a supernova remnant, an OB association, ionized gas, and high-density dusty filaments in close proximity. We investigate the relative importance of shock excitation by the SNR and photo-ionization by the OB stars, as well as possible interactions between the supernova remnant and its environment. (Methods): We apply multiwavelength mapping and photometry, along with spatially resolved infrared spectroscopy, to identifying the nature of the ISM using new infrared data from the Spitzer space observatory and X-ray, optical, and radio data from the literature. (Results): The N157B SNR has no infrared counterpart. Infrared emission from the region is dominated by the compact blister-type HII region associated with 2MASS J05375027-6911071 and excited by an O8-O9 star. This object is part of an extended infrared emission region that is associated with a molecular cloud. We find only weak emission from the shock-indicator [FeII], and both the excitation and the heating of the extended cloud are dominated by photo-ionization by the early O stars of LH99. (Conclusions): Any possible impact by the expanding SNR does not now affect the extended cloud of molecules and dust, despite the apparent overlap of SNR X-ray emission with infrared and Ha emission from the cloud. This implies that the supernova progenitor cannot have been more massive than about 25 solar masses.