Spitzer observations of the N157B supernova remnant and its surroundings

Free access article

Issue		A&A Volume 500, Number 2, June III 2009


Page(s)		807 - 815
Section		Interstellar and circumstellar matter
DOI		http://dx.doi.org/10.1051/0004-6361/200809849
Published online		01 April 2009

A&A 500, 807-815 (2009)
DOI: 10.1051/0004-6361/200809849

Spitzer observations of the N157B supernova remnant and its surroundings

E. R. Micelotta, B. R. Brandl, and F. P. Israel

Sterrewacht Leiden, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
e-mail: micelot@strw.leidenuniv.nl

Received 26 March 2008 / Accepted 16 February 2009

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 LH 99.
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 H $\alpha$ emission from the cloud. This implies that the supernova progenitor cannot have been more massive than about 25 $M_{\odot}$ .

Key words: ISM: supernova remnants -- ISM: individual objects: N157B -- galaxies: individual: LMC -- H II regions -- dust, extinction

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