A Spitzer Space Telescope study of Sn 2002hh: An infrared echo from a Type IIP supernova
We present late-time (590-994 days) mid-IR photometry of the normal but highly reddened Type IIP supernova SN 2002hh. Bright, cool, slowly fading emission is detected from the direction of the supernova. Most of this flux appears not to be driven by the supernova event but instead probably originates in a cool, obscured star formation region or molecular cloud along the line of sight. We also show, however, that the declining component of the flux is consistent with an SN-powered IR echo from a dusty progenitor CSM. Mid-IR emission could also be coming from newly condensed dust and/or an ejecta/CSM impact, but their contributions are likely to be small. For the case of a CSM-IR echo, we infer a dust mass of as little as 0.036 M☉ with a corresponding CSM mass of 3.6(0.01/ r(dg))M☉, where rdg is the dust-to-gas mass ratio. Such a CSM would have resulted from episodic mass loss whose rate declined significantly about 28,000 years ago. Alternatively, an IR echo from a surrounding, dense, dusty molecular cloud might also have been responsible for the fading component. Either way, this is the first time that an IR echo has been clearly identified in a Type IIP supernova. We find no evidence for or against the proposal that Type IIP supernovae produce large amounts of dust via grain condensation in the ejecta. However, within the CSM-IR echo scenario, the mass of dust derived implies that the progenitors of the most common of core-collapse supernovae may make an important contribution to the universal dust content.
© 2006 American Astronomical Society. Received 2006 April 11; accepted 2006 May 22. We thank Christophe Alard for helpful discussions, Steve Smartt for his progenitor mass limit estimate, and Mike Barlow for a computer readable version of the 11.2 μm image of the SN 2002hh field. C.L.G. was supported in part by PPARC grant PPA/G/S /2003/00040. R.K. was supported in part by EU RTN grant HPRN-CT-2002-00303. S.M. acknowledges financial support from the European Science Foundation. M.P. is supported by PPARC grant PPA/G/S/2001/00512. J.C.W. is supported in part by NSF grant AST 04-06740. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech.
Published - MEIapj06.pdf