Spitzer Space Telescope - General Observer Proposal #60101


Light Echoes of Historical Galactic Supernovae

Principal Investigator: Richard Arendt
           Institution: University of Maryland, Baltimore County

     Technical Contact: Richard Arendt, University of Maryland, Baltimore County

Co-Investigators: 
Jeonghee Rho, Spitzer Science Center                                  
Eli Dwek, NASA/GSFC                                                   

Science Category: ISM 
 Observing Modes: IRAC Post-Cryo Mapping
  Hours Approved: 26.6 

Abstract:
Spitzer's serendipitous discovery of light echoes from the supernovae (SN) that
gave birth to the Cas A supernova remnant (SNR) shows that we have to
opportunity to re-observe historical Galactic supernovae. Optical spectra of
these echoes have shown that the Cas A SN was of Type IIb. Similarly, Tycho's SN
has been spectroscopically established to be of Type Ia. The Cas A light echoes
are the only ones seen by Spitzer to date. However, this is because existing
observations of other young galactic SNRs have only included a single epoch of
observations (insufficient to reveal the highly transitory echoes), and have
only covered small fields in the immediate vicinity of the SNRs. We proposed to
obtain wide field (>0.5 degree) observations of the 7 youngest Galactic SNe,
having ages up to ~1000 yr. Where available, prior epoch observations will allow
definitive identification of light echoes. If the Cas A echoes are
representative, we can also identify echo candidates via their distinctive
4.5/3.6 micron colors. Variations (or lack thereof) in these colors as a
function of SN age and SN type, will allow us to place constraints on the
emission mechanism of the echoes (absorption and re-radiation vs. scattering).
Low extinction at 3.6 and 4.5 microns, means that Spitzer can located echoes of
distant SNe which may be too highly attenuated to observe at shorter
wavelengths.