NOAO >   Observing Info >   Approved Programs >   2011B-0197

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Proposal Information for 2011B-0197


PI: Robert Fesen, Dartmouth College, robert.fesen@dartmouth.edu
Address: Physics Department, 6127 Wilder Laboratory, Lebanon, NH 03755, USA

CoI: Dan Milisavljevic, Dartmouth College

Title: Mapping the Unshocked Interior Ejecta in the Cas A Supernova Remnant

Abstract: Cassiopeia A (Cas A) provides perhaps our best look at the explosion dynamics of a core-collapse supernova (CCSN). Exploratory spectra of Cas A obtained by us in 2010 showed that the KPNO 4m + MARS' exceptional far-red throughput is capable of detecting the remnant's faint interior [S III] 9069,9531 and [Fe II] 8617 line emissions, thereby allowing one to study the structure of the whole remnant, from its core to the outer layers. Our November 2010 HST/WFC3 [S III] images show that this faint interior emission, which is presumably photoionized by UV and X-ray flux from Cas A's bright main shell, is extensive and seemingly highly structured. Here we request eight (8) nights using the KPNO 4m + MARS to obtain far-red spectroscopy of Cas A in order to survey the remnant's interior unshocked S- and Fe-rich ejecta...an observation that seemed impossible just a year ago. The proposed observations, when combined with our extensive set of spectra of Cas A's bright outer ejecta, will yield the first complete map of a CCSN - from its center to the outer, bright reverse-shock heated layers. These observations will give us an extraordinarily rare look at the geometry of a remnant's inner volume of expanding cloud of S- and Fe-rich debris unmodified by reverse shock instabilities, thus offering a unique and powerful test of high-mass progenitor supernova explosion models.


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