Abstract
view Abstract Citations (52) References (41) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Reddening Measurements and Physical Conditions for Cassiopeia A from Optical and Near-Infrared Spectra Hurford, Alan P. ; Fesen, Robert A. Abstract Spectra of five fast-moving knots (FMKs) and two quasi-stationary flocculi (QSFs) in Cas A, covering the wavelength regions 4000-10,500 Å and 4300-6800 Å, respectively, are presented. FMK extinction values derived from observed [S ii] auroral/transauroral line ratios indicate an optical reddening range of Av ≃ 4.6-5.4 mag. Estimates of QSF extinctions obtained assuming an intrinsic Balmer ratio of Hα/Hβ = 3.0 are larger, lying in the range Av ≃ 5.3-6.2 mag. While these FMK and QSF reddening measurements are higher than Searle's value of Av = 4.3 mag, they are consistent with the radio-inferred extinction values of Troland et al. for their various locations in Cas A. The FMK reddening values indicate Av variations of at least ≃0.5 mag, and possibly up to ≃1 mag in Cas A's bright northern and northeastern shell emission. The higher QSF reddening values may be due to line-of-sight extinction variations or collisionally excited Hα emission. Adopting a reddening value ≃1 mag larger than Searle's value brings the dereddened oxygen line ratios of Cas A FMKs into better agreement with other young, oxygen-rich remnants and the 150-200 km s-1 shock/ionization front models of Sutherland and Dopita. Spectra of a faint FMK exhibiting weak oxygen emission but strong forbidden and permitted calcium lines are also presented. This FMK may represent a rare clump of relatively unmixed material originating from a thin (≃0.05 to 0.10 Msun), silicon-rich zone in the Cas A progenitor. Publication: The Astrophysical Journal Pub Date: September 1996 DOI: 10.1086/177775 Bibcode: 1996ApJ...469..246H Keywords: ISM: INDIVIDUAL NAME: CASSIOPEIA A; ISM: SUPERNOVA REMNANTS; ISM: DUST; EXTINCTION; ISM: STRUCTURE full text sources ADS | data products SIMBAD (24)
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