Spectroscopy of the Cas A Jet

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Session 83 -- Supernova Remnants
Display presentation, Friday, January 14, 9:30-6:45, Salons I/II Room (Crystal Gateway)

[83.06] Spectroscopy of the Cas A Jet

R.A. Fesen \& K.S. Gunderson (Dartmouth)

We present KPNO 4m PF images and Cryocam long slit spectra of the NE jet of the Cas A supernova remnant. Analysis of these data provide accurate radial velocity, space velocity, and relative line emission strength information for over 80 knots. The spectra sampled the jet's three main `sprays' of filaments, representing the bulk of the jet's optical emission, providing the first detailed kinematic and chemical composition picture of the jet. The jet's structure is quite extensive with [S~II] $\lambda\lambda$6716,6731 ejecta knots extending out to 12000 km s$^{-1}$ in expansion velocity -- nearly twice that of the remnant's main shell of ejecta. The knots' [S~II]/[O~I] ratio appears to increase somewhat with increasing radial distance, suggesting a possible S/O abundance gradient along the length of the jet. About a dozen new `mixed ejecta knots' showing H, [N~II], [O~I], and [S~II] emissions are identified, implying that mixing of the star's original inner and outer layers was not rare and limited to just the one peculiar knot detected previously. Both the jet's fast moving hydrogen rich knots (FMFs) and these new mixed ejecta knots lie within a surprisingly narrow velocity range between 7000 and 9500 km s$^{-1}$. The jet's kinematics and structure indicate an asymmetric explosion which may have relevance in the asymmetrical line emissions sometimes observed in extragalactic SNe.

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