SPEAR Far Ultraviolet Spectral Images of the Cygnus Loop
Abstract
We present far-ultraviolet (FUV) spectral images, measured at C IV 1550, He II 1640, Si IV+O IV] 1400, and O III] 1664, of the entire Cygnus Loop, observed with the Spectroscopy of Plasma Evolution from Astrophysical Radiation (SPEAR) instrument, also known as FIMS. The spatial distribution of FUV emission generally corresponds with a limb-brightened shell, and is similar to optical, radio and X-ray images. The features found in the present work include a ``carrot'', diffuse interior, and breakout features, which have not been seen in previous FUV studies. Shock velocities of 140-160 km/s is found from a line ratio of O IV] to O III], which is insensitive not only to resonance scattering but also to elemental abundance. The estimated velocity indicates that the fast shocks are widespread across the remnant. By comparing various line ratios with steady-state shock models, it is also shown that the resonance scattering is widespread.
Keywords
Cite
@article{arxiv.astro-ph/0601615,
title = {SPEAR Far Ultraviolet Spectral Images of the Cygnus Loop},
author = {Kwang-Il Seon and Wonyong Han and Uk-Won Nam and Jang-Hyun Park and Jerry Edelstein and Eric J. Korpela and Ravi Sankrit and Kyoung-Wook Min and Kwangsun Ryu and Il-Joong Kim},
journal= {arXiv preprint arXiv:astro-ph/0601615},
year = {2009}
}
Comments
13 pages, 3 figures, 1 table, accepted for publication in ApJL