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Dusty Blastwaves of Two Young LMC Supernova Remnants: Constraints on Postshock Compression | | Brian J. Williams
; Kazimierz J. Borkowski
; Stephen P. Reynolds
; Parviz Ghavamian
; John C. Raymond
; Knox S. Long
; William P. Blair
; Ravi Sankrit
; R. Chris Smith
; Sean Points
; P. Frank Winkler
; Sean P. Hendrick
; | | Date: |
6 Jan 2011 | | Abstract: | We present results from mid-IR spectroscopic observations of two young
supernova remnants (SNRs) in the Large Magellanic Cloud (LMC) done with the
{it Spitzer Space Telescope}. We imaged SNRs B0509-67.5 and B0519-69.0 with
{it Spitzer} in 2005, and follow-up spectroscopy presented here confirms the
presence of warm, shock heated dust, with no lines present in the spectrum. We
use model fits to {it Spitzer} IRS data to estimate the density of the
postshock gas. Both remnants show asymmetries in the infrared images, and we
interpret bright spots as places where the forward shock is running into
material that is several times denser than elsewhere. The densities we infer
for these objects depend on the grain omposition assumed, and we explore the
effects of differing grain porosity on the model fits. We also analyze archival
{it XMM-Newton} RGS spectroscopic data, where both SNRs show strong lines of
both Fe and Si, coming from ejecta, as well as strong O lines, which may come
from ejecta or shocked ambient medium. We use model fits to IRS spectra to
predict X-ray O line strengths for various grain models and values of the shock
compression ratio. For 0509-67.5, we find that compact (solid) grain models
require nearly all O lines in X-ray spectra to originate in reverse-shocked
ejecta. Porous dust grains would lower the strength of ejecta lines relative to
those arising in the shocked ambient medium. In 0519-69.0, we find significant
evidence for a higher than standard compression ratio of 12, implying efficient
cosmic-ray acceleration by the blast wave. A compact grain model is favored
over porous grain models. We find that the dust-to-gas mass ratio of the
ambient medium is significantly lower than what is expected in the ISM. | | Source: | arXiv, 1101.1250 | | Services: | Forum | Review | PDF | Favorites | |
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