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Freshly formed dust in the Cassiopeia A supernova remnant as revealed by the Spitzer space telescope

Rho, J. and Kozasa, T. and Reach, W. T. and Smith, J. D. and Rudnick, L. and DeLaney, T. and Ennis, J. A. and Gomez, H. and Tappe, A. (2008) Freshly formed dust in the Cassiopeia A supernova remnant as revealed by the Spitzer space telescope. Astrophysical Journal, 673 (1). pp. 271-282. ISSN 0004-637X. doi:10.1086/523835.

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We performed Spitzer Infrared Spectrograph mapping observations covering nearly the entire extent of the Cassiopeia A supernova remnant (SNR), producing mid-infrared (5.5-35 μm) spectra every 5"-10". Gas lines of Ar, Ne, O, Si, S, and Fe, and dust continua were strong for most positions. We identify three distinct ejecta dust populations based on their continuum shapes. The dominant dust continuum shape exhibits a strong peak at 21 μm. A line-free map of 21 μm peak dust made from the 19-23 μm range closely resembles the [Ar II], [O IV], and [Ne II] ejecta-line maps, implying that dust is freshly formed in the ejecta. Spectral fitting implies the presence of SiO2, Mg protosilicates, and FeO grains in these regions. The second dust type exhibits a rising continuum up to 21 μm and then flattens thereafter. This "weak 21 μm" dust is likely composed of Al2O3 and C grains. The third dust continuum shape is featureless with a gently rising spectrum and is likely composed of MgSiO3 and either Al2O3 or Fe grains. Using the least massive composition for each of the three dust classes yields a total mass of 0.020 M⊙. Using the most massive composition yields a total mass of 0.054 M⊙. The primary uncertainty in the total dust mass stems from the selection of the dust composition necessary for fitting the featureless dust as well as 70 μm flux. The freshly formed dust mass derived from Cas A is sufficient from SNe to explain the lower limit on the dust masses in high-redshift galaxies.

Item Type:Article
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URLURL TypeDescription
Rho, J.0000-0003-3643-839X
Reach, W. T.0000-0001-8362-4094
Smith, J. D.0000-0003-1545-5078
Additional Information:© 2008 The American Astronomical Society. Received 2007 March 20; accepted 2007 September 4. J. R. thanks U. Hwang for helpful discussion of X-ray emission of Cas A. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contract 1407. Partial support for this work was provided by NASA through an GO award issued by JPL/Caltech.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Subject Keywords:dust, extinction; supernovae : general; supernova remnants
Issue or Number:1
Record Number:CaltechAUTHORS:20090428-133336684
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Official Citation:Freshly Formed Dust in the Cassiopeia A Supernova Remnant as Revealed by the Spitzer Space Telescope J. Rho, T. Kozasa, W. T. Reach, J. D. Smith, L. Rudnick, T. DeLaney, J. A. Ennis, H. Gomez, and A. Tappe 2008 ApJ 673 271-282 doi: 10.1086/523835
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14102
Deposited By: Tony Diaz
Deposited On:10 Aug 2009 21:03
Last Modified:08 Nov 2021 22:43

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