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, A. Tappe

    Research output: Contribution to journalArticlepeer-review

    160 Scopus citations

    Abstract

    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 Al 2O3 and C grains. The third dust continuum shape is featureless with a gently rising spectrum and is likely composed of MgSiO 3 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.

    Original languageEnglish (US)
    Pages (from-to)271-282
    Number of pages12
    JournalAstrophysical Journal
    Volume673
    Issue number1
    DOIs
    StatePublished - Jan 20 2008

    Keywords

    • Dust, extinction
    • Supernova remnants
    • Supernovae: general

    Fingerprint Dive into the research topics of 'Freshly formed dust in the cassiopeia a supernova remnant as revealed by the Spitzer space telescope'. Together they form a unique fingerprint.

    Cite this