Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Freshly Formed Dust in the Cassiopeia A Supernova Remnant as Revealed by
  the Spitzer Space Telescope   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 micron) 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 micron. A line-free map of 21
micron-peak dust made from the 19-23 micron 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 micron and then flattens thereafter. This ``weak 21
micron'' 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 0.02
Msun. Using the most-massive composition yields a total mass of 0.054 Msun. 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 micron
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.

17
The categories of this paper are: q-fin
7
The categories of this paper are: hep-th
23
The categories of this paper are: solv-int
25
The categories of this paper are: patt-sol
0
The categories of this paper are: hep-ph
34
The categories of this paper are: chem-ph
19
The categories of this paper are: eess
22
The categories of this paper are: chao-dyn
28
The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
8
The categories of this paper are: hep-ex
32
The categories of this paper are: atom-ph
1
The categories of this paper are: cs
14
The categories of this paper are: math-ph
33
The categories of this paper are: plasm-ph
4
The categories of this paper are: cond-mat