A Spatially Resolved Study of the Cold Dust in NGC 205
2008
We present IRAC and MIPS observations of NGC 205, the dwarf
elliptical companion of M31, obtained with the Spitzer Space Telescope. The
extended dust emission is spatially concentrated in three main emission regions.
Based on our mid-to-far infrared flux density measurements alone, we derive a
total dust mass estimate of the order of 3.2 × 10^4 M_⊙, at a temperature of ~20K.
The gas mass associated with this component matches the predicted mass returned
by the dying stars from the last burst of star formation in NGC 205
(~0.5 Gyr ago). Analysis of the Spitzer data combined with previous 1.1mm
observations over a small central region or “Core” (18" diameter), suggest the
presence of very cold (T ~ 12K) dust and a dust mass 16 times higher than is estimated
from the Spitzer measurements alone. Assuming a gas to dust mass ratio
of 100, these two datasets, i.e. with and without the millimeter observations,
suggest a total gas mass range of 3.2 × 10^6 to 5 × 10^7 M_⊙.
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