The Silicate-Extinction Relationship as a Tracer of Evolution of Dust in Dense Cores

Details The Silicate-Extinction Relationship as a Tracer of Evolution of Dust in Dense Cores The Silicate-Extinction Relationship as a Tracer of Evolution of Dust in Dense Cores

May 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007sptz.prop40928h&link_type=abstract

Spitzer Proposal ID #40928

Computer Science

Scientific paper

Spitzer IRS spectra of stars background to the dense regions of cores have been used to determine the relationship between the silicate optical depth and extinction. We have found that the dust within these cores is best characterized by Av/tau(silicate) ~ 50 +/- 10, significantly different from previous studies of dust in the diffuse ISM, which yield Av/tau(silicate) ~ 18.5 +/- 2. This result suggests that significant grain growth has occurred in these cores and the dust composition is different than that in the diffuse ISM. One starless core has been well probed with IRS spectra of background stars, yielding Av/tau(silicate) ~ 30 +/- 5. Our findings suggest that real core-to-core variations may exist. In most cases, with only a couple lines of sight probed in each core, the data are not sufficient to characterize these variations. We propose to obtain IRS spectra of a carefully selected sample of bright background stars probing a wide range of extinction in each core, for a set of cores, in order to better characterize this silicate-extinction relation and any core-to-core variations. This relationship appears to be one of the most sensitive tracers of grain properties, and with additional constraints from supplementary 1-1000 micron observations, we investigate implications for grain growth and evolution in these dense environments.

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