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Session 92 - Very Young Stars, T-Tauri Stars, H-H Objects.
Oral session, Friday, January 09

[92.03] The Spectral Index of the Dust Emission at 1 cm Wavelength

L. G. Mundy, L. W. Looney (U. Maryland), J. Carlstrom (Univ. of Chicago), M. Joy (NASA MSFC)

We present observations of the \lambda=1 cm continuum emission from ten young stellar systems with the BIMA array. Accurate measurements of the flux at \lambda=1.1 cm and \lambda=0.9 cm were possible for eight of the systems. The power-law spectral index of the emission from these systems varies from 0.4 for L1551 IRS5 to 2.6 for NGC 1333 IRAS4. In the former case, the emission is dominated by free-free radiation; in the later, the emission arises mainly from dust. One of the target sources with detectable emission is the close binary system GG Tau which is known to have a circumbinary disk.

Combining our data with previous measurements at other wavelengths, and with modeling of the disks and envelopes, we estimate the relative contributions from free-free and dust emissions and derive estimates of the spectral index of the dust emission in several systems. The data allow us to look at the spectral index of the dust emissivity at \lambda=1 cm and to extend our analysis to other wavelengths to estimate the spectral index between 1 cm, 2.7 mm and 1.3 mm.

The wavelength dependence of the dust emissivity provides a rough measure of mean grain sizes in these systems, hence a view into the dust coagulation process and the building of planetesimals.

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Program listing for Friday