Home News About Us Contact Contributors Disclaimer Privacy Policy Help FAQ

Quick Search
My eDoc
Session History
Support Wiki
Direct access to
document ID:

          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 358702.0, MPI für Astronomie / Publikationen_mpia
Probing protoplanetary disks with silicate emission: Where is the silicate emission zone?
Authors:Kessler-Silacci, J. E.; Dullemond, C. P.; Augereau, J. C.; Merín, B.; Geers, V. C.; van Dishoeck, E. F.; Evans, N. J.; Blake, G. A.; Brown, J.
Date of Publication (YYYY-MM-DD):2007
Title of Journal:The Astrophysical Journal
Start Page:680
End Page:684
Audience:Not Specified
Abstract / Description:Recent results indicate that the grain size and crystallinity inferred from observations of silicate features may be correlated with the spectral type of the central star and/or disk geometry. In this paper, we show that grain size, as probed by the 10 mum silicate feature peak-to-continuum and 11.3 to 9.8 mum flux ratios, is inversely proportional to logL*. These trends can be understood using a simple two-layer disk model for passive irradiated flaring disks, CGPLUS. We find that the radius, R10, of the 10 mum silicate emission zone in the disk goes as (L*/Lsolar)0.56, with slight variations depending on disk geometry (flaring angle and inner disk radius). The observed correlations, combined with simulated emission spectra of olivine and pyroxene mixtures, imply a dependence of grain size on luminosity. Combined with the fact that R10 is smaller for less luminous stars, this implies that the apparent grain size of the emitting dust is larger for low-luminosity sources. In contrast, our models suggest that the crystallinity is only marginally affected, because for increasing luminosity, the zone for thermal annealing (assumed to be at T>800 K) is enlarged by roughly the same factor as the silicate emission zone. The observed crystallinity is affected by disk geometry, however, with increased crystallinity in flat disks. The apparent crystallinity may also increase with grain growth due to a corresponding increase in contrast between crystalline and amorphous silicate emission bands.
Free Keywords:Stars: Circumstellar Matter; Infrared: ISM; ISM: Lines and Bands; Stars: Planetary Systems: Protoplanetary Disks; Stars: Formation; Stars: Pre-Main-Sequence
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
The scope and number of records on eDoc is subject to the collection policies defined by each institute - see "info" button in the collection browse view.