DUST EVOLUTION IN PROTOPLANETARY DISKS AROUND HERBIG Ae/Be STARS-THE SPITZER VIEW

Journal Article · Mon Sep 20 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/721/1/431· OSTI ID:21464839

Juhasz, A; Bouwman, J; Henning, Th ^[1]; Acke, B; Van den Ancker, M E ^[2]; Meeus, G; Min, M ^[3]; Dominik, C ^[4]

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1. Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, 69117, Heidelberg D69117 (Germany)
2. European Southern Observatory, Karl Schwarzschild Strasse 2, 85748 Garching bei Muenchen (Germany)
3. Astrophysical Institute Potsdam, An der Sternwarte 16, 14482 Potsdam (Germany)
4. Astronomical Institute, University of Amsterdam, Kruislaan 403, 1098 AJ Amsterdam (Netherlands)

In this paper, we present mid-infrared spectra of a comprehensive set of Herbig Ae/Be stars observed with the Spitzer Space Telescope. The signal-to-noise ratio of these spectra is very high, ranging between about a hundred and several hundreds. During the analysis of these data we tested the validity of standardized protoplanetary dust models and studied grain growth and crystal formation. On the basis of the analyzed spectra, the major constituents of protoplanetary dust around Herbig Ae/Be stars are amorphous silicates with olivine and pyroxene stoichiometry, crystalline forsterite, and enstatite and silica. No other solid-state features, indicating other abundant dust species, are present in the Spitzer spectra. Deviations of the synthetic spectra from the observations are most likely related to grain shape effects and uncertainties in the iron content of the dust grains. Our analysis revealed that larger grains are more abundant in the disk atmosphere of flatter disks than in that of flared disks, indicating that grain growth and sedimentation decrease the disk flaring. We did not find, however, correlations between the value of crystallinity and any of the investigated system parameters. Our analysis shows that enstatite is more concentrated toward the warm inner disk than forsterite, in contrast to predictions of equilibrium condensation models. None of the three crystal formation mechanisms proposed so far can alone explain all our findings. It is very likely that all three play at least some role in the formation of crystalline silicates.

• OSTI ID: 21464839
• Journal Information: Astrophysical Journal, Vol. 721, Issue 1; Other Information: DOI: 10.1088/0004-637X/721/1/431; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
CRYSTALS
DUSTS
ENSTATITE
FLARING
GRAIN GROWTH
INFRARED SPECTRA
IRON
OLIVINE
PROTOPLANETS
SIGNAL-TO-NOISE RATIO
SILICA
STAR EVOLUTION
STARS
STELLAR ATMOSPHERES
STOICHIOMETRY
TELESCOPES
ATMOSPHERES
DIMENSIONLESS NUMBERS
ELEMENTS
EVOLUTION
METALS
MINERALS
OXIDE MINERALS
SILICATE MINERALS
SPECTRA
TRANSITION ELEMENTS