Astronomy and Astrophysics – Astronomy
Scientific paper
May 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011iaus..280p.275n&link_type=abstract
The Molecular Universe, Posters from the proceedings of the 280th Symposium of the International Astronomical Union held in Tole
Astronomy and Astrophysics
Astronomy
Scientific paper
Near-infrared molecular hydrogen line ratios have often been used as a tool to diagnose physical properties of various astronomical objects. Recent high spectral resolution and high sensitivity spectrometers have made it possible to detect emission lines of molecular hydrogen in protoplanetary disks. In this work we have observed the 2-1 S(1)/1-0 S(1) H2 line ratios towards T Tauri stars to diagnose the H2 excitation mechanisms and the evolutionary status of dust grains in protoplanetary disks. Using Subaru/IRCS+AO188, we observed the 1-0 S(1), 1-0 S(0), and 2-1 S(1) lines simultaneously with high sensitivity and high spectral resolution. As a result, we have succeeded in measuring an upper limit of 0.14 for the 2-1 S(1)/1-0 S(1)line ratio. In order to reproduce the observations, our model calculations suggest that the gas temperature in the disk surface should be high. The implication is that there must exist a significant population of small dust grains which heat the gas via the photoelectric effect. Our numerical calculation of dust evolution shows that radial migration of dust particles coupled with viscously accreting gas helps to increase the mass of dust grains in the inner disk, resulting in more favorable conditions for planetesimal formation.
Aikawa Yuri
Bary Jeff
Itoh Yusuke
Millar Terry
Nakagawa Yasuhiro
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