Recent ALMA images of HL Tau show gaps in the dusty disk that may be caused by planetary bodies. Given the young age of this system, if confirmed, this finding would imply very short timescales for planet formation, probably in a gravitationally unstable disk. To test this scenario, we searched for young planets by means of direct imaging in the L‧ band using the Large Binocular Telescope Interferometer mid-infrared camera. At the location of two prominent dips in the dust distribution at ˜70 AU (˜0.″5) from the central star, we reach a contrast level of ˜7.5 mag. We did not detect any point sources at the location of the rings. Using evolutionary models we derive upper limits of ˜10-15 MJup at ≤0.5-1 Ma for the possible planets. With these sensitivity limits we should have been able to detect companions sufficiently massive to open full gaps in the disk. The structures detected at millimeter wavelengths could be gaps in the distributions of large grains on the disk midplane caused by planets not massive enough to fully open the gaps. Future ALMA observations of the molecular gas density profile and kinematics as well as higher contrast infrared observations may be able to provide a definitive answer.
HUNTING for PLANETS in the HL TAU DISK / Testi, L.; Skemer, A.; Henning, Th.; Bailey, V.; Defrére, D.; Hinz, Ph.; Leisenring, J.; Vaz, A.; Esposito, S.; Fontana, A.; Marconi, A.; Skrutskie, M.; Veillet, C.. - In: THE ASTROPHYSICAL JOURNAL LETTERS. - ISSN 2041-8205. - ELETTRONICO. - 812:(2015), pp. L38-0. [10.1088/2041-8205/812/2/L38]
HUNTING for PLANETS in the HL TAU DISK
MARCONI, ALESSANDRO;
2015
Abstract
Recent ALMA images of HL Tau show gaps in the dusty disk that may be caused by planetary bodies. Given the young age of this system, if confirmed, this finding would imply very short timescales for planet formation, probably in a gravitationally unstable disk. To test this scenario, we searched for young planets by means of direct imaging in the L‧ band using the Large Binocular Telescope Interferometer mid-infrared camera. At the location of two prominent dips in the dust distribution at ˜70 AU (˜0.″5) from the central star, we reach a contrast level of ˜7.5 mag. We did not detect any point sources at the location of the rings. Using evolutionary models we derive upper limits of ˜10-15 MJup at ≤0.5-1 Ma for the possible planets. With these sensitivity limits we should have been able to detect companions sufficiently massive to open full gaps in the disk. The structures detected at millimeter wavelengths could be gaps in the distributions of large grains on the disk midplane caused by planets not massive enough to fully open the gaps. Future ALMA observations of the molecular gas density profile and kinematics as well as higher contrast infrared observations may be able to provide a definitive answer.
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