Transition disks are a distinguished group of few Myr-old systems caught in the phase of dispersing their inner dust disk. Three different processes have been proposed to explain this inside-out clearing: grain growth, photoevaporation driven by the central star, and dynamical clearing by a forming giant planet. Which of these processes lead to a transition disk? Distinguishing between them requires the combined knowledge of stellar accretion rates and disk masses. We propose here to use 43.8 hours of PACS spectroscopy to detect the OI 63 micron emission line from a sample of 21 well-known transition disks with measured mass accretion rates. We will use this line, in combination with ancillary CO millimeter lines, to measure their gas disk mass. Because gas dominates the mass of protoplanetary disks our approach and choice of lines will enable us to trace the bulk of the disk mass that resides beyond tens of AU from young stars. Our program will quadruple the number of transition disks currently observed with Herschel in this setting and for which disk masses can be measured. We will then place the transition and the ~100 classical/non-transition disks of similar age (from the Herschel KP Gas in Protoplanetary Systems) in the mass accretion rate-disk mass diagram with two main goals: 1) reveal which gaps have been created by grain growth, photoevaporation, or giant planet formation and 2) from the statistics, determine the main disk dispersal mechanism leading to a transition disk.
Publication
Herschel-PACS observations of far-IR lines in young stellar objects. I. OI and H2O at 63 mm | Riviere-Marichalar P. et al. | Astronomy & Astrophysics Volume 594 id.A59 25 pp. | 594 | 10.1051/0004-6361/201527829 | 2016A&A...594A..59R | http://adsabs.harvard.edu/abs/2016A%26A...594A..59R
Herschel Evidence for Disk Flattening or Gas Depletion in Transitional Disks | Keane J. T. et al. | The Astrophysical Journal Volume 787 Issue 2 article id. 153 24 pp. (2014). | 787 | 10.1088/0004-637X/787/2/153 | 2014ApJ...787..153K | http://adsabs.harvard.edu/abs/2014ApJ...787..153K
Instrument
PACS_PacsLineSpec_point
Temporal Coverage
2011-09-27T23:39:48Z/2012-09-04T10:33:22Z
Version
SPG v14.2.0
Mission Description
Herschel was launched on 14 May 2009! It is the fourth cornerstone mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.
European Space Agency, pascucci et al., 2013, 'Understanding the Origin of Transition Disks via Disk Mass Measurements', SPG v14.2.0, European Space Agency, https://doi.org/10.5270/esa-14k7up7
