Gas Disk Sizes from CO Line Observations: A Test of Angular Momentum Evolution

The Astrophysical Journal, vol. 931, pp. 6

Abstract

Abstract The size of a disk encodes important information about its evolution. Combining new Submillimeter Array observations with archival Atacama Large Millimeter/submillimeter Array data, we analyze millimeter continuum and CO emission line sizes for a sample of 44 protoplanetary disks around stars with masses of 0.15–2 M ⊙ in several nearby star-forming regions. Sizes measured from 12CO line emission span from 50 to 1000 au. This range could be explained by viscous evolution models with different α values (mostly of 10−4–10−3) and/or a spread of initial conditions. The CO sizes for most disks are also consistent with MHD wind models that directly remove disk angular momentum, but very large initial disk sizes would be required to account for the very extended CO disks in the sample. As no CO size evolution is observed across stellar ages of 0.5–20 Myr in this sample, determining the dominant mechanism of disk evolution will require a more complete sample for both younger and more evolved systems. We find that the CO emission is universally more extended than the continuum emission by an average factor of 2.9 ± 1.2. The ratio of the CO to continuum sizes does not show any trend with stellar mass, millimeter continuum luminosity, or the properties of substructures. The GO Tau disk has the most extended CO emission in this sample, with an extreme CO-to-continuum size ratio of 7.6. Seven additional disks in the sample show high size ratios (≳4) that we interpret as clear signs of substantial radial drift.

Authors 10

1. Feng Long

   Center for Astrophysics Harvard & Smithsonian

   Affiliation as printed

   Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA

2. Sean M. Andrews

   Center for Astrophysics Harvard & Smithsonian

   Affiliation as printed

   Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA; feng.long@cfa.harvard.edu

   Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA

3. Giovanni P. Rosotti Aachen Leiden Observatory

   Leiden University · University of Leicester · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands

   School of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK

4. D. Harsono

   Institute of Astronomy and Astrophysics, Academia Sinica · National Tsing Hua University · Academia Sinica

   Affiliation as printed

   Institute of Astronomy and Astrophysics, Academia Sinica, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan

   Institute of Astronomy, Department of Physics, National Tsing Hua University, Hsinchu, Taiwan

5. Paola Pinilla

   Max Planck Institute for Astronomy · University College London

   Affiliation as printed

   Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg, Germany

   Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK

6. David J. Wilner

   Center for Astrophysics Harvard & Smithsonian

   Affiliation as printed

   Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA; feng.long@cfa.harvard.edu

   Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA

7. Karin I. Öberg

   Center for Astrophysics Harvard & Smithsonian

   Affiliation as printed

   Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA; feng.long@cfa.harvard.edu

   Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA

8. Richard D. Teague

   Center for Astrophysics Harvard & Smithsonian

   Affiliation as printed

   Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA; feng.long@cfa.harvard.edu

   Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA

9. Leon Trapman

   University of Wisconsin–Madison

   Affiliation as printed

   Department of Astronomy, University of Wisconsin–Madison, 475 N. Charter Street, Madison, WI 53706, USA

10. Benoît Tabone

    Centre National de la Recherche Scientifique · Université Paris-Saclay · Institut d'Astrophysique Spatiale

    Affiliation as printed

    Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale, F-91405 Orsay, France

    Université Paris-Saclay, CNRS, Institut d'Astrophysique Spatiale, F-91405 Orsay, France