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

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posted on 2022-06-16, 08:21 authored by Feng Long, Sean M Andrews, Giovanni Rosotti, Daniel Harsono, Paola Pinilla, David J Wilner, Karin I Öberg, Richard Teague, Leon Trapman, Benoît Tabone

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.

History

Citation

2022 ApJ 931 6

Author affiliation

Department of Physics and Astronomy, University of Leicester

Version

  • VoR (Version of Record)

Published in

The Astrophysical Journal

Volume

931

Issue

1

Publisher

American Astronomical Society

issn

0004-637X

eissn

1538-4357

Acceptance date

2022-03-30

Copyright date

2022

Available date

2022-06-16

Language

en

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