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SUMMARY:Observed sizes of planet-forming disks trace viscous spreading
DTSTART;VALUE=DATE-TIME:20200512T072500Z
DTEND;VALUE=DATE-TIME:20200512T074500Z
DTSTAMP;VALUE=DATE-TIME:20240704T115618Z
UID:indico-contribution-24@meetings.aip.de
DESCRIPTION:Speakers: L. Trapman (Leiden University)\nThe evolution of pro
 toplanetary disks is set by the conservation of angular momentum\, where t
 he accretion of material onto the central star is balanced by viscous expa
 nsion of the outer disk or by disk winds extracting angular momentum witho
 ut changing the disk size. Studying the time evolution of disk sizes allow
 s us therefore to distinguish between viscous stresses or disk winds as th
 e main mechanism of disk evolution. Observationally\, estimates of the dis
 k gaseous outer radius are based on the extent of the CO rotational emissi
 on\, which\, during the evolution\, is also affected by the changing physi
 cal and chemical conditions in the disk.\nWe have used physical-chemical m
 odels to study how the extent of the CO emission changes with time in a vi
 scously expanding disk. We find that the gas outer radius ($R_{\\rm CO\,\\
  90\\%}$) measured from our models matches the expectations of a viscously
  spreading disk: $R_{\\rm CO\,\\ 90\\%}$ increases with time and for a giv
 en time $R_{\\rm CO\,\\ 90\\%}$ is larger for a disk with a higher viscosi
 ty $\\alpha_{\\rm visc}$. However\, in the extreme case where the disk mas
 s is low ($ \\leq 10^{-4}\\ \\mathrm{M}_{\\odot}$) and $\\alpha_{\\rm visc
 }$ is high ($\\geq 10^{-2}$)\, $R_{\\rm CO\,\\ 90\\%}$ will instead decrea
 se with time as a result of CO photodissociation in the outer disk. \nWe f
 ind that most observed gas outer radii in Lupus can be explained using a v
 iscously evolving disk that starts out small $(\\simeq 10\\ \\mathrm{AU})$
  and has a low viscosity $(\\alpha_{\\rm visc} = 10^{-4} - 10^{-3})$.\n\nh
 ttps://meetings.aip.de/event/1/contributions/24/
LOCATION:Leibniz Institute for Astrophysics Potsdam (AIP) Lecture Hall
URL:https://meetings.aip.de/event/1/contributions/24/
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