Photoevaporation of circumstellar disks revisited: The dust-free case

Kei E.I. Tanaka, Taishi Nakamoto, Kazuyuki Omukai

Research output: Contribution to journalArticlepeer-review

28 Citations (Scopus)


Photoevaporation by stellar ionizing radiation is believed to play an important role in the dispersal of disks around young stars. The mass-loss model for dust-free disks developed by Hollenbach et al. is currently regarded as the conventional one and has been used in a wide variety of studies. However, the rate in this model was derived using the crude so-called 1+1D approximation of ionizing radiation transfer, which assumes that diffuse radiation propagates in a direction vertical to the disk. In this study, we revisit the photoevaporation of dust-free disks by solving the two-dimensional axisymmetric radiative transfer for steady-state disks. Unlike that solved by the conventional model, we determine that direct stellar radiation is more important than the diffuse field at the disk surface. The radial density distribution at the ionization boundary is represented by a single power law with index -3/2 in contrast to the conventional double power law. For this distribution, the photoevaporation rate from the entire disk can be written as a function of the ionizing photon emissivity ΦEUV from the central star and the disk outer radius r d as follows: . This new rate depends on the outer disk radius rather than on the gravitational radius as in the conventional model, because of the enhanced contribution to the mass loss from the outer disk annuli. In addition, we discuss its applications to present-day as well as primordial star formation.

Original languageEnglish
Article number155
JournalAstrophysical Journal
Issue number2
Publication statusPublished - 2013 Aug 20


  • H ii regions
  • accretion, accretion disks
  • protoplanetary disks
  • radiative transfer
  • stars: Population III
  • stars: formation
  • stars: massive

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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