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Title: THE PROPAGATION OF Ly{alpha} IN EVOLVING PROTOPLANETARY DISKS

Abstract

We study the role resonant scattering plays in the transport of Ly{alpha} photons in accreting protoplanetary disk systems subject to varying degrees of dust settling. While the intrinsic stellar far-UV (FUV) spectrum of accreting T Tauri systems may already be dominated by a strong, broad Ly{alpha} line ({approx}80% of the FUV luminosity), we find that resonant scattering further enhances the Ly{alpha} density in the deep molecular layers of the disk. Ly{alpha} is scattered downward efficiently by the photodissociated atomic hydrogen layer that exists above the molecular disk. In contrast, FUV-continuum photons pass unimpeded through the photodissociation layer and (forward-)scatter inefficiently off dust grains. Using detailed, adaptive grid Monte Carlo radiative transfer simulations we show that the resulting Ly{alpha}/FUV-continuum photon density ratio is strongly stratified; FUV-continuum-dominated in the photodissociation layer and Ly{alpha}-dominated field in the molecular disk. The enhancement is greatest in the interior of the disk (r {approx} 1 AU) but is also observed in the outer disk (r {approx} 100 AU). The majority of the total disk mass is shown to be increasingly Ly{alpha} dominated as dust settles toward the midplane.

Authors:
;  [1]
  1. Department of Astronomy, University of Michigan, 500 Church St., Ann Arbor, MI 48109 (United States)
Publication Date:
OSTI Identifier:
21587477
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 739; Journal Issue: 2; Other Information: DOI: 10.1088/0004-637X/739/2/78; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; DENSITY; DISSOCIATION; DUSTS; FAR ULTRAVIOLET RADIATION; LYMAN LINES; MONTE CARLO METHOD; PHOTONS; PROTOPLANETS; RADIANT HEAT TRANSFER; RESONANCE SCATTERING; SIMULATION; T TAURI STARS; BINARY STARS; BOSONS; CALCULATION METHODS; ELECTROMAGNETIC RADIATION; ELEMENTARY PARTICLES; ENERGY TRANSFER; ERUPTIVE VARIABLE STARS; HEAT TRANSFER; INELASTIC SCATTERING; MASSLESS PARTICLES; PHYSICAL PROPERTIES; RADIATIONS; SCATTERING; STARS; ULTRAVIOLET RADIATION; VARIABLE STARS

Citation Formats

Bethell, Thomas J., and Bergin, Edwin A., E-mail: tbethell@umich.edu. THE PROPAGATION OF Ly{alpha} IN EVOLVING PROTOPLANETARY DISKS. United States: N. p., 2011. Web. doi:10.1088/0004-637X/739/2/78; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
Bethell, Thomas J., & Bergin, Edwin A., E-mail: tbethell@umich.edu. THE PROPAGATION OF Ly{alpha} IN EVOLVING PROTOPLANETARY DISKS. United States. doi:10.1088/0004-637X/739/2/78; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
Bethell, Thomas J., and Bergin, Edwin A., E-mail: tbethell@umich.edu. Sat . "THE PROPAGATION OF Ly{alpha} IN EVOLVING PROTOPLANETARY DISKS". United States. doi:10.1088/0004-637X/739/2/78; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
@article{osti_21587477,
title = {THE PROPAGATION OF Ly{alpha} IN EVOLVING PROTOPLANETARY DISKS},
author = {Bethell, Thomas J. and Bergin, Edwin A., E-mail: tbethell@umich.edu},
abstractNote = {We study the role resonant scattering plays in the transport of Ly{alpha} photons in accreting protoplanetary disk systems subject to varying degrees of dust settling. While the intrinsic stellar far-UV (FUV) spectrum of accreting T Tauri systems may already be dominated by a strong, broad Ly{alpha} line ({approx}80% of the FUV luminosity), we find that resonant scattering further enhances the Ly{alpha} density in the deep molecular layers of the disk. Ly{alpha} is scattered downward efficiently by the photodissociated atomic hydrogen layer that exists above the molecular disk. In contrast, FUV-continuum photons pass unimpeded through the photodissociation layer and (forward-)scatter inefficiently off dust grains. Using detailed, adaptive grid Monte Carlo radiative transfer simulations we show that the resulting Ly{alpha}/FUV-continuum photon density ratio is strongly stratified; FUV-continuum-dominated in the photodissociation layer and Ly{alpha}-dominated field in the molecular disk. The enhancement is greatest in the interior of the disk (r {approx} 1 AU) but is also observed in the outer disk (r {approx} 100 AU). The majority of the total disk mass is shown to be increasingly Ly{alpha} dominated as dust settles toward the midplane.},
doi = {10.1088/0004-637X/739/2/78; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 739,
place = {United States},
year = {2011},
month = {10}
}