The Structure and Emission of Accretion Disks Irradiated by Infalling Envelopes

We calculate the emission from steady viscous disks heated by radiation from an opaque infalling protostellar envelope. For typical envelope parameters used to explain the spectral energy distributions of protostellar sources, we find that the envelope heating raises the outer disk temperature dramatically. The resulting temperature distribution in the disk is a complicated function of both radial distance and vertical height above the disk midplane. We show that the visibility flux at λ = 0.87 mm and the spectral energy distribution from submillimeter to radio wavelengths of the flat-spectrum T Tauri star HL Tau can be explained by emission from an accretion disk irradiated by its infalling envelope, whereas thermal emission from an infalling envelope or radiation from a steady viscous accretion disk cannot explain the observations. Our results suggest that the radiation fields of collapsing protostellar envelopes may strongly affect the structure of pre-main-sequence accretion disks.

[1]  H. M. Lee,et al.  Optical properties of interstellar graphite and silicate grains , 1984 .

[2]  L. Hartmann,et al.  Flat spectrum T Tauri stars: The case for infall , 1994 .

[3]  C. Lada,et al.  Spectral evolution of young stellar objects , 1986 .

[4]  Scott J. Kenyon,et al.  Spectral energy distributions of T Tauri stars - Disk flaring and limits on accretion , 1987 .

[5]  P. Ho,et al.  Subarcsecond VLA Maps of the Disk and the Jet in HL Tauri , 1994 .

[6]  P. Ho,et al.  VLA Imaging of a Possible Circumstellar Disk around HL Tauri , 1992 .

[7]  P. Cassen,et al.  On the formation of protostellar disks , 1981 .

[8]  P. Andre',et al.  The Contribution of Disks and Envelopes to the Millimeter Continuum Emission from Very Young Low-Mass Stars , 1993 .

[9]  John E. Carlstrom,et al.  PROTOSTELLAR ACCRETION DISKS RESOLVED WITH THE JCMT-CSO INTERFEROMETER , 1994 .

[10]  P. Cassen,et al.  The collapse of the cores of slowly rotating isothermal clouds , 1984 .

[11]  L. Hartmann,et al.  Sheet Models of Protostellar Collapse , 1996 .

[12]  G. Arfken.  Mathematical Methods for Physicists , 1967 .

[13]  G. Fuller,et al.  Submillimeter photometry and disk masses of T Tauri disk systems , 1990 .

[14]  D. Lin,et al.  Is HL Tauri and FU Orionis system in quiescence , 1994 .

[15]  Steven V. W. Beckwith,et al.  Particle Emissivity in Circumstellar Disks , 1991 .

[16]  A. Natta.  The temperature profile of T Tauri disks , 1993 .

[17]  M. Hayashi,et al.  A dynamically accreting gas disk around HL Tauri , 1993 .

[18]  S. Beckwith,et al.  A Survey for Circumstellar Disks around Young Stellar Objects , 1990 .

[19]  N. Evans,et al.  SPHERICAL DISKS : MOVING TOWARD A UNIFIED SOURCE MODEL FOR L1551 , 1994 .

[20]  C. Masson,et al.  A 45 AU Radius Source around L1551-IRS 5: A Possible Accretion Disk , 1990 .

[21]  L. Hartmann,et al.  The Embedded Young Stars in the Taurus-Auriga Molecular Cloud. II. Models for Scattered Light Images , 1993 .

[22]  N. Evans,et al.  Testing models of low-mass star formation - High-resolution far-infrared observations of L1551 IRS 5 , 1991 .

[23]  D. Lin,et al.  USING FU ORIONIS OUTBURSTS TO CONSTRAIN SELF-REGULATED PROTOSTELLAR DISK MODELS , 1993, astro-ph/9312015.

[24]  D. Lin,et al.  The formation and initial evolution of protostellar disks , 1990 .

[25]  N. Calvet,et al.  Irradiation of Accretion Disks around Young Objects. I. Near-Infrared CO Bands , 1991 .

[26]  Christopher D. Koresko,et al.  Tomographic imaging of HL Tauri , 1989 .

[27]  J. Pollack,et al.  Composition and radiative properties of grains in molecular clouds and accretion disks , 1994 .

[28]  J. E. Pringle,et al.  Accretion Discs in Astrophysics , 1981 .

[29]  D. Lynden-Bell,et al.  The Evolution of viscous discs and the origin of the nebular variables. , 1974 .

[30]  R. Mundt,et al.  Radio Continuum Emission from Pre-Main Sequence Stars and Associated Structures , 1985 .

[31]  L. Hartmann,et al.  The embedded young stars in the Taurus-Auriga molecular cloud. I - Models for spectral energy distributions , 1993 .

[32]  P. Hartigan,et al.  Spectroscopic evidence for magnetospheric accretion in classical T Tauri stars , 1994 .