Formation of Narrow Dust Rings in Circumstellar Debris Disks

Abstract

Narrow dust rings observed around some young stars (e.g., HR 4796A) need to be confined. We present a possible explanation for the formation and confinement of such rings in optically thin circumstellar disks, without invoking shepherding planets. If an enhancement of dust grains (e.g., due to a catastrophic collision) occurs somewhere in the disk, photoelectric emission from the grains can heat the gas to temperatures well above that of the dust. The gas orbits with super(sub)-Keplerian speeds inward (outward) of the associated pressure maximum. This tends to concentrate the grains into a narrow region. The rise in dust density leads to further heating and a stronger concentration of grains. A narrow dust ring forms as a result of this instability. We show that this mechanism not only operates around early-type stars that have high UV fluxes, but also around stars with spectral types as late as K. This implies that this process is generic and may have occurred during the lifetime of each circumstellar disk. We examine the stringent upper-limit on the H2 column density in the HR 4796A disk and find it to be compatible with the presence of a significant amount of hydrogen gas in the disk. We also compute the OI and CII infrared line fluxes expected from various debris disks and show that these will be easily detectable by the upcoming Herschel mission. Herschel will be instrumental in detecting and characterizing gas in these disks.

Accepted for publication in ApJ; 14 pages, 7 figures

References in corpus (4)

• Photoevaporation of protoplanetary discs II: evolutionary models and observable properties
• The Carbon-Rich Gas in the Beta Pictoris Circumstellar Disk
• Discovery of an 86 AU Radius Debris Ring Around HD 181327
• First scattered light images of debris disks around HD 53143 and HD 139664

Cited by in corpus (15)

• A planetesimal orbiting within the debris disc around a white dwarf star
• Outer edges of debris discs: how sharp is sharp?
• A Survey for Massive Giant Planets in Debris Disks with Evacuated Inner Cavities
• Stirring in massive, young debris discs from spatially resolved Herschel images
• Resolved debris disk emission around eta Tel: a young Solar System or ongoing planet formation?
• A Low-Mass H2 Component to the AU Microscopii Circumstellar Disk
• A Ring of Warm Dust in the HD 32297 Debris Disk
• Effects of photophoresis on the evolution of transitional circumstellar disks
• Electromagnetic streaming instabilities of magnetized accretion disks with strong collisional coupling of species
• ALMA imaging of the M-dwarf Fomalhaut C's debris disc
• Tidal disruption versus planetesimal collisions as possible origins for the dispersing dust cloud around Fomalhaut
• Constraints on the gas content of the Fomalhaut debris belt. Can gas-dust interactions explain the belt's morphology?
• Physical conditions of gas components in debris disks of 49 Ceti and HD 21997
• Imaging the 44 AU Kuiper Belt-analogue debris ring around HD 141569A with GPI polarimetry
• The ALMA survey to Resolve exoKuiper belt Substructures (ARKS). X. Interpreting the peculiar dust rings around HD 131835