Far-Ultraviolet H2 Emission from Circumstellar Disks

Abstract

We analyze the far-ultraviolet (FUV) spectra of 33 classical T Tauri stars (CTTS), including 20 new spectra obtained with the Advanced Camera for Surveys Solar Blind Channel (ACS/SBC) on the Hubble Space Telescope. Of the sources, 28 are in the ~1 Myr old Taurus-Auriga complex or Orion Molecular Cloud, 4 in the 8-10 Myr old Orion OB1a complex and one, TW Hya, in the 10 Myr old TW Hydrae Association. We also obtained FUV ACS/SBC spectra of 10 non-accreting sources surrounded by debris disks with ages between 10 and 125 Myr. We use a feature in the FUV spectra due mostly to electron impact excitation of \h2 to study the evolution of the gas in the inner disk. We find that the \h2 feature is absent in non-accreting sources, but is detected in the spectra of CTTS and correlates with accretion luminosity. Since all young stars have active chromospheres which produce strong X-ray and UV emission capable of exciting \h2 in the disk, the fact that the non-accreting sources show no \h2 emission implies that the \h2 gas in the inner disk has dissipated in the non-accreting sources, although dust (and possibly gas) remains at larger radii. Using the flux at 1600 Å, we estimate that the column density of \h2 left in the inner regions of the debris disks in our sample is less than ~ 3x10^-6 g cm^-2, nine orders of magnitude below the surface density of the minimum mass solar nebula at 1 AU.

15 pages, 4 figures, accepted to ApJL

References in corpus (21)

• A Survey and Analysis of Spitzer Infrared Spectrograph Spectra of T Tauri Stars in Taurus
• H2O and OH gas in the terrestrial planet-forming zones of protoplanetary disks
• Probing T Tauri Accretion and Outflow with 1 Micron Spectroscopy
• The Complete Census of 70-um-Bright Debris Disks within the FEPS (Formation and Evolution of Planetary Systems) Spitzer Legacy Survey of Sun-like Stars
• The Different Evolution of Gas and Dust in Disks around Sun-like and Cool Stars
• Formation and Evolution of Planetary Systems (FEPS): Properties of Debris Dust around Solar-type Stars
• Spitzer observations of the Orion OB1 association: disk census in the low mass stars
• The Carbon-Rich Gas in the Beta Pictoris Circumstellar Disk
• X-ray Emission from T Tauri Stars and the Role of Accretion: Inferences from the XMM-Newton Extended Survey of the Taurus Molecular Cloud
• Formation and Evolution of Planetary Systems: Upper Limits to the Gas Mass in Disks Around Sun-like Stars
• Evolution of Mid-IR Excess Around Sun-like Stars: Constraints on Models of Terrestrial Planet Formation
• 25 Orionis: A Kinematically Distinct 10 Myr Old Group in Orion OB1a
• The Origins of Fluorescent H2 Emission From T Tauri~Stars
• X-ray emission from classical T Tauri stars: Accretion shocks and coronae?
• Braking the Gas in the beta Pictoris Disk
• The Formation and Evolution of Planetary Systems: Description of the Spitzer Legacy Science Database
• Atomic Diagnostics of X-ray Irradiated Protoplanetary Disks
• The TEXES Survey For H2 Emission From Protoplanetary Disks
• A slowly accreting ~10 Myr old transitional disk in Orion OB1a
• Quiescent H2 Emission From Pre-Main Sequence Stars in Chamaeleon I
• CO Fundamental Emission from V836 Tau

Cited by in corpus (53)

• Resolved Images of Large Cavities in Protoplanetary Transition Disks
• The Cosmic Origins Spectrograph
• Accretion Rates for T Tauri Stars Using Nearly Simultaneous Ultraviolet and Optical Spectra
• Resolved gas cavities in transitional disks inferred from CO isotopologues with ALMA
• Gas density drops inside dust cavities of transitional disks around young stars observed with ALMA
• On the gas content of transitional disks: a VLT/X-Shooter study of accretion and winds
• Dust Trapping by Vortices in Transitional Disks: Evidence for Non-ideal MHD Effects in Protoplanetary Disks
• Emission Lines from the Gas Disk around TW Hydra and the Origin of the Inner Hole
• A Far-ultraviolet Atlas of Low-resolution Hubble Space Telescope Spectra of T Tauri Stars
• A Hubble Space Telescope Survey of H2 Emission in the Circumstellar Environments of Young Stars
• A Closer Look at the LkCa 15 Protoplanetary Disk
• Hot Gas Lines in T Tauri Stars
• High-resolution Ultraviolet Radiation Fields of Classical T Tauri Stars
• NUV Excess in Slowly Accreting T Tauri Stars: Limits Imposed by Chromospheric Emission
• Water depletion in the disk atmosphere of Herbig AeBe stars
• The origin and evolution of transition discs: successes, problems and open questions
• PENELLOPE: the ESO data legacy program to complement the Hubble UV Legacy Library of Young Stars (ULLYSES) I. Survey presentation and accretion properties of Orion OB1 and $\sigma$-Orionis
• Gas and multi-species dust dynamics in viscous protoplanetary discs: the importance of the dust back-reaction
• Evolution of X-ray and FUV Disk-Dispersing Radiation Fields
• Hubble and Spitzer Space Telescope Observations of the Debris Disk around the Nearby K Dwarf HD 92945
• A survey for near-infrared H2 emission in Herbig Ae/Be stars: emission from the outer disks of HD 97048 and HD 100546
• The chemistry of disks around T Tauri and Herbig Ae/Be stars
• The Far-Ultraviolet "Continuum" in Protoplanetary Disk Systems II: CO Fourth Positive Emission and Absorption
• HST spectra reveal accretion in MY Lupi
• Probing the Final Stages of Protoplanetary Disk Evolution with ALMA
• Characterizing the stellar photospheres and near-infrared excesses in accreting T Tauri systems
• Wind-driven Accretion in Transitional Protostellar Disks
• The Far-Ultraviolet "Continuum" in Protoplanetary Disk Systems I: Electron-Impact H2 and Accretion Shocks
• Using FUV to IR Variability to Probe the Star-Disk Connection in the Transitional Disk of GM Aur
• GIARPS High-resolution Observations of T Tauri stars (GHOsT). III. A pilot study of stellar and accretion properties
• Circumstellar disks and planets. Science cases for next-generation optical/infrared long-baseline interferometers
• The 1600 Angstrom Emission Bump in Protoplanetary Disks: A Spectral Signature of H${}_2$O Dissociation
• CO and H2 Absorption in the AA Tauri Circumstellar Disk
• Forbidden line diagnostics of photoevaporative disc winds
• X-ray to NIR emission from AA Tauri during the dim state - Occultation of the inner disk and gas-to-dust ratio of the absorber
• Using Multiwavelength Variability to Explore the Connection between X-ray Emission, the Far-Ultraviolet H2 Bump, and Accretion in T Tauri Stars
• Binarity and Accretion in AGB Stars: HST/STIS Observations of UV Flickering in Y Gem
• HST/COS Spectra of DF Tau and V4046 SGR: First Detection of Molecular Hydrogen Absorption Against the Ly$\alpha$ Emission Line
• A UV-to-NIR Study of Molecular Gas in the Dust Cavity Around RY Lupi
• Long-lived protoplanetary disks in multiple systems: the VLA view of HD 98800
• Photoelectric charging of dust grains in the environment of Young Stellar Objects
• The UV Perspective of Low-Mass Star Formation
• [OI] disk emission in the Taurus star forming region
• The Radial Distribution and Excitation of H2 around Young Stars in the HST-ULLYSES Survey
• Disk evolution and the fate of water
• The Evolution of Protoplanetary Disks: Probing the Inner Disk of Very Low Accretors
• Residual Gas & Dust Around Transition Objects and Weak T Tauri Stars
• A comprehensive study of NGC 2023 with XMM-Newton and Spitzer
• HCO+ Detection of Dust-Depleted Gas in the Inner Hole of the LkCa 15 Pre-Transitional Disk
• Evidence of hot high velocity photoionized plasma falling on actively accreting T-Tauri Stars
• The Mysterious Affair of the H${}_2$ in AU Mic
• An Incipient Debris Disk in the Chamaeleon I Cloud
• Detection of H${}_2$ in the TWA 7 System: A Probable Circumstellar Origin