A HUBBLE SPACE TELESCOPE SURVEY OF H2 EMISSION IN THE CIRCUMSTELLAR ENVIRONMENTS OF YOUNG STARS

The formation timescale and final architecture of exoplanetary systems are closely related to the properties of the molecular disks from which they form. Observations of the spatial distribution and lifetime of the molecular gas at planet-forming radii (a < 10 AU) are important for understanding the formation and evolution of exoplanetary systems. Toward this end, we present the largest spectrally resolved survey of H{sub 2} emission around low-mass pre-main-sequence stars compiled to date. We use a combination of new and archival far-ultraviolet spectra from the Cosmic Origins Spectrograph and Space Telescope Imaging Spectrograph instruments on the Hubble Space Telescope to sample 34 T Tauri stars (27 actively accreting Classical T Tauri Stars and 7 non-accreting Weak-lined T Tauri Stars) with ages ranging from {approx}1 to 10 Myr. We observe fluorescent H{sub 2} emission, excited by Ly{alpha} photons, in 100% of the accreting sources, including all of the transitional disks in our sample (CS Cha, DM Tau, GM Aur, UX Tau A, LkCa 15, HD 135344B, and TW Hya). The spatial distribution of the emitting gas is inferred from spectrally resolved H{sub 2} line profiles. Some of the emitting gas is produced in outflowing material, but the majority of H{sub 2}more » emission appears to originate in a rotating disk. For the disk-dominated targets, the H{sub 2} emission originates predominately at a {approx}< 3 AU. The emission line widths and inner molecular radii are found to be roughly consistent with those measured from mid-IR CO spectra.« less

[1]  D. Lin,et al.  Toward a Deterministic Model of Planetary Formation. I. A Desert in the Mass and Semimajor Axis Distributions of Extrasolar Planets , 2004 .

[2]  THE ORIGINS OF FLUORESCENT H2 EMISSION FROM T TAURI STARS , 2006, astro-ph/0602404.

[3]  R. Neri,et al.  Dust properties of protoplanetary disks in the Taurus-Auriga star forming region from millimeter wavelengths , 2009, 0912.3356.

[4]  E. Feigelson,et al.  The η Chamaeleontis Cluster: A Remarkable New Nearby Young Open Cluster , 1999 .

[5]  L. Hartmann,et al.  On the Diversity of the Taurus Transitional Disks: UX Tauri A and LkCa 15 , 2007, 0710.2892.

[6]  Geoffrey A. Blake,et al.  CO ROVIBRATIONAL EMISSION AS A PROBE OF INNER DISK STRUCTURE , 2011, 1109.4579.

[7]  Stephen E. Strom,et al.  Demographics of Transition Objects , 2007, 0704.1681.

[8]  Rachel Lynn Akeson,et al.  Constraints on Circumstellar Disk Parameters from Multiwavelength Observations: T Tauri and SU Aurigae , 2002 .

[9]  T. Ayres.  StarCAT: A CATALOG OF SPACE TELESCOPE IMAGING SPECTROGRAPH ULTRAVIOLET ECHELLE SPECTRA OF STARS , 2010 .

[10]  The Far-Ultraviolet Spectra of TW Hydrae. II. Models of H2 Fluorescence in a Disk* , 2004, astro-ph/0402238.

[11]  S. Cabrit,et al.  The evolution of stars in the Taurus-Auriga T association , 2007, 0708.3040.

[12]  J. Valenti,et al.  The Far-Ultraviolet Spectrum of TW Hydrae. I. Observations of H2 Fluorescence , 2002, astro-ph/0201319.

[13]  L. Hartmann,et al.  Pre-Main-Sequence Evolution in the Taurus-Auriga Molecular Cloud , 1995 .

[14]  L. Hartmann,et al.  EVOLUTION OF X-RAY AND FAR-ULTRAVIOLET DISK-DISPERSING RADIATION FIELDS , 2011, 1102.0956.

[15]  Elizabeth A. Lada,et al.  Disk Frequencies and Lifetimes in Young Clusters , 2001, astro-ph/0104347.

[16]  T. Millar,et al.  Molecular Hydrogen Emission from Protoplanetary Disks. II. Effects of X-Ray Irradiation and Dust Evolution , 2006, Proceedings of the International Astronomical Union.

[17]  High-Resolution Submillimeter Constraints on Circumstellar Disk Structure , 2006, astro-ph/0610813.

[18]  G. Herczeg,et al.  HIGH-RESOLUTION SPECTROSCOPY OF [Ne ii] EMISSION FROM AA Tau AND GM Aur , 2009, 0904.1597.

[19]  T. Ray,et al.  Rotation of jets from young stars: New clues from the Hubble Space Telescope Imaging Spectrograph , 2003, astro-ph/0312300.

[20]  Jonathan P. Williams,et al.  Protoplanetary Disks and Their Evolution , 2011, 1103.0556.

[21]  Lynne A. Hillenbrand,et al.  UV Excess Measures of Accretion onto Young Very Low Mass Stars and Brown Dwarfs , 2008, 0801.3525.

[22]  Ithaca,et al.  A Survey and Analysis of Spitzer Infrared Spectrograph Spectra of T Tauri Stars in Taurus , 2006, astro-ph/0608038.

[23]  L. Loinard,et al.  VLBA Determination of the Distance to Nearby Star-forming Regions. I. The Distance to T Tauri with 0.4% Accuracy , 2007, 0708.2081.

[24]  F. Lahuis,et al.  H2O and OH Gas in the Terrestrial Planet-forming Zones of Protoplanetary Disks , 2008, 0802.0037.

[25]  L. Testi,et al.  Accretion Rates in Herbig Ae stars , 2006 .

[26]  J. Shull.  H2 resonance fluorescence with Lyman-alpha , 1978 .

[27]  E. Young,et al.  A Spitzer Space Telescope Study of Disks in the Young σ Orionis Cluster , 2007, astro-ph/0701476.

[28]  Sarah E. Dodson-Robinson,et al.  TRANSITIONAL DISKS AS SIGNPOSTS OF YOUNG, MULTIPLANET SYSTEMS , 2011, 1106.4824.

[29]  F. Cusano,et al.  Pre-main sequence spectroscopic binaries suitable for VLTI observations , , 2007, astro-ph/0702268.

[30]  J. Linsky,et al.  METAL DEPLETION AND WARM H2 IN THE BROWN DWARF 2M1207 ACCRETION DISK , 2010, 1004.1186.

[31]  N. Calvet,et al.  The Structure and Emission of the Accretion Shock in T Tauri Stars , 1998 .

[32]  K. H. Kim,et al.  DISK EVOLUTION IN THE THREE NEARBY STAR-FORMING REGIONS OF TAURUS, CHAMAELEON, AND OPHIUCHUS , 2009, 0909.0960.

[33]  P. Hartigan,et al.  ADAPTIVE OPTICS ECHELLE SPECTROSCOPY OF [Fe ii] 1.644 μm IN THE RW AUR JET: A NARROW SLICE DOWN THE AXIS OF THE FLOW , 2009, 0909.1524.

[34]  Michael F. Skrutskie,et al.  Circumstellar Material Associated with Solar-Type Pre-Main-Sequence Stars: A Possible Constraint on the Timescale for Planet Building , 1989 .

[35]  David Wilner,et al.  Evidence for a Developing Gap in a 10 Myr Old Protoplanetary Disk , 2002 .

[36]  Geoffrey A. Blake,et al.  Spectroastrometric Imaging of Molecular Gas within Protoplanetary Disk Gaps , 2008, 0805.3314.

[37]  L. Hartmann,et al.  Disks in Transition in the Taurus Population: Spitzer IRS Spectra of GM Aurigae and DM Tauri , 2005 .

[38]  T. Ray,et al.  HST/STIS observations of the RW Aurigae bipolar jet: mapping the physical parameters close to the source , 2009, 0910.0379.

[39]  M. Meyer,et al.  Detection of [Ne II] Emission from Young Circumstellar Disks , 2007, astro-ph/0703616.

[40]  E. Bergin,et al.  THE PROPAGATION OF Lyα IN EVOLVING PROTOPLANETARY DISKS , 2011, 1107.3514.

[41]  M. Fernández,et al.  High-resolution visible spectroscopy of the jet-driving star Th 28 , 2010 .

[42]  J. Stocke,et al.  HUBBLE/COS OBSERVATIONS OF THE Lyα FOREST TOWARD THE BL Lac OBJECT 1ES 1553+113 , 2010, 1005.2191.

[43]  Kevin France,et al.  The Cosmic Origins Spectrograph , 1998 .

[44]  J. Muzerolle,et al.  Long-lived disc accretion in the η Chamaeleontis pre-main sequence star cluster , 2004 .

[45]  Alexander Brown,et al.  Mapping the Circumstellar Environment of T Tauri with Fluorescent H2 Emission , 2003, astro-ph/0309142.

[46]  T. M. Gledhill,et al.  Circumstellar structure of RU Lupi down to au scales , 2001 .

[47]  G. Williger,et al.  The Environment of the Optically Brightest Herbig Ae Star, HD 104237 , 2004 .

[48]  P. Armitage,et al.  Constraints on a planetary origin for the gap in the protoplanetary disc of GM Aurigae , 2003, astro-ph/0302204.

[49]  J. Shull,et al.  The kinetic theory of H2 dissociation , 1983 .

[50]  L. Hartmann,et al.  Accretion and the Evolution of T Tauri Disks , 1998 .

[51]  J. Najita,et al.  Organic Molecules and Water in the Planet Formation Region of Young Circumstellar Disks , 2008, Science.

[52]  H. C. Stempels,et al.  Unveiling extremely veiled T Tauri stars , 2008, 0803.3006.

[53]  James Muzerolle,et al.  Unveiling the Inner Disk Structure of T Tauri Stars , 2003, astro-ph/0310067.

[54]  J. Greaves,et al.  Molecular hydrogen emission from discs in the η Chamaeleontis cluster , 2007, 0705.4601.

[55]  E. Feigelson,et al.  The epsilon chamaeleontis young stellar group and the characterization of sparse stellar clusters , 2003, astro-ph/0309059.

[56]  M. E. van den Ancker,et al.  Timescale of mass accretion in pre-main-sequence stars , 2009, 0911.3320.

[57]  L. Hartmann,et al.  Rotational and radial velocities of T Tauri stars , 1986 .

[58]  N. Calvet,et al.  CHEMISTRY OF A PROTOPLANETARY DISK WITH GRAIN SETTLING AND Lyα RADIATION , 2010, 1011.0446.

[59]  John S. Carr,et al.  ORGANIC MOLECULES AND WATER IN THE INNER DISKS OF T TAURI STARS , 2011, 1104.0184.

[60]  M. Min,et al.  A 10 μm spectroscopic survey of Herbig Ae star disks: Grain growth and crystallization , 2005, astro-ph/0503507.

[61]  S. Wolf,et al.  Formation and Evolution of Planetary Systems: Upper Limits to the Gas Mass in Disks around Sun-like Stars , 2006, astro-ph/0606669.

[62]  M. Schwartz,et al.  Discovery of Seven T Tauri Stars and a Brown Dwarf Candidatein the Nearby TW Hydrae Association , 1998, astro-ph/9812189.

[63]  C. Clarke,et al.  Photoevaporation of protoplanetary discs - II. Evolutionary models and observable properties , 2006, astro-ph/0603254.

[64]  J. Najita,et al.  CO Fundamental Emission from V836 Tauri , 2008, 0809.3949.

[65]  J. Muzerolle,et al.  A SPITZER IRS STUDY OF INFRARED VARIABILITY IN TRANSITIONAL AND PRE-TRANSITIONAL DISKS AROUND T TAURI STARS , 2010, 1012.3500.

[66]  Dispersion in the lifetime and accretion rate of T Tauri discs , 2003, astro-ph/0303343.

[67]  F. V. Leeuwen.  Validation of the new Hipparcos reduction , 2007, 0708.1752.

[68]  T. Henning,et al.  Star and Protoplanetary Disk Properties in Orion's Suburbs , 2009, 0907.2380.

[69]  J. E. Pringle,et al.  Predictions for the frequency and orbital radii of massive extrasolar planets , 2002 .

[70]  L. Hartmann,et al.  The Spatial Distribution of Fluorescent H2 Emission near T Tauri , 2003, astro-ph/0304531.

[71]  L. Hartmann,et al.  Disk Accretion Rates for T Tauri Stars , 1998 .

[72]  M. Karovska,et al.  Analysis of H2 Emission from Mira B in Ultraviolet Spectra from the Hubble Space Telescope , 2002 .

[73]  HST/STIS observations of the bipolar jet from RW Aurigae. , 2002, astro-ph/0207307.

[74]  H. C. Stempels,et al.  Surface magnetic fields on two accreting T Tauri stars: CV Cha and CR Cha , 2009, 0905.0914.

[75]  J. Najita,et al.  Gas in the Terrestrial Planet Region of Disks: CO Fundamental Emission from T Tauri Stars , 2003 .

[76]  Geoffrey A. Blake,et al.  THE STRUCTURE AND DYNAMICS OF MOLECULAR GAS IN PLANET-FORMING ZONES: A CRIRES SPECTRO-ASTROMETRIC SURVEY , 2011, 1103.3000.

[77]  E. Chiang,et al.  Inside-out evacuation of transitional protoplanetary discs by the magneto-rotational instability , 2007, 0706.1241.

[78]  William J. Forrest,et al.  MID-INFRARED SPECTRA OF TRANSITIONAL DISKS IN THE CHAMAELEON I CLOUD , 2009 .

[79]  T. Henning,et al.  ACCRETION IN EVOLVED AND TRANSITIONAL DISKS IN CEP OB2: LOOKING FOR THE ORIGIN OF THE INNER HOLES , 2010, 1001.3026.

[80]  J. Valenti,et al.  An IUE Atlas of Pre-Main-Sequence Stars. I. Co-added Final Archive Spectra from the SWP Camera , 2000 .

[81]  A. A. Kaas,et al.  New low-mass members of the Lupus 3 dark cloud : further indications of pre-main-sequence evolution strongly affected by accretion. , 2003 .

[82]  J. S. Carr,et al.  A SPITZER SURVEY OF MID-INFRARED MOLECULAR EMISSION FROM PROTOPLANETARY DISKS. II. CORRELATIONS AND LOCAL THERMAL EQUILIBRIUM MODELS , 2011, 1104.0948.

[83]  J. S. Bary,et al.  Detections of Rovibrational H2 Emission from the Disks of T Tauri Stars , 2003 .

[84]  J. Valenti,et al.  Observations of T Tauri Stars using Hubble Space Telescope GHRS. I. Far-Ultraviolet Emission Lines , 2001, astro-ph/0110436.

[85]  L. Hartmann,et al.  Probing the Dust and Gas in the Transitional Disk of CS Cha with Spitzer , 2007, 0707.0019.

[86]  L. Hillenbrand,et al.  THE COEVALITY OF YOUNG BINARY SYSTEMS , 2009, 0909.0509.

[87]  T. Ray,et al.  Asymmetries in Bipolar Jets from Young Stars , 1994 .

[88]  L. Hillenbrand,et al.  High-Resolution Spectroscopy of [Ne II] Emission from TW Hydrae , 2007, 0706.3901.

[89]  Peter Plavchan,et al.  NEW DEBRIS DISKS AROUND YOUNG, LOW-MASS STARS DISCOVERED WITH THE SPITZER SPACE TELESCOPE , 2009, 0904.0819.

[90]  E. Feigelson,et al.  AN IMPROVED HR DIAGRAM FOR CHAMAELEON I PRE-MAIN-SEQUENCE STARS , 1996 .

[91]  H. M. Gunther,et al.  Where are the hot ion lines in classical T Tauri stars formed , 2008, 0801.2273.

[92]  C. Dullemond,et al.  The pre-main sequence spectroscopic binary AK Scorpii revisited , 2003 .

[93]  B. Ercolano,et al.  HIGH-RESOLUTION SPECTROSCOPY OF Ne ii EMISSION FROM YOUNG STELLAR OBJECTS , 2011, 1201.0184.

[94]  Kevin France,et al.  THE FAR-ULTRAVIOLET “CONTINUUM” IN PROTOPLANETARY DISK SYSTEMS. II. CARBON MONOXIDE FOURTH POSITIVE EMISSION AND ABSORPTION , 2011, 1104.0670.

[95]  J. Najita,et al.  TRACING THE INNER EDGE OF THE DISK AROUND HD 100546 WITH ROVIBRATIONAL CO EMISSION LINES , 2009, 0907.0047.

[96]  R. Mathieu,et al.  Evidence for Cleared Regions in the Disks Around Pre-Main-Sequence Spectroscopic Binaries , 1997 .

[97]  Frantz Martinache,et al.  THE ROLE OF MULTIPLICITY IN DISK EVOLUTION AND PLANET FORMATION , 2011, 1109.4141.

[98]  C. Dullemond,et al.  TIME EVOLUTION OF VISCOUS CIRCUMSTELLAR DISKS DUE TO PHOTOEVAPORATION BY FAR-ULTRAVIOLET, EXTREME-ULTRAVIOLET, AND X-RAY RADIATION FROM THE CENTRAL STAR , 2009, 0909.1836.

[99]  David E. Trilling,et al.  Easy Come, Easy Go: Orbital Migration and the Frequency of Giant Planet Formation , 2000 .

[100]  J. Leisenring,et al.  Quiescent H2 Emission From Pre-Main-Sequence Stars in Chamaeleon I , 2008, 0801.2765.

[101]  J. Valenti,et al.  New Infrared Veiling Measurements and Constraints on Accretion Disk Models for Classical T Tauri Stars , 2001 .

[102]  M. Wyatt,et al.  Evolution of Debris Disks , 2008 .

[103]  W. Ward.  Protoplanet Migration by Nebula Tides , 1997 .

[104]  T. Henning,et al.  A search for mid-infrared molecular hydrogen emission from protoplanetary disks , 2007, 0710.2813.

[105]  Kevin France,et al.  Far-UV Continuum in Disks I : Accretion & H , 2010, 1101.0165.

[106]  P. Armitage.  Massive Planet Migration: Theoretical Predictions and Comparison with Observations , 2007, 0705.3039.

[107]  J. Valenti,et al.  An IUE Atlas of Pre-Main-Sequence Stars. II. Far-Ultraviolet Accretion Diagnostics in T Tauri Stars , 2000 .

[108]  Dynamical Masses of T Tauri Stars and Calibration of Pre-Main-Sequence Evolution , 2000, astro-ph/0008370.

[109]  D. Wilner,et al.  IMAGING THE MOLECULAR DISK ORBITING THE TWIN YOUNG SUNS OF V4046 Sgr , 2010, 1007.3993.

[110]  J. Valenti,et al.  CHARACTERIZING CO FOURTH POSITIVE EMISSION IN YOUNG CIRCUMSTELLAR DISKS , 2012, 1201.0937.

[111]  L. Hartmann,et al.  THE DISK POPULATION OF THE TAURUS STAR-FORMING REGION , 2009, 0911.5457.

[112]  D. Ebbets,et al.  The Cosmic Origins Spectrograph: on-orbit instrument performance , 2010, 1012.5827.

[113]  T. Ray,et al.  Hubble Space Telescope Space Telescope Imaging Spectrograph Observations of the Bipolar Jet from RW Aurigae: Tracing Outflow Asymmetries Close to the Source , 2002 .

[114]  D. M. Watson,et al.  UNVEILING THE STRUCTURE OF PRE-TRANSITIONAL DISKS , 2010, 1005.2365.

[115]  Research School of AstronomyAstrophysics,et al.  Spatially Resolved Molecular Hydrogen Emission in the Inner 200 AU Environments of Classical T Tauri Stars , 2007, 0711.3844.

[116]  Austin,et al.  Observational Constraints on the Formation and Evolution of Binary Stars , 2001, astro-ph/0103098.

[117]  Kevin France,et al.  CO AND H2 ABSORPTION IN THE AA TAURI CIRCUMSTELLAR DISK , 2011, 1109.1831.

[118]  M. Karovska,et al.  Molecular Hydrogen Emission Lines in Far Ultraviolet Spectroscopic Explorer Observations of Mira B , 2003, astro-ph/0310105.

[119]  Catherine Espaillat,et al.  RESOLVED IMAGES OF LARGE CAVITIES IN PROTOPLANETARY TRANSITION DISKS , 2011, 1103.0284.

[120]  J. Valenti,et al.  The Loopy Ultraviolet Line Profiles of RU Lupi: Accretion, Outflows, and Fluorescence , 2005, astro-ph/0504654.

[121]  J. Elias.  A study of the Taurus dark cloud complex , 1978 .

[122]  E. Feigelson,et al.  The η Chamaeleontis cluster: photometric study of the ROSAT‐detected weak‐lined T Tauri stars , 2001 .

[123]  Geoffrey A. Blake,et al.  HIGH-RESOLUTION 5 μm SPECTROSCOPY OF TRANSITIONAL DISKS , 2009 .

[124]  G. Kriss.  Improved Medium Resolution Line Spread Functions for COS FUV Spectra , 2011 .

[125]  T. Prusti,et al.  A SPITZER c2d LEGACY SURVEY TO IDENTIFY AND CHARACTERIZE DISKS WITH INNER DUST HOLES , 2010, 1008.2428.

[126]  J. Valenti,et al.  A FAR-ULTRAVIOLET ATLAS OF LOW-RESOLUTION HUBBLE SPACE TELESCOPE SPECTRA OF T TAURI STARS , 2012, 1205.4789.

[127]  J. S. Bloom,et al.  Near-Infrared Interferometric, Spectroscopic, and Photometric Monitoring of T Tauri Inner Disks , 2007, 0707.3833.

[128]  Periodic radial velocity variations in RU Lupi , 2006, astro-ph/0611560.

[129]  D. Padgett,et al.  THE SPITZER c2d LEGACY RESULTS: STAR-FORMATION RATES AND EFFICIENCIES; EVOLUTION AND LIFETIMES , 2008, 0811.1059.

[130]  U. Gorti,et al.  THE PHOTOEVAPORATIVE WIND FROM THE DISK OF TW Hya , 2011, 1105.0045.

[131]  T. Henning,et al.  A search for near-infrared molecular hydrogen emission in the CTTS LkH$\mathsf{\alpha}$ 264 and the debris disk 49 Ceti , 2007 .

[132]  K. Luhman.  A Census of the Chamaeleon I Star-forming Region , 2004, astro-ph/0402509.