High Dynamic Range Imaging and Spectroscopy of Circumstellar Disks Alycia Weinberger (Carnegie Institution of Washington) With lots of input from: Aki Roberge

10 6 yrs10 7 yrs10 8 yrs10 9 yrs  Persei Sun TW Hydrae Taurus, Ophiuchus star forming regions HyadesTucana Pleiades  Pic Planetary Formation Timeline Terrestrial planets form Era of heavy bombardment by comets CAI / Chondrule Formation Moon forming impact t0?t0? Giant planets form?

 How and when do gas giant planets form (e.g. core-accretion or gravitational instability)?  How do disk materials segregate and move through disks? How Do Planets Form from Disks? These are questions that involve GAS and DUST!

1. To distinguish gas giant and terrestrial planet regions, need spatial resolution of ~1 AU (on GAS and DUST) 1 AU at 150 pc = 7 mas  Diffraction limited 20 m at < 650 nm 2. To actually see the disk at 1 AU, need high contrast between dust scattering and instrumental diffraction/scattering “Requirements”

T Tauri Disks with Gaps 10 mas resolution (ALMA or 2x worse than 20 m at 500 nm) Hydrodynamic simulation of 1 M Jup planet opening gap at 5 AU (Wolf et al. 2002)

ALMA-VLST Synergy  Break Albedo/Optical Depth Degeneracy  Dust Composition (Grain Size and Growth)  Molecular (ALMA) and Atomic (VLST) Gas Composition [stay tuned] From combination of millimeter emission and optical scattered light on similar spatial scales Watch planet formation at 1-5 AU at the distance to Taurus!

T Tauri Contrast Ratios: Dust TW Hydrae Star: R = 9.8 mag Face on Disk at 20 AU:  14 mag/arcsec 2 Future: Same contrast at 1 AU? (Krist et al and Roberge et al. 2003)

Gas content can distinguish evolved from primordial material Sensitive line-of-sight UV spectroscopy (FUSE and STIS) For Example: AB Aur (~1 Myr old): ISM-like CO/ H 2  primordial  Pic (~15 Myr old): high CO/H 2  comets Lecavalier des Etangs et al. 2001; Roberge et al. 2000, 2001, 2002

UV Sensitively Traces Gas  N(H 2 ) <= cm -2  N(CO) = (6.3 ± 0.3) x cm -2  CO/H 2 > 6 x  CO would be destroyed in < 200 yr  CO must be from planetesimals orbiting several tens of AU from star

H/a ≈ 0.18 a 2/7 20 m telescope at =150 nm  1.5 mas resln  0.23 AU at 150 pc H=0.25 AU at a=1.5 AU 1.5 AU Gas/Dust Ratio Relevant to: Controlling magnetospheric accretion Controlling elemental enrichment Structure of Disks From Gas Resonant Scattering

Vertical Disk Profile (  Pic) Arcsec (from midplane) Intensity (Brandeker et al. 2003) Want to do this: At distance to Taurus (150 pc) For UV ground-state electronic transitions (e.g. OI, CI, SI, SiI, FeI …)

 How do terrestrial planets get their volatiles?  What is the relationship between giant planets and giant impacts? How Do Planets Interact With Their Disks?

Current State of the Art - High Contrast Imaging  High contrast imaging available only from HST: This is the only way to see dust very close to stars! Smith & Terrile (1984) Schneider & Weinberger (2004)

Disk Structure as Evidence for Low Mass Planets For optically thin disks and albedo ≈ 0.5: Integrated scattered light ≈ L IR / L * (Kuchner & Holman 2003)

5 Myr - HD NICMOSSTIS ACS (Weinberger et al. 1999, 2003; Augereau et al. 1999; Mouillet et al. 2001; Clampin et al. 2003) L IR / L * = 8 x 10 -3

8 Myr - HR 4796A 24  m emission (Koerner et al. 1998, ApJL) Visual reflection (Schneider et al. 2004, in prep) L IR / L * = 5 x 10 -3

12 Myr -  Pictoris Z (AU) Multiple Warps! STIS, Heap et al. (2000) Keck, Weinberger et al. (2003) L IR / L * = 2.5 x 10 -3

200 Myr - Fomalhaut  central cavity cleared of 90% of its dust  clump or arc produced by dust trapped in resonance with large planet 450  m Holland et al. 2003, ApJ 850  m L IR / L * = 1 x 10 -4

350 Myr - Vega (  Lyrae) Wilner et al Koerner et al Millimeter Emission L IR /L * = 2.5 x 10 -5

4.5 Gyr - Sun Zodiacal Light Albedo (~1  m): 0.2 Surface Density: r –0.4 Origin: Cometary & Asteroidal (75/25-50/50) T~230 K [286 K r –0.467 L (DIRBE)] a~100  m L IR /L  =10 –7 Smooth component + bands (asteroidal, resonance trapped) (eg. Kelsall et al., ApJ,1998)

Delivery of Volatiles  Where are the ices (particularly water ice) in disks?  Where is the “snow line?”  Watch era of heavy bombardment (Clark & McCord 1980)

Spatially Resolved Dust Spectroscopy Example: TW Hya, but want to do this for optically thin disks Albedo as a function of location: What is the collision versus aging rate? Roberge et al.: See Poster!

Bottom Line  Possibility for enormous progress in spatially resolved UV-O spectroscopy to look for:  Gas density, dynamics and location as function of time (when do planets form)  High excitation atomic lines formed in shocks or X-wind (how do planets form)  Water and methane ices (near-IR) as function of location in disk (how do planets form and get their volatiles)