How Unique Are Nearby Debris Disks? Alycia Weinberger (DTM/CIW)

Dustiness Are the disks we resolve “typical” for their ages?

Dustiness for their ages L IR / L * (Spangler et al. 2001) AU Mic * * HD * HD * HD * HD * BD * HD 69830

(Rieke et al. 2005) Stochastic or Steady-State?

Collisions Make Dust Kenyon & Bromley 2005 Planet building should generate copious dust.

Are These Disks Very Dusty? Fig 8 of Kenyon & Bromley 2005 Dust content actually observed exceeds this calculation: Primoridial Material? More planetesimals? Recent Collisions? HD HD (MMSN)

Composition

Disk Visible / Near-IR Colors HD Ared (V-J; J-K) HR 4796Ared (V-J;J-H)  Picneutral-red (B-I) AU Micneutral -blue (R-H) HD red (V-I), ?? (V-J) HD 92945neutral (V-I) Not Rayleigh Scattering Why?

Color of Silicates

Mid-Infrared Colors Access to temperature information: L=8.25L  (  Pic)

Mid-infrared imaging 12  m18  m Gemini South (T-ReCS); Telesco et al What causes the asymmetry to decrease with wavelength?

Silicate Distribution: Spatially Resolved Mid-IR Spectroscopy Wavelength (  m) Flux Density (Jy) 8 AU 16 AU Weinberger et al. 2003, ApJL Example:  Pic

Continuum Subtracted Spectra All Silicates Lie Close to the Star -- Planet Induced Collisions? Wavelength Silicate Line - Continuum R=0 R=8 AU R=16 AU R> 24 AU Weinberger et al. 2003

Grain Populations  Only see silicates out to 25 AU  Crystalline silicates centered at star, but small amorphous silicates not! Okamoto et al. 2004, Nature

Same ellipticity! Same PA! Different sizes! Ice Sublimation? Reflected & Emitted Light Weinberger et al Marsh et al. 2002

8  m (contour) PSF (grayscale) 8  m (contour) 11.7  m (grayscale) Disk is same size at 8 & 12  m!  PAHs! N E New Mid-Infrared Imaging

Spatially Resolved Spectra Terrestrial O 3 Central Disk Spectrum 24 AU (0.’’24) 168 AU (1.’’68) 192 AU (1.92 AU) - Backgd (Rainbow step every 24 AU) These are all PAHs not Silicates!

Increasing Line Strengths Central Disk Spectrum 72 AU 48 AU 24 AU Are PAHs being lifted off grains far from the star? Evidence of gooey organics? Flux / Continuum Wavelength (microns)

More typical composition F /VF v HD = MWC 758  Luminosity --- Same!  Age Same! But L IR Much Bigger Crystalline and amorphous silicates

Dustiness for their ages L IR / L * (Spangler et al. 2001) AU Mic * * HD * HD * HD * HD * BD

Signature of Huge Impact? CDE1 Forsterite Enstatite Amorphous olivine Amorphous pyroxene Blackbody HIP 8920: Small Grains (Song et al. 2005, Weinberger et al 2006)

Silicate Feature -Small Grains Fnu (Jy) Wavelength (microns) Silicate-less Debris Disk (Jura et al.) HIP 8920 Reach et al Zodi Hanner et al Song et al. 2005

Formation Region Did the NRDD form in environments similar to the Sun?

 Pic Association (  Pic, AU Mic) Looks Taurus-Like not Orion-Like Song et al TW Hy Association (HR 4796) also fairly spread/sparse

B-V Li 6708A Equivalent Width [mA] Pleiades (100 Myr) NGC 2264 (5 Myr) TW Hydrae Eta Chamaeleontis HD B and C HD Rejected Possible HD New Members (Kinematic) MA (~8Myr) Kinematic and Youth Selection

l [°] b [°] Galactic Coords of Young Stars

Where Did the Sun Form? 60 Fe with t 1/2 = 1.5 Myr Found in Solar System (Tachibana & Huss 2003) Truncation of the Kuiper Belt (e.g. Kobayashi, Ida & Tanaka 2005) Formation of Ice Giant and Saturn Compositions (Boss, Wetherill & Haghighipour 2002) Triggered Star Formation in Ionization Fronts Evidence for “Orion-Like” Environment:

e Courtesy Jean Schneider Exoplanet Encyclopedia Ecc. of Exosolar Planets

The 6 Year Future  Spitzer detections of new debris disks  Spitzer determinations of disk lifetimes  Spitzer mineralogy of dust  Ground mid-infrared interferometer measurements of inner disks and their compositions  SOFIA searches for H 2 emission  HST and AO imaging of Spitzer detected disks  Detection of disk rotation (  Eri)  Detection of planets in disks (ExAO?)

The End

Silicate Spectra (thick) HD A Myr HD A Myr UX Ori A3 1-2 Myr VX Cas A0 1 Myr Flux Density Wavelength (  m) Recall that the ages are not well known

Roberge et al. 2000, 2002, 2004 Gas : Dust Ratio AU MicBeta PicISM Spec. TypeM1A5 L (L solar ) M dust (M  ) 0.01 (Liu et al. 2004) 0.04 (Dent et al. 2000) M H2 / M dust < 4:1< 3:1100:1 When Gas:Dust Low and CO/H 2 high  Comet Sublimation not primordial gas/dust

A “Real” Debris Disk - Ours! Our Solar System has only a tenuous disk (Zodiacal Cloud) but also has planets [Cassini (1685)] Zodi: M planets ; 100x IR luminosity

Zodi Parameters 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)

Evidence for planets in debris disks What do we look for? Dust sculpted dynamically  Gaps  Asymmetries (e.g. arcs, warps)  Clumps

The Kuiper Belt