First Steps Toward Planet Formation in Brown Dwarfs Disks: Implications on Protoplanetary Disks

First steps toward Planet Formation in Brown Dwarfs disks: Implications on Protoplanetary Disks

Dániel Apai

Steward Observatory, The University of Arizona LAPLACE Team, NASA Astrobiology Institute

Ilaria Pascucci, Jeroen Bouwman, Antonella Natta, Thomas Henning, Kees Dullemond, Yancey Sechrest The Missing Step

Planetesimal theory: grain growth, planetesimals, planetary embryos, rocky planets and giant planet cores

Fred Ciesla 2005: at no point is a process identiﬁed that would lead to the melting of 80% of the material that is incorporated into the planetesimals. Chondrules imply that we are missing (at least) one step.

Planetary composition in large part depends on the composition of the feeding zone

Disc-Planet Connection, Cambridge, 2006, D. Apai Parameters of the Problem Stellar parameters: mass, luminosity, temperature, magnetic ﬁeld (?), UV-luminosity, stellar wind Disk parameters: radius, geometry/structure, turbulence, gas/dust ratio, metallicity, radial mixing Time Dependence:

D. Apai Disc-Planet Connection, Cambridge, 2006, D. Apai Where we Measure Dust Composition

Solar System: Meteorites (Asteroid Belt) Comets (Giant Planet region and beyond, observations) Is it “typical”?

Protoplanetary Disks: Herbig Ae/Be disks (6-12 AU, MIR spectroscopy) T Tauri stars (recent, ~1 AU, MIR spectroscopy)

Dust processing complex ⇒ Large parameter space essential

Disc-Planet Connection, Cambridge, 2006, D. Apai Disks around Brown Dwarfs

Crash Course:

- frequent (40-50% Luhman et al. 2005, Jaywardhana et al. 2003) 2 - accrete (scales with M , e.g. Muzerolle et al. 2003; talk by Natta) Chandra PR

- disk masses ~few MJup (Klein, Apai et al. 2003; Scholz et al. 2006, talk) - structure like TTS (ﬂat more frequent? Lada et al. 2006, Pascucci et al. in prep.) - lifetime: similar, maybe longer? (e.g. Hillenbrand et al. 1997, Carpenter poster)

Importance: - do planets form in such low-mass disks? - wildly different stellar and disk parameters - not weird objects - 9 out of 10 stars have very low mass!

Disc-Planet Connection, Cambridge, 2006, D. Apai Spitzer/IRS survey of Brown Dwarf Disks

Cycle-1 program of 17 brown dwarf disks in Cha I and ρ Oph (~1-3 Myr)

First results: Apai et al. 2005 Science Complete data set (rho Oph): Pascucci et al. ApJ in prep. Theory spin-offs: Dullemond, Apai, Walch 2006 ApJ Apai et al. in prep.

Cycle-3 program for an extended sample (+ K. Luhman & M. Meyer)

Disc-Planet Connection, Cambridge, 2006, D. Apai Processed Dust in BD Disks

Technical feat: High quality spectra of very faint disks

BD Disks: an evolutionary trend from unprocessed ISM-like dust to comet-like dust

Amorphous to Crystalline-rich, small grains to large grains (0.1 and 2 micron)

Disc-Planet Connection, Cambridge, 2006, D. Apai Grain growth

Silicate feature’s strength decreases with grain size (e.g. Przygodda et al 2003)

Diagnostics conﬁrms signiﬁcant grain growth in brown dwarf disks Similar to T Tauri and Herbig Ae/Be disks

Brown Dwarfs: Apai et al. 2005 T Tauri: Przygodda et al. 2004 Herbig Ae/Be: van Boekel et al. 2005

Disc-Planet Connection, Cambridge, 2006, D. Apai Dust Settling

Comparison of the continuum to ﬂared and ﬂat disk slopes [e.g. Chiang & Goldreich 1997]

(Conﬁrmed through disk modeling)

Most BD disks are in between the ﬂat and ﬂared models

Identiﬁable with the effect of dust settling on the SED [e.g. Dullemond & Dominik 2004, etc. and talks by Fromang, Nomura, Turner]

Disc-Planet Connection, Cambridge, 2006, D. Apai Dust Species and Spectral Decomposition

Amorphous Species:

Olivine Mg2xFe2(1-x)SiO4

Pyroxene MgxFe1-xSiO3

Silica SiO2 Crystalline Species: forsterite Mg2SiO4 enstatite MgSiO3

11-parameter Chi2 Optimization!

Disc-Planet Connection, Cambridge, 2006, D. Apai Iron Meteorites as remnants of planetesimals formed in the terrestrial planet region

William F. Bottke, David Nesvorny, Robert E. Grimm, Alessandro Morbidelli, David P. O’Brien 2006 Nature 439, 821

Review by Dániel Apai

Pallasite - Half metal, half olivine Formed where the asteroid’s silicate mantle and metal core mixed Pallasite, Albin, WY, D. Ball, ASU

Disc-Planet Connection, Cambridge, 2006, D. Apai Spectral Decomposition

Conﬁrms grain growth and high crystallinity

Quantitative information

Disc-Planet Connection, Cambridge, 2006, D. Apai Pascucci et al. 2006 Amorphous Species: Crystalline Species: Olivine Mg Fe SiO 2x 2(1-x) 4 forsterite Mg2SiO4 Pyroxene Mg Fe SiO x 1-x 3 enstatite MgSiO3 Silica SiO 2 Disc-Planet Connection, Cambridge, 2006, D. Apai Grain size and Crystallinity

Large dispersion in grain size and in crystallinity

Lack of small-grain- dominated crystalline disks

Bouwman et al. 2001; van Boekel et al. 2005

Brown Dwarfs: Apai et al. 2005 T Tauri: Przygodda et al. 2004 Herbig Ae/Be: van Boekel et al. 2005

Disc-Planet Connection, Cambridge, 2006, D. Apai Crystallinity - Stellar Mass/Temperature

1. BD Disks are the most crystalline 2. Stellar temperature - Crystallinity correlation is not valid 3. Crystallinity-Temperature anti-correlation

Brown Dwarfs: Apai et al. 2005 T Tauri: Meeus et al. 2004 Herbig Ae/Be: van Boekel et al. 2005 Apai et al. 2005

Disc-Planet Connection, Cambridge, 2006, D. Apai Crystallinity - Stellar Temperature

+ T Tauris from Przygodda et al. 2003 reanalyzed

Herbig Ae/Be stars with large PAH contribution show larger spread in crystallinity

Crystallinity - Stellar temperature anti-correlation

Apai et al. 2005 Pascucci et al. 2006 in prep.

Pascucci et al. 2006 Disc-Planet Connection, Cambridge, 2006, D. Apai Conclusions I.

Processing of solids is not understood Complex process - Large parameter space is essential

General: Lack of small grains+high crystallinity Crystallinity-Stellar Temperature Anti-Correlation

BD Disks: Grain growth, dust settling - First steps of PF

Apai et al. 2005 Science 310, 834 - Reprints at the registration desk!

Pascucci et al. 2006 ApJ, in prep.

Payne & Lodato Poster!

Disc-Planet Connection, Cambridge, 2006, D. Apai Crystallinity as a Tracer of Thermal History

High temperatures needed: thermal annealing / condensation at high temperatures

Radial mixing?

Disc-Planet Connection, Cambridge, 2006, D. Apai A Heritage from the Cloud Core? Centrifugal radius: radius of the infalling material

1. Slowly rotating cloud cores lead to highly crystalline disks

2. Initially highly crystalline disk, decay in crystallinity Dullemond, Apai, Walch 2006 ApJ

Disc-Planet Connection, Cambridge, 2006, D. Apai Shock Heating

Solar System chondrules formed via shock heating in situ

Harker & Desch 2003: Same shocks will anneal the amorphous grains in the GP region

⇒ No need for radial mixing in the Solar System

Single explanation for chondrules, crystals in comets and crystals in protoplanetary disks?

Origin of shocks? Planet-tracing bow-shocks, gravitational instabilities - is the density high enough?

Disc-Planet Connection, Cambridge, 2006, D. Apai Conclusions

BD Disks: First steps of PF

Crystallinity - Stellar temperature Anti-Correlation

Radial mixing? Shock-wave heating? Rotation rate?

Processing of Solids is Complex - Large parameter space is essential

Disc-Planet Connection, Cambridge, 2006, D. Apai Disc-Planet Connection, Cambridge, 2006, D. Apai Dust Composition Correlations: 1, Dust more processed in the inner disk than in the outer van Boekel et al. 2004 2, Large grains - crystals Bouwman et al. 2001, van Boekel et al. 2004 3, Crystallinity-stellar mass anti-corr. Apai et al. 2005; Pascucci et al. 2006

Radial distribution of dust species, thermal history [e.g. Gail 2004] Puzzle Mg and Fe-rich silicates [Wooden et al. PPV; Jaeger 1998] Extend study to longer wavelengths and over larger stellar parameter Pascucci et al. 2006 space Disc-Planet Connection, Cambridge, 2006, D. Apai Disc-Planet Connection, Cambridge, 2006, D. Apai Disc-Planet Connection, Cambridge, 2006, D. Apai Disc-Planet Connection, Cambridge, 2006, D. Apai Nickel-Iron composition Cores of differentiated and subsequently disrupted asteroids Iron Meteorites as remnantsWidmanstaetten of pattern planetesimals formed in the terrestrial planet region

William F. Bottke, David Nesvorny, Robert E. Grimm, Alessandro Morbidelli, David P. O’Brien 2006 Nature 439, 821

Review by Dániel Apai

Iron Meteorite, Rancho Gomelia, ASU

Disc-Planet Connection, Cambridge, 2006, D. Apai