1. Chemical constraints on Theories of Planet Formation Vincent Geers Institute for Astronomy, ETH Zurich Star & Planet Formation group A. Banzatti, S. Bruderer, F. Lahuis, I. Pascucci, Th. Henning, P. Ábrahám, A. Juhász M. Meyer, U. Gorti, E. Mamajek, D. Hollenbach, A. Benz

2. Outline EX Lup: molecular emission lines toward variable YSO Limits on timescale ice-giant formation with Herschel

3. Different Flavors of Planet Formation

4. The carbon problem Lee, Bergin & Nomura 2010 C under abundant in Earth and meteorites compared to what is available at formation => primordial carbon grains are destroyed, while silicon grains remain intact

5. Different Flavors of Planet Formation

6. Discontinuities in disks provide observational tests From M. Meyer, Physics World, November, 2009 Based on Dullemond et al. (2001) with artwork from R. Hurt (NASA)

7. Chemistry in planet-forming zone Wide range of molecules now detected in planet-forming zone (0.1-10AU) around few dozen YSOs (H 2 O, HCN, C 2 H 2, OH, CO) Concurrent C, N, O in inner disks imply complex chemistry! Pontoppidan et al. 2010

8. Gas disk chemistry may vary with stellar mass Pascucci et al. (2009)

9. EX Lup: temporal domain experiment EX Lup – young M star with disk – Eruptive variable star, on timescale of decades – Recent outburst in January 2008, accretion rate up ~40, luminosity ~4 (Aspin et al. 2010) – Spitzer observed it before and during outburst Unique experiment: What happens to the gas and dust content when only 1 parameter, luminosity, is changed?

10. Episodic formation of cometary material Witnessed formation of silicate crystals during outburst Previous big outburst in 1955 => no trace in 2005 => efficient removal of crystalline silicates from surface Ábrahám et al. 2009 Nature ISMPre-outburstOutburst Halley/Tempel comets

11. Water line variations in disk around EX Lup H 2 O features (Banzatti et al. in prep.) Quiescent phase March 2005 Outburst phase April 2008

12. Results of water modeling Line ratios suggest larger surface area with constant water abundance in outburst Grid of simple LTE models (N H2O, T, area) – best fit outburst : cooler water and 4-5 x larger emitting area than when in quiescence Ice line moving outward during outburst? Modified from Pontoppidan et al. 2010

13. C2H2, HCN, OH also change! OH: undetected in quiescence, detected in outburst – photo-dissociation from H 2 O ? (Tappe et al. 2008) – compare with predictions for self-shielding by Bethell & Bergin 2010 HCN & C 2 H 2 : detected in quiescence, not in outburst – Line flux ratio HCN/C 2 H 2 in quiescence consistent with solar-type star, cf. Pascucci et al. (2009) Banzatti et al. (in prep.) C2H2C2H2 HCN OH Quiescent phase March 2005 Outburst phase April 2008

14. What is the timescale for forming ice-giants? Do young 10-100 Myr stars with debris disk systems have enough gas (> 10 M earth ) to form planets like Uranus and Neptune? Debris disks assumed gas-poor, but counter- examples exist: 49 Cet, Beta Pic (10-20 Myr) Modest amounts of gas may still significantly influence grain dynamics, thus planetesimals growth

15. Herschel is best for limits of ice-giant formation! [OI] one of the strongest gas emission lines originating from 10-50 AU region (ice-giant planet forming zone) => sensitive probe of remnant gas available to form ice- giants Based on Gorti & Hollenbach 2008

16. Limits on ice-giant formation with Herschel Search for remnant gas in 10-100 Myr debris disks, with detected planets and/or signs of planet formation: – GT program (2.5 hr) : HR 8799, HD 15115 to be scheduled hopefully next window Nov-Jan – OT program (4.9 hr) : 4 young stars with well-studied dust distributions: HD 61005, HD377, MML17, RXJ1852.3-3700 Observations will probe down to 0.01 – 4 M earth of gas: – Non-detections => strong upper limits for formation of ice- giants (M ~ 10 M earth ) – Detections => will need follow-up (e.g. CO, [CII]) to determine relative abundances of C, N and O in photo- evaporating disks

17. Take home message EX Lup: molecular emission lines changing dramatically with luminosity during outburst : – H 2 O, OH lines stronger, C 2 H 2 and HCN weaker – Simple LTE model of water consistent with cooler water and larger emitting area Herschel will provide important constraints on timescale for formation of ice-giants

18. Gordon Research Conferences Origins of Solar Systems Composition of Forming Planets: A Tool to Understand Processes July 17-22, 2011 Mount Holyoke College South Hadley, MA Program available later this fall. Registration open at http://www.grc.org/ or Google GRC 2011 Origins