Vincent Geers Institute for Astronomy ETH Zurich Star amp Planet Formation group A Banzatti S Bruderer F Lahuis I Pascucci Th Henning P Ábrahám A Juhász ID: 356258
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Chemical constraints on Theories of Planet Formation
Vincent GeersInstitute for Astronomy, ETH ZurichStar & 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. BenzSlide2
Outline
EX Lup: molecular emission lines toward variable YSOLimits on timescale ice-giant formation with HerschelSlide3
Different Flavors of Planet FormationSlide4
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 intactSlide5
Different Flavors of Planet FormationSlide6
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) Slide7
Chemistry in planet-forming zone
Wide range of molecules now detected in planet-forming zone (0.1-10AU) around few dozen YSOs (H2O, HCN, C2H
2, OH, CO)Concurrent C, N, O in inner disks imply complex chemistry!Pontoppidan et al. 2010Slide8
Gas disk chemistry may vary with stellar mass
Pascucci
et al. (2009)Slide9
EX Lup: temporal domain experiment
EX Lupyoung M star with diskEruptive 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 outburstUnique experiment: What happens to the gas and dust content when only 1 parameter, luminosity, is changed?Slide10
Episodic formation of cometary material
Witnessed formation of silicate crystals during outburstPrevious big outburst in 1955 => no trace in 2005 => efficient removal of crystalline silicates from surface
Ábrahám et al. 2009 NatureISM
Pre-outburst
Outburst
Halley/
Tempel
cometsSlide11
Water line variations in disk around EX Lup
H2O features (Banzatti et al. in prep.)
Quiescent phaseMarch 2005Outburst phaseApril 2008Slide12
Results of water modeling
Line ratios suggest larger surface area with constant water abundance in outburstGrid of simple LTE models (NH2O, T, area)best fit outburst : cooler water and
4-5 x larger emitting area than when in quiescenceIce line moving outward during outburst? Modified from Pontoppidan et al. 2010Slide13
C2H2, HCN, OH also change!
OH: undetected in quiescence, detected in outburstphoto-dissociation from H2O ? (Tappe et al. 2008)
compare with predictions for self-shielding by Bethell & Bergin 2010HCN & C2H2: detected in quiescence, not in outburstLine flux ratio HCN/C2H2 in quiescence consistent with solar-type star, cf. Pascucci et al. (2009)
Banzatti
et al. (in prep.)
C
2
H
2
HCN
OH
OH
Quiescent
phase
March 2005
Outburst
phase
April 2008Slide14
What is the timescale for forming ice-giants?
Do young 10-100 Myr stars with debris disk systems have enough gas (> 10 Mearth) 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 growthSlide15
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 2008Slide16
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-JanOT program (4.9 hr) : 4 young stars with well-studied dust distributions: HD 61005, HD377, MML17, RXJ1852.3-3700Observations will probe down to 0.01 – 4 Mearth of gas:Non-detections => strong upper limits for formation of ice-giants (M ~ 10 Mearth)Detections => will need follow-up (e.g. CO, [CII]) to determine relative abundances of C, N and O in photo-evaporating disksSlide17
Take home message
EX Lup: molecular emission lines changing dramatically with luminosity during outburst :H2O, OH lines stronger, C2H2
and HCN weakerSimple LTE model of water consistent with cooler water and larger emitting areaHerschel will provide important constraints on timescale for formation of ice-giantsSlide18
Gordon Research Conferences
Origins of Solar SystemsComposition of Forming Planets: A Tool to Understand Processes
July 17-22, 2011Mount Holyoke CollegeSouth Hadley, MA Program available later this fall. Registration open athttp://www.grc.org/or Google “GRC 2011 Origins”Slide19