Core Accretion at Wide Separations: The Critical Role of Gas

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1 Core Accretion at Wide Separations: The Critical Role of Gas Marois et al Ruth Murray-Clay Harvard-Smithsonian Center for Astrophysics Kaitlin Kratter, Hagai Perets, Andrew Youdin

2 Wide separation gas giants/brown dwarfs/disk fragments exist Fomalhaut HR 8799 Kalas et al Marois et al. 2008

3 GI planets can only be failed binary stars Kratter, Murray-Clay, & Youdin, ApJ (2010) 10 0 M /M p * r (AU) p If this occurs, more brown dwarfs or even M stars should be found at AU around A stars. Data: Zuckerman & Song 2009; exoplanet.eu

4 GI planets can only be failed binary stars Kratter, Murray-Clay, & Youdin, ApJ (2010) 10 0 M /M p * r (AU) p If this occurs, more brown dwarfs or even M stars should be found at AU around A stars. Data: Zuckerman & Song 2009; exoplanet.eu

5 GI planets can only be failed binary stars Kratter, Murray-Clay, & Youdin, ApJ (2010) 10 0 M /M p * x If this occurs, more brown dwarfs or even M stars should be found at AU around A stars r (AU) p Data: Zuckerman & Song 2009; exoplanet.eu

6 GI planets can only be failed binary stars Kratter, Murray-Clay, & Youdin, ApJ (2010) 10 0 M /M p * x If this occurs, more brown dwarfs or even M stars should be found at AU around A stars r (AU) p Data: Zuckerman & Song 2009; exoplanet.eu

7 Core Accretion at Large Separations doesn t work if: H dust v H /Ω z Raccrete given by gravitational focusing onto Rcore given velocity vh

8 Gas can help Rafikov (2004) Ratm H dust <v H /Ω Inaba & Ikoma (2003)

9 Wind Shearing (WISH) Perets & Murray-Clay (2011) RHill RWISH

10 Binary Capture RHill RWISH dissipation due to interaction with gas Murray-Clay & Perets (in prep) (see also Ormel & Klahr 2010)

11 Decoupling at the Atmosphere + gravitational focusing into the atmosphere RHill RBondi capture by the atmosphere only if the small particle can RWISH decouple from the exterior gas

12 Decoupling at the Atmosphere + gravitational focusing into the atmosphere RWISH > RHill RHill Gravitational focusing just needs to get the small body to the RBondi atmosphere

13 We have numerically validated our expressions RH RB RWISH

14 We have numerically validated our expressions RWISH RH RB

15 α =0 α =

16 α =0 Hydro simulations: Poster α = Lambrechts & Johansen

17 Small bodies are accreted quickly, even at wide separations growth time (yr) well-coupled 70AU 10MEarth MEarth MPluto α = small body radius (cm)

18 Small bodies are accreted quickly, even at wide separations growth time (yr) well-coupled 70AU 10MEarth MEarth MPluto α = small body radius (cm)

19 Small bodies are accreted quickly, even at wide separations growth time (yr) well-coupled 70AU 10MEarth MEarth MPluto α = small body radius (cm)

20 Small bodies are accreted quickly, even at wide separations growth time (yr) well-coupled 70AU 10MEarth MEarth MPluto α = small body radius (cm)

21 Small bodies are accreted quickly, even at wide separations growth time (yr) well-coupled 70AU 10MEarth MEarth MPluto α = small body radius (cm)

22 Growth times at 70 AU can be short enough to nucleate an atmosphere Mcore (MEarth) time (yr) M crit (Rafikov 2006,2010) α =0 50% of MMSN solids in equal mass per log bin from mm to 10cm

23 Growth times at 70 AU can be short enough to nucleate an atmosphere Mcore (MEarth) time (yr) M crit (Rafikov 2006,2010) α =0 50% of MMSN solids in equal mass per log bin from mm to 10cm

24 Growth times at 70 AU can be short enough to nucleate an atmosphere Mcore (MEarth) time (yr) M crit α =

25 Summary: Cores can grow quickly in gas, even at wide separations Small bodies are easy to make, can have low velocity dispersions, and can be accreted from large distances. Size-dependent behavior: Wind shearing (WISH) Binary capture gravitational focusing into the Bondi radius decoupling at the planet s atmosphere