References:References:Sozzetti, A., et al. 2007, ApJ, 664, 1190Sozzetti, A., et al. 2007, ApJ, 664, 1190

Mandushev, G., et al. 2007, ApJ, 667, L195Mandushev, G., et al. 2007, ApJ, 667, L195

Sozzetti, A., et al. 2007a, ApJ, in preparationSozzetti, A., et al. 2007a, ApJ, in preparation

Sozzetti, A., et al. 2007b, ApJ, in preparationSozzetti, A., et al. 2007b, ApJ, in preparation

Kovacs, G., et al. 2007, ApJL, in press (arXiv0710.0602)Kovacs, G., et al. 2007, ApJL, in press (arXiv0710.0602)

Observational Tests of Observational Tests of Planet Formation Planet Formation

ModelsModelsA. SozzettiA. Sozzetti1,21,2, D. W. Latham, D. W. Latham11, , G. TorresG. Torres11, B. W. CarneyB. W. Carney 3 3, J. B. Laird, J. B. Laird44, , R. P. StefanikR. P. Stefanik11, ,

A. P. BossA. P. Boss55, D. Charbonneau, D. Charbonneau11, F. T. O’Donovan, F. T. O’Donovan66, M. J. Holman, M. J. Holman11, J. N. Winn, J. N. Winn77

1) CfA; 2) INAF-OATO; 3) UNC; 4) BGSU, 5) CIW 6) Caltech, 7) CIW1) CfA; 2) INAF-OATO; 3) UNC; 4) BGSU, 5) CIW 6) Caltech, 7) CIW

The Planet-Metallicity Connection IThe Planet-Metallicity Connection I

The Planet-Metallicity Connection IIThe Planet-Metallicity Connection II

The planet-metallicity connection is one of the most important aspects of the close relationship between characteristics and frequencies of planetary systems and the physical properties of the host stars which have The planet-metallicity connection is one of the most important aspects of the close relationship between characteristics and frequencies of planetary systems and the physical properties of the host stars which have been unveiled by the present sample of over 200 extrasolar planets. In particular, the likelihood of finding a planet around a given star rises sharply with stellar metallicity. Furthermore, a correlation may alsoexist been unveiled by the present sample of over 200 extrasolar planets. In particular, the likelihood of finding a planet around a given star rises sharply with stellar metallicity. Furthermore, a correlation may alsoexist between estimated inner core masses of transiting giant planets and the hosts' metal content. In both cases, the evidence collected so far appears to strongly support the orthodox mechanism of giant planet between estimated inner core masses of transiting giant planets and the hosts' metal content. In both cases, the evidence collected so far appears to strongly support the orthodox mechanism of giant planet formation by core accretion, as opposed to the heretic formation mode by disk instability. However, the relatively small numbers of metal-poor stars screened for planets so far, and the large uncertainties often formation by core accretion, as opposed to the heretic formation mode by disk instability. However, the relatively small numbers of metal-poor stars screened for planets so far, and the large uncertainties often present in the determination of both planet and stellar properties in transiting systems prevent one from drawing conclusions.present in the determination of both planet and stellar properties in transiting systems prevent one from drawing conclusions.We will describe two experiments designed to put the observed trends on firmer observational grounds, thus ultimately helping to discriminate between proposed planet formation models. First, we will present We will describe two experiments designed to put the observed trends on firmer observational grounds, thus ultimately helping to discriminate between proposed planet formation models. First, we will present results from a Doppler survey for giant planets orbiting within 2 AU of a well-defined sample of 200 field metal-poor dwarfs. Our data will crucially help to gauge the behavior of planet frequency in the metal-poor results from a Doppler survey for giant planets orbiting within 2 AU of a well-defined sample of 200 field metal-poor dwarfs. Our data will crucially help to gauge the behavior of planet frequency in the metal-poor regime. Then, I will describe a novel method for improving on the knowledge of stellar and planetary parameters of transiting systems through a careful analysis of spectro-photometric measurements. With this regime. Then, I will describe a novel method for improving on the knowledge of stellar and planetary parameters of transiting systems through a careful analysis of spectro-photometric measurements. With this approach, structural and evolutionary models of irradiated planets can be better informed, allowing for refined estimates of the heavy-element content of transiting planets and for improved understanding ot the approach, structural and evolutionary models of irradiated planets can be better informed, allowing for refined estimates of the heavy-element content of transiting planets and for improved understanding ot the core mass - stellar metallicity correlation.core mass - stellar metallicity correlation.

AbstractAbstract

The MThe Mcc – [Fe/H] – [Fe/H] ConnectionConnection

??Burrows et al. (ApJ, 2007): Burrows et al. (ApJ, 2007):

““The core mass of transiting The core mass of transiting planets scales linearly planets scales linearly (or more) with [Fe/H]”(or more) with [Fe/H]”

Guillot et al. (A&A, 2006): Guillot et al. (A&A, 2006): ““The heavy element content The heavy element content

of transiting extrasolar planets of transiting extrasolar planets should be a steep function should be a steep function

of stellar metallicity”of stellar metallicity”

??

Do inferred exoplanets core masses depend on metallicity?Do inferred exoplanets core masses depend on metallicity?

The MThe Mpp-R-Rpp Relation Relation

Roughly OK

Very large core?

Coreless??Coreless??

Default models Default models have trouble!have trouble!

Transiting planetsTransiting planetscome in many flavorscome in many flavors

What are theirWhat are theiractual interiors?actual interiors?

How did they form?How did they form?

Improving Stellar Improving Stellar and Planetary Parametersand Planetary Parameters

• Must determine RMust determine R**, M, M**, to derive M, to derive Mpp, R, Rpp

• RR**, M, M** are inferred by comparison with stellar evolution models are inferred by comparison with stellar evolution models• Use TUse Teffeff and a proxy for L and a proxy for L**, such as log(g), such as log(g)• But…But…1)1) TTeff eff must be reliable: check relative agreement of multiple methodsmust be reliable: check relative agreement of multiple methods2)2) Log(g) is usually not known precisely enough: use a new method Log(g) is usually not known precisely enough: use a new method

based on observables from the light-curvebased on observables from the light-curve

A Better Proxy: a/RA Better Proxy: a/R**

Main adjustable light-curve Main adjustable light-curve parameters: parameters:

R

Ri

R

ab

R

a p,cos,

ρρ**

XX

XX

Theoretical values of a/RTheoretical values of a/R** are compared are compared with the results from the light-curve fitwith the results from the light-curve fit

ResultsResults• We have determined precisely the stellar and planetary We have determined precisely the stellar and planetary

properties of a number of transiting systems (TrES-2, TrES-3, properties of a number of transiting systems (TrES-2, TrES-3, TrES-4), using a combination of high-quality spectroscopic and TrES-4), using a combination of high-quality spectroscopic and photometric dataphotometric data

• New approachNew approach: : compare theoretical isochrones with a reliablecompare theoretical isochrones with a reliable spectroscopic Tspectroscopic Teffeff and theand the photometric a/Rphotometric a/R**,, rather than the rather than the spectroscopic log(g).spectroscopic log(g).

• As a result, As a result, uncertaintiesuncertainties in stellar and planetary parameters ( in stellar and planetary parameters (RR**, , MM**, R, Rpp, M, Mpp, log(g, log(gpp))) ) are improved by factors of 2-5are improved by factors of 2-5

• The comparison between the measured planet and host’s The comparison between the measured planet and host’s parameters for these systems complicate the picture for planet parameters for these systems complicate the picture for planet structure theories. In particular, structure theories. In particular, metal-rich stars appear to be metal-rich stars appear to be orbited by hot Jupiters whose radii can be both small (requiring orbited by hot Jupiters whose radii can be both small (requiring large core masses) as well as quite inflated (consistent with large core masses) as well as quite inflated (consistent with coreless models).coreless models). At present, at least three systems At present, at least three systems (HAT-P-4, (HAT-P-4, WASP-1, and TrES-4) do not seem to support the existence of a WASP-1, and TrES-4) do not seem to support the existence of a simple relation between host star metallicity and planet’s core simple relation between host star metallicity and planet’s core mass.mass.

• This method is being applied to the other transiting systems, to This method is being applied to the other transiting systems, to best inform structural and evolutionary (and ultimately best inform structural and evolutionary (and ultimately formation) modelsformation) models

How do You Go About it?How do You Go About it?

• The star-planet interplay is complexThe star-planet interplay is complex• The parameter space is largeThe parameter space is large• Uncertainties are no lessUncertainties are no less

Determine stellar and planetary Determine stellar and planetary properties as best as you can!properties as best as you can!

From top to bottom, metallicities for the parent stars are: 0.23, From top to bottom, metallicities for the parent stars are: 0.23, 0.24,0.24,0.02, 0.14, and 0.13.0.02, 0.14, and 0.13.

The fThe fpp – [Fe/H] Relation I – [Fe/H] Relation I

Ida & Lin (ApJ, 2004), Kornet et al. (A&A, 2006):

“The probability of forming gas giant planets by core

accretion is roughly a linear function of Z”

Boss (ApJL, 2002): “The probability of forming gasgiant planets by disk instability is remarkably insensitive to Z”

N/AN/A

Do giant planets form by Core Accretion, Disk Instability, or both?Do giant planets form by Core Accretion, Disk Instability, or both?

FFpp ~ Z, for Z > 0.02) ~ Z, for Z > 0.02)FFpp ~ const, for Z < 0.02 ~ const, for Z < 0.02

Linear Dependence?Linear Dependence?Flat tail for [Fe/H] < 0.0?Flat tail for [Fe/H] < 0.0?

Low statistics for Low statistics for [Fe/H] < -0.5[Fe/H] < -0.5

Santos et al. (A&A, 2004):Santos et al. (A&A, 2004):No P, K, [Fe/H] thresholds:No P, K, [Fe/H] thresholds:

Fischer & Valenti (ApJ, 2005):Fischer & Valenti (ApJ, 2005):K > 30 m/s, P < 4 yr, -0.5<[Fe/H]<0.5: K > 30 m/s, P < 4 yr, -0.5<[Fe/H]<0.5:

]/[0.210 HFepF

Quadratic dependence?Quadratic dependence?Flat tail for [Fe/H]<0.0?Flat tail for [Fe/H]<0.0?

Low statistics for [Fe/H] < -0.5Low statistics for [Fe/H] < -0.5

The fThe fpp – [Fe/H] Relation II – [Fe/H] Relation II

Keck/HIRES Keck/HIRES Metal-Poor Planet SearchMetal-Poor Planet Search

• 200 stars200 stars from the Carney-Latham and Ryan samples from the Carney-Latham and Ryan samples • No close stellar companionsNo close stellar companions• Cut-offs: -2.0 < [Fe/H] < -0.6, TCut-offs: -2.0 < [Fe/H] < -0.6, T

effeff < 6000 K, V < 12 < 6000 K, V < 12• Reconnaissance for gas giant planets within 2 AUReconnaissance for gas giant planets within 2 AU• Campaign duration: 3 yearsCampaign duration: 3 years• Typical radial-velocity rms: ~ 9 m/sTypical radial-velocity rms: ~ 9 m/s

No clear RV trends are No clear RV trends are seen as a function of seen as a function of V, TV, Teffeff, [Fe/H], and , [Fe/H], and ΔΔTT

ResultsResults COMPLETENESS:COMPLETENESS:

- 6 observations, 3-yr baseline;6 observations, 3-yr baseline;

- RV RV = 9 m/s= 9 m/s

- 99.5% confidence level99.5% confidence level

- Sensitivity to companions: Sensitivity to companions: 1M1MJJ<M<Mppsin(i)<6Msin(i)<6MJ J (K > 100 m/s), with (K > 100 m/s), with orbital periods between a few days and orbital periods between a few days and 3 years3 years

- Strong dependence of detection - Strong dependence of detection thresholds on eccentricitythresholds on eccentricity

WE FIND NONE…WE FIND NONE…

Sozzetti et al. 2007a (in prep.):Sozzetti et al. 2007a (in prep.):K > 100 m/s, P < 3 yr, -1.0<[Fe/H]<0.5:K > 100 m/s, P < 3 yr, -1.0<[Fe/H]<0.5:

?10 ]/[0.2 CF HFep

• We observe a dearth of gas giant planets (K > 100 m/s) within 2 AU of metal-poor stars (-2.0 < [Fe/H] < -0.6), confirming and extending previous findings

• The resulting average planet frequency is Fp< 0.67% (1σ)

• Fp(-1.0<[Fe/H]<-0.5) appears to be a factor of several lower than Fp([Fe/H]>0.0), but it’s indistinguishable from Fp(-0.5<[Fe/H]<0.0)

• Is Fp([Fe/H]) bimodal or not? It is consistent with being so. However, need larger and better statistics to really discriminate…

• 1) Expand the sample size; 2) lower the mass sensitivity threshold; 3) search at longer periods. Next generation RV surveys and future high-precision space-borne astrometric observatories (SIM, Gaia) can help!