# Presentation: 861088

## Thayne Currie

**Thayne Currie**
- (CfA)
- Collaborators: Scott Kenyon (CfA), George Rieke (UA), Charles Lada (CfA), Zoltan Balog (UA), Peter Plavchan (IPAC), Jesus Hernandez (UM)

**Notes:**
1. name, 2. title, 3. paper, 4. collabs

## Over 280 known extrasolar planets (many more coming from COROT and Kepler)

- Wide diversity of exoplanet properties
- Important point: to understand exoplanets, must understand how they are formed:  provides context for (and may explain) observed exoplanet properties

## Planets Form in Disks around Young Stars

- (NASA/Shu, Adams, and Lizano 1987)

- Circumstellar Disk Evolution/Planet Formation

- t = 100 Myr- 1 Gyr

**Notes:**
Molecular cloud core, collapses, into embedded protostar with disk outflow and infall ,  switches thrown hand of God ....planets, focus on circumstellar disk evolution

## A Primer on Circumstellar Disk Evolution

- ‘**Primordial**’ disk: Accretion; Star+optically-thick disk emission from gas & dust.  Excess emission from > 1-2 microns (J—K band)

- ~1 – 3 (5?, 10?) Myr

- ‘Evolved primordial’(transition) disk: inner holes/gaps, grain growth, gas giant formation?; weak at < 5-10 microns; optically-thick > 10-30 microns

**Debris disk: **No/little gas; Optically-thin emission > 5-20 microns; dust replenishment  active ***Terrestrial***/ice giant formation;  Presence/absence of debris emission  constraints on planet formation

- 1 – 10?  Myr

- 3--10 Myr – 100 Myr/1 Gyr

- Kenyon & Hartmann 1987, 1995; Backman & Paresce 1993; Kenyon and Bromley 2004

**Notes:**
Embedded protostar with outflow, infalling material, accretion starting, these sources have SEDs peak in mid/far IR (bluer as protostar contracts);  infalling envelope material into disk, primordial disk, accretion onto star, grains grow from submicron sizes (ISM/protostar) to microns and larger (change in disk chemistry), planet formation processes starting; appear as a stellar photosphere + disk emission longwards of I/J band, comparable in mag to star

## Before Spitzer

- Accretion rate & Frequency of optically thick emission (primordial) declines w/ time (~5-10 Myr; Haisch, Lada & Lada 2001)
- Frequency of  ~10 micron emission, primordial & warm debris disks (TPF) also declines (Mamajek et al. 2004), is low during epoch of TPF (which is ~10—30 Myr; Kenyon & Bromley 2004)
- To constrain gas giant formation, TPF, icy planet formation, need ~3—30 Myr old clusters

## Outstanding Issues in Circumstellar Disk Evolution/Planet Formation

- Timescale for gas giant planet formation; primordial-to-debris disk transition
- Timescale for terrestrial planet formation/frequency of terrestrial planets
- Tracing history of icy planet formation/freq. of icy planets

## IC 348

- ~2—3 Myr old
- Stellar pop. well studied (Luhman et al.; Muench et al. 2007); Nearby: 320 pc
- Lada et al. 2006: Primordial disks (‘thick’) and ‘anemic’ disks (weaker emission than primordial).
- Evo state of ‘anemic’ disks not constrained
- Currie & Kenyon 2008: analyze IRAC/MIPS colors, new spectra, SED modeling
- Compare w/ Upper Sco.

## h and χ Persei

- 13—14 Myr old: critical age for planet formation; esp. terrestrial
- Low, uniform reddening: E(B-V)~0.5
- *_EXTREMELY_* populous: _very_ solid statistics

## h and χ Persei needed to constrain warm dust emission from terrestrial planet formation

**Terrestrial planet formation** at ~10--30 Myr  (e.g. Yin et al. 2002; Kenyon & Bromley 2006)
**Warm dust emission** (5-10 microns) **is rare **at > 5-10 Myr (Mamajek et al. 2004)
**Few high-mass/solar-mass stars** in other 10—30 Myr old clusters
**Massive clusters needed** to study frequency, lifetimes, and evolution of (warm) debris emission from terrestrial planet formation (FEPS too small): **h and ****χ**** Persei**

- Number of A stars for ~10-30 Myr old clusters

## h and χ Persei Observations

- _Observation_     _λ_     _sample size_   _diagnostic_
- Opt. Phot.      0.5-0.8  42,000            stellar phot.
- Hectospec      0.3-0.8  11,500            spec. type,
- (spectroscopy)                                 gas accretion
- 2MASS          1-2.2     11,000         star/hot dust
- (photometry)                                                 (~1000 K)
- IRAC              4.5-8  5,000-7,000    warm dust
- (photometry)                                  (~250-500 K)
- MIPS               24          616              cool dust
-  (photometry)                                  (~50-200 K)

*** ******IRAC survey probing warm dust from terrestrial planet formation is ***_***> 20x larger***_*** than all other surveys (e.g. FEPS Legacy Program)***

## NGC 2232

**NGC 2232**

- ~25 Myr old
- Negligible  reddening
- (E(B-V) ~0.05)
- Nearby: 320-360 pc
- Almost completely ignored by star formation community for past 30 years!!!
- IRAC/MIPS Obs.
- Reduction & Photometry from T. Currie & P. Plavchan
- Match with ROSAT archive, proper motion, spectra
- ~240 candidate/confirmed members; full confirmed B/A star membership list

- Currie et al. 2008b

## Constraining Planet Formation from Spitzer

- Primordial-to-debris disk transition; Timescale for gas giant planet formation (3-15 Myr)
- Timescale for terrestrial planet formation freq. of terrestrial planets
- (10-30 Myr)
- Tracing history of icy planet formation/freq. of icy planets
- (10-100 Myr)

- _Sample_
- IC 348; Upper Scorpius;
- h and χ Persei
- (IRAC/MIPS/spec)
- h and χ Persei
- (IRAC + some MIPS)
- h and χ Persei;
- NGC 2232
- (MIPS)

- _References_
- Lada et al. 2006; c2d; Carpenter et al. 2006; Currie & Kenyon 2008; Currie et al. 2007c, 2008c
- Currie et al. 2007a,b; Currie et al. 2008a,c
- Currie et al. 2008a,b
- See also FEPS; Trilling et al. 2008; Rieke et al. 2005

## Mid-IR colors of 3—5 Myr old stars are stellar mass dependent

- Carpenter et al. 2006; Currie & Kenyon 2008

- Upper Sco (5 Myr)

- IC 348 (2-3 Myr)

- ‘thick’   ‘anemic’ ‘diskless’

## SEDs of early to late-type ‘thick’, ‘anemic’, and ‘diskless’ sources
Primordial disk model (Kenyon & Hartmann 1987)
Evolved primordial disk model
Terrestrial zone debris disk model (2.0 Msun and 3.0 Msun models from Kenyon & Bromley 2004)
New optical spectroscopic observations: very high signal-to-noise, look for accretion signatures

**Primordial disk model** (Kenyon & Hartmann 1987)
**Evolved primordial disk model**
**Terrestrial zone debris disk model** (2.0 Msun and 3.0 Msun models from Kenyon & Bromley 2004)
- New optical spectroscopic observations: very high signal-to-noise, look for accretion signatures

- (NASA/JPL/D. Watson; D. Hines/JPL)

- Disk Modeling

**Notes:**
8 sources with good phot. From U through [8], spectra to confirm membership.  3 disk models: optthick flat, inner hole, DD

##  Early-type anemic sources: no gas accretion

Late-type anemic sources: many have gas accretion

- Currie & Kenyon 2008

-  Early-type anemic sources: no gas accretion
- Late-type anemic sources: many have gas accretion

- Early-type anemic sources: terrestrial planet formation
- Late-type anemic sources: evolved primordial disks

- Accretion Signatures and SEDs of 3—5 Myr old stars are stellar mass dependent

## Early-type anemic/diskless sources have Ld/L* typical of debris disks (10^-4 –10^-3)
Late-type sources (w/ MIPS detections) = evolved primordial disks
Intermediate types have both

- Early-type anemic/diskless sources have Ld/L* typical of debris disks (10^-4 –10^-3)
- Late-type sources (w/ MIPS detections) = evolved primordial disks
- Intermediate types have both

-  TPF can occur as soon as ~2—3 Myr
- _High-mass (> 2 Msun) stars get to debris disk phase faster_
- _High-mass stars must form gas giants by ~2--3 Myr_

- The Primordial to Debris Disk Transition is stellar mass dependent

- AB Aur

- 49 Cet

- AU Mic

- Hen 3-600

- (PD)

- (EPD)

- (DD)

- (DD)

- hxPer-S5 (DD)

## Gas Accretion at 13 Myr (h and χ Persei)

-  25/6,200 stars analyzed have accretion signatures (dash-dot); 16 strongly accreting (dark) (vast majority of long-lived accretors!)
- Spectral-type dependence of accretors (<0.1%  for < F8; ~1--2 % for > F8)?

-  Currie et al. 2007c, 669, 33L

## Hot Jupiters around ~0.5% of FGK stars 
Lack of hot Jupiters around higher-mass stars (MS A stars)
Not a selection bias or metallicity bias (J. Johnson et al. 2007, 2008)
Could characteristics of long-lived accreting disks explain distribution of hot Jupiters??

- Lack of hot Jupiters around higher-mass stars (MS A stars)
- Not a selection bias or metallicity bias (J. Johnson et al. 2007, 2008)
- Could characteristics of long-lived accreting disks explain distribution of hot Jupiters??

## IRAC-excess sources in h and χ Persei

**Notes:**
1. See sources here ...., 2. quantify population (would move all this to the left), 3. use 2MASS J for mass, lambda for stellocen dist.

## 8 sources w/: Ks-[5.8] (8) > 0.5 (0.75), H'spec/FAST spectroscopy, opt. photometry
Primordial disk model (Kenyon & Hartmann 1987)
Evolved primordial disk model
Terrestrial zone debris disk model (2.0 Msun model from Kenyon & Bromley 2004)
Spectroscopy: No evidence for accretion

**Primordial disk model** (Kenyon & Hartmann 1987)
**Evolved primordial disk model**
**Terrestrial zone debris disk model** (2.0 Msun model from Kenyon & Bromley 2004)
- Spectroscopy: No evidence for accretion

- (NASA/JPL/D. Watson; D. Hines/JPL)

- Disk Modeling

**Notes:**
8 sources with good phot. From U through [8], spectra to confirm membership.  3 disk models: optthick flat, inner hole, DD

## Warm debris disks in h and χ Persei: terrestrial planet formation

- Data = magenta dots
- Primordial disk model = dash/triangle

- T. Currie et al., 2007b, ApJ, 663, 105L

- Evolved primordial disk model = cyan
- Debris disk model = violet

- Ldisk/L* ~ 10-4 – 6 x 10-3

**Notes:**
Here are optthick model predictions, here are transition disk predictions, here are debris disk predictions   and here are data

## Warm, Terrestrial Zone Dust in h and χ Persei

- Warm, Terrestrial Zone Dust in h and χ Persei

-  IRAC excess emission from warm circumstellar dust
- Quantify IR Excess Population: Criteria- Ks-[IRAC] > 0.4+σ
- Disk frequency vs. J/spectral type and wavelength

**Notes:**
1. See sources here ...., 2. quantify population (would move all this to the left), 3. use 2MASS J for mass, lambda for stellocen dist.

## Constraints on Terrestrial Zone Disk Emission

- Currie et al. 2007a, ApJ, 659, 599; Currie et al. 2008c

- Warm circumstellar dust emission  is *spectral type/stellar mass dependent*
- Warm circumstellar dust emission is *wavelength/location-dependent*
- Debris Disks in vast majority of cases
- TPF runs to completion faster for high-mass stars than intermed. mass  stars

- All spectral-type bins (B0-B9; A0-A9; F0-F9;
-  G0-G5) have > 500 stars

## Wavelength-dependent frequency/Inside-out evolution of disks (h and χ Persei)

- Wavelength-dependent frequency/Inside-out evolution of disks (h and χ Persei)

- T. Currie, et al. 2008a, ApJ, 672, 558

## 1 early type [8] excess star, 4-5 late-type (weak) [8] excess sources

- Wavelength-dependent frequency/Inside-out evolution of disks (NGC 2232)

- 1 early type [8] excess star, 4-5 late-type (weak) [8] excess sources

- 8/15 early-type stars have [24] excess
- one AU Mic-like star (M0, Ks-[24] ~1.5)!
- f[8] << f[24] during TPF epoch

- u

- T. Currie et al., 2008b, ApJ submitted

## Understanding the Wavelength Dependent Disk Fraction:

**Terrestrial Zone (1.5-7.5 AU)**

**Ice giant/Kuiper belt (30-150 AU)**
**Model [24] excess sources with cold disk**

-  Inside-out Evolution of Debris Disks

- Debris Disk Evolution from Kenyon & Bromley 2004

## Understanding the Wavelength Dependent Disk Fraction: Inside-out Evolution of Debris Disks

_***Warmer***_*** Debris Disk region***
***Shorter***** wavelength emission, **_**shorter**_** lifetime of emission**

_***Colder***_*** Debris Disk Region***
***Longer***** wavelength emission, **_**longer**_** lifetime of emission**
- Kenyon & Bromley 2004, 2008

- Debris Disk Evolution from Kenyon & Bromley 2004

- Understanding the Wavelength Dependent Disk Fraction: Inside-out Evolution of Debris Disks

## Evolution of Mid-IR Emission:power-law decay in MIPS [24] from Rieke et al. (2005)

- Consistent with 1/t decline for     t ~ 30 – 1000 Myr
- 5-30 Myr range poorly sampled

-   Cepheus (4, 11.8 Myr)
- Orion OB1 (5,10 Myr)
-  Sco-Cen (5, 16-17 Myr)
- h and **χ** Persei (13 Myr)

- Now, add several clusters observed after:

- Compare with theory (high/low-mass disk)

## The Evolution of Debris Emission from Planet Formation:(from Currie et al. 2008a, ApJ, 672, 558)

- The Evolution of Debris Emission from Planet Formation:*(from Currie et al. 2008a, ApJ, 672, 558)*

- T. Currie et al., 2008a, ApJ, 672, 558

- High-mass debris disk
- Low-mass debris disk

- Cepheus --light blue
- Orion OB1-- cyan

- Sco-Cen -- violet
- h and **χ** Persei -- deep purple

## The Evolution of Debris Emission from Planet Formation:The Rise and Fall of Debris Disks

- The Evolution of Debris Emission from Planet Formation:*The Rise and Fall of Debris Disks*

- Rise in emission from 5-10 Myr
- Peak in emission from ~ 10-20 Myr
- 1/t decline in emission from ~ 30-1000 Myr
- Trend verified by Kolmogorov-Smirnov test; Wilcoxan Rank-Sum Test
- rise/peak consistent with debris disk models (Kenyon & Bromley), due to growth from ~100 km to > 1,000 km sizes

- T. Currie et al., 2008a, ApJ, 672, 558

## The Rise and Fall of Debris Disks(Current as of May, 5 2008)

*The Rise and Fall of Debris Disks**(Current as of May, 5 2008)*

- More clusters added: NGC 2362 (4-5 Myr); Eta Cha (8 Myr); BPMG (12 Myr); and NGC 2232 (25 Myr).  Age for NGC 2547 adjusted to 38 Myr   (Currie & Lada et al. 2008; Gautier et al. 2008; Rebull et al. 2008; Currie et al. 2008b)
- Rise (5—10 Myr) and Peak (10—20 Myr) confirmed; decline from 20—30 Myr not as steep as 1/t
- Peak should be later for lower-mass stars (Kenyon & Bromley 2008)

## Frequency of [24] Debris Emission around B/A stars *increases* with time from 5—25 Myr

*Frequency of [24] Debris Emission around B/A stars *increases* with time from 5—25 Myr*

- Multiple clusters have f([24] exc) > 45-50%
- [24] probes dust beyond ice line
- f(icy planets) > 50%

- T. Currie et al., 2008b, ApJ submitted

## Summary of Major Results

*Timescale for gas giant planet formation is a function of stellar mass: higher-mass stars enter debris disk stage sooner (Super Earths instead of Jupiters around A stars?) *
*Hot Jupiters may be due to very long-lived (> 10-15 Myr) accretion disks around low-mass stars (speculative! Needs more analysis)*
*Terrestrial planet formation process runs faster for higher-mass stars than intermediate-mass stars *
*Planet formation runs fastest in inner disk regions, finishes from the inside out*
*Mid-IR emission from planet formation ‘rises’ from 5-10 Myr, peaks from 10-20 Myr, and ‘falls’ from ~20/30 Myr – 1 Gyr*
*> 50-60% of early-type (A) stars should have icy planets*

- 1) Currie et al. 2007a, ApJ, 659, 599;  2) Currie et al. 2007b, ApJ, 663, 105L
-  3) Currie et al. 2007c, ApJ, 669, 33L; 4) Currie et al. 2008a, ApJ, 672, 558

## Future Work

- SWIRC h and χ Per J & H photometry, > *80000* stars
- Cycle 5 obs. for h and χ Per (~2 mags. deeper)
- More clusters (NGC 1960; NGC 6871, Spitzer Cycle 5)
- constraints on planet formation
- Benchmark study for JWST

- (T. Currie, core of h Persei, 1.65 micron SWIRC data, unpublished)