Planet Forming Disks:
A Function of Stellar Properties
Michael R. Meyer, Institute for Astronomy, ETH-Zurich
From Disks to Planets: Learning from Starlight - 2009 EARA Workshop
Different Flavors of Planet Formation
Are planetary systems like our own are common or
rare among sun-like stars in the Milky Way galaxy?
Q: What are the initial conditions of planet formation?
Q: What is the time available to form gas giant planets?
Q: What is the history of planetesimal collisions vs. radius?
Q: How do the above vary with stellar properties?
Because the answers are subtle,
need large samples over a wide range of ages.
From Active Accretion to Planetary Debris Disks...
Images courtesy of M. McCaughrean, C.R. O`Dell, NASA, and P. Kalas.
For recent review see Meyer et al. (2007) Protostars & Planets V
Planetary debris
disk ~ 100 Myr old
Solar system debris
disk 4.56 Gyr old!
12
Gas-rich disk ~ 1 Myr old
Different Wavelengths Trace Different Radii!
NIR
MID
FIR
0.1 1.0
10.0
sub-mm
100 AU
Star with
magnetospheric
accretion columns
Accretion disk
Disk driven
bipolar outflow
Infalling
envelope
Optically-thick/geometrically thin
Lynden-Bell & Pringle 1974, MNRAS, 168, 603.
Adams, Lada, & Shu 1988, Ap. J., 326, 865.
Star Luminosity, L*
Δ
L*
angle θ
flat, black disk
r
L* Sin θ
4πr2
Power/area absorbed ~
~
L* Δ
4πr 2 r
Power/area emitted = σT4
~
~
L*
r3
L*
r3
(r >> Δ)
T(r) ~ r
Also true for accretion energy.
-3/4
1
Radiative heating: isolated particle
Distance r
Particle radius a (spherical; rapidly spinning)
Temperature T
Absorbed radiative power:
πa
2
x
L
4πr
Emitted radiative power: 4πa 2 x σT 4
Luminosity L
T=(
L 1/4
16πσ ) r -1/2
Using εν for small particles: T ~ r
-2/5
cf L. Spitzer, Jr., Physical Processes in the Interstellar Medium, ch. 9.1
1
2
Blackbody Disk with Dynamically Cleared Gap
NIR MID FIR sub-mm
0.1 1.0 10.0 100 AU
SEDs of T Tauri Stars in Chamaeleon
Robberto et al. (2003).
Chiang & Goldreich 1997;
Dullemond et al. 2001;
see also Calvet et al. 2003
SEDs of T Tauri Stars: A
Consequence of Inner Holes?
What disk properties do we care about?*
Total disk mass: Mdisk, Mdisk/M*
Outer & inner radii: Rout, Rin
Surface density profile: Σ(r) = Σo r-p
Dust grain size distribution: n(a) ~ no a-q ; amin, amax
Dust grain opacity law: κν ~ νβ
Optical depth: τν = κν Σ(r)
Temperature profile: T(r) ~ To r-q
Scale height, Midplane density: H(r), ρo(r)
Viscosity: νv = α cs H ~ νvo rγ (MRI?)
Composition (gas, dust), Ionization, asymmetries, etc.
* <MEAN>
and σ as f(star, environment, time)…
Stellar Properties Influencing Disk Evolution
•
Mass:
•
Luminosity & Incident Spectra:
•
Angular Momentum:
•
Composition:
•
Companions versus Mass and Orbital Radius:
•
Formation environment:
Confounding Variables:
T Tauri Disk Evolution and Errors in Age
Transition Disks:
Espaillat et al. (2007);
Brown et al. (2007)
Few disk parameters correlate:
Bouwman et al. (2008)
Pascucci et al. (2008)
Cortes et al. (2008)
Watson et al. (2007)
How does chemistry affect planet formation?
Gail (2002); Cody & Sasselov (2005); Garaud & Lin (2007); Bond et al. (in prep)
Image courtesy N. Gehrels (PSU)
Gas disk chemistry may vary with stellar mass…
Pascucci et al. (2009); cf. Carr & Najita (2008); Pontoppidan et al. (2008)
Typical Disk Parameters
Parameter
Median
~1σ Range
Log(M(disk)/M(star))[all ~1 Myr]
[detected disks only]
Disk lifetime
Temperature power law [T(r)~r-q]
-3.0 dex
-2.3 dex
2-3 Myr
0.6
±1.3 dex
±0.5 dex
1-6 Myr
0.4-0.7
Parameter
Median
~1σ Range
R(inner)
R(outer)
0.1 AU
200 AU
Surface density power [Σ(r) ~ r-p] 0.6
[Hayashi min. mass nebula]
1.5
1.0
[steady state viscous α disk]
~0.08-0.4 AU
~90-480 AU
0.2-1.0
(predicted)
(predicted)
Surface density norm. Σo (5AU)
±1 dex
14 g cm-2
Taken from (or interpolated/extrapolated from):
Muzerolle et al. (2003), Andrews & Williams (2007), Hernandez et al. (2008), Isella et al. (2009)
Differences in Disk Temperature Profiles:
Garaud & Lin (2007) compared to Hersant et al. (2001)
Color_2
Star+
Dust
★
★ Star+
Dust+
Disk
★
★
Star
Star+
Disk
Color_1
NICMOS/HST Mosaic F810W/F110W/F150W of NGC 2024 (Liu, Meyer, Cotera, and Young 2003, AJ)
Terrestrial Planets?
Chrondrules?
CAI Formation?
Inner (< 0.1 AU) Accretion Disk Evolution 0.1-10 Myr
Does the observed
range in initial disk
mass (e.g. Andrews &
Williams, 2005)
explain the observed
range in disk
lifetimes?
Haisch et al. 2001;
Hillenbrand et al. (2002);
Muzerolle et al. (2003).
Haisch et al. 2001;
Hillenbrand et al. (2002);
Muzerolle et al. (2003).
< t > ~ 3 Myr
Frequency
Terrestrial Planets?
Chrondrules?
CAI Formation?
Inner (< 0.1 AU) Accretion Disk Evolution 0.1-10 Myr
Inner Disk Lifetime
FUV and (or?) X-rays in action…
Pascucci et al. (2007); Esplainat et al. (2007); Herzeg et al. (2007)
Primordial Gas disk lifetimes appear to be < 10 Myr.
No massive gas
disks detected
around 35 stars
with ages 3-100
Myr. Less than
0.1 Mjup remains
to form planets.
Hollenbach et al. 2005; Pascucci et al. 2006/7; Lahuis et al. 2007
Debris Gas? Chen et al. 2007; Roberge et al. 2006; Dent et al. 2005
Rotation-Inner Disk Connection:
Function of stellar mass? (Herbst et al. 2000; Currie et al.)
Function of environment? (Bouvier & Clarke 2000)
Not seen for debris disks (e.g. Greaves et al. in press)
Kundurthy et al. (2006); Rebull et al. (2004); Hartmann (2002))
Rapid Transition time thick to (very) thin inside 1 AU
74 stars 3-30 Myr old:
=> 5 gas-rich disks.
=> no optically-thin
hot dust (< 1 AU).
Silverstone et al. (2006);
Cieza et al. (2007);
and references therein.
Planets as a Function of Stellar Mass:
What Should We Expect?
Planetesimal Formation Timescales:
» tp ~ ρp x Rp / [ σd x Ωd]
– σd ~ M*/a and Ωd~ sqrt(M*/a3)
– following Goldreich et al. (2004); Kenyon & Bromley (2006).
– Normalize: @ 3 Myr - [3 Mearth, 5 AU, 1 Msun]
» tp ~ [ρp x Rp x a5/2]/ [M*3/2].
–
–
–
–
Gives Jupiter mass gas giant planet.
Massive planets farther out surrounding stars of higher mass.
Consistent with observations to date (Johnson et al. 2007).
Yet disks last longer around stars of lower mass!
[Lada et al. (2006); Carpenter et al. (2006).]
0.4
Evolution of Disks Around Sun-like Stars:
Tracing Planet Formation? (Field & Cluster)
LHB
0.0
0.1
0.2
0.3
CAIs Vesta/Mars
Chondrules
Earth-Moon
6.0
7.0
8.0
9.0
Siegler et al. ‘07; Currie et al. ‘07; Meyer et al. ‘08; Carpenter et al. ‘09
Planetesimals Dynamics: Water Worlds
Raymond et al. (2004; 2006); See also Kenyon and Bromley (2005)
Disk Models+Condensation+N-Body =
Diverse Terrestrial Planets through Chemistry?
J. Bond (PhD Thesis, Planetary Science, University of Arizona)
From Stellar Spectra to Planetesimal Composition:
M. Jura (2006); Ashwell et al. (2005); Winnick et al. (2002); Wilden et al. (2002)
Dust Production
The connection between planetesimal belts and
presence/absence of giant planets is not clear.
Plan
ets
No P
lanet
Time
s
No link between debris and RV planets found!
Could debris disks be more common than Gas Giants?
Moro-Martin et al. (2007a; 2007b) and Bryden et al. (2006)
See Beichman et al. (2005); Lovis et al. (2006); Alibert et al. (2006) regarding HD 69830.
Debris Disks vs. Metallicity:
More “diverse” than RV planet systems?
Greaves et al. ‘06; Bryden et al. ‘06; Najita et al. (in preparation).
Circumstellar Disk Evolution and Multiplicity:
Complex Story T Tauri Binaries vs. Separation
Simon & Prato (1995); Jensen et al. (1994)
Debris Disks not inhibited
by companions.
McCabe et al. (2006); White & Ghez (2001)
Trilling et al. (2007)
Patience et al. (2008); Pascucci et al. (2008)
Wyatt et al. (2003)
Ireland & Kraus et al. (2008); stay tuned…
Spitzer/FEPS (Meyer et al. 2006)
The Last Word:
Carpenter et al. (2008)
Evolution in Disk Luminosity:
A stars: Su et al. (2006)
G stars: Bryden et al. (2006)
M stars: Gautier et al. (2007)
Distribution of Inner Hole Sizes
Sub-mm Observations of Debris Disks:
Carpenter et al. (2005); Greaves et al. (2006; 2008); Liu et al. (2004)
Are planetary systems like our own are common or
rare among sun-like stars in the Milky Way galaxy?
Primordial Disk Evolution:
- disks around lower mass stars are less massive and live
longer than their more massive counterparts.
- large dispersion in evolutionary times could indicate
dispersion in initial conditions.
- evolution appears to proceed from inside-out as expected.
Are planetary systems like our own are common or
rare among sun-like stars in the Milky Way galaxy?
Change you can believe in!
- transition time from primordial to debris is << 1 Myr.
- planetesimal belts evolve quickly out to 3-30 AU.
- some evidence that warm debris more common in clusters?
Debris Disk Evolution:
- currently detectable systems are collision-dominated.
- more common around stars of higher mass.
- evolutionary paths are diverse.
- consistent with our solar system being common.
- connection to planetary systems unclear.
Are systems without debris those with dynamically full
planetary systems, or those without any planets?
A Picture is Worth 1024 x 1024 Points on an SED…
Em
ba
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go
un
til
af
ter
lau
nc
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A Picture is Worth 1024 x 1024 Points on an SED…
Spitzer @ MIPS-24
JWST-MIRI
Herschel
The starlight-disk connection…
Initial conditions of planet formation are set by star formation.
Star-forming environment could be critical.
Disks dissipation timescale is f(M*).
L* / T* / energetic radiation / rotation / multiplicity all play roles.
Star/disk composition/chemistry may be key.
“Hidden parameters” control disk evolution.