alycia j. weinberger - carnegie dtm catching planets in formation with gmt n what sets the...
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Alycia J. Weinberger -
Carnegie DTM
Catching Planets in Formation with GMT
What sets the stellar/substellar mass function and how universal is it?Do all stars form planets and if not, why not?What causes the diversity of planetary systems?
SP
EC
IME
NS
PE
CIM
EN
Weinberger - 10/4/2010
Nearby Star Forming Regions
Good News: Most are in the South Bad News: All are >100 pc away
Ophiuchus -24 120 pc ≤1 Myr Lupus -38 100 pc ≤ 1 Myr Corona Aust -37 170 pc ≤ 1 Myr Chamaeleon -77 170 pc 2.5 Myr Upper Sco -30 140 pc 5 Myr
4 AU at 150 pc = 27 mas (separate “inner” and “outer” Solar System)
Diffraction limit (/D) of GMT at 1.6 m is 13 mas
Weinberger - 10/4/2010
106
yrs107
yrs108
yrs109
yrs
CAI /ChondruleFormation
Moonforming
Impact (30+ Myr)
Current age of the Sun:
4.5x109 yrs.
Late Heavy Bombardment
(600 Myr)
Star-formation to solid formation
Massive, gas-rich disk
Planetesimal dominated disk
Dust / planet dominated disk
Gas RemovalGiant planets
form
Terrestrial planets
form
Planetary Formation Timescales
Astronomer’s t0
Alycia Weinberger 2009
Weinberger - 10/4/2010
• Substantial mismatch between predicted and observed distribution of exoplanets.
• Major uncertainties:• How do gas-giant planets form.• How much do planets migrate.• Are there many habitable (water, etc) planets.
•Need to extend observational phase space:• Probe lower masses.• Detect very young planets.• Determine composition.
Main Questions
Weinberger - 10/4/2010
Disks: How to make, compose and possibly destroy planets
Weinberger - 10/4/2010
Watching planet formation
335 yr
339 yr
346 yr
If planets form by gravitational instability (Boss 1997), spiral arms in disk may be observable in scattered light.
Need high contrast in near-infrared: 10-7 to 10-9
Synergy with ALMA
(Jang-Condell & Boss 2007)
10 mas 30 mas
Weinberger - 10/4/2010
Where is ice line / where is the water?
Giant planets may form more efficiently outside the ice-line
Water-rich planetesimals from outside the ice-line may deliver water to dry inner planets
Salyk et al. 2008, ApJLNIRSPEC, R~25,000
Weinberger - 10/4/2010
Imaging Ices
(Inoue et al. 2008)
Imaging of scattering from water ice in disks
mJy/sq.arcsec
(Honda et al. 2009)
HD 142527
Weinberger - 10/4/2010
What are gas densities in planet region?
“Spectroastrometry” Analogous to centroiding to
0.01 pixel Find gas within 1/100 of a
spatial resolution element (~0.3 mas for VLT, 0.1 mas for GMT)
Requires S/N>100 on continuum and resolving line kinematically
Need aperture for low line flux sources: detections are 10-16 - 10-17 W/m2
Need excellent calibration in high continuum/line sources
QuickTime™ and a decompressor
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Pontoppidan et al. 2008, ApJ, 684, 1323VLT CRIRES+AO, Tint=32 min, R~100K
S/N=280
-30 -20 -10 0 10 20 30 Velocity [km/s]
Weinberger - 10/4/2010
Observing planets in disks
(Jang-Condell & Kuchner 2010)
It should be possible to detect planets forming in the outer parts of classical T Tauri star disks
Weinberger - 10/4/2010
Effect of Companions?
Disk is transitional•Contains gas
Scattered Light• Large extent (400 AU)• Red visible – near-IR color
HD 141569A
Mid-IR Emission•Compact extent•PAHs
Star: A0, 16.5 L, 5 Myr old
(Weinberger et al. in prep)
Weinberger - 10/4/2010
Spatially resolved disk kinematics
AO allows disk rotation curves Combined constraint of
kinematics and size Consider the relevant
scales GMT DL at 5 m = 0.04 Closest sites of ongoing
star formation - 150 pc; GMT probes 6 AU (about where Jupiter formed)
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Goto et al. 2006, ApJ, 652, 758Subaru IRCS+AO, Tint=20 min, R~20K
When do planets form?When does gas in inner disk disappear?
Weinberger - 10/4/2010
Spatially Resolved Spectra of Emission
Te
rre
stri
al O
3
Central Disk Spectrum24 AU (0.’’24)
168 AU (1.’’68)
• • •
192 AU (1.92 AU) - Backgd
(Rainbow step every 24 AU)
Weinberger et al. in prep
~1.5 hr at Keck
Weinberger - 10/4/2010
Young Planets Themselves: Where they are and what they are made of
Weinberger - 10/4/2010
Free Floaters
•How many stars/brown dwarfs are there?•Do they have disks?•Is the disk lifetime the same as for stars?
Example: OphiuchusSize: ~7 X 7 Deg (cloud core plus extended region) GMACS FOV: 8 x 18’ NIRMOS FOV:5.5 x 5.5’
IMACS limiting magnitude I~21.5, S/N=30, in 4 hr @ R~2000
10-4 Lsun or 3- 5MJ
15% too faint (>21.5) for IMACS
IMACS 12x12’ (Gully-Santiago)
Weinberger - 10/4/2010
Analogs and Intrinsically Interesting
1 MJ object = 840 K, i.e. T dwarf, with K~19
~1 hr at R~400 with GMT
(Knapp et al. 2004)
Weinberger - 10/4/2010
Discovery Space for Planet Imaging
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Olivier Guyon (U. AZ)
Weinberger - 10/4/2010
Discovery Space for Young Planets
• Contrast of young giant planet and star ~10-6 makes them easier to image
•“TIGER” instrument is being developed as potential first-light imager.
(Phil Hinz, U. AZ)
Weinberger - 10/4/2010
Planet Spectroscopy
GMTIFS offset to “planet” location. Use spatial information to correct for scattered light at each wavelength. Preferable to long slit.
McElwain et al. 2008Keck, OSIRIS
Weinberger - 10/4/2010
Example: Pic Planet (~8 MJup)
•0.’’35 from and 7.7 mag fainter than the star
•“only” need 104 contrast•This is >10 /D for GMT
•L’/M=11.1 mag (in principle can get GMTNIRS spectrum at S/N=100 in 1 hr)
•Molecular composition•Auroral emission (magnetic field)•Variability (rotation, winds)
Quanz et al. 2010
Weinberger - 10/4/2010
Spectra of Young Exosolar Planets
Tiger
Fomalhaut planet appears dominated by a scattered light disk. Could learnabout both.
(Kalas et al. 2008)
Weinberger - 10/4/2010
Detecting Planets in Debris Disks
Figure Credit: Chris Stark (U MD)
Weinberger - 10/4/2010
Uses of 1st Generation Instruments for star and planet formation studies
•GMTNIRS - Probing stellar astrophysics, disk kinematics and disk and even planet composition, radial velocity studies•Tiger - Imaging disks and planets in disks, composition•GMTIFS - Imaging young planets, disks•GMTNIRS / GMACS - Studying free floating planets and brown dwarfs in star forming regions•GCLEF - Debris disk gas, radial velocity studies
GMT will enable many creative projects not envisioned yet and like each generation of large telescope, enable qualitative leaps in measurement ability.
Weinberger - 10/4/2010
Stellar and Disk Co-Evolution
(Tom Greene)
Weinberger - 10/4/2010
Embedded protostar with disk
1 100 Log() [m]
Log
(F
lux
Den
sity
)
Flat spectrum and/or “Class I”
Log
(F
lux
Den
sity
)
Class II
Want to learn simultaneously about the star and its disk
1 100 Log() [m]
Weinberger - 10/4/2010
Stellar Magnetic Fields
Disk evolution is supposedly magnetically drivenOnly a handful of stars have directly measured fields
(Johns-Krull et al. 2009)
Measure Zeeman splitting (or broadening) of lines such as Ti I.
Weinberger - 10/4/2010
Astrophysics of Young Stars
Log (Teff)
log
g
(Doppmann et al. 2005)
Keck 0.3-2 hr /source a R~18,000
A wide range of luminosities and gravities (and therefore ages) appear for stars of all types
Most embedded, veiled objects do seem younger than optically revealed ones (White & Hillenbrand 2004)-- need IR
Weinberger - 10/4/2010
Origin of Isotope Ratios
CO self-shielding: Lyons & Young (2005) suggested that irradiation of our young disk generated our 18O/17O/16O ratios
Need O to be incorporated into water
(R. Smith et al. 2009)
Weinberger - 10/4/2010
Direct Observations of Circumstellar Disks and origins of the diversity of planetary systems
Disk Spectroscopy Direct measurement of gas content and
temperature High spectral resolution proxy for spatial
resolution (gas close to the star moves fast) High spatial resolution to resolve the disk
directly (Spectroastrometry) Disk Imaging
Direct measurement of structure Composition from low-resolution spectroscopy of
emitted and scattered light
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