Debris Disk Science with GMTInseok Song, University of Georgia

for “Opening New Frontiers with the Giant Magellan Telescope” in Oct 2010

Zodiacal light: APOD: 2010 Sep 13, Taken in Namibia after a sunset in June.

Why Debris Disks?• NRC Astro2010 Report

Telescopes on the ground and in space have even directly imaged as distinct point sources a few large planets. … we can learn about planetary systems by measuring infrared and radio emission from giant disks of gas out of which planets can form.

…Terrestrial planets are relatively small and dim, and are easily lost in the exozodiacal light that is scattered by the dusty disks that typically orbit stars. The observational challenge is great, but armed with new technologies and advances in understanding of the architectures of nearby planetary systems…

Debris Disks and Planets• Debris disks act as indirect evidence of exo-planetary systems. But, at the

same time, they are obstacles in direct imaging of Earth-like planets.• Need to understand the architecture of debris disks

Breaking the degeneracy of SEDs

Debris disk studies are based on Spectral Energy Distribution (SED).

same SED with different grain configurations

large grains at rsmall

small grains at rlarge

grain population over rNeed a spatially resolved image of DD

Scattered imaging + thermal imaging

• Mplanet=5ME, ap=10AU, β=0.023• Poynting-Robertson effect caused a grain sorting based on particle size different appearance at different wavelengths. (Stark et al. 2009)

density scattered light 10μm image

Need to spatially resolve Debris Disks• 17 resolved debris disks in scattered light to date (optical and near-IR)

Need to spatially resolve Debris Disks• But only four debris disks imaged in thermal IR

To increase the number of spatially resolved debris disks

We need

1. Good targets

2. Larger telescope with a better IR imager

Some important facts• Adaptive secondary mirror: o excellent for thermal IR observations only two warm optics (M1 + M2)o AO corrected mid-IR observations (Strehl ratio > 98%)

• Extreme AO : Strehl > 99%

mid-IR imager (MIISE or TIGER): •5-25mu, •R=5-5000, •FOV=30”•FWHM = 40mas at 5mu,

Sun-Earth at 25pc away…

1AU 40mas

Can GMT/TIGER really resolve most Debris Disks?• MMT Adaptive Secondary result as a test case.• Expected Strehl ratio at mid-IR > 98%

Expected performance of TIGER• MMT Adaptive Secondary result as a test case.• Expected Strehl ratio at mid-IR > 98%

can do 10-4 suppression

Credit: Phil Hinz (Steward Observatory)

Kuiper Belt Disks

Other thermal IR instruments competing w GMT/TIGER

• Surface brightness high enough?• Enough targets for statistically meaningful studies?

JWST sensitivity

GMT sensitivity

Known Population of Debris Disks from IRAS

currently known debris disk from IRAS (Rhee et al. 2006)

Known Population of Debris Disks from IRAS

currently known debris disk from IRAS (Rhee et al. 2006)

HIP 7345, 20 Myr oldSimulated 1hr 18μm image

GMT/TIGER will image planets also…• Higher exoplanet flux at M and N bands especially for lower mass planets• Typical ages of debris disk stars are < 500 Myr (young, bright planets)

GMT M-band (5σ, 1hr) limit : 5.14 μJy200 Myr 10MJ planet or 50 Myr 5MJ are about 0.8mJy at M-band

detectable in 5min exposure with GMT/TIGER!

Y J H K L N

700 K planet400 K planet

M

We will image disk together with planets!

• GMT/TIGER can detect a 1 MJ planet at various ages.• Expect an image like this!!

Composite image of β Pictorisdisk:10μm, planet:3.6μm

More targets to come! Increasing the population of Debris Disks

• IRAS fully used• Spitzer being summ.• AKARI wasn’t useful

WISE (about 108 sources)

• SPICA (not all-sky)

WISE sky coverage as of 2010 Sep

Anticipated Results

• GMT should be able to obtain spatially resolved images of several dozen Debris Disks (both in scattered and thermal light)

• Some (or many or most) with embedded planets imaged (both in nearIR and thermal)

200 Myr F-star @50pcwith a 5MJ planet and

LIR/Lbol=4x10-4, Tdust=300K

GMT/TIGER1hr at M-band

Work To Do: Debris Disk Database

To prepare optimal GMT/TIGER debris disk studies, we need a central portal of debris disk database with a long-term commitment of maintenance (e.g., DwarfsArchive.org)

Thanks!!