High Contrast AO Imaging at the MMT with ARIES SDI

Laird Close, Beth Biller, Eric NielsenDon McCarthy

& MMT AO Group(Steward Obs)

High Contrast AO Imaging at the MMT with AO

MMT has world’s first (and so far only) adaptive secondary

Can produce very high strehl images in the thermal IR (see talks by Beth Biller, Wilson Liu & Ari Heinze tomorrow).

And ~20% Strehls in the NIR (subject of this talk)

First NIR AO science from the adaptive secondary: TheTheta Ori B mini-cluster

Close et al. 2003

Above we see images of the theta 1 Ori B "mini-cluster" made with the Indigo commercial IR video camera at H band. Significant orbital motion was observed of B3 orbiting B2 when we compared this image to those of previous years. Moreover, it appears that B2/B3 is bound to B1/B5 since nor orbital motion was observed. In addition, the very low mass (~0.2 Mo)  star B4 appears to be a common proper motion member of the B "mini-cluster". Since our orbital analysis shows B4 is in a very unstable position this "mini-cluster" may, in time, eject B4. This has been recently hypothesized to an important method of producing low mass stars and brown dwarfs through dynamical ejection processes.

Here we see that B4 appears like a common motion pair (4+/-15 km/s of relative motion) with the B group.

Simulations suggest that the faintest component (B4) will be ejected from this “mini-cluster” in less than 100 orbits!

Close et al. 2003

High Contrast AO Imaging at the MMT with ARIES

ARIES is the MMT’s NIR AO imager

PI Don McCarthy

The Simultaneous Differential Imaging (SDI) Technique

• Pioneered by Marois et al. 2000.

• Sample inside and outside of the strong CH4 (methane absorption) bandhead at 1.62 m in extrasolar giant planets (T < 1200 K)

• Subtract out star and speckles between filters – any CH4 rich companion should remain.

Nielsen et al. 2004 Biller et al. 2006

The SDI Instruments

Double Wollaston and Quad Filter– Calcite Prisms split beam into 4 identical beams while minimizing non common path error (Close et al. 2004).

• Installed in the ARIES camera at the MMT AO system by Don McCarthy and Laird Close (and in the CONICA camera inside the VLT NACO AO system by Laird Close and Rainer Lenzen).

• NACO and ARIES SDI fully commissioned.

Proof of Concept – SDI Discovery of the Methane Rich

Brown Dwarf SCR 1845B – Just 3.8 pc from Sun!

Biller et al. 2006

M8.5 + T5.5

ARIES SDI Images of the tight brown dwarf binary GL 569B

High Contrast AO Imaging at the MMT with ARIES SDI

GL 569B is a critical low mass, young, evolutionary track calibrator. We can determine from our SDI images that there are no T-dwarf (methane rich) companions to GL 569 A or B

Smooth MMTAO SDI AO PSF HD128311 K0 500Myr 2.2 & 3.2 Mj msin(i)

Smooth MMTAO ARIES AO PSF of HD128311after SDI subtraction

High Contrast AO Imaging at the MMT with ARIES SDI

Biller et al. 2006

ARIES MMTAO SDI Tentative Exoplanet candidate

Biller et al. 2006

The SDI Young Stars SurveySurvey object selection criterion:

• Age: less than 300 Myr, preferably less than 100 Myr.

• Distance: less than 50 pc – and the closer, the better.

• Spectral Type: focus on young solar analogues, but also pay attention to low mass stars.

• Datasets acquired for ~50 objects (at MMT and VLT with SDI).

SDI targets observed

Biller et al. 2006

Achievable Contrasts

K1V primary, 15 pc, ~70 Myr, V=6.88

Biller et al. 2006

So what does this all mean?

• For a ~50 object survey, we expect to detect ~4 planets (from Monte Carlo simulations using realistic scaling laws (Marcy et al. 2003) and models (Burrows et al. 2003))

• Even if we get a null result (no planets), we will be able to place strong constraints (> 2) on the frequency and semimajor axis distribution of young massive extrasolar planets >5 AU from their primaries.

Nielsen et al. 2006