Adaptive Optics at the MMT and First Science Results

Laird Close and the
The Center for Astronomical Adaptive Optics team
Steward Observatory
University of Arizona


The MMT adaptive secondary built by the University of Arizona (CAAO) and Arcetri Observatory (Italy). Note the thin (transparent here before coating) glass "shell" that is 2 mm thick and 640 mm wide. It "hovers" some 30 microns away from its thick reference body and is deformed by 336 voice coils pushing on magnets (dark dots) glued to the back surface.

The new technology deformable secondary mirror being mounted at the telescope

Figure 1: The new technology deformable secondary mirror being installed at the 6.5 meter MMT telescope at Mt. Hopkins, Arizona. The secondary mirror is a joint project of University of Arizona and the Italian National Institute of Astrophysics - Arcetri Observatory (shown from left to right: Michael Lloyd-Hart, Francois Wildi, & Laird Close)
Photo credit: CAAO, Steward Observatory
 
 

The New Deformable Secondary Mounted at the MMT telescope, Mt Hopkins, Arizona

Figure 2: A photo of the new technology Deformable Secondary Mirror mounted at the 6.5 meter Multiple-Mirror Telescope (MMT), Mt Hopkins, Arizona
Photo Credit: Francois Wildi, CAAO, Steward Observatory (fwildi@as.arizona.edu)
 

Here is a movie of the secondary correcting for wind buffeting in a 20 mph wind

Here is a movie of the positional error of the mirror while in the wind. The mirror worked quite well; only +/-30 nm of wavefront error was recorded while the mirror was holding "flat" in the wind while using only a fraction of its range (<1%).

So adaptive secondaries can operate in a telescope environment.

 


The MMT AO science camera ARIES (PI Don McCarthy) --the purple dewar mounted below the MMT AO "top box" (black).
 
 

The Indigo Infrared Video Camera (in black optics box to the left) and its control PC.
 

The MMT control room with the AO system running. Note the number of keyboards!
 
 
 

The main control computers for the MMT AO system. Doug Miller is running the user interface computer (left) and Guido Brusa (right) is running the secondary mirror control computer.  Note that the currents and positions of all 336 mirror actuators are displayed on the screen to the right.





A sharp image of a binary star made by the MMT AO system

Figure 3: A typical example of how the the Adaptive Optics (AO) system can make very sharp images (twice as sharp as the smaller 2.4 meter Hubble space telescope can make at H band --1.65 micron wavelengths).
Photo Credit: Laird Close, CAAO, Steward Observatory (lclose@as.arizona.edu)

Click to see a MOVIE (AVI format, 680kB) of the Adaptive Optics system "closing the loop" on this target (ADS 8939). Note how the binary nature of the star is completely hidden by the blurring of the atmosphere, but then after the loop is closed it is clearly a binary star. (Movie Credit: Guido Brusa, CAAO, Steward Observatory (gbrusa@as.arizona.edu))
 
 
 
 

There is a great improvement in image quality when turning on the MMT AO system

Figure 4: A typical example of how the the Adaptive Optics (AO) system can make very sharp images. With AO "OFF" this object appears to be just 2 stars. With AO turned "ON" it is clearly a tight group of 4 visual stars (2 of these are in a tight 0.1" binary, one is the bright guide star, and the other is a rarely seen very faint companion slightly to the right (and 100x fainter) than the bright star -- see white arrow). For more technical details about this image click here.
Photo Credit: Laird Close, CAAO, Steward Observatory (lclose@as.arizona.edu)

Click to see a MOVIE (AVI format, 2.2 MB) of the Adaptive Optics system "closing the loop, opening the loop, then closing the loop" on this target (Theta Ori 1 B). With AO this object appears to be just 2 stars, but with AO turned on it is revealed that the lower "star" is really a 0.1" binary. (Movie Credit: Guido Brusa, CAAO, Steward Observatory (gbrusa@as.arizona.edu))
 
 

A deep image of a single star shows a very smooth pattern which is close to perfect

Figure 5: A very deep image of a bright (V=6) single star at H (1.65 microns). The pattern of light (called a point spread function (PSF)) is almost exactly like that predicted for a 6.5 meter telescope (a Strehl of 100% is absolutely perfect and is never achieved in reality at a wavelength of 1.6 microns). This image has had some post-detection processing to remove a residual 0.020" rms jitter not corrected by the AO system. The raw AO image (no jitter correction) had a slightly lower Strehl 28% which is in agreement with theory when only 52 different modes are being corrected. Hence the AO system is working very close to the level expected for 52 modes of correction.
Photo Credit: Laird Close, CAAO, Steward Observatory (lclose@as.arizona.edu)
 
 

AO off and on at 10.3 microns

Figure 7: The first AO images made in the mid-infrared (wavelength of 10.3 microns). With AO on the Strehl is 96% whereas with it off it is only 58%. Note that the AO on image is nearly perfect. Such AO corrected images allows one to remove the starlight with deep nulling interferometry (talk with Phil Hinz to learn more about nulling with the MMT).
Photo Credit: Phil Hinz (Steward Observatory, phinz@as.arizona.edu)
 
 

A star before and after nulling

Figure 8: The first low-emmissivity (6%) nulling images. To the right 98% of the light from the central star is removed by nulling. This will reveal any nearby objects that would be hidden by the glare of the bright central star. This is a new and powerful technique that has great scientific promise to detect extra-solar planets and circumstellar disks etc.
Photo Credit: Phil Hinz (Steward Observatory, phinz@as.arizona.edu)
 



 




 SCIENCE WITH THE MMT ADAPTIVE SECONDARY

We utilized the following astrometric standards to calibrate the 0.088"/pix platescale.





THE TRAPEZIUM MASSIVE YOUNG STAR CLUSTER AT THE HEART OF THE ORION NEBULA
(Close et al. 2003a)




Above we see a 20x30" image of the core of the trapezium cluster (Gemini/Hokupa'a). Note that "A" is a binary as is "B".


Theta 1 Ori B


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.



An older Gemini/Hokupa'a image of theta 1 Ori B.




We see there is very little motion (<1.4 km/s) between B1/B5 and the B2/B3 stars. Since typical velocities in the cluster ~3 km/s (Hillenbrand & Hartmann (1998), and the escape velocity for the group is ~6 km/s, we believe that the B complex is likely bound.

Similarly it appears that B4 maybe bound to the B complex as well...



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




However, we did detect real motions of the tight binaries B2/B3 and A1/A2. In the case of the B2/B3 system (sep 52 AU) we found a velocity of 4.2+/-2 which is less than the escape velocity of ~6 km/s but more than the cluster dispersion.  In the case of A1/A2 system (sep. 94 AU) we found a large velocity of 16.5+/-5.7 km/s which suggests the system is bound. It is important to note that these velocities are consistent with those measured by Schertl et al. (2003) who also conclude (based on speckle observations) that there is significant motion between B2/B3 and A1/A2.


VERY HIGH STREHL MID-IR AO IMAGING

With a low emissivity adaptive secondary (~8% emissive) adaptive optics can finally reach Mid-IR wavelengths.

Even with 53 corrected Ao modes Strehl ratios of 98% are predicted at 10 microns. The Strehl ratios reached are 98+/-2% with MMT AO in 1" seeing at 9.8 microns. Similarly high strehls were reached at 11.7 and 18 microns.


Above we see the first Mid-IR AO images made of Post-AGB stars (Close et al. 2003b). AC Her is a post-AGB star that is transiting from the AGB to the planetary nebula phase (an RV Tauri star). Due to the very high Strehls achieved the PSF standards are an excellent match independent of seeing, airmass, or time. This creates a whole new world for AO science when PSF calibration can be done on different stars at different times. Note how similar the post-AGB star AC Her appears to the other 2 PSF stars. Also not how the morphology of AC Her is very different from that of the Keck 18 um image (upper right - false color).


Graphical proof of how similar AC Her is to the other PSF stars (Close et al. 2003b). Note how incompatible it is with the previous keck image (Jura et al. 2000).



Above we see how similar the PSF really are. If we simply subtract a scaled version of the alpha Her PSF from the AC Her 11.7 um image there is hardly any residual remaining. This is a remarkable degree of PSF subtraction considering that these 2 stars were observed 2 hours apart and at different airmasses.


DIRECT DETECTION OF A DISK AROUND RV BOO
(Biller et al. 2003)


We further exploited the excellent PSF stability to detect the thermal disk around the AGB star RV Boo (which is known to have keplarian CO disk).


We noticed that RV Boo was slightly more elliptical than the other PSFs at 9.8 microns.


RV Boo was uniquely wide and elliptical.



RV Boo's "disk" rotated on the sky with the parallactic angle



After Lucy deconvolution a small (R~50 AU) disk was revealed around RV Boo (At a PA=120 degrees, similar to the CO disk). Such a disk size at 10 microns is expected from the IRAS fluxes using a simple dust emission model (Biller et al. 2003).



FIRST LIGHT OF THE ARIES IR AO CAMERA

In the October MMT AO run we commissioned the ARIES IR camera (PI Don McCarthy). This camera will become the facility workhorse for the MMTAO system in the future. It has some interesting unique features like a SDI exo-planet imager (see below) as well as a 1024x1024 1-2.5um Hawaii array.


Here is a 0.1" FWHM image of a planetary nebula taken during commissioning of Aries with the MMTAO system (data Patrick Young, Steward Observatory). 

We have also made deep (K~22) images of extra-galactic fields with ARIES.
This image is of Quasar at z~2. We have been able to use this 1 hour long integration to detect very faint light from the "host galaxy" of the Quasar. The resolution in this image is 0.1" (in the Ks filter). Data from Xiaohui Fan and Daniel Eisenstein. Image courtesy of Xiaohui Fan, Daniel Eisenstein, Nick Siegler and Laird Close.


SDI IMAGING OF TITAN AT THE MMT

Laird Close and Don McCarthy have installed a simultaneous differential imager (SDI) device into the ARIES f/30 optical camera.

The SDI device will allow one to image both inside and outside the methane absorption feature at 1.575, 1.600 and 1.625 um simutaneously through 3 narrowband filters. This will allow one to image a star with an extra-solar planet. By a complex subtraction, the star's light can be mostly removed while the planet's flux is preserved.

We tested the MMT SDI device on the methane rich atmosphere of Titan on in Feb 2004.

Here is an image of Titan made with the SDI imager. The red light is 1.575um light and possibily the icy highlands of the moon. The dark areas are possibily the lower areas, which may be covered in liquid hydrocarbons. The blue light (1.625um) is the thick Methane atmosphere of Titan. Image reduction by Eric Nielsen.

 









CONCLUSIONS

1. The MMT adaptive secondary AO system is now ending commissioning. This has been a very large project and would not have been possible without the great efforts of F. Wildi, M. Lloyd-Hart, G. Brusa, P. Hinz, D. Miller, D. Fisher, A. Riccardi (Arcetri), R. Angel, P. Salinari (Arcetri), R. Allen, H.M. Martin, R. Sosa, M. Montoya, M. Rademacher, M. Rascon, D. Curly, N. Siegler, B. Hoffmann, D. McCarthy and the rest of the CAAO team.

2. The secondary performs as expected in the NIR. We can measure positions to 0.002" accuracies. This suggests that the theta 1 Ori B complex is bound. It is possible that the lowest mass member B4 is in an unstable location and may be ejected in the future.

3. The system has the lowest emissivity (8%) of any AO system.
The utilization of an adaptive secondary enables the new field of Mid-IR AO.

4. Mid-IR AO is very powerful because the Strehls ~98% at 10 microns.

5. Mid-IR AO has already resulted in the detection of a 0.2" disk around RV Boo (Biller et al. 2003) and the correct dust morphology around AC Her and Alpha Her (Close et al. 2003). We find that 300 AU sized 10 micron structures do not exist around AC Her. But ~60 AU sized dusty structures are possible as our observations of RV Boo suggest (Biller et al. 2003).

6. Any field that can benefit from high strehls at 10 microns will gain with Mid-IR AO.