HIGH-CONTRAST EXOPLANET IMAGING WITH CLIO2, THE HIGH-CONTRAST EXOPLANET IMAGING WITH CLIO2, THE...

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  • HIGH-CONTRAST EXOPLANET IMAGING WITH CLIO2, THE MAGELLAN ADAPTIVE OPTICS INFRARED CAMERA

    Katie M. Morzinski1ab, Laird M. Close1, Jared R. Males1b, Phil M. Hinz1, Alfio Puglisi2, Simone Esposito2, Armando Riccardi2, Enrico Pinna2, Marco Xompero2, Runa Briguglio2, Kate Follette1, Derek Kopon3, Andy Skemer1, Victor Gasho1, Alan Uomoto4, Tyson Hare4, Carmelo Arcidiacono2, Fernando Quiros-Pacheco, Javier Argomedo2, Lorenzo Busoni2, T.J. Rodigas5, and Ya-Lin Wu1

    1 University of Arizona, Steward Observatory, 933 N. Cherry Ave., Tucson, AZ 85721, USA 2 Istituto Nazionale di Astrofisica, Osservatorio Astrofisico di Arcetri, Largo E Fermi 5, 50125

    Firenze, Italy 3 Max-Planck-Institut für Astronomie, Kon̈igstuhl 17, D-69117 Heidelberg, Germany 4 Carnegie Observatories, OCIW, 813 Santa Barbara St., Pasadena, CA 91101, USA 5 Carnegie Institution DTM, 5241 Broad Branch Rd., Washington, DC 20015, USA

    Abstract. MagAO is the adaptive-secondary AO system on the 6.5-m Magellan Clay telescope. With a high actuator density and a sensitive pyramid WFS, MagAO achieves down to ∼130 nm rms WFE on bright guide stars in median seeing conditions (0.7” V band) at Las Campanas Observatory in Chile. MagAO’s infrared camera, Clio2, has a comprehensive suite of narrow and broad band filters that allow direct imaging of faint companions from 1–5 µm. We present first-light results from Clio2, including images of exoplanetary system β Pictoris. High-contrast imaging is an important goal of AO for ELTs, and results from MagAO/Clio2 are the next step along that path — particularly true for the GMT which is located very close to the Magellan site.

    1 Introduction

    The Giant Magellan Telescope (GMT) [1] is under fabrication at the Steward Observatory Mir- ror Laboratory at the University of Arizona. The GMT will consist of seven 8.4-m round seg- ments, arranged with one in the center and six around the limb; the first three segments have been cast at the Mirror Lab [2]. The “regular” Magellan telescopes, on the other hand, are twin 6.5-m telescopes located at Las Campanas Observatory in Chile. Steward Observatory pi- oneered the use of adaptive secondary mirrors (ASMs) in adaptive optics, which will be a key technology built in to the GMT [3,4]. MagAO is the ASM adaptive optics system we have built for the Magellan Clay telescope [5]. GMT will be on a neighboring peak to MagAO; therefore, the Magellan AO system is a trailblazer for the GMT under similar conditions.

    MagAO was successfully commissioned in 2012B and 2013A, and begins regular science operations in 2014A. The 585-actuator ASM is controlled at 1 kHz based on the wavefront measurements by a pyramid sensor. Advantages of the pyramid wavefront sensor include its sensitivity to faint NGS, and its flexibility for a range of conditions via pixel binning on the WFS CCD. Thus our faintest guide star limit is R∼14 for visible-light imaging with VisAO, and R∼16 for infrared imaging with Clio2. The pyramid WFS can control from 21–378 modes, allowing

    a ktmorz@arizona.edu b NASA Sagan Fellow

    Third AO4ELT Conference - Adaptive Optics for Extremely Large Telescopes Florence, Italy. May 2013 ISBN: 978-88-908876-0-4 DOI: 10.12839/AO4ELT3.13307

  • for extremely high Strehls on bright guide stars (on the order 130 nm phase rms WFE), and acceptable correction on faint guide stars. Advantages of the ASM for the deformable mirror include its high thermal throughput and high actuator density. The ASM has 561 illuminated actuators and effective spatial sampling of d∼23 cm.

    MagAO has two science cameras: a λ=0.55–1 µm camera VisAO, and a 1–5 µm IR camera Clio2. The two instruments are operated simultaneously, to obtain optical and infrared images at the same time. The beam splitter between VisAO and the WFS is selectable to send different proportions of the visible light to the two sides. Furthermore, VisAO is co-mounted with the pyramid WFS to minimize vibrations and non-common path aberrations. The pyramid WFS, VisAO, and Clio2 are all mounted on a ring located at the Nasmyth platform, the NAS ring, that rotates about the optical axis as the telescope slews and tracks. The ASM is installed at the secondary cage of the Clay telescope prior to each MagAO run. Figure 1 shows a schematic diagram of the MagAO instrument.

    Fig. 1. Schematic diagram of the MagAO instrument. The three main components are: (1) the AO system, with a pyramid wavefront sensor and an adaptive secondary mirror; (2) the co-mounted visible-light science camera, VisAO; and (3) the infrared science camera, Clio2.

    2 High-contrast imaging with MagAO/Clio2

    One of the key science goals for high-order or “extreme” adaptive optics (ExAO) is imag- ing faint exoplanets located very close to their bright stars. Because MagAO provides such exquisitely flat wavefronts, the stellar energy can be focused into the core, allowing for exo- planets to be imaged. During our first-light run in Nov.–Dec. 2012, we imaged the exoplanet host star, β Pictoris. β Pic is an A-star of ∼20 Myr age and 19 pc distance. Its exoplanet, β Pic b, is a super-Jovian planet at ∼9 AU. β Pic b was discovered via direct AO imaging with VLT/NaCo in 2009 [6].

    We imaged β Pic b on 2012 Dec. 4 with VisAO at Ys, as described in [7,8]. We imaged the planet with Clio2 at 3.1µm, L′,M′, 3.3µm on 2012 Dec. 1, 2, 4, 7 (respectively). Here we present the Clio2 observations. We begin with Clio2 PSFs demonstrating the instrument performance, shown in Figs. 2–4.

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    Third AO4ELT Conference - Adaptive Optics for Extremely Large Telescopes

  • Fig. 2. Pupil images. Left: Photograph of the ASM as seen from the Nasmyth platform (Nov. 2012). Clearly visible artifacts include the “slot” (a cut-out in the surface of the ASM to prevent a crack from spreading) and a “white dielectric material” (deposited by a bird). Center: Cross-hairs are used to align the optical axis (photo from Apr. 2013) — for more, see [9]. Right: Pupil image as captured with Clio2.

    Fig. 3. Model of MagAO/Clio2 imaging system, with no WFE. Left: Pupil model, based on above images (Fig. 2). We did not include the white dielectric material in the model, but we did include the slot as it was important in registering the ASM photo and Clio2 pupil images. Center: PSF model; Right: zoomed in.

    Fig. 4. On-sky MagAO/Clio2 PSFs of the 3.5th-mag. star β Pic. Left: 3.3µm; Right: M′. The on-sky data validate the model and show the exquisite wavefront control of the MagAO system.

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    Third AO4ELT Conference - Adaptive Optics for Extremely Large Telescopes

  • We see from Figs. 2–4 that MagAO/Clio2 performance closely matches simulation. We were thus able to image β Pic b at 3.1µm, 3.3µm, L′, and M′. In Fig. 5 we show the star and planet at 3.3 µm. This is the first time the planet has been imaged at this wavelength. An important CH4 spectral feature occurs at 3.3µm, and this detection will tell us about the methane content of the planet’s atmosphere.

    Fig. 5. 3.3µm image of β Pic A and b. Left: The star A, log scale. Right: The planet b, after subtracting the star’s PSF, linear scale. The planet is 0.46′′ from the star. See [10] for further details.

    3 Conclusions

    The MagAO system is commissioned and has produced its first results. An important application for ExAO is direct imaging of extrasolar planets, and we have imaged the exoplanet β Pic b at four passbands from 3–5 µm with MagAO/Clio2. The performance of MagAO will inform GMT plans and continue to deliver cutting-edge exoplanet results.

    References

    1. McCarthy, P., Proc. AO4ELT3 (2013), 16453 2. http://mirrorlab.as.arizona.edu/about/news 3. Bouchez, A., Proc. AO4ELT3 (2013), 17195 4. Esposito, S., et al., Proc. AO4ELT3 (2013), 15105 5. Close, L. M., et al., Proc. AO4ELT3 (2013), 13387 6. Lagrange, A.-M., et al., A&A 493 (2009), 2, L21 7. Males, J. R., et al., Proc. AO4ELT3 (2013), 13286 8. Males, J. R., et al., ApJ (2013), submitted 9. https://visao.as.arizona.edu/uncategorized/alignment-alignment-alignment/ 10. Morzinski, K. M., et al., ApJ (2014), in prep.

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    Third AO4ELT Conference - Adaptive Optics for Extremely Large Telescopes