The W. M. Keck Observatory Laser Guide Star Adaptive Optics System: Performance Characterization

Dam, Marcos A. van; Bouchez, Antonin H.; Mignant, D. Le; Johansson, Erik M. J.; Wizinowich, Peter; Campbell, Randy; Chin, Jason C. Y.; Hartman, Scott; Lafon, Robert E.; Stomski, Paul J.; Summers, Douglas M.

doi:10.1086/499498

Cited by 212 publications

(144 citation statements)

References 22 publications

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“…Data were taken in ten-minute exposures set in an objectsky-object pattern, for total on-source exposure times of 60 and 40 minutes for the Kcb and Hn4 filters, respectively. OSIRIS resolves below the seeing limit by utilizing Keck's laser guide star adaptive optics system (Wizinowich et al 2000;van Dam et al 2004;Wizinowich et al 2006;van Dam et al 2006). This LGS AO system uses a pulsed laser tuned to the Sodium D2 transition at 589 nm to excite atoms in the sodium layer of the atmosphere, around 95 km.…”

Section: Osiris Datamentioning

confidence: 99%

Shocked gas in IRAS F17207-0014: ISM collisions and outflows

Medling

Vivian

Kewley

et al. 2015

Monthly Notices of the Royal Astronomical Society

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We combine optical and near-infrared AO-assisted integral field observations of the merging ULIRG IRAS F17207-0014 from the Wide-Field Spectrograph (WiFeS) and Keck/OSIRIS. The optical emission line ratios [N II]/Hα, [S II]/Hα, and [O I]/Hα reveal a mixing sequence of shocks present throughout the galaxy, with the strongest contributions coming from large radii (up to 100% at ∼5 kpc in some directions), suggesting galactic-scale winds. The nearinfrared observations, which have approximately 30 times higher spatial resolution, show that two sorts of shocks are present in the vicinity of the merging nuclei: low-level shocks distributed throughout our field-of-view evidenced by an H 2 /Brγ line ratio of ∼0.6-4, and strong collimated shocks with a high H 2 /Brγ line ratio of ∼4-8, extending south from the two nuclear disks approximately 400 pc (∼0. ′′ 5). Our data suggest that the diffuse shocks are caused by the collision of the interstellar media associated with the two progenitor galaxies and the strong shocks trace the base of a collimated outflow coming from the nucleus of one of the two disks.

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Section: Osiris Datamentioning

confidence: 99%

Shocked gas in IRAS F17207-0014: ISM collisions and outflows

Medling

Vivian

Kewley

et al. 2015

Monthly Notices of the Royal Astronomical Society

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“…The performance of the Keck II LGS AO system is reported in van Dam et al (2006). The typical achieved on-axis KЈ-band Strehl ratio varies from 0.35 for NGS stars brighter than , to 0.27 for , to 0.1 for .…”

Section: Keck Lgs Science Capabilitymentioning

confidence: 99%

“…large telescope has presented numerous challenges, and this paper attempts to share the lessons learned in this process. A separate paper (van Dam et al 2006) describes the LGS AO system's performance and algorithms in more detail.…”

Section: Introductionmentioning

confidence: 99%

The W. M. Keck Observatory Laser Guide Star Adaptive Optics System: Overview

Wizinowich

Mignant

Bouchez

et al. 2006

PUBL ASTRON SOC PAC

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198

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ABSTRACT. The Keck Observatory began science observations with a laser guide star adaptive optics system, the first such system on an 8-10 m class telescope, in late 2004. This new capability greatly extends the scientific potential of the Keck II Telescope, allowing near-diffraction-limited observations in the near-infrared using natural guide stars as faint as 19th magnitude. This paper describes the conceptual approach and technical implementation followed for this system, including lessons learned, and provides an overview of the early science capabilities.

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“…The Galactic center has been extensively imaged between 2005 and 2007 with the Keck II 10 m telescope using the laser guide star adaptive optics (LGS AO) [26,27] system and the NIRC2 near infrared camera (P.I. K. Matthews).…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Testing for periodicities in near-IR light curves of Sgr A*

Do¹,

Ghez²,

Morris³

et al. 2008

J. Phys.: Conf. Ser.

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Abstract. We present the results of near-infrared (2 µm) monitoring of Sgr A*-IR with 1 minute time sampling using laser guide star adaptive optics (LGS AO) system at the Keck II telescope. Sgr A*-IR was observed continuously for up to three hours on each of seven nights, between 2006 May and 2007 August. Sgr A*-IR is detected at all times and is continuously variable. These observations allow us to investigate Nyquist sampled periods ranging from about 2 minutes to an hour. Of particular interest are periods of ∼20 min, which corresponds to a quasi-periodic (QPO) signal claimed based upon previous near-infrared observations and interpreted as the orbit of a 'hot spot' at or near the last stable orbit of a spinning black hole. We investigate these claims by comparing periodograms of the light curves with models for red noise and find no significant deviations that would indicate QPO activity at any time scale probed in the study. We find that the variability of Sgr A* is consistent with a model based on correlated noise with a power spectrum having a frequency dependence of ∼ f −2.5 , consistent with that observed in AGNs. Furthermore, the periodograms show power down to the minimum sampling time of 2 min, well below the period of the last stable orbit of a maximally spinning black hole, indicating that the Sgr A*-IR light curves observed in this study is unlikely to be from the Keplerian motion of a single 'hot spot' of orbiting plasma.

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The W. M. Keck Observatory Laser Guide Star Adaptive Optics System: Performance Characterization

Cited by 212 publications

References 22 publications

Shocked gas in IRAS F17207-0014: ISM collisions and outflows

Shocked gas in IRAS F17207-0014: ISM collisions and outflows

The W. M. Keck Observatory Laser Guide Star Adaptive Optics System: Overview

Testing for periodicities in near-IR light curves of Sgr A*

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