High resolution near-infrared imaging with tip-tilt adaptive optics.

Persistent Link:
http://hdl.handle.net/10150/187324
Title:
High resolution near-infrared imaging with tip-tilt adaptive optics.
Author:
Close, Laird Miller.
Issue Date:
1995
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The development and design of the first operational tip-tilt Cassegrain secondary mirror are presented. This system, F ASTTRAC, samples image motion at up to 50 Hz by tracking either infrared (m(K)≤11) or visible (m(R)≤16) guide stars up to 30" and 90" away from the science target respectively. The Steward Observatory 2Jm or 1.5m telescope secondaries act as rapid tip-tilt mirrors to stabilize image motion (≤0.1" rms; ∼5 Hz -3 dB frequency) based on the motion of the guide star. F ASTTRAC obtains nearly diffraction-limited resolutions in seeing conditions where D/r₀<4 in agreement with theoretical expectations. FASTTRAC's unique ability to guide on infrared stars has allowed the first adaptively corrected images of the heavily extincted Galactic Center to be obtained. Over a hundred excellent (0.28"<FWHM<0.6") images have been obtained of this region. These images do not detect any long term variations in the massive black hole candidate Sgr A*'s luminosity from June 1993 to September 1995. The average infrared magnitudes observed are K=12.1±0.3, H=13.7±0.3 and J=16.6±0.4 integrated over 0.5" at the position of Sgr A*. No significant rapid periodicities were observed from Sgr A* for amplitudes ~ 50% of the mean flux in the period range of 3-30 minutes. It is confirmed in the latest 0.28" FWHM image that there is 0.5" "bar" of emission running East-West at the position of Sgr A* as was earlier seen by Eckart et al. 1993. The observed fluxes are consistent with an inclined accretion disk around a ∼1x10⁶ M⨀ black hole. However, they are also explained by a line of hot luminous (integrated luminosity of ∼10^(3.5-4.6) central cluster stars positionally coincident with Sgr A* naturally explaining the observed 0.5" "bar". High-resolution images with FASTTRAC guiding on a faint (R=16) visible guide star, combined with spectra from the MMT, have shown that lRAS FSC 10214+4724 (z=2.28) gains its uniquely large luminosity of ∼1.2x10¹⁴h⁻²L⨀ by gravitational lensing magnification from a nearby (l.25" away) galaxy. The detection of a tentative 4000 Å continuum break at 5690±90 Å indicates that this lensing galaxy has a redshift of0.42±0.02. A simple lensing model predicts that 10214+4724 is a "normal" background ultraluminous IR galaxy with an intrinsic (unlensed) luminosity of ∼3.7 x10¹²h⁻²L⨀.
Type:
text; Dissertation-Reproduction (electronic)
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Astronomy; Graduate College
Degree Grantor:
University of Arizona
Committee Chair:
McCarthy, Donald W.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleHigh resolution near-infrared imaging with tip-tilt adaptive optics.en_US
dc.creatorClose, Laird Miller.en_US
dc.contributor.authorClose, Laird Miller.en_US
dc.date.issued1995en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe development and design of the first operational tip-tilt Cassegrain secondary mirror are presented. This system, F ASTTRAC, samples image motion at up to 50 Hz by tracking either infrared (m(K)≤11) or visible (m(R)≤16) guide stars up to 30" and 90" away from the science target respectively. The Steward Observatory 2Jm or 1.5m telescope secondaries act as rapid tip-tilt mirrors to stabilize image motion (≤0.1" rms; ∼5 Hz -3 dB frequency) based on the motion of the guide star. F ASTTRAC obtains nearly diffraction-limited resolutions in seeing conditions where D/r₀<4 in agreement with theoretical expectations. FASTTRAC's unique ability to guide on infrared stars has allowed the first adaptively corrected images of the heavily extincted Galactic Center to be obtained. Over a hundred excellent (0.28"<FWHM<0.6") images have been obtained of this region. These images do not detect any long term variations in the massive black hole candidate Sgr A*'s luminosity from June 1993 to September 1995. The average infrared magnitudes observed are K=12.1±0.3, H=13.7±0.3 and J=16.6±0.4 integrated over 0.5" at the position of Sgr A*. No significant rapid periodicities were observed from Sgr A* for amplitudes ~ 50% of the mean flux in the period range of 3-30 minutes. It is confirmed in the latest 0.28" FWHM image that there is 0.5" "bar" of emission running East-West at the position of Sgr A* as was earlier seen by Eckart et al. 1993. The observed fluxes are consistent with an inclined accretion disk around a ∼1x10⁶ M⨀ black hole. However, they are also explained by a line of hot luminous (integrated luminosity of ∼10^(3.5-4.6) central cluster stars positionally coincident with Sgr A* naturally explaining the observed 0.5" "bar". High-resolution images with FASTTRAC guiding on a faint (R=16) visible guide star, combined with spectra from the MMT, have shown that lRAS FSC 10214+4724 (z=2.28) gains its uniquely large luminosity of ∼1.2x10¹⁴h⁻²L⨀ by gravitational lensing magnification from a nearby (l.25" away) galaxy. The detection of a tentative 4000 Å continuum break at 5690±90 Å indicates that this lensing galaxy has a redshift of0.42±0.02. A simple lensing model predicts that 10214+4724 is a "normal" background ultraluminous IR galaxy with an intrinsic (unlensed) luminosity of ∼3.7 x10¹²h⁻²L⨀.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineAstronomyen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.chairMcCarthy, Donald W.en_US
dc.contributor.committeememberMelia, Fulvioen_US
dc.contributor.committeememberRix, Hans-Walteren_US
dc.identifier.proquest9620385en_US
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