THE GBT 67–93.6 GHz SPECTRAL LINE SURVEY OF ORION-KL

Frayer, David; Maddalena, R. J.; Meijer, M.; Hough, L.; White, S.; Norrod, R.; Watts, Galen; Stennes, M.; Simon, R.; Woody, D. P.; Srikanth, S.; Pospieszalski, M.W.; Bryerton, Eric; Whitehead, Mark; Ford, Pam; Sarpa, Marcia; Bloss, Marty

doi:10.1088/0004-6256/149/5/162

Cited by 8 publications

(7 citation statements)

References 29 publications

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“…The Orion Kleinmann-Low Nebula (Orion KL) is a good site for investigating the physical and chemical evolution of high-mass star-forming regions. It is the closest high-mass star-forming region (437 ± 19 pc; Hirota et al 2007), and it exhibits rich molecular line emission at the (sub)millimeter wavelengths (Blake et al 1987;Tercero et al 2010;Crockett et al 2014;Feng et al 2015;Frayer et al 2015;Pagani et al 2017;Peng et al 2017Peng et al , 2019. Observationally, this region is composed of four major components, the hot core, the compact ridge, the plateau, and the extended ridge, which are spatially and kinematically different (Blake et al 1987;Schilke et al 2001;Tercero et al 2010;Crockett et al 2014, e.g.,).…”

Section: Introductionmentioning

confidence: 96%

Sulfur-bearing Molecules in Orion KL

Luo

Feng

et al. 2019

ApJ

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We present an observational study of the sulfur (S)-bearing species towards Orion KL at 1.3 mm by combining ALMA and IRAM-30 m single-dish data. At a linear resolution of ∼800 au and a velocity resolution of 1 km s −1 , we have identified 79 molecular lines from 6 S-bearing species. In these S-bearing species, we found a clear dichotomy between carbon-sulfur compounds and carbonfree S-bearing species in various characteristics, e.g., line profiles, spatial morphology, and molecular abundances with respect to H 2 . Lines from the carbon-sulfur compounds (i.e., OCS, 13 CS, H 2 CS) exhibit spatial distributions concentrated around the continuum peaks and extended to the south ridge. The full width at half maximum (FWHM) linewidth of these molecular lines is in the range of 2 ∼ 11 km s −1 . The molecular abundances of OCS and H 2 CS decrease slightly from the cold (∼68 K) to the hot (∼176 K) regions. In contrast, lines from the carbon-free S-bearing species (i.e., SO 2 , 34 SO, H 2 S) are spatially more extended to the northeast of mm4, exhibiting broader FWHM linewidths (15 ∼ 26 km s −1 ). The molecular abundances of carbon-free S-bearing species increase by over an order of magnitude as the temperature increase from 50 K to 100 K. In particular, 34 SO/ 34 SO 2 and OCS/SO 2 are enhanced from the warmer regions (>100 K) to the colder regions (∼50 K). Such enhancements are consistent with the transformation of SO 2 at warmer regions and the influence of shocks.

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Section: Introductionmentioning

confidence: 96%

Sulfur-bearing Molecules in Orion KL

Luo

Feng

et al. 2019

ApJ

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“…The molecular lines and chemistry in Orion-KL have been extensively studied by numerous groups (Sutton et al 1985(Sutton et al , 1995Menten et al 1986;Blake et al 1987;Turner 1989Turner , 1991Mangum et al 1990;Minh et al 1993;Groesbeck 1995;Dickens et al 1997;Schilke et al 1997Schilke et al , 2001Slysh et al 1999;Ikeda et al 2001;Lee et al 2001;Liu et al 2001Liu et al , 2002Alakoz et al 2002;Minier & Booth 2002;White et al 2003;Beuther et al 2004Beuther et al , 2006Charnley 2004;Comito et al 2005;Friedel et al 2005;Persson et al 2007;Friedel & Snyder 2008;Remijan et al 2008;Goddi et al 2009;Crockett et al 2010;Gupta et al 2010;Margulès et al 2010;Favre et al 2011aFavre et al , 2011bZapata et al 2011;Friedel & Widicus Weaver 2012;Brouillet et al 2013;Crockett et al 2014;Favre et al 2014;Frayer et al 2015;Morris et al 2016;…”

Section: Orion-klmentioning

confidence: 99%

Deep, Broadband Spectral Line Surveys of Molecule-rich Interstellar Clouds

Weaver

Laas

Zou

et al. 2017

ApJS

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Spectral line surveys are an indispensable tool for exploring the physical and chemical evolution of astrophysical environments due to the vast amount of data that can be obtained in a relatively short amount of time. We present deep, broadband spectral line surveys of 30 interstellar clouds using two broadband λ=1.3 mm receivers at the Caltech Submillimeter Observatory. This information can be used to probe the influence of physical environment on molecular complexity. We observed a wide variety of sources to examine the relative abundances of organic molecules as they relate to the physical properties of the source (i.e., temperature, density, dynamics, etc.). The spectra are highly sensitive, with noise levels 25 mK at a velocity resolution of ∼0.35kms −1 . In the initial analysis presented here, column densities and rotational temperatures have been determined for the molecular species that contribute significantly to the spectral line density in this wavelength regime. We present these results and discuss their implications for complex molecule formation in the interstellar medium.

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“…Characterizing and correcting for these effects has been an ongoing project, and we are approaching reasonable performance at 116 GHz (Frayer 2017;Frayer et al 2018Frayer et al , 2019. The pointing model is the main focus of this paper, and while we will briefly address the GBT's focus tracking model, an in-depth treatment of this topic is left to other discussions.…”

Section: Introductionmentioning

confidence: 98%

“…The suite of Gregorian receivers covers 1.15 GHz to 116 GHz. The aperture and beam efficiencies for the GBT at the high-frequency end of the observing band were measured recently; at 86 GHz, the aperture efficiency is 34.7±3.2%, and the main beam efficiency is 44.2±4.3% (Frayer et al 2019).…”

Section: Introductionmentioning

confidence: 99%

“…The moving structure is supported by a wheel and track system to rotate about the azimuth axis. Built at first to have good performance below 15 GHz, the adjustable surface and homologous design made it upgradable to function at higher frequencies, with a goal of acceptable performance up to 116 GHz, where the current nighttime aperture efficiency reaches approximately 20% and the half-power beam width is about 6.4 (Frayer et al 2019). The subreflector is movable on six axes and is adjusted to compensate for flexure in the feed arm.…”

Section: Introductionmentioning

confidence: 99%

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Green Bank Telescope: Overview and analysis of metrology systems and pointing performance

White

Ghigo²,

Prestage

et al. 2022

A&A

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With a 100m×110m off-axis paraboloid dish, the Green Bank Telescope (GBT) is the largest fully steerable radio telescope on Earth. A major challenge facing large ground-based radio telescopes is achieving sufficient pointing accuracy for observing at high frequencies, up to 116 GHz in the case of the GBT. Accurate pointing requires the ability to blindly acquire source locations and perform ad hoc corrections determined by observing nearby calibrator sources in order to obtain a starting position accurate to within a small margin of error of the target's location. The required pointing accuracy is dependent upon the half-power beamwidth, and for the higher-frequency end of GBT observing, this means that pointing must be accurate to within a few arcseconds RMS. The GBT's off-axis design is advantageous in that it eliminates blockage of the dish and reduces sidelobe interference, and there is no evidence that the resulting asymmetric structure adversely affects pointing accuracy. However, factors such as gravitational flexure, thermal deformation, azimuth track tilt and irregularity, and small misalignments and offset errors within the telescope's structure cause pointing inaccuracies. A pointing model was developed for the GBT to correct for these effects. The model utilizes standard geometrical corrections along with metrology data from the GBT's structural temperature sensors and data from measurements of the track levels. In this paper we provide a summary of the GBT's pointing model and associated corrections, as well as a discussion of relevant metrology systems and an analysis of its current nighttime pointing accuracy.

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THE GBT 67–93.6 GHz SPECTRAL LINE SURVEY OF ORION-KL

Cited by 8 publications

References 29 publications

Sulfur-bearing Molecules in Orion KL

Sulfur-bearing Molecules in Orion KL

Deep, Broadband Spectral Line Surveys of Molecule-rich Interstellar Clouds

Green Bank Telescope: Overview and analysis of metrology systems and pointing performance

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