AAOmega: a scientific and optical overview

Saunders, Will; Bridges, Terry; Gillingham, Peter; Haynes, Roger; Smith, Greg; Whittard, John D.; Churilov, Vladimir; Lankshear, Allan; Croom, S. M.; Jones, Damien; Boshuizen, Christopher R.

doi:10.1117/12.550871

Cited by 93 publications

(44 citation statements)

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“…Data quality of the AAOmega spectra GAMA spectra are obtained with the AAOmega spectrograph (Saunders et al 2004;Smith et al 2004;Sharp et al 2006) on the 3.9 m AAT (Siding Spring Observatory, NSW, Australia). AAOmega possesses a dual beam system that allows a total coverage from 3750 to 8850 Å with the 5700 Å dichroic.…”

Section: Data Analysis With Marvinmentioning

confidence: 99%

Galaxy And Mass Assembly (GAMA): Improved emission lines measurements in four representative samples at 0.07 <z< 0.3

Rodrigues

Foster

Taylor

et al. 2016

A&A

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This paper presents a new catalog of emission lines based on the GAMA II data for galaxies between 0.07 < z < 0.34. The catalog includes four subsamples containing 3000 galaxies drawn from the GAMA II survey and spanning four redshift windows. The four samples are representative of intermediate-mass galaxies down to log M * > 9.4 at z ∼ 0.1 and log M * > 10.6 at z ∼ 0.30. We have developed a dedicated code called MARVIN that automates the main steps of the data analysis, but imposes visual individual quality control of each measurement. We use this catalog to investigate how the sample selection influences the shape of the stellar massmetallicity relation. We find that commonly used selection criteria on line detections and by AGN rejection could affect the shape and dispersion of the high-mass end of the M − Z relation. For log M * > 10.6, common selection criteria reject about 65% of the emission-line galaxies. We also find that the relation does not evolve significantly from z = 0.07 to z = 0.34 in the range of stellar mass for which the samples are representative (log M * > 10.6). For lower stellar masses (log M * < 10.2) we are able to show that the observed 0.15 dex metallicity decrease in the same redshift range is a consequence of a color bias arising from selecting targets in the r-band. We highlight that this color selection bias affects all samples selected in r-band (e.g., GAMA and SDSS), even those drawn from volume-limited samples. Previously reported evolution of the M − Z relation at various redshifts may need to be revised to evaluate the effect of this selection bias.

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Section: Data Analysis With Marvinmentioning

confidence: 99%

Galaxy And Mass Assembly (GAMA): Improved emission lines measurements in four representative samples at 0.07 <z< 0.3

Rodrigues

Foster

Taylor

et al. 2016

A&A

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“…This means that contamination of the spectra by Littrow ghosts [5,6,7] could easily corrupt a significant fraction of the data. Hence it was decided to tilt the gratings, with slanted fringes to preserve the Bragg condition within the DCG, to throw the Littrow ghost just off the detector.…”

Section: Hector Requirementsmentioning

confidence: 99%

“…AAOmega [7] suffers from complex and variable diffractive blazes, imperfectly understood but clearly caused by the detector and spider in the beam. Hence a decision was taken to have a collimator with unobstructed pupil.…”

Section: Hector Requirementsmentioning

confidence: 99%

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Very fast transmissive spectrograph designs for highly multiplexed fiber spectroscopy

Saunders

2016

SPIE Proceedings

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“…The flattened top of the LSF in effect decouples the contributions of the two sides, resulting in particular combinations of pixel phase and sample frequency that are optimum. The final LSF is that of an actual spectrograph, the AAOmega instrument operating at the AngloAustralian Telescope (Saunders et al 2004). This instrument uses multi-mode fibres and thus can be expected to give results similar to those of the convolved projected circle.…”

Section: Wavelength Accuracymentioning

confidence: 99%

Detector Sampling of Optical/IR Spectra: How Many Pixels per FWHM?

Robertson

2017

Publ. Astron. Soc. Aust.

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Most optical and IR spectra are now acquired using detectors with finite-width pixels in a square array. Each pixel records the received intensity integrated over its own area, and pixels are separated by the array pitch. This paper examines the effects of such pixellation, using computed simulations to illustrate the effects which most concern the astronomer end-user. It is shown that coarse sampling increases the random noise errors in wavelength by typically 10 − 20 % at 2 pixels/FWHM, but with wide variation depending on the functional form of the instrumental Line Spread Function (LSF; i.e. the instrumental response to a monochromatic input) and on the pixel phase. If line widths are determined they are even more strongly affected at low sampling frequencies. However, the noise in fitted peak amplitudes is minimally affected by pixellation, with increases less than about 5%. Pixellation has a substantial but complex effect on the ability to see a relative minimum between two closely-spaced peaks (or relative maximum between two absorption lines). The consistent scale of resolving power presented by Robertson (2013) to overcome the inadequacy of the Full Width at Half Maximum (FWHM) as a resolution measure is here extended to cover pixellated spectra. The systematic bias errors in wavelength introduced by pixellation, independent of signal/noise ratio, are examined. While they may be negligible for smooth well-sampled symmetric LSFs, they are very sensitive to asymmetry and high spatial frequency substructure. The Modulation Transfer Function for sampled data is shown to give a useful indication of the extent of improperly sampled signal in an LSF. The common maxim that 2 pixels/FWHM is the Nyquist limit is incorrect and most LSFs will exhibit some aliasing at this sample frequency. While 2 pixels/FWHM is nevertheless often an acceptable minimum for moderate signal/noise work, it is preferable to carry out simulations for any actual or proposed LSF to find the effects of various sampling frequencies. Where spectrograph end-users have a choice of sampling frequencies, through on-chip binning and/or spectrograph configurations, it is desirable that the instrument user manual should include an examination of the effects of the various choices.

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AAOmega: a scientific and optical overview

Cited by 93 publications

References 0 publications

Galaxy And Mass Assembly (GAMA): Improved emission lines measurements in four representative samples at 0.07 <z< 0.3

Galaxy And Mass Assembly (GAMA): Improved emission lines measurements in four representative samples at 0.07 <z< 0.3

Very fast transmissive spectrograph designs for highly multiplexed fiber spectroscopy

Detector Sampling of Optical/IR Spectra: How Many Pixels per FWHM?

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