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Galaxy And Mass Assembly (GAMA): AUTOZ spectral redshift measurements, confidence and errors

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posted on 2023-06-08, 21:14 authored by I K Baldry, M Alpaslan, A E Bauer, J Bland-Hawthorn, S Brough, M E Cluver, S M Croom, L J M Davies, S P Driver, M L P Gunawardhana, B W Holwerda, A M Hopkins, L S Kelvin, J Liske, Á R López-Sánchez, Jonathan LovedayJonathan Loveday, P Norberg, J Peacock, A S G Robotham, E N Taylor
The Galaxy And Mass Assembly (GAMA) survey has obtained spectra of over 230 000 targets using the Anglo-Australian Telescope. To homogenize the redshift measurements and improve the reliability, a fully automatic redshift code was developed (AUTOZ). The measurements were made using a cross-correlation method for both the absorption- and the emission-line spectra. Large deviations in the high-pass-filtered spectra are partially clipped in order to be robust against uncorrected artefacts and to reduce the weight given to single-line matches. A single figure of merit (FOM) was developed that puts all template matches on to a similar confidence scale. The redshift confidence as a function of the FOM was fitted with a tanh function using a maximum likelihood method applied to repeat observations of targets. The method could be adapted to provide robust automatic redshifts for other large galaxy redshift surveys. For the GAMA survey, there was a substantial improvement in the reliability of assigned redshifts and in the lowering of redshift uncertainties with a median velocity uncertainty of 33?km?s-1.

History

Publication status

  • Published

File Version

  • Published version

Journal

Monthly Notices of the Royal Astronomical Society

ISSN

0035-8711

Publisher

Oxford University Press

Issue

3

Volume

441

Page range

2440-2451

Department affiliated with

  • Physics and Astronomy Publications

Full text available

  • Yes

Peer reviewed?

  • Yes

Legacy Posted Date

2015-06-24

First Open Access (FOA) Date

2015-06-24

First Compliant Deposit (FCD) Date

2015-06-24

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