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

Authors

I. K. Baldry, Liverpool John Moores University
M. Alpaslan, University of St. Andrews
A. E. Bauer, Australian Astronomical Observatory
J. Bland-Hawthorn, University of Sydney
S. Brough, Australian Astronomical Observatory
M. E. Cluver, University of Cape Town
S. M. Croom, University of Sydney
L. J. M. Davies, University of Western Australia
S. P. Driver, University of Western Australia
M. L. P. Gunawardhana, Durham University
Benne W. Holwerda, University of Louisville
A. M. Hopkins, Australian Astronomical Observatory
L. S. Kelvin, Universitat Innsbruck
J. Liske, European Southern Observatory
A. R. Lopez-Sanchez, Australian Astronomical Observatory
J. Loveday, University of Sussex
P. Norberg, Durham University
J. A. Peacock, University of Edinburgh
A. S. G. Robotham, University of Western Australia
E. N. Taylor, University of Melbourne

Document Type

Article

Publication Date

7-2014

Department

Physics and Astronomy

Abstract

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.

Comments

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society Copyright: 2014. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

https://doi.org/10.1093/mnras/stu727

Original Publication Information

Baldry, I.K., et al. "Galaxy And Mass Assembly (GAMA): AUTOZ Spectral Redshift Measurements, Confidence and Errors." 2014. Monthly Notices of the Royal Astronomical Society 441(3): 2440-2451.

ThinkIR Citation

Baldry, I. K.; Alpaslan, M.; Bauer, A. E.; Bland-Hawthorn, J.; Brough, S.; Cluver, M. E.; Croom, S. M.; Davies, L. J. M.; Driver, S. P.; Gunawardhana, M. L. P.; Holwerda, Benne W.; Hopkins, A. M.; Kelvin, L. S.; Liske, J.; Lopez-Sanchez, A. R.; Loveday, J.; Norberg, P.; Peacock, J. A.; Robotham, A. S. G.; and Taylor, E. N., "Galaxy And Mass Assembly (GAMA) : AUTOZ spectral redshift measurements, confidence and errors." (2014). Faculty and Staff Scholarship. 202.
https://ir.library.louisville.edu/faculty/202

DOI

10.1093/mnras/stu727