Galaxy Tagging: photometric redshift refinement and group richness enhancement

Kafle, P.R.; Robotham, A.S.G.; Driver, S.P.; Deeley, S.; Norberg, P.; Drinkwater, M.J.; Davies, L.J.

doi:10.1093/mnras/sty1536

Galaxy Tagging: photometric redshift refinement and group richness enhancement

Kafle, P.R.; Robotham, A.S.G.; Driver, S.P.; Deeley, S.; Norberg, P.; Drinkwater, M.J.; Davies, L.J.

Authors

P.R. Kafle

A.S.G. Robotham

S.P. Driver

S. Deeley

Professor Peder Norberg peder.norberg@durham.ac.uk
Professor

M.J. Drinkwater

L.J. Davies

Abstract

We present a new scheme, galtag, for refining the photometric redshift measurements of faint galaxies by probabilistically tagging them to observed galaxy groups constructed from a brighter, magnitude-limited spectroscopy survey. First, this method is tested on the DESI light-cone data constructed on the GALFORM galaxy formation model to tests its validity. We then apply it to the photometric observations of galaxies in the Kilo-Degree Imaging Survey (KiDS) over a 1 deg2 region centred at 15h. This region contains Galaxy and Mass Assembly (GAMA) deep spectroscopic observations (i-band<22) and an accompanying group catalogue to r-band<19.8. We demonstrate that even with some trade-off in sample size, an order of magnitude improvement on the accuracy of photometric redshifts is achievable when using galtag. This approach provides both refined photometric redshift measurements and group richness enhancement. In combination these products will hugely improve the scientific potential of both photometric and spectroscopic datasets. The galtag software will be made publicly available at https://github.com/pkaf/galtag.git.

Citation

Kafle, P., Robotham, A., Driver, S., Deeley, S., Norberg, P., Drinkwater, M., & Davies, L. (2018). Galaxy Tagging: photometric redshift refinement and group richness enhancement. Monthly Notices of the Royal Astronomical Society, 479(3), 3746-3758. https://doi.org/10.1093/mnras/sty1536

Journal Article Type	Article
Acceptance Date	Jun 7, 2018
Online Publication Date	Jun 18, 2018
Publication Date	Sep 21, 2018
Deposit Date	Jul 11, 2018
Publicly Available Date	Jul 12, 2018
Journal	Monthly Notices of the Royal Astronomical Society
Print ISSN	0035-8711
Electronic ISSN	1365-2966
Publisher	Royal Astronomical Society
Peer Reviewed	Peer Reviewed
Volume	479
Issue	3
Pages	3746-3758
DOI	https://doi.org/10.1093/mnras/sty1536

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This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2018 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.