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CLASH: Photometric redshifts with 16 HST bands in galaxy cluster fields

Jouvel, S. and Zitrin, A. (2014) CLASH: Photometric redshifts with 16 HST bands in galaxy cluster fields. Astronomy and Astrophysics, 562 . Art. No. A86. ISSN 0004-6361.

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Context. The Cluster Lensing And Supernovae survey with Hubble (CLASH) is a Hubble Space Telescope (HST) Multi-Cycle Treasury programme that observes 25 massive galaxy clusters, 20 of which were X-ray-selected to preferably choose dynamically relaxed clusters, and 5 additional “high magnification” clusters, which were selected based on their optical lensing properties. CLASH aims to study the dark matter distribution of the clusters and find magnified high-redshift galaxies behind them. CLASH observations were carried out in 16 bands from UV to NIR to derive accurate and reliable estimates of photometric redshifts. Aims. We present the CLASH photometric redshifts using 16 HST bands and study the photometric redshift accuracy including a detailed comparison between photometric and spectroscopic redshifts for the strong lensing arcs using the measurements from the cluster MACSJ1206.2-0847. Methods. We used the publicly available Le Phare and BPZ photometric redshift estimation codes on 17 CLASH galaxy clusters for which the full photo-z data processing had been completed at the time of this analysis, and derive an estimate of the CLASH photo-z accuracy. Results. Using Le Phare code for objects with a S/N ≥ 10, we reach a precision of 3%(1 + z) for the strong lensing arcs, which is reduced to 2.4%(1 + z) after removing outliers. For galaxies in the cluster field, the corresponding values are 4%(1 + z) and 3%(1 + z). Using mock galaxy catalogues, we show that 3%(1 + z) precision is what is expected using the baseline sky substraction algorithm when taking into account extinction from dust, emission lines, and the finite range of SEDs included in the photo-z template library. An improved method for estimating galaxy colours that yields more accurate photometric redshifts will be explored in a forthcoming paper. We study photo-z results for different aperture photometry techniques and find that the SExtractor isophotal photometry works best. We check the robustness of the arcs photo-z results by rederiving the input photometry in the case of MACS1206. We describe and release a photometric redshift catalogue of the MACS1206 cluster we study. Conclusions. Our photo-z codes give similar results for the strong lensing arcs, as well as for galaxies of the cluster field. Results are improved when optimizing the photometric aperture shape that shows an optimal aperture size around 1′′ radius, giving results that are equivalent to isophotal photometry. Tailored photometry of the arcs improves the photo-z results by showing more consistency between the different arcs of the same strong lensing system.

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Additional Information:© 2014 ESO. Article published by EDP Sciences. Received 31 July 2013. Accepted 22 November 2013. Published online 11 February 2014. S.J. and O.H. acknowledge at UCL, O.L. acknowledges a Royal Society Wolfson Research Merit Award, a Leverhulme Senior Research Fellowship and an Advanced ERC Grant. S.J. is supported by the Spanish Science Ministry AYA2009-13936 Consolider-Ingenio CSD2007-00060, project 2009SGR1398 from Generalitat de Catalunya and by the European Commissions Marie Curie Initial Training Network CosmoComp (PITN- GA-2009-238356). The Dark Cosmology Centre is funded by the Danish National Research Foundation. S. Seitz acknowledges support from the Transregional Collaborative Research Centre TRR 33 “The Dark Universe” and from the DFG cluster of excellence “Origin and Structure of the Universe”. This research is partially supported by PRIN INAF 2010: “Architecture and Tomography of Galaxy Clusters”. A.F. acknowledges support from INAF through PRIN 2008 and 2010 grants. Support for A.Z. is provided by NASA through Hubble Fellowship grant #HST-HF-51334.01-A awarded by STScI. Part of this work was also supported by contract research “Internationale Spitzenforschung II/2-6” of the Baden Württemberg Stiftung. A.M. acknowledges support from AYA2006-14056 BES-2007-16280.
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)UNSPECIFIED
Royal Society Wolfson Research Merit AwardUNSPECIFIED
Leverhulme Senior Research FellowshipUNSPECIFIED
Spanish Science MinistryAYA2009-13936
Consolider-Ingenio CSD2007-00060
Generalitat de Catalunya2009SGR1398
European Commission Marie Curie Initial Training Network CosmoCompPITN- GA-2009-238356
Danish National Research FoundationUNSPECIFIED
Transregional Collaborative Research CentreTRR 33
DFG Cluster of ExcellenceUNSPECIFIED
INAF grantPRIN-2008
INAF grantPRIN-2010
NASA Hubble Fellowship grantHST-HF-51334.01-A
Baden Württemberg Stiftung Internationale SpitzenforschungII/2-6
Subject Keywords:galaxies: clusters: general, galaxies: distances and redshifts
Record Number:CaltechAUTHORS:20140428-075546682
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Official Citation:CLASH: Photometric redshifts with 16 HST bands in galaxy cluster fields S. Jouvel, O. Host, O. Lahav, S. Seitz, A. Molino, D. Coe, M. Postman, L. Moustakas, N. Benìtez, P. Rosati, I. Balestra, C. Grillo, L. Bradley, A. Fritz, D. Kelson, A. M. Koekemoer, D. Lemze, E. Medezinski, A. Mercurio, J. Moustakas, M. Nonino, M. Scodeggio, W. Zheng, A. Zitrin, M. Bartelmann, R. Bouwens, T. Broadhurst, M. Donahue, H. Ford, G. Graves, L. Infante, Y. Jimenez-Teja, R. Lazkoz, P. Melchior, M. Meneghetti, J. Merten, S. Ogaz and K. Umetsu A&A 562 A86 (2014) DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:45236
Deposited By: Ruth Sustaita
Deposited On:28 Apr 2014 17:51
Last Modified:09 Jul 2015 20:03

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