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Far-infrared constraints on the contamination by dust-obscured galaxies of high-z dropout searches

Boone, F.; Schaerer, D.; Pelló, R.; Lutz, D.; Weiss, A.; Egami, E.; Smail, I.; Rex, M.; Rawle, T.; Ivison, R.; Laporte, N.; Beelen, A.; Combes, F.; Blain, A.W.; Richard, J.; Kneib, J.-P.; Zamojski, M.; Dessauges-Zavadsky, M.; Altieri, B.; van der Werf, P.; Swinbank, M.; Pérez-Gonzá&lez, P.G.; Clement, B.; Nordon, R.; Magnelli, B.; Menten, K.M.

Far-infrared constraints on the contamination by dust-obscured galaxies of high-z dropout searches Thumbnail


Authors

F. Boone

D. Schaerer

R. Pelló

D. Lutz

A. Weiss

E. Egami

Profile image of Ian Smail

Ian Smail ian.smail@durham.ac.uk
Emeritus Professor

M. Rex

T. Rawle

R. Ivison

N. Laporte

A. Beelen

F. Combes

A.W. Blain

J. Richard

J.-P. Kneib

M. Zamojski

M. Dessauges-Zavadsky

B. Altieri

P. van der Werf

M. Swinbank

P.G. Pérez-Gonzá&lez

B. Clement

R. Nordon

B. Magnelli

K.M. Menten



Abstract

The spectral energy distributions (SED) of dusty galaxies at intermediate redshift may look similar to very high-redshift galaxies in the optical/near infrared (NIR) domain. This can lead to the contamination of high-redshift galaxy searches based on broad-band optical/NIR photometry by lower redshift dusty galaxies because both kind of galaxies cannot be distinguished. The contamination rate could be as high as 50%. This work shows how the far-infrared (FIR) domain can help to recognize likely low-z interlopers in an optical/NIR search for high-z galaxies. We analyze the FIR SEDs of two galaxies that are proposed to be very high-redshift (z > 7) dropout candidates based on deep Hawk-I/VLT observations. The FIR SEDs are sampled with PACS/Herschel at 100 and 160 μm, with SPIRE/Herschel at 250, 350 and 500 μm and with LABOCA/APEX at 870 μm. We find that redshifts > 7 would imply extreme FIR SEDs (with dust temperatures >100 K and FIR luminosities >1013 L⊙). At z ~ 2, instead, the SEDs of both sources would be compatible with those of typical ultra luminous infrared galaxies or submillimeter galaxies. Considering all available data for these sources from visible to FIR we re-estimate the redshifts and find z ~ 1.6–2.5. Owing to the strong spectral breaks observed in these galaxies, standard templates from the literature fail to reproduce the visible-to-near-IR part of the SEDs even when additional extinction is included. These sources strongly resemble dust-obscured galaxies selected in Spitzer observations with extreme visible-to-FIR colors, and the galaxy GN10 at z = 4. Galaxies with similar SEDs could contaminate other high-redshift surveys.

Citation

Boone, F., Schaerer, D., Pelló, R., Lutz, D., Weiss, A., Egami, E., …Menten, K. (2011). Far-infrared constraints on the contamination by dust-obscured galaxies of high-z dropout searches. Astronomy & Astrophysics, 534, Article A124. https://doi.org/10.1051/0004-6361/201117338

Journal Article Type Article
Publication Date Oct 1, 2011
Deposit Date Jan 25, 2012
Publicly Available Date Jun 14, 2013
Journal Astronomy and astrophysics.
Print ISSN 0004-6361
Electronic ISSN 1432-0746
Publisher EDP Sciences
Peer Reviewed Peer Reviewed
Volume 534
Article Number A124
DOI https://doi.org/10.1051/0004-6361/201117338
Keywords Galaxies, distances and redshifts, Dust, Extinction, Gravitational lensing, Weak, High-redshift.
Public URL https://durham-repository.worktribe.com/output/1529435

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