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Published October 2015 | Published + Submitted
Journal Article Open

Planck intermediate results XXVII. High-redshift infrared galaxy overdensity candidates and lensed sources discovered by Planck and confirmed by Herschel-SPIRE

Abstract

We have used the Planck all-sky submillimetre and millimetre maps to search for rare sources distinguished by extreme brightness, a few hundred millijanskies, and their potential for being situated at high redshift. These "cold" Planck sources, selected using the High Frequency Instrument (HFI) directly from the maps and from the Planck Catalogue of Compact Sources (PCCS), all satisfy the criterion of having their rest-frame far-infrared peak redshifted to the frequency range 353–857 GHz. This colour-selection favours galaxies in the redshift range z = 2–4, which we consider as cold peaks in the cosmic infrared background. With a 4.'5 beam at the four highest frequencies, our sample is expected to include overdensities of galaxies in groups or clusters, lensed galaxies, and chance line-of-sight projections. We perform a dedicated Herschel-SPIRE follow-up of 234 such Planck targets, finding a significant excess of red 350 and 500μm sources, in comparison to reference SPIRE fields. About 94% of the SPIRE sources in the Planck fields are consistent with being overdensities of galaxies peaking at 350μm, with 3% peaking at 500μm, and none peaking at 250μm. About 3% are candidate lensed systems, all 12 of which have secure spectroscopic confirmations, placing them at redshifts z> 2.2. Only four targets are Galactic cirrus, yielding a success rate in our search strategy for identifying extragalactic sources within the Planck beam of better than 98%. The galaxy overdensities are detected with high significance, half of the sample showing statistical significance above 10σ. The SPIRE photometric redshifts of galaxies in overdensities suggest a peak at z ≃ 2, assuming a single common dust temperature for the sources of T_d = 35 K. Under this assumption, we derive an infrared (IR) luminosity for each SPIRE source of about 4 × 10^(12)L_⊙, yielding star formation rates of typically 700 M_⊙ yr^(-1). If the observed overdensities are actual gravitationally-bound structures, the total IR luminosity of all their SPIRE-detected sources peaks at 4 × 10^(13)L_⊙, leading to total star formation rates of perhaps 7 × 10^3M_⊙ yr^(-1) per overdensity. Taken together, these sources show the signatures of high-z (z> 2) protoclusters of intensively star-forming galaxies. All these observations confirm the uniqueness of our sample compared to reference samples and demonstrate the ability of the all-skyPlanck-HFI cold sources to select populations of cosmological and astrophysical interest for structure formation studies.

Additional Information

© 2015 EDP Sciences. Received 11 August 2014. Accepted 12 March 2015. The development of Planck has been supported by: ESA; CNES and CNRS/INSU-IN2P3-INP (France); ASI, CNR, and INAF (Italy); NASA and DoE (USA); STFC and UKSA (UK); CSIC, MICINN, JA, and RES (Spain); Tekes, AoF, and CSC (Finland); DLR and MPG (Germany); CSA (Canada); DTU Space (Denmark); SER/SSO (Switzerland); RCN (Norway); SFI (Ireland); FCT/MCTES (Portugal); and PRACE (EU). A description of the Planck Collaboration and a list of its members, including the technical or scientific activities in which they have been involved, can be found at http://www.sciops.esa.int/index.php?project=planck&page=Planck_Collaborationhttp://www.sciops.esa.int index.php?project=planck. The Herschel spacecraft was designed, built, tested, and launched under a contract to ESA managed by the Herschel/Planck Project team by an industrial consortium under the overall responsibility of the prime contractor Thales Alenia Space (Cannes), and including Astrium (Friedrichshafen) responsible for the payload module and for system testing at spacecraft level, Thales Alenia Space (Turin) responsible for the service module, and Astrium (Toulouse) responsible for the telescope, with in excess of a hundred subcontractors. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. Based in part on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institute National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. Based in part on observations obtained with WIRCam, a joint project of CFHT, Taiwan, Korea, Canada, France, and the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institute National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. Based in part on observations carried out with the IRAM 30-m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). Based in part on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). Based in part on observations made at JCMT with SCUBA-2. The James Clerk Maxwell Telescope is operated by the Joint Astronomy Centre on behalf of the Science and Technology Facilities Council of the United Kingdom, the Netherlands Organisation for Scientific Research, and the National Research Council of Canada. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. We acknowledge the support from the CNES, the PNCG (Programme National de Cosmologie et Galaxies), ANR HUGE (ANR-09-BLAN-0224-HUGE) and ANR MULTIVERSE (ANR-11-BS56-015). We also acknowledge the support from Région Ile-de-France with DIM-ACAV. We acknowledge the Integrated Data & Operation Center (IDOC) at Institut d'Astrophysique Spatiale and Observatoire des Sciences de l'Univers de l'Université Paris Sud (OSUPS). Support for IDOC is provided by CNRS and CNES. We acknowledge final support from ASI/INAF agreement I/072/09/0 and PRIN-INAF 2012 project "Looking into the dust-obscured phase of galaxy formation through cosmic zoom lenses in the Herschel Astrophysical Large Area Survey." We acknowledges financial support from the Spanish CSIC for a JAE-DOC fellowship, cofunded by the European Social Fund and from the Ministerio de Economia y Competitividad, project AYA2012-39475-C02-01. This research made use of matplotlib Hunter (2007), and of APLpy, an open-source plotting package for Python hosted at http://aplpy.github.com. We thank E. Egami, B. Clément, E. Daddi, H. J. McCracken and A. Boucaud and for fruitful discussions and helpful advice.

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Created:
August 22, 2023
Modified:
October 25, 2023