Planck Far-infrared Detection of Hyper Suprime-Cam Protoclusters at z similar to 4: Hidden AGN and Star Formation Activity

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Kubo, Mariko ^[1] ; Toshikawa, Jun ^{[2, 3]} ; Kashikawa, Nobunari ^[4] ; Chiang, Yi-Kuan ^[5] ; Overzier, Roderik ^{[6, 7]} ; Uchiyama, Hisakazu ^{[1, 8]} ; Clements, David L. ^[9] ; Alexander, David M. ^[10] ; Matsuda, Yuichi ^{[1, 8]} ; Kodama, Tadayuki ^[11] ; Ono, Yoshiaki ^[3] ; Goto, Tomotsugu ^[12] ; Cheng, Tai-An ^[9] ; Ito, Kei ^[8]

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^[1] Natl Astron Observ Japan, 2-21-1 Osawa, Mitaka, Tokyo 1818588 - Japan

^[2] Univ Bath, Dept Phys, Bath BA2 7AY, Avon - England

^[3] Univ Tokyo, Inst Cosm Ray Res, Kashiwa, Chiba 2778582 - Japan

^[4] Univ Tokyo, Sch Sci, Dept Astron, Bunkyo Ku, 7-3-1 Hongo, Tokyo 1130033 - Japan

^[5] Johns Hopkins Univ, Dept Phys & Astron, 3400 N Charles St, Baltimore, MD 21218 - USA

^[6] Univ Sao Paulo, Inst Astron Geophys & Atmospher Sci, BR-05508090 Sao Paulo, SP - Brazil

^[7] Observ Nacl, Rua JoseCristino 77, BR-20921400 Rio De Janeiro, RJ - Brazil

^[8] Grad Univ Adv Studies SOKENDAI, Dept Astron Sci, Mitaka, Tokyo 1818588 - Japan

^[9] Imperial Coll London, Blackett Lab, Astrophys Grp, Prince Consort Rd, London SW7 2AZ - England

^[10] Univ Durham, Dept Phys, Ctr Extragalact Astron, Durham DH1 3LE - England

^[11] Tohoku Univ, Astron Inst, Sendai, Miyagi 9808578 - Japan

^[12] Natl Tsing Hua Univ, 101, Sect 2, Kuang Fu Rd, Hsinchu 30013 - Taiwan

• Tipo de documento: Artigo Científico
• Fonte: ASTROPHYSICAL JOURNAL; v. 887, n. 2 DEC 20 2019.
• Citações Web of Science: 0

Resumo

We perform a stacking analysis of Planck, AKARI, Infrared Astronomical Satellite, Wide-field Infrared Survey Explorer, and Herschel images of the largest number of (candidate) protoclusters at z similar to 3.8 selected from the Hyper Suprime-Cam Subaru Strategic Program. Stacking the images of the 179 candidate protoclusters, the combined infrared (IR) emission of the protocluster galaxies in the observed 12-850 mu m wavelength range is successfully detected with >5 sigma significance (at Planck). This is the first time that the average IR spectral energy distribution (SED) of a protocluster has been constrained at z similar to 4. The observed IR SEDs of the protoclusters exhibit significant excess emission in the mid-IR compared to that expected from typical star-forming galaxies (SFGs). They are reproduced well using SED models of intense starburst galaxies with warm/hot dust heated by young stars, or by a population of active galactic nucleus (AGN)/SFG composites. For the pure star-forming model, a total IR (from 8-1000 mu m) luminosity of 19.3(-4.2)(+0.6) x 10(13) L-circle dot and a star formation rate of 16.3(-7.8)(+1.0) M-circle dot yr(-1) are found, whereas for the AGN/SFG composite model, 5.1(-2.5)(+2.5) x 10(13) L-circle dot and 2.1(-1.7)(+6.3) x 10(3) M-circle dot yr(-1) are found. Uncertainty remains in the total SFRs; however, the IR luminosities of the most massive protoclusters are likely to continue increasing up to z similar to 4. Meanwhile, no significant IR flux excess is observed around optically selected QSOs at similar redshifts, which confirms previous results. Our results suggest that the z similar to 4 protoclusters trace dense, intensely star-forming environments that may also host obscured AGNs missed by the selection in the optical. (AU)

• Processo FAPESP: 18/02444-7 - O alvorecer das galáxias.
• Beneficiário: João Evangelista Steiner
• Linha de fomento: Auxílio à Pesquisa - Pesquisador Visitante - Brasil