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Detection of Hα emission from z > 3.5 submillimetre luminous galaxies with AKARI-FUHYU spectroscopy.

Sedgwick, C. and Serjeant, S. and Pearson, C. and Smail, I. and Im, M. and Oyabu, S. and Takagi, T. and Matsuhara, H. and Wada, T. and Lee, H.M. and Jeong, W.-S. and White, G.J. (2013) 'Detection of Hα emission from z > 3.5 submillimetre luminous galaxies with AKARI-FUHYU spectroscopy.', Monthly notices of the Royal Astronomical Society., 436 (1). pp. 395-400.


We present tentative Hα emission line detections of four submillimetre-detected galaxies at z > 3.5: the radio galaxies 8C1909+722 and 4C60.07 at signal-to-noise ratios (SNRs) of 3.1 and 2.5, and two submillimetre-selected galaxies (SMGs) near the first of these at SNRs of 10.0 and 2.4, made with the AKARI space telescope as part of the Follow-Up Hayai-Yasui-Umai mission programme. These are the highest redshift Hα detections in such galaxies, made possible by AKARI's unique near-infrared spectroscopic capability. The two radio galaxies had known redshifts and surrounding structure, and we have detected broad Hα components indicating the presence of dust-shrouded quasars. We conclude that powerful active galactic nuclei (AGNs) at z > 3.5 occur in peaks of the star formation density fields, supporting a close connection between stellar mass build-up and black hole mass assembly at this redshift. We also show that 4C60.07 is a binary AGN. The Hα detections of the two SMGs are the first redshift determinations for these sources, confirming their physical association around their companion radio galaxy. The Hα-derived star formation rates (SFRs) for the SMGs are lower than their far-infrared derived SFRs by a factor of ∼10, suggesting a level of dust obscuration similar to that found in studies at ∼1 < z < 2.7.

Item Type:Article
Keywords:Galaxies: active, Galaxies: evolution, Galaxies: starburst, Galaxies: star formation, Infrared: galaxies.
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Publisher statement:This article has been accepted for publication in Monthly notices of the Royal Astronomical Society © 2013 The Authors Published by Oxford University Press on behalf of Royal Astronomical Society. All rights reserved.
Date accepted:No date available
Date deposited:20 June 2014
Date of first online publication:November 2013
Date first made open access:No date available

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