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Central powering of the largest Lyman-α nebula is revealed by polarized radiation

Hayes, Matthew and Scarlata, Claudia and Siana, Brian (2011) Central powering of the largest Lyman-α nebula is revealed by polarized radiation. Nature, 476 (7360). pp. 304-307. ISSN 0028-0836.

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High-redshift Lyman-α (Lyα) blobs are extended, luminous but rare structures that seem to be associated with the highest peaks in the matter density of the Universe. Their energy output and morphology are similar to those of powerful radio galaxies, but the source of the luminosity is unclear. Some blobs are associated with ultraviolet or infrared bright galaxies, suggesting an extreme starburst event or accretion onto a central black hole. Another possibility is gas that is shock-excited by supernovae. But not all blobs are associated with galaxies, and these ones may instead be heated by gas falling into a dark-matter halo. The polarization of the Lyα emission can in principle distinguish between these options, but a previous attempt to detect this signature returned a null detection. Here we report observations of polarized Lyα from the blob LAB1 (ref. 2). Although the central region shows no measurable polarization, the polarized fraction (P) increases to ~20 per cent at a radius of 45 kiloparsecs, forming an almost complete polarized ring. The detection of polarized radiation is inconsistent with the in situ production of Lyα photons, and we conclude that they must have been produced in the galaxies hosted within the nebula, and re-scattered by neutral hydrogen.

Item Type:Article
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URLURL TypeDescription
Scarlata, Claudia 0000-0002-9136-8876
Siana, Brian0000-0002-4935-9511
Additional Information:© 2011 Macmillan Publishers. Received 02 April 2011. Accepted 20 June 2011. Published online 17 August 2011. We thank P. Ogle and J. Colbert for valuable suggestions about polarimetric observations; N. Panagia and T. Jones for comments on the manuscript; and D. Schaerer, N. Scoville, C. Lidman, A. Dey, M. Prescott and P. Lynam for discussions. This work was based on observations made with European Southern Observatory telescopes at the Paranal Observatory under programme ID 084.A-0954. M.H. was supported in part by the Swiss National Science Foundation, and also received support from Agence Nationale de la Recherche (reference ANR-09-BLAN-0234-01). All authors contributed to the proposal preparation. M.H. and C.S. observed and reduced the data. M.H. analysed the results. All authors contributed to the manuscript preparation.
Funding AgencyGrant Number
European Southern Observatory telescopes/Paranal Observatory 084.A-0954
Swiss National Science FoundationUNSPECIFIED
Agence Nationale de la RechercheANR-09-BLAN-0234-01
Subject Keywords:Astronomy
Issue or Number:7360
Record Number:CaltechAUTHORS:20110913-144816354
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Official Citation:Central powering of the largest Lyman-α nebula is revealed by polarized radiation Matthew Hayes, Claudia Scarlata & Brian Siana pp. 304-307
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:25315
Deposited By: Ruth Sustaita
Deposited On:14 Sep 2011 17:53
Last Modified:03 Oct 2019 03:05

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