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Published December 1, 2014 | Published + Submitted
Journal Article Open

ALMA Imaging of Gas and Dust in a Galaxy Protocluster at Redshift 5.3: [C II] Emission in "Typical" Galaxies and Dusty Starbursts ≈ 1 Billion Years after the Big Bang


We report interferometric imaging of [C II](^2 P_(3/2)→^2 P_(1/2)) and OH(^2Π_(1/2)J = 3/2→1/2) emission toward the center of the galaxy protocluster associated with the z = 5.3 submillimeter galaxy (SMG) AzTEC-3, using the Atacama Large (sub)Millimeter Array (ALMA). We detect strong [C II], OH, and rest-frame 157.7 μm continuum emission toward the SMG. The [C II](^2 P_(3/2)→^2 P_(1/2)) emission is distributed over a scale of 3.9 kpc, implying a dynamical mass of 9.7 × 10^(10) M_☉, and a star formation rate (SFR) surface density of Σ_(SFR) = 530 M_☉ yr^(–1) kpc^(–2). This suggests that AzTEC-3 forms stars at Σ^(SFR) approaching the Eddington limit for radiation pressure supported disks. We find that the OH emission is slightly blueshifted relative to the [C II] line, which may indicate a molecular outflow associated with the peak phase of the starburst. We also detect and dynamically resolve [C II](^2 P_(3/2)→^2 P_(1/2)) emission over a scale of 7.5 kpc toward a triplet of Lyman-break galaxies with moderate UV-based SFRs in the protocluster at ~95 kpc projected distance from the SMG. These galaxies are not detected in the continuum, suggesting far-infrared SFRs of <18-54 M_☉ yr^(–1), consistent with a UV-based estimate of 22 M_☉ yr^(–1). The spectral energy distribution of these galaxies is inconsistent with nearby spiral and starburst galaxies, but resembles those of dwarf galaxies. This is consistent with expectations for young starbursts without significant older stellar populations. This suggests that these galaxies are significantly metal-enriched, but not heavily dust-obscured, "normal" star-forming galaxies at z > 5, showing that ALMA can detect the interstellar medium in "typical" galaxies in the very early universe.

Additional Information

© 2014 American Astronomical Society. Received 2014 April 28; accepted 2014 October 15; published 2014 November 10. We thank the anonymous referee for a helpful and constructive report, Jim Braatz for assistance with setting up the observations, Mark Lacy for taking on the QA2 check of the data, and Alex Conley for help with the SED fitting. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This paper makes use of the following ALMA data: ADS/JAO.ALMA# 2011.0.00064.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. F.B. and A.K. acknowledge support from Collaborative Research Centre 956, sub-project A1, funded by the Deutsche Forschungsgemeinschaft (DFG). V.S. acknowledges support by the European Union's Seventh Framework program under grant agreement 337595 (ERC Starting Grant, "Cos-Mass"). Additional support for this work was provided by the NSF through award SOSPA0-002 from the NRAO.

Attached Files

Published - 0004-637X_796_2_84.pdf

Submitted - 1404.7159v2.pdf


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