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ALMA resolves turbulent, rotating [CII] emission in a young starburst galaxy atz= 4.8

De Breuck, Carlos, Williams, Rebecca J., Swinbank, Mark, Caselli, Paola, Coppin, Kristen, Davis, Timothy A., Maiolino, Roberto, Nagao, Tohru, Smail, Ian, Walter, Fabian, Weiß, Axel and Zwaan, Martin A. 2014. ALMA resolves turbulent, rotating [CII] emission in a young starburst galaxy atz= 4.8. Astronomy and Astrophysics 565 , A59. 10.1051/0004-6361/201323331

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Abstract

We present spatially resolved Atacama Large Millimeter/submillimeter Array (ALMA) [Cii] observations of the z = 4.7555 submillimetre galaxy, ALESS 73.1. Our 0.̋5 FWHM map resolves the [Cii] emitting gas which is centred close to the active galactic nucleus (AGN). The gas kinematics are dominated by rotation but with high turbulence, vrot/σint ~ 3.1, and a Toomre Q parameter <1 throughout the disk. By fitting three independent thin rotating disk models to our data, we derive a total dynamical mass of 3 ± 2 × 1010 M⊙. This is close to the molecular gas mass derived from previous CO(2-1) observations, and implies a CO to H2 conversion factor αCO < 2.3 M⊙ (K km s-1 pc2)-1. The mass budget also constrains the stellar mass to <3.1 × 1010 M⊙, and entails a gas fraction of fgas ≳ 0.4. The diameter of the dust continuum emission is <2 kpc, while the star-formation rate is as high as 1000 M⊙ yr-1. Combined with our stellar mass constraint, this implies an extreme specific star formation rate >80 Gyr-1, especially since there are no clear indications of recent merger activity. Finally, our high signal-to-noise [Cii] measurement revises the observed [Nii]/[Cii] ratio, which suggests a close to solar metallicity, unless the [Cii] flux contains significant contributions from Hii regions. Our observations suggest that ALESS73.1 is a nascent galaxy undergoing its first major burst of star formation, embedded within an unstable but metal-rich gas disk

Item Type: Article
Date Type: Published Online
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Publisher: EDP Sciences
ISSN: 0004-6361
Date of Acceptance: 3 April 2014
Last Modified: 21 Feb 2019 12:24
URI: http://orca.cf.ac.uk/id/eprint/87985

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