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

De Breuck, C.; Williams, R.J.; Swinbank, M.; Caselli, P.; Coppin, K.; Davis, T.A.; Maiolino, R.; Nagao, T.; Smail, I.; Walter, F.; Weiß, A.; Zwaan, M.A.

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


Authors

C. De Breuck

R.J. Williams

M. Swinbank

P. Caselli

K. Coppin

T.A. Davis

R. Maiolino

T. Nagao

Profile image of Ian Smail

Ian Smail ian.smail@durham.ac.uk
Emeritus Professor

F. Walter

A. Weiß

M.A. Zwaan



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.

Citation

De Breuck, C., Williams, R., Swinbank, M., Caselli, P., Coppin, K., Davis, T., …Zwaan, M. (2014). ALMA resolves turbulent, rotating [CII] emission in a young starburst galaxy at z = 4.8. Astronomy & Astrophysics, 565, https://doi.org/10.1051/0004-6361/201323331

Journal Article Type Article
Publication Date May 12, 2014
Deposit Date Nov 17, 2014
Publicly Available Date Nov 24, 2014
Journal Astronomy and astrophysics.
Print ISSN 0004-6361
Electronic ISSN 1432-0746
Publisher EDP Sciences
Peer Reviewed Peer Reviewed
Volume 565
DOI https://doi.org/10.1051/0004-6361/201323331
Keywords Galaxies: high-redshift, Galaxies: starburst, Galaxies: kinematics and dynamics, Galaxies: ISM.
Public URL https://durham-repository.worktribe.com/output/1419873

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Copyright Statement
Reproduced with permission from Astronomy & Astrophysics, © ESO 2014.






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