Volume 542, June 2012
|Number of page(s)||4|
|Published online||13 June 2012|
ALMA reveals a chemically evolved submillimeter galaxy at z = 4.76
1 The Hakubi Center for Advanced Research, Kyoto University, Kyoto 606-8302, Japan
2 Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
3 Cavendish Laboratory, Univerisy of Cambridge, 19 J. J. Thomson Ave., Cambridge CB3 0HE, UK
4 European Southern Observatory, Karl Schwarzschild Strasse 2, 85748 Garching, Germany
5 School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK
6 East Asian ALMA Regional Center, National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan
Received: 2 May 2012
Accepted: 21 May 2012
The chemical properties of high-z galaxies provide important information for constraining galaxy evolutionary scenarios. However, widely used metallicity diagnostics based on rest-frame optical emission lines are unusable for heavily dust-enshrouded galaxies (such as submillimeter galaxies; SMGs), especially at z > 3. Here we focus on the flux ratio of the far-infrared fine-structure emission lines [N ii] 205 μm and [C ii] 158 μm to assess the metallicity of high-z SMGs. Through ALMA cycle 0 observations, we have detected the [N ii] 205 μm emission in a strongly [C ii]-emitting SMG, LESS J033229.4–275619 at z = 4.76. The velocity-integrated [N ii]/[C ii] flux ratio is 0.043 ± 0.008. This is the first measurement of the [N ii]/[C ii] flux ratio in high-z galaxies, and the inferred flux ratio is similar to the ratio observed in the nearby universe (~0.02−0.07). The velocity-integrated flux ratio and photoionization models suggest that the metallicity in this SMG is consistent with solar, implying that the chemical evolution has progressed very rapidly in this system at z = 4.76. We also obtain a tight upper limit on the CO(12 − 11) transition, which translates into CO(12−11)/CO(2−1) < 3.8 (3σ). This suggests that the molecular gas clouds in LESS J033229.4–275619 are not significantly affected by the radiation field emitted by the AGN in this system.
Key words: galaxies: high-redshift / galaxies: individual: LESS J033229.4 / 275619 / submillimeter: galaxies / submillimeter: ISM
© ESO, 2012
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.