The [C II]/[N II] ratio in 3 < z < 6 sub-millimetre galaxies from the South Pole Telescope survey - Archive ouverte HAL Access content directly
Journal Articles Monthly Notices of the Royal Astronomical Society Year : 2020

## The [C II]/[N II] ratio in 3 < z < 6 sub-millimetre galaxies from the South Pole Telescope survey

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1
D. J. M. Cunningham
• Function : Author
S. C. Chapman
• Function : Author
M. Aravena
C. de Breuck
• Function : Author
M. Béthermin
Chian-Chou Chen
• Function : Author
Chenxing Dong
• Function : Author
A. H. Gonzalez
• Function : Author
T. R. Greve
• Function : Author
K. C. Litke
• Function : Author
J. Ma
• Function : Author
M. Malkan
• Function : Author
D. P. Marrone
• Function : Author
T. Miller
• Function : Author
• Function : Author
C. Reuter
• Function : Author
K. Rotermund
• Function : Author
J. S. Spilker
• Function : Author
A. A. Stark
• Function : Author
M. Strandet
• Function : Author
J. D. Vieira
• Function : Author
A. Weiss
• Function : Author

#### Abstract

We present Atacama Compact Array and Atacama Pathfinder Experiment observations of the [N II] 205 μm fine-structure line in 40 sub-millimetre galaxies lying at redshifts z = 3-6, drawn from the 2500 deg2 South Pole Telescope survey. This represents the largest uniformly selected sample of high-redshift [N II] 205 μm measurements to date. 29 sources also have [C II] 158 μm line observations allowing a characterization of the distribution of the [C II] to [N II] luminosity ratio for the first time at high redshift. The sample exhibits a median L $_{{\rm{[C\,{\small II}]}}}$ /L $_{{\rm{[N\,{\small II}]}}}$ ≍ 11.0 and interquartile range of 5.0 -24.7. These ratios are similar to those observed in local (Ultra)luminous infrared galaxies (LIRGs), possibly indicating similarities in their interstellar medium. At the extremes, we find individual sub-millimetre galaxies with L $_{{\rm{[C\,{\small II}]}}}$ /L $_{{\rm{[N\,{\small II}]}}}$ low enough to suggest a smaller contribution from neutral gas than ionized gas to the [C II] flux and high enough to suggest strongly photon or X-ray region dominated flux. These results highlight a large range in this line luminosity ratio for sub-millimetre galaxies, which may be caused by variations in gas density, the relative abundances of carbon and nitrogen, ionization parameter, metallicity, and a variation in the fractional abundance of ionized and neutral interstellar medium.

### Dates and versions

insu-03667099 , version 1 (13-05-2022)

### Identifiers

• HAL Id : insu-03667099 , version 1
• ARXIV :
• BIBCODE :
• DOI :

### Cite

D. J. M. Cunningham, S. C. Chapman, M. Aravena, C. de Breuck, M. Béthermin, et al.. The [C II]/[N II] ratio in 3 < z < 6 sub-millimetre galaxies from the South Pole Telescope survey. Monthly Notices of the Royal Astronomical Society, 2020, 494, pp.4090-4097. ⟨10.1093/mnras/staa820⟩. ⟨insu-03667099⟩

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