Letter to the Editor

Strong [CII] emission at high redshift ^*,**

¹ INAF – Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone, Italy e-mail: maiolino@oa-roma.inaf.it
² School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK
³ Research Center for Space and Cosmic Evolution, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577, Japan
⁴ Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
⁵ European Southern Observatory, Karl Schwarzschild Strasse 2, 85748 Garching, Germany
⁶ INAF – Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
⁷ INFN, Sezione di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy

Received: 3 April 2009
Accepted: 21 April 2009

Abstract

We report the detection of the [Cii]157.74 μm fine-structure line in the lensed galaxy BRI 0952-0115 at , using the APEX telescope. This is the first detection of the [Cii] line in a source with at high redshift. The line is much stronger than previous [Cii] detections at high-z (a factor of 5–8 higher in flux), partly due to the lensing amplification. The ratio is 10^-2.9, which is higher than observed in local galaxies with similar infrared luminosities. Together with previous observations of [Cii] at high redshift, our result suggests that the [Cii] emission in high-redshift galaxies is enhanced relative to local galaxies with the same infrared luminosity. This finding may result from selection effects of the few current observations of [Cii] at high redshift and, in particular, from non detections that may not have been published (although the few published upper limits are still consistent with the [Cii] enhancement scenario). If the trend is confirmed with larger samples, it would indicate that high-z galaxies are characterized by different physical conditions than for their local counterparts. Regardless of the physical origin of the trend, this effect would increase the potential of the [Cii]158 μm line to search and characterize high-z sources.