ALMA detection of [C II] 158 μm emission from a strongly lensed z = 2.013 star-forming galaxy
Aims. Our objectives are to determine the properties of the interstellar medium (ISM) and of star formation in typical star-forming galaxies at high redshift. Methods. Following up on our previous multi-wavelength observations with HST, Spitzer, Herschel, and the Plateau de Bure Interferometer (PdBI), we have studied a strongly lensed z = 2.013 galaxy, the arc behind the galaxy cluster MACS J0451+0006, with ALMA to measure the [C II] 158 μm emission line, one of the main coolants of the ISM. Results. Emission of the [C II] line from the southern part of this galaxy is detected at 10σ. Taking strong gravitational lensing into account, which provides a magnification of μ = 49, the intrinsic lensing-corrected [C II] luminosity is L[CII] = 1.2 × 10^8L⊙. The observed ratio of [C II]-to-IR emission, L[CII]/L_(FIR) ≈ (1.2−2.4) × 10^(-3), is found to be similar to that in nearby galaxies. The same also holds for the observed ratio L_([CII])/L_(CO)= 2.3 × 10^3, which is comparable to that of star-forming galaxies and active galaxy nuclei (AGN) at low redshift. Conclusions. We utilize strong gravitational lensing to extend diagnostic studies of the cold ISM to an order of magnitude lower luminosity (L_(IR) ~ (1.1−1.3) × 10^(11)L⊙) and SFR than previous work at high redshift. While larger samples are needed, our results provide evidence that the cold ISM of typical high-redshift galaxies has physical characteristics similar to normal star-forming galaxies in the local Universe.
© 2015 ESO. Article published by EDP Sciences. Received 18 December 2014; Accepted 11 February 2015; Published online 13 March 2015. Based on ALMA observations 2011.0.00130.S. This work was supported by the Swiss National Science Foundation. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2011.0.00130.S. ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. We gratefully thank the ALMA staff of NAASC for their assistance in preparing the observations, which form the basis of this Letter.
Published - aa25542-14.pdf