Ionized nitrogen at high redshift

Abstract

We present secure [NII[ detections in two mm-bright, strongly lensed objects at high redshift, APM08279+5255 (z=3.911) and MM18423+5938 (z=3.930), using the IRAM Plateau de Bure Interferometer. Due to its ionization energy [NII] is a good tracer of the ionized gas phase in the interstellar medium. The measured fluxes are S([NII])=(4.8+/-0.8) Jy km/s and (7.4+/-0.5) Jy km/s respectively, yielding line luminosities of L([NII]) =(1.8+/-0.3) x 10^9 μ^{-1} Lsun for APM08279+5255 and L([NII]) =(2.8+/-0.2) x 10^9 μ^{-1} Lsun for MM18423+5938. Our high-resolution map of the [NII] and 1 mm continuum emission in MM18423+5938 clearly resolves an Einstein ring in this source, and reveals a velocity gradient in the dynamics of the ionized gas. A comparison of these maps with high-resolution EVLA CO observations enables us to perform the first spatially-resolved study of the dust continuum-to-molecular gas surface brightness (Sigma_{FIR} Sigma_{CO}^N, which can be interpreted as the star formation law) in a high-redshift object. We find a steep relation (N=1.4+/-0.2), consistent with a starbursting environment. We measure a [NII]/FIR luminosity ratio in APM0828+5255 and MM18423+5938 of 9.0 x 10^{-6} and 5.8 x 10^{-6}, respectively. This is in agreement with the decrease of the [NII]/FIR ratio at high FIR luminosities observed in local galaxies.

5 Figures, 1 Table. Accepted for publication in ApJ

References in corpus (12)

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• Highly-excited CO emission in APM08279+5255 at z=3.9
• Detection of the 205 um [NII] Line from the Carina Nebula
• A bright z=5.2 lensed submillimeter galaxy in the field of Abell 773: HLSJ091828.6+514223
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• A Detection of [CII] line emission in the z=4.7 QSO BR1202-0725
• Physical conditions of the interstellar medium of high-redshift, strongly lensed submillimetre galaxies from the Herschel-ATLAS
• First Detection of the [OIII] 88 micron Line at High Redshifts: Characterizing the Starburst and Narrow Line Regions in Extreme Luminosity Systems
• First detections of the [NII] 122 μm line at high redshift: Demonstrating the utility of the line for studying galaxies in the early universe
• Atomic Carbon in APM 08279+5255 at z=3.91
• A Sensitive Search For [NII] Emission in a z=6.4 Quasar Host Galaxy
• SMA High Angular Resolution Imaging of the Lensed Quasar APM08279+5255

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