Ionized Nitrogen at High Redshift
Abstract
We present secure [N II]205 μm detections in two millimeter-bright, strongly lensed objects at high redshift, APM 08279+5255 (z = 3.911) and MM 18423+5938 (z = 3.930), using the IRAM Plateau de Bure Interferometer. Due to its ionization energy [N II]205 μm is a good tracer of the ionized gas phase in the interstellar medium. The measured fluxes are S([N II]205 μm) = (4.8 ± 0.8) Jy km s-1 and (7.4 ± 0.5) Jy km s-1, respectively, yielding line luminosities of L([N II]205 μm) = (1.8 ± 0.3) × 109 μ-1 L ⊙ for APM 08279+5255 and L([N II]205 μm) = (2.8 ± 0.2) × 109 μ-1 L ⊙ for MM 18423+5938. Our high-resolution map of the [N II]205 μm and 1 mm continuum emission in MM 18423+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 (ΣFIRvpropΣ N CO, 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 [N II]205 μm/FIR luminosity ratio in APM 08279+5255 and MM 18423+5938 of 9.0 × 10-6 and 5.8 × 10-6, respectively. This is in agreement with the decrease of the [N II]205 μm/FIR ratio at high FIR luminosities observed in local galaxies.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2012
- DOI:
- 10.1088/0004-637X/752/1/2
- arXiv:
- arXiv:1203.6852
- Bibcode:
- 2012ApJ...752....2D
- Keywords:
-
- galaxies: individual: MM 18423+5938;
- galaxies: ISM;
- quasars: individual: APM 08279+5255;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 5 Figures, 1 Table. Accepted for publication in ApJ