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First detections of the [n ii] 122 μm line at high redshift: demonstrating the utility of the line for studying galaxies in the early universe

Ferkinhoff, Carl, Brisbin, Drew, Nikola, Thomas, Parshley, Stephen C., Stacey, Gordon J., Phillips, Thomas G., Falgarone, Edith, Benford, Dominic J., Staguhn, Johannes G. and Tucker, Carole Elizabeth 2011. First detections of the [n ii] 122 μm line at high redshift: demonstrating the utility of the line for studying galaxies in the early universe. Astrophysical Journal Letters 740 (1) , L29. 10.1088/2041-8205/740/1/L29

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We report the first detections of the [N II] 122 μm line from a high-redshift galaxy. The line was strongly (>6σ) detected from SMMJ02399–0136, and H1413+117 (the Cloverleaf QSO) using the Redshift (z) and Early Universe Spectrometer on the Caltech Submillimeter Observatory. The lines from both sources are quite bright with line to far-infrared (FIR) continuum luminosity ratios that are ~7.0 × 10–4 (Cloverleaf) and 2.1 × 10–3 (SMMJ02399). With ratios 2-10 times larger than the average value for nearby galaxies, neither source exhibits the line-to-continuum deficits seen in nearby sources. The line strengths also indicate large ionized gas fractions, ~8%-17% of the molecular gas mass. The [O III]/[N II] line ratio is very sensitive to the effective temperature of ionizing stars and the ionization parameter for emission arising in the narrow-line region (NLR) of an active galactic nucleus (AGN). Using our previous detection of the [O III] 88 μm line, the [O III]/[N II] line ratio for SMMJ02399–0136 indicates that the dominant source of the line emission is either stellar H II regions ionized by O9.5 stars, or the NLR of the AGN with ionization parameter log(U) = –3.3 to –4.0. A composite system, where 30%-50% of the FIR lines arise in the NLR also matches the data. The Cloverleaf is best modeled by a superposition of ~200 M82-like starbursts accounting for all of the FIR emission and 43% of the [N II] line. The remainder may come from the NLR. This work demonstrates the utility of the [N II] and [O III] lines in constraining properties of the ionized medium.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: galaxies: active; galaxies: high-redshift; galaxies: individual (SMMJ02399-136, H1413+117); galaxies: starburst; submillimeter: galaxies
Publisher: Institute of Physics
ISSN: 2041-8205
Last Modified: 04 Jun 2017 04:03

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