The [NII] 205 micron and [CII] 158 micron line emissions of four star forming Submillimeter Galaxies at z∼3-5.7

Submillimeter investigations of far-infrared (FIR) fine structure lines are a useful probe for the study of galaxies and the warm, neutral gas of the interstellar medium (ISM) in the early universe. Fine structure lines of carbon, oxygen, and nitrogen reveal characteristics of the ISM and the star-forming regions in it. The [NII] 205 μm line is used as a tracer of C+ gas due to the very similar critical densities to the [CII] 158 μm line and the fact that the line ratio of [CII]158/[NII]205 in the ionized gas is constant. We used these properties to compute the percentage of ionized and neutral C+ gas in the PDR versus the HII region. We present data for the [NII] 205 μm and [CII] 158 μm line emissions, acquired with the Atacama Large Millimeter/Submillimeter Array (ALMA) telescope, to investigate the star forming properties of lensed, submillimeter galaxies at high redshifts between z~3-5.7. Through data reduction and interpretation, line ratios of 10 or higher were obtained, signifying a higher percentage of neutral [CII] in PDR's compared to HII region - 65% to 80% of neutral [CII] comes from the PDR's.