Detection of the 205 μm [N ii ] Line from the Carina Nebula

Abstract

We report the first detection of the 205 µm 3 P 1 → 3 P 0 [NII] line from a ground-based observatory using a direct detection spectrometer. The line was detected from the Carina star formation region using the South Pole Imaging Fabry-Perot Interferometer (SPIFI) on the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) at South Pole. The [NII] 205 µm line strength indicates a low-density (n ∼ 32 cm −3 ) ionized medium, similar to the low-density ionized halo reported previously in its [OIII] 52 and 88 µm line emission. When compared with the ISO [CII] observations of this region, we find that 27% of the [CII] line emission arises from this low-density ionized gas, but the large majority (∼ 73%) of the observed [CII] line emission arises from the neutral interstellar medium. This result supports and underpins prior conclusions that most of the observed [CII] 158 µm line emission from Galactic and extragalactic sources arises from the warm, dense photodissociated surfaces of molecular clouds. The detection of the [NII] line demonstrates the utility of Antarctic sites for THz spectroscopy.

Far-infrared line imaging of the starburst ring in NGC 1097 with theHerschel/PACS spectrometer

“…2 205 μm ratio in ionized gas is expected to be ∼3 (Oberst et al 2006) and thus most (∼90%) of the [CII] 158 μm emission we measure is coming from neutral gas. The gas heating efficiency, measured by the ([OI] + [CII])/FIR ratio, seems to stay constant in the mapped area.…”

TheHerschelDwarf Galaxy Survey

“…Because [C ] can be found in the low-density ionized gas, part of its emission can correlate with the [N ] emission. Hence the [N ] lines can, in principle, be used to disentangle the fraction of [C ] from the ionized gas to that from the PDR alone (Oberst et al 2006). (Rubin et al 1994).…”

ALMA reveals a chemically evolved submillimeter galaxy atz= 4.76

“…Note that there are many [N ii] 122 μm detections in nearby galaxies (e.g., Graciá-Carpio et al 2011) and also in a few high-z galaxies (Ferkinhoff et al 2011). Although there are attempts to infer the [N ii] 205 μm flux from the [N ii] 122 μm emission (e.g., Decarli et al 2012), this method may introduce a large systematic error because the flux ratio of [N ii] 122 μm and [N ii] 205 μm varies by a factor of ∼10, i.e., it is strongly dependent on the gas density (see Oberst et al 2006).…”