A 205 µm [N II] Map of the Carina Nebula

Abstract

We present the results of a ~250 arcmin² mapping of the 205 μm [N II] fine-structure emission over the northern Carina Nebula, including the Car I and Car II H II regions. Spectra were obtained using the South Pole Imaging Fabry-Perot Interferometer (SPIFI) at the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) at the South Pole. We supplement the 205 μm data with new reductions of far-IR fine-structure spectra from the Infrared Space Observatory (ISO) Long Wavelength Spectrometer (LWS) in 63 μm [O I], 122 μm [N II], 146 μm [O I], and 158 μm [C II]; the 146 μm [O I] data include 90 raster positions which have not been previously published. Morphological comparisons are made with optical, radio continuum, and CO maps. The 122/205 line ratio is used to probe the density of the low-ionization gas, and the 158/205 line ratio is used to probe the fraction of C⁺ arising from photodissociation regions (PDRs). The [O I] and [C II] lines are used to construct a PDR model of Carina. When the PDR properties are compared with other sources, Carina is found to be more akin to 30 Doradus than galactic star-forming regions such as Orion, M17, or W49; this is consistent with the view of Carina as a more evolved region, where much of the parent molecular cloud has been ionized or swept away. These data constitute the first ground-based detection of the 205 μm [N II] line, and the third detection overall since those of COBE FIRAS and the Kuiper Airborne Observatory in the early 1990s.