ASTRONOMY COLLOQUIUM

Far-infrared fine structure lines, such as [CII], [NII], [OI], and [OIII], are powerful tools for understanding the evolution of the interstellar medium (ISM) and star formation in galaxies. They trace the different phases of the ISM, including the ionized medium, warm and cold atomic clouds, clouds in transition from atomic to molecular, and dense and warm photon-dominated regions (PDRs). In particular, the [CII] 158 μm line is the brightest far-infrared cooling line in galaxies and reprocesses UV starlight from newly formed stars, making it a potential tracer of star formation activity. Recent studies have shown that the [CII] line can be used to study the global gas kinematics of star-forming regions, which can be used to determine the stellar feedback energy injection into the ISM. The [NII] 122 μm and 205 μm lines are important tracers of the density structure of the ionized medium and can also be used to characterize the impact of stellar feedback into the ISM. 

In this talk, I will review work using observations of the [CII] and [NII] lines taken with Herschel and SOFIA to characterize the evolution of the ISM and star formation in the Milky Way, the Magellanic Clouds, and the M51 grand design spiral galaxy. I will also introduce the ASHTROS stratospheric balloon, featuring a 2.5 meter telescope, that will launch in December 2024 from Antarctica. ASHTROS will produce large-scale maps of the [NII] 122 μm and 205 μm lines to characterize the kinematics and density structure of the ionized gas in galactic and extragalactic sources.