Velocity-Resolved Fine Structure Line Observations and Star Formation: New Results and New Capabilities

Abstract: What controls star formation? is a key question in astrophysics, and one very important aspect of this is the interaction of newly-formed stars with their surroundings. The radiative and mechanical feedback from young, massive stars can be dramatic. The altered composition and increased temperature that result make atomic and ionic fine structure lines ideal probes of stellar feedback. The value of such observations is dramatically increased if the spectral lines are velocity-resolved so that the momentum and energy impact on the stars’surroundings can be determined. But such observations must be carried out from suborbital or space observatories due to absorption in the Earth’s atmosphere. The fine structure lines of ionized carbon, and atomic oxygen are the most important and have been widely observed with high spectral resolution starting with the Herschel HIFI instrument and continuing with upGREAT on SOFIA. In this talk I will discuss some recent fine structure line observations focusing on the effects of star formation on the surrounding interstellar medium and possible problems with measuring the rate of star formation. I will conclude by presenting two fine structure line spectroscopic balloon missions. GUSTO was launched on 31 December 2023, and until 27 February 2024 surveyed the 205 μm line of [NII] and 158 μm line of [CII] in the central portion of the Milky Way and the Large Magellanic Cloud. ASTHROS, which is to follow at the end of 2027, has a much larger 2.5m diameter telescope, and will observe both [NII] fine structure lines to derive the electron density in selected regions.