We report the detection of Voigt spectral line profiles of radio recombination lines (RRLs) toward Sagittarius B2(N) with the 100-m Green Bank Telescope (GBT). These results constitute the first known, unambiguous detection of the Voigt spectral line shape of RRLs. At radio wavelengths, astronomical spectra are highly populated with radio recombination lines, which serve as ideal probes of the physical conditions in molecular cloud complexes. An analysis of the Hn alpha lines presented herein shows that RRLs of higher principal quantum number (n>90) are generally best described by theoretical Voigt profiles, direct evidence of pressure broadening by electron collisions, and clearly diverge from the typical Gaussian shape. Given the complexity of the Sgr B2(N) region and large range of spatial resolution covered by the archival data, a detailed analysis was beyond the scope of this paper. However, the observations clearly show that the GBT is an excellent instrument for measuring very accurate line profiles given its high sensitivity, spectral resolution and spectral baselines. Further analysis of these data can provide important information about the physical conditions and dynamics of the ionized gas and future high spectral resolution GBT observations of RRL emission will undoubtably continue to enhance our knowledge of ionized regions in the ISM.
Citation: Astronomical Journal
Pub Type: Journals
astronomy, H II regions, line profiles, radio continuum, radio recombination lines, pressure broadening