2014/04/08 by Miwa Goto, T. R. Geballe, Nick Indriolo +4 · 1 citation
Physics and Astronomy · #Absorption (acoustics) #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Astrophysics and Star Formation Studies #Galactic Center #Hydrogen #Infrared #Ionization #Line (geometry) #Sky #Spectral line #Stars #astro-ph.GA
paper · pdf · doi:10.1088/0004-637x/786/2/96
15 pages, 12 figures, 7 tables ApJ accepted
arxiv created 2014/04/08 · openalex publication_date 2014/04/22 · arxiv updated 2015/06/19 · openalex created_date 2019/06/27 · openalex updated_date 2026/08/05
We have obtained improved spectra of key fundamental band lines of H , R (1, 1) l , R (3, 3) l , and R (2, 2) l , and ro-vibrational transitions of CO on sightlines toward the luminous infrared sources GCIRS 3 and GCIRS 1W, each located in the Central Cluster of the Galactic center within several arcseconds of Sgr A*. The spectra reveal absorption occurring in three kinds of gaseous environments: (1) cold dense and diffuse gas associated with foreground spiral/lateral arms; (2) warm and diffuse gas absorbing over a wide and mostly negative velocity range, which appears to fill a significant fraction of the Galaxy's Central Molecular Zone (CMZ); and (3) warm, dense and compact clouds with velocities near +50 km s −1 probably within 1–2 pc of the center. The absorptions by the first two cloud types are nearly identical for all the sources in the Central Cluster, and are similar to those previously observed on sightlines from Sgr A* to 30 pc east of it. Cloud type (3), which has only been observed toward the Central Cluster, shows distinct differences between the sightlines to GCIRS 3 and GCIRS 1W, which are separated on the sky by only 0.33 pc in projection. We identify this material as part of an inward extension of the circumnuclear disk previously known from HCN mapping. Lower limits on the products of the hydrogen ionization rate ζ and the path length L are 2.3 × 10 5 cm s −1 and 1.5 × 10 3 cm s −1 for the warm and diffuse CMZ gas and for the warm and dense clouds in the core, respectively. The limits indicate that the ionization rates in these regions are well above 10 −15 s −1 .