2001/02/08 by Cornelia Lang, Cornelia C. Lang, W. M. Goss +2 · 1 citation
Chemistry · Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Cosmic Phenomena #Astrophysics and Star Formation Studies #Center (category theory) #Chemistry #Full width at half maximum #Galactic Center #Gamma-ray bursts and supernovae #Geometry #H II region #Ion #Ionization #Line (geometry) #Magnetic field #Molecular cloud #Optics #Photoionization #Physics #Protein filament #Star formation #Stars #astro-ph
paper · pdf · doi:10.1086/320373
29 pages, 22 figures embedded (some poor quality), accepted to the Astronomical Journal (May 2001 issue), higher resolution figures available from [email protected]
arxiv created 2001/02/08 · openalex publication_date 2001/05/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The Very Large Array has been used at 8.3 GHz in the DnC and CnB array configurations to carry out an H92α recombination line study of the ionized gas in the Arched Filaments H II complex, which defines the western edge of the Galactic center Radio Arc. The Arched Filaments consist of a series of curved filamentary ridges which extend over 9' × 6' (22 × 16 pc) and are intersected in two places by linear, nonthermal, magnetic filaments. The H92α observations cover the entire Arched Filaments region using a four-field mosaic, with an angular resolution of 12 8 × 8 10; an additional higher resolution (3 6 × 2 7) field was imaged in the SW portion of the H II complex. High-resolution continuum images are also presented. The H92α line properties of the ionized gas (line-to-continuum ratio, FWHM line width, T ) are consistent with photoionization from hot stars and consistent with the physical properties of other Galactic center H II regions. The LTE electron temperatures vary only slightly across the entire extent of the source and have an average value of 6200 K. The velocity field is very complex, with velocities ranging from +15 to -70 km s -1 and the majority of velocities having negative values. Large velocity gradients (2–7 km s -1 pc -1 , with gradients in some regions larger than 10 km s -1 pc -1 ) occur along each of the filaments, with the velocities becoming increasingly negative with decreasing distance from the Galactic center. The negative velocities and the sense of the velocity gradients can be understood in terms of the orbital path of the underlying molecular cloud about the Galactic center. The magnitudes of the velocity gradient are consistent with the cloud residing on an inner, elongated orbit which is due to the Galaxy's stellar bar, or with a radially infalling cloud. The ionization of the Arched Filaments can be accounted for completely by the massive Arches stellar cluster, which consists of more than 150 O stars and produces a few × 10 51 photons s -1 . This cluster is likely to be located 10–20 pc from the Arched Filaments, which can explain the uniformity of ionization conditions in the ionized gas.