1997/11/15 by T. Joseph W. Lazio, James M. Cordes, J. M. Cordes · 2 citations
Engineering · Physics and Astronomy · #Active galactic nucleus #Astronomical Observations and Instrumentation #Astronomy #Astrophysics #Disc #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy formation and evolution #Milky Way #Physics #Quasar #Spiral galaxy #Stellar, planetary, and galactic studies #Very Long Baseline Array #astro-ph
paper · pdf · doi:10.1086/313084
19 pages, LaTeX2e with AASTeX macro aaspp4, accepted for publication in ApJS, Vol. 115, 1998 April; Figures 1, 3, and 4 included, for figures of individual sources see http://astrosun.tn.cornell.edu/students/lazio/Anticenter/anticenterI.html
arxiv created 1997/11/15 · openalex publication_date 1998/04/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
We report multifrequency Very Long Baseline Array observations of 12 active galactic nuclei seen toward the Galactic anticenter. All of the sources are at | b | < 10°, and seven have | b | < 0 5. Our VLBA observations can detect an enhancement in the angular broadening of these sources due to an extended H II disk, if the orientation of the H II disk in the outer Galaxy is similar to that of the H I disk. Such an extended H II disk is suggested by the C IV absorption in a quasar's spectrum, the appearance of H I disks of nearby spiral galaxies, and models of Lyα cloud absorbers and the Galactic fountain. We detect 11 of the 12 sources at one or more frequencies; nine of the sources are compact and suitable for an angular broadening analysis. A preliminary analysis of the observed angular diameters suggests that the H II disk does not display considerable warping or flaring and does not extend to large Galactocentric distances ( R ≳ 100 kpc). A companion paper (Lazio & Cordes) combines these observations with those in the literature and presents a more comprehensive analysis.