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Spatially Resolved Very Large Array 74 MHz Observations Toward the Galactic Center
Author(s) -
Brogan C. L.,
Nord M.,
Kassim N.,
Lazio J.,
Anantharamaiah K.
Publication year - 2003
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.200385023
Subject(s) - galactic center , physics , astrophysics , center (category theory) , absorption (acoustics) , astronomy , line of sight , ionization , galaxy , optics , ion , chemistry , quantum mechanics , crystallography
We present the highest resolution and sensitivity low frequency image (<300 MHz) of the Galactic center to date using the Very Large Array at 74 MHz in its A, B, C, & D configurations. The resulting images have a resolution of 2.1′ × 1.2′ and a dynamic range of ∼400 From this data we have been able to identify a region of enhanced 74 MHz emission about 5° in extent that is coincident with the high density molecular gas surrounding the Galactic center known as the Central Molecular Zone. In addition to giving an unprecedented view of the extended nonthermal emission surrounding the Galactic center, the 74 MHz image shows deep free‐free absorption across the Galactic center itself, as well as, part of the Galactic center radio lobe, and a number of H II regions in the field. This absorption is due to ionized thermal gas in front of, or in some cases embedded in, the nonthermal Galactic center (GC) emission. Such absorption allows us to unambiguously place some of the H II regions in the direction of the GC along the line of sight for the first time. The morphology, nature, and relationship to the Galactic center of the 74 MHz absorption and emission is discussed.