H110α observations of Sagittarius a West: Ionized gas at peculiar velocities at the galactic center

Farhad Yusef-Zadeh*, Jun Hui Zhao, W. M. Goss

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


We present Very Large Array measurements of H110α radio recombination line emission from Sgr A West with a resolution of 11″ × 20″. These observations detected a number of new kinematic components showing a dramatically different velocity field than expected from circular motion of ionized gas in Sgr A West about the dynamical center of the Galaxy. Recent high-resolution molecular observations show a cloud of absorbing gas at -180 km s-1 within 30″ of the Galactic center. We find evidence of an ionized counterpart to this highly blueshifted molecular gas. This result places this highly blueshifted neutral gas in a hot UV dominated environment of the Galactic center. We suggest that the blueshifted clouds are photoionized externally by the intense UV radiation field at the Galactic center. We also detect H110α emission from large-scale linear features known as the "streamers," which run primarily perpendicular to the Galactic plane and lie exterior to the "three-arm" spiral structure of Sgr A West and the circumnuclear disk. These observations support an earlier suggestion that the streamers are thermal features whose kinematics deviate from circular motion.

Original languageEnglish (US)
Pages (from-to)646-652
Number of pages7
JournalAstrophysical Journal
Issue number2
StatePublished - Apr 1 1995


  • Galaxy: center
  • ISM: individual (Sagittarius A)
  • Radio lines: ISM

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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